JPH10219158A - High-performance ink jet printing water-base ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ink jet printing ink which can be easily divided into droplets in nozzles and can give a print excellent in safety, water resistance, weather resistance, stability and adhesive to a substrate by mixing a radiation- curable water-insoluble viscous macromer emulsified in an aqueous medium with a water-soluble polymerizable monomer. SOLUTION: The aqueous medium mainly consists of water and may contain additives such as ethanol or ethylene glycol and other water-soluble substances in an amount of 3-30wt.% desirable in safety. The water-insoluble viscous macromer is a compound being radiation-curable and substantially water- insoluble and having a viscosity of 100cP or above, desirably 1,000cP or above at 20 deg.C and is exemplified by an unsaturated polyester resin or a polyurethane acrylate. The water-soluble polymerizable monomer is one which is polymerizable under the curing conditions for the macromer and is exemplified by a polyhydric alcohol mono(meth)acrylate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-based ink for ink-jet printing, and more particularly, to a water-based ink for high-performance ink-jet printing, which has good ink stability and good weatherability and water resistance of printed matter. About.

[0002]

2. Description of the Related Art
As an ink for inkjet printing, a water-soluble dye dissolved in water has been used. Such an ink generally has good stability during storage of the ink and stability during printing, but has serious drawbacks in terms of water resistance and weather resistance of the printed matter.

Many proposals have been made to solve such disadvantages. For example, a radiation curable aqueous ink for inkjet printing in which a radiation-curable water-insoluble viscous macromer is contained in an aqueous medium in an emulsion state has been proposed (JP-A-8-48).
922). According to the ink described in such a publication,
Although the water resistance and weather resistance of the printed matter are remarkably improved, there is still room for improvement in terms of the stability of the ink and the adhesiveness to a printing object, which are increasingly required in recent inks.

Accordingly, it is an object of the present invention to easily atomize a nozzle without danger of environmental pollution or explosion, and furthermore, it is excellent in water resistance and weather resistance, furthermore, the stability of ink and the adhesion to a printing material. An object of the present invention is to provide an inkjet printing ink having excellent properties.

[0005]

Means for Solving the Problems As a result of intensive studies, the present inventors have achieved the above object by an aqueous ink containing a specific macromer and a polymerizable water-soluble monomer in an aqueous medium. I found that.

The present invention has been made based on the above-mentioned findings, and it is an object of the present invention to contain a water-insoluble viscous macromer which is dispersed in an aqueous medium in an emulsion state and which can be cured by radiation, and a polymerizable water-soluble monomer. The object has been achieved by providing a radiation curable aqueous ink for inkjet printing (hereinafter, simply referred to as "aqueous ink").

Another object of the present invention is to provide a printed matter obtained by printing with the above-mentioned aqueous ink for radiation curable ink jet printing and then curing the ink with ultraviolet rays.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, the above-mentioned aqueous medium is a medium containing water as a main component. For example, as the aqueous medium, a medium containing water as a main component and an alcohol such as methanol, ethanol, or isopropanol added as an additive can be used. In addition, polyhydric alcohols such as ethylene glycol, diethylene glycol and glycerin and other water-soluble substances can be used as additives. These additives are preferably 1 to 40% by weight, more preferably 3 to 40% by weight, based on the weight of the aqueous medium.
It is desirable to use up to 30% by weight. It is preferable that the amount of the additive be within the above range since there is no risk of environmental pollution or explosion.

The aqueous medium can be used in an amount of preferably 50 to 95% by weight, more preferably 60 to 93% by weight, based on the weight of the aqueous ink. When the amount of the aqueous medium is less than 50% by weight, the aqueous ink has a high viscosity, and it may be difficult to atomize the ink-jet nozzle. It may be difficult.

In the present invention, the water-insoluble viscous macromer (hereinafter simply referred to as "macromer") which is dispersed in an emulsion state and which can be radiation-cured is either cured directly by radiation or aids an initiator by radiation. A compound which has a viscosity of 100 cp or more at 20 ° C. which can be hardened rapidly and is substantially insoluble in water. In the present invention, the macromer may be used alone or in combination of two or more.

As described above, in the present invention, it is essential that the macromer has a viscosity at 20 ° C. of 100 cp or more. The macromer preferably has a viscosity of at least 500 cp, more preferably at least 1,000 cps. Even if the viscosity of the macromer at 20 ° C. is very high, the viscosity of the aqueous ink of the present invention itself can be kept low since the macromer is used in the form of an emulsion dispersed in an aqueous medium. The upper limit of the viscosity of the macromer is not particularly limited, and may be, for example, a resin.

The molecular weight of the above macromer is appropriately selected from the range where the viscosity at 20 ° C. becomes 100 cp or more. That is, in the present specification, the macromer is not specified by the molecular weight, but is specified by the viscosity at 20 ° C.

[0013] Preferably, in the present invention, the macromer is polyfunctional. The use of the polyfunctional macromer further improves the resistance of the obtained printed matter, such as water resistance and weather resistance. As the functional group, for example, acryloyl group, methacryloyl group, acrylic group, methacryl group,
Examples include an allyl group and a vinyl group. One macromer may contain one or more functional groups.

The macromer does not need to be completely water-insoluble, but is substantially water-insoluble and may be slightly water-soluble as long as it can form an emulsion dispersion in an aqueous medium. Good. Specific examples of the macromer include, for example, unsaturated polyester resins, polyester acrylates, polyurethane acrylates, epoxy acrylates, and the like;
(Published by Sogo Gijutsu Center on February 28, 1989)
And the like described on pages 151 to 218.

The macromer is preferably used in an amount of 1 to 40% by weight, more preferably 2 to 30% by weight, based on the weight of the aqueous ink. If the amount of the macromer is less than 1% by weight, the physical properties of the printed matter may deteriorate, and if it exceeds 40% by weight, the stability of the obtained ink may deteriorate.

In the present invention, a polymerizable water-soluble monomer is used together with the macromer. In the present specification, the “polymerizable water-soluble monomer” (hereinafter, simply referred to as “water-soluble monomer”) is a monomer that can dissolve in water at an arbitrary ratio at normal temperature, and the macromer is It means a monomer that polymerizes under the condition of curing by the action of radiation. Examples thereof include (meth) acrylic acid monoester of polyhydric alcohol, N-
Examples thereof include (meth) acrylates of alkylamino alcohols, polyethylene glycol (meth) acrylates, and N-alkyl (meth) acrylates. More specific examples include butanediol monoacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, N,
N-dimethylaminoethyl acrylate, N, N-dimethylaminoethyl methacrylate, methoxypolyethylene glycol acrylate, polyethylene glycol diacrylate, N, N-dimethylacrylamide, N
-Methylolacrylamide, N-vinylformamide, acryloylmorpholine and the like. It is also possible to use mixtures of these monomers. The amount of the water-soluble monomer used is preferably 30 to 500% by weight, more preferably 50 to 200% by weight, based on the weight of the macromer. If the amount of the water-soluble monomer used is less than 30% by weight, the stability of the obtained ink may be insufficient.
When the content is more than 10% by weight, the durability of the printed matter may be deteriorated.

In the present invention, a photopolymerization initiator or a thermal polymerization initiator can be used in combination, if necessary. The photopolymerization initiator and the thermal polymerization initiator are used for curing the ink printed on the printing substrate. Generally, such a photopolymerization initiator or a thermal polymerization initiator is preferably used in an amount of 0.1% based on the weight sum of the macromer and the water-soluble monomer.
It is used in an amount of 1 to 20% by weight, more preferably 1.0 to 10% by weight. If the amount is less than 0.1% by weight, the curing of the ink may be delayed, and if the amount is more than 20% by weight, resistance such as adhesion and weather resistance may not be improved. If the type of radiation is a high-energy ray such as an electron beam or a γ-ray, the above-mentioned photopolymerization initiator and thermal polymerization initiator need not be particularly used.

The photopolymerization initiator is not particularly limited as long as an active species such as a radical generated by light reacts efficiently with the polymerizable double bond in the macromer. For example, benzophenone, benzoin ethyl ether, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpho Linopropanone-1,2,4,6-
Examples thereof include trimethylbenzoyldiphenylphosphine oxide, bisacylphosphine oxide, and 2,4-diethylthioxanthone. These photopolymerization initiators can be used alone or in combination of two or more.

Examples of the thermal polymerization initiator include ammonium persulfate, potassium persulfate, and benzoyl peroxide.

As the radiation used for curing the ink after printing, various energy rays and heat can be used, and examples thereof include gamma rays, X rays, ultraviolet rays, and electron beams. Among them, it is preferable to use ultraviolet rays from the viewpoint of cost and safety. When ultraviolet rays are used, various light sources such as mercury lamps can be used.

As described above, in the present invention, the macromer and the water-soluble monomer are used in combination. In particular, when acryloyl morpholine is used as the water-soluble monomer, the irritancy to the human body is low, and the stability of the obtained ink is particularly excellent. Further, two or more macromers and two or more water-soluble monomers may be used in combination. By using two or more kinds of the above macromers, preferable characteristics of each macromer can be realized in the cured printed coating film. That is, for example, when two types of macromers A and B are used in combination, assuming that macromer A is excellent in adhesion and macromer B is excellent in water resistance of the coating film, the printing coating obtained using these macromers is The film is preferable in that both the adhesiveness and the coating film water resistance are excellent.

The method for preparing the aqueous ink of the present invention is not particularly limited, and a conventionally known method used for preparing an emulsion can be used. For example,
(A) When only one type of the above macromer is used,
The macromer can be mixed with other components to form an emulsion, and the aqueous ink of the present invention can be prepared. Further, more preferably, the macromer can be made into an aqueous emulsion in advance, and this can be mixed with other components.

(B) When two or more of the above macromers are used in combination, the macromers can be mixed with other components to form an emulsion; or, more preferably, all the macromers are previously prepared as a single In the form of an emulsion, which can be mixed with other components. Furthermore, only a part of the macromer may be made into an emulsion in advance, and this may be mixed with other macromers and other components to form an emulsion.
Some macromers are previously made into a single emulsion, and similarly, the remaining macromers are made into a separate single emulsion, and these are mixed with other components to form an emulsion. Can be prepared.

When a surfactant is used in forming the macromer into an emulsion, a good emulsion can be obtained. Such a surfactant can be appropriately selected depending on the type of the macromer. For example, a method of selecting a surfactant preferable for the emulsion stability of the macromer from surfactants described in Handbook of Surfactants (issued by Sangyo Tosho Co., Ltd.) is preferable. In the present invention, for example, a polyoxyethylene alkyl phenyl ether-based nonionic surfactant and a polyoxyethylene alkyl ether sulfate-based anionic surfactant can be used, and particularly, an anionic surfactant can be used. It is preferable from the viewpoint of stability. The amount of surfactant added is selected as needed for stabilization of the macromer emulsion,
Generally, it is preferred that the water-based ink be based on a weight of 0.
It can be used in an amount of 5 to 10% by weight, more preferably 1 to 5% by weight.

In the aqueous ink of the present invention, a coloring agent is used together with the above-mentioned various components. As the colorant, various dyes and pigments can be used, but in order to improve the weather resistance and the like of the printed matter, the use of a fine particle pigment is extremely preferable. In general, in inks for ink jet printing, the use of pigments has an unfavorable effect on atomization of ink in a nozzle, stability of ink, and the like, or worsens abrasion-resistant stains of printed matter, but in the aqueous ink of the present invention, Since the stability of the pigment is remarkably improved by the combined use of the macromer and the water-soluble monomer, the pigment can also be suitably used. The particle size of the pigment is generally 1 μm
Or less, and particularly preferably 0.3 μm or less. If the particle size exceeds 1 μm, the suitability for the nozzle may be deteriorated. Pigments that can be used in the present invention may be those known per se, such as carbon black, inorganic pigments such as titanium oxide, phthalocyanine pigments,
Organic pigments such as naphthol pigments, azo pigments, quinacridone pigments, nitro pigments and fluorescent pigments can be mentioned.
When a pigment is used, it is preferable to mix the pigment in the form of an aqueous dispersion (solids concentration: 5 to 50% by weight) during the preparation of the ink from the viewpoint of improving the dispersibility of the pigment.

In the aqueous ink of the present invention, for example, a wetting agent may be added as an optional component. The wetting agent is added for the purpose of preventing the ink from drying and the nozzle from being clogged when the ink ejection is stopped. Examples of the wetting agent include glycerin, diethylene glycol, triethylene glycol,
Aliphatic polyhydric alcohols such as polypropylene glycol, ethylene glycol monoethyl ether, and diethylene glycol monomethyl ether, and alkyl ether derivatives of these polyhydric alcohols can be used. The amount of the wetting agent is not particularly limited as long as it is within a range that satisfies physical properties such as printability and viscosity as an aqueous ink for ink jet printing. Is appropriate.

In the aqueous ink of the present invention, an antifoaming agent can be added as another optional component. As the defoaming agent, a silicon-based defoaming agent, an acetylene glycol-based defoaming agent, a fluorine-based defoaming agent, an ether-based defoaming agent, and the like can be used. The antifoaming agent is generally added in an amount of 0.01 to 5.0% by weight based on the weight of the aqueous ink.

The water-based ink of the present invention mainly comprises the components described above.
In order to improve printability, image bleeding property, storage stability, and the like, other additives, for example, a penetrant, a bactericidal / antifungal agent, and the like may be added. Further, in order to adapt to ink-jet printing, it is preferable that the viscosity of the aqueous ink is adjusted to 15 cp (20 ° C.) or less by adjusting the blending amount of each component.

[0029]

The present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited to these examples. In the examples, unless otherwise specified.
"Parts" and "%" are based on weight. The viscosity is 20
It was measured at ° C.

Example 1 After mixing and stirring the following components, the mixture was filtered through a filter having a size of 5.0 μm or less to prepare an aqueous ultraviolet curable ink for inkjet printing. -Carbon black 5 parts-Diethylene glycol 10 parts-Water-dispersible bifunctional urethane acrylate 60% aqueous emulsion (macromer, viscosity: 10,000 cp) 20 parts-Acryloylmorpholine 12 parts-Photopolymerization initiator (benzoin ethyl ether) 0・ 1 part ・ Defoaming agent (silicone) 0.2 part ・ Water 52.7 parts

The obtained aqueous ink was printed on plain paper, polycarbonate and polyvinyl chloride sheets by an ink jet printer, and then cured by irradiating ultraviolet rays from a distance of 15 cm using an 80 W / cm metal halide lamp. The following test was conducted. Table 1 shows the results.

(1) Adhesion Measured using a cross cut cellotape test (cellophane tape peeling according to JIS K 5400). (2) Water resistance In the case of plain paper, the printed paper was immersed in tap water for 24 hours and evaluated. In the case of polycarbonate and polyvinyl chloride, Kanakin No. 3 using a Gakushin type friction machine
Rubbed 500g-200 times. (3) Weather resistance It was measured by a weather O meter for 1,000 hours. (4) Alcohol resistance In the case of plain paper, it was immersed in ethanol for 24 hours and evaluated. In the case of polycarbonate and polyvinyl chloride, use a Gakushin type friction machine to make Kanakin-3 100g-
Rubbed 10 times. (5) Ink stability After storing the ink at 40 ° C. for 3 months, it was determined that no agglomerates or the like were generated in the ink and that no nozzle clogging or the like occurred during inkjet printing. Judged. In Table 1, ◎ indicates very good, ○ indicates good, △ indicates somewhat good, and × indicates bad.

Example 2 An aqueous ink was prepared by the same operation as in Example 1 using the following components, and the same test as in Example 1 was performed. Table 1 shows the results.・ Naphthol red 6 parts ・ Diethylene glycol 10 parts ・ 40% aqueous emulsion of water-dispersible hexafunctional polyester acrylate (macromer, viscosity: 30,000 cp) 20 parts ・ Acryloylmorpholine 8 parts ・ Photopolymerization initiator (benzoin ethyl ether) 1 part ・ Defoaming agent (silicone) 0.2 part ・ Water 54.8 parts

Example 3 An aqueous ink was prepared by the same operation as in Example 1 using the following components, and the same test as in Example 1 was performed. Table 1 shows the results.・ 2 parts of disazo yellow ・ 10 parts of diethylene glycol ・ 15 parts of 40% aqueous emulsion of water-dispersible trifunctional urethane acrylate (macromer, viscosity: 20,000 cp) 15 parts ・ 9 parts of 2-hydroxyethyl acrylate ・ Photopolymerization initiator (benzoin ethyl ether) 1 part)-Antifoaming agent (silicone) 0.2 part-Water 62.8 parts

Comparative Example 1 Using the following components, an ink having the following composition was prepared in the same manner as in Example 1, and the same test as in Example 1 was performed. Table 1 shows the results.・ 5 parts phthalocyanine blue ・ 5 parts water-soluble polymer (polyvinyl alcohol) ・ 14 parts diethylene glycol ・ 76 parts water

Comparative Example 2 Using the following components, an ink having the following composition was prepared in the same manner as in Example 1, and the same test as in Example 1 was performed. Table 1 shows the results.・ 5 parts of quinacridone red ・ 14 parts of diethylene glycol ・ 20 parts of acryloyl morpholine ・ 1 part of photopolymerization initiator (benzoin ethyl ether) ・ 60 parts of water

Comparative Example 3 Using the following components, an ink having the following composition was prepared in the same manner as in Example 1, and the same test as in Example 1 was performed. Table 1 shows the results.・ Disazo Yellow 5 parts ・ Diethylene glycol 14 parts ・ 40% aqueous emulsion of water-dispersible hexafunctional polyester acrylate (macromer, viscosity: 30,000 cp) 8 parts ・ Photopolymerization initiator (benzoin ethyl ether) 1 part ・ Water 72 parts

[0038]

[Table 1]

As is evident from the results shown in Table 1, the aqueous inks of Examples 1 to 3 (products of the present invention) had better printability, water resistance and weather resistance than the aqueous inks of Comparative Examples 1 to 3. It is understood that it has excellent alcohol resistance and ink stability, and can be applied to various plastic materials as well as paper. In particular, as is clear from Comparative Examples 2 and 3, it can be seen that the performance of the obtained ink is not improved even if only one of the macromer and the water-soluble monomer is used.

[0040]

According to the water-based ink of the present invention, atomization at the nozzle is easy and there is no danger of environmental pollution or explosion. Further, the water-based ink of the present invention is excellent in water resistance and light resistance, and is also excellent in stability of the ink and adhesiveness to a printing object (paper and various plastic materials).

Claims (4)

[Claims] 1. A radiation curable aqueous solution for inkjet printing, comprising: a water-insoluble viscous macromer which is dispersed in an emulsion state and is radiation-curable in an aqueous medium, and a polymerizable water-soluble monomer. ink. 2. The radiation-curable aqueous ink for inkjet printing according to claim 1, wherein the polymerizable water-soluble monomer is acryloylmorpholine. 3. A water-based ink for radiation-curable ink jet printing according to claim 1, which contains a pigment as a coloring agent. 4. A printed matter obtained by printing with the aqueous ink for radiation curable inkjet printing according to claim 1, 2 or 3, and then curing the ink with ultraviolet rays.