CN116745129A

CN116745129A - Photosensitive resin structure for flexographic printing plate and method for producing flexographic printing plate

Info

Publication number: CN116745129A
Application number: CN202180090270.4A
Authority: CN
Inventors: 秋山弘贵; 宫本慎二
Original assignee: Asahi Kasei Corp
Current assignee: Asahi Kasei Corp
Priority date: 2021-01-20
Filing date: 2021-12-14
Publication date: 2023-09-12

Abstract

A photosensitive resin structure for a flexographic printing plate, comprising at least a support (a), a photosensitive resin composition layer (b) laminated on the support (a), and an infrared ablation layer (c) laminated on the photosensitive resin composition layer (b), wherein the infrared ablation layer (c) contains a resin having a prescribed structural unit (c 1).

Description

Photosensitive resin structure for flexographic printing plate and method for producing flexographic printing plate

Technical Field

The present invention relates to a photosensitive resin structure for flexographic printing plates and a method for producing flexographic printing plates.

Background

Further higher definition of printed images has been demanded in recent years. On the other hand, the following methods have been widely used in the manufacturing process of flexographic printing plates: the digital image is directly drawn by a laser using CTP (off-line direct plate making; computer To Plate) technology without using a negative film.

In the CTP technique, as a master for producing a flexographic printing plate, a master in which a photosensitive resin composition layer, an infrared ablation layer which can be cut off by infrared rays, and a cover film are laminated in this order on a substrate such as PET (polyethylene terephthalate) resin is generally used.

An infrared ablative layer capable of ablation with infrared rays generally contains an infrared absorber, which is a material opaque to radiation other than infrared rays, and a resin.

As a technique for realizing further higher definition of a printed image and improvement of ink transferability at the time of printing, a technique of disposing microcells (microcells) on a surface of a printing plate has been conventionally known. In addition, the laser drawing device used in the process of manufacturing the flexographic printing plate also has a high resolution, and the laser resolution is also expected to be increased from 2540DPI to 4000 and 5080DPI, and further, to 8000DPI, etc.

In the above-described cases, in order to form finer micro units, micromachining in laser drawing is further required in flexographic printing plates. For this reason, in the process of manufacturing a flexographic printing plate, a technique for obtaining an infrared ablation layer excellent in infrared laser drawing property is demanded.

As for the infrared ablation layer, for example, patent document 1 proposes a technique of using a copolymer of a monovinyl-substituted aromatic hydrocarbon and a conjugated diene or a copolymer of a monovinyl-substituted aromatic hydrocarbon and a conjugated diene, which is hydrogenated, as a resin. In addition, patent document 2 proposes a technique of using polyamide as a resin, and patent document 3 proposes a technique of using partially saponified polyvinyl acetate having a saponification degree of 60 to 100 mol% and a cationic polymer as a resin. Further, patent document 4 proposes a technique of using a modified olefin as a resin.

Prior art literature

Patent literature

Patent document 1: japanese patent No. 4080068

Patent document 2: japanese patent No. 2916408

Patent document 3: japanese patent laid-open publication 2016-188900

Patent document 4: japanese patent application laid-open No. 2015-11330

Disclosure of Invention

Problems to be solved by the invention

However, even when the infrared ablation layer obtained by using the adhesive is used, the infrared ablation layer cannot obtain energy sufficient for ablation in a fine pattern (1×1 pixel, 2×2 pixel image, etc.) at a high resolution of 8000DPI or the like, and it is difficult to form fine microcells.

Accordingly, in view of the above-described problems of the prior art, an object of the present invention is to provide a photosensitive resin structure for flexographic printing plates having an infrared ablation layer excellent in laser sensitivity even when sufficient drawing energy is not obtained due to a high resolution, and a method for producing a flexographic printing plate using the same.

Solution for solving the problem

The present inventors have conducted intensive studies to solve the above problems, and as a result, found that: the present invention has been accomplished by solving the above problems by providing a photosensitive resin structure for flexographic printing plates comprising a photosensitive resin composition layer and an infrared ablation layer having a specific structure.

Namely, the present invention is as follows.

[ 1 ] A photosensitive resin structure for flexographic printing plates, comprising at least:

a support (a);

a photosensitive resin composition layer (b) laminated on the support (a); and

an infrared ablation layer (c) laminated on the photosensitive resin composition layer (b),

the infrared ablation layer (c) contains a resin having a structural unit c1 represented by the following general formula (1).

(in the formula (1), R ₁ And R is ₂ Each independently represents a nonpolar group; r is R ₃ And R is ₄ Each independently represents a hydrogen atom or a nonpolar group. )

The photosensitive resin structure for flexographic printing plates according to [ 1 ], wherein the content of the structural unit (c 1) is 40% by mass or more and 100% by mass or less relative to the total amount of the resins.

The photosensitive resin structure for flexographic printing plates according to [ 1 ] or [ 2 ], wherein R is represented by the general formula (1) ₃ And R is ₄ Each independently is a hydrogen atom, alkyl, aryl, cycloalkyl, phenyl, alkenyl, aralkyl, cycloalkenyl, alkynyl, silyl, siloxane group.

The photosensitive resin structure for flexographic printing plates according to any one of [ 1 ] to [ 3 ], wherein R of the general formula (1) ₃ And R is ₄ Is a hydrogen atom.

The photosensitive resin structure for flexographic printing plates according to any one of [ 1 ] to [ 4 ], wherein R of the general formula (1) ₁ And R is ₂ Each independently is alkyl, aryl, cycloalkyl, phenyl, alkenyl, aralkyl, cycloalkenyl, alkynyl, silyl, siloxane.

The photosensitive resin structure for flexographic printing plates according to any one of [ 1 ] to [ 5 ], wherein R of the general formula (1) ₁ And R is ₂ Each independently is an alkyl group or a phenyl group.

The photosensitive resin structure for flexographic printing plates according to any one of [ 1 ] to [ 6 ], wherein R of the general formula (1) ₁ And R is ₂ Is alkyl.

The photosensitive resin structure for flexographic printing plates according to any one of [ 1 ] to [ 7 ], wherein the resin further comprises a structural unit (c 2), and the structural unit (c 2) is different from the structural unit (c 1) and contains an aromatic group in a side chain.

The photosensitive resin structure for flexographic printing plates according to any one of [ 1 ] to [ 8 ], wherein the structural unit (c 2) comprises a structural unit derived from a monovinyl-substituted aromatic hydrocarbon.

The photosensitive resin structure for flexographic printing plates according to any one of [ 1 ] to [ 9 ], wherein the infrared ablation layer (c) contains carbon black, and the pH of the carbon black is 2.0 to 5.0.

The photosensitive resin structure for flexographic printing plates according to any one of [ 1 ] to [ 10 ], wherein the infrared ablation layer (c) contains a dispersing agent,

the solubility parameter (SP value) of the dispersant is 9.5 to 12.5.

The photosensitive resin structure for flexographic printing plates according to any one of [ 1 ] to [ 11 ], wherein the compounding ratio (resin/carbon black) of the resin in the infrared ablation layer (c) to the carbon black is in the range of 80/20 to 50/50.

[ 13 ] A method for producing a flexographic printing plate, comprising the steps of:

a first step of irradiating ultraviolet rays from the support (a) side;

a second step of irradiating the infrared ablation layer (c) with infrared rays to draw a pattern;

a third step of exposing the photosensitive resin composition layer (b) to ultraviolet light using the infrared ablation layer (c) on which the pattern is formed as a mask; and

and a fourth step of removing the unexposed portions of the infrared ablation layer (c) and the photosensitive resin composition layer (b).

[ 14 ] A flexible printing method using the photosensitive resin structure for a flexible printing plate according to any one of [ 1 ] to [ 12 ], comprising the steps of:

a first step of irradiating ultraviolet rays from the support (a) side;

a third step of exposing the photosensitive resin composition layer (b) to ultraviolet light using the infrared ablation layer (c) on which the pattern is formed as a mask;

a fourth step of removing the unexposed portions of the infrared ablation layer (c) and the photosensitive resin composition layer (b) to produce a flexographic printing plate; and

and a fifth step of printing using the flexographic printing plate.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, there can be provided a photosensitive resin structure for a flexographic printing plate having an infrared ablation layer excellent in laser sensitivity even when sufficient drawing energy is not obtained due to a high resolution, and a method for manufacturing a flexographic printing plate using the same.

Drawings

Fig. 1 is a schematic cross-sectional view of a photosensitive resin structure for flexographic printing plates according to the present embodiment.

Fig. 2 is a schematic diagram showing a method for producing a flexographic printing plate using the photosensitive resin structure for a flexographic printing plate according to the present embodiment.

Detailed Description

Hereinafter, embodiments of the present invention (hereinafter referred to as "the present embodiment") will be described in detail, but the present invention is not limited thereto, and various modifications may be made without departing from the spirit thereof.

[ photosensitive resin Structure for flexographic printing plate ]

The photosensitive resin structure for a flexographic printing plate of the present embodiment comprises at least a support (a), a photosensitive resin composition layer (b) laminated on the support (a), and an infrared ablation layer (c) laminated on the photosensitive resin composition layer (b), wherein the infrared ablation layer (c) comprises a resin having a structural unit (c 1) represented by the following general formula (1).

Fig. 1 shows a schematic cross-sectional view of a photosensitive resin structure for flexographic printing plates (hereinafter also referred to simply as "the structure") according to the present embodiment. The present structure comprises a support (a), a photosensitive resin composition layer (b) having a relief pattern of a flexographic printing plate formed thereon, and an infrared ablation layer (c) functioning as a mask when the relief pattern is formed thereon, and other layers may be provided between the layers as required. The present structure will be described in detail below.

(support (a))

The support (a) used in the present structure is not particularly limited, and examples thereof include polyester film, polyamide film, polyacrylonitrile film, and polyvinyl chloride film.

Among them, the support (a) is preferably a polyester film. The polyester used for the support (a) is not particularly limited, and examples thereof include polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate.

The thickness of the support (a) is not particularly limited, but is preferably 50 to 300. Mu.m.

In addition, an adhesive layer may be provided on the support (a) for the purpose of improving the adhesion between the support (a) and a photosensitive resin composition layer (b) described later. The adhesive layer is not particularly limited, and examples thereof include an adhesive layer described in WO 2004/104701.

(photosensitive resin composition layer (b))

In the present structure, the support (a) has a photosensitive resin composition layer (b). The photosensitive resin composition layer (b) may be directly laminated on the support (a), or may be indirectly laminated via the adhesive layer or the like.

The photosensitive resin composition layer (b) is not particularly limited, and may contain, for example, a thermoplastic elastomer (b-1), preferably further contains an ethylenically unsaturated compound (b-2), a photopolymerization initiator (b-3), and a liquid diene. The photosensitive resin composition layer (b) may further contain an auxiliary additive component as needed. The components are described in detail below.

< thermoplastic elastomer (b-1) >)

The thermoplastic elastomer (b-1) is not particularly limited, and examples thereof include copolymers having structural units derived from monovinyl-substituted aromatic hydrocarbons and structural units derived from conjugated dienes. The thermoplastic elastomer (b-1) may further have a structural unit derived from another monomer. By using such a thermoplastic elastomer, the brush resistance of the flexographic printing plate produced by using the present structure tends to be further improved.

The thermoplastic elastomer (b-1) may be a random copolymer or a block copolymer, and is preferably a block copolymer having a polymer block of a monovinyl-substituted aromatic hydrocarbon and a polymer block of a conjugated diene. By using such a thermoplastic elastomer, the brush resistance of the flexographic printing plate produced by using the present structure tends to be further improved.

The monovinyl-substituted aromatic hydrocarbon constituting the thermoplastic elastomer (b-1) is not particularly limited, and examples thereof include styrene, t-butylstyrene, 1-diphenylethylene, N-dimethyl-p-aminoethylstyrene, N-diethyl-p-aminoethylstyrene, vinylpyridine, p-methylstyrene, p-methoxystyrene, t-butylstyrene, α -methylstyrene, 1-diphenylethylene and the like. These may be used alone or in combination of at least 2 kinds.

Among them, styrene is preferable as the monovinyl-substituted aromatic hydrocarbon from the viewpoint of being able to mold the photosensitive resin composition layer (b) smoothly at a relatively low temperature.

The conjugated diene constituting the thermoplastic elastomer (b-1) is not particularly limited, and examples thereof include butadiene, isoprene, 2, 3-dimethyl-1, 3-butadiene, 2-methyl-1, 3-pentadiene, 1, 3-hexadiene, 4, 5-diethyl-1, 3-octadiene, 3-butyl-1, 3-octadiene, chloroprene and the like. These may be used alone or in combination of at least 2 kinds.

Among them, butadiene is preferable as the conjugated diene from the viewpoint of the brush resistance of the flexographic printing plate produced using the present structure.

From the viewpoint of the tackiness at ordinary temperature, the number average molecular weight (Mn) of the thermoplastic elastomer (b-1) is preferably 20,000 or more and 300,000 or less, more preferably 50,000 or more and 200,000 or less. The number average molecular weight can be measured by Gel Permeation Chromatography (GPC) and expressed as molecular weight in terms of polystyrene.

When the thermoplastic elastomer (b-1) is a block copolymer having a polymer block of a monovinyl-substituted aromatic hydrocarbon and a polymer block of a conjugated diene, the thermoplastic elastomer (b-1) includes a linear block copolymer represented by the following general formula (I) and/or a linear block copolymer or a radial block copolymer represented by the following general formula (II).

General formula group (I):

(A-B) _n 、A-(B-A) _n 、A-(B-A) _n -B、B-(A-B) _n

general formula group (II):

[(A-B) _k ] _m -X、[(A-B) _k -A] _m -X、[(B-A) _k ] _m -X、[(B-A) _k -B] _m -X

in the general formula groups (I) and (II), A represents a polymer block formed from a monovinyl-substituted aromatic hydrocarbon. In addition, B represents a polymer block formed from a conjugated diene. X represents the residue of a coupling agent such as silicon tetrachloride, tin tetrachloride, epoxidized soybean oil, polyhalogenated hydrocarbon compound, carboxylic acid ester compound, polyvinyl compound, bisphenol type epoxy compound, alkoxysilane compound, halosilane compound, ester compound or the residue of a polymerization initiator such as polyfunctional organolithium compound.

In the general formula groups (I) and (II), n, k and m represent integers of 1 or more, for example, 1 to 5.

The content of the conjugated diene and the monovinyl-substituted aromatic hydrocarbon in the thermoplastic elastomer (b-1) can be determined by using a nuclear magnetic resonance apparatus ¹ H-NMR). Specifically, as ¹ The H-NMR measurement apparatus used herein was JNM-LA400 (trade name, manufactured by JEOL Co., ltd.), deuterated chloroform as a solvent, 50mg/mL as a sample concentration, 400MHz as an observation frequency, TMS (tetramethylsilane) as a chemical shift standard, 2.904 seconds as a pulse delay, 64 times as a number of scans, 45℃as a pulse width, and 25℃as a measurement temperature.

In the thermoplastic elastomer (b-1), the copolymerization ratio (mass ratio) of the monovinyl-substituted aromatic hydrocarbon and the conjugated diene is preferably in the range of 10/80 to 90/20, more preferably in the range of 10/90 to 85/15, and even more preferably in the range of 10/90 to 60/40, from the viewpoint of the brush resistance of a flexographic printing plate produced using the present structure.

When the proportion of the monovinyl-substituted aromatic hydrocarbon is 10 or more in terms of the above-mentioned copolymerization ratio (mass ratio), the photosensitive resin composition layer (b) can have a sufficient hardness, and can be suitably printed by a usual printing pressure. In addition, when the proportion of monovinyl-substituted aromatic hydrocarbon is 90 or less in terms of the above-mentioned copolymerization ratio (mass ratio), the photosensitive resin composition layer (b) can obtain an appropriate hardness, and the ink can be sufficiently transferred to the printing target in the printing step.

If necessary, other functional groups may be introduced into the thermoplastic elastomer (b-1), or chemical modification such as hydrogenation may be performed, or other components may be copolymerized.

From the viewpoint of the brush resistance of the flexographic printing plate obtained by using the present structure, the content of the thermoplastic elastomer (b-1) in the photosensitive resin composition layer (b) is preferably 40 mass% or more, more preferably 40 mass% or more and 80 mass% or less, still more preferably 45 mass% or more and 75 mass% or less, when the total amount of the photosensitive resin composition layer (b) is 100 mass%.

< ethylenically unsaturated Compound (b-2) >

As described above, the photosensitive resin composition layer (b) preferably contains the ethylenically unsaturated compound (b-2). The ethylenically unsaturated compound (b-2) is a compound having an unsaturated double bond capable of undergoing radical polymerization.

Examples of the ethylenically unsaturated compound (b-2) include, but are not particularly limited to, olefins such as ethylene, propylene, vinyltoluene, styrene and divinylbenzene; acetylenes; (meth) acrylic acid and/or derivatives thereof; halogenated olefins; unsaturated nitriles such as acrylonitrile; unsaturated amides such as acrylamide and methacrylamide, and derivatives thereof; unsaturated dicarboxylic acids such as maleic anhydride, maleic acid, fumaric acid, and derivatives thereof; vinyl acetate esters; n-vinylpyrrolidone; n-vinylcarbazole; n-substituted maleimide compounds, and the like.

Among them, (meth) acrylic acid and/or its derivatives are preferable as the ethylenically unsaturated compound (b-2) from the viewpoints of ultraviolet curability and brushing resistance of the cured photosensitive resin composition layer (b).

The derivatives are not particularly limited, and examples thereof include alicyclic compounds having cycloalkyl groups, bicycloalkyl groups, cycloalkenyl groups, bicycloalkenyl groups, and the like; an aromatic compound having a benzyl group, a phenyl group, a phenoxy group, a naphthalene skeleton, an anthracene skeleton, a biphenyl skeleton, a phenanthrene skeleton, a fluorene skeleton, or the like; compounds having an alkyl group, a haloalkyl group, an alkoxyalkyl group, a hydroxyalkyl group, an aminoalkyl group, a glycidyl group, or the like; ester compounds with polyols such as alkylene glycol, polyoxyalkylene glycol, polyalkylene glycol, trimethylolpropane, etc.; and compounds having a polysiloxane structure such as polydimethylsiloxane and polydiethylsiloxane.

The ethylenically unsaturated compound (b-2) may be a heteroaromatic compound containing an element such as nitrogen or sulfur.

The (meth) acrylic acid and/or its derivative is not particularly limited, and examples thereof include diacrylates and dimethacrylates of alkane diols such as hexanediol and nonanediol; diacrylates and dimethacrylates of ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, polyethylene glycol, butylene glycol; trimethylolpropane tri (meth) acrylate; dimethylol tricyclodecane di (meth) acrylate; isobornyl (meth) acrylate; phenoxy polyethylene glycol (meth) acrylate; pentaerythritol tetra (meth) acrylate, and the like. These may be used alone or in combination of at least 2 kinds.

From the viewpoint of mechanical strength of a flexographic printing plate obtained by using the present structure, it is preferable to use at least 1 or more (meth) acrylate, and more preferably at least 1 or more difunctional (meth) acrylate as the ethylenically unsaturated compound (b-2).

The number average molecular weight (Mn) of the ethylenically unsaturated compound (b-2) is preferably 100 or more from the viewpoint of improving the non-volatility of the ethylenically unsaturated compound (b-2) at the time of producing and/or storing the present structure, and is preferably less than 1000 from the viewpoint of compatibility with other components, more preferably 200 or more and 800 or less.

From the viewpoint of the brush resistance of the flexographic printing plate obtained by using the present structure, the content of the ethylenically unsaturated compound (b-2) in the photosensitive resin composition layer (b) is preferably 2% by mass or more and 30% by mass or less, more preferably 2% by mass or more and 25% by mass or less, and still more preferably 2% by mass or more and 20% by mass or less, when the total amount of the photosensitive resin composition layer (b) is 100% by mass.

< photopolymerization initiator (b-3) >)

The photosensitive resin composition layer (b) preferably contains a photopolymerization initiator (b-3). The photopolymerization initiator (b-3) is a compound that absorbs light energy to generate radicals, and examples thereof include a disintegrating type photopolymerization initiator, a hydrogen abstraction type photopolymerization initiator, a compound having a site functioning as a hydrogen abstraction type photopolymerization initiator and a site functioning as a disintegrating type photopolymerization initiator in the same molecule, and the like.

Examples of the photopolymerization initiator (b-3) include, but are not particularly limited to, benzophenones such as benzophenone, 4-bis (diethylamino) benzophenone, 3', 4' -benzophenone tetracarboxylic anhydride, and 3,3', 4' -tetramethoxybenzophenone; anthraquinones such as t-butylanthraquinone and 2-ethylanthraquinone; thioxanthones such as 2, 4-diethylthioxanthone, isopropylthioxanthone, and 2, 4-dichlorothioxanthone; michler's ketone; acetophenones such as diethoxyacetophenone, 2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropane-1-one, benzildimethylketal, 1-hydroxycyclohexyl-phenyl ketone, 2-methyl-2-morpholino (4-thiomethylphenyl) propane-1-one, 2-methyl-1- (4-methylthiophenyl) -2-morpholino-propane-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinylphenyl) -butanone, trichloroacetophenone, and the like; benzoin ethers such as benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether; acyl phosphine oxides such as 2,4, 6-trimethylbenzoyl diphenyl phosphine oxide, bis (2, 6-dimethoxybenzoyl) -2, 4-trimethylpentylphosphine oxide, and bis (2, 4, 6-trimethylbenzoyl) -phenylphosphine oxide; methyl benzoate; 1, 7-bisacridylheptane; 9-phenylacridine; azo compounds such as azobisisobutyronitrile, azo compounds and tetrazene compounds. These may be used alone or in combination of at least 2 kinds.

Among them, from the viewpoint of the brush resistance of the flexographic printing plate produced using the present structure, the photopolymerization initiator (b-3) is preferably a compound having a carbonyl group, and more preferably an aromatic carbonyl compound such as benzophenone or thioxanthone.

From the viewpoint of the brush resistance of the flexographic printing plate produced using the present structure, the content of the photopolymerization initiator (b-3) in the photosensitive resin composition layer (b) is preferably 0.1 mass% or more and 10 mass% or less, more preferably 0.1 mass% or more and 5 mass% or less, and still more preferably 0.5 mass% or more and 5 mass% or less, when the total amount of the photosensitive resin composition layer (b) is 100 mass%.

< liquid diene >

The photosensitive resin composition layer (b) preferably contains a liquid diene. Liquid diene refers to a compound having a carbon-carbon double bond in liquid form. Here, in the present specification, "liquid state" of "liquid diene" means: has a property of being capable of easily flowing and deforming and solidifying into a deformed shape by cooling. The liquid diene has an elastomeric property that is deformed instantaneously by an external force when the external force is applied and returns to its original shape in a short time when the external force is removed.

The liquid diene is not particularly limited, and examples thereof include liquid polybutadiene, liquid polyisoprene, a modified product of liquid polybutadiene, a modified product of liquid polyisoprene, a copolymer of liquid acrylonitrile-butadiene, and a liquid styrene-butadiene copolymer. The liquid diene is a copolymer having a diene component of 50% by mass or more.

Among them, liquid polybutadiene is preferable as the liquid diene from the viewpoint of mechanical properties of the present structure and the flexographic printing plate obtained using the same.

In addition, from the viewpoint of making the hardness of the present structure and the flexographic printing plate obtained using the same appropriate, the 1, 2-vinyl bond amount of the liquid diene, preferably the liquid polybutadiene, is preferably 1% or more and 80% or less, more preferably 5% or more and 70% or less, and still more preferably 5% or more and 65% or less.

Here, "1, 2-vinyl bond amount" means: of the conjugated diene monomers incorporated in the form of 1, 2-bonds, 3, 4-bonds and 1, 4-bonds, the proportion of the conjugated diene monomer incorporated in the form of 1, 2-bonds. The amount of 1, 2-vinyl bonds can be determined on the basis of the liquid polybutadiene ¹ The peak ratio of H-NMR (magnetic resonance spectrum) was obtained.

In 1, 2-polybutadiene which is a liquid polybutadiene having a 1, 2-vinyl bond, the vinyl group as a double bond is a side chain, and thus, the reactivity of radical polymerization is high, and it is preferable from the viewpoint of improving the hardness of the photosensitive resin composition layer (b).

In addition, the liquid polybutadiene is usually a mixture of 1, 2-polybutadiene having a 1, 2-vinyl bond and 1, 4-polybutadiene having a 1, 4-vinyl bond, but it is effective to contain 1, 4-polybutadiene in the liquid diene in order to improve the flexibility of the present structure and a flexographic printing plate obtained using the same. The 1, 4-polybutadiene includes cis-type 1, 4-polybutadiene and trans-type 1, 4-polybutadiene. Since both of the cis-type and trans-type of 1, 4-polybutadiene have a vinyl group as a double bond in the interior, the reactivity in radical polymerization is low, and a soft resin can be formed.

When a plurality of liquid polybutadiene having different amounts of 1, 2-vinyl bonds are mixed and used, the average value thereof is used as the above-mentioned amount of 1, 2-vinyl bonds.

From the viewpoint of easily adjusting the reactivity of the photosensitive resin composition layer (b), it is preferable to adjust the total amount of 1, 2-vinyl bonds by mixing liquid polybutadiene having a 1, 2-vinyl bond content of 10% or less with liquid polybutadiene having a 1, 2-vinyl bond content of 80% or more. More preferably, the amount of 1, 2-vinyl bonds in the whole is adjusted by mixing liquid polybutadiene having an amount of 1, 2-vinyl bonds of 5% or less with liquid polybutadiene having an amount of 1, 2-vinyl bonds of 80% or more.

The number average molecular weight of the liquid diene is not particularly limited as long as it is liquid at 20 ℃, but is preferably 500 to 60000, more preferably 500 to 50000, still more preferably 800 to 50000, from the viewpoints of the brush resistance and handling properties of a flexographic printing plate obtained using the present structure.

From the viewpoint of the present structure and the brush resistance of the flexographic printing plate obtained using the same, the content of the liquid diene in the photosensitive resin composition layer (b) is preferably 10 mass% or more and 40 mass% or less, more preferably 15 mass% or more and 40 mass% or less, and still more preferably 20 mass% or more and 40 mass% or less, when the total amount of the photosensitive resin composition layer (b) is 100 mass%.

< auxiliary additive component >

The auxiliary additive component is not particularly limited, and examples thereof include a polymer containing a polar group, a plasticizer other than a liquid diene, a heat polymerization inhibitor other than a stabilizer, an antioxidant, an ultraviolet absorber, a dye and a pigment.

The polar group-containing polymer is not particularly limited, and examples thereof include water-soluble or water-dispersible copolymers having polar groups such as hydrophilic groups including carboxyl groups, amino groups, hydroxyl groups, phosphate groups, sulfonate groups, and salts thereof. More specifically, examples thereof include a carboxyl group-containing acrylonitrile-butadiene rubber, a carboxyl group-containing styrene-butadiene rubber, a carboxyl group-containing polymer of an aliphatic conjugated diene, an emulsion polymer of an ethylenically unsaturated compound having a phosphate group or a carboxyl group, a sulfonic acid group-containing polyurethane, a carboxyl group-containing butadiene latex, and the like. These polar group-containing polymers may be used alone in an amount of 1 or in an amount of 2 or more.

Among them, from the viewpoint of obtaining high resolution in a flexographic printing plate obtained by using the present structure, a carboxyl group-containing butadiene latex is preferable as the polar group-containing polymer.

The plasticizer other than the liquid diene is not particularly limited, and hydrocarbon oils such as naphthenic oils and paraffinic oils; liquid acrylonitrile-butadiene copolymer, liquid styrene-butadiene copolymer, and the like, and a conjugated diene rubber mainly composed of a liquid diene; polystyrene having a number average molecular weight of 2000 or less; ester plasticizers such as sebacate and phthalate. These other plasticizers may have hydroxyl groups, carboxyl groups. Further, a photopolymerizable reactive group such as a (meth) acryloyl group may be added to these other plasticizers. The other plasticizers may be used alone or in combination of at least 2 kinds.

As the heat polymerization inhibitor and the antioxidant, those generally used in the field of resin materials or rubber materials can be used. Specifically, a phenol-based material can be used.

The phenol-based material is not particularly limited, and examples thereof include vitamin E, tetrakis- (methylene-3- (3 ',5' -di-t-butyl-4 ' -hydroxyphenyl) propionate) methane, 2, 5-di-t-butylhydroquinone, 2, 6-di-t-butyl-p-cresol, 2-t-butyl-6- (3-t-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, and the like. The heat polymerization inhibitor and the antioxidant may be used alone or in combination of at least 1 kind and at least 2 kinds.

The ultraviolet absorber is not particularly limited, and examples thereof include known benzophenone compounds, salicylate compounds, acrylonitrile compounds, metal complex salt compounds, and hindered amine compounds. In addition, a dye/pigment shown below may be used as the ultraviolet absorber.

Examples of such ultraviolet absorbers include, but are not particularly limited to, 2-ethoxy-2 '-ethyloxanilide and 2,2' -dihydroxy-4-methoxybenzophenone.

The dye/pigment is effective as a coloring means for improving observability.

The dye is not particularly limited, and examples thereof include basic dyes, acid dyes, direct dyes, and the like which exhibit water solubility; as water-insoluble sulfur dyes, oil-soluble dyes, disperse dyes, and the like. In particular, anthraquinone dyes, indigo dyes, azo dyes, and more preferably azo oil-soluble dyes are preferable.

The pigment is not particularly limited, and examples thereof include natural pigments, synthetic inorganic pigments, and synthetic organic pigments. Examples of the synthetic organic pigment include azo pigments, triphenylmethane pigments, quinoline pigments, anthraquinone pigments, and phthalocyanine pigments.

When the total amount of the photosensitive resin composition layer (b) is 100% by mass, the total amount of the auxiliary additive components is preferably 0% by mass or more and 10% by mass or less, more preferably 0% by mass or more and 5% by mass or less, and still more preferably 0% by mass or more and 3% by mass or less.

(Infrared ablative layer (c))

In the present structure, an infrared ablation layer (c) is laminated on the photosensitive resin composition layer (b). The infrared ablation layer (c) contains a predetermined resin, can be cut by an infrared laser, and has a function as a light shielding layer other than infrared.

In order to process the infrared ablation layer (c) with high definition, it is necessary to increase the sensitivity of the infrared ablation layer (c) to laser light. Here, "sensitivity to laser light is high" means that: when the same laser energy is used for drawing, the ablated volume is larger, especially toward the depth direction.

As a result of the study, the present inventors found that: in order to improve the laser sensitivity of the infrared ablation layer (c), it is important that the resin contained in the infrared ablation layer is easily depolymerized. "depolymerization" means: the reaction of decomposing the polymer into monomers by the reverse reaction of the polymerization reaction.

The infrared ablation layer instantaneously reaches a high temperature of several hundred degrees due to the irradiation of infrared rays. In this case, if the resin is easily depolymerized, the main chain in the resin is efficiently decomposed even by ablation in a short period of time, and the molecular weight is rapidly reduced and removed from the infrared ablation layer. On the other hand, in a resin which is difficult to depolymerize, for example, a resin having a polar group in a side chain, only decomposition of the side chain occurs during ablation, and breakage of the main chain is less likely to occur. Therefore, the resin remains in the infrared ablation layer after the irradiation with infrared rays. Known are: the resin obtained by polycondensation forms a ring structure upon decomposition, and then the main chain is broken. Thus, in the infrared ablation as a short-time heat treatment, a decrease in molecular weight is less likely to occur, and laser sensitivity is deteriorated.

For these mechanisms, it is important that the infrared ablation layer (c) contains a resin that is easily depolymerized. It is generally known that: the cleavage of the main chain is likely to start from a thermally unstable portion existing in a polymer such as a branch. However, in this case, if the side chains located at the branches have polarity as described above, the side chains are likely to be decomposed predominantly, and the main chain is unlikely to be broken, which is not preferable.

Therefore, it is important that the side chain of the resin contained in the infrared ablation layer (c) is a nonpolar group. In addition, when backbone cleavage occurs, the contribution of chain transfer within or between molecules can be ignored. Therefore, it is preferable not to have tertiary hydrogen which is easily taken out by chain transfer. That is, it is important that the moiety located at the symmetry plane of the branch is also a nonpolar group.

(resin)

The resin contained in the infrared ablation layer (c) of the present embodiment has a structural unit (c 1) containing a quaternary carbon atom bonded to two nonpolar groups as shown in the following general formula (1), and may have other structural units as required.

In the present embodiment, "monomer" refers to a compound before polymerization, and "structural unit" refers to a predetermined repeating unit formed by polymerization of a monomer.

The nonpolar group in the general formula (1) is not particularly limited as long as it is a group composed of a carbon atom and/or a silicon atom and a hydrogen atom, and examples thereof include an alkyl group, an aryl group, a cycloalkyl group, a phenyl group, an alkenyl group, an aralkyl group, a cycloalkenyl group, an alkynyl group, a silyl group, a siloxane group, and the like. The nonpolar group does not include a hydrogen atom.

Wherein R is selected from the viewpoint of laser sensitivity of the infrared ablation layer (c) ₁ 、R ₂ 、R ₃ And R is ₄ The groups shown are preferably alkyl, phenyl, and in addition, more preferably: r is R ₁ And R is ₂ The radicals shown are alkyl, phenyl, and R ₃ And R is ₄ Is alkyl, phenyl; alternatively, R ₁ And R is ₂ The radicals shown are alkyl, benzeneAnd R is a radical ₃ And R is ₄ Is a hydrogen atom. This tends to further improve the developability in a solvent-based developer described later. Further, the above-described configuration tends to further improve the dispersibility of carbon black and the developability in an aqueous developer, which will be described later.

In addition, from the viewpoint of developability in an aqueous developer and a solvent-based developer described later, R is the formula ₁ The groups shown are preferably alkyl, phenyl, acyl.

The number of carbon atoms of the nonpolar group is preferably 1 to 20, more preferably 1 to 10, and still more preferably 1 to 5.

The monomer satisfying the general formula (1) is not particularly limited, and examples thereof include isobutylene, 2-methyl-2-butene, 2, 3-dimethyl-2-butene, monomers obtained by replacing a methyl group thereof with another alkyl group such as an ethyl group, and modified products thereof; monomers obtained by substituting methyl groups of alpha-methylstyrene, cis- (1-methyl-1-propenyl) benzene, trans- (1-methyl-1-propenyl) benzene, and other alkyl groups such as ethyl groups, and modified products thereof; 1, 1-diphenylethylene, and the like.

By providing the resin with the structural unit (c 1), not only is the resin alone excellent in developing property with respect to the solvent-based developer, but also the highly polar carbon black, which will be described later, can be dispersed while maintaining the high dispersibility, thereby exhibiting high developing property with respect to the aqueous developer.

In the general formula (1), R ₃ And R is ₄ Preferably a hydrogen atom, alkyl group, aryl group, cycloalkyl group, phenyl group, alkenyl group, aralkyl group, cycloalkenyl group, alkynyl group, silyl group, siloxane group, more preferably both hydrogen atoms. Accordingly, the depolymerization property of the resin is further improved, and therefore, the laser sensitivity of the infrared ablation layer (c) tends to be further improved. In addition to further improving the developability in a solvent-based developer, there is a tendency that the dispersibility of carbon black is further improved and the developability in an aqueous developer is further improved.

Specific examples of the substance satisfying such a constitution include isobutylene, α -methylstyrene, and a substance obtained by replacing a methyl group thereof with another alkyl group such as an ethyl group. The use of a monomer having a phenyl group such as α -methylstyrene tends to further improve the pinhole resistance of the infrared ablation layer (c). In addition, the use of such a monomer tends to further improve the developability in aqueous developer and solvent-based developer.

Further, in the general formula (1), R ₁ And R is ₂ Each independently is preferably an alkyl group, an aryl group, a cycloalkyl group, a phenyl group, an alkenyl group, an aralkyl group, a cycloalkenyl group, an alkynyl group, a silyl group, a siloxane group, more preferably an alkyl group, a phenyl group, and even more preferably each independently is an alkyl group. By letting R ₁ And/or R ₂ Is alkyl, thereby enabling rubbery elasticity. Therefore, soft portions in the elastomer can be formed, and the flexibility of the infrared ablation layer (c) tends to be further improved. In addition, by making R ₁ And/or R ₂ The phenyl group tends to form the structure smoothly at a relatively low temperature.

The structural unit (c 1) may be used alone or in combination of 1 or more than 2. For example, the resin may have R as the structural unit (c 1) ₁ And R is ₂ Structural unit being alkyl and R ₁ And R is ₂ One of which is an alkyl group and the other is a structural unit of a phenyl group. This can improve the characteristics of both the alkyl group and the phenyl group.

Specific examples of the substance satisfying such a constitution include isobutylene and a substance obtained by replacing a methyl group thereof with another alkyl group such as an ethyl group.

The content of the structural unit (c 1) is preferably 40 mass% or more, more preferably 50 mass% or more, still more preferably 60 mass% or more, still more preferably 70 mass% or more, and still more preferably 80 mass% or more, based on the total amount of the resin. The content of the structural unit (c 1) is preferably 100 mass% or less, more preferably 95 mass% or less, further preferably 90 mass% or less, further preferably 85 mass% or less, and further preferably 80 mass% or less, based on the total amount of the resin. The upper and lower limits of these values may be combined arbitrarily.

The laser sensitivity and flexibility of the infrared ablation layer (c) tend to be further improved by setting the content of the structural unit (c 1) to 40 mass% or more. In addition, the pinhole resistance of the infrared ablation layer (c) tends to be further improved by setting the content of the structural unit (c 1) to 100 mass% or less.

Further, when the content of the structural unit (c 1) is within the above range, the developability in the solvent-based developer is further improved, and the dispersibility of carbon black is further improved, so that the developability in the aqueous developer tends to be further improved.

The resin used in the infrared ablation layer (c) preferably contains a structural unit (c 2) having an aromatic group in a side chain, in addition to the structural unit (c 1). The structural unit (c 2) is preferably a structural unit (c 2) derived from a monovinyl-substituted aromatic hydrocarbon. The monovinyl aromatic hydrocarbon may be chemically bonded to the monomer represented by the general formula (1), or may be added as a resin, and it is preferable to form a copolymer by chemical bonding from the viewpoints of dispersibility and uniformity of laser processing due to dispersibility. The resin tends to have further improved pinhole resistance by containing the structural unit (c 2) derived from the monovinyl-substituted aromatic hydrocarbon.

The monovinylaromatic hydrocarbon compound is not particularly limited, and examples thereof include monomers such as styrene, t-butylstyrene, N-dimethyl-p-aminoethylstyrene, N-diethyl-p-aminoethylstyrene, vinylpyridine, p-methylstyrene, and t-butylstyrene. Among them, styrene is preferable since the present structure can be molded smoothly at a relatively low temperature. The number of the structural units (c 2) may be 1 alone, or 2 or more may be used in combination.

The content of the structural unit (c 2) is preferably 0 mass% or more, more preferably 5 mass% or more, further preferably 10 mass% or more, further preferably 15 mass% or more, and further preferably 20 mass% or more, relative to the total amount of the resin. The content of the structural unit (c 2) is preferably 60 mass% or less, more preferably 55 mass% or less, further preferably 50 mass% or less, further preferably 45 mass% or less, and further preferably 40 mass% or less, based on the total amount of the resin. The upper and lower limits of these values may be combined arbitrarily.

When the content of the structural unit (c 2) is 0 mass% or more, pinhole resistance of the infrared ablation layer (c) tends to be further improved. Further, the laser sensitivity and flexibility of the infrared ablation layer (c) tend to be further improved by setting the content of the structural unit (c 2) to 60 mass% or less. The term "0 mass% or more" includes both the system including the structural unit (c 2) and the system not including the structural unit (c 2). The upper and lower limits of these values may be combined arbitrarily.

The content and ratio of the structural units (c 1) and (c 2) in the resin used for the infrared ablation layer (c) may be determined by using a nuclear magnetic resonance apparatus ¹ H-NMR).

The infrared ablation layer (c) may contain other resins in addition to the above resins. In this case, the content of the resin is preferably 50% by mass or more, more preferably 70% by mass or more and 100% by mass or less, with respect to the total resin components of the infrared ablation layer (c). When the content of the resin is within the above range, the laser sensitivity and flexibility of the infrared ablation layer (c) tend to be further improved. In the case of using a resin having a polar group in a side chain as the other resin, it is preferable that the resin is contained in an amount of 70% or more in the total resin components from the viewpoint of laser sensitivity.

The content of the resin is preferably 20 mass% or more, more preferably 30 mass% or more, and still more preferably 40 mass% or more, relative to the total amount of the infrared ablation layer (c). The content of the resin is preferably 90 mass% or less, more preferably 80 mass% or less, and even more preferably 70 mass% or less, based on the total amount of the infrared ablation layer (c). The upper and lower limits of these values may be combined arbitrarily.

When the content of the resin is 20 mass% or more, pinhole resistance and flexibility of the infrared ablation layer (c) tend to be further improved. Further, the laser sensitivity and the shielding property of the infrared ablation layer (c) tend to be further improved by setting the content of the resin to 90 mass% or less.

Further, when the content of the resin is within the above range, the developability in a solvent-based developer and an aqueous developer and the dispersibility of carbon black tend to be further improved.

(Infrared absorbing substance)

The infrared ablation layer (c) may contain an infrared absorbing material for ablation. The infrared absorbing material is usually a monomer or compound having strong absorption in the range of 750 to 2000 nm.

The infrared absorbing material is not particularly limited, and examples thereof include inorganic pigments such as carbon black, graphite, copper chromite, and chromium oxide; pigments such as a polymalocyanine compound, a cyanine pigment, and a metal thiolate pigment. The sensitivity to infrared laser light becomes higher as the particle diameter becomes smaller, and in particular, carbon black can be used in a wide range of particle diameters of 13nm to 85nm, and is preferable as an infrared absorbing substance. Carbon black can also function as a masking material as described below. These infrared absorbing substances are added in a range that imparts sensitivity that enables ablation by the laser beam used.

(masking substance)

The infrared ablation layer (c) serves as a mask, and thus may contain a shielding material against non-infrared rays such as ultraviolet rays. As the shielding substance for non-infrared rays, a substance that reflects or absorbs ultraviolet light may be used. Examples thereof include ultraviolet absorbers, carbon black, and graphite.

The total content of the infrared absorbing material and the shielding material is preferably 10 mass% or more and 80 mass% or less, more preferably 20 mass% or more and 70 mass% or less, and still more preferably 30 mass% or more and 60 mass% or less, with respect to the total amount of the infrared ablation layer (c). When the total content of the infrared absorbing substance and the shielding substance is within the above range, the laser sensitivity and the shielding property tend to be further improved.

(carbon black)

In order to make the infrared ablation layer (c) exhibit excellent developability with respect to a solvent-based developer, it is important that the resin in the infrared ablation layer (c) exhibit low polarity. However, if the polarity of the resin is low, the developability with respect to an aqueous developer is lowered. On the other hand, in order to make the infrared ablation layer (c) exhibit excellent developability with an aqueous developer, it is important to make the resin in the infrared ablation layer (c) exhibit high polarity, and if the resin is high polarity, the developability with a solvent-based developer is reduced.

Thus, as a result of the study, it was found that: by combining a resin having a specific structure with carbon black having a low polarity, the infrared ablation layer (c) exhibits excellent developability both for a solvent-based developer and for an aqueous developer.

In the infrared ablation layer (c) of the present embodiment, carbon black is preferably contained as an infrared absorbing material for performing ablation processing and as a shielding material for non-infrared rays serving as a mask.

From the viewpoint of exhibiting high developability for both the solvent-based developer and the aqueous developer, the pH of the carbon black is preferably 2.0 or more and 5.5 or less. The carbon black having a low pH is more hydrophilic than the conventional carbon black in a state in which a plurality of functional groups are introduced into the surface thereof. This makes it possible to exhibit excellent developability particularly with respect to an aqueous developer.

The pH of the carbon black is more preferably 2.5 to 5.0, and still more preferably 2.5 to 4.5. The pH of the carbon black is a value measured by a glass electrode pH meter by preparing a mixture of carbon black and distilled water according to ASTM D1512.

Carbon black is classified into, for example, furnace black, channel black, thermal black, acetylene black, lamp black, and the like according to the production method thereof, and furnace black is preferable in order to obtain desired properties.

The furnace black is produced by a method of obtaining carbon black by blowing petroleum-based or coal-based oil as a raw material into a high-temperature gas and incompletely burning the oil, and can be produced by a well-known method.

As the carbon black, carbon black satisfying the above-described range and conventionally used for forming a black matrix can be used. Specific examples thereof include Tokai Carbon Co., ltd., TOKABLACK#8300 from Mitsubishi chemical corporation, MA7, MA8, MA11, MA14, MA77, MA100R, MA100S, MA, MA230, #970, #1000, #2350, #2360, and the like.

In order to ensure light-shielding properties against ultraviolet rays in the step of exposing the photosensitive resin structure for printing plate, the infrared ablation layer (c) of the structure is preferably thicker, and the infrared ablation layer (c) is preferably thinner from the viewpoint of improving the ablation properties.

The content of the carbon black is preferably 10% by mass or more and 70% by mass or less, more preferably 20% by mass or more and 60% by mass or less, and still more preferably 30% by mass or more and 50% by mass or less, relative to the total amount of the infrared ablation layer (c). When the content of carbon black is within the above range, the laser sensitivity and the shielding property tend to be further improved.

The compounding ratio of the resin to the carbon black (resin/carbon black) in the infrared ablation layer (c) is preferably in the range of 80/20 to 50/50, more preferably in the range of 75/25 to 55/45, and even more preferably in the range of 70/30 to 60/40. When the compounding ratio (resin/carbon black) is in the above range, the laser sensitivity and the shielding property tend to be further improved.

(dispersant)

The infrared ablation layer (c) preferably contains a dispersant for the purpose of assisting the dispersibility of the carbon black. Here, as the dispersant, a compound having an adsorption portion capable of interacting with the surface functional group of the infrared absorber and a resin compatible portion compatible with the binder polymer is preferable. By using such a dispersant, the dispersibility of carbon black tends to be further improved, and the developability in an aqueous developer tends to be further improved.

The adsorption part of the dispersant is not particularly limited, and examples thereof include an amino group, an amide group, a urethane group, a carboxyl group, a carbonyl group, a sulfone group, and a nitro group. Among them, amino groups, amide groups, and urethane groups are preferable.

The resin compatible part is not particularly limited, and examples thereof include saturated alkyl groups, unsaturated alkyl groups, polyethers, polyesters, poly (meth) acrylic acids, and polyols.

The solubility parameter (SP value) of the dispersant is preferably 9.5 or more and 12.5 or less, more preferably 10.0 or more and 12.0 or less. When the solubility parameter (SP value) is within the above range, the dispersibility of carbon black tends to be further improved, and the developability in an aqueous developer tends to be further improved.

The solubility parameter SP value δ in the present embodiment is defined as in the following formula (1).

δ＝(ΔE/V) ^1/2 [(cal/cm ³ ) ^1/2 ]···(1)

Where V is the molar molecular volume of the solvent and ΔE is the cohesive energy (evaporation energy).

The molar molecular volume and cohesive energy of the solvent can also be determined from known values, for example, as in the literature "POLYMER ENGINEERING AND SCIENCE, vol.14,147-154,1974".

On the other hand, when the above-mentioned parameter is not a known value, the solubility parameter (SP value) may be measured by a method called cloud point titration.

Specifically, first, a poor solvent having a lower SP value than the above-mentioned poor solvent is gradually added dropwise to a solution obtained by dissolving a sample having an unknown SP value in a good solvent having a known SP value, and the volume of the poor solvent in which the solute starts to precipitate is measured. Next, a poor solvent having a higher SP value than the above-mentioned poor solvent was gradually added dropwise to a solution obtained by dissolving a sample having an unknown SP value in a good solvent having a known SP value, and the volume of the poor solvent in which the solute starts to precipitate was measured. The volume of each poor solvent obtained here can be obtained by applying the following formula (2).

δ＝(V _ml ^1/2 ·δ _ml +V _mh ^1/2 ·δ _mh )/(V _ml ^1/2 +V _mh ^1/2 )···(2)

Here, V _ml Volume of poor solvent with low SP value, V _mh Volume, delta, of poor solvent with high SP value _ml SP value, delta of poor solvent with low SP value _mh The SP value of the poor solvent having a high SP value.

All SP values described in examples below were measured by the cloud point titration method.

The content of the dispersant in the infrared ablation layer (c) of the present embodiment is preferably selected and added in a range that enables the infrared absorber to be uniformly dispersed in the infrared ablation layer (c) and ensures the strength of the infrared ablation layer (c). If the content of the dispersant is small, the infrared absorber cannot be sufficiently dispersed in the infrared ablation layer (c), and if the dispersant is too large, the strength of the film may be lowered and pinholes may be frequently generated.

From this viewpoint, the content of the dispersant is preferably 0.1% by mass or more and 50% by mass or less, more preferably 1% by mass or more and 30% by mass or less, and still more preferably 3% by mass or more and 20% by mass or less, relative to the entire infrared ablation layer (c).

From the viewpoint of dispersibility of the carbon black, the content of the dispersant is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and still more preferably 3 parts by mass or more, relative to 100 parts by mass of the carbon black, from the viewpoint of dispersibility of the carbon black. From the viewpoint of film strength of the infrared ablation layer, the content of the dispersant is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less, based on 100 parts by mass of the carbon black.

In the flexographic printing original plate of the present embodiment, the dispersant of the infrared ablation layer (c) preferably has a branched structure. In the case of having a branched structure, the crystallinity of the dispersant is low, and therefore, high dispersibility can be obtained.

The weight average molecular weight of the dispersant of the infrared ablation layer (c) of the present embodiment is preferably selected within a range that enables the infrared absorber to be uniformly dispersed in the infrared ablation layer and the dispersant does not bleed out.

When the dispersing agent bleeds out, the dispersing agent cannot interact with the infrared absorbent such as carbon black, and therefore, poor dispersion occurs, peeling becomes heavy, and the infrared absorbent such as carbon black aggregates to cause pinholes.

From this viewpoint, the weight average molecular weight of the dispersant as measured by gel permeation column chromatography (GPC) and in terms of standard polystyrene is preferably 1000 to 10000, more preferably 2000 to 7000, still more preferably 2500 to 5000.

(film thickness)

In order to ensure the shielding property against ultraviolet rays in the step of exposing the present structure, the infrared ablation layer (c) of the present structure is preferably thicker, and in order to improve the ablation property, the infrared ablation layer (c) is preferably thinner.

From the above viewpoints, the film thickness of the infrared ablation layer (c) is preferably 0.1 μm or more and 20 μm or less, more preferably 0.5 μm or more and 15 μm or less, and still more preferably 1.0 μm or more and 10 μm or less.

As the non-infrared shielding effect of the infrared ablation layer (c), the optical density of the infrared ablation layer (c) is preferably 2 or more, more preferably 3 or more.

The optical density can be measured by using a D200-II permeation densitometer (manufactured by GretagMacbeth). The optical density is a so-called visual sense (ISO visual), and the light to be measured is in a wavelength range of about 400 to 750 nm.

The method for forming the infrared ablation layer (c) is not particularly limited, and when carbon black is used as both an infrared absorbing material and a non-infrared shielding material, the following methods are exemplified: first, a resin solution is prepared using a predetermined solvent, carbon black and a dispersant are added thereto, the carbon black is dispersed in the resin solution, and then the resin solution is coated on a cover film such as a polyester film, and thereafter the cover film is laminated or pressure-bonded to the photosensitive resin composition layer (b) to be transferred to a non-infrared shielding layer which can be cut by an infrared laser.

As a method of dispersing carbon black in a resin solution, a method of using forced stirring by a stirring blade and stirring by ultrasonic waves or various mills in combination is effective. Alternatively, a method in which the resin, carbon black and dispersant are premixed in an extruder or kneader and then dissolved in a solvent is effective because good dispersibility of carbon black is obtained. In addition, the carbon black may be forcibly dispersed in the resin in a latex solution state.

The solvent such as a solution or dispersion for forming the infrared ablation layer (c) may be appropriately selected in consideration of the solubility of the resin or infrared absorber used. The solvent may be used alone, or two or more solvents may be used in combination.

In addition, for example, it is also effective to mix a solvent having a relatively low boiling point with a solvent having a relatively high boiling point and control the volatilization rate of the solvent, thereby improving the film quality of the infrared ablation layer (c).

The solvent used for forming the infrared ablation layer (c) is not particularly limited, and examples thereof include toluene, xylene, cyclohexane, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, amyl acetate, methyl ethyl ketone, acetone, cyclohexanone, ethylene glycol, propylene glycol, ethanol, water, propylene glycol monomethyl ether acetate, dimethylacetamide, dimethylformamide, n-propanol, isopropanol, 1, 4-dioxane, tetrahydrofuran, diethyl ether, n-hexane, n-heptane, n-pentane, acetonitrile, and the like.

The cover film for forming the infrared ablation layer (c) of the present structure is preferably a film having excellent dimensional stability, and for example, a polyethylene terephthalate film or the like is preferable.

The cover film may be used in an untreated state, or may be a film which is given a function by a mold release treatment, antistatic treatment, or the like, as required.

(intermediate layer (d))

The structure may further have 1 or more intermediate layers (d) between the photosensitive resin composition layer (b) and the infrared ablation layer (c). The intermediate layer (d) is not particularly limited, and may be an oxygen barrier layer, an adhesive layer, and/or a protective layer, for example. The respective layers will be described below.

In order to produce a print with high definition and highlight areas, it is necessary to form tiny dots in the flexographic printing plate. From the viewpoint of forming such minute points, the intermediate layer (d) is preferably an oxygen-blocking layer having oxygen-blocking ability.

When the photosensitive resin composition layer (b) is cured by irradiation with ultraviolet rays, the curing is performed by radical polymerization. In the radical polymerization, if oxygen is present together, the radical generating compound reacts with oxygen to inhibit the polymerization reaction. If the polymerization reaction is suppressed in this way, there is a possibility that unreacted portions remain in the exposed portion of the photosensitive resin composition layer (b). Since this unreacted portion is removed in the fourth step described later, the pattern finally formed on the flexographic printing plate has a shape having a curved portion at the front end. This is because: the portion of the photosensitive resin composition layer (b) on the infrared ablation layer (c) side is particularly susceptible to inhibition of polymerization by oxygen, and the photosensitive resin composition layer (b) located immediately below the infrared ablation layer (c) is susceptible to generation of unreacted portions.

In contrast, if the coexistence amount of oxygen is reduced during ultraviolet curing, the polymerization reaction is less likely to be suppressed, and the finally formed pattern has a planar shape at the tip. Therefore, when a pattern having a flat portion at the tip is to be produced, it is effective to reduce oxygen in contact with the photosensitive resin composition layer (b) by providing the intermediate layer (d) with oxygen-blocking ability.

The intermediate layer (d) may be an adhesive layer for improving the adhesion between the photosensitive resin composition layer (b) and the infrared ablation layer (c). This tends to further improve the handling property.

The intermediate layer (d) may also have a function of protecting the infrared ablation layer (c). In the conventional process for producing a flexographic printing plate, when the infrared ablation layer (c) on which the cover film is laminated is conveyed as a film, the infrared ablation layer (c) in the roll rubs against the cover film laminated thereon because the infrared ablation layer (c) is in contact with the roll or wound and wound up during film roll conveyance. Thus, the infrared ablation layer (c) may be physically defective and pinholes may be generated. In addition, when the photosensitive resin composition layer (b) and the infrared ablation layer (c) are laminated by a method in which the photosensitive resin composition layer (b) is coated on the infrared ablation layer (c) while being extrusion-molded, pinholes may be generated due to friction generated when the heat-melted photosensitive resin composition flows on the infrared ablation layer (c).

In order to prevent pinholes from being formed in the infrared ablation layer (c), the intermediate layer (d) constituting the present structure preferably has physical strength and heat resistance as a protective layer.

[ method for producing flexographic printing plate ]

The method for manufacturing a flexographic printing plate according to the present embodiment uses the present structure and includes the following steps: first, a first step of irradiating ultraviolet rays from the support (a) side; a second step of irradiating the infrared ablation layer (c) with infrared rays to draw a pattern; a third step of exposing the photosensitive resin composition layer (b) to ultraviolet light using the patterned infrared ablation layer (c) as a mask; and a fourth step of removing the unexposed portions of the infrared ablation layer (c) and the photosensitive resin composition layer (b).

Thereafter, if necessary, a post-exposure treatment is performed, and a flexographic printing plate (relief printing plate) is obtained from the cured product of the photosensitive resin composition layer. From the viewpoint of imparting releasability, the surface of the flexographic printing plate may be brought into contact with a liquid containing an organosilicon compound and/or a fluorine compound.

Fig. 2 is a schematic diagram showing a method for producing a flexographic printing plate using the photosensitive resin structure for a flexographic printing plate according to the present embodiment. Each step is described in detail below.

(first step)

In the first step, the method of irradiating the photosensitive resin composition layer (b) with ultraviolet light from the support (a) side is not particularly limited, and may be performed using a known irradiation unit. The wavelength of the ultraviolet light to be irradiated at this time is preferably 150 to 500nm, more preferably 300 to 400nm.

The light source of ultraviolet rays is not particularly limited, and for example, a low-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a metal halide lamp, a xenon lamp, a zirconium lamp, a carbon arc lamp, a fluorescent lamp for ultraviolet rays, and the like can be used.

The first step may be performed before or after the second step described later.

(second step)

In the second step, the method of irradiating the infrared ablation layer (c) with infrared rays to draw a pattern is not particularly limited, and may be performed using a known irradiation unit. The irradiation of infrared rays to the infrared ablation layer (c) may be performed from the infrared ablation layer (c) side.

In the case where the present structure has a cover film, the cover film is first peeled off before the irradiation with infrared rays. Thereafter, the infrared ablation layer (c) is patterned by infrared rays, and the resin in the infrared ray irradiated portion is decomposed to draw a pattern. Thus, a mask of the infrared ablation layer (c) can be formed on the photosensitive resin composition layer (b).

In the first step, examples of suitable infrared laser light include ND/YAG laser light (for example, 1064 nm) and diode laser light (for example, 830 nm). Laser systems suitable for CTP platemaking technology are commercially available, and for example, the diode laser system CDI Spark (ESKO GRAPHICS corporation) can be used. The laser system includes a rotary drum for holding the structure, an IR laser irradiation device, and a design computer from which image information is directly transferred to the laser device.

(third step)

In the third step, the photosensitive resin composition layer (b) is irradiated with ultraviolet rays using the patterned infrared ablation layer (c) as a mask to perform pattern exposure. At this time, the light passing through the mask accelerates the curing reaction of the photosensitive resin composition layer (b), and the irregularities of the pattern formed on the infrared ablation layer (c) are reversed and transferred to the photosensitive resin composition layer (b). The irradiation of ultraviolet rays may irradiate the entire surface of the structure.

The third step may be performed in a state where the structure is mounted on the laser drum, and the structure is usually removed from the laser device and irradiated with a conventional irradiation unit. The irradiation unit may use the same unit as that illustrated in the ultraviolet irradiation in the first step.

(fourth step)

The fourth step is a step of removing the unexposed portions of the infrared ablation layer (b) and the photosensitive resin composition layer (c). The method of removing in the fourth step (developing step) is not particularly limited, and a conventionally known method can be applied.

Specifically, as described above, the unexposed portion is removed by exposing the photosensitive resin composition layer (b) of the present structure to light and then rinsing the unexposed portion with a solvent for solvent development or a cleaning liquid for water development, or by bringing the unexposed portion heated to 40 to 200 ℃ into contact with a predetermined absorbing layer capable of absorbing the same, and removing the absorbing layer.

Thereafter, a flexographic printing plate is manufactured by performing post-exposure treatment as needed.

In the case where the intermediate layer (d) is provided between the infrared ablation layer (c) and the photosensitive resin composition layer (b), the removal may be performed simultaneously in the development step.

The developing solvent used for solvent development of the unexposed portion is not particularly limited, and examples thereof include esters such as heptyl acetate and 3-methoxybutyl acetate; hydrocarbons such as petroleum fractions, toluene, decalin, etc.; a solvent obtained by mixing alcohols such as propanol, butanol and pentanol with a chlorine-based organic solvent such as tetrachloroethylene. Washing out of the unexposed portion is performed by spraying from a nozzle or brushing by a brush.

As the cleaning liquid for water development, water, an alkaline aqueous solution, a neutral detergent, and a surfactant can be suitably used.

Examples of the surfactant include anionic surfactants, amphoteric surfactants, and nonionic surfactants. These may be used alone or in combination of at least 2 kinds.

The anionic surfactant is not particularly limited, and examples thereof include sulfate, higher alcohol sulfate, higher alkyl ether sulfate, sulfated olefin, alkylbenzenesulfonate, α -olefin sulfonate, phosphate, dithiophosphate, and the like.

The amphoteric surfactant is not particularly limited, and examples thereof include amino acid type amphoteric surfactants, betaine type amphoteric surfactants, and the like.

The nonionic surfactant is not particularly limited, and examples thereof include polyethylene glycol type surfactants such as higher alcohol ethylene oxide adducts, alkylphenol ethylene oxide adducts, fatty acid ethylene oxide adducts, polyol fatty acid ester ethylene oxide adducts, higher alkylamine ethylene oxide adducts, fatty acid amide ethylene oxide adducts, and polypropylene glycol ethylene oxide adducts; and polyol surfactants such as glycerin fatty acid esters, pentaerythritol fatty acid esters, fatty acid esters of sorbitol and sorbitan, alkyl esters of polyhydric alcohols, fatty acid amides of alkanolamines, and the like.

In addition, a pH adjuster may be used in the alkaline aqueous solution. The pH adjuster may be an organic material or an inorganic material, and is preferably capable of adjusting the pH to 9 or higher. The pH adjuster is not particularly limited, and examples thereof include sodium hydroxide, sodium carbonate, potassium carbonate, sodium silicate, sodium metasilicate, sodium succinate, and the like.

The heat-developable absorbent layer is not particularly limited, and examples thereof include nonwoven materials, paper materials, fiber fabrics, open-cell foams, and porous materials. Among them, nonwoven materials formed of nylon, polyester, polypropylene, and polyethylene, and combinations of these nonwoven materials are preferable, and nonwoven continuous webs of nylon or polyester are more preferable.

[ Flexible printing method ]

The flexographic printing method according to the present embodiment uses the photosensitive resin structure for flexographic printing plates and includes the following steps: a first step of irradiating ultraviolet rays from the support (a) side; a second step of irradiating the infrared ablation layer (c) with infrared rays to draw a pattern; a third step of exposing the photosensitive resin composition layer (b) to ultraviolet light using the patterned infrared ablation layer (c) as a mask; a fourth step of removing the unexposed portions of the infrared ablation layer (c) and the photosensitive resin composition layer (b) to produce a flexographic printing plate; and a fifth step of printing using the flexographic printing plate.

The first to fourth steps in the flexographic printing method are as described above.

(fifth step)

The fifth step is a step of printing using the flexographic printing plates obtained in the first to fourth steps. The printing method using the flexographic printing plate is not particularly limited as long as the ink is attached to the convex portion of the flexographic printing plate and transferred to the substrate.

Examples

The present invention will be described more specifically below with reference to specific examples and comparative examples, but the present invention is not limited to the following examples at all.

[ manufacture of flexographic printing plates ]

In the following examples and comparative examples, photosensitive resin structures for flexographic printing plates were produced.

(1) production of a laminate of a support and a photosensitive resin composition layer)

A photosensitive resin composition was prepared by kneading 60 parts by mass of TUFPRENE A (manufactured by Asahi Kabushiki Kaisha, styrene-butadiene-styrene block copolymer), 30 parts by mass of B-2000 (manufactured by Japanese Petroleum chemical Co., ltd., liquid polybutadiene), 7 parts by mass of 1, 9-nonanediol diacrylate, 2 parts by mass of 2, 2-dimethoxy-2-phenylacetophenone, and 0.3 part by mass of 2, 6-di-tert-butyl-p-cresol using a pressure kneader.

Next, a photosensitive resin composition was put into an extrusion molding machine, a support (polyethylene terephthalate film) was stuck to a single surface of the photosensitive resin composition layer extruded from a T-die, and a release film (diafil MRV100 manufactured by mitsubishi chemical corporation) was stuck to a surface of the photosensitive resin composition layer opposite to the support lamination side, to obtain a laminate of the support and the photosensitive resin composition layer.

((2) manufacture of resin used in the IR-ablative layer)

< production of resin 1 >

After nitrogen substitution was performed in a polymerization vessel of a 2L separable flask, 456.1mL of n-hexane (dried using a molecular sieve) and 656.5mL of chlorobutane (dried using a molecular sieve) were added using a syringe, and after cooling the polymerization vessel in a dry ice/methanol bath at-70 ℃, 161.1g (2871 mmol) of isobutylene monomer was contained in the polymerization vessel, and a liquid feed tube made of Teflon (registered trademark) was connected to a pressure-resistant glass liquefaction vessel equipped with a three-way cock, and the isobutylene monomer was fed into the polymerization vessel under nitrogen pressure. 0.647g (2.8 mmol) of p-dicumyl chloride and 1.22g (14 mmol) of N, N-dimethylacetamide were added. Next, 8.67mL (79.1 mmol) of titanium tetrachloride was further added to start polymerization. Stirring was carried out at the same temperature for 1.5 hours from the start of polymerization, and then about 1mL of the polymerization solution was taken out from the polymerization solution for sampling. Next, a mixed solution of 77.9g (748 mmol) of styrene monomer, 23.9mL of n-hexane and 34.3mL of chlorobutane, which had been previously cooled to-70℃was added to the polymerization vessel. After 45 minutes from the addition of the mixed solution, about 40mL of methanol was added to terminate the reaction.

After the solvent and the like were distilled off from the reaction solution, the mixture was dissolved in toluene and washed with water 2 times. Further, a toluene solution was added to a large amount of methanol to precipitate a polymer, and the obtained polymer was dried under vacuum at 60 ℃ for 24 hours, thereby obtaining a resin 1. By means of ¹ When the content of styrene was determined by H-NMR, it was 30% by mass.

< production examples of resins 2 to 9 >

Resins 2 to 9 were obtained in the same manner as in resin 1 except that the types of monomers and the compounding ratios used were changed as in table 1 below. The constituent materials and physical properties of the resins are shown in table 1 below.

< production example of resin 10 >

A vessel equipped with a stirrer was charged with 2kg of water, 65g of calcium phosphate, 40g of calcium carbonate and 0.40g of sodium lauryl sulfate to obtain a mixed solution. Next, 25kg of water was charged into a 60L reactor and the temperature was raised to 80℃to charge 21.5kg of a mixed solution and methyl methacrylate, 110g of lauroyl peroxide and 430g of 2-ethylhexyl thioglycolate. Thereafter, suspension polymerization was carried out while maintaining about 75℃and, after the exothermic peak was observed, the temperature was raised to 92℃at a rate of 1℃per minute. Further, the polymerization reaction was substantially completed after curing for 60 minutes.

Subsequently, the mixture was cooled to 50℃and 20% by mass sulfuric acid was charged to dissolve the suspending agent. Then, the polymerization reaction solution was poured into a sieve having a mesh of 1.68mm to remove aggregates, and the resultant bead polymer was subjected to washing, dehydration and drying to obtain a resin 10.

TABLE 1

((3) manufacture of an Infrared ablative layer laminate)

< production example of infrared ablation layer laminate 1 >

Resin 1:6.5 parts by mass of toluene: 54.0 parts by mass of cyclohexanone: 36.0 parts by mass of a solvent was mixed to dissolve the resin 1. Thereafter, 3.5 parts by mass of carbon black (Mitsubishi chemical corporation, # 1000) was further charged, and the mixture was mixed for 4 hours by a bead mill to obtain a carbon black dispersion.

The carbon black dispersion thus obtained was applied to a PET film of 100 μm thickness, which was a cover film, so that the film thickness after drying became 2.5 μm, and the drying treatment was performed at 90 ℃ for 2 minutes, to obtain an infrared ablation layer laminate 1, which was a laminate of an infrared ablation layer and a cover film.

< production example of infrared ablation layer laminate 2 to 10 >

The infrared ablation layer laminates 2 to 10 were obtained in the same manner as the infrared ablation layer laminate 1 except that the resins used were changed as shown in table 2 below.

< production example of infrared ablation layer laminate 11 >

TUFPRENE 315 (styrene-butadiene block copolymer, manufactured by Asahi Kabushiki Kaisha Co., ltd.) was mixed with 7.8 parts by mass, 70.4 parts by mass of toluene and 17.6 parts by mass of propylene glycol 1-monomethyl ether 2-acetate (PMA), and TUFPRENE 315 was dissolved in a solvent. Thereafter, carbon black (MCF-88, mitsubishi chemical corporation) was further charged, and the mixture was mixed for 4 hours by a bead mill to obtain a carbon black dispersion.

The carbon black dispersion obtained in the above manner was used, and the infrared ablation layer laminate 11 was obtained in the same manner as the infrared ablation layer laminate 1.

< production example of the infrared ablation layer laminate 12 >

7.8 parts by mass of polyamide (MACROMELT 6900, manufactured by HENKEL Co., ltd.), 44.0 parts by mass of toluene and 44.0 parts by mass of 2-propanol were mixed, and the polyamide was dissolved in a solvent. Thereafter, carbon black (MCF-88, mitsubishi chemical corporation) was further charged, and the mixture was mixed with a bead mill for 4 hours to obtain a carbon black dispersion.

The carbon black dispersion obtained in the above manner was used, and the infrared ablation layer laminate 12 was obtained in the same manner as the infrared ablation layer laminate 1.

< production example of the infrared ablation layer laminate 13 >

10 parts by mass of GOHSENOL KL-05 (polyvinyl acetate having a saponification degree of 78 to 82 mol%, manufactured by Japanese synthetic chemical industry Co., ltd.), 10 parts by mass of epsilon-caprolactam, 90 parts by mass of nylon salt of N- (2-aminoethyl) piperazine and adipic acid, and 100 parts by mass of water were charged into a stainless steel autoclave, and after replacing the internal air with nitrogen gas, the mixture was heated at 180℃for 1 hour to prepare a water-soluble polyamide. Next, 10 parts by mass of the water-soluble polyamide obtained by removing the water was dissolved in 40 parts by mass of water, 20 parts by mass of methanol, 20 parts by mass of n-propanol and 10 parts by mass of n-butanol to obtain a solution.

To the obtained solution, carbon black (Mitsubishi chemical corporation, # 1000) was mixed and dispersed by a three-roll mill to obtain a carbon black dispersion.

The carbon black dispersion obtained in the above manner was used, and an infrared ablation layer laminate 13 was obtained in the same manner as in the infrared ablation layer laminate 1.

< example of production of Infrared ablative layer laminate 14 >

To a heated closed vessel equipped with a stirring device, 41 parts of toluene was charged, 3.0 parts of modified polyolefin HARDLEN 13-LP (manufactured by Toyobo Co., ltd.) was added while stirring, and stirring and dissolution were performed at 40 ℃. After naturally cooling to room temperature, 88 parts of MCF-88 parts by Mitsubishi chemical corporation as carbon black was added as an infrared absorbing substance, and after premixing for 90 minutes, the carbon black was dispersed by using a sand mill (second stage). Thereafter, the mixture was heated again to 40℃and 38.8 parts of toluene, 3 parts of methyl ethyl ketone and 13-LP 8.2 parts of HARDLEN were added thereto and stirred to dissolve (third stage), whereby carbon black was produced in a mass ratio of: resin=35: 65.

The carbon black dispersion obtained in the above manner was used, and the infrared ablation layer laminate 14 was obtained in the same manner as the infrared ablation layer laminate 1.

< production example of infrared ablation layer laminate 15 >

SEPTON 2005 (manufactured by Kuraray Co., ltd., styrene: 20wt%, propylene structure (R) ₁ Is methyl, R ₂ ～R ₄ Hydrogen atom): 40 wt%) 7.8 parts by mass, 70.4 parts by mass of toluene and 17.6 parts by mass of propylene glycol 1-monomethyl ether 2-acetate (PMA) were mixed and SEPTON 2005 was dissolved in a solvent. Thereafter, carbon black (MCF-88, mitsubishi chemical corporation) was further charged, and the mixture was mixed with a bead mill for 4 hours to obtain a carbon black dispersion.

The carbon black dispersion obtained in the above manner was used, and an infrared ablation layer laminate 15 was obtained in the same manner as in the infrared ablation layer laminate 1.

TABLE 2

	Resin composition	Carbon black	Resin/carbon black mass ratio
				Infrared ablation layer laminate 1	Resin 1	#1000	65/35
Infrared ablation layer laminate 2	Resin 2	#1000	65/35
				Infrared ablation layer laminate 3	Resin 3	#1000	65/35
Infrared ablation layer laminate 4	Resin 4	#1000	65/35
				Infrared ablation layer laminate 5	Resin 5	#1000	65/35
Infrared ablation layer laminate 6	Resin 6	#1000	65/35
				Infrared ablation layer laminate 7	Resin 7	#1000	65/35
Infrared ablation layer laminate 8	Resin 8	#1000	65/35
				Infrared ablation layer laminate 9	Resin 9	#1000	65/35
Infrared ablation layer laminate 10	Resin 10	#1000	65/35
				Infrared ablation layer laminate 11	TUFPRENE315	MCF-88	65/35
Infrared ablation layer laminate 12	MACROMELT6900	MCF-88	65/35
				Infrared ablation layer laminate 13	Polyvinyl acetate/water-soluble polyamide	#1000	80/20
Infrared ablation layer laminate 14	HARDLEN13-LP	MCF-88	65/35
				Infrared ablation layer laminate 15	SEPTON2005	MCF-88	65/35

(4) production of photosensitive resin Structure for flexographic printing plate)

Example 1 ]

The release film was peeled from the laminate of the support and the photosensitive resin composition layer, the infrared ablation layer laminate 1 was laminated in an atmosphere of a temperature of 25 ℃ and a humidity of 40% so that the infrared ablation layer was in contact with the photosensitive resin composition layer, and the laminate was placed on a heating plate set to 120 ℃ so that the surface of the cover film was in contact with the heating portion of the heating plate, and heated for 1 minute, to obtain a photosensitive resin structure 1 for a flexographic printing plate of example 1.

The photosensitive resin structure 1 for flexographic printing plates of example 1 produced in the above-described manner was evaluated as follows. The evaluation results are shown in table 3 below. The evaluation was performed by cutting the photosensitive resin structure for flexographic printing plates to a size of 10cm×15cm and peeling off the cover film.

(evaluation method)

< evaluation of laser sensitivity >

A photosensitive resin structure for flexographic printing plates was set in Esko CDI SPARK2530, and laser drawing was performed on a test image having an image pattern of 2 pixels in total formed by 2X 1 pixels under the conditions of a resolution of 8000dpi and a laser intensity of 3.0J.

Thereafter, the ablated portion was observed with a laser microscope (VK-X100, manufactured by kenshi corporation; the objective lens is 100 times), and the length of the surface of the infrared ablation layer in the longitudinal direction (2 pixels side) and the length of the interface with the photosensitive resin composition layer, which was cut by the laser light, were measured, and the interface with the photosensitive resin composition layer and the length of the surface of the infrared ablation layer were evaluated as indicators of laser sensitivity as follows.

(evaluation criterion)

A: the length of the hole penetrating through the interface with the photosensitive resin composition and the surface of the infrared ablation layer is 0.50 or more

B: the length of the interface with the photosensitive resin composition/the surface of the infrared ablation layer is 0.40 or more and less than 0.50

C: the length of the interface with the photosensitive resin composition/the surface of the infrared ablation layer is 0.30 or more and less than 0.40

D: the length of the interface between the hole penetrating and the photosensitive resin composition and the surface of the infrared ablation layer is less than 0.30

E: the holes not being penetrated

< evaluation of flexibility >

The photosensitive resin structure for flexographic printing plates was bent 180 ° with the vicinity of the center as a starting point and with the support inside (the degree of contact between the supports), and then tested for the occurrence of wrinkles on the surface of the infrared ablation layer, and evaluated as follows.

(evaluation criterion)

A: no wrinkles were generated.

B: wrinkles are generated only slightly at the end of the structure.

C: wrinkles are generated, and a plurality of wrinkles are generated at the end of the structure.

D: wrinkles are generated, and wrinkles are observed not only at the end portions of the structure but also near the center.

E: wrinkles are generated on the entire surface of the structure.

< pinhole evaluation >

The infrared ablation layer laminate 1 was laminated at a temperature of 180 ℃ so that the infrared ablation layer was in contact with the photosensitive resin composition layer, to obtain a sample. In this sample, the cover film of the infrared ablation layer was removed, and then placed on a light table for microscopic examination. In the infrared ablation layer, the number of pinholes with a length of 20 μm or more is counted, the average value is calculated, and the number of pinholes per m is calculated ² ) The values of (2) were evaluated as follows.

(evaluation criterion)

A: the number of pinholes is on average less than 2 (pieces/m ² )。

B: the number of pinholes was 2 (m/m on average ² ) Above and less than 5 (m) ² )。

C: the number of pinholes was 5 (m/m on average ² ) Above and less than 10 (m) ² )。

D: the number of pinholes was 10 (m/m on average ² ) Above and less than 20 (m) ² )。

E: the number of pinholes was 20 (m/m on average ² ) The above.

< examples 2 to 10 and comparative examples 1 to 5>

Photosensitive resin structures 2 to 15 for flexographic printing plates of examples 2 to 15 were produced and evaluated in the same manner as in example 1 except that the types of the infrared ablation layer laminates were changed to infrared ablation layer laminates 2 to 12, respectively. The evaluation results are shown in table 3 below.

TABLE 3

	Photosensitive resin structure for flexible printing	Infrared ablation layer laminate	Laser sensitivity	Flexibility of	Pinhole resistance evaluation
						Example 1	1	1	A(0.52)	A	A
Example 2	2	2	B(0.48)	B	A
						Example 3	3	3	B(0.45)	C	A
Example 4	4	4	A(0.53)	A	B
						Example 5	5	5	A(0.57)	A	B
Example 6	6	6	A(0.54)	A	A
						Example 7	7	7	C(0.36)	A	A
Example 8	8	8	C(0.32)	A	A
						Example 9	9	9	A(0.54)	A	C
Comparative example1	11	11	E	A	D
						Comparative example 2	12	12	E	A	E
Comparative example 3	13	13	E	A	E
						Comparative example 4	14	14	E	B	B
Comparative example 5	15	15	E	A	B
						Comparative example 6	10	10	A(0.57)	D	C

((101-1) Synthesis of hydrophilic copolymer)

125 parts by mass of an aqueous solution of (α -sulfo (1-nonylphenoxy) methyl-2- (2-propenyloxy) ethoxy-poly (oxy-1, 2-ethanediyl) ammonium salt "ADEKA readap" (manufactured by the rising electric industries, inc.) 2 parts by mass of a reactive emulsifier, an oily mixture of a monomer mixture comprising 10 parts by mass of styrene, 60 parts by mass of butadiene, 23 parts by mass of butyl acrylate, 5 parts by mass of methacrylic acid and 2 parts by mass of acrylic acid and 2 parts by mass of t-dodecyl mercaptan, and an aqueous solution comprising 28 parts by mass of water, 1.2 parts by mass of sodium peroxodisulfate, 0.2 parts by mass of sodium hydroxide and 2 parts by mass of (α -sulfo (1-nonylphenoxy) methyl-2- (2-propenyloxy) ethoxy-poly (oxy-1, 2-ethanediyl)) were initially charged to a pressure-resistant reaction vessel equipped with a stirring device and a temperature adjusting jacket, the oily mixture was consumed for 5 hours and was added at a constant rate, and the aqueous solution was subjected to copolymerization at a constant flow rate of 6 hours, and the latex was obtained after the polymerization was cooled at a constant flow rate, and the latex was obtained.

Further, the resulting copolymer latex was adjusted to pH 7 with sodium hydroxide, then, unreacted monomers were removed by gas stripping, and filtration was performed with a 200-mesh metal mesh, and finally, the concentration of the solid content of the filtrate was adjusted to 40 mass%, to obtain an aqueous dispersion of a hydrophilic copolymer.

The resulting aqueous dispersion of the hydrophilic copolymer was dried by using a vacuum dryer at 50℃to remove water, thereby obtaining a hydrophilic copolymer.

((101-2) preparation of base film (support)

The adhesive layer solution applied to the support (base film) was dissolved in toluene at a ratio of 55 parts by mass of TUFPRENE 912 (manufactured by Asahi Kabushiki Kaisha, trade name), 38 parts by mass of paraffin oil (average carbon number: 33, average molecular weight: 470, density: 0.868 at 15 ℃) 2.5 parts by mass of 1, 9-nonanediol diacrylate, 1.5 parts by mass of 2, 2-dimethoxy-phenylacetophenone, 3 parts by mass of EPOXYESTER3000M (manufactured by Kyowa chemical Co., ltd., trade name) and 1.5 parts by mass of VALIFAST YELLOW 3150 (manufactured by ORIENT CHEMICAL INDUSTRIES Co., trade name), to obtain a solution having a solid content of 25%.

Thereafter, the resultant film was applied to one side of a polyester film having a thickness of 100 μm by using a knife coater so that the ultraviolet transmittance (UV transmittance) became 10%, and dried at 80℃for 1 minute, to obtain a support (base film) having an adhesive layer.

The UV transmittance of the support was calculated by measuring the transmittance intensity by using an ultraviolet light exposure machine AFP-1500 (trade name, manufactured by Asahi Kabushiki Kaisha Co., ltd.) and a UV illuminometer MO-2 type machine (trade name, UV-35 filter, manufactured by ORC).

(production of laminate of support and photosensitive resin composition layer) (101-3)

32 parts by mass of the hydrophilic copolymer prepared in the above (101-1) was kneaded with a styrene-butadiene-styrene copolymer [ D-KX405: 28 parts by mass of liquid polybutadiene [ LBR-352 ] was added little by little after mixing at 140℃for 15 minutes, which was manufactured by CLAYTON Co., ltd.): 32 parts by mass of Kuraray company, 8 parts by mass of 1, 9-nonanediol diacrylate, 5 parts by mass of 1, 6-hexanediol dimethacrylate, 2 parts by mass of 2, 2-dimethoxyphenylacetophenone, 1 part by mass of 2, 6-di-tert-butyl-p-cresol, and methanol-modified silicone oil [ KF-6000: 1 part by mass of the liquid mixture was added and mixed for 20 minutes to obtain a photosensitive resin composition.

Next, a photosensitive resin composition was fed into an extrusion molding machine, a surface on which the adhesive layer of the support was formed was adhered to a single surface of the photosensitive resin composition layer extruded from a T-die, and a release film (diafil MRV100, manufactured by mitsubishi chemical company) was adhered to a surface of the photosensitive resin composition layer opposite to the support layer, thereby obtaining a laminate of the support and the photosensitive resin composition layer.

((102) manufacture of resin used in an infrared ablation layer)

< production of resin 101 >

After the solvent and the like were distilled off from the reaction solution, the mixture was dissolved in toluene and washed with water 2 times. Further, a toluene solution was added to a large amount of methanol to precipitate a polymer, and the obtained polymer was dried under vacuum at 60 ℃ for 24 hours, thereby obtaining a resin 101. By means of ¹ When the content of styrene was determined by H-NMR, it was 30% by mass.

< production examples of resins 102 to 105 >

Resins 102 to 105 were obtained in the same manner as resin 101 except that the types of monomers and the compounding ratios used were changed as shown in table 4 below. The constituent materials and physical properties of the resins are shown in table 4 below.

TABLE 4

((103) manufacture of Infrared ablative layer laminate)

< production example of infrared ablation layer laminate 101 >

Resin 1:6.5 parts by mass of toluene: 54.0 parts by mass of cyclohexanone: 36.0 parts by mass of a solvent was mixed to dissolve the resin 1. Thereafter, 3.5 parts by mass of carbon black (manufactured by Mitsubishi chemical corporation, #1000, ph=3.5) and 1.2 parts by mass of Solsperse39000 (manufactured by Lubrizol corporation, SP value: 11.5) were further charged, and thereafter, the mixture was mixed for 4 hours by a bead mill to obtain a carbon black dispersion.

The carbon black dispersion thus obtained was applied to a PET film of 100 μm thickness, which was a cover film, so that the film thickness after drying became 3.0 μm, and the drying treatment was performed at 90 ℃ for 2 minutes to obtain an infrared ablation layer laminate 101, which was a laminate of an infrared ablation layer and a cover film.

< production example of infrared ablation layer laminate 102 to 107, 109 to 119, 129 >

The infrared ablation layer stacks 102 to 107, 109 to 119, and 129 were obtained in the same manner as the infrared ablation layer stack 101 except that the resin used was changed as shown in table 5 below.

The MA77 (manufactured by mitsubishi chemical company) used as the Carbon black had a pH of 2.5,TOKA BLACK#8300 (manufactured by Tokai Carbon co., ltd.) and a pH of 5.0,TOKA BLACK#5500 (manufactured by Tokai Carbon co., ltd.) of 6.0. These pH values were obtained by preparing a mixture of carbon black and distilled water according to ASTM D1512 and measuring the mixture with a glass electrode pH meter (the same applies hereinafter).

Further, DISPARON DA-703-50 (manufactured by Nanyaku chemical Co., ltd.) used as the dispersant had an SP value of 11.0,Solsperse S11200 (manufactured by Lubrizol Co., ltd.) and an SP value of 9.5,Solsperse S18000 (manufactured by Lubrizol Co., ltd.) and an SP value of 8.1,AJISPER PB881 (Ajinomoto Fine Techno Co., ltd.) and an SP value of 12.1. These SP values were obtained by cloud point titration (the same applies hereinafter).

< example of production of infrared ablation layer laminate 108 >

To a heated closed vessel equipped with a stirrer, 41 parts of toluene was charged, 3.0 parts of chloropropene SUPERCHOLON HP-205 (manufactured by Japanese paper Co., ltd., degree of chlorination: 68%) was added while stirring, and stirring and dissolution were performed at 40 ℃. After naturally cooling to room temperature, #1000 parts by Mitsubishi chemical corporation and 1.1 parts by dispersant S39000 were added as infrared absorbing materials, and after 90 minutes of premixing, the carbon black was dispersed by a sand mill (second stage). Thereafter, the mixture was heated again to 40℃and 38.8 parts of toluene, 3 parts of methyl ethyl ketone and 8.2 parts of SUPERCHOON HP-205 were added thereto, followed by stirring and dissolution (third stage), to prepare a coating liquid for an infrared ablation layer having a mass ratio of carbon black to resin=35:65.

The carbon black dispersion obtained in the above manner was used, and an infrared ablation layer laminate 108 was obtained in the same manner as the infrared ablation layer laminate 101.

< example of production of Infrared ablative layer laminate 120 >

The infrared ablation layer laminate 120 was obtained in the same manner as the infrared ablation layer laminate 8 except that the carbon black used was changed to Printex35 (ph=9.5, manufactured by Degussa corporation).

< example of production of Infrared ablative layer laminate 121 >

7.8 parts by mass of a hydrogenated product of a styrene-butadiene-styrene copolymer elastomer (TUFTEC H1051, manufactured by Asahi Kabushiki Kaisha), 70.4 parts by mass of toluene and 17.6 parts by mass of propylene glycol 1-monomethyl ether 2-acetate (PMA) were mixed to dissolve the resin. Thereafter, 4.2 parts by mass of carbon black (manufactured by mitsubishi chemical Co., ltd., #30, pH=8.0) and 0.6 parts by mass of Solsperse39000 (manufactured by Lubrizol Co., ltd., japan) were further charged, and the mixture was mixed for 4 hours by a bead mill to obtain a carbon black dispersion.

The same procedure as for the infrared ablation layer laminate 1 was repeated except for using the obtained carbon black dispersion to obtain an infrared ablation layer laminate 121.

< example of production of Infrared ablative layer laminate 122 >

The same procedure as for the infrared ablation layer laminate 121 was repeated except that the carbon black used was changed to #1000 (ph=3.5, manufactured by mitsubishi chemical company).

< example of production of Infrared ablative layer laminate 123 >

7.8 parts by mass of polyamide (MACROMELT 6900, manufactured by HENKEL Co., ltd.), 44.0 parts by mass of toluene and 44.0 parts by mass of 2-propanol were mixed to dissolve the resin. Thereafter, 4.2 parts by mass of carbon black (manufactured by mitsubishi chemical Co., ltd., #30, pH=8.0) and 0.6 parts by mass of Solsperse39000 (manufactured by Lubrizol Co., ltd., japan) were further charged, and the mixture was mixed for 4 hours by a bead mill to obtain a carbon black dispersion.

The obtained carbon black dispersion was used, and an infrared ablation layer laminate 123 was obtained in the same manner as the infrared ablation layer laminate 101.

< example of production of the infrared ablation layer laminate 124 >

The same procedure as for the infrared ablation layer laminate 123 was repeated except that the carbon black used was changed to #1000, to obtain an infrared ablation layer laminate 124.

< example of production of infrared ablation layer laminate 125 >

10 parts by mass of GOHSENOL KL-05 (polyvinyl acetate having a saponification degree of 78 to 82 mol%, manufactured by Japanese synthetic chemical industry Co., ltd.), 10 parts by mass of epsilon-caprolactam, 90 parts by mass of nylon salt of N- (2-aminoethyl) piperazine and adipic acid, and 100 parts by mass of water were charged into a stainless steel autoclave, and after replacing the internal air with nitrogen gas, the mixture was heated at 180℃for 1 hour to prepare a water-soluble polyamide. Next, 10 parts by mass of the water-soluble polyamide obtained by removing the water was dissolved in 40 parts by mass of water, 20 parts by mass of methanol, 20 parts by mass of n-propanol and 10 parts by mass of n-butanol to obtain a solution. Carbon black (MA-100, ph=3.5, manufactured by mitsubishi chemical corporation) was mixed with the solution, and the mixture was kneaded and dispersed by using a three-roll mill to obtain a carbon black dispersion.

The same procedure as for the infrared ablation layer laminate 101 was conducted except that the obtained carbon black dispersion was used, to obtain an infrared ablation layer laminate 125.

< example of production of infrared ablation layer laminate 126 >

The same procedure as for the infrared ablation layer laminate 125 was repeated except that the carbon black used was changed to #30, to obtain an infrared ablation layer laminate 126.

< example of production of Infrared ablative layer laminate 127 >

0.5 parts by mass of an acid-modified polymer (UC-3510, manufactured by Toyama Synthesis Co., ltd.), 1.3 parts by mass of a hydrogenated product of a styrene-butadiene-styrene elastomer (TUFTEC H1051, manufactured by Asahi Kabushiki Kaisha Co., ltd.) and 44 parts by mass of toluene were mixed to dissolve the resin. Thereafter, 4.2 parts by mass of carbon black (manufactured by mitsubishi chemical Co., ltd., #30, pH=8.0) and 0.6 parts by mass of Solsperse39000 (manufactured by Lubrizol Co., ltd., japan) were further charged, and the mixture was mixed for 4 hours by a bead mill to obtain a carbon black dispersion.

The same procedure as for the infrared ablation layer laminate 101 was conducted except that the obtained carbon black dispersion was used, to obtain an infrared ablation layer laminate 127.

The constituent materials are shown in table 5 below.

< example of production of infrared ablation layer laminate 128 >

The same procedure as for the infrared ablation layer laminate 127 was conducted except that the carbon black used was changed to #1000, to obtain an infrared ablation layer laminate 128.

TABLE 5

((104) production of photosensitive resin Structure for flexographic printing plate)

< example 101>

The release film was peeled from the laminate of the support and the photosensitive resin composition layer, the infrared ablation layer laminate 101 was laminated in an atmosphere of a temperature of 25 ℃ and a humidity of 40% so that the infrared ablation layer was in contact with the photosensitive resin composition layer, and the laminate was placed on a heating plate set to 120 ℃ so that the surface of the cover film was in contact with the heating portion of the heating plate, and the laminate was heated for 1 minute, to obtain a photosensitive resin structure 101 for a flexographic printing plate of example 101.

The photosensitive resin structure 101 for flexographic printing plates of example 101 produced in the above-described manner was evaluated as follows. The evaluation results are shown in table 6 below. The evaluation was performed by cutting the photosensitive resin structure for flexographic printing plates to a size of 10cm×15cm and peeling off the cover film.

(evaluation method)

< evaluation of developability with respect to solvent-based developer >

A photosensitive resin structure for flexographic printing plates was stuck to a rotating drum of an "AFP-1500" developing machine (product name of Asahi Kabushiki Kaisha Co., ltd.) with double-sided tape using 3-methoxybutyl acetate as a developer, fixed, developed at a liquid temperature of 25℃and dried at 60℃for 2 hours. The time required for development was measured at 0.8 mm.

Similarly, the release film is peeled from the laminate of the support and the photosensitive resin composition layer, and developed. The developability of the infrared ablation layer was evaluated based on how much the development time was changed due to the presence of the infrared ablation layer.

(evaluation criterion)

A: the development time deterioration due to the presence of the infrared ablative layer was less than 30 seconds.

B: the development time is deteriorated by the presence of the infrared ablation layer for 30 seconds or more and less than 1 minute.

C: the development time is deteriorated by the presence of the infrared ablation layer for 1 minute or more and less than 2 minutes.

D: the development time is deteriorated by the presence of the infrared ablation layer for 2 minutes or more and less than 3 minutes.

E: due to the presence of the infrared ablation layer, the cleaning was not sufficient even if the addition was performed for 3 minutes or more.

< evaluation of developability with aqueous developer >

A developing machine (JOW-A3-P) made by Nissan SOAP was filled with a 1% aqueous solution of NISSAN SOAP, and the cover film of the infrared ablation layer of the printing master obtained in (2) was peeled off, and developed at a liquid temperature of 40 ℃. It was allowed to dry at 60℃for 10 minutes. The time required for development was measured at 0.8 mm.

(evaluation criterion)

A: even in the presence of the infrared ablative layer, the development time was deteriorated by less than 1 minute.

B: the development time is deteriorated by the presence of the infrared ablation layer for 1 minute or more and less than 2 minutes.

C: the development time is deteriorated by the presence of the infrared ablation layer for 2 minutes or more and less than 3 minutes.

D: the development time is deteriorated by the presence of the infrared ablation layer for 3 minutes or more and less than 5 minutes.

E: due to the presence of the infrared ablation layer, the cleaning was not sufficient even when the addition time was 5 minutes or longer.

< evaluation of carbon Black dispersibility >

After the photosensitive resin structure for flexographic printing plates is cut to an appropriate size, resin embedding is performed using an ultraviolet curable resin. After embedding the resin, a cross section prepared by the Cryo-microtome method was used as an SEM observation sample.

Cross-sectional processing conditions

The using device comprises: ultra-thin slicer UC6 (manufactured by LEICA company)

Setting the temperature: -80 DEG C

Setting the cutting thickness: 100nm of

(SEM observation conditions)

Measurement device: scanning electron microscope S4800 (Hitachi Co., ltd.)

Acceleration voltage: 1.0kV

Observation magnification: 5.0k

The infrared ablation layer was observed, and based on the obtained cross-sectional SEM observation image, evaluation was performed as follows.

(evaluation criterion)

A: the carbon black was uniformly dispersed, and no agglomerated mass was observed.

B: the carbon black is uniformly dispersed, and the number of the aggregation blocks is less than 2 in one field of view.

C: the carbon black is uniformly dispersed, and the number of the aggregation blocks is less than 5 in one field of view.

E: the carbon black is unevenly present, and there are 5 or more clusters in one field of view, or there are widely regions where the carbon black is absent.

< examples 102 to 119 and comparative examples 101 to 110>

Photosensitive resin structures 102 to 129 for flexographic printing plates of examples 102 to 119 and comparative examples 101 to 110 were produced and evaluated in the same manner as in example 101 except that the types of the infrared ablation layer stacks were changed to infrared ablation layer stacks 102 to 129, respectively. The evaluation results are shown in table 6 below.

TABLE 6

Industrial applicability

The photosensitive resin structure for flexographic printing plates of the present invention has wide industrial applicability in general commercial printing fields.

Description of the reference numerals

1 … A photosensitive resin structure for flexographic printing plate, a … support, a b … photosensitive resin composition layer, a b '… pattern-exposed photosensitive resin composition layer, a c … infrared ablation layer, and a c' … patterned infrared ablation layer.

Claims

1. A photosensitive resin structure for flexographic printing plates, comprising at least:

a support (a);

a photosensitive resin composition layer (b) laminated on the support (a); and

the infrared ablation layer (c) comprises a resin having a structural unit c1 represented by the following general formula (1),

here, in the formula (1), R ₁ And R is ₂ Each independently represents a nonpolar group; r is R ₃ And R is ₄ Each independently represents a hydrogen atom or a nonpolar group.

2. The photosensitive resin structure for flexographic printing plates according to claim 1, wherein the content of the structural unit (c 1) is 40 mass% or more and 100 mass% or less with respect to the total amount of the resin.

3. The photosensitive resin structure for flexographic printing plates according to claim 1 or 2, wherein R of the general formula (1) ₃ And R is ₄ Each independently is a hydrogen atom, alkyl, aryl, cycloalkyl, phenyl, alkenyl, aralkyl, cycloalkenyl, alkynyl, silyl, siloxane group.

4. The photosensitive resin structure for flexographic printing plates according to any one of claims 1 to 3, wherein R of the general formula (1) ₃ And R is ₄ Is a hydrogen atom.

5. The photosensitive resin structure for flexographic printing plates according to any one of claims 1 to 4, wherein R of the general formula (1) ₁ And R is ₂ Each independently is alkyl, aryl, cycloalkyl, phenyl, alkenyl, aralkyl, cycloalkenyl, alkynyl, silyl, siloxane.

6. The photosensitive resin structure for flexographic printing plates according to any one of claims 1 to 5, wherein R of the general formula (1) ₁ And R is ₂ Each independently is an alkyl group or a phenyl group.

7. The photosensitive resin structure for flexographic printing plates according to any one of claims 1 to 6, wherein R of the general formula (1) ₁ And R is ₂ Is alkyl.

8. The photosensitive resin structure for flexographic printing plates according to any one of claims 1 to 7, wherein the resin further has a structural unit (c 2), the structural unit (c 2) being different from the structural unit (c 1) and containing an aromatic group in a side chain.

9. The photosensitive resin structure for flexographic printing plates according to any one of claims 1 to 8, wherein the structural unit (c 2) comprises a structural unit derived from a monovinyl-substituted aromatic hydrocarbon.

10. The photosensitive resin structure for flexographic printing plates according to any of claims 1 to 9, wherein the infrared ablation layer (c) contains carbon black,

The pH of the carbon black is 2.0 to 5.0.

11. The photosensitive resin structure for flexographic printing plates according to any of claims 1 to 10, wherein the infrared ablation layer (c) contains a dispersant,

the solubility parameter (SP value) of the dispersant is 9.5 to 12.5.

12. The photosensitive resin structure for flexographic printing plates according to any one of claims 1 to 11, wherein a compounding ratio (resin/carbon black) of the resin in the infrared ablation layer (c) to the carbon black is in a range of 80/20 to 50/50.

13. A method for producing a flexographic printing plate using the photosensitive resin structure for flexographic printing plate according to any one of claims 1 to 12, comprising the steps of:

a first step of irradiating ultraviolet rays from the support (a) side;

14. A flexible printing method using the photosensitive resin structure for a flexible printing plate according to any one of claims 1 to 12, comprising the steps of:

a first step of irradiating ultraviolet rays from the support (a) side;

and a fifth step of printing using the flexographic printing plate.