JP6149586B2 - Core-shell type resin fine particle dispersion for water-based ink and water-based ink composition - Google Patents

Description

The present invention relates to a core-shell type resin fine particle dispersion for water-based ink (hereinafter sometimes simply referred to as resin fine particle dispersion) and a water-based ink composition. More specifically, excellent compatibility between the core component and the shell component makes it possible to achieve excellent coating properties (non-polar film substrate, low-temperature drying conditions, substrate adhesion, water rub resistance, blocking resistance) And a water-based ink composition using the resin fine particle dispersion. The resin fine particle dispersion has excellent storage stability, re-dissolvability, and plate washability).

A water-based ink composition is generally composed of a pigment, a pigment dispersion resin, water, a humectant component, and a binder resin. Among these, the binder resin is added for the purpose of improving the physical properties of the printed film (substrate adhesion, water resistance, abrasion resistance, scratch resistance, etc.), and can achieve both excellent printability and film properties. For this reason, many core-shell type resin fine particle dispersions obtained by emulsion polymerization of a core component using a water-soluble resin (shell component) as an emulsifier are often used. Such water-based ink compositions have been developed mainly for base materials such as paper and cardboard, but in recent years from the viewpoint of energy saving, low cost, and reduction of environmental burden, olefins and the like are also used under low temperature drying conditions. For non-polar film base materials, it is required to exhibit excellent coating properties (base material adhesion, water friction resistance), and at the same time, development of a binder resin composition that can cope with it is also required. Yes.

Patent Document 1 discloses a binder resin composition of an all-acrylic core-shell resin fine particle dispersion for both a shell component and a core component. However, since this resin fine particle dispersion has insufficient dispersion stability of the shell component and the particle nucleation of the core component is unstable, there are many aggregates generated during the synthesis, and it is difficult to control the particle size. . Therefore, since the film-forming property is poor and it is difficult to form a uniform coating film under low temperature drying, it is not possible to express good coating film properties (substrate adhesion, water friction resistance) with respect to a nonpolar film substrate. . Furthermore, since the stability in the ink composition is poor, the storage stability of the ink composition is significantly reduced.

In Patent Document 2 and Patent Document 3, the binder of the core-shell type resin fine particle dispersion in which the water-soluble resin (shell component), the composition of the core component, the molecular weight, the ratio of the core component to the shell component, the particle diameter, the glass transition temperature, and the like are defined. A resin composition is disclosed. However, in these resin fine particle dispersions, the compatibility of the core component and the shell component, the core component and the pigment dispersion resin, etc. is not considered at all in the resin design. Therefore, since the compatibility is poor and the film forming property is poor, a uniform coating film is formed under low-temperature drying conditions, and sufficient coating film properties (substrate adhesion, water friction resistance) with respect to the nonpolar film substrate are obtained. It is difficult to express.

Patent Document 4 and Patent Document 5 disclose a core-shell type resin fine particle dispersion in which a keto group or an aldo group is introduced into a water-soluble resin (shell component) or a core component. Certainly, by introducing a cross-linking group such as a keto group or an aldo group, it is possible to expect improvement in coating film properties such as substrate adhesion to a nonpolar film substrate. However, even in these resin fine particle dispersions, the compatibility between the core component and the shell component is not taken into consideration at all, and a non-uniform coating film is formed under low temperature drying conditions, and sufficient coating is applied to the nonpolar film substrate. It is difficult to develop film properties (base material adhesion, water friction resistance). Furthermore, if a crosslinking group is inadvertently introduced, the compatibility of the core component and the shell component is adversely inhibited, resulting in a more inhomogeneous coating film, which may reduce the coating film resistance. Further, since re-solubility is not taken into account, it may cause deterioration of plate clogging.

Japanese Patent Laid-Open No. 02-263811 Japanese Patent Laid-Open No. 08-176486 JP 2012-116924 A Japanese Patent Application Laid-Open No. 07-026196 Japanese Patent Laid-Open No. 08-113749

Even under low temperature drying conditions, it exhibits excellent coating properties (substrate adhesion, water rub resistance, blocking resistance) for nonpolar film substrates, while ink storage stability, resolubility, An object of the present invention is to provide a core-shell type resin fine particle dispersion for water-based inks which is also excellent in plate cleaning properties, and a water-based ink composition using the same.

That is, the present invention
A core-shell resin fine particle dispersion for water-based ink obtained by polymerizing an ethylenically unsaturated monomer (B) in an aqueous medium in the presence of the water-soluble resin (A) ,
The present invention relates to a core-shell resin fine particle dispersion for water-based ink, which is the following (1) to (4).
(1) Except when the water-soluble resin (A) is an aromatic ethylenically unsaturated monomer (a-1) and a carboxyl group-containing ethylenically unsaturated monomer (a-2) (a-1 And a water-soluble resin that is a polymer of an ethylenically unsaturated monomer (a ) ,
In 100% by weight of ethylenically unsaturated monomer (a), 20 to 70% by weight of aromatic ethylenically unsaturated monomer (a-1), carboxyl group-containing ethylenically unsaturated monomer (a-2 30 to 40% by weight.
(2) The ethylenically unsaturated monomer (B) is an aromatic ethylenically unsaturated monomer (b-1) and an ethylenically unsaturated monomer represented by the general formula (1) (b- 2) and an ethylenically unsaturated monomer having as essential components,
In 100% by weight of ethylenically unsaturated monomer (B), 15-40% by weight of aromatic ethylenically unsaturated monomer (b-1) and 60 of ethylenically unsaturated monomer (b-2) Contains ~ 85% by weight.
(3) The amount of the water-soluble resin (A) is 40 to 60 parts by weight with respect to 100 parts by weight of the total of the ethylenically unsaturated monomer (B).
(4) The core-shell type resin fine particle dispersion for water-based ink has an average particle size of 45 to 90 nm and a glass transition temperature of −10 to 30 ° C.
General formula (1)

R represents an alkyl group having 1 to 4 carbon atoms.

Furthermore, the present invention relates to the above core-shell type resin fine particle dispersion for water-based ink, wherein the weight average molecular weight is 200,000 to 500,000.

Furthermore, the present invention contains the keto group-containing ethylenically unsaturated monomer in an amount of 1 to 3% by weight in a total of 100% by weight of the ethylenically unsaturated monomer (B). The present invention relates to a core-shell type resin fine particle dispersion.

Furthermore, the present invention contains a pigment (C), a pigment dispersion resin (D), water (C), a hydrophilic solvent (E), and the above-described core-shell resin fine particle dispersion for water-based ink. The present invention relates to an ink composition.

Furthermore, the present invention is a water-soluble resin obtained by polymerizing an ethylenically unsaturated monomer (d) containing an aromatic ethylenically unsaturated monomer (d-1) in the pigment dispersion resin (D),
In 100% by weight of ethylenically unsaturated monomer (d),
20 to 70% by weight of the aromatic ethylenically unsaturated monomer (d-1),
10 to 40% by weight of carboxyl group-containing ethylenically unsaturated monomer (d-2)
It contains regarding said water-based ink composition characterized by containing.

Furthermore, the present invention relates to the aqueous ink composition described above, wherein the minimum film forming temperature of the aqueous ink composition is 0 ° C. or lower.

Furthermore, the present invention is a hydrophilic solvent (E) is directed to the above-described aqueous ink composition characterized by containing a diethylene glycol monoalkyl ether solvent.

Furthermore, the present invention relates to the above water-based ink composition, wherein the diethylene glycol monoalkyl ether solvent system is any one of diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, and diethylene glycol monobutyl ether.

Furthermore, this invention relates to said water-based ink composition used for flexographic printing or gravure printing.

  According to the present invention, even under low-temperature drying conditions, it exhibits excellent coating film properties (substrate adhesion, water rub resistance, blocking resistance) with respect to nonpolar film substrates, while ink storage stability, It was possible to provide a core-shell resin fine particle dispersion for water-based inks and a water-based ink composition that are excellent in re-dissolvability and plate cleaning properties.

First, the core-shell type resin fine particle dispersion for water-based ink of the present invention (hereinafter sometimes simply referred to as resin fine particle dispersion) will be described.

The resin fine particle dispersion used in the present invention is obtained by emulsion polymerization of an ethylenically unsaturated monomer (B) using a radical polymerization initiator in an aqueous medium in the presence of the water-soluble resin (A). Can do.
A method for producing a resin fine particle dispersion will be specifically described. First, an aqueous medium, a basic compound, and a water-soluble resin (A) are charged into a reaction vessel and dissolved by heating. Thereafter, the radical polymerization initiator is added while dropping the ethylenically unsaturated monomer (B) under a nitrogen atmosphere. Since the color of the solution in the reaction vessel turns pale after the reaction starts, the formation of particle nuclei can be confirmed. The target resin fine particle dispersion can be obtained by further reacting for several hours after the completion of dropping of the ethylenically unsaturated monomer. The ethylenically unsaturated monomer (B) may be added dropwise to the reaction vessel as it is, or may be added dropwise after an emulsion is prepared in advance with an aqueous medium. The water-soluble resin (A) acts as a protective colloid (shell component) in the aqueous medium and stabilizes the generated particle core (core component). Since the resin fine particle dispersion obtained by this method has a viscosity close to Newtonian, it is very excellent in printability.

The water-soluble resin (A) used for synthesizing the resin fine particle dispersion has an aromatic skeleton because it has excellent adsorption to the particle core and dispersion stability, and good compatibility with the pigment dispersion resin. And what has a carboxyl group is preferable. The water-soluble resin (A) is an ethylenically unsaturated monomer (a) including an aromatic ethylenically unsaturated monomer (a-1) and a carboxyl group-containing ethylenically unsaturated monomer (a-2). Can be obtained by solution polymerization or bulk polymerization with a radical initiator, and neutralizing a carboxyl group in the resin with a basic compound.

Examples of the aromatic ethylenically unsaturated monomer (a-1) include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, m-methylstyrene, vinylnaphthalene, benzyl acrylate, benzyl methacrylate, Examples include phenoxyethyl acrylate, phenoxyethyl methacrylate, phenoxydiethylene glycol acrylate, phenoxydiethylene glycol methacrylate, phenoxytetraethylene glycol acrylate, phenoxytetraethylene glycol methacrylate, phenoxyhexaethylene glycol acrylate, phenoxyhexaethylene glycol methacrylate, phenyl acrylate, and phenyl methacrylate.

Examples of the carboxyl group-containing ethylenically unsaturated monomer (a-2) include maleic acid, fumaric acid, itaconic acid, citraconic acid, or alkyl or alkenyl monoesters thereof, hexahydrophthalic acid β- (meta ) Acryloxyethyl monoester, β- (meth) acryloxyethyl monoester succinic acid, acrylic acid, methacrylic acid, crotonic acid, cinnamic acid and the like.
The ethylenically unsaturated monomer (a) does not deviate from the contents of the aromatic ethylenically unsaturated monomer (a-1) and the ethylenically unsaturated monomer (a-2) defined above. In the range, an ethylenically unsaturated monomer (a-3) copolymerizable with them can be used in combination.

As the copolymerizable ethylenically unsaturated monomer (a-3), for example,
Methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, pentyl (meth) acrylate, heptyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate Straight chain or branched alkyl group-containing ethylenically unsaturated monomers such as nonyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, etc. Mer;
Alicyclic alkyl group-containing ethylenically unsaturated monomers such as cyclohexyl (meth) acrylate and isobornyl (meth) acrylate;
Fluorinated alkyl group-containing ethylenically unsaturated monomers such as trifluoroethyl (meth) acrylate and heptadecafluorodecyl (meth) acrylate;
(Meth) acrylamide, N-methoxymethyl- (meth) acrylamide, N-ethoxymethyl- (meth) acrylamide, N-propoxymethyl- (meth) acrylamide, N-butoxymethyl- (meth) acrylamide, N-pentoxymethyl -(Meth) acrylamide, N, N-di (methoxymethyl) acrylamide, N-ethoxymethyl-N-methoxymethylmethacrylamide, N, N-di (ethoxymethyl) acrylamide, N-ethoxymethyl-N-propoxymethylmeta Acrylamide, N, N-di (propoxymethyl) acrylamide, N-butoxymethyl-N- (propoxymethyl) methacrylamide, N, N-di (butoxymethyl) acrylamide, N-butoxymethyl-N- (methoxymethyl) meta Acrylic net N, N-di (pentoxymethyl) acrylamide, N-methoxymethyl-N- (pentoxymethyl) methacrylamide, N, N-dimethylaminopropylacrylamide, N, N-diethylaminopropylacrylamide, N, N-dimethyl Amide group-containing ethylenically unsaturated monomers such as acrylamide and N, N-diethylacrylamide;
2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, glycerol mono (meth) acrylate, 4-hydroxyvinylbenzene, 1-ethynyl-1-cyclohexanol, allyl Hydroxyl group-containing ethylenically unsaturated monomers such as alcohol;
Etc.

As the radical initiator, a known oil-soluble polymerization initiator can be used. For example, benzoyl peroxide, tert-butyl peroxybenzoate, tert-butyl hydroperoxide, tert-butyl peroxy (2-ethylhexanoate), organic peroxides such as tert-butylperoxy-3,5,5-trimethylhexanoate, di-tert-butyl peroxide;
2,2′-azobisisobutyronitrile, 2,2′-azobis-2,4-dimethylvaleronitrile, 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 1,1 Mention may be made of azobis compounds such as' -azobis-cyclohexane-1-carbonitrile.

Examples of basic compounds used as neutralizing agents include amines such as ammonia, trimethylamine, triethylamine, butylamine, 2-dimethylaminoethanol, 2-diethylaminoethanol, diethanolamine, triethanolamine, aminomethylpropanol, and morpholine;
Hydroxide salts such as potassium hydroxide and sodium hydroxide;
Etc.

In 100% by weight of the ethylenically unsaturated monomer (a), the aromatic ethylenically unsaturated monomer (a-1) is preferably 20 to 70% by weight, more preferably 50 to 70% by weight. It is a range. If it is less than 20% by weight, the efficiency of adsorption to the particle nuclei is reduced, aggregates are likely to be generated, and the resin fine particle dispersion becomes unstable. Furthermore, compatibility with the pigment-dispersed resin also decreases, and as a result, the storage stability of the ink and the physical properties of the coating film (substrate adhesion, water friction resistance) are deteriorated. On the other hand, even when it exceeds 70% by weight, the dispersibility of the water-soluble resin (A) is reduced, so that agglomerates are easily generated and the resin fine particle dispersion becomes unstable. As a result, the storage stability of the ink and the physical properties of the coating film (substrate adhesion, water friction) are adversely affected.

  In 100% by weight of the ethylenically unsaturated monomer (a), the carboxyl group-containing ethylenically unsaturated monomer (a-2) is preferably 30 to 40% by weight. If it is less than 30% by weight, the dispersibility of the water-soluble resin (A) is reduced, so that agglomerates are easily generated and the storage stability of the ink is deteriorated. In addition, redissolvability and plate cleaning properties are also deteriorated. Furthermore, since the film forming property is also deteriorated, the compatibility between the shell component and the core component is adversely affected, and the physical properties of the coating film (base material adhesion property, water friction property) become poor. On the other hand, when it exceeds 40% by weight, the physical properties of the coating film (substrate adhesion, water friction resistance, blocking resistance) are deteriorated due to the occurrence of poor drying in the coating film and the increase of the components eluted into water.

A commercially available product may be used as the water-soluble resin (A) as long as it satisfies the above-described composition conditions. Commercially available products include, for example, BASF JONCRYL67, JONCRYL678, JONCRYL586, JONCRYL611, JONCRYL680, JONCRYL682, JONCRYL693, JONCRYL690, JONCRYL52J, JONCRYL57J, JONCRYL57J, JONCRYL57J, JONCRYL57J, JONCRYL57J, JONCRYL57J.

  Furthermore, it is preferable that the acid value of water-soluble resin (A) is 100-300 mgKOH / g. When the acid value of the water-soluble resin (A) is less than 100 mgKOH / g, the dispersion stability of the resin fine particle dispersion is lowered and the storage stability of the ink is deteriorated, or the compatibility between the shell component and the core portion is reduced. In some cases, the physical properties of the coating film (base material adhesion, water friction resistance) may be reduced. On the other hand, if it exceeds 300 mgKOH / g, the coating properties (base adhesion, water rub resistance, blocking resistance) will be adversely affected due to the occurrence of poor drying in the coating and the increase in the amount of components eluted into water. There is. The acid value mentioned here means the number of mg of potassium hydroxide required to neutralize the acidic component contained in 1 g of resin.

Furthermore, it is preferable that the weight average molecular weights of water-soluble resin (A) are 5000-30000, More preferably, it is 6000-15000. When the weight average molecular weight is less than 5,000, the dispersion stability of the resin fine particle dispersion is lowered, the storage stability of the ink is lowered, and the physical properties of the coating film (substrate adhesion, It may adversely affect water friction resistance and blocking resistance). On the other hand, when the weight average molecular weight exceeds 30000, the thickening becomes remarkable, the storage stability of the ink is lowered, the compatibility between the shell component and the core component is inhibited, and the physical properties of the coating (adhesion of the substrate) Performance, water friction resistance). The weight average molecular weight here refers to a value in terms of polystyrene by GPC (gel permeation chromatography) measurement.

As a manufacturing method of water-soluble resin (A), it mentions about a styrene- (meth) acrylic acid- (meth) acrylic-acid alkylester copolymer, for example. An organic solvent is charged into the reaction vessel and the temperature is raised. Any organic solvent can be used as long as it does not adversely affect the reaction and the subsequent treatment and can dissolve the obtained resin. After raising the temperature, radical polymerization is carried out by adding a radical initiator while dropping styrene, (meth) acrylic acid, and alkyl (meth) acrylate in a nitrogen atmosphere. The radical polymerization can be performed by a known polymerization method, and is particularly preferably performed by solution polymerization. About the obtained resin solution, after neutralizing with a basic compound, it may be diluted with ion-exchanged water as it is, or the organic solvent may be replaced with ion-exchanged water. A water-soluble resin (A) can be obtained by the above process.

Next, the ethylenically unsaturated monomer (B) used in the present invention will be described. The ethylenically unsaturated monomer has an aromatic ethylenically unsaturated monomer (b-1) and an ethylenically unsaturated monomer (b-2) composed of the general formula (1) as essential components. In the ethylenically unsaturated monomer (B) forming the core portion, the two components of ethylenically unsaturated monomer are contained in a specified amount, so that the compatibility of the shell component and the core component during drying is achieved. Improves dramatically and forms a homogeneous coating. Therefore, even for nonpolar film base materials such as olefins, excellent film properties (base material adhesion, water friction resistance) can be exhibited under low temperature drying conditions. On the contrary, if the amount is outside the predetermined amount, even if the film is formed apparently, the film is a heterogeneous coating film, and sufficient coating film properties cannot be exhibited on the film substrate.

The aromatic ethylenically unsaturated monomer (b-1) is preferably 15 to 40% by weight in 100% by weight of the ethylenically unsaturated monomer (B). If it is less than 15% by weight, the particle nucleation becomes unstable and adversely affects the particle size control, and the compatibility between the shell component and the core component deteriorates to form a heterogeneous coating film. Substrate adhesion, water friction resistance) will be deteriorated. On the other hand, when the content exceeds 40% by weight, the compatibility between the shell component and the core component is deteriorated, so that the physical properties of the coating film (base material adhesion, water friction resistance) are deteriorated.

Examples of the aromatic ethylenically unsaturated monomer (b-1) include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, m-methylstyrene, vinylnaphthalene, benzyl acrylate, benzyl methacrylate, Examples include phenoxyethyl acrylate, phenoxyethyl methacrylate, phenoxydiethylene glycol acrylate, phenoxydiethylene glycol methacrylate, phenoxytetraethylene glycol acrylate, phenoxytetraethylene glycol methacrylate, phenoxyhexaethylene glycol acrylate, phenoxyhexaethylene glycol methacrylate, phenyl acrylate, and phenyl methacrylate.

The ethylenically unsaturated monomer (b-2) is preferably 60 to 85% by weight in 100% by weight of the ethylenically unsaturated monomer (B). If it is less than 60% by weight, the compatibility between the shell component and the core component is deteriorated and a non-homogeneous coating film is formed, so that the physical properties of the coating film (base material adhesion, water friction resistance) are lowered. On the other hand, when the content exceeds 85% by weight, the compatibility between the shell component and the core component is deteriorated, and the physical properties of the coating film (base material adhesion, water friction resistance) are lowered.

Examples of the ethylenically unsaturated monomer (b-2) include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, and the like. Among them, butyl acrylate from the viewpoint of developing excellent coating film properties. Is more preferable.

The ethylenically unsaturated monomer (B) does not deviate from the contents of the aromatic ethylenically unsaturated monomer (b-1) and the ethylenically unsaturated monomer (b-2) defined above. In the range, an ethylenically unsaturated monomer (b-3) copolymerizable with them can be used in combination.

As the copolymerizable ethylenically unsaturated monomer (b-3), for example,
Methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, pentyl (meth) acrylate, heptyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate Straight chain or branched alkyl group-containing ethylenically unsaturated monomers such as nonyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, etc. Mer;
Alicyclic alkyl group-containing ethylenically unsaturated monomers such as cyclohexyl (meth) acrylate and isobornyl (meth) acrylate;
Fluorinated alkyl group-containing ethylenically unsaturated monomers such as trifluoroethyl (meth) acrylate and heptadecafluorodecyl (meth) acrylate;

(Meth) acrylamide, N-methoxymethyl- (meth) acrylamide, N-ethoxymethyl- (meth) acrylamide, N-propoxymethyl- (meth) acrylamide, N-butoxymethyl- (meth) acrylamide, N-pentoxymethyl -(Meth) acrylamide, N, N-di (methoxymethyl) acrylamide, N-ethoxymethyl-N-methoxymethylmethacrylamide, N, N-di (ethoxymethyl) acrylamide, N-ethoxymethyl-N-propoxymethylmeta Acrylamide, N, N-di (propoxymethyl) acrylamide, N-butoxymethyl-N- (propoxymethyl) methacrylamide, N, N-di (butoxymethyl) acrylamide, N-butoxymethyl-N- (methoxymethyl) meta Acrylic net N, N-di (pentoxymethyl) acrylamide, N-methoxymethyl-N- (pentoxymethyl) methacrylamide, N, N-dimethylaminopropylacrylamide, N, N-diethylaminopropylacrylamide, N, N-dimethyl Amide group-containing ethylenically unsaturated monomers such as acrylamide and N, N-diethylacrylamide;
2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, glycerol mono (meth) acrylate, 4-hydroxyvinylbenzene, 1-ethynyl-1-cyclohexanol, allyl Hydroxyl group-containing ethylenically unsaturated monomers such as alcohol;

Maleic acid, fumaric acid, itaconic acid, citraconic acid, or alkyl or alkenyl monoesters thereof, hexahydrophthalic acid β- (meth) acryloxyethyl monoester, succinic acid β- (meth) acryloxyethyl monoester, Carboxyl group-containing ethylenically unsaturated monomers such as acrylic acid, methacrylic acid, crotonic acid and cinnamic acid;
Contains 2-sulfonic acid groups such as sodium 2-acrylamido-2-methylpropanesulfonate, methallyl sulfonic acid, methallyl sulfonic acid, sodium methallyl sulfonate, allyl sulfonic acid, sodium allyl sulfonate, ammonium allyl sulfonate, and vinyl sulfonic acid Ethylenically unsaturated monomers;

Allyl (meth) acrylate, 1-methylallyl (meth) acrylate, 2-methylallyl (meth) acrylate, 1-butenyl (meth) acrylate, 2-butenyl (meth) acrylate, 3-butenyl (meth) acrylate, 1,3- Methyl-3-butenyl (meth) acrylate, 2-chloroallyl (meth) acrylate, 3-chloroallyl (meth) acrylate, o-allylphenyl (meth) acrylate, 2- (allyloxy) ethyl (meth) acrylate, allyl lactyl (meth) Acrylate, citronellyl (meth) acrylate, geranyl (meth) acrylate, rosinyl (meth) acrylate, cinnamyl (meth) acrylate, diallyl maleate, diallyl itaconic acid, vinyl (meth) acrylate, vinyl crotonic acid Vinyl oleate, vinyl linolenate, 2- (2′-vinyloxyethoxy) ethyl (meth) acrylate, ethylene glycol di (meth) acrylate, triethylene glycol (meth) acrylate, tetraethylene glycol (meth) acrylate, trimethylol Propane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, 1,1,1-trishydroxymethylethane diacrylate, 1,1,1-trishydroxymethylethane triacrylate, 1,1,1-trishydroxymethyl Ethylenically unsaturated monomers having two or more ethylenically unsaturated groups such as propane triacrylate, divinylbenzene, divinyl adipate, diallyl isophthalate, diallyl phthalate, diallyl maleate;

Epoxy group-containing ethylenically unsaturated monomers such as glycidyl (meth) acrylate and 3,4-epoxycyclohexyl (meth) acrylate;
Keto group-containing ethylenically unsaturated monomers such as diacetone (meth) acrylamide and acetoacetoxy (meth) acrylate;
γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropyltributoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-acryloxy Propyltrimethoxysilane, γ-acryloxypropyltriethoxysilane, γ-acryloxypropylmethyldimethoxysilane, γ-methacryloxymethyltrimethoxysilane, γ-acryloxymethyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane Alkoxysilyl group-containing ethylenically unsaturated monomers such as vinyltributoxysilane and vinylmethyldimethoxysilane;
Examples include, but are not limited to, methylol group-containing ethylenically unsaturated monomers such as N-methylol (meth) acrylamide, N, N-dimethylol (meth) acrylamide, and alkyl etherified N-methylol (meth) acrylamide. It is not something. These can be used alone or in combination of two or more.

Among the copolymerizable ethylenically unsaturated monomers (b-3) shown above, by using a keto group-containing ethylenically unsaturated monomer in combination, the substrate adhesion of the coating film, water friction resistance Can be further improved by a synergistic effect. A keto group derived from an ethylenically unsaturated monomer reacts with a hydrazide compound in the ink composition to form a keto-hydrazide bridge upon drying.

In 100% by weight of the ethylenically unsaturated monomer (B), the keto group-containing ethylenically unsaturated monomer is preferably 1 to 3% by weight. If it is less than 1% by weight, the effect of crosslinking may not be confirmed in the physical properties of the coating film. On the other hand, when it exceeds 3% by weight, the compatibility of the shell component and the core component is deteriorated, and on the contrary, the physical properties of the coating film may be adversely affected. In addition, re-dissolvability and plate cleaning properties may be adversely affected. Introduction of keto group-containing ethylenically unsaturated monomer that is optimal for the composition of the core-shell type resin particle dispersion of the present invention in order to achieve both excellent compatibility between the core component and shell component and the effect of keto-hydrazide crosslinking. The amount is optimally in the range of 1 to 3% by weight.

The amount of the water-soluble resin (A) used at the time of synthesizing the core-shell type resin fine particle dispersion is preferably 40 to 60 parts by weight with respect to 100 parts by weight of the total amount of the ethylenically unsaturated monomer (B). If it is less than 40 parts by weight, the particle nuclei become unstable during the synthesis of the resin fine particle dispersion, aggregates are generated, and the storage stability of the ink is adversely affected. In addition, since compatibility between the core portion and the shell portion is inhibited during film formation, physical properties of the coating film (base material adhesion, water friction resistance) are also deteriorated. On the other hand, when the amount exceeds 60 parts by weight, drying failure occurs and the amount of components eluted into water increases, so that the physical properties of the coating film (base material adhesion, water friction resistance, blocking resistance) are significantly reduced.

The average particle diameter of the core-shell resin fine particle dispersion is preferably in the range of 45 to 90 nm. When the average particle size is less than 45 nm, the dispersion stability of the resin fine particle dispersion in the ink composition is lowered, which adversely affects the storage stability, re-dissolvability, and plate washability of the ink. On the other hand, if it exceeds 90 nm, the film formation at the time of drying becomes insufficient, and the physical properties of the coating film (substrate adhesion, water friction resistance, blocking resistance) deteriorate. The average particle size referred to here is a volume average particle size measured by a dynamic light scattering method in which the water dilution of the resin fine particle aqueous dispersion (C) is irradiated with laser light and the Brownian motion of the particle is detected from the scattered light. The value of the diameter.

The glass transition temperature (Tg) of the core-shell resin fine particle dispersion is preferably in the range of −10 to 30 ° C. When the glass temperature is less than −10 ° C., the coating film strength is lowered and the coating film properties (substrate adhesion, water friction resistance, blocking resistance) are deteriorated. On the other hand, even when the glass transition temperature exceeds 30 ° C., the movement of the molecular chain under low temperature drying is inhibited, so the film formation and the compatibility between the core component and the shell component become insufficient, and the physical properties of the coating film (base Material adhesion, water friction resistance) deteriorates.

The above glass transition temperature refers to the theoretical value calculated from the FOX equation below.
<FOX type> 1 / Tg = W1 / Tg1 + W2 / Tg2 + ... + Wi / Tgi + ... + Wn / Tgn
[In the above FOX formula, the glass transition temperature of the homopolymer of each monomer constituting the polymer composed of n types of monomers is Tgi (K), the mass fraction of each monomer is Wi, and (W1 + W2 + ... + Wi +... Wn = 1). ]

The weight average molecular weight of the core-shell type resin fine particle dispersion is preferably in the range of 200,000 to 500,000. When the weight average molecular weight is less than 200,000, the stability of the resin fine particles in the ink solvent is lowered, the ink physical properties (storage stability, re-dissolvability) are deteriorated, and the coating strength is lowered. Physical properties (base material adhesion, water friction resistance, blocking resistance) may be deteriorated. On the other hand, if it exceeds 500,000, the re-solubility of the ink is lowered or the movement of the molecular chain under low temperature drying is inhibited, so the film formation and the compatibility between the core component and the shell component become insufficient, and the coating resistance Physical properties (base material adhesion, water friction resistance) may deteriorate.

  Water is mentioned as an aqueous medium used at the time of the synthesis | combination of a resin fine particle dispersion. A hydrophilic organic solvent can also be used as long as the object of the present invention is not impaired.

  The polymerization initiator used in obtaining the resin fine particle dispersion used in the present invention is not particularly limited as long as it has the ability to initiate radical polymerization, and is a known oil-soluble polymerization initiator or water-soluble polymerization initiator. Can be used.

The oil-soluble polymerization initiator is not particularly limited, and examples thereof include benzoyl peroxide, tert-butyl peroxybenzoate, tert-butyl hydroperoxide, tert-butyl peroxy (2-ethylhexanoate), and tert-butyl peroxide. Organic peroxides such as oxy-3,5,5-trimethylhexanoate, di-tert-butyl peroxide;
2,2′-azobisisobutyronitrile, 2,2′-azobis-2,4-dimethylvaleronitrile, 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 1,1 Mention may be made of azobis compounds such as' -azobis-cyclohexane-1-carbonitrile. These can be used alone or in combination of two or more.

In the present invention, a water-soluble polymerization initiator is preferably used. For example, ammonium persulfate (APS), potassium persulfate (KPS), hydrogen peroxide, 2,2′-azobis (2-methylpropionamidine) dihydro Conventionally known materials such as chloride can be preferably used.

Moreover, when performing emulsion polymerization, a reducing agent can be used together with a polymerization initiator if desired. Thereby, it becomes easy to accelerate the emulsion polymerization rate or to perform the emulsion polymerization at a low temperature.

Examples of such a reducing agent include reducing organic compounds such as metal salts such as ascorbic acid, ersorbic acid, tartaric acid, citric acid, glucose, formaldehyde sulfoxylate, sodium thiosulfate, sodium sulfite, sodium bisulfite, Examples include reducing inorganic compounds such as sodium bisulfite, ferrous chloride, Rongalite, thiourea dioxide, and the like. These reducing agents are preferably used in an amount of 0.05 to 5.0 parts by weight with respect to 100 parts by weight of the ethylenically unsaturated monomer. In addition, it can superpose | polymerize also by a photochemical reaction, radiation irradiation, etc. irrespective of an above described polymerization initiator. The polymerization temperature is not less than the polymerization start temperature of each polymerization initiator. For example, in the case of a peroxide-based polymerization initiator, it may be usually about 80 ° C. The polymerization time is not particularly limited, but is usually 2 to 24 hours.

Further, if necessary, sodium acetate, sodium citrate, sodium bicarbonate, etc. as a buffering agent, and octyl mercaptan, 2-ethylhexyl thioglycolate, octyl thioglycolate, stearyl mercaptan, lauryl mercaptan as a chain transfer agent A suitable amount of mercaptans such as t-dodecyl mercaptan can be used.

When the resin fine particle dispersion used in the present invention is obtained by radical polymerization, a surfactant may be used in combination with the water-soluble resin (A) as necessary.

As the surfactant, for example,
Alkyl ethers (for example, Adalon KH-05, KH-10, KH-20, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Adeka Soap SR-10N, SR-20N manufactured by ADEKA Corporation, manufactured by Kao Corporation Latemul PD-104, etc.), sulfosuccinic acid ester type (commercially available products include, for example, Latemul S-120, S-120A, S-180P, S-180A, Kayo Co., Ltd., Elemiol JS-2, Sanyo Chemical Co., Ltd. ), Alkylphenyl ethers or alkylphenyl esters (commercially available products include, for example, Aqualon H-2855A, H-3855B, H-3855C, H-3856, HS-05, HS-10 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) , HS-20, HS-30, Adeka Soap SDX-2 manufactured by ADEKA Corporation 2, SDX-223, SDX-232, SDX-233, SDX-259, SE-10N, SE-20N, etc.), (meth) acrylate sulfate ester system (commercially available products include, for example, Anne manufactured by Nippon Emulsifier Co., Ltd. Tox MS-60, MS-2N, Sanyo Kasei Kogyo Co., Ltd., Eleminol RS-30, etc.), phosphoric acid ester type (for example, H-3330PL manufactured by Daiichi Kogyo Seiyaku Co., Ltd., ADEKA Co., Ltd. Anionic reactive emulsifiers such as rear soap PP-70);

Alkyl ether type (As commercial products, for example, Adeka Soap ER-10, ER-20, ER-30, ER-40 manufactured by ADEKA Corporation, Latemul PD-420, PD-430, PD-450 manufactured by Kao Corporation Etc.), alkylphenyl ethers or alkylphenyl esters (commercially available products include, for example, Aqualon RN-10, RN-20, RN-30, RN-50, ADEKA, Inc., Adekaria, manufactured by Daiichi Kogyo Seiyaku Co., Ltd. Soap NE-10, NE-20, NE-30, NE-40, etc.), (meth) acrylate sulfate ester (commercially available products include, for example, RMA-564, RMA-568, RMA-1114 manufactured by Nippon Emulsifier Co., Ltd. Nonionic reactive emulsifiers such as

Higher fatty acid salts such as sodium oleate, alkylaryl sulfonates such as sodium dodecylbenzene sulfonate, alkyl sulfate salts such as sodium lauryl sulfate, polyoxyethylene alkyl ether sulfate salts such as sodium polyoxyethylene lauryl ether sulfate, Polyoxyethylene alkylaryl ether sulfates such as sodium polyoxyethylene nonylphenyl ether sulfate, alkyl sulfosuccinates such as sodium monooctyl sulfosuccinate, sodium dioctyl sulfosuccinate, sodium polyoxyethylene lauryl sulfosuccinate and derivatives thereof, Anionic non-reactive emulsification of polyoxyethylene distyrenated phenyl ether sulfates ;

Polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether and polyoxyethylene stearyl ether, polyoxyethylene alkyl phenyl ethers such as polyoxyethylene octylphenyl ether and polyoxyethylene nonylphenyl ether, sorbitan monolaurate, sorbitan mono Sorbitan higher fatty acid esters such as stearate and sorbitan trioleate, polyoxyethylene sorbitan higher fatty acid esters such as polyoxyethylene sorbitan monolaurate, polyoxyethylene such as polyoxyethylene monolaurate and polyoxyethylene monostearate Glycerin higher fatty acid ester such as higher fatty acid esters, oleic acid monoglyceride, stearic acid monoglyceride Le ethers, polyoxyethylene polyoxypropylene block copolymer, nonionic non-reactive emulsifier polyoxyethylene distyrenated phenyl ether;
Etc.

Next, the water-based ink composition of the present invention will be described. The aqueous ink composition of the present invention contains a pigment (C), a pigment dispersion resin (D), a resin fine particle dispersion, a hydrophilic solvent (E), and water.

The resin fine particle dispersion is preferably used in an amount of 5 to 40% by weight in terms of solid content in 100% by weight of the water-based ink composition, and more preferably 10 to 30% by weight. If the resin fine particle aqueous dispersion (C) is less than 5% by weight in terms of solid content, the printability deteriorates and the binding between the substrate and the pigment or between the pigments becomes insufficient. (Base material adhesion, water friction resistance) may decrease. On the other hand, when the resin fine particle dispersion exceeds 40% by weight in terms of solid content, the viscosity of the ink composition is remarkably increased, which adversely affects the storage stability of the ink or the occurrence of poor drying in the coating film. Physical properties (base material adhesion, water rub resistance) may deteriorate.

As the pigment dispersion resin (D) used for pigment dispersion, any water-soluble resin can be used as long as it maintains ink stability and has pigment dispersion ability.
Examples of water-soluble resins include:
Polyvinyl alcohol, polyvinyl pyrrolidone (commercially available products such as K-30, K-60, K-90, etc. manufactured by ISP), polyethylene glycol, poly (meth) acrylic acid, (meth) acrylic acid- (meth) acrylic acid Alkyl ester copolymer, styrene- (meth) acrylic acid- (meth) acrylic acid alkyl ester copolymer, styrene- (meth) acrylic acid copolymer, maleic acid- (meth) acrylic acid alkyl ester copolymer, Styrene-maleic acid copolymer, styrene-maleic acid- (meth) acrylic acid alkyl ester copolymer, styrene-maleic acid half ester copolymer, vinyl naphthalene- (meth) acrylic acid copolymer, vinyl naphthalene-malein Acid copolymer, vinylpyrrolidone- (meth) acrylic acid alkyl ester copolymer, vinylpyrrolidone- Styrene copolymer, vinylpyrrolidone-vinyl acetate copolymer, vinyl acetate-crotonic acid copolymer, vinyl acetate- (meth) acrylic acid copolymer, vinyl acetate-crotonic acid copolymer, polyvinyl sulfonic acid, polyvinyl sulfone Sodium sulfonate, polystyrene sulfonate, sodium polystyrene sulfonate (Polynas PS-1, Polynas PS-5, etc., manufactured by Tosoh Corporation), styrene sulfonic acid-maleic acid copolymer, polyitaconic acid, polyhydroxyethyl (meth) acrylate, poly Water-soluble vinyl copolymers such as (meth) acrylamide, (meth) acrylamide- (meth) acrylic acid copolymer, polyvinyl methyl ether, methyl vinyl ester, carboxy vinyl polymer;
A water-soluble polyurethane resin which is a urethane resin obtained by polyaddition reaction of polyisocyanate and polyol, and the entire resin is water-solubilized by introduction of hydrophilic groups;
A water-soluble polyester resin which is a polyester resin obtained by polycondensation reaction of a polyvalent carboxylic acid and a polyol, and the entire resin is water-solubilized by introduction of a hydrophilic group;
Cellulose derivatives such as methyl cellulose, ethyl cellulose, propyl cellulose, ethyl methyl cellulose, hydroxyalkyl cellulose, hydroxypropyl methyl cellulose, carboxymethyl cellulose, alkali metal carboxymethyl cellulose, alkali metal cellulose sulfate, cellulose graft polymer;
Polypeptides such as polyglutamic acid and polyaspartic acid;
However, it is not particularly limited to these. These can be used alone or in combination of two or more.

Among the water-soluble resins mentioned above, from the viewpoint of excellent pigment adsorption ability and dispersion stability, the pigment dispersion resin (D) is a meth) acrylic acid- (meth) acrylic acid alkyl ester copolymer, styrene- ( (Meth) acrylic acid- (meth) acrylic acid alkyl ester copolymer, styrene- (meth) acrylic acid copolymer, maleic acid- (meth) acrylic acid alkyl ester copolymer, styrene-maleic acid copolymer, styrene A maleic acid- (meth) acrylic acid alkyl ester copolymer and a styrene-maleic acid half ester copolymer are preferred. Further, these resins may be synthesized by solution polymerization or bulk polymerization using a radical initiator, or commercially available products may be used. Moreover, the basic compound described above can be used as needed.

As commercially available products, for example, BASF Corp. JONCRYL67, JONCRYL678, JONCRYL586, JONCRYL611, JONCRYL683, JONCRYL690, JONCRYL57J, JONCRYL60J, JONCRYL61J, JONCRYL62J, JONCRYL63J, JONCRYLHPD-96J, JONCRYL501J, JONCRYLPDX-6102B, manufactured by BYK Chemie DISPERBYK, DISPERBYK180, DISPERBYK187 , DISPERBYK190, DISPERBYK191, DISPERBYK194, DISPERBYK2010, DISPERBYK2015, DISPERBYK2090, DISPERBYK2091, DISPERBYK2095, DISPERBYK2155, Zeneca SOLSPERS41000, Sartomer, SMA1000H, SMA1440H, SMA2000H, SMA3000H, etc.

Further, from the viewpoint of compatibility with the resin fine particle dispersion, the pigment dispersion resin (D) is composed of an aromatic ethylenically unsaturated monomer (d-1), a carboxyl group-containing ethylenically unsaturated monomer (d-2). Is a water-soluble resin obtained by polymerizing an ethylenically unsaturated monomer (d), and an aromatic ethylenically unsaturated monomer in a total of 100% by weight of the ethylenically unsaturated monomer (d). It is preferable to contain 20 to 70% by weight of (d-1) and 10 to 40% by weight of the carboxyl group-containing ethylenically unsaturated monomer (d-2). When the amount of the aromatic ethylenically unsaturated monomer (d-1) is less than 20% by weight, compatibility with the resin fine particle dispersion is reduced during film formation, and physical properties of the coating film (substrate adhesion, water friction resistance) ) May decrease. On the other hand, even when it exceeds 70% by weight, the compatibility with the resin fine particle dispersion may be lowered, and the physical properties of the coating film (base material adhesion, water friction resistance) may be lowered. When the carboxyl group-containing ethylenically unsaturated monomer (d-2) is less than 10% by weight, compatibility with the resin fine particle dispersion may be reduced during film formation, and film properties may be deteriorated. On the other hand, if it exceeds 40% by weight, drying failure may occur and the physical properties of the coating film (substrate adhesion, water friction resistance, blocking resistance) may be deteriorated. The pigment-dispersed resin (D) having the above composition is very excellent in compatibility with the resin fine particle dispersion, and forms a uniform coating film even under low-temperature drying. Therefore, it can be expected to further improve the physical properties of the coating film by combining them.

As the aromatic ethylenically unsaturated monomer (d-1), the above aromatic ethylenically unsaturated monomer (a-1)
And the ethylenically unsaturated monomers mentioned in the above.

  As a carboxyl group-containing ethylenically unsaturated monomer (d-2), the ethylene unsaturated monomer etc. which were mentioned by said carboxyl group-containing ethylenically unsaturated monomer (a-2) are mentioned.

The pigment dispersion resin (D) is preferably used in the range of 10 to 60 parts by weight in terms of solid content with respect to 100 parts by weight of the pigment. When the pigment dispersion resin is less than 10 parts by weight with respect to 100 parts by weight of the pigment, the pigment dispersion stability may be lowered, and the dispersion stability and storage stability of the ink composition may be deteriorated. On the other hand, when the pigment dispersion resin exceeds 60 parts by weight with respect to 100 parts by weight of the pigment, the viscosity of the ink composition is remarkably increased, which may adversely affect the storage stability of the ink. Moreover, since generation | occurrence | production of the poor drying of a coating film and the elution component to water increase, about a coating-film physical property (base-material adhesiveness, water-friction resistance, blocking resistance), it may fall.

As the pigment (C), for example, achromatic pigments such as carbon black, titanium oxide, calcium carbonate, or chromatic organic pigments can be used. Examples of organic pigments include insoluble azo pigments such as toluidine red, toluidine maroon, Hansa Yellow, Benzidine Yellow, and pyrazolone red, soluble azo pigments such as Ritol Red, Helio Bordeaux, Pigment Scarlet, and Permanent Red 2B, alizarin, indanthrone, and thioindigo. Derivatives from vat dyes such as maroon, phthalocyanine organic pigments such as phthalocyanine blue and phthalocyanine green, quinacridone organic pigments such as quinacridone red and quinacridone magenta, perylene organic pigments such as perylene red and perylene scarlet, isoindolinone yellow , Isoindolinone organic pigments such as isoindolinone orange, pyranthrone organic pigments such as pyranthrone red and pyranthrone orange, thioy Digo-based organic pigments, condensed azo-based organic pigments, benzimidazolone-based organic pigments, quinophthalone-based organic pigments such as quinophthalone yellow, isoindoline-based organic pigments such as isoindoline yellow, and other pigments such as flavanthrone yellow and acylamide yellow Nickel azo yellow, copper azomethine yellow, perinone orange, anthrone orange, dianthraquinonyl red, dioxazine violet and the like.

  When organic pigments are exemplified by color index (CI) numbers, C.I. I. Pigment Yellow 12, 13, 14, 17, 20, 24, 74, 83, 8893, 109, 110, 117, 120, 125, 128, 129, 137, 138, 139, 147, 148, 150, 151, 153 154, 155, 166, 168, 180, 185, C.I. I. Pigment orange 16, 36, 43, 51, 55, 59, 61, C.I. I. Pigment Red 9, 48, 49, 52, 53, 57, 97, 122, 123, 149, 168, 177, 180, 192, 202, 206, 215, 216, 217, 220, 223, 224, 226, 227, 228, 238, 240, C.I. I. Pigment violet 19, 23, 29, 30, 37, 40, 50, C.I. I. Pigment blue 15, 15: 1, 15: 3, 15: 4, 15: 6, 22, 60, 64, C.I. I. Pigment green 7, 36, C.I. I. Pigment brown 23, 25, 26, and the like.

  Specific examples of carbon black include “Special Black 350, 250, 100, 550, 5, 4, 4A, 6” “Printex U, V, 140 U, 140 V, 95, 90, 85, 80, 75, 55, manufactured by Degussa. 45, 40, P, 60, L6, L, 300, 30, 3, 35, 25, A, G ", Cabot's" REGAL 400R, 660R, 330R, 250R "," MOGUL E, L ", Mitsubishi Chemical “MA7, 8, 11, 77, 100, 100R, 100S, 220, 230” “# 2700, # 2650, # 2600, # 200, # 2350, # 2300, # 2200, # 1000, # 990, # 980, # 970, # 960, # 950, # 900, # 850, # 750, # 650, # 52, # 50, # 47, # 45, # 4 5L, # 44, # 40, # 33, # 332, # 30, # 25, # 20, # 10, # 5, CF9, # 95, # 260 ”and the like.

Specific examples of titanium oxide include “Taipeku CR-50, 50-2, 57, 80, 90, 93, 95, 953, 97, 60, 60-2, 63, 67, 58, 58- manufactured by Ishihara Sangyo Co., Ltd. 2, 85 "" Tipekes R-820, 830, 930, 550, 630, 680, 670, 580, 780, 780-2, 850, 855 "," Tipekes A-100, 220 "," Tipekes W-10 "," Tipekes " PF-740, 744 "" TTO-55 (A), 55 (B), 55 (C), 55 (D), 55 (S), 55 (N), 51 (A), 51 (C) " "TTO-S-1, 2", "TTO-M-1, 2", "Titanics JR-301, 403, 405, 600A, 605, 600E, 603, 805, 806, 701, 800, 808" manufactured by Teika "Titanic EN-1, C, 3, 4, 5 ", and the like manufactured by Du Pont" Taipyua R-900,902,960,706,931 ". The organic pigments such as yellow, magenta, cyan and black are preferably blended at a ratio of 5 to 30% by weight in 100% by weight of the water-based ink composition. Moreover, in the case of white titanium oxide, it is preferable to mix | blend normally in the ratio of 10 to 60 weight%.

Furthermore, the water-based ink composition of the present invention contains a hydrophilic solvent (E) for the purpose of controlling the wettability to the substrate and the drying property of the ink.

In 100% by weight of the water-based ink composition, the hydrophilic solvent (E) is preferably contained in an amount of 1 to 10% by weight, more preferably in the range of 2 to 5% by weight. If the hydrophilic solvent (E) is less than 1% by weight, the printability may be deteriorated and the physical properties of the coating film (substrate adhesion, water friction resistance) may be lowered. On the other hand, when the content of the hydrophilic solvent (E) exceeds 10% by weight, the coating film is poorly dried, and the physical properties of the coating film (substrate adhesion, water friction resistance, blocking resistance) are deteriorated. There is a case.

Examples of the hydrophilic solvent (E) include monohydric alcohols such as ethanol, 1-propanol, 2-propanol, 1-butanol, 2-methyl-1-propanol, 2-butanol, and 2-methyl-2-propanol. solvent;
Ethylene glycol, 1,3-propanediol, propylene glycol, 1,2-butanediol, 1,4-butanediol, pentylene glycol, 1,2-hexanediol, 1,6-hexanediol, diethylene glycol, triethylene glycol Glycol solvents such as tetraethylene glycol;
Ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monoethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, diethylene glycol monoisopropyl ether, triethylene glycol monoisopropyl Ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, diethylene glycol monoisobutyl ether, triethylene glycol monoisobutyl ether, ethylene glycol monohexyl ether , Diethylene glycol monohexyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, glycol ethers such as tripropylene glycol monomethyl ether solvent;
Lactam solvents such as N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 2-pyrrolidone, ε-caprolactam;
Examples include amide solvents such as formamide, N-methylformamide, N, N-dimethylformamide, Idemitsu ecamide M-100, and equamide B-100. These can be used alone or in combination of two or more.

Among the hydrophilic solvents (E), it is preferable to use a diethylene glycol monoalkyl ether solvent from the viewpoint of maintaining the dispersion stability of the ink, controlling the drying property, and promoting the film formation of the resin. Among them, it is more preferable to use any of diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, and diethylene glycol monobutyl ether.

The diethylene glycol monoalkyl ether solvent is preferably contained in an amount of 0.3 to 4% by weight in 100% by weight of the hydrophilic solvent (E) contained in the aqueous ink composition of the present invention. If the hydrophilic solvent (E) is less than 0.3% by weight, the effect of promoting film formation and compatibility may not be sufficiently obtained. On the other hand, if the content of the diethylene glycol monoalkyl ether solvent exceeds 4% by weight, the coating film will be poorly dried and the physical properties of the coating film (substrate adhesion, water rub resistance, blocking resistance) will decrease. There is a case.

In the water-based ink composition of the present invention, a water-soluble hydrazide compound can be appropriately used for the purpose of improving adhesion to a substrate and forming a keto-hydrazide bridge. Examples of the water-soluble hydrazide compound include adipic acid dihydrazide and water-soluble resins in which a polyfunctional hydrazide group is modified.
When the resin fine particle dispersion contains a keto group, it is preferably added so that the hydrazide group is equimolar with respect to the keto group.

For the purpose of further improving the adhesion to the substrate, the water-based ink composition of the present invention has a carbodiimide group, a keto group, etc., as long as the storage stability of the ink and the compatibility between the resins are not adversely affected. A resin fine particle dispersion containing a reactive group can be used in combination. Examples of commercially available reactive group-containing resin fine particle dispersions include Nisshinbo Co., Ltd., Carbodilite E-02, E-03A, SV-02, V-02, V-02-L2, V-04, manufactured by BASF, Acronal YJ2716D, YJ2720D, YJ2727DN, YJ2741D, YJ2746DS, manufactured by DSM, NEOCRYLA-1127, A-1125, A-1120, A-1131 and the like can be mentioned.

The addition amount of the reactive resin fine particle dispersion used in combination is preferably about 0.5 to 15% by weight in terms of solid content in 100% by weight of the water-based ink composition.

In the aqueous ink composition of the present invention, a commercially available wax fine particle dispersion can be used for the purpose of improving the friction resistance of the coating film. Examples of the wax resin fine particle dispersion include Chemipearl W100, W200, W300, W310, W306, W400, W401, W4005, W410, W500, WF640, W700, W800, W900, W950, WH201, and WP100 manufactured by Mitsui Chemicals. Is mentioned.

The amount of the wax fine particle dispersion added is about 1 to 5% by weight in terms of solid content in 100% by weight of the water-based ink composition in consideration of the balance between the improvement of the friction resistance in the physical properties of the coating film and the adverse effect on the hue. Is preferred.

Also. The water-based ink composition of the present invention can use various surface conditioners for the purpose of adjusting the leveling property to the substrate. As the surface conditioner, for example, Surfinol 104E, 104H, 104A, 104PA, 104PG-50, 104S, 420, 440, 465, 485, SE, SE-F, PSA-336, 61, 2502, manufactured by Nissin Chemical Co., Ltd. , DYNOL 604, 607, BYK-381, 3441, 302, 307, 325, 331, 333, 342, 345, 346, 347, 348, 349, 378, 3455, etc., manufactured by BYK Chemie.

The addition amount of the surface modifier is preferably about 0 to 1% by weight in terms of solid content in 100% by weight of the water-based ink composition in consideration of the balance of adverse effects on the physical properties of the coating film.

The minimum film forming temperature (MFT) of the water-based ink composition of the present invention is preferably 0 ° C. or lower. When it exceeds 0 ° C., the film forming property at the time of drying becomes insufficient, and the physical properties of the coating film may be deteriorated.

The water-based ink composition of the present invention has good substrate adhesion to nonpolar film substrates such as polypropylene, polyethylene and polyethylene terephthalate even under low temperature drying conditions, and has excellent water rub resistance and blocking resistance. Therefore, it is possible to expand to water-based flexographic printing and gravure printing, which has been difficult to expand on substrates such as nonpolar film substrates. Moreover, it can be used for the purpose of improving the physical properties of the coating film even on conventional substrates such as permeable substrates such as fine paper, art paper, and coated paper.

Although it is a drying process of a water-based ink composition, any temperature can be applied as long as it does not adversely affect the substrate. In aqueous flexographic printing, it is common to process at a low temperature of 40 to 100 ° C. for 1 to 200 seconds.

  EXAMPLES The present invention will be described more specifically with reference to the following examples. However, the following examples do not limit the scope of rights of the present invention. In the examples, “part” represents “part by weight” and “%” represents “% by weight”.

<Production of water-soluble resin (A)>
[Production Example 1]
In a separate reaction vessel equipped with a stirrer, thermometer, two dropping funnels, and reflux, 94.0 parts of methyl isobutyl ketone was charged and heated to 100 ° C. under nitrogen reflux with stirring. Next, in two dropping funnels, 55.0 parts of styrene, 30.0 parts of acrylic acid, and 15.0 parts of lauryl methacrylate were dropped from one side over 3 hours. From the other side, 6.0 parts of dimethyl 2,2′-azobisisobutyrate was dissolved in 12.0 parts of methyl isobutyl ketone and added dropwise over 4 hours. After completion of the dropwise addition, the reaction was completed by further reacting for 10 hours. After cooling, the obtained water-soluble resin (A) solution was neutralized by adding 23.3 parts of 25% aqueous ammonia. Furthermore, ion exchange water was added, solvent substitution was performed while heating, and the aqueous solution of water-soluble resin (A) was obtained. Finally, the solid content of the water-soluble resin (A) solution was adjusted to 35.0% with ion-exchanged water. The acid value of the water-soluble resin (A) was 220, and the weight average molecular weight was 12,800.
[Production Examples 2 to 11]
A water-soluble resin (A) solution was prepared in the same manner as in Production Example 1 with the composition shown in Table 1. 25% ammonia water as a neutralizing agent was added so that the carboxyl group of the water-soluble resin (A) and ammonia were equimolar. Further, the same operation as in Production Example 1 was performed to prepare a water-soluble resin (A) aqueous solution having a solid content of 35%. About water-soluble resin (A), the acid value and the weight average molecular weight were evaluated.

[Acid value]
Number of milligrams of potassium hydroxide required to neutralize acidic components contained in 1 g of resin. The water-soluble resin (A) thus dried was subjected to potentiometric titration with a potassium hydroxide / ethanol solution according to the method described in JIS K2501.

[Weight average molecular weight]
The weight average molecular weight is a value in terms of polystyrene as measured by GPC (gel permeation chromatography). The dried water-soluble resin (A) is dissolved in tetrahydrofuran to prepare a 0.1% solution, which is prepared by Tosoh HLC-8320-GPC (column number M-0053, molecular weight measurement range of about 2,000 to about 4,000,000). The weight average molecular weight was measured.

<Manufacture of core-shell type resin fine particle dispersion>
[Example 1]
In another reaction vessel equipped with a stirrer, a thermometer, two dropping funnels, and a reflux condenser, 91.8 parts of ion-exchanged water and 114.3 parts of the water-soluble resin (A) solution prepared in Production Example 1 were stirred The temperature was raised to 80 ° C. under nitrogen reflux. Next, in two dropping funnels, 20.0 parts of styrene, 18.0 parts of benzyl methacrylate and 62.0 parts of n-butyl acrylate were dropped from one side over 2 hours. From the other side, 5.0 parts of a 20% aqueous solution of ammonium persulfate was added dropwise over 2 hours. After completion of the dropwise addition, the mixture was further reacted for 4 hours to obtain a resin fine particle dispersion. The solid content of the resin fine particle dispersion was adjusted to 45% with ion-exchanged water. The obtained resin fine particle dispersion had an average particle size of 84 nm, a weight average molecular weight of 470000, an acid value of 63, and a glass transition temperature of 2.0 ° C. The acid value of the resin fine particle dispersion was calculated from the acid value of the water-soluble resin (A) and the charged amount. The glass transition temperature (Tg) was calculated from the composition of the ethylenically unsaturated monomer by the FOX equation described above. The amount of aggregates generated during synthesis per kg of the resin fine particle dispersion was 0.05 g.

[Examples 2 to 15 and Comparative Examples 1 to 17]
Core-shell type resin fine particle dispersions were prepared in the same manner as in Example 1 with the blending compositions shown in Tables 2 and 3. For Examples 10, 12, 13, and 14, after synthesis, adipic acid dihydrazide as a crosslinking agent was added so that the hydrazide group was equimolar with respect to the keto group in the resin fine particle dispersion. The solid content of the resin fine particle dispersion was all adjusted to 45.0%. About the obtained resin fine particle dispersion, the acid value and the glass transition temperature (Tg) were calculated in the same manner as in Example 1, and the average particle diameter, the weight average molecular weight, and the presence or absence of aggregates were evaluated.

[Average particle size]
The resin fine particle dispersion was diluted with water 500 times, and about 5 ml of the diluted solution was measured by a dynamic light scattering measurement method (measurement device manufactured by Nikkiso Co., Ltd.). The peak of the volume particle size distribution data (histogram) obtained at this time was defined as the average particle size.

[Presence or absence of aggregates]
The resin fine particle dispersion was filtered with a 180 mesh (100 μm) filter cloth, and the amount of aggregate per kg of the resin fine particle dispersion generated during synthesis was measured. The evaluation criteria are as follows.
○: Less than 0.1 g Δ: 0.1 g or more, less than 0.5 g x: 0.5 g or more

<Production of water-based ink composition>

<Manufacture of pigment dispersion resin (D)>
[Production Example 12]
In a separate reaction vessel equipped with a stirrer, thermometer, two dropping funnels, and reflux, 94 parts of methyl isobutyl ketone was charged, and the temperature was raised to 100 ° C. under nitrogen reflux while stirring. Next, in two dropping funnels, 50 parts of styrene, 5 parts of α-methylstyrene, 30 parts of methacrylic acid, and 15 parts of lauryl methacrylate were dropped from one side over 3 hours. From the other side, 5 parts of dimethyl 2,2′-azobisisobutyrate was dissolved in 10 parts of methyl isobutyl ketone and added dropwise over 4 hours. After completion of the dropwise addition, the reaction was completed by further reacting for 10 hours. After cooling, the resulting pigment-dispersed resin (D) solution was neutralized by adding 19.5 parts of 25% aqueous ammonia. Furthermore, ion exchange water was added, solvent substitution was performed while heating, and the aqueous solution of water-soluble resin (A) was obtained. Finally, ion exchange water was further added to adjust the solid content of the water-soluble resin (A) solution to 30%. The acid value of the pigment dispersion resin (D) was 186, and the weight average molecular weight was 10,500.

[Production Examples 13 to 22]
With the composition shown in Table 4, pigment dispersion resin (D) aqueous solutions of Production Examples 13 to 22 were prepared in the same manner as Production Example 12. 25% aqueous ammonia as a neutralizing agent was added so as to be equimolar with respect to the carboxyl group of the pigment dispersion resin (D). Resin (D) aqueous solution was prepared. Further, as in Production Examples 23 and 24, when a commercially available solid resin is used as a pigment dispersant, ion-exchanged water and 25% ammonia water (ammonia is equivalent to the carboxyl group of the pigment dispersion resin (D), etc.) Molar amount) was added and water-solubilized with heating and stirring to adjust the solid content to 30%. Table 5 shows an outline of the commercially available solid resin used. About the pigment dispersion resin (D), the acid value and the weight average molecular weight were evaluated by the same method as the water-soluble resin (A).

<Production of concentrated pigment dispersion>

[Production Example 25]
<Production of concentrated white pigment dispersion>
67.5 parts of pigment [Taipeke CR80 made by Ishihara Sangyo Co., Ltd.], 21.3 parts of pigment dispersant aqueous solution (solid content 30%) of Production Example 12, 5.8 parts of ion exchange water, surface conditioner [Surfinol 420 Nissin Chemical Co., Ltd.] 0.4 parts was dispersed with a paint conditioner for 2 hours to obtain a concentrated white pigment dispersion.

[Production Examples 26 to 37]
A concentrated white pigment dispersion was prepared in the same manner as in Production Example 25 with the formulation shown in Table 6.

[Production Example 38]
<Manufacture of concentrated indigo pigment dispersion>
35.9 parts of pigment [Lionol Blue FG7330 manufactured by Toyocolor Co., Ltd.], 21.5 parts of pigment dispersant aqueous solution (solid content 30%) of Production Example 12, 39.7 parts of ion-exchanged water, surface conditioner [Surfinol 420 Nissin Chemical Industry Co., Ltd.] 0.4 parts was dispersed with a paint conditioner for 2 hours to obtain a concentrated indigo pigment dispersion.

[Production Examples 39 to 50]
A concentrated indigo pigment dispersion was prepared in the same manner as in Production Example 38 with the formulation shown in Table 7.

<Preparation of water-based ink composition>
[Example 16]
With respect to 40.2 parts of the resin fine particle aqueous dispersion obtained in Example 1, 47.5 parts of concentrated white pigment dispersion of Production Example 25, 5.0 parts of Chemipearl W500, N-propanol part 2 as a hydrophilic solvent 0.5 parts, 2.0 parts of diethylene glycol monoethyl ether, and 2.8 parts of ion-exchanged water were added, followed by kneading to obtain a white aqueous ink composition.

[Examples 17 to 41 and Comparative Examples 18 to 34]
With the composition shown in Table 8 and Table 9, it was prepared in the same manner as in Example 1 to obtain a white aqueous ink composition.

[Example 42]
With respect to 40.9 parts of the resin fine particle aqueous dispersion obtained in Example 1, 41.6 parts of concentrated indigo pigment dispersion of Production Example 36, 4.5 parts of Chemipearl W500, N-propanol part 3 as a hydrophilic solvent 0.0 part and 10.0 parts of ion-exchanged water were added, and then kneaded to obtain an indigo water-based ink composition.

[Examples 43 to 67 and Comparative Examples 35 to 51]
With the composition shown in Table 10 and Table 11, it was prepared in the same manner as in Example 41 to obtain an indigo water-based ink composition.

[Minimum film forming temperature]
The minimum film-forming temperature (MFT) was measured by applying a water-based ink composition to a glass plate with a 300 µ applicator and applying a thermal gradient tester (manufactured by Rigaku Corporation).

<Evaluation of water-based ink composition>
About the water-based ink composition prepared above, storage stability, re-dissolvability, and plate washability were evaluated as ink physical properties. The aqueous ink composition was applied to a treated OPP (biaxially oriented polypropylene film) substrate using Flexiproof 100 (anilox roller 80 lines / cm). After coating, the substrate was heat-treated in an oven at 60 ° C. for 1 minute to obtain a coating film for evaluation. Using this, the coating film physical properties (base material adhesion, water rub resistance, blocking resistance) were evaluated. Tables 12 to 15 show the results.

[Storage stability]
The aqueous ink composition was evaluated for changes in viscosity over time under conditions of 40 ° C. and 1 week. The viscosity was measured using a Zahn cup (No. 4).
The evaluation criteria are as follows. (Practical level is more than ○)
A: Change in the viscosity of the ink is less than ± 10% B: Change in the viscosity of the ink is ± 10% or more and less than ± 15% Δ: Change in the viscosity of the ink is ± 15% or more and less than ± 20% × ; The viscosity change of the ink is ± 20% or more.

[Resolubility]
The aqueous ink composition was coated on the treated OPP with a bar coater (No. 8) and allowed to stand at room temperature for 15 minutes.
After standing, the ink was dripped onto the coated surface, and the time until the ink was redissolved was measured while wiping with time. The evaluation criteria are as follows. (Practical level is more than ○)
◎: Re-dissolve within 30 seconds ○; Re-dissolve within 60 seconds Δ; Re-dissolve within 120 seconds ×: Not re-dissolve after 120 seconds

[Plate washability]
With respect to the flexiproof 100 plate, the plate washability was evaluated using various solvents after ink coating.
The evaluation criteria are as follows. (Practical level is more than △)
○: Washable with alcohol solvent or magic phosphorus (manufactured by Kao Corporation).
Δ: Washable with magic phosphorus (manufactured by Kao Corporation).
X: Cannot be washed with an alcohol solvent or magic phosphorus (Kao Corporation).

[Base material adhesion]
Cellophane tape (18 mm width manufactured by Nichiban Co., Ltd.) was applied to the coating film for evaluation, a peel test was performed in the vertical direction, and the substrate adhesion was evaluated from the ratio of the area where the ink was peeled off.
The evaluation criteria are as follows. (Practical level is more than ○)
◎: No ink peeling ○: Some ink peeling (less than 10%)
Δ: Ink peeling (10% or more, less than 50%)
×: Ink peeling is considerable (50% or more)

[Water friction resistance]
The evaluation coating film was immersed in water for 1 minute. After immersion, using Kanakine (JIS L 0803) as a friction element, the surface of the coating film dipped in water was reciprocated 500 times with a load of 500 g using a Gakushin tester (manufactured by Tester Sangyo Co., Ltd.). The water friction resistance was evaluated from the ratio of the area where the ink was peeled off. The evaluation criteria are as follows. (Practical level is more than ○)
◎: No ink peeling ○: Ink peeling slightly (less than 5%)
Δ: Ink peeling (5% or more, less than 30%)
×: Ink peeling is considerable (30% or more)

[Blocking resistance]
About the coating film for evaluation, the coating surface and the back surface were overlapped, a load of 5 kg / cm ² was applied by a blocking tester, and the coating film was left in a constant temperature and humidity room at a temperature of 40 ° C. and a humidity of 80% for 24 hours. Then, the coating film for evaluation was taken out and the presence or absence of show-through was confirmed. The evaluation criteria are as follows. (Practical level is ○)
○: The ink is not show-through on the back surface ×: The ink is show-through on the back surface

As shown in Table 12 and Table 14, white aqueous ink compositions (Examples 16 to 41) and indigo water based ink compositions (Examples 42 to 67) using the core-shell type resin fine particle dispersions of Examples 1 to 15 were used. ) Has good ink physical properties (storage stability, re-dissolvability, plate washability), and excellent coating properties (substrate adhesion, water friction resistance, It was confirmed that blocking resistance was developed. All of these items satisfy practically possible levels. On the other hand, white aqueous ink compositions (Comparative Examples 18 to 34) and indigo water based ink compositions (Comparative Examples 35 to 51) using the core-shell type resin fine particle dispersions of Comparative Examples 1 to 17 are Comparative Examples 31 and 48. In all cases except for, the physical properties of the coating film were poor. In Comparative Examples 31 and 48, the physical properties of the coating film were good, but the storage stability of the ink composition was poor.

Claims (9)

A core-shell resin fine particle dispersion for water-based ink obtained by polymerizing an ethylenically unsaturated monomer (B) in an aqueous medium in the presence of the water-soluble resin (A) ,
A core-shell resin fine particle dispersion for water-based ink, which is the following (1) to (4).
(1) Except when the water-soluble resin (A) is an aromatic ethylenically unsaturated monomer (a-1) and a carboxyl group-containing ethylenically unsaturated monomer (a-2) (a-1 ) And a water-soluble resin that is a polymer of an ethylenically unsaturated monomer (a ) ,
In 100% by weight of ethylenically unsaturated monomer (a), 20 to 70% by weight of aromatic ethylenically unsaturated monomer (a-1), carboxyl group-containing ethylenically unsaturated monomer (a-2 30 to 40% by weight.
(2) The ethylenically unsaturated monomer (B) is an aromatic ethylenically unsaturated monomer (b-1) and an ethylenically unsaturated monomer represented by the general formula (1) (b- 2) an ethylenically unsaturated monomer having as essential components,
In 100% by weight of ethylenically unsaturated monomer (B), 15-40% by weight of aromatic ethylenically unsaturated monomer (b-1) and 60 of ethylenically unsaturated monomer (b-2) Contains ~ 85% by weight.
(3) The amount of the water-soluble resin (A) is 40 to 60 parts by weight with respect to 100 parts by weight of the total of the ethylenically unsaturated monomer (B).
(4) The core-shell type resin fine particle dispersion for water-based ink has an average particle size of 45 to 90 nm and a glass transition temperature of −10 to 30 ° C.
General formula (1)
R represents an alkyl group having 1 to 4 carbon atoms.
  The core-shell type resin fine particle dispersion for water-based ink according to claim 1, wherein the core-shell type resin fine particle dispersion has a weight average molecular weight of 200,000 to 500,000.   3. The water-based ink according to claim 1, wherein the keto group-containing ethylenically unsaturated monomer is contained in an amount of 1 to 3 wt% in a total of 100 wt% of the ethylenically unsaturated monomer (B). Core shell type resin fine particle dispersion.   A water-based ink composition comprising a pigment (C), a pigment-dispersing resin (D), water, a hydrophilic solvent (E), and the core-shell resin fine particle dispersion for water-based ink according to any one of claims 1 to 3. object. The pigment dispersion resin (D) is a water-soluble resin obtained by polymerizing an ethylenically unsaturated monomer (d) containing an aromatic ethylenically unsaturated monomer (d-1),
In 100% by weight of ethylenically unsaturated monomer (d), 20 to 70% by weight of aromatic ethylenically unsaturated monomer (d-1), carboxyl group-containing ethylenically unsaturated monomer (d-2) The water-based ink composition according to claim 4, which comprises 10 to 40% by weight.   6. The water-based ink composition according to claim 4, wherein the minimum film-forming temperature of the water-based ink composition is 0 ° C. or lower. Hydrophilic solvent (E) The aqueous ink composition according to claim 4-6, wherein any one that is characterized by containing a diethylene glycol monoalkyl ether solvent.   8. The aqueous ink composition according to claim 7, wherein the diethylene glycol monoalkyl ether solvent system is any one of diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, and diethylene glycol monobutyl ether.   The water-based ink composition according to any one of claims 4 to 8, which is used for flexographic printing or gravure printing.