JP2638247B2 - UV curable coating composition for coating printed images - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to a method for producing a printed image by using a compounding agent comprising a radically polymerizable compound, a thermoplastic resin and an ultraviolet polymerization initiator as a base material when a surface of a printed image is processed. The present invention relates to an ultraviolet-curable coating composition for coating printed images, comprising:

(Prior art) Surface processing of printed images is performed by varnishing (vinyl coating), pressing (press coating),
Alternatively, instead of laminating (print lamination), etc., in recent years, several UV curable coatings have been developed from various advantages such as high solid content, energy saving, rapid curing at low temperature, prevention of air pollution, improvement of working environment, etc. Cover, clothing, medicine, cosmetics, and records.

(Problems to be Solved by the Invention) However, since these coating agents do not contain volatile components, the ultraviolet curing components are almost 100% coating agents.
While the point that rapid curing is ensured without going through the evaporative drying step is very advantageous, it is difficult to adjust the viscosity for easy printing, and in addition to the problem of remarkable volume shrinkage upon curing,
The resulting cured film is usually hard and brittle. This not only tends to cause a problem in fluidity relating to printability, but also causes defects in glossiness of the obtained cured printed image, adhesion to printing ink, and post-processability such as bending.

Further, in order to improve the problem of adhesion to the printing surface, an ultraviolet-curable coating agent containing a ketone resin or an epoxy resin (Japanese Patent Publication No. 60-48353) has been reported. It is effective only on the printing surface with oil-based ink, and cannot provide wide-ranging adhesion to various diversified inks. Further, there has been a problem that satisfactory fluidity, glossiness, blocking resistance, and post-processing properties such as bending processing relating to printability have not been obtained.

(Means for Solving the Problems) In order to solve the above problems, the present inventors have conducted various studies, and as a result, have found that a monomer having a molecular weight of 500 or less (a) having two ethylenically unsaturated groups in the molecule. ) And a styrene-based resin (b) having a softening point of 70 ° C. or higher, a UV-curable coating composition based on an appropriate amount blended system adheres to both printed and non-printed parts, and has rapid curability and anti-blocking properties. The present invention has been found to be effective in solving many problems such as fluidity, scratch resistance, fluidity relating to printability, and post-workability such as bending and punching, and has completed the present invention. .

That is, the present invention provides 25 to 65 parts by weight of a monomer (a) having two ethylenically unsaturated groups in a molecule having a molecular weight of 500 or less, and 20 to 60 parts by weight of a styrene resin (b) having a softening point of 70 ° C. or more. The present invention relates to an ultraviolet-curable coating composition obtained by blending an additive for printing paint with a compounding agent consisting of 1 part by weight and 1 to 15 parts by weight of an ultraviolet polymerization initiator (c) as a base material.

More specifically, gravure, flexographic or offset printing and other methods of printing printed matter,
In order to prevent set-off of print marks, impart gloss to printed matter and decorate the printed matter, and protect the printed matter from dirt and scratches, two or more ethylenically unsaturated groups in the molecule having a molecular weight of 500 or less are used in surface processing. Monomer (a) having a softening point of 70 ° C
A one-part, solvent-free, UV-curable coating composition obtained by blending the above-mentioned styrenic resin (b) and the UV polymerization initiator (c) as a base material with an additive for a printing paint. is there. The ultraviolet-curable coating composition of the present invention is applied to the printing surface, and then dried and cured by irradiating ultraviolet rays, the coating film has excellent adhesion to the printing ink of the already-printed application surface, It exhibits excellent properties such as high gloss, blocking resistance, scratch resistance and water resistance.

The components of the ultraviolet-curable coating composition of the present invention will be described below.

Monomer (a) having two ethylenically unsaturated groups in a molecule having a molecular weight of 500 or less as a radical polymerizable compound
Is a component for adjusting ultraviolet curability, crosslink density, adhesion and the like. These include 1,4-butanediol di (meth) acrylate, 1,5-pentanediol di (meth) acrylate, 1,6-hexanediol (meth) acrylate, 1,8-octanediol diacrylate, 9-nonanediol diacrylate, neopentyl glycol di (meth) acrylate, bisphenol A-modified di (meth) acrylate, bis (acryloxyneopentyl glycol) adipate, dicyclopentanyl di (meth)
There are acrylates, di (meth) acrylates such as neopentyl glycol hydroxypivalate di (meth) acrylate, divinylbenzenes and the like, and one or more of them may be used in combination depending on required physical properties. Here, the molecular weight of the monomer (a) having two ethylenically unsaturated groups in the molecule is 500 or less, but when the molecular weight exceeds 500, the viscosity of the ultraviolet-curable coating composition is increased,
Further, since the crosslink density and the curability are lowered, problems arise in leveling property, curing speed, blocking resistance, scratch resistance and the like during coating, which is not preferable. On the other hand, the usage ratio is 25-
65 parts by weight is preferable, and when less than 25 parts by weight, the viscosity of the ultraviolet-curable coating composition increases, and the crosslinking density and the curability decrease, so that the leveling property at the time of coating, the curing speed, the blocking resistance, Problems arise in scratch resistance and the like, which is not preferable. On the other hand, when the amount exceeds 65 parts by weight, the crosslinking density becomes extremely large, and curing shrinkage occurs, which causes a problem in adhesion, which is not preferable.

The styrene-based resin (b) having a softening point of 70 ° C. or more as a thermoplastic resin has a high refractive index of (n ²⁵ _D ) = 1.50 or more. It is also a component and is also a component that is effective at the same time for adhesion to printing ink, relaxation of curing shrinkage, adjustment of crosslinking density, and the like. This includes polystyrene resin, poly α-methylstyrene resin,
There are UV-polymerizable resins such as vinyl toluene α-methylstyrene copolymer resin and styrene-modified polyterpene resin, or non-polymerizable resins.Copolymers containing styrene include those with a softening point of 70 ° C or higher, and required physical properties May be used alone or in combination of two or more. Here, the softening point of the styrene-based resin is 70 ° C. or higher. However, when the softening point is lower than 70 ° C., a problem of blocking after curing is preferable. And the compounding ratio is 20-
60 parts by weight is not preferred. If the amount is less than 20 parts by weight, the amount of the ethylenically unsaturated monomer (a) used is relatively too large, so that the crosslinking density becomes extremely large and sufficient adhesion cannot be obtained. If it exceeds 60 parts by weight,
The viscosity of the UV-curable coating composition is increased, and the leveling property and the crosslink density at the time of coating are reduced, so that the scratch resistance is poor.

The ultraviolet polymerization initiator (c) includes benzoin, benzoin methyl ether, benzoin isopropyl ether, benzophenone, Michler's ketone, 1-naphthalenesulfonyl chloride, 2,5-naphthalenedisulfonyl chloride, azoisobutyronitrile, 1-azobis-1-
Cyclohexanecarbonitrile, benzyldimethylketal, 2-methylanthraquinone, biimidazole, thioxanthone, 2,4-diisopropylthioxanthone,
There are 2,2-diethoxyacetophenone, benzoyl peroxide 2,4-dichlorobenzoyl peroxide and the like, and one or more of these may be used in combination. Here, it is preferable to use an appropriate amount in the range of 1 to 15 parts by weight. When the amount is less than 1 part by weight, the curing speed becomes extremely low, and the workability for high-speed curing cannot be supported. When the amount exceeds 15 parts by weight, the effect of increasing the curing speed is limited. In addition, the ultraviolet polymerization initiator not contributing to the curing remains to cause adverse effects due to the deterioration of the film properties, and the cost is increased, which is not preferable.

The present invention comprises the above-mentioned composition as a base material, but if necessary, its purpose, use, etc., may be a monomer having one ethylenically unsaturated group, a monomer having three or more ethylenically unsaturated groups. A resin other than a styrene resin having a softening point of 70 ° C. or higher, a colorant, and other additives for paint printing ink can be optionally added. However, the total amount should be the minimum necessary, and is preferably less than 30 parts by weight.

Monomers having one ethylenically unsaturated group in the molecule include methyl (meth) acrylate, ethylene (meth)
Mono (meth) acrylate acids such as acrylate, butyl (meth) acrylate, glycidyl (meth) acrylate, cyclohexyl (meth) acrylate, acrylics, methacrylic acid, vinyltoluene, α-methylstyrene, styrene, N-vinyl-caprolactam , N-vinyl-2-pyrrolidone and the like, and the ratio is limited to 10 parts by weight. If the amount exceeds 10 parts by weight, the crosslinking density is reduced, and problems such as high-speed curing, surface tack, blocking resistance and the like are not preferred.

Examples of the monomer having three or more ethylenically unsaturated groups in the molecule include multifunctional compounds such as trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, and dipentaerythritol hexa (meth) acrylate. (Meth) acrylates and the like, and the mixing ratio is limited to 10 parts by weight. If the amount exceeds 10 parts by weight, the crosslink density becomes high, so that it is good in forming a tough film.However, it causes more curing shrinkage than necessary, and as a result, the coated printed material is deformed or peeled. It is not preferable because stress is exerted and adhesion is poor, and post-processability is also reduced.

Resins other than the styrene resin having a softening point of 70 ° C. or higher include vegetable oils and their polymers, rosin-modified phenolic resins, rosin-modified ester resins, various alkyd resins,
P-toluenesulfonic acid amide formalin resin, acrylated melamine resin, saturated polyester resin, unsaturated polyester resin, polyurethane resin, epoxy resin, various kinds of petroleum resin, etc. Is 10 parts by weight or less, and it is preferable to use a compatible resin. This is because, if the amount exceeds 10 parts by weight, problems arise in surface tack, blocking resistance, or adhesion to printing ink.

In order to enhance the curability, an ultraviolet sensitizer can be used, and the amount thereof is added, if necessary, to a small amount usually used.

When coloring is required, all conventionally used coloring materials such as pigments and dyes for various printing inks and paints can be used.

As other various additives for printing and paint, conventionally used additives such as leveling agents, defoamers, waxes, plasticizers, etc. can be used except for organic solvents.

(Effect of the Invention) Since the UV-curable coating composition of the present invention is a solvent-free, one-pack type UV-curable transparent coating material, when the surface of a printed image is processed, contamination of the working environment due to evaporation of the solvent. Improvement of air pollution, energy conservation, space saving, high-speed printing, low-temperature and high-speed curing, etc.
Applicable for overprinting in-line processing, furthermore, paper warpage due to heating and curing shrinkage,
Alternatively, there is found a great effect that high-quality overprint processing is possible without causing problems such as blocking and scratching, and having high gloss and cosmetics with excellent adhesion, and its industrial value is extremely high. There are advantages.

(Examples) Next, in order to more specifically describe the present invention, examples and comparative examples are shown below.

Examples 1 to 5 and Comparative Examples 1 to 4 According to Table 1, each component was blended and mixed and dissolved to obtain UV-curable coating compositions I to IX. These were tested in the following manner.

The test method is offset printing on paper, and after 1-2 seconds, the above-mentioned UV-curable coating composition is overprinted by a wet method using a roll coater, and this is immediately irradiated with ultraviolet rays to obtain a surface-treated product of the printing paper. Done in a way to get. The conditions are as follows.

(1) Paper used One court ball manufactured by Jujo Paperboard Co., Ltd. (2) Offset printing (3) Roll coat overlay printing (4) UV irradiation

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-112767 (JP, A) JP-A-59-179608 (JP, A) JP-A-61-31476 (JP, A)

Claims (1)

(57) [Claims] (1) 25 to 65 parts by weight of a monomer (a) having two or less ethylenically unsaturated groups in a molecule having a molecular weight of 500 or less and a softening point of 70
A printed image obtained by mixing a styrene-based resin (b) of 20 to 60 parts by weight and an ultraviolet polymerization initiator (c) of 1 to 15 parts by weight at a temperature of not less than 1 ° C. with an additive for printing paint as a base material UV curable coating composition for coating.