JP2928289B2 - Composition for photosensitive flexographic plate slip film and photosensitive flexographic plate - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a composition for a photosensitive flexographic printing slip film and a photosensitive flexographic printing plate coated with the slip film.

(Prior art) A photosensitive flexographic plate is a relief printing rubber plate that forms a relief using a photosensitive elastomer composition molded to a certain thickness, and a negative or positive film is adhered to a photosensitive layer. It is manufactured by a method of exposing selected portions of the photosensitive composition layer by irradiating with actinic light and then removing the unexposed portions to form a relief. Since the surface of the photosensitive flexographic plate has strong adhesiveness, air bubbles enter between the negative or positive film and the plate cannot be accurately reproduced, so the surface of the flexographic plate is usually about 0.5 to 0.5 to prevent sticking. It is coated with a 20 μm thick polymer film called a slip film.

Conventionally, polyamides and cellulosic polymers have been mainly used as polymers for slip films.
Generally, a slip film is prepared by directly applying a solution of the above-described polymer to the surface of the photosensitive flexographic plate and drying it, or laminating a preformed thin film on the surface of the photosensitive flexographic plate. After the exposure, the unexposed portion of the photosensitive layer is washed and removed (developed) with a solvent (developer) after exposure, and is dissolved and removed together. Polyamide-based slip films have suitable strength and elasticity, but have extremely poor solubility in repeated use and low-purity developers. A slip film using a cellulosic polymer has good solubility in a developing solution, but lacks elasticity and has problems such as cracking when the plate is bent, and thus needs to be solved.

(Problems to be Solved by the Invention) The inventors of the present invention have made intensive studies to solve the above-mentioned drawbacks, and as a result, a polymerizable monomer in a photosensitive composition in which a specific hydrogenated block copolymer is required as a slip film. It was found that it did not dissolve in a monomer (photosensitive solution), was excellent in solubility in a developing solution, and was excellent in detachability from a negative film, and based on this finding, the present invention was completed.

According to the present invention, there is provided a block copolymer of an aromatic vinyl compound having an aromatic vinyl compound content of 5 to 60% by weight and a conjugated diene. A composition for a photosensitive flexographic slip film comprising at least 70% of a hydrogenated block copolymer, and a photosensitive flexographic plate coated with a slip film formed from the composition Is provided.

The block copolymer in the present invention is a polymerization catalyst based on an alkali metal such as lithium, sodium and potassium, and n-butyllithium as a particularly suitable polymerization catalyst, se
Using an organic lithium compound such as c-butyllithium, tert-butyllithium, hexamethylenedilithium, butadienyldilithium, or isoprenyldilithium, an aromatic vinyl compound and a conjugated diene can be obtained by a known method, for example,
JP-B-36-19286, JP-B-43-17979, JP-B-45-319
No. 51, which is obtained by hydrogenating a conjugated diene in a block copolymer obtained by block copolymerization according to a method described in JP-A-51-51. The block copolymer in the present invention is mainly composed of at least one polymer block (A) containing at least one aromatic vinyl compound having an aromatic vinyl compound content of 5 to 60% by weight and at least one conjugated diene. The block copolymer may be a linear or radial structure as long as it is a block copolymer containing at least 70% of the conjugated diene is hydrogenated. .

In general formulas, (AB) _n , AB-A) _n , BA
-B) _n linear block copolymer (where n is an integer of 1 or more) and [(BA) _{n m + 2} X, [(AB) _{n
m + 2} X, [(B-A _n B _{m + 2} X, [(A-B _n A
_{m + 2} X, wherein m and n are integers of 1 or more, and X is a coupling residue.
In these block copolymers, the boundary between block A and block B does not necessarily need to be clearly distinguished.

The polymer block mainly composed of an aromatic vinyl compound refers to a copolymer block of an aromatic vinyl compound containing 50% by weight or more of an aromatic vinyl compound and a conjugated diene or another copolymerizable vinyl monomer. Shows a homopolymer block of an aromatic vinyl compound, and a polymer block mainly composed of a conjugated diene is defined as a polymer block containing at least 50% by weight of a conjugated diene and another copolymerizable vinyl monomer such as an aromatic vinyl compound. It shows a copolymer block or a homopolymer block of a conjugated diene.

The aromatic vinyl compound or other vinyl monomer in the copolymer block may be distributed uniformly or in a tapered shape.

The block copolymer used in the present invention may be any mixture of the block copolymers represented by the above general formula.

Particularly preferred block copolymers in the present invention are block copolymers containing at least two polymer blocks mainly containing an aromatic vinyl compound and at least one polymer block mainly containing a conjugated diene.

In the present invention, the content of the aromatic vinyl compound in the block copolymer is 5 to 60% by weight. If the amount is less than 5% by weight, the required strength of the slip film cannot be obtained, and if it exceeds 60% by weight, the elasticity decreases. And cracks are likely to occur. Preferably it is 10 to 40% by weight.

In addition, the hydrogenation rate of the conjugated diene in the conjugated diene polymer block is 70% or more.
Does not function as a slip film. Preferably, it is between 85% and 100%.

As the aromatic vinyl compound constituting the block copolymer in the present invention, styrene, o-methylstyrene, p
-Methylstyrene, α-methylstyrene, vinylnaphthalene and the like. One or more of these are used. Particularly preferred is styrene. Examples of the conjugated diene include 1,3-butadiene, isoprene, 2,3-dimethyl, 1,3-butadiene, and 1,3-pentadiene. One or more of these are used. Particularly preferred are 1,3-butadiene and isoprene.

The weight average molecular weight of the block copolymer in the present invention is
The number average molecular weight of the block (A) is preferably in the range of 4,000 to 50,000,
The number average molecular weight of the block (B) is preferably in the range of 10,000 to 250,000.

When a slip film is formed from the block copolymer of the present invention, a releasing agent may be added to the block copolymer in an amount of 1 to 20 parts by weight / copolymer 10 in order to improve the desorption property.
0 parts by weight can be added.

Usually, examples of the release agent include silicone oil, long-chain alkyl fatty acid, long-chain alkyl fatty acid ester, paraffin wax, and chlorinated paraffin wax.

A general photosensitive flexographic plate is a 1 to 8 mm thick photosensitive layer and a protective film mainly made of polyester on the back surface thereof and a 0.1 to 20 μm thick film having a function of improving adhesion to a negative film on the surface of the photosensitive layer. It has a multilayer structure consisting of a slip film and a protective film mainly made of polyester, which can be peeled off on the slip film. The photosensitive layer is, for example,
And base additives as described in JP-A-43374, etc., an addition-polymerizable ethylenically unsaturated monomer, a photopolymerization initiator, a polymerization inhibitor and other additives.

The method for forming the slip film is not particularly limited in the present invention, but is usually formed on the back surface of the protective film, and is laminated on the photosensitive layer by bringing this surface into close contact with the surface of the photosensitive layer.

First, a silicone as a release agent is applied to a protective film (a polyethylene terephthalate film having a thickness of 75 to 150 μm is usually used), and a solution of the block copolymer of the present invention is dried on the silicone. It is applied using a bar coater, an applicator or the like so as to have a predetermined thickness, and dried. The surface of the slip film formed on the protective film thus obtained is brought into close contact with the surface of the photosensitive layer by pressing with a roller or the like. When forming the relief, peel off the cover film, adhere the negative film to the exposed slip film, irradiate it with ultraviolet light, expose it, dissolve the unexposed part of the slip film and the photosensitive layer with a halogen-based developer,
The removal operation is usually performed.

(Effect of the Invention) Thus, according to the present invention, it has sufficient strength and elasticity,
A photosensitive flexographic slip film having the following excellent characteristics as compared with the prior art is provided.

(1) The solubility in an unsaturated ethylenic compound (polymerizable monomer) is small, so that the compound is less transferred from the photosensitive layer and is hardly changed with time.

(2) The adhesiveness of the surface is low, and the removability of the negative film is possible.

(3) It has appropriate elasticity, is strong in bending and does not crack.

(4) It is easily dissolved in a developer.

When the block copolymer in the present invention is used as a slip film, it is possible to prepare a relief excellent in reproducibility of a fine pattern in preparing a relief.

(Example) Hereinafter, the present invention will be described more specifically with reference to examples. Parts and% in Examples, Comparative Examples and Reference Examples are based on weight unless otherwise specified. The hydrogenation rate was determined from the iodine value according to JIS K0070B method.

Example 1 A photosensitive layer using a polystyrene-polyisoprene-polystyrene block copolymer (hereinafter abbreviated as SIS) was coated with the polymer shown in Table 1 as a slip film, and the performance of the slip film was tested. did.

Photosensitive layer composition SIS (Quintac 3420, manufactured by Zeon Corporation) 1,000 g, trimethanolpropane triacrylate 100 g, Irger Cure 651 (manufactured by Ciba Geigy) 2
0 g was prepared by kneading in a 2 l Banbury at 150 ° C. for 15 minutes.
The obtained composition was sandwiched between two 0.1 mm-thick polyethylene terephthalate (hereinafter abbreviated as PET) films and molded into a 3 mm-thick film by a vacuum press to prepare a photosensitive layer. 10 g of each polymer for a slip film shown in Table 1 was dissolved in 90 g of a solution of ethanol / chloroform = 1/9 (weight ratio), and the thickness after drying was 1 on a PET film coated with silicone on the surface.
The solution was coated so as to have a thickness of about 10 μm, dried at 60 ° C. for 30 minutes, and brought into close contact with the surface of the photosensitive layer using a roller. The following characteristics were evaluated using the photosensitive flexographic plate coated with the slip film thus obtained. The results are shown in Table 2.

(1) Solubility: solubility of a slip film in a developing solution (trichloroethane / isopropyl alcohol = 7/3 volume ratio).

(2) Change over time: The presence or absence of a change in the adhesiveness of the surface of the slip film one month after mounting on the photosensitive layer, and the presence or absence of peeling of the film from the photosensitive layer.

(3) Dense, detachable: adhesion of the negative film to the surface of the slip film and easy peeling of the negative film.

(4) Elasticity and bending resistance: Whether or not cracks occurred in the slip film when the photosensitive flexographic plate was bent by about 30 degrees.

(5) Reproducibility: balance of reproducibility of relief fine lines after exposure and development.

The evaluation results are as follows: ○ when there is no problem in use for each item, △ when there is a need for improvement in performance but it can be used,
Unusable cases are indicated by x. In the comprehensive evaluation results, ◎ indicates that there is particularly excellent performance, ○ indicates that there is no problem in use, Δ indicates that there is a problem in performance but can be used, and X indicates that it cannot be used.

In addition, the polymer No. 3 in Table 1 was produced as follows.

Under a nitrogen gas atmosphere, 0.11 part of n-butyllithium was added to an n-hexane solution containing 15 parts of 1,3-butadiene and 20 parts of styrene, and polymerized at 70 ° C. for 2 hours, and then 45 parts of 1,3-butadiene was further added. And an n-hexane solution containing 20 parts of styrene were added thereto, and polymerized at 70 ° C. for an hour. The obtained polymer was a block copolymer (abbreviated as SB-SB) having a styrene content of 40% and a styrene / butadiene copolymer-styrene / butadiene copolymer structure.

The hydrogenated SIS and the hydrogenated SB-SB were prepared by adding 5 parts of Raney nickel catalyst to a solution containing a block copolymer.
100 parts of a polymer were added, and the reaction was carried out at 50 ° C. and a hydrogen pressure of 1.8 atm.

Example 2 A block copolymer (SBS) was obtained by sequentially polymerizing styrene and butadiene, and hydrogenated in the same manner as in Example 1 to produce a hydrogenated block copolymer shown in Table 3.

The slip film properties of these block copolymers were evaluated in the same manner as in Example 1. The results are shown in Table 4.

Claims (2)

(57) [Claims] 1. A block copolymer of an aromatic vinyl compound having an aromatic vinyl compound content of 5 to 60% by weight and a conjugated diene, wherein at least 70% of the conjugated diene is hydrogenated. A composition for a photosensitive flexographic printing slip film, comprising a copolymer. 2. A photosensitive flexographic plate coated with a slip film formed from the composition according to claim 1.