Ink set

Abstract

The present invention provides an ink set for surface printing, a surface-printed material, and a surface-printing method for packaging materials having a printed layer on their surface, wherein the printed layer has excellent adhesion, and furthermore, even when the packaged material is boiled in water, the possibility of the printed layer losing its color is eliminated. [Solution] An ink set for surface printing having one or more color ink compositions and one or more white ink compositions, wherein the ink set satisfies at least the following conditions (A) and (B). (A) The colored ink composition contains a coloring pigment, a polyurethane resin, an amide compound, a wax, a subresin, and a solvent. (B) The white ink composition contains a white pigment, a polyurethane resin, an amide compound, a wax, and a solvent.

Description

Technical Field

[0001] The present invention relates to an offset ink set for surface printing and a surface printed matter.

Background Art

[0002] For foods, confectionery, pet foods, etc., packaging materials using various plastic films are used from the viewpoints of design, economy, content protection, transportability, etc. Also, many packaging materials are subjected to gravure printing or flexographic printing with the intention of imparting design and message appeal to consumers.

[0003] And in order to obtain these packaging materials, as surface printing, there may be a case of performing overprint printing that is printed on the surface of the base film of the packaging material, or an adhesive or an anchor agent may be applied to the printed surface printed on the surface of the base film of the packaging material as necessary, and the film may be subjected to lamination processing. In these printings, a layer made of a white ink composition may be provided on at least a part of the surface of the base film, and further, a color ink composition layer other than white may be provided on a part or all of the layer above the layer, or a color ink composition layer may be provided directly without providing a white ink composition layer on the surface of the base film. As described in Patent Documents 1 and 2, among packaging materials, there is one made of a laminated film provided with a printing layer in an inner layer. Since the ink layer is not the outermost layer in such a packaging material, the ink layer does not come into direct contact with hot water or the like, so the color development of the ink layer does not deteriorate.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention aims to provide a packaging material having a printed layer on its surface, wherein the printed layer has excellent adhesion, and furthermore, even when the printed layer is boiled in water while the contents are packaged inside, the possibility of a decrease in the color development of the printed layer is eliminated. [Means for solving the problem]

[0006] The inventors of the present invention have found that the above problems can be solved by using the following ink set for surface printing as a basis, and have arrived at the present invention described below. 1. An ink set for surface printing having 1 or more color ink compositions and 1 or more white ink compositions, and satisfying all of the following conditions (A) to (D). (A) The colored ink composition contains a coloring pigment, a polyurethane resin, an amide compound, a wax, a subresin, and a solvent. (B) The white ink composition contains a white pigment, a polyurethane resin, an amide compound, a wax, and a solvent. (C) The subresin content in 100 parts by mass of the total solids of the colored ink composition is 1.5 to 7.5 parts by mass, and the subresin content in 100 parts by mass of the total solids of the white ink composition is 0 parts by mass or 1.5 parts by mass or less. (D) When the colored ink composition is a black ink composition, the ratio of the subresin content in 100 parts by mass of the total solids of the white ink composition to the subresin content in 100 parts by mass of the total solids of the black ink composition is 0 to 500%. 2. The ink set for surface printing according to claim 1, wherein the subresin is one or more selected from polymerized rosin, maleic acid-modified rosin, and chlorinated polyolefin resin. 3. The chlorinated polyolefin resin is a chlorinated polypropylene resin, as described in 1 or 2, for surface printing ink sets. A surface-printed material having a structure in which a white ink layer and a colored ink layer are sequentially formed on a substrate by printing with an ink set for surface printing described in any of 4.1 to 4.3. A surface printing method comprising the steps of printing a white ink composition onto a substrate using a surface printing ink set described in any of sections 5.1 to 5.3, and then printing a color ink composition on top of it. Packaging material having the printed surface described in 6.4. [Effects of the Invention]

[0007] According to the present invention, a specific ink set consisting of a white ink composition and a colored ink composition is used, and by performing surface printing without a laminate layer on a substrate layer using these ink compositions, a surface-printed material is obtained in which the outermost layer is an ink composition layer with sufficient adhesive strength. Furthermore, even when packaging formed using this printing method is subjected to boiling treatment, the printed layer of the colored ink composition does not experience a decrease in color development, thus providing excellent aesthetic appeal after boiling treatment. [Brief explanation of the drawing]

[0008] [Figure 1] A figure showing an example of a printed material of the present invention. [Modes for carrying out the invention]

[0009] This invention relates to an ink set for surface printing (hereinafter simply referred to as "ink set"), etc., based on the following matters, and the ink set can be used to obtain various printing methods and printed materials for various applications, packaging materials, and laminates according to the present invention. According to the ink set of the present invention, as shown in Figure 1, surface printing is performed by forming a color ink layer on a substrate via a white ink composition layer, and even if the packaging container, in which the color ink layer and the white ink composition layer are the outermost layers, is boiled in hot water, the color development of the color ink composition layer does not deteriorate.

[0010] [Inventive ink set] The ink set of the present invention comprises a colored ink composition and a white ink composition, and is a set of ink compositions that satisfy all of the following conditions (A) to (D). Note that the colored ink composition and the white ink composition in the ink set may each be one type of ink composition, or may consist of multiple types of ink compositions. Furthermore, each ink composition in the present invention is neither a heat-curing type nor an energy-ray curing type ink composition, nor is it an aqueous ink composition. It is preferably a non-aqueous solvent-type ink composition. (A) The colored ink composition contains a coloring pigment, polyurethane resin, amide compound, wax, subresin, and solvent. (B) The white ink composition contains a white pigment, a polyurethane resin, an amide compound, a wax, and a solvent. (C) The subresin content in 100 parts by mass of the total solids of the colored ink composition is 1.5 to 7.5 parts by mass, and the subresin content in 100 parts by mass of the total solids of the white ink composition is 0 parts by mass or 1.5 parts by mass or less. (D) When the white ink composition contains subresin, the ratio of the subresin content in 100 parts by mass of the total solids of the colored ink composition to the subresin content in 100 parts by mass of the total solids of the white ink composition is 0 to 500%.

[0011] [Components common to conditions (A) and (B)] (Polyurethane resin) The polyurethane resins contained in the colored ink composition and the white ink composition can be selected and used independently of each other. The polyurethane resin used in conditions (A) and (B) may be any polyurethane resin known for use in ink compositions, and is a resin obtained from a polyisocyanate compound and a high-molecular-weight polyol compound, having two or more urethane bonds in its molecule, and having structural units derived from the high-molecular-weight polyol compound, including structures derived from polyester polyol compounds and / or structural units derived from polyether polyol compounds. Polyurethane resins include, for example, polyurethane resins obtained by reacting a polyisocyanate compound, a polyol compound containing a structure derived from a polyester polyol and / or a structure derived from a polyether polyol, a chain extender, and a reaction stopper (a polyurethane resin obtained by reacting a urethane prepolymer obtained by reacting a polyisocyanate compound with a polyol compound containing a structure derived from a polyester polyol compound and / or a structure derived from a polyether polyol compound, and then further reacting it with a chain extender and a reaction stopper).

[0012] (Polyisocyanate compounds) The polyisocyanate compound is preferably a diisocyanate compound, and includes aliphatic diisocyanate compounds such as hexamethylene diisocyanate and 2,2,4-trimethylhexamethylene diisocyanate; alicyclic diisocyanate compounds such as 1,4-cyclohexane diisocyanate, isophorone diisocyanate, and hydrogenated xylylene diisocyanate; aromatic aliphatic diisocyanate compounds such as xylylene diisocyanate and α,α,α',α'-tetramethylxylylene diisocyanate; and aromatic diisocyanate compounds such as toluene diisocyanate and diphenylmethane diisocyanate. Among these, polyisocyanate compounds are preferably alicyclic or aromatic aliphatic diisocyanate compounds, with isophorone diisocyanate and α,α,α',α'-tetramethylxylylene diisocyanate being more preferred, from the viewpoint of easy reaction control and a good balance of performance of the resulting polyurethane resin.

[0013] In addition, as other diisocyanate compounds, aromatic diisocyanate compounds such as 1,3- and / or 1,4-phenylene diisocyanate, 4,4-diisocyanatobiphenyl, 3,3-dimethyl-4,4-diisocyanatobiphenyl, alicyclic diisocyanate compounds such as cyclohexylene diisocyanate, methylcyclohexylene diisocyanate (hydrogenated TDI), aliphatic diisocyanate compounds such as ethylene diisocyanate, tetramethylene diisocyanate, dodecamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and aromatic aliphatic diisocyanate compounds such as m- and / or p-xylylene diisocyanate (XDI) can also be used.

[0014] (Polymeric polyol compound) Among the polymeric polyol compounds, as the compounds having a structure derived from a polyester polyol compound and / or a structure derived from a polyether polyol compound, known polyester polyol compounds and polyether polyol compounds can be used. As the above-mentioned polymeric polyol compound, those having a number average molecular weight of 1,000 to 8,000 are preferable, those having a number average molecular weight of 1,000 to 5,500 are more preferable, and those having a number average molecular weight of 1,000 to 4,000 are even more preferable.

[0015] (Polyester polyol compound) The polyester polyol compound is a polyester diol compound obtained by reacting a low molecular weight diol component (linear glycols such as ethylene glycol, 1,3-propanediol, 1,4-butanediol; branched glycols such as 1,2-propanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol; ether-based diols such as diethylene glycol, triethylene glycol) with a dicarboxylic acid component (saturated and unsaturated aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, maleic acid; aromatic dicarboxylic acids such as phthalic acid). Examples include polyester polyol compounds such as polyester diols and polycaprolactone diols obtained by condensing one or more dibasic acids such as adipic acid, sebacic acid, and phthalic acid with one or more glycols such as ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, and 3-methyl-1,5-pentanediol; polyalkylene glycols such as polyethylene glycol and polypropylene glycol; and polyether polyol compounds such as alkylene oxide adducts of bisphenol A, such as ethylene oxide and propylene oxide. These polymer polyol compounds can be used individually or in combination of two or more.

[0016] Among the polyester polyol compounds mentioned above, 3-methyl-1,5-pentylene adipate diol with a number average molecular weight of 1,000 to 8,000, obtained by a condensation reaction of adipic acid and 3-methyl-1,5-pentanediol, is preferred, and 3-methyl-1,5-pentylene adipate diol with a number average molecular weight of 1,000 to 4,000 is even more preferred. When other polymeric polyol compounds are used in combination with 3-methyl-1,5-pentylene adipate diol, the number of hydroxyl groups of the other polymeric polyol compounds can be 70% or less of the total number of hydroxyl groups of all polymeric polyol compounds, more preferably 55% or less, and even more preferably 40% or less.

[0017] (Polyether polyol compounds) Polyether polyol compounds are polyester diol compounds obtained by ring-opening reactions of cyclic ester compounds (such as lactones), or polyether diol compounds obtained by polyadding oxyalkylenes (such as ethylene oxide and propylene oxide) or tetrahydrofuran to diol compounds (such as poly)alkylene glycol compounds and bisphenols). In addition, known materials such as polypropylene glycol can be used. The number-average molecular weight of polypropylene glycol is preferably 250 or more, more preferably 500 or more, and even more preferably 750 or more, from the viewpoint of imparting various physical properties when it is formed as a polyurethane. The number-average molecular weight of polypropylene glycol is preferably 5,000 or less, more preferably 4,000 or less, and even more preferably 3,000 or less, from the viewpoint of reactivity with isocyanate. The number-average molecular weight can be calculated using the following formula. Formula: Number-average molecular weight = 1000 × 56.1 × valence of hydroxyl group / hydroxyl value

[0018] Polyols may include polyol compounds other than polypropylene glycol (other polyol compounds), such as polyester polyol compounds such as polyester diol compounds, polyether polyol compounds such as polyether diol compounds (excluding the above-mentioned polypropylene glycol), polycarbonate polyol compounds such as polycarbonate diol compounds, and polymer diols such as polybutadiene glycol compounds. When using the above-mentioned polyester polyol compound in combination with the above-mentioned polyether polyol compound, the amount of polyether polyol compound such as polypropylene glycol may be 10 to 50 parts by mass per 100 parts by mass of the polyester polyol compound. Alternatively, it may be not necessary to use them in combination.

[0019] (Other polyol compounds) Other polyol compounds, such as low molecular weight polyol compounds, may be used in combination with a total of 100 parts by mass of high molecular weight polyol compounds, including polyester polyol compounds and polyether polyol compounds. When used in combination, the amount of other polyol compounds should be 50 parts by mass or less, more preferably 35 parts by mass or less, and even more preferably 20 parts by mass or less.

[0020] (Low molecular weight polyol compounds) When reacting a high-molecular-weight polyol compound with an isocyanate compound, in addition to the high-molecular-weight polyol compound, one or more alkanediols such as 1,4-pentanediol, 2,5-hexanediol, and 3-methyl-1,5-pentanediol, or low-molecular-weight polyol compounds such as ethylene glycol, propylene glycol, 1,4-butanediol, and 1,3-butanediol may be mixed and carried out the reaction. When a low molecular weight polyol compound is used in combination with the above polyester polyol compound, it may or may not be used in combination with the polyester polyol compound, depending on the amount of the low molecular weight polyol compound. If used in combination, the amount of the low molecular weight polyol compound, such as ethylene glycol, may be 1 to 10 parts by mass.

[0021] High polymer polyol compounds may be used in combination with polyether polyol compounds from the viewpoint of improving the oil resistance and resolubility of the printed layer. When using polyether polyol compounds, the polyurethane resin may consist of 100% structures derived from the polyether polyol compound among the polyol-derived structural units, or it may contain structures derived from the polyether polyol compound in a range of 50% or less, 40% or less, or 35% or less.

[0022] When other polymeric polyol compounds are used in combination, their number-average molecular weight is preferably 200 or more, more preferably 400 or more, in order to improve the oil resistance of the printing ink composition layer. Furthermore, the number-average molecular weight of the other polyol compounds is preferably 2,000 or less, more preferably 1,000 or less, and even more preferably 800 or less.

[0023] Chain extenders are compounds that have two or more functional groups (amino groups, hydroxyl groups, etc.) that can react with isocyanate groups within their molecule. Compounds containing two or more amino groups within their molecule include diamines with two primary amino groups (ethylenediamine, 1,3-propylenediamine, 1,4-butylenediamine, hexamethylenediamine, isophoronediamine, etc.), diamines with one primary amino group and one secondary amino group (2-ethylaminoethylamine, etc.), and polyamines with two primary amino groups and one or more secondary amino groups (diethylenetriamine, triethylenetetramine, etc.). Hydroxyl group-containing compounds that contain two or more hydroxyl groups within their molecule include low molecular weight diols (ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, triethylene glycol, etc.). Compounds having two amino groups and one hydroxyl group in their molecule include aminoethylethanolamine, aminopropylethanolamine, and 1 molar adducts of ethylene oxide to the diamines having two primary amino groups mentioned above.

[0024] Furthermore, as a chain extender, from the viewpoint of introducing functional groups such as hydroxyl groups and amino groups into the polyurethane resin molecule, compounds having three or more functional groups such as amino groups and hydroxyl groups can be used. Compounds having three or more functional groups such as amino groups and hydroxyl groups include glycerin and aminoethylethanolamine.

[0025] Reaction stoppers are compounds that have one or more functional groups (amino groups, hydroxyl groups, etc.) that can react with isocyanate groups in their molecules. Examples of reaction stoppers include monoalcohols (methanol, ethanol, etc.), monoamines (n-butylamine, di-n-butylamine, etc.), alkanolamines (monoethanolamine, ethylethanolamine, diethanolamine) and diamines (ethylenediamine) that have one amino group and one hydroxyl group in their molecules. Compounds listed as chain extenders can also be used as reaction stoppers. From the viewpoint of introducing functional groups such as hydroxyl groups and amino groups to the molecular ends of polyurethane resins, alkanolamines that have one amino group and one hydroxyl group in their molecules, and the compounds exemplified as chain extenders can be used as reaction stoppers.

[0026] In the production of a urethane prepolymer obtained by reacting a diisocyanate compound with a diol compound, the ratio (equivalent ratio) (equivalents of NCO in the total amount of diisocyanate compound / equivalents of OH in the total amount of diol compound) of the number of NCO groups in the total amount of diol compound is preferably 1.1 to 3, and more preferably 1.2 to 2. In this specification, each "equivalent" below is obtained by multiplying the number of moles of a specific group in the total amount of the compound in question in the composition by the valence of that specific group.

[0027] It is preferable to react the chain extension agent in an amount that is in a ratio of approximately 0.5 to 0.95 equivalents to the equivalent amount of the remaining isocyanate groups in the prepolymer, where the equivalent amount is set to 1. Furthermore, it is preferable to react the reaction termination agent in a ratio of approximately 1 to 2 moles per mole of the polyurethane resin after chain extension.

[0028] The weight-average molecular weight of polyurethane resin is preferably 5,000 to 50,000, more preferably 10,000 to 30,000. This weight-average molecular weight can be measured by gel permeation chromatography (GPC). For example, using a Water2690 GPC instrument (Waters Corporation) and a PLgel, 5μ, MIXED-D column (Polymer Laboratories), chromatography can be performed under the following conditions: tetrahydrofuran as the developing solvent, column temperature 25°C, flow rate 1 ml / min, RI detector, sample injection concentration 10 mg / ml, and injection volume 100 microliters. The weight-average molecular weight can then be determined as polystyrene equivalent.

[0029] The polyurethane resin is preferably a polyurethane resin having functional groups such as hydroxyl groups and amino groups. Methods for obtaining such a polyurethane resin can include using a compound having three or more of the above-mentioned functional groups (amino groups, hydroxyl groups, etc.) as a chain extender, or reacting a diisocyanate compound with a diol compound in a molar ratio of less than 1.0 times that of the diol compound without using a chain extender or reaction stopper. When the polyurethane resin has amino groups, the amine value is preferably in the range of 0.1 to 10 mgKOH / g. The amine value refers to the amine value per gram of solids and can be measured using a 0.1N aqueous hydrochloric acid solution by potentiometric titration (for example, COMTITE (AUTO TITRATOR COM-900, BURET B-900, TITSTATION K-900), manufactured by Hiranuma Sangyo Co., Ltd.), and then converted to the equivalent amount of potassium hydroxide.

[0030] The amount of polyurethane resin in the colored ink composition is not particularly limited. The polyurethane resin content of the color ink composition is preferably 10.0% by mass or more, more preferably 20.0% by mass or more, and even more preferably 30.0% by mass or more, based on the total solid content. It is also preferably 60.0% by mass or less, more preferably 50.0% by mass or less, and even more preferably 45.0% by mass or less. By having a polyurethane resin content within the above range, the ink composition achieves good adhesion and conformability to the substrate when the substrate is a flexible material such as a film.

[0031] The amount of polyurethane resin in the white ink composition is not particularly limited. The polyurethane resin content of the white ink composition is preferably 5.0% by mass or more, more preferably 10.0% by mass or more, and even more preferably 15.0% by mass or more, of the total solid content. It is also preferably 25.0% by mass or less, more preferably 23.0% by mass or less, and even more preferably 20.0% by mass or less. By having a polyurethane resin content within the above range, the white ink composition exhibits sufficient whiteness and provides good adhesion and conformability to the substrate when the substrate is a flexible material such as a film.

[0032] (Amide compounds) The amide compounds contained in the colored ink composition and the white ink composition can be selected and used independently of each other. The amide compounds used under conditions (A) and (B) are compounds having an amide bond, formed by reacting an amine compound with a carboxylic acid compound, and can include amide compounds such as saturated fatty acid amides, unsaturated fatty acid amides, and modified fatty acid amides. As the above-mentioned amide compounds, known amide compounds such as caprylic acid amide, capric acid amide, lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, arachidin acid amide, behenic acid amide, hydroxystearic acid amide, palmitoleic acid amide, oleic acid amide, linoleic acid amide, linolenic acid amide, erucic acid amide, undecylenic acid amide, and arachidonic acid amide can be used.

[0033] The content of amide compounds in the colored ink composition is not particularly limited. The amide compound content is preferably 0.2% by mass or more, more preferably 0.5% by mass or more, and even more preferably 0.7% by mass or more, of the total solid content of the colored ink composition. It is also preferably 2.0% by mass or less, more preferably 1.5% by mass or less, and even more preferably 1.0% by mass or less. Because the amide compound content is within the above range, the printed layer of the colored ink composition exhibits excellent blocking resistance.

[0034] The content of the amide compound in the white ink composition is not particularly limited. The amide compound content is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and even more preferably 0.3% by mass or more, of the total solid content of the white ink composition. It is also preferably 2.0% by mass or less, more preferably 1.5% by mass or less, and even more preferably 1.0% by mass or less. By having the amide compound content within the above range, the printed layer of the white ink composition exhibits excellent blocking resistance.

[0035] (wax) The waxes contained in the colored ink composition and the white ink composition can be selected and used independently of each other. Known waxes such as polyethylene wax, polypropylene wax, Fischer-Tropsch wax, carnauba wax, paraffin wax, and microstarin wax can be used. The average particle size of the wax is preferably 3 μm to 10 μm from the viewpoint of scratch resistance and printability. The average particle size of the wax particles is the volume-based cumulative 50% particle size (median diameter (D50)) measured by laser diffraction / light scattering.

[0036] The amount of wax in the colored ink composition is not particularly limited. The wax content is preferably 2.0% by mass or more, more preferably 4.0% by mass or more, and even more preferably 5.0% by mass or more, of the total solid content of the color ink composition. It is also preferably 10.0% by mass or less, more preferably 8.0% by mass or less, and even more preferably 7.5% by mass or less. By keeping the wax content within the above range, the printed layer of the colored ink composition exhibits even greater resistance to blocking.

[0037] The wax content in the white ink is not particularly limited. The wax content of the white ink composition is preferably 1.0% by mass or more, more preferably 1.5% by mass or more, and even more preferably 2.0% by mass or more, of the total solid content. It is also preferably 5.0% by mass or less, more preferably 4.5% by mass or less, and even more preferably 4.0% by mass or less. By having the wax content within the above range, the printed layer of the white ink composition has even better blocking resistance.

[0038] (solvent) For white and colored inks, it is preferable to use solvents that do not contain aromatic hydrocarbon organic solvents, taking environmental considerations into account. Organic solvents that do not contain aromatic hydrocarbon organic solvents mainly include alcohol-based organic solvents such as methanol, ethanol, n-propanol, isopropanol, and butanol; ketone-based organic solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; ester-based organic solvents such as methyl acetate, ethyl acetate, propyl acetate, and butyl acetate; aliphatic hydrocarbon organic solvents such as n-hexane, n-heptane, and n-octane; and alicyclic hydrocarbon organic solvents such as cyclohexane, methylcyclohexane, ethylcyclohexane, cycloheptane, and cyclooctane. Considering environmental aspects, it is preferable to minimize the use of ketone-based organic solvents as much as possible among the above organic solvents.

[0039] The content of the organic solvent is not particularly limited. For example, the content of the organic solvent in the ink composition is preferably 15.0% by mass or more, more preferably 25.0% by mass or more. Furthermore, considering the printability of the ink composition, the content of the organic solvent is preferably 90.0% by mass or less, more preferably 80.0% by mass or less. By having the organic solvent content within the above range, the ink composition has excellent printability.

[0040] [Components specific to condition (A)] (Subresin) In the present invention, the subresin used as condition (A) is preferably soluble in an organic solvent and is one or more selected from rosin-based resins such as polymerized rosin and maleic acid rosin, chlorinated polyolefins, vinyl chloride-vinyl acetate resins, polyamide resins, etc. Among these, rosin-based resins such as polymerized rosin and maleic acid-modified rosin, and chlorinated polyolefin resins such as chlorinated polypropylene are preferred.

[0041] Condition (C) is that the subresin content in 100 parts by mass of the total solids of the color ink composition is 1.5 to 7.5 parts by mass. Preferably, it is 2.0 parts by mass or more. Furthermore, 7.0 parts by mass or less is preferred, 6.7% by mass or less is more preferred, 5.0% by mass or less is even more preferred, and 4.0% by mass or less is most preferred. Furthermore, the subresin content in 100 parts by mass of the total solids of the white ink composition is 0 parts by mass or 1.5 parts by mass or less. It may be 0 parts by mass. When subresin is included, it is preferably 1.3 parts by mass or less. When the subresin content in the colored ink composition and the white ink composition is within the above range, excellent initial adhesion after printing and effectiveness in preventing color degradation after boiling are achieved.

[0042] Condition (D) is that when the colored ink composition is a black ink composition, the ratio of the subresin content in 100 parts by mass of the total solids of the white ink composition to the subresin content in 100 parts by mass of the total solids of the black ink composition is 0 to 500%. If this ratio is not 0%, it is preferably 300% or less, more preferably 100% or less, and even more preferably 50% or less. Within this range, the initial adhesion after printing and the effect of preventing color deterioration after boiling are excellent.

[0043] (Rosin-based resin) Examples of rosin-based resins include polymerized rosin, maleic acid rosin, gum rosin, tall oil rosin, and wood rosin. Generally, rosin is an amber-colored, amorphous resin obtained from pine trees. Although it is a mixture because it is obtained from natural sources, it may also be used by isolating each of its constituent components, such as abietic acid, neoabietic acid, palastic acid, pimaric acid, isopimaric acid, sandaracopimalic acid, and dehydroabietic acid. In this invention, these are also defined as rosin. Rosin-based resins are resins obtained by modifying the rosin mentioned above, and are specifically listed below. (1) Hydrogenated rosin: This is a type of rosin in which hydrogen is added to the conjugated double bond (hydrogenation) to improve weather resistance. (2) Disproportionated rosin: Disproportionation is a modification in which two molecules of rosin react, and two molecules of abietic acid with conjugated double bonds become one aromatic molecule and the other a molecule with a single double bond. Generally, it has lower weather resistance than hydrogenated rosin, but it has improved weather resistance compared to untreated rosin. (3) Rosin-modified phenolic resin: Rosin-modified phenolic resin is often used as the main binder in offset printing inks. Rosin-modified phenolic resin can be obtained by known manufacturing methods. (4) Rosin esters: These are ester resins derived from rosin and have long been used as tackifiers for adhesives and glues. (5) Maleic acid rosin (rosin-modified maleic acid resin): This is produced by adding maleic anhydride to rosin, and may also include rosin in which a hydroxyl group-containing compound such as glycerin is esterified with the anhydride group and grafted onto it as needed. (6) Polymerized rosin: A derivative containing dimerized resin acid derived from natural resin rosin. In addition, known rosins and rosin derivatives can also be used, and these can be used alone or in combination.

[0044] The acid value of the rosin resin is preferably 100 to 350 mg KOH / g, more preferably 200 to 350 mg KOH / g, and even more preferably 250 to 350 mg KOH / g. Among rosin resins, maleic acid rosin and / or polymerized rosin are preferred.

[0045] (Chlorinated polyolefin) Examples of chlorinated polyolefins include, but are not limited to, chlorinated polypropylene resins and chlorinated polyethylene resins. Modified chlorinated polyolefins are also acceptable, and examples include chlorinated polyolefins graft-polymerized with polymerizable acrylic compounds (acrylic acid, methacrylic acid, or alkyl esters thereof, etc.) or unsaturated polycarboxylic acids (maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, etc.), or polyolefins graft-polymerized with the above unsaturated polycarboxylic acids that have been chlorinated. The chlorine content in the chlorinated polyolefin is preferably 1% by mass or more, more preferably 10% by mass or more, relative to the total chlorinated polyolefin. Furthermore, it is preferably 40% by mass or less, more preferably 30% by mass or less.

[0046] (PVC-vinyl acetate resin) PVC-vinyl acetate resins are basically vinyl chloride-vinyl acetate copolymers in which vinyl chloride and vinyl acetate are essential components. These copolymers are obtained by copolymerizing with other radical polymerizable monomers as needed. In this process, the ester bonds of the vinyl acetate-derived parts are saponified, and compounds containing amino groups are used as other radical polymerizable monomers. Alternatively, amino groups are introduced into the vinyl chloride-derived parts by dehydrochlorination of an amino group-containing hydrocarbon compound. For example, amino group-containing vinyl chloride-vinyl acetate-vinyl alcohol copolymers can also be used.

[0047] (Polyamide resin) The polyamide resin is obtained by reacting an acid component, which may mainly contain polymerized fatty acids and also partially contain aliphatic, alicyclic, and aromatic dicarboxylic acids or aliphatic monocarboxylic acids, with an amine component, which may mainly contain aliphatic, alicyclic, aromatic aliphatic, and aromatic polyamines alone or in mixtures, and also partially contain primary and secondary monoamines. Here, polymerized fatty acids are generally obtained by polymerization of unsaturated fatty acids or their esters with 16 to 22 carbon atoms, and include monobasic fatty acids, dimerized polymerized fatty acids, and trimerized polymerized fatty acids. Examples of aliphatic dicarboxylic acids include succinic acid, adipic acid, azelaic acid, and maleic acid; examples of alicyclic dicarboxylic acids include cyclohexanedicarboxylic acid; and examples of aromatic dicarboxylic acids include isophthalic acid and terephthalic acid. Furthermore, examples of aliphatic monocarboxylic acids include acetic acid, stearic acid, oleic acid, and linoleic acid.

[0048] On the other hand, aliphatic polyamines among the amine components include aliphatic diamines such as ethylenediamine, propylenediamine, hexamethylenediamine, and methylaminopropylamine, as well as aliphatic polyamines such as diethylenetriamine and triethylenetetramine. Alicyclic polyamines include cyclohexylenediamine and isophoronediamine. Aromatic aliphatic polyamines include xylylenediamine, and aromatic polyamines include phenylenediamine and diaminodiphenylmethane. Furthermore, primary and secondary monoamines include butylamine, octylamine, diethylamine, monoethanolamine, monopropanolamine, diethanolamine, and dipropanolamine. From the standpoint of oil resistance, heat resistance, and PVC blocking resistance of the ink composition, it is preferable to use a polyamide resin that has a hydroxyl group in its molecule and uses an alkanolamine as the primary or secondary monoamine component among polyamide resins. As a method for synthesizing polyamide resin from the above acid and amine components, it is desirable to set the carboxyl group / amino group ratio of the reactants to 0.9 / 1.0 to 1.0 / 0.9, preferably 1.0 / 1.0, the reaction temperature to 160 to 280°C, preferably 180 to 230°C, and to carry out the reaction under reduced pressure of about 100 torr in the final stage.

[0049] [Components specific to condition (A)] (Coloring pigments contained in the colored ink composition) The coloring pigment is not limited to any pigment other than a white pigment. For example, the coloring pigment is generally an inorganic pigment or organic pigment used in gravure printing ink compositions containing organic solvents. Inorganic pigments include red iron oxide, antimony red, cadmium red, cadmium yellow, cobalt blue, Prussian blue, ultramarine, carbon black, and graphite. Organic pigments include azo, phthalocyanine, anthraquinone, perylene, perinone, quinacridone, thioindigo, dioxazine, isoindolinone, quinophthalone, azomethine azo, dicutopyrrolopyrrole, and isoindoline pigments. In particular, the colored ink may be black ink containing carbon black.

[0050] The content of coloring pigments is not particularly limited. Depending on the desired degree of coloring of the printed layer, the pigment content in the color ink composition may be 0.5% by mass or more, 5.0% by mass or more, 30.0% by mass or less, or 20.0% by mass or less. When the color ink composition is a black ink composition, the carbon black content in the total solids of the ink composition is preferably 5.0% by mass or more, more preferably 10.0% by mass or more, and even more preferably 15.0% by mass or more. It is also preferably 70.0% by mass or less, more preferably 60.0% by mass or less, and even more preferably 50.0% by mass or less. When the colored ink composition is other than the black ink composition, the content of the colored ink in the total solids in the ink composition is preferably 10.0% by mass or more, more preferably 20.0% by mass or more, and even more preferably 40.0% by mass or more. Also, it is preferably 85.0% by mass or less, more preferably 80.0% by mass or less, and even more preferably 77.0% by mass or less. By keeping the content of the coloring pigment within the above range, the ink composition achieves good coloring power, ink composition stability, and cohesiveness of the ink composition coating film. The colored ink composition may also contain a white pigment, as long as it does not impair the effects of the present invention.

[0051] [Components specific to condition (B)] (White pigment contained in the white ink composition) The white pigment is not particularly limited, but titanium dioxide is preferred. The content of the white pigment is not particularly limited. Considering the desired degree of coloring of the printed layer, the pigment content in the total solids of the white ink composition is preferably 40.0% by mass or more, more preferably 50.0% by mass or more, and even more preferably 55.0% by mass or more. Also preferably 90.0% by mass or less, more preferably 80.0% by mass or less, and even more preferably 78.0% by mass or less. By having the white pigment content within the above range, the ink composition can be obtained to have good coloring power and opacity, ink composition stability, and cohesiveness of the ink composition coating film. In addition, coloring pigments may also be added in a range that does not hinder the color development of the white ink composition.

[0052] [Any component common to both the colored ink composition and the white ink composition] (Cellulose resin) Examples of cellulose-based resins include nitrocellulose (nitro group substituted), cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate and other lower acyl group substituted products, and methylcellulose, ethylcellulose and other lower alkyl substituted products.

[0053] (Acrylic resin) Examples include polymers and copolymers thereof consisting of (meth)acrylates. Examples of such (meth)acrylates include alkyl (meth)acrylates such as ethyl, propyl, or butyl (meth)acrylate; and hydroxyalkyl (meth)acrylates such as hydroxymethyl, hydroxyethyl, hydroxypropyl, hydroxybutyl, and hydroxypentyl (meth)acrylate.

[0054] (Other resins) These include polypropylene dimer acid resins, maleic acid resins, petroleum resins, terpene resins, ketone resins, and dammar resins.

[0055] (Extender pigments) Both ink compositions may contain extender pigments such as calcium carbonate, kaolin clay, barium sulfate, aluminum hydroxide, silica, and talc, and the amount of these pigments can be appropriately determined considering the characteristics and printing effects of both ink compositions.

[0056] (Additives) Additives that can be independently and optionally added to the colored ink composition and the white ink composition of the present invention include pigment dispersants, defoaming agents, plasticizers, antiblocking agents, adhesion improvers, infrared absorbers, ultraviolet absorbers, fragrances, flame retardants, and the like.

[0057] (solvent) The ink composition of the present invention is preferably non-aqueous. Furthermore, the organic solvent of the ink composition is preferably a mixed solvent system of an ester-based solvent and an alcohol-based solvent (hereinafter sometimes referred to as "mixture"). In this case, the solubility of the polyurethane resin tends to be higher, and printability such as gradation reproduction and fogging prevention tends to be better, which is preferable because it allows for the design of a wide range of printing ink compositions to suit the required performance.

[0058] [Preparation method common to both colored ink composition and white ink composition] The method for preparing the colored ink composition and the white ink composition of the present invention is not particularly limited. For example, the ink composition can be prepared by adding the above components sequentially or simultaneously and mixing them in a bead mill, ball mill, sand mill, attritor, roll mill, pearl mill, high-speed agitator, paint conditioner, etc.

[0059] [The present invention: printed materials, printing methods, and packaging materials] (base material) The substrate (support) for obtaining the printed material may be metal, paper, or resin, but a resin film is preferred. Furthermore, a primer layer may be formed beforehand, or known surface treatments such as corona discharge treatment may be performed, or these surface treatments may be omitted. Since the effect of the present invention is to obtain favorable results even when the printed layer is subjected to boiling treatment, it is preferable that the substrate be designed for boiling treatment. The resin film is a film made of polyester such as polyethylene terephthalate and polyethylene naphthalate, polycycloolefin, polyacetate, polyethersulfone, polycarbonate, polyamide, polyimide, (meth)acrylic polymer, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyl alcohol, polyarylate, polyphenylene sulfide, and cellulosic polymers such as diacetylcellulose and triacetylcellulose. The resin film may also be an anti-fog film that has been coated or kneaded with an anti-fogging agent. The substrate may also be a foaming substrate that has the property of foaming when heated, or a substrate that does not have such property.

[0060] (Printing method) The printed material of the present invention is obtained by coating (printing) the above-described color ink composition and white ink composition onto a substrate (support) whose surface to be printed on may be surface-treated, and then drying it. The printing method is not particularly limited, and known means such as gravure printing and flexographic printing, as well as known printing apparatus and known printing conditions, can be employed. The drying process after printing may also be carried out by evaporating the solvent with hot air or the like.

[0061] [Printing methods and packaging materials] To use the material for packaging, the entire surface or a portion of the surface of the substrate (support) is printed with a white ink composition. After the printed film dries, printing is performed with a colored ink composition. At this time, the areas where the colored ink composition is printed may be on the printed layer of the white ink composition. Alternatively, it may be on areas not printed with the white ink composition, i.e., the surface of the substrate (support). Furthermore, the colored ink composition may be printed on an area that spans both the areas printed with the white ink composition and the areas that are not printed. The present invention exhibits particularly excellent effects when printing with a colored ink composition on a printed layer made of a white ink composition. [Examples]

[0062] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "%" means "mass%" and "parts" means "parts by mass".

[0063] <Solvent> Mixed solvent 1 (a mixture of ethyl acetate and isopropanol in a mass ratio of 80:20) Mixed solvent 2 (methylcyclohexane and isopropanol mixed in a mass ratio of 55:45) <Pigments> Pigment for white ink: Titanium dioxide Pigments for colored inks: Carbon black as a pigment for black ink. Pigments for colored inks: Pigment Red 146 as a pigment for red ink. Pigments for colored inks: Pigment blue 15:4 for blue ink.

[0064] <Resin varnish> Cellulose resin varnish 1 was obtained by diluting cellulose resin (product name "TS1 / 4", manufactured by TNC Corporation) with mixed solvent 1 to a solid content of 23.5% by mass. Acrylic resin varnish 1 was obtained by diluting an acrylic resin (product name "Dianal LR948", acid value 13 mg KOH / g, hydroxyl value 35 mg KOH / g, glass transition temperature 79°C, mass average molecular weight 30000, manufactured by Mitsubishi Chemical Corporation) with mixed solvent 1 to a solid content of 45% by mass. <Subresin> DR1 (product name "Dymarex", polymerized rosin, manufactured by Eastman Chemical Company) MR1 (Product name "Marquid No. 33", rosin maleate, acid value 290-320 mg KOH / g, softening point 140-160°C, manufactured by Arakawa Chemical Industries, Ltd.) CL-PP1 (Product name "Superclon 370M", chlorinated polyolefin solution, solid content 50%, manufactured by Nippon Paper Industries Co., Ltd.)

[0065] <Additives> Amid 1 was obtained by diluting lauric acid amide (trade name "Diamid Y", manufactured by Nippon Chemical Corporation) with mixed solvent 2 to a solid content of 20.0% by mass. Wax 1 (Product name "Polycon PA-60", polyethylene wax, median diameter (d50) 6.0 μm, solid content 26% by mass, Polycon Co., Ltd.)

[0066] Polyurethane resin varnish 1 (PU1 resin varnish) (30% solid content) In a four-necked flask equipped with a stirrer, condenser, and nitrogen gas inlet, 140 parts by mass of 3-methyl-1,5-pentylene adipate diol with a number average molecular weight of 2000, 60 parts by mass of polypropylene glycol with a number average molecular weight of 2000, and 44.4 parts by mass of isophorone diisocyanate were charged, and the mixture was reacted at 100-105°C for 6 hours while introducing nitrogen gas. After cooling to near room temperature, 528 parts by mass of ethyl acetate and 93 parts by mass of isopropanol were added, followed by the addition of 15.6 parts by mass of isophorone diamine to extend the chain, and then 0.98 parts by mass of monoethanolamine and 0.96 parts by mass of ethylenediamine to stop the reaction, yielding polyurethane resin varnish 1 (solid content 30% by mass, theoretical molecular weight 16700, resin amine value 3.4 mg KOH / g).

[0067] Polyurethane resin varnish 2 (PU2 resin varnish) (solid content 30% by mass) In a four-necked flask equipped with a stirrer, condenser, and nitrogen gas inlet, 200 parts by mass of 3-methyl-1,5-pentylene adipate diol with a number average molecular weight of 2000, 3.8 parts by mass of ethylene glycol, and 36.0 parts by mass of isophorone diisocyanate were charged, and the mixture was reacted at 100-105°C for 6 hours while introducing nitrogen gas. After cooling to near room temperature, 495 parts by mass of ethyl acetate and 87 parts by mass of isopropanol were added, followed by the addition of 8.8 parts by mass of isophorone diamine to extend the chain, and then 0.56 parts by mass of monoethanolamine and 0.55 parts by mass of ethylenediamine to stop the reaction, yielding polyurethane resin varnish 2 (solid content 30% by mass, theoretical molecular weight 27400, resin amine value 2.0 mg KOH / g).

[0068] <Preparation of Ink Composition> Each material was mixed with paint conditioner so that the solid content concentration matched the mass percentage (mass%) shown in Table 1, and then mixed solvent 1 was added to prepare the ink composition. Furthermore, the concentrations of the pigments for the colored inks, carbon black, pigment red 146, and pigment blue 15:4 in the solvent-containing colored ink composition are all 10.0% by mass, and the concentration of titanium dioxide in the white ink composition is 35.0% by mass.

[0069] (Evaluation methods and criteria) To 100 parts of the obtained ink composition, 40 parts of mixed solvent 1 were added to dilute it, yielding a diluted ink composition for printing. To this diluted ink composition, 5% by mass of "Lamiol R curing agent" (manufactured by Sakata Inx Co., Ltd.) was added relative to the total amount of the ink composition before dilution to obtain dilutions of each ink composition.

[0070] Diluted color ink compositions were applied to obtain single-colored materials under the following "Conditions for Preparing Colored Materials". The results of the initial adhesion and the decrease in color development after boiling are shown in Table 2. The following "printing conditions" were used to print and dry a diluted white ink composition, and then print and dry a diluted colored ink composition on top of it to obtain a printed material using gravure printing with overprinting. The resulting printed materials were evaluated for color degradation after boiling according to the following evaluation method. The results are shown in Table 3.

[0071] <Conditions for preparing painted specimens> Using a bar coater with a wire diameter of 0.15 mm, the ink composition was applied to a polypropylene film substrate (product name "P-1111", 30 μm thick, manufactured by Toyobo Co., Ltd.) to obtain a colored product of the ink composition.

[0072] <Initial adhesion> Initial adhesion was evaluated by applying Nichiban cellophane tape (12 mm wide) to the colored surface of the colored material obtained one hour after preparation using the above-described coloring conditions, and to the printed surface of the printed material obtained by overprinting gravure printing, and then rapidly peeling it off. The rate at which the coating peeled off (the ratio of the area of ​​the peeled coating to the area of ​​the peeled cellophane tape) was used to evaluate the initial adhesion. A score of ○ or △ or higher was considered acceptable. Furthermore, the initial adhesion results to the printed surface differed depending on the color ink composition. The initial adhesion results for each colored color ink composition shown in Table 2 were the same as the initial adhesion results for each printed material shown in Table 3, which were obtained using the respective color ink compositions. ○: No peeling of the coating was observed. ○△: Paint peeling is less than 25% of the surface area. △: Paint peeling covers 25% or more but less than 50% of the surface area. △×: Paint peeling covers 50% or more but less than 75% of the surface area. ×: Paint film peeling exceeds 75% of the surface area.

[0073] <Printing conditions> Base film: For the evaluation of initial adhesion and color degradation after boiling, a polypropylene film (product name "P-1111", 30 μm, manufactured by Toyobo Co., Ltd.) was used as the substrate. Printing machine: Gravure proofing machine Printing plate for ink composition: Helio 175 ine / inch (design: solid color printing plate) Printing speed: 40m / min Drying conditions: 50℃

[0074] <Reduction in color after boiling> The colored samples obtained under the above coloring sample preparation conditions and the printed samples obtained under the above printing conditions were each immersed in 95°C hot water for 40 minutes, and the printed surface was visually inspected and evaluated. The printed layer was in direct contact with the hot water. The visual inspection was conducted by 10 people who routinely evaluate the color development of printed materials. A score of △ or higher was considered acceptable. ○: No decrease in color development was observed in any of the participants. ○△: 8-9 people did not show any decrease in color development. △: 5-7 people noticed a slight decrease in color (at a usable level). ×: A clear decrease in color development was observed, or clear unevenness in color development occurred.

[0075] [Table 1]

[0076] TIFF2026081665000003.tif81170

[0077] [Table 2]

[0078] [Table 3]

[0079] In Table 1, inks 1-4, 8, 9, and 11 are color ink compositions in accordance with the present invention. Inks 5-7 have an excessive subresin content, while ink 10 does not contain subresin. According to Table 2, when inks 1-4, 8, 9, and 11 were applied to the substrate in a single color without printing on the white ink composition's printing layer, the initial adhesion was good (○ or ○△). Furthermore, all evaluators gave inks 1, 2, 8, 9, and 11 a ○△ rating for color degradation after boiling (8-9 people did not notice any color degradation). However, while inks 3 and 4 had good initial adhesion, the degree of color degradation after boiling was ×, indicating a clear decrease in color. However, in Examples 1 to 10, where printing layers of black ink 1-4, 8, 9, and 11, red ink 1, and cyan ink 1 were formed on top of a printing layer of a specific white ink composition, as shown in each example in Table 3, the initial adhesion of the colored ink composition layers was good. Furthermore, the color development after boiling, including black ink 3 and 4, was clearly improved compared to the case where no white ink composition layer was provided, as shown in Table 2.

[0080] In contrast, the black inks 5-7 in Table 1, which are not color ink compositions in accordance with the present invention, have an excessive subresin content. As shown in Table 2, when printing is done in a single color without printing on the white ink composition's printing layer, at the very least, the initial adhesion is inferior, and all examiners clearly observed a decrease in color development after boiling. As shown in Table 3, in Comparative Examples 1-3 and 7, in which a layer of black ink composition 5-7 was formed on top of a white ink composition layer, the color development after boiling remained reduced and did not improve. As shown in Table 2, the initial adhesion of ink 10, which does not contain subresin, was inferior. Since the initial adhesion did not change whether or not it was used in combination with a white ink composition layer, Comparative Example 4, which used ink 10, still had inferior initial adhesion of the layer derived from ink 10. Furthermore, White 2 and White 4 shown in Table 1 are white ink compositions that do not conform to the present invention because they contain an excessive amount of subresin. Comparative Examples 5, 6, and 8 are examples in which these white ink compositions were used, and as a result, the printed layers of the colored ink compositions printed on them showed a clear decrease in color development after boiling.

Claims

1. An ink set for surface printing having one or more color ink compositions and one or more white ink compositions, and satisfying all of the following conditions (A) to (D). (A) The colored ink composition contains a coloring pigment, a polyurethane resin, an amide compound, a wax, a subresin, and a solvent. (B) The white ink composition contains a white pigment, a polyurethane resin, an amide compound, a wax, and a solvent. (C) The subresin content in 100 parts by mass of the total solids of the colored ink composition is 1.5 to 7.5 parts by mass, and the subresin content in 100 parts by mass of the total solids of the white ink composition is 0 parts by mass or 1.5 parts by mass or less. (D) When the colored ink composition is a black ink composition, the ratio of the subresin content in 100 parts by mass of the total solids of the white ink composition to the subresin content in 100 parts by mass of the total solids of the black ink composition is 0 to 500%.

2. The ink set for surface printing according to claim 1, wherein the subresin is one or more selected from polymerized rosin, maleic acid-modified rosin, and chlorinated polyolefin resin.

3. The ink set for surface printing according to claim 1 or 2, wherein the chlorinated polyolefin resin is a chlorinated polypropylene resin.

4. A surface-printed material having a structure in which a white ink layer and a color ink layer are sequentially formed on a substrate by printing with the surface-printing ink set described in claim 1 or 2.

5. A surface printing method comprising the steps of printing a white ink composition onto a substrate and then printing a color ink composition thereon using the surface printing ink set described in claim 1 or 2.

6. A packaging material having the printed surface described in claim 4.

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