Water-based ink composition, first laminate, second laminate, and packaging material

Abstract

Provided are an aqueous ink composition excellent in adhesion to a metal layer and blocking resistance of a resulting printed coating film, and excellent in pigment dispersibility when containing a pigment, a first laminate and a second laminate having a printed layer formed using the aqueous ink composition, and a packaging material including the second laminate. 【Solution means】An aqueous ink composition containing a binder resin (A) and an aqueous medium, wherein the binder resin (A) includes an aqueous ethylene-(meth)acrylic acid copolymer resin (A1), an aqueous emulsion type (meth)acrylic resin (A2), and an aqueous polyurethane resin (A3), and the contents in terms of solid content in the binder resin (A) are such that the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) is 15 to 50% by mass, the aqueous emulsion type (meth)acrylic resin (A2) is 10 to 45% by mass, and the aqueous polyurethane resin (A3) is 25 to 60% by mass.

Description

Technical Field

[0001] The present invention relates to an aqueous ink composition, a first laminate, a second laminate, and a packaging material.

Background Art

[0002] For flexible packaging materials such as plastic films used for packaging foods, daily necessities, etc., design and functionality are displayed using gravure printing or flexographic printing. Conventionally, the main type of ink and varnish for flexible packaging has been an oil-based type using organic solvents, but in recent years, there has been a strong demand for an aqueous type from the perspective of environmental issues and the like.

[0003] In addition, as a base material used for packaging materials, not only plastic films but also metal foils such as aluminum foils and metal vapor deposition films such as aluminum vapor deposition films are widely used for the purpose of imparting functions such as gas barrier properties and water vapor barrier properties. When configuring a packaging material using a base material having such a metal layer, an aqueous ink layer is often directly formed on the metal layer. Therefore, having excellent adhesion to the metal layer is very important as a required physical property of the aqueous ink.

[0004] Furthermore, important required physical properties of the aqueous ink include high pigment dispersibility and blocking resistance of the resulting printed coating film. Regarding pigment dispersibility, it is necessary to have good fluidity when the pigment is dispersed and to prevent aggregation and sedimentation of the pigment even after dispersion. When high pigment dispersibility is provided, an aqueous ink layer with excellent printability and excellent appearance can be formed. Regarding blocking resistance, it is important to prevent appearance defects and processing defects caused by the transfer of the printed coating film to the opposite surface in contact with the printed coating film when the printed matter is wound up after printing.

[0005] By the way, the binder resin contained in the aqueous ink is an important component that most affects the physical properties of the ink, and various aqueous binder resins have been studied so far. As an example, (meth)acrylic resins, polyurethane resins, and ethylene-acrylic acid copolymers can be mentioned.

[0006] For example, in Patent Document 1, an aqueous ink composition using a polyurethane resin and an ethylene-acrylic acid copolymer resin has been reported, and in Patent Document 2, an aqueous ink composition using a (meth)acrylic resin and an ethylene-acrylic acid copolymer resin has been reported.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] The aqueous ink composition described in Patent Document 1 contains a specific polyurethane resin and a specific ethylene-acrylic acid copolymer resin, so that the obtained printed coating film is excellent in adhesion to a plastic film and laminate strength, but has low pigment dispersibility and insufficient blocking resistance of the obtained printed coating film. The aqueous ink composition described in Patent Document 2 has a specific (meth)acrylic resin and an ethylene-acrylic acid copolymer resin, so that it has good pigment dispersibility and compatibility, but the blocking resistance is not sufficient.

[0009] In order to compensate for the disadvantages of the binder resin and make use of its advantages, studies have been conducted on the combined use of a plurality of binder resins. However, rather, only the adverse effects due to the disadvantages are prominent, and in most cases, the problem that the object cannot be achieved occurs. In particular, when using three or more types of binder resins, the above problem is remarkable. Furthermore, as the number of types of binder resins to be mixed increases, it is necessary to consider problems of compatibility and stability, so it is very difficult to achieve a well-balanced formulation.

[0010] The present invention aims to provide an aqueous ink composition that is excellent in adhesion to a metal layer and blocking resistance of a resulting printed coating film, and excellent in pigment dispersibility when containing a pigment, a first laminate and a second laminate having a printed layer formed using the aqueous ink composition, and a packaging material including the second laminate. [Means for Solving the Problems]

[0011] The present invention has the following aspects. [1] An aqueous ink composition containing a binder resin (A) and an aqueous medium, wherein the binder resin (A) includes an aqueous ethylene-(meth)acrylic acid copolymer resin (A1), an aqueous emulsion type (meth)acrylic resin (A2), and an aqueous polyurethane resin (A3), and the content of the solid content of the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) with respect to the total mass of the solid content of the binder resin (A) is 15 to 50% by mass, the content of the solid content of the aqueous emulsion type (meth)acrylic resin (A2) is 10 to 45% by mass, and the content of the solid content of the aqueous polyurethane resin (A3) is 25 to 60% by mass. [2] The aqueous ink composition according to [1], wherein the minimum film-forming temperature at a film thickness of 100 μm of the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) is 22°C or lower. [3] The aqueous ink composition according to [1] or [2], wherein the average particle diameter of the aqueous emulsion type (meth)acrylic resin (A2) is 0.3 μm or less. [4] The aqueous ink composition according to any one of [1] to [3], wherein the aqueous polyurethane resin (A3) is a polycarbonate-based polyurethane resin. [5] The aqueous ink composition according to any one of [1] to [4], wherein the aqueous emulsion type (meth)acrylic resin (A2) has a unit based on styrene. [6] The aqueous ink composition according to any one of [1] to [5], wherein the average particle diameter of the aqueous emulsion type (meth)acrylic resin (A2) is 0.2 μm or less. [7] The aqueous ink composition according to any one of [1] to [6], which is for flexographic or gravure printing. [8] A first laminate comprising a substrate and a printed layer formed on one surface of the substrate using the aqueous ink composition according to [7], wherein the substrate is a metal foil or a metal vapor-deposited film. [9] A second laminate in which a resin layer, or an adhesive layer and a resin layer, are laminated on the surface of the printed layer in the first laminate according to [8].

[10] A packaging material comprising the first laminate according to [8] or the second laminate according to [9]. [Advantages of the Invention]

[0012] According to the present invention, there can be provided an aqueous ink composition excellent in adhesion of the obtained printed coating film to a metal layer and blocking resistance, and excellent in pigment dispersibility when containing a pigment; a first laminate and a second laminate having a printed layer formed using the aqueous ink composition; and a packaging material comprising the second laminate. [Brief Description of the Drawings]

[0013]

Figure 1

Figure 2

[0014] Hereinafter, the present invention will be described in detail. The following embodiments are merely illustrative for explaining the present invention, and it is not intended to limit the present invention only to these embodiments. The present invention can be implemented in various modes without departing from its gist. "Unit" is a general term for an atomic group derived from one molecule of the above monomer, which is directly formed by polymerization of the monomer, and an atomic group obtained by chemically converting a part of the above atomic group. Note that "unit based on a monomer" may also be simply referred to as "monomer unit". For example, "unit based on styrene" may also be referred to as "styrene unit". In the present invention, "aqueous" in the aqueous ink composition means containing water as a medium. The proportion of water in the medium of the aqueous ink composition is preferably 50% by mass or more, more preferably 70% by mass or more, and still more preferably 90% by mass or more based on the total mass of the medium. "Medium" means volatile components such as water and organic solvents. The "solid content" of the aqueous ink composition refers to the components excluding the medium among the components contained in the aqueous ink composition, and is the component that will finally form the coating film layer. Specifically, it is measured in accordance with JIS K 5601-1-2:2008. Note that the solid content is also referred to as the non-volatile content. (Meth)acrylic is a general term for "acrylic" and "methacrylic". "Aqueous resin" is a general term for "water-soluble resin" and "water-dispersible resin". Examples of the water-dispersible resin include emulsion type and dispersion type. Note that the medium of the aqueous resin is included in the medium of the aqueous ink composition. The weight average molecular weight of the binder resin is the weight average molecular weight in terms of standard polystyrene molecular weight and is measured by gel permeation chromatography (GPC). The glass transition temperature of the binder resin is measured in accordance with JIS K 7121:2012 as follows. That is, using a differential scanning calorimeter, the glass transition temperature is determined from the intersection of the baseline and the tangent of the endothermic curve in the curve (DSC curve) obtained by heating 10 mg of the binder resin from -100 °C to 160 °C at a rate of 20 °C / min. The acid value of the binder resin is expressed as the number of milligrams of potassium hydroxide required to neutralize acid groups such as carboxyl groups per 1 g of the solid content (non-volatile content) of the sample, and is measured in accordance with JIS K 5601-2-1:1999. The minimum film-forming temperature of the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) and the aqueous emulsion type (meth)acrylic resin (A2) is measured in accordance with JIS K 6828-2:2003. The average particle diameter of the aqueous emulsion type (meth)acrylic resin (A2) is the particle diameter (median diameter: D50) at a cumulative frequency of 50% based on volume, which is calculated from the particle diameter distribution obtained by measuring the particle diameter distribution based on volume by the dynamic light scattering method. The average particle diameter of waxes other than paraffin wax is the particle diameter (median diameter: D50) at a cumulative frequency of 50% based on the number, which is calculated from the particle diameter distribution obtained by measuring the particle diameter distribution based on the number by the Coulter counter method. The Coulter counter method is a method of electrically measuring the particle diameter and particle diameter distribution of particles by passing the particles dispersed in a medium through pores and detecting the change in the electrical signal when the particles pass through. The average particle diameter of paraffin wax is the particle diameter (median diameter: D50) at a cumulative frequency of 50% based on volume, which is calculated from the particle diameter distribution obtained by measuring the particle diameter distribution based on volume by the dynamic light scattering method, and is also referred to as the volume average particle diameter. The penetration of wax is determined in accordance with JIS K 2235. The measurement temperature is 25°C. The symbol "~" indicating a numerical range means that the numerical values described before and after it are included as the lower limit value and the upper limit value.

[0015] ≪Aqueous Ink Composition≫ The aqueous ink composition according to one embodiment of the present invention contains a binder resin (A) and an aqueous medium. The aqueous ink composition may further contain components other than the binder resin (A) and the aqueous medium (hereinafter also referred to as "optional components") as necessary, as long as the effects of the present invention are not impaired.

[0016] <Binder Resin (A)> The binder resin (A) includes an aqueous ethylene-(meth)acrylic acid copolymer resin (A1), an aqueous emulsion-type (meth)acrylic resin (A2), and an aqueous polyurethane resin (A3). Further, within a range not impairing the effects of the present invention, other resins other than the aqueous ethylene-(meth)acrylic acid copolymer resin (A1), the aqueous emulsion-type (meth)acrylic resin (A2), and the aqueous polyurethane resin (A3) may be contained as necessary. The other resins are preferably resins compatible with the aqueous ethylene-(meth)acrylic acid copolymer resin (A1), the aqueous emulsion-type (meth)acrylic resin (A2), and the aqueous polyurethane resin (A3).

[0017] <aqueous ethylene-(meth)acrylic acid copolymer resin (A1)> The aqueous ethylene-(meth)acrylic acid copolymer resin (A1) is a resin having an ethylene unit and a (meth)acrylic acid unit. The carboxy groups derived from the (meth)acrylic acid units in the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) are neutralized with a neutralizing agent. By the above neutralization, the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) becomes an aqueous self-emulsifying resin. That is, the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) is an aqueous dispersion-type ethylene-(meth)acrylic acid copolymer resin. Further, it may have other monomer units according to the required physical properties. The aqueous ink composition of the present embodiment contains the aqueous ethylene-(meth)acrylic acid copolymer resin (A1), whereby the adhesion of the obtained printed coating film to the metal layer is improved. Further, the compatibility with other binder resins in the aqueous ink composition is also likely to be improved.

[0018] The content of the ethylene unit with respect to the total mass of the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) is preferably 50 to 85% by mass, more preferably 60 to 80% by mass, and even more preferably 65 to 75% by mass. When the content of the ethylene unit is less than the above lower limit value, the adhesion of the obtained printed coating film to the metal layer is likely to decrease. When the content of the ethylene unit exceeds the above upper limit value, the stability and pigment dispersibility in the aqueous ink composition are likely to decrease.

[0019] The content of the (meth)acrylic acid unit relative to the total mass of the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) is preferably 15 to 50% by mass, more preferably 20 to 40% by mass, and even more preferably 25 to 35% by mass. When the content of the (meth)acrylic acid unit is less than the above lower limit value, the stability and pigment dispersibility in the aqueous ink composition are likely to decrease. When the content of the (meth)acrylic acid unit exceeds the above upper limit value, the adhesion to the metal layer of the obtained printed coating film is likely to decrease.

[0020] The content of other monomer units relative to the total mass of the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) is preferably 0 to 30% by mass, more preferably 0 to 20% by mass, and even more preferably 0 to 10% by mass. When the content of other monomer units exceeds the above upper limit value, the adhesion to the metal layer of the obtained printed coating film is likely to decrease. Furthermore, the stability and pigment dispersibility in the aqueous ink composition are likely to decrease. Examples of the monomer of other monomer units include (meth)acrylate monomers, carboxy group-containing monomers, and other monomers, which will be described in the aqueous emulsion type (meth)acrylic resin (A2) described later.

[0021] Examples of the neutralizing agent used when neutralizing the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) include organic amines, aqueous ammonia, and alkali metal hydroxides. Specifically, alkylamines such as diethylamine, triethylamine, and ethylenediamine, and alkanolamines such as monoethanolamine, ethyethanolamine, dimethylethanolamine, and diethylethanolamine are mentioned as organic amines, and sodium hydroxide, potassium hydroxide, etc. are mentioned as alkali metal hydroxides. Among them, from the viewpoints of the volatility of the neutralizing agent and the stability in the aqueous ink composition, alkanolamines and aqueous ammonia are preferred, and alkanolamines are more preferred.

[0022] The acid value of the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) is preferably 100 mgKOH / g or more, more preferably 120 mgKOH / g or more, and even more preferably 140 mgKOH / g or more. The upper limit value of the acid value of the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) is not particularly limited. For example, it is preferably 250 mgKOH / g or less, more preferably 230 mgKOH / g or less, and even more preferably 210 mgKOH / g or less. When the acid value of the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) is less than the above lower limit value, the stability and pigment dispersibility in the aqueous ink composition tend to decrease. The acid value of the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) means the acid value before the above water-based conversion (neutralization).

[0023] The glass transition temperature of the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) is preferably 60°C or lower, more preferably 30°C or lower, and even more preferably 10°C or lower. The lower limit value of the glass transition temperature of the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) is not particularly limited. When the glass transition temperature of the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) exceeds the above upper limit value, the adhesion of the obtained printed coating film to the metal layer and the laminating strength tend to decrease.

[0024] The minimum film-forming temperature of the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) at a film thickness of 100 μm is preferably 22°C or lower, more preferably 21°C or lower, and even more preferably 20°C or lower. The lower limit value of the minimum film-forming temperature of the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) at a film thickness of 100 μm is not particularly limited. For example, it is preferably 0°C or higher, more preferably 5°C or higher, and even more preferably 10°C or higher. When the minimum film-forming temperature of the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) at a film thickness of 100 μm exceeds the above upper limit value, the adhesion of the obtained printed coating film to the metal layer and the laminating strength tend to decrease.

[0025] The weight average molecular weight of the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) is preferably from 10,000 to 150,000, more preferably from 20,000 to 100,000, and even more preferably from 30,000 to 80,000.

[0026] As the aqueous ethylene-(meth)acrylic acid copolymer resin (A1), commercially available products may be used. Examples of commercially available products include "Zexen Series" manufactured by Sumitomo Seika Chemical Co., Ltd., "Chemiparle S Series" manufactured by Mitsui Chemicals, Inc., "Aquatex AC Series" manufactured by Japan Coating Resin Co., Ltd., and product names such as "MFHS1279", "MP498345N", "MP4983R", "MP4990R" manufactured by Michelman Japan Co., Ltd. The aqueous ethylene-(meth)acrylic acid copolymer resin (A1) may be used alone or in combination of two or more.

[0027] <aqueous emulsion type (meth)acrylic resin (A2)> The aqueous emulsion type (meth)acrylic resin (A2) is a kind of water-dispersible (meth)acrylic resin and is an emulsion type resin having a core-shell structure. The core part of the aqueous emulsion type (meth)acrylic resin is preferably a hydrophobic (meth)acrylic resin. The shell part is preferably a hydrophilic (meth)acrylic resin. The core part and the shell part may be bonded by a crosslinking agent. In addition, from the viewpoint of excellent blocking resistance of the obtained printed coating film and compatibility with other resins, the aqueous emulsion type (meth)acrylic resin (A2) preferably has styrene-based monomer units in either one or both of the core part and the shell part of the (meth)acrylic resin. The aqueous ink composition of the present embodiment contains the aqueous emulsion type (meth)acrylic resin (A2), whereby the blocking resistance of the obtained printed coating film is improved. Furthermore, the pigment dispersibility in the aqueous ink composition is improved.

[0028] The core part of the aqueous emulsion type (meth)acrylic resin (A2) is a resin containing (meth)acrylate-based monomer units. As the core part of the aqueous emulsion type (meth)acrylic resin, for example, a homopolymer composed of only one kind of (meth)acrylate monomer unit, a copolymer composed of two or more kinds of (meth)acrylate monomer units, and a copolymer composed of (meth)acrylate monomer units and monomer units other than (meth)acrylate monomers can be mentioned. For the shell part of the aqueous emulsion type (meth)acrylic resin (A2), a copolymer containing a carboxy group-containing monomer unit is preferable. As the shell part of the aqueous emulsion type (meth)acrylic resin, for example, a homopolymer composed of only a carboxy group-containing monomer unit, a copolymer composed of two or more kinds of carboxy group-containing monomer units, and a copolymer composed of a carboxy group-containing monomer unit and monomer units other than the carboxy group-containing monomer (for example, (meth)acrylate monomer units) can be mentioned.

[0029] Examples of the (meth)acrylate monomers include alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate; cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate; aryl (meth)acrylates such as phenyl (meth)acrylate; aralkyl (meth)acrylates such as benzyl (meth)acrylate; and hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate. These (meth)acrylate monomers may be used alone or in combination of two or more.

[0030] Examples of the carboxy group-containing monomer include (meth)acrylic acid, maleic acid (maleic anhydride), fumaric acid, and itaconic acid (itaconic anhydride). These carboxy group-containing monomers may be used alone or in combination of two or more.

[0031] Examples of monomers other than (meth)acrylate monomers and carboxy group-containing monomers include styrene monomers such as styrene, α-methylstyrene, and halogenated styrene; conjugated diene compounds such as 1,3-butadiene, isoprene, and chloroprene; aromatic vinyl compounds such as divinylbenzene; vinyl cyanide compounds such as acrylonitrile and methacrylonitrile; acrylamides such as N,N-dimethyl(meth)acrylamide and N,N-diethyl(meth)acrylamide; and unsaturated carboxylic acid esters such as diethyl maleate, dibutyl maleate, dibutyl fumarate, diethyl itaconate, and dibutyl itaconate. These monomers may be used alone or in combination of two or more.

[0032] The polymerization method of the aqueous emulsion type (meth)acrylic resin (A2) is not particularly limited, and examples thereof include radical polymerization, anionic polymerization, and cationic polymerization. In particular, as radical polymerization, bulk polymerization, solution polymerization, emulsion polymerization, suspension polymerization, etc. are included. Among them, emulsion polymerization is preferred. Emulsion polymerization is a method of polymerizing monomers used in polymerization in an aqueous medium in the presence of an emulsifier and a polymerization initiator. The acrylic emulsion resin may be produced by compounding after producing the core part and the shell part respectively. Also, it may be produced by multi-stage emulsion polymerization. The polymerization mode may be any of a random copolymer, a block copolymer, a graft copolymer, etc.

[0033] The aqueous emulsion type (meth)acrylic resin (A2) may be a self-crosslinking type. Examples of additional monomers used as self-crosslinking emulsion-type (meth)acrylic resins include alkoxysilyl group-containing monomers, hydrazine group-containing monomers, epoxy group-containing monomers, methylol group-containing monomers, alkoxymethyl group-containing monomers, adipic acid dihydrazide, diacetone acrylamide, vinyl acetoacetate, allyl acetoacetate, and acetoacetoxyalkyl (meth)acrylates. Examples of epoxy group-containing monomers include glycidyl (meth)acrylate, 2,3-epoxycyclohexyl (meth)acrylate, 3,4-epoxycyclohexyl (meth)acrylate, and allyl glycidyl ether. Examples of acetoacetoxyalkyl (meth)acrylates include acetoacetoxyethyl (meth)acrylate, acetoacetoxypropyl (meth)acrylate, acetoacetoxybutyl (meth)acrylate, and 2,3-di(acetoacetoxy)propyl (meth)acrylate. These monomers may be used alone or in combination of two or more.

[0034] The mass ratio of the core part to the shell part of the aqueous emulsion-type (meth)acrylic resin (A2) (core part: shell part) is preferably 20:80 to 80:20, more preferably 25:75 to 75:25, and even more preferably 30:70 to 70:30. When the mass ratio of the core part to the shell part is such that the core part is more and the shell part is less than the above range, the stability, adhesion to the substrate, and film-forming property decrease. When the mass ratio of the core part to the shell part is such that the core part is less and the shell part is more than the above range, the abrasion resistance, water abrasion resistance, and blocking resistance decrease.

[0035] The acid value of the aqueous emulsion type (meth)acrylic resin (A2) is preferably 150 mgKOH / g or less, more preferably 100 mgKOH / g or less, and even more preferably 60 mgKOH / g or less. The lower limit of the acid value of the aqueous emulsion type (meth)acrylic resin (A2) is not particularly limited, but for example, 5 mgKOH / g or more is preferable, 10 mgKOH / g or more is more preferable, and 15 mgKOH / g or more is even more preferable. If the acid value of the emulsion type (meth)acrylic resin (A2) exceeds the above upper limit value, the stability and water resistance friction resistance are likely to decrease.

[0036] The glass transition temperature of the aqueous emulsion type (meth)acrylic resin (A2) is preferably 50°C or less, more preferably 30°C or less, and even more preferably 10°C or less. The upper limit of the glass transition temperature of the aqueous emulsion type (meth)acrylic resin (A2) is not particularly limited, but for example, -40°C or more is preferable, -30°C or more is more preferable, and -20°C or more is even more preferable. If the glass transition temperature of the aqueous emulsion type (meth)acrylic resin (A2) exceeds the above upper limit value, the adhesion of the obtained printed coating film to the metal layer and the laminate strength are likely to decrease.

[0037] The minimum film-forming temperature of the aqueous emulsion type (meth)acrylic resin (A2) is preferably 50°C or less, more preferably 30°C or less, and even more preferably 10°C or less. The lower limit of the minimum film-forming temperature of the aqueous emulsion type (meth)acrylic resin (A2) is not particularly limited. If the minimum film-forming temperature of the aqueous emulsion type (meth)acrylic resin (A2) exceeds the above upper limit value, the film-forming property, the adhesion to the metal layer, and the laminate strength are likely to decrease.

[0038] The average particle diameter of the aqueous emulsion type (meth)acrylic resin (A2) is preferably 0.3 μm or less, more preferably 0.26 μm or less, and even more preferably 0.2 μm or less. The lower limit of the average particle diameter of the aqueous emulsion type (meth)acrylic resin (A2) is not particularly limited, but for example, 0.01 μm or more is preferable, 0.02 μm or more is more preferable, and 0.03 μm or more is even more preferable. When the average particle diameter of the aqueous emulsion type (meth)acrylic resin (A2) exceeds the above upper limit value, the blocking resistance of the obtained printed coating film is likely to decrease.

[0039] The weight average molecular weight of the aqueous emulsion type (meth)acrylic resin (A2) is preferably 50,000 to 700,000, more preferably 80,000 to 600,000, and even more preferably 100,000 to 500,000.

[0040] As the aqueous emulsion type (meth)acrylic resin (A2), commercially available products may be used. Examples of commercially available products include the product name "Hiros-X series" manufactured by Seiko PMC Co., Ltd., the trade name "Joncryl series" manufactured by BASF Japan Ltd., the product name "Neocryl series" manufactured by Covestro, etc. The aqueous emulsion type (meth)acrylic resin (A2) may be used alone or in combination of two or more.

[0041] <Aqueous polyurethane resin (A3)> The aqueous polyurethane resin (A3) is a resin obtained by making a polyurethane resin having a urethane bond and a carboxy group into an aqueous form. The above polyurethane resin can be produced from a polyvalent isocyanate compound, a polyol compound, and a compound having a carboxy group and at least two active hydrogen-containing groups. For example, by reacting a diisocyanate compound, a polyol compound, a compound having a carboxy group and at least two active hydrogen-containing groups, and an extender as necessary, a urethane prepolymer having a carboxy group in the molecule and an isocyanate group at the terminal is synthesized, and then self-emulsification is carried out by adding a neutralizing agent and water, and it is synthesized by reacting with a diamine compound as necessary. That is, the aqueous polyurethane resin (A3) is an aqueous dispersion type polyurethane resin. The aqueous polyurethane resin (A3) is an aqueous dispersion type resin, similar to the aqueous ethylene-(meth)acrylic acid copolymer resin (A1). However, the aqueous polyurethane resin (A3) is distinguished from the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) in that it has a urethane bond. By including the aqueous polyurethane resin (A3), the blocking resistance of the obtained printed coating film is improved in the aqueous ink composition of the present embodiment.

[0042] The aqueous polyurethane resin (A3) of the present embodiment is not particularly limited, but a polycarbonate-based polyurethane resin, a polyether-based polyurethane resin, and a polyester-based polyurethane resin are preferable. Among them, a polycarbonate-based polyurethane resin and a polyester-based polyurethane resin are more preferable from the viewpoint of excellent compatibility with the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) and the aqueous emulsion type (meth)acrylic resin (A2). Further, a polycarbonate-based polyurethane resin is particularly preferable from the viewpoint of excellent blocking resistance.

[0043] Examples of the polyvalent isocyanate compound include aliphatic, alicyclic, aromatic polyvalent isocyanate compounds, etc. Specific examples of the polyvalent isocyanate compound include aliphatic diisocyanates such as trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, 2,6-diisocyanate methyl caproate; alicyclic diisocyanates such as hydrogenated diphenylmethane diisocyanate, isophorone diisocyanate, norbornene diisocyanate, 1,3-cyclopentane diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate), 4,4'-methylenebis(cyclohexyl isocyanate), methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 1,4-bis(isocyanate methyl)cyclohexane, 1,3-bis(isocyanate methyl)cyclohexane; aromatic diisocyanates such as m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4- or 2,6-tolylene diisocyanate, 4,4'-toluidine diisocyanate, dianisidine diisocyanate, 4,4'-diphenyl ether diisocyanate; multimerized polyvalent isocyanate compounds having an allophanate structure, a nurate structure, a biuret structure, etc. using the above diisocyanates; triisocyanates such as 1,3,5-triisocyanate benzene, 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate hexane; polyisocyanates such as 4,4'-diphenyl dimethylmethane-2,2'-5,5'-tetraisocyanate. These polyisocyanate compounds may be used individually or in combination of two or more thereof.

[0044] Examples of the polyol compound include polyether polyols obtained by polymerizing oxirane compounds such as ethylene oxide, propylene oxide, butylene oxide, and tetrahydrofuran using low molecular weight polyols such as ethylene glycol, propylene glycol, trimethylolpropane, and glycerin as initiators; saturated or unsaturated glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, pentanediol, 3-methyl-1,5-pentanediol, octanediol, 1,9-nonanediol, 1,8-nonanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, bisphenol A, and hydrogenated bisphenol A, and dibasic acids such as adipic acid, maleic acid, fumaric acid, phthalic anhydride, isophthalic acid, terephthalic acid, succinic acid, oxalic acid, malonic acid, glutaric acid, pimelic acid, azelaic acid, sebacic acid, and suberic acid, or acid anhydrides or dimer acids corresponding thereto, and polyester polyols obtained by dehydration condensation thereof; polyolefin polyols such as polyethylene polyol and polypropylene polyol; polyether ester polyols obtained by reacting the above-mentioned dibasic acids or their dialkyl esters with the above-mentioned polyether polyols; and polycarbonate polyols obtained by reacting the above-mentioned glycols with methyl carbonate, diphenyl carbonate, ethylene carbonate, phosgene, or the like. Among them, for the reasons described above, it is preferable to use polycarbonate polyol, polyether polyol, or polyester polyol, and it is more preferable to use polycarbonate polyol. The polyol compound may be used individually or in combination of two or more thereof.

[0045] Compounds having a carboxy group and at least two active hydrogen-containing groups are necessary for introducing the carboxy group required for making the polyurethane resin aqueous. The active hydrogen-containing group is a functional group capable of reacting with an isocyanate group, and typical examples include a hydroxyl group and an amino group. Specifically, 2,2-dimethylolpropionic acid, 2,2-dimethylolbutyric acid, 2,2-dimethylolvaleric acid, diaminopropionic acid, lysine, ornithine, asparagine, glutamine, diaminobenzoic acid, etc. can be mentioned. The compound having a carboxy group and at least two active hydrogen-containing groups may be used alone or in combination of two or more.

[0046] The neutralizing agent is used for neutralizing the carboxy group in the resin in order to make the polyurethane resin aqueous. Specifically, ammonia; organic amines such as monoethylamine, diethylamine, trimethylamine, triethylamine, triisopropylamine, tributylamine, triethanolamine, methyldiethanolamine, monoethanolamine, dimethylethanolamine, diethylethanolamine, morpholine, N-methylmorpholine, 2-amino-2-ethyl-1-propanol; inorganic alkalis such as sodium hydroxide and potassium hydroxide, etc. can be mentioned. Among them, from the viewpoint of drying property, ammonia, trimethylamine, and triethylamine are preferable. The neutralizing agent may be used alone or in combination of two or more.

[0047] Examples of the chain extender include diamine compounds. The diamine compound is used for the purpose of forming a urea bond while extending by reacting with the isocyanate group at the terminal of the obtained urethane prepolymer. Specifically, hydroxyl group-containing diamine compounds such as 2-hydroxyethyl ethylenediamine, 2-hydroxyethyl propylenediamine, di-2-hydroxyethyl ethylenediamine, di-2-hydroxyethyl propylenediamine, 2-hydroxypropyl ethylenediamine, and di-2-hydroxypropyl ethylenediamine; ethylenediamine, propylenediamine, hexamethylenediamine, isophoronediamine, dicyclohexylmethane-4,4'-diamine, etc. may be mentioned. The chain extender may be used alone or in combination of two or more.

[0048] In the synthesis of the aqueous polyurethane resin (A3) used in the present invention, in addition to those described above, if necessary, a chain extender or a reaction terminator other than known diamine compounds may be used. Also, a hydrolyzable silicon group-containing compound may be reacted with the reaction product of the polyisocyanate compound and the polyol compound to introduce a silanol group.

[0049] The glass transition temperature of the aqueous polyurethane resin (A3) is preferably -10 to 130°C, more preferably 20 to 120°C, and even more preferably 40 to 100°C. When the glass transition temperature of the aqueous polyurethane resin (A3) is at or above the above lower limit value, the blocking resistance of the obtained printed coating film is likely to be improved. When the glass transition temperature of the aqueous polyurethane resin (A3) is at or below the above upper limit value, the adhesion to the metal layer of the obtained printed coating film is likely to be improved.

[0050] The weight average molecular weight of the aqueous polyurethane resin (A3) is preferably 3,000 to 100,000, more preferably 7,000 to 90,000, and even more preferably 20,000 to 80,000. When the weight average molecular weight of the aqueous polyurethane resin (A3) is less than the above lower limit value, the blocking resistance and laminating strength of the obtained printed coating film are likely to decrease. When the weight average molecular weight of the aqueous polyurethane resin (A3) exceeds the above upper limit value, the adhesion to the metal layer of the obtained printed coating film is likely to decrease.

[0051] <Other resins> In the aqueous ink composition of the present invention, various other aqueous resins can be used in combination as long as the effects of the present invention are not impaired, according to various required physical properties. The aqueous resins that can be used in combination are not particularly limited. For example, any of water-soluble type, emulsion type, and dispersion type may be used. Examples of the resin include water-soluble (meth)acrylic resin, (meth)acrylic urethane resin, polyolefin resin, polyester resin, and the like.

[0052] <Composition of binder resin (A)> The content of the solid component of the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) relative to the total mass of the solid component of the binder resin (A) is 15 to 50% by mass, preferably 18 to 47% by mass, and more preferably 22 to 42% by mass. When the content of the solid component of the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) is less than the above lower limit value, the adhesion of the obtained printed coating film to the metal layer and the laminating strength are likely to decrease. When the content of the solid component of the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) exceeds the above upper limit value, the blocking resistance of the obtained printed coating film is likely to decrease.

[0053] The content of the solid component of the aqueous emulsion type (meth)acrylic resin (A2) relative to the total mass of the solid component of the binder resin (A) is 10 to 45% by mass, preferably 14 to 43% by mass, and more preferably 16 to 41% by mass. When the content of the solid component of the aqueous emulsion type (meth)acrylic resin (A2) is less than the above lower limit value, the pigment dispersibility in the aqueous ink composition is likely to decrease. Also, the blocking resistance of the obtained printed coating film is likely to decrease. When the content of the solid component of the aqueous emulsion type (meth)acrylic resin (A2) exceeds the above upper limit value, the adhesion of the obtained printed coating film to the metal layer and the laminating strength are likely to decrease.

[0054] The content of the solid component of the aqueous polyurethane resin (A3) relative to the total mass of the solid component of the binder resin (A) is 25 to 60% by mass, preferably 28.5 to 58% by mass, and more preferably 30 to 55% by mass. When the content of the solid component of the aqueous polyurethane resin (A3) is less than the above lower limit value, the blocking resistance of the obtained printed coating film tends to decrease. When the content of the solid component of the aqueous polyurethane resin (A3) exceeds the above upper limit value, the adhesion to the metal layer of the obtained printed coating film tends to decrease.

[0055] The mass ratio of the content of the solid component of the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) to the content of the solid component of the aqueous emulsion type (meth)acrylic resin (A2) is preferably 0.30 to 2.50, more preferably 0.35 to 2.10, and even more preferably 0.45 to 1.80.

[0056] The mass ratio of the content of the solid component of the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) to the content of the solid component of the aqueous polyurethane resin (A3) is preferably 0.41 to 2.00, more preferably 0.45 to 1.60, and even more preferably 0.50 to 1.30.

[0057] The mass ratio of the content of the solid component of the aqueous emulsion type (meth)acrylic resin (A2) to the content of the solid component of the aqueous polyurethane resin (A3) is preferably 0.15 to 1.40, more preferably 0.25 to 1.30, and even more preferably 0.30 to 1.20.

[0058] The mass ratio of the content of the solid component of the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) to the total content of the solid components of the aqueous emulsion type (meth)acrylic resin (A2) and the aqueous polyurethane resin (A3) is preferably 0.20 to 1.20, more preferably 0.25 to 0.90, and even more preferably 0.30 to 0.80.

[0059] The mass ratio of the solid content of the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) and the aqueous polyurethane resin (A3) to the solid content of the aqueous emulsion type (meth)acrylic resin (A2) is preferably 0.15 to 1.40, more preferably 0.25 to 1.30, and even more preferably 0.30 to 1.20.

[0060] The mass ratio of the solid content of the aqueous polyurethane resin (A3) to the total solid content of the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) and the aqueous emulsion type (meth)acrylic resin (A2) is preferably 0.35 to 1.60, more preferably 0.40 to 1.40, and even more preferably 0.45 to 1.20.

[0061] The total solid content of the aqueous ethylene-(meth)acrylic acid copolymer resin (A1), the aqueous emulsion type (meth)acrylic resin (A2), and the aqueous polyurethane resin (A3) with respect to the total mass of the solid content of the binder resin (A) is preferably 80 to 100% by mass, more preferably 90 to 100% by mass, and even more preferably 95 to 100% by mass.

[0062] The binder resin (A) preferably does not contain a non-aqueous resin. A non-aqueous resin means a resin other than a water-soluble resin and a water-dispersible resin. The solid content of the non-aqueous resin with respect to the total mass of the solid content of the binder resin (A) is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 0% by mass.

[0063] <aqueous medium> Examples of the aqueous medium include water; a mixed solvent of water and an organic solvent. The organic solvent is not particularly limited as long as it is soluble in water. Examples thereof include alcohol solvents such as methanol, ethanol, n-propanol, i-propanol, n-butanol, and i-butanol; ketone solvents such as acetone; and glycol ether solvents such as propylene glycol monomethyl ether. The organic solvent may be used alone or in combination of two or more. As the aqueous medium used in the aqueous ink composition of the present invention, from the viewpoints of health hazards and reduction of VOCs, and the drying property after printing, the content of the organic solvent in the aqueous medium is preferably 1 to 50% by mass, more preferably 1 to 20% by mass, and even more preferably 1 to 10% by mass.

[0064] <Optional component> The aqueous ink composition of the present embodiment may contain, if necessary, a binder resin (A) and optional components other than the aqueous medium. Examples of the optional components include pigments, waxes, thickeners, anti-settling agents, ultraviolet absorbers, antioxidants, leveling agents, viscoelasticity modifiers, surface tension modifiers, rheology modifiers, light stabilizers, defoamers, lubricants, dispersants, stabilizers, pH adjusters, fillers, fungicides, antistatic agents, metal fine particles, magnetic powders, and the like. The optional components may be used alone or in combination of two or more.

[0065] (Pigment) The aqueous ink composition of the present embodiment may be a colored ink containing a pigment or a medium not containing a pigment. As the pigment, known pigments as colorants can be used, and examples include organic pigments and inorganic pigments. Examples of the organic pigments include azo pigments such as monoazo and condensed azo; threne pigments such as anthraquinone, perinone, perylene, and thioindigo; phthalocyanine pigments such as phthalocyanine blue and phthalocyanine green; quinacridone pigments; dioxazine pigments; isoindolinone pigments; pyrrolopyrrole pigments; aniline black; and organic fluorescent pigments. Examples of the inorganic pigments include natural products such as clay, barite, mica, and talc; ferrocyanides such as ultramarine, sulfides such as zinc sulfide; sulfates such as barium sulfate; oxides such as chromium oxide, zinc white, titanium oxide, and iron oxide; hydroxides such as aluminum hydroxide; silicates such as calcium silicate and ultramarine; carbonates such as calcium carbonate and magnesium carbonate; carbon such as carbon black and graphite; metal powders such as aluminum powder, bronze powder, and zinc powder; and fired pigments. The pigment may be used alone or in combination of two or more kinds.

[0066] (Wax) The aqueous ink composition of the present embodiment may further contain wax for the purpose of improving the abrasion resistance and blocking resistance of the printed coating film. As the wax, an aqueous wax is preferable. An aqueous wax is a wax dispersed in water to form an emulsion or dispersion. The wax dispersed in water may be a conventionally known wax, and examples thereof include polyethylene wax, polypropylene wax, modified paraffin wax, carnauba wax, and polytetrafluoroethylene wax. Among them, it is preferable to use polyethylene wax and polypropylene wax. The wax may be used alone or in combination of two or more kinds.

[0067] The average particle diameter of the wax is preferably 0.1 to 15 μm, more preferably 0.5 to 12 μm, and even more preferably 1 to 10 μm. When the average particle diameter of the wax is equal to or greater than the above lower limit value, the friction resistance and blocking resistance are likely to be improved. When the average particle diameter of the wax is equal to or less than the above upper limit value, the printability and color development are likely to be improved.

[0068] The penetration of the wax is preferably 20 or less, more preferably 15 or less, and even more preferably 12 or less. The lower limit value of the penetration of the wax is not particularly limited, but for example, it is preferably 0.1 or more, more preferably 1 or more, and even more preferably 2 or more. When the penetration of the wax exceeds the above upper limit value, the blocking resistance of the obtained printed coating film is likely to decrease.

[0069] <Composition of the aqueous ink composition> The content of the solid component of the binder resin (A) with respect to the total mass of the aqueous ink composition is preferably 10 to 50% by mass, more preferably 14 to 40% by mass, and even more preferably 18 to 35% by mass. The content of the solid component of the binder resin (A) with respect to the total mass of the solid components of the aqueous ink composition is preferably 40 to 100% by mass, more preferably 45 to 100% by mass, and even more preferably 50 to 99.5% by mass. When the content of the solid component of the binder resin (A) is less than the above lower limit value, the adhesion of the obtained printed coating film to the metal layer and the lamination strength are likely to decrease. In addition, the pigment dispersibility in the aqueous ink composition is likely to decrease. When the content of the solid component of the binder resin (A) exceeds the above upper limit value, the fluidity of the aqueous ink composition is likely to decrease.

[0070] The content of the aqueous medium with respect to the total mass of the aqueous ink composition is preferably 20 to 90% by mass, more preferably 30 to 85% by mass, and even more preferably 40 to 80% by mass. When the content of the aqueous medium is less than the above lower limit value, the fluidity and printability of the aqueous ink composition are likely to decrease. When the content of the aqueous medium exceeds the above upper limit value, the blocking resistance and drying property of the obtained printed coating film are likely to decrease.

[0071] The aqueous ink composition preferably does not contain a medium other than the aqueous medium. A medium other than the aqueous medium means an organic solvent that is not miscible with water. The content of the organic solvent not dissolved in water with respect to 100 parts by mass of the aqueous medium is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, even more preferably 5 parts by mass, and may also be 0 parts by mass.

[0072] When the aqueous ink composition contains a pigment, the content of the pigment with respect to the total mass of the aqueous ink composition is preferably 1 to 50% by mass, more preferably 1 to 40% by mass, and even more preferably 1 to 30% by mass. When the content of the pigment is less than the above lower limit value, the hiding power and color development of the obtained printed coating film are likely to decrease. When the content of the pigment exceeds the above upper limit value, the adhesion of the obtained printed coating film to the metal layer is likely to decrease. In addition, the fluidity of the aqueous ink composition is likely to decrease.

[0073] When the aqueous ink composition contains wax, the content of the solid component of the wax is preferably 0.01 to 5% by mass, more preferably 0.05 to 3% by mass, and still more preferably 0.1 to 1% by mass with respect to the total mass of the aqueous ink composition. When the aqueous ink composition contains wax, the content of the solid component of the wax is preferably 0.05 to 10% by mass, more preferably 0.1 to 5% by mass, and still more preferably 0.5 to 3% by mass with respect to the total mass of the solid components of the aqueous ink composition. If the content of the wax is less than the above lower limit, the abrasion resistance and blocking resistance of the obtained printed coating film tend to decrease. If the content of the wax exceeds the above upper limit, the printability and color developability tend to decrease.

[0074] When the aqueous ink composition contains a binder resin (A), an aqueous medium, a pigment, and optional components other than wax, the content of these optional components is not particularly limited as long as the effects of the present invention are not impaired. For example, with respect to the total mass of the solid components of the aqueous ink composition, the content of the solid components of the above optional components is preferably more than 0% by mass and 20% by mass or less, more preferably more than 0% by mass and 15% by mass or less, and still more preferably more than 0% by mass and 10% by mass or less. Note that the content of the above optional components may be 0% by mass.

[0075] <Manufacturing method> The aqueous ink composition of the present embodiment can be obtained, for example, by dissolving or dispersing an aqueous ethylene-(meth)acrylic acid copolymer resin (A1), an aqueous emulsion type (meth)acrylic resin (A2), an aqueous polyurethane resin (A3), and optional components as required in an aqueous medium. The mixing method of each component is not particularly limited, and each component can be mixed by various methods. The method of dissolving or dispersing each component in an aqueous medium is not particularly limited and can be carried out using a known disperser. Examples of the disperser include a paint shaker, a ball mill, an attritor, a sand mill, a bead mill, a dyno mill, a roll mill, an ultrasonic mill, a high-pressure collision disperser, and the like. At this time, one kind of disperser may be used for one or a plurality of dispersion treatments, or two or more kinds of dispersers may be used in combination for a plurality of dispersion treatments.

[0076] <Function and effect> The aqueous ink composition of the present embodiment described above contains the aqueous ethylene-(meth)acrylic acid copolymer resin (A1), the aqueous emulsion type (meth)acrylic resin (A2), the aqueous polyurethane resin (A3), and the aqueous medium described above, thereby being excellent in the adhesion and blocking resistance of the obtained printed coating film to the metal layer. Further, when a pigment is contained in the aqueous ink composition, the pigment dispersibility is also excellent. From the results of the examples described later, it is considered that the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) contributes to the improvement of the adhesion of the obtained printed coating film to the metal layer. It is also considered to contribute to the improvement of the compatibility with other resins. Further, the aqueous emulsion type (meth)acrylic resin (A2) is considered to contribute to the improvement of the blocking resistance of the obtained printed coating film and the improvement of the pigment dispersibility of the aqueous ink composition. Furthermore, the aqueous polyurethane resin (A3) is considered to contribute to the improvement of the blocking resistance of the obtained printed coating film.

[0077] In an oil-based ink composition, studies have been conducted to enhance the adhesion to a metal layer. However, in order to improve the adhesion of the obtained printed coating film to the metal layer, an operation of baking at a high temperature is required. On the other hand, in the aqueous ink composition of the present embodiment, the obtained printed coating film has high adhesion to the metal layer even without baking (that is, even at room temperature). The reason is considered as follows. As factors of the printing coating film that contribute to the adhesion to the metal layer, there are roughly two: hydrogen bonding with hydroxyl groups on the metal layer surface and van der Waals forces. In either case, it is important that the resin contributing to the adhesion is uniformly and sufficiently close to the metal layer surface. For this purpose, it is preferable that the resin has a lower surface tension than the metal layer surface and excellent wettability. Furthermore, it is also preferable that the SP (Solubility Parameter) values of the resin and the metal layer are close. In the present invention, it is considered that the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) plays the role of the resin. That is, since the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) has the above properties and further has physical adhesiveness, it is considered that these contribute to the adhesion to the metal layer. On the other hand, when the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) is not used, it is considered that an operation of increasing fluidity and uniformly and sufficiently approaching the metal layer surface by melting the binder resin in the printing coating film by baking is necessary.

[0078] Also, for the aqueous emulsion type (meth)acrylic resin (A2) to be stabilized in an aqueous medium as an emulsion, the shell part is very hydrophilic. This hydrophilic group adsorbs on the pigment surface where it is dispersed, and can prevent the aggregation of pigments. Therefore, it is considered that the pigment dispersibility of the aqueous ink composition is improved. Furthermore, based on the above theory, the smaller the average particle diameter of the aqueous emulsion type (meth)acrylic resin (A2), the larger the surface area, and the higher the ratio of the shell part that can interfere with the pigment surface. Therefore, it is considered to be more excellent in pigment dispersibility. Note that when a water-soluble (meth)acrylic resin is used instead of the aqueous emulsion type (meth)acrylic resin (A2), although the pigment dispersibility is excellent, the physical properties of the printing coating film tend to be inferior. To exhibit excellent blocking resistance, the balance between the flexibility and hardness of the printing coating film is important. Since the aqueous emulsion type (meth)acrylic resin (A2) can greatly contribute to the hardness of the printing coating film, it is considered to be excellent in blocking resistance. Furthermore, the aqueous polyurethane resin (A3) has a soft segment mainly composed of a long-chain polyol, and the flexibility derived from the soft segment can greatly contribute to the important flexibility for expressing the above-described antiblocking property. Therefore, it is considered to have excellent antiblocking property. Furthermore, it also has a hard segment mainly composed of isocyanate, short-chain polyol, and short-chain amine, and the cohesive force derived from the hard segment is also considered to affect the strength of the printed coating film. In particular, by using a carbonate-based one, it is considered to be more excellent in antiblocking property. Note that the use of the three resins of the aqueous ethylene-(meth)acrylic acid copolymer resin (A1), the aqueous emulsion-type (meth)acrylic resin (A2), and the aqueous polyurethane resin (A3) does not necessarily result in the expression of the above functions. The inventors of the present application have found that by containing specific amounts of the respective resins, all of the above functions are expressed.

[0079] <Use> The aqueous ink composition of the present embodiment may be used as a first laminate obtained by printing on a substrate having a metal layer to form an ink layer, or may be used as a second laminate provided with a resin layer or an adhesive layer and a resin layer on the surface of the printed layer of the first laminate. In the case of the second laminate having an adhesive layer and a resin layer, they are laminated in the order of the printed layer, the adhesive layer, and the resin layer. Examples of the substrate include a metal foil and a metal vapor deposition film. The laminate having the above configuration using the substrate is suitable as, for example, a packaging material.

[0080] FIG. 1 shows an example of a first laminate according to an embodiment of the present invention. FIG. 2 shows an example of a second laminate according to an embodiment of the present invention. Note that the dimensional ratios in FIGS. 1 and 2 are different from the actual ones for convenience of explanation. The first laminate 10 in FIG. 1 is a printed matter including a substrate 11 and a printed layer 12 provided on one surface of the substrate 11. Hereinafter, the printed layer means a printed coating film. The second laminate 20 in Fig. 2 is a printed matter including a base material 21, a first printing layer 22 provided on one surface of the base material 21, and a resin layer 23 provided on the surface of the first printing layer opposite to the base material.

[0081] The base materials 11 and 21 are metal foils or metal vapor-deposited films. An adhesive layer may be located between the first printing layer 22 and the resin layer 23.

[0082] Examples of the metal foil include soft aluminum foil and hard aluminum foil. As for the metal vapor-deposited film, it is sufficient that the entire surface or a part of a known plastic film is subjected to metal vapor deposition treatment. Examples of the film include those obtained by vapor-depositing a metal on plastic films such as polyolefin (polyethylene (PE), milky white polyethylene, polypropylene (PP), etc.), polyester (e.g., polyethylene terephthalate (PET), etc.), polystyrene (PS), stretched polypropylene (OPP), polyamide (NY), etc. These films may be used alone or in combination of two or more.

[0083] Examples of the adhesive used for the adhesive layer include ethylene-(meth)acrylic acid copolymer resin, a mixture of polyol and isocyanate curing agent, polyethyleneimine-based resin, polybutadiene-based resin, or modified products thereof. Examples of the resin used for the resin layer include polyethylene, polypropylene, etc.

[0084] The printing method may be a known printing method and is not particularly limited. For example, known coating methods such as gravure printing method, flexographic printing method, brush coating, gravure coater method, die coater method, bar coater method, spray coating method, flow coating method, dip coating method, spin coating method, and curtain coating method can be used. Among these, the gravure printing method and the flexographic printing method are more preferable due to high quality and productivity.

[0085] In the production of the second laminate, the formation of the resin layer is preferably carried out by the extrusion lamination method. The extrusion lamination method is a method of extruding a resin melted at a high temperature onto the surface of the printing layer of the first laminate to form a resin layer. In the case where the adhesion between the printing layer and the resin layer is not sufficient, an adhesive may be applied in advance onto the printing layer of the first laminate to form an adhesive layer, and the resin melted at a high temperature may be extruded onto the surface of the adhesive layer to form a resin layer.

[0086] <Packaging material> The packaging material of this embodiment includes the above-mentioned second laminate. The packaging material of this embodiment can be used as various labels such as plastic labels attached to packaging containers for beverages, foods such as side dishes and boxed lunches, and daily necessities such as cosmetics. Among them, it is particularly suitable as a label for food and beverage products.

Examples

[0087] Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

[0088] [Raw materials used] <Aqueous ethylene-(meth)acrylic acid copolymer resin (A1)> · A1-1: Ethylene-(meth)acrylic acid copolymer resin, solid content: 25% by mass, acid value: 170 mgKOH / g, glass transition temperature: less than 10 °C, average particle diameter: 8.7 nm, minimum film-forming temperature at a film thickness of 100 μm: 17 °C. · A1-2: Ethylene-(meth)acrylic acid copolymer resin, solid content: 25% by mass, acid value: 62.2 mgKOH / g, minimum film-forming temperature at a film thickness of 100 μm: 25 °C.

[0089] <Aqueous emulsion type (meth)acrylic resin (A2)> · A2-1: Styrene-(meth)acrylic resin, manufactured by Seiko PMC Co., Ltd., trade name "Hiros-X RE-218", solid content: 40% by mass, acid value: 49 mgKOH / g, glass transition temperature: 0 °C, average particle diameter: 0.035 μm, minimum film-forming temperature: less than 5 °C. ·A2-2: Styrene-(meth)acrylic resin, manufactured by Seiko PMC Co., Ltd., product name "Hiros-X PE-1304", solid content: 33% by mass, acid value: 142 mgKOH / g, glass transition temperature: 9 °C, average particle diameter: 0.25 μm, minimum film formation temperature: less than 5 °C. ·A2-3: Styrene-(meth)acrylic resin, manufactured by Seiko PMC Co., Ltd., product name "Hiros-X TE-1124", solid content: 60% by mass, acid value: 25 mgKOH / g, glass transition temperature: -21 °C, average particle diameter: 0.33 μm, minimum film formation temperature: less than 5 °C. ·A2-4: (Meth)acrylic resin, manufactured by Seiko PMC Co., Ltd., product name "Hiros-X UE-1051", solid content: 42.5% by mass, acid value: 62 mgKOH / g, glass transition temperature: -24 °C, average particle diameter: 0.05 μm, minimum film formation temperature: less than 5 °C.

[0090] <Waterborne polyurethane resin (A3)> ·A3-1: Polycarbonate-based polyurethane resin, manufactured by DSM NeoResins, product name "NeoRez R-9603", solid content: 33% by mass. ·A3-2: Polyester-based polyurethane resin, manufactured by Mitsui Chemicals, Inc., product name "Takelac W-5030", solid content: 30% by mass. ·A3-3: Polyether-based polyurethane resin, manufactured by Arakawa Chemical Industries, Ltd., product name "Urianol W321", solid content: 35% by mass.

[0091] <Waterborne medium (B)> ·B1: Amino alcohol, manufactured by Nippon Emulsion Co., Ltd., product name "Amino alcohol 2Mabs". ·B2: Isopropyl alcohol. ·B3: Tap water.

[0092] <Optional component (C)> (Pigment) ·C1-1: C.I.Pigment Black 7, manufactured by Orion Engineered Carbons Co., Ltd., product name "Special Black 4A". · C1-2: C.I. Pigment Red 185, manufactured by Hoechst, trade name "Nopalm Carmine HF4C".

[0093] · C2: Wax, manufactured by Mitsui Chemicals, Inc., trade name "Chemparl W-500", solid content: 40% by mass, penetration: 10, average particle size: 2.5 μm. · C3: Dispersant, manufactured by BYK, trade name "DISPERBYK-190", solid content: 40% by mass.

[0094] [Examples 1 to 13, Comparative Examples 1 to 6] <Preparation of Aqueous Ink Composition> According to the compositions shown in Tables 1 and 2, an aqueous ethylene-(meth)acrylic acid copolymer resin (A1), an aqueous emulsion type (meth)acrylic resin (A2), an aqueous polyurethane resin (A3), an aqueous medium, and optionally a pigment and optional components were mixed. Then, the obtained mixture was kneaded with a paint shaker to obtain an aqueous ink composition. The unit of the numerical values of each component in Tables 1 and 2 is parts by mass, and except for the aqueous medium, it means the amount of the solid content. Also, the blanks in Tables 1 and 2 mean that the component was not blended. Further, the total of (A) means the total solid content of the binder resin (A), (A1) / (A) means the content of the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) relative to the total mass of the solid content of the binder resin (A), (A2) / (A) means the content of the aqueous emulsion type (meth)acrylic resin (A2) relative to the total mass of the solid content of the binder resin (A), and (A3) / (A) means the content of the aqueous polyurethane resin (A3) relative to the total mass of the solid content of the binder resin (A).

[0095] <Preparation of Printed Matter> The prepared aqueous ink composition was diluted with water so that the viscosity at 20 °C measured using a Zahn cup #3 was 18 seconds, and an ink for printing was prepared. Using a gravure printing press equipped with a Helio 175 lines / inch gravure engraving plate (manufactured by Matsuo Sangyo Co., Ltd., product name "K Printing Proofer") or an anilox roll with a cell volume of 13 cc, the prepared printing ink was applied to the matte surface of an aluminum foil (manufactured by Toyo Aluminum Co., Ltd., product name "Aluminum Foil C", thickness: 20 μm). Thereafter, drying was carried out at 20 °C for 2 hours to produce a printed matter (first laminate). Note that Example 13 was printed by flexographic printing, and the examples other than Example 13 were printed by gravure printing.

[0096] <Production of laminate> On the surface of the ink layer of the produced printed matter, an anchor coat agent (manufactured by Dainichi Seiko Kogyo Co., Ltd., product name "Seikadine 5000W") was applied at a dry coating amount of 0.6 g / m 2 using a gravure printing press (manufactured by Matsuo Sangyo Co., Ltd., product name "K Printing Proofer") so as to be, and then dried with a dryer for 10 seconds to form an anchor coat layer (adhesive layer). An LLDPE (manufactured by Nippon Polyethylene Co., Ltd., product name "Kernel KC570S") was melted and extruded onto the formed anchor coat layer to form a resin layer on the above adhesive layer, and a laminate (second laminate) was obtained.

[0097] <Evaluation of adhesion to aluminum foil> After a cellophane adhesive tape (manufactured by Nichiban Co., Ltd.) was attached to the surface of the printed coating film of the obtained printed matter, this cellophane tape was quickly peeled off, and the state of the printed coating film remaining on the aluminum foil was visually confirmed, and the adhesion of the printed coating film to the aluminum foil was evaluated according to the following evaluation criteria. 3 to 5 are considered qualified. 5: The printed coating film has not peeled off at all. 4: The ratio of the area of the peeled printed coating film to the total area of the printed coating film is more than 0% and 5% or less. 3: The ratio of the area of the peeled printed coating film to the total area of the printed coating film is more than 5% and 20% or less. 2: The ratio of the area of the peeled printed coating film to the total area of the printed coating film is more than 20% and 50% or less. 1: The ratio of the area of the peeled printed coating film to the total area of the printed coating film is more than 50%.

[0098] <Evaluation of pigment dispersibility> The state of the prepared aqueous ink composition was visually confirmed, and the pigment dispersibility was evaluated according to the following evaluation criteria. 3 to 5 is considered qualified. 5: It has good fluidity. 4: Slight thickening was confirmed. 3: Thickening was confirmed. 2: It has thixotropy and the fluidity is partially impaired. 1: Gelation was confirmed.

[0099] <Evaluation of blocking resistance> The printed surface (printed coating film) of the printed matter immediately after production (before drying) and the paper (test piece) were overlapped, and a load of 7 kg / cm 2 was applied, and it was stored in a constant temperature chamber at 40 °C and 50% humidity for 24 hours. Then, the test piece was peeled off, and the blocking resistance was evaluated according to the evaluation criteria shown below. 3 to 5 is considered qualified. 5: There is no ink transfer to the non-printed surface. 4: The ink transfer to the non-printed surface is more than 0% and 5% or less with respect to the total area of the printed coating film. 3: The ink transfer to the non-printed surface is more than 5% and 20% or less with respect to the total area of the printed coating film. 2: The ink transfer to the non-printed surface is more than 20% and 50% or less with respect to the total area of the printed coating film. 1: The ink transfer to the non-printed surface is more than 50% with respect to the total area of the printed coating film.

[0100] <Evaluation of laminating strength> The obtained laminate was cut into strips with a width of 15 mm, and a T-peel test was carried out using a tensile testing machine (manufactured by A&D Company, Ltd., trade name "Tensilon RTG-1225") under the condition of a tensile speed of 300 mm / min to measure the T-peel strength between the printed coating film and LLDPE, and the lamination strength was evaluated according to the criteria shown below. 5: The T-peel strength is 2.0 N or more. 4: The T-peel strength is 1.5 N or more and less than 2.0 N. 3: The T-peel strength is 1.0 N or more and less than 1.5 N. 2: The T-peel strength is 0.5 N or more and less than 1.0 N. 1: The T-peel strength is less than 0.5 N.

[0101] <Evaluation of Compatibility> According to the compositions shown in Tables 1 and 2, only the binder resin (A) was blended and diluted with water so that the viscosity at 20°C measured using a Zahn cup #3 was 18 seconds. Immediately after that and after storage at 20°C for 24 hours, the state of the mixed varnish of the binder resin (A) was confirmed, and the compatibility was evaluated according to the criteria shown below. 3: No increase in viscosity was observed either immediately after or after storage. 2: A slight increase in viscosity was observed immediately after, but no further increase in viscosity was observed after storage. 1: An increase in viscosity was confirmed both immediately after and after storage.

[0102]

Table 1

[0103]

Table 2

[0104] In Examples 1 to 13 of the present invention, when the aqueous ink composition contains a pigment, it was found that the pigment dispersibility was excellent. Also, the compatibility was excellent. Furthermore, the printed coating film obtained using the aqueous ink composition was excellent in adhesion to aluminum foil, blocking resistance, and laminate strength. The printed coating film obtained using the aqueous ink composition of Comparative Example 4 that does not contain the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) was inferior in adhesion to aluminum foil. Also, the aqueous ink composition was inferior in compatibility. The aqueous ink composition of Comparative Example 5 that does not contain the aqueous emulsion type (meth)acrylic resin (A2) was inferior in pigment dispersibility when containing a pigment. Furthermore, the printed coating film obtained using the aqueous ink composition was inferior in blocking resistance. The printed coating film obtained using the aqueous ink composition of Comparative Example 6 that does not contain the aqueous polyurethane resin (A3) was inferior in blocking resistance. Note that Comparative Examples 1 to 3 are aqueous ink compositions containing the aqueous ethylene-(meth)acrylic acid copolymer resin (A1), the aqueous emulsion type (meth)acrylic resin (A2), and the aqueous polyurethane resin (A3), but depending on the respective contents, it was found that the physical properties were inferior. Specifically, the printed coating film obtained using the aqueous ink composition of Comparative Example 1 in which the solid content of the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) exceeds 50% by mass was inferior in blocking resistance. Conversely, the printed coating film obtained using the aqueous ink composition of Comparative Example 2 in which the solid content of the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) is less than 15% by mass (and the solid content of the aqueous emulsion type (meth)acrylic resin (A2) exceeds 45% by mass) was inferior in adhesion to aluminum foil and laminate strength. Also, the compatibility of the aqueous ink composition was inferior. The printed coating film obtained using the aqueous ink composition of Comparative Example 3 in which the solid content of the aqueous emulsion type (meth)acrylic resin (A2) is less than 10% by mass and the solid content of the aqueous polyurethane resin (A3) exceeds 60% by mass was inferior in blocking resistance. Also, the aqueous ink composition was inferior in pigment dispersibility when containing a pigment. From the above, it is considered that the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) contributes to improving the adhesion of the obtained printed coating film to the metal layer and the compatibility with other resins. Further, the aqueous emulsion type (meth)acrylic resin (A2) is considered to contribute to improving the blocking resistance of the obtained printed coating film and the pigment dispersibility of the aqueous ink composition. Furthermore, the aqueous polyurethane resin (A3) is considered to contribute to improving the blocking resistance of the obtained printed coating film.

Industrial Applicability

[0105] The aqueous ink composition of the present invention achieves an excellent level in all of the adhesion to the metal layer, the pigment dispersibility, and the blocking resistance, and is useful as an ink for packaging materials.

Explanation of Symbols

[0106] 10 First laminate 11 Substrate 12 Printing layer 20 Second laminate 21 Substrate 22 First printing layer 23 Resin layer

Claims

1. An aqueous ink composition comprising a binder resin (A) and an aqueous medium, wherein the binder resin (A) comprises an aqueous ethylene-(meth)acrylic acid copolymer resin (A1), an aqueous emulsion type (meth)acrylic resin (A2), and an aqueous polyurethane resin (A3), and the content of the solid content of the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) relative to the total mass of the solid content of the binder resin (A) is 15 to 50% by mass, the content of the solid content of the aqueous emulsion type (meth)acrylic resin (A2) is 10 to 45% by mass, and the content of the solid content of the aqueous polyurethane resin (A3) is 25 to 60% by mass.

2. The aqueous ink composition according to Claim 1, wherein the minimum film-forming temperature of the aqueous ethylene-(meth)acrylic acid copolymer resin (A1) at a film thickness of 100 μm is 22°C or lower.

3. The aqueous ink composition according to Claim 1, wherein the average particle diameter of the aqueous emulsion type (meth)acrylic resin (A2) is 0.3 μm or less.

4. The aqueous ink composition according to Claim 1, wherein the aqueous polyurethane resin (A3) is a polycarbonate-based polyurethane resin.

5. The aqueous ink composition according to Claim 1, wherein the aqueous emulsion type (meth)acrylic resin (A2) has a unit based on styrene.

6. The aqueous ink composition according to Claim 1, wherein the average particle diameter of the aqueous emulsion type (meth)acrylic resin (A2) is 0.2 μm or less.

7. The aqueous ink composition according to any one of Claims 1 to 6, which is for flexographic or gravure printing.

8. A first laminate comprising a substrate and a printed layer formed on one surface of the substrate using the aqueous ink composition according to Claim 7, wherein the substrate is a metal foil or a metal vapor deposition film.

9. A second laminate in which a resin layer, or an adhesive layer and a resin layer are laminated on the surface of the printed layer in the first laminate according to Claim 8.

10. A packaging material comprising the second laminate according to Claim 9.

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