Ink composition for wallpaper, laminate, and wallpaper

Abstract

To provide a wallpaper ink composition that exhibits excellent gradation reproduction, resolubility, redispersibility, leveling properties, and abrasion resistance of the resulting printed layer. [Solution] A wallpaper ink composition comprising an aqueous (meth)acrylic resin (A), silica (B), a free neutralizing agent (C), and an aqueous medium, wherein (A) comprises either or both of a (meth)acrylic resin emulsion (A1) and a (meth)acrylic resin dispersion (A2), the glass transition temperature of (A) is 60 to 100°C, (B) comprises small particle size silica (B1) and large particle size silica (B2), (B1) is hydrophilic fumed silica and (B2) is hydrophilic silica, the particle size distribution of (B) has a peak with a particle size of 0.8 μm or less derived from (B1) and a peak with a particle size of 2 to 10 μm derived from (B2), and the solid content of (A) is 56 to 77% by mass, (B1) is 0.1 to 4.0% by mass and (B2) is 4.0 to 24.0% by mass relative to the total mass of solids.

Description

[Technical Field]

[0001] This invention relates to an ink composition for wallpaper, a laminate, and wallpaper. [Background technology]

[0002] Wallpaper, used as an interior material for homes and other buildings, is manufactured by laminating a plastic film such as polyvinyl chloride resin onto a base material such as paper or nonwoven fabric, and then printing a design onto the surface. In recent years, wallpaper designs have become more diverse, and the importance of ink compositions using gravure printing and other methods is increasing in order to express high-definition patterns and deep textures.

[0003] Traditionally, wallpaper inks have been known to use synthetic resins as a binder, to which pigments and various additives are blended. Furthermore, silica is sometimes added to wallpaper inks to improve blocking resistance and to impart a matte finish.

[0004] In the wallpaper manufacturing process, heat foaming and embossing (stamping) are performed after printing, so the ink composition is required to have various properties that can withstand these harsh processing conditions. Leveling properties are also one of the characteristics required of wallpaper inks. Improved leveling properties result in smoother gradations, making it easier to reproduce the intended pattern and achieve a uniform, beautiful, smooth surface. Furthermore, resolubility and redispersibility, which affect the efficiency of the manufacturing line, are also required. Inks for wallpaper must also be able to form a printed layer that has excellent durability (abrasion resistance) against physical contact during installation and occupancy.

[0005] Patent Document 1 discloses an aqueous printing ink composition for wallpaper (wallpaper ink) characterized by containing an inorganic acid and / or organic acid, (B) 7 to 50% by weight of a vinyl monomer having an amino group having a specific structure in its molecule, 1 to 30% by weight of a vinyl monomer having an acetylacetoxy group in its molecule, and the remainder being 20 to 92% of other copolymerizable vinyl monomers, after copolymerization of the monomer mixture, an acrylic resin that is water-soluble in the presence of (A), (C) an acrylic resin emulsion, and (D) a crosslinking agent.

[0006] Patent Document 2 discloses an aqueous ink for wallpaper (wallpaper ink) containing a vinyl chloride resin emulsion of a polymer consisting of (A) a polycarbonate-based urethane oligomer having a number average molecular weight of 5,000 to 50,000 and (B) a monomer composition containing vinyl chloride monomers.

[0007] Patent Document 3 discloses an aqueous coating agent for wallpaper (wallpaper ink) characterized by comprising a water-soluble or water-dispersible polyurethane resin (A) having an anionic group or anion-forming group in the molecule, and having a solubility parameter (SP value) of 11 to 12 and a glass transition temperature of 40 to 150°C. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 08-218026 [Patent Document 2] International Publication No. 2020 / 166660 [Patent Document 3] Japanese Patent Publication No. 2000-198962 [Overview of the project] [Problems that the invention aims to solve]

[0009] However, the conventional wallpaper inks described in Patent Documents 1 to 3 do not satisfy all of the following requirements at a high level: gradation reproduction, resolubility, redispersibility, leveling properties, and abrasion resistance of the resulting printed layer. If the tonal reproduction is insufficient, the continuous change in tone (gradation) in the gradient area is lost during printing, resulting in a phenomenon known as tone jumping, where a boundary appears in certain areas. Tone jumping is a major cause of image quality degradation.

[0010] The present invention aims to provide a wallpaper ink composition that is excellent in gradation reproduction, resolubility, redispersibility, leveling properties, and abrasion resistance of the resulting printed layer, a laminate comprising a printed layer formed using the above wallpaper ink composition, and wallpaper comprising the above laminate. [Means for solving the problem]

[0011] The present invention has the following aspects. [1] A wallpaper ink composition comprising an aqueous (meth)acrylic resin (A), silica (B), a free neutralizing agent (C), and an aqueous medium, The aqueous (meth)acrylic resin (A) comprises either or both of (meth)acrylic resin emulsion (A1) and (meth)acrylic resin dispersion (A2), The glass transition temperature of the aqueous (meth)acrylic resin (A) is 60 to 100°C. The silica (B) includes small-diameter silica (B1) and large-diameter silica (B2). The small-diameter silica (B1) is hydrophilic fumed silica. The aforementioned large-diameter silica (B2) is hydrophilic silica, The particle size distribution of the silica (B) includes a peak with a particle size of 0.8 μm or less derived from the small-diameter silica (B1) and a peak with a particle size of 2 to 10 μm derived from the large-diameter silica (B2). The solid content of the aqueous (meth)acrylic resin (A) is 56 to 77% by mass relative to the total mass of solids in the wallpaper ink composition. The content of the small-diameter silica (B1) is 0.1 to 4.0% by mass with respect to the total mass of the solid content of the ink composition for wallpaper, An ink composition for wallpaper, wherein the content of the large-diameter silica (B2) is 4.0 to 24.0% by mass with respect to the total mass of the solid content of the ink composition for wallpaper. [2] The ink composition for wallpaper according to [1], further comprising a film-forming auxiliary agent. [3] The ink composition for wallpaper according to [2], wherein the film-forming auxiliary agent contains either one or both of texanol and dipropylene glycol n-butyl ether. [4] The free neutralizing agent (C) contains at least one selected from the group consisting of ammonia and amine-based neutralizing agents, and the content of the free ammonia and the amine-based neutralizing agent is 0.2 to 2.5% by mass with respect to the total mass of the ink composition for wallpaper. The ink composition for wallpaper according to any one of [1] to [3]. [5] The ink composition for wallpaper according to any one of [1] to [4], further comprising a thickening agent, and the thickening agent contains a urethane association type thickening agent. [6] The ink composition for wallpaper according to any one of [1] to [5], further comprising a leveling agent, and the leveling agent contains an acetylene diol-based leveling agent. [7] The ink composition for wallpaper according to any one of [1] to [6], which is for gravure printing. [8] A laminate comprising a wallpaper base material and a printed layer formed on one surface of the wallpaper base material using the ink composition for wallpaper according to any one of [1] to [6]. [9] A laminate comprising a wallpaper base material and a printed layer formed on one surface of the wallpaper base material using the ink composition for wallpaper according to [7].

[10] A wallpaper comprising the laminate according to [8].

[11] A wallpaper comprising the laminate according to [9].

Advantages of the Invention

[0012] According to the present invention, it is possible to provide an ink composition for wallpaper excellent in gradation reproducibility, redissolvability, redispersibility, leveling property, and abrasion resistance of the obtained printed layer, a laminate including a printed layer formed using the ink composition for wallpaper, and a wallpaper including the laminate.

Embodiments for Carrying Out the Invention

[0013] Hereinafter, the present invention will be described in detail. The following embodiments are merely illustrative for explaining the present invention, and it is not intended to limit the present invention only to these embodiments. The present invention can be implemented in various modes without departing from its gist. The definitions in this specification are as follows. "Aqueous medium" means a liquid medium containing water. "Liquid medium" means a volatile liquid such as water and organic solvents. "Aqueous (meth)acrylic resin" is a general term for "water-soluble (meth)acrylic resin" and "water-dispersible (meth)acrylic resin ((meth)acrylic resin emulsion, (meth)acrylic resin dispersion)". The content of the aqueous (meth)acrylic resin is in terms of all solid components. The "solid content" of the ink composition for wallpaper refers to the components in the ink composition for wallpaper excluding the liquid medium, which are the components that finally form the ink layer, and specifically can be measured in accordance with JIS K 5601-1-2:2008. The same applies to the solid content of the aqueous (meth)acrylic resin. "Coating film" refers to the coating film formed by the ink composition for wallpaper of the present invention. That is, in this specification, "printed layer" and "coating film" are synonymous. "(Meth)acrylate" is a general term for "acrylate" and "methacrylate". "(Meth)acrylic acid" is a general term for "acrylic acid" and "methacrylic acid".

[0014] The glass transition temperature of the aqueous (meth)acrylic resin can be measured in accordance with JIS K 7121:2012 as follows. Using a differential scanning calorimeter, the glass transition temperature is determined from the intersection point of the baseline and the tangent to the endothermic curve in the curve (DSC curve) obtained by heating 10 mg of the solid content of aqueous (meth)acrylic resin from -100°C to 160°C at a rate of 20°C / min.

[0015] The acid value of aqueous (meth)acrylic resin is expressed in milligrams as the amount of potassium hydroxide required to neutralize acidic groups such as carboxyl groups per gram of sample solid content, and can be measured in accordance with JIS K 5601-2-1:1999.

[0016] ≪Ink composition for wallpaper≫ The wallpaper ink composition of this embodiment (hereinafter also simply referred to as "ink composition") comprises an aqueous (meth)acrylic resin (A), silica (B), a free neutralizing agent (C), and an aqueous medium. The aqueous (meth)acrylic binder resin (A) comprises either or both of a (meth)acrylic resin emulsion (A1) and a (meth)acrylic resin dispersion (A2). The ink composition may further contain a film-forming aid. The ink composition may further contain a thickening agent. The ink composition may further contain a leveling agent. The ink composition may further contain a coloring pigment. The ink composition may further contain other components besides aqueous (meth)acrylic resin (A), silica (B), free neutralizing agent (C), aqueous medium, film-forming aid, thickener, leveling agent, and coloring pigment.

[0017] <Water-based (meth)acrylic resin (A)> Aqueous (meth)acrylic resin (A) is a binder component. Aqueous (meth)acrylic resin (A) has units based on (meth)acrylate.

[0018] Examples of aqueous (meth)acrylic resins include homopolymers of (meth)acrylate, copolymers of two or more (meth)acrylates, and copolymers of (meth)acrylate and monomers other than (meth)acrylate. The ratio of (meth)acrylate units to the total mass of all monomer units constituting the aqueous (meth)acrylic resin is preferably 10 to 100% by mass, and more preferably 20 to 100% by mass.

[0019] Examples of (meth)acrylates include alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and lauryl (meth)acrylate; cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate; aryl (meth)acrylates such as phenyl (meth)acrylate; aralkyl (meth)acrylates such as benzyl (meth)acrylate; and hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. (Meth)acrylate may be used alone or in combination of two or more types.

[0020] When the aqueous (meth)acrylic resin (A) is a (meth)acrylic resin dispersion (A2) or a water-soluble (meth)acrylic resin, it is preferable that it has units based on a hydrophilic group-containing monomer. Examples of hydrophilic group-containing monomers include the above-mentioned hydroxyl-containing (meth)acrylate and units based on acidic group-containing monomers described later. When the aqueous (meth)acrylic resin (A) is a (meth)acrylic resin emulsion (A1), it is preferable that the (meth)acrylic resin emulsion (A1) has units based on an acidic group-containing monomer, and more preferably has units based on a carboxyl group-containing monomer.

[0021] Examples of monomers containing a carboxyl group include (meth)acrylic acid, maleic acid (maleic anhydride), fumaric acid, and itaconic acid (itaconic anhydride). The carboxyl group-containing monomer may be used alone or in combination of two or more types.

[0022] Examples of monomers other than (meth)acrylates and carboxyl group-containing monomers include conjugated diene compounds such as 1,3-butadiene, isoprene, and chloroprene; aromatic vinyl compounds such as styrene, α-methylstyrene, halogenated styrene, and divinylbenzene; vinyl cyanide compounds such as acrylonitrile and methacrylonitrile; acrylamides such as N,N-dimethyl(meth)acrylamide and N,N-diethyl(meth)acrylamide; and unsaturated carboxylic acid esters such as diethyl maleate, dibutyl maleate, dibutyl fumarate, diethyl itaconate, and dibutyl itaconate. These monomers may be used individually or in combination of two or more.

[0023] The aqueous (meth)acrylic resin (A) preferably contains either or both of (meth)acrylic resin emulsion (A1) and (meth)acrylic resin dispersion (A2), and more preferably contains (meth)acrylic resin emulsion (A1), from the viewpoint of lightfastness and heat resistance to yellowing of the resulting printed layer.

[0024] (Meth)acrylic resin emulsion (A1) is an emulsion-type (meth)acrylic resin. (Meth)acrylic resin emulsion (A1) typically has a core-shell structure. The core portion of the core-shell structure is preferably a hydrophobic (meth)acrylic resin. The shell portion of the core-shell structure is preferably a hydrophilic (meth)acrylic resin. The core portion and the shell portion may be bonded together by a crosslinking agent.

[0025] The hydrophobic (meth)acrylic resin of the core is typically a resin containing units based on (meth)acrylate. Examples of such resins include homopolymers of (meth)acrylate, copolymers of two or more (meth)acrylates, and copolymers of (meth)acrylate and monomers other than (meth)acrylate. The (meth)acrylate is preferably one that does not have a carboxyl group. The (meth)acrylate and monomers other than (meth)acrylate are as described above.

[0026] The hydrophilic (meth)acrylic resin of the shell is typically a resin containing units based on carboxyl group-containing monomers. Examples of such resins include homopolymers of carboxyl group-containing monomers, copolymers of two or more carboxyl group-containing monomers, and copolymers of a carboxyl group-containing monomer and a monomer other than a carboxyl group-containing monomer. The monomer other than the carboxyl group-containing monomer can be any monomer that does not have a carboxyl group, and may be (meth)acrylate or a monomer other than (meth)acrylate. The carboxyl group-containing monomers are as described above.

[0027] The (meth)acrylic resin emulsion (A1) may be self-crosslinking. If the (meth)acrylic resin emulsion (A1) is self-crosslinking, the (meth)acrylic resin emulsion (A1) typically contains constituent units based on reactive functional group-containing monomers. These constituent units may be contained in the core, the shell, or both. Examples of monomers containing reactive functional groups include monomers containing alkoxysilyl groups, monomers containing hydrazine groups, monomers containing epoxy groups, monomers containing methylol groups, monomers containing alkoxymethyl groups, dihydrazide adipate, diacetone acrylamide, vinyl acetoacetate, allyl acetoacetate, and acetoacetoxyalkyl (meth)acrylate. Examples of epoxy group-containing monomers include glycidyl (meth)acrylate, 2,3-epoxycyclohexyl (meth)acrylate, 3,4-epoxycyclohexyl (meth)acrylate, and allyl glycidyl ether. Examples of acetoacetoxyalkyl (meth)acrylates include acetoacetoxyethyl (meth)acrylate, acetoacetoxypropyl (meth)acrylate, acetoacetoxybutyl (meth)acrylate, and 2,3-di(acetoacetoxy)propyl (meth)acrylate. Reactive functional group-containing monomers may be used individually or in combination of two or more.

[0028] The total content of units based on (meth)acrylate and units based on carboxyl group-containing monomers relative to the total mass of all monomer units constituting the (meth)acrylic resin emulsion (A1) is preferably 20 to 100% by mass, more preferably 50 to 100% by mass, and even more preferably 80 to 100% by mass.

[0029] In the (meth)acrylic resin emulsion (A1), the mass ratio of the core portion to the shell portion (core portion:shell portion) is preferably 20:80 to 90:10, more preferably 25:75 to 85:15, and even more preferably 30:70 to 80:20. If the amount of core portion is greater than the above range and the amount of shell portion is less, the storage stability of the ink composition, the film-forming properties, and the adhesion of the resulting printed layer to the wallpaper substrate will be slightly reduced. If the amount of core portion is less than the above range and the amount of shell portion is greater, the blocking resistance, abrasion resistance, and water abrasion resistance of the resulting printed layer will be slightly reduced.

[0030] The acid value of the (meth)acrylic resin emulsion (A1) is preferably 60 mgKOH / g or less, more preferably 55 mgKOH / g or less, even more preferably 50 mgKOH / g or less, and may also be 0 mgKOH / g or more, 1 mgKOH / g or more, 5 mgKOH / g or more, 10 mgKOH / g or more, or 20 mgKOH / g or more. The above upper and lower limits can be combined as appropriate. If the acid value exceeds the above upper limit, the alkali resistance and water friction resistance of the resulting printed layer will be slightly reduced.

[0031] The average particle size of the (meth)acrylic resin emulsion (A1) is preferably 38 to 600 nm, more preferably 39 to 400 nm, and even more preferably 40 to 350 nm. If the average particle size of the (meth)acrylic resin emulsion (A1) is below the lower limit, the adhesion, alkali resistance, and water friction resistance of the resulting printed layer to the wallpaper substrate will be slightly reduced. If the average particle size of the (meth)acrylic resin emulsion (A1) is above the upper limit, the stability of the ink composition will be slightly reduced. The average particle size of (meth)acrylic resin emulsion (A1) is the particle size at which the volume-based cumulative frequency reaches 50% (median diameter: D50) calculated from the volume-based particle size distribution obtained by dynamic light scattering.

[0032] The glass transition temperature of the aqueous (meth)acrylic resin (A) is 60 to 100°C, preferably 62 to 90°C, and more preferably 65 to 85°C. If the glass transition temperature of the aqueous (meth)acrylic resin (A) is below the above lower limit, the heat resistance of the resulting printed layer will decrease. In addition, the resolubility of the ink composition will decrease. If the resolubility of the ink composition is low, when the aqueous ink remaining in the cells of the gravure plate or on the flexographic plate dries, it can cause transfer defects. Resolubility refers to the ability to redissolve the ink composition in the aqueous medium that constitutes the ink composition before it dries and causes transfer defects. If the glass transition temperature of the aqueous (meth)acrylic resin (A) is above the above upper limit, the adhesion of the resulting printed layer to the wallpaper substrate will decrease.

[0033] The weight-average molecular weight of the aqueous (meth)acrylic resin (A) is preferably 30,000 to 1,000,000, more preferably 50,000 to 900,000, and even more preferably 70,000 to 800,000. If the weight-average molecular weight of the aqueous (meth)acrylic resin (A) is below the lower limit, the abrasion resistance, water abrasion resistance, and blocking resistance of the resulting printed layer will be slightly reduced. If the weight-average molecular weight of the aqueous (meth)acrylic resin (A) is above the upper limit, the storage stability of the ink composition will be slightly reduced. The weight-average molecular weight of aqueous (meth)acrylic resin (A1) is the weight-average molecular weight converted to the standard polystyrene molecular weight and is measured by gel permeation chromatography (GPC). The same applies to other resins.

[0034] The aqueous (meth)acrylic resin (A) may be one manufactured by a known manufacturing method or a commercially available product. In the production of aqueous (meth)acrylic resin (A), the polymerization method of the monomer is not particularly limited, but examples include radical polymerization, anionic polymerization, cationic polymerization, etc. In particular, radical polymerization includes bulk polymerization, solution polymerization, emulsion polymerization, suspension polymerization, etc. Among these, emulsion polymerization is preferred. Emulsion polymerization is a method of polymerization in which the monomers used for polymerization are polymerized in an aqueous medium in the presence of an emulsifier and a polymerization initiator. (Meth)acrylic resin emulsion (A1) may be produced by compounding the core and shell parts after producing them separately, or it may be produced by multi-step emulsion polymerization. The polymerization mode may be any of random copolymer, block copolymer, graft copolymer, etc.

[0035] Water-based (meth)acrylic resin (A) may be used alone or in combination of two or more types. When using (meth)acrylic resin emulsion (A1) as the water-based (meth)acrylic resin (A), (meth)acrylic resin emulsion (A1) may be used alone or in combination of two or more types. When using (meth)acrylic resin dispersion (A2) as the water-based (meth)acrylic resin (A), one type of (meth)acrylic resin dispersion (A2) may be used alone, or two or more types may be used in combination.

[0036] <Silica (B)> Silica (B) includes small-diameter silica (B1) and large-diameter silica (B2).

[0037] Small-diameter silica (B1) is hydrophilic fumed silica. If small-diameter silica (B1) is hydrophilic silica other than hydrophilic fumed silica, the redispersibility decreases. It is thought that hydrogen bonds form between silanol groups on the surface of hydrophilic fumed silica, creating a network structure, and the resulting thixotropy suppresses sedimentation. An example of hydrophilic fumed silica is fumed silica with an untreated surface. Untreated fumed silica exhibits high hydrophilicity because it has hydroxyl groups (silanol groups) on its surface.

[0038] The average particle size of small-diameter silica (B1) is preferably 0.025 μm or less, more preferably 0.020 μm or less, and even more preferably 0.015 μm or less. When the average particle size of small-diameter silica (B1) is below the above upper limit, the particle size of the peak originating from small-diameter silica (B1) in the particle size distribution of silica (B) tends to be 0.8 μm or less. The lower limit of the average particle size of small-diameter silica (B1) is not particularly limited, but it may be, for example, 0.001 μm or larger, or even 0.005 μm or larger. The average particle size of small-diameter silica (B1) is the particle size at which the cumulative frequency of 50% of the number of particles occurs (D50), calculated from the particle size distribution obtained by measuring the particle size distribution of primary particles using a scanning electron microscope (SEM) and a transmission electron microscope (TEM).

[0039] The specific surface area of ​​small-diameter silica (B1) is 50-350 m². 2 / g is preferred, and 70-280m 2 / g is more preferable, 150-250m 2 / g is even more preferable. If the specific surface area of ​​small-diameter silica (B1) is less than the above lower limit, the fluidity of the ink will decrease slightly. If the specific surface area of ​​small-diameter silica (B1) exceeds the above upper limit, the re-agitability will decrease slightly. The specific surface area of ​​small-diameter silica (B1) is measured by the BET method. Specifically, nitrogen gas is adsorbed onto the surface of small-diameter silica (B1) as the adsorbed gas, and the amount of adsorbed gas is measured using the BET formula based on the relationship between the pressure and the amount of adsorbed gas. The specific surface area obtained from this measurement is defined as the specific surface area of ​​small-diameter silica (B1).

[0040] Commercially available products may be used as the small-diameter silica (B1). Examples of commercially available products include AEROSIL® 200, AEROSIL 300, and AEROSIL 90G manufactured by EVONI. Small-diameter silica (B1) may be used alone or in combination of two or more types.

[0041] Large-diameter silica (B2) is hydrophilic silica. An example of hydrophilic silica is untreated silica. Untreated silica exhibits high hydrophilicity because it has hydroxyl groups (silanol groups) on its surface. Large-diameter silica (B2) may be either naturally occurring or synthetic, and may be crystalline or amorphous. Synthesis can be carried out using either a dry or wet method. Known dry methods include combustion and arc synthesis. Known wet methods include sedimentation and gel synthesis.

[0042] The average particle size of large-diameter silica (B2) is preferably 2.9 to 12.0 μm, more preferably 3.5 to 10.0 μm, and even more preferably 5.0 to 8.0 μm. When the average particle size of large-diameter silica (B2) is above the lower limit and below the upper limit, the particle size of the peak originating from large-diameter silica (B2) in the particle size distribution of silica (B) tends to be in the range of 2 to 10 μm. The average particle size of large-diameter silica (B2) is the particle size at which the cumulative frequency of the volume is 50% (D50), calculated from the particle size distribution of secondary particles obtained by laser diffraction and scattering.

[0043] The specific surface area of ​​large-diameter silica (B2) is 250-450 m². 2 / g is preferred, and 260-400m 2 / g is more preferable, 270-340m 2 / g is even more preferable. The method for measuring the specific surface area of ​​large-diameter silica (B2) is the same as the method for measuring the specific surface area of ​​small-diameter silica (B1).

[0044] Commercially available large-diameter silica (B2) may be used. Examples of commercially available products include SYLYSIA® 370, SYLYSIA 430, and SYLYSIA 380, manufactured by Fuji Silysia Chemical Co., Ltd. Large-diameter silica (B2) may be used alone or in combination of two or more types.

[0045] Silica (B) may further contain other silicas other than small-diameter silica (B1) and large-diameter silica (B2). Other types of silica include hydrophilic silica and hydrophobic silica other than small-diameter silica (B1) and large-diameter silica (B2). Hydrophobic silica is obtained by hydrophobicizing the surface of untreated silica. Commercially available hydrophobic silica may be used, or silica produced by hydrophobicizing its surface may be used. Hydrophobicization of the silica surface can be carried out using a surface treatment agent and a known method. Examples of surface treatment agents include dimethyldichlorosilane, hexamethyldisilazane, octylsilane, and silicone oil. One surface treatment agent may be used alone, or two or more may be used in combination. Silica (B) preferably does not contain other silica.

[0046] The particle size distribution of silica (B) includes peaks originating from small-diameter silica (B1) with particle sizes of 0.8 μm or less, and peaks originating from large-diameter silica (B2) with particle sizes of 2 to 10 μm. Multiple peaks may exist in the range of particle sizes 0.8 μm or less. Multiple peaks may exist in the range of particle sizes 2 to 10 μm. Peaks originating from other types of silica may also be present. The particle size distribution of silica (B) is measured using the ink composition as a sample by laser diffraction and scattering.

[0047] The silica (B) exhibits excellent redispersibility when it contains small-diameter silica (B1) and the particle size of the peak derived from small-diameter silica (B1) is 0.8 μm or less. If small-diameter silica (B1) is not present, or if the particle size of the peak derived from small-diameter silica (B1) exceeds 0.8 μm, the redispersibility decreases. The particle size of the peak derived from small-diameter silica (B1) is preferably 0.7 μm or less, and more preferably 0.5 μm or less. The lower limit of the particle size of the peak originating from small-diameter silica (B1) is not particularly limited, but it may be, for example, 0.05 μm or larger, or even 0.2 μm or larger. The particle size of the peak derived from small-diameter silica (B1) can be adjusted by the average particle size of the small-diameter silica (B1).

[0048] When silica (B) contains large-diameter silica (B2) and the particle size of the peak derived from large-diameter silica (B2) is 2 to 10 μm, the resulting printed layer exhibits excellent gradation reproducibility, redispersibility, and abrasion resistance. If large-diameter silica (B2) is not included, or if the particle size of the peak derived from large-diameter silica (B2) is less than 2 μm, gradation reproducibility decreases. If the particle size of the peak derived from large-diameter silica (B2) exceeds 10 μm, redispersibility and abrasion resistance of the resulting printed layer decrease. The particle size of the peak derived from large-diameter silica (B2) is preferably 2.5 to 7.5 μm, and more preferably 3.5 to 5.5 μm. The particle size of the peak derived from large-diameter silica (B2) can be adjusted by the average particle size of the large-diameter silica (B2).

[0049] <Free neutralizing agent (C)> The neutralizing agent is used to neutralize acidic groups (e.g., sulfonic acid groups, carboxyl groups) in the aqueous (meth)acrylic resin (A) in order to make it aqueous. Any excess neutralizing agent is present in the ink composition as free neutralizing agent (C). Examples of neutralizing agents include ammonia; organic amines such as monoethylamine, diethylamine, trimethylamine, triethylamine, triisopropylamine, tributylamine, triethanolamine, methyldiethanolamine, monoethanolamine, dimethylethanolamine, diethylethanolamine, morpholine, N-methylmorpholine, 2-amino-2-methyl-1-propanol, and 2-amino-2-ethyl-1-propanol (amine-based neutralizing agents); and inorganic alkalis such as sodium hydroxide and potassium hydroxide. In particular, from the viewpoint of drying properties, at least one selected from the group consisting of ammonia and amine-based neutralizing agents is preferred, and at least one selected from the group consisting of ammonia, trimethylamine, triethylamine, triethanolamine, and 2-amino-2-methyl-1-propanol is more preferred. The neutralizing agent may be used alone or in combination of two or more types.

[0050] <Aqueous medium> Examples of aqueous media include water and mixed solvents of water and organic solvents. The organic solvent is not particularly limited as long as it is soluble in water, but examples include alcoholic solvents such as methanol, ethanol, n-propanol, i-propanol, n-butanol, and i-butanol; and ketoneic solvents such as acetone. However, even if glycols and glycol derivatives are liquid and soluble in water at 25°C, they are not included in aqueous media in this specification. Glycol derivatives mean glycol ethers and glycol esters. The above glycol derivatives are film-forming aids as described later in this specification. The above glycol is another component as described later in this specification. Organic solvents may be used individually or in combination of two or more types.

[0051] <Membrane-forming agent> To lower the minimum film-forming temperature of the ink composition and to form a uniform and strong printed layer even at low temperatures, the ink composition may contain additional film-forming aids. Examples of film-forming aids include glycol derivatives that are liquid at 25°C. Examples include glycol ethers such as butyl cellosolve, diethylene glycol butyl ether, polypropylene glycol methyl ether, propylene glycol methyl ether, propylene glycol-n-propyl ether, dipropylene glycol-n-butyl ether, dipropylene glycol methyl ether, tripropylene glycol methyl ether, dipropylene glycol dimethyl ether, and tripropylene glycol-n-butyl ether, as well as glycol esters such as texanol. The film-forming aid may be used alone or in combination of two or more types. The film-forming aid preferably contains either or both texanol and dipropylene glycol-n-butyl ether, as these are excellent in lowering the minimum film-forming temperature. Either or both texanol and dipropylene glycol-n-butyl ether may be used in combination with other film-forming aids.

[0052] <Thickening agent> A thickening agent may be further added to the ink composition for the purpose of increasing its viscosity and improving its stability. Examples of thickeners include polyurethane-based thickeners, acrylic-based thickeners, polyamide-based thickeners, cellulose-based thickeners, and clay minerals such as bentonite. Among these, polyurethane-based thickeners are preferred because they are excellent at improving the storage stability of the ink composition, and among these, associated polyurethane-based thickeners (hereinafter also referred to as "urethane associated thickeners") are particularly preferred.

[0053] Associative thickeners are polymers that have both hydrophobic and hydrophilic groups in their molecules. The hydrophobic groups of the thickener interact with each other or with hydrophobic substances such as resins through intermolecular interactions, forming a network structure and further increasing the viscosity of the ink composition. In addition, the viscosity of the ink composition is further increased by the association of the hydrophilic groups of the thickener with the hydrophilic groups of the emulsion surface of the (meth)acrylic resin emulsion (A1). Examples of hydrophobic groups in association-type thickeners include alkyl groups and phenyl groups. Examples of hydrophilic groups in association-type thickeners include hydroxyl groups, amide groups, and carboxyl groups.

[0054] Examples of urethane-associated thickeners include urethane-modified polyethers and polyether polyol-based urethane prepolymers.

[0055] Examples of commercially available urethane-associated thickeners include the "SN Thickener" series manufactured by Sunopco Corporation. The thickening agent may be used alone or in combination of two or more types.

[0056] <Leveling agent> By including a leveling agent in the ink composition, leveling properties and tonal reproduction can be improved. Examples of leveling agents include acetylenediol-based leveling agents, silicone-based leveling agents (such as polyether-modified polydimethylsiloxane and polyester-modified polydimethylsiloxane), and (meth)acrylic-based leveling agents (such as polyacrylate), with acetylenediol-based leveling agents being preferred. Leveling agents may be used individually or in combination of two or more types.

[0057] <Coloring pigments> The coloring pigment may be any pigment known as a coloring agent, such as organic pigments or inorganic pigments. Examples of organic pigments include azo pigments such as monoazo and condensed azo; surene pigments such as anthraquinone, perinone, perylene, and thioindigo; phthalocyanine pigments such as phthalocyanine blue and phthalocyanine green; quinacridone pigments; dioxazine pigments; isoindolinone pigments; pyrrolopyrrole pigments; aniline black; and organic fluorescent pigments. Examples of inorganic pigments include ferrocyanides such as Prussian blue, sulfides such as zinc sulfide; oxides such as chromium oxide, zinc oxide, titanium oxide, and iron oxide; hydroxides such as aluminum hydroxide; silicates such as ultramarine; carbon such as carbon black and graphite; metal powders such as aluminum powder, bronze powder, and zinc powder; and calcined pigments. Coloring pigments may be used individually or in combination of two or more types.

[0058] The ink composition of this embodiment may or may not contain a coloring pigment. An ink composition containing an extender pigment such as silica but not a coloring pigment is known as an extender and is used to adjust the concentration of an ink (containing a coloring pigment).

[0059] <Other ingredients> Other components include, for example, binder resins other than aqueous (meth)acrylic resin (A), extender pigments other than silica, anti-settlement agents, UV absorbers, antioxidants, dispersants, waxes, corrosion inhibitors, defoamers, lubricants, stabilizers, surface modifiers, surfactants, silicone-based additives, foam inhibitors, drying agents, release agents, and wetting agents. These other components may be used individually or in combination of two or more.

[0060] Other binder resins include, for example, aqueous resins other than aqueous (meth)acrylic resin (A). Examples of such aqueous resins include aqueous urethane resin, aqueous polyolefin resin, aqueous vinyl chloride resin (aqueous polyvinyl chloride resin, aqueous vinyl chloride-vinylidene chloride copolymer resin, aqueous vinyl chloride-(meth)acrylic acid copolymer resin, aqueous vinyl chloride-(meth)acrylate copolymer resin, aqueous vinyl chloride-vinyl acetate copolymer resin, etc.), and aqueous ethylene-vinyl acetate copolymer resin.

[0061] Examples of extender pigments other than silica include barium sulfate, calcium sulfate, calcium carbonate, magnesium carbonate, calcium silicate, magnesium silicate, alumina, zirconia, tin oxide, clay, barite, mica, talc, and kaolin. These extender pigments may be used individually or in combination of two or more.

[0062] Examples of drying agents include glycols, which are liquid at 25°C. Examples of release agents include glycols that are solid at 25°C. Examples of such glycols include polyethylene glycol (PEG) with a number-average molecular weight of 1500 or more.

[0063] <Composition of the ink composition> The solid content of the aqueous (meth)acrylic resin (A) is 56 to 77% by mass, preferably 59 to 75% by mass, more preferably 62 to 73% by mass, and even more preferably 65 to 71% by mass, based on the total mass of solids in the ink composition. If the content of aqueous (meth)acrylic resin (A) is below the lower limit, the redispersibility, abrasion resistance of the resulting printed layer, and adhesion to the substrate will decrease. If the content of aqueous (meth)acrylic resin (A) exceeds the upper limit, the gradation reproduction and resolubility will decrease.

[0064] The solid content of the aqueous (meth)acrylic resin (A) is preferably 11 to 28% by mass, more preferably 13 to 25% by mass, and even more preferably 15 to 21% by mass, relative to the total mass of the ink composition. If the content of aqueous (meth)acrylic resin (A) is below the lower limit, the redispersibility, abrasion resistance of the resulting printed layer, and adhesion to the substrate will be slightly reduced. If the content of aqueous (meth)acrylic resin (A) exceeds the upper limit, the gradation reproduction and resolubility will be slightly reduced.

[0065] The solids content of the aqueous (meth)acrylic resin (A) is preferably 70 to 100% by mass, more preferably 80 to 100% by mass, and even more preferably 90 to 100% by mass, relative to the total mass of solids of the binder resin. It may also be 100% by mass.

[0066] The total solid content of the (meth)acrylic resin emulsion (A1) and (meth)acrylic resin dispersion (A2) is preferably 56 to 77% by mass, more preferably 59 to 75% by mass, even more preferably 62 to 73% by mass, and particularly preferably 65 to 71% by mass, based on the total mass of solids of the ink composition.

[0067] The total solid content of the (meth)acrylic resin emulsion (A1) and (meth)acrylic resin dispersion (A2) is preferably 11 to 28% by mass, more preferably 13 to 25% by mass, and even more preferably 15 to 21% by mass, based on the total mass of the ink composition.

[0068] The total solid content of the (meth)acrylic resin emulsion (A1) and (meth)acrylic resin dispersion (A2) is preferably 70 to 100% by mass, more preferably 80 to 100% by mass, and even more preferably 90 to 100% by mass, relative to the total mass of solid content of the aqueous (meth)acrylic resin (A). If the solid content of the (meth)acrylic resin emulsion (A1) and (meth)acrylic resin dispersion (A2) is below the above lower limit, the heat resistance of the resulting printed layer will be slightly reduced.

[0069] The content of small-diameter silica (B1) is 0.1 to 4.0% by mass, preferably 0.2 to 3.5% by mass, more preferably 0.3 to 2% by mass, and even more preferably 0.5 to 1% by mass, relative to the total mass of solids in the ink composition. If the content of small-diameter silica (B1) is below the lower limit, the redispersibility decreases. If the content of small-diameter silica (B1) exceeds the upper limit, the leveling properties decrease.

[0070] The content of small-diameter silica (B1) is preferably 0.03 to 1.1% by mass, more preferably 0.06 to 0.8% by mass, and even more preferably 0.1 to 0.5% by mass, relative to the total mass of the ink composition. If the content of small-diameter silica (B1) is below the lower limit, the redispersibility is slightly reduced. If the content of small-diameter silica (B1) exceeds the upper limit, the leveling properties are slightly reduced.

[0071] The content of large-diameter silica (B2) is 4.0 to 24.0% by mass of the total mass of solids in the ink composition, preferably 5.0 to 20.0% by mass, more preferably 8.0 to 18.0% by mass, and even more preferably 11.0 to 17.0% by mass. If the content of large-diameter silica (B2) is below the lower limit, the gradation reproduction will decrease. If the content of large-diameter silica (B2) exceeds the upper limit, the redispersibility and the abrasion resistance of the resulting printed layer will decrease.

[0072] The content of large-diameter silica (B2) is preferably 0.9 to 7.2% by mass, more preferably 1.5 to 6.5% by mass, and even more preferably 2 to 5.5% by mass, relative to the total mass of the ink composition. If the content of large-diameter silica (B2) is below the lower limit, the gradation reproducibility will be slightly reduced. If the content of large-diameter silica (B2) exceeds the upper limit, the redispersibility and the abrasion resistance of the resulting printed layer will be slightly reduced.

[0073] The total content of small-diameter silica (B1) and large-diameter silica (B2) is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 98% by mass or more, and particularly preferably 100% by mass, relative to the total mass of silica (B).

[0074] The mass ratio of small-diameter silica (B1) to large-diameter silica (B2) is preferably 0.01 to 0.3, more preferably 0.02 to 0.2, and even more preferably 0.03 to 0.1. If the mass ratio of small-diameter silica (B1) to large-diameter silica (B2) is below the lower limit, the redispersibility decreases slightly. If the mass ratio of small-diameter silica (B1) to large-diameter silica (B2) exceeds the upper limit, the leveling properties decrease slightly.

[0075] The content of the free neutralizing agent (C) is preferably 0.05 to 2.8% by mass, more preferably 0.2 to 2.5% by mass, and even more preferably 0.5 to 1.5% by mass, based on the total mass of the ink composition. Ammonia or an amine-based neutralizing agent is preferred as the neutralizing agent. If the content of the free neutralizing agent (C) is below the lower limit, the redispersibility of the ink composition is slightly reduced. If the content of the free neutralizing agent (C) exceeds the upper limit, the drying properties of the ink composition and the abrasion resistance of the resulting printed layer are slightly reduced.

[0076] The content of the aqueous medium is preferably 30 to 85% by mass, more preferably 40 to 82% by mass, and even more preferably 50 to 80% by mass, relative to the total mass of the ink composition. If the content of the aqueous medium is below the lower limit, the gradation reproduction and resolubility will be slightly reduced. If the content of the aqueous medium is above the upper limit, the drying properties will be slightly reduced.

[0077] If the ink composition contains a film-forming aid, the content of the film-forming aid is preferably 0.5 to 8% by mass, more preferably 1 to 6% by mass, and even more preferably 2 to 5% by mass, based on the total mass of the ink composition. If the content of the film-forming aid is below the lower limit, the drying properties will be slightly reduced. If the content of the film-forming aid exceeds the upper limit, the stability of the ink will be slightly reduced.

[0078] If the film-forming aid contains either or both texanol and dipropylene glycol-n-butyl ether, the total content of texanol and dipropylene glycol-n-butyl ether is preferably 50% by mass or more, more preferably 80% by mass or more, and may be 100% by mass, based on the total mass of the film-forming aid.

[0079] When the ink composition contains a leveling agent, the solid content of the leveling agent is preferably 0.05 to 5% by mass, more preferably 0.1 to 3% by mass, and even more preferably 0.2 to 0.8% by mass, relative to the total mass of the ink composition. Acetylenediol-based leveling agents are preferred. If the leveling agent content is below the lower limit, the gradation reproduction and leveling properties will be slightly reduced. If the leveling agent content exceeds the upper limit, the adhesion to the substrate and drying properties will be slightly reduced.

[0080] When the ink composition contains a thickening agent, the solid content of the thickening agent is preferably 0.1 to 5% by mass, more preferably 0.5 to 3% by mass, and even more preferably 1 to 2% by mass, relative to the total mass of the ink composition. A urethane-associated thickening agent is preferred as the thickening agent.

[0081] When the ink composition contains a coloring pigment, the content of the coloring pigment is preferably 1 to 40% by mass, more preferably 3 to 30% by mass, and even more preferably 5 to 20% by mass, relative to the total mass of the ink composition. If the content of the coloring pigment is below the lower limit, the opacity and color development of the resulting printed layer will be slightly reduced. If the content of the coloring pigment exceeds the upper limit, the adhesion of the resulting printed layer to the substrate will be slightly reduced. In addition, the ink fluidity of the ink composition may decrease.

[0082] The content of other components is not particularly limited as long as it does not impair the effects of the present invention, but for example, it is preferably 0 to 20% by mass, more preferably 0 to 15% by mass, even more preferably 0 to 10% by mass, particularly preferably 0 to 5% by mass, and particularly preferably 0 to 1% by mass, based on the total mass of the ink composition. If the ink composition contains other components, the content of these other components is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.5% by mass or more, relative to the total mass of the ink composition. If the content of these other components is above the above lower limit, the effects of these other components will be fully realized.

[0083] The solid content is preferably 15 to 45% by mass, more preferably 20 to 40% by mass, and even more preferably 22 to 35% by mass, based on the total mass of the ink composition.

[0084] <Method for manufacturing wallpaper ink composition> The ink composition of this embodiment can be obtained, for example, by mixing an aqueous (meth)acrylic resin (A), silica (B) (small-diameter silica (B1), large-diameter silica (B2), and other silica as needed), a neutralizing agent (free neutralizing agent (C)), an aqueous medium, and optional components (one or more of the following: film-forming aid, thickener, leveling agent, coloring pigment, and 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 each component other than the aqueous medium in the aqueous medium. The method for dissolving or dispersing each component in an aqueous medium is not particularly limited and can be carried out using known dispersers. Examples of dispersers include paint shakers, ball mills, attritors, sand mills, bead mills, dyno mills, roll mills, dissolvers, 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.

[0085] <Applications, laminates, wallpaper> The ink composition of this embodiment is typically printed on a wallpaper substrate to form an ink layer. Examples of substrates for wallpaper include those in which a plastic film mainly composed of synthetic resin such as polyvinyl chloride (PVC) resin is laminated on a support such as paper or nonwoven fabric.

[0086] Examples of resins that make up plastic films include olefin resins such as polyvinyl chloride, polyethylene, and polypropylene; polyester resins such as ethylene-vinyl alcohol copolymer and polyethylene terephthalate (PET); (meth)acrylic resins; urethane resins; and styrene resins. These plastic films may be used individually or in combination of two or more types.

[0087] In addition to the resin mentioned above, the plastic film may contain foaming agents, plasticizers, fillers, flame retardants, stabilizers, pigments, and other additives as appropriate.

[0088] Examples of foaming agents include thermally decomposed chemical foaming agents such as azodicarbonamide (ADCA) and azobisisobutyronitrile, and foaming aids such as zinc oxide may be used in combination as needed. These foaming agents decompose thermally in the heating process described later (for example, at 180°C to 230°C) to generate gas, which expands the plastic film and imparts rich cushioning and design properties to the wallpaper.

[0089] As plasticizers, phthalate ester plasticizers such as diisononyl phthalate (DINP) and dioctyl phthalate (DOP), as well as non-phthalate plasticizers, are used.

[0090] Any known printing method may be used. The ink composition of this embodiment is suitable for gravure printing or flexographic printing, and is more suitable for gravure printing.

[0091] A laminate can be obtained by printing on a plastic film substrate for wallpaper using the ink composition of this embodiment.

[0092] The printed layer formed using the ink composition of this embodiment has high processability in both mechanical and chemical embossing.

[0093] In mechanical embossing, a cooled embossing roll is pressed against a plastic film that has been softened by heating and foaming to perform physical embossing. The heating temperature is, for example, 130 to 180°C. At this time, the printed layer is subjected to rapid tensile stress, but in the printed layer formed using the ink composition of this embodiment, the occurrence of film breakage and cracks is suppressed even at the bottom and rising portions of deep embossed grooves.

[0094] In chemical embossing, the foam inhibitor blended into the ink composition migrates into the plastic film during the heating process, locally inhibiting the decomposition reaction of the foaming agent. In this method, a steep step is created at the boundary between the foamed and non-foamed areas. However, the printed layer obtained from the ink composition of this embodiment has excellent leveling properties, allowing the inhibitor to penetrate uniformly, thus enabling the formation of a sharp and precise textured design. Furthermore, even at the formed steep step, the printed layer follows the shape changes of the substrate and is firmly adhered without peeling or cracking.

[0095] The wallpaper of this embodiment comprises the laminate described above. The wallpaper may further have a coating layer on the surface of the printed layer of the laminate. Examples of the coating layer include a layer made of treatment agents such as an antifouling agent, a matting agent, and an antibacterial agent.

[0096] <Mechanism of Action> The wallpaper ink composition of the present invention comprises an aqueous (meth)acrylic resin (A), silica (B), a free neutralizing agent (C), and an aqueous medium. As shown in the examples described later, the inclusion of an aqueous (meth)acrylic resin (A) with a glass transition temperature of 60-100°C improves resolubility and the abrasion resistance of the resulting printed layer. Furthermore, by keeping the content of aqueous (meth)acrylic resin (A) within a specific range, gradation reproduction, redispersibility, resolubility, abrasion resistance of the resulting printed layer, and adhesion to the substrate are improved. Furthermore, if silica (B) contains both small-diameter silica (B1) and large-diameter silica (B2), and the particle size distribution of silica (B) contains peaks originating from both small-diameter silica (B1) and large-diameter silica (B2) within a specific range, and the content of small-diameter silica (B1) and large-diameter silica (B2) is within a specific range, then tonal reproduction, redispersibility, leveling, and the abrasion resistance of the resulting printed layer are improved. It is thought that small-diameter silica (B1) enhances redispersibility by suppressing the sedimentation and aggregation of large-diameter silica (B2). [Examples]

[0097] 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. Unless otherwise specified, "%" means "mass%".

[0098] [Raw materials used] <(Meth)acrylic resin emulsion (A1)> A1-1: Solids content: 40%, Glass transition temperature: 80°C, Weight-average molecular weight: 220,000, Average particle size: 131 nm. A1-2: Solids content: 45%, Glass transition temperature: 82°C, Weight-average molecular weight: 130,000, Average particle size: 220 nm. A1-3: Solids content: 50%, Glass transition temperature: 70°C, Weight-average molecular weight: 193,000, Average particle size: 163 nm. A1-4: Solids content: 40%, Glass transition temperature: 53°C, Weight-average molecular weight: 145,000, Average particle size: 190 nm. A1-5: Solids content: 40%, Glass transition temperature: 105℃, Weight-average molecular weight: 210,000, Average particle size: 205nnm.

[0099] <Small diameter silica (B1)> • B1-1: Hydrophilic fumed silica, manufactured by EVONIK, product name "AEROSIL 200", solids content: 100%, average particle size: 0.012 μm, specific surface area by BET method: 200 m² 2 / g. ·B1-2: Hydrophilic fumed silica, manufactured by EVONIK, product name "AEROSIL 300", solid content: 100%, average particle size: 0.007 μm, specific surface area by BET method: 300 m 2 / g. ·B1-3: Hydrophilic fumed silica, manufactured by EVONIK, product name "AEROSIL 90G", solid content: 100%, average particle size: 0.02 μm, specific surface area by BET method: 90 m 2 / g. ·B1-4: Hydrophilic fumed silica, manufactured by EVONIK, product name "AEROSIL 50", solid content: 100%, average particle size: 0.03 μm, specific surface area by BET method: 50 m 2 / g. ·B1-5: Hydrophilic silica, manufactured by Nissan Chemical Industries, Ltd., product name "Snowtex ST-N-40", solid content: 40%, average particle size: 0.022 μm, specific surface area by BET method: 122.5 m 2 / g.

[0100] <Large-diameter silica (B2)> ·B2-1: Hydrophilic silica, manufactured by Fuji Silysia Chemical Ltd., product name "SYLYSIA 37", solid content: 100%, average particle size: 6.4 μm, specific surface area by BET method: 300 m 2 / g. ·B2-2: Hydrophilic silica, manufactured by Fuji Silysia Chemical Ltd., product name "SYLYSIA 430", solid content: 100%, average particle size: 4.1 μm, specific surface area by BET method: 350 m 2 / g. ·B2-3: Hydrophilic silica, manufactured by Fuji Silysia Chemical Ltd., product name "SYLYSIA 380", solid content: 100%, average particle size: 9.0 μm, specific surface area by BET method: 300 m 2 / g. [[ID=3l]] ·B2-4: Hydrophilic silica, manufactured by Fuji Silysia Chemical Ltd., product name "SYLYSIA 530", solid content: 100%, average particle size: 2.7 μm, specific surface area by BET method: 500 m 2 / g. B2-5: Hydrophilic silica, manufactured by Fuji Silysia Chemical Co., Ltd., product name "SYLYSIA 470", solids content: 100%, average particle size: 14.1 μm, specific surface area by BET method: 350 m² 2 / g.

[0101] <Neutralizing agent> C-1:2-amino-2-methyl-1-propanol, manufactured by ANGUS, product name "AMP-90", active ingredient: 90%. C-2: Ammonia water, active ingredient: 28%.

[0102] <Aqueous medium> ·Water: Purified water.

[0103] <Membrane-forming agent> • Auxiliary agent 1: Texanol, active ingredient: 100%. • Auxiliary agent 2: Dipropylene glycol-n-butyl ether, manufactured by Dow Chemical, trade name "Dawanol DPnB", active ingredient: 100%.

[0104] <Thickening agent> • UR: Urethane association type thickener, manufactured by Sunopco Corporation, product name "SN Thickener 623N", solids content: 30%. • AC: Acrylic thickener, manufactured by Sunopco Corporation, product name "SN Thickener 636", solids content: 30%.

[0105] <Other optional components> • Release agent: PEG6000, active ingredient: 100%. • Corrosion inhibitor: Manufactured by Sanwa Kasei Co., Ltd., product name "Fujilight BT-50A", solid content: 38.5%. • Defoaming agent: BASF product, product name "Foamstar SI2210", solids content: 20%. • Leveling agent: Acetylenediol-based leveling agent, manufactured by Kawaken Fine Chemical Co., Ltd., product name "Acetylenel E13T", solids content: >98%.

[0106] [Examples 1-20, Comparative Examples 1-14] <Preparation of wallpaper ink composition> According to the compositions shown in Tables 1-4, (meth)acrylic resin emulsion (A1), small-diameter silica (B1), large-diameter silica (B2), a neutralizing agent, an aqueous medium, and any optional components were mixed, and the resulting mixture was kneaded in a paint shaker to obtain an ink composition.

[0107] In Tables 1-4, "NV" indicates solid content (however, for active ingredients that are not solids, such as free neutralizing agents (C) and film-forming aids, it represents the active ingredient). The amount of each component is the solid content (mass%) relative to the total mass of the ink composition (however, for active ingredients that are not solids, it represents the active ingredient content). The content of free neutralizing agent (C) is the amount of neutralizing agent that is not used to neutralize acidic groups such as carboxyl groups in the resin and is free. This free neutralizing agent comes from neutralizing agents included as non-solid components in aqueous (meth)acrylic resin (A), such as (meth)acrylic resin emulsion (A1), and neutralizing agents added additionally during the preparation of the ink composition. The "residue" of water is the amount that makes the sum of all components (total amount of ink composition) 100%. A blank space means that the component was not included. The NV base content in the table (content of (A) in NV, content of (B1) in NV, content of (B2) in NV) refers to the content (mass%) of the solids of the component in question relative to the total mass of solids in the ink composition. For example, the content of (A) in NV refers to the content of the solids of aqueous (meth)acrylic resin (A) relative to the total mass of solids in the ink composition.

[0108] <Creating printed materials> 95 parts by mass of the ink composition prepared in each example was mixed with 5 parts by mass of a blue ink composition (manufactured by Dainichi Seika Kogyo Co., Ltd., product name "Hydric WP 63 Blue (D)"). The resulting mixture was diluted with water to a viscosity of 18 seconds at 20°C, as measured using a Zahn cup #3, to prepare a printing ink. Using a gravure printing press (manufactured by Matsuo Sangyo Co., Ltd., product name "K Printing Proofer") equipped with a Helio 175 lines / inch gravure engraving plate (solid plate, stepless gradation plate), the prepared printing ink was applied to the surface of the foaming agent-containing polyvinyl chloride resin layer of a wallpaper sheet (laminated paper / foaming agent-containing polyvinyl chloride resin, thickness: 0.25 mm). The sheet was then dried at 80°C for 30 seconds to produce a printed material.

[0109] <Evaluation of redistribution> The ink compositions prepared in each example were placed in 200g poly bottles and left to stand at 40°C for one week. Afterward, they were shaken in a paint shaker for a specified time, the state of the sediment was visually inspected, and the redispersibility was evaluated according to the evaluation criteria shown below. A score of 5 to 3 was considered acceptable. The disappearance of sedimentation was confirmed after shaking for 5 minutes and 30 seconds. The disappearance of the sedimentation was confirmed after shaking for 4 minutes and 60 seconds. 3: The disappearance of sedimentation is confirmed after shaking for 5 minutes. The disappearance of the sedimentation was confirmed after 2 minutes and 15 minutes of shaking. The disappearance of the sedimentation was confirmed after shaking for 1 minute and 15 minutes.

[0110] <Evaluation of abrasion resistance> The obtained printed material (solid color) was subjected to a foaming treatment with 220°C hot air for 40 seconds. Afterward, the printed surface was subjected to an abrasion resistance test using a JSPS-type abrasion fastness tester (manufactured by Tester Sangyo Co., Ltd., product name "AB-301"), in which a white cloth (metal cloth No. 3) with a load of 200 gf was rubbed back and forth 100 times. The staining of the white cloth (metal cloth No. 3) was then visually assessed according to the criteria for abrasion color fading shown in JIS A6921:2014, and the abrasion resistance was evaluated according to the following criteria. A score of 5 to 3 is considered acceptable. 5: The contamination is equivalent to level 5 on the contamination grayscale. 4: The contamination is equivalent to level 4 on the contamination grayscale. 3: The contamination is equivalent to level 3 on the contamination grayscale. 2: The contamination is equivalent to level 2 on the contamination grayscale. 1: Contamination exceeding level 1 on the grayscale for contamination.

[0111] <Evaluation of tonal reproduction> The entire printed surface of the obtained print (infinitely gradient plate) was visually inspected, and the tonal reproduction quality was evaluated according to the evaluation criteria shown below. A score of 5 to 3 is considered acceptable. 5: No tone jumps are observed. 4: Very slight tone jumps are observed. 3: Minor tone jumps are observed. 2: Tone jumps are observed. 1: A noticeable tone jump is observed.

[0112] <Evaluation of drying properties> The printed surface of the obtained printed material (solid color) was subjected to an abrasion resistance test using a Japan Society for the Promotion of Science (JSPS) type friction fastness tester (manufactured by Tester Sangyo Co., Ltd., product name "AB-301"), by rubbing it back and forth five times with a white cloth (metal width 3) under a load of 200 gf. Afterwards, the appearance of the printed layer was visually inspected, and the drying properties were evaluated according to the evaluation criteria shown below. A score of 5 to 3 is considered a pass. 5: The area of ​​the printed layer that has migrated to the white cloth (gold cloth No. 3) is less than 5%. 4. The area of ​​the printed layer that has migrated to the white cloth (gold cloth No. 3) is 5% or more and less than 20%. 3. The percentage of the printed layer area that has migrated to the white cloth (gold cloth No. 3) side is 20% or more and less than 50%. 2: The area of ​​the printed layer that has migrated to the white cloth (gold cloth No. 3) is 50% or more and less than 80%. 1: The area of ​​the printed layer that has migrated to the white cloth (gold cloth No. 3) is 80% or more.

[0113] <Evaluation of resolubility> A Helio 175 line / inch gravure engraving plate, still coated with printing ink immediately after printing, was dried at 80°C for 10 seconds. One drop of water was then added and allowed to stand for 10 seconds. Afterward, the water was wiped off, the condition of the plate at the drop site was checked, and its resolubility was evaluated according to the following criteria. A score of 5-3 was considered acceptable. 5. No ink remains on the printing plate. 4: A very small amount of ink remains on the printing plate. 3: A small amount of ink remains on the printing plate. 2: Ink remains on the printing plate. 1: The ink has hardened on the printing plate and cannot be wiped off.

[0114] <Evaluation of adhesion to the substrate> The resulting printed material (solid color) was subjected to a foaming treatment with 220°C hot air for 40 seconds. Afterward, cellophane adhesive tape (manufactured by Nichiban Co., Ltd.) was applied to the printed surface of the material. The tape was then quickly removed, and the condition of the remaining printed layer on the substrate was visually inspected. The adhesion of the printed layer to the substrate was evaluated according to the following criteria. A score of 5 to 3 was considered acceptable. 5: The printed layer has not peeled off at all. 4. The ratio of the area of ​​the peeled-off printed layer to the total area of ​​the printed layer is greater than 0% and 5% or less. 3. The ratio of the area of ​​the peeled-off printed layer to the total area of ​​the printed layer is greater than 5% and less than or equal to 20%. 2: The ratio of the area of ​​the peeled-off printed layer to the total area of ​​the printed layer is greater than 20% and less than or equal to 50%. 1: The area of ​​the peeled-off printed layer is more than 50% of the total area of ​​the printed layer.

[0115] <Evaluation of leveling ability> The printed surface of the obtained printed material (solid color) was visually inspected, and the leveling properties were evaluated according to the evaluation criteria shown below. A score of 5 to 3 is considered acceptable. 5: The printed coating is uniform. 4: Very slight unevenness can be observed in the printed coating. 3: Slight unevenness can be observed in the printed coating. 2: Unevenness in the printed coating is observed. 1: Significant unevenness in the printed coating is observed.

[0116] The evaluation results are shown in Tables 1-4.

[0117] [Table 1]

[0118] [Table 2]

[0119] [Table 3]

[0120] [Table 4]

[0121] The ink compositions of Examples 1 to 20 exhibited excellent gradation reproduction, resolubility, redispersibility, leveling properties, and abrasion resistance of the printed layer. They also demonstrated good drying properties and adhesion of the printed layer to the substrate. On the other hand, the ink compositions of Comparative Examples 1 to 14 were inferior in one or more of the following: color reproducibility, resolubility, redispersibility, leveling properties, and abrasion resistance of the printed layer. Some of the ink compositions also had poor adhesion of the printed layer to the substrate. [Industrial applicability]

[0122] The wallpaper ink composition of the present invention is useful because it has excellent gradation reproduction, resolubility, redispersibility, leveling properties, and abrasion resistance of the resulting printed layer.

Claims

1. A wallpaper ink composition comprising an aqueous (meth)acrylic resin (A), silica (B), a free neutralizing agent (C), and an aqueous medium, The aqueous (meth)acrylic resin (A) comprises either or both of the (meth)acrylic resin emulsion (A1) and the (meth)acrylic resin dispersion (A2). The glass transition temperature of the aqueous (meth)acrylic resin (A) is 60 to 100°C. The silica (B) includes small-diameter silica (B1) and large-diameter silica (B2). The small-diameter silica (B1) is hydrophilic fumed silica. The aforementioned large-diameter silica (B2) is hydrophilic silica. The particle size distribution of the silica (B) includes a peak with a particle size of 0.8 μm or less derived from the small-diameter silica (B1) and a peak with a particle size of 2 to 10 μm derived from the large-diameter silica (B2). The solid content of the aqueous (meth)acrylic resin (A) is 56 to 77% by mass relative to the total mass of solids in the wallpaper ink composition. The content of the small-diameter silica (B1) is 0.1 to 4.0% by mass relative to the total mass of solids in the wallpaper ink composition. A wallpaper ink composition wherein the content of the large-diameter silica (B2) is 4.0 to 24.0% by mass relative to the total mass of the solids of the wallpaper ink composition.

2. The wallpaper ink composition according to claim 1, further comprising a film-forming aid.

3. The wallpaper ink composition according to claim 2, wherein the film-forming aid comprises either or both texanol and dipropylene glycol-n-butyl ether.

4. The wallpaper ink composition according to claim 1, wherein the free neutralizing agent (C) comprises at least one selected from the group consisting of ammonia and amine-based neutralizing agents, and the content of the free ammonia and amine-based neutralizing agent is 0.2 to 2.5% by mass with respect to the total mass of the wallpaper ink composition.

5. The wallpaper ink composition according to claim 1, further comprising a thickening agent, wherein the thickening agent comprises a urethane association type thickening agent.

6. The wallpaper ink composition according to claim 1, further comprising a leveling agent, wherein the leveling agent comprises an acetylenediol-based leveling agent.

7. A wallpaper ink composition according to any one of claims 1 to 6, for use in gravure printing.

8. A laminate comprising a wallpaper substrate and a printed layer formed on one surface of the wallpaper substrate using the wallpaper ink composition described in any one of claims 1 to 6.

9. A laminate comprising a wallpaper substrate and a printed layer formed on one surface of the wallpaper substrate using the wallpaper ink composition described in claim 7.

10. Wallpaper comprising the laminate described in claim 8.

11. Wallpaper comprising the laminate described in claim 9.

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