Water-based white ink

Abstract

To provide a water-based white ink with excellent sedimentation stability and good coating film strength after printing.SOLUTION: A water-based white ink comprises a white pigment (A), a water-insoluble polymer (B) and a water-soluble polymer (C). The mass ratio of the white pigment (A) to the water-insoluble polymer (B) (mass of the white pigment (A) / mass of the water-insoluble polymer (B)) is less than 1.0. The mass ratio of the water-soluble polymer (C) to the white pigment (A) (mass of the water-soluble polymer (C) / mass of the white pigment (A)) is more than 0.015 and less than 1.0. The acid value of the water-soluble polymer (C) is 150 mg KOH / g or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a water-based white ink. The water-based white ink of this invention can be particularly suitable for use as an inkjet ink. [Background technology]

[0002] Inks are broadly classified into two types: organic solvent-based inks, which use organic solvents as their main solvent component, and water-based inks, which use water as their main solvent component. Because organic solvent-based inks are less safe for human use and emit odors due to the organic solvents, water-based inks using aqueous solvents have been attracting attention in recent years. Furthermore, in recent years, inkjet recording devices, a digital printing method that does not require platemaking, have come into use to accommodate the printing of a wide variety of products in small batches. Rutile-type titanium dioxide, an inorganic pigment, is frequently used as a colorant in white inks for water-based inkjet printers. A method is employed in which a titanium dioxide dispersion (also called titanium dioxide paste or titanium dioxide slurry) containing a high concentration of rutile-type titanium dioxide is prepared, and this titanium dioxide dispersion is mixed with a water-soluble organic solvent, a resin dispersion, additives, water, etc., to produce white ink. For example, Patent Document 1 shows that in an aqueous ink containing rutile-type titanium dioxide and a polymer dispersant, by using a high-acid value dispersant containing 72% by mass or more of components derived from anionic group-containing monomers, an aqueous white ink with excellent foam suppression properties that is less prone to foaming during redispersion can be obtained. Furthermore, Patent Document 2 describes an aqueous inkjet ink containing at least water, titanium dioxide, a pigment dispersant, and an organic solvent, wherein the titanium dioxide has a pigment surface treated with an organic compound, the amount of base on the pigment surface of the titanium dioxide is 28 μmol / g or more, the pigment dispersant is an acidic dispersant with an acid value of 5 mg KOH / g or more and 150 mg KOH / g or less, and the organic solvent contains at least one organic solvent having a boiling point of 200°C or more and 265°C or less and a surface tension of 20 mN / m or more and 30 mN / m or less. This aqueous inkjet ink is characterized by having excellent printability and discharge stability on substrates with low absorbency, and excellent ink properties such as storage stability, settling properties, and opacity. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Patent No. 6881836 [Patent Document 2] Japanese Patent Publication No. 2015-124348 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, while Patent Document 1 describes an aqueous white ink and its raw material, titanium dioxide dispersion, which is an invention relating to a dispersant with low foaming properties, it has been found that there are problems with the strength of the coating film after printing when a dispersant with a high acid value is used. Furthermore, there was a need to further improve the sedimentation stability of the white pigment and the coating strength of the aqueous white ink described in Patent Document 2. The object of the present invention is to provide an aqueous white ink that exhibits excellent settling stability and good coating film strength after printing. [Means for solving the problem]

[0005] In view of the above-mentioned problems, the inventors conducted research and found that an aqueous white ink containing a white pigment (A), a water-insoluble polymer (B), and a water-soluble polymer (C), wherein the mass ratio of white pigment (A) to water-insoluble polymer (B) (mass of white pigment (A) / mass of water-insoluble polymer (B)) is less than 1.0, the mass ratio of water-soluble polymer (C) to white pigment (A) (mass of water-soluble polymer (C) / mass of white pigment (A)) is greater than 0.015 and less than 1.0, and the acid value of water-soluble polymer (C) is 150 mgKOH / g or less exhibits excellent settling stability and good coating film strength after printing, thus completing the present invention. [Effects of the Invention]

[0006] The present invention provides a water-based white ink that exhibits excellent settling stability and good coating film strength after printing. [Modes for carrying out the invention]

[0007] The aqueous white ink of this disclosure comprises a white pigment (A), a water-insoluble polymer (B), and a water-soluble polymer (C).

[0008] <White pigment (A)> The white pigment (A) in this disclosure is not particularly limited, and any known inorganic white pigment can be used. Examples include silicas such as alkaline earth metal sulfates, carbonates, fine silicic acid, and synthetic silicates, calcium silicate, alumina, alumina hydrate, titanium dioxide, zinc oxide, talc, and clay. The inorganic white pigment may also be surface-treated by various surface treatment methods. Among these, surface-treated titanium dioxide is preferred because it exhibits relatively good dispersibility in aqueous media. For example, to avoid the influence of photocatalysis, titanium dioxide surface-treated with an inorganic substance is preferred, and titanium dioxide surface-treated with silica and alumina is preferred. Furthermore, it is also preferable to use titanium dioxide that has been surface-treated with a silane coupling agent after being surface-treated with silica and alumina. In titanium dioxide surface-treated with silica and alumina, known rutile-type and anatase-type titanium dioxide can be used as titanium dioxide, and rutile-type titanium dioxide is more preferred. Examples of rutile-type titanium dioxide include Typake R-820, Typake R-830, Typake R-930, Typake R-550, Typake R-630, Typake R-680, Typake R-670, Typake R-680, Typake R-670, Typake R-780, Typake R-850, Typake CR-50, Typake CR-57, and Ipeque CR-Super70, Typeque CR-80, Typeque CR-90, Typeque CR-93, Typeque CR-95, Typeque CR-97, Typeque CR-60, Typeque CR-63, Typeque CR-67, Typeque CR-58, Typeque CR-85, Typeque UT771 (manufactured by Ishihara Sangyo Co., Ltd.), Typeque R-100, Typeque R-101, TyPure R-102, TyPure R-103, TyPure R-104, TyPure R-105, TyPure R-108, TyPure R-900, TyPure R-902, TyPure R-960, TyPure R-706, TyPure R-931 (manufactured by DuPont), R-25, R-21, R-32, R-7E, R-5N, R-61N, R-62N Examples include R-42, R-45M, R-44, R-49S, GTR-100, GTR-300, D-918, TCR-29, TCR-52, FTR-700 (manufactured by Sakai Chemical Industry Co., Ltd.), JR-403, JR-605, JR-806, JR-701, JR-805, JR-701, JR-800, JR-405, MT600B, MT150W (manufactured by Teika Co., Ltd.), etc.

[0009] The content of rutile-type titanium dioxide in 100 parts by mass of the white pigment (A) of this disclosure is preferably 80 parts by mass or more, more preferably 90 parts by mass or more, even more preferably 95 parts by mass or more, and particularly preferably 100 parts by mass. The average particle size of the white pigment (A) in this disclosure is preferably 100 nm or more, more preferably 150 nm or more, even more preferably 200 nm or more, preferably 500 nm or less, more preferably 400 nm or less, and even more preferably 300 nm or less. If the average particle size is 100 nm or less, non-settling and dispersion stability in aqueous media are more easily achieved, but the whiteness and opacity are inferior, which may reduce the practical usability as a white ink. On the other hand, if the average particle size is 500 nm or more, there are no problems in terms of whiteness and opacity, but the discharge stability tends to be insufficient. The average particle size of titanium dioxide as a raw material is determined by taking the average of 20 particle size measurements using electron microscope images.

[0010] <Water-insoluble polymer (B)> The water-insoluble polymer (B) of the present disclosure may be added for use as a binder resin in aqueous white ink. As the water-insoluble polymer (B) in this disclosure, acrylic resins, styrene-acrylic resins, and urethane resins are preferred from the viewpoint of improving the abrasion resistance and adhesion of the coating film to the substrate. Among these, acrylic resins are preferred from the viewpoint of improving adhesion to poorly absorbent substrates such as plastics, and it is more preferable that the water-insoluble polymer contains a polymer having structural units derived from cyclic aliphatic group-containing monomers, in order to obtain good adhesion to poorly adhering olefin substrates such as biaxially oriented polypropylene (OPP) without the need for primer printing or the like. The structural units derived from the cyclic aliphatic group-containing monomers of this disclosure only need to have the same structure as the structure in which at least one carbon-carbon double bond of the cyclic aliphatic group-containing monomer is replaced by a carbon-carbon single bond. They are not limited to structural units formed by polymerization of the cyclic aliphatic group-containing monomers, but may also be structural units formed by, for example, post-reactions after polymerization.

[0011] As structural units derived from cyclic aliphatic group-containing monomers, those represented by the following formula (1) are preferred. In the following formula (1), R 1 R represents a hydrogen atom or an alkyl group with 1 to 4 carbon atoms. 2 This represents a cyclic aliphatic group.

[0012] [Chemical formula]

[0013] Examples of the alicyclic group in formula (1) include a cyclopentyl group, a cyclohexyl group, an adamantyl group, an isobornyl group, a dicyclopentanyl group, a dicyclopentenyl group, etc. Among them, a cyclopentyl group, a cyclohexyl group, and an isobornyl group are preferred, and a cyclohexyl group and an isobornyl group are more preferred. As the alicyclic group-containing monomer of the present disclosure, a monomer having a carbon-carbon double bond is preferred, and examples thereof include a (meth)acrylate monomer having an alicyclic hydrocarbon group. The (meth)acrylate monomer having an alicyclic hydrocarbon group is preferably a compound having a monovalent alicyclic hydrocarbon group and a monovalent (meth)acrylate group, and the monovalent alicyclic hydrocarbon group and the monovalent (meth)acrylate group are directly bonded to each other. Examples of the alicyclic hydrocarbon group include a monocyclic group, a polycyclic group, a bridged cyclic group, etc. The number of carbon atoms of the alicyclic hydrocarbon group is preferably 4 to 20. The alicyclic hydrocarbon group is preferably an alicyclic group having 4 to 20 carbon atoms, particularly 5 to 12 carbon atoms. The number of carbon atoms of the alicyclic hydrocarbon group is particularly preferably 15 or less, for example, 10 or less. It is preferable that the carbon atom in the ring of the alicyclic hydrocarbon group is directly bonded to the ester group in the (meth)acrylate group. Specific examples of the alicyclic hydrocarbon group are a cyclohexyl group, a t-butylcyclohexyl group, an isobornyl group, a dicyclopentanyl group, and a dicyclopentenyl group. The (meth)acrylate group is an acrylate group or a methacrylate group, and a methacrylate group is preferred. Specific examples of monomers having a cyclic aliphatic hydrocarbon group include cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, benzyl (meth)acrylate, isobornyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and dicyclopentenyl (meth)acrylate. Cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate are preferred, and cyclohexyl (meth)acrylate and isobornyl (meth)acrylate are more preferred. These cyclic aliphatic group-containing monomers can be used individually or in combination of several types. The content of structural units derived from monomers having cyclic aliphatic hydrocarbon groups in 100 parts by mass of the water-insoluble polymer (B) of the present disclosure may be 30 parts by mass or more, preferably 35 parts by mass or more, more preferably 40 parts by mass or more, even more preferably 45 parts by mass or more, and may be 95 parts by mass or less, preferably 90 parts by mass or less, and more preferably 85 parts by mass or less.

[0014] The water-insoluble polymer (B) of the present disclosure may have structural units derived from monomers other than those derived from cyclic aliphatic group-containing monomers. Other monomer-derived structural units are not limited to structural units formed by polymerization of the other monomers described below, but may also include structural units formed by post-reactions after polymerization, for example. Other monomers include monofunctional monomers and polyfunctional monomers. Monofunctional monomers and polyfunctional monomers may be used individually or in combination. Examples of monofunctional monomers include (meth)acrylic acid esters having linear alkyl groups, (meth)acrylic acid esters having branched alkyl groups, acid group-containing monomers, hydroxyl group-containing (meth)acrylates, oxo group-containing monomers, fluorine atom-containing monomers, nitrogen atom-containing monomers, epoxy group-containing monomers, alkoxyalkyl (meth)acrylates, silane group-containing monomers, carbonyl group-containing monomers, aziridinyl group-containing monomers, styrene monomers, aralkyl (meth)acrylates, and addition polymerizable oxazolines, but are not limited to these examples. The linear alkyl group-containing (meth)acrylic acid esters of this disclosure include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, behenyl (meth)acrylate, methoxyethyl (meth)acrylate, ethyl carbitol (meth)acrylate, ethoxypolyethylene glycol (meth)acrylate, aminoethyl (meth)acrylate, chloroethyl (meth)acrylate, trifluoroethyl (meth)acrylate, and (meth) Examples include heptadecafluorooctylethyl acrylate, and from the viewpoint of adhesion and scratch resistance, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, and behenyl (meth)acrylate are preferred, and methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, octyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, and behenyl (meth)acrylate are more preferred. Examples of (meth)acrylic acid esters having a branched alkyl group in this disclosure include isopropyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, neopentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isodecyl (meth)acrylate, isostearyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, methoxytripropylene glycol (meth)acrylate, and hexafluoropropyl (meth)acrylate. From the viewpoint of adhesion and scratch resistance, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, neopentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isodecyl (meth)acrylate, and isostearyl (meth)acrylate are preferred, and isobutyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and isostearyl (meth)acrylate are more preferred.

[0015] Examples of acid group-containing monomers of this disclosure include (meth)acrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, citraconic acid, maleic anhydride, monomethyl maleic acid, monobutyl maleic acid, monomethyl itaconic acid, monobutyl itaconic acid, vinylbenzoic acid, and other carboxyl group-containing aliphatic monomers. However, the present invention is not limited to these examples. These acid group-containing monomers may be used individually or in combination of two or more. Among these acid group-containing monomers, acrylic acid, methacrylic acid, and itaconic acid are preferred, and acrylic acid and methacrylic acid are more preferred, from the viewpoint of improving the dispersion stability, adhesion, and scratch resistance of the aqueous dispersion when the water-insoluble polymer (B) is emulsion particles. Examples of hydroxyl group-containing (meth)acrylates in this disclosure include, but are not limited to, hydroxyl group-containing (meth)acrylates with ester groups having 1 to 18 carbon atoms, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. Among these hydroxyl group-containing monomers, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred from the viewpoint of improving adhesion and scratch resistance. These hydroxyl group-containing (meth)acrylates may be used individually or in combination of two or more types. Examples of oxo group-containing monomers in this disclosure include, but are not limited to, (di)ethylene glycol (methoxy)(meth)acrylates such as ethylene glycol (meth)acrylate, ethylene glycol methoxy(meth)acrylate, diethylene glycol (meth)acrylate, and diethylene glycol methoxy(meth)acrylate. These oxo group-containing monomers may be used individually or in combination of two or more types.

[0016] Examples of fluorine atom-containing monomers in this disclosure include, but are not limited to, fluorine atom-containing alkyl (meth)acrylates with 2 to 6 carbon atoms in the ester group, such as trifluoroethyl (meth)acrylate, tetrafluoropropyl (meth)acrylate, and octafluoropentyl (meth)acrylate. These fluorine atom-containing monomers may be used individually or in combination of two or more types. Examples of nitrogen atom-containing monomers in this disclosure include, but are not limited to, acrylamide compounds such as (meth)acrylamide, N-monomethyl(meth)acrylamide, N-monoethyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, Nn-propyl(meth)acrylamide, N-isopropyl(meth)acrylamide, methylenebis(meth)acrylamide, N-methylol(meth)acrylamide, N-butoxymethyl(meth)acrylamide, dimethylaminoethyl(meth)acrylamide, N,N-dimethylaminopropylacrylamide, and diacetoneacrylamide; nitrogen atom-containing (meth)acrylate compounds such as dimethylaminoethyl(meth)acrylate and diethylaminoethyl(meth)acrylate; N-vinylpyrrolidone; and (meth)acrylonitrile. These nitrogen atom-containing monomers may be used individually or in combination of two or more types. Examples of epoxy group-containing monomers in this disclosure include, but are not limited to, epoxy group-containing (meth)acrylates such as glycidyl (meth)acrylate, α-methylglycidyl (meth)acrylate, and glycidyl allyl ether. These epoxy group-containing monomers may be used individually or in combination of two or more types. Among these epoxy group-containing monomers, glycidyl (meth)acrylate is preferred from the viewpoint of improving adhesion and scratch resistance. Examples of the alkoxyalkyl (meth)acrylates of this disclosure include, but are not limited to, methoxyethyl (meth)acrylate, methoxybutyl (meth)acrylate, ethoxybutyl (meth)acrylate, and trimethylolpropane tripoxy (meth)acrylate. These alkoxyalkyl (meth)acrylates may be used individually or in combination of two or more types. Examples of silane group-containing monomers of this disclosure include, but are not limited to, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(methoxyethoxy)silane, γ-(meth)acryloyloxypropyltrimethoxysilane, 2-styrylethyltrimethoxysilane, vinyltrichlorosilane, γ-(meth)acryloyloxypropylhydroxysilane, and γ-(meth)acryloyloxypropylmethylhydroxysilane. These silane group-containing monomers may be used individually or in combination of two or more types.

[0017] Examples of carbonyl group-containing monomers in this disclosure include, but are not limited to, acrolein, homyl styrene, vinyl ethyl ketone, (meth)acryloxyalkyl propenal, acetonyl (meth)acrylate, diacetone (meth)acrylate, 2-hydroxypropyl (meth)acrylate acetyl acetate, butanediol-1,4-acrylate acetyl acetate, and 2-(acetoacetoxy)ethyl (meth)acrylate. These carbonyl group-containing monomers may be used individually or in combination of two or more types. Examples of the aziridinyl group-containing monomers of this disclosure include (meth)acryloylaziridine and 2-aziridinylethyl (meth)acrylate, but are not limited to these examples. These aziridinyl group-containing monomers may be used individually or in combination of two or more types. Examples of styrene monomers in this disclosure include, but are not limited to, styrene, α-methylstyrene, p-methylstyrene, tert-methylstyrene, chlorostyrene, and vinyltoluene. These styrene monomers may be used individually or in combination of two or more types. The styrene monomers may have functional groups on the benzene ring, such as methyl groups, alkyl groups such as tert-butyl groups, nitro groups, nitrile groups, alkoxyl groups, acyl groups, sulfone groups, hydroxyl groups, and halogen atoms. Among the styrene monomers, styrene is preferred from the viewpoint of improving water resistance. Examples of aralkyl (meth)acrylates in this disclosure include, but are not limited to, aralkyl (meth)acrylates having an aralkyl group with 7 to 18 carbon atoms, such as benzyl (meth)acrylate, phenylethyl (meth)acrylate, methylbenzyl (meth)acrylate, and naphthylmethyl (meth)acrylate. These aralkyl (meth)acrylates may be used individually or in combination of two or more types.

[0018] Examples of addition-polymerizable oxazolines in this disclosure include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, and 2-isopropenyl-4-methyl-2-oxazoline. Each of these addition-polymerizable oxazolines may be used individually or in combination of two or more. Among these addition-polymerizable oxazolines, 2-isopropenyl-2-oxazoline is preferred because it is readily available. Examples of polyfunctional monomers include, but are not limited to, polyfunctional monomers such as 2-isopropenyl-5-methyl-2-oxazoline and 2-isopropenyl-5-ethyl-2-oxazoline. These include, for example, ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, ethylene oxide-modified 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, propylene oxide-modified neopentyl glycol di(meth)acrylate, and triply Di(meth)acrylates of polyhydric alcohols with 1 to 10 carbon atoms, such as polyethylene glycol di(meth)acrylate; alkyl di(meth)acrylates with 2 to 50 moles of ethylene oxide added, such as polyethylene glycol di(meth)acrylate with 2 to 50 moles of propylene oxide added, polypropylene glycol di(meth)acrylate with 2 to 50 moles of propylene oxide added, and tripropylene glycol di(meth)acrylate, which have 2 to 50 moles of alkylene oxide groups with 2 to 4 carbon atoms; ethoxylated glycerin tri (meth)acrylates of polyhydric alcohols with 1 to 10 carbon atoms, such as (meth)acrylate, propylene oxide-modified glycerol tri(meth)acrylate, ethylene oxide-modified trimethylolpropane tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol monohydroxytri(meth)acrylate, trimethylolpropane triethoxytri(meth)acrylate; pentaerythritol tetra(meth)acrylate, dipentaerythritol Tetra(meth)acrylates of polyhydric alcohols with 1 to 10 carbon atoms, such as litol tetra(meth)acrylate and ditrimethylolpropane tetra(meth)acrylate; penta(meth)acrylates of polyhydric alcohols with 1 to 10 carbon atoms, such as pentaerythritol penta(meth)acrylate and dipentaerythritol (monohydroxy)penta(meth)acrylate; hexa(meth)acrylates of polyhydric alcohols with 1 to 10 carbon atoms, such as pentaerythritol hexa(meth)acrylate;Examples include epoxy group-containing (meth)acrylates such as bisphenol A di(meth)acrylate, 2-(2'-vinyloxyethoxyethyl)(meth)acrylate, and epoxy(meth)acrylate; and polyfunctional (meth)acrylates such as urethane(meth)acrylate, but are not limited to these examples. These polyfunctional monomers may be used individually or in combination of two or more.

[0019] From the viewpoint of imparting UV stability or UV absorption, it is preferable that the water-insoluble polymer (B) of this disclosure contains UV-stable monomers, UV-absorbing monomers, etc., as monomer components, within a range that does not hinder the objectives of the present invention. Examples of UV-stable monomers in this disclosure include 4-(meth)acryloyloxy-2,2,6,6-tetramethylpiperidine, 4-(meth)acryloylamino-2,2,6,6-tetramethylpiperidine, 4-(meth)acryloyloxy-1,2,2,6,6-pentamethylpiperidine, 4-(meth)acryloyl-1-methoxy-2,2,6,6-tetramethylpiperidine, 4-cyano-4-(meth)acryloyloxy-2,2,6,6-tetramethylpiperidine, 1-(meth)acryloyl-4-(meth)acryloylamino-2,2,6,6-tetramethylpiperidine, and 4-crotonoylamino- Examples of piperidine group-containing monomers include 2,2,6,6-tetramethylpiperidine, 4-(meth)acryloylamino-1,2,2,6,6-pentamethylpiperidine, 4-cyano-4-(meth)acryloylamino-2,2,6,6-tetramethylpiperidine, 4-crotonoyloxy-2,2,6,6-tetramethylpiperidine, 1-(meth)acryloyl-4-cyano-4-(meth)acryloylamino-2,2,6,6-tetramethylpiperidine, and 1-crotonoyl-4-crotonoyloxy-2,2,6,6-tetramethylpiperidine, but the present invention is not limited to these examples. These monomers may be used individually or in combination of two or more types. Among these UV-stable monomers, piperidyl group-containing (meth)acrylates such as 4-(meth)acryloyloxy-2,2,6,6-tetramethylpiperidine, 4-(meth)acryloyloxy-1,2,2,6,6-pentamethylpiperidine, and 4-cyano-4-(meth)acryloyloxy-2,2,6,6-tetramethylpiperidine are preferred from the viewpoint of improving adhesion and scratch resistance. Examples of UV-absorbing monomers in this disclosure include benzotriazole-based UV-absorbing monomers and benzophenone-based UV-absorbing monomers, but the present invention is not limited to these examples. These monomers may be used individually or in combination of two or more types. Examples of benzotriazole-based UV-absorbing monomers include 2-[2'-hydroxy-5'-(meth)acryloyloxymethylphenyl]-2H-benzotriazole, 2-[2'-hydroxy-5'-(meth)acryloyloxyethylphenyl]-2H-benzotriazole, 2-[2'-hydroxy-5'-(meth)acryloyloxymethylphenyl]-5-tert-butyl-2H-benzotriazole, and 2-[2'-hydroxy-5'-(meth )acryloylaminomethyl-5'-tert-octylphenyl]-2H-benzotriazole, 2-[2'-hydroxy-5'-(meth)acryloyloxypropylphenyl]-2H-benzotriazole, 2-[2'-hydroxy-5'-(meth)acryloyloxyhexylphenyl]-2H-benzotriazole, 2-[2'-hydroxy-3'-tert-butyl-5'-(meth)acryloyloxyethylphenyl]-2H-benzotriazole , 2-[2'-hydroxy-3'-tert-butyl-5'-(meth)acryloyloxyethylphenyl]-5-chloro-2H-benzotriazole, 2-[2'-hydroxy-5'-tert-butyl-3'-(meth)acryloyloxyethylphenyl]-2H-benzotriazole, 2-[2'-hydroxy-5'-(meth)acryloyloxyethylphenyl]-5-chloro-2H-benzotriazole, 2-[2'-hydroxy-5'-(meth)ac Examples include liloyloxyethylphenyl]-5-cyano-2H-benzotriazole, 2-[2'-hydroxy-5'-(meth)acryloyloxyethylphenyl]-5-tert-butyl-2H-benzotriazole, and 2-[2'-hydroxy-5'-(β-(meth)acryloyloxyethoxy)-3'-tert-butylphenyl]-4-tert-butyl-2H-benzotriazole, but the present invention is not limited to these examples. These monomers may be used individually or in combination of two or more.

[0020] Examples of benzophenone-based UV-absorbing monomers include 2-hydroxy-4-(meth)acryloyloxybenzophenone, 2-hydroxy-4-[2-hydroxy-3-(meth)acryloyloxy]propoxybenzophenone, 2-hydroxy-4-[2-(meth)acryloyloxy]ethoxybenzophenone, 2-hydroxy-4-[3-(meth)acryloyloxy-2-hydroxypropoxy]benzophenone, and 2-hydroxy-3-tert-butyl-4-[2-(meth)acryloyloxy]butoxybenzophenone, but the present invention is not limited to these examples. These monomers may be used individually or in combination of two or more types. As other monomers in this disclosure, from the viewpoint of further improving adhesion to corona-treated PET, OPP, etc., piperidine group-containing monomers, nitrogen atom-containing monomers, and addition-polymerizable oxazolines are preferred, among which piperidine group-containing monomers and addition-polymerizable oxazolines are more preferred, and 4-(meth)acryloyloxy-2,2,6,6-tetramethylpiperidine, 4-(meth)acryloyloxy-1,2,2,6,6-pentamethylpiperidine, and 2-isopropenyl-2-oxazoline are even more preferred. Furthermore, if a hydroxyl group-containing (meth)acrylate is included as a monofunctional monomer, emulsion particles without coarse particles are easily obtained, the discharge stability of the ink containing the emulsion particles is excellent, and from the viewpoint of further improving adhesion, it is preferable to include a hydroxyl group-containing (meth)acrylate.

[0021] The content of structural units derived from other monomers in 100 parts by mass of the water-insoluble polymer (B) of the present disclosure may be 5 parts by mass or more, preferably 10 parts by mass or more, more preferably 15 parts by mass or more, may be 70 parts by mass or less, preferably 65 parts by mass or less, more preferably 60 parts by mass or less, and even more preferably 55 parts by mass or less. The acid value of the water-insoluble polymer (B) in this disclosure does not have to have an acid value, but it may be 50 mg KOH / g or less, preferably 40 mg KOH / g or less, more preferably 35 mg KOH / g or less, and even more preferably 30 mg KOH / g or less. By having the acid value of the water-insoluble polymer (B) within the above range, a water-based ink with a suitable viscosity for inkjet printing can be obtained, and an effect of improving scratch resistance can be expected. Furthermore, the acid value of the water-insoluble polymer (B) in this disclosure may be 1 mg KOH / g or higher from the viewpoint of suppressing aggregation and suppressing viscosity changes when used as an ink. The glass transition temperature of the water-insoluble polymer (B) of the present disclosure may be -10°C or higher, preferably 0°C or higher, more preferably 5°C or higher, even more preferably 10°C or higher, and may be 90°C or lower, preferably 80°C or lower, more preferably 70°C or lower, and even more preferably 60°C or lower. The glass transition temperature (Tg) of a polymer is calculated using the glass transition temperature of the homopolymer of the monomer components used as raw materials for the polymer, using the formula: 1 / Tg = Σ(Wm / Tgm) / 100 This refers to the temperature determined based on Fox's formula, which is expressed as follows: [In the formula, Wm represents the content (mass%) of monomer m in the inner layer monomer component constituting the resin layer, and Tgm represents the glass transition temperature (absolute temperature: K) of the homopolymer of monomer m]. In this specification, unless otherwise specified, the glass transition temperature of a polymer refers to the glass transition temperature determined based on Fox's formula.

[0022] The water-insoluble polymer (B) of the present disclosure may be emulsion particles dispersed in a water-based solvent when added to an aqueous white ink. The emulsion particles of the present disclosure may be a single layer or may have a multilayer structure. If the emulsion particles of the present disclosure have a multilayer structure, it is preferable that there are two to four layers, and more preferably two or three layers. In emulsion particles having a multilayer resin layer, the inner layer means the innermost layer of the emulsion particle, the outer layer means the other layers excluding the innermost layer, and the outermost layer means the outermost layer formed. When the water-insoluble polymer (B) of the present disclosure is an emulsion particle having a multilayer structure, the content of structural units derived from monomers having cyclic aliphatic hydrocarbon groups in 100 parts by mass of monomer components forming the inner layer may be 30 parts by mass or more, preferably 35 parts by mass or more, more preferably 40 parts by mass or more, even more preferably 45 parts by mass or more, and may be 95 parts by mass or less, preferably 90 parts by mass or less, and more preferably 85 parts by mass or less. When the water-insoluble polymer (B) of the present disclosure is an emulsion particle having a multilayer structure, the content of structural units derived from other monomers in 100 parts by mass of monomer components forming the inner layer may be 5 parts by mass or more, preferably 10 parts by mass or more, more preferably 15 parts by mass or more, may be 70 parts by mass or less, preferably 65 parts by mass or less, more preferably 60 parts by mass or less, and even more preferably 55 parts by mass or less.

[0023] When the water-insoluble polymer (B) of the present disclosure is an emulsion particle having a multilayer structure, in 100 parts by mass of monomer components forming the inner layer, the other monomer-derived structural units are more preferably 2-hydroxyethyl (meth)acrylate, (meth)acrylic acid, 2-ethylhexyl (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, behenyl (meth)acrylate, (meth)acrylonitrile, glycidyl (meth)acrylate, styrene, 2-isopropenyl-2-oxazoline, 4-(meth)acryloyloxy-2,2,6,6-tetramethylpiperidine, and 4-(meth)acryloyloxy-1,2,2,6,6-pentamethylpiperidine.

[0024] When the water-insoluble polymer (B) of the present disclosure is an emulsion particle having a multilayer structure, the content of structural units derived from monomers having cyclic aliphatic hydrocarbon groups in 100 parts by mass of monomer components forming the outer layer may be 30 parts by mass or more, preferably 35 parts by mass or more, more preferably 40 parts by mass or more, even more preferably 45 parts by mass or more, and may be 95 parts by mass or less, preferably 90 parts by mass or less, and more preferably 85 parts by mass or less. When the water-insoluble polymer (B) of the present disclosure is an emulsion particle having a multilayer structure, the content of structural units derived from other monomers in 100 parts by mass of monomer components forming the outer layer may be 5 parts by mass or more, preferably 10 parts by mass or more, more preferably 15 parts by mass or more, may be 70 parts by mass or less, preferably 65 parts by mass or less, more preferably 60 parts by mass or less, and even more preferably 55 parts by mass or less.

[0025] When the water-insoluble polymer (B) of the present disclosure is an emulsion particle having a multilayer structure, in 100 parts by mass of monomer components forming the outer layer, the other monomer-derived structural units are more preferably 2-hydroxyethyl (meth)acrylate, (meth)acrylic acid, 2-ethylhexyl (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, behenyl (meth)acrylate, (meth)acrylonitrile, glycidyl (meth)acrylate, styrene, 2-isopropenyl-2-oxazoline, 4-(meth)acryloyloxy-2,2,6,6-tetramethylpiperidine, and 4-(meth)acryloyloxy-1,2,2,6,6-pentamethylpiperidine. When the water-insoluble polymer (B) of the present disclosure is an emulsion particle having a multilayer structure, the content of structural units derived from monomers having cyclic aliphatic hydrocarbon groups in 100 parts by mass of monomer components forming the outermost layer may be 30 parts by mass or more, preferably 35 parts by mass or more, more preferably 40 parts by mass or more, even more preferably 45 parts by mass or more, and may be 95 parts by mass or less, preferably 90 parts by mass or less, and more preferably 85 parts by mass or less. When the water-insoluble polymer (B) of the present disclosure is an emulsion particle having a multilayer structure, the content of structural units derived from other monomers in 100 parts by mass of monomer components forming the outermost layer may be 5 parts by mass or more, preferably 10 parts by mass or more, more preferably 15 parts by mass or more, may be 70 parts by mass or less, preferably 65 parts by mass or less, more preferably 60 parts by mass or less, and even more preferably 55 parts by mass or less.

[0026] When the water-insoluble polymer (B) of the present disclosure is an emulsion particle having a multilayer structure, in 100 parts by mass of monomer components forming the outermost layer, the other monomer-derived structural units are more preferably 2-hydroxyethyl (meth)acrylate, (meth)acrylic acid, 2-ethylhexyl (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, behenyl (meth)acrylate, (meth)acrylonitrile, glycidyl (meth)acrylate, styrene, 2-isopropenyl-2-oxazoline, 4-(meth)acryloyloxy-2,2,6,6-tetramethylpiperidine, and 4-(meth)acryloyloxy-1,2,2,6,6-pentamethylpiperidine. The mass ratio of the polymer layer constituting the inner layer to the polymer layer constituting the outer layer of the present disclosure (mass of polymer constituting the inner layer / mass of polymer constituting the outer layer) is preferably 10 / 90 to 90 / 10, more preferably 20 / 80 to 80 / 20, even more preferably 30 / 70 to 70 / 30, and even more preferably 40 / 60 to 60 / 40, from the viewpoint of improving flexibility, blocking resistance, adhesion to the substrate, and scratch resistance. The mass ratio of the polymer layer constituting the inner layer to the polymer layer constituting the outermost layer (polymer layer constituting the inner layer / polymer layer constituting the outermost layer) of the present disclosure is preferably 10 / 90 to 90 / 10, more preferably 20 / 80 to 80 / 20, even more preferably 30 / 70 to 70 / 30, and even more preferably 40 / 60 to 60 / 40, from the viewpoint of improving flexibility, blocking resistance, adhesion to the substrate, and scratch resistance.

[0027] The acid value of the polymer constituting the inner layer of this disclosure does not have to have an acid value, but it may be 50 mg KOH / g or less, preferably 40 mg KOH / g or less, more preferably 35 mg KOH / g or less, and even more preferably 30 mg KOH / g or less. By having the acid value of the inner layer of the water-insoluble polymer (B) within the above range, a water-based ink with a suitable viscosity for inkjet applications can be obtained, and improvements in adhesion, scratch resistance, and ejection stability can be expected. Furthermore, the acid value of the polymer constituting the inner layer of this disclosure may be 1 mg KOH / g or more from the viewpoint of suppressing aggregates and suppressing viscosity changes when used as an ink.

[0028] The acid value of the polymer constituting the outer layer of this disclosure does not have to have an acid value, but it may be 50 mg KOH / g or less, preferably 40 mg KOH / g or less, more preferably 35 mg KOH / g or less, and even more preferably 30 mg KOH / g or less. By having the acid value of the outer layer of the water-insoluble polymer (B) within the above range, a water-based ink with a suitable viscosity for inkjet use can be obtained, and improvements in adhesion, scratch resistance, and ejection stability can be expected. Furthermore, the acid value of the polymer constituting the outer layer of this disclosure may be 1 mg KOH / g or more from the viewpoint of suppressing aggregates and suppressing viscosity changes when used as an ink. The acid value of the polymer constituting the outermost layer of this disclosure does not have to have an acid value, but it may be 50 mg KOH / g or less, preferably 40 mg KOH / g or less, more preferably 35 mg KOH / g or less, and even more preferably 30 mg KOH / g or less. By having the acid value of the outermost layer of the water-insoluble polymer (B) within the above range, a water-based ink with a suitable viscosity for inkjet applications can be obtained, and improvements in adhesion, scratch resistance, and ejection stability can be expected. Furthermore, the acid value of the polymer constituting the outermost layer of this disclosure may be 1 mg KOH / g or more from the viewpoint of suppressing aggregation and suppressing viscosity changes when used as an ink.

[0029] The glass transition temperature of the polymer constituting the inner layer of this disclosure is -10°C or higher, preferably 0°C or higher, from the viewpoint of adhesion and scratch resistance, and the upper limit of the glass transition temperature is preferably 120°C or lower, more preferably 100°C or lower, from the viewpoint of adhesion and scratch resistance. The glass transition temperature of the polymer forming the inner layer can be adjusted by adjusting the type and amount of monomers forming the inner layer. The glass transition temperature of the polymer constituting the outer layer of this disclosure is 0°C or higher, preferably 10°C or higher, from the viewpoint of adhesion, scratch resistance, and film-forming properties. The upper limit of the glass transition temperature is preferably 100°C or lower, more preferably 90°C or lower, from the viewpoint of adhesion and scratch resistance. The glass transition temperature of the polymer forming the outer layer can be adjusted by adjusting the type and amount of monomers forming the outer layer. The glass transition temperature of the polymer constituting the outermost layer of this disclosure is 0°C or higher, preferably 10°C or higher, from the viewpoint of adhesion, scratch resistance, and film-forming properties. The upper limit of the glass transition temperature is preferably 100°C or lower, more preferably 90°C or lower, from the viewpoint of adhesion and scratch resistance. The glass transition temperature of the polymer forming the outermost layer can be adjusted by adjusting the type and amount of monomers forming the outermost layer. Unless otherwise specified, the glass transition temperatures of the polymers constituting each of the above layers refer to the glass transition temperatures determined based on Fox's equation, similar to the glass transition temperature of the water-insoluble polymer (B).

[0030] <Water-soluble polymer (C)> The water-soluble polymer (C) of this disclosure may be added to an aqueous white ink for use as a pigment dispersant (hereinafter also referred to as a dispersant). The acid value of the water-soluble polymer (C) of this disclosure is preferably 150 mg KOH / g or less, more preferably 100 mg KOH / g or less, and even more preferably 50 mg KOH / g or less, from the viewpoint of dispersion stability and high coating strength. The lower limit of the dispersant (B) of this disclosure is not particularly limited, but may be 5 mg KOH / g or more, 6 mg KOH / g or more, or 7 mg KOH / g or more. For the water-soluble polymer (C) of this disclosure, it is preferable to use a dispersant with a pH of 5 to 11, but from the viewpoint of dispersion stability, an acidic dispersant with a pH of less than 7 is preferred. The water-soluble polymer (C) of this disclosure is more preferably an ionic water-soluble polymer, and may be a water-soluble polymer having an anionic group. The anionic group contained in the water-soluble polymer (C) of this disclosure is preferably a carboxyl group, a sulfo group, or a phosphate group, with the carboxyl group being more preferred. The water-soluble polymer (C) of this disclosure is not particularly limited, but examples include acrylic polymers, styrene-acrylic polymers, maleic acid polymers, styrene-maleic acid polymers, α-olefin-maleic acid polymers, urethane polymers, ester polymers, sulfonic acid polymers, and phosphate polymers. Among these, acrylic polymers and styrene-acrylic polymers are preferred from the viewpoint of preventing hard cake formation. Furthermore, introducing polyalkylene glycol groups into the water-soluble polymer (C) is expected to improve the hard cake formation prevention effect. Preferably, the dispersant contains polypropylene glycol groups or polyethylene glycol groups as the polyalkylene glycol groups.

[0031] As described above, water-soluble polymers (C) with an acid value of 150 mgKOH / g or less can be obtained by known techniques, but they are also commercially available and can all be used. Examples of commercially available products include, but are not limited to, Disperbyk-102, Disperbyk-111, Disperbyk-190, Disperbyk-191, Disperbyk-194N, Disperbyk-2010, Disperbyk-2012, and Disperbyk-2015 from BIC Chemie Japan, TEGO Dispers-715N, TEGO Dispers-750W, and TEGO Dispers-755W from Evonik Japan, and Efka6230 from BASF. Furthermore, examples of dispersants containing polyalkylene glycol groups and having an acid value of 150 mgKOH / g or less include, but are not limited to, Disperbyk-190 and Disperbyk-2015 from BIC Chemie Japan.

[0032] <Crosslinking agent> The aqueous white ink of this disclosure may contain a crosslinking agent. The crosslinking agent of this disclosure preferably has a functional group that reacts with an acid group (particularly a carboxyl group). Examples of functional groups that react with an acid group (particularly a carboxyl group) include oxazoline groups, epoxy groups, carbodiimide groups, isocyanate groups, and silane groups, with oxazoline groups, epoxy groups, carbodiimide groups, and isocyanate groups being preferred, oxazoline groups and carbodiimide groups being more preferred, and carbodiimide groups being even more preferred from the viewpoint of storage stability and coating film strength after low-temperature drying. In this specification, low temperature may be 120°C or lower, 110°C or lower, or 100°C or lower. Specifically, the crosslinking agents of this disclosure include oxazoline group-containing compounds, epoxy group-containing compounds, carbodiimide group-containing compounds, isocyanate group-containing compounds, and silane group-containing compounds. These crosslinking agents may be used individually or in combination of two or more types. Among these crosslinking agents, oxazoline group-containing compounds, epoxy group-containing compounds, and carbodiimide group-containing compounds are preferred from the viewpoint of improving the water resistance, sedimentation stability, and image uniformity of the aqueous ink using the aqueous dispersion, oxazoline group-containing compounds and carbodiimide group-containing compounds are more preferred, and carbodiimide group-containing compounds are even more preferred from the viewpoint of sedimentation stability and crosslinking properties at low temperatures. The crosslinking agents of this disclosure may be used individually or in combination of two or more types. Examples of oxazoline group-containing compounds in this disclosure include 2,2'-bis(2-oxazoline), 2,2'-methylene-bis(2-oxazoline), 2,2'-ethylene-bis(2-oxazoline), 2,2'-trimethylene-bis(2-oxazoline), 2,2'-tetramethylene-bis(2-oxazoline), 2,2'-hexamethylene-bis(2-oxazoline), and 2,2'-octamethylene-bis(2-oxazoline). Examples include 2,2'-ethylene-bis(4,4'-dimethyl-2-oxazoline), 2,2'-p-phenylene-bis(2-oxazoline), 2,2'-m-phenylene-bis(2-oxazoline), 2,2'-m-phenylene-bis(4,4'-dimethyl-2-oxazoline), bis(2-oxazolinylcyclohexane) sulfide, bis(2-oxazolinylnorbornane) sulfide, and oxazoline ring-containing polymers. Examples of oxazoline group-containing compounds include commercially available products from Nippon Shokubai Co., Ltd., such as Epocross WS-500, Epocross WS-700, Epocross WS-700, Epocross K-2010, Epocross K-2020, and Epocross K-2030. Examples of epoxy group-containing compounds in this disclosure include polyglycidyl ethers such as ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerin triglycidyl ether, glycerol polyglycidyl ether, polyglycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, sorbitol polyglycidyl ether, pentaerythritol polyglycidyl ether, resorcinol diglycidyl ether, neopentyl glycol diglycidyl ether, and hydrogenated bisphenol A type diglycidyl ether. Examples of carbodiimide group-containing compounds in this disclosure include aromatic carbodiimide compounds and aliphatic carbodiimide compounds. Examples of commercially available carbodiimide group-containing compounds in this disclosure include Carbodilite SV-02, Carbodilite V-02, Carbodilite V-02-L2, Carbodilite V-04, Carbodilite V-06, Carbodilite V-10, Carbodilite SW-12G, Carbodilite E-02, and Carbodilite E-05 (all trade names). Examples of isocyanate group-containing compounds of this disclosure include aromatic polyisocyanates such as xylene diisocyanate, diphenylmethane diisocyanate, triphenylmethane triisocyanate, and tolylene diisocyanate; aliphatic or alicyclic polyisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, and hydrogenated aromatic polyisocyanates; dimers or trimers of these polyisocyanates; and adduct compounds comprising these polyisocyanates and polyols such as trimethylolpropane. These isocyanate group-containing compounds can be used individually or in combination of two or more. Furthermore, as an isocyanate group-containing compound, a blocked isocyanate compound may be used, in which the active isocyanate group in the polyisocyanate compound has been pre-reacted with a blocking agent such as phenol to inactivate it. Using a blocked isocyanate compound can improve the sedimentation stability of the aqueous dispersion of the present invention and the ink using it. Examples of silane group-containing compounds in this disclosure include alkoxysilane compounds such as bis-(3-triethoxysilylpropyl)-tetrasulfan, bis-(3-triethoxysilylpropyl)-disulfan, and ethoxysiloxane oligomers, as well as hydrolysates of these alkoxysilane compounds. The isocyanate group-containing compounds of this disclosure include, for example, "Coronate L," "Coronate HX," "Coronate HL," "Coronate HL-S," "Coronate 2234," "Aquanate 105," "Aquanate 130," "Aquanate 140," "Aquanate 200," "Aquanate 210" (all manufactured by Tosoh Corporation; "Coronate" and "Aquanate" are registered trademarks), "Desmodule N3400" (manufactured by Sumitomo Bayer Urethane Co., Ltd. (now Bayer AG); "Desmodule" is a registered trademark), "Duranate D-201," "Duranate TSE-100," "Duranate TSS-100," "Duranate 24A-100," and "Duranate E-405- Examples of commercially available products include "80T", "Duranate WB40-100", "Duranate WB40-80D", "Duranate WT20-100", "Duranate WT30-100", "Duranate WT31-100", "Duranate WL70-100", "Duranate WR80-70P", "Duranate WE50-100", "Duranate WM44-L70G" (all manufactured by Asahi Kasei Chemicals Corporation, "Duranate" is a registered trademark), "Takenate D-110N", "Takenate D-120N", "Takenate M-631N", and "MTERT-Orestar NP1200" (all manufactured by Mitsui Chemicals Polyurethane, Inc., "Takenate" and "Orestar" are registered trademarks).

[0033] The crosslinking agent of this disclosure may contain multiple functional groups. The amount of functional groups contained in the crosslinking agent of this disclosure is preferably 100 g / mol or more, more preferably 150 g / mol or more, even more preferably 200 g / mol or more, preferably 700 g / mol or less, more preferably 650 g / mol or less, and even more preferably 600 g / mol or less. Functional groups included in the crosslinking agent of this disclosure include oxazoline groups, epoxy groups, carbodiimide groups, isocyanate groups, silane groups, and the like. The functional groups contained in the crosslinking agent of this disclosure can react with reactive groups that react with the functional groups contained in the crosslinking agent of the main component (water-insoluble polymer (B), or, if a wax component is included, the water-insoluble polymer (B) and the wax component), thereby forming a crosslinked structure. Reactive groups that react with the functional groups of the crosslinking agent of this disclosure include acid groups, hydroxyl groups, and amino groups. Examples of acid groups include carboxyl groups, sulfonic acid groups, and phosphate groups, with carboxyl groups being more preferred. The one-to-one equivalent ratio of the functional group of the crosslinking agent of this disclosure to the main component (water-insoluble polymer (B), or, if a wax component is included, the water-insoluble polymer (B) and the wax component) can be calculated, for example, from the following formula. Amount of crosslinking agent = Reactive group of main ingredient / (56.1 × 1000) × Equivalent amount of crosslinking agent × Amount of main ingredient

[0034] The amount of crosslinking agent is preferably 0.1 to 5 times the obtained value, from the viewpoint of improving sedimentation stability, scratch resistance, adhesion, blocking resistance, and cellophane tape peel resistance. The amount of functional groups contained in the crosslinking agent can be measured by known methods depending on the type of functional group, or by referring to catalog values, or by freeze-drying the polymer solution and analyzing it by 1H-NMR, and calculating the amount of each functional group from the absorption peak intensity derived from each functional group and the absorption peak intensity derived from other monomers.

[0035] <Wax ingredients> The water-based white ink disclosed herein can be further improved in terms of scratch resistance, water resistance, and adhesion by including a wax component. The wax components of this disclosure include natural waxes and synthetic waxes. Examples of natural waxes include petroleum-based waxes, plant-based waxes, and animal / plant-based waxes. Examples of petroleum-based waxes include paraffin wax, microcrystalline wax, and petrolatum. Examples of plant-based waxes include carnauba wax, candelilla wax, rice wax, and wood wax. Examples of animal / plant-based waxes include lanolin and beeswax. Examples of synthetic waxes include synthetic hydrocarbon waxes and modified waxes. Examples of synthetic hydrocarbon waxes include polyolefin waxes, (meth)acrylic waxes, and Fischer-Tropsch waxes. Examples of modified waxes include paraffin wax derivatives, montan wax derivatives, and microcrystalline wax derivatives. From the viewpoint of improving adhesion and scratch resistance, polyolefin waxes and (meth)acrylic waxes are preferred. The (meth)acrylic wax is not particularly limited and may be manufactured using a monomer having an alkyl group with 10 or more carbon atoms. Examples of (meth)acrylic monomers having an alkyl group with 10 or more carbon atoms include lauryl (meth)acrylate, tridecyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, behenyl (meth)acrylate, or polymers manufactured from derivatives thereof.

[0036] Commercially available (meth)acrylic waxes can also be used. Preferred commercial products include ST100 and ST200 manufactured by Nippon Shokubai Co., Ltd.

[0037] Polyolefin waxes are not particularly limited and include, for example, waxes and copolymers made from olefins or their derivatives such as ethylene, propylene, and butylene. Specifically, examples include polyethylene waxes, polypropylene waxes, polybutylene waxes, copolymer waxes made of ethylene and monomers having carboxylic acid groups such as methacrylic acid or acrylic acid, and oxidized polyethylene waxes. Among these, polyethylene waxes, polypropylene waxes, copolymer waxes made of ethylene and monomers having carboxylic acid groups such as methacrylic acid or acrylic acid, and oxidized polyethylene waxes are preferred from the viewpoint of improving adhesion and scratch resistance. The oxidized polyethylene wax of this disclosure is obtained by oxidizing polyethylene wax and has a polyethylene-derived skeleton (polyethylene skeleton). The polyethylene skeleton mainly has structural units derived from ethylene. The polyethylene skeleton may be a homopolyethylene (a homopolymer of ethylene) skeleton, a block polyethylene (a block copolymer of ethylene and another olefin) skeleton, or a random polyethylene (a random copolymer of ethylene and another olefin) skeleton. Examples of other olefins include alkenes such as propylene, isobutylene, 1-butene, 1-pentene, and 1-hexene. These components may be linear or branched. The number of carbon atoms in the other olefin components is, for example, 2 to 6.

[0038] The ethylene content (content of structural units derived from ethylene) in the polyethylene skeleton is, for example, 60 mol% or more, and may be 70 mol% or more. If the polyethylene skeleton is a block polyethylene skeleton or a random polyethylene skeleton, the ethylene content (content of structural units derived from ethylene) in the polyethylene skeleton is, for example, 95 mol% or less, and may be 90 mol% or less. From the viewpoint of obtaining better adhesion and scratch resistance, the polyethylene oxide wax preferably includes high-density polyethylene oxide wax. Commercially available polyethylene oxide waxes can also be used. Preferred commercially available products include BYK's AQUACER497, AQUACER515, AQUACER531, and AQUACER1547. The wax components can be used individually or in combination of two or more types. The wax component of this disclosure is preferably in the form of solid wax particles dissolved or dispersed in a solvent, and more preferably in the form of an emulsion dispersed in a solvent. The solvent is preferably an aqueous medium, and more preferably the same aqueous medium used as the solvent for an aqueous ink composition.

[0039] The volume-average particle diameter (nm) of the wax particles in this disclosure is preferably 25 nm to 500 nm, and more preferably 30 nm to 400 nm. The volume-average particle diameter of the wax particles is not particularly limited, but can be measured by dynamic light scattering, laser diffraction / scattering, Coulter counter, microscopy, etc. The average particle diameter described in this embodiment is the average particle diameter (hydrodynamic diameter) obtained by cumulant analysis using a multi-sample nanoparticle diameter measurement system [manufactured by Otsuka Electronics Co., Ltd., product name: nanoSAQLA], which is a particle diameter measurement device using dynamic light scattering, after determining the autocorrelation function by photon correlation. From the viewpoint of adhesion, the melting point of the wax component of this disclosure is preferably 20°C or higher, more preferably 25°C or higher, even more preferably 30°C or higher, preferably 150°C or lower, more preferably 140°C or lower, and even more preferably 130°C or lower. The melting point (Tm2) of wax component (B) can be measured by a melting point measuring device in accordance with JIS K 0064 or the like. The acid value (mgKOH / g) of the wax component in this disclosure may or may not be present from the viewpoint of adhesion, but is preferably 0 mgKOH / g, preferably 100 mgKOH / g or less, more preferably 90 mgKOH / g or less, and even more preferably 80 mgKOH / g or less.

[0040] The aqueous white ink of this disclosure may contain water or other water-soluble organic solvents from the viewpoint of controlling ink viscosity, wetting spread on the recording medium to be printed, improving image quality, and ejection stability. Examples of water-soluble organic solvents include glycols such as propylene glycol, 1,3-propanediol, glycerin, dipropylene glycol, tripropylene glycol, diethylene glycol, triethylene glycol, and tetraethylene glycol; monoethylene glycol ethers such as monoethylene glycol monomethyl ether, monoethylene glycol monoethyl ether, monoethylene glycol monopropyl ether, monoethylene glycol monoisopropyl ether, monoethylene glycol monobutyl ether, and monoethylene glycol monoisobutyl ether; and monopropylene glycol ethers such as monopropylene glycol monomethyl ether, monopropylene glycol monoethyl ether, monopropylene glycol monopropyl ether, monopropylene glycol monoisopropyl ether, monopropylene glycol monobutyl ether, and monopropylene glycol monoisobutyl ether. Polyethylene glycol ethers such as polyethylene glycol monomethyl ether (number of EO added moles = 2 to 10, preferably 2 to 4), polyethylene glycol monoethyl ether (number of EO added moles = 2 to 10, preferably 2 to 4), polyethylene glycol monoethyl ether (number of EO added moles = 2 to 10, preferably 2 to 4), polyethylene glycol monopropyl ether (number of EO added moles = 2 to 10, preferably 2 to 4), polyethylene glycol monoisopropyl ether (number of EO added moles = 2 to 10, preferably 2 to 4), polyethylene glycol monobutyl ether (number of EO added moles = 2 to 10, preferably 2 to 4), polyethylene glycol monoisobutyl ether (number of EO added moles = 2 to 10, preferably 2 to 4);Examples of polypropylene glycol ethers include polypropylene glycol monomethyl ether (number of EO added moles = 2 to 10, preferably 2 to 4), polypropylene glycol monoethyl ether (number of EO added moles = 2 to 10, preferably 2 to 4), polypropylene glycol monopropyl ether (number of EO added moles = 2 to 10, preferably 2 to 4), polypropylene glycol monoisopropyl ether (number of EO added moles = 2 to 10, preferably 2 to 4), polypropylene glycol monobutyl ether (number of EO added moles = 2 to 10, preferably 2 to 4), and polypropylene glycol monoisobutyl ether. Among these, propylene glycol, diethylene glycol, triethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monoisobutyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, monoethylene glycol monoisopropyl ether, and monopropylene glycol monopropyl ether are preferred. These water-soluble organic solvents may be used individually or in combination of two or more types.

[0041] <Other additives> The aqueous white ink of this disclosure may contain other additives. Other additives that can be added as appropriate include defoamers, plasticizers, leveling agents, fungicides, rust inhibitors, matting agents, flame retardants, thixotropes, tackifiers, thickeners, lubricants, antistatic agents, surfactants, reaction retarders, antioxidants, UV absorbers, hydrolysis inhibitors, weather stabilizers, and anti-tack agents. The proportions of each additive are selected as appropriate depending on the purpose and application. Examples of defoaming agents in this disclosure include silicone-based defoaming agents, polyether-based defoaming agents, fatty acid ester-based defoaming agents, and acetylene glycol-based defoaming agents. Among these, silicone-based defoaming agents and acetylene glycol-based defoaming agents are preferred because they have excellent ability to properly maintain surface tension and interfacial tension and hardly generate foam.

[0042] <Water-based white ink> The content of the white pigment (A) in 100 parts by mass of the aqueous white ink of this disclosure is preferably 2 parts by mass or more, more preferably 3 parts by mass or more, even more preferably 4 parts by mass or more, preferably 25 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less. The water-insoluble polymer (B) content in 100 parts by mass of the aqueous white ink of this disclosure may be 1 part by mass or more, preferably 3 parts by mass or more, more preferably 5 parts by mass or more, may be 50 parts by mass or less, preferably 40 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less. The content of the water-soluble polymer (C) in 100 parts by mass of the aqueous white ink of this disclosure is preferably 0.1% by mass or more and 2.0% by mass or less, and more preferably 0.2% by mass or more and 1.0% by mass or less. The mass ratio of the white pigment (A) to the water-insoluble polymer (B) in 100 parts by mass of the aqueous white ink of this disclosure (mass of white pigment (A) / mass of water-insoluble polymer (B)) is preferably less than 1.0, more preferably less than 0.9, and even more preferably less than 0.8. The mass ratio (mass of water-soluble polymer (C) / mass of white pigment (A)) in 100 parts by mass of the aqueous white ink of this disclosure is preferably greater than 0.015, more preferably greater than 0.017, even more preferably greater than 0.020, preferably less than 0.20, more preferably less than 0.15, and even more preferably less than 0.10. The crosslinking agent content in 100 parts by mass of the aqueous white ink of this disclosure may be 0.01 parts by mass or more, preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, may be 10 parts by mass or less, preferably 8 parts by mass or less, and more preferably 6 parts by mass or less, from the viewpoint of discharge stability, sedimentation stability, image uniformity, and prevention of sedimentation of the white pigment (A) in the aqueous white ink.

[0043] The wax component content in 100 parts by mass of the aqueous white ink of this disclosure may be 0.01 parts by mass or more, preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, may be 8 parts by mass or less, preferably 6 parts by mass or less, and more preferably 4 parts by mass or less, from the viewpoint of discharge stability and sedimentation stability. The amount of water-soluble organic solvent in 100 parts by mass of the aqueous white ink of this disclosure may be 5 parts by mass or more, preferably 8 parts by mass or more, more preferably 10 parts by mass or more, may be 50 parts by mass or less, preferably 45 parts by mass or less, and more preferably 40 parts by mass or less, from the viewpoint of controlling the wetting spread on the recording medium to be printed and improving image quality. The water content in 100 parts by mass of the water-soluble organic solvent in the aqueous white ink of this disclosure is preferably 40 parts by mass or more, more preferably 45 parts by mass or more, even more preferably 50 parts by mass or more, preferably 65 parts by mass or less, and more preferably 60 parts by mass or less. In 100 parts by mass of the aqueous white ink of this disclosure, the mass ratio of the water-insoluble polymer (B) to the crosslinking agent (mass of water-insoluble polymer (B) / mass of crosslinking agent) may be 99 / 1 to 60 / 40, preferably 99 / 1 to 65 / 35, and more preferably 95 / 5 to 70 / 30, from the viewpoint of adhesion, scratch resistance, blocking resistance, and image uniformity.

[0044] In the aqueous white ink disclosed herein, the particle volume concentration of particles with a diameter of 1.0 μm or larger is set to 400 × 10 because if it is too large, it can cause nozzle clogging when used as an inkjet ink. 6 It is preferable that the concentration is 200 × 10⁻³ or less. 6 μm 3It is more preferably / m or less, and even more preferably 100×10 6 μm3 / ml or less. On the other hand, if it is too small, the productivity of the white ink may decrease. Therefore, from the viewpoints of suppressing nozzle clogging and productivity when used as an inkjet ink, the particle volume concentration of particles with a diameter of 1.0 μm or more in the aqueous white ink is 2×10 6 ~400×10 6 μm3 / ml is preferable, 6×10 6 ~200×10 6 μm 3 / ml is more preferable, and 10×10 6 ~100×10 6 μm3 / ml is even more preferable. The particle volume concentration of particles with a diameter of 1.0 μm or more in the aqueous white ink of the present disclosure can be measured by a known method, specifically, by a Coulter counter method or the like.

[0045] <Use> [[ID=2,6]]Since the aqueous white ink of the present disclosure has excellent adhesion and excellent scratch resistance, for example, it can be suitably used as an ink such as an aqueous inkjet ink, a flexographic ink, an offset printing ink, a lithographic printing ink, a gravure printing ink, a screen printing ink, etc., especially as an aqueous inkjet ink for surface printing where the ink surface is exposed on the front side without being laminated, or as an aqueous inkjet ink for back printing where high adhesion to a laminate film is required.

[0046] <Printed matter> The aqueous white ink of the present disclosure can form a printed matter or an image having a predetermined pattern by discharging the aqueous ink onto a recording medium in a predetermined pattern using, for example, an inkjet recording apparatus. Examples of recording media include paper, paper laminated with resin films such as polyethylene, polypropylene, and polystyrene (such as coated paper), metal plates such as aluminum, zinc, and copper, resin films such as cellulose, polyethylene terephthalate, polystyrene, olefin resins, polycarbonate, polyvinyl acetal, polyvinyl chloride, polyamide, nylon, and acrylic resins, paper with a metal coating, and resin films with a metal coating. Resin films are preferred as recording media for printing the aqueous ink of this disclosure, and among these, application to polyethylene terephthalate and olefin resins is preferred. Examples of olefin resins include polyethylene and polypropylene, with particular preference for application to polypropylene such as biaxially oriented polypropylene film (OPP) and unoriented polypropylene film (CPP). The aqueous white ink of this disclosure is preferably formed on a resin film, and the embodiment thereof is a laminate having a printed layer formed from the aqueous ink on the resin film. The disclosed laminate may or may not have a primer layer between the resin film and the printed layer, but from a productivity standpoint it is preferable not to have one, and it is preferable to form the printed layer directly on the resin film. The disclosed laminate is laminated in the order of resin film and printed layer, and may or may not have a protective film (laminate layer) on the printed layer, but from a productivity standpoint it is preferable not to have one, and by using the aqueous ink of the disclosed, it is expected that a laminate with excellent adhesion to the substrate and good scratch resistance can be obtained even without a primer layer or protective film (laminate layer). [Examples]

[0047] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" means "parts by mass" and "%" means "percent mass". <Measurement of primary particle size of rutile-type titanium dioxide> This was calculated from scanning electron microscope observations. <Measurement of the mass amounts of each element contained in rutile-type titanium oxide> The elemental mass parts contained in rutile-type titanium oxide were measured using X-ray fluorescence (XRF) with a RIGAKU ZSX Primus II. <D50 particle size, D99 particle size, and particle concentration of 1 μm or larger for titanium dioxide dispersion and aqueous white ink> The volume-based particle size was evaluated using the Multisizer 4e manufactured by Beckman Coulter, Inc. <Measurement of sedimentation stability of water-based white ink> After placing 50g of the sample in a 100cc plastic container and letting it stand at 50°C for 3 months, ○; When the container is gently shaken, the difference in non-volatile content between the supernatant liquid and the bottom of the container is less than 0.1%. ×; When the container is gently shaken, the difference in non-volatile content between the supernatant liquid and the bottom of the container is 0.1% or more. <Measurement of coating film strength of water-based white ink> Corona-treated polyester film [manufactured by Futamura Chemical Co., Ltd., product name: Taiko Polyester Film FE2001] and corona-treated OPP film [manufactured by Futamura Chemical Co., Ltd., product name: FOR-AQ] were used as substrates, and water-based white ink was applied using a bar coater (#3) and dried at 100°C for 1 minute to obtain PET and OPP test sheets.

[0048] -Evaluation Method- <Scratch resistance> The printed image of each test sheet was rubbed with a nylon nonwoven fabric, and its scratch resistance was evaluated based on the following evaluation criteria. [Evaluation Criteria] ○: The printed image does not peel off at all even when rubbed. ○(-): When the printed image is rubbed, only a very small portion of the image peels off. △: The printed image may peel off slightly if rubbed. ×: Rubbing the printed image will cause the image to peel off clearly. <Water resistance> The printed image on each test sheet was rubbed with a water-soaked nylon nonwoven fabric, and its water resistance was evaluated based on the following evaluation criteria. [Evaluation Criteria] ○: The printed image does not peel off at all even when rubbed. ○(-): When the printed image is rubbed, only a very small portion of the image peels off. △: The printed image may peel off slightly if rubbed. ×: Rubbing the printed image will cause the image to peel off clearly. <Adhesion> Adhesive tape (Nichiban Co., Ltd., Cellotape® No. 405, 24 mm wide) was applied to each test sheet at room temperature and left undisturbed for 1 minute. After that, the sheets were peeled off in a 180° direction and the adhesion was evaluated based on the following evaluation criteria. [Evaluation Criteria] ○: The printed image does not peel off at all. ○(-): 1-20% of the printed image peels off. △: 21-50% of the printed image peels off. ×: 51-100% of the printed image peels off.

[0049] [Manufacturing Example 1] <Preparation of Titanium Oxide Dispersion> 40.77 parts of pure water, 4.13 parts of Disperbyk-190 (manufactured by Bic Chemie Japan, a polyalkylene glycol group-containing acrylic water-soluble resin, acid value 10 mg KOH / g, active ingredient concentration 40%) as a dispersant, 55.00 parts of titanium dioxide JR-403 (manufactured by Teika, primary particle size 250 nm) as rutile-type titanium dioxide, and 0.10 parts of Orfin D10-PG (manufactured by Nisshin Chemical Industry Co., Ltd., an acetylene-based surfactant) as an antifoaming agent were added to a 250 mL poly container. Subsequently, 100 g of 0.1 mm diameter zirconia beads were added as a dispersion medium. After sealing the poly container and treating it with a paint shaker for 300 minutes, the zirconia beads were filtered by suction filtration using paper filter paper with a mesh size of 7 μm to obtain titanium dioxide dispersion 1 with a rutile-type titanium dioxide concentration of 55% by mass. The volume concentration of particles with a diameter of 1.0 μm or larger in titanium dioxide dispersion 1 is 50 × 10⁻⁶. 6 μm 3 It was less than / ml.

[0050] <Preparation of water-insoluble polymers> 520 parts of deionized water were placed in a flask equipped with a dropping funnel, stirrer, nitrogen gas inlet tube, thermometer, and reflux condenser. A first-stage dropwise pre-emulsion was prepared in the dropping funnel, consisting of 163 parts of deionized water, 80 parts of a 25% aqueous solution of emulsifier [ADEKA Corporation, product name: Adekaryasorb SR-10], 322 parts of cyclohexyl methacrylate, 103 parts of 2-ethylhexyl acrylate, and 75 parts of 2-hydroxyethyl methacrylate. 74 parts of this pre-emulsion, representing 5% of the total monomer components, were added to the flask. The temperature was raised to 70°C while slowly blowing in nitrogen gas, and 30 parts of a 5% aqueous solution of ammonium persulfate were added to initiate polymerization. Subsequently, the remaining portion of the dropwise pre-emulsion was uniformly added dropwise to the flask over a period of 120 minutes.

[0051] After the dropwise dispensing was complete, the contents of the flask were maintained at 70°C for 60 minutes. Subsequently, a second-stage dropwise dispensing pre-emulsion consisting of 163 parts deionized water, 80 parts 25% aqueous solution of emulsifier [ADEKA Corporation, product name: Adeka Riasorb SR-10], 310 parts cyclohexyl methacrylate, 105 parts 2-ethylhexyl acrylate, 75 parts 2-hydroxyethyl methacrylate, and 10 parts 4-(meth)acryloyloxy-1,2,2,6,6-pentamethylpiperidine [ADEKA Corporation, product name: Adeka Stab LA-82], along with 30 parts 5% aqueous solution of ammonium persulfate, was uniformly added to the flask over 120 minutes.

[0052] After the dropwise addition was complete, the contents of the flask were maintained at 70°C for 60 minutes, and the pH was adjusted to 8 by adding 25% aqueous ammonia to complete the polymerization. After the resulting reaction solution was cooled to room temperature, a water-insoluble polymer was prepared by filtering through a 300-mesh wire mesh. The obtained water-insoluble polymer was a resin emulsion, consisting of emulsion particles with a two-layer structure having an inner layer and an outer layer. The non-volatile content of this water-insoluble polymer was 50%, the acid value derived from the carboxyl groups of the polymer was 0 mgKOH / g, the glass transition temperature of the inner layer resin constituting the resin emulsion particles contained in the emulsion was 32°C, and the glass transition temperature of the outer layer resin was also 32°C. The minimum film thickening temperature was 40°C, and the average particle size was 150 nm.

[0053] <Preparation of water-based white ink> [Example 1] As a water-soluble organic solvent, 15.0 parts propylene glycol, 5.0 parts tripropylene glycol monobutyl ether, 18.2 parts of the above titanium dioxide dispersion 1, 30 parts of the above water-insoluble polymer as a binder resin, 0.5 parts KF-6011 (manufactured by Shin-Etsu Chemical Co., Ltd., PEG-11 methyl ether dimethicone (polyether-modified silicone surfactant)) as a surfactant, 1.5 parts Epocross WS500 (oxazoline-based crosslinking agent manufactured by Nippon Shokubai Co., Ltd.) as a crosslinking agent, 3 parts AQUACER531 (manufactured by BIC Chemie Japan, oxidized high-density polyethylene-based wax emulsion) as a wax component, and ion-exchanged water totaling 100 parts by mass were mixed in a homodisperser at 1000 rpm, and filtered through a 3 μm filter [Advantec Co., Ltd., MCP-3-C10S] to obtain aqueous white ink 1.

[0054] [Examples 2-6, Comparative Examples 1-6] A water-based white ink was prepared using the same method as in Example 1, except that the amounts of white pigment (A) and water-insoluble polymer (B) in 100 parts by mass of the water-based white ink, and the mass ratio of water-soluble polymer (C) to white pigment (A) were changed as shown in Table 1. Table 2 shows the various evaluation results for the aqueous white inks 1 to 12 prepared in Examples 1 to 6 and Comparative Examples 1 to 6. The volume concentration of particles with a diameter of 1.0 μm or larger in the aqueous white inks described in Examples 1 to 6 is 100 × 10⁻⁶. 6 μm 3 It was less than / ml.

[0055] [Table 1]

[0056] [Table 2]

[0057] The abbreviations listed in each table mean the following: BYK-190; manufactured by BYChemie Japan, a polyalkylene glycol group-containing acrylic water-soluble resin, acid value 10 mg KOH / g, active ingredient concentration 40%. HL415-NH3; A water-soluble polymer dispersant prepared by adjusting the pH of a polyacrylic acid aqueous solution Aquaric HL415 manufactured by Nippon Shokubai Co., Ltd. to pH 7.5 with a 25% ammonia aqueous solution manufactured by Wako Pure Chemical Industries, Ltd. Acid value 750 mg KOH / g, molecular weight (MW) 11700, active ingredient concentration 39%. Joncryl HPD196; manufactured by BASF, styrene-acrylic water-soluble resin, acid value 200 mg KOH / g, active ingredient concentration 36%

[0058] Water-based white inks 1-6 exhibited excellent sedimentation stability and post-printing film strength. On the other hand, the water-based white inks 7 to 12, which are outside the scope of the present invention, could not achieve both sedimentation stability and coating film strength after printing.

Claims

1. A water-based white ink comprising a white pigment (A), a water-insoluble polymer (B), a water-soluble polymer (C), and a crosslinking agent, The mass ratio of the white pigment (A) to the water-insoluble polymer (B) (mass of white pigment (A) / mass of water-insoluble polymer (B)) is less than 1.

0. The mass ratio of the water-soluble polymer (C) to the white pigment (A) (mass of water-soluble polymer (C) / mass of white pigment (A)) is greater than 0.015 and less than 0.

1. A water-based white ink in which the acid value of the water-soluble polymer (C) is 150 mg KOH / g or less.

2. The aqueous white ink according to claim 1, wherein the water-soluble polymer (C) is a dispersant.

3. The aqueous white ink according to claim 1, wherein the white pigment (A) is rutile-type titanium dioxide.

4. The aqueous white ink according to claim 1, wherein the content of white pigment (A) per 100 parts by mass of aqueous white ink is 2 parts by mass or more and 25 parts by mass or less.

5. The aqueous white ink according to claim 1, wherein the water-insoluble polymer (B) has structural units derived from a cyclic aliphatic group-containing monomer.

6. Furthermore, the aqueous white ink according to claim 1, which also contains a wax component.

7. A printed article obtained using the aqueous white ink described in claim 1.

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