JP3451571B2 - Photosensitive composition and photosensitive rubber plate - Google Patents

Description

TECHNICAL FIELD The present invention relates to a photosensitive rubber plate and a photosensitive composition.
More specifically, it relates to a photosensitive rubber plate which is excellent in transparency and strength balance and has a high water washing speed after exposure, and a photosensitive composition for obtaining the same.

BACKGROUND OF THE INVENTIONFlexographic printing plates are produced by a method in which a negative film is adhered to a photosensitive plate surface, a portion of the photosensitive layer is exposed to active light, and then an unexposed portion is washed off to form a relief. It Further, as a cleaning solvent used for cleaning the unexposed portion, a conventional organic solvent is being changed to an aqueous solvent which is less likely to cause environmental pollution.

A material for a photosensitive layer of a photosensitive rubber plate such as a flexographic printing plate is excellent in transparency for light to reach a deep portion of an exposure layer, and has a good balance between adhesion to a printing material and strength of the plate itself ( Hereinafter, it may be referred to as "strength balance"), and a high water washing rate is required to facilitate the relief formation after exposure.

The photosensitive layer material, styrene-butadiene block copolymer, a thermoplastic elastomer such as styrene-isoprene block copolymer and a hydrophilic copolymer as a main component, to which a photopolymerizable ethylenically unsaturated monomer and A photosensitive elastomer composition containing a photopolymerization initiator is known.

However, the photosensitive rubber plate using this photosensitive elastomer composition is inferior in transparency, has poor strength balance, and has a low water washing speed after exposure.

DISCLOSURE OF THE INVENTION It is an object of the present invention to provide a photosensitive rubber plate excellent in transparency and strength balance and having a high water washing speed after exposure, and a photosensitive composition for obtaining the same.

The present inventors have conducted extensive studies in order to achieve the above object, and blended a hydrophilic copolymer and a styrene-butadiene-styrene type block copolymer having a large vinyl bond content in the conjugated diene monomer unit portion. It was found that the photosensitive rubber plate made of the photosensitive composition described above has excellent transparency and strength balance, and the water washing speed after exposure is fast, and based on this finding,
The present invention has been completed.

Thus, according to the present invention, at least one polymer block A consisting of a polymer having 95% by weight or more of an aromatic vinyl monomer as a structural unit and 20% by weight or more of a conjugated diene monomer as a structural unit. 20-65 parts by weight of a block copolymer having a vinyl bond content of the conjugated diene monomer unit portion of at least one polymer block B made of a conjugated diene-based polymer having a vinyl bond content of 15 to 70%, Hydrophilic copolymer 35 to 80 parts by weight (however, the total amount of block copolymer and hydrophilic copolymer is 100 parts by weight), photopolymerizable ethylenically unsaturated monomer 5 to 300 parts by weight Parts and 0.1 to 10 parts by weight of a photopolymerization initiator are provided.

Further, according to the present invention, there is provided a photosensitive rubber plate having a laminated structure including a support and a layer of the photosensitive composition formed on the main surface thereof.

BEST MODE FOR CARRYING OUT THE INVENTION   Hereinafter, the present invention will be described in detail.

The photosensitive composition of the present invention contains a block copolymer, a hydrophilic copolymer, a photopolymerizable ethylenically unsaturated monomer and a photopolymerization initiator.

The block copolymer, which is the first component of the photosensitive composition of the present invention, comprises a polymer block A composed of a polymer having an aromatic vinyl monomer as a main constituent unit, and a conjugated diene monomer as an essential constituent unit. And a polymer block B composed of a conjugated diene-based polymer in which the vinyl bond content of the conjugated diene monomer unit portion is 15 to 70%.

The polymer block A constituting the block copolymer is made of a polymer having an aromatic vinyl monomer as a main constituent unit.

Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene,
p-methylstyrene, p-tert-butylstyrene, 1,3
-Dimethylstyrene, vinyltoluene, chlorostyrene, vinylnaphthalene, vinylanthracene and the like. Of these aromatic vinyl monomers, styrene is preferred.

The amount of the aromatic vinyl monomer constituting the polymer block A is 95% by weight or more, preferably 99% by weight or more, based on all the monomer units constituting the polymer block A. Monomers other than the aromatic vinyl monomer that constitutes the polymer block A are not particularly limited.

The weight average molecular weight of the polymer block A is usually 3,000.
˜200,000, preferably 8,000 to 100,000. Also,
The glass transition temperature of the polymer block A is usually 25 ° C. or higher, preferably 50 ° C. or higher.

The polymer block B constituting the block copolymer is a polymer having a conjugated diene monomer as an essential constituent unit. That is, the polymer block B is a homopolymer of a conjugated diene monomer or a copolymer of a conjugated diene monomer and an ethylenically unsaturated monomer copolymerizable therewith.

The amount of the conjugated diene monomer constituting the polymer block B is 20% by weight or more, preferably 40% by weight or more, more preferably 70% by weight, based on all the monomer units constituting the polymer block B. That is all. If it is less than 20% by weight, the strength balance of the photosensitive rubber plate obtained by using the photosensitive composition is deteriorated.

Examples of the conjugated diene monomer include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene and chloroprene. Of these conjugated diene monomers, butadiene,
Isoprene is preferred.

Examples of the ethylenically unsaturated monomer copolymerizable with the conjugated diene monomer include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-tert-butylstyrene and 1,3-dimethylstyrene. , Vinyltoluene,
Aromatic vinyl monomers such as chlorostyrene, vinylnaphthalene, and vinylanthracene; methyl acrylate, ethyl acrylate, propyl acrylate, n-amyl acrylate, isoamyl acrylate, hexyl acrylate, ethylhexyl acrylate, octyl acrylate , Hydroxyethyl acrylate, hydroxypropyl acrylate,
Glycidyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-methacrylic acid
Ethylenically unsaturated carboxylic acid ester monomers such as amyl, isoamyl methacrylate, hexyl methacrylate, ethylhexyl methacrylate, octyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, glycidyl methacrylate; methacrylonitrile, acrylonitrile Vinyl cyanide monomers such as; ethylenically unsaturated glycidyl ethers such as allyl glycidyl ether; ethylenically unsaturated carboxylic acid amide monomers such as acrylamide and methacrylamide; vinyl halides such as vinyl chloride; vinyl acetate, etc. Carboxylic acid vinyl ester; ethylenically unsaturated monocarboxylic acid such as acrylic acid and methacrylic acid; ethylenically unsaturated polycarboxylic acid such as maleic acid, fumaric acid and citraconic acid; monoethyl maleate and italy Ethylene moieties esters of unsaturated polycarboxylic acids such as phosphate monomethyl the like. Of these ethylenically unsaturated monomers, aromatic vinyl monomers, especially styrene, are preferred.

The polymer block B is one in which the conjugated diene monomer unit portion of the polymer constituting the polymer block B has a vinyl bond content of 15 to 70%, preferably 25 to 55%. Vinyl bond content 15
If it is less than%, the transparency of the photosensitive rubber plate is lowered, the balance of strength is deteriorated, and the washing speed with water becomes slow. 70
If it exceeds%, the strength of the photosensitive rubber plate is lowered.

The vinyl bond content in the polymer block B is 1,2-
Among the conjugated diene monomers incorporated in the form of bond, 3,4-bond or 1,4-bond, 1,2-bond and 3,4-bond
Percentage of conjugated diene monomer incorporated in a bond-wise fashion. The vinyl bond content is a value measured using a nuclear magnetic resonance apparatus.

The weight average molecular weight of the polymer block B is usually 5,000.
˜500,000, preferably 10,000 to 300,000. The glass transition temperature of the polymer block B is 10 ° C. or lower, preferably 0.
It is below ℃.

The glass transition temperature is a value measured by TDC or the like of a polymer obtained by polymerizing a composition of monomers constituting the polymer block A or B alone.

The weight ratio of the polymer block A and the polymer block B is
Usually, (polymer block A / polymer block B =) 5/95 ~
95/5, preferably 10/90 to 90/10, more preferably 15/8
5 to 75/25.

The block copolymer has a total weight average molecular weight of
Usually, it is 8,000 to 2,000,000, preferably 18,00 to 1,000,000.

In the present invention, the weight average molecular weight is a value measured by gel permeation chromatography (hereinafter abbreviated as GPC) and converted into the molecular weight of standard polystyrene. The weight average molecular weight of the polymer block A or B is the polymer block A constituting the block copolymer.
Alternatively, the weight average molecular weight was measured after each formation of B, and it was determined from the increment of the weight average molecular weight between each step.

The block copolymer which is the first component of the photosensitive composition of the present invention is not limited by the combined structure of the polymer block A and the polymer block B, and may be, for example, a compound represented by the general formula (AB) _n −.
A, (A-B) _n -A-B, B- (A-B) _n -A-
B, (AB) _m- X, ((AB) _n- A) _m- X,
(B-A- (B-A) _n ) _m- X, (B-A- (B-
A) _n- B) _m- X (wherein A is a polymer block A, B is a polymer block B, X is a residue of a coupling agent or a polyfunctional ionic polymerization initiator, and n is 1 or more, preferably Is an integer of 1 to 5 and m is an integer of 2 or more, preferably 2 to 5. As the coupling agent, tin tetrachloride, silicon tetrachloride, epoxidized ester, polyvinyl compound, carboxylic acid ester, polyhalogenated carbonized. Such as hydrogen,
Examples of the polyfunctional ionic polymerization initiator include polyfunctional organic lithium compounds. ) Is included. Among these, those having a structure represented by the general formula ABA are preferable.

The block copolymer used in the present invention can be usually obtained by polymerizing the above-mentioned monomer using a polymerization initiator such as an organic lithium compound. Specifically, a monomer mixture containing an aromatic vinyl monomer as a main component is polymerized to form a polymer block A, and then a monomer mixture containing a conjugated diene monomer as an essential component is added. After polymerizing to form a polymer block B connected to the molecular end of the polymer block A, another polymer block A connected to the polymer block B by further adding an aromatic vinyl monomer and polymerizing the polymer block A is added. It can be obtained by a method of forming or forming the polymer block A and the polymer block B connected thereto as described above, and then adding a coupling agent.

The adjustment of the vinyl bond content of the polymer block B is not limited by that means. Usually, the amount or type of polar compound used in obtaining the polymer block B by polymerization,
It is carried out by controlling the polymerization temperature and the like.

The amount of the block copolymer in the photosensitive composition of the present invention is the total amount of the block copolymer and the hydrophilic copolymer described below.
Of 100 parts by weight, 20 to 65 parts by weight, preferably 25 to 55 parts by weight, and more preferably 30 to 45 parts by weight. If it exceeds 65 parts by weight, the rate of water washing of the photosensitive rubber plate obtained by using the photosensitive composition will be reduced. On the other hand, if it is less than 20 parts by weight, the processability of the photosensitive composition and the water-based ink resistance of the photosensitive rubber plate will decrease.

The hydrophilic copolymer, which is the second component of the photosensitive composition of the present invention, has a -OH group, -COOH as a pendant in its molecular chain.
Group, -CN group, -NH ₂ group, -SO ₃ H group, -SO ₂ H group, -PO (O
H) ₂ groups, hydrophilic groups such as -PO (OH)-groups, preferably -PO
Those having a phosphoric acid ester group such as (OH) ₂ group and -PO (OH)-group are bonded.

The hydrophilic copolymer is usually obtained by radical copolymerizing the ethylenically unsaturated monomer having the hydrophilic group and a monomer copolymerizable therewith.

Examples of the ethylenically unsaturated monomer having a hydrophilic group include ethylenically unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid; ethylenically unsaturated polycarboxylic acids such as maleic acid, fumaric acid, citraconic acid and itaconic acid. Partial esterification products of ethylenically unsaturated polyvalent carboxylic acids such as monoethyl maleate and monomethyl itaconate; hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate; methacrylonitrile, acrylonitrile, etc. Vinyl cyanide monomer; phosphoric acid ethylene acrylate, phosphoric acid trimethylene acrylate, phosphoric acid propylene acrylate, phosphoric acid tetramethylene acrylate, phosphoric acid (bis) ethylene acrylate, phosphoric acid (bis) trimethylene acrylate, phosphoric acid (bis Such as tetramethylene acrylate, diethylene glycol acrylate phosphate, triethylene glycol acrylate phosphate, polyethylene glycol acrylate phosphate, (bis) diethylene glycol acrylate phosphate, (bis) triethylene glycol acrylate phosphate, (bis) polyethylene glycol acrylate and their corresponding methacrylates Examples thereof include phosphoric acid ester group-containing ethylenically unsaturated monomers. Among these ethylenically unsaturated monomers having a hydrophilic group, phosphoric acid ester group-containing ethylenically unsaturated monomers, particularly phosphoric acid ethylene acrylate, phosphoric acid propylene acrylate, phosphoric acid (bis) ethylene acrylate, phosphoric acid (bis)
Propylene acrylate and the corresponding methacrylates are preferred.

The amount of the ethylenically unsaturated monomer having a hydrophilic group is usually 5 to 5 of all the monomers used for obtaining the hydrophilic copolymer.
30% by weight, preferably 5 to 20% by weight. 5% by weight
When the amount is less than 1, the washing speed of water of the photosensitive rubber plate obtained by using the photosensitive composition tends to decrease. If it exceeds 30% by weight, the processability of the photosensitive composition and the water-based ink resistance of the photosensitive rubber plate tend to decrease.

Examples of the monomer copolymerizable with the ethylenically unsaturated monomer having a hydrophilic group include styrene, o-methylstyrene, and m.
-Aromatic vinyl monomers such as methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, vinyltoluene, chlorostyrene, vinylnaphthalene, vinylanthracene, divinylbenzene and trivinylbenzene; Methyl acrylate, ethyl acrylate, propyl acrylate, n-amyl acrylate, isoamyl acrylate, hexyl acrylate, ethylhexyl acrylate, octyl acrylate, glycidyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, N-amyl methacrylate, isoamyl methacrylate, hexyl methacrylate, ethylhexyl methacrylate, octyl methacrylate, glycidyl methacrylate, ethylene glycol diacrylate, trimethylol propanate Ethylenically unsaturated carboxylic acid ester monomers such as reacrylate and propylene glycol diacrylate; Ethylenically unsaturated glycidyl ether such as allyl glycidyl ether; Conjugation of 1,3-butadiene, isoprene, chloroprene, 1,3-pentadiene, etc. Examples thereof include diene monomers.

Among these monomers copolymerizable with a monomer having a hydrophilic group, a conjugated diene monomer, particularly 1,3-butadiene or isoprene is preferable in order to improve the strength balance of the photosensitive rubber plate. Used. The amount of conjugated diene monomer is
Of all the monomers used to obtain the hydrophilic copolymer, usually,
It is 40 to 90% by weight, preferably 50 to 80% by weight. If it is less than 40% by weight, the strength of the photosensitive rubber plate is lowered. 90% by weight
If it exceeds the range, the speed of washing the photosensitive rubber plate with water decreases.

A polyfunctional ethylenically unsaturated monomer is preferably used in order to enhance the processability of the photosensitive composition and the transparency and strength of the photosensitive rubber plate. Ethylene glycol diacrylate as a polyfunctional ethylenically unsaturated monomer,
Examples thereof include acrylic acid esters of polyhydric alcohols such as trimethylolpropane triacrylate and propylene glycol diacrylate, and corresponding methacrylic acid esters; and polyfunctional aromatic vinyl monomers such as divinylbenzene and trivinylbenzene. Of these polyfunctional ethylenically unsaturated monomers, ethylene glycol dimethacrylate or divinylbenzene are preferred. The amount of polyfunctional ethylenically unsaturated monomer is usually 10% by weight or less based on the total monomers used for obtaining the hydrophilic copolymer.

The hydrophilic copolymer used in the photosensitive composition of the present invention has a number average molecular weight of usually 10,000 to 500, from the viewpoint of improving the processability of the photosensitive composition and the strength of the photosensitive rubber plate.
000, preferably 20,000 to 200,000. The number average molecular weight is a value measured by GPC and converted into the molecular weight of standard polystyrene.

Examples of the photopolymerizable ethylenically unsaturated monomer which is the third component of the photosensitive composition of the present invention include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene and p.
Aromatic vinyl monomers such as -tert-butylstyrene, 1,3-dimethylstyrene, vinyltoluene, chlorostyrene, vinylnaphthalene, vinylanthracene, divinylbenzene and trivinylbenzene; ethylenic vinyl monomers such as acrylonitrile and methacrylonitrile. Saturated nitrile monomer;
Methyl acrylate, ethyl acrylate, propyl acrylate, n-amyl acrylate, isoamyl acrylate,
Hexyl acrylate, ethylhexyl acrylate, octyl acrylate, glycidyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate,
N-amyl methacrylate, isoamyl methacrylate, hexyl methacrylate, ethylhexyl methacrylate, octyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, glycidyl methacrylate, ethylene glycol diacrylate , Trimethylolpropane triacrylate, 1,4-butanediol diacrylate, 1,4-butanediol dimethacrylate, propylene glycol diacrylate, 1,
6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, methoxyethylene glycol acrylate, methoxypropylene glycol methacrylate, methoxyethylene glycol methacrylate,
Ethylenically unsaturated carboxylic acid ester monomers such as methoxypropylene glycol acrylate, diethyl maleate and dimethyl itaconate; ethylenically unsaturated glycidyl ethers such as allyl glycidyl ether; 1,3-butadiene, isoprene, chloroprene, 1,3 -Conjugated diene monomers such as pentadiene; ethylenically unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid; ethylenically unsaturated polycarboxylic acids such as maleic acid, fumaric acid, citraconic acid and itaconic acid; monoethyl maleate , Partial esterification products of ethylenically unsaturated polycarboxylic acid such as monomethyl itaconate; phosphoric acid ethylene acrylate, phosphoric acid trimethylene acrylate, phosphoric acid propylene acrylate, phosphoric acid tetramethylene acrylate, phosphoric acid (bis) ethylene acrylate, phosphoric acid Su) trimethylene acrylate,
Phosphoric acid (bis) tetramethylene acrylate, phosphoric acid diethylene glycol acrylate, phosphoric acid triethylene glycol acrylate, phosphoric acid polyethylene glycol acrylate, phosphoric acid (bis) diethylene glycol acrylate, phosphoric acid (bis) triethylene glycol acrylate, phosphoric acid (bis) polyethylene glycol acrylate and their corresponding And a phosphoric acid ester group-containing ethylenically unsaturated monomer such as methacrylate. These photopolymerizable ethylenically unsaturated monomers can be used in appropriate combination. Among these photopolymerizable ethylenically unsaturated monomers, diacrylate or dimethacrylate is preferable.

The amount of the photopolymerizable ethylenically unsaturated monomer is 5 to 300 parts by weight, preferably 10 to 200 parts by weight, based on 100 parts by weight of the total amount of the block copolymer and the hydrophilic copolymer. .
If the amount is less than 5 parts by weight, curing of the photosensitive composition due to actinic light will be insufficient, resulting in a decrease in strength of the photosensitive rubber plate. vice versa
When it exceeds 300 parts by weight, the strength and solvent resistance of the photosensitive rubber plate are deteriorated.

The photopolymerization initiator which is the fourth component of the photosensitive composition of the present invention includes an α-diketone such as diacetyl and benzyl; an acyloin such as benzoin and pivaloin; an acylo such as benzoin methyl ether, benzoin ethyl ether and benzoin isopropyl ether. Inethers; polynuclear quinones such as anthraquinone and 1,4-naphthoquinone; and the like.

The amount of the photopolymerization initiator is 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the total amount of the block copolymer and the hydrophilic copolymer. If the amount is less than 0.1 parts by weight, curing of the photosensitive composition due to actinic light will be insufficient, resulting in a decrease in strength of the photosensitive rubber plate. On the other hand, if it exceeds 10 parts by weight, the photopolymerization rate decreases.

In the photosensitive composition of the present invention, the first to
In addition to the four components, a plasticizer; a storage stabilizer; an ozone resistance agent; a styrene-butadiene random copolymer, an acrylonitrile-butadiene random copolymer, a styrene-isoprene random copolymer, a methyl methacrylate-butadiene random copolymer. And the like; and homopolymers such as polybutadiene and polyisoprene;

A plasticizer is added to improve the plasticity of the photosensitive composition and uniformly mix and mold the first to fourth components. As a plasticizer, hydrocarbon oil such as naphthenic oil and paraffin oil; molecular weight
3000 or less polystyrene; polyacrylate; liquid 1,2
-Polybutadiene, liquid 1,4-polybutadiene and terminal modified products thereof; liquid acrylonitrile-butadiene copolymer, liquid styrene-butadiene copolymer and carboxylated products thereof.

Further, a storage stabilizer is added to enhance the storage stability of the photosensitive composition. Examples of storage stabilizers include phenols such as hydroquinone, pyrogallol, p-methoxyphenol, t-butylcatechol, 2,6-di-t-butyl-p-cresol and benzoquinone; quinones such as benzoquinone, p-toluquinone and p-xyloquinone. And amines such as phenyl-α-naphthylamine.

The photosensitive composition of the present invention is usually prepared by kneading using a kneader such as a kneader or a roll mill.

The order of kneading is not particularly limited, in order to obtain a uniform composition, after kneading the hydrophilic copolymer and the block copolymer, the photopolymerizable ethylenically unsaturated monomer and the photopolymerization initiator It is better to add and knead.

The photosensitive rubber plate of the present invention has a laminated structure composed of a support and a layer of the photosensitive composition formed on the main surface thereof.

The support usually comprises a flexible film or sheet, and optionally has a release layer or an undercoat layer comprising an adhesive or a primer. As the support, a flexible film such as a polyethylene terephthalate film, a polypropylene film, or a polyimide film; a polyethylene terephthalate film or a polypropylene film on which an elastic composition such as natural rubber, synthetic rubber, or soft vinyl chloride resin is backed. A flexible sheet made of polyimide or the like can be used.

To form a layer of the photosensitive composition on the main surface of the support,
A conventionally known method may be adopted. For example, after the photosensitive composition is molded into a sheet using a molding machine such as an extruder, a pressing machine, a calender, or simultaneously with molding, it is adhered to a support or chloroform, carbon tetrachloride as a photosensitive composition, A solution obtained by dissolving the first to fourth components in a solvent such as trichloroethane, methyl ethyl ketone, diethyl ketone, benzene, toluene, tetrahydrofuran,
It is formed by pouring into a sheet frame and then evaporating the solvent to form a sheet, or by adhering it to a support or at the same time as forming.

The photosensitive rubber plate of the present invention is preferably provided with a thin layer of a non-adhesive water-soluble polymer as a coating layer on the layer of the photosensitive composition.

Since the surface of the photosensitive composition layer usually has strong adhesiveness,
When the original film is directly applied to the surface, air bubbles enter between the photosensitive composition and the original film, and active light is diffusely refracted, and the exposure and curing of the photosensitive layer do not proceed, resulting in relief reproducibility. In addition, since it is difficult to remove the original image film adhered to the surface of the photosensitive composition layer without damaging it, there is a problem that it cannot be reused. By providing a thin layer of non-tacky water-soluble polymer, the above problems are eliminated.

The photosensitive rubber plate of the present invention may be further provided with a cover film. The cover film is made of a flexible resin film. The cover film forms a protector film layer on the photosensitive composition layer (or on the thin layer of the water-soluble polymer when the thin layer is provided). A release layer may be provided on the surface of the cover film that contacts the photosensitive composition layer. Examples of the cover film include polyethylene terephthalate film, polyethylene film, polypropylene film, polystyrene film and the like.

The thickness of the film is usually 75-200 μm, preferably 100
~ 150 μm. If it is less than 75 μm, the film strength is insufficient and the molded photosensitive rubber plate is easily deformed. Conversely, 200μ
If it exceeds m, the film strength will be too strong and it will be difficult to peel the film from the layer of the photosensitive composition.

In the photosensitive rubber plate of the present invention, a foam may be laminated on the surface of the support opposite to the surface on which the photosensitive composition layer is formed. Printing pressure during flexographic printing can be adjusted by laminating the foams.

Since the photosensitive rubber plate of the present invention is excellent in water washability,
Relief formation can be easily performed with an aqueous developer. The aqueous developer is usually composed of water, alcohol, an aqueous solution or an alcohol solution. Examples of the aqueous solution include alkaline aqueous solutions such as alkali metal salts and alkaline earth metal salts, and aqueous solutions in which a surfactant and the like are dissolved. Of these water-based developers, an aqueous solution in which a surfactant is dissolved is suitable.

Next, the present invention will be described in more detail with reference to Examples.
The invention is in no way limited by these examples. The parts and% in Examples and Comparative Examples are based on weight unless otherwise specified.

The photosensitive composition and the photosensitive rubber plate were evaluated based on the following test methods.

[Water washability] A photosensitive rubber plate was cut into small pieces of 30 mm × 30 mm, and the small pieces were washed with a photosensitive flexo plate washing machine (JOW-A manufactured by JEOL Seiki).
_2- SS type), the time until the thickness of the small piece reaches 2 mm when washed with an aqueous solution of polyoxyethylene nonylphenyl ether having a concentration of 2% and a temperature of 50 ° C. was calculated and displayed according to the following criteria.

  A: Less than 8 minutes.

  B: 8 minutes or more and less than 11 minutes.

  C: 11 minutes or more and less than 14 minutes.

  D: 14 minutes or more.

A score of A indicates that the water washability is excellent, and B to
It shows that the water washability is inferior in the order of C to D.

[Transparency] A photosensitive rubber plate was cut into a size of 30 mm × 30 mm to obtain a small piece, and the transmission density of this small piece was measured using a Macbeth densitometer (transmission type). The smaller the value, the better the transparency.

One surface of the photosensitive rubber plate [reproducibility of relief images, using ultraviolet exposure machine (JEOL Seiki JE-A ₂ -SS-type), the thickness of the cured layer is 1.5mm
It was exposed to the degree. Next, the polyester film on the non-exposed surface was peeled off, a negative film for reproducibility evaluation was brought into close contact with the surface, and this surface was exposed for 15 minutes using the ultraviolet exposure device. The negative film was peeled off, and the unexposed portion was dissolved and removed with a polyoxyethylene nonylphenyl ether aqueous solution having a concentration of 2% and a temperature of 50 ° C. afterwards,
It was dried at 70 ° C. for 20 minutes, and the surface from which the unexposed portion was removed was re-exposed for 10 minutes by using the above-mentioned ultraviolet exposure machine to prepare a relief image for reproducibility evaluation.

This relief image was observed with a 50 × stereoscopic microscope and evaluated according to the following criteria.

Reproducibility of convex fine line The minimum width of the convex fine line which was reproduced without distortion and thickening with the same width as the convex fine line of the negative film was measured. The smaller the value is, the better the reproducibility of the convex thin line is.

Reproducibility of 0.7 mm wide concave fine wire The groove depth of the 0.7 mm wide concave fine wire was measured. The larger the value is, the better the reproducibility of the concave thin line is.

[Strength balance] When the flat surface of the rubber printing plate used for the evaluation of relief image reproducibility was broken at a tensile speed of 500 mm / min and a marked line distance of 20 mm in accordance with JIS K-6301 "Tensile test method". The product of the tensile strength and the elongation (tensile product) was obtained. The larger the value of tensile product, the better the strength balance.

(Preparation of Block Copolymer) Reference Example 1 2300 parts of dehydrated and purified cyclohexane, 0.4 part of tetramethylethylenediamine and 0.8 part of n-butyllithium were charged in a polymerization vessel made of stainless steel and previously agitated with a stirrer made of stainless steel,
Then, 100 parts of styrene was added and polymerization was carried out at 70 ° C. for 1 hour. Then, 800 parts of 1,3-butadiene were added over 1 hour while maintaining the inside of the polymerization vessel at 70 ° C.
Polymerize for a minute, then add 100 parts of styrene to 70 ° C
Polymerization was carried out for 1 hour, and finally 0.05 part of methanol was added to obtain a block copolymer solution.

To this solution, 5 parts of 2,6-di-tert-butyl-4-methylphenol and 5 parts of trisnonylphenyl phosphate were added, the solvent was removed by the steam coagulation method, and the water was removed using a vacuum dryer. To obtain a block copolymer.

Reference Example 2 2300 parts of dehydrated and purified cyclohexane, 0.75 parts of tetramethylethylenediamine and 1.21 parts of n-butyllithium were charged in a polymerization vessel made of stainless steel, which had been previously replaced with nitrogen, and equipped with a stirrer, and then 200 parts of styrene was added and polymerization was carried out at 70 ° C. for 1 hour. did. Then, 800 parts of 1,3-butadiene was added over 1 hour while maintaining the inside of the polymerization vessel at 70 ° C, and after addition was completed, 3 more parts were added.
Polymerization was carried out for 0 minutes, 1.6 parts of paradibromobenzene was then added, the reaction was carried out at 70 ° C. for 2 hours, and finally 0.08 parts of methanol was added to obtain a block copolymer solution. 2,6 in this solution
5 parts of di-tert-butyl-4-methylphenol and 5 parts of trisnonylphenyl phosphate were added, the solvent was removed by a steam coagulation method, and water was further removed using a vacuum dryer to obtain a block copolymer. Got

Reference Example 3 A block copolymer was obtained in the same manner as in Reference Example 1 except that the amount of tetramethylethylenediamine used in Reference Example 1 was changed to 0.92 part.

Reference Example 4 A block copolymer was obtained in the same manner as in Reference Example 1 except that the amount of tetramethylethylenediamine used in Reference Example 1 was changed to 0.22 part.

Reference Example 5 A block copolymer was obtained in the same manner as in Reference Example 1 except that the tetramethylethylenediamine used in Reference Example 1 was not used.

The styrene content of these block copolymers,
Table 1 shows the butadiene content, the vinyl bond content in the butadiene block, and the weight average molecular weight.

(Preparation of Hydrophilic Copolymer) Reference Example 6 An autoclave was charged with 200 parts of water, and then 60 parts of butadiene, 9 parts of methyl acrylate, 20 parts of ethylene methacrylate phosphate, 10 parts of styrene, 1 part of divinylbenzene.
Parts, 4 parts of sodium dosylbenzenesulfonate, 0.3 parts of potassium persulfate and 0.4 parts of t-dodecyl mercaptan are added and heated to 50 ° C. to start the polymerization reaction.
When the amount reached 100%, a terminating agent was added to terminate the reaction, followed by cooling with water to obtain a polymer emulsion. This emulsion
Add 0.7% N-mono (polyoxyethylene) dodecylamine aqueous solution to coagulate, separate the obtained crumb, wash with water, dehydrate, and vacuum dry at 60 ° C to obtain number average molecular weight.
100,000 hydrophilic copolymers were obtained.

Example 1 65 parts of the hydrophilic copolymer obtained in Reference Example 6, 35 parts of a block copolymer, 50 parts of liquid polybutadiene (Nisso PB, B1000 manufactured by Nippon Soda) and 2,6-di-t-butyl-p. -Kneading 0.2 parts of cresol in a kneader at 150 ° C until uniform, then lowering the kneader temperature to 120 ° C, 10 parts of 1,6-hexanediol diacrylate, 5 parts of 1,6-hexanediol dimethacrylate, Benzoin methyl ether 1
Parts and 0.02 parts of methylhydroquinone were added and further kneaded to obtain a photosensitive composition.

This photosensitive composition is placed in a frame mold having a spacer thickness of 3.0 mm and an opening at the top and bottom, and a thickness of 0 is provided above and below the opening of the frame mold.
A 1 mm polyester film was coated, heated and pressurized at 110 to 130 ° C. and 150 kgf using a press machine, and then cooled to obtain a photosensitive rubber plate having a total thickness of 3.0 mm. The evaluation results of this photosensitive rubber plate are shown in Table 2.

Examples 2 to 5 and Comparative Examples 1 to 2 A photosensitive composition and a photosensitive composition were prepared in the same manner as in Example 1 except that the hydrophilic copolymer or the block copolymer used in Example 1 was changed to the formulation shown in Table 2. A photosensitive rubber plate was obtained. Table 2 shows the evaluation results of these photosensitive rubber plates.

From the above, it can be seen that the composition containing the styrene-butadiene-styrene type block copolymer having a vinyl bond content of 10.3% (Comparative Example 1) is inferior in water washability, strength balance and image reproducibility. . In addition, the amount of styrene-butadiene-styrene block copolymer is 70% by weight.
It can be seen that the composition (Comparative Example 2) markedly deteriorates the water washability.

On the other hand, the photosensitive composition of the present invention containing a styrene-butadiene-styrene type block copolymer having a vinyl bond content of 15 to 70% is excellent in transparency, strength balance, image reproducibility and water washability. I understand.

In particular, the photosensitive composition of the present invention containing the S-B-S block copolymer having a vinyl bond content of 20 to 55% is excellent in transparency, strength balance, image reproducibility and water washability. You can see that

INDUSTRIAL APPLICABILITY The photosensitive composition of the present invention is excellent in transparency and strength balance and has a high water washing speed after exposure. Therefore, a negative film is brought into close contact with the film to expose it to light to expose it to an unexposed portion. Can be suitably used for a flexographic printing plate which is washed and removed to form a relief. Further, since the photosensitive composition of the present invention can wash and remove the unexposed portion with an aqueous solvent, it is easy to treat the washing waste liquid after washing and there is little risk of environmental pollution.

Continuation of the front page (56) Reference JP-A-6-202331 (JP, A) JP-A-5-165216 (JP, A) JP-A-4-271351 (JP, A) JP-A-5-232698 (JP , A) JP-A-2-7055 (JP, A) JP-A-59-100433 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03F ^7/ 00-7/18 G03F 7/26-7/42

Claims (13)

(57) [Claims] 1. At least one polymer block A comprising a polymer having 95% by weight or more of an aromatic vinyl monomer as a constitutional unit, and 20% by weight or more of a conjugated diene monomer as a constitutional unit. 20-65 parts by weight of a block copolymer having at least one polymer block B composed of a conjugated diene polymer having a vinyl bond content of the conjugated diene monomer unit portion of 15 to 70%, hydrophilic Copolymer 35 to 80 parts by weight (however, the total amount of the block copolymer and the hydrophilic copolymer is 100 parts by weight), the photopolymerizable ethylenically unsaturated monomer 5 to 300 parts by weight, and A photosensitive composition containing 0.1 to 10 parts by weight of a photopolymerization initiator. 2. The block copolymer according to claim 1, wherein the weight ratio of the polymer block A to the polymer block B is 5/95 to 95/5. Photosensitive composition. 3. The photosensitive composition according to claim 1, wherein the block copolymer has a total weight average molecular weight of 8,000 to 2,000,000. 4. The photosensitive composition according to claim 1, wherein the block copolymer comprises a polystyrene block A and a polybutadiene block B or a polyisoprene block B. 5. The photosensitive composition according to claim 1, which is a block copolymer having a block structure represented by the general formula ABA. 6. A block copolymer comprising a polystyrene block A and a polybutadiene block B, represented by the general formula ABA, and the weight of the polymer block A and the polymer block B. The ratio is 5/95 to 95/5 and the weight average molecular weight of the entire block copolymer is 8,000 to 2,000,0.
The photosensitive composition according to claim 1, wherein the photosensitive composition is 00. 7. A hydrophilic copolymer containing a phosphoric acid ester group, as claimed in any one of claims 1 to 6.
A photosensitive composition according to any one of items. 8. A hydrophilic copolymer containing a phosphoric acid ester group in an amount of 5 to 30% by weight of an ethylenically unsaturated monomer, a conjugated diene monomer of 40 to 90% by weight, and a polyfunctional ethylenically unsaturated monomer. 0 to
10% by weight and 0 to 55% by weight of a monomer copolymerizable therewith
7. The photosensitive composition according to any one of claims 1 to 6, which is obtained by copolymerizing 9. The hydrophilic copolymer has a number average molecular weight of 10,0.
The photosensitive composition according to any one of claims 1 to 6, which is 00 to 500,000. 10. A hydrophilic copolymer comprising 5 to 30% by weight of an ethylenically unsaturated monomer containing a phosphoric acid ester group, 40 to 90% by weight of a conjugated diene monomer, and a polyfunctional ethylenically unsaturated monomer. A copolymer having 0 to 10% by weight of the copolymer and 0 to 55% by weight of a monomer copolymerizable therewith, and having a number average molecular weight of the hydrophilic copolymer of 10,000 to 500,000. 7. The photosensitive composition according to any one of claims 1 to 6, which is characterized. 11. The photosensitive composition according to any one of claims 1 to 6, wherein the photopolymerizable ethylenically unsaturated monomer is diacrylate or dimethacrylate. 12. A photosensitive rubber plate having a laminated structure comprising a support and a layer of the photosensitive composition according to any one of claims 1 to 11 formed on the main surface thereof. 13. A negative film is brought into close contact with one surface of the photosensitive rubber plate according to claim 12, and light is irradiated from above, and the unexposed portion of the photosensitive rubber plate is treated with an aqueous developer. Flexographic printing plate after removal.