Foaming ink composition for metal printing, method for manufacturing metal printed matter, and metal printed matter

Abstract

To provide a foaming ink composition for metal printing, a method for manufacturing a metal printed matter, and a metal printed matter in which excellent matte feel by irregularity can be imparted at a desired position of a metal printing medium, and misting, scumming or blanket residue in printing is hard to occur.SOLUTION: A foaming ink composition for metal printing contains resin, solvent, pigment, extender pigment and thermally expandable microcapsule, and the extender pigment contains talc and silica.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a foamable ink composition for metal printing, a method for producing a metal print, and a metal print. More specifically, the present invention relates to a foamable ink composition for metal printing, a method for producing a metal print, and a metal print that can impart an excellent matte finish due to unevenness to desired positions on a metal print medium and are less likely to cause misting or plate or blanket residue during printing. [Background technology]

[0002] Conventionally, methods have been developed for decorating the surface of metal printing media such as beverage cans by creating fine irregularities. For example, there is a method using a matte overprint varnish containing a matting agent. However, while this method can decorate the entire surface of the metal printing media, it cannot decorate only a portion of the metal printing media. Therefore, ink compositions containing thermally expandable microcapsules (foaming agents) that expand when heated have been developed (for example, Patent Document 1). Patent Document 1 discloses a foaming matte ink for printing on two-piece cans that contains a thermally expandable hollow microfiller. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-279852 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the matte ink described in Patent Document 1 is prone to misting during high-speed printing, and also prone to leaving residue on the plate or blanket during high-speed printing.

[0005] The present invention has been made in consideration of the above circumstances, and aims to provide a foam ink composition for metallic printing, a method for producing a metallic printed product, and a metallic printed product that can impart an excellent matte finish due to unevenness to desired positions on a metallic printing medium and are less likely to cause misting or plate or blanket residue during printing. [Means for solving the problem]

[0006] The foam ink composition for metal printing, the method for producing a metal printed product, and the metal printed product of the present invention, which solve the above-mentioned problems, mainly include the following features.

[0007] (1) A foamable ink composition for metal printing, comprising a resin, a solvent, a pigment, an extender pigment, and thermally expandable microcapsules, wherein the extender pigment comprises talc and silica.

[0008] With this configuration, the foamable ink composition for metal printing can impart an excellent matte finish due to the unevenness at desired positions on a metal printing medium. Furthermore, the foamable ink composition for metal printing is less likely to cause misting or to leave residue on the plate or blanket during printing.

[0009] (2) The foamable ink composition for metal printing according to (1), wherein the mass ratio of the talc to the silica is 50 / 50 to 90 / 10.

[0010] With this configuration, the foamable ink composition for metal printing is less likely to mist.

[0011] (3) The foamable ink composition for metal printing according to (1) or (2), wherein the solvent comprises a hydrophilic solvent and a hydrophobic solvent.

[0012] With this configuration, the foamable ink composition for metal printing is less likely to mist. Furthermore, when producing a metal print, the foamable ink composition for metal printing has excellent compatibility with the aqueous overprint varnish that forms the overprint layer, making it less likely to cause cissing. As a result, the resulting overprint layer is less likely to develop unintended large irregularities due to cissing.

[0013] (4) The foamable ink composition for metal printing according to any one of (1) to (3), wherein the content of the thermally expandable microcapsules is 0.5 to 4.5% by mass.

[0014] With this configuration, the foamable ink composition for metal printing can impart a superior matte finish due to the unevenness at desired positions on a metal printing medium. Furthermore, the foamable ink composition for metal printing is less likely to leave residue on the plate or blanket during printing.

[0015] (5) The foamable ink composition for metal printing according to any one of (1) to (4), wherein the resin is an alkyd resin.

[0016] With this configuration, the foamable ink composition for metal printing has excellent compatibility with solvents and is less likely to cause misting or to leave residue on the plate or blanket during printing.

[0017] (6) A method for producing a metallic printed product, comprising: an ink layer forming step of printing the foamable ink composition for metal printing according to any one of (1) to (5) on a metallic printing medium; an overprint layer forming step of forming an overprint layer on the ink layer; and a heat curing step of heating the ink layer and the overprint layer to simultaneously heat cure the ink layer and the overprint layer, wherein the heat curing step comprises: a heating step of foaming the thermally expandable microcapsules with heat and then breaking the bubbles; and a convex portion forming step of heat curing the ink layer containing the broken bubbles of the thermally expandable microcapsules and the overprint layer to form convex portions.

[0018] According to this configuration, the foamable ink composition for metallic printing described above is used. Therefore, the resulting metallic print has convex portions containing broken thermally expandable microcapsules at desired positions on the metallic print medium, imparting an excellent matte finish. Furthermore, the metallic print is less likely to produce misting or plate or blanket residue during printing during its production process.

[0019] (7) A metallic printed matter comprising a metallic printing medium, an ink layer formed on the metallic printing medium and printed with the foamable ink composition for metallic printing described in any one of (1) to (5), and an overprint layer formed on the ink layer, the metallic printed matter having convex portions formed by the thermally expandable microcapsules that have collapsed after foaming.

[0020] According to this configuration, the resulting metallic print has convex portions containing broken thermally expandable microcapsules formed at desired positions on the metallic print medium, and an excellent matte finish can be imparted. [Effects of the Invention]

[0021] According to the present invention, it is possible to provide a foam ink composition for metallic printing, a method for producing a metallic printed product, and a metallic printed product, which can impart an excellent matte finish due to unevenness to desired positions on a metallic printing medium and are less likely to cause misting, plate residue, or blanket residue during printing. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a schematic cross-sectional view of a laminate according to one embodiment of the present invention before a heat curing step is carried out. [Figure 2] FIG. 2 is a schematic cross-sectional view illustrating a state in which thermally expandable microcapsules are foamed and expanded in a thermal curing step according to one embodiment of the present invention. [Figure 3] FIG. 3 is a schematic cross-sectional view illustrating a state in which thermally expandable microcapsules are broken and shrunk and then cured in a thermal curing step according to one embodiment of the present invention. [Figure 4]FIG. 4 is a schematic cross-sectional view illustrating a state in which an ink layer is formed on a metal printing medium in the ink layer forming step, and then thermally cured to expand the thermally expandable microcapsules. [Figure 5] FIG. 5 is a schematic cross-sectional view illustrating thermally expandable microcapsules that have been broken by heat and cured together with the ink layer. [Figure 6] FIG. 6 is a schematic cross-sectional view illustrating a state in which an overprint layer is formed on the thermally cured thermally expandable microcapsules and ink layer. [Figure 7] FIG. 7 is a schematic cross-sectional view illustrating a state in which an overprint layer is formed on thermally cured thermally expandable microcapsules (but the cells are not broken) and an ink layer. DETAILED DESCRIPTION OF THE INVENTION

[0023] <Foamable ink composition for metal printing> A foamable ink composition for metal printing (hereinafter also referred to as the "ink composition") according to one embodiment of the present invention contains a resin, a solvent, a pigment, an extender pigment, and thermally expandable microcapsules. The extender pigment contains talc and silica. Each of these components will be described below.

[0024] (resin) The resin is not particularly limited. Examples of the resin include alkyd resin, polyester resin, petroleum resin, epoxy resin, ketone resin, etc. Among these, the resin is preferably an alkyd resin.

[0025] The alkyd resin is compatible with the solvents described below, and when an overprint layer is formed on the ink layer obtained from the ink composition, it is blended to ensure suitability for aqueous overprint varnish, to provide pigment dispersion stability, to impart ink viscoelasticity suitable for printing, and to improve ink transferability to metal printing media.

[0026] The alkyd resin has a backbone made of a condensate of a polybasic acid and a polyhydric alcohol and is modified with a fatty acid. The alkyd resin of this embodiment may be a resin modified with a fatty acid or a hydrogenated fatty acid, an oil or a hydrogenated oil, a monobasic acid, or the like.

[0027] The method for producing the alkyd resin is not particularly limited. For example, the method for producing the alkyd resin is a known method such as a transesterification method using oil as a raw material or a fatty acid method using fatty acids as a raw material.

[0028] Examples of polybasic acids include aromatic dibasic acids such as phthalic anhydride, isophthalic acid, and terephthalic acid; alicyclic dibasic acids such as tetrahydrophthalic anhydride, hexahydrophthalic anhydride, and 1,4-cyclohexanedicarboxylic acid; aliphatic dibasic acids such as succinic anhydride, maleic anhydride, himic anhydride, adipic acid, sebacic acid, azelaic acid, and fumaric acid; and polybasic acids such as trimellitic anhydride and methylcyclohexene tricarboxylic anhydride.

[0029] Examples of polyhydric alcohols include dihydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, 1,6-hexanediol, bisphenol A, and hydrogenated bisphenol A; trihydric alcohols such as glycerin, trimethylolethane, trimethylolpropane, and tris(2-hydroxyethyl)isocyanurate; and tetrahydric or higher alcohols such as pentaerythritol and dipentaerythritol.

[0030] Examples of oils and fatty acids include linseed oil, tung oil, safflower oil, soybean oil, tall oil, rice bran oil, palm oil, castor oil, dehydrated castor oil, sunflower oil, coconut oil, fatty acids from these oils, caprylic acid, pelargonic acid, capric acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, stearic acid, isostearic acid, oleic acid, linoleic acid, linolenic acid, ricinoleic acid, eleostearic acid, 12-hydroxystearic acid, etc. Monobasic acids other than these fatty acids, such as benzoic acid, pt-butylbenzoic acid, and abietic acid, may also be used in combination.

[0031] The fatty acid content of the alkyd resin is preferably 10% by mass or more, more preferably 20% by mass or more, based on the total mass of the alkyd resin. Furthermore, the fatty acid content of the alkyd resin is preferably 40% by mass or less, more preferably 30% by mass or less, based on the total mass of the alkyd resin. Having a fatty acid content within the above range provides the ink composition with excellent compatibility with solvents, offering the advantage of excellent printability. Furthermore, it facilitates the formation of an overprint layer when producing a metal print.

[0032] The alkyd resin of the present embodiment may be any of various modified alkyd resins, such as rosin-modified alkyd resins and silicone-modified alkyd resins.

[0033] The weight-average molecular weight of the alkyd resin is preferably 3,000 or more, and more preferably 4,000 or more. Furthermore, the weight-average molecular weight of the alkyd resin is preferably 30,000 or less, and more preferably 25,000 or less. When the weight-average molecular weight of the alkyd resin is within the above range, misting in terms of printability of the ink composition is likely to be suppressed. Furthermore, the alkyd resin has an appropriate resin viscosity, and the resulting ink composition has a good balance between ink shape and printability. In this embodiment, the weight-average molecular weight can be measured by size exclusion chromatography (SEC).

[0034] The acid value of the alkyd resin is not particularly limited. For example, the acid value is preferably 0.1 mgKOH / g or more, and more preferably 1.0 mgKOH / g or more. The acid value is preferably 30 mgKOH / g or less, and more preferably 15 mgKOH / g or less. By having the acid value within the above range, the ink composition can ensure appropriate fluidity and minimize the impact on transferability. In this embodiment, the acid value is defined as the number of milligrams of potassium hydroxide required to neutralize the free fatty acids contained in 1 g of resin.

[0035] The ink composition of this embodiment may contain, in addition to the alkyd resin, a conventionally used ink resin, such as an oil-free polyester resin, a petroleum resin, an epoxy resin, a ketone resin, a rosin-modified phenolic resin, a rosin-modified maleic acid resin, an amino resin, or a benzoguanamine resin, depending on the required performance, such as printability.

[0036] The polyester resin is not particularly limited, and an example thereof is a polyester resin obtained by reacting an alcohol with a carboxylic acid using a known esterification polymerization reaction.

[0037] Examples of alcohols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2-ethyl-2-butyl-1,3propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,2-pentanediol, 3-methyl-1,5-pentanediol, hexanediol, octanediol, 1,4-butynediol, 1,4-butylenediol, diethylene glycol, triethylene glycol, dipropylene glycol, glycerin, trimethylolpropane, trimethylolethane, 1,2,6-hexanetriol, 1,2,4-butanetriol, sorbitol, pentaerythritol, 1,4-cyclohexanediol, 1,2-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, spiroglycol, and isosorbide.

[0038] Examples of carboxylic acids include formic acid, acetic acid, propionic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, oleic acid, linoleic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, benzoic acid, phthalic acid, terephthalic acid, isophthalic acid, phthalic anhydride, 1,4-cyclohexanedicarboxylic acid, trimellitic acid, trimellitic anhydride, tetrahydrophthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic acid, and hexahydrophthalic anhydride.

[0039] The weight average molecular weight of the polyester resin is preferably 500 to 6,000, and more preferably 1,400 to 5,500.

[0040] The resin content is not particularly limited. For example, the resin content in the ink composition is preferably 15% by mass or more, and more preferably 20% by mass or more. The resin content in the ink composition is preferably 70% by mass or less, and more preferably 60% by mass or less. When the resin content is within the above range, the ink composition can achieve good printability and coating strength.

[0041] (solvent) The solvent is a solvent that dissolves the resin. The solvent is not particularly limited. For example, the solvent may be various hydrophilic solvents, hydrophobic solvents, etc. In this embodiment, the hydrophilic solvent is a solvent whose water solubility at 20°C is 1 g / 100 g or more, and the hydrophobic solvent is a solvent whose water solubility at 20°C is less than 1 g / 100 g.

[0042] The ink composition of this embodiment preferably contains a hydrophilic solvent and a hydrophobic solvent. This makes the ink composition less susceptible to misting. Furthermore, when producing a metal print, the ink composition has excellent compatibility with the aqueous overprint varnish that constitutes the overprint layer, making it less susceptible to cissing. As a result, the resulting overprint layer is less likely to develop unintended large irregularities due to cissing.

[0043] Hydrophilic solvent The hydrophilic solvent is not particularly limited, and examples thereof include glycol-based solvents, glycol ether-based solvents, lactam-based solvents, and amide-based solvents.

[0044] The glycol-based solvent is a polyalkylene glycol, an alkylene glycol, or the like.

[0045] The glycol ether solvent is a polyalkylene glycol ether, an alkylene glycol ether, or the like.

[0046] The hydrophilic solvent of this embodiment preferably contains a polyalkylene glycol, which makes the ink composition less susceptible to cissing and has excellent suitability for aqueous varnishes, even when an overprint layer made of aqueous overprint varnish is provided on the resulting ink layer.

[0047] The polyalkylene glycol is not particularly limited. Examples of polyalkylene glycols include polyethylene glycol, polypropylene glycol, polyethylene oxide-propylene oxide (a copolymer of ethylene oxide and propylene oxide), poly(methyl-ethylene) glycol, polybutylene glycol, etc. The polyalkylene glycol may also be a random copolymer, an alternating copolymer, a block copolymer, or a mixture thereof of polyalkylene glycols obtained using two or more different alkylene oxides.

[0048] Examples of polyalkylene glycol ethers include polyoxypropylene ethers of butyl alcohol, polyoxyethylene ethers of 2-ethyl-1-hexanol, polyoxyethylene ethers of 2-ethyl-1-heptanol, polyoxyethylene ethers of 2-ethyl-1-octanol, polyoxyethylene ethers of lauryl alcohol (dodecan-1-ol), polyoxyethylene ethers of cetyl alcohol (hexadecan-1-ol), polyoxyethylene ethers of stearyl alcohol (1-octadecanol), polyoxyethylene ethers of oleyl alcohol ((E)-octadec-9-en-1-ol), and polyoxyethylene ethers of a mixture of stearyl alcohol and cetyl alcohol (cetylstearyl alcohol).

[0049] The water solubility of the hydrophilic solvent at 20° C. may be 1 g / 100 g or more, preferably 5 g / 100 g or more, and more preferably 10 g / 100 g or more. Specifically, the hydrophilic solvent is preferably polypropylene glycol, polyoxyethylene monomethyl ether, or polyethylene glycol, and more preferably polypropylene glycol or polyoxyethylene monomethyl ether.

[0050] Hydrophobic solvent The hydrophobic solvent is not particularly limited, and examples thereof include hydrocarbons having 8 to 20 carbon atoms, aliphatic carboxylic acid alkyl esters having a total of 4 to 16 carbon atoms, and aliphatic alcohols having a melting point of 20°C or lower and having 8 to 26 carbon atoms.

[0051] The hydrocarbons having 8 to 20 carbon atoms include various chain hydrocarbons, cyclic hydrocarbons, and the like.

[0052] Saturated chain hydrocarbons include octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, isooctane, isononane, isodecane, isoundecane, isododecane, isotridecane, isotetradecane, isopentadecane, and isohexadecane. Unsaturated chain hydrocarbons include octene, nonene, decene, undecene, dodecene, tridecene, tetradecene, pentadecene, and hexadecene.

[0053] Alicyclic hydrocarbons include isopropylcyclohexane, butylcyclohexane, decylcyclopentane, tetralin, and limonene. Aromatic hydrocarbons include alkyl (carbon number 2 to 14) benzenes (butylbenzene, octylbenzene, etc.) and dialkyl (carbon number 2 to 14 in total) benzenes (o-xylene, 1,4-di-n-propylbenzene, etc.).

[0054] In the aliphatic carboxylic acid alkyl ester having a total of 4 to 16 carbon atoms, the carboxylic acid component and the alcohol component constituting the ester are not particularly limited as long as they are an aliphatic carboxylic acid and an aliphatic alcohol that result in an ester having a total of 4 to 16 carbon atoms.

[0055] The aliphatic carboxylic acid component is a saturated or unsaturated aliphatic monocarboxylic acid, a saturated or unsaturated aliphatic dicarboxylic acid, a saturated or unsaturated aliphatic tri- to tetra- or higher polycarboxylic acid, or the like.

[0056] Saturated or unsaturated aliphatic monocarboxylic acids include formic acid, acetic acid, propionic acid, acrylic acid, butyric acid, α-methylbutyric acid, 2-butenoic acid, valeric acid, α,β-dimethylvaleric acid, caproic acid, caprylic acid, capric acid, lauric acid, coconut oil fatty acid, myristic acid, and hydroxycarboxylic acids (such as glycolic acid, lactic acid, and gluconic acid).

[0057] The saturated or unsaturated aliphatic dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, β,β-dimethylglutaric acid, adipic acid, azelaic acid, sebacic acid, maleic acid, fumaric acid, itaconic acid, and hydroxycarboxylic acids (such as glyceric acid, tartaric acid, and malic acid).

[0058] Examples of saturated or unsaturated aliphatic tri-, tetra- or higher carboxylic acids include 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, and oxycarboxylic acids (such as citric acid).

[0059] The aliphatic alcohol component is a saturated or unsaturated aliphatic monohydric alcohol, a saturated or unsaturated aliphatic dihydric alcohol, a saturated or unsaturated aliphatic trihydric to tetrahydric or higher polyhydric alcohol, or the like.

[0060] Examples of saturated or unsaturated aliphatic monohydric alcohols include methanol, ethanol, n-propanol, n-butanol, n-pentanol, n-hexanol, n-heptanol, n-octanol, n-decanol, lauryl alcohol, myristyl alcohol, isopropanol, isobutanol, sec-butanol, t-butanol, isopentanol, activated amyl alcohol, t-pentanol, 2-ethylhexanol, allyl alcohol, crotyl alcohol, methylvinylcarbinol, methoxybutanol, ethoxyethanol, and 3-methoxy-3-methylbutanol.

[0061] The saturated or unsaturated aliphatic dihydric alcohols include ethylene glycol, propylene glycol, 1,3-propanediol, 1,3- or 1,4-butanediol, 1,6-hexanediol, 1,10-decanediol, and 4-pentene-2,3-diol.

[0062] Examples of saturated or unsaturated aliphatic trihydric, tetrahydric or higher polyhydric alcohols include glycerin, 1,3,6-hexanetriol and pentaerythritol.

[0063] Specific examples of aliphatic carboxylic acid alkyl esters having a total of 4 to 16 carbon atoms include methylcyclohexyl acetate, 2-ethylhexyl acetate, methoxybutyl acetate, ethoxyethyl acetate, butoxyethoxyethyl acetate, 3-methoxy-3-methylbutyl acetate, 1,6-diacetoxyhexane, methyl octylate, methyl laurate, dimethyl succinate, diethyl succinate, dimethyl adipate, diethyl adipate, di-2-ethylhexyl sebacate, glycerin trimethyl ester, and pentaerythritol tetraethyl ester.

[0064] The aliphatic alcohols having a melting point of 20° C. or less and a carbon number of 8 to 26 include saturated aliphatic alcohols, unsaturated aliphatic alcohols, and the like.

[0065] Saturated aliphatic alcohols include n-octanol, n-nonanal, n-decanol, 2-ethylhexanol, 2-ethyldecanol, isostearyl alcohol, 3,3-dibutyloctadecanol, tripropylene glycol, and tridecanol.

[0066] Examples of unsaturated aliphatic alcohols include 2-octen-1-ol, 2-dodecen-1-ol, 2-undecen-1-ol, 2-tetradecen-1-ol, 2-pentadecen-1-ol, 5-hexen-1-ol, 6-hepten-1-ol, 8-nonen-1-ol, 10-undecen-1-ol, 11-dodecen-1-ol, 12-tridecen-1-ol, 15-hexadecen-1-ol, oleyl alcohol, linoleyl alcohol, linolenyl alcohol, isooleyl alcohol, and 7-octadecen-1,18-diol.

[0067] Returning to the explanation of the solvent as a whole, the content of the solvent is not particularly limited. For example, the content of the solvent in the ink composition is preferably 5% by mass or more, and more preferably 10% by mass or more. Furthermore, the content of the solvent in the ink composition is preferably 40% by mass or less, and more preferably 30% by mass or less. By keeping the solvent content within the above range, the ink composition is less likely to mist when printing on the surface of a metal printing medium, and is less likely to cissate even when applying an aqueous overprint varnish to the resulting ink layer.

[0068] In particular, the content of the hydrophilic solvent in the ink composition is preferably 10% by mass or more, and more preferably 15% by mass or more. Furthermore, the content of the hydrophilic solvent in the ink composition is preferably 35% by mass or less, and more preferably 30% by mass or less. By keeping the content of the hydrophilic solvent within the above range, the ink composition is less likely to cause cissing, even when a water-based overprint varnish is applied to the resulting ink layer.

[0069] The content of the hydrophobic solvent in the ink composition is preferably 5% by mass or more, and more preferably 15% by mass or more. The content of the hydrophobic solvent in the ink composition is preferably 20% by mass or less, and more preferably 15% by mass or less. By having the content of the hydrophobic solvent within the above range, the ink composition exhibits appropriate fluidity and is less likely to mist when printing on the surface of a metal printing medium.

[0070] (pigment) The pigment is not particularly limited. For example, the pigment may be any of various inorganic pigments or organic pigments. Note that the pigment in this embodiment does not include the extender pigments described below.

[0071] The inorganic pigments and organic pigments preferably have heat resistance, light resistance, and retort resistance. Inorganic pigments include titanium oxide, silica, carbon black, etc. Organic pigments include phthalocyanine pigments, azo pigments, quinacridone pigments, diketopyrrolopyrrole pigments, quinophthalone pigments, etc.

[0072] The content of the pigment can be adjusted appropriately depending on the type and purpose. For example, the content of the pigment in the ink composition is preferably 10% by mass or more, and more preferably 15% by mass or more. Furthermore, the content of the pigment in the ink composition is preferably 60% by mass or less, and more preferably 45% by mass or less. When the content of the pigment is within the above range, the ink composition exhibits good coloring power and hiding power, and also has excellent dispersion stability.

[0073] (extender pigment) The extender pigment is blended to suppress misting of the resulting ink composition and to reduce plate residue and blanket residue.

[0074] The extender pigment of this embodiment contains talc and silica.

[0075] ·talc The talc is not particularly limited. For example, the talc may be any of various talcs or calcined talc.

[0076] The average particle size of the talc is preferably 10 μm or less, more preferably 5 μm or less. The average particle size of the talc is preferably 0.1 μm or more, more preferably 0.2 μm or more. When the average particle size of the talc is within the above range, misting of the ink composition is easily suppressed. In this embodiment, the average particle size of the talc can be measured by a laser diffraction / scattering method based on the Mie scattering theory.

[0077] The specific surface area of talc measured by the BET method (BET specific surface area) is 10m 2 / g or more, and 15m 2 / g or more. The specific surface area of talc measured by the BET method (BET specific surface area) is 40 m 2 / g or less, and 2 When the specific surface area of the talc is within the above range, the flowability of the ink composition can be easily adjusted and the transferability is excellent.

[0078] ·silica The silica may be various types of hydrophobic silica, hydrophilic silica, or the like.

[0079] Hydrophobic silica is organically modified silica, and examples thereof include compounds obtained by reactively bonding organohalosilanes, dimethylsiloxanes, hexamethyldisilazane, dimethyldichlorosilane, trimethoxyoctylsilane, trimethylsilane, etc. to silanol groups on the surface of mineral-derived or synthetic silica particles; compounds obtained by mixing silica particles with dimethylpolysiloxanes or dimethylhydrogenpolysiloxanes having hydroxyl groups at their ends and heating the mixture at 200 to 300°C to bond alkylpolysiloxanes to the surface of the silica particles; and compounds obtained by vapor-phase adsorption of silicone oil onto the surface of silica particles.

[0080] The hydrophilic silica is silica having a pH value of 7.0 or less, particularly 3.5 to 5.0, and includes natural silica obtained by finely grinding quartz, silica sand, etc., and synthetic silica such as dry silica and wet silica.

[0081] The hydrophilic silica is preferably fumed silica having silanol groups (Si-OH groups) on the surface.

[0082] The specific surface area of silica measured by the BET method (BET specific surface area) is 60m 2 / g or more, and 170m 2 The specific surface area of silica measured by the BET method (BET specific surface area) is preferably 250 m / g or more. 2 / g or less, and 2 / g or less is more preferable. When the BET specific surface area of silica is within the above range, the ink composition has easy adjustment of fluidity and excellent transferability. In this embodiment, the BET specific surface area of silica can be calculated according to the BET method.

[0083] Returning to the explanation of the extender pigment as a whole, the ink composition of this embodiment preferably has a mass ratio of talc to silica of 50 / 50 to 90 / 10, more preferably 60 / 40 to 80 / 20, and even more preferably 65 / 35 to 70 / 30. By having the mass ratio of talc to silica within the above range, the ink composition is less likely to mist.

[0084] The content of the extender pigment is not particularly limited. For example, the content of the extender pigment in the ink composition is preferably 3% by mass or more, and more preferably 5% by mass or more. Furthermore, the content of the extender pigment in the ink composition is preferably 15% by mass or less, and more preferably 10% by mass or less. When the content of the extender pigment is within the above range, the ink composition is less likely to mist or leave residue on the plate or blanket during printing.

[0085] (Thermal Expandable Microcapsules) Thermally expandable microcapsules are microcapsules that have the property of foaming and expanding when heated, and breaking down and shrinking to some extent when further heated.

[0086] The thermally expandable microcapsules can be composed of an outer wall and a gas or liquid contained within the outer wall.

[0087] The outer wall is not particularly limited as long as it is a polymer that has gas barrier properties and is stretchable and elastic when heated. For example, the outer wall may be made of a thermoplastic resin such as vinylidene chloride resin, vinylidene chloride-acrylonitrile copolymer, or vinyl acetate-acrylic ester copolymer.

[0088] The enclosed gas or liquid is not particularly limited as long as it is a thermally expandable substance that vaporizes under normal heating conditions, for example, at temperatures of 50 to 200° C. Examples of the enclosed gas or liquid include substances with relatively low thermal conductivity, such as trichlorofluoromethane, dichlorofluoromethane, normal butane, isobutane, butylene, pentane, and hexane.

[0089] The average particle diameter D50 of the thermally expandable microcapsules is preferably 3 μm or more, more preferably 5 μm or more. The average particle diameter D50 of the thermally expandable microcapsules is preferably 15 μm or less, more preferably 10 μm or less. In this embodiment, the average particle diameter D50 of the thermally expandable microcapsules is defined as the diameter of the particle size at which the cumulative value in the particle size distribution of the microcapsules is 50%. The average particle diameter D50 of the thermally expandable microcapsules can be measured by a laser diffraction scattering method using a particle size distribution analyzer (LS 13320, manufactured by Beckman Coulter, Inc.). When the average particle diameter D50 of the thermally expandable microcapsules is within the above range, the ink composition is less likely to deposit the thermally expandable microcapsules on the plate or blanket when producing a metallic printed product, and is less likely to leave any plate or blanket residue. As a result, the resulting metallic printed product is less likely to have unevenness and can be produced stably over a long period of time. Therefore, the resulting metallic print is likely to have clear irregularities (protrusions) on the surface of the ink layer due to the mechanism described below, and can be given a sufficiently matte finish.

[0090] The content of the thermally expandable microcapsules in the ink composition is preferably 0.5% by mass or more, and more preferably 1.0% by mass or more. Furthermore, the content of the thermally expandable microcapsules in the ink composition is preferably 4.5% by mass or less, and more preferably 3.0% by mass or less. By having the content of the thermally expandable microcapsules within the above range, the ink composition can impart a superior matte finish due to unevenness to desired positions on the metal printing medium. Furthermore, the ink composition is less likely to leave plate or blanket residues during printing.

[0091] The thermally expandable microcapsules of this embodiment expand and foam upon heating. For example, the maximum average particle size of the thermally expandable microcapsules after expansion is preferably 20 μm or more, more preferably 40 μm or more. Furthermore, the average particle size of the thermally expandable microcapsules after expansion is preferably 80 μm or less, more preferably 60 μm or less. When the average particle size after expansion is within the above range, the resulting metallic printed matter has a matte feel in the uneven surface and excellent coating film strength.

[0092] The thermally expandable microcapsules of this embodiment reach their maximum particle size after expansion, and then, upon further heating, at least some of the microcapsules break and shrink. In the shrunk state, the thermally expandable microcapsules themselves are cured, or the ink layer (and overprint layer) is cured, thereby maintaining the shape in a somewhat shrunk state. The average particle size after shrinkage is preferably 15 μm or more, more preferably 20 μm or more. Furthermore, the average particle size of the thermally expandable microcapsules after shrinkage is preferably 60 μm or less, more preferably 50 μm or less. When the average particle size after shrinkage is within the above range, the resulting metallic printed product has a matte feel in the uneven surface and excellent coating film strength.

[0093] As will be described later in connection with the method for producing a metallic printed matter, the ink composition of this embodiment utilizes the expansion and collapse of thermally expandable microcapsules to provide irregularities (protrusions) at desired positions on a metallic printing medium. Such protrusions allow the metallic printed matter to exhibit an excellent matte finish.

[0094] (optional ingredient) The ink composition of this embodiment may contain optional components such as a dispersant in addition to the components described above.

[0095] The dispersant is not particularly limited, and examples thereof include carbodiimide-based dispersants, polyester amine-based dispersants, fatty acid amine-based dispersants, modified polyacrylate-based dispersants, modified polyurethane-based dispersants, multi-chain polymeric nonionic dispersants, and polymeric ionic surfactants.

[0096] When a dispersant is contained, the content of the dispersant is not particularly limited. For example, the content of the dispersant is preferably 1 to 20% by mass, where the pigment is taken as 100% by mass.

[0097] The method for preparing the ink composition of the present embodiment is not particularly limited. For example, the ink composition can be prepared by a conventional method using a roll mill, a ball mill, a bead mill, or the like.

[0098] <Metal Printing Method> A method for producing a metallic printed product according to one embodiment of the present invention includes an ink layer forming step of printing the foamable ink composition for metallic printing on a metallic printing medium, an overprint layer forming step of forming an overprint layer on the ink layer, and a thermal curing step of heating the ink layer and the overprint layer to simultaneously thermally cure them. The thermal curing step includes a heating step of thermally foaming thermally expandable microcapsules and then breaking the bubbles, and a convex portion forming step of thermally curing the ink layer containing the broken bubbles and the overprint layer to form convex portions. Each step will be described below. Note that in the following description, explanations of components common to those described above in relation to the ink composition embodiment will be omitted as appropriate.

[0099] (Ink layer formation process) The ink layer forming step is a step of printing the ink composition described above onto a metal printing medium.

[0100] The metal printing medium is not particularly limited. For example, the metal printing medium may be a metal substrate such as stainless steel, aluminum, tin-plated steel, or tin-free steel, or a metal substrate having a base coat (primer) layer formed on the metal substrate. The base coat layer may be formed using a base coat composition, such as a size paint or white coating, commonly used in metal printing. The metal substrate may also be laminated with a PET film.

[0101] The method for printing the ink composition on the metallic printing medium is not particularly limited. For example, the printing method may be a conventional printing method such as an offset method using dampening water, a dry offset method, or a waterless lithographic offset method. The method for producing a metallic printed product of this embodiment uses the ink composition described above. Therefore, the metallic printed product is less likely to mist when printed on the surface of the metallic printing medium.

[0102] The resulting ink layer is subjected to the subsequent overprint layer forming step before being dried and cured.

[0103] (Overprint layer formation process) The overprint layer forming step is a step of forming an overprint layer on an ink layer.

[0104] The method for forming the overprint layer is not particularly limited. For example, the overprint layer can be formed by applying an aqueous overprint varnish.

[0105] The water-based overprint varnish is not particularly limited. For example, the water-based overprint varnish may contain a water-soluble resin (such as a water-soluble acrylic resin, a water-soluble polyester resin, a water-soluble alkyd resin, or a water-soluble epoxy resin), a film strengthener (wax), a film-forming aid (a high-boiling point solvent), a wetting agent (a surfactant), a water-miscible organic solvent, and water.

[0106] The overprint layer can be formed by applying a water-based overprint varnish using a roll coater or the like.

[0107] Fig. 1 is a schematic cross-sectional view of a laminate 1 before the thermal curing step of this embodiment is carried out. As shown in Fig. 1, the laminate 1 has an ink layer 3 and an overprint layer 4 formed on a metallic printing medium 2. The ink layer 3 contains thermally expandable microcapsules 5.

[0108] The thickness of the ink layer, excluding the thickness of the thermally expandable microcapsules, is preferably 0.5 μm or more, more preferably 2 μm or more, and is preferably 10 μm or less, more preferably 6 μm or less, excluding the thickness of the thermally expandable microcapsules.

[0109] On the other hand, the thickness of the overprint layer is preferably 3 μm or more, more preferably 5 μm or more, and is preferably 10 μm or less, more preferably 8 μm or less.

[0110] The resulting laminate is then subjected to a heat curing step.

[0111] (thermal curing process) The thermal curing step is a step in which the ink layer and the overprint layer are heated to thermally cure them simultaneously. That is, in the method for producing a metallic printed product of this embodiment, after the ink layer is formed in the ink layer forming step, the overprint layer forming step is subsequently carried out while the ink layer is in a wet state. As a result, the ink layer and the overprint layer, which are in a wet state, are thermally cured simultaneously in the thermal curing step.

[0112] The heat curing conditions are not particularly limited as long as they allow at least a portion of the thermally expandable microcapsules to expand and foam, and then to break and shrink. For example, the heat curing temperature is preferably 150°C or higher, more preferably 180°C or higher. The heat curing temperature is preferably 250°C or lower, more preferably 220°C or lower. The heat curing time is preferably 5 seconds or longer, more preferably 10 seconds or longer. The heat curing time is preferably 15 minutes or shorter, more preferably 10 minutes or shorter. By keeping the heat curing conditions within the above ranges, at least a portion of the thermally expandable microcapsules will properly foam and break.

[0113] 2 is a schematic cross-sectional view illustrating the state in which the thermally expandable microcapsules 5 expand and foam in the thermal curing step of this embodiment. As shown in FIG. 2, when heat is applied to the thermally expandable microcapsules 5, the encapsulated gas or liquid expands and foams. As a result, the thermally expandable microcapsules 5 deform the ink layer 3 and the overprint layer 4 outward, forming irregularities (protrusions 6).

[0114] FIG. 3 is a schematic cross-sectional view illustrating the state in which thermally expandable microcapsules break and shrink during the thermal curing process of this embodiment, and then harden. As shown in FIG. 3, the broken thermally expandable microcapsules 51 have hollow internal spaces 51a into which the ink composition constituting the ink layer 3 and the aqueous overprint varnish constituting the overprint layer 4 flow. The broken microcapsules 51 also shrink somewhat. Further application of heat in this state causes the overprint layer 4 to thermally cure, thereby maintaining the shape in a somewhat shrunk state. As a result, a metallic print 7 can be produced having protrusions 61 formed by the thermally expandable microcapsules 51 that have broken after foaming.

[0115] FIG. 3 illustrates protrusions formed in two locations. In the metallic print, protrusions of various heights can be formed as multiple thermally expandable microcapsules break. As a result, the metallic print can have an excellent matte finish. FIG. 3 also illustrates protrusions 61 formed from microcapsules 51 that have shrunk after breaking. In addition to such protrusions 61, this embodiment may also include protrusions (not shown) formed by microcapsules (not shown) that have expanded somewhat but not broken.

[0116] Here, with reference to FIGS. 4 to 7, an example of a metallic print formed when the ink layer is thermally cured before forming the overprint layer will be described. FIG. 4 is a schematic cross-sectional view illustrating a state in which an ink layer 3 is formed on a metallic print medium 2 by an ink layer formation step, and then thermally cured to expand the thermally expandable microcapsules 5. FIG. 5 is a schematic cross-sectional view illustrating thermally expandable microcapsules 52 whose bubbles have been broken by heat and cured together with the ink layer 3. FIG. 6 is a schematic cross-sectional view illustrating a state in which an overprint layer 4 has been formed on the thermally cured thermally expandable microcapsules 52 and ink layer 3. FIG. 7 is a schematic cross-sectional view illustrating a state in which an overprint layer 4 has been formed on the thermally cured thermally expandable microcapsules 5 (however, the bubbles have not been broken) and ink layer 3.

[0117] As shown in FIG. 4, when heat is applied to the thermally expandable microcapsules 5, the encapsulated gas or liquid expands and foams. As a result, the thermally expandable microcapsules 5 deform the ink layer 3 outward, forming irregularities (protrusions 62). As shown in FIG. 5, the thermally expandable microcapsules 52 then break, and the ink layer 3 flows into the hollow internal space 52a. The broken thermally expandable microcapsules 52 also shrink somewhat. When further heat is applied in this state, the thermally expandable microcapsules 52 themselves harden, or the ink composition that constitutes the ink layer 3 hardens, thereby maintaining their shape in a somewhat shrunk state.

[0118] Thereafter, an overprint layer forming step is carried out, and the overprint layer is appropriately thermally cured. As shown in Fig. 6, the resulting metal print 8 differs from the metal print 7 of this embodiment (see Fig. 3) in that the surface irregularities (protrusions 63) are gentle. Fig. 6 shows an example in which such a gentle protrusion 63 is formed in one location.

[0119] Furthermore, when heat is applied to the thermally expandable microcapsules 5 shown in FIG. 4, the encapsulated gas or liquid expands and foams. However, some thermally expandable microcapsules 5 may remain expanded without breaking, or may shrink slightly and remain expanded. Such thermally expandable microcapsules are then subjected to the overprint layer formation process. FIG. 7 is a schematic cross-sectional view illustrating the state in which an overprint layer 4 is formed on the thermally cured thermally expandable microcapsules 5 (but not broken) and the ink layer 3. As shown in FIG. 7, the resulting metal print 9 has gently sloping surface irregularities (protrusions 64), unlike the metal print 7 of this embodiment (see FIG. 3). FIG. 7 shows an example in which one such gently sloping protrusion 64 is formed.

[0120] As shown in Figures 6 and 7, when the ink layer is thermally cured after the ink layer formation step, the resulting metallic print has smooth convex portions. As a result, it is difficult to obtain a matte finish due to the unevenness of the metal print.

[0121] Returning to the description of this embodiment, the method for producing a metallic printed product of this embodiment uses the ink composition described above. Therefore, the resulting metallic printed product has convex portions containing thermally expandable microcapsules that have been foamed and then broken at desired positions on the metallic printing medium, imparting an excellent matte finish. Furthermore, the metallic printed product is less likely to produce misting or plate or blanket residue during printing during the production process.

[0122] <Metal printed matter> A metallic printed product according to one embodiment of the present invention is formed on a metallic printing medium and comprises an ink layer printed with the foamable ink composition for metallic printing described above, and an overprint layer formed on the ink layer. The metallic printed product has convex portions formed by thermally expandable microcapsules that have collapsed after foaming. Each of these will be described below. Note that in the following description, explanations of configurations common to those described above in relation to the embodiments of the ink composition and method for producing a metallic printed product will be omitted as appropriate.

[0123] As shown in Figure 3, the metallic printed matter 7 of this embodiment comprises a metallic printing medium 2, an ink layer 3 formed on the metallic printing medium 2 and printed with the above-mentioned foam ink composition for metallic printing, and an overprint layer 4 formed on the ink layer 3.

[0124] The metallic printed product 7 has protrusions 61 formed by thermally expandable microcapsules 51 that have burst after foaming. Figure 3 shows an example of protrusions 61 formed in two places. The metallic printed product 7 can have protrusions 61 of various heights formed by multiple thermally expandable microcapsules 51 that have burst. As a result, the metallic printed product 7 can have an excellent matte finish. Note that Figure 3 shows an example of protrusions 61 made of microcapsules 51 that have shrunk after bursting. In addition to such protrusions 61, this embodiment may also include protrusions (not shown) formed by microcapsules (not shown) that have expanded somewhat but not yet burst.

[0125] In this way, the metallic printed matter of this embodiment does not have a single convex portion 62 gently formed along the width direction (direction perpendicular to the thickness) of one broken thermally expandable microcapsule 52, as in another metallic printed matter 8 shown in Fig. 6, but rather, as shown in Fig. 3, one or more convex portions (two convex portions 61 in Fig. 3) formed along the width direction (direction perpendicular to the thickness) of one broken thermally expandable microcapsule 51. As a result, the metallic printed matter 7 can be given an excellent matte finish.

[0126] The method for manufacturing the metal print of this embodiment is not particularly limited. For example, the metal print of this embodiment can be manufactured by the manufacturing method described above in relation to the embodiment of the method for manufacturing the metal print. [Example]

[0127] The present invention will be described in more detail below with reference to examples and comparative examples. The present invention is not limited to these examples. The values in the tables are based on mass %.

[0128] Details of the raw materials used and the synthesis method are as follows. <Resin> (Method for synthesizing alkyd resin) 25.0 parts of coconut oil fatty acid, 35.0 parts of phthalic anhydride, 20.0 parts of trimethylolpropane, and 20.0 parts of pentaerythritol were esterified in a conventional manner to obtain a fatty acid-modified alkyd resin with a fatty acid content of 25%, oxidation rate of 7.0 mg KOH / g, and weight-average molecular weight of 6,000. (Method for synthesizing polyester resin) 50 parts of tetrahydrophthalic anhydride, 35 parts of hexanediol, and 15 parts of trimethylolpropane were esterified in a conventional manner to obtain a polyester resin having an oxidation state of 7.0 mgKOH / g and a weight average molecular weight of 4,500. <Solvent> Hydrophilic solvent: Polypropylene glycol, Sannix PP400, manufactured by Sanyo Chemical Industries, Ltd., water solubility at 20°C > 1 g / 100 g Hydrophilic solvent: Polyoxyethylene monomethyl ether, Nonion EH-208, manufactured by NOF Corporation, water solubility at 20°C > 1 g / 100 g Hydrophobic solvent: Tridecanol, alcohol-based solvent, Tridecanol, manufactured by KH Neochem Co., Ltd., water solubility at 20°C <0.01 g / 100 g Hydrophobic solvent: Isostearyl alcohol, alcohol-based solvent, Fine Oxocol 180A, manufactured by Nissan Chemical Industries, Ltd., water solubility at 20°C <0.01 g / 100 g Hydrophobic solvent: Linear alkylbenzene, hydrocarbon solvent, LAB, Mitsui & Co., Ltd., water solubility at 20°C <0.01g / 100g <Pigments> CIPigment.Yellow 83 <Extender pigment> Talc: Magnesium silicate hydrate, High Filler #5000PJ, manufactured by Matsumura Sangyo Co., Ltd., average particle size (D50) 4.5 μm Silica: Silicon dioxide, Aerosil R972V, manufactured by Nippon Aerosil Co., Ltd., hydrophobic silica Calcium carbonate: Shiraenka T-DD, manufactured by Shiraishi Kogyo Co., Ltd., rosin-treated synthetic calcium carbonate <Thermal expansion microcapsules> Thermally expandable microcapsule 1: EXPANCEL461DU20, manufactured by Nippon Phillite Co., Ltd., average particle size (D50) 6 to 9 μm Thermally expandable microcapsule 2: EXPANCEL051DU40, manufactured by Nippon Phillite Co., Ltd., average particle size (D50) 9 to 15 μm Thermally expandable microcapsule 3: Matsumoto Microsphere F-80VSD, manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd., average particle size (D50) 5 to 8 μm

[0129] Example 1 The ink composition of Example 1 was prepared by mixing the components according to the formulation shown in Table 1 and then forming the ink using a three-roll mill. The resulting ink composition was evaluated for plate residue, blanket residue, unevenness (matt finish) of the coating surface, aqueous finishing varnish properties, and misting using the following evaluation methods. The results are shown in Table 1.

[0130] <Examples 2 to 14 and Comparative Examples 1 to 3> Ink compositions were prepared and evaluated in the same manner as in Example 1, except that the formulation was changed as shown in Table 1. The results are shown in Table 1.

[0131] <Remaining plates and blankets> Using a high-speed printability tester PM-904PT, 0.3 cc of the ink composition was supplied, smoothed, and then transferred from the transfer roll to a metal substrate (aluminum) at 8 m / s. The weight percentage of the ink composition on the transfer roll that was transferred to the metal substrate was measured and evaluated according to the following criteria. (Evaluation criteria) AA: The metastasis rate was over 30%. A: The metastasis rate was 20-29%. B: The metastasis rate was 15-19%. C: The metastasis rate was less than 14%.

[0132] <Unevenness of the coating surface> The ink layer (wet state) prepared in the above plate and blanket residue tests was coated with a water-based overprint varnish (Aquaprime 105, manufactured by AkzoNobel) at a coating amount of 25 to 35 mg / 100 cm. 2 The coating was performed under the conditions of a varnish coating speed of 2.0 m / s, and then baked at 200°C for 3 minutes to produce a printed coating film. The surface irregularities of this printed coating film were visually inspected and evaluated according to the following evaluation criteria. (Evaluation criteria) AA: The surface was uneven and had a very matte feel. A: The surface was uneven and had a matte finish. B: The surface was slightly uneven but had a matte feel, and there was no problem with the quality. C: The surface was smooth and not uneven.

[0133] <Suitable for water-based finishing varnish> The ink layer (wet state) prepared in the above plate and blanket residue tests was coated with a water-based overprint varnish (Aquaprime 105, manufactured by AkzoNobel) at a coating amount of 25 to 35 mg / 100 cm. 2The coating was performed under the conditions of 100°C, 200°C, and a varnish coating speed of 2.0 m / s. The coating was then baked for 3 minutes at 200°C to produce a printed coating film. The printed coating film was visually inspected for the presence or absence of cissing of the overprint varnish and evaluated according to the following evaluation criteria. (Evaluation criteria) A: No repelling of the overprint varnish occurred. B: There was a slight amount of cissing of the overprint varnish, but it was not a quality problem. C: Significant repelling of overprint varnish occurred.

[0134] <Misting> 2.62 cc of the ink composition was placed on the roll of the ink meter, and the roll was rotated at 40°C and 2400 rpm for 5 seconds. The amount of the ink composition splashed onto the bottom of the roll was evaluated according to the following evaluation criteria. (Evaluation criteria) AA: The amount of ink composition scattered was 10 mg or less. A: The amount of scattered ink composition was 10 to 19 mg. B: The amount of scattered ink composition was 20 to 29 mg. C: The amount of scattered ink composition was 30 mg or more.

[0135] [Table 1]

[0136] As shown in Table 1, the ink compositions of Examples 1 to 14 of the present invention suppressed misting, left little plate or blanket residue, and were excellent in suitability for aqueous finishing varnish when printed on the surface of a metal printing medium. Furthermore, the ink compositions of Examples 1 to 14 easily formed unevenness, and provided an excellent matte finish. [Explanation of symbols]

[0137] 1. Laminate 2 Metal printing media 3 Ink layer 4 Overprint Layer 5, 51, 52 Thermally Expandable Microcapsules 51a, 52a interior space 6, 61, 63, 64 Convex parts 7, 8, 9 Metal prints

Claims

1. The composition includes a resin, a solvent, a pigment, an extender pigment, and thermally expandable microcapsules, The foamable ink composition for metal printing, wherein the extender pigment comprises talc and silica.

2. 2. The foamable ink composition for metal printing according to claim 1, wherein the mass ratio of the talc to the silica is 50 / 50 to 90 / 10.

3. 3. The foamable ink composition for metal printing according to claim 1, wherein the solvent comprises a hydrophilic solvent and a hydrophobic solvent.

4. 3. The foamable ink composition for metal printing according to claim 1, wherein the content of the thermally expandable microcapsules is 0.5 to 4.5% by mass.

5. 3. The foamable ink composition for metal printing according to claim 1, wherein the resin is an alkyd resin.

6. 3. A method for producing a metallic printed product, comprising: an ink layer forming step of printing the foamable ink composition for metal printing according to claim 1 or 2 on a metallic printing medium; an overprint layer forming step of forming an overprint layer on the ink layer; and a heat curing step of heating the ink layer and the overprint layer to simultaneously heat cure the ink layer and the overprint layer, wherein the heat curing step comprises: a heating step of foaming the thermally expandable microcapsules by heat and then breaking the bubbles; and a convex portion forming step of heat curing the ink layer containing the broken bubbles of the thermally expandable microcapsules and the overprint layer to form convex portions.

7. 3. A metallic printed product comprising: a metallic printing medium; an ink layer formed on the metallic printing medium and printed with the foamable ink composition for metallic printing according to claim 1; and an overprint layer formed on the ink layer, the metallic printed product having convex portions formed by the thermally expandable microcapsules that have collapsed after foaming.

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