JP6906385B2 - Cohesive ink for inkjet printing and printing method - Google Patents

Description

The present invention relates to a cohesive ink for inkjet printing and a printing method using the cohesive ink for inkjet printing.

Patent Document 1 describes an inkjet recording method using a clear ink composition containing an amino group-containing resin, water, a poorly water-soluble alkanediol, and a wetting agent which is solid at 20 ° C. and a relative humidity of 60%. It is disclosed.

Further, Patent Document 2 describes a printing method in which color ink, resin ink, and reactive ink are applied to a non-absorbent and low-absorbent recording medium by an inkjet recording method using a water-based ink set to print an image. Is disclosed.

Further, Patent Document 3 describes that in an inkjet recording method in which recording is performed by adhering droplets of a recording liquid to a material to be recorded, the material to be recorded is applied to a base material or a coating layer provided on the base material. It is disclosed that it contains a specific polyallylamine salt.

Japanese Unexamined Patent Publication No. 2015-128903 (published on July 16, 2015) Japanese Unexamined Patent Publication No. 2010-115854 (published on May 27, 2010) Japanese Unexamined Patent Publication No. 61-72581 (published on April 14, 1986)

According to the inkjet recording methods described in Patent Document 1 and Patent Document 2, an image can be formed by an inkjet recording method on an ink non-absorbent and low-absorbency recording medium such as a plastic film. However, since the clear ink composition described in Patent Document 1 contains a poorly water-soluble alkanediol, there is a problem that the poorly water-soluble alkanediol is separated when the water content in the clear ink composition evaporates even a little. ing.

Further, since the color ink, the resin ink, and the reactive ink described in Patent Document 2 contain a surfactant, there is a problem that the ink easily foams.

Further, the inkjet recording method described in Patent Document 3 has a problem that the adhesion of the ink applied to the plastic base material is not good.

The present invention has been made in view of the above problems, and an object of the present invention is an inkjet in which adhesion to a plastic substrate and wettability are good, foaming is suppressed, and separation of components is suppressed. It is to provide a cohesive ink for printing.

As a result of diligent studies by the inventors in order to solve the above-mentioned problems, the following invention has been reached.

That is, the cohesive ink for inkjet printing according to one aspect of the present invention is a cohesive ink for forming agglomerates with the ink containing the anionic resin by contacting with the ink containing the anionic resin, and is polyethylene. It is characterized by containing an amine-based polymer in which at least one of the hydrogens is substituted with -CH2NH2 group, a poorly water-soluble alcan diol, an alcohol, and 1,2-hexanediol.

Further, in the cohesive ink for inkjet printing according to one aspect of the present invention, it is more preferable that the amine-based polymer is polyallylamine.

Further, in the cohesive ink for inkjet printing according to one aspect of the present invention, the poorly water-soluble alkanediol is more preferably 1,2-octanediol.

Further, in the cohesive ink for inkjet printing according to one aspect of the present invention, the content of the amine-based polymer is more preferably 0.5% by weight or more and 10% by weight or less.

Further, in the cohesive ink for inkjet printing according to one aspect of the present invention, it is more preferable that the weight average molecular weight of the amine-based polymer is 1000 or more and 50,000 or less.

Further, in the cohesive ink for inkjet printing according to one aspect of the present invention, it is more preferable that the ink containing the anionic resin is a water-based ink.

The printing method according to one aspect of the present invention includes a cohesive ink coating step of applying the cohesive ink for inkjet printing according to one aspect of the present invention on a substrate, and after the cohesive ink coating step or the cohesive ink coating step. At substantially the same time, the colored ink coating step of coating the colored ink containing the colorant and the ink containing the anionic resin on the substrate is included, and the colored ink coating step is performed after the cohesive ink coating step. In this case, the coloring ink coating step is performed before the cohesive ink applied on the base material is completely dried, and the cohesive ink is anionic by coming into contact with the ink containing the anionic resin. It is characterized by forming agglomerates with ink containing a resin.

According to one aspect of the present invention, there is provided a cohesive ink for inkjet printing, which has good adhesion and wettability to a plastic substrate, suppresses foaming, and suppresses separation of components, and related techniques thereof. It has the effect of being able to do it.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to this, and can be carried out in a mode in which various modifications are added within the range described. Unless otherwise specified in the present specification, "A to B" representing a numerical range means "A or more and B or less".

[1. Aggregate ink for inkjet printing]
The cohesive ink for inkjet printing according to one aspect of the present invention (hereinafter, may be simply referred to as “aggregate ink”) may be referred to as an ink containing an anionic resin (hereinafter, may be referred to as “anionic resin-containing ink”). An ink for forming an agglomerate with an ink containing the anionic resin when in contact with the ink, and at least one of the hydrogens of the polyethylene is an amine type in which _{two -CH 2} NH groups are substituted. It contains a polymer, a poorly water-soluble alcohol, an alcohol, and 1,2-hexanediol.

The cohesive ink for inkjet printing according to one aspect of the present invention has good adhesion and wettability to a plastic base material (recording medium). Therefore, by using such a cohesive ink in the inkjet recording method, desired characters, images, and the like can be satisfactorily printed even on a plastic base material. Further, in the cohesive ink for inkjet printing according to one aspect of the present invention, foaming is suppressed and the components in the cohesive ink are well compatible with water without being separated. Therefore, such agglomerated ink is excellent in handleability.

In a preferred embodiment, the surface tension of the cohesive ink for inkjet printing according to one aspect of the present invention is 35 mN / m or less, more preferably 30 mN / m or less. When the surface tension of the cohesive ink is within the above range, the wettability to the plastic substrate is good. The surface tension of the cohesive ink can be measured using a Wilhelmy type tensiometer.

Further, in a preferred embodiment, the cohesive ink for inkjet printing according to one aspect of the present invention has an adhesion score of 7 or more, more preferably 10 to a plastic substrate evaluated by the method described later in Examples. Is. When the adhesion score is within the above range, the adhesion to the plastic substrate is good. The plastic base material will be described later.

[Amine-based polymer]
The cohesive ink for inkjet printing according to one aspect of the present invention contains an amine-based polymer to improve adhesion to a plastic substrate.

The amine-based polymer refers to a polyethylene in which at least one hydrogen is substituted with _{two -CH 2} NH groups. In the amine-based polymer, preferably, 50% or more of hydrogen _{in polyethylene is substituted with -CH 2} NH ₂ groups, and more preferably, 80% or more of hydrogen in polyethylene is -CH. ₂ NH Substituted with _{2 groups.}

（前記構造式（１）中、ｎは１５以上の整数である。）
ポリアリルアミンは、前記構造式（１）中、ｎは、１５以上の整数であるものであることが好ましい。ｎが１５以上であることによって、プラスチック基材に対する密着性が良好となる。 Examples of the amine-based polymer include polyallylamine in which allylamine is polymerized. Specifically, examples of polyallylamine include PAA-15C, PAA-08 and PAA-03 (all manufactured by Nittobo Medical Co., Ltd.). The structural formulas of these polyallylamines are represented by the following structural formula (1).

(In the structural formula (1), n is an integer of 15 or more.)
In the structural formula (1), n is preferably an integer of 15 or more in the polyallylamine. When n is 15 or more, the adhesion to the plastic base material is good.

Further, in the above-mentioned amine-based polymer, a part of hydrogen in polyethylene may be further substituted with a substituent other than _{-CH 2} NH _{2 groups as long as the effect of the present invention is not impaired.} In the _{form in which a part of hydrogen of polyethylene is substituted with a substituent other than −CH 2} NH ₂ groups, the substitution rate by the substituent is more preferably 10% or less of the hydrogen in polyethylene.

The content of the amine-based polymer in the cohesive ink for inkjet printing according to one aspect of the present invention is preferably 0.5% by weight or more and 10% by weight or less with respect to the total amount of the cohesive ink. When the content of the amine-based polymer is within the above range, the adhesion to the plastic substrate is good.

Further, in the cohesive ink for inkjet printing according to one aspect of the present invention, the weight average molecular weight of the amine polymer is preferably 1000 or more and 50,000 or less, and more preferably 3000 or more and 15,000 or less.

When the weight average molecular weight of the amine-based polymer is 1000 or more, the adhesion to the plastic substrate is good. Further, when the weight average molecular weight of the amine-based polymer is 50,000 or less, the ejection stability of the cohesive ink during inkjet printing is good.

For example, the above-mentioned PAA-15C has a weight average molecular weight of 15,000, PAA-08 has a weight average molecular weight of 8000, and PAA-03 has a weight average molecular weight of 3000. The "weight average molecular weight" in the specification of the present application means a value in terms of polyethylene glycol measured by a gel permeation chromatography (GPC) method.

[Slightly water-soluble alkanediol]
By containing the poorly water-soluble alkanediol, the cohesive ink for inkjet printing according to one aspect of the present invention can reduce the surface tension of the cohesive ink and improve the wettability to the substrate.

Surfactants may be added to reduce the surface tension of the liquid, but the liquid tends to foam. Further, depending on the type of surfactant, the solubility in water may be poor, and the surface tension may not be sufficiently lowered. On the other hand, since the cohesive ink for inkjet printing according to one aspect of the present invention contains a poorly water-soluble alkanediol, the surface tension can be sufficiently reduced even if it does not contain a surfactant. Furthermore, since it does not contain a surfactant, foaming of coagulated ink can be suppressed.

Here, the poorly water-soluble means that the solubility in water at 20 ° C. (the amount of solute with respect to 100 g of water) is less than 1.0 g.

Further, the hydrocarbon group portion of the poorly water-soluble alkanediol may be either a straight chain or a branched chain.

Examples of the poorly water-soluble alkanediol include 1,2-octanediol and the like. Among these, the poorly water-soluble alkanediol is preferably 1,2-octanediol. These may be used alone or in combination of two or more.

The content of the poorly water-soluble arcanediol in the cohesive ink for inkjet printing according to one aspect of the present invention is preferably 0.1% by weight or more and 2% by weight or less, preferably 0.2% by weight, based on the total amount of the cohesive ink. It is more preferably 0% by weight or more and 1% by weight or less, and further preferably 0.3% by weight or more and less than 0.8% by weight. When the content of the poorly water-soluble alkanediol is 0.1% by weight or more, the wettability to the plastic substrate is good. Further, when the content of the poorly water-soluble alkanediol is 2% by weight or less, the separation of the components can be suppressed.

〔alcohol〕
The cohesive ink for inkjet printing according to one aspect of the present invention contains alcohol. Here, the alcohol is a water-soluble alcohol and is different from 1,2-hexanediol.

Here, water-soluble means that the solubility in water at 20 ° C. (the amount of solute with respect to 100 g of water) is 10.0 g or more.

The cohesive ink for inkjet printing according to one aspect of the present invention can improve the compatibility of the poorly water-soluble alkanediol with water by containing alcohol together with 1,2-hexanediol described later. As a result, the cohesive ink for inkjet printing according to one aspect of the present invention suppresses the separation of the poorly water-soluble alkanediol.

The above-mentioned alcohol is not particularly limited as long as it is water-soluble and is different from 1,2-hexanediol, and a monohydric alcohol or a polyhydric alcohol can be preferably used. It is assumed that the above-mentioned alcohol also includes a compound in which a part of the hydroxy group of the polyhydric alcohol is substituted with a substituent such as a methyl group.

Among these alcohols, the above-mentioned alcohol is particularly preferably a monohydric alcohol. When monovalent alcohol is used, it is not necessary to increase the alcohol content in the cohesive ink in order to suppress the separation of the poorly water-soluble alkanediol, so that the drying property of the inkjet printed matter is suppressed from being deteriorated. Can be done.

Examples of such monovalent alcohols include 3-methoxy-3-methyl-1-butanol, 3-methoxybutanol, diacetone alcohol, dipropylene glycol monomethyl ether, dipropylene glycol monobutyl ether, diethylene glycol monomethyl ether, and diethylene glycol. Monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, triethylene glycol monomethyl ether, triethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, propylene glycol mono Examples thereof include phenyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, and ethylene glycol monobutyl ether. These alcohols may be used alone or in combination of two or more.

The alcohol content in the cohesive ink for inkjet printing according to one aspect of the present invention is preferably 0.1% by weight or more and 20% by weight or less with respect to the total amount of the cohesive ink. When the alcohol content is 0.1% by weight or more, the separation of the components can be suppressed. Further, when the alcohol content is 20% by weight or less, the drying property of the inkjet printed matter is improved.

[1,2-Hexanediol]
The cohesive ink for inkjet printing according to one aspect of the present invention can improve the compatibility of the poorly water-soluble alkanediol with water by containing 1,2-hexanediol together with the above-mentioned alcohol.

The content of 1,2-hexanediol in the cohesive ink for inkjet printing according to one aspect of the present invention is preferably 0.1% by weight or more and 5% by weight or less with respect to the total amount of the cohesive ink. By setting the content of 1,2-hexanediol to 0.1% by weight or more, separation of the components can be suppressed. Further, by setting the content of 1,2-hexanediol to 5% by weight or less, the drying property of the inkjet printed matter becomes good.

Further, the sum of the contents of 1,2-hexanediol, alcohol and poorly water-soluble alkanediol contained in the aggregated ink is 0.3% by weight or more and 27% by weight or less with respect to the total amount of the aggregated ink. Is preferable, and more preferably 0.3% by weight or more and 25.1% by weight or less. When the sum of the contents of 1,2-hexanediol, alcohol, and poorly water-soluble alkanediol is within the above range, the surface tension of the aggregated ink is sufficiently increased while improving the compatibility of the poorly water-soluble alkanediol with water. Can be lowered.

Further, when the sum of the contents of 1,2-hexanediol, alcohol and the poorly water-soluble alkanediol is 100% by weight, the content of the poorly water-soluble alkanediol is 0.4% by weight or more and 50% by weight. % Or less is preferable. When the content of the poorly water-soluble alkanediol is within the above numerical range, the compatibility of the poorly water-soluble alkanediol with water can be improved.

Further, when the sum of the contents of 1,2-hexanediol and alcohol contained in the cohesive ink is 100% by weight, the content of 1,2-hexanediol is 5% by weight or more and 90% by weight. The following is preferable.

〔solvent〕
The cohesive ink according to one aspect of the present invention contains a solvent for dissolving each of the above-mentioned components. Examples of the solvent include water and a water-soluble solvent. Examples of the water-soluble solvent include polyhydric alcohols, lower alkyl ethers of polyhydric alcohols, heterocycles, sulfur-containing compounds, polyfunctional compounds, urea derivatives and the like.

[Ink containing anionic resin]
The cohesive ink for inkjet printing according to one aspect of the present invention is an ink for forming agglomerates with the anionic resin-containing ink by contacting with the anionic resin-containing ink. The anionic resin-containing ink may be any ink containing an anionic resin. Examples of the anionic group include COO ⁻ , SO ₃ ^{− and the} like. The anionic resin-containing ink is preferably a water-based ink. Further, the anionic resin-containing ink may be an anionic resin emulsion or an anionic resin dissolved in a solvent. Further, it may contain a color material, and may not contain a color material as in the case of ink containing only medium, for example. The anionic resin emulsion is an emulsion of a resin having an anionic group. Examples of the anionic resin emulsion include acrylic resin emulsions, urethane resin emulsions, polyester resin emulsions, epoxy resin emulsions, vinyl chloride resin emulsions and the like. These may be used alone or in combination of two or more. Examples of the solvent or dispersion medium of the water-based ink include water or a water-soluble solvent. Examples of the water-soluble solvent include polyhydric alcohols, lower alkyl ethers of polyhydric alcohols, heterocycles, sulfur-containing compounds, polyfunctional compounds, urea derivatives and the like.

[Manufacturing method of cohesive ink for inkjet printing]
The cohesive ink for inkjet printing according to one aspect of the present invention is a mixture of an amine-based polymer, a poorly water-soluble alkanediol, alcohol, and 1,2-hexanediol in water so as to have the above-mentioned content. Can be manufactured by

[Use]
The cohesive ink for inkjet printing according to one aspect of the present invention can be suitably used for printing by an inkjet recording method.

[2. Printing method]
The printing method according to one aspect of the present invention is colored after the cohesive ink coating step of applying the cohesive ink for inkjet printing on the substrate, the cohesive ink coating step, or substantially at the same time as the cohesive ink coating step. It includes a coloring ink application step of applying a coloring ink containing an agent on a substrate.

By including the coagulation ink coating step and the coloring ink coating step, the cohesive ink for printing and the coloring ink can be brought into contact with each other on the base material to generate agglomerates. As a result, desired characters, images, etc. can be printed on the base material.

As described above, the cohesive ink for inkjet printing according to one aspect of the present invention has good adhesion to a plastic base material. Therefore, according to the printing method according to one aspect of the present invention, it can also be applied to a plastic base material. It is possible to print desired characters, images, etc. satisfactorily. Further, since the cohesive ink for inkjet printing according to one aspect of the present invention has a low surface tension, it has high wettability to a base material. Therefore, according to the printing method according to one aspect of the present invention, the size of the dots of the colored ink can be increased.

Further, since the printing method according to one aspect of the present invention uses the cohesive ink for inkjet printing according to one aspect of the present invention, it is possible to suppress foaming and separation of components of the cohesive ink during printing.

The printing method according to one aspect of the present invention preferably includes a step of applying the anionic resin emulsion onto the substrate after the cohesive ink coating step or substantially at the same time as the cohesive ink coating step.

〔Base material〕
In the printing method according to one aspect of the present invention, the base material is not particularly limited and can be appropriately selected depending on the intended purpose.

In the printing method according to one aspect of the present invention, since the above-mentioned cohesive ink for inkjet printing is applied in the cohesive ink coating step, the adhesion of the colored ink to the plastic base material can be improved, and the adhesion of the colored ink to the plastic base material can also be improved. It can be printed suitably. Examples of the plastic base material include a base material containing polypropylene (PP), polyethylene terephthalate (PET), polyvinyl chloride, polystyrene, polycarbonate, polyacrylate, acrylonitrile-butadiene-styrene copolymer synthetic resin (ABS), and the like. be able to.

[Colored ink]
Examples of the colorant contained in the coloring ink include pigments and dyes.

The content of the colorant in the coloring ink is not particularly limited, and can be appropriately selected depending on the intended purpose.

In addition to the colorant, the colored ink may contain a preservative, an antioxidant, a pH adjuster, a viscosity adjuster, a surfactant and the like.

[Cohesive ink application process]
The cohesive ink coating step is a step of applying cohesive ink for inkjet printing onto a substrate.

As a method of applying the cohesive ink to the base material, for example, an inkjet recording method can be adopted. The amount of the cohesive ink to be applied to the base material is not particularly limited, and can be appropriately set according to the purpose.

[Colored ink application process]
The coloring ink coating step is a step of applying the coloring ink containing a colorant and the ink containing an anionic resin onto the substrate after the cohesive ink coating step or substantially at the same time as the cohesive ink coating step. .. When the colored ink coating step is performed after the cohesive ink coating step, the colored ink coating step is performed before the cohesive ink applied on the substrate is completely dried. The term "before complete drying" includes before the drying treatment is performed, and even after the drying treatment is started, before the components to be volatilized by drying in the ink to be dried are completely volatilized. It can be said that this ink has not completely cured. When the anionic resin-containing ink comes into contact with the agglomerated ink before the agglomerated ink is completely dried, the components in the agglomerated ink can come into contact with the anionic resin, and the agglomerated ink and the anionic resin-containing ink are agglomerated. Can produce things.

In the coloring ink coating step, the coloring ink may be applied so that the above-mentioned cohesive ink and the coloring ink come into contact with each other after the cohesive ink coating step or substantially at the same time as the cohesive ink coating step. When the agglomerated ink and the colored ink come into contact with each other, agglomerates are formed, and the colored ink can be adhered well to the base material.

Here, the “after the cohesive ink coating step” is not particularly limited as long as a predetermined time has elapsed after the cohesive ink is applied (after the cohesive ink has landed on the substrate). For example, it may be immediately after the cohesive ink is applied, after the cohesive ink is applied, and after the cohesive ink is completely dried.

Further, "substantially at the same time as the cohesive ink coating process" means that the cohesive ink and the colored ink are applied (landed) on the substrate at the same time or substantially at the same time.

The method of applying the colored ink to the substrate is not particularly limited, and for example, an inkjet recording method can be adopted.

Further, as a method of applying the colored ink to the base material substantially at the same time as the cohesive ink coating step, for example, the cohesive ink head that ejects the cohesive ink and the colored ink head that ejects the colored ink are moved in the moving direction of the head ( By arranging them in-line along the scanning direction), preferably adjacent to each other, and ejecting the cohesive ink and the colored ink while moving (scanning) the cohesive ink head and the colored ink head integrally on the substrate. It can be carried out. In this case, the colored ink may land on the substrate slightly earlier than the cohesive ink.

In the coloring ink coating step, the weight of the coloring ink when the weight of the cohesive ink is 1, is preferably 1 or more and 20 or less per dot when landing on the base material. When the weight of the colored ink is 1 when the weight of the cohesive ink is 1, the weight of the colored ink is 1 or more per dot when it lands on the base material, so that a good image can be obtained. Further, when the weight of the colored ink when the weight of the cohesive ink is 1 is 20 or less per dot when it lands on the base material, the colored ink can be sufficiently agglomerated.

In the printing method according to one aspect of the present invention, the anionic resin-containing ink is also applied onto the substrate after the cohesive ink coating step or substantially at the same time as the cohesive ink coating step. “After the cohesive ink coating step” and “substantially at the same time as the cohesive ink coating step” are as described in the parts described for the coating of the colored ink.

By applying the anionic resin-containing ink onto the base material, the anionic resin and the agglutinating ink can be brought into contact with each other on the base material to form agglomerates. As a result, desired characters, images, etc. can be printed on the base material.

The method of applying the anionic resin-containing ink on the substrate is not particularly limited as long as the anionic resin-containing ink can be applied so that the agglomerated ink and the anionic resin come into contact with each other. Can be adopted.

The application of the anionic resin-containing ink may be performed before the application of the coloring ink, may be performed after the application, or may be performed substantially at the same time.

As shown in Examples described later, for example, an anionic resin can be mixed in the colored ink in advance. This makes it possible to simultaneously perform the anionic resin-containing ink and the colored ink. That is, the colored ink and the anionic resin-containing ink may be one ink in which the colorant and the anionic resin are mixed in advance.

The amount of the anionic resin-containing ink applied is preferably 1/3 or more and 30 or less per dot when the weight of the anionic resin when the weight of the cohesive ink is 1 is landed on the substrate. .. A good image can be obtained when the weight of the anionic resin when the weight of the cohesive ink is 1 is 1/3 or more per dot when it lands on the base material. Further, when the weight of the anionic resin when the weight of the cohesive ink is 1 is 30 or less per dot when it lands on the base material, the colored ink can be sufficiently agglomerated.

Further, the weight ratio of the coating amount of the anionic resin to the coating amount of the coloring ink and the weight ratio of the coloring agent and the anionic resin are not particularly limited and can be appropriately set according to the purpose.

The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and the embodiments obtained by appropriately combining the technical means disclosed in the different embodiments. Is also included in the technical scope of the present invention.

The present invention will be described with reference to examples, but the present invention is not limited thereto.

[Example 1]
20% by weight PAA-15C (manufactured by Nittobo Medical Co., Ltd.), 2.0% by weight 1,2-hexanediol, 0.5% by weight 1,2-octanediol, 2.0% by weight 3-methoxy -3-Methyl-1-butanol and 75.5% by weight of water were mixed to produce a cohesive ink for inkjet printing. The concentration of polyallylamine in PAA15-C is 15% by weight. Therefore, the content of polyallylamine in the cohesive ink for inkjet printing is 3% by weight.

[Examples 2 to 5, Comparative Examples 1 to 7]
A cohesive ink for inkjet printing was produced by the same method as in Example 1 except that the composition of the cohesive ink was as shown in Table 1. The polymer content in the cohesive ink for inkjet printing of Examples 2 to 5 and Comparative Examples 1 to 7 was 5% by weight.

≪Evaluation of cohesive ink for inkjet printing≫
The characteristics of the cohesive ink for inkjet printing produced in Examples and Comparative Examples were evaluated as follows.

(Transparency evaluation)
The cohesive ink for inkjet printing was placed in a 100 ml glass container, covered and shaken 20 times in a sealed state, and the transparency of the liquid immediately after that was visually confirmed.

(Bubbling evaluation)
Put the cohesive ink for inkjet printing in a 100 ml glass container, shake it 20 times with the lid closed, and let it stand for 1 minute. After that, visually check whether the surface of the liquid is foaming. did.

(Surface tension evaluation)
The surface tension of the cohesive ink for inkjet printing was measured using a Wilhelmy type tensiometer.

(Evaluation of adhesion to PP)
Using an inkjet printer in which the cohesive ink ejection head for inkjet printing and the colored ink ejection head are arranged in-line along the moving direction of the head, the cohesive ink for inkjet printing and the colored ink are applied onto the PP substrate. By arranging the stored heads inline, printing was performed substantially at the same time. Here, the colored ink was produced by mixing 91% by weight of cyan ink and 9% by weight of an acrylic resin emulsion.

A coating film of cohesive ink for inkjet printing and colored ink printed on a PP substrate is cut into an X shape using a cutter, and a cellophane tape having a size of 18 mm × 18 mm (manufactured by Nichiban Co., Ltd., model number: CT405AP) is cut on the portion. -18) was attached and peeled off vigorously in a direction of about 60 ° with respect to the substrate surface. The adhesiveness of the ink to the PP substrate was evaluated by visually confirming the proportion of the coating film that did not peel off and evaluating it on a scale of 10 using a score of 0 to 10. Regarding the score evaluation method, the score "X" (X is an integer of 0 to 10) means that the ratio of the coating film not peeled off by the above-mentioned method is X%. For example, a score of "3" means that the proportion of the coating film that did not peel off is 30% (30%).

(Evaluation of adhesion to PET)
The adhesion to PET was evaluated by the same method as the above-mentioned method for evaluating adhesion to PP, except that the base material was a PET base material.

The results are shown in Table 2 below.

All of the cohesive inks of Examples 1 to 5 had a surface tension of 30 mN / m or less, and the surface tension was sufficiently low. Furthermore, the cohesive ink did not foam or the components did not separate after shaking. In addition, all of the cohesive inks of Examples 1 to 5 had good adhesion to plastic substrates such as PP and PET.

On the other hand, the cohesive inks of the comparative examples did not have sufficient transparency, foaming, surface tension, and adhesion to the plastic substrate, and none of them showed good results.

The cohesive ink for inkjet printing and the printing method according to one aspect of the present invention can be suitably used for the inkjet recording method.

Claims (8)

A cohesive ink for forming agglomerates with an ink containing the anionic resin by contacting with the ink containing the anionic resin.
Among hydrogen polyethylene, seen containing an amine-based polymer in which at least one is substituted with -CH ₂ NH ₂ group, a poorly water-soluble alkane diol, and a monohydric alcohol, and 1,2-hexanediol, and,
The content of the poorly water-soluble alkanediol is 0.1% by weight or more and 2% by weight or less with respect to the total amount of the aggregated ink.
Aggregate ink for inkjet printing that is virtually free of surfactants. The cohesive ink for inkjet printing according to claim 1, wherein the amine-based polymer is polyallylamine. The cohesive ink for inkjet printing according to claim 1 or 2, wherein the poorly water-soluble alkanediol is 1,2-octanediol. The cohesive ink for inkjet printing according to any one of claims 1 to 3, wherein the content of the amine-based polymer is 0.5% by weight or more and 10% by weight or less with respect to the total amount of the cohesive ink. The cohesive ink for inkjet printing according to any one of claims 1 to 4, wherein the amine-based polymer has a weight average molecular weight of 1000 or more and 50,000 or less. The cohesive ink for inkjet printing according to any one of claims 1 to 5, wherein the ink containing the anionic resin is a water-based ink. A cohesive ink coating step of applying the cohesive ink for inkjet printing according to any one of claims 1 to 6 onto a substrate, and a cohesive ink coating step.
After the cohesive ink coating step, or substantially at the same time as the cohesive ink coating step, a coloring ink coating step of applying a coloring ink containing a colorant and an ink containing an anionic resin onto a substrate is included.
When the colored ink coating step is performed after the cohesive ink coating step, the colored ink coating step is performed before the cohesive ink applied on the substrate is completely dried.
A printing method in which the agglutinating ink is brought into contact with the ink containing the anionic resin to form agglomerates with the ink containing the anionic resin. The inkjet printing according to any one of claims 1 to 6, wherein the content of the poorly water-soluble alkanediol is 0.1% by weight or more and 0.8% by weight or less with respect to the total amount of the cohesive ink. Cohesive ink.