JP3277365B2 - Radiation curable ink and printed matter using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation-curable ink and a printed material using the same.

[0002]

2. Description of the Related Art Conventionally, when ink-jet printing is performed on a base material such as paper, film or board, a receiving layer is coated on the base material in order to accelerate ink absorption and reduce bleeding. I have. As the coating agent for forming the receiving layer, a material obtained by dissolving a water-soluble polymer in an aqueous medium and further adding silica, alumina, aluminum hydroxide, or the like as a filler is used.

[0003]

However, these coating agents are generally coated on the entire surface of the base material and are coated relatively thickly. Therefore, the coating agent is subjected to a long process to evaporate water in the coating agent. Is performed. Therefore, it is suitable not only for coating the entire surface of the substrate, but also for printing only the required portion of the substrate, and a receiving layer capable of completing coating or printing quickly without the need for a step of evaporating water. There has been a need for forming inks. Therefore, an object of the present invention is to provide an ink that satisfies such needs.

[0004]

SUMMARY OF THE INVENTION The present invention provides a radiation-curable ink comprising a liquid water-soluble monomer, a monomer-soluble hydrophobic polymer, and natural fiber powder.

[0005] In the present invention, the liquid water-soluble monomer is a radiation-polymerizable monomer that can be dissolved in water at an arbitrary ratio at normal temperature. Examples include (meth) acrylates of polyhydric alcohols, (meth) acrylates of N-alkylamino alcohols,
Polyethylene glycol (meth) acrylate,
N-alkyl (meth) acrylamide, vinyl ether of polyhydric alcohol and the like can be mentioned.

More specific examples include butanediol monoacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, N, N-
Examples thereof include diethylaminoethyl methacrylate, N, N-dimethylaminoethyl acrylate, N, N-dimethylaminoethyl methacrylate, N, N-dimethylacrylamide, acryloylmorpholine, and 2-hydroxyethyl vinyl ether. Also,
Mixtures of these monomers can also be used.

Further, a water-insoluble monomer of 80 parts by weight or less can be mixed with 100 parts by weight of these water-soluble monomers. Further, a polymerizable oligomer can be used in combination.

Examples of the water-insoluble monomer include phenoxyethyl acrylate, isobornyl acrylate, hexanediol diacrylate and the like.

Next, the hydrophobic polymer which is an essential component of the ink of the present invention will be described. In selecting this hydrophobic polymer, two criteria apply. The first criterion is that the hydrophobic polymer dissolves in the aforementioned water-soluble monomer or a mixture of 100 parts by weight of the water-soluble monomer and 80 parts by weight or less of the water-insoluble monomer. The second criterion is that a hydrophobic polymer is formed into a film and immersed in water at 25 ° C. for 2 hours.
g or more of water is absorbed and swelled, or the polymer itself is not substantially dissolved in water.

Examples of the hydrophobic polymer satisfying the above two criteria include (meth) acrylate (co) polymer, vinyl chloride-vinyl acetate copolymer, polyester, cellulose acetate butyrate, and butyral resin. it can.

In the ink of the present invention, the amount of the hydrophobic polymer to be added per 100 parts by weight of the liquid water-soluble monomer is
It is preferably from 5 to 80 parts by weight. If the added amount is below this range, the water resistance and ink adhesion of the obtained printed matter may be deteriorated, and the storage stability and printability of the ink containing no hydrophobic polymer are extremely poor.

When a hydrophilic polymer (water-soluble polymer) is used in place of the hydrophobic polymer, the water resistance of the receiving layer of the printed matter is poor, and the adhesion to plastic is also poor.

Examples of natural fiber powders include cellulose fiber powders such as pulp, cotton and hemp, polypeptide fiber powders such as wool, silk and collagen fibers, and other fiber powders. Also, a mixture of these powders can be suitably used.

The average particle size of these natural fiber powders is preferably 1 to 20 μm, more preferably 3 to 15 μm.
It is. If the average particle diameter is 20 μm or more or 1 μm or less, printability and print acceptability may be poor.

The radiation-curable ink of the present invention comprises a liquid water-soluble monomer and natural fiber powder. Preferably, the amount of the natural fiber powder is 15 to 100 parts by weight of the liquid water-soluble monomer. ３００300 parts by weight are used. More preferably, the amount of the natural fiber powder is used in an amount of 30 to 150 parts by weight, more preferably 60 to 120 parts by weight, per 100 parts by weight of the liquid water-soluble monomer. If the amount of the natural fiber powder exceeds 300 parts by weight, the printing characteristics of the ink may deteriorate, and if it is less than 15 parts by weight, the receiving performance may decrease.

In the present invention, powders such as silica, alumina, aluminum hydroxide, and a crosslinked monomer-insoluble water-absorbent resin powder can be used as a filler other than the natural fiber powder, if necessary.

Examples of other additives include oligomers such as oligoester acrylates, oligomers of acrylic acid esters having a polymerizable double bond, and oligomers such as oligourethane acrylates.

More detailed examples of oligomers and monomers are described in Kiyomi Kato, “Ultraviolet Curing System”, published by Sogo Gijutsu Center (February 28, 1989).
It is shown on the page.

In the present invention, α-rays, γ-rays, X-rays, ultraviolet rays, visible rays and the like can be used as radiation for promoting the polymerization of monomers.

When ultraviolet rays or visible rays are used as radiation, a photopolymerization initiator for initiating polymerization is used in combination.

Therefore, the radiation curable ink according to another configuration of the present invention contains a photopolymerization initiator for initiating polymerization of monomers.

Examples of the photopolymerization initiator are not particularly limited as long as radicals or other active species generated by light react with the polymerizable double bond in the above-mentioned monomer or oligomer. Examples include benzoin ethyl ether, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexylphenyl ketone,
-Methyl-1- (4- (methylthio) phenyl) -2-
Morpholinopropanone-1, bisacylphosphine oxide and the like can be mentioned. These photopolymerization initiators can be used alone or in combination of two or more.

Further examples of photopolymerization initiators include those described in Kiyomi Kato, "Ultraviolet Curing System", published by Sogo Gijutsu Center (published February 28, 1989), pp. 65-148. Examples thereof include a polymerization initiator. The use amount of these photopolymerization initiators is not particularly limited, but is generally about 1 to 10% by weight, preferably about 2 to 5% by weight.

Further, the ink of the present invention may contain a leveling agent, an antifoaming agent, a dye, a pigment and the like, if necessary.

The ink of the present invention can be generally printed by any printing method such as gravure printing, flexographic printing, and screen printing. However, in order to impart sufficient receiving performance to the printed layer, the thickness of the printed layer is preferably 5 to 5. It is desirable that the thickness be about 100 μm, more preferably about 10 to 40 μm.

Therefore, the most preferable example is screen printing in which the thickness of the printing layer is easily adjusted to the above range. Further, the ink of the present invention can be used after being coated by a coating method.

In any case, the ink of the present invention is cured by irradiation with radiation or light acting on a photopolymerization initiator after printing or coating to give a printed layer.

The printing layer thus obtained is rich in receptivity and provides a preferable receiving layer. In addition, this receiving layer can be easily formed not only on paper but also on a base material such as a plastic film, a plastic plate, or a metal plate.

When ink-jet printing or the like is performed on the receiving layer, the printed ink is promptly received and absorbed by the receiving layer, so that ink-jet printing can be performed almost without bleeding.

In particular, if the ink of the present invention is used and a receiving layer is provided on the back surface of a compact disc as an optical information medium, the use and characteristics of the compact disc can be easily determined by aqueous ink jet printing or the like. It is extremely useful because it can be recorded.

[0031]

EXAMPLES Hereinafter, the performance of the receiving layer printed on the base material will be described with reference to examples. The drying property of the inkjet printed matter and the sharpness of the image when the inkjet printing is performed on the receiving layer are described. It was judged in degrees.

Examples 1 to 3 and Comparative Examples 1 to 4 Various raw materials were blended at the weight ratios shown in Table 1 below, and these were dispersed using a stirrer to prepare various photocurable inks.

[0033]

[Table 1] The thus prepared photocurable ink was screen-printed on the back surface of a polycarbonate compact disc using a 300-mesh screen, irradiated with ultraviolet rays, and cured to form a 25 μm thick receiving layer.

Next, printing was performed on the receiving layer using an aqueous color ink using an ink jet printer, and the ink jet printing performance was examined. Table 2 shows the results of examining the sharpness of the image and the easiness of drying the ink after printing. In the evaluation in Table 2, ◎ indicates very good, ○ indicates good, △ indicates slightly poor, and × indicates bad.

[0035]

[Table 2] As is clear from the results shown in Table 2, when the photocurable inks of Examples 1 to 3 were used, the drying property and the image quality were higher than when the photocurable inks of Comparative Examples 1 to 4 were used. It can be seen that the sharpness is excellent. The ink (receiving layer) also has excellent water resistance and adhesion.

[0036]

As described above, the radiation-curable ink of the present invention can print not only the entire surface of the substrate but also only the necessary portions, and can print quickly without the need for a step of evaporating water. Can be completed. And the resulting print layer is rich in receptivity,
A printed material having a preferred receiving layer can be provided. In addition, if the printing medium is a compact disc, it is possible to easily record the use, characteristics, and the like of the compact disc thereon by aqueous inkjet printing or the like.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-11-116875 (JP, A) JP-A-9-157573 (JP, A) JP-A 1-318073 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) C09D 11/00-11/20

Claims (8)

(57) [Claims] 1. A radiation-curable ink comprising a liquid water-soluble monomer, a monomer-soluble hydrophobic polymer, and natural fiber powder. 2. The radiation-curable ink according to claim 1, further comprising a photopolymerization initiator. 3. The radiation-curable ink according to claim 1, comprising 5 to 80 parts by weight of a monomer-soluble hydrophobic polymer and 15 to 300 parts by weight of a natural fiber powder per 100 parts by weight of the liquid water-soluble monomer. . 4. The composition according to claim 2, comprising 5 to 80 parts by weight of the monomer-soluble hydrophobic polymer, 15 to 300 parts by weight of natural fiber powder, and a photopolymerization initiator per 100 parts by weight of the liquid water-soluble monomer. Radiation curable ink. 5. The natural fiber powder has an average particle size of 1 to 20 μm.
The radiation-curable ink according to any one of claims 1 to 4, wherein 6. The radiation-curable ink according to claim 1, wherein the natural fiber is a cellulose or a polypeptide-based fiber. 7. A printed matter obtained by printing on a synthetic resin substrate with the ink according to any one of claims 1 to 6. 8. The printed matter according to claim 7, wherein the synthetic resin substrate is a compact desk.