JP2020090612A - Ink for inkjet, and printed matter - Google Patents

Abstract

To provide an IJ ink for inkjet recording being an ink for aqueous inkjet, which is excellent in dispersibility and storage stability, has good printability to a base material having high hydrophobicity such as coat paper, art paper and a vinyl chloride sheet, and is excellent in clogging property of an inkjet nozzle, and a printed matter using the same.SOLUTION: An ink for inkjet contains a colorant (A), a betaine structure-containing resin (B) and a water-soluble resin (C), in which the betaine structure-containing resin (B) contains at least an aromatic group, an alkyl group having 4 or more and 24 or less carbon atoms, and a betaine structure.SELECTED DRAWING: None

Description

INDUSTRIAL APPLICABILITY The present invention has good printability and scratch resistance on a substrate having high hydrophobicity such as coated paper, art paper, and vinyl chloride sheet, in addition to general printing substrates, and an inkjet nozzle. And an inkjet ink excellent in clogging and a printed matter using the ink.

In order to form a clear image by high-speed printing required in recent years, it is necessary to improve the drying property after the aqueous IJ ink has landed on the recording medium. The drying mechanism of ink is classified into evaporation and permeation into the recording medium.However, since ink jet ink contains a high boiling water-soluble solvent that is positioned as a moisturizer to prevent nozzle drying, ink evaporation There was a limit to increase the speed, and the contribution of the permeability to the recording medium was very large.
If the ink permeates slowly into the recording medium, a large amount of ink remains on the paper surface, causing color unevenness, or in the case of multicolor printing, ink mixing occurs. In particular, a recording medium having a non-water-absorbent substrate or a hardly water-absorbent substrate, such as coated paper, art paper, and vinyl chloride sheet, is likely to cause color unevenness and color mixture because the ink penetrates slowly.

Patent Document 1 discloses that by adding a high-boiling point water-soluble solvent having high penetrability into a recording medium, it is possible to prevent nozzle drying and improve penetrability into a recording medium, thereby improving printability. There is.

Patent Document 2 discloses that a polymer compound having a betaine structure can be used to improve dischargeability of an inkjet ink, solvent resistance of a printed matter, substrate adhesion, and color unevenness.

Patent Document 3 discloses that by adding a phosphorylcholine-like group-containing polymer, nozzle clogging is less likely to occur even when an inkjet ink after long-term storage or high-temperature storage is used.

Patent Document 4 discloses that an inkjet ink using a homopolymer of a phosphorylcholine group-containing monomer has high storage stability and good restartability (ink clogging property) of the inkjet. ..

JP, 2012-188582, A JP, 2014-65840, A JP, 2002-249684, A JP 2001-335724 A

However, since a solvent having a high permeability is generally a water-soluble solvent having a high hydrophobicity, the use of such a solvent causes the dispersant to be desorbed from the pigment, resulting in pigment aggregation. Patent Document 1 discloses that a dispersant is strongly adsorbed even when an osmotic solvent is added, and in order to maintain stable pigment dispersibility, pigment aggregation is prevented with a highly hydrophobic pigment dispersion resin containing a long alkyl chain. However, once the ink is dried on the nozzles of the inkjet printer due to the use of the highly hydrophobic dispersion resin, the redissolvability in water or a water-soluble solvent becomes low. Therefore, it has been known that when the continuous printing is temporarily stopped and the reprinting is started after a certain period of time, nozzle clogging of the inkjet ink (defective re-ejection property) occurs.

The ink composition containing the polymer compound containing a betaine structure of Patent Document 2 has a maleimide structure and thus has excellent solvent resistance and adhesiveness of the printed matter after UV irradiation, but the water resistance of the printed matter not subjected to UV irradiation treatment. It is desired to improve the ink resistance, scratch resistance, and ink nozzle clogging (re-ejection).

Regarding the inkjet ink containing the phosphorylcholine-like group-containing polymer of Patent Document 3, it is desired to improve the nozzle clogging property (re-ejection property).

The inkjet recording ink containing the phosphorylcholine group-containing polymer of Patent Document 4 is expected to be further improved in nozzle clogging (re-ejection), and also has problems of water resistance and scratch resistance.

Therefore, an object of the present invention is to provide a water-based inkjet ink having good clogging of inkjet nozzles, water resistance, and scratch resistance.

That is, the present invention relates to the following [1] to [5].

[1] An inkjet ink containing a colorant (A), a betaine structure-containing resin (B), and a water-soluble solvent (C),
The inkjet ink, wherein the betaine structure-containing resin (B) is a vinyl-based polymer containing the following repeating unit b1, repeating unit b2, and repeating unit b3.
Repeating unit b1: Repeating unit having an aromatic ring in the side chain Repeating unit b2: Repeating unit having an alkyl group having 4 to 24 carbon atoms in the side chain (provided that repeating units b1 and b3 and an acid group in the side chain are included. (Excluding repeating units)
Repeating unit b3: a repeating unit having at least one betaine structure represented by the following general formulas 1 to 4

General formula 1

General formula 2

General formula 3

General formula 4

[In general formulas 1 to 4,
R ₁ is a hydrogen atom or a methyl group,
R ₂ is an alkylene group having 1 to 6 carbon atoms,
R ₃ and R ₄ are each independently an alkyl group having 1 to 4 carbon atoms,
R ₅ is an alkylene group having 1 to 4 carbon atoms, X is an oxygen atom or NH,
Y is CO ₂ ⁻ or SO ₃ ⁻ ,
R ₆ is a hydrogen atom or a methyl group,
R ₇ is a hydrogen atom or a methyl group,
R ₈ is an alkylene group having 1 to 6 carbon atoms or a hydroxyalkylene group having 1 to 6 carbon atoms,
R ₉ is a hydrogen atom or a methyl group,
One of R _{10 to} R ₁₄ is directly bonded to the * moiety,
Four of R _{10 to} R ₁₄ are each independently a hydrogen atom or an alkyl group having 1 to 6 carbon atoms,
R ₁₅ is an alkylene group having 1 to 6 carbon atoms or a hydroxyalkylene group having 1 to 6 carbon atoms,
R ₁₆ is a hydrogen atom or a methyl group,
R ₁₇ is _{(CH 2 -CHR 22 O) m} (CH 2 -CHR 22) group _{(wherein, R 22} represents a hydrogen atom, a methyl group or an ethyl group, m represents an integer of 0.),
R ₁₈ is (CH ₂ )g (here, g represents an integer of 0 to 10),
R _{19 to} R ₂₁ each independently represent an alkyl group having 1 to 8 carbon atoms or a hydroxyalkyl group. ]

[2] The inkjet ink according to [1], wherein the betaine structure-containing resin (B) is a vinyl-based polymer further containing the following repeating unit b5.
Repeating unit b5: Repeating unit having an acid group in the side chain

[3] The inkjet ink according to [1] or [2], wherein the betaine structure-containing resin (B) has a mass average molecular weight of 3,000 to 150,000.

[4] The inkjet ink according to any one of [1] to [3], wherein the colorant (A) contains an organic pigment.

[5] A printed matter obtained by printing the inkjet ink according to any one of [1] to [4] on a recording medium.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide an inkjet ink having excellent clogging of an inkjet nozzle, water resistance, and scratch resistance.

The inkjet ink of the present invention comprises a colorant (A), a betaine structure-containing resin (B) which is a vinyl polymer containing at least the following repeating unit b1, repeating unit b2 and repeating unit b3, and a water-soluble solvent (C). It is characterized by containing.
Repeating unit b1: Repeating unit having an aromatic ring in the side chain Repeating unit b2: Repeating unit having an alkyl group having 4 to 24 carbon atoms in the side chain (provided that repeating units b1 and b3 and an acid group in the side chain are included. (Excluding repeating units)
Repeating unit b3: The repeating unit resin (B) having at least one of the betaine structures represented by the general formulas 1 to 4 contains the repeating unit having a specific betaine structure and the specific repeating units b1 and b2. It exhibits excellent effects of clogging of inkjet nozzles, water resistance, and scratch resistance.
Hereinafter, the inkjet pigment ink of the invention (hereinafter, referred to as ink or pigment ink) will be described with reference to preferred embodiments.

<Colorant (A)>
The IJ ink of the present invention contains a colorant. As the colorant, conventionally known ones such as organic pigments, inorganic pigments, special pigments and dyes can be appropriately selected and used, and pigments are preferably used. The IJ ink of the present invention contains a pigment in an amount of 0.1% by mass or more and 20% by mass or less, more preferably 0.1% by mass or more and 12% by mass or less in 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 the yellow pigment that can be used in the present invention include C.I. I. Pigment Yellow 1, 2, 3, 12, 13, 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, 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.
Examples of cyan pigments include C.I. I. Pigment Blue 1, 2, 3, 15:3, 15:4, 16, 22, C.I. I. Vat Blue 4, 6 etc. are mentioned.
Furthermore, organic pigments of colors other than the above may be used, and in that case, 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, it is also possible to use self-dispersion pigments and the like.

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

Further, examples of the black pigment include carbon black manufactured by a furnace method and a channel method. For example, these carbon blacks have a primary particle size of 11 to 40 mμm (nm), a specific surface area by 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 having characteristics such as 10 are preferable. The following are examples of commercially available products having such characteristics. For example, No. 33, 40, 45, 52, 900, 2200B, 2300, MA7, MA8, MCF88 (manufactured by Mitsubishi Chemical), RAVEN1255 (manufactured by Colombian Carbon), REGAL330R, 400R, 660R, MOGUL L, ELFTEX415 (manufactured by Cabot) ), Nipex90, Nipex150T, Nipex 160IQ, Nipex 170IQ, Nipex 75, Printex 85, Printex 95, Printex 90, Printex 35, and Printex U (above, manufactured by Evonik Degussa), and any of them can be preferably used.

[Other colorants]
(dye)
In the present invention, a dye may be used in combination with the pigment. Examples of dyes that can be used include acid dyes in the color index, direct dyes, basic dyes, reactive dyes and food dyes, but are not limited to these, and a carboxyl group or a sulfo group in the molecule is used. Any material may be included as long as it is contained and is 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, and the like.

C. as a direct dye. 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 can be mentioned.

C. as a basic dye. 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 and the like can be mentioned.

The water-soluble dye is not limited to these, and includes phenols, naphthols, anilines, pyrazolones, pyridones, thiazoles, open-chain active methylene compounds, pyrazolotriazoles, pyrrolotriazoles, etc. Any aryl or heteryl azo dye or azomethine dye may be used as long as it contains a water-soluble group represented by a carboxyl group or a sulfo group in the molecule and is substantially soluble in the ink.

<Betaine structure-containing resin (B)>
As described above, the inkjet ink of the present invention contains the betaine structure-containing resin (B) which is a vinyl-based polymer containing the following repeating units b1 to b3. The betaine structure-containing resin (B) is not particularly limited as long as it is a vinyl-based polymer containing the repeating units b1 to b3, and may be used alone, or a plurality of betaine structure-containing resins (B) may be used in combination. Good.
Repeating unit b1: Repeating unit having an aromatic ring in the side chain Repeating unit b2: Repeating unit having an alkyl group having 4 to 24 carbon atoms in the side chain (provided that repeating units b1 and b3 and an acid group in the side chain are included. (Excluding repeating units)
Repeating unit b3: a repeating unit having at least one betaine structure represented by the following general formulas 1 to 4

General formula 1

General formula 2

General formula 3

General formula 4

[In general formulas 1 to 4,
R ₁ is a hydrogen atom or a methyl group,
R ₂ is an alkylene group having 1 to 6 carbon atoms,
R ₃ and R ₄ are each independently an alkyl group having 1 to 4 carbon atoms,
R ₅ is an alkylene group having 1 to 4 carbon atoms, X is an oxygen atom or NH,
Y is CO ₂ ⁻ or SO ₃ ⁻ ,
R ₆ is a hydrogen atom or a methyl group,
R ₇ is a hydrogen atom or a methyl group,
R ₈ is an alkylene group having 1 to 6 carbon atoms or a hydroxyalkylene group having 1 to 6 carbon atoms,
R ₉ is a hydrogen atom or a methyl group,
One of R _{10 to} R ₁₄ is directly bonded to the * moiety,
Four of R _{10 to} R ₁₄ are each independently a hydrogen atom or an alkyl group having 1 to 6 carbon atoms,
R ₁₅ is an alkylene group having 1 to 6 carbon atoms or a hydroxyalkylene group having 1 to 6 carbon atoms,
R ₁₆ is a hydrogen atom or a methyl group,
R ₁₇ is _{(CH 2 -CHR 22 O) m} (CH 2 -CHR 22) group _{(wherein, R 22} represents a hydrogen atom, a methyl group or an ethyl group, m represents an integer of 0.),
R ₁₈ is (CH ₂ )g (here, g represents an integer of 0 to 10),
R _{19 to} R ₂₁ each independently represent an alkyl group having 1 to 8 carbon atoms or a hydroxyalkyl group. ]

The repeating units b1 to b3 described above can be formed by polymerizing the following monomers b1x, b2x, and b3x.
Monomer b1x: monomer having an aromatic ring monomer b2x: monomer having an alkyl group having 4 to 24 carbon atoms (monomer b1x, monomer b3x, monomer b4x described later, (Excluding the below-mentioned monomer b5x)
Monomer b3x: a monomer having at least one betaine structure represented by the general formulas 100 to 400

General formula 100

General formula 200

General formula 300

General formula 400

[In the general formulas 100 to 400,
R ₁ is a hydrogen atom or a methyl group,
R ₂ is an alkylene group having 1 to 6 carbon atoms,
R ₃ and R ₄ are each independently an alkyl group having 1 to 4 carbon atoms,
R ₅ is an alkylene group having 1 to 4 carbon atoms, X is an oxygen atom or NH,
Y is CO ₂ ⁻ or SO ₃ ⁻ ,
R ₆ is a hydrogen atom or a methyl group,
R ₇ is a hydrogen atom or a methyl group,
R ₈ is an alkylene group having 1 to 6 carbon atoms or a hydroxyalkylene group having 1 to 6 carbon atoms,
R ₉ is a hydrogen atom or a methyl group,
One of R _{10 to} R ₁₄ is directly bonded to the * moiety,
Four of R _{10 to} R ₁₄ are each independently a hydrogen atom or an alkyl group having 1 to 6 carbon atoms,
R ₁₅ is an alkylene group having 1 to 6 carbon atoms or a hydroxyalkylene group having 1 to 6 carbon atoms,
R ₁₆ is a hydrogen atom or a methyl group,
R ₁₇ is _{(CH 2 -CHR 22 O) m} (CH 2 -CHR 22) group _{(wherein, R 22} represents a hydrogen atom, a methyl group or an ethyl group, m represents an integer of 0.),
R ₁₈ is (CH ₂ )g (here, g represents an integer of 0 to 10),
R _{19 to} R ₂₁ each independently represent an alkyl group having 1 to 8 carbon atoms or a hydroxyalkyl group. ]

(Monomer b1x: Monomer having aromatic ring)
The monomer b1x strengthens the π-π interaction between the betaine structure-containing resin (B) and the colorant, and enables adsorption to the extremely strong colorant and fine dispersion. As a result, the betaine structure-containing resin (B) can maintain strong adsorption without desorption from the colorant to the solvent, and can maintain a finely dispersed state for a long period of time.
Specific examples of the monomer b1x include, for example, styrene, α-methylstyrene, 2-methylstyrene, chlorostyrene, benzyl(meth)acrylate, phenyl(meth)acrylate, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxyethyl-2-hydroxyethyl phthalate, 2-(meth)acryloyloxypropyl phthalate, EO-modified cresol (meth)acrylate, neopentyl glycol benzoate (meth)acrylate, nonylphenoxy polyethylene glycol (meth ) Acrylate, nonylphenoxy polypropylene glycol (meth)acrylate, paracumylphenoxyethylene glycol (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, EO-modified tribromophenyl (meth)acrylate, EO-modified phthalate Examples thereof include acid (meth)acrylate, ethoxylated orthophenylphenol (meth)acrylate, naphthyloxypolyethylene glycol (meth)acrylate, vinylnaphthalene, vinylcarbazole and 4-hydroxyvinylbenzene.

(Monomer b2x: Monomer having an alkyl group having 4 to 24 carbon atoms (excluding monomer b1x, monomer b3x, monomer b4x described later, and monomer b5x described later))
Since the monomer b2x has an alkyl group having 4 to 24 carbon atoms in its structure, it has a high hydrophobic interaction with the pigment. Therefore, by using it together with the monomer b1x, it is possible to realize very strong adsorption to the colorant and fine dispersion, and as a result, it is possible to maintain the fine dispersion state for a long period of time.
Specific examples of the monomer b2x include, for example, 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 Examples thereof include (meth)acrylate and behenyl (meth)acrylate.
From the viewpoint of versatility and polymerizability, it is particularly preferable to select alkyl (meth)acrylates such as lauryl (meth)acrylate, stearyl (meth)acrylate, behenyl (meth)acrylate and the like. Further, the number of carbon atoms for achieving a higher degree of improvement in dispersibility and storage 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 b3x: a monomer having at least one betaine structure represented by the general formulas 100 to 400)
The monomer b3x has a betaine structure represented by the general formulas 100 to 400 and has high hydrophilicity. Therefore, while being used in combination with the monomer b1x and the monomer b2x to contribute to the aqueousization of the betaine structure-containing resin (B) and to stabilize the dispersed state of the colorant, the moisturizing effect The effect of suppressing clogging of the inkjet nozzle is obtained.

Specific examples of the monomer represented by the general formula 100 include, for example, N-(meth)acryloyloxymethyl-N,N-dimethylammoniummethyl-α-carboxybetaine, N-(meth)acryloyloxyethyl-N. , N-dimethylammoniummethyl-α-carboxybetaine, N-(meth)acryloyloxypropyl-N,N-dimethylammoniummethyl-α-carboxybetaine, N-(meth)acryloyloxybutyl-N,N-dimethylammoniummethyl -Α-carboxybetaine, N-(meth)acryloyloxymethyl-N,N-diethylammoniummethyl-α-carboxybetaine, N-(meth)acryloyloxyethyl-N,N-diethylammoniummethyl-α-carboxybetaine, N-(meth)acryloyloxypropyl-N,N-diethylammoniummethyl-α-carboxybetaine, N-(meth)acryloyloxybutyl-N,N-diethylammoniummethyl-α-carboxybetaine, and the like N-(meth ) Acryloyloxyalkyl-N,N-dialkylammoniumalkyl-α-carboxybetaine; N-(meth)acrylamidopropyl-N,N-dimethylammoniummethyl-α-carboxybetaine, N-(meth)acrylamidopropyl-N,N N-(meth)acrylamidoalkyl-N,N-dialkylammoniumalkyl-α-carboxybetaines such as diethylammoniummethyl-α-carboxybetaine; N-(meth)acrylamidopropyl-N,N-dimethylammoniummethyl-α N-(meth)acrylamidoalkyl-N,N-dialkylammoniumalkyl-α-carboxybetaine, such as -carboxybetaine, N-(meth)acrylamidopropyl-N,N-diethylammoniummethyl-α-carboxybetaine; N- (Meth)acryloyloxymethyl-N,N-dimethylammoniummethyl-α-sulfobetaine, N-(meth)acryloyloxymethyl-N,N-dimethylammoniumethyl-α-sulfobetaine, N-(meth)acryloyloxymethyl -N,N-dimethylammoniumpropyl-α-sulfobetaine, N-(meth)acryloyloxymethyl-N,N-dimethylammoniumbutyl-α-sulfobetaine, N-(meth)acryloyloxyethyl-N,N-dimethyl Ammonium methyl-α-su Rufobetaine, N-(meth)acryloyloxyethyl-N,N-dimethylammoniumethyl-α-sulfobetaine, N-(meth)acryloyloxyethyl-N,N-dimethylammoniumpropyl-α-sulfobetaine, N-(meth ) Acryloyloxyethyl-N,N-dimethylammoniumbutyl-α-sulfobetaine, N-(meth)acryloyloxypropyl-N,N-dimethylammoniummethyl-α-sulfobetaine, N-(meth)acryloyloxypropyl-N , N-dimethylammoniumethyl-α-sulfobetaine, N-(meth)acryloyloxypropyl-N,N-dimethylammoniumpropyl-α-sulfobetaine, N-(meth)acryloyloxypropyl-N,N-dimethylammoniumbutyl -Α-sulfobetaine, N-(meth)acryloyloxybutyl-N,N-dimethylammoniummethyl-α-sulfobetaine, N-(meth)acryloyloxybutyl-N,N-dimethylammoniumethyl-α-sulfobetaine, N-(meth)acryloyloxybutyl-N,N-dimethylammoniumpropyl-α-sulfobetaine, N-(meth)acryloyloxybutyl-N,N-dimethylammoniumbutyl-α-sulfobetaine, etc. ) Acryloyloxyalkyl-N,N-dimethylammoniumalkyl-α-sulfobetaine; N-(meth)acryloyloxymethoxymethoxy-N,N-dimethylammoniummethyl-α-sulfobetaine, N-(meth)acryloyloxymethoxymethoxy -N,N-dimethylammoniumethyl-α-sulfobetaine, N-(meth)acryloyloxymethoxymethoxy-N,N-dimethylammoniumpropyl-α-sulfobetaine, N-(meth)acryloyloxymethoxymethoxy-N,N -Dimethylammoniumbutyl-α-sulfobetaine, N-(meth)acryloyloxyethoxyethoxy-N,N-dimethylammoniummethyl-α-sulfobetaine, N-(meth)acryloyloxyethoxyethoxy-N,N-dimethylammoniumethyl -Α-sulfobetaine, N-(meth)acryloyloxyethoxyethoxy-N,N-dimethylammoniumpropyl-α-sulfobetaine, N-(meth)acryloyloxyethoxyethoxy-N,N-dimethylammoniumbutyl-α-sulfo Betaine, N-(meth)acryloyloxypropoxypropoxy-N,N-dimethylammoniummethyl-α-sulfobetaine, N-(meth)acryloyloxypropoxypropoxy-N,N-dimethylammoniumethyl-α-sulfobetaine, N-(meth ) Acryloyl oxypropoxy propoxy-N,N-dimethylammonium propyl-α-sulfobetaine, N-(meth)acryloyloxypropoxypropoxy-N,N-dimethylammonium butyl-α-sulfobetaine, N-(meth)acryloyloxybutoxy Butoxy-N,N-dimethylammoniummethyl-α-sulfobetaine, N-(meth)acryloyloxybutoxybutoxy-N,N-dimethylammoniumethyl-α-sulfobetaine, N-(meth)acryloyloxybutoxybutoxy-N, N-(meth)acryloyloxyalkoxyanercoxy-N, such as N-dimethylammoniumpropyl-α-sulfobetaine, N-(meth)acryloyloxybutoxybutoxy-N,N-dimethylammoniumbutyl-α-sulfobetaine, etc. N-dimethylammoniumalkyl-α-sulfobetaine; N-(meth)acrylamidopropyl-N,N-dimethylammoniumpropyl-α-sulfobetaine, N-(meth)acrylamidopropyl-N,N-dimethylammoniumbutyl-α- N-(meth)acrylamidoalkyl-N,N-dialkylammoniumalkyl-α-sulfobetaines such as sulfobetaine,

Specific examples of the monomer represented by the general formula 200 include 1-vinyl-3-(3-sulfopropyl)imidazolium inner salt and 1-vinyl-3-(3-sulfobutyl)imidazolium inner salt. 1-vinyl-2-alkyl such as 1-vinyl-2-methyl-3-(3-sulfopropyl)imidazolium inner salt and 1-vinyl-2-methyl-3-(4-sulfobutyl)imidazolium inner salt -3-(4-sulfoalkyl)imidazolium inner salt and the like can be mentioned.

Specific examples of the monomer represented by the general formula 300 include 2-vinyl-1-(3-sulfopropyl)pyridinium inner salt, 2-vinyl-1-(3-sulfobutyl)pyridinium inner salt, and the like. 2-vinyl-1-(3-sulfoalkyl)pyridinium inner salt; 4-vinyl-1-(3-sulfopropyl)pyridinium inner salt, 4-vinyl-1-(3-sulfobutyl)pyridinium inner salt, etc. 4-vinyl-1-(3-sulfoalkyl)pyridinium internal salt and the like can be mentioned.

Specific examples of the monomer represented by the general formula 400 include 2-methacryloyloxyethylphosphorylcholine.

In addition, as the monomer b3x, a commercially available product or a synthetic product may be used. For example, a betaine compound described below is added to the tertiary amino group of the monomer b4x having a tertiary amino group described below. It may be obtained by reacting the agent (E).

From the viewpoint of polymer production and purification, the vinyl polymer preferably contains a repeating unit having at least one betaine structure represented by the general formulas 1 to 3. Further, the betaine structure in the repeating unit may be one obtained by a polymerization reaction using a monomer b3x having at least one of the betaine structures represented by the general formulas 100 to 300, or a tertiary amino group described later. Even if a betaine structure is introduced by reacting a betaine agent (E) described later with the tertiary amino group in the repeating unit having a tertiary amino group formed using the monomer b4x having From the viewpoint of polymer production and purification, the betaine agent (described below) may be added to the tertiary amino group in the repeating unit having a tertiary amino group formed by using the monomer b4x having a tertiary amino group. It is preferred to react E).

The vinyl polymer in the present application is preferably a reaction product of a vinyl polymer containing a monomer b1x, a monomer b2x and the following monomer b4x in a copolymer composition and a betaine agent (E).
Monomer b1x: Monomer having an aromatic ring b2x: Monomer having an alkyl group having 4 to 24 carbon atoms (monomer b1x, monomer b3x, monomer b4x, described later) (Excluding monomer b5x)
Monomer b4x: A monomer having a tertiary amino group which is at least one of the following general formulas 5 to 7

General formula 5

General formula 6

General formula 7

[In general formulas 5 to 7,
R ₁ is a hydrogen atom or a methyl group,
R ₂ is an alkylene group having 1 to 6 carbon atoms,
R ₃ and R ₄ are each independently an alkyl group having 1 to 4 carbon atoms,
X is an oxygen atom or NH,
R ₆ is a hydrogen atom or a methyl group,
R ₇ is a hydrogen atom or a methyl group,
R ₉ is a hydrogen atom or a methyl group,
One of R _{10 to} R ₁₄ is directly bonded to the * moiety,
Four of R _{10 to} R ₁₄ are each independently a hydrogen atom or an alkyl group having 1 to 6 carbon atoms,
** represents a reaction site with the betaine agent (E). ]

(Monomer b4x: Monomer represented by at least one of the general formulas 5 to 7)
The monomer b4x has a tertiary amino group and can react with a betaine agent (E) described later to be betaineized. Specifically, it is copolymerized with the monomer b1x and the monomer b2x. After that, the betaine agent (E) is reacted to obtain a vinyl polymer having a betaine structure. The betaine structure site thus introduced plays a role of making the resin (B) containing a betaine structure aqueous and a role of stabilizing the dispersed state of the colorant, and due to its moisturizing effect, clogging of the inkjet head is caused. Has the effect of suppressing.

Specific examples of the monomer represented by the general formula 5 include, for example,
N-(meth)acryloyloxymethyl-N,N-dimethylamine,
N-(meth)acryloyloxyethyl-N,N-dimethylamine,
N-(meth)acryloyloxypropyl-N,N-dimethylamine,
N-(meth)acryloyloxybutyl-N,N-dimethylamine,
N-(meth)acryloyloxymethyl-N,N-diethylamine,
N-(meth)acryloyloxyethyl-N,N-diethylamine,
N-(meth)acryloyloxypropyl-N,N-diethylamine,
N-(meth)acryloyloxybutyl-N,N-diethylamine,
N-(meth)acryloyloxyalkyl-N,N-dialkylamines such as;
N-(meth)acrylamidopropyl-N,N-dimethylamine,
N-(meth)acrylamidopropyl-N,N-diethylamine,
N-(meth)acrylamidoalkyl-N,N-dialkylamines such as;
N-(meth)acryloyloxymethoxymethoxy-N,N-dimethylamine,
N-(meth)acryloyloxyethoxyethoxy-N,N-dimethylamine,
N-(meth)acryloyloxypropoxypropoxy-N,N-dimethylamine,
N-(meth)acryloyloxybutoxybutoxy-N,N-dimethylamine,
And N-(meth)acryloyloxyalkoxyalkoxy-N,N-dimethylamine.

Specific examples of the monomer represented by the general formula 6 include 1-vinylimidazole and 1-vinyl-2-methyl-imidazole.

Specific examples of the monomer represented by the general formula 7 include vinylpyridine such as 4-vinyl-pyridine and 2-vinyl-pyridine.

<Betaine agent (E)>
The betaine agent (E) can react with the tertiary amino group of the monomer represented by the general formulas 5 to 7 to introduce at least one betaine structure represented by the general formulas 1 to 3. There is no particular limitation so long as it is a cyclic sulfonic acid ester (E1), ω-halogenated alkyl sulfonic acid metal salt (E2), cyclic carboxylic acid ester (E3) and ω-halogenated alkyl carboxylic acid metal salt ( At least one selected from the group consisting of E4) is included.

Examples of the cyclic sulfonic acid ester (E1) include 1,2-ethanesultone, 1,3-propanesultone, and 1,4-butanesultone.

Examples of the ω-halogenated alkyl sulfonic acid metal salt (E2) include, for example, sodium 2-chloroethane sulfonate, sodium 2-bromoethane sulfonate, sodium 3-chloropropane sulfonate, sodium 3-bromopropane sulfonate, and 4-chloro. Examples thereof include sodium butane sulfonate and sodium 4-bromobutane sulfonate.

Examples of the cyclic carboxylic acid ester (E3) include β-propiolactone, γ-butyrolactone, δ-valerolactone and the like.

Examples of the ω-halogenated alkylcarboxylic acid metal salt (E4) include sodium 2-chloroacetate, sodium 2-bromoacetate, sodium 3-chloropropionate, sodium 3-bromopropionate, sodium 4-chlorobutyrate, and 4 -Sodium bromobutyrate, sodium 5-chloropentanoate, sodium 5-bromopentanoate and the like can be mentioned.

(Monomer b5x: Monomer having an acid group)
The betaine structure-containing resin (B) is preferably a vinyl polymer further containing a repeating unit b5 having an acid group in its side chain. The repeating unit b5 described above can be formed by copolymerizing the following monomer b5x.
Monomer b5x: Monomer having an acid group

Specific examples of the monomer b5x include, for example, maleic acid, fumaric acid, itaconic acid, citraconic acid, or alkyl or alkenyl monoesters thereof, phthalic acid β-(meth)acryloxyethyl monoester, and isophthalic acid β. -(Meth)acryloxyethyl monoester, terephthalic acid β-(meth)acryloxyethyl monoester, succinic acid β-(meth)acryloxyethyl monoester, acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, vinyl Examples thereof include sulfonic acid, Nt-butylacrylamide sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, and EO-modified phosphoric acid (meth)acrylate.
In order to improve storage stability to a higher degree, carboxylic acid-containing (meth)acrylate is preferable, and acrylic acid or methacrylic acid is more preferable.

When the betaine structure-containing resin (B) is a vinyl-based polymer further containing a repeating unit b5 having an acid group in its side chain, the acid group is neutralized with a neutralizing agent (F) such as an organic amine described below. It is preferable to use.
By having an acid group neutralized with an organic amine in the betaine structure-containing resin (B), it is possible to stabilize the colorant dispersed state by electrification repulsion which is stronger than that of the betaine structure, while contributing to the aqueousization. You can Further, since the neutralizing agent (F) volatilizes and returns to the acid group in the drying step after printing, the hydrophobicity of the betaine structure-containing resin (B) is improved, and the water resistance of the printed matter can be improved.

Regarding the neutralization step, for example, the acid group derived from the repeating unit b5 in the betaine structure-containing resin (B) which is a vinyl-based polymer containing the repeating unit b1, the repeating unit b2, the repeating unit b3, and the repeating unit b5 will be described later. May be used after neutralizing with a neutralizing agent (F)
After copolymerizing the monomer b1x, the monomer b2x, the monomer b4x, and the monomer b5x, they are reacted with a betaine agent (E) to introduce a betaine structure, and further, an acid group derived from the monomer b5x. May be used after being neutralized with a neutralizing agent (F).

<Neutralizer (F)>
As the neutralizing agent (F), various organic amines such as ammonia water, dimethylaminoethanol, diethanolamine, and triethanolamine can be used. Dimethylaminoethanol has a high boiling point and is particularly preferable from the viewpoint of ink ejection property. The copolymer after neutralization is dispersed or dissolved in the aqueous liquid medium.

(Other monomer b6x)
The betaine structure-containing resin (B) may appropriately contain other monomer b6x as a copolymerization component.
Examples of the other monomer b6x include alkyl (meth)acrylates having 1 to 3 carbon atoms such as methyl (meth)acrylate, ethyl (meth)acrylate and propyl (meth)acrylate;
Α-olefin-based ethylenically unsaturated monomers such as 1-propylene;
2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-(meth)acryloyloxyethyl-2-hydroxyethylphthalic acid, glycerol mono(meth)acrylate A monomer having a hydroxyl group such as 1-ethynyl-1-cyclohexanol and allyl alcohol;
(Meth)acrylamide, 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(ethoxymethyl)acrylamide, N-ethoxymethyl-N-propoxymethylmeta Acrylamide, N,N-di(propoxymethyl)acrylamide, N-butoxymethyl-N-(propoxymethyl)methacrylamide, N,N-di(butoxymethyl)acrylamide, N-butoxymethyl-N-(methoxymethyl)meth Acrylamide, N,N-di(pentoxymethyl)acrylamide, N-methoxymethyl-N-(pentoxymethyl)methacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, diacetone (meth)acrylamide, etc. A monomer having a primary to tertiary amide group;
(Meth)acrylic acid dimethylaminoethyl methyl chloride salt, trimethyl-3-(1-(meth)acrylamide-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)acrylamide-1,1-dimethylethyl)ammonium chloride;
Polyethylene glycol (meth)acrylate, methoxy polyethylene glycol (meth)acrylate, ethoxy polyethylene glycol (meth)acrylate, propoxy polyethylene glycol (meth)acrylate, n-butoxy polyethylene glycol (meth)acrylate, n-pentoxy polyethylene glycol (meth) Acrylate, phenoxy polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxy polypropylene glycol (meth)acrylate, ethoxy polypropylene glycol (meth)acrylate, propoxy polypropylene glycol (meth)acrylate, n-butoxy polypropylene glycol (meth)acrylate , N-pentaxy polypropylene glycol (meth)acrylate, phenoxy polypropylene glycol (meth)acrylate, polytetramethylene glycol (meth)acrylate, methoxypolytetramethylene glycol (meth)acrylate, phenoxytetraethylene glycol (meth)acrylate, hexaethylene Monomers having polyether chains 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;
Allyl (meth)acrylate, 1-methylallyl (meth)acrylate, 2-methylallyl (meth)acrylate, 1-butenyl (meth)acrylate, 2-butenyl (meth)acrylate, 3-(meth)acrylic acid 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, rosinyl (meth)acrylate, cinnamyl (meth)acrylate, diallyl maleate, diallyl itaconic acid, Ethylenically unsaturated group-containing (meth)acrylates such as vinyl (meth)acrylate, vinyl crotonic acid, 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 ) A perfluoroalkyl group-containing ethylenically unsaturated monomer having a perfluoroalkyl group having 1 to 20 carbon atoms, such as acrylate, perfluorooctylamyl (meth)acrylate, and perfluorooctylundecyl (meth)acrylate;
A (meth)acrylate-based monomer having a polymer structure in the side chain such as an ethylenically unsaturated compound having a polyester chain such as lactone-modified (meth)acrylate;
Nitrile group-containing ethylenically unsaturated monomers such as (meth)acrylonitrile;
Fatty acid vinyl compounds such as vinyl acetate, vinyl butyrate, vinyl propionate, vinyl hexanoate, vinyl caprylate, vinyl laurate, vinyl palmitate, and vinyl stearate; vinyl ether ethylenically unsaturated monoesters such as butyl vinyl ether and ethyl vinyl ether. Quantity;
Allyl monomers such as allyl acetate and allyl cyanide;
Vinyl monomers such as vinyl cyanide, vinyl cyclohexane and vinyl methyl ketone;
Ethynyl monomers such as acetylene and ethynyltoluene;
Perfluorobutyl ethylene, perfluorohexyl ethylene, perfluorooctyl ethylene, perfluorodecyl ethylene and other perfluoroalkyl, alkylenes and other perfluoroalkyl group-containing ethylenically unsaturated compounds, etc. A monomer having an unsaturated bond;
And the like, and one or more of these groups can be used.

<Mass ratio of monomers b1x to b5x>
The betaine structure-containing resin (B) includes a method (1) for synthesizing a copolymer using a monomer b3x containing a betaine structure, and a betaine conversion after synthesizing a copolymer using a monomer b4x having a tertiary amino group. There is a method (2) of reacting with the agent (E) to synthesize a copolymer having a betaine structure.

The mass composition ratio of the monomers b1x, b2x, b3x, b5x, which are the constituent components of the copolymer produced by the synthesis method (1), is
Monomer b1x: 1 to 50 mass%, monomer b2x: 1 to 65 mass%, monomer b3x: 1 to 95 mass%, monomer b5: 0 to 50 mass% are preferable, and among them, ,
More preferably, the monomer b1x is 1 to 40 mass%, the monomer b2x is 1 to 55 mass%, the monomer b3x is 1 to 70 mass%, and the monomer b5 is 5 to 45 mass%.
Further, the total amount of the monomer b1x, the monomer b2x, the monomer b3x and the monomer b5x is preferably 70% by mass or more. When the total amount of the four components is 70% by mass or more, dispersibility, long-term storage stability, and clogging of inkjet nozzles are improved.

The mass composition ratio of the monomers b1x, b2x, b4x, b5x, which are the constituent components of the copolymer produced by the synthesis method (2), is
Monomer b1x: 1 to 50 mass%, monomer b2x: 1 to 65 mass%, monomer b4x: 1 to 95 mass%, monomer b5x: 0 to 50 mass% are preferable, and ,
More preferably, the monomer b1x is 1 to 40% by mass, the monomer b2x is 1 to 55% by mass, the monomer b4x is 1 to 70% by mass, and the monomer b5x is 0 to 45% by mass.
Further, the total amount of the monomer b1x, the monomer b2x, the monomer b4x, and the monomer b5x is preferably 70% by mass or more. When the total of the four components is 70% by mass or more, dispersibility, long-term storage stability, and inkjet clogging are improved.

<Mass average molecular weight and acid value of betaine structure-containing resin (B)>
The weight average molecular weight of the betaine structure-containing resin (B) is preferably in the range of 2,000 to 300,000, more preferably 3,000 to 150,000.
When the betaine structure-containing resin (B) is formed by copolymerizing an ethylenically unsaturated monomer having an acid group (monomer b5x), the betaine structure-containing resin (calculated from the composition ratio of the monomer b5x ( The acid value of B) is preferably 50 mgKOH/g or more and 600 mgKOH/g or less, and more preferably 100 mgKOH/g or more and 500 mgKOH/g or less.
When the acid value of the betaine structure-containing resin (B) is 50 mgKOH/g or more, the betaine structure containing resin (B) is easily dissolved in water, the dispersibility and storage stability of the pigment ink are improved, and the ejection stability is further improved. To do. Further, when it is 600 mgKOH/g or less, the adhesive force of the betaine structure-containing resin (B) to the pigment surface is improved, and the storage stability of the pigment ink is improved. The mass average molecular weight and acid value of the betaine structure-containing resin (B) in the present invention can be measured by a conventional method.

<Content of Betaine Structure-Containing Resin (B)>
In the inkjet ink of the present invention, the content of the betaine structure-containing resin (B) is preferably 3% by mass or more and 70% by mass or less, and more preferably 5% by mass with respect to the total mass of the colorant in the ink. % To 60% by mass, particularly preferably 10% to 45% by mass.

The betaine structure-containing resin (B) described above is preferably contained in the range of 0.1% by mass to 8% by mass with respect to the total mass of the ink.

<Water-soluble solvent (C)>
The inkjet ink of the present invention contains a water-soluble solvent (C).
The water-soluble solvent (C) is not particularly limited, and diols, glycol ethers and the like are effective. Since these solvent species have high boiling points, they function sufficiently as a moisturizing agent, and the ink ejection stability is good.

(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 can be mentioned.

(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 monomethyl ether. 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 Examples include toxy-1-butanol, 3-methoxy-3-methyl-1-butanol and the like.

Among these, highly 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, 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 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.

Further, depending on the type of substrate to be printed, a water-soluble nitrogen-containing complex such as 2-pyrrolidone, N-methylpyrrolidone, N-ethylpyrrolidone, N-methyloxazolidinone or N-ethyloxazolidinone may be used for the purpose of improving the solubility. A ring compound can also be added.

These water-soluble solvents (C) may be used alone or in combination of two or more. The content of the water-soluble organic solvent in the ink is preferably 3% by mass or more and 60% by mass or less of the total mass of the ink, and more preferably 3% by mass or more and 50% by mass or less. is there.

In the inkjet ink of the present invention, water may be used in combination with the water-soluble solvent (C).

As water, it is preferable to use not ion-exchanged water (deionized water) but general water containing various ions.

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

<Inkjet ink>
The inkjet 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. This improves water resistance, solvent resistance, scratch resistance, and the like.

(Water-soluble binder resin)
The water-soluble binder resin (hereinafter, also referred to as water-soluble resin) is
Excluding the betaine structure-containing resin (B), for example, acrylic, styrene-acrylic, styrene-maleic acid, acrylonitrile-acrylic, vinylnaphthalene-acrylic, vinyl acetate-acrylic, polyurethane, Examples thereof include polyester resins, polyethyleneimine, polyvinylamine, polyacrylamide, polyallylamine, polyethylene oxide, polyvinylpyrrolidone, polyvinyl alcohol, polyvinyl acetal, water-soluble cellulose, gelatin, proteins such as casein, and various resins such as starch. Further, as other water-soluble resin, it is possible to copolymerize a monomer having a phosphoric acid group or a sulfonic acid group, or to make it water-soluble by copolymerizing a monomer having a polyethylene oxide group 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 storage stability of the ink. For example, acrylic resins, styrene-acrylic resins, styrene-maleic acid resins, vinylnaphthalene-acrylic resins, vinyl acetate-acrylic resins can be mentioned. More preferably, acrylic and styrene-acrylic resins can be mentioned. Further, the block polymer is preferable to the random polymer from the viewpoint of the storage stability of the ink and the water resistance of the printed matter.

The mass 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 emulsion excludes the betaine structure-containing resin (B), and includes (meth)acrylic acid-based resin emulsion, styrene-(meth)acrylic acid-based resin emulsion, styrene-maleic acid-based resin emulsion, and styrene-butadiene-based emulsion. Examples thereof include resin emulsions, styrene resin emulsions, butadiene resin emulsions, (meth)acrylic acid ester resin emulsions, vinyl chloride resin emulsions and vinyl acetate resin emulsions.
Among them, styrene-(meth)acrylic acid-based resin emulsion and (meth)acrylic acid ester-based resin emulsion are preferable from the viewpoint of image forming property.

The binder resins as described above 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.

<Other dispersants>
In the inkjet ink of the invention, other dispersants may be used in combination with the betaine structure-containing resin (B). When a dispersant is used in combination, the betaine structure-containing resin (B) is preferably 5% by mass or more, and more preferably 10% of the total mass of the betaine structure-containing resin (B) and other dispersants. It is at least mass%.

<Other resins>
The inkjet ink of the present invention may contain a natural resin such as rosin, shellac, and starch, or a synthetic resin other than the above-mentioned betaine structure-containing resin (B), if necessary. In this case, it is preferable that the natural resin or the synthetic resin is contained in an amount not exceeding the addition amount of the above-mentioned betaine structure-containing resin (B).

<Additive>
In addition to the above components, the inkjet ink of the present invention may optionally contain an additive such as a surfactant, a defoaming agent and an antiseptic agent in order to obtain an ink having desired physical properties. It can be added. An example of the addition amount of these additives 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 ink of the present invention comprising the above components include the following methods, but the present invention is not limited thereto. First, a pigment is added to an aqueous medium in which a betaine structure-containing resin (B) and a water-soluble solvent or water are mixed, and after mixing and stirring, a dispersion treatment is carried out using a dispersion means described later, if necessary. According to the centrifugal separation treatment, a desired pigment dispersion liquid is obtained. Next, to this pigment dispersion, a water-soluble solvent (C) and, if necessary, an additive component such as a binder resin or a surfactant, which is appropriately selected as described above, are added, and the mixture is stirred and if necessary. And filtered to obtain the ink of the present invention.

In the method for producing the ink of the present invention, as described above, the pigment dispersion liquid obtained by performing the dispersion treatment is used for the preparation of the ink, but before the dispersion treatment performed in the preparation of the pigment dispersion liquid, It is effective to do premixing. That is, the premixing may be performed by adding a pigment to an aqueous medium in which the betaine structure-containing resin (B) and water are mixed. Such premixing operation is preferable because it improves wettability of the pigment surface and promotes adsorption of the betaine structure-containing resin (B) on the pigment surface. In premixing, it is preferable to stir and mix with a high speed mixer or the like until uniform.

The disperser used in the dispersion treatment of the above-mentioned pigment may be any disperser generally used, and examples thereof include a ball mill, a roll mill, a sand mill, a bead mill and a nanomizer. Among them, the bead mill is preferably used. Examples of such a material include a super mill, a sand grinder, an agitator mill, a grain mill, a dyno mill, a pearl mill and a cobol mill (all are trade names).

Further, in the above-described premixing and dispersion treatment of the pigment, the betaine structure-containing resin (B) was dissolved or dispersed in the mixed solvent of the water-soluble solvent (C) and water even when dissolved or dispersed in only water. It may be the case. Particularly, in the dispersion treatment, when the betaine structure-containing resin (B) is dissolved or dispersed in the mixed solvent of the water-soluble solvent (C) and water used as the synthetic solvent of the betaine structure-containing resin (B) as described above. In some cases, a more stable dispersion can be obtained in the dispersion treatment process.

Since the ink of the present invention is for inkjet recording, it is preferable to use a pigment having an optimum particle size distribution as the pigment. That is, in order to suitably use the ink containing the pigment particles in the ink jet recording method, it is preferable to use a pigment having an optimum particle size distribution from the requirement of the nozzle clogging resistance and the like. Ink having a narrow particle size distribution of the pigment and finely dispersed, that is, an ink having a smaller volume cumulative median diameter (D50) by the dynamic light scattering method has lower storage stability, printability, ejection property and clogging. The property is also good.

The method for obtaining a pigment having a desired particle size distribution includes the following methods. To reduce the size of the crushing media of the above-mentioned disperser, to increase the filling rate of the crushing media, to increase the processing time, to classify with a filter or centrifuge after crushing, and these There are methods such as combinations of the above methods.

<Recording medium>
A known recording medium can be used as the recording medium for printing the inkjet ink of the present invention. For example, it is a paper medium such as high-quality paper, coated paper, art paper, cast paper, synthetic paper, inkjet-dedicated paper, or a plastic medium such as a polyvinyl chloride sheet, PET film, or PP film. Further, the non-water-absorbent substrate or the hardly-absorbent substrate refers to a recording medium that hardly absorbs water or has a slow absorption rate, such as paper media such as coated paper, art paper, cast paper, polycarbonate, and hard vinyl chloride. Examples include plastic base materials such as soft vinyl chloride, polystyrene, expanded polystyrene, PMMA, polypropylene, polyethylene, and PET, metal base materials such as aluminum and stainless steel, glass, and wood.

Hereinafter, the present invention will be described based on examples, but the present invention is not limited thereto. In addition, in an Example, "part" and "%" represent a "mass part" and "mass %", respectively. The methods for measuring the weight average molecular weight (Mw) and the acid value of the polymer are as follows.

(Mass average molecular weight of polymer (Mw))
As the mass average molecular weight (Mw) of the polymer, a value measured in terms of standard polystyrene by gel permeation chromatography (GPC) was adopted. The measuring device and the measuring conditions were basically based on the following condition 1, and allowed to be the condition 2 depending on the solubility of the sample. However, depending on the polymer species, an appropriate carrier (eluent) and a column suitable for it were further selected and used. For other matters, refer to JIS K7252-1 to 4:2008. The poorly soluble polymer compound was measured at a concentration capable of dissolving it under the following conditions.
(Condition 1)
Column: Shodex OHpark SB-800RL
ShodexOHpark SB-800RH
Shodex 0Hpark SB-802.5 HQ
Shodex0Hpark SB-806M HQ
The column which connected was used.
Carrier: Phosphate buffer aqueous solution Measuring temperature: 40°C
Sample concentration: 0.2 mass%
Detector: RI (refractive index) detector (condition 2)
Column: A column in which two TOSOHTSK gelSuperAWM-Hs were connected 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

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

<Method for producing resin (B) containing betaine structure>
(Synthesis example 1)
98 parts of butyldiglycol was charged into a reaction vessel equipped with a gas introduction tube, a thermometer, a condenser, and a stirrer, and after substituting with nitrogen gas, the mixture was heated to 110° C. and stirred. Next, from 20 parts of styrene, 20 parts of stearyl methacrylate, 60 parts of N-methacryloyloxyethyl-N,N-dimethylammoniumbutyl-α-sulfobetaine, and 2 parts of dimethyl 2,2′-azobis(2-methylpropionate). The following solution was prepared and added dropwise from the dropping funnel over 2 hours to carry out a polymerization reaction. After completion of dropping, the mixture was further reacted at 110° C. for 3 hours to obtain a copolymer solution having a mass average molecular weight of about 37,500.
Furthermore, 300 parts of ion-exchanged water was added to obtain a resin (B1-1) solution containing a betaine structure having a nonvolatile content of 20%.

(Synthesis example 2)
98 parts of butyldiglycol was charged into a reaction vessel equipped with a gas introduction tube, a thermometer, a condenser, and a stirrer, and after substituting with nitrogen gas, the mixture was heated to 110° C. and stirred. Next, 15 parts of styrene, 40 parts of behenyl acrylate, 5 parts of N-methacryloyloxyethyl-N,N-dimethylammoniumbutyl-α-sulfobetaine, 40 parts of acrylic acid, dimethyl 2,2′-azobis(2-methylpropio). A solution consisting of 2 parts of the same was prepared and added dropwise from the dropping funnel over 2 hours to carry out a polymerization reaction. After completion of dropping, the mixture was further reacted at 110° C. for 3 hours to obtain a copolymer solution having a mass average molecular weight of about 38,000 and an acid value of 311 (mgKOH/g).
After cooling to room temperature, 49.5 parts of dimethylaminoethanol was added to neutralize. This is the amount that 100% of acrylic acid is neutralized. Further, 250 parts of ion-exchanged water was added to obtain a betaine structure-containing resin (B1-2) solution having a nonvolatile content of 20%.

(Synthesis examples 3 to 11)
Compounds shown in Table 1 were synthesized in the same manner as in Synthesis Example 2 to obtain the betaine structure-containing resins (B1-3) to (B1-11) solutions of Synthesis Examples 3 to 10.

(Synthesis example 12)
98 parts of butyldiglycol was charged into a reaction vessel equipped with a gas introduction tube, a thermometer, a condenser, and a stirrer, and after substituting with nitrogen gas, the mixture was heated to 110° C. and stirred. Next, 15 parts of styrene, 40 parts of stearyl methacrylate, 5 parts of N-methacryloyloxyethyl-N,N-dimethylamine, 40 parts of acrylic acid, and 2 parts of dimethyl 2,2'-azobis(2-methylpropionate). A solution was prepared and added dropwise from a dropping funnel over 2 hours to carry out a polymerization reaction. After completion of the dropping, the reaction was further continued at 110° C. for 3 hours, and it was confirmed by solid content measurement that the conversion rate exceeded 98%, followed by cooling to room temperature. Next, 6.5 parts of 1,4-butane sultone (an amount equivalent to 1.5 times that of the N-methacryloyloxyethyl-N,N-dimethylamine) was added, and the mixture was heated to 80° C. and stirred for 20 hours, and the mass average was obtained. A copolymer solution having a molecular weight of about 35,000 and an acid value of 311 (mgKOH/g) was obtained. After cooling to room temperature, 49.5 parts of dimethylaminoethanol was added to neutralize. This is the amount that 100% of acrylic acid is neutralized. Further, 279 parts of ion-exchanged water was added to obtain a betaine structure-containing resin (B2-1) solution having a nonvolatile content of 20%.
In addition, as shown in the following reaction formula 8, N-methacryloyloxyethyl-N,N-dimethylammonium butyl-α-sulfo, which is one of the monomers (b3x), is formed by a ring-opening reaction of 1,4-butanesultone. A betaine structure similar to that of Synthesis Example 1 using betaine can be introduced.

Reaction formula (8)

(Synthesis examples 13 and 14)
Compounds shown in Table 2 were synthesized in the same manner as in Synthesis Example 11 to obtain the betaine structure-containing resins (B2-2) and (B2-3) solutions of Synthesis Examples 13 and 14.

(Comparative Synthesis Example 1)
The betaine structure-containing resin (HB-1) solution of Comparative Synthesis Example 1 was obtained by synthesizing with the compounding composition shown in Table 1 in the same manner as in Synthesis Example 1.

(Comparative Synthesis Examples 2 and 3)
Compounds having the composition shown in Table 1 were synthesized in the same manner as in Synthesis Example 2 to obtain the betaine structure-containing resin (HB-2) and the resin having no betaine structure (HB-3) solutions of Comparative Synthesis Examples 2 and 3. It was

The abbreviations in Tables 1 and 2 are shown below.
St: Styrene BzMA: Benzyl methacrylate BMA: Butyl methacrylate STMA: Stearyl methacrylate VA: Behenyl acrylate DMBS: N-methacryloyloxyethyl-N,N-dimethylammonium butyl-α-sulfobetaine DMPS: N-acrylamidopropyl-N,N- Dimethylammonium propyl-α-sulfobetaine DMMC: N-methacryloyloxyethyl-N,N-dimethylammoniummethyl-α-carbobetaine VSPI: 1-vinyl-3-(3-sulfopropyl)imidazolium inner salt VSPP:2- Vinyl-1-(3-sulfopropyl)pyridinium inner salt MPC:2-methacryloyloxyethylphosphorylcholine AA:acrylic acid MAA:methacrylic acid DM:N-methacryloyloxyethyl-N,N-dimethylamine VI:1-vinylimidazole VP : 2-vinylpyridine DMAE: dimethylaminoethanol V601: dimethyl 2,2'-azobis(2-methylpropionate) (radical polymerization initiator)

<Method for producing binder resin>
(Fixing resin 1)
93.4 parts of butanol were charged into a reaction vessel equipped with a gas introduction tube, a thermometer, a condenser, and a stirrer, and the atmosphere was replaced with nitrogen gas. The inside of the reaction vessel was heated to 110° C., and 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 dimethyl 2,2′-azobis(2- A mixture of 6.0 parts of methyl propionate) was added dropwise over 2 hours to carry out a polymerization reaction. After completion of the dropping, the mixture was further reacted at 110° C. for 3 hours, 0.6 part of dimethyl 2,2′-azobis(2-methylpropionate) was added, and the reaction was further continued at 110° C. for 1 hour to prepare an aqueous solution. A resinous solution was obtained. The mass average molecular weight of the water-soluble resin was about 15,000.
Further, after cooling to room temperature, 10.4 parts of dimethylaminoethanol was added to neutralize. This is the amount that neutralizes methacrylic acid by 100%. Further, 200 parts of water was added to make it aqueous. 1 g of this was sampled, heated and dried at 180° C. for 20 minutes to measure the nonvolatile content, and water was added so that the nonvolatile content of the previously hydrated resin solution was 30%. From this, an aqueous solution of the fixing resin 1 having a solid content of 30% was obtained.

(Fixing resin 2)
A reaction vessel equipped with a stirrer, a thermometer, a dropping funnel, and a reflux condenser was charged with 40 parts of ion-exchanged water and 0.2 part of Aqualon KH-10 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as a surfactant, and separately. , 2-ethylhexyl acrylate 40 parts, methyl methacrylate 50 parts, styrene 7 parts, dimethyl acrylamide 2 parts, methacrylic acid 1 part, deionized water 53 parts and Aqualon KH-10 as a surfactant (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.). 1% of the pre-emulsion premixed with 1.8 parts was further added. After the internal temperature was raised to 60° C. and the atmosphere was sufficiently replaced 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 keeping the inside of the reaction system at 60°C for 5 minutes, the rest of the pre-emulsion and the 5% aqueous solution of potassium persulfate and the 1% aqueous solution of anhydrous sodium bisulfite are kept for 1.5 hours while keeping the internal temperature at 60°C. It dripped over, and continued stirring for further 2 hours. After confirming that the conversion 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 ion-exchanged water to obtain a resin fine particle water dispersion. The solid content was obtained from the residue remaining after baking at 150° C. for 20 minutes. The obtained resin fine particle water dispersion was used as a fixing resin 2.

<Method for producing pigment dispersion>
(Pigment dispersion (GB-1))
After pre-dispersing a mixture having the following composition with a disper so as to be uniform, main dispersion was performed for 2 hours using a Dyno-mill having a volume of 0.6 L filled with 1800 g of zirconia beads having a diameter of 0.5 mm, and a pigment dispersion (GB- 1) was obtained.
Blue pigment (Pigment Blue 15:3): 20 parts Betaine structure-containing resin (B1-1) solution: 35 parts Ion-exchanged water: 45 parts

(Pigment Dispersion (GB-2 to 22), Comparative Pigment Dispersion (HGB-1 to 3))
Pigment Dispersions (GB-2 to 22) in the same manner as Pigment Dispersion (GB-1), except that the types and mass ratios of the pigment and the betaine structure-containing resin (B) were changed as described in Table 3. ) And comparative pigment dispersions (HGB-1 to 3) were obtained.

The abbreviations in Table 3 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

<Inkjet ink manufacturing method>
[Example 1]
(Inkjet ink (IJ-1))
An inkjet ink (IJ-1) was obtained by stirring and mixing with a disper a mixture having the following composition so as to be uniform.
Pigment dispersion (GB-1): 25 parts 1,3-propanediol: 10 parts Propylene glycol: 5 parts Water-soluble binder resin (fixing resin 1): 25 parts Ion-exchanged water: 35 parts

[Examples 2 to 23, Comparative Examples 1 to 3]
(Inkjet ink (IJ-2 to 23), Comparative inkjet ink (HIJ-1 to 3))
InkJet Ink (IJ-2 to 23) and Comparative InkJet in the same manner as (IJ-1) except that the types and blending amounts of the pigment dispersion, the binder resin, and the water-soluble solvent were changed as described in Table 4. Inks (HIJ-1 to 3) were obtained.

The abbreviations in Table 4 are shown below.
BDG: Butyldiglycol HeDG: Hexyldiglycol, (diethyleneglycol monohexylether)
1,2-HD: 1,2-hexanediol 1,2-BD: 1,2-butanediol 1,3-PD: 1,3-propanediol PG: propylene glycol

<Evaluation of inkjet ink>
The obtained inkjet inks (IJ-1 to 23) and comparative inkjet inks (HIJ-1 to 3) were evaluated for clogging, water resistance, scratch resistance, dispersibility, storage stability and printability by the following methods. .. Table 5 shows the evaluation results.

(Clogging property)
The IJ ink was packed in a cartridge of an inkjet printer (“PM-750C” manufactured by Epson Corp.) and continuously discharged for 5 minutes. After that, the ink is continuously ejected again for 6, 12, and 24 hours in an environment of 30° C. and 50% RH, and the state of ejected droplets is visually observed to confirm nozzle clogging and droplet aggregation. The evaluation was performed according to the occurrence of defective ejection, defective ejection, and the like.
⊚: No ejection failure even after standing still for 24 hours (good)
◯: No defective discharge after standing for 12 hours, but defective discharge after standing for 24 hours (usable)
Δ: No discharge failure even after standing for 6 hours, but discharge failure is observed after standing for 12 hours (usable)
X: Discharge failure is observed after standing still for 6 hours (unusable)

(Water resistance of printed matter)
The IJ ink was packed in a cartridge of an inkjet printer (“PM-750C” manufactured by Epson Corporation), and coated on a coated paper (OK Top Coat + manufactured by Oji Paper Co., Ltd., 104.7 g/m ² , square meter, absorption speed: 4) of 3 cm×3 cm. A single color solid image was printed. The printed matter was rubbed 100 times with a cotton swab moistened with water under a load of 50 g to evaluate the ease of peeling of the coating film surface.
◯: There is no peeling of the coating film surface (good)
△: The coating surface was slightly peeled off (usable)
X: Most of the coating surface has peeled off (cannot be used)

(Scratch resistance of printed matter)
The IJ ink was packed in a cartridge of an inkjet printer (“PM-750C” manufactured by Epson Corporation), and coated on a coated paper (OK Top Coat + manufactured by Oji Paper Co., Ltd., 104.7 g/m ² , square meter, absorption speed: 4) of 3 cm×3 cm. A single color solid image was printed. The printed matter was rubbed 100 times with a dry cotton swab under a load of 100 g to evaluate the ease of peeling of the coating film surface.
◯: The coating surface does not peel off at all (good)
△: The coating surface was slightly peeled off (usable)
X: Most of the coating surface has peeled off (cannot be used)

(Dispersibility (D50))
The obtained IJ ink was diluted by adding water so that the loading index value of the laser dynamic light scattering method (UPA150EX, manufactured by Nikkiso Co., Ltd.) was within the range of 0.8 to 1.2, and was 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 thermostat at 70° C. for 2 weeks to accelerate the aging, the viscosity of the ink before and after the aging was measured, and the viscosity change rate was calculated. The viscosity was measured using an E-type viscometer (“ELD-type viscometer” manufactured by Toki Sangyo Co., Ltd.) at a rotation speed of 50 rpm at 25° C.
◯: Viscosity change rate is less than ±5% (good)
Δ: Viscosity change rate is ±5% or more and less than ±10% (usable)
X: Viscosity change rate is ±10% or more (cannot be used)

(Printability of coated paper)
The IJ ink was packed in a cartridge of an inkjet printer (“PM-750C” manufactured by Epson Corporation), and printed on coated paper (OK Top Coat+ manufactured by Oji Paper Co., Ltd., 104.7 g/m ² , square meter absorption rate 4). The printed sample was observed with a magnifying glass to evaluate dot connection and color unevenness. The best printability was set to 5, and the worst printability was set to 1, and a comparative evaluation was made with a score of 1-5. An evaluation of 3 to 5 is a level at which there is no practical problem.

As is clear from the results in Table 5, all of the IJ inks of the present application containing the betaine structure-containing resin (B) have excellent clogging of inkjet nozzles, water resistance and scratch resistance, and dispersibility and storage stability. The balance between the printability and the printability was also good.
Particularly, when the betaine structure-containing resin (B) having a repeating unit having an acid group in the side chain was used, excellent clogging property, water resistance and scratch resistance were exhibited.
On the other hand, Comparative Examples 1 and 2 did not have the repeating unit b1 or the repeating unit b2, so that the dispersibility was poor, and as a result, the storage stability and the clogging property were greatly deteriorated. In addition, the water resistance and scratch resistance were also poor. Further, in Comparative Example 3, since it did not have a betaine structure, the clogging property was significantly inferior.

Claims (5)

An inkjet ink containing a colorant (A), a betaine structure-containing resin (B), and a water-soluble solvent (C),
The inkjet ink, wherein the betaine structure-containing resin (B) is a vinyl polymer containing the following repeating unit b1, repeating unit b2 and repeating unit b3.
Repeating unit b1: Repeating unit having an aromatic ring in the side chain Repeating unit b2: Repeating unit having an alkyl group having 4 to 24 carbon atoms in the side chain (provided that repeating units b1 and b3 and an acid group in the side chain are included. (Excluding repeating units)
Repeating unit b3: Repeating unit having the betaine structure represented by the following general formulas 1 to 4 General formula 1

General formula 2

General formula 3

General formula 4


[In general formulas 1 to 4,
R ₁ is a hydrogen atom or a methyl group,
R ₂ is an alkylene group having 1 to 6 carbon atoms,
R ₃ and R ₄ are each independently an alkyl group having 1 to 4 carbon atoms,
R ₅ is an alkylene group having 1 to 4 carbon atoms, X is an oxygen atom or NH,
Y is CO ₂ ⁻ or SO ₃ ⁻ ,
R ₆ is a hydrogen atom or a methyl group,
R ₇ is a hydrogen atom or a methyl group,
R ₈ is an alkylene group having 1 to 6 carbon atoms or a hydroxyalkylene group having 1 to 6 carbon atoms,
R ₉ is a hydrogen atom or a methyl group,
One of R _{10 to} R ₁₄ is directly bonded to the * moiety,
Four of R _{10 to} R ₁₄ are each independently a hydrogen atom or an alkyl group having 1 to 6 carbon atoms,
R ₁₅ is an alkylene group having 1 to 6 carbon atoms or a hydroxyalkylene group having 1 to 6 carbon atoms,
R ₁₆ is a hydrogen atom or a methyl group,
R ₁₇ is _{(CH 2 -CHR 22 O) m} (CH 2 -CHR 22) group _{(wherein, R 22} represents a hydrogen atom, a methyl group or an ethyl group, m represents an integer of 0.),
R ₁₈ is (CH ₂ )g (here, g represents an integer of 0 to 10),
R _{19 to} R ₂₁ each independently represent an alkyl group having 1 to 8 carbon atoms or a hydroxyalkyl group. ] The inkjet ink according to claim 1, wherein the betaine structure-containing resin (B) is a vinyl-based polymer further containing the following repeating unit b5.
Repeating unit b5: Repeating unit having an acid group in the side chain The inkjet ink according to claim 1, wherein the betaine structure-containing resin (B) has a mass average molecular weight of 3,000 to 150,000. The inkjet ink according to any one of claims 1 to 3, wherein the colorant (A) contains an organic pigment. A printed matter obtained by printing the inkjet ink according to claim 1 on a recording medium.