JPH06202331A - Photosensitive elastomer composition and photosensitive flexographic printing plate usint the same - Google Patents

Abstract

PURPOSE:To easily form a smooth sheet and to obtain enough rubber elasticity by incorporating a specified thermoplastic elastomer block copolymer, conjugate diene elastomer copolymer, elastomer compsn., etc. CONSTITUTION:This elastomer compsn. contains a thermoplastic elastomer block copolymer (a), elastomer copolymer (b), and elastomer polymer (c). The copolymer (a) contains a polymer block (B) essentially consisting of conjugate dienes between two polymer blocks (A) essentially consisting of aromatic vinyl compd. The elastomer copolymer (b) consists of monomers having at least two non-conjugate double bonds and conjugate diene monomers or vinyl monomers which are copolymerizable with these monomers. The elastomer polymer (c) consists of copolymer of conjugate diene monomers or vinyl monomers which are copolymerizable with these diene monomers, or derivs. of these. The proportion of each component is (a): 5-25wt.%, (b):15-60wt.%, and (c): 5-40wt.%.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a photosensitive elastomer composition and a photosensitive flexographic plate obtained by using the composition.

[0002]

2. Description of the Related Art A rubber plate conventionally used as a plate material for flexographic printing has a method of engraving directly on the rubber plate,
It has been manufactured by hot-pressing a thermosetting resin onto an original plate obtained by etching a metal plate to form a master mold, and pouring rubber into the master mold to vulcanize the rubber. However, these methods are complicated and require skill, and are expensive and time-consuming because they consist of many steps.Because the precision of the obtained rubber plate itself is low, post-processing such as back-polishing is required before use. It had the drawback of being necessary.

In order to solve this drawback, in recent years, a photosensitive elastomer composition has been used, and a negative film is brought into close contact with the surface of the composition layer, followed by irradiation with actinic light. There has been proposed a method for producing a flexographic plate by eluting and removing with a solvent to form a relief image.

JP-B-51-43374 discloses that a conjugated diene is mainly contained between at least two thermoplastic non-elastomeric polymer blocks mainly composed of an aromatic vinyl compound and having a glass transition temperature of 25 ° C. or higher. Described above, a photosensitive composition using a thermoplastic elastomeric block copolymer, to which an elastomeric polymer block having a glass transition temperature of 10 ° C. or less is bonded, is described. However, the flexographic plate using this has insufficient rubber elasticity as compared with the conventionally molded rubber plate, or the plate-making product contracts, causing a warping phenomenon (hereinafter referred to as curling phenomenon) of the printing plate. In some cases, there was a problem in reproducibility during printing.

JP-A-63-48545 discloses an elastomer comprising a monomer having at least two non-conjugated double bonds and a conjugated diene monomer or a vinyl monomer copolymerizable therewith. There is described an elastomer composition for a photosensitive flexographic plate using a linear polymer. However, the flexographic plate using this is (1) poor in processability, especially sheet formability in the extrusion process. (2) It takes time to wash out the relief image, that is, to remove the unexposed portion, and the reproducibility of the image itself is insufficient. There was such a problem.

[0006]

DISCLOSURE OF THE INVENTION The present invention overcomes the drawbacks of the conventional photosensitive flexographic plate, and (1) a smooth sheet can be easily formed. (2) A relief image faithful to the original image can be obtained in a short time by using a halogen-based organic solvent. (3) The curling property of the flexographic plate after plate making is good (curling phenomenon is unlikely to occur). (4) Has sufficient rubber elasticity. It is an object of the present invention to provide a photosensitive elastomer composition having the above excellent properties and a photosensitive flexographic plate using the composition.

[0007]

As a result of intensive studies to solve the above-mentioned drawbacks, the present inventors have found that (a) a specific thermoplastic elastomer block copolymer, and (b) a non-conjugated double bond. And a conjugated diene-based elastomeric copolymer with a monomer having, and (c) an elastomeric composition in which other conjugated diene-based elastomeric polymers are used in specific ratios, respectively, and at least one terminal ethylene group It was found that a photosensitive elastomer composition comprising an addition-polymerizable unsaturated monomer having ## STR3 ## and a photopolymerization initiator is suitable as one having the above-mentioned preferable properties, and the present invention is completed based on this finding. Came to.

Thus, according to the present invention, (1) an elastomeric composition, (2) an addition-polymerizable unsaturated monomer having at least one terminal ethylene group and (3) a photopolymerization initiator, 1) contains (a) at least two polymer blocks (A) mainly containing an aromatic vinyl compound and a polymer block (B) mainly containing a conjugated diene between the polymer blocks (A) (B) Elastomer-like block copolymer containing at least two non-conjugated double bonds and a conjugated diene-based monomer or a vinyl monomer copolymerizable therewith Copolymer and (c) at least one selected from the group consisting of a conjugated diene-based monomer or a copolymer with a vinyl monomer copolymerizable therewith or a derivative thereof, (a), ( B) Each elastomeric polymer other than The photosensitive elastomer composition which is characterized in that which was used in the specific ratio, and a photosensitive flexographic plate was prepared the composition as a sheet is provided. Hereinafter, the present invention will be described in detail.

The component (a) in the elastomeric composition (1) of the present invention is a solvent-soluble thermoplastic elastomeric block copolymer having at least one ABA unit.

The polymer block (A) is one or more polymers of aromatic vinyl compounds such as styrene, α-methylstyrene, methylstyrene and ethylstyrene, or a monomer copolymerizable with the aromatic vinyl compound. It is a thermoplastic and non-elastomeric polymer block having a number average molecular weight of 2000 to 100,000 and a glass transition temperature of 25 ° C. or higher.

On the other hand, the polymer block (B) is one or more polymers of conjugated dienes such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene and 1,3-pentadiene, or An elastomeric polymer composed of a copolymer of a conjugated diene and a copolymerizable monomer, having a number average molecular weight of 2,500 to 100,000 and a glass transition temperature of 10 ° C or lower.

In the ABA type block copolymer (a) according to the present invention, the polymer blocks (A) and (B) are arranged in a fixed order. In addition to this, the fact that the copolymer itself is soluble in the solvent contributes to high washability of the photosensitive composition obtained by the present invention and high reproducibility of the relief image of a flexographic plate using the photosensitive composition. It seems to contribute.

The structure of the ABA type block copolymer (a) according to the present invention may be linear or radial.

In the present invention, the polymer block (A) is preferably polystyrene or poly (α-methylstyrene), and the polymer block (B) is preferably polybutadiene or polyisoprene. The ratio of the polymer block (A) and the polymer block (B) is not particularly limited as long as the block copolymer becomes an elastomer. However, the proportion of the polymer block (B) in all the blocks is usually 60 to 90% by weight, preferably 65 to 85% by weight.

By using the thermoplastic elastomer block copolymer, the sheet moldability and washability of the photosensitive elastomer composition obtained in the present invention are improved. Further, the reproducibility of the relief image of the flexographic plate prepared by using the photosensitive composition is improved. The amount used is 5 to 25% by weight, preferably 10 to 25% by weight, based on 100 as the total weight of the photosensitive elastomer composition. When the amount of the component (a) used is less than 5% by weight, sheet formability, relief image reproducibility and washability are not improved. On the other hand, if it exceeds 25% by weight, the rubber elasticity is insufficient and the curling phenomenon easily occurs.

The component (b) in the elastomeric composition (1) of the present invention is a monomer having at least two non-conjugated double bonds (hereinafter sometimes referred to as polyene monomer).
And a conjugated diene-based monomer, or a vinyl monomer copolymerizable with each of the above monomers, is an elastomeric copolymer. As the monomer forming the skeleton, (A) 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, chloroprene and other conjugated diene-based monomers (B ) Aromatic vinyl monomers such as styrene and α-methylstyrene (C) Vinyl cyan monomers such as acrylonitrile, methacrylonitrile and α-chloroacrylonitrile. Incidentally, the vinyl monomer is not limited to these examples, and is used within a range that does not impair the gist of the present invention, as long as it is copolymerizable with the conjugated diene monomer and the polyene monomer shown below. be able to.

The polyene monomer is a monomer that causes a crosslinking reaction during the copolymerization reaction. By this cross-linking reaction, partial cross-linking is formed in the elastomeric copolymer (b) according to the present invention, which results in smoothness / shrinkability of a sheet obtained by using the photosensitive composition of the present invention and curling of a flexographic plate. Contributes to the improvement of sex.

Examples of the polyene monomer include divinylbenzene, divinyl sulfide, divinyl sulfone, divinyl oxalate, N, N'-methylenebisacrylamide, allyl acrylate, allyl methacrylate,
Vinyl acrylate, vinyl methacrylate, allyl vinyl ether, allyl acrylamide, allyl methacrylamide, diallyl acrylamide, diallyl ether, diallyl oxalate, diallyl malonate, diallyl adipate, trimethylolpropane triallyl ether, ethylene glycol diacrylate, ethylene glycol dimethacrylate. , Polyethylene glycol diacrylate, propylene glycol diacrylate, bisphenol dimethacrylate, trimethylolpropane trimethacrylate and the like.

Elastomeric Copolymer According to the Invention
In (b), at least one polyene monomer is
The total weight of the conjugated diene-based monomer and the vinyl monomer copolymerizable with the conjugated diene-based monomer is 100 and is usually about 0.05 to 5.0.
It is used in an amount of approximately 0.1% by weight, preferably approximately 0.1 to 3% by weight. When the amount of the polyene monomer is less than 0.05% by weight, the sheet moldability of the photosensitive elastomer composition of the present invention is not improved. On the other hand, when the amount exceeds 5% by weight, the photosensitive composition becomes brittle, so that the processability such as sheet moldability is deteriorated and the washability is deteriorated.

Elastomeric Copolymer According to the Invention
In (b), the ratio of the conjugated diene-based monomer and vinyl monomer used as the main skeleton to be used is not particularly limited as long as the component (b) becomes an elastomer at room temperature. When a vinyl monomer whose homopolymer becomes a resin at room temperature is used, the content of the vinyl monomer in the component (b) is usually 60% by weight or less, preferably 50% by weight or less. To do.

Elastomeric Copolymer According to the Invention
(B) is a method known in the art, for example, using at least two polyene monomers and a conjugated diene monomer or a vinyl monomer copolymerizable therewith, for example, JP-A-63-4854.
It is manufactured by the method described in Japanese Patent Publication No. Preferred examples of the elastomeric copolymer are polybutadiene, acrylonitrile-butadiene copolymer, and styrene-butadiene copolymer using divinylbenzene as a polyene monomer.

By using the elastomeric copolymer (b), the rubber elasticity of the photosensitive elastomer composition obtained in the present invention is improved, and a sheet having a smooth and small shrinkage is produced by using the photosensitive composition, and A flexographic plate with improved curling property can be obtained. The amount used is 15 to 60% by weight, preferably 15 to 40% by weight, based on 100 as the total weight of the photosensitive elastomer composition. If this amount is less than 15% by weight, the above-mentioned rubber elasticity and curling property are not improved, and the smoothness of the sheet is not sufficient. On the other hand, when it exceeds 60% by weight, the amount of partial cross-linking in the photosensitive composition is too much, so that the solubility in an organic solvent, that is, the wash-out property deteriorates, and the usability as a flexographic plate deteriorates.

The component (c) in the elastomeric composition (1) of the present invention is selected from the group consisting of a conjugated diene monomer or a copolymer with a vinyl monomer copolymerizable therewith, or a derivative thereof. At least one selected from the above (a) and (b)
Other than solvent-soluble elastomeric polymers. By using the polymer, the proportion of the solvent-soluble component in the photosensitive composition obtained by the present invention is increased. This is believed to contribute to the washability of the photosensitive composition.

Elastomeric polymer according to the present invention (c)
Examples of the monomer that forms the skeleton of (A) 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, conjugated diene-based monomers such as chloroprene ( B) Aromatic vinyl monomers such as styrene and α-methylstyrene (C) Vinyl cyan monomers such as acrylonitrile, methacrylonitrile and α-chloroacrylonitrile. The vinyl monomer is not limited to these examples, and any vinyl monomer that can be copolymerized with the conjugated diene monomer can be used within the range not impairing the gist of the present invention.

Elastomeric polymer according to the present invention (c)
Examples of polybutadiene, polyisoprene, polychloroprene, styrene-isoprene copolymer, styrene-butadiene copolymer, methacrylic acid-butadiene copolymer, methacrylic acid-styrene-butadiene copolymer, acrylonitrile-butadiene copolymer Examples thereof include coalesce, acrylonitrile-butadiene-methacrylic acid copolymer, and butyl rubber.

By using the polymer as the component (c), the wash-out property of the photosensitive elastomer composition of the present invention is improved, and at the same time, the reproducibility of the relief image on the flexographic plate is further improved. The amount used is 5 to 40% by weight, preferably 5 to 35% by weight, based on 100 as the total weight of the photosensitive elastomer composition. If the amount used is less than 5% by weight, neither the wash-out property nor the reproducibility of the relief image is improved, and if the amount used exceeds 40% by weight, the shrinkability and smoothness of the sheet become insufficient and the curling phenomenon easily occurs.

The photosensitive elastomer composition of the present invention is
An addition-polymerizable unsaturated monomer containing at least one terminal ethylene group as the component (3), which contains the three types of elastomeric compositions obtained as described above as the component (1). It is necessary to contain a photopolymerization initiator as a component).

The addition polymerizable unsaturated monomer having at least one terminal ethylene group used as the component (2) in the present invention includes ethylene glycol, propylene glycol, 1,4-butanediol and 1,6. 2 to 2 alkylene glycol units, such as hexanediol
Diacrylates of three polyalkylene glycols and their corresponding dimethacrylates; Diacrylates of polyhydric alcohols such as trimethylolalkane and tetramethylolalkane (alkane is methane, ethane, propane) and these Dimethacrylates; acrylamides such as acrylamide, methacrylamide, diacetone acrylamide, N, N'-methylenebisacrylamide, N, N'-hexamethylenebisacrylamide, and corresponding methacrylamides; styrene, vinyltoluene, Aromatic vinyl compounds such as divinylbenzene; unsaturated nitrile compounds such as acrylonitrile and methacrylonitrile; diallyl phthalate and triallyl cyanurate. These may be used alone or in combination of two or more, and the amount thereof is usually 5 in the photosensitive elastomer composition.
~ 30% by weight.

The photopolymerization initiator used as the component (3) in the present invention includes acyloins such as benzoin and pivaloine; acyloin ethers such as benzoin methyl ether, benzoin ethyl ether and benzoin isopropyl ether; anthraquinone, 1, 4-
Examples thereof include polynuclear quinones such as naphthoquinone. These may be used alone or in combination of two or more, and the amount thereof is usually 0.1% in the photosensitive elastomer composition.
It is from 01 to 5% by weight.

In the present invention, components other than those described above can be added to the photosensitive elastomer composition as required. Examples of such components include plasticizers, thermal polymerization inhibitors, antiaging agents, dyes and the like.

In the present invention, the plasticizer is used for production of the photosensitive elastomer composition, molding, promotion of removal of unexposed portions, and adjustment of hardness of exposed and cured portions. Hydrocarbon oils such as naphthene oil and paraffin oil; liquid 1,2- and 1,4-polybutadiene, and their hydroxides or carboxylates; liquid acrylonitrile-butadiene copolymers and their carboxyls. Compounds; liquid styrene-butadiene copolymers; low molecular weight polystyrenes having a molecular weight of 3000 or less, α-methylstyrene-vinyltoluene copolymers, petroleum resins, polyacrylates, polyester resins, polyterpene resins and the like. These may be used alone or in combination of two or more, and are usually added in the range of 2 to 60% by weight in the photosensitive elastomer composition depending on the target characteristics.

In the present invention, the thermal polymerization inhibitor is used for preventing the polymerization of the addition-polymerizable unsaturated monomer by heat during the preparation of the photosensitive elastomer composition. As useful substances,
Hydroxy aromatic compounds such as hydroquinone, p-methoxyphenol, pt-butylcatechol, 2,6-di-t-butyl-p-cresol and pyrogallol; quinones such as benzoquinone, p-toluquinone and p-xyloquinone; Examples thereof include amines such as phenyl-α-naphthylamine. These may be used alone or in combination of two or more, and the amount thereof is usually 0.001 to 2% by weight in the photosensitive elastomer composition.

The photosensitive elastomer composition of the present invention can be prepared in a number of ways. For example, it can be mixed and kneaded using a kneader, a roll mill or the like which is a usual rubber kneading machine, and can be prepared as a sheet having a desired thickness by using a molding machine such as an extruder, a press or a calender. Further, if desired, the photosensitive elastomer composition of the present invention, chloroform, carbon tetrachloride, trichloroethane, diethyl ketone, methyl ethyl ketone, benzene,
It can be prepared as a sheet by dissolving in a suitable solvent such as toluene or tetrahydrofuran, pouring this mixture into a frame and evaporating the solvent. A sheet with high thickness accuracy can be obtained by subjecting this sheet to hot pressing, extrusion or calendering.

The photosensitive elastomer composition of the present invention comprises
In order to prevent the contamination or damage of the photosensitive composition layer during storage or operation after being formed into a sheet, a peelable thin transparent film layer such as polypropylene, polyethylene or polyethylene terephthalate is formed on the surface of the base film. It can be provided as a layer or a protector film layer.

The surface of the photosensitive elastomer composition of the present invention is highly flexible because it suppresses the tackiness of the surface of the photosensitive composition layer and enables reuse of the negative film after irradiation with active light. A thin coating layer may be provided. In this case, when the unexposed portion is eluted with a solvent after the exposure of the photosensitive composition layer is completed, the coating material layer must be eluted and removed at the same time. Soluble polyamide, cellulose derivative and the like are often used as the coating material layer.

To develop the photosensitive elastomer composition of the present invention (elution of unexposed areas), one or more halogen-based solvents such as trichloroethane, trichlorethylene, perchlorethylene; or these and methanol, ethanol, isopropyl alcohol, butanol. A mixture with alcohol such as is used. However, when used as a mixture, the proportion of alcohol is preferably up to about 30% by weight.

By using the photosensitive elastomer composition of the present invention, it becomes possible to manufacture a flexographic plate which is easy to form into a sheet, has a smooth surface when formed into a sheet, and has sufficient rubber elasticity. A relief image having a high resolution can be obtained by using, and a printing plate in which the curling phenomenon does not easily occur can be obtained.

Due to its high photosensitivity, the photosensitive elastomer composition of the present invention is used not only for flexographic printing plates, but also for photoresists and screens for screen printing, as well as for paints.
It can be preferably used as a coating material, an adhesive, a film, a sheet material, an impregnated material, and other molded articles.

[0039]

EXAMPLES The present invention will be described in more detail by way of examples, which should not be construed as limiting the invention thereto. The parts and% in Examples and Comparative Examples are based on weight unless otherwise specified. The evaluation of the obtained elastomer composition and flexographic plate was carried out based on the following test methods.

(A) Shrinkability of Sheet Using an 8-inch roll, 400 g of each composition was wound around the roll for 3 minutes under the conditions of a roll temperature of 110 ° C. and a roll gap of 1 mm. After that, stop the roll, put two reference lines on each composition sheet, and immediately from the sheet-shaped sample, the width is 3 cm.
I cut out a strip. These are placed on a smooth stainless plate spread with a dusting agent such as talc, and the length L (cm) of the reference line after standing for 24 hours at room temperature is measured to determine the shrinkage ratio S.

[0041]

[Equation 1]

It was determined by Here, L ₀ is the length of the reference line put on each composition on the roll, and in this example, 1
It was set to 1.0 cm.

Based on this value, the shrinkage of the sheet was evaluated according to the following criteria. The shrinkage ratio is less than 5: 5%. The shrinkage rate is 4: 5 to 10%. The shrinkage ratio is 3:10 to 20%. 2: Shrinkage rate of 20 to 30%. The shrinkage rate is 1: 30% or more. The smaller the shrinkage, the higher the rating, indicating that the sheet can be easily molded.

(B) Sheet smoothness Each composition was put into a sheet-shaped mold having a spacer thickness of 3.0 mm, and the top and bottom were sandwiched with a polyester film having a thickness of 0.1 mm, and heated to 110 to 130 ° C. by a press machine. After cooling, a sheet having a thickness of 3.0 mm was formed. Then, the polyester film on the upper surface of the sheet was peeled off, and the surface condition of the sheet after 24 hours was visually observed and evaluated according to the following criteria. ◯: The surface condition is extremely smooth. Δ: A surface state in which a fine uneven pattern is recognized. X: The surface condition is a wavy, uneven surface. The smoother the surface condition, the better the sheet moldability.

(C) Wash-out property A 3 cm square piece was cut out from a sheet of each composition having a thickness of 3.0 mm obtained by the same method as in (b) above, and used as a sample for this test. This sample was trichloroethane / isopropyl alcohol (mixing ratio = 8) using a photosensitive flexo plate washout machine (JOW-A ₂ -SS type manufactured by JEOL Seiki).
It is washed with a mixed solvent of 0/20), and the washable thickness is
The time required to reach 2 mm was determined and evaluated according to the following criteria. A: The washout time to the predetermined thickness is less than 3 minutes. B: Washing out time to a predetermined thickness is 3 to 5 minutes. C: It takes 5 minutes or more to wash out to a predetermined thickness. A score of A indicates excellent washability.

(D) Evaluation of relief image One side of a sheet of each composition having a thickness of 3.0 mm obtained by the same method as in the above (b) was exposed to an ultraviolet exposure machine (JE-A ₂ manufactured by JEOL Seiki). -SS type), the thickness of the cured layer is 1.5
It was exposed so that the thickness would be about mm. Next, the polyester film on the non-exposed surface was peeled off, and a negative film for reproducibility evaluation was brought into close contact with the surface, and this surface was removed by the light source 15
Exposed for a minute. Peel off the negative film, trichloroethane / isopropyl alcohol (mixing ratio = 80/20)
The unexposed portion was dissolved and removed with the mixed solvent of. Then 50 ° C
Was dried for 30 minutes, and the surface from which the unexposed portion was removed was re-exposed for 10 minutes with the light source to prepare a relief image for reproducibility evaluation. This relief image was observed with a stereoscopic microscope of 50 times for the reproduction state of fine lines in the convex image portion and the engraved state of fine lines in the concave image portion, and evaluated according to the following criteria.

Reproducibility of 0.2 (mm) wide convex fine line When the convex fine line is not distorted or thick and is reproduced with the same width as the negative, it is regarded as “completely reproduced state” and Was evaluated according to the standard. A: The state in which the negative is completely reproduced. B: A state in which the negative is almost reproduced. C: A state in which reproduction of the negative is incomplete. The score A indicates that the printing plate has excellent image reproducibility.

Reproducibility of 0.7 (mm) wide concave fine line A state in which the concave fine line has no wavy jagged shape, a sharp edge, and the groove of the concave fine line is deeply engraved is "completely reproduced. It was regarded as "state" and evaluated according to the following criteria. A: The groove of the concave fine line is deep, and the edge is also carved sharply. B: The groove of the concave fine wire is slightly shallow, but there is no problem in practical use. C: The groove of the concave thin line is shallowly carved, which is a practical problem. The score A indicates that the printing plate has excellent image reproducibility.

(E) Rubber elasticity In accordance with the BS-903 Pt.A.8 trypso test method, measurement was carried out using the flat portion of the relief image evaluation sample. The return angle θ _d after the pendulum hits the sample is calculated, and the impact resilience value R is

[0050]

[Equation 2]

It was determined by In addition, θ ₀ is the angle of the pendulum before the test, which is 45 ° in this embodiment.

Based on this value, the rubber elasticity value was evaluated according to the following criteria. A: The impact resilience value is 60% or more. B: The impact resilience value is 50 to 60%. C: The impact resilience value is less than 50%. The higher the impact resilience value, the higher the rating, indicating that the rubber has sufficient rubber elasticity.

(F) Curling property Instead of the negative film for relief image evaluation, the dimensions of the outer frame: length × width = 18 × 14 (cm); the dimensions of the inner frame: length × width = 1
Same as (d) above, except that a negative film having a size of 5 × 11 (cm) and having a surface of an inner frame as a light transmitting part and a space between the outer frame and the inner frame as a non-image part was used. By the method, a sample for curling property evaluation was obtained. This sample was placed at temperature 23
The sample was placed on a horizontal and smooth desk surface for 1 week in a room kept at 55 ° C. and 55% humidity, and the heights at which the end faces of the four corners of the sample floated from the desk surface were measured. This was evaluated according to the following criteria. A: Lifting height from the desk surface is less than 10 (mm). B: Lifting height from the desk surface is 10 to 20 (mm). C: Lifting height from the desk surface is 20 to 30 (mm). D: Lifting height from the desk surface is 30 (mm) or more. The score A indicates that the printing plate has excellent curling property.

Based on the evaluation of the above items, comprehensive evaluation was carried out according to the following criteria. When 5 or more of all evaluation items are satisfied
◎ Sheet Shrinkage and smoothness are higher than average, and other items are C
○ When there is a problem in practical use, and there is no maximum score in each evaluation item △ When there is a minimum score in any of sheet shrinkability, smoothness, and curlability ×

Example 1 The following compounding ingredients were kneaded with a kneader at a kneading temperature of 150 ° C. to obtain an elastomeric composition (1). Compounding agent (parts by weight) Styrene-Butadiene-Styrene block copolymer (SBS) ¹⁾ 35 Styrene-Butadiene-Polyene copolymer (S, B-Polyene) ²⁾ 50 Styrene-Butadiene copolymer (SBR-1) ³⁾ 15 Liquid polybutadiene ⁴⁾ 40 2,6-Di-t-butyl-p-cresol (BHT) 2 Note 1) Shell Chemical Califlex TR KX-65 Note 2) Nippon Zeon Nipol 1009 Note 3) Nippon Synthetic Rubber SBR-1500 Note 4) Nippon Soda Nisso PB, B-1000

At the stage of uniform kneading, the temperature was lowered to 110 ° C., the following compounding ingredients were added, and the mixture was further kneaded to obtain a photosensitive elastomer composition. Compounding agent (parts by weight) 1,4-butanediol acrylate 10 1,6-hexanediol dimethacrylate 5 benzoin methyl ether 1 methylhydroquinone 0.02

The compositions (a) to (f) were evaluated using this composition. The resulting photosensitive composition had good shrinkability and smoothness, and there was no problem in washability when a flexographic plate was prepared using the composition. Further, the curling property was good, the rubber image had sufficient rubber elasticity, and the relief image was faithful to the original image. Furthermore, when the flexographic printing plate on which this relief image was obtained was subjected to actual flexographic printing, a printed matter faithful to the original image was obtained. The evaluation results are shown in Table 1.

Example 2 The following compounding ingredients were kneaded with a kneader at a kneading temperature of 150 ° C. to obtain an elastomer composition (1). Compounding agent (parts by weight) Styrene-Butadiene-Styrene Block Copolymer (SBS) 30 Styrene-Butadiene-Polyene Copolymer (S, B-Polyene) 50 Styrene-Butadiene Copolymer (SBR-1) 20 Liquid Polybutadiene 50 2,6-Di-t-butyl-p-cresol 2

At the stage of uniform kneading, the temperature was lowered to 110 ° C., the following compounding ingredients were added, and the mixture was further kneaded to obtain a photosensitive elastomer composition. Compounding agent (parts by weight) 1,6-hexanediol diacrylate 15 benzoin methyl ether 1 methylhydroquinone 0.02

Using this composition, the same evaluations as in Example 1 were carried out. The composition obtained had good shrinkability and smoothness, and there was no problem in washability when a flexographic plate was prepared using the composition. Also, curling is good,
It had sufficient rubber elasticity and the relief image was also faithful to the original image. The evaluation results are shown in Table 1.

Examples 3 to 6 and Comparative Examples 1 to 5 Example 1 with other compounding agents and kneading conditions except that the elastomeric composition (1) shown in Table 1 was used.
In the same manner as above, a photosensitive elastomer composition was prepared and evaluated. The results are shown in Table 1.

[0062]

[Table 1]

As is clear from Table 1, the photosensitive elastomer compositions according to the present invention of Examples 1 to 6 are excellent in sheet moldability and curling property and have sufficient rubber elasticity.
Further, since the composition has good washability and good reproducibility of the relief image, it is suitable as a material for a photosensitive flexographic plate.

On the other hand, as an elastomer composition
Comparative Examples 1 to 3 using only two of the three components (a), (b), and (c), Comparative Example 4 in which the amounts of (a) and (b) were reduced, and the amount of (c) In Comparative Example 5 in which the amount was reduced, the formability and curling property of the sheet were poor, and the rubber elasticity was also insufficient. Further, there was a problem in washability when a flexographic plate was prepared using the composition, and the obtained relief image did not sufficiently reproduce the original image.

[0065]

EFFECT OF THE INVENTION By using the photosensitive elastomer composition obtained in the present invention, a sheet having a smooth surface can be easily molded. Further, the flexographic plate obtained by using the composition has the following excellent properties. (1) Excellent curling property. (2) Has sufficient rubber elasticity. (3) Excellent washability. (4) It is possible to form a relief image that is true to the original image.

Claims (4)

[Claims] 1. A photosensitive elastomer composition comprising (1) an elastomeric composition, (2) an addition-polymerizable unsaturated monomer having at least one terminal ethylene group, and (3) a photopolymerization initiator, (1) is (a) 5 to 25% by weight, based on the total weight of the photosensitive elastomer composition, at least two polymer blocks (A) mainly composed of an aromatic vinyl compound and the polymer blocks (A). ), A thermoplastic elastomer block copolymer containing a polymer block (B) mainly containing a conjugated diene, (b) 15-60 wt% of a single block having at least two non-conjugated double bonds. And an elastomeric copolymer of a monomer and a conjugated diene monomer or a vinyl monomer copolymerizable therewith, and (c) 5 to 40% by weight of a conjugated diene monomer or a copolymer thereof Possible with vinyl monomer A photosensitive elastomer composition comprising at least one elastomeric polymer selected from polymers and their derivatives. 2. The photosensitive elastomer composition according to claim 1, wherein the block copolymer is polystyrene-polyisoprene-polystyrene or polystyrene-polybutadiene-polystyrene. 3. The elastomeric copolymer containing a monomer having at least two non-conjugated double bonds is a styrene-butadiene-based copolymer or an acrylonitrile-polybutadiene-based copolymer. The photosensitive elastomer composition of. 4. A photosensitive flexographic plate prepared by using the composition according to claim 1 as a sheet.