JPH05140500A - Actinic radiation curable overprint varnish - Google Patents

Abstract

PURPOSE:To obtain an overprint varnish which has a good adhesion to ink in the absence of a primer and less soaks into paper by blending a specific styrene-acrylic ester copolymer, a radiation-curable (meth)acrylic ester monomer, an additive and a photopolymerization initiator. CONSTITUTION:The objective varnish comprises 20-80wt.% styrene-acrylic ester copolymer having a weight-average molecular weight of 5,000-200,000, the copolymer comprising 10-80wt.% styrene monomer and 1-20wt.% monomer of a (meth) acrylic ester of a 1-18C alcohol and a polymerizable monomer having a hydrophilic functional group and copolymerizable with the monomer, 20-90wt.% monomer or oligomer of an ultraviolet or electron beam curable mono- or polyfunctional (meth)acrylic ester, 0-15wt.% wax such as polymer wax or polyethylene wax and a silicon additive, and 0-15wt.% photopolymerization initiator.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active energy ray-curable overprint varnish, and more particularly to an oil-based ink which is cured by irradiation with radiation such as ultraviolet rays or electron rays and which does not require a primer. Alternatively, the present invention relates to an active energy ray curable overprint varnish which has good adhesion to water-based ink and has little darkening of paper due to penetration.

[0002]

2. Description of the Related Art Overprint varnish is used for the purpose of protecting the printing surface of paper, plastic film and the like, improving blocking resistance, abrasion resistance and scratch resistance, and at the same time obtaining printed matter of high gloss. It is a coating agent that is applied and printed. Specific examples of gloss processing are found in glossiness of paper containers, labels, seals, record jackets, cover and sack of books, cover of magazines and catalogs, postcards, posters and the like. Typical methods of gloss processing include so-called vinyl drawing, press coating, print laminating and the like.

Recently, various active energy ray-curable overprint varnishes of unsaturated polyester, epoxy acrylate, urethane acrylate, polyester acrylate, etc. have been widely used. became. These UV or electron beam curable paints have blocking resistance,
While it has the advantage that high gloss can be obtained at the same time as improving abrasion resistance and chemical resistance, it has the drawback of poor adhesion to various inks due to distortion caused by shrinkage during curing, which is unique to UV curable resins. There is. It is necessary to coat the primer in order to improve the adhesion. When the primer is not applied, the phenomenon that the UV-curable paint soaks into the paper to give no gloss and the paper is blackened easily occurs. Especially for the coat ball paper used in the paper container,
In order to prevent the darkening phenomenon due to penetration
Is a processing method in which the coating is applied and then the ultraviolet curable resin is applied, which has a drawback that the processing cost becomes high in such a situation.

[0004]

The present invention is intended to solve the above problems. That is, the present invention is an active agent that is cured by irradiation with radiation such as ultraviolet rays or electron beams, has good adhesion to oil-based inks and water-based inks without using a primer, and has little darkening due to penetration into paper. The aim is to provide an energy-ray curable overprint varnish.

[0005]

In order to achieve the above object, the inventors of the present invention used a styrene-acrylic polymer as a base.
The inventors have made earnest studies on the composition of the polymer. As a result, a specific styrene-acrylic copolymer was used as a base polymer, and the specific molecular weight of the copolymer was adjusted based on the specific balance between the hydrophilic monomer and the lipophilic monomer of the acrylic monomer. The inventors have found that a composition of a styrene-acrylic acid ester copolymer and a photocurable compound having a (meth) acryloyl group solves all the above problems, and has completed the present invention.

That is, the present invention provides "styrene-based monomer 10-
80% by weight (a) and an alcohol (meth) acrylic acid ester monomer (b) having 1-18 carbon atoms and a polymerizable monomer having a hydrophilic functional group copolymerizable with these monomers. 20-80% by weight of a styrene-acrylic acid ester-based copolymer (component A) having a weight average molecular weight of 5000-200000 consisting of a monomer 1-20% by weight (c), an ultraviolet ray or electron beam curable monofunctional compound, or Monomers or oligomers of polyfunctional (meth) acrylic acid ester-20-
90% by weight (component B), waxes such as polymer wax and polyethylene wax, silicon-based additives, etc. 0-15
Active energy ray curable overprint varnish comprising 0 to 15% by weight (component C) and 0 to 15% by weight of a photopolymerization initiator (component D).

Examples of the constituent monomer (a) of the component (A) in the present invention include styrene, methylstyrene,
Examples thereof include styrenes such as vinyltoluene, and among them, styrene is preferable. The composition ratio of styrenes is
It is determined in consideration of the adhesiveness of the obtained overprint varnish (hereinafter referred to as OP varnish) to the ink printing surface, and is usually 20-80% by weight, preferably 20-60% by weight. The number of carbon atoms of the monomer (b) of component A is 1-18
Specific examples of the acrylic acid esters or methacrylic acid esters include methyl (meth) acrylate, (meth)
Ethyl acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, lauryl (meth) acrylate, (meth) acrylic Examples thereof include dodecyl acid, hexadecyl (meth) acrylate, octadecyl (meth) acrylate, cyclohexyl (meth) acrylate, allyl (meth) acrylate, oleyl (meth) acrylate, and benzyl (meth) acrylate. Among these, preferred ones have 1 carbon atom
It is an aliphatic (meth) acrylic acid ester of -8. The composition ratio of the (meth) acrylic acid ester is determined in consideration of the adhesiveness and proper viscosity of the resulting active energy ray curable overprint varnish.

The component A in the present invention further has a group such as a carboxyl group, a hydroxyl group or an amino group as a hydrophilic monomer (component c) which is copolymerizable for imparting adhesion to the water-soluble ink. It contains a polymerizable monomer as a constituent. Examples thereof include acrylic acid, methacrylic acid, itaconic acid, maleic anhydride, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, N-methyl acrylate, and the like. The composition ratio is 1 because it balances hydrophilicity and lipophilicity.
-20% by weight is suitable. The molecular weight of this styrene-acrylic acid ester-based polymer is about 5000-200000.
If it is smaller than this, penetration into the paper cannot be prevented, and if it is larger than this, the viscosity of the OP varnish becomes too large and the application becomes difficult. The styrene-acrylic ester copolymer can be produced by a known polymerization method.

The monomer or oligomer (B) of the UV- or electron-beam-curable monofunctional or polyfunctional (meth) acrylic acid ester contained in the OP varnish of the present invention is not particularly limited, and various known ones are known. Things can be used. Specific examples thereof include ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tripropylene glycol diacrylate and tetra. Ethylene glycol diacrylate, trimethylolpropane triacrylate, bisphenol
Examples thereof include diol A diolate, EO-modified bisphenol A diacrylate, pentaerythritol lute acrylate, dipentaerythritol hexaacrylate, and various urethane acrylates. The amount or type of the monomer and oligomer used depends on the OP to be obtained.
It can be determined by focusing on the coating viscosity of the varnish and the physical properties of the coating film. If the proportion of this monomer and oligomer in the OP varnish is too low, the gloss of the coating film tends to decrease,
In the OP varnish, usually about 20-80% by weight, preferably
It is set to 60-80% by weight.

In the present invention, the component C is a so-called surface modifier which is added to improve the physical properties of the coating film of the obtained OP varnish, that is, blocking property, abrasion resistance and slip property, and is a low molecular weight polyethylene wax. , Polymer wax,
Alternatively, they are various silicone-based additives. The amount and type of use can be appropriately selected, but it is generally 0 to 15% by weight in the OP varnish. In addition, a leveling agent, a defoaming agent and the like are added as needed.

In curing the OP varnish of the present invention, a photopolymerization initiator (D) is used when it is cured with ultraviolet light, while it is unnecessary when it is cured with an electron beam. As the photopolymerization initiator, various known ones can be used without particular limitation, and the amount thereof used is 0.1-15% by weight, preferably 0.5-12% by weight in the OP varnish. However, if it is too small, the curability is lowered, which is not preferable, and if it is too large, the mechanical strength of the cured film deteriorates. Specific examples of the photopolymerization initiator include Irgacure-184,
Irgacure-651, Irgacure-907 (manufactured by Ciba-Geigy), Darocur-1173 (manufactured by Merck),
Benzophenone, methyl o-benzoylbenzoate, p-
Examples thereof include dimethyl benzoate, thioxanthone, alkylthioxanthone, amines and the like.

As described above, the OP varnish of the present invention can be easily prepared by mixing and mixing predetermined amounts of the components A and B as essential components and the components C and D as optional components. .. The viscosity of the OP varnish of the present invention during coating varies depending on the coating method, but can be appropriately determined by diluting it with a solvent such as ethyl acetate or methyl ethyl ketone.

The OP varnish of the present invention can be overcoated with both oil-based inks and water-based inks, and imparts high gloss to printed matter and improves abrasion resistance and blocking. You can Further, even if the OP varnish of the present invention is diluted with a solvent such as ethyl acetate, the UV monomer and the solvent do not penetrate into the undercoat to darken the color or reduce the gloss.

As a method for coating the OP varnish of the present invention, known means such as a roll coater, a gravure coater and a flex coater can be applied. The general OP varnish curing method can be applied to the OP varnish of the present invention. For example, O of the present invention
If necessary, dilute the P varnish with a solvent, apply it to the printing surface, dry the solvent, and then irradiate it with ultraviolet rays (a high-pressure mercury lamp, a metal halide lamp, etc. can be used), or irradiate with an electron beam. Can be easily cured. The irradiation dose of ultraviolet rays and electron beams is appropriately adjusted depending on the number of lights and the irradiation time.

[0015]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In addition, in each example, a part and% show a weight part and weight% unless there is particular notice.

(Synthesis of Copolymer) Although a styrene-acrylic acid ester copolymer can be produced by a known method, the copolymer used in the OP varnish of the present invention is a solution polymerization method. Is preferred. Specific examples of the monomer composition of the styrene-acrylic acid ester copolymer obtained by the solution polymerization method and the weight average molecular weight thereof are given below. In the table, the unit of composition ratio is parts by weight.

Table 1 (1) Copolymer Copolymer Copolymer Copolymer (1) (2) (3) (4) Styrene 55 55 55 47.5 47.5 Butyl acrylate 5 2-ethylhexyl acrylate To 15.7 28.0 Methyl methacrylate 39 20.3 24.7 2-Hydroxyethyl acrylate 6.0 13.3 6.0 Methacrylic acid 1 3.0 12.5 12.5 Weight average Molecular weight 13976 15324 13076 17790

Table 1 (2) Copolymer Copolymer Copolymer (5) (6) (7) Styrene 5 20 30 Butyl Acrylate 5 2-Ethylhexyl Acrylate 30 4 Methyl Meta Acrylate 89.835 64 2-hydroxyethyl acrylate 5 methacrylic acid 0.210 2 weight average molecular weight 144543 18728 13254

Examples 1 to 6 and Comparative Examples 1 to 6 (Preparation of OP varnish) The styrene-acrylic acid ester copolymer (component A), ultraviolet or electron beam curable resin (component B), slip agent ( Component C), a photopolymerization initiator (component D) and ethyl acetate as a solvent were mixed to obtain an OP varnish having a solid content of 50%. The composition of the OP varnish is shown in Table 2 (1) and Table 2 (2).

(Preparation of test paper and application of OP varnish) Coat ball paper was coated with oil-based gravure ink (trade name "KPZ").
"Primary color indigo", made by Godo Ink) and water-based gravure ink (trade name "Aqueous grass", made by Godo Ink) were developed using bar coater # 4 and used as gravure ink test paper. did. In addition, UV curable offset ink
I-tester was used to develop the color on the coat ball paper and irradiate it with ultraviolet rays (high-pressure mercury lamp, 80 W / cm, cured under conveyor speed of 10 m / min.) To prepare the offset ink. The test paper was used. The OP varnishes obtained in Examples 1 to 6 and Comparative Examples 1 to 4 were applied to the thus obtained test paper with a bar coater # 4, and ultraviolet rays (high pressure mercury lamp, 80 W / cm, conveyor-speed
10 m / min. Curing conditions) were applied to cure. As is clear from the test results of adhesion, abrasion resistance, and penetration into the base in Tables 2 (1) and 2 (2), the OP varnish of the present invention shows excellent results in these properties.

Table 2 (1) Example Example Example Example Example Example Example (1) (2) (3) (4) (5) (6) UV resin (1) 92.4 92.4 92.4 92.4 92.4 (2) ) 92.4 Copolymer (1) 66.0 (2) 66.0 92.4 (4) 66.0 66.0 (7) 66.0 IRGACURE 184 6.5 6.5 6.5 6.5 7.6 6.5 IRGACURE 907 0.9 0.9 0.9 0.9 0.9 0.9 Additive 3.4 3.4 3.4 3.4 3.4 3.4 Solvent 166 166 196 166 166 166 166 Adhesion (gravure ink) Oil-based ink ○ ○ ○ ○ ○ ○ Water-based ink ○ ○ ○ ○ ○ ○ Substrate ○ ○ ○ ○ ○ ○ (Offset ink) ○ ○ ○ ○ ○ ○ Abrasion resistance ○ ○ ○ ○ ○ ○ Penetration into the substrate ○ ○ ○ ○ ○ ○

Comparative Example Comparative Example Comparative Example Comparative Example (1) (2) (3) (4) UV Resin (1) 92.4 92.4 92.4 92.4 Copolymer (2) 20 (5) 66 (6) 66 IRGACURE 184 6.5 6.5 6.5 6.5 IRGACURE 907 0.9 0.9 0.9 0.9 Additive 3.4 3.4 3.4 3.4 Solvent 166 166 120 100 Adhesion (gravure ink) Oil-based ink △ × △ × Water-based ink × ○ ○ × Underground × × ○ × (Offset ink) × × × × Penetration into the base ○ × × ×

Composition of UV resin (1) Pentaerythritol triacrylate (KAYAR AD PET-30 manufactured by Nippon Kayaku) 30 parts EO-modified bisphenol A diacrylate (KA YARAD R-551 Nippon Kayaku) 30 parts dipentaerythritol hexaacrylate (KAY ARAD DPHA manufactured by Nippon Kayaku) 40 parts UV resin (2) composition bisphenol A epoxy acrylate (KAYA RAD R-114 manufactured by Nippon Kayaku) 20 parts pentaerythritol triacrylate (manufactured by KAYAR AD PET-30 Nippon Kayaku) 45 parts EO modified product of bisphenol A diacrylate (KA YARAD R-551 manufactured by Nippon Kayaku) 35 parts Composition of additives Slip-Aid SL-425 (manufactured by San Nopco) 12 parts (2.4 parts as solid content) DC-11 PA (manufactured by Toray Dow Corning) 10 parts (1.0 part as solid content)

(Test method) Adhesion: The adhesion between the ink layer and the OP varnish layer was evaluated by the following evaluation criteria by a sero tape peeling test. ◯: Completely peeled from the base material layer. ○-△: Peeled off from the OP varnish layer very slightly. (Triangle | delta): It peels from an equivalent OP varnish layer. X: Only the OP varnish layer is peeled off. Immersion property: A primer (acrylic polymer) is coated on a non-printed base material, and an OP varnish is applied on the base material, and the OP varnish is directly applied on the base material without coating the primer. It was evaluated from the glossiness and darkness of the coated test piece. Gloss is a gloss meter (Horiba Seisakusho Incident angle 60
The light receiving angle was 60 °. ◯: The difference in glossiness between the primer-treated surface and the untreated surface is 10 or less Δ: The difference in glossiness between the primer-treated surface and the untreated surface is 10-20 ×: The glossiness between the primer-treated surface and the untreated surface The abrasion resistance: OP varnish surfaces of the same test paper were rubbed 500 times under a load of 300 g, and scratches on the varnish surface were visually observed.

[0025]

EFFECT OF THE INVENTION An ultraviolet-curable OP varnish having a good adhesion to ink without a primer and little penetration into paper was obtained.

Claims (1)

[Claims] 1. A styrenic monomer 10-80% by weight (a).
And a C1-18 alcoholic (meth) acrylic acid ester-based monomer (b) and a polymerizable monomer having a hydrophilic functional group copolymerizable with these monomers 1-20 wt. %
The weight average molecular weight of (c) is 5000-200.
Styrene-acrylic acid ester copolymer 20
-80% by weight (component A), UV or electron beam curable monofunctional or polyfunctional (meth) acrylic acid ester monomer or oligomer 20-90% by weight (component B), polymer wax, polyethylene wax 0-15% by weight (component C)
And an active energy ray-curable overprint varnish comprising 0 to 15% by weight of a photopolymerization initiator (component D).