JP7139779B2 - Inkjet ink and printed matter - Google Patents

Description

In addition to general printing substrates, the present invention has good printability and abrasion resistance particularly on highly hydrophobic substrates such as coated paper, art paper, vinyl chloride sheets, etc., and ink jet nozzles. The present invention relates to an inkjet ink excellent in clogging resistance and a printed matter using the ink.

In order to form a clear image by high-speed printing, which is required in recent years, it is necessary to improve the drying property after the water-based IJ ink lands on the recording medium. The ink drying mechanism is classified into evaporation and penetration into the recording medium. Inkjet ink contains a high-boiling water-soluble solvent, which is positioned as a moisturizing agent for the purpose of preventing the nozzle from drying out. There was a limit to increasing the speed, and the contribution of permeability to the recording medium was very large.
If the penetration into the recording medium is slow, a large amount of ink will remain on the paper surface, resulting in color unevenness, and in the case of multi-color printing, the inks will be mixed. In particular, non-absorbent or non-absorbent recording media, such as coated paper, art paper and vinyl chloride sheets, are slow to absorb ink and tend to cause color unevenness and color mixture.

Patent Document 1 discloses that the addition of a high-boiling-point water-soluble solvent that is highly permeable to a recording medium prevents the nozzle from drying out and improves the permeation to the recording medium, thereby improving printability. there is

Patent Document 2 discloses the use of a polymer having an amine oxide structure as a carbon dispersant. However, there is no description of applying these dispersants as dispersants for inkjet inks.

Patent Document 3 discloses that an ink composition containing an amine oxide compound does not cause nozzle clogging and is excellent in dispersion stability, water resistance and washing resistance. Patent Literature 4 discloses that an ink composition containing an amine oxide compound prevents non-ejection and curving in the ejection direction during re-ejection after suspension of ejection. Further, Patent Document 5 discloses that an inkjet ink using a dye, an alcohol-based organic solvent, and an amidoamine oxide compound has excellent resolubility and dissolution stability even after being placed in a low-temperature environment. there is

JP 2012-188582 A JP 2010-119949 A JP-A-2000-063718 JP 2012-180425 A JP 2017-008199 A

However, since solvents with high penetrability are generally water-soluble solvents with high hydrophobicity, the use of these solvents desorbs the dispersant from the pigment and causes pigment aggregation. In Patent Document 1, in order to strongly adsorb a dispersant even when a penetrating solvent is added and to keep the pigment dispersibility stable, a highly hydrophobic pigment dispersing resin containing a long alkyl chain is used to prevent pigment aggregation. However, due to the use of a highly hydrophobic dispersing resin, once the ink dries, the re-solubility in water or a water-soluble solvent becomes low, and the nozzle clogging resistance of the inkjet ink may be poor.

In addition, when a large amount of amine oxide low-molecular-weight compound is added to improve nozzle clogging after being left for a long time, pigment dispersibility is impaired and liquid viscosity increases, causing nozzle clogging and deterioration of storage stability. easier. Furthermore, since it is a low-molecular-weight compound, it is difficult to adjust the surface tension of the ink, resulting in poor print quality. There is

An object of the present invention is to provide an IJ ink for inkjet recording, which has excellent printability on general printing substrates, and particularly printability and scratch resistance on non-water-absorbent or water-absorbent recording media. To provide a water-based ink jet ink which is excellent in clogging property of ink jet nozzles.

The present application relates to the following inventions [1] to [8].

[1] An inkjet ink containing a colorant (A), an amine oxide group-containing acrylic polymer (B), and a water-soluble organic solvent (C).

[2] The inkjet ink of [1], wherein the amine oxide group-containing acrylic polymer (B) has at least one structure represented by the following general formulas 1 to 3.

[In general formulas 1 to 3,
X is a divalent linking group;
y is 0 or 1;
R ¹ is an alkylene group having 1 to 6 carbon atoms,
R ² and R ³ are each independently an alkyl group having 1 to 4 carbon atoms;
R ⁴ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms;
Four of R ⁵ to R ⁹ each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and one of R ⁵ to R ⁹ represents the main chain of the amine oxide group-containing acrylic polymer. represents the bonding position with
* represents the bonding position with the main chain of the amine oxide group-containing acrylic polymer. ]

[3] The inkjet ink of [1] or [2], wherein the amine oxide group-containing acrylic polymer (B) contains the monomer (b2) and the monomer (b3) as monomers constituting the polymer.
Monomer (b2): Aromatic ring-containing monomer Monomer (b3): Alkyl group-containing monomer having 4 to 24 carbon atoms (excluding those containing an aromatic ring or an acidic group)

[4] The inkjet ink of [3], wherein the amine oxide group-containing acrylic polymer (B) further contains a monomer (b4) as a monomer constituting the polymer.
Monomer (b4): acidic group-containing monomer

[5] The inkjet ink of any one of [1] to [4], wherein the amine oxide group-containing acrylic polymer (B) has a mass average molecular weight of 1,500 to 150,000.

[6] The inkjet ink of any one of [1] to [5], wherein the colorant (A) contains an organic pigment.

[7] The inkjet ink of any one of [1] to [6], wherein the water-soluble organic solvent (C) contains at least one selected from the group consisting of glycol ethers and diols.

[8] A printed material obtained by printing the inkjet ink of any one of [1] to [7] on a recording medium.

According to the present invention, a water-based ink which has good printability and scratch resistance on recording media such as general printing substrates, particularly non-water-absorbing substrates or low-water-absorbing substrates, and excellent resistance to clogging of inkjet nozzles. An inkjet ink and a printed matter using the same can be provided.

The inkjet ink (hereinafter also referred to as IJ ink) of the present invention will be described below with reference to preferred embodiments.

<Colorant (A)>
The IJ ink of the present invention contains a colorant. As the coloring agent, it is possible to appropriately select and use conventionally known ones such as organic pigments, inorganic pigments, special pigments, and dyes, and pigments are preferably used. The IJ ink of the present invention contains a pigment in a range of 0.1% by mass to 20% by mass, more preferably 0.1% by mass to 12% by mass, based on the total mass of the ink. It is preferable that the In the present invention, the following pigments can be used.

[Organic pigment]
Examples of yellow pigments that can be used in the present invention include C.I. I. Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 20, 24, 74, 83, 86, 93, 94, 95, 109, 110, 117, 120, 125, 128, 137, 138, 139, 147, 148, 150, 151, 154, 155, 166, 168, 180, 185, 213 and the like.
Examples of magenta pigments include C.I. I. Pigment Red 5, 7, 9, 12, 31, 48, 49, 52, 53, 57, 97, 112, 122, 147, 149, 150, 168, 177, 178, 179, 202, 206, 207, 209, 238, 242, 254, 255, 269, C.I. I. Pigment Violet 19, 23, 29, 30, 37, 40, 50 and the like.
Cyan pigments include, for example, C.I. I. Pigment Blue 1, 2, 3, 15:3, 15:4, 16, 22, C.I. I. Vat Blue 4, 6 and the like.
Furthermore, organic pigments of colors other than those described above can also be used. Including such cases, any pigment may be used alone in each color ink, or two or more pigments may be mixed. Of course, the present invention is not limited to these. In addition to the above, self-dispersing pigments and the like can also be used.

[Inorganic pigment]
Examples of inorganic pigments that can be used in the present invention include coloring pigments such as red iron oxide, antimony red, cadmium yellow, cobalt blue, ultramarine blue, and prussian blue, and extender pigments such as calcium carbonate, kaolin, clay, and sulfuric acid. Barium, aluminum hydroxide, talc and the like can be mentioned.
White pigments such as zinc oxide (C.I. Pigment White 4), litbon (C.I. Pigment White 5), titanium oxide (C.I. Pigment White 6), zinc sulfide (C.I. Pigment White 7 ), zirconium oxide (C.I. Pigment White 12), calcium carbonate (C.I. Pigment White 18), hydrous aluminum silicate (C.I. Pigment White 19), barium sulfate (C.I. Pigment White 21, 22), alumina white (CI Pigment White 24), talc (CI Pigment White 26), anhydrous/hydrous silicic acid (Pigment White 27), and hydrated calcium silicate (Pigment White 28).

Examples of black pigments include carbon black produced by the furnace method and the channel method. For example, these carbon blacks have a primary particle diameter of 11 to 40 mμm (nm), a specific surface area by the BET method of 50 to 400 m ² /g, a volatile content of 0.5 to 10% by mass, and a pH value of 2 to 2. Those with properties such as 10 are preferred. Commercially available products having such properties include the following. For example, No. 33, 40, 45, 52, 900, 2200B, 2300, MA7, MA8, MCF88 (manufactured by Mitsubishi Chemical), RAVEN1255 (manufactured by Columbian Carbon), REGAL330R, 400R, 660R, MOGUL L, ELFTEX415 (manufactured by Cabot) ), Nipex 90, Nipex 150T, Nipex 160IQ, Nipex 170IQ, Nipex 75, Printex 85, Printex 95, Printex 90, Printex 35, Printex U (manufactured by Evonik Degussa) and the like, any of which can be preferably used.

[Other coloring agents]
(dye)
In the present invention, dyes may be used in combination with pigments. Dyes that can be used include, but are not limited to, acid dyes, direct dyes, basic dyes, reactive dyes, and food dyes in the color index, and those having a carboxyl group or sulfo group in the molecule. Any substance may be used as long as it is contained and substantially dissolved in the ink.

Specific examples of these dyes include C.I. I. Acid Yellow 17, 23, 42, 44, 79, 142, C.I. I. acid red 1, 8, 13, 14, 18, 26, 27, 35, 37, 42, 52, 82, 87, 89, 92, 97, 106, 111, 114, 115, 134, 186, 249, 254, 289, C.I. I. Acid Blue 9, 29, 45, 92, 249, C.I. I. Acid Black 1, 2, 7, 24, 26, 94, etc.

As a direct dye C.I. I. Direct Yellow 1, 12, 24, 26, 33, 44, 50, 86, 120, 132, 142, 144, C.I. I. direct red 1, 4, 9, 13, 17, 20, 28, 31, 39, 80, 81, 83, 89, 225, 227, C.I. I. Direct Blue 1, 2, 6, 15, 22, 25, 71, 76, 79, 86, 87, 90, 98, 163, 165, 199, 202, C.I. I. Direct Black 19, 22, 32, 38, 51, 56, 71, 74, 75, 77, 154, 168, 171, and the like.

C.I. I. basic yellow 1, 2, 11, 13, 14, 15, 19, 21, 23, 24, 25, 28, 29, 32, 36, 40, 41, 45, 49, 51, 53, 63, 64, 65, 67, 70, 73, 77, 87, 91, C.I. I. Basic Red 2, 12, 13, 14, 15, 18, 22, 23, 24, 27, 29, 35, 36, 38, 39, 46, 49, 51, 52, 54, 59, 68, 69, 70, 73, 78, 82, 102, 104, 109, 112, C.I. I, basic blue 1, 3, 5, 7, 9, 21, 22, 26, 35, 41, 45, 47, 54, 62, 65, 66, 67, 69, 75, 77, 78, 89, 92, 93, 105, 117, 120, 122, 124, 129, 137, 141, 147, 155, basic violet 1, 3, 10, C.I. I. basic black 2, 8, etc.;

Water-soluble dyes include, but are not limited to, phenols, naphthols, anilines, pyrazolones, pyridones, thiazoles, open-chain active methylene compounds, pyrazolotriazoles, pyrrolotriazoles, and the like. An aryl or heteryl azo dye or an azomethine dye containing a water-soluble group represented by a carboxyl group or a sulfo group in the molecule and substantially soluble in the ink may be used.

<Amine oxide group-containing acrylic polymer (B)>
The IJ ink of the present invention contains an amine oxide group-containing acrylic polymer (B). By using a polymer having an amine oxide structure, even if it is added to an ink containing a highly hydrophobic water-soluble solvent, the dispersibility of the colorant, storage stability, print quality of the printed matter, abrasion resistance, It exerts a remarkable effect of suppressing clogging of the inkjet head due to its moisturizing effect without impairing the water resistance.

The amine oxide group-containing acrylic polymer (B) preferably contains at least one of the structures represented by the following general formulas 1 to 3, and particularly preferably contains a structure represented by the general formula 1. .

[In general formulas 1 to 3,
X is a divalent linking group;
y is 0 or 1;
R ¹ is an alkylene group having 1 to 6 carbon atoms,
R ² and R ³ are each independently an alkyl group having 1 to 4 carbon atoms;
R ⁴ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms;
Four of R ⁵ to R ⁹ each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and one of R ⁵ to R ⁹ represents the main chain of the amine oxide group-containing acrylic polymer. represents the bonding position with
* represents the bonding position with the main chain of the amine oxide group-containing acrylic polymer. ]

The amine oxide group-containing acrylic polymer (B) may be an acrylic polymer containing a structural unit containing an amine oxide group, and can be obtained using a conventionally known method. preferable.
(1) Acrylic copolymers of amine oxide group-containing monomers and other monomers.
(2) Copolymers of amine oxides of tertiary amino groups in the tertiary amino group-containing monomer (b1) and other monomers.
(3) Amine oxides of tertiary amino groups in copolymers of the tertiary amino group-containing monomer (b1) and other monomers.

(2) or (3) is preferable, and (3) is more preferable, from the viewpoint of availability of raw material monomers and reduction of side reaction products. The reaction of a tertiary amino group with an amine oxidizing agent (hereinafter also referred to as an oxidizing agent) is hereinafter also referred to as "oxidation".

The amine oxide group-containing acrylic polymer (B) using the tertiary amino group-containing monomer (b1), other monomers, and an oxidizing agent is described below. A monomer is a monomer that constitutes a (meth)acrylic polymer, and is also simply referred to as a monomer.

[Tertiary amino group-containing monomer (b1)]
The tertiary amino group-containing monomer (b1) may have a tertiary amino group, and among them, those containing the structures of the above-mentioned general formulas 1 to 3 are preferable.
As a monomer that forms the structure of general formula 1,
For example, N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, N,N-diethylaminopropyl (meth)acrylate, N, N-dimethylaminoethyl (meth)acrylamide, N,N-diethylaminoethyl (meth)acrylamide, N,N-dimethylaminopropyl (meth)acrylamide, N,N-diethylaminopropyl (meth)acrylamide, N,N-dimethylamino vinyl propionate, vinyl N,N-diethylaminopropionate, N,N-dimethylallylamine, p-dimethylaminomethylstyrene, p-dimethylaminoethylstyrene, p-diethylaminomethylstyrene, p-diethylaminoethylstyrene, N,N- dimethylvinylamine, N,N-diethylvinylamine, N,N-diphenylvinylamine,
Alternatively, reaction products of unsaturated group-containing acid anhydrides such as maleic anhydride, itaconic anhydride and citraconic anhydride with N,N-dimethyl-1,3-propanediamine and the like,
Examples include reaction products of epoxy group-containing unsaturated compounds such as glycidyl (meth)acrylate and N,N-dimethyl-1,3-propanediamine.

As a monomer that forms the structure of general formula 2,
For example -2-vinylpyridine, 3-vinylpyridine, 4-vinylpyridine-2-methyl-3-vinylpyridine-2-methyl-4-vinylpyridine, 3-methyl-4-vinylpyridine-2-methyl-5- Vinylpyridine, 3-methyl-5-vinylpyridine, 4-methyl-5-vinylpyridine-2-lauryl-4-vinylpyridine-2-lauryl-5-vinylpyridine-2-(t-butyl)-4-vinyl and pyridine-2-(t-butyl)-5-vinylpyridine.

As a monomer that forms the structure of general formula 3,
For example, 1-vinylimidazole-2-methyl-1-vinylimidazole, 4-methyl-1-vinylimidazole, 5-methyl-1-vinylimidazole-2-lauryl-1-vinylimidazole, 4-(t-butyl) -1-vinylimidazole and the like.

[Oxidation]
In the case of (2) above, a solution containing a tertiary amino group-containing monomer (b1), in the case of (3) above, a copolymer containing a tertiary amino group-containing monomer (b1) in the copolymer composition The tertiary amino group can be oxidized by adding an oxidizing agent to the solution containing and reacting at 20° C. to 100° C. for 0.1 to 100 hours, preferably 1 to 100 hours.

As the oxidizing agent, an oxidizing agent such as peroxide or ozone is used.
Examples of peroxides include hydrogen peroxide, ammonium persulfate, sodium persulfate, peracetic acid, metachloroperbenzoic acid, benzoyl peroxide, t-butyl hydroperoxide, etc. Hydrogen peroxide is preferred, and is usually an aqueous solution. used in the form Since the peroxide also functions as a radical generator, it is preferable to oxidize the copolymer containing the tertiary amino group-containing monomer (b1) in the copolymerization composition after polymerization. Generally, the amount of the oxidizing agent used is 0.2 to 3 times the molar equivalent of the oxidizable functional group, that is, the tertiary amino group, and further 0.5 to 2 times the molar equivalent. It is more preferred to use molar equivalents.
The obtained amine oxide group-containing acrylic polymer (B) can also be used after treating the residual peroxide by a known method. Specific examples include reducing agent addition treatment, ion exchange treatment, activated carbon treatment, treatment with a metal catalyst, and the like.

The amine oxide group-containing acrylic polymer (B) preferably contains the following monomer (b2) and monomer (b3) as other monomers in the copolymer composition. Moreover, it is preferable to further include a monomer (b4) in the copolymer composition. By using the above monomers (b2) to (b4), the effect of further enhancing the dispersibility, storage stability, printability and water resistance of the printed matter, and ejection property of the IJ ink is exhibited.
Monomer (b2): Aromatic ring-containing monomer Monomer (b3): Alkyl group-containing monomer having 4 to 24 carbon atoms (excluding those containing an aromatic ring or an acidic group)
Monomer (b4): a monomer having an acidic group

[Other monomers]
(Monomer (b2): aromatic ring-containing monomer)
The monomer (b2) strengthens the π-π interaction between the amine oxide group-containing acrylic polymer (B) and the colorant (A), and exhibits a very strong adsorption force to the colorant and stabilization in the ink. to enable. As a result, the amine oxide group-containing acrylic polymer (B) does not desorb from the colorant (A) into the ink, and is able to maintain strong colorant adsorption, allowing the stable state in the ink to be maintained for a long period of time. can be maintained.
Specific examples of the monomer (b2) include styrene, α-methylstyrene-2-methylstyrene, chlorostyrene, benzyl (meth)acrylate-2-(meth)acryloyloxyethyl phthalate-2-(meth)acryloyloxy Ethyl-2-hydroxyethyl phthalate-2-(meth)acryloyloxypropyl phthalate, EO-modified cresol (meth)acrylate, neopentyl glycol benzoate (meth)acrylate, nonylphenoxypolyethylene glycol (meth)acrylate, nonylphenoxypolypropylene glycol ( meth) acrylate, paracumylphenoxyethylene glycol (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxy polyethylene glycol (meth) acrylate, EO-modified tribromophenyl (meth) acrylate, EO-modified phthalate (meth) acrylate, ethoxylation orthophenylphenol (meth)acrylate, naphthyloxypolyethylene glycol (meth)acrylate, vinylnaphthalene, vinylcarbazole and the like.

(Monomer (b3): Alkyl group-containing monomer having 4 to 24 carbon atoms (excluding those containing an aromatic ring or an acidic group))
The monomer (b3) has an alkyl group with 4 or more and 24 or less carbon atoms and has a high hydrophobic interaction. Therefore, by using it together with the monomer (b2), very strong colorant adsorption and stabilization in the ink can be achieved, and the stable state in the ink can be maintained for a long period of time.
Specific examples of the monomer (b3) include vinyl laurate, vinyl palmitate, vinyl stearate, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, butyl (meth)acrylate, pentyl (meth)acrylate, heptyl (meth)acrylate-2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, undecyl ( meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate ) acrylate or behenyl (meth)acrylate.
From the viewpoint of versatility and polymerizability, it is particularly preferable to select (meth)acrylic acid alkyl esters such as lauryl (meth)acrylate, stearyl (meth)acrylate, and behenyl (meth)acrylate. Further, the number of carbon atoms for further improving the stability is preferably in the range of 12 or more and 24 or less, more preferably in the range of 18 or more and 24 or less.

(Monomer (b4): acidic group-containing monomer)
The amine oxide group-containing acrylic polymer (B) preferably further contains an acidic group-containing monomer (b4) in the copolymer composition.
Specific examples of the monomer (b4) include maleic acid, fumaric acid, itaconic acid, citraconic acid, or alkyl or alkenyl monoesters thereof, β-(meth)acryloxyethyl phthalate monoester, β-isophthalate ( meth)acryloxyethyl monoester, terephthalic acid β-(meth)acryloxyethyl monoester, succinic acid β-(meth)acryloxyethyl monoester, acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, vinylsulfonic acid , Nt-butylacrylamidesulfonic acid-2-acrylamido-2-methylpropanesulfonic acid, EO-modified phosphoric acid (meth)acrylate, and the like. Carboxylic acid-containing (meth)acrylates are preferred, and those containing acrylic acid or methacrylic acid are more preferred in order to improve storage stability in ink and water resistance of printed matter.

Various organic amines such as aqueous ammonia, dimethylaminoethanol, diethanolamine and triethanolamine can be used as the neutralizing agent for neutralizing the acidic groups of the monomer (b4). Dimethylaminoethanol has a high boiling point and is particularly preferred from the viewpoint of ink ejection properties. The copolymer after neutralization is dispersed or dissolved in an aqueous liquid medium.

(Other monomer (b5))
The amine oxide group-containing acrylic polymer (B) may contain a monomer (b5) other than the monomers (b2) to (b4) described above in the copolymer composition.
Other monomers (b5) include alkyl (meth)acrylates having 1 to 3 carbon atoms such as methyl (meth)acrylate, ethyl (meth)acrylate and propyl (meth)acrylate;
α-olefinic ethylenically unsaturated monomers such as 1-propylene;
2-hydroxyethyl (meth)acrylate-2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate-2-(meth)acryloyloxyethyl-2-hydroxyethyl phthalate, glycerol mono(meth)acrylate , 4-hydroxyvinylbenzene, 1-ethynyl-1-cyclohexanol, monomers having a hydroxyl group such as allyl alcohol;
(Meth)acrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, N-methoxymethyl-(meth)acrylamide, N-ethoxymethyl-(meth)acrylamide, N-propoxymethyl-(meth)acrylamide, N -butoxymethyl-(meth)acrylamide, N-pentoxymethyl-(meth)acrylamide, N,N-di(methoxymethyl)acrylamide, N-ethoxymethyl-N-methoxymethylmethacrylamide, N,N-di(ethoxy methyl)acrylamide, N-ethoxymethyl-N-propoxymethylmethacrylamide, N,N-di(propoxymethyl)acrylamide, N-butoxymethyl-N-(propoxymethyl)methacrylamide, N,N-di(butoxymethyl) Acrylamide, N-butoxymethyl-N-(methoxymethyl)methacrylamide, N,N-di(pentoxymethyl)acrylamide, N-methoxymethyl-N-(pentoxymethyl)methacrylamide, monomers having an acrylamide group ;
(Meth)acrylic acid dimethylaminoethylmethyl chloride salt, trimethyl-3-(1-(meth)acrylamido-1,1-dimethylpropyl)ammonium chloride, trimethyl-3-(1-(meth)acrylamidopropyl)ammonium chloride, and a monomer having a chloride salt such as trimethyl-3-(1-(meth)acrylamido-1,1-dimethylethyl)ammonium chloride;

Polyethylene glycol (meth)acrylate, methoxypolyethyleneglycol (meth)acrylate, ethoxypolyethyleneglycol (meth)acrylate, propoxypolyethyleneglycol (meth)acrylate, n-butoxypolyethyleneglycol (meth)acrylate, n-pentoxypolyethyleneglycol (meth)acrylate Acrylate, phenoxy polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, methoxypolypropylene glycol (meth) acrylate, ethoxy polypropylene glycol (meth) acrylate, propoxy polypropylene glycol (meth) acrylate, n-butoxy polypropylene glycol (meth) acrylate , n-pentoxypolypropylene glycol (meth)acrylate, phenoxypolypropylene glycol (meth)acrylate, polytetramethylene glycol (meth)acrylate, methoxypolytetramethylene glycol (meth)acrylate, phenoxytetraethylene glycol (meth)acrylate, hexaethylene Monomers having a polyether chain such as glycol (meth)acrylate and methoxyhexaethylene glycol (meth)acrylate;
Alkoxy (meth) acrylates such as methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, propoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, ethoxypropyl (meth) acrylate;
aromatic ester (meth)acrylates such as phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate;

Allyl (meth)acrylate, 1-methylallyl (meth)acrylate, 2-methylallyl (meth)acrylate, 1-butenyl (meth)acrylate, 2-butenyl (meth)acrylate, 3-(meth)acrylate butenyl, 1,3-methyl-3-butenyl (meth)acrylate, 2-chloroallyl (meth)acrylate, 3-chloroallyl (meth)acrylate, o-allylphenyl (meth)acrylate, (meth)acrylic acid 2-(allyloxy)ethyl, allyllactyl (meth)acrylate, citronellyl (meth)acrylate, geranyl (meth)acrylate, rhodinyl (meth)acrylate, cinnamyl (meth)acrylate, diallyl maleate, diallyl itaconic acid, Ethylenically unsaturated group-containing (meth)acrylates such as vinyl (meth)acrylate, vinyl crotonate, vinyl oleate, vinyl linolenate, and 2-(2'-vinyloxyethoxy)ethyl (meth)acrylate ;
Perfluoromethylmethyl (meth)acrylate, perfluoroethylmethyl (meth)acrylate-2-perfluorobutylethyl (meth)acrylate-2-perfluorohexylethyl (meth)acrylate-2-perfluorooctylethyl (meth)acrylate -2-perfluoroisononylethyl (meth)acrylate -2-perfluorononylethyl (meth)acrylate -2-perfluorodecylethyl (meth)acrylate, perfluoropropylpropyl (meth)acrylate, perfluorooctylpropyl (meth)acrylate ) Perfluoroalkyl group-containing ethylenically unsaturated monomers having a perfluoroalkyl group having 1 to 20 carbon atoms such as acrylate, perfluorooctyl amyl (meth) acrylate, perfluorooctyl undecyl (meth) acrylate;

A (meth)acrylate monomer having a polymer structure in a side chain such as an ethylenically unsaturated compound having a polyester chain such as a lactone-modified (meth)acrylate;
(meth) nitrile group-containing ethylenically unsaturated monomers such as acrylonitrile;
Fatty acid vinyl compounds such as vinyl acetate, vinyl butyrate, vinyl propionate, vinyl hexanoate, vinyl caprylate, vinyl laurate, vinyl palmitate and vinyl stearate; Ammer;
allyl monomers such as allyl acetate and allyl cyanide;
vinyl monomers such as vinyl cyanide, vinylcyclohexane, vinyl methyl ketone;
Ethynyl monomers such as acetylene and ethynyltoluene;
Perfluoroalkyl groups such as perfluorobutylethylene, perfluorohexylethylene, perfluorooctylethylene, perfluorodecylethylene, perfluoroalkyl group-containing ethylenically unsaturated compounds such as alkylenes, etc. a monomer having an unsaturated bond;
etc., and one or more of these groups can be used.

[Production of amine oxide group-containing acrylic polymer (B)]
The amine oxide group-containing acrylic polymer (B) is preferably a tertiary amino group-containing monomer (b1) or an amine oxide product of the tertiary amino group-containing monomer (b1), and optionally a monomer (b2), a monomer ( After copolymerizing b3) or monomer (b4) or the like to obtain a copolymer, the acid group derived from monomer (b4) is neutralized with a neutralizing agent and used.
By having an acid group neutralized with an amine in the amine oxide group-containing acrylic polymer (B), while contributing to waterability, the coloring agent in the ink is enhanced by stronger charge repulsion than the amine oxide structure. Stabilization can also be achieved. In addition, the neutralizing agent volatilizes and returns to acid groups in the drying process after printing, thereby improving the hydrophobicity of the amine oxide group-containing acrylic polymer (B) and improving the water resistance of the printed matter.

(Composition ratio of monomers (b2) to b4)
The composition ratio ((b2):(b3):(b4):(b1)) of the monomers constituting the amine oxide group-containing acrylic polymer (B) is
preferably 0-50:0-65:0-50:1-95,
more preferably 1-40:1-55:1-45:1-70,
Especially preferred is 5-35:10-55:5-45:1-60.
Further, when the total amount of monomers is 100% by mass, the total amount of monomers (b2) to (b1) is preferably 70% by mass or more. When the amount is 70% by mass or more, the dispersibility of the colorant in the ink, the long-term storage stability, and the suppression of clogging of the inkjet nozzle are improved.

(Weight average molecular weight and acid value of amine oxide group-containing acrylic polymer (B))
The weight average molecular weight of the amine oxide group-containing acrylic polymer (B) is preferably 2,000 to 300,000, more preferably 5,000 to 150,000. When the amine oxide group-containing acrylic polymer (B) is obtained by copolymerizing a monomer having an acid group (monomer (b4)), the amine oxide group-containing acrylic polymer (B) calculated from the composition ratio of the monomer (b4) is preferably 50 to 600 mgKOH/g, more preferably 100 to 500 mgKOH/g. When the acid value of the amine oxide group-containing acrylic polymer (B) is 50 mgKOH/g or more, the amine oxide group-containing acrylic polymer (B) is easily soluble in water, and the colorant stability and storage stability of the IJ ink are improved. Further, ejection stability is improved. Moreover, when it is 600 mgKOH/g or less, the adhesion of the amine oxide group-containing acrylic polymer (B) to the surface of the colorant is improved, and the storage stability of the IJ ink is improved. The weight average molecular weight and acid value of the amine oxide group-containing acrylic polymer (B) in the present invention can be measured by conventional methods.

The obtained amine oxide group-containing acrylic polymer (B) can be used as it is, but if necessary, the amine oxide group-containing copolymer can be isolated and purified by known methods such as reprecipitation and solvent distillation before use. You can also Moreover, the amine oxide group-containing acrylic polymer (B) may be used alone, or a plurality of types may be used in combination. Furthermore, a commercially available dispersing resin may be used in combination.

In the present invention, other methods for introducing amine oxide groups into the amine oxide group-containing acrylic polymer (B) include, for example, epoxy group-containing unsaturated compounds such as glycidyl (meth)acrylate and 2-isocyanatoethyl (meth)acrylate. A copolymer obtained by using a reaction product of an isocyanate group-containing unsaturated compound such as hydroxyethyl-N,N-dimethylamine oxide and an amine oxide group-containing compound such as hydroxyethyl-N,N-dimethylamine oxide can also be used.

[Content of amine oxide group-containing acrylic polymer (B)]
In the IJ ink of the present invention, the content of the amine oxide group-containing acrylic polymer (B) is preferably 3% by mass or more and 70% by mass or less, more preferably 5% by mass or more and 60% by mass, based on the total mass of the pigment in the ink. % by mass or less, particularly preferably 10% by mass or more and 45% by mass or less. Moreover, the content of the amine oxide group-containing acrylic polymer (B) is preferably 0.1% by mass or more and 8% by mass or less with respect to the total mass of the ink.

When the amine oxide group-containing acrylic polymer (B) is used in combination with another dispersing resin such as a commercially available dispersing resin, the content of the amine oxide group-containing acrylic polymer (B) is the same as that of the amine oxide group-containing acrylic polymer (B). is preferably 5% by mass or more, more preferably 10% by mass or more, based on the total amount of the dispersion resin.

In the IJ ink of the present invention, if necessary, natural resins such as rosin, shellac and starch, and synthetic resins other than the above-mentioned amine oxide group-containing acrylic polymer (B) can be preferably used. In this case, the natural resin or synthetic resin is preferably contained in an amount that does not exceed the amount of the pigment dispersing resin added.

<Water-soluble organic solvent (C)>
The IJ ink of the present invention contains a water-soluble organic solvent (C). More preferably, it is a mixed medium with water, and the water is preferably ion-exchanged water (deionized water). Although the water-soluble organic solvent (C) is not particularly limited, it is preferably at least one selected from glycol ethers and diols. Since these solvents have high boiling points and function as moisturizing agents, the ejection stability of the ink is improved.

[Diols]
Specific examples of diols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1-2-butanediol, 1-2-pentanediol, 1-2-hexanediol, 1- 2-heptanediol, 1-2-octanediol, and the like.

[Glycol ethers]
Specific examples of glycol ethers include ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, ethylene glycol monopropyl ether, diethylene glycol mono Propyl ether, triethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, diethylene glycol monoisopropyl ether, triethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, ethylene glycol monopentyl ether, diethylene glycol monopentyl ether, triethylene glycol monopentyl ether, ethylene glycol monohexyl ether, diethylene glycol monohexyl ether, triethylene glycol monohexyl ether, ethylene glycol mono-2-ethylhexyl ether, diethylene glycol mono-2-ethylhexyl ether, triethylene glycol mono-2-ethylhexyl ether, Propylene Glycol Monoethyl Ether, Dipropylene Glycol Monoethyl Ether, Tripropylene Glycol Monoethyl Ether, Propylene Glycol Monopropyl Ether, Dipropylene Glycol Monopropyl Ether, Tripropylene Glycol Monopropyl Ether, Propylene Glycol Monobutyl Ether, Dipropylene Glycol Monobutyl Ether , tripropylene glycol monobutyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, pentaethylene glycol dimethyl ether, triethylene glycol diethyl ether, tetraethylene glycol diethyl ether, pentaethylene glycol diethyl ether, triethylene glycol methyl ethyl ether, tetraethylene glycol Methyl ethyl ether, pentaethylene glycol methyl ethyl ether-2-methoxy-1-propanol, 1-methoxy-2-propanol, 3-methoxy-1-butanol, 3-methoxy-3-methylbutanol, 1-methoxy-2- butanol-2-me Toxy-1-butanol, 3-methoxy-3-methyl-1-butanol and the like.

Among these, the most effective are ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monopentyl ether, diethylene glycol monohexyl ether, and triethylene glycol. Monomethyl Ether, Triethylene Glycol Monoethyl Ether, Triethylene Glycol Monopropyl Ether, Triethylene Glycol Monobutyl Ether, Tetraethylene Glycol Monomethyl Ether, Tetraethylene Glycol Monobutyl Ether, Propylene Glycol Monopropyl Ether, Propylene Glycol Monobutyl Ether, Dipropylene Glycol Monomethyl ether, tripropylene glycol monomethyl ether, 1-2-propanediol, 1,3-propanediol, 1-2-butanediol, 1,3-butanediol, 1-2-pentanediol, 1,5-pentanediol, 1-2-hexanediol, 1,6-hexanediol, and 2-methyl-2,4-pentanediol.

Furthermore, depending on the type of substrate to be printed, water-soluble nitrogen-containing complexes such as -2-pyrrolidone, N-methylpyrrolidone, N-ethylpyrrolidone, N-methyloxazolidinone, and N-ethyloxazolidinone may be used for the purpose of improving the solubility. Ring compounds can also be added.

These water-soluble organic solvents (C) may be used singly or in combination. The content of the above water-soluble organic solvent in the ink is generally in the range of 3% by mass to 60% by mass, more preferably 3% by mass to 50% by mass, based on the total weight of the ink. is in the range of The content of water is in the range of 10% by mass to 90% by mass, more preferably 30% by mass to 80% by mass, based on the total weight of the ink.

The water content is 10% by mass or more and 90% by mass or less, preferably 30% by mass or more and 80% by mass or less, more preferably 40% by mass or more and 70% by mass or less, of the total mass of the ink. is.

<Inkjet ink>
The IJ ink of the present invention preferably further contains a binder resin. The binder resin preferably contains a water-soluble binder resin or an aqueous emulsion. By containing these binder resins, the durability of the printed coating film can be improved. As a result, water resistance, solvent resistance, abrasion resistance, etc. are improved.

(Water-soluble binder resin)
Water-soluble binder resins (hereinafter also referred to as water-soluble resins) are those other than the amine oxide group-containing acrylic polymer (B). Acrylic, vinylnaphthalene-acrylic, vinyl acetate-acrylic, polyurethane, polyester, polyethyleneimine, polyvinylamine, polyacrylamide, polyallylamine, polyethylene oxide, polyvinylpyrrolidone, polyvinyl alcohol, polyvinylacetal, water-soluble cellulose, Examples include proteins such as gelatin and casein, and resins such as starch. As for other water-soluble resins, it is also possible to make them water-soluble by copolymerizing monomers having phosphate groups or sulfonic acid groups, or by copolymerizing monomers containing polyethylene oxide groups in the molecule. is. There is no particular limitation as long as it is a water-soluble resin, and commercially available resins can also be suitably used.

Among the above, a water-soluble resin having a carboxyl group is particularly preferable from the viewpoint of ink storage stability. Examples thereof include acrylic, styrene-acrylic, styrene-maleic acid, vinylnaphthalene-acrylic, and vinyl acetate-acrylic. More preferred are acrylic and styrene-acrylic resins. Furthermore, block polymers are more preferable than random polymers in terms of storage stability of ink and water resistance of printed matter.

The weight average molecular weight of the water-soluble resin is preferably 2,500 to 100,000, more preferably 5,000 to 50,000. The acid value of the water-soluble resin is preferably 30 mgKOH/g or more and 500 mgKOH/g or less, more preferably 35 mgKOH/g or more and 300 mgKOH/g or less.

(Aqueous emulsion)
The aqueous emulsions excluding the amine oxide group-containing acrylic polymer (B) include (meth)acrylic acid resin emulsions, styrene-(meth)acrylic acid resin emulsions, styrene-maleic acid resin emulsions, styrene -butadiene resin emulsion, styrene resin emulsion, butadiene resin emulsion, (meth)acrylic acid ester resin emulsion, vinyl chloride resin emulsion, vinyl acetate resin emulsion and the like.
Among them, styrene-(meth)acrylic acid resin emulsions and (meth)acrylic acid ester resin emulsions are preferable from the viewpoint of image forming properties.

The above binder resins may be used alone or in combination. The content of the binder resin in the ink is preferably 1% by mass or more and 30% by mass or less, more preferably 3% by mass or more and 20% by mass or less, in terms of solid content.

(Additive)
Additives such as surfactants, antifoaming agents, and antiseptics can be added to the IJ ink of the present invention as necessary in order to obtain ink having desired physical properties. An example of the amount of these additives added is 0.05% by mass or more and 10% by mass or less, preferably 0.2% by mass or more and 5% by mass or less, based on the total mass of the ink.

<Manufacture of inkjet ink>
Examples of the method for producing the IJ ink of the present invention include, but are not limited to, the following. First, a coloring agent is added to a mixture containing an amine oxide group-containing acrylic polymer (B) and an aqueous medium containing water, and the mixture is stirred. When the colorant is an organic pigment, a dispersing treatment is performed using a dispersing means described later, and if necessary, a centrifugal separation treatment is performed to obtain a desired pigment dispersion. Next, an additional water-soluble organic solvent (C), a binder resin, a surfactant, and other additive components are added to the pigment dispersion if necessary, stirred, and filtered if necessary to obtain an IJ ink. .

As described above, when a pigment dispersion is used to prepare an IJ ink, premixing is effective before the pigment dispersion treatment. That is, premixing may be performed by adding a pigment to an aqueous medium in which the amine oxide group-containing acrylic polymer (B) and water are mixed. Such a premixing operation is preferable because it can improve the wettability of the pigment surface and promote adsorption of the amine oxide group-containing acrylic polymer (B) to the pigment surface. Premixing is preferably carried out by stirring and mixing with a high-speed mixer or the like until uniform.

The dispersing machine used in the dispersing treatment of the above-described pigment may be any dispersing machine that is generally used, and examples thereof include ball mills, roll mills, sand mills, bead mills, nanomizers, and the like. Among them, a bead mill is preferably used. Examples of such mills include super mill, sand grinder, agitator mill, grain mill, dyno mill, pearl mill and covol mill (all trade names).

Furthermore, in the premixing and dispersion treatment of the pigment described above, even when the amine oxide group-containing acrylic polymer (B) is dissolved or dispersed only in water, it dissolves in a mixed solvent of the water-soluble organic solvent (C) and water. Alternatively, it may be distributed. Especially in the dispersion treatment, the amine oxide group-containing acrylic polymer (B) is dissolved or In some cases, when dispersed, a stable dispersion can be obtained in the process of dispersion treatment.

Since the ink of the present invention is for inkjet recording, it is preferable to use a pigment having an optimum particle size distribution. That is, in order to use the ink containing pigment particles suitably for the ink jet recording method, it is preferable to use a pigment having an optimum particle size distribution from the requirements such as nozzle clogging resistance. Methods for obtaining a pigment having a desired particle size distribution include the following methods. Reducing the size of the grinding media of the disperser as mentioned above, increasing the filling rate of the grinding media, lengthening the processing time, classifying with a filter or centrifuge after grinding, and these There is a method such as a combination of the methods of

<Printed Matter>
A known print medium can be used for the printed matter obtained using the IJ ink of the present invention. Examples of print media include paper media such as high-quality paper, coated paper, art paper, cast paper, synthetic paper, and inkjet paper, and plastic media such as polyvinyl chloride sheets, PET films, and PP films. In addition, a non-water-absorbing substrate or a non-absorbing substrate indicates a recording medium that does not easily absorb water or has a slow absorption speed, and includes paper media such as coated paper, art paper, cast paper, polycarbonate, and hard vinyl chloride. , soft vinyl chloride, polystyrene, styrofoam, PMMA, polypropylene, polyethylene, PET and other plastic substrates, aluminum, stainless steel and other metal substrates, glass, wood, and the like.

EXAMPLES The present invention will be described below based on examples, but the present invention is not limited by these. In the examples, "parts" and "%" represent "mass parts" and "mass%", respectively. Methods for measuring the mass average molecular weight (Mw) and acid value of the polymer are as follows.

(Polymer mass average molecular weight (Mw))
A value measured by gel permeation chromatography (GPC) in terms of standard polystyrene was adopted as the mass average molecular weight (Mw) of the polymer. The measurement apparatus and measurement conditions were based on condition 1 below, and condition 2 was used depending on the solubility of the sample. However, depending on the type of polymer, an appropriate carrier (eluent) and a column compatible with it were selected and used. For other matters, JISK7252-1 to 4:2008 were referred to. For poorly soluble polymer compounds, measurements were made at a soluble concentration under the following conditions.
(Condition 1)
Column: Shodex OHpark SB-800RL
Shodex OHpark SB-800RH
Shodex0Hpark SB-802.5 HQ
Shodex0Hpark SB-806M HQ
was used.
Carrier: Phosphate buffer solution Measurement temperature: 40°C
Sample concentration: 0.2% by mass
Detector: RI (refractive index) detector (Condition 2)
Column: A column formed by connecting two TOSOHTSKgelSuperAWM-H was used.
Carrier: 10 mM LiBr/N-methylpyrrolidone Measurement temperature: 40°C
Carrier flow rate: 1.0 ml/min
Sample concentration: 0.1% by mass
Detector: RI (refractive index) detector Injection volume: 0.1 ml

(Acid value of polymer)
The acid value of the polymer was determined by dissolving 1 g of resin solid content in an aqueous pyridine solution and titrating with an aqueous 0.5N potassium hydroxide solution.

<Method for Producing Amine Oxide Group-Containing Acrylic Polymer (B)>
(Amine oxide group-containing acrylic polymer (B-1))
A reaction vessel equipped with a stirrer, a thermometer, a dropping funnel and a reflux vessel was charged with 99.0 parts of ethyl acetate, and the inside temperature was raised to 75° C. and the inside was sufficiently replaced with nitrogen. A separately prepared mixture of 1.0 parts of 2,2'-azodiisobutyronitrile, 50 parts of N,N-dimethylaminoethyl methacrylate, and 50 parts of ethyl acrylate was heated to 75°C. Dropping was continued for 3 hours while maintaining, and stirring was further continued for 2 hours. After confirming that the conversion rate exceeded 98% by solid content measurement, the mixture was cooled to obtain a copolymer solution having a weight average molecular weight of about 37,000.
Next, 30.9 parts of 35% hydrogen peroxide solution as an oxidizing agent (equimolar amount to the N,N-dimethylaminoethyl methacrylate used) is added to the copolymer solution and reacted at 70° C. for 16 hours. performed oxidation of the amino group. After confirming that the amine oxide conversion rate exceeded 98%, deionized water was added to obtain an aqueous solution of an amine oxide group-containing acrylic polymer (B-1) having a nonvolatile content of 20%. Incidentally, the method disclosed in JP-A-10-182589 was used for the above amine oxide conversion rate.

(Amine oxide group-containing acrylic polymer (B-2))
A reaction vessel equipped with a stirrer, a thermometer, a dropping funnel and a reflux vessel was charged with 99.0 parts of ethyl acetate, and the inside temperature was raised to 75° C. and the inside was sufficiently replaced with nitrogen. A separately prepared mixture of 1.0 parts of 2,2'-azodiisobutyronitrile, 60 parts of N,N-dimethylaminoethyl methacrylate, 20 parts of styrene, and 20 parts of stearyl methacrylate was added to the inside. Dropping was continued for 3 hours while maintaining the temperature at 75° C., and stirring was continued for 2 hours. After confirming that the conversion rate exceeded 98% by measuring the solid content, the mixture was cooled to obtain a copolymer solution having a weight average molecular weight of about 33,000.
Next, to the copolymer solution, 37.1 parts of 35% hydrogen peroxide solution as an oxidizing agent (equimolar amount of N,N-dimethylaminoethyl methacrylate used) is added and reacted at 70° C. for 16 hours. performed oxidation of the amino group. After confirming that the amine oxide conversion rate exceeded 98%, deionized water was added to obtain an aqueous solution of an amine oxide group-containing acrylic polymer (B-2) having a nonvolatile content of 20%.

(Amine oxide group-containing acrylic polymer (B-3))
A reaction vessel equipped with a stirrer, a thermometer, a dropping funnel and a reflux vessel was charged with 99.0 parts of ethyl acetate, and the inside temperature was raised to 75° C. and the inside was sufficiently replaced with nitrogen. Separately prepared 2,2′-azodiisobutyronitrile 1.0 parts, N,N-dimethylaminoethyl methacrylate 5 parts, styrene 15 parts, behenyl acrylate 40 parts, acrylic acid 40.0 parts was added dropwise for 3 hours while maintaining the internal temperature at 75° C., and stirring was further continued for 2 hours. After confirming that the conversion rate exceeded 98% by measuring the solid content, the mixture was cooled to obtain a copolymer solution having a mass average molecular weight of about 34,000 and an acid value of 311 (mgKOH/g).
Next, to the copolymer solution, 3.1 parts of 35% hydrogen peroxide solution as an oxidizing agent (equal molar amount to the N,N-dimethylaminoethyl methacrylate used) is added, and reacted at 70° C. for 16 hours. performed oxidation of the amino group. After confirming that the amine oxide conversion rate exceeded 98%, it was cooled to room temperature.
Next, 49.5 parts of dimethylaminoethanol was added for neutralization. This is the amount for 100% neutralization of acrylic acid. Further, ion-exchanged water was added to obtain an aqueous solution of an amine oxide group-containing acrylic polymer (B-3) having a non-volatile content of 20%.

(Amine oxide group-containing acrylic polymer (B-4 to 11))
Aqueous solutions of amine oxide group-containing acrylic polymers (B-4 to 11) were obtained in the same manner as in (B-1) except that the composition shown in Table 1 was used.

(Acrylic polymer (HB-1))
An aqueous solution of acrylic polymer (HB-1) for comparison was obtained in the same manner as (B-1) except that the composition shown in Table 1 was used. Since (HB-1) does not contain an amine oxide group, the oxidation step was not performed.

Abbreviations in Table 1 are shown below.
St: styrene BzMA: benzyl methacrylate BMA: butyl methacrylate STMA: stearyl methacrylate VA: behenyl acrylate AA: acrylic acid MAA: methacrylic acid DMAEMA: N,N-dimethylaminoethyl methacrylate DEAEMA: N,N-diethylaminoethyl methacrylate DMAPAA: N, N-dimethylaminopropyl acrylamide VP: 2-vinylpyridine VI: 1-vinylimidazole EA: ethyl acrylate HPO: 35% hydrogen peroxide water DMAE: dimethylaminoethanol AIBN: 2,2'-azobis(isobutyronitrile)

<Method for producing binder resin>
(Binder resin 1)
A reaction vessel equipped with a gas inlet tube, a thermometer, a condenser and a stirrer was charged with 93.4 parts of butanol and purged with nitrogen gas. Heat the inside of the reaction vessel to 110 ° C., 70.0 parts of methyl methacrylate, 10.0 parts of lauryl methacrylate, 10.0 parts of stearyl methacrylate, 10.0 parts of methacrylic acid, and V-601 (manufactured by Wako Pure Chemical Industries) 6 0 part of the mixture was added dropwise over 2 hours to carry out a polymerization reaction. After the dropwise addition was completed, the mixture was further reacted at 110°C for 3 hours, then 0.6 parts of V-601 (manufactured by Wako Pure Chemical Industries) was added, and the reaction was further continued at 110°C for 1 hour to obtain a water-soluble resin solution. . The weight average molecular weight of the water-soluble resin was about 15,000.
Furthermore, after cooling to room temperature, 10.4 parts of dimethylaminoethanol was added for neutralization. This is the amount for 100% neutralization of methacrylic acid. Furthermore, 200 parts of water was added to make the solution aqueous. 1 g of this was sampled, dried by heating at 180° C. for 20 minutes, and the non-volatile content was measured. Thus, an aqueous solution of binder resin 1 having a solid content of 30% was obtained.

(Binder resin 2)
A reaction vessel equipped with a stirrer, thermometer, dropping funnel, and reflux vessel is charged with 40 parts of ion-exchanged water and 0.2 parts of Aqualon KH-10 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as a surfactant. -2-40 parts of ethylhexyl acrylate, 50 parts of methyl methacrylate, 7 parts of styrene, 2 parts of dimethylacrylamide, 1 part of methacrylic acid, 53 parts of deionized water and Aqualon KH-10 as a surfactant (Daiichi Kogyo Seiyaku Co., Ltd.) An additional 1% of the pre-mixed pre-emulsion of 1.8 parts was added. After raising the internal temperature to 60° C. and sufficiently replacing with nitrogen, 10 parts of a 5% aqueous solution of potassium persulfate and 20 parts of a 1% aqueous solution of anhydrous sodium bisulfite were added to initiate polymerization. After holding the inside of the reaction system at 60°C for 5 minutes, the remainder of the pre-emulsion and the remainder of the 5% aqueous solution of potassium persulfate and the remainder of the 1% aqueous solution of anhydrous sodium bisulfite were added while maintaining the internal temperature at 60°C for 1.5 hours. The mixture was added dropwise over a period of time, and the stirring was continued for an additional 2 hours. After confirming that the conversion rate exceeded 98% by measuring the solid content, the temperature was cooled to 30°C. Diethylaminoethanol was added to adjust the pH to 8.5, and the solid content was adjusted to 40% with deionized water to obtain an aqueous emulsion (aqueous dispersion of fine resin particles). The solid content was obtained from the residue after baking at 150°C for 20 minutes. The resulting aqueous emulsion was used as Binder Resin 2.

<Method for producing pigment dispersion>
(Pigment dispersion (GB-1))
After pre-dispersing the mixture of the following composition uniformly with a disper, main-dispersion was performed for 2 hours using a Dyno mill with a volume of 0.6 L filled with 1800 g of zirconia beads with a diameter of 0.5 mm to obtain a pigment dispersion (GB- 1) was obtained.
Blue pigment (CI Pigment Blue 15:3): 20.0 parts Acrylic polymer (B-1): 35.0 parts Ion-exchanged water: 45.0 parts

(Pigment dispersions (GB-2 to 21), (HGB-1 to 2))
Pigment dispersions (GB-2 to 21) and comparative pigment dispersions (GB-2 to 21) were prepared in the same manner as the pigment dispersion (GB-1), except that the types and amounts of the pigments and acrylic polymers were changed to those shown in Table 2. HGB-1-2) were obtained.

Abbreviations in Table 2 are shown below.
Blue pigment: C.I. I. Pigment Blue 15:3
Red pigment: C.I. I. Pigment Red 122
Yellow pigment: C.I. I. Pigment Yellow 14
Black pigment: C.I. I. Pigment Black 7
AR289: C.I. I. Acid Red 289 (dye)
Amphitol 20N: Kao Corporation "Amphitol 20N": Lauryl dimethylamine oxide (solid content concentration: 35% by mass)

<Method for producing inkjet ink>
[Example 1]
(Inkjet ink (IJ-1))
A mixture having the following composition was uniformly stirred and mixed with a disper to obtain an inkjet ink (IJ-1).
Pigment dispersion (GB-1) 25.0 parts Propylene glycol 15.0 parts Ion-exchanged water 35.0 parts Binder resin 1 aqueous solution 25.0 parts

[Examples 2 to 21, Comparative Examples 1 to 3]
(Inkjet ink (IJ-2 to 21), (HIJ-1 to 3))
Inkjet inks (IJ-2 to 21) were prepared in the same manner as in Example 1, except that the types and amounts of the pigment dispersion, binder resin, water-soluble organic solvent, and other components were changed as shown in Table 3. And comparative inkjet inks (HIJ-1 to 3) were obtained.

Abbreviations in Table 3 are shown below.
BDG: butyl diglycol HeDG: diethylene glycol monohexyl ether (hereinafter also referred to as hexyl diglycol)
1,2-HD: 1,2-hexanediol 1,2-BD: 1,2-butanediol 1,3-PD: 1,3-propanediol PG: propylene glycol amphithol 20N: "Amphitol" manufactured by Kao Corporation 20N": Lauryl dimethylamine oxide (solid content concentration: 35% by mass)

<Evaluation of inkjet ink>
The resulting inkjet inks (IJ-1 to 21) and comparative inkjet inks (HIJ-1 to 3) were evaluated for printability, scratch resistance, clogging resistance, dispersibility, storage stability, water resistance, and ejection properties as follows. evaluated by the method. Table 4 shows the evaluation results.

(Printability on coated paper)
The IJ ink was filled in a cartridge of an inkjet printer (manufactured by Epson "PM-750C") and printed on coated paper (Oji Paper OK Topcoat+, basis weight 104.7 g/m ² , absorption speed 4). The printed sample was observed with a magnifying glass to evaluate dot connection and color unevenness. The best printability was assigned 5, and the worst printability was assigned 1, and a comparative evaluation was made on a scale of 1 to 5. An evaluation of 3 to 5 is a level at which there is no practical problem.

(Scratch resistance of printed matter)
IJ ink is packed in a cartridge of an inkjet printer ("PM-750C" manufactured by Epson) and coated paper (Oji Paper OK Top Coat +, basis weight 104.7 g/m ² , absorption rate 4). A single-color solid image was printed. The print was rubbed 100 times with a dry cotton swab under a load of 100 g to evaluate the peelability of the coating film surface.
○: No peeling of the coating film surface (good)
△: The coating film surface was slightly peeled off (usable)
×: The coating surface is completely peeled off, or marked peeling (cannot be used)

(clogging resistance)
The IJ ink was filled in a cartridge of an inkjet printer (manufactured by Epson "PM-750C") and continuously discharged for 5 minutes. After that, it is left to stand for 48 hours in an environment of 30°C and 50% RH, and the ink is continuously discharged again. The state of the ejected droplets is visually observed. was evaluated according to the frequency of occurrence of ejection failure.
◎: No ejection failure (good)
○: Discharge failure slightly observed (usable)
×: Many ejection failures are observed (cannot be used)

(Dispersibility (D50))
The obtained IJ ink is diluted with water so that the loading index value of the laser dynamic light scattering method (UPA150EX, manufactured by Nikkiso Co., Ltd.) falls within the range of 0.8 to 1.2, and is diluted with the same machine at 25 ° C. The median diameter (D50) of the cumulative volume was measured.

(Storage stability)
The IJ ink was stored in a constant temperature machine at 70° C. for 2 weeks and accelerated over time, and the viscosity of the ink was measured before and after aging to calculate the viscosity change. Viscosity was measured using an E-type viscometer (“ELD type viscometer” manufactured by Toki Sangyo Co., Ltd.) at 25° C. and a rotation speed of 50 rpm.
○: Viscosity change rate is less than ± 5% (good)
△: Viscosity change rate is ±5% or more and less than ±10% (usable)
×: Viscosity change rate is ±10% or more (cannot be used)

(Water resistance of printed matter)
IJ ink is packed in a cartridge of an inkjet printer ("PM-750C" manufactured by Epson) and coated paper (Oji Paper OK Top Coat +, basis weight 104.7 g/m ² , absorption rate 4). A single-color solid image was printed. The print was rubbed 100 times with a cotton swab soaked with water with a load of 50 g applied to evaluate the peelability of the coating film surface.
○: No peeling of the coating film surface (good)
△: The coating film surface was slightly peeled off (usable)
×: The coating surface is completely peeled off, or marked peeling (cannot be used)

(Ejectability)
The IJ ink was continuously ejected, and the state of ejected droplets was visually observed to evaluate the frequency of occurrence of ejection failures such as nozzle clogging, poor droplet gathering, and flight curl.
◎: No ejection failure (good)
○: Discharge failure is slightly observed (usable)
×: Many ejection failures are observed (cannot be used)

From the results in Table 4, all the IJ inks of the present application containing the amine oxide group-containing acrylic polymer (B) have good printability and scratch resistance on coated paper substrates that are difficult to absorb. It was shown that there is an excellent effect in preventing clogging of inkjet nozzles. In particular, when the amine oxide group-containing acrylic polymer (B) containing the monomers (b2) to (b4) in the copolymer composition is included, not only excellent printability, scratch resistance, and clogging resistance, but also ink dispersibility and storage The balance among stability, water resistance, and jettability was also good.
On the other hand, when a polymer having no amine oxide group was used, the result was poor clogging resistance (Comparative Example 1). When an amine oxide low-molecular-weight compound is used in combination, a stable dispersed state cannot be obtained, so clogging resistance is not improved, and the printability and abrasion resistance are also inferior (Comparative Examples 2 and 3).

Claims (6)

An inkjet ink containing a colorant (A), an amine oxide group-containing acrylic polymer (B) and a water-soluble organic solvent (C) ,
An inkjet ink in which the amine oxide group-containing acrylic polymer (B) contains a monomer (b2), a monomer (b3), and a monomer (b4) as monomers constituting the polymer .
Monomer (b2): aromatic ring-containing monomer
Monomer (b3): an alkyl group-containing monomer having 4 to 24 carbon atoms (excluding those containing an aromatic ring or an acidic group).
Monomer (b4): acidic group-containing monomer 2. The inkjet ink according to claim 1, wherein the amine oxide group-containing acrylic polymer (B) has at least one structure represented by the following general formulas 1 to 3.

[In general formulas 1 to 3,
X is a divalent linking group;
y is 0 or 1;
R ¹ is an alkylene group having 1 to 6 carbon atoms,
R ² and R ³ are each independently an alkyl group having 1 to 4 carbon atoms;
R ⁴ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms;
Four of R ⁵ to R ⁹ each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and one of R ⁵ to R ⁹ represents the main chain of the amine oxide group-containing acrylic polymer. represents the bonding position with
* represents the bonding position with the main chain of the amine oxide group-containing acrylic polymer. ] 3. The inkjet ink according to claim 1, wherein the amine oxide group-containing acrylic polymer (B) has a mass average molecular weight of 1,500 to 150,000. 4. The inkjet ink according to any one of claims 1 to 3 , wherein the colorant (A) contains an organic pigment. 5. The inkjet ink according to any one of claims 1 to 4 , wherein the water-soluble organic solvent (C) contains at least one selected from the group consisting of glycol ethers and diols. A printed material obtained by printing the inkjet ink according to any one of claims 1 to 5 on a recording medium.