JPH11334234A - Printing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To give a high gloss, a high adhesion and a high frictional resistance to a final printed matter by a method wherein an ultraviolet curing coating varnish is used in an offset printing in-line system. SOLUTION: In this offset printing, a coating varnish is applied onto a paper, on which an offset ink is in a still non-dried state, so as to harden the varnish by irradiating ultraviolet rays in order to obtain a final printed matter. In this case, the coating varnish contains 0.5-30 wt.% rosin-modified phenolic resin having a weight average molecular weight of 5,000-250,000, 30-95 wt.% liquid epoxy resin and 0.5-30 wt.% photocationic polymerization 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 printing method for obtaining a printed material having high gloss and high abrasion resistance. More specifically, the present invention relates to an economical printing method for applying a coating varnish on paper after offset printing, curing the coated varnish by irradiating ultraviolet rays, and imparting high gloss and high friction resistance to a final printed product.

[0002]

2. Description of the Related Art Conventionally, the surface of a printed material has been post-processed in order to add functions such as abrasion resistance and water resistance to the printed material, and to enhance gloss and improve appearance and give a high-quality image. Is being done.

Almost all printed materials used for paper containers, postcards, book covers and the like used for outer packaging of frozen foods, cosmetics, confectionery and the like are subjected to post-processing.

[0004] The post-processing method is an in-line method in which a coating varnish is applied in a state in which the ink on the surface is not dried after printing on paper, or an in-line method in which the coating varnish is once prepared as a printed material and separately applied by a coating device or the like. There is an off-line method.

As one of post-processing methods of the in-line system, there is a method of applying an oil-based coating varnish using a printing unit of an offset printing machine. However, this method does not provide sufficient gloss and abrasion resistance. Since the drying properties of the oil-based coating varnish itself are insufficient, a backing-preventing spray powder is required after printing. In addition, there is a method in which a coating device such as a roll coater is installed after a printing machine, and an aqueous coating varnish is applied in-line. However, when this aqueous coating varnish is used, friction resistance is imparted, but sufficient gloss cannot be imparted, and it is necessary to perform hot pressing again.

[0006] On the other hand, an ultraviolet curable coating varnish which is cross-linked and cured by irradiation with ultraviolet light is used off-line. Although the coating surface of the UV-curable coating varnish processing has high gloss, sufficient adhesion to the printing ink surface is often not obtained, and the productivity is inferior due to separate post-processing.

[0007] In order to eliminate the disadvantages of post-processing, an in-line type UV-curable coating varnish has been studied. In-line type UV-curable varnish is applied directly to offset ink without using an anchoring agent. When cured, despite the glossiness immediately after the curing, the gloss was greatly reduced with the drying of the offset ink, and although there were advantages on the dry side, the print quality was poor.

There have been proposed various types of ultraviolet-curable compositions using a radical polymerization initiator and a type using a cationic polymerization initiator, and all of the ultraviolet-curable compositions are dried in an in-line system in an undried state. When applied on a certain offset ink, a gloss reduction phenomenon occurs.

JP-A-9-40760 discloses a resin composition having good adhesion to plastic films and metals, which is useful as a coating material for drawn cans coated with a polyester film. This composition is an ultraviolet curable resin composition containing a liquid epoxy compound, a cationic photopolymerization initiator, a petroleum resin, a terpene resin, and a rosin resin. However, this composition had an insufficient function of imparting gloss. This publication also suggests that the UV-curable resin composition is applied on offset ink in an undried state, which results in good adhesion to the ink and paper and gloss and rub resistance of the printed matter. There is no description that it is expected to be provided.

[0010] On the other hand, printing in which an anchor agent is continuously applied after offset printing and then an ultraviolet curable varnish is applied does not cause a decrease in gloss and gives a printed matter having good adhesion and rub resistance. However, this method requires installing two coating apparatuses after the printing press, which is not economical.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and to provide an ultraviolet-curable offset printing in-line system which is excellent in productivity and can perform from printing to post-processing consistently. It is an object of the present invention to provide a printing method that can impart high gloss, high adhesiveness and high rub resistance to a final print using a coating varnish.

[0012]

Means for Solving the Problems As a result of repeated studies to solve the above-mentioned problems, the present inventors have found that a specific rosin-modified phenol resin, a liquid epoxy resin and a cationic photopolymerization initiator are mixed at a specific ratio. The present inventors have found that these problems can be solved by applying an ultraviolet curing type coating varnish used in combination to an offset sheet-fed printing in-line method, and have completed the present invention.

That is, the present invention relates to a printing method for obtaining a final printed product by applying a coating varnish on paper in which an offset ink is in an undried state in offset printing, and curing the coated varnish by irradiation of ultraviolet rays. Weight average molecular weight 5,000-250,000
0 to 30% by weight of a rosin-modified phenolic resin,
The present invention relates to a printing method comprising, as essential components, 30 to 95% by weight of a liquid epoxy resin and 0.5 to 30% by weight of a cationic photopolymerization initiator. Further, the present invention relates to a printing method wherein the rosin-modified phenol resin used in the coating varnish has a weight average molecular weight of 10,000 to 200,000 and an acid value of 10 to 50 mgKOH / g.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.

The printing method of the present invention typically incorporates a coating device and an ultraviolet irradiation device after the printing press,
Subsequent to printing, it can be carried out by applying a coating varnish in a state where the ink on the paper is not dried, and then irradiating ultraviolet rays to obtain a final print. According to the method of the present invention, the coating varnish can be applied directly on paper without using an anchoring agent.

As a printing machine, for example, lithographic offset printing in which an image is formed using a plate having a lipophilic image area and a hydrophilic non-image area by utilizing the repulsion of fountain solution and oil-based ink can be performed. A printing unit or a unit having a printing unit capable of performing waterless lithographic offset printing using a plate having a silicone layer as a non-image portion and no fountain solution can be used.

As a coating apparatus, a direct gravure coater, offset gravure coater, reverse roll coater, transfer roll coater and the like can be used. Further, the final printing unit of the printing press can be used as a coating device. The coating amount is in the range of 1 to 10 g / m ² . Preferably 3 to 8 g /
m ² .

Generally, an ultraviolet irradiation device is 80 to 2
A high-pressure mercury lamp with a power of 40 W / cm, a metal halide lamp or the like is used as a light source, and usually 2 to 8 lamps are installed in parallel. The running speed of the paper is 60 to 160 m / min.

Next, the coating varnish used in the present invention will be described in detail. The rosin-modified phenol resin used in the coating varnish has a weight average molecular weight in the range of 5,000 to 250,000,
It is preferably from 10,000 to 200,000, more preferably from 30,000 to 180,000.

When the weight-average molecular weight is lower than 5,000, a gloss reduction phenomenon occurs when used in an in-line system. On the other hand, when the molecular weight is higher than 250,000, the viscosity of the coating varnish increases, the leveling is deteriorated, and the gloss of the printed matter is reduced.

When the blending amount of the rosin-modified phenolic resin is 0.
If it is less than 5% by weight, the effect of suppressing the gloss reduction phenomenon is small,
If it exceeds 30% by weight, the coating varnish becomes hard and leveling is poor. The acid value of the rosin-modified phenolic resin is in the range of 10 to 50 mgKOH / g, preferably 15 to 30 mgKOH / g. Acid value is 10
Lower resins are difficult to manufacture, and above 50 may increase the viscosity of the varnish and impair gloss.

The rosin-modified phenolic resin used in the present invention can be synthesized, for example, by the following method. Rosin and a polyhydric alcohol such as pentaerythritol and glycerin are added in the presence of an optional catalyst for 250 minutes.
The reaction is carried out at -280 ° C until the acid value becomes 20 mgKOH / g or less to prepare a rosin ester. Separately, a novolak-type phenol resin obtained by condensing p-alkylphenol and formaldehyde under an acidic catalyst or a resol-type phenol resin obtained by condensing with a basic catalyst is prepared. The rosin ester is melted at a temperature of 200 to 250 ° C., and a novolak-type phenol resin or a resol-type phenol resin is gradually dropped to prepare a rosin-modified phenol resin. Alternatively, rosin, p-alkylphenol, formaldehyde, a catalyst, and a polyhydric alcohol may be charged at once, and condensation and esterification may be performed to prepare a rosin-modified phenol resin. The rosin-modified phenol resin used in the present invention has a softening point of 135 to 190.
C., and preferably in the range of 140 to 180 ° C., a commercially available rosin-modified phenol resin generally used for oil-based offset inks can be used.

The liquid epoxy resin used in the present invention comprises:
Known monofunctional or polyfunctional alicyclic epoxy resin, aliphatic epoxy resin, as long as it dissolves the rosin-modified phenolic resin and other resin components to lower the viscosity.
Although an aromatic epoxy resin can be used, an alicyclic epoxy resin is preferably used from the viewpoint of photocationic polymerizability.

For example, as the alicyclic epoxy resin,
3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (commercial product example; UV
R-6110 manufactured by Union Carbide Co., Ltd., Celloxide 2021 manufactured by Daicel Chemical Industries, Ltd., bis (3,4-epoxycyclohexyl adipate) (commercial product example; UVR-
6128 Union Carbide Co., Ltd.), ε-caprolactone-modified trifunctional alicyclic epoxy resin (commercially available product; GT-302 manufactured by Daicel Chemical Industries, Ltd.), cyclohexane dimethanol diglycidyl ether, and the like. Examples of the aliphatic epoxy resin include 2-ethylhexyl glycidyl ether, tert-amyl glycidyl ether, dodecyl glycidyl ether, octadecyl glycidyl ether, ethylene glycol butyl glycidyl ether,
Examples include triethylene glycol methyl glycidyl ether, diethylene glycol diglycidyl ether, butanediol diglycidyl ether, hexanediol diglycidyl ether, ethylene glycol diglycidyl ether, and tetraethylene glycol diglycidyl ether. Bisphenol A type resin (commercially available product; EP-828 Yuka Shell Epoxy Co., Ltd., YD-8125 Toto Kasei Co., Ltd.), bisphenol F type epoxy resin (YDF
-8170 manufactured by Toto Kasei Co., Ltd., brominated epoxy resin (commercial product example: YDB-400 manufactured by Toto Kasei Co., Ltd., F
R-1500 manufactured by Kyoeisha Chemical Co., Ltd., propylene oxide-modified bisphenol A type epoxy resin (commercially available product; B
PO-20E manufactured by Shin Nippon Rika Co., Ltd.). In addition, hydrogenated bisphenol A type epoxy resin,
And hydrogenated bisphenol F type epoxy resins.

The liquid epoxy resin of the present invention has not only a function as a photocationic polymerizable compound but also a function as a diluting solvent for other resin components in the coating varnish, and its compounding amount is 30 to 95% by weight. Used in range. Preferably it is 50 to 85% by weight.

In the present invention, a cationic photopolymerizable compound represented by a vinyl ether compound can be used in addition to the liquid epoxy resin. For example, as typical monofunctional vinyl ethers, 2-ethylhexyl vinyl ether, te
rt-amyl vinyl ether, dodecyl vinyl ether, octadecyl vinyl ether, ethylene glycol butyl vinyl ether, triethylene glycol methyl vinyl ether, and the like. Examples of the polyfunctional vinyl ether are diethylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, and cyclohexane dimethanol Examples include vinyl ether, ethylene glycol divinyl ether, and tetraethylene glycol divinyl ether.

As the cationic photopolymerization initiator, for example,
Triarylsulfonium complex salts as described in U.S. Pat. No. 4,231,951, U.S. Pat.
Aromatic sulfonium or iodonium salts of halogen-containing complex ions as described in US Pat. No. 6,828;
Aromatic onium salts of Group VIa elements as described in US Pat. No. 255; US Pat. No. 4,069,055, including aromatic onium salts of Group Va elements used it can. The photopolymerization initiator is contained in the coating varnish in an amount of 0.5 to 30% by weight. More preferably, it is 1 to 20% by weight. If it is less than 0.5% by weight, curing of the coating varnish cannot be achieved, and if it exceeds 30% by weight, the rub resistance of the cured film becomes insufficient.

The following can be used as optional components in the coating varnish of the present invention as long as the photocationic polymerization performance is not impaired.

As the resin, alkyd resin, acrylic resin, polyester resin, maleic acid resin, styrene-acrylic resin, styrene-maleic acid resin and the like can be used. Known clays such as printing inks and paints as pigments,
Silica, extender pigments such as aluminum hydroxide, azo compounds, quinacridone compounds, phthalocyanine blue, milori blue, organic pigments such as carbazole dioxazine bio red, titanium oxide, zinc white, inorganic pigments such as carbon black can be used, particularly, Nonpolar or neutral pigments are preferably used.

As the additive, for example, paraffin, silicone, polyethylene or polytetrafluoroethylene wax can be used as a lubricant.

The coating varnish of the present invention can be produced by a generally known method.

For example, when forming a coating varnish,
Preparation is performed by blending a photopolymerization initiator, various additives, and the like with the above-described polymer-dissolved varnish, and stirring and mixing.
When a colored coating varnish is used, a rosin-modified phenol resin is heated and dissolved in a liquid epoxy resin to prepare a polymer-dissolved varnish, and a dye, a pigment,
A dispersing agent and the like are blended, and the mixture is kneaded and dispersed by various dispersing machines such as a three-roll mill and a bead mill, and then a photopolymerization initiator, various additives, and the like are added to produce the mixture. The coating varnish is adjusted to a viscosity of 0.5 to 22 Pa · s. Preferably, it is in the range of 0.5 to 3.0 Pa · s.

It is desirable that the prepared coating varnish is stored in a container protected from light.

[0034]

EXAMPLES The present invention will now be described specifically with reference to examples, but the present invention is not limited to these examples. In the examples, all parts are by weight unless otherwise specified.

[Production Example 1 of Polymer-Dissolved Varnish] A reaction vessel equipped with a stirrer and a cooler was charged with a weight average molecular weight of about 150,
Rosin-modified phenolic resin with an acid value of 19 mg KO
H / g) and 20 parts of a liquid epoxy resin 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (bifunctional alicyclic epoxy resin) 60 parts were added, and the mixture was heated and stirred at 200 ° C. for 60 minutes to obtain a polymer. Dissolution varnish A was obtained.

[Production Example 2 of Polymer-Dissolved Varnish] A reaction vessel having a stirrer and a cooler was charged with a weight average molecular weight of about 70,0.
Rosin-modified phenolic resin with an acid value of 23 mg KOH
/ G) 20 parts and liquid epoxy resin 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (bifunctional alicyclic epoxy resin) 60 parts were added, and heated and stirred at 200 ° C. for 30 minutes to dissolve the polymer. Varnish B was obtained.

[Production Example 3 of Polymer-Dissolved Varnish] A reaction vessel having a stirrer and a cooler was placed in a reaction vessel having a weight average molecular weight of about 100,
Rosin-modified phenolic resin with an acid value of 28 mg KO
H / g) 20 parts and liquid epoxy resin 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (bifunctional alicyclic epoxy resin) 60 parts were added, and the mixture was heated and stirred at 200 ° C. for 30 minutes. Dissolution varnish C was obtained.

[Production Example 4 of Polymer Dissolved Varnish] A weight average molecular weight of about 30,0 was added to a reaction vessel having a stirrer and a cooler.
00 rosin-modified phenolic resin (acid value 20 mg KOH
/ G) 20 parts and liquid epoxy resin 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (bifunctional alicyclic epoxy resin) 60 parts were added, and heated and stirred at 200 ° C. for 60 minutes to dissolve the polymer. Varnish D was obtained.

[Production Example 5 of Polymer-Dissolved Varnish] A reaction vessel having a stirrer and a cooler was charged with a weight average molecular weight of about 30,0.
00 rosin-modified phenolic resin (acid value 20 mg KOH
/ G) 40 parts and 60 parts of liquid epoxy resin 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (bifunctional alicyclic epoxy resin) are added, and heated and stirred at 200 ° C. for 60 minutes to dissolve the polymer. Varnish E was obtained.

[Production Example 6 of Polymer-Dissolved Varnish] In a reaction vessel having a stirrer and a cooler, 20 parts of petroleum resin (weight average molecular weight: about 1,100, softening point: 140 ° C.) and liquid epoxy resin 3,4-epoxy Cyclohexylmethyl-3,4-
70 parts of epoxycyclohexanecarboxylate (bifunctional alicyclic epoxy resin) was added, and the mixture was heated and stirred at 200 ° C. for 60 minutes to obtain a polymer dissolving varnish F.

Example 1 4 parts of polymer dissolving varnish A, 79 parts of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (bifunctional alicyclic epoxy resin), 10 parts of limonene dioxide (liquid) (Epoxy resin), 5 parts of triarylsulfonium salt (photocationic catalyst), 1 part of wax and 1 part of leveling agent are disperse-mixed, and UV-curable at 0.8 Pa · s (B-type viscometer, 25 ° C.) Coating varnish 1 was obtained.

Example 2 40 parts of a polymer dissolving varnish B, 45 parts of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (bifunctional alicyclic epoxy resin) and 8 parts of limonene dioxide (liquid) Epoxy resin), 5 parts of a triarylsulfonium salt (photocationic catalyst), 1 part of a wax and 1 part of a leveling agent are disperse-mixed and 1.2 Pa · s (B-type viscometer,
5 ° C.) was obtained.

Example 3 40 parts of polymer dissolving varnish C, 45 parts of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (alicyclic epoxy resin), 8 parts of limonene dioxide (liquid epoxy resin) ), 5 parts of a triarylsulfonium salt (photocationic catalyst), 1 part of a wax and 1 part of a leveling agent, and 2.9 Pa · s (B-type viscometer, 25 parts).
C.) was obtained.

Example 4 40 parts of polymer dissolving varnish D, 45 parts of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (alicyclic epoxy resin), 8 parts of limonene dioxide (liquid epoxy resin) ), 5 parts of a triarylsulfonium salt (photocationic catalyst), 1 part of a wax and 1 part of a leveling agent are disperse-mixed, and the mixture is 1.0 Pa · s (B-type viscometer, 25 parts).
° C) UV-curable coating varnish 4 was obtained.

Example 5 40 parts of a polymer dissolving varnish A, 33 parts of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (bifunctional alicyclic epoxy resin) and 20 parts of limonene dioxide ( Liquid epoxy resin), 5 parts of triarylsulfonium salt (photocationic catalyst), 1 part of wax and 1 part of leveling agent, and UV-curing at 1.4 Pa · s (B-type viscometer, 25 ° C.) Mold coating varnish 5
I got

Example 6 Polymer dissolving varnish A (40 parts), 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (bifunctional alicyclic epoxy resin) (43 parts) and 3-vinylcyclohexene monoxide were used. 10 parts (vinyl group-containing alicyclic epoxy resin), triarylsulfonium salt (photocationic catalyst)
Was mixed with 1 part of wax and 1 part of a leveling agent to obtain an ultraviolet-curable coating varnish 6 of 1.1 Pa · s (B-type viscometer, 25 ° C.).

Example 7 Polymer dissolving varnish A (40 parts), 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (bifunctional alicyclic epoxy resin) (43 parts), ε-caprolactone-modified triol (weight) 10 parts of an average molecular weight of about 300), 5 parts of a triarylsulfonium salt (photocationic catalyst), 1 part of a wax and 1 part of a leveling agent by disper mixing.
An ultraviolet-curable coating varnish 7 of 1.5 Pa · s (B-type viscometer, 25 ° C.) was obtained.

Example 8 40 parts of a polymer dissolving varnish A, 43 parts of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (bifunctional alicyclic epoxy resin) and 10 parts of triethylene glycol divinyl ether were used. Parts, 5 parts of a triarylsulfonium salt (photocationic catalyst), 1 part of a wax and 1 part of a leveling agent, and disperse-mixed to give a 1.2 Pa · s (B-type viscometer, 25 ° C.) UV-curable coating varnish 8
I got

Example 9 Polymer Dissolution Varnish E62.
5 parts and 3,4-epoxycyclohexylmethyl-3,4
-20.5 parts of epoxycyclohexanecarboxylate (bifunctional cycloaliphatic epoxy resin), 10 parts of limonene dioxide (liquid epoxy resin), 5 parts of triarylsulfonium salt (photocationic catalyst), 1 part of wax and leveling agent Disperse and mix with 1 part, 1.5Pa · s
(B-type viscometer, 25 ° C.) UV-curable coating varnish 9 was obtained.

Comparative Example 1 93 parts of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (bifunctional alicyclic epoxy resin), 5 parts of triarylsulfonium salt (photocationic catalyst), 1 part of the wax and 1 part of the leveling agent were disper-mixed to obtain an ultraviolet-curable coating varnish 10 of 0.6 Pa · s (B-type viscometer, 25 ° C.).

Comparative Example 2 80 parts of polymer dissolving varnish E, 13 parts of limonene dioxide (liquid epoxy resin), 5 parts of a triarylsulfonium salt (photocationic catalyst),
One part of the wax and 1 part of the leveling agent were disperse-mixed to obtain an ultraviolet-curable coating varnish 11 of 1.4 Pa · s (B-type viscometer, 25 ° C.).

(Comparative Example 3) <Radical polymerization type coating varnish for in-line> 45 parts of ethylene oxide 2 mol modified bisphenol A type diacrylate, 13 parts of a commercially available acrylic resin oligomer, 20 parts of dipentaerythritol hexa (penta) acrylate 15 parts of ethylene glycol diacrylate, 5 parts of 1-hydroxyhexylbenzophenone (radical initiator), wax 1
Parts and 1 part of the leveling agent by dispersing and stirring.
An ultraviolet curable coating varnish 12 having a Pa · s (B type viscometer, 25 ° C.) was obtained.

Comparative Example 13 Polymer Dissolving Varnish G90
Part, limonene dioxide 3 parts (liquid epoxy resin), triarylsulfonium salt (photocationic catalyst) 5 parts,
One part of the wax and 1 part of the leveling agent were disper-mixed to obtain an ultraviolet-curable coating varnish 13 of 2.0 Pa · s (B-type viscometer, 25 ° C.).

(Reference Example) <Oil-based offset varnish> A coating varnish usually used for offset printing (offset gloss OP varnish;
(Sakata Inx Co., Ltd.) was used in place of the UV-curable coating varnish and evaluated.

[Preparation of test piece] Ink roll 0.175 ml of ink for offset sheet-fed printing (manufactured by Sakata Inx Co., Ltd.) by means of an RI-2 type color developing machine split roll (manufactured by Meiji Seisakusho).
/ 204cm ² with Jetstar paper (manufactured by Daishowa Paper)
After coating twice, the coating varnishes prepared in Examples and Comparative Examples heated to 40 ° C. while the ink was not dried were colored with a 165-line hand pull fur. Continued
160W / cm metal halide lamp (Hereus U
Using a V apparatus: using a focal length of 13 cm, a condensing type, and one light), irradiation was performed at a speed of 40 m / min to obtain a test piece.
In addition, it was confirmed that the surface of the test piece was tack-free due to finger erosion.

[Evaluation of Adhesive Property] A cellophane tape peeling test was performed to evaluate the state of peeling from the interface between the ink and the coating agent. Excellent: There is no peeling of the coating material surface, or it is peeled from paper (base material). Good: Part of the coating film peels off from the interface with the ink. Poor: The coating agent peels without resistance at the interface between the ink and the coating agent.

[Evaluation of Friction Resistance] Using a dyed rub fastness tester (manufactured by Daiei Kagaku Seiki Seisaku-sho, Ltd.), the printed surfaces of the two test pieces were reciprocated 1,000 times with a load of 1 kg, and visually evaluated. . Excellent: Each test piece surface is not damaged. Good: Several scratches are made on the surface of each test piece. Poor: Countless scratches are formed on the surface of each test piece, or the coating film is peeled off.

[Evaluation of Gloss Value] Gloss value obtained by measuring a test piece with a gloss meter (60 °) one day later. Usually 75
If the value is greater than or equal to the above value, it is recognized as glossy.

[0059]

[Table 1]

[0060]

As described in the above Examples, Comparative Examples and Reference Examples, ultraviolet curing using the specific rosin-modified phenolic resin of the present invention, a liquid epoxy resin and a cationic photopolymerization initiator in a specific ratio is carried out. By applying the mold coating varnish to the offset printing in-line method, it is possible to impart higher gloss to the final printed matter, and also to impart properties excellent in adhesion and abrasion resistance.

Claims (2)

[Claims] In offset printing, a printing method in which a coating varnish is applied to paper in which an offset ink is in an undried state and cured by irradiation of ultraviolet rays to obtain a final printed product, wherein the coating varnish has a weight average molecular weight of 5 0.5 to 30% by weight of a rosin-modified phenol resin of 2,000 to 250,000 and a liquid epoxy resin 3
0 to 95% by weight, and 0.5 to 30% of a cationic photopolymerization initiator.
% By weight as an essential component. 2. The rosin-modified phenol resin used in the coating varnish has a weight average molecular weight of 10,000.
0 to 200,000 and an acid value of 10 to 50 mg KO
The printing method according to claim 1, wherein the printing method is H / g.