JP7696411B2 - Inkjet ink - Google Patents

Description

The present invention relates to inkjet inks.

Ink used in a recording method in which ink is ejected from the nozzles of a printer head and sprayed directly onto a print medium is required to be ejected stably, and to have functions such as image uniformity and adhesion to the print medium. Furthermore, since the medium after printing is wound into a roll, it is also necessary that blocking is suppressed. In recent years, ink compositions for aqueous inks having the above functions are required due to environmental considerations. In addition, there is a demand for printing on recording media for commercial printing using non-printing media such as coated paper, polyester films such as polyethylene terephthalate (PET), polyvinyl chloride films, polypropylene films such as biaxially oriented polypropylene film (OPP), polyethylene films, nylon films, and other films of non-absorbent resins.

Patent Document 1 describes an acrylic resin emulsion for aqueous inkjet inks, which contains acrylic resin particles having an acid value of 1 to 100 mgKOH/g, and is characterized in that the ratio (As/At) of the molar content of acidic group-containing monomer in the surface region of the acrylic resin particles, as measured at a ¹ H spin diffusion time of 5 ms, to the molar content of acidic group-containing monomer in the entire acrylic resin particle, is 9 or more, as well as an aqueous inkjet ink composition containing the emulsion.

There was a demand for the ink to have even better ejection stability and blocking resistance when forming images.

JP 2014-141672 A

Therefore, the objective of the present invention is to provide an inkjet ink that has excellent ejection stability (image uniformity) and blocking resistance when an image is formed.

As a result of extensive research into solving the above problems, the inventors discovered that an inkjet ink containing a specific water-soluble polymer compound, resin emulsion particles, and water is suitable as an aqueous ink and can solve the above problems, thus completing the present invention.

That is, the inkjet ink of the present invention contains a nonionic water-soluble polymer compound containing an amide bond, resin emulsion particles, and water.
The nonionic water-soluble polymer compound containing an amide bond is preferably polyvinylpyrrolidone.
The weight average molecular weight of the nonionic water-soluble polymer compound containing an amide bond is preferably 5,000 to 500,000.
The content of the nonionic water-soluble polymer compound containing an amide bond is preferably 0.05 to 10% by mass.
The resin emulsion particles preferably contain a (meth)acrylic polymer.
The acid value derived from the carboxyl groups of the resin emulsion particles is preferably 0 to 6 mgKOH/g.

The inkjet ink of the present invention provides an inkjet ink that has excellent ejection stability and blocking resistance when an image is formed.

1. Ink-jet ink The ink-jet ink of the present invention contains a nonionic water-soluble polymer compound containing an amide bond, resin emulsion particles (resin particles), and water.

The inkjet ink of the present invention contains a nonionic water-soluble polymer compound containing an amide bond. Examples of the nonionic water-soluble polymer compound containing an amide bond include polyvinylpyrrolidone and polyacrylamide, and among these, polyvinylpyrrolidone is preferred.

The weight average molecular weight of the nonionic water-soluble polymer compound containing the amide bond is preferably 5,000 to 500,000, and more preferably 10,000 to 200,000. The weight average molecular weight refers to the weight average molecular weight (PEO equivalent) measured using gel permeation chromatography (Tosoh Corporation, product number: HLC-8320GPC, column: Shodex KD-806M, carrier solution: DMF).

The content of the nonionic water-soluble polymer compound containing an amide bond is preferably from 0.05 to 10% by mass, and more preferably from 0.1 to 2% by mass.
The ink-jet ink of the present invention contains a nonionic water-soluble polymer compound containing an amide bond, and therefore has excellent ejection stability and excellent blocking resistance when an image is formed.

1-2 Resin Emulsion Particles The resin emulsion particles contained in the inkjet ink of the present invention may preferably contain a structural unit derived from a monofunctional monomer and/or a polyfunctional monomer. The structural units derived from the monofunctional monomer and the polyfunctional monomer are obtained by polymerizing a monomer containing a monofunctional monomer and a polyfunctional monomer. The monofunctional monomer and the polyfunctional monomer may be used alone or in combination.

Examples of monofunctional monomers include, but are not limited to, ethylenically unsaturated double bond-containing monomers. These monomers may be used alone or in combination of two or more types.

In this specification, "(meth)acrylate" means "acrylate" or "methacrylate", and "(meth)acrylic" means "acrylic" or "methacrylic".

Examples of the ethylenically unsaturated double bond-containing monomer include, but are not limited to, acid group-containing monomers, alkyl (meth)acrylates, hydroxyl group-containing (meth)acrylates, piperidine group-containing monomers, 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-based monomers, aralkyl (meth)acrylates, and addition-polymerizable oxazolines.
These ethylenically unsaturated double bond-containing monomers may be used alone or in combination of two or more kinds.

Examples of the acid group-containing monomer include carboxyl group-containing aliphatic monomers such as (meth)acrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, citraconic acid, maleic anhydride, maleic acid monomethyl ester, maleic acid monobutyl ester, itaconic acid monomethyl ester, itaconic acid monobutyl ester, and vinyl benzoic acid, but the present invention is not limited to these examples. These acid group-containing monomers may be used alone or in combination of two or more kinds. Among these acid group-containing monomers, acrylic acid, methacrylic acid, and itaconic acid are preferred from the viewpoint of improving the dispersion stability of the resin emulsion particles, and acrylic acid and methacrylic acid are more preferred.

Examples of alkyl (meth)acrylates include alkyl (meth)acrylates having an ester group with 1 to 18 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, sec-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, tridecyl (meth)acrylate, cyclohexyl (meth)acrylate, n-lauryl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, and isobornyl (meth)acrylate, but are not limited to these examples. These alkyl (meth)acrylates may be used alone or in combination of two or more.

Examples of hydroxyl group-containing (meth)acrylates include hydroxyl group-containing (meth)acrylates having an ester group with 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, but are not limited to these examples. These hydroxyl group-containing (meth)acrylates may be used alone or in combination of two or more types.

Examples of piperidine group-containing monomers 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, 4-chloro Examples of the monomers include, but are not limited to, 1-(meth)acryloyl-4-cyano-4-(meth)acryloylamino-2,2,6,6-tetramethylpiperidine, 1-(meth)acryloyl-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. These piperidine group-containing monomers may be used alone or in combination of two or more.

Examples of oxo group-containing monomers include (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, but are not limited to these examples. These oxo group-containing monomers may be used alone or in combination of two or more types.

Examples of fluorine atom-containing monomers include fluorine atom-containing alkyl (meth)acrylates having 2 to 6 carbon atoms in the ester group, such as trifluoroethyl (meth)acrylate, tetrafluoropropyl (meth)acrylate, and octafluoropentyl (meth)acrylate, but are not limited to these examples. These fluorine atom-containing monomers may be used alone or in combination of two or more types.

Examples of nitrogen atom-containing monomers include acrylamide compounds such as (meth)acrylamide, N-monomethyl(meth)acrylamide, N-monoethyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-n-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, but are not limited to these examples. These nitrogen atom-containing monomers may be used alone or in combination of two or more.

Examples of epoxy group-containing monomers 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 alone or in combination of two or more types.

Examples of alkoxyalkyl (meth)acrylates include, but are not limited to, methoxyethyl (meth)acrylate, methoxybutyl (meth)acrylate, ethoxybutyl (meth)acrylate, and trimethylolpropane tripropoxy (meth)acrylate. These alkoxyalkyl (meth)acrylates may be used alone or in combination of two or more.

Examples of silane group-containing monomers 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 alone or in combination of two or more types.

Examples of carbonyl group-containing monomers include acrolein, fomunilstyrol, vinyl ethyl ketone, (meth)acryloxyalkylpropenal, acetonyl (meth)acrylate, diacetone (meth)acrylate, 2-hydroxypropyl (meth)acrylate acetylacetate, butanediol-1,4-acrylate acetylacetate, and 2-(acetoacetoxy)ethyl (meth)acrylate, but are not limited to these examples. These carbonyl group-containing monomers may be used alone or in combination of two or more types.

Examples of aziridinyl group-containing monomers include, but are not limited to, (meth)acryloylaziridine and 2-aziridinylethyl (meth)acrylate. These aziridinyl group-containing monomers may be used alone or in combination of two or more types.

Examples of styrene-based monomers include, but are not limited to, styrene, α-methylstyrene, p-methylstyrene, tert-methylstyrene, chlorostyrene, and vinyltoluene. These styrene-based monomers may be used alone or in combination of two or more. The styrene-based monomer may have a functional group on the benzene ring, such as a methyl group, an alkyl group such as a tert-butyl group, a nitro group, a nitrile group, an alkoxyl group, an acyl group, a sulfone group, a hydroxyl group, or a halogen atom. Among styrene-based monomers, styrene is preferred from the viewpoint of increasing water resistance.

Examples of aralkyl (meth)acrylates include 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, but are not limited to these examples. These aralkyl (meth)acrylates may be used alone or in combination of two or more types.

Examples of addition-polymerizable oxazolines include, but are not limited to, 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-methyl-2-oxazoline, and 2-isopropenyl-5-ethyl-2-oxazoline. These addition-polymerizable oxazolines may be used alone or in combination of two or more kinds. Of these addition-polymerizable oxazolines, 2-isopropenyl-2-oxazoline is preferred because it is easily available.

Suitable monofunctional monomers include, for example, alkyl (meth)acrylates, hydroxyl group-containing (meth)acrylates, piperidine group-containing monomers, oxo group-containing monomers, fluorine atom-containing monomers, nitrogen atom-containing monomers, epoxy group-containing monomers, and styrene-based monomers. These monomers may be used alone or in combination of two or more. Among the monofunctional monomers, from the viewpoint of further improving adhesion (scratch resistance) 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. In addition, when a hydroxyl group-containing (meth)acrylate is included as a monofunctional monomer, emulsion particles free of coarse particles are easily obtained, and from the viewpoint of excellent ejection stability of ink containing the emulsion particles, it is preferable to include a hydroxyl group-containing (meth)acrylate.

The content of the piperidine group-containing monomer, the addition polymerizable oxazoline, and the hydroxyl group-containing (meth)acrylate in the monomer component is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and even more preferably 0.5% by mass or more, respectively, from the viewpoint of further improving weather resistance and adhesion, and is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less, respectively, from the viewpoint of improving water resistance. The content of the piperidine group-containing monomer, the addition polymerizable oxazoline, and the hydroxyl group-containing (meth)acrylate in the monomer component is more preferably 0.1 to 30% by mass, even more preferably 0.2 to 20% by mass, and even more preferably 0.5 to 10% by mass, respectively.

In addition, when the resin emulsion particles are formed in multiple layers, the piperidine group-containing monomer, and/or the addition-polymerizable oxazoline, and/or the hydroxyl group-containing (meth)acrylate may be contained in the monomer components constituting any of the layers, but from the viewpoint of further improving adhesion, it is preferable that they are contained in the monomer components constituting at least the outermost layer. Therefore, it is preferable that the monomer component contains a piperidine group-containing monomer, and/or an addition polymerizable oxazoline, and/or a hydroxyl group-containing (meth)acrylate, and when the resin emulsion particle is formed in multiple layers, it is preferable that the monomer component constituting at least the outermost layer contains a piperidine group-containing monomer, and/or an addition polymerizable oxazoline, and/or a hydroxyl group-containing (meth)acrylate, and the content of the piperidine group-containing monomer, addition polymerizable oxazoline, and hydroxyl group-containing (meth)acrylate in the monomer component is each more preferably 0.1 to 30% by mass, even more preferably 0.2 to 20% by mass, and even more preferably 0.5 to 10% by mass.

Examples of polyfunctional monomers include polyhydric alcohols having 1 to 10 carbon atoms, such as 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 tripropylene glycol di(meth)acrylate. di(meth)acrylates of alkylene oxide groups having 2 to 4 carbon atoms, such as polyethylene glycol di(meth)acrylate having an added mole number of 2 to 50 of ethylene oxide, polypropylene glycol di(meth)acrylate having an added mole number of 2 to 50 of propylene oxide, and tripropylene glycol di(meth)acrylate; ethoxylated glycerin tri(meth)acrylate, propylene oxide-modified glycerol tri(meth)acrylate, ethylene oxide-modified trimethylolpropane tri(meth)acrylate, tri(meth)acrylates of polyhydric alcohols having 1 to 10 carbon atoms, such as pentaerythritol tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, and ditrimethylolpropane tetra(meth)acrylate; tetra(meth)acrylates of polyhydric alcohols having 1 to 10 carbon atoms, such as pentaerythritol penta(meth)acrylate, dipentaerythritol tetra(meth)acrylate, and ditrimethylolpropane tetra(meth)acrylate; Examples of the polyhydric alcohol having 1 to 10 carbon atoms include penta(meth)acrylates of polyhydric alcohols having 1 to 10 carbon atoms, such as pentaerythritol (monohydroxy)penta(meth)acrylate; hexa(meth)acrylates of polyhydric alcohols having 1 to 10 carbon atoms, such as pentaerythritol hexa(meth)acrylate; 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 alone or in combination of two or more types.

Among the polyfunctional monomers, from the viewpoint of achieving both blocking resistance and adhesion, alkyl di(meth)acrylates having 4 to 8 carbon atoms in the alkyl group having two hydroxyl groups, polyethylene glycol di(meth)acrylates having 2 to 50 moles of ethylene oxide added, polypropylene glycol di(meth)acrylates having 2 to 50 moles of propylene oxide added, tri(meth)acrylates of polyhydric alcohols, tetra(meth)acrylates of polyhydric alcohols, penta(meth)acrylates of polyhydric alcohols, and hexa(meth)acrylates of polyhydric alcohols are preferred, and ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylates having 2 to 50 moles of ethylene oxide added, 1,4-butanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, and ditrimethylolpropane tetra(meth)acrylate are more preferred.

The resin emulsion particles preferably contain a (meth)acrylic polymer, and more preferably contain structural units derived from styrene.

(Structural unit derived from ultraviolet absorbing monomer)
From the viewpoint of imparting ultraviolet absorbing properties to the resin emulsion particles, an ultraviolet absorbing monomer may be contained in the monomer component within the scope that does not impair the object of the present invention.

Examples of ultraviolet absorbing monomers include, but are not limited to, benzotriazole-based ultraviolet absorbing monomers and benzophenone-based ultraviolet absorbing monomers. These ultraviolet absorbing monomers may be used alone or in combination of two or more types.

Examples of benzotriazole-based ultraviolet 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)acryloyloxymethylphenyl]-5-tert-butyl-2H-benzotriazole. p) 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-benzotriazo 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)acryloyloxyethylphenyl]-5-chloro-2H-benzotriazole, Examples of the benzotriazole-based ultraviolet absorbing monomer include, but are not limited to, 2-[2'-hydroxy-5'-(meth)acryloyloxyethylphenyl]-5-cyano-2H-benzotriazole, 2-[2'-hydroxy-5'-(β-(meth)acryloyloxyethoxy)-3'-tert-butylphenyl]-4-tert-butyl-2H-benzotriazole, etc. These benzotriazole-based ultraviolet absorbing monomers may be used alone or in combination of two or more kinds.

Examples of benzophenone-based ultraviolet absorbing monomers include, but are not limited to, 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. These benzophenone-based ultraviolet absorbing monomers may be used alone or in combination of two or more.

(Crosslinking Agent)
The resin emulsion particles can be provided with crosslinking properties by further containing a crosslinking agent. The crosslinking agent may be one that initiates a crosslinking reaction at room temperature or one that initiates a crosslinking reaction by heat. In the inkjet ink of the present invention, the blocking resistance and adhesion can be further improved by containing a crosslinking agent in the resin emulsion particles.

Suitable crosslinking agents include, for example, oxazoline group-containing compounds, isocyanate group-containing compounds, aminoplast resins, and the like. These crosslinking agents may be used alone or in combination of two or more. Among these crosslinking agents, oxazoline group-containing compounds are preferred from the viewpoint of improving the storage stability of the inkjet ink of the present invention.

An oxazoline group-containing compound is a compound having two or more oxazoline groups in the molecule. Examples of oxazoline group-containing compounds 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), 2,2'-octamethylene-bis(2-oxazoline), 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, oxazoline ring-containing polymers, etc., are included, but are not limited to these examples. These oxazoline group-containing compounds may be used alone or in combination of two or more kinds. Among the oxazoline group-containing compounds, from the viewpoint of improving reactivity, water-soluble oxazoline group-containing compounds are preferred, and water-soluble oxazoline ring-containing polymers are more preferred.

The oxazoline ring-containing polymer contains an addition-polymerizable oxazoline as an essential component, and can be easily prepared by polymerizing a monomer component that contains a monomer copolymerizable with the addition-polymerizable oxazoline as necessary.

As the addition-polymerizable oxazoline, the same ones as those exemplified in the section on ethylenically unsaturated double bond-containing monomers can be preferably used.

Oxazoline group-containing compounds are readily available commercially, for example, under the trade names Epocross WS-500, Epocross WS-700, Epocross K-2010, Epocross K-2020, and Epocross K-2030 manufactured by Nippon Shokubai Co., Ltd. Among these, water-soluble oxazoline group-containing compounds such as Epocross WS-500 and Epocross WS-700 manufactured by Nippon Shokubai Co., Ltd. are preferred from the viewpoint of improving reactivity.

An isocyanate group-containing compound is a compound that contains an isocyanate group that can react with a hydroxyl group contained as a functional group in a hydroxyl group-containing monomer used as a monomer component.

Examples of isocyanate group-containing compounds include water-dispersible (blocked) polyisocyanates. Note that (blocked) polyisocyanates refer to polyisocyanates and/or blocked polyisocyanates.

Examples of water-dispersible polyisocyanates include polyisocyanates that have been given hydrophilicity through polyethylene oxide chains and are dispersed in water with an anionic or nonionic dispersant.

Examples of polyisocyanates include diisocyanates such as hexamethylene diisocyanate and isophorone diisocyanate; and derivatives (modified products) of polyisocyanates such as trimethylolpropane adducts, biuret adducts, and isocyanurates of these diisocyanates, but are not limited to these examples. These polyisocyanates may be used alone or in combination of two or more types.

Water-dispersible polyisocyanates are readily available commercially, for example, under the trade names AQUANATE 100, AQUANATE 110, AQUANATE 200, and AQUANATE 210 manufactured by Nippon Polyurethane Industry Co., Ltd.; under the trade names Bayhydur TPLS-2032 and SUB-Isocyanate L801 manufactured by Sumika Bayer Urethane Co., Ltd.; under the trade names Takenate WD-720, Takenate WD-725, and Takenate WD-220 manufactured by Mitsui Takeda Chemical Co., Ltd.; and under the trade name Resamine D-56 manufactured by Dainichiseika Color & Chemicals Co., Ltd.

Water-dispersible blocked polyisocyanates are obtained by blocking the isocyanate groups of water-dispersible polyisocyanates with a blocking agent. Examples of blocking agents include diethyl malonate, ethyl acetoacetate, ε-caprolactam, butanone oxime, cyclohexanone oxime, 1,2,4-triazole, dimethyl-1,2,4-triazole, 3,5-dimethylpyrazole, and imidazole, but the blocking agents are not limited to these examples. These blocking agents may be used alone or in combination of two or more. Among these blocking agents, those that cleave at a temperature of 160°C or less, preferably 150°C or less, are desirable. Examples of suitable blocking agents include butanone oxime, cyclohexanone oxime, and 3,5-dimethylpyrazole. Among these, butanone oxime is more preferable.

Water-dispersible blocked polyisocyanates are readily available commercially, for example, as products manufactured by Mitsui Takeda Chemical Co., Ltd. under the trade names Takenate WB-720, Takenate WB-730, Takenate WB-920, etc.; and as products manufactured by Sumika Bayer Urethane Co., Ltd. under the trade names Bayhydur BL116, Bayhydur BL5140, Bayhydur BL5235, Bayhydur TPLS2186, Desmodur VPLS2310, etc.

Aminoplast resins are addition condensation products of compounds containing amino groups, such as melamine and guanamine, with formaldehyde, and are also called amino resins.

Examples of aminoplast resins include melamine resins such as dimethylol melamine, trimethylol melamine, tetramethylol melamine, pentamethylol melamine, hexamethylol melamine, fully alkylated methylated melamine, fully alkylated butylated melamine, fully alkylated isobutylated melamine, fully alkylated mixed etherified melamine, methylol group-type methylated melamine, imino group-type methylated melamine, methylol group-type mixed etherified melamine, and imino group-type mixed etherified melamine; and guanamine resins such as butylated benzoguanamine, methyl/ethyl mixed alkylated benzoguanamine, methyl/butyl mixed alkylated benzoguanamine, and butylated glycoluril, but are not limited to these examples. These aminoplast resins may be used alone or in combination of two or more types.

Aminoplast resins are readily available commercially, for example, under the trade names Mycoat 506, Mycoat 1128, Cymel 232, Cymel 235, Cymel 254, Cymel 303, Cymel 325, Cymel 370, Cymel 771, and Cymel 1170 manufactured by Mitsui Cytec Co., Ltd.

The amount of the aminoplast resin is preferably adjusted so that the mass ratio of the solid content of the polymer component contained in the resin emulsion particles to the solid content of the aminoplast resin [solid content of polymer component/solid content of aminoplast resin] is usually 60/40 to 99/1.
Among the above crosslinking agents, addition-polymerizable oxazolines are preferred from the viewpoint of further improving adhesion to corona-treated PET, OPP, and the like.

In addition to the above-mentioned crosslinking agents, crosslinking agents such as carbodiimide compounds, zirconium compounds, zinc compounds, titanium compounds, aluminum compounds, and other polyvalent metal compounds can be used in the present invention as long as the object of the present invention is not impaired.

1-2-1 Acid Value Derived from Carboxyl Groups of Resin Emulsion Particles The acid value derived from the carboxyl groups of the resin emulsion particles contained in the inkjet ink of the present invention is preferably 0 to 6, and can be adjusted by adjusting the composition of the monomers used in the polymerization of the resin emulsion particles.

The acid value derived from the carboxyl groups of the resin emulsion particles is the number of mg of potassium hydroxide required to neutralize the carboxyl groups present in 1 g of the resin emulsion particles. When the polymerization component contained in the resin emulsion particles is an ethylenically unsaturated double bond-containing monomer and the resin emulsion particles do not contain other carboxyl groups, it is possible to approximate the number of mg of potassium hydroxide required to neutralize the carboxyl groups present in 1 g of the ethylenically unsaturated double bond-containing monomer component as the acid value. In this specification, the acid value derived from the carboxyl groups of the resin emulsion particles is a value that does not include the acid value derived from acid groups other than the carboxyl groups in the emulsifier and initiator. The acid value is preferably 0 to 5, more preferably 0 to 4, even more preferably 0 to 1, and particularly preferably 0. By lowering the acid value derived from the carboxyl groups of the resin emulsion particles, the image uniformity when made into an ink can be improved.

1-2-2 Glass Transition Temperature The resin emulsion particles preferably contain a polymer component having a glass transition temperature of 55°C or higher and a polymer component having a glass transition temperature of less than 55°C.
The glass transition temperature of the polymer component can be adjusted by adjusting the composition of the monomers used in the monomer component.

In this specification, the glass transition temperature (Tg) of a polymer component is expressed by the formula:
1/Tg=Σ(Wm/Tgm)/100
(In the formula, Wm represents the content (mass%) of monomer m in the monomer components constituting the polymer component, and Tgm represents the glass transition temperature (absolute temperature: K) of a homopolymer of monomer m.)
The term "temperature" refers to the temperature calculated based on the Fox equation,

The glass transition temperatures of the polymer components are, for example, 95°C for homopolymers of acrylic acid, 130°C for homopolymers of methacrylic acid, 105°C for homopolymers of methyl methacrylate, 100°C for homopolymers of styrene, 83°C for homopolymers of cyclohexyl methacrylate, 20°C for homopolymers of n-butyl methacrylate, -70°C for homopolymers of 2-ethylhexyl acrylate, -56°C for homopolymers of n-butyl acrylate, and -40°C for homopolymers of hydroxyethyl methacrylate. For homopolymers, it is 55°C, for homopolymers of acrylamide, it is 165°C, for monomers of 4-(meth)acryloyloxy-2,2,6,6-tetramethylpiperidine, it is 130°C, for homopolymers of 4-methacryloyloxy-1,2,2,6,6-pentamethylpiperidine, it is 130°C, for homopolymers of 2-[2'-hydroxy-5'-methacryloyloxyethylphenyl]-2H-benzotriazole, it is 100°C, and for homopolymers of 2-isopropenyl-2-oxazoline, it is 100°C.

The glass transition temperature of the polymer component is a value calculated based on the Fox formula, but it is preferable that the actual measured value of the glass transition temperature of the polymer component is the same as the value calculated based on the Fox formula. The actual measured value of the glass transition temperature of the polymer component can be calculated, for example, by measuring the differential scanning calorimetry.

In this specification, the glass transition temperature of a polymer component means the glass transition temperature calculated based on the above formula, unless otherwise specified. For monomers with unknown glass transition temperatures, such as special monomers and polyfunctional monomers, if the total amount of monomers with unknown glass transition temperatures in the monomer component is 10% by mass or less, the glass transition temperature is calculated using only monomers with known glass transition temperatures. If the total amount of monomers with unknown glass transition temperatures in the monomer component exceeds 10% by mass, the glass transition temperature of the (meth)acrylic adhesive resin is calculated by differential scanning calorimetry (DSC), differential calorimetry (DTA), thermomechanical analysis (TMA), etc.

An example of a differential scanning calorimetry measuring device is a product manufactured by Seiko Instruments Inc., product number: DSC220C. In addition, when measuring differential scanning calorimetry, there is no particular limitation on the method of drawing a differential scanning calorimetry (DSC) curve, the method of obtaining a first derivative curve from a differential scanning calorimetry (DSC) curve, the method of performing smoothing processing, the method of determining the target peak temperature, etc. For example, when using the above-mentioned measuring device, it is sufficient to draw a curve from data obtained by using the measuring device. In this case, analysis software capable of performing mathematical processing can be used. Examples of the analysis software include analysis software [manufactured by Seiko Instruments Inc., product number: EXSTAR6000], but are not limited to only these examples. Note that the peak temperature obtained in this way may contain an error due to drawing of about 5°C above or below.

The resin emulsion particles may be core-shell resin emulsion particles in which a polymer component having a glass transition temperature of 55° C. or more and a polymer component having a glass transition temperature of less than 55° C. are laminated, or may be emulsion particles in which a polymer component having a glass transition temperature of 55° C. or more and a polymer component having a glass transition temperature of less than 55° C. are uniformly mixed, or may be a mixture of resin emulsion particles made of a polymer component having a glass transition temperature of 55° C. or more and a resin emulsion particle made of a polymer component having a glass transition temperature of less than 55° C. The core part of the core-shell resin emulsion particles may be made of a polymer component having a glass transition temperature of 55° C. or more and the shell part may be made of a polymer component having a glass transition temperature of less than 55° C., or vice versa. By including a polymer component having a glass transition temperature of 55° C. or more and a polymer component having a glass transition temperature of less than 55° C., the resin emulsion particles can achieve both adhesion to the substrate and blocking resistance.

The emulsion particle structure may be, for example, a substantially uniform mixed composition as long as it contains a polymer component with a glass transition temperature of 55°C or higher and a polymer component with a glass transition temperature of less than 55°C, but a multi-layer structure is preferable. Specifically, the multi-layer structure refers to a core-shell structure consisting of an outermost shell portion and a core portion inside the shell portion. The core portion may be of substantially uniform composition or may be of multi-layer structure (further core-shell). It is preferable that the core portion be of substantially uniform composition.

The content ratio of the polymer component having a glass transition temperature of 55°C or more to the polymer component having a glass transition temperature of less than 55°C is preferably 1:99 to 70:30, more preferably 1:99 to 40:60, and particularly preferably 1:99 to 30:70, by mass ratio (polymer component having a glass transition temperature of 55°C or more:polymer component having a glass transition temperature of less than 55°C). When the resin emulsion particles contain two or more types of polymer components, the average glass transition temperature is preferably 0 to 30°C.

The resin emulsion particles contained in the inkjet ink of the present invention are preferably core-shell resin emulsion particles in which the core portion contains a polymer component having a glass transition temperature of 55°C or higher, and the shell portion contains a polymer component having a glass transition temperature of less than 55°C. Here, when the emulsion particles are composed of an outermost shell portion and a core portion of substantially uniform composition, the "glass transition temperature of the shell portion" and the "glass transition temperature of the core portion" have their literal meanings, and when the "core portion" is composed of multiple layers, the "glass transition temperature of the shell portion" means the glass transition temperature of the outermost layer, and the "glass transition temperature of the core portion" means the average glass transition temperature of the core portion composed of multiple layers.

The glass transition temperature of the polymer component of the core portion is preferably 60°C or higher, more preferably 70°C or higher, even more preferably 80°C or higher, particularly preferably 90°C or higher, and most preferably 95°C or higher. From the viewpoint of blocking resistance, the upper limit of the glass transition temperature of the polymer component of the core portion is preferably as high as possible, but if it is too high, film formation failure may occur, so the upper limit is preferably 300°C or lower, and more preferably 200°C or lower.

The glass transition temperature of the polymer component of the shell portion is preferably 40°C or lower, more preferably 30°C or lower, even more preferably 25°C or lower, even more preferably 20°C or lower, particularly preferably 15°C or lower, and most preferably 10°C or lower. The lower limit of the glass transition temperature of the polymer component of the shell portion is preferably -70°C or higher, more preferably -50°C or higher, even more preferably -30°C or higher, and particularly preferably -20°C or higher.

The combination of the glass transition temperatures of the polymer component of the core portion and the polymer component of the shell portion is as follows:
Preferably, the glass transition temperature of the polymer component of the core portion is 55° C. or higher (more preferably, the glass transition temperature of the polymer component of the core portion is 200° C. or lower), and the glass transition temperature of the polymer component of the shell portion is 25° C. or lower (more preferably, the glass transition temperature of the polymer component of the shell portion is −20° C. or higher);
More preferably, the glass transition temperature of the polymer component of the core portion is 90° C. or higher (more preferably, the glass transition temperature of the polymer component of the core portion is 200° C. or lower), and the glass transition temperature of the polymer component of the shell portion is less than 55° C. (more preferably, the glass transition temperature of the polymer component of the shell portion is −20° C. or higher);
More preferably, the glass transition temperature of the polymer component of the core portion is 90° C. or higher (and even more preferably, the glass transition temperature of the polymer component of the core portion is 200° C. or lower), and the glass transition temperature of the polymer component of the shell portion is 25° C. or lower (and even more preferably, the glass transition temperature of the polymer component of the shell portion is −20° C. or higher).

The shell portion preferably contains a piperidine group-containing monomer, and/or an addition polymerizable oxazoline, and/or a hydroxyl group-containing (meth)acrylate. The content of the piperidine group-containing monomer, the addition polymerizable oxazoline, and the hydroxyl group-containing (meth)acrylate in the shell portion is preferably 0.1 to 30% by mass, more preferably 0.2 to 20% by mass, and even more preferably 0.5 to 10% by mass, based on 100% by mass of the total amount of the monomers constituting the shell portion.
The core portion preferably contains a styrene-based monomer. The content of the styrene-based monomer in the core portion is preferably 1 to 70% by mass relative to 100% by mass of the total amount of monomers constituting the core portion.

1-2-3 Other characteristics (weight average molecular weight)
In the ink-jet ink of the present invention, the weight average molecular weight of the polymer component constituting the resin emulsion particles is, from the viewpoint of further improving water resistance and adhesion, preferably 100,000 or more, more preferably 300,000 or more, even more preferably 550,000 or more, and particularly preferably 600,000 or more. The upper limit of the weight average molecular weight of the polymer component is preferably 5,000,000 or less, from the viewpoint of improving film-forming properties and water resistance.

In this specification, the weight average molecular weight of the polymer components constituting the resin emulsion particles refers to the weight average molecular weight (polystyrene equivalent) measured using gel permeation chromatography (Tosoh Corporation, product number: HLC-8120GPC, columns: TSKgel G-5000HXL and TSKgel GMHXL-L in series).

(Volume average particle size)
The volume average particle diameter of the resin emulsion particles contained in the inkjet ink of the present invention is preferably 30 nm or more, more preferably 50 nm or more, from the viewpoint of improving the image uniformity of the resin emulsion particles, and is preferably 350 nm or less, more preferably 300 nm or less, from the viewpoint of further improving the storage stability and water resistance.

In this specification, the volume average particle size of the resin emulsion particles means the volume average particle size measured using a particle size distribution measuring device (manufactured by Particle Sizing Systems, product name: NICOMP Model 380) using the dynamic light scattering method.

1-2-4 Method for Producing Resin Emulsion Particles The inkjet ink of the present invention preferably contains an emulsion containing resin emulsion particles, which are a polymer component obtained by emulsion polymerization of the above-mentioned monomer components.
The resin emulsion particles contained in the inkjet ink of the present invention are preferably produced by emulsion polymerizing the above-mentioned monomer components in the presence of an emulsifier.

Methods for emulsion-polymerizing the monomer components include, for example, an aqueous medium containing a water-soluble organic solvent such as a lower alcohol such as methanol and water, a method in which an emulsifier is dissolved in a medium such as water and the monomer components and a polymerization initiator are dropped under stirring, and a method in which a monomer component that has been emulsified in advance using an emulsifier and water is dropped into water or an aqueous medium, but are not limited to these methods. The amount of the medium may be appropriately set taking into consideration the amount of non-volatile content contained in the resulting emulsion. The medium may be charged in advance in a reaction vessel or may be used as a pre-emulsion. The medium may also be used, if necessary, when emulsion-polymerizing the monomer components to produce the emulsion.

When emulsion polymerizing the monomer components, the monomer components, emulsifier, and medium may be mixed and then emulsion polymerization may be carried out, or the monomer components, emulsifier, and medium may be emulsified by stirring to prepare a pre-emulsion and then emulsion polymerization may be carried out, or at least one of the monomer components, emulsifier, and medium may be mixed with the remaining pre-emulsion and then emulsion polymerization may be carried out. The monomer components, emulsifier, and medium may each be added all at once, added in portions, or added dropwise continuously.

When forming an outer layer made of a polymer component for the outer layer (shell) on the resin emulsion particles contained in the emulsion obtained above, the outer layer can be formed on the resin emulsion particles by emulsion polymerization of the monomer component in the emulsion in the same manner as described above. When forming an outer layer on the resin emulsion particles on which the outer layer (intermediate layer) has been formed, the outer layer can be formed on the resin emulsion particles by emulsion polymerization of the monomer component in the emulsion in the same manner as described above. In this way, resin emulsion particles having a multi-layer structure (core-shell resin emulsion particles) can be prepared by the multi-stage emulsion polymerization method.

When preparing the core-shell resin emulsion particles, one or more stages of emulsion polymerization may be carried out before the emulsion polymerization for forming the inner layer made of the polymer components for the inner layer (core), and one or more stages of emulsion polymerization may be carried out between the emulsion polymerization for forming the inner layer and the emulsion polymerization for forming the intermediate layer. One or more stages of emulsion polymerization may be carried out between the emulsion polymerization for forming the intermediate layer and the emulsion polymerization for forming the outer layer. Furthermore, one or more stages of emulsion polymerization may be carried out after the emulsion polymerization for forming the outer layer.

(emulsifier)
Examples of the emulsifier used in the emulsion polymerization include anionic emulsifiers, nonionic emulsifiers, cationic emulsifiers, amphoteric emulsifiers, and polymeric emulsifiers. These emulsifiers may be used alone or in combination of two or more kinds.

Examples of anionic emulsifiers include alkyl sulfate salts such as ammonium dodecyl sulfate and sodium dodecyl sulfate; alkyl sulfonate salts such as ammonium dodecyl sulfonate, sodium dodecyl sulfonate and sodium alkyl diphenyl ether disulfonate; alkyl aryl sulfonate salts such as ammonium dodecyl benzene sulfonate and sodium dodecyl naphthalene sulfonate; polyoxyethylene alkyl sulfonate salts; polyoxyethylene alkyl sulfate salts; polyoxyethylene alkyl aryl sulfate salts; dialkyl sulfosuccinate salts; aryl sulfonic acid-formaldehyde condensates; Examples of the salts include fatty acid salts such as ammonium laurate and sodium stearylate; sulfate esters or salts thereof having an allyl group such as bis(polyoxyethylene polycyclic phenyl ether) methacrylate sulfonate salts, propenyl-alkyl sulfosuccinate salts, polyoxyethylene (meth)acrylate sulfonate salts, polyoxyethylene (meth)acrylate phosphonate salts, and sulfonate salts of allyloxymethyl alkyloxy polyoxyethylene; sulfate ester salts of allyloxymethyl alkoxyethyl polyoxyethylene, and ammonium polyoxyalkylene alkenyl ether sulfate salts, but are not limited to these examples.

Nonionic emulsifiers include, but are not limited to, polyoxyethylene alkyl ethers, polyoxyethylene alkylaryl ethers, condensates of polyethylene glycol and polypropylene glycol, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, fatty acid monoglycerides, condensations of ethylene oxide and aliphatic amines, allyloxymethylalkoxyethylhydroxypolyoxyethylene, and polyoxyalkylene alkenyl ethers.

Examples of cationic emulsifiers include alkyl ammonium salts such as dodecyl ammonium chloride, but are not limited to these examples.

Examples of amphoteric emulsifiers include, but are not limited to, betaine ester emulsifiers.

Examples of polymeric emulsifiers include poly(meth)acrylates such as sodium polyacrylate; polyvinyl alcohol; polyhydroxyalkyl(meth)acrylates such as polyhydroxyethyl acrylate; and copolymers in which one or more of the monomers constituting these polymers are copolymerized components, but are not limited to these examples.

As the emulsifier, from the viewpoint of further improving water resistance and image uniformity, an emulsifier having a polymerizable group, i.e., a so-called reactive emulsifier, is preferred, and from the viewpoint of environmental protection, a non-nonylphenyl type emulsifier is preferred.

Examples of reactive emulsifiers include propenyl-alkyl sulfosuccinate salts, (meth)acrylic acid polyoxyethylene sulfonate salts, (meth)acrylic acid polyoxyethylene phosphonate salts (e.g., Sanyo Chemical Industries, Ltd., product name: Eleminol RS-30, etc.), polyoxyethylene alkylpropenyl phenyl ether sulfonate salts (e.g., Daiichi Kogyo Seiyaku Co., Ltd., product name: Aqualon HS-10, etc.), sulfonate salts of allyloxymethyl alkyloxy polyoxyethylene (e.g., Daiichi Kogyo Seiyaku Co., Ltd., product name: Aqualon KH-10, etc.), sulfonate salts of allyloxymethyl nonyl phenoxyethyl hydroxy polyoxyethylene (e.g., ADEKA Corporation, product names: Adeka Reasoap SR-10, SR-20, SR-30, etc.), allyloxymethyl alkoxy Examples of such esters include, but are not limited to, ethyl hydroxypolyoxyethylene sulfate salts (e.g., manufactured by ADEKA CORPORATION, product names: ADEKA REASOAP SR-10, SR-30, etc.), bis(polyoxyethylene polycyclic phenyl ether) methacrylated sulfonate salts (e.g., manufactured by Nippon Nyukazai Co., Ltd., product name: Antox MS-60, etc.), allyloxymethylalkoxyethylhydroxypolyoxyethylene (e.g., manufactured by ADEKA CORPORATION, product name: ADEKA REASOAP ER-20, etc.), polyoxyethylene alkylpropenylphenyl ether (e.g., manufactured by Daiichi Kogyo Seiyaku Co., Ltd., product name: Aqualon RN-20, etc.), and allyloxymethylnonylphenoxyethylhydroxypolyoxyethylene (e.g., manufactured by ADEKA CORPORATION, product name: ADEKA REASOAP NE-10, etc.).

The amount of emulsifier per 100 parts by mass of monomer component is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, even more preferably 2 parts by mass or more, and particularly preferably 3 parts by mass or more, from the viewpoint of improving polymerization stability, and is preferably 10 parts by mass or less, more preferably 6 parts by mass or less, from the viewpoint of improving water resistance.

(Polymerization initiator)
Examples of the polymerization initiator include azo compounds such as azobisisobutyronitrile, 2,2-azobis(2-methylbutyronitrile), 2,2-azobis(2,4-dimethylvaleronitrile), 2,2-azobis(2-diaminopropane)hydrochloride, 4,4-azobis(4-cyanovaleric acid), and 2,2-azobis(2-methylpropionamidine); persulfates such as ammonium persulfate and potassium persulfate; and peroxides such as hydrogen peroxide, benzoyl peroxide, parachlorobenzoyl peroxide, lauroyl peroxide, and ammonium peroxide, but the invention is not limited to these examples. These polymerization initiators may be used alone or in combination of two or more kinds.

The amount of polymerization initiator per 100 parts by mass of monomer component is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, from the viewpoint of increasing the polymerization rate and reducing the amount of remaining unreacted monomer component, and is preferably 1 part by mass or less, more preferably 0.5 parts by mass or less, from the viewpoint of improving water resistance.

The method of adding the polymerization initiator is not particularly limited. Examples of the addition method include batch charging, divided charging, and continuous dropwise addition. In order to hasten the completion of the polymerization reaction, a portion of the polymerization initiator may be added before or after the addition of the monomer components to the reaction system.

In addition, to promote the decomposition of the polymerization initiator, a suitable amount of a polymerization initiator decomposer, such as a reducing agent such as sodium hydrogen sulfite or a transition metal salt such as ferrous sulfate, may be added to the reaction system.

(Chain Transfer Agent)
In addition, a chain transfer agent can be used to adjust the weight average molecular weight of the resin emulsion particles. Examples of the chain transfer agent include 2-ethylhexyl thioglycolate, tert-dodecyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, mercaptoacetic acid, mercaptopropionic acid, 2-mercaptoethanol, α-methylstyrene, and α-methylstyrene dimer, but are not limited to these examples. These chain transfer agents may be used alone or in combination of two or more kinds. The amount of the chain transfer agent per 100 parts by mass of the monomer component is preferably 0.01 to 10 parts by mass from the viewpoint of appropriately adjusting the weight average molecular weight of the resin emulsion particles.

(Other conditions)
In addition, additives such as a pH buffer, a chelating agent, and a film-forming aid may be added to the reaction system as necessary. The amount of the additive varies depending on the type of additive and cannot be determined in general. Usually, the amount of the additive per 100 parts by mass of the monomer component is preferably about 0.01 to 5 parts by mass, more preferably about 0.1 to 3 parts by mass.

The atmosphere in which the monomer components are emulsion polymerized is not particularly limited, but from the viewpoint of increasing the efficiency of the polymerization initiator, it is preferable to use an inert gas such as nitrogen gas.

The polymerization temperature when emulsion-polymerizing the monomer components is not particularly limited, but is usually preferably 50 to 100°C, more preferably 60 to 95°C. The polymerization temperature may be constant or may be changed during the polymerization reaction.

There is no particular limit to the polymerization time for emulsion polymerization of the monomer components, and it may be set appropriately depending on the progress of the polymerization reaction, but it is usually about 2 to 9 hours.

When the monomer components are emulsion-polymerized, some or all of the acidic groups in the resulting polymer component may be neutralized with a neutralizing agent. The neutralizing agent may be used after the monomer components are added in the final stage, for example, between the first and second stages of polymerization reaction, or at the end of the initial emulsion polymerization reaction.

Neutralizing agents include, for example, alkaline substances such as hydroxides of alkali metals or alkaline earth metals, such as sodium hydroxide; carbonates of alkali metals or alkaline earth metals, such as sodium hydrogen carbonate and calcium carbonate; and organic amines, such as ammonia, monomethylamine, and dimethylaminoethanol, but are not limited to these examples. Among these neutralizing agents, volatile alkaline substances such as ammonia are preferred from the viewpoint of improving water resistance, and sodium hydrogen carbonate is preferred from the viewpoint of improving the storage stability of the resin emulsion particles. The neutralizing agent can be used, for example, as an aqueous solution.

When the monomer components are emulsion-polymerized, a suitable amount of a silane coupling agent may be used to improve water resistance. Examples of silane coupling agents include silane coupling agents having a polymerizable unsaturated bond such as a (meth)acryloyl group, a vinyl group, an allyl group, or a propenyl group, but the present invention is not limited to these examples. Note that "(meth)acryloyl" means "acryloyl" or "methacryloyl".

By emulsion polymerizing the monomer components in the manner described above, an emulsion containing resin emulsion particles is obtained.

When forming an outer layer on the resin emulsion particles obtained as described above, it is preferable to emulsion-polymerize the monomer components that make up the outer layer after the polymerization reaction rate during the production of the resin emulsion particles reaches 90% or more, preferably 95% or more, from the viewpoint of forming a layer-separated structure within the resin emulsion particles.

After forming the inner layer of the resin emulsion particle and before forming the outer layer, a layer made of other polymer components may be formed as necessary, as long as the purpose of the present invention is not hindered. Therefore, when producing the resin emulsion particles contained in the inkjet ink of the present invention, after forming the inner layer of the resin emulsion particle and before forming the outer layer, a layer made of other polymer components may be formed as necessary, as long as the purpose of the present invention is not hindered.

The monomer components used to form the outer layer can be the same as the monomer components used as the raw materials for the inner layer of the resin emulsion particle. The emulsion polymerization method and polymerization conditions for forming the outer layer can be the same as the method and polymerization conditions for producing the inner layer of the resin emulsion particle.

In this manner, resin emulsion particles having an inner layer and an outer layer can be obtained. If necessary, a surface layer made of other polymer components may be further formed on the surface of the outer layer, as long as the object of the present invention is not hindered.

After preparing the inner layer of the resin emulsion particle in the above manner, an outer layer is formed on the inner layer to obtain a resin emulsion particle having an inner layer and an outer layer.

The content of water is preferably from 20% by mass to 80% by mass, and more preferably from 25% by mass to 70% by mass, based on 100 parts by mass of the ink-jet ink of the present invention.

1-4 Solvent The ink-jet ink of the present invention may contain an organic solvent.
Examples of the organic solvent include glycols such as propylene glycol, 1,3-propanediol, glycerin, dipropylene glycol, tripropylene glycol, diethylene glycol, triethylene glycol, and tetraethylene glycol; ethers of monoethylene glycol 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; ethers of monopropylene glycol 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; tripropylene glycol monomethyl ether; monomethyl ether of polyethylene glycol (EO addition mole number=2 to 10, preferably 2 to 4), and polyethylene glycol (EO addition mole number=2 to 10, preferably 2 to 4). ethers of polyethylene glycol such as monoethyl ether, monopropyl ether of polyethylene glycol (number of moles of EO added=2 to 10, preferably 2 to 4), monoisopropyl ether of polyethylene glycol (number of moles of EO added=2 to 10, preferably 2 to 4), monobutyl ether of polyethylene glycol (number of moles of EO added=2 to 10, preferably 2 to 4), and monoisobutyl ether of polyethylene glycol (number of moles of EO added=2 to 10, preferably 2 to 4); monomethyl ether of polypropylene glycol (number of moles of EO added=2 to 10, preferably 2 to 4), Examples of the ethers of polypropylene glycol include monoethyl ether of polypropylene glycol (EO addition mole number = 2 to 10, preferably 2 to 4), monopropyl ether of polypropylene glycol (EO addition mole number = 2 to 10, preferably 2 to 4), monoisopropyl ether of polypropylene glycol (EO addition mole number = 2 to 10, preferably 2 to 4), monobutyl ether of polypropylene glycol (EO addition mole number = 2 to 10, preferably 2 to 4), and monoisobutyl ether of polypropylene glycol (EO addition mole number = 2 to 10, preferably 2 to 4). Among these, propylene glycol, diethylene glycol, triethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, and diethylene glycol monoisobutyl ether are preferred. These organic solvents may be used alone or in combination of two or more.
The content of the organic solvent is preferably from 1 to 60% by mass, and more preferably from 10 to 50% by mass, based on 100 parts by mass of the ink-jet ink of the present invention.

1-5 Pigment The inkjet ink of the present invention preferably further contains a pigment. Examples of pigments include organic pigments and inorganic pigments, which may be used alone or in combination of two or more kinds. If necessary, they may also be used in combination with an extender pigment.

Examples of organic pigments include azo pigments such as benzidine and Hansa Yellow, diazo pigments, azomethine pigments, methine pigments, anthraquinone pigments, phthalocyanine pigments such as phthalocyanine blue, perinone pigments, perylene pigments, diketopyrrolopyrrole pigments, thioindigo pigments, iminoisoindoline pigments, isoindolinone pigments such as iminoisoindolinone, dioxazine pigments, quinacridone pigments such as quinacridone red and quinacridone violet, flavanthrone pigments, indanthrone pigments, anthrapyrimidine pigments, carbazole pigments, monoarylide yellow, diarylide yellow, benzimidazolone yellow, tolyl orange, naphthol orange, and quinophthalone pigments.
The hue is not particularly limited, and any chromatic pigment such as yellow, magenta, cyan, blue, red, orange, and green can be used, and specific examples include one or more products having product numbers selected from the group consisting of C.I. Pigment Yellow, C.I. Pigment Red, C.I. Pigment Orange, C.I. Pigment Violet, C.I. Pigment Blue, and C.I. Pigment Green.
These organic pigments may be used alone or in combination of two or more kinds.

Examples of inorganic pigments include titanium dioxide, antimony trioxide, zinc oxide, lithopone, white lead, red iron oxide, black iron oxide, chromium oxide green, carbon black, yellow lead, molybdenum red, ferric ferrocyanide (Prussian blue), ultramarine, lead chromate, etc., as well as flat-shaped pigments such as mica, clay, aluminum powder, talc, and aluminum silicate, and extender pigments such as calcium carbonate, magnesium hydroxide, aluminum hydroxide, barium sulfate, and magnesium carbonate. Furthermore, examples of carbon black include furnace black, thermal lamp black, acetylene black, and channel black. These inorganic pigments may be used alone or in combination of two or more types.

The amount of pigment per 100 parts by mass of nonvolatile matter in the inkjet ink is preferably 50 parts by mass or more, more preferably 60 parts by mass or more, from the viewpoint of improving the concealing property of the printed matter formed from the inkjet ink of the present invention, and is preferably 90 parts by mass or less, from the viewpoint of further improving adhesion.

1-6 Other Components The ink-jet ink of the present invention may contain other resin emulsion particles in addition to the resin emulsion particles contained in the ink-jet ink described above, within the scope of not impairing the object of the present invention.

The inkjet ink of the present invention may also contain additives such as UV absorbers, UV stabilizers, fillers, surfactants, dispersants, thickeners, wetting agents, plasticizers, stabilizers, defoamers, dyes, antioxidants, preservatives, and leveling agents in appropriate amounts, provided that the object of the present invention is not impaired. For example, acetylene glycol-based, polyether-modified silicone-based, and fluorine-based surfactants can be added.

The dispersant is preferably an ionic dispersant. The content of the dispersant 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, relative to 100 parts by mass of the inkjet ink of the present invention.

1-7 Ink characteristics (minimum film-forming temperature)
From the viewpoint of further improving adhesion, the minimum film-forming temperature of the ink-jet ink of the present invention is preferably 40° C. or lower, more preferably 20° C. or lower, and even more preferably 0° C. or lower.

In this specification, the minimum film-forming temperature of an inkjet ink refers to the temperature at which cracks appear when the inkjet ink is applied to a glass plate placed on a thermal gradient tester with an applicator to a thickness of 0.2 mm and dried.

(Non-volatile content)
[0043] The non-volatile content in the inkjet ink of the present invention is preferably 5% by mass or more, more preferably 7% by mass or more, from the viewpoint of improving hiding power or color density, and is preferably 50% by mass or less, more preferably 40% by mass or less, from the viewpoint of improving storage stability.

In this specification, the amount of non-volatile content in an inkjet ink is determined by weighing 1 g of the inkjet ink, drying it in a hot air dryer at a temperature of 150° C. for 1 hour, and taking the resulting residue as the non-volatile content, and is calculated using the formula:
[Non-volatile content in inkjet ink (mass%)]
= ([mass of residue] ÷ [1 g of inkjet ink]) × 100
This means the value calculated based on

The inkjet ink of the present invention can be suitably used as an aqueous inkjet ink, and can also be suitably used as an aqueous ink for non-liquid absorbing films, which will be described later.
In particular, it can be suitably used as a water-based inkjet ink for non-liquid-absorbing films.
The aqueous inkjet ink of the present invention is preferably used as an aqueous inkjet ink. The aqueous inkjet ink of the present invention is also preferably used as an aqueous ink for a non-liquid-absorbing film, which will be described later. The aqueous inkjet ink for a non-liquid-absorbing film is particularly preferably used.
The inkjet ink of the present invention can be suitably used in printing on recording media for commercial printing, in particular, films of non-liquid-absorbing resins, such as coated paper, polyester films such as polyethylene terephthalate (PET), polyvinyl chloride films, polypropylene films such as biaxially oriented polypropylene film (OPP), polyethylene films, and nylon films.

[Printed materials]
The inkjet ink of the present invention can be used for printing on substrates such as conventionally known coated paper and resin films, and can be used to produce printed matter.

<Print material>
The printing substrate is preferably a non-absorbent film, for example, a non-absorbent coated paper, a polyester film such as polyethylene terephthalate (PET), a polyvinyl chloride film, a polypropylene film such as biaxially oriented polypropylene film (OPP), a polyethylene film, a nylon film, and other non-absorbent resin films. Among these, biaxially oriented polypropylene film (OPP) and polyethylene terephthalate (PET) are more preferable.
Among non-absorbent films, those in which the surface on which the inkjet ink of the present invention is printed is chemically or physically modified by corona treatment, anchor coat treatment, etc. are preferred. This provides better adhesion to the water-based ink of the present invention or the coating formed by the inkjet ink of the present invention. Corona-treated biaxially oriented polypropylene film (OPP) and corona-treated polyethylene terephthalate (PET) are particularly preferred.

By printing the inkjet ink of the present invention onto a substrate, it is possible to provide a printed material that has excellent image uniformity, adhesion, and blocking resistance.

[Method of manufacturing printed matter]
The inkjet ink of the present invention can be used for inkjet printing, and preferred inkjet printing methods include the thermal method, the piezoelectric method, and the charge deflection control method (continuous ejection method).

The method for producing a printed matter using the inkjet ink of the present invention can provide a method for producing a printed matter that has excellent image uniformity, adhesion, and blocking resistance.

Next, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. In the following examples, "parts" means "parts by mass" and "%" means "% by mass" unless otherwise specified.

<Glass transition temperature of polymer component>
The glass transition temperature (Tg) of a polymer component is calculated by the following formula using the glass transition temperature of a homopolymer of a monomer used in the monomer component constituting the polymer component:
1/Tg=Σ(Wm/Tgm)/100
(In the formula, Wm represents the content (mass%) of monomer m in the monomer components constituting the polymer component, and Tgm represents the glass transition temperature (absolute temperature: K) of a homopolymer of monomer m.)
The results were calculated based on the Fox formula:

<Acid value derived from carboxyl group of resin emulsion particles>
The acid value derived from the carboxyl groups of the resin emulsion particles was obtained by approximating the acid value to the number of mg of potassium hydroxide required to neutralize the carboxyl groups present in 1 g of the monomer component used.

Example 1
In a flask equipped with a dropping funnel, a stirrer, a nitrogen gas inlet tube, a thermometer and a reflux condenser, 716 parts of deionized water were charged. In the dropping funnel, 209 parts of deionized water, 60 parts of a 25% aqueous solution of an emulsifier [made by ADEKA Corporation, trade name: Adeka Reasorb SR-10], 100 parts of cyclohexyl methacrylate, 250 parts of methyl methacrylate, 100 parts of styrene, 40 parts of n-butyl acrylate and 10 parts of hydroxyethyl methacrylate were prepared as a first-stage dropping pre-emulsion, of which 77 parts, which corresponds to 5% of the total amount of all monomer components, was added to the flask, and the temperature was raised to 70°C while slowly blowing in nitrogen gas, and 10 parts of a 5% aqueous solution of ammonium persulfate was added to initiate polymerization. Thereafter, the remaining part of the dropping pre-emulsion and 15 parts of a 5% aqueous solution of ammonium persulfate were uniformly dropped into the flask over 120 minutes.

After the dropping was completed, the contents of the flask were maintained at 70°C for 60 minutes, and then a pre-emulsion for the second dropping step consisting of 209 parts of deionized water, 60 parts of a 25% aqueous solution of an emulsifier [made by ADEKA Corporation, product name: ADEKA REASORB SR-10], 6 parts of acrylic acid, 134 parts of methyl methacrylate, 50 parts of styrene, 300 parts of 2-ethylhexyl acrylate, and 10 parts of hydroxyethyl methacrylate, and 15 parts of a 5% aqueous solution of ammonium persulfate were added dropwise uniformly into the flask over a period of 120 minutes.

After the dropwise addition was completed, 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 terminate the polymerization. The resulting reaction liquid was cooled to room temperature and then filtered through a 300-mesh wire screen to prepare an emulsion. The non-volatile content of this emulsion was 45%, the acid value derived from the carboxyl groups of the resin emulsion particles was 5.0 mg KOH/g, the glass transition temperature of the inner layer resin constituting the resin emulsion particles contained in the emulsion was 78°C, and the glass transition temperature of the outer layer resin was -25°C. The minimum film-forming temperature was below 0°C, and the average particle size was 145 nm.

While stirring 16 parts of the obtained emulsion with a homodisper at a rotation speed of 1000 min ⁻¹ , 25 parts of white paste, 30 parts of propylene glycol, 10 parts of tripropylene glycol monomethyl ether, 10 parts of diethylene glycol monobutyl ether, 0.2 parts of a surfactant [KF-6011, manufactured by Shin-Etsu Chemical Co., Ltd.], 1 part of polyvinylpyrrolidone K-30 (weight average molecular weight 70,000, manufactured by Nippon Shokubai Co., Ltd.) (0.5 parts as solid content), and ion-exchanged water to make a total of 100 parts were added, and the mixture was further stirred for 30 minutes, and then filtered with a 3 μm filter [MCP-3-C10S, manufactured by Advantec Co., Ltd.] to prepare ink-jet ink 1.
The white paste was prepared by dispersing 411 parts of deionized water, 67 parts of a dispersant [AQUALIC HL-415, manufactured by Nippon Shokubai Co., Ltd.], 30 parts of 25% aqueous ammonia, 60 parts of propylene glycol, 1000 parts of titanium oxide [CR-95, manufactured by Ishihara Sangyo Kaisha, Ltd.], and 200 parts of glass beads (diameter 1 mm) in a disperser at a rotation speed of 3000 min ⁻¹ for 120 minutes, and then filtering the mixture through a 300-mesh wire screen.

Comparative Example 1
Ink-jet ink C1 was prepared in the same manner as in Example 1, except that polyvinylpyrrolidone K-30 in Example 1 was changed to 2.5 parts (0.5 parts as solid content) of anionic sodium polyacrylate (manufactured by Nippon Shokubai Co., Ltd., AQUALIC DL-522, weight average molecular weight 200,000).

Comparative Example 2
Ink-jet ink C2 was prepared in the same manner as in Example 1, except that polyvinylpyrrolidone K-30 in Example 1 was changed to 0.5 parts (0.5 parts as solid content) of nonionic polyvinyl alcohol (JC-25, weight average molecular weight 110,000, manufactured by Japan Vinyl Acetate & Poval Co., Ltd.).

Comparative Example 3
Ink-jet ink C3 was prepared in the same manner as in Example 1, except that polyvinylpyrrolidone K-30 in Example 1 was changed to 0.5 parts (0.5 parts as solid content) of nonionic polyethylene glycol (manufactured by Sumitomo Seika Chemicals Co., Ltd., PEO-1, weight average molecular weight 150,000).

Comparative Example 4
Ink-jet ink C4 was prepared in the same manner as in Example 1, except that polyvinylpyrrolidone K-30 in Example 1 was changed to 0.5 parts (0.5 parts as solid content) of polyvinylpyrrolidone K-85 (manufactured by Nippon Shokubai Co., Ltd., weight average molecular weight 1,100,000).

Preparation of Inkjet Printed Matter In an environment of a temperature of 25±1° C. and a relative humidity of 30±5%, a print evaluation device (manufactured by GENESIS Corporation) equipped with an inkjet recording head “KJ4B-YH06WST-STDV” (manufactured by KYOCERA Corporation) was filled with the inkjet inks obtained in the Examples and Comparative Examples.
The following conditions were set: head voltage 26 V, frequency 4 kHz, ejection liquid amount 12 pl, head temperature 32° C., resolution 600 dpi, and negative pressure −4.0 kPa.
A recording medium, a corona-treated PET film (Taiko Polyester Film FE2001, manufactured by Futamura Chemical Co., Ltd.), was fixed to a conveying table so that the longitudinal direction of the recording medium was the same as the conveying direction.
A print command was transferred to the print evaluation device, and a solid image was printed on the recording medium with the inkjet ink by the inkjet recording method at a deposition amount of 100% (12 pl, 600 x 600 dpi).
Immediately afterwards, the film was dried in a dryer at 70° C. for 10 seconds.

The following physical properties were examined using the images obtained. The results are shown in Table 1. Any physical property rated "x" was deemed to be unsatisfactory.

(1) Discharge stability (image uniformity)
The solid image was visually observed and the uniformity of the image was evaluated according to the following criteria.
.circle.: No white streaks or color unevenness occurred in the solid image.
A: Some white streaks are observed in the solid image.
x: White streaks and color unevenness are noticeable in solid images.

(2) Blocking Resistance A piece of PET that had not been corona-treated was placed on the printed surface of a solid image printed on the surface of the printed material, and a load of 2 N/ ^cm2 was applied at 25° C. for 1 hour. The two pieces were then quickly peeled off, and the blocking resistance was evaluated according to the following criteria.
◎: No resistance at all ○: Almost no resistance ×: Significant resistance

(3) Scratch resistance (adhesion)
A print having a solid image printed thereon was rubbed with a fingernail, and scratch resistance (adhesion) was evaluated according to the following criteria.
⊚: The printed surface does not peel off at all.
◯: Almost no peeling of the printed surface occurs.
×: Printed surface peels off.

The results in Table 1 show that the inkjet inks of the examples have superior ejection stability and blocking resistance of the formed images compared to the inkjet inks of the comparative examples.

According to the inkjet ink of the present invention, it is possible to provide an inkjet ink having excellent ejection stability and blocking resistance of the formed image. The inkjet ink of the present invention is particularly suitable for printing on recording media for commercial printing using polyester films such as polyethylene terephthalate (PET), polyvinyl chloride films, polypropylene films such as biaxially oriented polypropylene film (OPP), polyethylene films, nylon films, and other films made of non-absorbent resins.

Claims (7)

a nonionic water-soluble polymer compound containing an amide bond;
Resin emulsion particles;
Water,
and an organic solvent,
the nonionic water-soluble polymer compound containing an amide bond is polyvinylpyrrolidone having a weight-average molecular weight of 5,000 to 500,000;
the organic solvent comprises at least one selected from the group consisting of propylene glycol, diethylene glycol, triethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, and diethylene glycol monoisobutyl ether;
the total content of the organic solvents is 10% by mass or more and 60% by mass or less, based on 100% by mass of the ink-jet ink;
The minimum film-forming temperature is 40° C. or less,
Further, the composition contains a polyether-modified silicone surfactant ,
An ink-jet ink that is a water-based ink-jet ink for non-liquid-absorbing films. 2. The ink-jet ink according to claim 1, wherein the content of the nonionic water-soluble polymer compound containing an amide bond is 0.05 to 10% by mass. The ink-jet ink according to claim 1 or 2, wherein the resin emulsion particles contain a (meth)acrylic polymer. 4. The ink-jet ink according to claim 1, wherein the resin emulsion particles have an acid value derived from a carboxyl group of 0 to 6 mgKOH/g. Further containing a pigment,
5. The ink-jet ink according to claim 1, wherein the amount of the pigment per 100 parts by mass of the non-volatile content of the ink-jet ink is 50 parts by mass or more and 90 parts by mass or less. Further comprising a dispersant,
6. The ink-jet ink according to claim 1, wherein the content of the dispersant is from 0.1% by mass to 2.0% by mass, both inclusive, relative to 100% by mass of the ink-jet ink. The ink-jet ink according to any one of claims 1 to 6, wherein the non-volatile content of the ink-jet ink is 5% by mass or more and 50% by mass or less.