JP4895900B2 - Photosensitive resin composition - Google Patents

Description

  The present invention relates to a photosensitive resin composition suitably used as a flexographic printing plate and the like, and a photosensitive resin composition for flexographic printing using the same.

A general photosensitive resin composition for flexographic printing, as described in Patent Documents 1 to 3, comprises a non-hydrogenated thermoplastic elastomer, a photopolymerizable unsaturated monomer, and a photopolymerization initiator. What is contained is common. Constituents for flexographic printing plates use a polyester film or the like as a support, and the above photosensitive resin composition, and further, if necessary, smooth contact with the negative film on the photosensitive resin composition. For this purpose, a protective layer or an ultraviolet shielding layer containing an infrared-sensitive substance that can be removed with an infrared laser is provided.
In order to make a flexographic printing plate from such a photosensitive resin composition for a flexographic printing plate, first, the entire surface of the structure is exposed to ultraviolet rays through a support (back exposure), and the resin composition is photopolymerized to form a thin uniform film. A cured layer is provided, and then image exposure (relief exposure) is performed on the surface of the photosensitive resin layer through a negative film or directly from above the ultraviolet shielding layer, and unexposed portions are washed away with a developing solvent, or from 40 ° C. to The unexposed portion heated to 200 ° C. is brought into contact with an absorbable absorbent layer such as a nonwoven fabric, and the unexposed portion is removed by removing the absorbent layer. Thereafter, it is generally produced by post-processing exposure on the surface of the resin structure on which irregularities are formed. Therefore, if the transparency of the photosensitive resin composition is low, ultraviolet light is scattered and it is difficult to obtain sharp image reproducibility.

In flexographic printing, a radiation curable ink containing an ester solvent or a reactive monomer is supplied to the surface of a convex portion of a printing plate with an ink supply roll or the like, and the resin plate is brought into contact with the substrate to be printed. In general, the printing is performed by a printing machine having a mechanism for transferring the ink on the surface of the part to the printing material. For this reason, if the durability against the ester solvent ink is low, the image may become thicker or the outlines will be filled, resulting in poor print quality, long-time printing, or when wiping off ink on the surface of the printing plate after printing. The printing plate may be destroyed.
Furthermore, in flexographic printing, when printing a concave line (white line) portion of a printing plate, a line (edge edge) near the white line has a low ink density in parallel with the white line, unlike the pattern on the printing plate. There is a problem in that a part appears. Further, in UV flexographic printing, if ozone is generated and the ozone resistance of the printing plate is low, there is a problem that cracks occur on the surface of the printing plate after printing for a long time.

So far, in order to improve various performances, mixing of various block copolymers has been proposed for the photosensitive resin composition.
Patent Document 4 proposes a non-hydrogenated block copolymer having a copolymer block of isoprene and butadiene in order to improve the transparency of the photosensitive resin, the mechanical strength, the ester solvent resistance of the printing plate, and the like. In the examples, a mixture of the above non-hydrogenated block copolymer and a non-hydrogenated styrene-isoprene block copolymer or a non-hydrogenated styrene-butadiene block copolymer is exemplified.
However, since it is a mixture of non-hydrogenated block copolymers, the achievement of both the solvent resistance and ozone resistance of the printing plate is not always sufficient.

In Patent Document 5, in order to improve the transparency of the photosensitive resin, the mechanical strength, and the ozone resistance of the printing plate, at least a vinyl aromatic hydrocarbon block and a copolymer block of vinyl aromatic hydrocarbon and conjugated diene are included. The use of a block copolymer containing a block in which 90% or more of the conjugated diene is hydrogenated is proposed. In the examples, the above-mentioned hydrogenated block copolymer and a non-hydrogenated styrene isoprene block copolymer are used. The use of a mixture is illustrated.
However, since the hydrogenation rate is high and the number of alkylene units in the block copolymer exceeds 45 wt%, the transparency of the photosensitive resin composition and the anti-fogging property of the character part of the printing plate are not always sufficient.
JP 2000-155418 A Japanese Patent Laid-Open No. 02-108632 Japanese Patent Laid-Open No. 04-342258 International Publication No. 2004/097523 Pamphlet U.S. Patent No. 20040072951

  An object of the present invention is to provide a photosensitive resin composition having high transparency, high ozone resistance when used as a printing plate, and capable of suppressing edge blurring generated in the vicinity of white lines during printing.

As described above, in the prior art, there is no document describing mixing of a block copolymer having an alkylene unit content of less than 5 to 50 wt% and a block copolymer having a non-hydrogenated isoprene block.
As a result of intensive studies to solve the above problems, the present inventors have found that a block copolymer having an alkylene unit content of 5 to 50 wt% and a non-hydrogenated block copolymer having an isoprene block The present inventors have found that this problem can be solved by using a photosensitive resin composition having a specific ratio at a specific ratio, and have reached the present invention.

That is, the present invention is as follows.
[1] (a) a block copolymer containing an alkylene unit, (b) a substantially non-hydrogenated block copolymer containing a polymer block containing isoprene, (c) a photopolymerizable monomer and (d ) Containing a photopolymerization initiator, the alkylene unit in the block copolymer (a) is 5 to 45 wt%, and the mass ratio (a) / block copolymer (a) to the block copolymer (b) The photosensitive resin composition whose (b) is 0.5-10.
[2] The photosensitive resin composition according to [1], wherein the alkylene unit in the block copolymer (a) is 10 to 30 wt%.
[3] The block copolymer (a) includes a polymer block containing a vinyl aromatic hydrocarbon unit, a polymer block (A) containing a butadiene unit and an alkylene unit, and the polymer block (A) The photosensitive resin composition according to [1] or [2], wherein the alkylene unit is 5 to 80 wt%.
[4] The photosensitive resin composition according to [3], wherein the alkylene unit in the polymer block (A) is 5 to 55 wt%.
[5] A block copolymer (a) is obtained by hydrogenating a polymer block mainly composed of vinyl aromatic hydrocarbon units and a block copolymer containing a polymer block mainly composed of butadiene [1] ]-[4] Any photosensitive resin composition.
[6] A block copolymer in which the block copolymer (a) includes a polymer block mainly composed of vinyl aromatic hydrocarbons and a polymer block mainly composed of butadiene having a 1,2-butadiene ratio of 20 to 80 mol%. [5] The photosensitive resin composition obtained by hydrogenating a polymer.
[7] The photosensitive resin composition according to any one of [1] to [6], wherein the block copolymer (b) further includes a polymer block mainly composed of vinyl aromatic hydrocarbons.
[8] The photosensitive resin composition according to any one of [1] to [7], further comprising a liquid conjugated diene rubber having a vinyl content in the diene of 40 mol% or more.
[9] The photosensitive resin composition according to [8], which contains one or more liquid conjugated diene rubbers, and the vinyl content in the total diene content of the liquid conjugated diene rubber is 40 mol% or more.
[10] The photosensitive resin composition according to any one of [1] to [9], wherein the photopolymerizable monomer (c) contains 2 wt% or more of a monomer having 2 mol of a methacrylate group per molecule.
[11] A photosensitive resin composition for flexographic printing plates, comprising a support and a layer of the photosensitive resin composition according to any one of [1] to [10].
[12] The photosensitive resin composition for flexographic printing according to [11], which has an ultraviolet shielding layer containing an infrared-sensitive substance that can be excised with an infrared laser on the layer of the photosensitive resin composition.

  According to the present invention, it is possible to provide a photosensitive resin composition having high transparency, high ozone resistance when used as a printing plate, and capable of suppressing edge blurring generated in the vicinity of white lines during printing.

Hereinafter, the present invention will be specifically described with a focus on preferred embodiments.
The composition of the present invention is a block copolymer containing an alkylene unit (hereinafter referred to as a block copolymer (a) from the viewpoint of transparency of the photosensitive resin composition and suppression of edge blurring that occurs in the vicinity of white lines during printing. ) And a substantially non-hydrogenated block copolymer (hereinafter sometimes abbreviated as block copolymer (b)) containing a polymer block containing isoprene. To do. The mass ratio of the block copolymer (a) to the block copolymer (b) is 0.5 or more from the viewpoint of high ozone resistance of the printing plate. On the other hand, it is 10 or less from the viewpoint of suppressing edge blurring that occurs in the vicinity of a white line in printing. The range of 0.6 to 9.5 is more preferable, and the range of 0.7 to 9.5 is more preferable. The total mass of the block copolymer (a) and the block copolymer (b) is as follows: block copolymer (a), block copolymer (b), photopolymerizable monomer (c) described later, and photopolymerization initiator. When the total of (d) is 100 parts by mass, it is preferably 69 to 95 parts by mass, more preferably 75 to 90 parts by mass, and still more preferably 80 to 90 parts by mass.

[Block copolymer (a)]
The alkylene unit in the block copolymer (a) refers to a monoolefin unit such as an ethylene unit, a propylene unit, a butylene unit, or a hexylene unit. The alkylene unit can be introduced into the block copolymer by polymerization of a monoolefin or hydrogenation of a previously produced diene polymer.
The content of the alkylene unit is 45 wt% or less from the viewpoint of improving the transparency of the resulting photosensitive resin composition. On the other hand, it is 5 wt% or more in terms of ozone resistance when used as a printing plate. The range of 5 to 35 wt% is more preferable, and the range of 10 to 30 wt% is more preferable from the viewpoint of the transparency of the photosensitive resin composition, the ozone resistance and the solvent resistance of the printing plate.

As a block type of the block copolymer (a), a polymer block containing a vinyl aromatic hydrocarbon unit (more preferably main component) and a diene unit (more preferably main component) are included in terms of economy. ) A polymer block, a polymer block containing (more preferably mainly) a diene unit and an alkylene unit, and a polymer block containing (more preferably mainly) an alkylene unit are preferred. Here, “mainly” means occupying 60 wt% or more of the block, more preferably 80 wt% or more, and still more preferably 90 wt% or more.
The diene unit is preferably 1,3-butadiene and / or isoprene from the viewpoint of economy, and butadiene is more preferable from the viewpoint of printing durability of the printing plate.

  Among the above, the block copolymer (a) is a vinyl aromatic compound in terms of compatibility with a photopolymerizable monomer and a plasticizer added if necessary, and in terms of anti-scratching of the character part of the printing plate. It is preferable to include a polymer block containing a hydrocarbon unit (more preferably mainly) and a polymer block containing a diene unit and an alkylene unit (more preferably mainly). In view of the high cold flow property of the photosensitive resin component, the high image reproducibility of the printing plate, and the high wear resistance, the polymer block containing vinyl aromatic hydrocarbon units and the weight containing butadiene units and alkylene units are included. A block copolymer containing a polymer block (hereinafter sometimes abbreviated as “polymer block (A)”) is preferred, more preferably a polymer block mainly composed of vinyl aromatic hydrocarbon units, a butadiene unit and A block copolymer containing a polymer block mainly composed of an alkylene unit is preferred. Note that “mainly” refers to occupying 60 wt% or more of the block as described above, more preferably 80 wt% or more, and still more preferably 90 wt% or more.

The content of the alkylene unit in the polymer block (A) is preferably 80 wt% or less from the viewpoint of the transparency of the photosensitive resin composition and the anti-fogging property of the printing plate. On the other hand, 5 wt% or more is preferable from the viewpoint of ozone resistance of the printing plate. As for content of the alkylene unit in a polymer block (A), the range of 5-55 wt% is more preferable, and the range of 5-35 wt% is further more preferable.
The number average molecular weight of the polymer block (A) is preferably from 20,000 to 250,000, preferably from 20,000 to 250,000, due to the cold flow resistance of the photosensitive resin component and the high scratch resistance of the characters on the printing plate. Is more preferable, and 40,000 to 150,000 are more preferable. Here, the number average molecular weight (Mn) is a molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC).

From the viewpoint of image reproducibility of the printing plate, the polymer block (A) preferably has a 1,2-butadiene ratio of 1 wt% or more, more preferably 10 wt% or more, and further preferably 20 wt% or more.
From the viewpoint of moldability of the photosensitive resin composition, the polymer block (A) preferably has a sum of 1,2-butadiene units and butylene units of 20 wt% or more, more preferably 35 wt%, and 50 wt%. The above is more preferable.
The block copolymer (a) is a block having a polymer block mainly composed of vinyl aromatic hydrocarbons and a polymer block mainly composed of butadiene having a 1,2-butadiene ratio of 20 to 80 mol% in butadiene. It is preferable to obtain the copolymer by hydrogenation from the viewpoint of image reproducibility of the printing plate and anti-scratch property. Note that “mainly” refers to occupying 60 wt% or more of the block as described above, more preferably 80 wt% or more, and still more preferably 90 wt% or more.

Examples of the vinyl aromatic hydrocarbon include styrene, t-butylstyrene, divinylbenzene, 1,1-diphenylstyrene, N, N-dimethyl-p-aminoethylstyrene, N, N-diethyl-p-aminoethylstyrene, Monomers such as vinyl pyridine, p-methyl styrene, tertiary butyl styrene, α-methyl styrene, 1,1-diphenylethylene are exemplified, and styrene is particularly preferable. These monomers may be used alone or in combination of two or more.
The number average molecular weight of the polymer block mainly composed of vinyl aromatic hydrocarbon is preferably 100,000 or less from the viewpoint of the formation of a microimage on the printing plate, and from the viewpoint of cold flow resistance of the photosensitive resin component, It is preferably at least 30,000. The range of 50,000 to 80,000 is more preferable, and the range of 50,000 to 60,000 is more preferable.

The content of the vinyl aromatic hydrocarbon is 25 wt% or less from the viewpoint of moldability of the photosensitive resin composition, anti-fogging property of the character part of the printing plate, and hardness maintenance of the printing plate when the flexographic ink component adheres. It is preferable that On the other hand, 13 wt% or more is preferable from the viewpoint of the cold flow property of the photosensitive resin component. The range of 15-24 wt% is more preferable, and the range of 18-23 wt% is more preferable.
The content of vinyl aromatic hydrocarbon can be measured by ultraviolet spectroscopy (UV). The content and ratio of 1,4-butadiene, 1,2-butadiene, ethylene or butylene can be measured with a nuclear magnetic resonance apparatus (1H-NMR).

As conditions for 1H-NMR, JNM-LA400 (trademark) manufactured by 1H-NMR, a solvent, deuterated chloroform, a sample concentration of 50 mg / ml, an observation frequency of 400 MHz, a chemical shift standard, TMS (tetramethylsilane), pulse delay 2.904 seconds, number of scans 64 times, pulse width 45 °, and measurement temperature 26 ° C.
The number average molecular weight of the block copolymer (a) is preferably 150,000 or more from the viewpoint of the high cold flow property of the photosensitive resin component and the high anti-scratch property of the character part of the printing plate. 200,000 or more is more preferable, and 250,000 or more is more preferable.
The production example of the block copolymer (a) is not particularly limited. However, in terms of economy, a block copolymer comprising a block mainly composed of vinyl aromatic hydrocarbon units and a block mainly composed of butadiene is hydrogenated. A method obtained by addition is preferred.

Block copolymer (a), for example, the following formula (I) or _{(A-B) n, A-} (B-A) n, A- (B-A) n -B, B- (A- B) _n (I)
The following general formula (II)
[(AB) _k ] _m -X, [(AB) _k -A] _m -X (II)
[(BA) _k ] _m -X, [(BA) _k -B] _m -X
A linear block copolymer or a radial block copolymer represented by the formula (in the above formula, A represents a polymer block mainly composed of vinyl aromatic hydrocarbons. B represents a polymer block mainly composed of butadiene. X is, for example, silicon tetrachloride, tin tetrachloride, epoxidized soybean oil, polyhalogenated hydrocarbon compound, carboxylic acid ester compound, polyvinyl compound, bisphenol type epoxy compound, alkoxysilane compound, halogenated silane compound, ester compound Or a residue of an initiator such as a polyfunctional organolithium compound, where n, k and m are integers of 1 or more, generally 1 to 5). . Moreover, the structures represented by the above general formula may be arbitrarily combined. The coupling agent compound may be used alone or in a mixture of two or more.

The block copolymer before hydrogenation is obtained by, for example, a method of polymerizing styrene using an organolithium compound as a polymerization initiator in an inert hydrocarbon solvent, then polymerizing butadiene, and optionally repeating these operations. It is done. After deactivating active species by adding water, alcohol, acid or the like, the solution can be obtained by, for example, performing steam stripping or the like to separate the polymerization solvent and then drying.
In addition, after polymerization by a method different from the above, that is, the same method as described above, an appropriate coupling agent is added to the organolithium compound in a predetermined amount to the block before hydrogenation. It is also possible to obtain a copolymer.

  The block copolymer (a) is obtained by hydrogenating unsaturated double bonds derived from butadiene in the polymer block containing butadiene during the block copolymer obtained above. The hydrogenation method is not particularly limited, and is performed using a known technique. After completion of the hydrogenation, the obtained solution of the hydrogenated thermoplastic elastomer (a) is separated from the polymerization solvent by, for example, steam stripping, and then dried to dry the block copolymer containing alkylene units ( a) is obtained.

  In addition, an arbitrary antioxidant may be added to the block copolymer (a) containing an alkylene unit as desired. Examples of the antioxidant include 2,4-bis (n-octylthiomethyl) -O-cresol, 2,4-bis (n-dodecylthiomethyl) -O-cresol, 2,4-bis (phenylthio). Methyl) -3-methyl-6-tert-butylphenol, n-octadecyl-3- (3 ′, 5′di-tert-butyl-4′-hydroxyphenyl) propionate, 2,2′-methylenebis (4-ethyl- 6-tert-butylphenol), tetrakis- [methylene-3- (3 ′, 5′-di-tert-butyl-4′-hydroxyphenyl) propionate] -methane, 1,3,5-trimethyl-2,4 6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, 2,6-di-tert-butyl-4-methylphenol, 2 6-di-tert-butyl-4-ethylphenol, 2-tert-butyl-6- (3-tert-butyl-2-hydroxy-5-methylbenzyl) -4-methylphenyl acrylate, 2,4-di- tert-amyl-6- [1- (3,5-di-tert-amyl-2-hydroxyphenyl) ethyl] phenyl acrylate, 2- [1- (2-hydroxy-3,5-di-tert-pentylphenyl) ) -Ethyl] -4,6-di-tert-pentylphenyl acrylate, 3,9-bis [2- [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) -propionyloxy] -1 , 1-dimethylethyl] -2,4,8,10-tetraoxaspiro [5,5] undecane, etc., hindered phenol compounds, pentaeryst Ru-tetrakis- (β-lauryl-thio-propionate), dilauryl-3,3′-thiodipropionate, dimyristyl-3,3′-thiodipropionate, distearyl-3,3′-thiodipropionate And phosphorus compounds such as tris (nonylphenyl) phosphite, cyclic neopentanetetraylbis (octadecyl phosphite), tris (2,4-di-tert-butylphenyl) phosphite It is done. These can be used alone or in admixture of two or more. Although these addition amounts are arbitrary, they are 3 mass parts or less with respect to 100 mass parts of block copolymers (a).

[Block copolymer (b)]
Preferable examples of the block copolymer (b) include a polymer block containing a vinyl aromatic hydrocarbon (more preferably mainly) and a polymer block containing isoprene (more preferably mainly). The block copolymer containing is mentioned.
The block copolymer (b) is substantially non-hydrogenated. Here, “substantially non-hydrogenated” means that the amount of alkylene units by hydrogenation of the block copolymer (b) is 5 wt% or less in the block copolymer (b). 3 wt% or less is more preferable, and 1 wt% or less is more preferable.

The vinyl aromatic hydrocarbon content in the block copolymer (b) is preferably 12 wt% or more from the viewpoint of the high cold flow resistance of the photosensitive resin component. On the other hand, 30 wt% or less is preferable from the viewpoint of high scratch resistance of the character portion of the printing plate. A range of 12 wt% to 25 wt% is more preferable.
The example of a vinyl aromatic hydrocarbon is the same as the example of the block copolymer (a) containing said alkylene unit.
The number average molecular weight of the block copolymer (b) is preferably 80,000 or more from the viewpoint of the high cold flow resistance of the photosensitive resin component. 350,000 or less is preferable at the point of the high moldability of the photosensitive resin composition. The range of 150,000 to 350,000 is more preferable. Furthermore, a molecular weight range of 200,000 to 350,000 having a branched structure is more preferable.

[Photopolymerizable monomer (c)]
Examples of the photopolymerizable monomer (c) include esters such as acrylic acid, methacrylic acid, fumaric acid and maleic acid, derivatives of acrylamide and methacrylamide, allyl esters, styrene and derivatives thereof, and N-substituted maleimide compounds.
Specific examples include diacrylates and dimethacrylates of alkanediols such as hexanediol and nonanediol, or diacrylates and dimethacrylates of ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, polyethylene glycol, butylene glycol, and trimethylol. Propane tri (meth) acrylate, dimethylol tricyclodecane di (meth) acrylate, isobornyl (meth) acrylate, phenoxypolyethylene glycol (meth) acrylate, pentaerythritol tetra (meth) acrylate, N, N'-hexamethylenebisacrylamide And methacrylamide, styrene, vinyl toluene, divinyl benzene, diacryl phthalate, triallyl cyanu Rate, diethyl fumarate, dibutyl fumarate, dioctyl fumarate, distearyl fumarate, butyl octyl fumarate, diphenyl fumarate, dibenzyl ester fumarate, dibutyl maleate, dioctyl maleate, Examples thereof include bis (3-phenylpropyl) fumarate, dilauryl fumarate, dibehenyl fumarate, N-lauryl maleimide, and the like. These may be used alone or in combination of two or more.

The content of the photopolymerizable monomer (c) in the photosensitive resin composition is 1 wt% or more from the viewpoint of high scratch resistance of the character part of the printing plate, and high cold flow resistance and printing of the photosensitive resin composition. 20 wt% or less is preferable from the viewpoint of high flexibility of the plate. The range of 2 wt% to 15 wt% is more preferable, and the range of 4 wt% to 12 wt% is more preferable.
From the viewpoint of even higher scratch resistance of the character part of the printing plate, it is preferable to contain 2 wt% or more of a monomer having 2 moles of metacleat group per molecule in the resin composition.

[Photoinitiator (d)]
The photopolymerization initiator (d) is a compound that absorbs light energy and generates radicals, and various known compounds can be used, and various organic carbonyl compounds, particularly aromatic carbonyl compounds are preferred. It is.
Specific examples include thioxanthones such as benzophenone, 4,4-bis (diethylamino) benzophenone, t-butylanthraquinone, 2-ethylanthraquinone, 2,4-diethylthioxanthone, isopropylthioxanthone, and 2,4-dichlorothioxanthone; Ethoxyacetophenone, 2,2-methoxy-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethyl ketal, 1-hydroxycyclohexyl-phenylketone, 2-methyl-2-morpholino (4 Acetophenones such as -thiomethylphenyl) propan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone; benzoin methyl ether, benzoin ethyl ether, ben Benzoin ethers such as zoin isopropyl ether and benzoin isobutyl ether; 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, bis (2 Acylphosphine oxides such as 1,4,6-trimethylbenzoyl) -phenylphosphine oxide; methylbenzoylformate; 1,7-bisacridinylheptane; 9-phenylacridine; These may be used alone or in combination of two or more.

If the content of the photopolymerization initiator (d) is too low, the formation of fine spots and characters will be reduced, and if it is too high, the transmittance of active light such as ultraviolet rays will be reduced, so in the photosensitive resin composition A range of 0.1 wt% to 10 wt% is preferable. The range of 0.5 wt% to 5 wt% is more preferable.
A decay type photopolymerization initiator and a hydrogen abstraction type photopolymerization initiator may be used in combination. In view of high image reproducibility of the printing plate and high abrasion resistance, the amount of the hydrogen drawing type photopolymerization initiator in the photosensitive resin composition is preferably 1.0 wt% or less. 0.5 wt% or less is more preferable.

[Photosensitive resin composition]
In addition to the essential components described above, the photosensitive resin composition of the present invention includes various auxiliary additives such as plasticizers, thermal polymerization inhibitors, ultraviolet absorbers, antihalation agents, light stabilizers, photoluminescence tags ( A substance that is excited by an external energy source and emits the obtained energy in the form of light and / or radiation) can be added.
Examples of the plasticizer include hydrocarbon oils such as naphthenic oil and paraffin oil; conjugated diene rubber mainly composed of liquid diene such as liquid acrylonitrile-butadiene copolymer and liquid styrene-butadiene copolymer; polystyrene having a number average molecular weight of 2000 or less. , Sebacic acid ester, phthalic acid ester and the like. These may be provided with a photopolymerizable reactive group.
Among these, from the viewpoint of high flexibility of the printing plate and high image reproducibility, a conjugated diene rubber mainly having a viscosity of 2000 Pa · s or less, that is, a liquid diene at 30 ° C. is preferable. Here, the viscosity can be measured according to JIS-K-7117.

The diene is preferably isoprene and / or butadiene from the viewpoint of availability, and butadiene is more preferable from the viewpoint of anti-caking property.
Two or more kinds of conjugated diene rubbers mainly composed of a diene having a viscosity of 2000 Pa · s or less at 30 ° C. may be used in combination.
The vinyl content in the total amount of diene contained in at least one kind of conjugated diene rubber is preferably 40 mol% or more from the viewpoint of high formability of minute images and high anti-caking property. 60 mol% or more is more preferable, and 80 mol% or more is more preferable. The vinyl content in the conjugated diene rubber can be determined from the aforementioned 1H-NMR (nuclear magnetic resonance spectrum).

In the total amount of conjugated diene rubber having a viscosity of 2000 Pa · s or less at 30 ° C. contained in the photosensitive resin composition, the vinyl content relative to the amount of diene is the ability to form minute images and the high scratch resistance of the text on the printing plate. Or 40 mol% or more is preferable because of high ink resistance. 60 mol% or more is more preferable, and 70 mol% or more is further more preferable.
The number average molecular weight (Mn) in the conjugated diene rubber is preferably lower in terms of handleability and the compatibility of the photosensitive resin composition, while it is preferably higher in terms of anti-scratch property, and ranges from 1000 to 50000. Is good. The range of 2000-30000 is more preferable, and the range of 3000-20000 is more preferable.

[Photosensitive resin composition for flexographic printing]
The photosensitive resin constituent for flexographic printing of the present invention comprises a support and a layer of the above-mentioned photosensitive resin composition, and as a preferred embodiment, a support layer, at least one photosensitive resin layer, a slip layer or a red layer. It includes a photosensitive resin composition for flexographic printing comprising an ultraviolet shielding layer or the like that can be excised with an external laser.
Examples of the support include polypropylene films, polyethylene films, polyester films such as polyethylene terephthalate and polyethylene naphthalate, and polyamide films. A dimensionally stable polyester film having a thickness in the range of 75 to 300 μm is preferred. It is preferable to have an adhesive layer on the support. Examples of the adhesive layer include a composition having a binder polymer such as polyurethane, polyamide or thermoplastic elastomer and an adhesive active component such as an isocyanate compound or an ethylenically unsaturated compound. Furthermore, various auxiliary additive components such as plasticizers, thermal polymerization inhibitors, ultraviolet absorbers, antihalation agents, light stabilizers, photopolymerization initiators, photopolymerizable monomers, dyes and the like are added to the adhesive layer. I can do it. In order to obtain a higher adhesive force between the adhesive layer and the polyester film as the support, it is more preferable to provide at least one undercoat layer.

  Since the photosensitive resin composition usually has adhesiveness, a solvent is applied to the surface of the resin layer in order to improve the contact property with the negative film overlaid at the time of plate making or to enable reuse of the negative film. A soluble thin flexible protective layer may be provided. The protective layer must be made of a substance soluble in a solvent used as a washing solution, for example, and should be thin and flexible. Examples of this include crystalline 1,2-polybutadiene, soluble polyamide, partially saponified polyvinyl acetate, cellulose ester, and the like. Of these, soluble polyamide is preferred. These substances can be dissolved in a suitable solvent and the solution can be coated directly on the surface of the photosensitive resin layer, or once coated on a film of polyester, polypropylene, etc. and then laminated together with this film on the photosensitive resin layer. It may be transferred.

  In addition, the flexible protective layer may be an ultraviolet shielding layer containing an infrared sensitive substance, and the flexible layer itself may be used as a negative by direct excision with an infrared laser (hereinafter referred to as laser drawing). In any case, when the unexposed portion is washed out after the exposure is completed, the thin flexible protective layer is removed at the same time. The ultraviolet shielding layer is composed of a binder polymer, an infrared sensitive material, and a non-infrared radiation shielding material. Examples of the binder polymer include polyamide, polyester, and a copolymer composed of monovinyl substituted aromatic hydrocarbon and conjugated diene. Among these, a copolymer composed of a monovinyl-substituted aromatic hydrocarbon such as styrene, α-methylstyrene, or vinyl toluene and a conjugated diene such as 1,3-butadiene or isoprene is preferable. When a non-infrared radiation shielding layer is formed using these binder polymers, the affinity with the photosensitive composition resin is high and the adhesion is good.

  Moreover, when using polyester as a binder polymer, it is preferable that it is a number average molecular weights 300-10,000. Examples of particularly preferred polyesters include those synthesized from alkanediol and adipic acid, those synthesized from alkanediol and phthalic acid, polycaprolactone, or a combination of two or more of these polyesters. it can. The polyester may contain various functional groups such as an amino group, a nitro group, a sulfonic acid group, and a halogen as long as the compatibility with the binder polymer is not impaired.

  As the infrared sensitive substance, a simple substance or a compound having strong absorption in the range of 750 to 2000 nm is usually used. Examples of such include inorganic pigments such as carbon black, graphite, copper chromite and chromium oxide, and dyes such as polyphthalocyanine compounds, cyanine dyes and metal thiolate dyes. These infrared absorbing substances are added within a range that provides sensitivity that can be removed by the laser beam used. In general, the addition of 10 to 80% by mass is effective. As the non-infrared radiation shielding substance, a substance that reflects or absorbs radiation such as ultraviolet rays can be used. Radiation absorbers such as ultraviolet rays, carbon black, graphite and the like are good examples, and the addition amount is set so that a required optical density can be achieved. In general, it is necessary to add an optical density of 2 or more, preferably 3 or more.

An infrared laser having a wavelength of 750 to 2000 nm can be used. As this type of infrared laser, a 750-880 nm semiconductor laser and a 1060 nm Nd-YAG laser are generally used.
The photosensitive resin composition for flexographic printing plates of the present invention can be prepared by various methods. For example, the following method is mentioned. First, the raw material of the photosensitive resin composition is dissolved and mixed in a suitable solvent such as chloroform, tetrachloroethylene, methyl ethyl ketone, toluene, etc., and cast into a mold to evaporate the solvent. Can be made. Further, it can be molded to a desired thickness by a calender roll or a press after kneading with a kneader, roll mill or screw extruder without using a solvent, but the present invention is not limited to these adjustment methods. .

  When a protective layer or an ultraviolet shielding layer is to be provided on the surface of the photosensitive resin layer, it is dispersed or dissolved in a suitable solvent by forced stirring with a stirring blade or ultrasonic stirring, It may be pre-kneaded using a drier and then dispersed or dissolved in a suitable solvent, and then the dispersion or solution may be directly coated on the photosensitive resin layer. Further, a cover sheet made of polyester, polypropylene or the like may be provided on the protective layer or the ultraviolet shielding layer. Alternatively, the cover sheet may be coated with a solution of a protective layer or an ultraviolet shielding layer to form a protective film, and then the protective film may be laminated or press-bonded to the photosensitive layer to transfer the protective film.

The protective film and the support are usually adhered to the photosensitive resin composition by roll lamination after forming the sheet of the photosensitive resin composition, and a photosensitive resin layer with higher thickness accuracy can be obtained by heating and pressing after lamination.
In order to make a flexographic printing plate from a photosensitive resin composition for a flexographic printing plate, the following method is generally used. First, the entire surface is exposed to ultraviolet light through the support (back exposure), the photosensitive resin composition is cured to provide a thin uniform cured layer, and then provided through a negative film or on the photosensitive resin composition layer. After the ultraviolet shielding layer is laser-drawn, image exposure (relief exposure) is performed directly on the surface of the photosensitive resin layer from above the ultraviolet shielding layer. Then, the unexposed portion is washed away with a developing solvent, or the unexposed portion heated to 40 ° C. to 200 ° C. is brought into contact with the absorbing layer, and the absorbing layer is removed to remove the unexposed portion. Thereafter, it is manufactured by post-processing exposure.

Either the exposure from the negative film side or the ultraviolet shielding layer side (relief exposure) or the exposure from the support side (back exposure) may be performed first, or both may be performed simultaneously.
Examples of the exposure light source include a high-pressure mercury lamp, an ultraviolet fluorescent lamp, a carbon arc lamp, and a xenon lamp.
Developer solvents used for solvent development of unexposed areas include esters such as heptyl acetate and 3-methoxybutyl acetate; hydrocarbons such as petroleum fractions, toluene and decalin; and chlorine-based solvents such as tetrachloroethylene What mixed alcohols, such as a propanol, a butanol, and a pentanol, into the organic solvent can be mention | raise | lifted.

The unexposed portion is washed out by spraying from a nozzle or brushing with a brush.
Examples of the heat-development absorbing layer include non-woven materials, paper materials, fiber fabrics, open cell foams, and porous materials. Preferred absorbent layers are nonwoven materials made of nylon, polyester, polypropylene, polyethylene, and combinations of these nonwoven materials. A particularly preferred absorbent layer is a nonwoven continuous web of nylon or polyester.
As post-processing exposure, a method of irradiating the surface with light having a wavelength of 300 nm or less is common. If necessary, light larger than 300 nm may be used in combination.

A flexographic printing plate comes into contact with a printing medium on a printing machine during printing, but if the printing plate is too soft, a fine printed matter cannot be obtained due to deformation due to compression, and if it is too hard, a printed matter having a uniform solid surface is obtained. Since it is difficult to obtain, the Shore A hardness of the printing plate having a thickness of 2.5 mm is preferably in the range of 50 ° to 68 °.
This hardness can be achieved, for example, by adjusting the amount of the block copolymer (a), the photopolymerizable monomer (c), or a plasticizer as necessary.
The resin composition of the present invention is useful for both solvent development and thermal development, but can be suitably used for solvent development, particularly from the viewpoint of high image reproducibility of a printing plate.

Hereinafter, the present invention will be described more specifically with reference examples, examples, and comparative examples, but the present invention is not limited to these examples. The measurement methods and evaluation methods used in Reference Examples, Examples and Comparative Examples are as follows.
(1) Measuring method (1-1) Number average molecular weight (Mn)
The number average molecular weight (Mn) is a polystyrene equivalent molecular weight measured by gel permeation chromatography (GPC). LC-10 (manufactured by Shimadzu Corporation, trademark) is used for the apparatus, two TSKgelGMHXL (4.6 mm ID × 30 cm) are used for the column, the oven temperature is 40 ° C., and the solvent is tetrahydrofuran (1.0 ml / min). went.

(2) Evaluation method (2-1) Transparency of photosensitive resin composition A photosensitive resin composition is sandwiched between 100 μm polyester films, and a pressure of 200 kg / cm ² is used at 130 ° C. with a press using a spacer. For 4 minutes, a 3 mm-thick structure was prepared, and turbidity (haze) was measured using a visible light haze meter (Model 1001DP, trademark, manufactured by Nippon Denshoku Industries Co., Ltd.). Smaller turbidity is preferred for excellent print quality. A turbidity of 20% or less was rated as ◯, a turbidity exceeding 20% was bad and marked as x.
(2-2) Resistance to ester solvent of flexographic printing plate-swelling thickness change A solid portion of the printing plate was cut into 5 cm x 3 cm and immersed in a mixed solution of 20 wt% ethyl acetate / 80 wt% isopropyl alcohol. The thickness before immersion and the change in thickness (mm) after immersion for 6 hours were measured. The smaller the change in thickness, the higher the ester solvent resistance. The swelling thickness change is preferably 0.07 mm or less.

(2-3) Ozone resistance of flexographic printing plates Simulates cracks (ozone durability of printing plates) generated in printing plates by ozone generated by corona discharge treatment during film printing and ozone generated by UV flexographic printing. Therefore, an ozone exposure test was performed in a state where the resin plate excluding the support from the printing plate was pulled, and the crack generation time was measured and evaluated.
In addition, the sample for this evaluation was created with the following method. A photosensitive resin composition for flexographic printing having a thickness of 2.5 mm was prepared by the same method as shown in the following examples except that a polyester film not coated with an adhesive was used as the support. The solid part of the obtained resin plate was cut into a size of 2 cm × 15 cm to obtain a sample. Using an ozone weather meter OMS-HVCR (trademark, manufactured by Suga Test Instruments Co., Ltd.), the sample was stretched 15% in an atmosphere of a measurement temperature of 40 ° C. and an ozone concentration of 75 pphm. Observed visually. The time when the crack was visually confirmed was determined as the crack occurrence time.
A longer crack generation time is better, and a case in which no cracks are generated for 3 hours or more was considered acceptable.

(2-4) Scratch resistance As shown in Fig. 1 (viewed from above), the resistance to scratching of a printing plate is simulated, using a part with characters of 2 to 8 points in size. Then, using a NP-type printing durability tester (trade name, contactor: cloth, 8 cm × 6 cm, load 1 kg, manufactured by Shinmura Printing Co., Ltd.), observe the degree of destruction of the characters with a microscope 50 times when rubbed left and right did. If the 4 point character is not destroyed, ◎ If the 4 point character is destroyed, but if the 6 point character is not destroyed, it is marked as ◯. If the 6 point character is destroyed, the problem is x. did.

(2-5) Printing evaluation—Suppression of edge blurring In flexographic printing, when printing a concave line (white line) portion of a printing plate, a white line is formed near the white line, unlike a pattern on the printing plate. There is a problem that a line (edge blur) with a low ink density appears in parallel. Of course, it is preferable that no end scraping occurs.
Evaluation of edge blurring suppression performance was performed with a 500 μm wide concave (outlined) line on the printing plate, visually observed on the printed matter, ◎ indicates that it did not occur, and ○ indicates that a very small amount occurred. Badly generated was marked with x.
“Process X cyan” (trademark, manufactured by Toyo Ink Manufacturing Co., Ltd.) was used as the solvent ink, and an OPP film was used as the substrate. The anilox roll was 800 lpi (cell volume 3.8 cm ³ / m ² ), the cushion tape was “3M1020” (trademark, manufactured by Sumitomo 3M Limited), and the printing speed was 100 m / min.

[Reference example]
(1) Block copolymer (a)
(1-1) Block copolymers (a) -1 and (a) -2
A 10 L stainless steel reactor equipped with a jacket and a stirrer was sufficiently purged with nitrogen, and then charged with 7000 cc of cyclohexane, 1 g of tetrahydrofuran, 3.7 g of N, N, N ′, N′-tetramethylethylenediamine and 170 g of styrene, and warm water was added to the jacket. Water was passed through and the contents were set to about 70 ° C. Thereafter, an n-butyllithium cyclohexane solution (1.15 g in pure content) was added to initiate styrene polymerization. After styrene is completely polymerized, 830 g of butadiene (1,3-butadiene) is added to continue the polymerization. After the polymerization of butadiene is completely completed, 0.83 g of tetramethoxysilane is added to perform a coupling reaction. I let you. A part of the obtained block copolymer solution was sampled, and then the solvent was removed by heating. The obtained block copolymer had a styrene content of 17 wt% and a 1,2-butadiene ratio in the polyptadiene part of 57 mol%. The styrene content was measured using ultraviolet spectroscopy (UV). The 1,2-butadiene ratio was measured using a nuclear magnetic resonance apparatus (1H-NMR).

Next, using the remaining block copolymer solution, butadiene was hydrogenated at a temperature of 70 ° C. using biscyclopentadiphenyltitanium chloride and n-butyllithium as a hydrogenation catalyst. The hydrogenation rate was controlled by measuring the amount of hydrogen gas supplied with a flow meter and stopping the gas supply when the target hydrogenation rate was achieved. Thereafter, 10 g of water was added, and after stirring, 3.0 g of n-octadecyl-3- (3 ′, 5′di-tert-butyl-4′-hydroxyphenyl) propionate, 2,4-bis (n-octyl) 1.5 g of (thiomethyl) -O-cresol was added, and the resulting solution was subjected to steam stripping to remove the solvent and obtain a hydrous crumb. Subsequently, it contains a block copolymer (a) -1 having a branched structure containing an alkylene unit which is dehydrated and dried by a hot roll and hydrogenated 10 mol% of a double bond of butadiene, and an alkylene unit hydrogenated of 23 mol%. A sample of block copolymer (a) -2 having a branched structure was obtained. The ratios of the alkylene units in the block copolymers (a) -1 and (a) -2 were 8 wt% and 19 wt%, respectively. Moreover, the alkylene unit in the polymer block (A) containing a butadiene unit and an alkylene unit was 10 wt% and 23 wt%, respectively. The hydrogenation rate (the ratio of alkylene units) was confirmed using a nuclear magnetic resonance apparatus (1H-NMR).
The amount of styrene- (butadiene / alkylene) diblock body was 22 wt% in the block copolymer for both (a) -1 and (a) -2. The number average molecular weight of the block copolymer excluding the styrene- (butadiene / alkylene) diblock was 280,000 for both (a) -1 and (a) -2.

(1-2) Block copolymer (a) -3
A 10 L stainless steel reactor equipped with a jacket and a stirrer was sufficiently purged with nitrogen, and then charged with 7000 cc of cyclohexane, 1 g of tetrahydrofuran, 0.8 g of N, N, N ′, N′-tetramethylethylenediamine, and 80 g of styrene, and warm water was added to the jacket. Water was passed through and the contents were set to about 70 ° C. Thereafter, an n-butyllithium cyclohexane solution (0.57 g in pure content) was added to initiate styrene polymerization. After the styrene was completely polymerized, 840 g of butadiene (1,3-butadiene) was added to continue the polymerization. After the polymerization of butadiene was completely completed, 80 g of styrene was added to continue the polymerization. A part of the obtained block copolymer solution was sampled, and then the solvent was removed by heating. The obtained block copolymer had a styrene content of 16 wt% and a 1,2-butadiene ratio in the polybutadiene portion of 50 mol%. The styrene content was measured using ultraviolet spectroscopy (UV). The 1,2-butadiene ratio was measured using a nuclear magnetic resonance apparatus (1H-NMR).

  Next, using the remaining block copolymer solution, butadiene was hydrogenated at a temperature of 70 ° C. using biscyclopentadiphenyltitanium chloride and n-butyllithium as a hydrogenation catalyst. The hydrogenation rate was controlled by measuring the amount of hydrogen gas supplied with a flow meter and stopping the gas supply when the target hydrogenation rate was achieved. Thereafter, 10 g of water was added, and after stirring, 3.0 g of n-octadecyl-3- (3 ′, 5′di-tert-butyl-4′-hydroxyphenyl) propionate, 2,4-bis (n-octyl) 1.5 g of (thiomethyl) -O-cresol was added, and the resulting solution was subjected to steam stripping to remove the solvent and obtain a hydrous crumb. Subsequently, the sample was dehydrated and dried with a hot roll to obtain a sample of a block copolymer (a) -3 having a linear molecular structure containing alkylene units in which 48 mol% of double bonds of butadiene were hydrogenated. The ratio of alkylene units in the block copolymer (a) -3 was 40 wt%. Moreover, the alkylene unit in the polymer block (A) containing a butadiene unit and an alkylene unit was 47 wt%. The hydrogenation rate (the ratio of alkylene units) was confirmed using a nuclear magnetic resonance apparatus (1H-NMR). The number average molecular weight of the obtained block copolymer (a) -3 was 190,000.

(1-3) Block copolymer (a) -4, (a) -5
As the block copolymer (a) -4, “G1726” (trademark, manufactured by KRATON, which is a linear styrene-ethylene / butylene-styrene block copolymer having a molecular structure, the amount of alkylene units in the block copolymer is 70 wt%) was used.
As block copolymer (a) -5, “Septon 1001” which is a linear styrene-ethylene / propylene block copolymer having a molecular structure (manufactured by Kuraray Co., Ltd., trademark, amount of alkylene units in block copolymer) Was 65 wt%).

(1-4) Block copolymer (b)
Block copolymer (b) -1: “D-1107” which is a linear styrene-isoprene block copolymer having a molecular structure (manufactured by KRATON, trademark, isoprene content in the block copolymer is 85 wt%)
Block copolymer (b) -2: “SL-128” which is a styrene-isoprene block copolymer having a branched molecular structure (manufactured by ZEON CORPORATION, trademark, the amount of isoprene in the block copolymer is 86 wt% )
Block copolymer (b) -3: “HIBLER 5125” which is a styrene-isoprene block copolymer (manufactured by Kuraray Co., Ltd., trademark, isoprene content in the block copolymer is 80 wt%)
Block copolymer (b) -4: “KX405” which is a styrene-butadiene block copolymer having a linear molecular structure (manufactured by KRATON, trademark, butadiene content in the block copolymer is 76 wt%)

[Examples 1 to 10 and Comparative Examples 1 to 6]
(1) Preparation of photosensitive resin composition Each component shown in Tables 1 to 3 was mixed at 140 ° C for 40 minutes with a kneader in which the internal atmosphere was replaced with nitrogen to obtain a photosensitive resin composition. The evaluation results of transparency of the obtained photosensitive resin composition are shown in Tables 2-3.
(2) Creation of photosensitive resin structure Using the photosensitive resin compositions obtained in Examples 6 to 10 and Comparative Examples 3 to 6, a photosensitive resin structure was obtained by the following method. As a solution for the adhesive layer to be coated on the support, 55 parts by mass of “Tufrene 912” (trade name, manufactured by Asahi Kasei Chemicals Co., Ltd.), which is a block copolymer of styrene and 1,3-butadiene, paraffin oil (average Carbon number 33, average molecular weight 470, density 0.868 at 15 ° C.) 38 parts by mass, 1,9-nonanediol diacrylate 2.5 parts by mass, 2,2-dimethoxy-phenylacetophenone 1.5 parts by mass The epoxy ester 3000M (trade name, manufactured by Kyoeisha Chemical Co., Ltd.) was dissolved in toluene at a ratio of 3 parts by mass to obtain a solution having a solid content of 25%. Then, using a knife coater, the 100 μm thick polyester film was formed on one side. , the coating amount after drying was such that such that 10-14g / m ^2, and dried for 1 minute at 80 ° C., the adhesive layer To obtain a support that.
As a protective film, a polyamide resin “Macromelt 6900” (trademark, manufactured by Henkel Japan Co., Ltd.) was dissolved in a mixed solvent prepared with a mass ratio of toluene / isopropyl alcohol = 50/50 using ultrasonic waves, After preparing a uniform solution having a solid content of 12 wt%, a knife coater was applied on the polyester film to be a cover sheet having a thickness of 100 μm so that the coating amount after drying was 4-5 g / m ^2. Obtained by drying at 80 ° C. for 1 minute.
The photosensitive resin composition was sandwiched between the surface coated with the adhesive surface of the obtained support and the surface coated with the polyamide layer of the protective film, and then heated using a 3 mm spacer. A pressure of 200 kg / cm ² was applied for 4 minutes at 130 ° C. with a machine, and then cooled to obtain a photosensitive resin structure 25 cm long × 25 cm wide × 3 mm thick.

(3) Preparation of flexographic printing plate The cover sheet of the photosensitive resin composition for flexographic printing plate of (2) is peeled off, and a negative film is adhered to the polyamide protective film layer on the photosensitive resin layer. The polyamide layer is placed on the glass plate of an “AFP-1500” exposure machine (trade name, manufactured by Asahi Kasei Chemicals Corporation), and the relief depth is first determined from the support side using an ultraviolet fluorescent lamp having a central wavelength of 370 nm. After performing the whole surface exposure of 200 mJ to 500 mJ / cm ² so that the thickness becomes 0.85 mm, an image (relief) exposure of 6000 mJ / cm ^{2 was} continuously performed through the negative film. The image of the negative film is 1%, 2%, 3%, 5%, 10%, 30%, 50%, 60%, 70%, 80%, 90%, 95% 100% (hereinafter referred to as “solid”) halftone dots, 500 μm wide concave / convex lines, and characters containing 2 to 8 points in size as shown in FIG. 1 were used.

The exposure intensity at this time was measured by measuring UV rays from the lower lamp on the side of the back exposure using a UV-35 filter with a UV illuminance meter MO-2 manufactured by Oak Manufacturing Co., Ltd. The intensity | strength which measured the ultraviolet-ray from the upper lamp | ramp which is 10.3 mW / cm < ² > and a relief exposure side was 12.5 mW / cm < ² >.
Next, using 3-methoxybutyl acetate as a developer, the structure was attached to a cylinder of an “AFP-1500” developing machine (trademark, manufactured by Asahi Kasei Chemicals Corporation) with a double-sided tape, and the liquid temperature was 25 ° C. for 5 minutes. Development was carried out and the film was dried at 60 ° C. for 2 hours. Thereafter, as post-processing exposure, the entire plate surface is exposed at 2000 mJ / cm ² using a germicidal lamp having a central wavelength of 254 nm, and subsequently exposed to 1000 mJ / cm ² using an ultraviolet fluorescent lamp to be a flexographic printing plate. Got. Here, the post-exposure amount with the germicidal lamp is calculated from the illuminance measured using the UV-25 filter of the MO-2 type machine.
Table 3 shows the evaluation results of the obtained printing plate.

From Table 2, a block copolymer (a) containing an alkylene unit, a block copolymer containing a polymer block (b) mainly composed of non-hydrogenated isoprene, a photopolymerizable monomer (c) and photopolymerization start A photosensitive resin composition containing an agent (d), wherein the transparency of the photosensitive resin composition can be obtained only when the content of alkylene units in the block copolymer (a) is 50 wt% or less. I understand that.
From Table 3, a block copolymer (a) containing an alkylene unit, a block copolymer (b) containing a polymer block mainly composed of non-hydrogenated isoprene, a photopolymerizable monomer (c), and photopolymerization start A photosensitive resin composition containing an agent (d), wherein the alkylene unit in the block copolymer containing alkylene units is in the range of 5 to 50 wt%, and the block copolymer containing alkylene units / non-hydrogenated When the ratio of the block copolymer containing a polymer block mainly composed of isoprene is in the range of 0.5 to 10.0, the transparency of the photosensitive resin composition is high, and the ester solvent resistance of the printing plate is high. , High ozone resistance of printing plates, high scratch resistance of printing plate characters, and high suppression performance of edge scraping generated near white lines in printing.

  The present invention is suitably used in the field of a photosensitive resin composition suitably used as a flexographic printing plate and the like and a photosensitive resin composition for flexographic printing using the same.

Schematic which shows the evaluation method of the chipping resistance of the printing plate obtained by the Example and the comparative example

Explanation of symbols

1 Contact body / weight 2 Printing plate 3 Negative film

Claims (12)

  (A) a block copolymer containing alkylene units, (b) a substantially non-hydrogenated block copolymer containing a polymer block containing isoprene, (c) a photopolymerizable monomer and (d) a photopolymerization. An initiator is included, the alkylene unit in the block copolymer (a) is 5 to 45 wt%, and the mass ratio (a) / (b) of the block copolymer (a) to the block copolymer (b) Is photosensitive resin composition which is 0.5-10.   The photosensitive resin composition of Claim 1 whose alkylene unit in a block copolymer (a) is 10-30 wt%.   The block copolymer (a) includes a polymer block containing a vinyl aromatic hydrocarbon unit, a polymer block (A) containing a butadiene unit and an alkylene unit, and an alkylene unit in the polymer block (A). The photosensitive resin composition according to claim 1, wherein is 5 to 80 wt%.   The photosensitive resin composition of Claim 3 whose alkylene unit in a polymer block (A) is 5-55 wt%.   The block copolymer (a) is obtained by hydrogenating a block copolymer containing a polymer block mainly composed of vinyl aromatic hydrocarbon units and a polymer block mainly composed of butadiene. The photosensitive resin composition as described in any one.   The block copolymer (a) is a block copolymer comprising a polymer block mainly composed of vinyl aromatic hydrocarbons and a polymer block mainly composed of butadiene having a 1,2-butadiene ratio of 20 to 80 mol%. The photosensitive resin composition of Claim 5 obtained by hydrogenation.   The photosensitive resin composition as described in any one of Claims 1-6 in which a block copolymer (b) contains the polymer block which has a vinyl aromatic hydrocarbon as a main component further.   Furthermore, the photosensitive resin composition as described in any one of Claims 1-7 containing the liquid conjugated diene rubber whose vinyl content in a diene is 40 mol% or more.   The photosensitive resin composition according to claim 8, wherein the photosensitive resin composition comprises at least one liquid conjugated diene rubber, and the vinyl content in the total amount of diene of the liquid conjugated diene rubber is 40 mol% or more.   The photosensitive resin composition as described in any one of Claims 1-9 which contains 2 wt% or more of monomers which have 2 mol of methacrylate groups per molecule as a photopolymerizable monomer (c).   The photosensitive resin structure for flexographic printing plates containing a support body and the layer of the photosensitive resin composition as described in any one of Claims 1-10.   The photosensitive resin composition for flexographic printing according to claim 11, wherein the photosensitive resin composition for flexographic printing has an ultraviolet shielding layer that can be excised with an infrared laser and contains an infrared sensitive substance on the photosensitive resin composition layer.

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