JPS5940640A - Water-developable photosensitive resin composition used for flexographic plate - Google Patents

Abstract

PURPOSE:To obtain the titled water-developable type photosensitive resin compsn. forming a flexographic plate having superior rubber elasticity and ink resistance, etc., by incorporating polyethylene glycol, a photopolymerizable monomer, and a photosensitizing agent in a specified water-soluble polymer compsn. CONSTITUTION:A water-soluble polymer is prepared by mixing (A) hydroxypropyl cellulose contg. 2-4 substd. hydroxypropyl groups per one unit of glucose anhydride and having 5,000-20,000 cps viscosity of the 2wt% aq. soln. at 20 deg.C, with (B) partially saponified polyvinyl acetate having 45-85mol% saponification degree and 400-800 polymn. degree in 50:50-85:15 A/B wt. ratio. The titled resin compsn. is obtained by mixing 50-90pts.wt. polyethylene glycol represented by the shown formula (n being 1-4) and 5-90pts.wt. photopolymerizable monomer and 0.05-5pts.wt. photosensitizer with 100pts.wt. of the obtained water- soluble polymer.

Description

[Detailed description of the invention] The present invention relates to a photosensitive resin composition for printing plates.

More specifically, the photosensitive resin layer formed on the support using the photosensitive resin Mi composition is irradiated with actinic rays such as ultraviolet rays through a negative or positive film having a transparent image, and then the photosensitive resin layer is soaked in water This photosensitive resin composition can provide a relief image faithful to a negative or positive upon development, and the relief image has satisfactory rubber elasticity and ink resistance, and can be used as an excellent flexographic printing plate.

Recently, flexographic printing plates obtained from photosensitive resin compositions have been increasingly used in place of conventional engraved or molded rubber flexographic printing plates. In order for such a composition to be particularly useful for making flexographic printing plates, the composition must first have adequate rubber elasticity after exposure, and secondly, the composition in the unexposed areas must be easily resistant to heat during development. And quick elution,
It can be removed and the resulting plate is resistant to the inks used in flexographic printing.

By the way, examples of conventionally provided photosensitive resin compositions for flexible printing plates include those disclosed in Japanese Patent Publication No. 56-46580 and Japanese Patent Publication No. 55-34415. The composition disclosed in the former contains crystalline 1,2-polybutadiene, a photopolymerizable monomer, and a photosensitizer as main components, and the composition disclosed in the latter is obtained by the former composition. The rubber hardness of the printed printing plate is increased (decreased).
In order to improve polymers, etc.) and/or have an alkyl group in the side chain and have an alkyl group of 10 at normal pressure.
Compounds having a boiling point below 0°C (e.g., phenylated alkyl phthalates such as diisodecyl phthalate and cyhexyl phthalate, dialkyl adipates such as dioctyl adipate and diisodecyl adipate, trialkyl trimellitate, and trioctyl trimellitate) melitates,
Stearyl vinyl ether (alkyl vinyl ether) is added.

When making a flexographic printing plate from such a conventionally known composition, the developer may be aromatic hydrocarbons (e.g., benzene, xylene, toluene, etc.) or halogenated hydrocarbons (e.g., chloroform, trichloroethane, trichloroethylene, tetrachloroethylene, etc.). ) organic solvents are used, so special consideration must be taken to prevent pollution problems such as environmental pollution during evaporation, evaporation, and wastewater treatment, and the use of such organic solvents increases plate-making costs. reflect. Furthermore, the flexographic printing plates obtained with the above-mentioned conventionally known compositions exhibit good durability against water-based inks and alcohol-based inks;
Compared to inks containing ethyl acetate, methyl ethyl ketone, or xylene for general use (5 to 15% ff1l), there is a drawback that they do not have the same durability as the D ink.

Another example of such a photosensitive resin composition for organic solvent-developable flexible printing plates that still has room for improvement is styrene with a high styrene content as a binder disclosed in JP-A-52-503. Examples include a composition using a butadiene block copolymer and a liquid prepolymer of polybutadiene or a butadiene-styrene copolymer, and a composition disclosed in Japanese Patent Publication No. 43374/1983, which uses a polystyrene/polybutadiene/polystyrene block copolymer as a binder. It will be done.

In order to improve the drawbacks of the above-mentioned organic solvent developable photosensitive resin compositions, a composition using a carboxylated butadiene-acrylonitrile copolymer as a binder has been proposed (see US Patent Application No. 027,445). According to this composition, an aqueous solution of an alkaline substance and a hydrophilic organic solvent is used as a developer, so even if the above-mentioned problem caused by the use of an organic solvent in an organic solvent developable composition is solved, the problem is not solved. It is only a matter of reducing the problem, but does not substantially eliminate it completely. Furthermore, the ink resistance of the obtained plate material has the same drawbacks as those of organic solvent developable compositions.

The present invention was devised to solve the problems of conventional wave flj, and its main purpose is to provide a photosensitive bright resin composition for flexographic printing plates that can be developed with only water. . Another object of the present invention is to provide a composition capable of forming a flexographic printing plate having good resistance to solvent-mixed inks and inks containing only water-based inks and alcohol-based inks.

A further object of this invention is to provide a composition that can shorten the plate making time. Still another object is to provide a composition that can form a flexographic plate having excellent rubber elasticity.

Such purpose includes a water-soluble polymer, polyethylene glycol, a photopolymerizable monomer, and a photosensitizer, and the water-soluble polymer partially binds hydroxypropyl cellulose.
U polyvinyl acetate from 50:50 to 85:15 (n amount ratio range) combination, 100% of this water-soluble polymer
Polyethylene glycol 50-90 in weight part
parts by weight, 5 to 90 parts by weight of the photopolymerizable monolubricant, and 0.05 to 5 parts by weight (■ parts) of the photosensitizer, (■) The hydroxypropylcellulose has hydroxypropyl groups, IIIE water contains 2.0 to 4.0 moles substituted per level of glucose, and the viscosity of the 2% by weight water solution is 5000 to 20000 CPS (20″C); (2) the above partially saponified polyacetic acid; Vinyl has saponification degree of 45~
(3) The polyethylene glycol has a general formula Fl 0-(CH3C
H20), l-1 (in the formula, n is 1 to 4).

By the way, in the present invention, it is conventional to construct a photosensitive resin composition by using a cellulose derivative such as droxypropyl cellulose as a binder in combination with a photopolymerizable monomer and a photosensitizer. It is publicly known (see Japanese Patent Publication Nos. 50-34965 and 49-17482). However, none of these known compositions provides a rubber elasticity useful as a flexographic printing plate. In addition, a photosensitive finger composition containing partially saponified polyvinyl acetate as a binder used in the present invention is also known (Japanese Patent Application Laid-Open No. 1983-1970).
No. 87903 (Hata Teru) has been put to practical use in letterpress printing of newspapers, but it is not a composition that essentially provides rubber elasticity.

Thus, in the present invention, 1 is used as the main binder.
The hydroxypropyl cellulose and partially saponified polyvinyl acetate used alone are photosensitive.
Although the composition of the oil composition provides a hard plate, and the addition of a large amount of plasticizer provides a flexible plate, it does not exhibit behavior characteristic of comb elasticity. However, when polyethylene glycol a, hydroxypropyl cellulose, and partially saponified polyvinyl acetate are used in combination as in the present invention, a plate having good rubber elasticity is provided. .

This is not at all easy (this is not a knowledge that can be obtained), but given that lumber F, which itself has rubber elasticity, is generally used as a binder, it is a unique knowledge of the present invention. be.

The hydroxypropyl cellulose used in the present invention contains 2.0 to 4.0 moles of hydroxypropyl group substituted per anhydroglucose intermediate position, and has a hydroxypropyl group of 5000 to 20000 Cps (at 20°C) in a 2% aqueous solution. It has viscosity. Too little hydroxypropyl will reduce the plasticizer miscibility and hydrophilicity of the composition, while too much will reduce the flexibility and rubber elasticity of the #1 composition. . If the viscosity becomes too low below the regulation value, the mechanical strength will decrease. On the other hand, if it becomes too high, the solubility in water decreases.

The partially saponified polyvinyl acetate used in the present invention has a degree of saponification of 45 to 85 mol% and a degree of polymerization of 400 to 800. If the degree of saponification is lower than 45 mol%, flexibility of the Mi product can be obtained, but water developability (poor)
If it exceeds 5 mol%, the composition will have poor flexibility. If the degree of polymerization is too low, the mechanical strength will drop drastically. On the other hand, if it is too high, the flexibility of the composition will be affected and at the same time the water solubility will decrease.

Polyethylene glycol used in the present invention, general formula 1
A compound having a molecular weight of 10(CH2CH20)nH (where n is 1 to 4) is preferable in terms of miscibility with the other two binders and moldability of the composition.

In the present invention, the above-mentioned components need to be blended within a specific range from the viewpoints of rubber elasticity, ink resistance and water developability. That is, hydroxypropyl cellulose and partially saponified polyvinyl acetate were mixed at a layer ratio of 50
: 50 to 85:15 of polyethylene glycol to 100 weight parts of both formulations.
It is blended in a range of 90 parts by weight. If the amount of hydroxypropylene cellulose blended is too small, the composition will not have comb elasticity, and when the plate is subjected to printing, the relief will be crushed and a clear printed pattern will not be obtained. If the amount of partially saponified polyvinyl acetate blended is too small, the plate-making process of the composition will suffer from problems. If there is too much polyethylene glycol in the blender, the composition will not exhibit rubber elasticity, while if it is too small, the hardness of the composition will become too high.

The photopolymerizable monomer used in the present invention may be one that is most miscible with the composition and has a photopolymerizable unsaturated group, such as 2-hydroxyethyl (
meth) ° acrylate, 2-hydroxypropyl (meth) °r acrylate, ethylene glycol di-2-hydroxypropyl di(meth)acrylate, pyrene glycol di-2-hydroxypropyl diacrylate, glycerin di-2-hydroxypropyl diacrylate,
Polyethylene glycol 2-hydroxyethyl acrylate phthalate, 2-hydroxypropyl 2-hydroxypropyl acrylate phthalate, di-2-hydroxypropyl acrylate phthalate, polyethylene glycol di(mel)acrylate (poly = n = 1-
14), polyethylene glycol di(meth)acrylate (poly=n=1 to 9), and the like, which can be used alone or in combination of two or more. Other photopolymerizable monomers that can be used in Use 1 include, for example, trimethylolpropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, (meth)acrylamide, N,N-methylenebisacrylamide, butyl(meth)acrylate, Acrylate, butyl di(meth)acrylate, isobutyl(meth)acrylate, hexyl(meth)acrylate, ■, 6-hexanethiol di(meth)acrylate, neobentylcy(meth)acrylate, 2-ethylhexyl(meth)acrylate, lauryl acrylate, Examples include stearyl acrylate.

These photopolymerizable *i forms may be used in an amount of 5 to 90 parts by weight based on 100 parts by weight of the total amount of hydroxypropyl cellulose and partially saponified polyvinyl acetate. Curing may be insufficient or the originally required rubber elasticity may not be obtained due to photocuring.

The photosensitizer used in the present invention may be one commonly used in the field as long as it has uniform rTJ ability in the composition; for example, benziine, benzoin alkyl ether (alkyl is methyl, ethyl , isopropyl, n-butyl, etc.), anthracene, P-dinitrobenzene, 2-chloro-4-nitroaniline, 9-a-antranyl aldehyde, benzophenone, bendi/', P I P-tetramethyl Diaminobenzophenone, 1.2-benzanthraquinone, 1.2-
Examples include naphthoquinone and 4-naphthoquinone, and 11 types or a mixture of two or more types can be used.

These photosensitizers may be used in an amount of 0.05 to 5 parts by weight based on 100 parts by weight of the total amount of hydroxypropyl cellulose and partially saponified polyvinyl acetate.

In the present invention, in addition to the above-mentioned components, the following components may be incorporated into the composition as required.

That is, thermal polymerization inhibitors (e.g., hydroquinone, P-methoxyphenol, [-)-thylcatechol, 2゜6-di-L
-butyl-P-cresol, etc.), internal elements or dyes for halation prevention 1F (e.g., eosin, rose bengal, methyl violet, methylene blue, malachite green, etc.), diathesis 4, glass fiber, glass peas, etc. It is a drug.

In order to create a flexographic printing plate from a composition having the above-mentioned composition, first, a mixture of the above-mentioned components is melt-molded at 90°C or higher to form a photosensitive resin sheet having a thickness of 0.1 to 10 am. This sheet can be attached to a regular support (
For example, it can also be used by adhering to plastic sheets, synthetic rubber sheets, metal plates). Next, the negative of the original is brought into close contact with the photosensitive resin sheet in a vacuum printing frame, and exposed to light from a conventional irradiation source (eg, high-pressure mercury lamp, chemical lamp). After exposure, the negative chips are removed and the unexposed areas of the photosensitive resin sheet are eluted with water. Elution may be carried out by immersing the sheet in water with a sponge, brush, etc., or by spraying the sheet with water.

After the elution is completed, the resulting plate is dried and then further exposed over the entire surface for finishing.

Next, the present invention will be specifically explained with reference to Examples and Comparative Examples. Note that parts refer to parts by weight.

Example 1 Hydroxypropylcellulose (Hydroxypropyl group substituted mole number 3.5.2% aqueous solution viscosity IW (20°C)
13,000 cPs) and 23 parts of partially saponified polyvinyl acetate (degree of saponification 72.4 mol%, degree of polymerization 400) (both powders) (this was impregnated with 38 parts of tetraethylene glycol). This was heated to 170°C for 2
After rolling for 0 minutes, it was cooled and when the temperature reached 130°C, 7 parts of 2-hydroxypropyl acrylate, 7 parts of propylene glycol di-2-hydroxypropyl diacrylate, 1 g of benzoin dimethyl ether, 2
0.74 parts of ゜6-di[-butyl-P-cresol] and 0.26 parts of methylhydroquinone were added, and the mixture was further kneaded with rolls for 20 minutes.

The resulting composition was sandwiched between two 100μ thick polyethylene terephthalate films (upper and lower) to a thickness of 2.74 m.
yrt spacer and press at 120°C for 30 seconds at 1101 1 (g/cl) to form a photosensitive layer of 2.74
Photosensitive sheet 2.13 nm and support 0.10 mm
4 mm was obtained.

Next, a negative with a transparent image was applied to the photosensitive layer of a photosensitive sheet and exposed for 5 minutes, then the sheet was immersed in water at 2°C and a nylon brush (diameter 100μ, length 20 pieces) ) for 6 minutes, a 17 ref image with a depth of 1.0 mm (1.0 mm) was obtained, with a faithful eye-shore A hardness of 55°. When the exposed composition was tested based on Tl5-6301, it was confirmed that it was a rubber elastic body with a tensile strength of 30 kg/l·7j, an elongation rate of 125%, and a rebound modulus of 30%.

Example 2 Same as Example 1 (by straining, hydroxypropylcellulose (hydroxypropyl M-substituted-E: number of molecules 3.5.2
Overlay % aqueous solution viscosity (20°C) 13000 cps) 20
part, partially saponified polyvinyl acetate (saponification degree 57 mol%,
Polymerization degree 400) 20 parts, tetraethylene glycol 32
parts, tetraethylene glycol diacrylate) 12 parts, tetraethylene glycol dimethacrylate 12 parts,
With a composition of Mi consisting of 2 parts of benzoin butyl ether, 1.3 parts of 2,6-di[-butyl-P-cresol and 0.7 parts of methylhydroquinone, the total n-
A photosensitive sheet with a thickness of 3.00 mm was obtained.

Next f The photosensitive sheet here was exposed for 15 seconds from the support side, then exposed for 3 minutes with Jig 1 layer (condensed film applied), and washed with water for 4 minutes using a commercially available elution device (used for nylon plates). An IJ-F image was obtained that was faithful to the negative with a depth of approximately 0.8 mm and a Shore A hardness of 65 degrees.At the same time, the exposed composition was tested in the same manner as in Example 1, and the tensile strength was 25 Kg/ ct7, elongation rate 140%,
It was confirmed that it was a rubber elastic body with a rebound modulus of 31%.

Ratio 1 Bite Example 1 In the same manner as in Example 1, 40 parts of partially saponified polyvinyl acetate (degree of saponification 57 mol%, degree of polymerization 400), 40 parts of glycerin, 7 parts of 2-hydroxypropyl acrylate, propylene glycol di 2 = 7 parts of hydroxypropyl acrylate, 2ff of benzoin isopropifurether
i, 2.6-di[-butyl-P-cresol 1.7 parts and methylhydroquinone 0.3 parts, with a total thickness of 3.5 parts. A photosensitive sheet of Omtt was obtained.

Next, this photosensitive sheet was placed on a support for 30 seconds, then a negative film was applied to the photosensitive layer and exposed for 5 minutes, and as in Example 2, it was exposed to water for 3 minutes. Sa1
．． Two relief paintings of one elephant were obtained. At the same time, the composition after exposure was tested in the same manner as in Example 1, and the tensile strength B
I(g/cyJ, elongation rate was 220%. Shore A hardness was low at 50, but the rubber elasticity performance required for a flexographic printing plate was not obtained.

Comparative Example 2 In the same manner as in Example 1, hydroxypropylcellulose (number of moles substituted with hydroxypropyl group 3.5.2% by weight aqueous solution viscosity (20°C) 13° o o o cps) 40
part, tetraethylene glycol 42gL2-Hydroxypropylacrylate part, benzoin isopropyl ether 2ml12.6-di[-butyl-resol 1. With a composition containing 0.3 parts of methylhydroquinone and 0.3 parts of methylhydroquinone, the total thickness? , an Omyn photosensitive sheet was obtained.

Next, this photosensitive sheet was exposed to light in the same manner as Example 1, and then the developing process was started, but the water mass was difficult to form and the depth was 0.
The limit was to obtain 21,171 relief images.

Patent applicant: Nippon Paint Co., Ltd.

Claims (1)

[Claims] 1. Contains a water-soluble polymer, polyethylene glycol, a photopolymerizable monomer, and a photosensitizer; : Consisting of a combination of weight ratios ranging from 50 to 85:15, 50 to 90 parts by weight of polyethylene glycol and 5 to 90 parts by weight of photopolymerizable monomer to 10 parts by weight of this water-soluble polymer. and a photosensitizer at a ratio of 0.05 to 5 parts, (1) the hydroxypropyl cellulose has 2 moles of hydroxypropyl group substituted per anhydroglucose unit;
,0 to 4.0, and the viscosity of its 2% aqueous solution is 500
(2) The partially saponified polyvinyl acetate has a saponification degree of 45 to 20,000 cps (20°C).
85 mol%, degree of polymerization 400-800, (3) the polyethylene glycol has the general formula I'0-(CH2CH
20). 11 A water-developable photosensitive resin composition for a flexographic printing plate, characterized in that it has the following formula: n is 1 to 4.