JPS6370241A - Photosensitive elastomer composition - Google Patents

Abstract

PURPOSE:To obtain a photosensitive elastomer compsn. which has excellent image reproducibility and is suitable for production of a flexographic printing plate by constituting the photosensitive elastomer compsn. of a specific block polymer, addition polymerizable compd. and photopolymn. initiator. CONSTITUTION:The photosensitive elastomer compsn. is constituted of the linear elastomer-like A-B type block copolymer bonded with a terminal group having polymerizable ethylenic double bonds at least one end of the molecular chain (A is the polymer block of a monovinyl arom. compd. and B is the polymer block of a conjugated diene monomer), the addition polymerizable compd. having at least one ethylenic double bonds and the photopolymn. initiator. The A-B type block polymer which is linear and has about 1-10 pieces, more preferably 1-3 pieces of the unit consisting of (A-B) and repeated in the molecular chain is used. The content thereof is preferably 60-95wt% of the compsn. The content of the addition polymerizable compd. is preferably 5-30wt% of the compsn.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a photosensitive elastomer composition.

(Prior art) Conventionally, rubber plates used for flexographic printing have been produced by directly engraving on a rubber plate, or by corroding a metal plate.
Manufacture a matrix using glass stick, etc., and add 9 pieces to this matrix.
It has been manufactured by pouring and vulcanizing the rubber. However, these methods are complex and require skill, and involve many steps, which 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 all the drawbacks that it needed.

In order to solve this drawback, in recent years a method has been proposed in which a flexographic printing plate is directly manufactured using a photosensitive elastomer composition.

For example, Japanese Patent Publication No. 51-43374 discloses that at least two thermoplastic non-elastomeric polymer blocks having a glass transition temperature of 25° C. or higher and 10 It has been shown to be effective to use solvent soluble thermoplastic elastomeric block copolymers with structures bonded by elastomeric blocks having glass transition temperatures below .degree. However, a flexographic printing plate obtained by molding a photosensitive composition using such a block copolymer and irradiating it with light has weaker plate strength than a conventional vulcanized rubber plate.
In addition, there is a drawback that the plate swells with the solvent during the development (washing out with a solvent) process in the production of printing plates, resulting in a decrease in image reproducibility.) Improvements are desired.

(Problems to be Solved by the Invention) The object of the present invention is therefore to provide a photosensitive elastomer composition which is particularly suitable for the production of flexographic printing plates and which does not have the above-mentioned disadvantages.

(Means for Solving the Problems) The object of the present invention is to (1) form a linear elastomer A-B in which a terminal group having a polymerizable ethylenic double bond is bonded to at least one end of the molecular chain; type block copolymer (
A represents a polymer block of a monovinyl aromatic compound, B represents a polymer block of a conjugated diene monomer),
(2) This is achieved by using a photosensitive elastomer composition comprising an addition polymerizable compound having at least one ethylenic double bond and a photopolymerization initiator.

The linear, elastomeric A-B type block copolymer used in the present invention is an elastomeric block in which a terminal group having a radically polymerizable ethylenic double bond is bonded to at least one end of the copolymer chain. It is a copolymer.

! Lock A is a polymer block of a monovinyl aromatic compound such as styrene or α-methylstyrene, and is a polymer of 18i or more of the compound or a copolymer of the compound and a monomer copolymerizable with it. It is a thermoplastic non-elastomeric polymer block containing a glass transition temperature of 25° C. or higher. What do you particularly like? It is a block of listyrene.

Block B is 1,3-butadiene, isop, ren, 1.
It is a polymer block of a conjugated diene monomer such as 3-pentadiene or chloroglene, or one or more polymers of the monomer, or the monomer and a monomer copolymerizable therewith. It is an elastomeric polymer block containing a copolymer and having a glass transition temperature of 10°C or less. Particularly preferred are polybutadiene blocks or polyisoprene blocks.

In the present invention, the AB type block copolymer is (A-B
), and there are about 1 to 10 of these units in the molecular chain,
Preferably, 1 to 3 linear repeats are used. The ratio of block B to block B is not particularly limited as long as the block copolymer becomes an elastomer, but the preferred ratio of block B to all blocks is 60 to 90% by weight.

The weight average molecular weight of block A by GPC is usually 2.0.
The weight average molecular weight of block B is usually in the range of 10.000 to 1000.000.

The block copolymer of the present invention is characterized in that, in addition to the above structure, a terminal group having a radically polymerizable ethylenic double bond is bonded to at least one end of the block copolymer chain.

The method for producing the block copolymer of the present invention is not particularly limited and may be any conventional anionic polymerization method, but one example is the method disclosed in US Pat. No. 3,786,116. According to this method, a living block copolymer of polystyrene-polyisoprene is produced by sequential polymerization, and then ethylene oxide or propylene oxide is added to form a block copolymer having stable anionic end groups. Thereafter, it is reacted with methacrylic acid nolide or the like to produce a block copolymer in which a terminal group having a radically polymerizable double bond is bonded to the end of the polymer chain.

A monomer containing a halogen such as chlorine, bromine, or fluorine is used as a compound that reacts with the block copolymer having a stable anionic terminal group to form a terminal group having a radically polymerizable double bond.

Such monomers include halogen-containing vinyl ethers such as 1-chloroethyl vinyl ether, 3-chloropropyl vinyl ether, haloalkyl vinyl ethers, vinyl chloroacetate, vinyl 3-chloroglopionate, and vinyl 2-bromoundecanoate. , 2-rioo
) fAt-1,3-pucdiene, 2-chloromethyl-3
-diene halides such as methyl-1°3-butadiene,
Examples include (meth)acrylic acid halides such as acrylic acid chloride and methacrylic acid chloride, vinylpenzyl chloride promnorbornene, and prommethylnorgormene. These compounds are bonded to one end of the copolymer chain if a monofunctional polymerization initiator is used during the production of the block copolymer, and to both ends of the copolymer chain if a difunctional polymerization initiator is used.

Since the block copolymer used in the present invention has a radically polymerizable terminal group as described above, a flexo plate is prepared by mixing this block copolymer with a radically polymerizable monomer and a photopolymerization initiator. By producing and exposing the diblock copolymer to light, crosslinking occurs between molecular chains of the diblock copolymer, and as a result, the strength of the flexographic plate after exposure is improved and the reproducibility of the relief image is also significantly improved.

The content of the block copolymer of the present invention in the photosensitive elastomer composition of the present invention is usually 30% by weight or more, but in consideration of rubber elasticity and ease of molding, it is used in the range of 60 to 95% by weight. Preferably. 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 entomer composition of the present invention, in addition to the block copolymer of the present invention, addition polymerizable compounds having at least one Ca, -C; Polymerization initiators can be used, and these are not particularly limited.

Examples of the addition polymerizable compound having at least one cH2-cc group include ethylene glycol, diethylene glycol, phlopylene gelicol, diethylene glycol,
polyethylene glycol, polypropylene glycol,
Diacrylates and dimethacrylates such as 1,4-butanediol and 1.6-hexanediol, triacrylates and trimethacrylates of trimethylolprono-benzene, pentaerythritol tetraacrylate and tetramethacrylate, and boar'-\xamethylene. Bisacrylamide and methacrylamide, diacetone acrylamide and methacrylamide, styrene, vinyltoluene, divinylbenzene, diallyl phthalate,
Examples include triallyl cyanurate, which may be used alone or in combination of two or more.

The amount of the compound used is usually in the photosensitive composition (the same applies below)
It is 5 to 30% by weight.

As photopolymerization initiators, benzophenone, benzoin,
Alkyl ethers of benzoin, such as methyl, ethyl, isozolobyl and isobutyl ethers of benzoin,
α-Methylbenzoin, α-methylbenzoin methyl ether, α-methoxybenzoin methyl ether, pentuin phenyl ether, α-t-butyl pentuin,
Anthraquinone, benzanthraquinone, 2-ethylanthraquinone, 2-chloroanthraquinone, 2-2'-
Examples include dimethoxyphenylacetophenone, 2,2-jethoxyphenylacetophenone, 2,2-jethoxyacetophenone, benzyl, pivaloin, and the like. These photopolymerization initiators are 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 the above may be included in the photosensitive composition as necessary. can be done. Examples of such components include plasticizers, thermal polymerization inhibitors, and antiaging agents.

The curing agent assists in the production and storage of the photosensitive elastomer composition, promotes the removal of unexposed portions of the photosensitive elastomer composition, and further adjusts the hardness of the exposed and cured portions.

Depending on these target properties, the plasticizer is added in an amount ranging from 2 to 40% by weight. Useful substances include hydrocarbon oils such as naphthenic oil and nografine oil, low molecular weight polystyrene (molecular weight 3000 or less), and α-methylstyrene.
Vinyltoluene copolymers, petroleum resins, polyacrylates, polyethylene, polyester resins, I-literpene resins, liquid 1,2- and 1,4-polybutadiene, and their hydroxides, carboxymolated products, liquid acrylonitrile-butadiene copolymers , carboxymolated products thereof, and liquid styrene-butadiene copolymers.

Examples of thermal polymerization inhibitors include 2,6-di-t-butyl-4-methylphenol, methoxyphenol, 2,6
Examples include -di-t-butyl-p-cresol, t-butylcatechol, pyrogallol, naphthylamine, β-naphthol, t-butylhydroxyanine, and hydroquinone. Usage amount is usually 0.001 ~
It is 2% by weight.

The photosensitive elastomer compositions of this invention can be prepared in many ways. For example, by mixing and kneading using a normal rubber kneading machine such as a Nigu or a roll mill,
A sheet of desired thickness can be prepared using a molding machine such as an extruder, press, or calendar. If desired, the photosensitive elastomer composition of the present invention can also be used in a solvent such as lye+oform, carbon tetrachloride, 1.1.1-)lychloroethane, trichlorethylene, tetrachlorethylene, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone. The sheet can be prepared by pouring a mixture dissolved in a suitable solvent such as benzene, toluene, tetrahydrofuran, etc. into a frame mold and evaporating the solvent, or the sheet can be heated, pressed, extruded or calendered. A sheet with good thickness accuracy can be obtained.

The sheet-formed photosensitive elastomer composition of the present invention contains polyethylene on the surface of the photosensitive layer to prevent the photosensitive layer from being contaminated or damaged during storage or handling.
A peelable or thin transparent film layer of polypropylene, polyester, polystyrene, etc. can be provided.

In addition, in the photosensitive two-stomer composition of the present invention, the original image is superimposed on the photosensitive layer during exposure and actinic rays are irradiated, but in order to improve contact with the original image and to enable reuse of the original image. A thin, flexible layer that is solvent soluble may be provided for this purpose. 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, it is possible to obtain relief images with high resolution without being dull, which makes it possible to produce flexographic plates with improved strength after exposure.

The photosensitive elastomer composition of the present invention has high photosensitivity and has excellent properties as a printing plate for flexographic printing.
In addition to these, there are also paints, coating materials, adhesives, films, etc. for photoresists and screen printing screens.
It can be used for sheet materials, impregnated materials, and other molded products.

(Example) The present invention will be described in more detail with reference to Examples below. In addition, the parts and percentages in Examples and Comparative Examples are based on weight without any particular omission.

Example 1 (A) Synthesis of terminally modified block copolymer Using the pressure-resistant reactor of 51, a mixed solvent L875 of n-butane/cyclohexane at a ratio of 30/70 was used! ? , dibutyl ether 20
112 mmol of styrene in the presence of 10 mmol of initiator n-butyllithium at 30° C. for 1 hour. ! M was polymerized, followed by addition of isoprene 687.5 F, and polymerization was carried out for 1.5 hours while controlling the temperature by reflux cooling so that the reaction temperature was between 50°C and 60°C. Subsequently, 11 mmol of ethylene oxide was added to make the active end of the isogrene block a stable anion, and 12 mmol of acrylic acid chloride was further added to react with the active polymer end. Methanol 5-1 was added to the reaction mixture as a reaction terminator.
After adding 4 g of 4-methyl-2,6-di-t-butylphenol as an oxidation stabilizer, this mixed solution was added little by little to 8
The solution was dropped into water heated to 5 to 95°C to evaporate the solvent. The obtained polymer was cut into strips and dried with hot air at 85°C.

A block copolymer having radically polymerizable terminal groups was thus obtained.

(B) Preparation of photosensitive composition 100 g of the block copolymer obtained above was mixed with penzoin methyl ether, 5 g of vO,6,11,4-butanediol dimethacrylate, and 2,6-di-t-butyl. -4
-Methylphenol 0.01N was added and thoroughly mixed to prepare a photosensitive composition.

(C) Physical properties of cured product 1) The above photosensitive composition was cured using a 300W high-pressure mercury lamp.
A cured product was obtained by exposure treatment for a minute. The obtained cured product had a hardness of 40 (measured according to JIS K6301) and an elasticity of 49% (measured at 25° C. using a Dunlop IJ psometer). Furthermore, the strength, elongation, and hardness change (difference immediately after pressurization and after 10 seconds, expressed as ΔH8) at S@ (25°C) were determined according to JISK6301, and the results shown in Table 1 were obtained.Table 1 Notes ) (1) Cyrsl manufactured by De Bonn was used.

2) The above photosensitive composition was sandwiched between 0.1-thick polyester films and formed into a 3-thickness sheet using a vacuum press. The film was peeled off, a negative film was applied, and the film surface was irradiated with the ultraviolet lamp for 3 to 6 minutes.

After exposure, the photosensitive original plate was washed and developed with a trichloroethane solution to obtain a relief image (relief height: 1.4 m). The resolution of the obtained plate was determined by visually observing and photographing the obtained relief image, and evaluating the reproducibility limits of the ruled lines (thin lines) of the 6 cubic meters and concave chambers and the halftone dots at halftone density of 3% and 95%. . The results are shown in Table 2.

Table 2 Relief images obtained using the composition of the present invention have a reproducibility limit of 150 lines/inch for halftone dots and a fine line of 100 μm for ruled lines, which is much better than the commercially available comparative example. The relief image was sharp and highly accurate. In addition, the relief height of the commercial product of the comparative example was higher than that of the product of the present invention, the swelling due to the solvent during development was large, and the convex ruled lines were twisted (wavy distortion).

Corrugated printing was carried out continuously at a temperature of 45°C using a flexo plate obtained with the composition of the present invention, but the printing durability was more than 500,000 copies. No sagging was observed.

Example 2 A block copolymer with bonded terminal groups listed in Table 3 was prepared in the same manner as in Example 1, a photosensitive composition was prepared with the same formulation as in Example 1, and the strength characteristics of each cured product were determined. and the resolution (reproducibility limit) of the flexographic plate was evaluated. The results are shown in Table 3.

Table 3 Example 3 A block copolymer bonded with a terminal group having a radically polymerizable double bond (acrylic acid chloride was used as the source of the terminal group) having the composition shown in Table 4 in the same manner as in Example 1. was prepared. Using each of these, a cured product and a 7 lexo plate were obtained using the same recipe and method as in Example 1. The strength characteristics and resolution were evaluated and the results shown in Table 4 were obtained.

Claims (1)

[Claims] (1) A linear elastomeric A-B type block copolymer in which a terminal group having a polymerizable ethylenic double bond is bonded to at least one end of the molecular chain (A is a polymer block of a monovinyl aromatic compound). , B represents a polymer block of a conjugated diene monomer), (2) an addition polymerizable compound having at least one ethylenic double bond, and (3) a photopolymerization initiator. thing.