White ink composition, laminate, laminate laminate, and packaging material

Abstract

To provide a white ink composition with excellent hot lamination strength and highlight transfer properties. [Solution] An oil-based white ink composition comprising a polyurethane resin (A), cellulose acetate propionate (B), titanium dioxide pigment (C), water (D), and an organic solvent (E), wherein the 100% modulus of the polyurethane resin (A) is 0.4 to 3.5 MPa, the content of the polyurethane resin (A) on a solids basis is 10 to 25% by mass relative to the solids of the white ink composition, the content of cellulose acetate propionate (B) on a solids basis is 0.5 to 7% by mass relative to the solids of the white ink composition, the titanium dioxide pigment (C) is surface-treated, the amount of surface treatment of the titanium dioxide pigment (C) relative to the titanium dioxide is 6.5 to 9.5% by mass, and the content of water (D) is 1 to 5% by mass relative to the total mass of the white ink composition.

Description

Technical Field

[0001] The present invention relates to a white ink composition, a laminate, a laminated laminate, and a packaging material.

Background Art

[0002] For packaging of foods, daily necessities, etc., a packaging material using a plastic film as a base material is used. In such a packaging material, printing such as gravure printing is performed on the base material for the purpose of decoration, information description, etc., and a printing layer is formed. In applications where strict physical properties are required, a packaging material having a laminate structure in which the printing layer is sandwiched between the base material and the sealant layer may be used. Among the inks used for packaging materials having a laminate structure, white ink is often placed on the back side of each color ink in order to improve the visibility of the overall design, and since it is used the most, excellent physical properties are required. Representative required physical properties include initial adhesion to the base material (initial adhesion), laminate strength, and transferability from the printing plate to the base material. In recent years, the required physical properties have become even more advanced. For example, laminate strength under high-temperature environments (hot laminate strength) is required for laminate strength, and highlight transferability is required for transferability.

[0003] A packaging material having a laminate structure has opportunities to be exposed to various heats such as heat sealing during bag making, boiling after filling the contents, and retorting from the manufacturing to the use of the flexible package. The laminate strength in the packaging material having a laminate structure is greatly related to the printing layer made of white ink located between the base material and the sealant layer, and in particular, the adhesion of the binder resin contained in the printing layer contributes greatly. However, when exposed to heat, the binder resin softens and the adhesion decreases, and the required laminate strength cannot be obtained, resulting in many problems. Therefore, further improvement of the hot laminate strength is required.

[0004] On the other hand, printability is also an important physical property required of white ink. To obtain accurate and clear printed materials, excellent transferability from the printing plate to the substrate is required. While solid areas with a large amount of ink tend to have excellent transferability, in highlight areas with a small amount of ink, the propulsion force for transfer from the printing plate to the substrate is weak, often resulting in problems such as no transfer or insufficient transfer. Therefore, excellent highlight transferability is also an important physical property required of white ink.

[0005] Patent Document 1 discloses a liquid ink composition containing a polyurethane resin, an anti-blocking agent, an organic solvent, water, and a pigment. Patent Document 2 discloses a gravure ink containing a binder resin, a chlorinated polyolefin resin, an organic solvent, and water. Patent Document 3 discloses a laminate printing ink composition for flexible packaging that contains a specific polyurethane resin. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2018-177854 [Patent Document 2] Japanese Patent Publication No. 2018-184584 [Patent Document 3] Japanese Patent Publication No. 2020-189902 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, the liquid ink composition in Patent Document 1, the gravure ink in Patent Document 2, and the laminate printing ink composition for flexible packaging in Patent Document 3 all have room for further improvement in terms of hot lamination strength and highlight transfer properties.

[0008] This invention has been made in view of the above circumstances, and its objective is to provide a white ink composition that is excellent in hot lamination strength and highlight transfer, a laminate using the same, a laminated laminate, and a packaging material. [Means for solving the problem]

[0009] The present invention has the following aspects. [1] An oil-based white ink composition, It contains polyurethane resin (A), cellulose acetate propionate (B), titanium dioxide pigment (C), water (D), and an organic solvent (E). The 100% modulus of the polyurethane resin (A) is 0.4 to 3.5 MPa. The content of the polyurethane resin (A) on a solids basis is 10 to 25% by mass relative to the solids of the white ink composition. The content of the cellulose acetate propionate (B) on a solid content basis is 0.5 to 7% by mass relative to the solid content of the white ink composition. The titanium oxide pigment (C) is surface-treated, and the titanium oxide pigment (C ) The amount of surface treatment is 6.5 to 9.5% by mass. A white ink composition in which the water (D) content is 1 to 5% by mass relative to the total mass of the white ink composition. [2] The white ink composition according to [1], wherein the 100% modulus of the polyurethane resin (A) is 0.4 to 2.0 MPa. [3] The white ink composition according to [1] or [2], wherein the viscosity of the cellulose acetate propionate (B) measured in accordance with ASTM D 1343 is 60 to 90 poise. [4] Any of the white ink compositions according to [1] to [3] above, wherein the surface treatment of the titanium oxide pigment (C) is alumina treatment and silica treatment. [5] Furthermore, it contains terpene phenol resin (F), A white ink composition according to any of the [1] to [4] above, wherein the content of the terpene phenol resin (F) on a solid content basis is 1 to 8% by mass relative to the solid content of the white ink composition. [6] A white ink composition according to any of the above [1] to [5] for gravure printing. [7] A laminate comprising, in this order, a plastic film substrate and a printed layer formed using any of the white ink compositions [1] to [6] above. [8] A laminated structure in which a resin layer, or an adhesive layer and a resin layer, is laminated on the surface of the printed layer of the laminate of [7]. [9] Packaging material comprising the laminated body of [8] above. [Effects of the Invention]

[0010] According to the present invention, a white ink composition with excellent hot lamination strength and highlight transfer properties, a laminate using the same, a laminated laminate, and a packaging material can be provided. [Modes for carrying out the invention]

[0011] The present invention will now be described in detail. The following embodiments are merely illustrative for illustrating the present invention and are not intended to limit the present invention to these embodiments. The present invention can be implemented in various forms without departing from its spirit. In this specification, the "~" symbol indicating a numerical range means that the numbers before and after it are included as the lower and upper limits, respectively. A "printed coating" is a coating (printed layer) formed from an ink composition. "Solid content" refers to non-volatile components that ultimately form the coating film. Solid content is measured in accordance with JIS K 5601-1-2:2008.

[0012] [White ink composition] The white ink composition of this embodiment is an oily white ink composition, and contains a polyurethane resin (A), a cellulose acetate propionate (B), a titanium oxide pigment (C), water (D), and an organic solvent (E). Hereinafter, cellulose acetate propionate is also referred to as CAP. The fact that the white ink composition is "oily" means that the proportion of the organic solvent in the medium in the white ink composition is 80% by mass or more. The white ink composition may further contain a terpene phenol resin (F). The white ink composition may further contain other components other than the polyurethane resin (A), CAP (B), titanium oxide pigment (C), water (D), organic solvent (E), and terpene phenol resin (F).

[0013] <Polyurethane resin (A)> Examples of the polyurethane resin (A) include a reaction product of a polyisocyanate compound and a polyol compound, and a thermoplastic polyurethane resin soluble in the organic solvent (E). The polyurethane resin (A) may be used alone or in combination of two or more. The polyurethane resin (A) may be a commercially available product or a product produced by a conventionally known method. For example, the polyurethane resin (A) can be obtained by reacting a urethane prepolymer, which is a reaction product of a polyisocyanate compound and a polyol compound, with a chain extender and a reaction terminator as necessary.

[0014] Examples of polyisocyanate compounds include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-xylylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4-diisocyanate, 2,2-diphenylpropane-4,4-diisocyanate, 3,3-dimethyldiphenylmethane-4,4-diisocyanate, 4,4-diphenylpropane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, naphth Examples include aromatic diisocyanates such as lene-1,4-diisocyanate, naphthylene-1,5-diisocyanate, and 3,3-dimethoxydiphenyl-4,4-diisocyanate; aliphatic diisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, and lysine diisocyanate; and alicyclic diisocyanates such as isophorone diisocyanate, norbornane diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated xylylene diisocyanate, and hydrogenated diphenylmethane diisocyanate. Polyisocyanate compounds may be used individually or in combination of two or more.

[0015] Examples of polyol compounds include polyester polyols, polycarbonate polyols, and polyether polyols. Polyol compounds may be used individually or in combination of two or more.

[0016] Examples of polyester polyols include polyester polyols or polyester amide polyols obtained by a dehydration polycondensation reaction between polycarboxylic acids and polyhydric alcohols or secondary to tertiary amines. Examples of polycarboxylic acids include succinic acid, adipic acid, sebacic acid, azelaic acid, terephthalic acid, isophthalic acid, orthophthalic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, hexahydroorthophthalic acid, and polycarboxylic acids such as naphthalenedicarboxylic acid and trimellitic acid, as well as their acid esters and acid anhydrides. Polycarboxylic acids may be used individually or in combination of two or more. Examples of polyhydric alcohols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 1,8-octanediol, 1,9-nonanediol, diethylene glycol, dipropylene glycol, 1,4-cyclohexanedimethanol, ethylene oxide or propylene oxide adducts of bisphenol A, trimethylolpropane, glycerin, and low molecular weight alcohol compounds such as pentaerythritol, as well as low molecular weight amino alcohol compounds such as monoethanolamine and diethanolamine. Polyhydric alcohols may be used individually or in combination of two or more. Examples of secondary and tertiary amines include low-molecular-weight amine compounds such as hexamethylenediamine, xylylenediamine, and isophoronediamine. A single secondary or tertiary amine may be used, or two or more may be used in combination. As polyester polyols, for example, lactone-based polyester polyols obtained by ring-opening polymerization of cyclic ester (lactone) monomers such as ε-caprolactone and γ-valerolactone using low molecular weight alcohol compounds and low molecular weight amino alcohol compounds as initiators can also be used.

[0017] Examples of polycarbonate polyols include those obtained by the dehydrochlorination reaction of a low molecular weight alcohol compound with phosgene, and those obtained by the transesterification reaction of a low molecular weight alcohol compound with a carbonate compound. Examples of low molecular weight alcohol compounds include those similar to those used in the synthesis of polyester polyols. Examples of carbonate compounds include diethylene carbonate, dimethyl carbonate, diethyl carbonate, and diphenyl carbonate.

[0018] Examples of polyether polyols include those obtained by ring-opening polymerization of cyclic ethers using hydroxyl group-containing compounds such as low molecular weight alcohol compounds, low molecular weight amine compounds, low molecular weight amino alcohol compounds, and phenols as initiators. Examples of low molecular weight alcohol compounds, low molecular weight amine compounds, and low molecular weight amino alcohol compounds are the same as those used in the synthesis of polyester polyols. Examples of cyclic ethers include alkylene oxides such as ethylene oxide, propylene oxide, and butylene oxide, as well as tetrahydrofuran. Specific examples of polyether polyols include polyoxyethylene polyol, polyoxypropylene polyol, polytetramethylene ether polyol, and polyoxyethylene polyoxypropylene polyol. As the polyether polyol, polyester ether polyols initiated from the aforementioned polyester polyols or polycarbonate polyols can also be used.

[0019] As a chain elongator, a compound having two or more functional groups (such as amino groups and hydroxyl groups) that can react with an isocyanate group in the molecule can be used. Examples of chain elongators include diamine compounds such as ethylenediamine, 1,3-propylenediamine, 1,4-butylenediamine, hexamethylenediamine, isophoronediamine, and 2-ethylaminoethylamine; polyamine compounds such as diethylenetriamine and triethylenetetramine; low molecular weight diol compounds such as ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, and triethylene glycol; aminoethylethanolamine, and aminopropylethanolamine. A single chain elongator may be used alone, or two or more may be used in combination.

[0020] Examples of reaction stoppers include monoalkylamines such as n-propylamine and n-butylamine; dialkylamines such as di-n-butylamine; alkanolamines such as monoethanolamine and diethanolamine; and monoalcohols such as methanol and ethanol. Reaction stoppers may be used individually or in combination of two or more.

[0021] The 100% modulus of polyurethane resin (A) is 0.4 to 3.5 MPa, preferably 0.4 to 2.0 MPa, and particularly preferably 0.4 to 1.0 MPa. If the 100% modulus of the polyurethane resin is below the lower limit, the initial adhesion to transparent vapor-deposited PET film, blocking resistance, and highlight transfer properties decrease. If it exceeds the upper limit, the hot lamination strength and adhesion to biaxially oriented polypropylene (OPP) film decrease.

[0022] The 100% modulus is determined by the following measurement method. Method for measuring 100% modulus: Polyurethane resin (A) is applied to release paper using an applicator to create a dry film with a thickness of 30 μm, and then heat-dried. The resulting film is aged for 24 hours under 25°C conditions to prepare the film for test specimens. After aging, the film is peeled from the release paper and cut into strips measuring 6 cm x 1.5 cm to prepare the test specimens. Under 25°C conditions, the prepared test specimens are stretched in the longitudinal direction of the specimen at a tensile speed of 20 cm / min using an autograph. From the obtained stress-strain curve, the stress at the point when the elongation of the test specimen reaches 100% (twice the original length) is read. The measurement is performed three times, and the average value is taken as the 100% modulus of polyurethane resin (A).

[0023] The 100% modulus of polyurethane resin (A) can be controlled, for example, by the type, properties, and composition of the polyisocyanate and polyol compounds. Alternatively, the 100% modulus can be controlled by making the polyurethane resin (A) composed of a hard segment and a soft segment, and adjusting the composition and properties of at least one of the hard and soft segments. An example of controlling the 100% modulus is shown below. Long-chain polyol compounds are used as the polyol compounds, and the molecular weight of the long-chain polyol compounds is adjusted. Long-chain polyol compounds are polyol compounds with a number-average molecular weight of 400 or more. When the molecular weight of the long-chain polyol compound is reduced, the 100% modulus of the polyurethane resin (A) tends to increase. The ratio of hard segments to soft segments in the polyurethane resin (A) is adjusted. Increasing the proportion of hard segments tends to increase the 100% modulus of the polyurethane resin (A). The proportion of hard segments can be controlled, for example, by adjusting the proportion of at least one of urethane bonds and urea bonds in the polyurethane resin (A). As the proportion of urethane bonds and urea bonds increases, the proportion of hard segments in the polyurethane resin (A) tends to increase. The proportion of urethane bonds and urea bonds can be quantified using the amine value.

[0024] The amine value of polyurethane resin (A) is preferably 1.0 mg KOH / g or less, more preferably 0.85 mg KOH / g or less, and particularly preferably 0.70 mg KOH / g or less. If the amine value exceeds the above upper limit, the two-component stability decreases slightly. The amine value is measured by neutralization titration using hydrochloric acid, in accordance with JIS K 7237.

[0025] The hydroxyl value of polyurethane resin (A) is preferably 5.0 mgKOH / g or less, more preferably 4.0 mgKOH / g or less, and particularly preferably 3.0 mgKOH / g or less. If the hydroxyl value exceeds the above upper limit, the compatibility decreases slightly. The hydroxyl value is measured in accordance with JIS K 1557-1.

[0026] The glass transition temperature of polyurethane resin (A) is preferably -80 to 0°C, more preferably -70 to -10°C, and particularly preferably -60 to -20°C. If the glass transition temperature is below the lower limit, the hot lamination strength will decrease slightly. If the glass transition temperature exceeds the upper limit, the adhesion will decrease slightly. The glass transition temperature is determined in accordance with JIS K 7121, using a differential scanning calorimeter to obtain a curve (DSC curve) obtained by heating 10 mg of the sample from -100°C to 160°C at a rate of 20°C / min. The value is determined from the intersection of the baseline and the tangent to the endothermic curve.

[0027] The softening point of polyurethane resin (A) is preferably 50 to 140°C, more preferably 60 to 130°C, and particularly preferably 70 to 120°C. If the softening point is below the lower limit, the hot lamination strength will decrease slightly. If the softening point exceeds the upper limit, the hot lamination strength will decrease slightly. The softening point is determined by the ring-and-ball method in accordance with JIS K 5601-2-2:1999.

[0028] The mass-average molecular weight of polyurethane resin (A) is preferably 40,000 to 150,000, more preferably 60,000 to 140,000, and particularly preferably 80,000 to 130,000. If the mass-average molecular weight is below the lower limit, the hot lamination strength will decrease slightly. If the mass-average molecular weight exceeds the upper limit, the compatibility will decrease slightly. The mass-average molecular weight is a value calculated on a standard polystyrene basis using gel permeation chromatography (GPC).

[0029] The number-average molecular weight of the polyurethane resin (A) is preferably 9,000 to 80,000, more preferably 20,000 to 70,000, and particularly preferably 40,000 to 65,000. If the number-average molecular weight is below the lower limit, the hot lamination strength will decrease slightly. If the number-average molecular weight exceeds the upper limit, the compatibility will decrease slightly. The number-average molecular weight is a value calculated on a standard polystyrene basis using gel permeation chromatography (GPC).

[0030] <CAP(B)> CAP(B) is a type of cellulose derivative containing an acetyl group and a propionyl group within its molecule. CAP(B) may be used alone or in combination of two or more types.

[0031] The acetyl group content of CAP(B) is preferably 0.5 to 4.0% by mass, more preferably 1.0 to 3.0% by mass, and particularly preferably 1.2 to 2.6% by mass, relative to the total mass of CAP(B). The propionyl group content of CAP(B) is preferably 40 to 55% by mass, more preferably 42 to 52% by mass, and particularly preferably 44 to 49% by mass, based on the total mass of CAP(B). The hydroxyl group content of CAP(B) is preferably 1.0 to 4.0% by mass, more preferably 1.3 to 3.5% by mass, and particularly preferably 1.6 to 2.8% by mass, relative to the total mass of CAP(B).

[0032] The viscosity of CAP(B) is preferably 60-90 poise, more preferably 70-90 poise, and particularly preferably 70-80 poise. If the viscosity of CAP(B) is below the lower limit, the highlight transferability decreases slightly, and if it exceeds the upper limit, the one-component stability decreases slightly. The viscosity of CAP(B) is measured in accordance with ASTM D 1343.

[0033] The melting point of CAP(B) is preferably 180 to 240°C, more preferably 182 to 225°C, and particularly preferably 185 to 220°C. If the melting point of CAP(B) is below the lower limit, the hot lamination strength will be slightly reduced. If the melting point of CAP(B) exceeds the upper limit, the one-component stability will be slightly reduced. The melting point is measured using a differential thermal analyzer (TG-DSC, product name "TG-8110", manufactured by Rigaku Corporation) under the condition of heating from room temperature (25°C) at a heating rate of 10°C / min.

[0034] <Titanium dioxide pigment (C)> Titanium dioxide pigment (C) is surface-treated and has a layer (surface-treated layer) formed by the surface treatment on the surface of the titanium dioxide particles.

[0035] Examples of surface treatments include inorganic treatments such as alumina treatment, silica treatment, zirconia treatment, titania treatment, zinc treatment, and tin compound treatment. Two or more surface treatments may be combined. For titanium dioxide pigment (C), it is preferable that it has been treated with alumina and silica as surface treatments. If alumina treatment is not applied, dispersibility and gloss are slightly reduced, and if silica treatment is not applied, heat resistance and opacity are slightly reduced.

[0036] Titanium oxide pigment (C )The amount of surface treatment (mass of the surface treatment layer, or the sum of the two or more surface treatments) is 6.5 to 9.5% by mass, preferably 6.5 to 8.5% by mass, and particularly preferably 7.0 to 8.0% by mass. If the amount of surface treatment is below the lower limit, the hot lamination strength, initial adhesion to the OPP film, and one-component stability will decrease. If it exceeds the upper limit, the hot lamination strength and one-component stability will decrease.

[0037] When the surface treatment includes alumina treatment and silica treatment, the mass ratio of the amount of alumina treatment to the amount of silica treatment (alumina treatment amount: silica treatment amount) is preferably 1:0.5 to 1:2.5, more preferably 1:0.6 to 1:2.3, and particularly preferably 1:0.8 to 1:2.0.

[0038] The average particle size of the titanium dioxide pigment (C) is preferably 0.20 to 0.35 μm, and more preferably 0.23 to 0.30 μm. If the average particle size of the titanium dioxide pigment (C) is below the lower limit, stability and opacity will be slightly reduced, and if it exceeds the upper limit, adhesion and lamination strength will be slightly reduced. The average particle size is determined by directly measuring the size of primary particles from images observed using a transmission electron microscope (TEM). Specifically, the average particle size of titanium dioxide is determined by measuring the particle size of 100 randomly selected primary particles and averaging these particle sizes.

[0039] The oil absorption amount of titanium dioxide pigment (C) is preferably 18-25 g / 100 g, and more preferably 20-23 g / 100 g. If the oil absorption amount of titanium dioxide pigment (C) is below the lower limit, the opacity will be slightly reduced, and if it exceeds the upper limit, the adhesion and lamination strength will be slightly reduced. The oil absorption capacity is determined in accordance with JIS K 5101-13-1:2004.

[0040] <Organic solvent (E)> Examples of organic solvents (E) include aromatic organic solvents such as toluene and xylene; aliphatic hydrocarbon organic solvents such as cyclohexane and methylcyclohexane; ketone organic solvents such as methyl ethyl ketone and methyl isobutyl ketone; ester organic solvents such as ethyl acetate, n-propyl acetate, isopropyl acetate, and isobutyl acetate; and alcohol organic solvents such as methanol, ethanol, n-propanol, and isopropanol. Note that organic solvents that fall under the category of slow-drying solvents, as described later, will be treated as slow-drying solvents, not as organic solvent (E).

[0041] From an environmental perspective, the organic solvent (E) is preferably an organic solvent that is substantially free of toluene (a toluene-free organic solvent). In other words, the white ink composition is preferably a toluene-free white ink composition that is substantially free of toluene. More preferably, the organic solvent (E) is an organic solvent that is substantially free of aromatic organic solvents such as toluene and xylene. "Substantially free" means that they are not intentionally included.

[0042] From the viewpoint of stably dissolving the polyurethane resin (A), the organic solvent (E) preferably contains an ester-based organic solvent and an alcohol-based organic solvent. The content of ester-based organic solvents in organic solvent (E) is preferably 50 to 95% by mass, based on the total amount of organic solvent (E). The content of alcohol-based organic solvents in organic solvent (E) is preferably 5 to 50% by mass, based on the total amount of organic solvent (E).

[0043] <Terpene phenol resin (F)> Terpene phenol resin (F) is a resin obtained by copolymerizing terpenes and phenols. Other monomers besides terpenes and phenols may also be copolymerized. Examples of terpenes include monoterpenes such as α-pinene, β-pinene, limonene, terpinolene, myrcene, and 3-carene; and sesquiterpenes such as longifolene and caryophyllene. Examples of phenols include phenol, bisphenol A, cresol, and xylenol. Examples of monomers other than terpenes and phenols include vinyl compounds such as styrene, α-methylstyrene, and (meth)acrylic compounds, and rosin-derived monomers such as maleic anhydride, fumaric acid, and abietic acid.

[0044] The acid value of the terpene phenol resin (F) is preferably 10 to 150 mg KOH / g, more preferably 20 to 100 mg KOH / g, and particularly preferably 30 to 80 mg KOH / g. If the acid value is below the above upper limit, the one-component stability (thickening) will be slightly reduced. If the acid value exceeds the above upper limit, the one-component stability (varnish separation) will be slightly reduced. The acid value is measured by a neutralization titration method in accordance with JIS K 0070:1992. The acid value can be adjusted using phenols and other monomers such as (meth)acrylic acid, maleic anhydride, fumaric acid, abietic acid, and other rosin-derived acid group-containing monomers.

[0045] The softening point of the terpene phenol resin (F) is preferably 80 to 200°C, more preferably 90 to 190°C, and particularly preferably 100 to 180°C. If the softening point is below the lower limit, the hot lamination strength and blocking resistance will be slightly reduced. If the softening point exceeds the upper limit, the compatibility and adhesion will be slightly reduced.

[0046] Commercially available terpene phenol resin (F) can be used. Examples of commercially available terpene phenol resin (F) include the "Tamanol series" manufactured by Arakawa Chemical Industries, Ltd., and the "YS Polystar" series manufactured by Yasuhara Chemical Co., Ltd.

[0047] <Other ingredients> Other components include, for example, slow-drying solvents, pigments other than titanium dioxide pigment (C), pigment derivatives, extender pigments, waxes, anti-blocking agents, fatty acid amides, chelating agents, curing agents, anti-settling agents, UV absorbers, antioxidants, antistatic agents, leveling agents, thickeners, defoaming agents, plasticizers, dispersants, flame retardants, stabilizers, etc. Other resins other than polyurethane resin (A), CAP (B), and terpene phenol resin (F) are also examples. These components may be used individually or in combination of two or more.

[0048] Slow-drying solvents are organic solvents whose evaporation rate is less than 1 when butyl acetate is set to 1. Examples of slow-drying solvents include propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, and n-butanol.

[0049] Examples of curing agents include isocyanate-based curing agents and blocked isocyanate-based curing agents. Among these, isocyanate-based curing agents are preferred from the viewpoint of mild aging conditions and crosslinking rate. One type of curing agent may be used alone, or two or more types may be used in combination.

[0050] Isocyanate-based curing agents are compounds (polyisocyanates) having two or more isocyanate groups in one molecule. Examples of isocyanate-based curing agents include aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate (MDI), 2,2'-MDI, 2,4'-MDI, 2,4-tolylene diisocyanate (TDI), 2,6-TDI, m-xylylene diisocyanate (XDI), and 1,4-phenylene diisocyanate; isophorone diisocyanate (IPDI), 1,3-bis(isocyanatomethyl)cyclohexane (hydrogenated XDI), and dicyclohexylmethane-4,4'-diisocyanate. Examples include alicyclic diisocyanates such as hydrogenated MDI and 1-methylcyclohexane-2,4-diisocyanate (hydrogenated TDI); aliphatic diisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), and 2,4,4-trimethylhexamethylene diisocyanate; and isocyanate prepolymers such as adducts of various diisocyanates, isocyanurates of various diisocyanates, biuret compounds of HDI, and allophanates of HDI. Among these, HDI, IPDI, XDI, or their adducts, isocyanurates, biuretes, and allophanates are preferred from the viewpoint of further improving the curl resistance of the coating film; HDI, IPDI, XDI, or their adducts are more preferred; HDI adducts, IPDI adducts, and XDI adducts are even more preferred; and HDI adducts are particularly preferred. Isocyanate-based curing agents may be used individually or in combination of two or more types.

[0051] Adduct compounds are a general term for isocyanate compounds with two or more functions, obtained by reacting a polyisocyanate having two or more isocyanate groups in one molecule (e.g., diisocyanate) with a low molecular weight active hydrogen-containing compound with two or more functions (e.g., low molecular weight triols such as trimethylolpropane and glycerin). Examples of adduct compounds include reaction products of HDI and trimethylolpropane (TMP), reaction products of XDI and TMP, and reaction products of IPDI and TMP.

[0052] As for other resins, chlorinated polyolefin resins are preferred. When the white ink composition contains a chlorinated polyolefin resin, the adhesion of the resulting printed layer to the substrate tends to improve. Chlorinated polyolefin resin is a resin in which at least some of the hydrogen atoms in the polyolefin resin are replaced with chlorine atoms. Preferred polyolefin resins are homopolymers or copolymers of α-olefin unsaturated hydrocarbons such as polypropylene, poly-1-butene, and poly-4-methyl-1-pentene, with polypropylene being more preferred. Chlorinated polyolefin resins can be produced by polymerizing monomers in which at least some of the hydrogen atoms in the monomers used to produce the polyolefin are replaced with chlorine atoms. Chlorinated polyolefin resins may be used individually or in combination of two or more types.

[0053] The chlorine content of the chlorinated polyolefin resin is preferably 15 to 60% by mass, more preferably 20 to 55% by mass, and particularly preferably 25 to 50% by mass. When the chlorine content of the chlorinated polyolefin resin is above the lower limit, alkali desorption properties and compatibility tend to improve. When the chlorine content of the chlorinated polyolefin resin is below the upper limit, the adhesion of the resulting printed layer to the substrate tends to improve. The chlorine content of chlorinated polyolefin resin is the amount of chlorine atoms relative to the total mass of the chlorinated polyolefin resin.

[0054] <Content of each ingredient> The content of polyurethane resin (A) on a solids basis is 10 to 25% by mass relative to the solids of the white ink composition, preferably 11 to 23% by mass, and more preferably 12 to 20% by mass. If the content of polyurethane resin (A) is below the lower limit, the hot lamination strength and adhesion to the OPP film will decrease. If the content of polyurethane resin (A) exceeds the upper limit, the highlight transfer properties will decrease.

[0055] The solid content of CAP(B) is 0.5 to 7% by mass relative to the solid content of the white ink composition, preferably 0.6 to 5.0% by mass, and more preferably 0.8 to 3.0% by mass. If the CAP(B) content is below the lower limit, the highlight transfer properties will decrease. If the CAP(B) content exceeds the upper limit, the hot lamination strength will decrease.

[0056] The content of titanium dioxide pigment (C) on a solids basis is preferably 66 to 80% by mass, more preferably 70 to 79% by mass, and particularly preferably 72 to 78% by mass, relative to the solids of the white ink composition. If the content of titanium dioxide pigment (C) is below the lower limit, the opacity will be slightly reduced. If the content of titanium dioxide pigment (C) exceeds the upper limit, the hot lamination strength and adhesion will be slightly reduced.

[0057] The water (D) content is 1 to 5% by mass relative to the total mass of the white ink composition, preferably 1.1 to 4.0% by mass, and more preferably 1.2 to 3.0% by mass. If the water (D) content is below the lower limit, the highlight transfer properties will decrease. If the water (D) content exceeds the upper limit, the hot lamination strength and one-component stability will decrease.

[0058] The content of organic solvent (E) is preferably 20 to 70% by mass, more preferably 25 to 65% by mass, and particularly preferably 30 to 60% by mass, relative to the total mass of the white ink composition. If the content of organic solvent (E) is below the lower limit, the highlight transferability and printability will be slightly reduced. If the content of organic solvent (E) exceeds the upper limit, the one-component stability will be slightly reduced.

[0059] When the white ink composition contains terpene phenol resin (F), the content of terpene phenol resin (F) on a solids basis is preferably 1 to 8% by mass, more preferably 1.5 to 7.0% by mass, and particularly preferably 2.0 to 5.0% by mass, relative to the solids content of the white ink composition. If the content of terpene phenol resin (F) is below the above lower limit, the effect of improving initial adhesion to OPP film cannot be sufficiently obtained. If the content of terpene phenol resin (F) exceeds the above upper limit, the initial adhesion to transparent vapor-deposited PET film, hot lamination strength, and blocking resistance are slightly reduced.

[0060] When the white ink composition contains a slow-drying solvent, the content of the slow-drying solvent is preferably 0.5 to 12% by mass, more preferably 1.0 to 10% by mass, and particularly preferably 1.5 to 8.0% by mass, relative to the total mass of the white ink composition. If the content of the slow-drying solvent is below the lower limit, the effect of improving highlight transferability cannot be sufficiently obtained. If the content of the slow-drying solvent exceeds the upper limit, the hot lamination strength and blocking resistance will decrease slightly.

[0061] When the white ink composition contains a curing agent, the amount of curing agent in terms of solid content is preferably 1.0 to 10% by mass, more preferably 2.0 to 7.0% by mass, and particularly preferably 2.5 to 3.5% by mass, relative to the solid content of the white ink composition. If the curing agent content is below the lower limit, the effects of improving hot lamination strength and adhesion cannot be sufficiently obtained. If the curing agent content exceeds the upper limit, the two-component stability and printability will be slightly reduced.

[0062] When the white ink composition contains chlorinated polyolefin resin, the content of chlorinated polyolefin resin on a solids basis is preferably 0.1 to 2.0% by mass, more preferably 0.3 to 1.5% by mass, and particularly preferably 0.5 to 1.0% by mass, relative to the solids content of the white ink composition. If the content of chlorinated polyolefin resin is below the above lower limit, the effect of improving initial adhesion to OPP film cannot be sufficiently obtained. If the content of chlorinated polyolefin resin exceeds the above upper limit, the one-component stability is slightly reduced.

[0063] When the white ink composition contains a dispersant, the amount of dispersant in terms of solid content is preferably 0.05 to 2.0% by mass, more preferably 0.08 to 1.0% by mass, and particularly preferably 0.1 to 0.5% by mass, relative to the solid content of the white ink composition. If the amount of dispersant is below the lower limit, the effects of improving highlight transferability and one-component stability cannot be sufficiently obtained. If the amount of dispersant exceeds the upper limit, the laminate strength and blocking resistance will be slightly reduced.

[0064] <Method for manufacturing white ink composition> The white ink composition of this embodiment can be obtained, for example, by mixing polyurethane resin (A), CAP (B), titanium dioxide pigment (C), water (D), organic solvent (E), optionally terpene phenol resin (F), and optionally other components. The method of mixing each component is not particularly limited, and the components can be mixed by various methods. For example, one method is to dissolve or disperse polyurethane resin (A), CAP (B), titanium dioxide pigment (C), water (D), terpene phenol resin (F) if necessary, and other components if necessary, in an organic solvent (E). If a curing agent is included, it is preferable to add the curing agent immediately before using the white ink composition. The method for dissolving or dispersing each component in the organic solvent (E) is not particularly limited and can be carried out using known dispersers. Examples of dispersers include paint shakers, dissolvers, ball mills, attritors, sand mills, bead mills, dyno mills, roll mills, ultrasonic mills, and high-pressure impact dispersers. In this case, the dispersion treatment may be performed once or multiple times using one type of disperser, or multiple dispersion treatments may be performed using two or more types of dispersers in combination.

[0065] <Mechanism of Action> The white ink composition of this embodiment exhibits excellent hot lamination strength and highlight transfer properties. It also has excellent initial adhesion to the substrate, showing good initial adhesion even to transparent vapor-deposited PET film, which is a substrate that is relatively difficult to adhere to. By setting the 100% modulus of polyurethane resin (A) within a specific range, the balance between hot lamination strength, highlight transferability, and initial adhesion to transparent vapor-deposited PET film can be optimized. If the 100% modulus of polyurethane resin (A) is below the lower limit, the cell separation of the white ink becomes poor, and the highlight transferability decreases. Conversely, if it exceeds the upper limit, the resin hardens too much, resulting in insufficient softening and fluidity under heating conditions, and a decrease in hot lamination strength. Thus, by setting the 100% modulus of polyurethane resin (A) within a specific range, it is possible to achieve high thermal stability while maintaining the transferability of the white ink composition. CAP(B) contributes to improving the printability of the white ink composition. By adjusting the CAP(B) content to a specific level, the white ink composition can be given appropriate viscosity, strengthening the propulsion force that transfers the white ink in the highlight areas to the film. This prevents insufficient transfer of white ink in the highlight areas and improves highlight transferability. By incorporating water (D) in a specific amount into the white ink composition, the surface properties of the white ink are adjusted, improving highlight transferability. In white ink systems primarily composed of organic solvents (E), water (D) plays a role in fine-tuning the overall stability and surface tension of the white ink composition. This promotes the transfer of the white ink from the printing plate to the film, particularly in the highlight areas. As a result, dot defects are suppressed, and excellent highlight transferability is achieved. However, if the water (D) content exceeds the upper limit, the white ink composition, being organic solvent-based, will experience thickening, gelation, or varnish separation (separation of pigment and binder), leading to a decrease in storage stability. Furthermore, the increase in residual moisture inhibits the adhesion interface of the printed coating, reducing the hot lamination strength. Titanium oxide pigment (C )By setting the total surface treatment amount within a specific range, the dispersion stability of the titanium dioxide pigment (C) and its adhesion to the polyurethane resin (A) can be optimized. If the surface treatment amount is below the lower limit, the adhesion of the white ink composition to the film decreases. If it exceeds the upper limit, the organic solvent (E) in the white ink composition becomes more easily adsorbed. As a result, the amount of solvent remaining in the printed coating increases, and when heated, the residual solvent inhibits the adhesion interface of the printed coating, reducing the hot lamination strength. Based on these mechanisms of action, the white ink composition of this embodiment is expected to satisfy all required physical properties at a high level, including hot lamination strength, highlight transferability, and initial adhesion to transparent vapor-deposited PET film.

[0066] <Uses of white ink composition> The white ink composition of this embodiment is used to form a printed layer on any substrate such as a plastic film. The white ink composition of this embodiment is particularly suitable as an ink when forming a printed layer by gravure printing. In other words, the white ink composition of this embodiment is suitable for gravure printing. When a laminate in which a printed layer is formed on a substrate, or a laminate containing such a laminate, is used as a packaging material, the white ink composition of this embodiment is suitable as an ink for printing on the back side of the substrate (the side on which the packaged object is placed). In other words, the white ink composition of this embodiment is suitable for reverse printing.

[0067] [Laminated structure] The laminate of this embodiment comprises, in this order, a plastic film substrate and a printed layer (hereinafter also referred to as the white ink layer) formed using the white ink composition of this embodiment.

[0068] The plastic film substrate comprises a plastic film. Examples of plastics that make up plastic films include polyolefins such as polyethylene (PE) and polypropylene (PP), polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN), polystyrene (PS), polyamide (NY), polycarbonate, polyimide, and polyvinyl chloride. Examples of PE include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and high-density polyethylene (HDPE). One type of plastic may be used alone, or two or more types may be used in combination. Plastic films may or may not be subjected to stretching treatment. Stretching treatments include biaxial stretching and uniaxial stretching. Examples of stretched plastic films include biaxially oriented PP (OPP) film and biaxially oriented NY (ONY) film. At least one side of the plastic film may be surface-treated. Examples of surface treatments include corona discharge treatment, plasma treatment, flame treatment, and solvent treatment. The plastic film may be used individually or two or more types may be laminated together. The thickness of the plastic film is, for example, 10 to 50 μm. The plastic film substrate may be a vapor-deposited film in which a vapor-deposited layer is formed on the surface of the plastic film. Examples of vapor-deposited layers include transparent vapor-deposited layers such as aluminum oxide and silicon oxide, and metal vapor-deposited layers such as aluminum, with transparent vapor-deposited layers being preferred. The thickness of the vapor-deposited layer is, for example, 1 to 200 nm.

[0069] A transparent vapor-deposited PET film is preferred as the plastic film substrate. Transparent vapor-deposited PET film is made by vapor-depositing inorganic oxides such as aluminum oxide and silicon oxide onto a PET film. It possesses high barrier properties that prevent the permeation of oxygen and water vapor while maintaining transparency. For this reason, it is used as packaging material for food and pharmaceuticals to preserve their quality. However, the vapor-deposited layer has strong non-polar properties, and by applying a vapor-deposited layer to the PET film, the wettability of the ink decreases, and even if it is wetted, it is extremely difficult to achieve excellent initial adhesion. In particular, achieving good initial adhesion with white ink, which has a high pigment content and relatively little binder resin that contributes to adhesion, has been a particularly difficult physical property to achieve conventionally. The white ink composition of this embodiment provides excellent initial adhesion even to transparent vapor-deposited PET film.

[0070] The thickness of the white ink layer is, for example, 0.5 to 3 μm. The white ink layer may be applied to the entire surface of one side of the plastic film substrate or to a portion of it. Preferably, at least a portion of the white ink layer is in contact with one side of the plastic film substrate. If the plastic film substrate is a vapor-deposited film such as a transparent vapor-deposited PET film, preferably, at least a portion of the white ink layer is in contact with the vapor-deposited layer of the vapor-deposited film.

[0071] The laminate of this embodiment may further comprise other layers besides the plastic film substrate and the white ink layer. Other layers may be provided on the side of the plastic film substrate opposite to the white ink layer, or between the plastic film substrate and the white ink layer, or on the side of the white ink layer opposite to the plastic film substrate. However, a laminate having a resin layer on the opposite side of the plastic film side of the white ink layer will be treated as a laminate laminate described later, rather than a laminate according to this embodiment. Other layers include, for example, a printed layer formed using an ink composition other than the white ink composition of this embodiment (hereinafter also referred to as "other ink layers"), a metal vapor deposition layer, an inorganic vapor deposition layer, a matte layer, a varnish layer, and the like. Other ink layers are typically provided for purposes such as decoration or inscription of information. When the laminate or a laminate laminate equipped with this laminate is used as packaging material, it is preferable that the other ink layers be located on the front side (opposite the side where the packaged object is placed) than the white ink layer.

[0072] The laminate of this embodiment can be obtained, for example, by coating one surface of a plastic film substrate with the ink composition of this embodiment to form a printed layer. When a laminate or a laminate containing such a laminate is used as a packaging material, it is preferable that one side of the plastic film is the side that becomes the back side when used as a packaging material.

[0073] There are no particular limitations on the method of coating the white ink composition, and various known coating methods can be used. Examples include gravure printing, flexographic printing, brush coating, gravure coater method, die coater method, bar coater method, spray coating method, flow coating method, dip coating method, spin coating method, and curtain coating method. Of these, gravure printing and flexographic printing are preferred because they have excellent drying properties and can be used for high-speed printing, and gravure printing is particularly preferred because it can ensure an appropriate coating amount and has excellent tonal reproduction. Therefore, it is preferable that the printed layer is a layer formed by gravure printing. After applying the white ink composition, drying is performed as necessary. The drying method should be such that the organic solvent in the white ink composition is removed, and examples include heat drying and natural drying. When heat drying is used, the drying temperature is preferably 30 to 60°C, and more preferably 35 to 55°C.

[0074] The laminate of this embodiment is suitable as a packaging material, particularly a flexible packaging material. It is also suitable for use in the manufacture of laminated materials, which will be described later. Here, "flexible packaging" refers to packaging materials made of flexible materials, i.e., flexible packaging, which is used for packaging food, daily necessities, and other items.

[0075] [Laminated structure] The laminate of this embodiment is formed by laminating a resin layer, or an adhesive layer and a resin layer, on the printed layer side of the laminate of this embodiment. In other words, it is a laminate in which a plastic film substrate, a printed layer, and a resin layer are laminated in this order, or a laminate in which a plastic film substrate, a printed layer, an adhesive layer, and a resin layer are laminated in this order. Other layers may be present between the layers.

[0076] The resin layer typically functions as a sealant layer. Examples of resins that make up the resin layer include heat-sealable resins such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE), and polypropylene (PP). The resin layer may consist of one type of resin or two or more types. The resin layer may be a single layer or a multi-layer layer. The thickness of the resin layer is, for example, 2 to 100 μm.

[0077] Depending on the method of laminating the laminate and the resin layer, any known adhesive can be used to form the adhesive layer. Adhesives used in the dry lamination method include, for example, two-component adhesives consisting of a mixture of a polyol and an isocyanate curing agent. Examples of polyols include polyester polyols and polyether polyols. Specifically, examples include the product names "Seikabond E-263 / C-75N" and "Seikabond A-159 / C89(F)" manufactured by Dainichi Seika Kogyo Co., Ltd. Examples of adhesives used in the extrusion lamination method include two-component adhesives consisting of a mixture of polyol and isocyanate curing agent. Specifically, examples include the product names "Seikadine 2710A / Seikadine 2710C" manufactured by Dainichi Seika Kogyo Co., Ltd. The thickness of the adhesive layer can be expressed, for example, as the mass of the adhesive layer per unit area (dry application amount of adhesive), which is approximately 0.01 to 5 g / m². 2 That is the case.

[0078] The laminated structure of this embodiment can be manufactured by known methods. Specifically, known lamination methods such as the dry lamination method, in which an adhesive is applied to the printed layer side of the laminate or to the surface of the resin film forming the resin layer, dried, and then pressed together, or the extrusion lamination method, in which an adhesive called an anchor coating agent is applied to the printed layer side of the laminate as needed, and then the molten resin forming the resin layer is extruded, can be used.

[0079] The laminated material of this embodiment is suitable as a packaging material, particularly as a flexible packaging material. [Examples]

[0080] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the invention.

[0081] [Raw materials used] <Polyurethane resin (A)> A1: Polyurethane resin, solids content: 33% by mass, 100% modulus: 0.67 MPa, amine value: 0.4 mg KOH / g, hydroxyl value: 0.32 mg KOH / g, mass-average molecular weight: 121260, number-average molecular weight: 59820. A2: Polyurethane resin, solids content: 36% by mass, 100% modulus: 0.81 MPa, amine value: 0.8 mg KOH / g, hydroxyl value: 0.36 mg KOH / g, mass-average molecular weight: 91000, number-average molecular weight: 46000. A3: Polyurethane resin, solids content: 30% by mass, 100% modulus: 2.9 MPa, amine value: 0 mg KOH / g, hydroxyl value: 3 mg KOH / g, glass transition temperature: -39°C, softening point: 80°C, mass-average molecular weight: 70050, number-average molecular weight: 25100. A4: Polyurethane resin, solids content: 30% by mass, 100% modulus: 3.6 MPa, amine value: 0.5 mg KOH / g, hydroxyl value: 1.3 mg KOH / g, glass transition temperature: -24.0°C, softening point: 130°C, mass-average molecular weight: 50480, number-average molecular weight: 20110. A5: Polyurethane resin, solids content: 25% by mass, 100% modulus: 4.3 MPa, amine value: 0 mg KOH / g, hydroxyl value: 0 mg KOH / g, glass transition temperature: -44°C, softening point: above 130°C, mass-average molecular weight: 79220, number-average molecular weight: 26280. A6: Polyurethane resin, solids content: 36% by mass, 100% modulus: 0.37 MPa, amine value: 0.84 mg KOH / g, hydroxyl value: 0 mg KOH / g, mass-average molecular weight: 41000, number-average molecular weight: 10000.

[0082] <CAP(B)> ·B1: "CAP-482-20": "CAP-482-0.5" = 100:0 (mass ratio), viscosity: 76.5poise. ·B2: "CAP-482-20": "CAP-482-0.5" = 85:15 (mass ratio), viscosity: 65.3poise. ·B3: "CAP-482-20": "CAP-482-0.5" = 70:30 (mass ratio), viscosity: 54.0poise. Here, "CAP-482-20" and "CAP-482-0.5" were the following: "CAP-482-20": Manufactured by Eastman Chemical Company, product name "CAP-482-20", viscosity: 76.5 poise, acetyl group content: 1.3 mass%, propionyl group content: 48 mass%, hydroxyl group content: 1.7 mass%, melting point: 188~210℃, solids content: 100 mass%. "CAP-482-0.5": Manufactured by Eastman Chemical Company, product name "CAP-482-0.5", viscosity: 1.53 poise, acetyl group content: 2.5% by mass, propionyl group content: 45% by mass, hydroxyl group content: 2.6% by mass, melting point: 188~210℃, solids content: 100% by mass.

[0083] <Titanium dioxide pigment (C)> C1: Surface treatment amount: 8.5 mass%, alumina treatment: 3.0 mass%, silica treatment: 5.5 mass%, average particle size: 0.29 μm, oil absorption: 22 g / 100 g, solids content: 100 mass%. C2: Surface treatment amount: 6.9 mass%, alumina treatment: 3.5 mass%, silica treatment: 3.4 mass%, average particle size: 0.25 μm, oil absorption: 21 g / 100 g, solids content: 100 mass%. C3: Surface treatment amount: 6.0 mass%, alumina treatment: 2.0 mass%, silica treatment: 4.0 mass%, average particle size: 0.25 μm, oil absorption: 21 g / 100 g, solids content: 100 mass%. ·C4: Surface treatment amount: 11.0% by mass, alumina treatment: 4.5% by mass, silica treatment: 6.5% by mass, average particle size: 0.23μm, oil absorption: 25g / 100g, solid content: 100% by mass. C5: Surface treatment amount: 7.0 mass%, alumina treatment: 3.6 mass%, zirconia treatment: 3.4 mass%, average particle size: 0.23 μm, oil absorption: 18 g / 100 g, solids content: 100 mass%.

[0084] <Water(D)> ·Purified water

[0085] <Organic solvent (E)> E1: A mixed solvent of ethyl acetate (EtAc), n-propyl acetate (NPAc), and isopropanol (IPA), with EtAc:NPAc:IPA = 2:2:1 (mass ratio).

[0086] <Terpene phenol resin (F)> F1: Manufactured by Arakawa Chemical Industries, Ltd., product name "Tamanol 803L", acid value: 45-60 mgKOH / g, softening point: 145-160°C, solids content: 100% by mass.

[0087] <Other ingredients> • Hardener: Hexamethylene diisocyanate adduct, solids content: 30% by mass. • Chlorinated PO: Chlorinated polyolefin resin, manufactured by Nippon Paper Industries Co., Ltd., product name "Supercron 814HS", chlorine content: 41% by mass, solids content: 100% by mass. • Dispersant: BYK Corporation, product name "DISPERBYK-180", solids content: 81% by mass. • Slow-drying solvent: Propylene glycol monomethyl ether.

[0088] [Examples 1-16, Comparative Examples 1-11] <Preparation of white ink composition> According to the compositions shown in Tables 1-4, polyurethane resin (A), CAP (B), titanium dioxide pigment (C), water (D), organic solvent (E), and optionally terpene phenol resin (F) and other components were mixed. The resulting mixture was then kneaded in a paint shaker to obtain a white ink composition. The curing agent was added immediately before the preparation of the laminate as described below. In Tables 1-4, "NV." represents the solid content. "%" represents mass percent. The content of each component, except for water (D), organic solvent (E), and slow-drying solvent, is the content of the active ingredient. The "residue" of organic solvent (E) is the amount that makes the sum of all components (total amount of white ink composition) 100% by mass.

[0089] <Fabrication of laminates> The prepared white ink composition was diluted with the same organic solvent used in the formulation so that its viscosity at 25°C, as measured using a Zahn cup #3, was 16 seconds, thereby preparing a white ink for printing. Using a gravure printing press (manufactured by Matsuo Sangyo Co., Ltd., product name "K Printing Proofer") equipped with a 175 lines / inch, 28 μm gravure plate (solid plate) and a Helio 175 lines / inch gravure plate (stepless gradation plate), the prepared white ink for printing was applied to the vapor-deposited surface of a transparent vapor-deposited PET film (manufactured by Toray Film Processing Co., Ltd., product name "Barrierox SB-R2", thickness: 12 μm), the corona-treated surface of a PET film (manufactured by Toyobo Co., Ltd., product name "Toyobo Ester Film E5102", thickness: 12 μm), and the corona-treated surface of an OPP film (manufactured by Futamura Chemical Co., Ltd., product name "FOR", thickness: 25 μm) to form a printed coating. The laminate was then dried at 25°C for 24 hours to create the laminate.

[0090] <Fabrication of laminated structures> In the preparation of the above laminate, a printed coating film was formed on a transparent vapor-deposited PET film using a 175-line / inch, 28 μm gravure plate (solid color plate). After drying, a dry laminating adhesive (manufactured by Dainichi Seika Kogyo Co., Ltd., product name "Seikabond E594 / C-100") was applied to the surface of the printed coating film of the laminate at a dry application rate of 3 g / m². 2 To achieve this, the material was applied using a gravure printing press (Matsuo Sangyo Co., Ltd., product name "K Printing Proofer"), and then dried with a dryer for 10 seconds to form an adhesive layer. An unoriented polypropylene (CPP) film (Toray Film Processing Co., Ltd., product name "Trefan ZK207", 60 μm thick) was then placed on top and heat-pressed at 80°C. After that, aging was performed at 40°C for 48 hours to obtain a laminated structure.

[0091] <Evaluation of initial adhesion to transparent vapor-deposited PET film> In the preparation of the above laminate, a printed coating was formed on a transparent vapor-deposited PET film using a 175-line / inch, 28 μm gravure printing plate (solid color plate). Immediately after printing, cellophane tape (manufactured by Nichiban Co., Ltd.) was applied to the surface of the printed coating before drying. The cellophane tape was then quickly removed, and the condition of the printed coating remaining on the substrate was visually inspected. The adhesion to the transparent vapor-deposited PET film was evaluated according to the following evaluation criteria. A score of 3 to 5 is considered acceptable. 5: The printed coating has not peeled off. 4. The percentage of the area where the printed coating has peeled off is greater than 0% and less than or equal to 10%. 3. The percentage of the area where the printed coating has peeled off is greater than 10% but less than or equal to 20%. 2: The percentage of the area where the printed coating has peeled off is greater than 20% but less than or equal to 50%. 1: The area where the printed coating has peeled off exceeds 50%.

[0092] <Evaluation of hot lamination strength> The laminated material obtained from the above-described process was cut into strips 15 mm wide, and a T-type peel test was performed using a tensile testing machine (A&D Corporation, product name "Tensilon RTG-1225") under heated conditions of 120°C and a tensile speed of 300 mm / min. The hot lamination strength was evaluated according to the criteria shown below. A score of 3 to 5 is considered acceptable. 5: The T-type peel strength is 3.5N or higher. 4: The T-type peel strength is 3.0 N or higher and less than 3.5 N. 3: The T-type peel strength is 2.0 N or greater, and less than 3.0 N. 2: The T-type peel strength is 1.0 N or greater and less than 2.0 N. 1: The T-type peel strength is less than 1.0 N.

[0093] <Evaluation of highlight transferability> In the preparation of the above laminate, the highlight areas (5% halftone density) of the laminate, which had a printed coating formed on a PET film using a Helio 175 lines / inch gravure plate (stepless gradation plate), were visually observed, and the highlight transfer properties of the ink were comprehensively evaluated according to the criteria shown below. A score of 3 to 5 is considered acceptable. 5: No dead pixels or tone jumps (where the boundaries are visible rather than creating a smooth gradient) are observed throughout the entire gradient, resulting in a smooth, continuous gradation. 4: There are extremely slight dot defects in the highlight areas, but no tone jumps are observed, and the gradation is good. 3: Minor dead pixels are observed in the highlight areas, or minor tone jumps are detected. 2: Noticeable dead pixels in the highlight areas, as well as significant tone jumps and unevenness. 1: Almost no transition is observed in the highlight areas, and large tone jumps and unevenness occur, resulting in a failure to reproduce gradations.

[0094] <Evaluation of single-component stability> A white ink composition prepared in the same manner as described above, except without the addition of a hardener, was collected in a metal can, sealed tightly, and left to stand at 25°C for 7 days. After standing, the state of varnish separation and sedimentation of the white ink composition was visually observed, and the one-component stability was comprehensively evaluated according to the following criteria. A score of 3 to 5 is considered acceptable. 5: No varnish layer was observed on the surface, and no sediment was found when the bottom of the metal can was scraped with a spatula. 4: Although a very thin varnish layer is observed on the surface, it mixes easily with the white ink composition by stirring with a spatula, and there is very little sediment. 3: A clear varnish layer is visible on the surface, or slight sediment can be detected when scraping the bottom of the metal can with a spatula, but the sediment can be loosened by short-term agitation with a dissolver. 2: The surface varnish layer is thick and clearly separates from the white ink composition, or the sediment at the bottom of the metal can is hard and requires time to stir with a dissolver. 1: The entire white ink composition has gelled, or the precipitate has solidified.

[0095] <Evaluation of overlapping printing> A gravure printing press was operated under high load conditions using gravure ink, and ink scraping was performed on the plate surface using a doctor blade. This operation was set to easily cause slight ink cover on the plate surface immediately after the start of operation (0 minutes) in order to strictly evaluate ink cover. The state of the plate surface was observed at 0 minutes, 5 minutes, and 10 minutes after the start of printing, and the degree of ink transfer to non-image areas of the printed material (cover) at those points was comprehensively evaluated according to the criteria shown below. A score of 3 to 5 is considered acceptable. Even after 5 minutes and 10 seconds, the amount of overprint and residue on the printing plate was suppressed to the same level as at 0 minutes, and there was almost no overprinting on the non-image areas of the printed material. Compared to the 4:00 mark, the residue on the printing plate deteriorates very slightly after 5 minutes and 10 minutes, but no increase in overprint on the non-image areas of the printed material is observed, and there are no practical problems. Compared to the 3:00 mark, there was a slight increase in residue on the printing plate at 5 and 10 minutes later, but the degree of overprinting on the non-image areas of the printed material was also minor and remained within an acceptable range. 2. At 5 or 10 minutes, the amount of residue on the printing plate increases significantly, and moderate to severe overhang is observed in the non-image areas of the printed material. 1: Immediately after starting operation, there is a very large amount of residue on the printing plate, and the non-image areas of the printed material are contaminated over a wide area, which is a practical problem.

[0096] The evaluation results for each example are shown in Tables 1-4.

[0097] [Table 1]

[0098] [Table 2]

[0099] [Table 3]

[0100] [Table 4]

[0101] [Application Examples] In the preparation of the above laminate, the highlight areas (5% halftone dot density) of the laminate, in which a printed coating film was formed on an OPP film (manufactured by Futamura Chemical Co., Ltd., product name "FOR", thickness: 25 μm) using a Helio 175 line / inch gravure plate (stepless gradation plate), were visually observed, and it was confirmed that all of the white ink compositions in the examples exhibited excellent highlight transfer properties. Next, in the preparation of the laminate described above, a printed coating film was formed on an OPP film (Futamura Chemical Co., Ltd., product name "FOR", thickness: 25 μm) using a 175-line / inch, 28 μm gravure plate (solid color plate). After drying, a dry laminating adhesive (Dainichi Seika Kogyo Co., Ltd., product name "Seikabond E594 / C-100") was applied to the surface of the printed coating film of the laminate at a dry application rate of 3 g / m². 2 To achieve this, the ink was applied using a gravure printing press (Matsuo Sangyo Co., Ltd., product name "K Printing Proofer"), and then dried with a dryer for 10 seconds to form an adhesive layer. An LLDPE film (Mitsui Chemicals Tohcello Co., Ltd., product name "TUX HC", 60 μm thick) was placed on top of this and heat-pressed at 80°C. After that, aging was performed at 40°C for 48 hours to obtain a laminated structure. In this laminated structure, it was confirmed that all of the white ink compositions in the examples exhibited excellent hot lamination strength, and that there were no problems in use even when the substrate was an OPP film. The evaluation of the hot lamination strength was performed at a temperature of 100°C, and all other test conditions were the same as those in the examples. [Industrial applicability]

[0102] The white ink composition of the present invention exhibits excellent initial adhesion to transparent vapor-deposited PET film, hot lamination strength, and highlight transfer, making it useful as a white ink for reverse printing.

Claims

1. An oil-based white ink composition used for forming the gravure printing layer of a laminate laminate, which comprises a plastic film substrate and a gravure printing layer in that order, wherein a resin layer, or an adhesive layer and a resin layer, is laminated on the surface of the gravure printing layer of the laminate laminate, It contains polyurethane resin (A), cellulose acetate propionate (B), titanium dioxide pigment (C), water (D), and an organic solvent (E). The 100% modulus of the polyurethane resin (A) is 0.4 to 3.5 MPa. The content of the polyurethane resin (A) on a solids basis is 10 to 25% by mass relative to the solids of the white ink composition. The content of the cellulose acetate propionate (B) on a solid content basis is 0.5 to 7% by mass relative to the solid content of the white ink composition. The titanium oxide pigment (C) is subjected to alumina treatment and silica treatment, and the total amount of alumina treatment and silica treatment relative to the titanium oxide pigment (C) is 6.5 to 9.5% by mass. A white ink composition in which the water (D) content is 1 to 5% by mass relative to the total mass of the white ink composition.

2. The white ink composition according to claim 1, wherein the 100% modulus of the polyurethane resin (A) is 0.4 to 2.0 MPa.

3. The white ink composition according to claim 1, wherein the viscosity of the cellulose acetate propionate (B), as measured in accordance with ASTM D 1343, is 60 to 90 poise.

4. Furthermore, it contains terpene phenol resin (F), The white ink composition according to claim 1, wherein the content of the terpene phenol resin (F) on a solid content basis is 1 to 8% by mass relative to the solid content of the white ink composition.

5. A laminate comprising, in this order, a plastic film substrate and a gravure printing layer formed using the white ink composition described in any one of claims 1 to 4.

6. A laminated structure comprising a resin layer, or an adhesive layer and a resin layer, laminated on the surface of the gravure printing layer of the laminate according to claim 5.

7. A packaging material comprising the laminated structure described in claim 6.

8. The packaging material according to claim 7, which is a flexible packaging material.

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