Metallic printing ink composition and printed matter

Abstract

To provide an ink composition for metal printing excellent in aggregation resistance, fluidity and misting resistance, and to provide a metal printed matter using the same.SOLUTION: An ink composition for metal printing comprising a resin, a pigment, a solvent, and a fatty acid glyceride, wherein a content of the fatty acid glyceride is 0.3 to 10 mass% in the ink composition. In the ink composition for metal printing, the fatty acid glyceride is a fatty acid triglyceride. The above ink composition for metal printing, wherein the fatty acid glyceride is a fatty acid triglyceride in which the constituent fatty acid has 12 to 20 carbon atoms.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an ink composition for metallic printing. More specifically, the present invention relates to an ink composition for metallic printing that exhibits good resistance to aggregation when an overprint varnish is applied onto the ink composition, and also has excellent fluidity and misting resistance, as well as to a metallic print using the ink and a method for producing the same. [Background technology]

[0002] Metal containers are used in a wide variety of applications, including beverage containers, general-purpose cans, and candy cans. Metal containers are primarily manufactured using two methods. One method involves printing and painting a sheet metal plate, followed by cutting, welding, and other processes to create the desired can body. The other method involves punching a metal plate, ironing it, and then forming it into a cylindrical shape with a bottom, and then printing and painting the body of the can. The latter method is specifically called a seamless can.

[0003] Metal printing ink compositions are printed on the surfaces of metal containers to provide various designs, ingredient labels, etc. When printing on metal containers, printing ink is supplied from an ink fountain, transferred to the image area of ​​the printing plate via multiple rolls, and then transferred to a blanket, after which it is printed on the metal substrate. Metal printing can be performed using a lithographic offset method or a dry offset method using a resin relief plate.

[0004] In a method for coating a substrate of a metal print, an ink composition is printed on the substrate, and then an overprint varnish is applied to the printed layer, followed by a curing process to form a coating. The process of applying the overprint varnish can be performed using a dry-on-wet method in which the ink composition is cured before the overprint varnish is applied, or a wet-on-wet method in which the overprint varnish is applied without curing the ink composition.

[0005] From the standpoint of productivity, the wet-on-wet method is widely adopted for seamless cans used for alcoholic beverages, carbonated drinks, soft drinks, coffee drinks, etc.

[0006] When obtaining a coating film using the wet-on-wet method, there have been issues such as uneven density and repellency due to aggregation of the ink composition, resulting in reduced design reproducibility. As printing speeds increase, ink compositions tend to exhibit poorer performance in terms of transfer and adhesion to metal substrates, making aggregation more likely. In recent years, this problem has become more likely to occur when using aqueous overprint varnishes that have reduced solvent content in order to reduce environmental impact. As a result, ink compositions have been developed that use a resin composition to improve wettability to metal substrates (e.g., Patent Document 1), and ink compositions that incorporate a low-polarity solvent in addition to the resin composition (e.g., Patent Document 2).

[0007] However, in response to the recent trend toward improving productivity, the process of printing ink compositions has become even faster, while at the same time, requirements for designs expressed by printing have become increasingly strict, and ink compositions are being required to have higher design reproducibility and printability regardless of printing conditions or materials. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 4897733 [Patent Document 2] Patent No. 7353551 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention provides an ink composition for metallic printing that exhibits good resistance to aggregation when an overprint varnish is applied, and also has excellent fluidity and misting resistance, as well as a metallic printed product using the ink, and a method for producing the same. [Means for solving the problem]

[0010] As a result of extensive research into the above-mentioned problems, the inventors have found that the above-mentioned problems can be solved by using the ink for metal printing described below, and have thus achieved the present invention.

[0011] That is, the present invention relates to an ink composition for metal printing, which comprises a resin, a pigment, a solvent, and a fatty acid glyceride, and the content of the fatty acid glyceride in the ink composition is 0.3 to 10 mass %.

[0012] The present invention also relates to an ink composition for metal printing, in which the fatty acid glyceride is a fatty acid triglyceride.

[0013] The present invention further relates to an ink composition for metal printing, in which the fatty acid glyceride is a fatty acid triglyceride in which the constituent fatty acid has 12 to 20 carbon atoms.

[0014] The present invention further relates to an ink composition for metal printing, wherein the resin is a polyester resin and / or a petroleum resin.

[0015] The present invention further relates to an ink composition for metal printing, wherein the solvent is an aromatic hydrocarbon.

[0016] The present invention further relates to a metallic print having a printed layer made of an ink composition for metallic printing on a metal medium, and an overprint layer provided on the printed layer.

[0017] Furthermore, the present invention relates to a method for producing a metallic printed item, which comprises forming a printed layer on a metal medium by dry offset printing or offset printing of an ink composition for metallic printing, and then applying an overprint varnish onto the printed layer to form an overprint layer. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide an ink composition for metal printing that has excellent printability, such as agglomeration resistance, flowability, and misting resistance. DETAILED DESCRIPTION OF THE INVENTION

[0019] The following describes in detail embodiments of the present invention. Note that the embodiments and explanations of the requirements described are examples of embodiments of the present invention, and can be implemented with appropriate modifications within the scope of the present invention.

[0020] (Ink composition for metal printing) The ink composition for metal printing of this embodiment (hereinafter also referred to as the ink composition) contains a resin, a pigment, a solvent, and a fatty acid glyceride as essential components. Each component will be described below.

[0021] <Fatty acid glycerides> Fatty acid glyceride components have a structure in which the hydroxyl groups of glycerin are replaced by fatty acids. When one of the three hydroxyl groups of glycerin is replaced by a fatty acid, it becomes a fatty acid monoglyceride; when two hydroxyl groups are replaced by fatty acids, it becomes a fatty acid diglyceride; and when three hydroxyl groups are replaced by fatty acids, it becomes a fatty acid triglyceride.

[0022] The fatty acid glyceride component may contain one type of fatty acid glyceride selected from the group consisting of fatty acid monoglycerides, fatty acid diglycerides, and fatty acid triglycerides, or may contain two or more types of fatty acid glycerides.

[0023] The content of fatty acid glyceride in the ink composition is adjusted appropriately depending on the type and purpose, but is generally 0.3% by mass or more and 10% by mass or less, preferably 0.5% by mass or more and 8% by mass or less, more preferably 0.8% by mass or more and 5% by mass or less, and most preferably 1% by mass or more and 3% by mass or less. By ensuring that the fatty acid glyceride content is within the above range, the ink composition exhibits sufficient transfer and adhesion to the printing substrate regardless of environmental factors such as printing speed and temperature, and exhibits good aggregation resistance even when an overprint varnish is applied. The ink composition also exhibits excellent fluidity and on-press stability.

[0024] The fatty acid glyceride that can be used in the present invention is not particularly limited, and any known fatty acid glyceride can be used. The fatty acid glyceride may be a natural fatty acid glyceride or a synthetic fatty acid glyceride. From the viewpoint of aggregation resistance, fatty acid diglycerides and / or fatty acid triglycerides are preferred, and fatty acid triglycerides are more preferred.

[0025] The fatty acid glyceride is preferably a fatty acid triglyceride in which the constituent fatty acids have 12 to 20 carbon atoms, i.e., a fatty acid triglyceride in which the three hydroxyl groups of glycerin are substituted with fatty acids having 12 to 20 carbon atoms, and more preferably a fatty acid triglyceride in which the constituent fatty acids have 12 to 18 carbon atoms. When the number of carbon atoms of the fatty acid constituting the fatty acid triglyceride is within the above range, the ink composition has excellent flowability and anti-misting properties.

[0026] The fatty acids constituting the fatty acid glycerides may be saturated fatty acids or unsaturated fatty acids, and the unsaturated fatty acids may be monounsaturated fatty acids or polyunsaturated fatty acids.

[0027] <Resin> The resin of the present embodiment is not particularly limited. Examples of the resin include polyester resin, petroleum resin, epoxy resin, ketone resin, rosin-modified phenolic resin, melamine resin, and benzoguanamine resin. Among these, the resin is preferably a polyester resin and / or a petroleum resin, and among polyester resins, an alkyd resin is more preferable. These resins may be used alone or in combination of two or more.

[0028] Alkyd resins exhibit good compatibility with solvents, and when an overprint layer is formed on an ink layer made of an ink composition, they ensure suitability for overprint varnish, provide pigment dispersion stability, impart ink viscoelasticity suitable for printing, and provide excellent ink transferability to metal printing media.

[0029] The alkyd resin is not particularly limited. One example is an alkyd resin having a skeleton of a condensate of a polybasic acid and a polyhydric alcohol and 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.

[0030] The 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, the 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. The oils and fatty acids may be used in combination.

[0031] The content of structural units derived from fatty acids in the alkyd resin is preferably 20 to 65% by mass, more preferably 30 to 55% by mass. A printing ink composition containing an alkyd resin with a fatty acid content within the above range has excellent compatibility with fatty acid glycerides and solvents, and exhibits good aggregation resistance and on-machine stability.

[0032] Furthermore, a portion of the fatty acids may be replaced with a monobasic acid other than fatty acids. As other monobasic acids, benzoic acid, pt-butylbenzoic acid, abietic acid, 12-hydroxystearic acid, etc. may be used in combination.

[0033] 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. Polybasic acids may be used in combination.

[0034] The polyhydric alcohol includes 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. Polyhydric alcohols may be used in combination.

[0035] The method for producing an alkyd resin is not particularly limited. Examples of methods for producing an alkyd resin include known methods such as the transesterification method using oil as a raw material and the fatty acid method using fatty acids as a raw material. For example, the fatty acid, polybasic acid, and polyhydric alcohol described above are charged together with xylene into a reaction vessel equipped with a stirrer, a reflux condenser, and a thermometer, and the mixture is heated to 240°C with stirring under a nitrogen atmosphere to carry out an esterification reaction. After confirming that the desired acid value has been reached, the reaction is terminated to obtain an alkyd resin.

[0036] The polyester resin (excluding alkyd resins) is not particularly limited. For example, the polyester resin is a condensation product of a polybasic acid and a polyhydric alcohol, and is a polyester resin obtained by reacting a polybasic acid with a polyhydric alcohol using a known esterification reaction.

[0037] Polyhydric 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, Examples of suitable polyhydric alcohols include dihydric alcohols such as triethylene glycol, dipropylene glycol, 1,4-cyclohexanediol, 1,2-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, spiroglycol, and isosorbide; trihydric alcohols such as glycerin, trimethylolpropane, trimethylolethane, 1,2,6-hexanetriol, and 1,2,4-butanetriol; and trihydric or higher alcohols such as sorbitol and pentaerythritol. Polyhydric alcohols may be used in combination.

[0038] Examples of polybasic acids include aromatic dibasic acids such as phthalic acid, phthalic anhydride, isophthalic acid, and terephthalic acid; alicyclic dibasic acids such as tetrahydrophthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic acid, hexahydrophthalic anhydride, and 1,4-cyclohexanedicarboxylic acid; aliphatic dibasic acids such as oxalic acid, malonic acid, succinic acid, succinic anhydride, maleic anhydride, himic anhydride, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and fumaric acid; and polybasic acids such as trimellitic anhydride and methylcyclohexene tricarboxylic anhydride. Monobasic acids may also be used in combination. Examples of monobasic 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, and benzoic acid.

[0039] The petroleum resin is not particularly limited, and examples thereof include aromatic petroleum resins, aliphatic petroleum resins, dicyclopentadiene petroleum resins, and petroleum resins copolymerized from these raw materials. Commercially available petroleum resins can be used. Aromatic petroleum resins include Neopolymer L-90, Neopolymer 120, Neopolymer 130, Neopolymer 140, Neopolymer 150, Neopolymer 170S, Neopolymer 160, Neopolymer E-100, Neopolymer E-130, and Neopolymer S manufactured by ENEOS Materials Corporation, and Petocol LX, Petocol 120, Petocol 130, and Petocol 140 manufactured by Tosoh Corporation. Aliphatic petroleum resins include Quinton A100, Quinton B170, Quinton M100, Quinton R100, and Quinton C200H manufactured by Nippon Zeon Co., Ltd., and T-REZ RB100 and T-REZ RB093 manufactured by ENEOS Materials. Dicyclopentadiene petroleum resins include Quinton 1105, Quinton 1325, Quinton 1340, and Quinton 1500 manufactured by Nippon Zeon Co., Ltd., and T-REZ manufactured by ENEOS Materials. HA085, T-REZ HA103, T-REZ HA105; copolymer petroleum resins such as Quinton D100, Quinton N180, Quinton P195N, Quinton S100, Quinton S195, Quinton U185, Quinton G100B, Quinton G115, Quinton D200, Quinton E200SN, and Quinton N295, all manufactured by Zeon Corporation; and Petrotack 60, Petrotack 70, Petrotack 90, Petrotack 100V, and Petrotack 90HS, all manufactured by Tosoh Corporation.

[0040] The styrene-equivalent weight-average molecular weight of the resin is preferably 500 or more and 40,000 or less. When the weight-average molecular weight of the resin is within the above range, the compatibility with the solvent is excellent, and the aggregation resistance and on-machine stability are good. In addition, the ink composition maintains the coating properties. In this embodiment, the weight-average molecular weight is a value measured by gel permeation chromatography (GPC).

[0041] The content of the resin in the ink composition is not particularly limited as long as it can be adjusted to a predetermined ink tack value suitable for metal printing. For example, the content of the resin in the ink composition is preferably 15 to 60 mass %, and more preferably 20 to 50 mass %. By keeping the content of the resin within the above range, the ink composition maintains its printability, such as on-press stability, and also exhibits excellent coating properties.

[0042] <Pigments> The pigment of the present embodiment is not particularly limited, and any known inorganic or organic pigment for printing ink can be used alone or in combination.

[0043] 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.

[0044] The content of the pigment in the ink composition is adjusted as appropriate depending on the type and purpose. For example, the content of the pigment in the ink composition is preferably 10 to 60 mass %, more preferably 15 to 45 mass %. When the content of the pigment is within the above range, the ink composition has excellent printing suitability, such as aggregation resistance and on-press stability, and exhibits good coloring power and hiding power, as well as excellent dispersion stability.

[0045] <Solvent> As the solvent in this embodiment, known solvents used in ink compositions for metal printing can be used alone or in combination.

[0046] The solvent may be a high-boiling petroleum-based solvent such as an aliphatic hydrocarbon, an alicyclic hydrocarbon, or an aromatic hydrocarbon, having a boiling point of about 200° C. to 400° C. In addition to petroleum-based solvents, higher alcohols, fatty acid esters, etc. may also be used.

[0047] The solvent is preferably an aromatic hydrocarbon such as alkylbenzene. When the solvent is an aromatic hydrocarbon, it exhibits good compatibility with the fatty acid glyceride and resin, and is excellent in aggregation resistance and flowability. The content of the aromatic hydrocarbon in the solvent is adjusted appropriately depending on the type and purpose. For example, the content of the aromatic hydrocarbon in the solvent is preferably 50 to 100% by mass or more, more preferably 70 to 100% by mass.

[0048] The content of the solvent is not particularly limited. For example, the content of the solvent in the ink composition is preferably 10 to 60 mass %, more preferably 15 to 50 mass %. When the content of the solvent is within the above range, the ink composition can be easily adjusted to an ink tack value that shows good printability in metal printing.

[0049] <Other ingredients> In addition to the components described above, the ink composition of this embodiment may contain additives that are typically added to ink compositions, such as pigment dispersants, extender pigments, driers, acid catalysts, waxes, viscosity modifiers, and storage stabilizers.

[0050] ·How to adjust printing ink 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 three-roll mill, a ball mill, a bead mill, or the like.

[0051] The form of the ink composition of this embodiment varies depending on the type and content of resin, pigment, solvent, and additives. For example, the tack value is preferably 4 to 12, and more preferably 5 to 10. Here, the tack value is the value measured using a digital incometer (manufactured by Toyo Seiki Seisakusho, Ltd.) with 1.31 cc of ink, at a room temperature of 25°C, a roller temperature of 30°C, and a rotation speed of 400 rpm for 1 minute. A tack value within the above range provides excellent agglomeration resistance and misting resistance.

[0052] The flow value is preferably 25 to 50, and more preferably 30 to 45. Here, the flow value indicates the value measured using a horizontal plate viscometer (spread meter) (manufactured by Yasuda Seiki Seisakusho Co., Ltd.) at room temperature of 25°C and after 60 seconds, as the spread diameter (unit: mm). When the flow value is in the above range, good transferability is exhibited.

[0053] ·Metal printing method The printing method for the ink composition of this embodiment is not particularly limited, and can be appropriately selected from dry offset methods using resin relief plates or waterless lithographic plates, and offset methods using water-based lithographic plates. The film thickness of the ink composition is optional, but should be in the range of 0.5 to 6 μm. By ensuring that the film thickness of the ink composition is in the above range, a metal print can be obtained that is excellent in on-press stability and misting resistance, and exhibits good coloring power and hiding power.

[0054] Furthermore, examples of metal printing media on which the ink composition of the present embodiment is printed include, but are not limited to, aluminum plates, steel plates, and coated plates obtained by laminating these with polyester films, etc. These substrates may be subjected to chemical conversion treatment, plating treatment, or base coating such as size coating, white coating, or silver coating.

[0055] The method for producing a metal printed product of this embodiment includes the steps of providing a printing layer on a substrate using an ink composition, applying an overprint varnish to the printing layer, and then performing a curing treatment. The printed / coated product of the present invention also includes, on a substrate, a printing layer formed using a printing ink composition and an overprint layer formed using an overprint varnish. The curing treatment is preferably heat curing, and although the heating conditions are not particularly limited, one example includes a first baking step at a temperature of 180°C to 300°C for approximately 3 to 90 seconds, and a second baking step at a temperature of 180°C to 300°C for approximately 30 to 150 seconds.

[0056] The overprint varnish is preferably a thermosetting one, and any conventionally known overprint varnish for metal containers can be used without any particular limitation. Examples include polyester-melamine, polyester-epoxy-melamine, and polyester-acrylic-melamine varnishes. The overprint varnish may be either water-based or solvent-based. [Example]

[0057] The present invention will be described below based on examples and comparative examples, but the present invention is not limited to these examples. Note that the numbers in the tables below are based on mass.

[0058] Details of the raw materials used and the synthesis method are as follows.

[0059] <Fatty acid glycerides> Homotex PT (fatty acid (C10) monoglyceride, manufactured by Kao Corporation) Poem DO-100V (fatty acid (C18:1) diglyceride, manufactured by Riken Vitamin Co., Ltd.) Coconard ML (fatty acid (C8, C10, C12) triglycerides: Kao Corporation) Delica Premier O (fatty acid (C12-C20) triglyceride: manufactured by Nisshin Oillio Co., Ltd.) <Resin> (Synthesis of alkyd resin 1) 45 parts of coconut oil fatty acid, 28 parts of phthalic anhydride, 37 parts of pentaerythritol, and 10 parts of xylol were charged into a four-neck flask equipped with a stirrer, and an esterification reaction was carried out at 220-230°C while circulating xylol under a nitrogen stream until the acid value reached 5.0 mgKOH / g. After the reaction was completed, the xylol was distilled off at 240°C to obtain alkyd resin 1 with a weight-average molecular weight of 8,000 and a number-average molecular weight of 2,500. The amount of dehydration was 10 parts. (Synthesis of alkyd resin 2) 55 parts of linseed oil, 13 parts of glycerin, and 5 parts of pentaerythritol were placed in a four-neck flask equipped with a stirrer and maintained at 240-250°C for 1 hour to carry out an alcohol exchange reaction. The mixture was then cooled to 180°C, and 30 parts of phthalic anhydride and recycled xylol were added. The reaction was continued at 230-240°C until the acid value reached 5.0 mgKOH / g. After the reaction was completed, the xylol was distilled off at 240°C to obtain alkyd resin 2 with a weight-average molecular weight of 20,000 and a number-average molecular weight of 3,500. The amount of dehydration was 3 parts. (Synthesis of 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 acid value of 7.0 mgKOH / g, a weight average molecular weight of 4,500, and a number average molecular weight of 2,300. (petroleum resin) Neopolymer S (ENEOS Corporation) (weight average molecular weight 1,100) <Solvent> LAB (Linear Alkyl Benzene, manufactured by Mitsui & Co., Ltd.) D-SOL300 (paraffinic hydrocarbon, manufactured by Mitsubishi Corporation Chemicals) <Pigments> LIONOL BLUE FG-7351 (Phthalocyanine Blue 15:3, manufactured by Toyo Color Co., Ltd.) MA-77 (carbon black, manufactured by Mitsubishi Chemical Corporation)

[0060] Inks were prepared using the raw materials and blending amounts shown in Table 1. The ink compositions of Examples 1 to 14 and Comparative Examples 1 to 4 were evaluated in the following manner, and the results are shown in Table 1. The content of unreacted linseed oil in alkyd resin 2 was approximately 0.1% of the total mass of the ink of Comparative Example 2.

[0061] <Agglomeration resistance> Using a high-speed printability tester (PM904PT manufactured by SMT Corporation), 0.2 cc of ink was supplied and homogenized, then transferred to a test rubber roll and then transferred to an aluminum plate at a printing speed of 8 m / s. Immediately afterwards, a thermosetting overprint varnish was applied onto the printed ink layer at a speed of 2 m / s to a film thickness of 20 μm. (Evaluation criteria) A: No aggregation of ink into overprint varnish occurs. B: Slight aggregation of ink into overprint varnish is observed. C: A small amount of ink aggregation in the overprint varnish is observed. D: Clear aggregation of ink into overprint varnish is observed. The practical evaluations are A, B and C.

[0062] <Liquidity> The fluidity of the prepared ink composition was evaluated using a spread meter (manufactured by Yasuda Seiki Seisakusho Co., Ltd.) (based on JIS K 5701). (Evaluation criteria) A: The diameter of the ink spread after 60 seconds was 35 mm or more. B: The diameter of the ink spread after 60 seconds was 30 mm or more and less than 35 mm. C: The diameter of the ink spread after 60 seconds was 25 mm or more and less than 30 mm. D: The diameter of the ink spread after 60 seconds was less than 25 mm. The practical evaluations are A, B and C.

[0063] <Misting resistance> 2.62 cc of the ink composition was evenly placed on the rubber roll of a digital incometer (manufactured by Toyo Seiki Seisakusho, Ltd.), and the roll was rotated at 40°C and 2400 rpm for 5 minutes. The amount of ink composition scattered onto the bottom of the roll was evaluated according to the following evaluation criteria. (Evaluation criteria) A: The amount of ink composition scattered was 20 mg or less. B: The amount of scattered ink composition was 20 mg or more and less than 50 mg. C: The amount of scattered ink composition was 50 mg or more and less than 100 mg. D: The amount of scattered ink composition was 100 mg or more.

[0064] The formulations of the examples and comparative examples are as follows: (Examples 1 to 14) The ink composition contains a resin, a pigment, a solvent, and a fatty acid glyceride, and the fatty acid glyceride component is contained in the ink composition in an amount of 0.3 to 10 mass %. (Comparative Examples 1 and 2) The difference from the compositions of the examples is that fatty acid glycerides are not included. (Comparative Examples 3 and 4) The difference from the compositions of the examples is that the fatty acid glyceride component contained in the ink composition is not in the range of 0.3 to 10 mass %.

[0065] [Table 1]

Claims

1. An offset ink composition for metal printing comprising a resin, a pigment, a solvent, and a fatty acid glyceride, wherein the content of the resin in the ink composition is 15 to 60% by mass, the content of the solvent in the ink composition is 10 to 60% by mass, and the content of the fatty acid glyceride in the ink composition is 0.3 to 10% by mass.

2. 2. The offset ink composition for metal printing according to claim 1, wherein the fatty acid glyceride is a fatty acid triglyceride.

3. 2. The offset ink composition for metal printing according to claim 1, wherein the fatty acid glyceride is a fatty acid triglyceride in which the constituent fatty acid has 12 to 20 carbon atoms.

4. 2. The offset ink composition for metal printing according to claim 1, wherein the resin is a polyester resin and / or a petroleum resin.

5. 2. The offset ink composition for metal printing according to claim 1, wherein the solvent is an aromatic hydrocarbon.

6. A metal printed product having a printing layer formed on a metal medium and comprising the offset ink composition for metal printing according to any one of claims 1 to 5, and an overprint layer formed on the printing layer and comprising an overprint varnish.

7. A method for producing a metal printed item, comprising: forming a printed layer on a metal medium by dry offset printing or offset printing the offset ink composition for metal printing according to any one of claims 1 to 5; and applying an overprint varnish onto the printed layer to form an overprint layer.

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