JPH059017B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a photosensitive elastomer composition. (Prior art) Conventionally, rubber plates used for flexographic printing have been produced by engraving directly on the rubber plate, or by corroding a metal plate to produce an original plate, casting a matrix made of plastic or the like, and injecting rubber into this matrix. It has been manufactured by pouring and vulcanizing. However, these methods are complex and require skill, involve many steps, and require a lot of money and time. Furthermore, the precision of the obtained rubber plate itself is low, so post-processing such as back-shaving is required before use. It had drawbacks such as the need for In order to solve this drawback, in recent years, methods have been proposed for directly producing flexographic printing plates using photosensitive elastomer compositions. For example, Japanese Patent Publication No. 51-43374 discloses that the elastomeric polymer contains at least two thermoplastic non-elastomeric polymer blocks having a glass transition temperature of 25° C. or higher and a 10% bond between the non-elastomeric polymer blocks. The use of solvent soluble thermoplastic elastomeric, linear block copolymers with a structure bonded by elastomeric blocks having glass transition temperatures below 0.degree. C. has been shown to be effective. However, such block copolymers have excellent moldability and solubility, making it easy to manufacture printing plates. is not sufficient and improvements are required. (Problems to be Solved by the Invention) Therefore, an object of the present invention is to provide a photosensitive elastomer composition suitable for a flexographic printing plate that has excellent image reproducibility. (Means for Solving the Problems) The objects of the present invention described above are (1) an elastomeric block copolymer, (2) an addition polymerizable compound having at least one CH ₂ =C group, and (3) an elastomeric block copolymer. In the photosensitive elastomer composition comprising a photopolymerization initiator, the block copolymer is an elastomeric block copolymer that is nonlinear and comprises an elastomeric polymer block and a non-elastomeric polymer block. This can be achieved by using a photosensitive elastomer composition characterized in that it is used. The nonlinear, elastomeric block copolymer used in the present invention is a so-called star-shaped or radial block copolymer obtained by combining living A-B type block copolymers obtained by conventional anionic polymerization with a polyfunctional coupling agent. It is a multi-branched block copolymer called a copolymer. Coupling agents or branching agents are derived from polyfunctional silicon halides such as silicone tetrachloride, silicone tetrabromide, trichlorosilane, trichloroethylsilane, and tribramobenzylsilane, dicarboxylic acids such as dimethyl adipate and diethyl adipate, and monofunctional alcohols. diesters, other known non-polymerizable compounds such as polyepoxides, polyisocyanates, and polyamines, and unsaturated nitrile compounds such as acrylonitrile and methacrylonitrile,
1,4-divinylbenzene, 1,3-divinylbenzene, 1,2-divinylbenzene, 1,2,4
- When added to a solution of living polymers such as polyvinyl aromatic compounds such as trivinylbenzene, 1,2-divinylnaphthalene, and 1,3-diisopropenylbenzene, they polymerize into oligomers and become polyfunctional on the spot. Includes compounds that form branching agents. The number of branches can be set to about 3 to 20 by appropriately changing the type and amount of the compound used, but in the present invention, the number of branches is set to about 3 to 20 from the viewpoint of washability after development and image reproducibility. A range of 10 is preferred. In the block copolymer of the present invention, block A is one of monovinyl aromatic compounds such as styrene, α-methylstyrene, methylstyrene, and ethylstyrene.
It is a thermoplastic, non-elastomeric polymer block with a glass transition temperature of 25°C or higher, which is composed of one or more polymers or a copolymer of the compound and a monomer copolymerizable therewith. Block B is 1,3
-butadiene, isoprene, 2,3-dimethyl-
A polymer with a glass transition temperature of 10°C or less, consisting of one or more polymers of conjugated dienes such as 1,3-butadiene and 1,3-pentadiene, or copolymers of conjugated dienes and monomers that can be copolymerized. It is an elastomeric polymer. Polystyrene is particularly preferred as block A, and polybutadiene or polyisoprene is particularly preferred as block B, from the viewpoint of availability of raw materials and ease of production. The proportion of block A and block B is not particularly limited as long as the block copolymer becomes an elastomer, but the proportion of block A in all blocks is 10 to 40% by weight, preferably 15 to 25% by weight. . The number average molecular weight of blocks A-B by GPC is usually 10,000 to 500,000, but preferably
50000-250000. The photosensitive elastomer composition using the non-linear elastomeric block copolymer of the present invention is characterized by excellent wash-out properties after development and excellent image reproducibility (resolution of relief images). . The content of the block copolymer in the photosensitive elastomer composition of the present invention is usually 30% by weight or more, and in consideration of rubber elasticity and ease of molding, it is preferably used in the range of 60 to 95% by weight. preferable. If necessary, other elastomeric polymers may be used in combination as long as the gist of the present invention is not impaired. In the photosensitive elastomer composition of the present invention, at least one CH ₂ molecule other than the block copolymer of the present invention is used, which is conventionally used for producing the composition.
An addition polymerizable compound having a =C group and a photopolymerization initiator can be used, and these are not particularly limited. Examples of addition polymerizable compounds having at least one CH ₂ =C group include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, polyethylene glycol,
Diacrylates and dimethacrylates such as polypropylene glycol, 1,4 butanediol, 1,6 hexanediol, triacrylates and trimethacrylates of trimethylolpropane, pentaerythritate tetraacrylate and tetramethacrylate, N,N'-
Examples include hexamethylene bisacrylamide and methacrylamide, diacetone acrylamide and methacrylamide, styrene, vinyltoluene, divinylbenzene, diacryl phthalate, and triallyl dianurate, which may be used singly or in combination of two or more. The amount of the compound used is usually 5 to 30% by weight in the photosensitive composition (the same applies hereinafter). Photoinitiators include benzophenone, benzoin, alkyl ethers of benzoin, such as methyl, ethyl, isopropyl and isobutyl ethers of benzoyl, α-methylbenzoyl, α
-Methylbenzoyl methyl ether, α-methoxybenzoin methyl ether, benzoin phenyl ether, α-t-butylbenzoin, anthraquinone, benzanthraquinone, 2-ethylanthraquinone, 2-chloroanthraquinone, 2-
2'-dimethoxydiphenylacetophenone, 2,2
-diethoxyphenylacetophenone, 2,2-
Examples include diethoxyacetophenone, benzyl, bivaloin, etc. These photopolymerization initiators may be used alone or in combination of two or more, and the amount used is usually 0.01 to 5% by weight. In the present invention, components other than those mentioned above may also be included in the photosensitive composition as required. Such components include plasticizers, thermal polymerization inhibitors, antiaging agents, and the like. The plasticizer assists in the production and molding of the photosensitive elastomer composition, promotes the removal of unexposed areas of the photosensitive elastomer composition, and further adjusts the hardness of exposed and cured areas. Depending on these targeted properties, plasticizers are added in amounts ranging from 2 to 40% by weight. Useful substances include hydrocarbon oils such as naphthenic oil and paraffin oil, low molecular weight polystyrene (molecular weight below 3000), α-methylstyrene-vinyltoluene copolymer, petroleum resin, polyacrylate, polyethylene, polyester resin, polyterpene resin. , liquid 1,2- and 1,4-polybutadiene, hydroxides and carboxylated products thereof, liquid acrylonitrile-butadiene copolymers, carboxylated products thereof, and liquid styrene-butadiene construction polymers. Examples of thermal polymerization inhibitors include 2,6-di-t
-butyl-4-methylphenol, methoxyphenol, 2,6-di-t-butyl-p-cresol, t-butylcatechol, pyrogallol, naphthylamine, β-naphthol, t-butylhydroxyanisole, hydroquinone, etc. can. The amount used is usually 0.001 to 2% by weight. The photosensitive elastomer compositions of this invention can be prepared in many ways. For example, the mixture can be mixed and kneaded using a kneader or a roll mill, which are ordinary rubber kneading machines, and then prepared into a sheet of a desired thickness using a molding machine such as an extruder, press, or calendar. If desired, the photosensitive elastomer composition of the present invention may be used in a solvent such as chloroform, carbon tetrachloride, 1,1,1-trichloroethane, trichlorethylene, tetrachlorethylene, methyl ethyl ketone, diethyl ketone, etc.
Methyl isobutyl ketone, benzene, toluene,
A mixture dissolved in an appropriate solvent such as tetrahydrofuran is injected into a frame mold and the solvent is evaporated to prepare the sheet.Furthermore, this sheet can be heat-pressed, extruded, or calendered to achieve a highly accurate thickness. A sheet is obtained. The sheet-formed photosensitive elastomer composition of the present invention has a peelable material such as polyethylene, polypropylene, polyester, polystyrene, etc. on the surface of the photosensitive layer to prevent the photosensitive layer from being contaminated or damaged during storage or handling. A thin transparent film layer can be provided. In addition, when the photosensitive elastomer composition of the present invention is exposed to light, the original image is superimposed on the photosensitive layer and irradiated with actinic rays. may be provided with a thin flexible layer that is solvent soluble. In this case, it is desirable that this layer be removed at the same time when the unexposed portions are eluted with a solvent after exposure of the photosensitive layer is completed. By using the photosensitive elastomer composition of the present invention, cold flow properties during storage of the photosensitive flexo original plate are prevented, and the original plate has extremely excellent surface smoothness. By removing these parts, a relief image with high resolution can be obtained. The photosensitive elastomer composition of the present invention has high photosensitivity and has excellent properties as a printing plate for flexographic printing, but it can also be used for photoresists, screen printing screens, paints, coating materials, adhesives, etc. Film, sheet physical properties, impregnated materials,
It can also be used for other molded products. (Example) The present invention will be described in more detail with reference to Examples below. In addition, the number of copies and percentages in Examples and Comparative Examples
Unless otherwise specified, data are based on weight. Example 1 (Synthesis of random hyperbranched copolymer elastomer) Using a pressure-resistant reactor (No. 5), 1.875 kg of a mixed solvent with a ratio of n-butane/cyclohexane = 2/8, 36 mmol of dibutyl ether, and n-butyl initiator. In the presence of 18 mmol of lithium, 112.5 g of styrene was first polymerized at 60°C for 1 hour, followed by 691.1 g (10.15 mmol) of isoprene, and the reaction temperature was 30°C.
Polymerization was carried out for 1.5 hours while controlling the temperature by reflux cooling so that the temperature was between .degree. and 40.degree. Subsequently, 18.0 mmol of divinylbenzene was added to perform a coupling reaction. 4- as a polymerization terminator in the reaction mixture.
Methyl-2,6-di-t-butylphenol 4
After adding g, this mixed solution was dropped little by little into water heated to 85 to 95°C to volatilize the solvent. The obtained polymer was cut into pieces and dried with hot air at 85°C. The number of branches of the obtained polymer was determined by GPC measurement.
The average was 6. To 100 g of the block copolymer obtained above, 0.6 g of benzoyl methyl ether, 5 g of 1,4-butanediol methacrylate, and 2,6-di-t
0.01 g of -butyl-4-methylphenol was added to 500 ml of cyclohexane solution, heated at 60 DEG C., thoroughly mixed for 3 hours using a propeller stirrer, and the solvent was removed using a vacuum dryer to prepare a photosensitive composition. The resulting photosensitive composition was sandwiched between 0.1 mm thick polyester films and formed into a 3 mm thick sheet using a vacuum press machine. Remove the film cover, apply a negative film, and irradiate the film surface with an ultraviolet lamp (300W high-pressure mercury lamp) for 3 to 6 minutes. After exposure, wash and develop the photosensitive original plate with trichloroethane solution to create a relief image (relief height 1.1 mm) was obtained.
For comparison, a commercially available flexo original plate (Sirel®) using an A-B-A linear block copolymer was also
Cyrel (product of Dupont) was also evaluated. The evaluation was carried out by visually observing and photographing the relief image obtained after 5 minutes of post-exposure, and the convex and concave ruled lines (thin lines) and halftone dot density were 3% and 95%.
The reproducibility limit of halftone dots was evaluated. The results are shown in Table 1.

[Table] The relief image obtained using the composition of the present invention has a dot limit of 150 lines/inch and a ruled line of 150 lines/inch.
It showed much better redefinability than the commercially available comparative example, up to a fine line of 100 μm, and the relief image was sharp and highly accurate. In addition, the relief height of the commercially available product was higher than that of the product of the present invention, the swelling caused by the solvent during development was large, and the convex ruled lines were twisted (wavy distortion). Corrugated board printing was carried out continuously at a temperature of 45°C using the flexographic plate obtained with the composition of the present invention, and the printing durability was more than 500,000 copies. ' was not accepted. Example 2 Using the branched block copolymer shown in Table 2 obtained in the same manner as in Example 1, a photosensitive composition was prepared using the same recipe and method as in Example 1, and a flexographic plate was manufactured. The limits of ruled lines were evaluated and the results shown in Table 2 were obtained.

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Claims (1)

[Claims] 1. In a photosensitive elastomer composition comprising an elastomeric block copolymer, (2) an addition polymerizable compound having at least one CH ₂ =C group, and (3) a photopolymerization initiator, as the block copolymer, A photosensitive elastomer composition characterized in that it uses an elastomeric block copolymer which is non-linear and consists of an elastomeric polymer block and a non-elastomeric polymer block.