JPH06214389A - Photosensitive elastomer composition - Google Patents

Abstract

PURPOSE:To provide a compsn. contg. a water-swellable resin, easy to produce and capable of forming an image when imagewise exposed and developed with an aq. developer. CONSTITUTION:This photosensitive elastomer compsn. contains 25-85wt.% polymer of conjugated diene type hydrocarbon having 20,000-200,000 number average molecular weight or copolymer of conjugated diene type hydrocarbon and a monoolefinic unsatd. compd. having 20,000-200,000 number average mol.wt., 10-70wt.% water-swellable resin, 1-40wt.% nongaseous ethylenic unsatd. compd. and a photopolymn. initiator as essential components.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photosensitive elastomer composition for a flexographic printing plate which can be developed with an aqueous alkaline developer or an aqueous developer such as an alkaline water-organic solvent system.

[0002]

2. Description of the Related Art Conventionally, a flexographic printing rubber plate is produced by corroding a metal plate to produce an original plate, producing a master plate from plastics or the like, and then pouring rubber into the master plate to apply pressure thereto. Has been manufactured. However, this method has many drawbacks such as costly and time-consuming, and the precision of the obtained rubber plate itself is low, which requires back-polishing when used. It was

Therefore, in recent years, an alternative method has been developed, and a method using a photosensitive elastomer composition has been developed and put into practical use.

Then, as such a method, 25 ° C.
At least two thermoplastic non-elastomeric polymer blocks having the above glass transition temperature and a structure in which the non-elastomeric polymer blocks are bonded by an elastomeric block having a glass transition temperature of 10 ° C. or lower,
A method for producing a printing plate for flexographic printing using a photosensitive layer mainly composed of a solvent-soluble thermoplastic elastomer block copolymer, an ethylenically unsaturated compound and a photopolymerization initiator (Japanese Patent Publication No. 51-4337). Japanese Examined Japanese Patent Sho 56-292
No. 60) is known. However, these printing plates have to use an organic solvent as a developer, but they have problems of harmfulness to humans, air pollution, and fire hazard depending on the solvent used. In fact, its use is becoming difficult due to the large amount of capital investment and pollution regulations that have become increasingly severe in recent years.

In order to solve such a problem, studies have been conducted on a photosensitive elastomer composition which can be developed with an aqueous developer, and some proposals have been made.

For example, a conjugated diene hydrocarbon (A) and an α, β-ethylenically unsaturated carboxylic acid (B) are used as essential components, and a monoolefin unsaturated compound (C) is added thereto as A: 10 to 95 mol. %, B: 5 to 90 mol%, C:
A method using a photosensitive resin composition containing a copolymer, a photopolymerizable unsaturated monomer, and a photosensitizer contained in a proportion of 0 to 85 mol% (JP-A-52-134655), and the entire composition (A) 55-85 wt. Of a high molecular weight butadiene / acrylonitrile copolymer having a number average molecular weight of 20,000-75,000, an acrylonitrile content of 10-50% by weight and a carboxyl content of 1-15% by weight. %, (B) number average molecular weight of 750 to 10,000, 0
5-40% by weight of a low molecular weight butadiene polymer having an acrylonitrile content of 50% by weight and a carboxyl content of 0-15% by weight [where polymer (a) and polymer (b) are present]
Containing at least 2% by weight of carboxyl groups in combination with), and (c) forming a high-molecular polymer by free-radical-initiated chain growth addition polymerization having at least one terminal ethylene group. 2 to 40% by weight of a non-gaseous ethylenically unsaturated compound which is capable of being compatible with the above-mentioned polymers (a) and (b), and (d) is activated by actinic radiation for initiating the polymerization of the unsaturated compound. A light-sensitive elastic composition (Japanese Patent Publication No. 58-33884) characterized in that it contains 0.001 to 10% by weight of an organic radiation-sensitive free radical producing system is proposed.

[0007] These techniques are characterized in that by introducing a polar group such as a carboxyl group into the skeletal polymer, a photosensitive resin which can be developed with an aqueous alkali solution or an alkaline water-organic solvent system and has rubber elasticity is used. I have.

[0008]

However, since these photosensitive elastomer compositions have polar groups such as carboxyl groups introduced into the backbone polymer, they have no solvent resistance to alcohol-based inks and cannot be used for ordinary flexographic printing. There is a problem.

[0009]

[Means for Solving the Problems] Under such circumstances,
As a result of various studies conducted by the present inventors, a photosensitive elastomer composition containing styrene-butadiene rubber, styrene-isoprene rubber, nitrile-butadiene rubber, butadiene rubber or the like as a backbone polymer is added to a predetermined amount of a water-swellable resin. Based on this finding, it was found that a material exhibiting excellent properties for a flexographic printing plate can be obtained by containing the above.

That is, the present invention is based on the total weight of the composition. (A) Number average molecular weight of 20,000 to 200,000
25. A conjugated diene hydrocarbon polymer having 0 or a copolymer of a conjugated diene hydrocarbon having a number average molecular weight of 20,000 to 200,000 and a monoolefin unsaturated compound 25.
To 85% by weight, (b) water-swellable resin 10 to 70% by weight, (c) non-gaseous ethylenically unsaturated compound 1 to 40
The present invention provides a photosensitive elastomer composition containing, by weight, (d) a photopolymerization initiator as an essential component.

The component (a) used in the present invention is a number average molecular weight of 2 obtained by polymerizing a conjugated diene hydrocarbon.
A polymer having a number average molecular weight of 20,000 to 200,000, which is obtained by polymerizing a polymer having a molecular weight of 20,000 to 200,000, or a conjugated diene-based carbohydrate and an unsaturated compound of a monoolefin.
It is a copolymer of 0.

As the conjugated diene hydrocarbon, 1,3-
Butadiene, isoprene, chloroprene and the like are used. The conjugated diene hydrocarbon may be used alone or 2
You may mix and use more than one kind. Polymers composed of these conjugated diene hydrocarbons can impart the flexibility, that is, the rubber elasticity, which must be provided as a flexographic printing plate.

As the monoolefin unsaturated compound,
Styrene, α-methylstyrene, o-methylstyrene,
m-Methylstyrene, p-methylstyrene, acrylonitrile, methacrylonitrile, vinyl chloride, vinylidene chloride, acrylamide, methacrylamide, vinyl acetate, acrylic acid ester, methacrylic acid ester and the like are used.

Examples of the polymer obtained by polymerizing a conjugated diene hydrocarbon or a copolymer obtained by polymerizing a conjugated diene hydrocarbon and a monoolefin unsaturated compound include a butadiene polymer, an isoprene polymer, Chloroprene polymer, styrene-butadiene copolymer, styrene-
Isoprene copolymer, styrene-chloroprene copolymer, acrylonitrile-butadiene copolymer, acrylonitrile-isoprene copolymer, acrylonitrile-chloroprene copolymer, methyl methacrylate-butadiene copolymer, methyl methacrylate-isoprene copolymer ,
Methyl methacrylate-chloroprene copolymer, methyl acrylate-butadiene copolymer, methyl acrylate-isoprene copolymer, methyl acrylate-chloroprene copolymer, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-isoprene-styrene Examples thereof include copolymers and acrylonitrile-chloroprene-styrene copolymers.

Preferred as the polymer used in the present invention are random polymers such as styrene-butadiene copolymer, styrene-isoprene copolymer, acrylonitrile-butadiene copolymer and styrene-butadiene-styrene block copolymer, styrene. -Isoprene-styrene block copolymer, crystalline 1,2-polybutadiene and other thermoplastic elastomers, but the photosensitive elastomer composition for flexographic printing is usually compared from the time the sheet is manufactured to the time it is processed into a printing plate. Because it is stored for a long time,
Random polymers such as styrene-butadiene copolymers and acrylonitrile-butadiene copolymers cause cold flow and deteriorate thickness accuracy. Therefore, it is preferable to use a thermoplastic elastomer such as a thermoplastic elastomer block copolymer or crystalline 1,2-polybutadiene. The thermoplastic elastomer block copolymer is represented by the following general formula. (A−B) _n −A (B−A) _{n + 1} −B (A−B) _{n + 1} (A−B) _m X

However, A is a thermoplastic non-elastomeric polymer block having a glass transition temperature of 20 ° C. or higher, such as polystyrene or poly (α-methylstyrene), and B is a glass transition temperature of 10 ° C. or lower. It is an elastomeric block having, for example, polybutadiene, polyisoprene, etc., and X is a polyfunctional residue having m bonds, for example, Si, Sn, etc. In addition, n is 1 to 1
0 and m are numbers 2 to 7. The content of the elastomer component is 85% by weight or less based on the developability with respect to an aqueous developer,
Further, it is required to be 25% by weight or more for the sake of resistance to alcohol-based ink. It is preferably in the range of 50 to 75% by weight, most preferably 65 to 75% by weight.

As the component (b), a polymer compound having a weight gain of 500% or more when soaked in water or a liquid containing 70% or more of water at 20 ° C. for 24 hours, that is, a so-called water-swellable resin is used. . This is obtained by cross-linking an originally water-soluble hydrophilic polymer by various methods to make it insoluble in water, or by chelating it with a metal or the like.

A specific example is shown in Japanese Examined Patent Publication No. 56-50.
The hard segment having an average molecular weight of about 1,000 or more described in Japanese Patent No. 886, and the segment having an average molecular weight of about 1,000 or more and containing an ethylenically unsaturated group (hereinafter,
In the combination of (unsaturated segment), in the unsaturated group of the block copolymer or graft copolymer having at least one (hard segment)-(unsaturated segment)-(hard segment) bond form in the molecule,
Hydrophilic hydrophilic compound obtained by adding a thioalcohol group-containing hydrophilic compound having at least one carboxyl group, amino group or hydroxyl group, and then esterifying, aminating, alkylating or sulfuric acid esterifying the above-mentioned carboxyl group, amino group or hydroxyl group. Block copolymers and graft copolymers, those obtained by modifying polyethylene glycol (polyethylene oxide) to make them insoluble in water, polymer products obtained by grafting acrylonitrile or the like to starch and further hydrolyzing it, and cross-linked acrylic acid polymers.

Among the above water-swellable resins, Japanese Patent Publication No. 56-
The water-swellable polymer described in 50886 is preferable. The content thereof is 10 based on the total composition in consideration of the developability with respect to an aqueous developer and the alcohol-based ink resistance.
-70% by weight, preferably 20-50% by weight, most preferably 20-30% by weight.

Next, as the non-gaseous ethylenically unsaturated compound as the component (c) used in the present invention, esters such as acrylic acid, methacrylic acid, fumaric acid, maleic acid, derivatives of acrylamide and methacrylamide, and acryl. Examples thereof include esters, styrene and derivatives thereof, N-substituted maleimide compounds and the like. Specific examples thereof include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, butylene glycol diacrylate and dimethacrylate, or trimethylolpropane triacrylate and trimethacrylate, pentaerythritol tetraacrylate. And tetramethacrylate, N, N′-hexamethylenebisacrylamide and methacrylamide,
Diacetone acrylamide and methacrylamide, styrene, vinyltoluene, divinylbenzene, diallyl phthalate, triallyl cyanurate, fumaric acid diethyl ester, fumaric acid dibutyl ester, fumaric acid dioctyl ester, fumaric acid distearyl ester, fumaric acid butyl octyl ester, Fumaric acid diphenyl ester, fumaric acid dibenzyl ester, maleic acid dibutyl ester, maleic acid dioctyl ester, fumaric acid bis (3-phenylpropyl) ester, fumaric acid dilauryl ester, fumaric acid dibehenyl ester, N-methylmaleimide, N -Ethylmaleimide, N-propylmaleimide, N-butylmaleimide, N-pentylmaleimide, Nn-hexylmaleimide, N-cyclohexylmaleimide, N n- octyl maleimide, N-2-
Examples thereof include, but are not limited to, ethylhexyl maleimide, Nn-decyl maleimide, N-lauryl maleimide, and the like. These may be used alone or in combination of two or more.

Further, these ethylenically unsaturated compounds do not have film forming ability in the state before photopolymerization. Among these ethylenically unsaturated compounds, fumarate and malate are superior to acrylic acid derivatives and methacrylic acid derivatives in terms of stability during the heat molding process and storage of the unexposed sheet. Further, fumarate is superior to malate in terms of reactivity, and it is preferable to use fumarate. The addition amount depends on the type and the characteristics of the flexographic plate to be obtained, but it is necessary to be 1% by weight or more. If the amount is less than this, insolubilization in the developing solution does not occur sufficiently even when irradiated with light, and in the washing out step with the developing solution after image printing, a part of the portion that should be the relief is washed off, and a satisfactory plate is obtained. Can't get On the other hand, if the amount added is too large, the obtained plate becomes hard and brittle, and the rubber elasticity is reduced, so that it may not be used in flexographic printing. The preferable addition amount is 5 to 30.
% By weight.

Next, as a photopolymerization initiator effective for the photosensitive elastomer composition which is the component (d) of the present invention, benzophenone, Michler's ketone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl are used. Ether, α-methylolbenzoin, α-methylolbenzoin methyl ether, α-methoxybenzoin methyl ether, benzoin phenyl ether, α-t-butylbenzoin, benzyl, pivaloin, anthraquinone,
Benzanthraquinone, 2-ethylanthraquinone, 2
-Chloranthraquinone can be mentioned as an example. Such a photopolymerization initiator is added in a polymerization effective amount, that is, at least 0.01% by weight or more. Generally 0.
It is preferably added in the range of 1 to 2% by weight.

In addition to the above-mentioned essential components, the photosensitive elastomer composition of the present invention may contain 0.001 to 2% by weight of a thermal polymerization inhibitor. Examples of the thermal polymerization inhibitor include 2,6-di-t-butyl-p-cresol, p-methoxyphenol, pentaerythritol tetrakis [3- (3 ', 5'-di-t-butyl-4'
-Hydroxy) phenylpropionate], hydroquinone, t-butylcatechol, t-butylhydroxyanisole, 4,4'-butylidenebis (3-methyl-6-
t-Butyl) phenol and the like can be mentioned.

The photosensitive elastomer composition of the present invention may optionally contain a plasticizer. This plasticizer promotes the removal of the unexposed portion of the photosensitive elastomer composition, improves the physical properties of the cured portion, and the like, and further assists the production of the photosensitive elastomer composition layer, particularly molding. A range of 2 to 40% by weight is added depending on the characteristics to be set. Examples thereof include hydrocarbon oils such as naphthene oil and paraffin oil, polyethylene glycol, polyethylene glycol ester, number average molecular weight 5
Liquid rubbers of 500 or less, for example, liquids 1, 2 and 1, 4
Examples thereof include polybutadiene, liquid acrylonitrile butadiene copolymer, liquid styrene butadiene copolymer, stearic acid, polypentadiene, polyurethane and ethylene propylene diene rubber. Oligomers which themselves have a film-forming ability in an uncured state are not preferable because they lower the developing ability of an aqueous developer such as an alkaline aqueous solution or an alkaline water-organic solvent.

The above-mentioned plasticizer can also be used as a compatibilizer for improving transparency. In addition, plasticizers such as triphenyl phosphate, dioctyl phthalate, dioctyl adipate, diethyl phthalate, phosphoric acid, octyl diphenyl phosphate and tributoxyethyl phosphate serve as compatibilizers.

Since the photosensitive elastomer composition of the present invention causes tackiness depending on its composition, it is possible to improve the contact property with the transparent image carrier to be overlaid thereon and to reuse the transparent image carrier. For this purpose, a thin film laminate layer of polyethylene, polypropylene, polyester, polystyrene or the like can be provided on the surface thereof. The film is stripped off after exposure through the transparent image carrier overlying it has been completed.

For the same purpose, a thin flexible layer soluble in an aqueous developer may be provided in place of the film. In this case, when the unexposed portion is eluted after the exposure through the transparent image carrier is completed, the layer is also removed by dissolution or the like at the same time.

The photosensitive elastomer composition of the present invention can be produced by mixing the respective components. A kneader, a roll mill or the like can be used as the mixing means, and a layer having a desired thickness can be produced by hot press molding, calendering or extrusion molding.

The protective film and the support film can be brought into close contact with the photosensitive layer by roll laminating after forming the sheet. It is possible to obtain a more accurate photosensitive layer by hot pressing after lamination.

When a thin flexible layer such as polyvinyl alcohol, gum arabic, polyacrylamide, cellulose acetate phthalate or hydroxypropyl cellulose is to be provided on the surface of the photosensitive layer, it is dissolved in a suitable solvent. The solution may be directly coated on the surface of the photosensitive layer, or may be once coated on a film of polyester, polypropylene or the like, and then the whole film may be laminated on the photosensitive layer and transferred.

Examples of the actinic ray source used for insolubilizing the photosensitive elastomer composition of the present invention in a solvent include a low pressure mercury lamp, a high pressure mercury lamp, an ultraviolet fluorescent lamp, a carbon arc lamp, a xenon lamp, a zirconium lamp, and sunlight. There is.

After the photosensitive elastomer composition of the present invention is irradiated with light through a transparent image carrier to form an image, the developing solution used for eluting the unexposed area is exposed and then exposed. It is necessary that the resulting image part has almost no effect on the image part.

The composition of the developer depends on the nature and amount of the hydrophilic polymer contained in the photosensitive elastomer composition, but it is water or a solvent containing 70% or more of water and sodium hydroxide, sodium carbonate, It may contain an alkali such as sodium silicate or sodium borate, a surfactant, or a water-soluble organic solvent. The liquid temperature of the developing solution may be around 25 ° C, but it is preferably 50 to 70 ° C in order to enhance the developability. Further, the developing time is set to a time at which the required relief depth can be obtained.

The photosensitive elastomer composition of the present invention has excellent properties as a printing plate for flexographic printing, but in addition to this, it can be used for photoresists and screens for screen printing.

[0035]

The photosensitive elastomer composition of the present invention differs from the prior art photosensitive elastomer compositions in that it contains a water-swellable resin. Such a composition can be easily produced and can be developed with an aqueous developer after image exposure to produce an image.

Further, although the prior art photosensitive elastomer composition in which a polar group such as a carboxyl group is introduced into the skeleton polymer is not resistant to alcohol-based ink, the photosensitive elastomer composition of the present invention is surprisingly alcohol-containing. It has the advantage of being solvent resistant to the base ink.

[0037]

The present invention will be described in detail with reference to examples.
Parts in each example are parts by weight.

Example 1 Styrene-butadiene-styrene block copolymer [Kraton 1101 (trade name) manufactured by Shell Petrochemical Co., Ltd.] 40
Parts, water-swelling resin [Daisen Seika's Dieswell (trade name)] 20 parts, liquid polybutadiene [Nippon Petrochemical B-2000 (trade name)] 30 parts, di-n-octyl fumarate 8 parts , Lauryl maleimide 2 parts, 2,2-dimethoxy-2-phenylacetophenone 2 parts, 2,6-t-
0.2 part of butyl-p-cresol was kneaded with a kneader.

This is sandwiched between 100 μ polyester films and placed inside a spacer having a thickness of 3 mm to 140 ° C.
To obtain a photosensitive elastomer composition sheet.

Next, the polyester film on one side was peeled off, a transparent image carrier was adhered to the surface, and the film was exposed for 30 minutes with light having an intensity of 2.5 mW / cm ² using an ultraviolet fluorescent lamp.

After removing the transparent image carrier, sodium hydroxide / 2- (2-butoxyethoxy) ethanol / water solution (sodium hydroxide 0.3 part, 2- (2-butoxyethoxy) ethanol 7 parts, water 93 parts, liquid) When the unexposed area was eluted using a brush at a temperature of 60 to 65 ° C. for 20 minutes, a relief that faithfully reproduced the original image was obtained.

Example 2 and Comparative Example 1 The photosensitive elastomer composition shown in Table 1 was kneaded with a kneader and pressed into a sheet.

[0043]

[Table 1]

The light intensity of each of the above sheets is 2.2 to 2.3.
mW / cm ² of ultraviolet fluorescent lamp on both sides for 40 minutes (one surface 2
After irradiation with light (0 minutes), it was immersed in isopropyl alcohol / ethyl acetate / n-hexane (75/20/5). The swelling rate of each plate after 4 hours is shown in Table 2.

[0045]

[Table 2]

From Table 2, the compositions (B) and (C) which can be developed with an aqueous developer are the solvent development type compositions (D),
The swelling rate is higher than that of (E), and there is a problem in terms of solvent resistance. However, since the composition (A) of Example 1 of the present invention has the same swelling ratio as the solvent-developing type composition, it has the same solvent resistance as the solvent-developing type composition. Became clear.

Claims (1)

[Claims] 1. A conjugated diene hydrocarbon polymer having a number average molecular weight of 20,000 to 200,000 or a number average molecular weight of 20,000 to 20 based on the total weight of the composition.
25-85% by weight of a copolymer of a conjugated diene hydrocarbon having a molecular weight of 10,000 and a monoolefin unsaturated compound,
(B) 10 to 70% by weight of water-swellable resin, (c) 1 to 40% by weight of non-gaseous ethylenically unsaturated compound, and (d)
A photosensitive elastomer composition containing a photopolymerization initiator as an essential component.