JP5692960B2 - UV curable coating agent - Google Patents

Description

  The present invention relates to an ultraviolet curable coating agent that is cured by ultraviolet rays for applying an ink receiving layer to a substrate such as a synthetic resin.

  Conventionally, optical information recording media such as compact discs (hereinafter referred to as CDs) and digital video discs (hereinafter referred to as DVDs) have been developed as means for storing various information such as audio data and image data in addition to computer information. Has been widespread.

On the surface of the optical information recording medium, a title or design indicating the recorded contents is implemented by a conventionally known printing means such as ink jet printing or screen printing. When performing inkjet printing etc. on a substrate such as synthetic resin, the substrate does not absorb ink, so a coating agent etc. is applied to the surface of the substrate and cured to form an ink receiving layer, and printing is performed thereon doing.
The printability of the ink receiving layer is required to combine excellent ink absorption, dryness of printed images, bleeding resistance of printed images, tack resistance, and water resistance. Several agents have been proposed.

Patent Document 1 describes an ultraviolet curable coating agent composed of a filler, an ultraviolet curable resin, and a hydrophilic polymer. Patent Document 2 describes a radiation-curable coating agent composed of a water-soluble monomer, a hydrophilic polymer, and a dye fixing body.
JP-A-8-96409 JP 2003-25710 A

  However, in the case where a hydrophilic polymer is used for the coating agent for forming the ink receiving layer for the purpose of increasing the ink absorbency as described above, the ink absorbability increases, but the tack resistance decreases, that is, the slippage is poor. Since blocking is likely to occur, there is a problem that sufficient printing characteristics may not be obtained. Therefore, there has been a demand for a coating agent that forms an ink receiving layer having both of these characteristics.

  An object of the present invention is to provide an ultraviolet curable coating agent that forms an ink-receiving layer having improved ink absorption, drying of printed images, and bleeding resistance, as well as improved tack resistance.

In addition to a hydrophilic polymer, a water-soluble monomer, and a photopolymerization initiator, the inventors of the present invention have an ultraviolet curable coating agent containing 0.05 to 2.5% by mass of a fatty acid amide as a slip agent. The inventors have found that an ink receiving layer that has cleared the above-mentioned problems can be formed by forming a film on the surface of the material, and the present invention has been achieved.
That is, the present invention
(1) An ultraviolet curable coating agent curable with ultraviolet rays, which contains a hydrophilic polymer, a water-soluble monomer, a photopolymerization initiator, and a slip agent, and 0.05% fatty acid amide as the slip agent UV-curable ink-receiving layer coating agent for optical information recording medium, characterized by containing ~ 2.5% by mass,
(2) The ultraviolet curable ink-receiving layer coating agent for optical information recording media according to (1), wherein the fatty acid amide is oleic acid amide,
Is to provide.

  The UV curable coating agent described in the present invention can be formed on a substrate by being coated with UV and cured to form an ink receiving layer, and this ink receiving layer has excellent ink absorptivity. In addition, it has good dryness of the printed image, dryness of the printed image, bleed resistance of the printed image, and tack resistance.

In the present invention, examples of the hydrophilic polymer include those having a polar group such as an acrylamide group. Specific examples include homopolymers and copolymers such as acrylamide, acroylmorpholine, dimethylacrylamide, diethylacrylamide, and N-dimethylaminopropylacrylamide. The weight average molecular weight of the hydrophilic polymer is preferably 5000 or more and 200000 or less, and more preferably 5000 or more and 70000 or less. If it is less than 5,000, it is difficult to obtain the effect of improving the ink absorbency due to the addition of the hydrophilic polymer, and if it exceeds 200,000, it becomes difficult to apply the film due to an increase in viscosity, and a decrease in tack resistance is observed.
The ultraviolet curable coating agent of the present invention preferably contains 10 to 40% by mass of a hydrophilic polymer.

In order to further improve the ink absorbability, a water-soluble monomer is added to the ultraviolet curable coating agent of the present invention. The water-soluble monomer in the present invention is an ultraviolet polymerizable monomer that can be dissolved in water at an arbitrary ratio at room temperature. Specifically, 2-hydroxyethyl acrylate, butanediol monoacrylate, N, N-diethylaminoethyl methacrylate, N, N-dimethylaminoethyl acrylate, N, N-dimethylacrylamide, methoxymethylacrylamide, ethoxymethylacrylamide, propo Toxic methyl acrylamide, acryloyl morpholine, butoxymethyl acrylamide, methoxypolyethylene glycol acrylate, 2 (2-ethoxyethoxy) ethyl acrylate, 2-hydroxyethyl vinyl ether and the like can be mentioned. Particularly preferred is acryloylmorpholine.
The ultraviolet curable coating agent of the present invention preferably contains 60% by mass or more of acryloylmorpholine.

Examples of the photopolymerization initiator in the present invention include benzoin such as benzoin, benzoin methyl ether, benzoin ethyl ether, and benzoin isopropyl ether, or ethers thereof, benzophenone compounds such as benzophenone, benzyl compounds such as benzyl, benzylmethyl ketal, and benzylethyl ketal. Compound, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one And the like, and the like. Commercially available Darocur 1173 (manufactured by Ciba Japan Co., Ltd.) and Darocur 2959 are suitable.
The addition amount of the photopolymerization initiator is 1 to 10% by mass, preferably 2 to 7% by mass of the ultraviolet curable coating agent. If the amount is too small, sufficient curability cannot be obtained. If the amount is too large, there is a possibility that the coating strength is reduced or yellowing occurs.

The ultraviolet curable coating agent of the present invention contains a fatty acid amide as a slip agent. Examples of fatty acid amides include palmitic acid amide, stearic acid amide, behenic acid amide, oleic acid amide, erucic acid amide and the like. In particular, oleic acid amide is preferable because it has a high effect of improving slip property. These fatty acid amides are contained in a liquid ultraviolet curable coating agent, and after the coating agent is cured by ultraviolet rays to form a layer, the tack resistance of the layer surface is remarkably improved. Thereby, the problem of tackiness which is likely to occur due to the hydrophilic polymer which is another component can be solved.
The content of the fatty acid amide is 0.05 to 2.5% by mass of the ultraviolet curable coating agent, and preferably 1 to 2.5% by mass from the viewpoint of solubility and dispersibility in other compositions. . When it is less than 0.05% by mass, the effect is hardly exhibited. Moreover, when it contains 3 mass% or more, it will become difficult to harden | cure by an ultraviolet-ray.

Hereinafter, the present invention will be specifically described based on examples.
(Sample preparation)
(Synthesis of hydrophilic polymer)
Various hydrophilic polymers shown below were prepared as materials for the ultraviolet curable coating agent.

Hydrophilic polymer (a): N, N-dimethylaminopropylacrylamide polymer N, N-dimethylaminopropylacrylamide was placed in a 1-liter separable flask equipped with a cooling tube, a nitrogen introduction tube, and a horizontal wing. 60 g (manufactured by Kojin Co., Ltd.) and 510 g of methanol (manufactured by Kanto Chemical Co., Ltd.) were added, and the inside of the reaction flask was replaced with nitrogen gas (manufactured by Keisho Co., Ltd.) while stirring. Thereafter, a solution obtained by dissolving 0.64 g of azobisisoptyronitrile (manufactured by Wako Pure Chemical Industries, Ltd.) in 30 g of methanol was added, and the temperature was raised to 65 ° C. to carry out a polymerization reaction for 8 hours. After this polymerization reaction, the solvent was distilled off from the reaction solution at 30 ° C. under reduced pressure to obtain 57 g of a tan solid.
This yellow-brown solid was prepared by using polyethylene oxide as a standard, using a mixed aqueous solution of sodium nitrate 0.1M (manufactured by Wako Pure Chemical Industries, Ltd.) and acetic acid 0.5M (manufactured by Wako Pure Chemical Industries, Ltd.) as an eluent. As a substance, Ultra Hydrogel 500 (trade name, manufactured by Waters) was used as a column, and GPC analysis was performed at an eluent flow rate of 1 ml / min and a column temperature of 30 ° C. As a result, the weight average molecular weight of the tan solid was 15400.

Hydrophilic polymer (b): N, N-dimethylacrylamide polymer In the above-described separable flask, 60 g of N, N-dimethylacrylamide (manufactured by Kojin Co., Ltd.) and 510 g of methanol (manufactured by Kanto Chemical Co., Ltd.) And the inside of the reaction flask was replaced with nitrogen gas while stirring as described above. Thereafter, a solution obtained by dissolving 1.00 g of azobissoptyronitrile in 30 g of methanol was added, and the temperature was raised to 75 ° C. to carry out a polymerization reaction for 8 hours. After this polymerization reaction, the solvent was distilled off from the reaction solution at 30 ° C. under reduced pressure to obtain 58 g of a tan solid. This yellowish brown solid was subjected to GPC analysis in the same manner as described above. As a result, the weight average molecular weight was 63800.

<Examples 1-3, Comparative Examples 1-4>
A predetermined amount of raw materials were mixed at the blending ratio shown in Table 1 below to prepare a sample of an ultraviolet curable coating agent.

(Formation of ink receiving layer)
The sample of the ultraviolet curable coating agent produced as described above was applied to a 100 μm thick PET (Polyethylene Terephthalate) film with a bar coater (RKPrint Coat Instruments, trade name: K-202) so that the film thickness was 15 to 25 μm. .
Then, the coating film was cured at an accumulated radiation amount of 350 mJ / cm 2 with an ultraviolet irradiation device (Oak Seisakusho, trade name: OHD-320M) to form an ink receiving layer.

(Evaluation of printability)
On the ink receiving layer formed as described above, a solid image of black, blue, yellow, and red was printed adjacently by an inkjet color printer (trade name: PM-A890, manufactured by Seiko Epson Corporation). And the printing situation was comparatively evaluated. As the printing status, as shown below, the drying property, the bleeding property, and the tack resistance were evaluated in three stages of ○, Δ, and ×. The evaluation results are shown in Table 1.

-After 5 minutes of dry printing, paper (manufactured by ASKUL, trade name: Multi-Paper Spar Economy) was pressed against the printed surface, and the degree to which the ink was transferred to the paper was evaluated.
○: Ink is not transferred at all Δ: A little ink is transferred ×: A lot of ink is transferred

-The degree to which the printed image on the bleedable coating film bleeds was evaluated.
○: Slightly blurring △: Slightly blurring ×: Slightly blurring

-The printed image on the tack-resistant coating film was touched with a dry finger, and the degree of tackiness was evaluated.
○: Not sticky △: Feels a little sticky ×: Clearly sticky (sticky)

(result)
In Comparative Example 1, which comprises acryloylmorpholine and a polymerization initiator and does not contain a hydrophilic polymer and a slip agent, the drying property after printing is poor. On the other hand, in Comparative Examples 2 and 3 containing the hydrophilic polymers (a) and (b), although the drying property was improved, a decrease in tack resistance was observed.
In Examples 1, 2, and 3 containing a hydrophilic polymer and 1% by mass or 2.5% by mass of a slip agent in addition to acryloyl morpholine and a polymerization initiator, drying property, bleeding property, and tack resistance are both good. It was possible to obtain optimum printability.
In addition, what increased slip agent to 4 mass% did not harden | cure by predetermined ultraviolet irradiation amount, and printing could not be performed.

  The ultraviolet curable coating agent of the present invention can be applied to various base materials including a synthetic resin and impart good ink jet printing characteristics to the base material. It can be applied to printing on substrates such as CDs and DVDs, which have conventionally been difficult to print.

Claims (1)

A hydrophilic polymer;
A water-soluble monomer,
A photopolymerization initiator;
Containing a slip agent,
An ultraviolet curable coating agent that cures with ultraviolet rays,
The hydrophilic polymer is a polymer of N, N-dimethylacrylamide or a polymer of N, N-dimethylaminopropylacrylamide,
The water-soluble monomer is acryloylmorpholine;
An ultraviolet curable ink-receiving layer coating agent for optical information recording media, comprising 0.05 to 2.5% by mass of oleic acid amide as the slip agent.