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

Abstract

Provided are: a foaming ink composition for metal printing that is capable of imparting an excellent matte finish due to unevenness to a desired position on a metal printing medium and is unlikely to cause misting or piling or blanket piling during printing; a method for producing metal printed matter; and metal printed matter. The foaming ink composition for metal printing contains a resin, a solvent, a pigment, an extender pigment, and thermally expandable microcapsules. The extender pigment contains talc and silica.

Description

Foamed ink composition for metal printing, method for producing metal prints, and metal prints

[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.

[0002] Conventionally, methods for decorating the surface of metallic printing media such as beverage cans by providing minute irregularities have been developed. For example, a method using a matte overprint varnish containing a matting agent is available. However, while this method can decorate the entire surface of the metallic printing media, it cannot decorate only a portion of the metallic printing media. Therefore, ink compositions containing thermally expandable microcapsules (foaming agents) that expand upon heating have been developed (see, 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.

[0003] Japanese Patent Application Publication No. 10-279852

[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.

[0006] One aspect of the present invention that solves the above-mentioned problems is a foamable ink composition for metal printing, which comprises a resin, a solvent, a pigment, an extender pigment, and thermally expandable microcapsules, wherein the extender pigment comprises talc and silica.

[0007] In addition, one embodiment of the present invention, which solves the above-mentioned problem, is a method for producing a metal printed product, which includes an ink layer forming step of printing the above-mentioned foamable ink composition for metal printing on a metal 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 includes 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.

[0008] Furthermore, one embodiment of the present invention that solves the above problem is a metal printed product comprising a metal printing medium, an ink layer formed on the metal printing medium and printed with the above foaming ink composition for metal printing, and an overprint layer formed on the ink layer, and having convex portions formed by the thermally expandable microcapsules that have collapsed after foaming.

[0009] FIG. 1 is a schematic cross-sectional view of a laminate before a thermal curing step according to one embodiment of the present invention is performed. FIG. 2 is a schematic cross-sectional view illustrating a state in which thermally expandable microcapsules have foamed and expanded during a thermal curing step according to one embodiment of the present invention. FIG. 3 is a schematic cross-sectional view illustrating a state in which thermally expandable microcapsules have broken bubbles, shrunk, and then hardened during a thermal curing step according to one embodiment of the present invention. FIG. 4 is a schematic cross-sectional view illustrating a state in which an ink layer is formed on a metallic printing medium by an ink layer formation step, and then the thermally expandable microcapsules are expanded by thermal curing. FIG. 5 is a schematic cross-sectional view illustrating thermally expandable microcapsules whose bubbles have broken due to heat and hardened together with the ink layer. FIG. 6 is a schematic cross-sectional view illustrating a state in which an overprint layer has been formed on the thermally cured thermally expandable microcapsules and ink layer. FIG. 7 is a schematic cross-sectional view illustrating a state in which an overprint layer has been formed on the thermally cured thermally expandable microcapsules (but whose bubbles have not broken) and ink layer.

[0010] <Foamable ink composition for metal printing> A foamable ink composition for metal printing (hereinafter also referred to as 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.

[0011] (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.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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 of 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, p-t-butylbenzoic acid, and abietic acid, may also be used in combination.

[0018] 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 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 alkyd resin. Having a fatty acid content within the above range offers the advantage of excellent compatibility with solvents and good printability. Furthermore, it is easy to form an overprint layer when producing a metal print.

[0019] 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.

[0020] 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).

[0021] 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. Furthermore, 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 any influence 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] The weight average molecular weight of the polyester resin is preferably 500 to 6,000, and more preferably 1,400 to 5,500.

[0027] The content of the resin is not particularly limited. For example, the content of the resin in the ink composition is preferably 15% by mass or more, and more preferably 20% by mass or more. Furthermore, the content of the resin in the ink composition is preferably 70% by mass or less, and more preferably 60% by mass or less. When the content of the resin is within the above range, the ink composition can achieve good printability and coating strength.

[0028] (Solvent) The solvent is a solvent that dissolves the resin. There are no particular limitations on the solvent. 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.

[0029] 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.

[0030] 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.

[0031] The glycol-based solvent is a polyalkylene glycol, an alkylene glycol, or the like.

[0032] The glycol ether solvent is a polyalkylene glycol ether, an alkylene glycol ether, or the like.

[0033] 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.

[0034] 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, and polybutylene glycol. 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.

[0035] Examples of polyalkylene glycol ethers include polyoxypropylene ether of butyl alcohol, polyoxyethylene ether of 2-ethyl-1-hexanol, polyoxyethylene ether of 2-ethyl-1-heptanol, polyoxyethylene ether of 2-ethyl-1-octanol, polyoxyethylene ether of lauryl alcohol (dodecan-1-ol), polyoxyethylene ether of cetyl alcohol (hexadecan-1-ol), polyoxyethylene ether of stearyl alcohol (1-octadecanol), polyoxyethylene ether of oleyl alcohol ((E)-octadec-9-en-1-ol), and polyoxyethylene ether of a mixture of stearyl alcohol and cetyl alcohol (cetylstearyl alcohol).

[0036] 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.

[0037] Hydrophobic Solvent The hydrophobic solvent is not particularly limited. Examples of the hydrophobic solvent 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 less and having 8 to 26 carbon atoms.

[0038] The hydrocarbons having 8 to 20 carbon atoms include various chain hydrocarbons, cyclic hydrocarbons, and the like.

[0039] 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.

[0040] Alicyclic hydrocarbons include isopropylcyclohexane, butylcyclohexane, decylcyclopentane, tetralin, limonene, etc. Aromatic hydrocarbons include alkyl (carbon number 2 to 14) benzenes (butylbenzene, octylbenzene, etc.) and dialkyl (carbon number in total 2 to 14) benzenes (o-xylene, 1,4-di-n-propylbenzene, etc.).

[0041] 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.

[0042] The aliphatic carboxylic acid component may be a saturated or unsaturated aliphatic monocarboxylic acid, a saturated or unsaturated aliphatic dicarboxylic acid, a saturated or unsaturated aliphatic tri-, tetra- or higher polycarboxylic acid, or the like.

[0043] Examples of 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 oxycarboxylic acids (such as glycolic acid, lactic acid, and gluconic acid).

[0044] Examples of 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).

[0045] 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).

[0046] The aliphatic alcohol component may be a saturated or unsaturated aliphatic monohydric alcohol, a saturated or unsaturated aliphatic dihydric alcohol, or a saturated or unsaturated aliphatic trihydric, tetrahydric or higher polyhydric alcohol.

[0047] 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.

[0048] 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.

[0049] Saturated or unsaturated aliphatic trihydric, tetrahydric or higher polyhydric alcohols include glycerin, 1,3,6-hexanetriol, and pentaerythritol.

[0050] 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.

[0051] The aliphatic alcohols having a melting point of 20° C. or less and having 8 to 26 carbon atoms include saturated aliphatic alcohols, unsaturated aliphatic alcohols, and the like.

[0052] Saturated aliphatic alcohols include n-octanol, n-nonanal, n-decanol, 2-ethylhexanol, 2-ethyldecanol, isostearyl alcohol, 3,3-dibutyloctadecanol, tripropylene glycol, and tridecanol.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] (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.

[0058] 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.

[0059] 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.

[0060] (Extender Pigment) The extender pigment is blended to suppress misting of the resulting ink composition and to reduce plate residue and blanket residue.

[0061] The extender pigment of this embodiment contains talc and silica.

[0062] Talc is not particularly limited. For example, the talc may be any of various talcs or calcined talc.

[0063] 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.

[0064] The specific surface area of ​​talc measured by the BET method (BET specific surface area) is 10 m 2 / g or more, and 2 The specific surface area of ​​talc measured by the BET method (BET specific surface area) is preferably 40 m 2 / g or less, and 2 When the specific surface area of ​​the talc is within the above range, the fluidity of the ink composition can be easily adjusted and the transferability is excellent.

[0065] Silica Silica includes various types of hydrophobic silica and hydrophilic silica.

[0066] Hydrophobic silica is organically modified silica, and examples thereof include compounds obtained by reactively bonding organohalosilanes, dimethylsiloxanes, hexamethyldisilazane, dimethyldichlorosilane, trimethoxyoctylsilane, trimethylsilane, or the like to silanol groups present on the surfaces of mineral-derived or synthetic silica particles; compounds obtained by mixing silica particles with dimethylpolysiloxane or dimethylhydrogenpolysiloxane having hydroxyl groups at the terminals and heating the mixture at 200 to 300°C to bond alkylpolysiloxanes to the surfaces of the silica particles; and compounds obtained by vapor-phase adsorption of silicone oil onto the surfaces of silica particles.

[0067] 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.

[0068] The hydrophilic silica is preferably fumed silica having silanol groups (Si—OH groups) on the surface.

[0069] The specific surface area of ​​silica measured by the BET method (BET specific surface area) is 60 m 2 / g or more, and 2 The specific surface area of ​​silica measured by the BET method (BET specific surface area) is preferably 250 m 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 fluidity of the ink composition can be easily adjusted and the transferability is excellent. In this embodiment, the BET specific surface area of ​​silica can be calculated according to the BET method.

[0070] Returning to the explanation of the extender pigment as a whole, in the ink composition of this embodiment, the mass ratio of talc to silica is preferably 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.

[0071] 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.

[0072] (Thermal Expandable Microcapsules) Thermal expandable microcapsules are microcapsules that have the property of foaming and expanding when heated, and breaking and shrinking to some extent when further heated.

[0073] The thermally expandable microcapsules can be composed of an outer wall and a gas or liquid contained within the outer wall.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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 surface irregularities and excellent coating film strength.

[0079] 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, and more preferably 20 μm or more. Furthermore, the average particle size of the thermally expandable microcapsules after shrinkage is preferably 60 μm or less, and more preferably 50 μm or less. When the average particle size after shrinkage is within the above range, the resulting metallic print has a matte feel in the surface irregularities and excellent coating strength.

[0080] As will be described later in connection with the method for producing a metallic print, the ink composition of this embodiment utilizes the expansion and collapse of thermally expandable microcapsules to provide irregularities (protrusions) at desired positions on the metallic print medium. Such protrusions allow the metallic print to exhibit an excellent matte finish.

[0081] (Optional Components) In addition to the components described above, the ink composition of this embodiment may contain optional components such as a dispersant.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] <Method for producing a metallic printed product> 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 of the thermally expandable microcapsules and the overprint layer to form convex portions. Each of these steps will be described below. Note that in the following description, explanations of configurations common to those described above in relation to the ink composition embodiment will be omitted as appropriate.

[0086] (Ink Layer Forming Step) The ink layer forming step is a step of printing the ink composition described above onto a metal printing medium.

[0087] 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.

[0088] 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.

[0089] The resulting ink layer is subjected to the subsequent overprint layer forming step before being dried and cured.

[0090] (Overprint Layer Forming Step) The overprint layer forming step is a step of forming an overprint layer on an ink layer.

[0091] 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.

[0092] 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.

[0093] The overprint layer can be formed by applying a water-based overprint varnish using a roll coater or the like.

[0094] Fig. 1 is a schematic cross-sectional view of a laminate 1 before the thermal curing step of this embodiment is performed. 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.

[0095] 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.

[0096] 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.

[0097] The resulting laminate is then subjected to a heat curing step.

[0098] (Thermal curing step) 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.

[0099] The thermal 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 thermal curing temperature is preferably 150°C or higher, more preferably 180°C or higher. The thermal curing temperature is preferably 250°C or lower, more preferably 220°C or lower. The thermal curing time is preferably 5 seconds or longer, more preferably 10 seconds or longer. The thermal curing time is preferably 15 minutes or shorter, more preferably 10 minutes or shorter. By keeping the thermal curing conditions within the above ranges, at least a portion of the thermally expandable microcapsules will properly foam and break.

[0100] 2 is a schematic cross-sectional view illustrating the state in which the thermally expandable microcapsules 5 expand and foam during 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).

[0101] 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, followed by curing. 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.

[0102] Figure 3 illustrates two protrusions formed. In the metallic print, multiple thermally expandable microcapsules may break, forming protrusions of various heights. As a result, the metallic print may have an excellent matte finish. Note that Figure 3 illustrates a protrusion 61 formed from microcapsules 51 that have shrunk after breaking. In this embodiment, in addition to such protrusions 61, protrusions (not shown) formed by microcapsules (not shown) that have expanded somewhat but not broken may also be included.

[0103] Here, with reference to Figures 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. Figure 4 is a schematic cross-sectional view illustrating the state in which an ink layer 3 is formed on a metallic print medium 2 by an ink layer formation process, and then thermally cured to expand the thermally expandable microcapsules 5. Figure 5 is a schematic cross-sectional view illustrating the state in which the thermally expandable microcapsules 52 have been broken by heat and cured together with the ink layer 3. Figure 6 is a schematic cross-sectional view illustrating the state in which an overprint layer 4 has been formed on the thermally cured thermally expandable microcapsules 52 and ink layer 3. Figure 7 is a schematic cross-sectional view illustrating the state in which an overprint layer 4 has been formed on the thermally cured thermally expandable microcapsules 5 (but whose bubbles have not been broken) and ink layer 3.

[0104] As shown in Figure 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 Figure 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 constituting the ink layer 3 hardens, thereby maintaining their shape in a somewhat shrunk state.

[0105] Thereafter, an overprint layer forming process 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.

[0106] 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 heat-cured thermally expandable microcapsules 5 (but not broken) and the ink layer 3. As shown in FIG. 7 , the resulting metallic print 9 has gently sloping surface irregularities (protrusions 64), unlike the metallic print 7 of this embodiment (see FIG. 3 ). FIG. 7 shows an example in which one such gently sloping protrusion 64 is formed.

[0107] 6 and 7, when the ink layer is thermally cured after the ink layer formation step, the resulting metallic print has smooth convex portions, making it difficult to achieve a matte finish due to the unevenness of the metal print.

[0108] 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.

[0109] <Metal Printed Product> A metal printed product according to one embodiment of the present invention is formed on a metal printing medium and comprises an ink layer printed with the foamable ink composition for metal printing described above, and an overprint layer formed on the ink layer. The metal 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 metal printed product will be omitted as appropriate.

[0110] 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 foamed ink composition for metallic printing, and an overprint layer 4 formed on the ink layer 3.

[0111] The metallic printed product 7 has convex portions 61 formed by thermally expandable microcapsules 51 that have burst after foaming. FIG. 3 illustrates convex portions 61 formed in two locations. The metallic printed product 7 can have convex portions 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. FIG. 3 illustrates convex portions 61 formed by microcapsules 51 that have shrunk after bursting. In addition to such convex portions 61, this embodiment may also include convex portions (not shown) formed by microcapsules (not shown) that have expanded somewhat but not yet burst.

[0112] In this way, the metallic print 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 the other metallic print 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 print 7 can be given an excellent matte finish.

[0113] 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.

[0114] An embodiment of the present invention has been described above. The present invention is not particularly limited to the above embodiment. Note that the above embodiment mainly describes an invention having the following configuration.

[0115] (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.

[0116] 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.

[0117] (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.

[0118] With this configuration, the foamable ink composition for metal printing is less likely to mist.

[0119] (3) The foamable ink composition for metal printing according to (1) or (2), wherein the solvent comprises a hydrophilic solvent and a hydrophobic solvent.

[0120] 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.

[0121] (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 mass %.

[0122] 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.

[0123] (5) The foamable ink composition for metal printing according to any one of (1) to (4), wherein the resin is an alkyd resin.

[0124] 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.

[0125] (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.

[0126] 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.

[0127] (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.

[0128] 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.

[0129] 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 %.

[0130] Details of the raw materials used and the synthesis method are as follows. <Resin> (Method of 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 by a conventional method to obtain a fatty acid-modified alkyd resin having a fatty acid content of 25%, an oxidation state of 7.0 mg KOH / g, and a weight-average molecular weight of 6,000. (Method of synthesizing polyester resin) 50 parts of tetrahydrophthalic anhydride, 35 parts of hexanediol, and 15 parts of trimethylolpropane were esterified by a conventional method to obtain a polyester resin having an oxidation state of 7.0 mg KOH / g and a weight-average molecular weight of 4,500. <Solvents> 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 alkyl benzene, hydrocarbon-based solvent, LAB, manufactured by Mitsui & Co., Ltd., water solubility at 20°C < 0.01 g / 100 g <Pigments> C.I. Pigment. Yellow 83 <Extender pigments> Talc: hydrated magnesium silicate, 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: Hakuenka T-DD, manufactured by Shiraishi Kogyo Co., Ltd., rosin-treated synthetic calcium carbonate <Thermal expandable microcapsules> Thermal expandable microcapsule 1: EXPANCEL461DU20, manufactured by Nippon Phillite Co., Ltd., average particle size (D50) 6 to 9 μm Thermal 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

[0131] 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 mixture into 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.

[0132] Examples 2 to 14, 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.

[0133] <Plate Remaining, Blanket Remaining> Using a high-speed printability tester PM-904PT, 0.3 cc of ink composition was supplied and leveled, 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 evaluation criteria. (Evaluation Criteria) AA: The transfer rate was 30% or more. A: The transfer rate was 20 to 29%. B: The transfer rate was 15 to 19%. C: The transfer rate was 14% or less.

[0134] <Unevenness of coating surface> A water-based overprint varnish (Aquaprime 105, manufactured by AkzoNobel) was applied to the ink layer (wet state) prepared in the above-mentioned plate residue and blanket residue tests in a coating amount of 25 to 35 mg / 100 cm. 2 The coating was performed under the conditions of 2.0 m / s, and a varnish coating speed of 2.0 m / s. The coating was 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 irregular, with a very high matte finish. A: The surface was irregular, with a matte finish. B: The surface irregularities were somewhat weak, but there was a matte finish and there were no quality issues. C: The surface was smooth with no irregularities.

[0135] <Suitability for aqueous finishing varnish> A water-based overprint varnish (Aquaprime 105, manufactured by AkzoNobel) was applied to the ink layer (wet state) prepared in the above-mentioned plate residue and blanket residue tests in a coating amount of 25 to 35 mg / 100 cm. 2 The coating was performed under conditions of 100°C, 100°F, and a varnish coating speed of 2.0 m / s. The coating was then baked at 200°C for 3 minutes 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 cissing of the overprint varnish occurred. B: Slight cissing of the overprint varnish occurred, but this was not a problem in terms of quality. C: Significant cissing of the overprint varnish occurred.

[0136] <Misting> 2.62 cc of ink composition was placed on the roll of an incometer, and the roll was rotated at 40°C and 2400 rpm for 5 seconds. The amount of ink composition scattered onto the bottom of the roll was evaluated according to the following evaluation criteria. (Evaluation criteria) AA: The amount of scattered ink composition 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.

[0137]

[0138] 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.

[0139] REFERENCE SIGNS LIST 1 Laminate 2 Metallic printing medium 3 Ink layer 4 Overprint layer 5, 51, 52 Thermally expandable microcapsules 51a, 52a Internal space 6, 61, 63, 64 Convex portion 7, 8, 9 Metallic printed matter

Claims

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.

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

3. The foamable ink composition for metal printing according to claim 1 or 2, wherein the solvent comprises a hydrophilic solvent and a hydrophobic solvent.

4. The foamable ink composition for metal printing according to claim 1 or 2, wherein the content of the thermally expandable microcapsules is 0.5 to 4.5% by mass.

5. The foamable ink composition for metal printing according to claim 1 or 2, wherein the resin is an alkyd resin.

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 claim 1 or 2 onto 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 thermally expandable microcapsules and the overprint layer to form convex portions.

7. 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 or 2, and an overprint layer formed on the ink layer, and having convex portions formed by the thermally expandable microcapsules that have collapsed after foaming.

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