JP7528444B2 - Water-based colorant dispersion and method for producing same - Google Patents

Description

The present invention relates to an aqueous colorant dispersion for use in inkjet recording inks, etc.

Inkjet recording inks are shifting from water-based dye inks to water-based pigment inks, which have superior water and light resistance.

Patent Document 1 discloses an aqueous pigment dispersion for inkjet printers, which contains a pigment coated with a polymeric dispersant, an aqueous organic solvent, and a basic compound, the pigment to polymeric dispersant content ratio being 40/60 to 95/5, the polymeric dispersant being a block polymer consisting of a methacrylate-based hydrophobic polymer block and a hydrophilic polymer block containing 30 to 5% by mass of methacrylic acid, the dispersity PDI of the polymer and the PDI of the hydrophobic polymer block constituting the block polymer are both 1.5 or less, and where the average molecular weight of the block polymer is Mnab, the average molecular weight of the hydrophobic block is Mna, and the average molecular weight of the hydrophilic block is Mnb, the requirements of Mna≧Mnb or Mna<Mnb≦2Mna are satisfied.

Patent document 2 also discloses a pigment whose surface is coated with a resin, the resin containing an α-olefin unit in the main chain, and the amount of the resin adsorbed on the pigment is 10% by mass or more and 50% by mass or less relative to the uncoated pigment, and an aqueous pigment dispersion using the pigment.

Patent Document 3 discloses an aqueous pigment dispersion comprising a pigment and a polymer dispersant formed by crosslinking a water-insoluble polymer having a carboxy group with a water-insoluble polyfunctional epoxy compound, in which at least a portion of the carboxy groups of the water-insoluble polymer are neutralized with an alkali metal compound, and the acid value, degree of neutralization, and degree of crosslinking of the neutralized water-insoluble polymer satisfy specific ranges.

JP 2012-36251 A JP 2018-162430 A JP 2018-65997 A

However, with conventional colorant dispersions, there was a problem that the colorant dispersion state would change if the storage temperature changed significantly, resulting in the generation of coarse particles and poor filterability. In addition, continuous printing with inkjet recording inks could cause problems such as clogged printer nozzles and poor printing.

The present invention aims to provide an aqueous colorant dispersion that is less likely to lose dispersion stability of the colorant even when subjected to temperature changes, and can be used to prepare an inkjet recording ink that allows for continuous printing.

The aqueous colorant dispersion of the present invention comprises a colorant (A), an acid group-containing resin (B) having an acid value of 1 to 300 mgKOH/g, an aqueous medium (C), a crosslinking agent (D), and a basic compound (E),
The acid group-containing resin (B) satisfies the following (1) neutralization value and (1) crosslinking value.
The neutralization value of the acid group-containing resin (B) is 0.5 or more and less than 1.0, and the crosslinking value is 0.7 or more and 1.5 or less,
(1) Neutralization value = number of molar equivalents of basic functional groups of basic compound (E) / number of molar equivalents of acidic functional groups of acid group-containing resin (B) (2) Crosslinking value = number of molar equivalents of crosslinking functional groups of crosslinking agent (D) / number of molar equivalents of acidic functional groups of acid group-containing resin (B).

The present invention provides an aqueous colorant dispersion and an inkjet recording ink that are less likely to lose dispersion stability even when subjected to temperature changes and that can be used to prepare inkjet recording ink that allows for continuous printing.

The following terms are defined in this specification. "C.I." stands for Color Index number. "(Meth)acrylate" refers to acrylate and methacrylate. The monomer is an ethylenically unsaturated group-containing compound. The ethylenically unsaturated group is a vinyl group, an allyl group, an acryloyl group, or a methacryloyl group.

The aqueous colorant dispersion of the present invention comprises a colorant (A), an acid group-containing resin (B) having an acid value of 1 to 300 mgKOH/g, an aqueous medium (C), a crosslinking agent (D), and a basic compound (E),
The acid group-containing resin (B) satisfies the following defined (1) neutralization value and (2) crosslinking value.
The neutralization value of the acid group-containing resin (B) is 0.5 or more and less than 1.0, and the crosslinking value is 0.7 or more and 1.5 or less,
(1) Neutralization value = number of molar equivalents of basic functional groups of basic compound (E) / number of molar equivalents of acidic functional groups of acid group-containing resin (B) (2) Crosslinking value = number of molar equivalents of crosslinking functional groups of crosslinking agent (D) / number of molar equivalents of acidic functional groups of acid group-containing resin (B).
The aqueous colorant dispersion of the present invention can greatly improve the dispersion stability of the colorant (A) by including the acid group-containing resin (B) that satisfies the predetermined neutralization value and crosslinking value. Therefore, even when the aqueous colorant dispersion is stored in an environment with large temperature changes, coarse particles are unlikely to be generated. In addition, the inkjet recording ink using the aqueous colorant dispersion has the effect of preventing printing voids during continuous printing.

<Colorant (A)>
The water-based colorant dispersion of the present invention contains a colorant (A). The colorant (A) is a pigment or dye that is insoluble in an aqueous medium. A water-soluble dye can be used in combination with the colorant (A).
Pigments include, for example, C.I. Pigment Red 3, 5, 19, 22, 31, 38, 42, 43, 48:1, 48:2, 48:3, 48:4, 48:5, 49:1, 53:1, 57:1, 57:2, 58:4, 63:1, 81, 81:1, 81:2, 81:3, 81:4, 88, 104, 108, 112, 122, 123, 144, 146, 147, 149, 150, 166, 168, 169, 170, 176, 177, 178, 179, 184, 185, 202, 208, 216, 226, 242, 254, 255, 257, 269, 291;
C.I. Pigment Green 7, 26, 36, 50, 58, 59, 62, 63;
C.I. Pigment Blue 1, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 17, 17:1, 22, 27, 28, 29, 36, 60;
C.I. Pigment Orange 13, 16, 20, 34, 36, 38, 43, 62, 64, 71, 73;
C.I. Pigment Yellow 1,3,12,13,14,17,34,35,37,55,74,81,83,93,94,95,97,108,109,110,120,128,137,138,139,150,153,154,155,157,166,167,168,174,180,185,193,213,234;
C.I. Pigment Violet 3,19,23,29,30,37,50,88;
C.I. Pigment Black 7, 28, 26;
C.I. Pigment White 6, 18, 21, etc.
Disperse dyes include, for example, C.I. Disperse Red 11, 50, 53, 54, 55, 55:1, 59, 60, 65, 70, 72, 73, 75, 86, 88, 91, 92, 93, 111, 126, 127, 134, 135, 143, 145, 146, 152, 153, 154, 158, 159, 164, 167:1, 177, 181, 190, 190:1, 204, 206, 207, 221, 239, 240, 258, 277, 278, 283, 311, 323, 343, 348, 356, 362;
C.I. Bat Red 41;
C. I. Disperse Green 6:1,9;
C.I. Disperse Blue 19,26,26:1,35,55,56,58,60,64,64:1,72,72:1,73,81,81:1,87,91,95,108,113,128,131,141,143,145,148,154,158,165,165:1,165:2,176,183,185,197,198,201,214,224,225,257,266,267,287,354,358,359,360,365,368;
C.I. Disperse Orange 1, 1:1, 5, 13, 20, 25, 25:1, 29, 31:1, 33, 49, 54, 55, 56, 66, 73, 76, 118, 119, 163;
C.I. Disperse Yellow 3,5,7,8,23,39,42,51,54,60,64,71,79,82,83,86,93,99,100,119,122,124,126,160,184:1,186,198,199,201,204,224,237;
C.I. Disperse Violet 8,17,23,27,28,29,33,36,57;
C.I. Disperse Brown 2; and the like.
Examples of water-soluble dyes include direct dyes, acid dyes, food dyes, basic dyes, and reactive dyes. For example, C.I. Direct Red 2, 4, 9, 23, 26, 31, 39, 62, 63, 72, 75, 76, 79, 80, 81, 83, 84, 89, 92, 95, 111, 173, 184, 207, 211, 212, 214, 218, 223, 224, 225, 226, 227, 232, 233, 240, 241, 242, 243, 247;
C.I. Direct Violet 7,9,47,48,51,66,90,93,94,95,98,100,101;
C.I. Direct Yellow 8,9,11,12,27,28,29,33,35,39,41,44,50,53,58,59,68,86,87,93,95,96,98,100,106,108,109,110,130,132,142,144,161,163;
C.I. Direct Blue 1,10,15,22,25,55,67,68,71,76,77,78,80,84,86,87,90,98,106,108,109,151,156,158,159,160,168,189,192,193,194,199,200,201,202,203,207,211,213,214,218,225,229,236,237,244,248,249,251,252,264,270,280,288,289,291;
C.I. Direct Black 9, 17, 19, 22, 32, 51, 56, 62, 69, 77, 80, 91, 94, 97, 108, 112, 113, 114, 117, 118, 121, 122, 125, 132, 146, 154, 166, 168, 173, 199
C.I. Acid Red 35, 42, 52, 57, 62, 80, 82, 111, 114, 118, 119, 127, 128, 131, 143, 151, 154, 158, 249, 254, 257, 261, 263, 266, 289, 299, 301, 305, 336, 337, 361, 396, 397;
C.I. Acid Violet 5,34,43,47,48,90,103,126;
C.I. Acid Yellow 17,19,23,25,39,40,42,44,49,50,61,64,76,79,110,127,135,143,151,159,169,174,190,195,196,197,199,218,219,222,227;
C.I. Acid Blue 9, 25, 40, 41, 62, 72, 76, 78, 80, 82, 92, 106, 112, 113, 120, 127: 1, 129, 138, 143, 175, 181, 205, 207, 220, 221, 230, 232, 247, 258, 260, 264, 271, 277, 278, 279, 280, 288, 290, 326
C. I. Acid Black 7, 24, 29, 48, 52: 1, 172;
C.I. Reactive Red 3, 13, 17, 19, 21, 22, 23, 24, 29, 35, 37, 40, 41, 43, 45, 49, 55;
C.I. Reactive Violet 1,3,4,5,6,7,8,9,16,17,22,23,24,26,27,33,34;
C.I. Reactive Yellow 2, 3, 13, 14, 15, 17, 18, 23, 24, 25, 26, 27, 29, 35, 37, 41, 42;
C.I. Reactive Blue 2,3,5,8,10,13,14,15,17,18,19,21,25,26,27,28,29,38;
C.I. Reactive Black 4, 5, 8, 14, 21, 23, 26, 31, 32, 34;
C.I. Basic Red 12,13,14,15,18,22,23,24,25,27,29,35,36,38,39,45,46;
C.I. Basic Violet 1,2,3,7,10,15,16,20,21,25,27,28,35,37,39,40,48;
C.I. Basic Yellow 1,2,4,11,13,14,15,19,21,23,24,25,28,29,32,36,39,40;
C.I. Basic Blue 1,3,5,7,9,22,26,41,45,46,47,54,57,60,62,65,66,69,71;
C.I. Basic Black 8; and the like.

The colorant (A) may be used alone or in combination of two or more types.

<Acid Group-Containing Resin (B) Having an Acid Value of 1 to 300 mgKOH/g>
The acid group-containing resin (B) having an acid value of 1 to 300 mgKOH/g (hereinafter referred to as acid group-containing resin (B)) may be either a random polymerized resin or a block polymerized resin as long as it has an acid value of 1 to 300 mgKOH/g. The acid group of the acid group-containing resin (B) is preferably a carboxy group, and is preferably a polymer containing an α-olefin unit.
Examples of the acid group-containing resin (B) include a resin containing an α-olefin unit in the main chain described in JP-A-2018-162430, an A-B block resin described in JP-A-2012-36251, and a water-insoluble resin described in JP-A-2018-65997. Among these, a resin containing an α-olefin unit in the main chain is preferred. Since the aqueous colorant dispersion contains the acid group-containing resin (B), the dispersion stability of the colorant is not easily impaired even when there is a temperature change, and therefore an inkjet recording ink capable of continuous printing can be produced.

The acid value of the acid group-containing resin (B) is 1 to 300 mgKOH/g. The acid value is preferably 30 to 250 mgKOH/g, more preferably 90 to 200 mgKOH/g, and even more preferably 90 to 170 mgKOH/g. By setting the acid value within the above range, the dispersion stability of the colorant is less likely to be impaired, and the filterability of the water-based colorant dispersion is improved.

The acid value in the present invention was calculated by calculating the theoretical value of the number of moles of acid groups contained in 1 g of resin from the monomer composition, and assuming that the number of moles of acid groups is equal to the number of moles of potassium hydroxide (molecular weight 56.1) required for neutralization, and the acid value (mgKOH/g) was calculated. Note that when maleic anhydride is contained in the resin structure, the acid value is calculated assuming that maleic anhydride is hydrolyzed and exists as maleic acid. The reason for this is that it is known that maleic anhydride is very easily hydrolyzed in water to become maleic acid (the hydrolysis half-life of maleic anhydride in water at 25°C and pH 7 is said to be about 22 seconds). Therefore, it is considered that in the aqueous colorant dispersion of the present invention, it exists as maleic acid, not as maleic anhydride.

Examples of acid groups include sulfo groups, carboxy groups, and phosphate groups. Of these, carboxy groups are preferred.

The number average molecular weight (Mn) of the acid group-containing resin (B) is preferably 1,000 to 100,000, more preferably 1,000 to 50,000, and even more preferably 6,000 to 30,000. By setting the number average molecular weight within this range, the efficiency of coating the surface of the colorant (A) is improved.

[Resin containing α-olefin units in the main chain]
The resin containing α-olefin units in the main chain preferably contains a carboxy group-containing monomer unit in addition to the α-olefin units.

The α-olefin unit is formed from an α-olefin, which is preferably a monomer having 5 to 50 carbon atoms, more preferably a monomer having 10 to 30 carbon atoms.
Examples of the α-olefin include 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, and 1-octadecene.

α-Olefins can be used alone or in combination of two or more types.

Examples of the carboxyl group-containing monomer unit include a (meth)acrylic acid unit, a maleic acid unit, a maleic acid half ester unit, a fumaric acid unit, a fumaric acid half ester unit, a tetrahydrophthalic acid unit, and a tetrahydrophthalic acid half ester unit. Among these, a maleic acid unit is preferred. The maleic acid unit preferably contains at least one of a maleic anhydride unit and a maleic acid ester unit.
The maleic acid unit is derived from a maleic anhydride unit, and in addition to being able to form a maleic acid unit by hydrolyzing the acid anhydride, the acid anhydride can be reacted with an alcohol or the like to form a maleic acid ester unit, and the acid group-containing resin (B) can be modified according to various embodiments. Of course, the maleic anhydride unit may be left. In addition, maleic anhydride has the characteristics of being highly polymerizable with α-olefin, and being able to easily achieve both hydrophilicity retention and grafting in an aqueous solution. Furthermore, maleic anhydride can be used as a graft polymer. Examples of compounds that form a graft polymer include hydroxyl group-containing compounds and amino group-containing compounds, which will be described later. The graft polymer can be obtained by any of the following methods: a method in which a target compound is grafted to maleic anhydride in advance and then polymerized with α-olefin; a method in which a target compound is grafted after maleic anhydride and α-olefin are polymerized; and a method in which the two methods are combined.

Examples of the carboxyl group-containing monomer include (meth)acrylic acid, (meth)acrylic acid dimer, itaconic acid, maleic acid, maleic acid monomethyl ester, maleic anhydride, fumaric acid, fumaric acid monoethyl ester, tetrahydrophthalic acid, tetrahydrophthalic acid monomethyl ester, crotonic acid, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxypropyl phthalate, 2-(meth)acryloyloxyethyl hexahydrophthalate, 2-(meth)acryloyloxypropyl hexahydrophthalate, ethylene oxide-modified succinic acid (meth)acrylate, β-carboxyethyl (meth)acrylate, and ω-carboxypolycaprolactone (meth)acrylate, and compounds having a betaine structure.

Resins containing α-olefin units in the main chain can be synthesized, for example, by the method described in JP 2007-58125 A. Commercially available resins include Diacalna M30 (manufactured by Mitsubishi Chemical Corporation) and the Ceramer series (manufactured by Baker Petrolite Co., Ltd.).

The resin containing α-olefin units in the main chain can contain other monomer units in addition to the α-olefin units and carboxy group-containing monomer units.
Examples of the other monomer units include hydrophilic group-containing monomer units, (meth)acrylic acid ester units, and vinyl monomer units.
The hydrophilic group-containing monomer unit is formed from a monomer containing a hydroxyl group, a sulfo acid group, a phosphoric acid group, or an amino group.
Examples of the hydroxyl group-containing monomer include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2 (or 3)-hydroxypropyl (meth)acrylate, 2 (or 3 or 4)-hydroxybutyl (meth)acrylate, and cyclohexanedimethanol mono(meth)acrylate; or (meth)acrylamide-based monomers having a hydroxyl group, such as N-(2-hydroxyethyl) (meth)acrylamide, N-(2-hydroxypropyl) (meth)acrylamide, and N-(2-hydroxybutyl) (meth)acrylamide; or vinyl ether-based monomers having a hydroxyl group, such as Examples of the monomer include hydroxyalkyl vinyl ethers such as 2-hydroxyethyl vinyl ether, 2-(or 3-)hydroxypropyl vinyl ether, 2-(or 3- or 4-)hydroxybutyl vinyl ether, and allyl ether monomers having a hydroxy group, for example, hydroxyalkyl allyl ethers such as 2-hydroxyethyl allyl ether, 2-(or 3-)hydroxypropyl allyl ether, 2-(or 3- or 4-)hydroxybutyl allyl ether, and further, hydroxy group-containing monomers such as ethylenically unsaturated monomers obtained by adding alkylene oxide and/or lactone to the above-mentioned hydroxyalkyl (meth)acrylates, N-(hydroxyalkyl)(meth)acrylamides, hydroxyalkyl vinyl ethers, or hydroxyalkyl allyl ethers.
Examples of the sulfo group-containing monomer include vinyl sulfonic acid, p-styrene sulfonic acid, sodium p-styrene sulfonate, 3-(acryloyloxy)propane-1-sulfonic acid, potassium 3-(acryloyloxy)propane-1-sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, acrylonitrile-tert-butylsulfonic acid, and compounds having an ethylenically unsaturated double bond having a betaine structure.
Examples of the phosphoric acid-containing monomer include vinylphosphonic acid and 2-acryloyloxyethyl acid phosphate.
Examples of the amino group-containing monomer include primary amino group-containing monomers such as 6-vinyl-1,3,5-triazine-2,4-diamine; secondary amino group-containing monomers such as N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(meth)acrylamide, N-hexyl(meth)acrylamide, and N-dodecyl(meth)acrylamide; and tertiary amino group-containing monomers such as 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, and N,N-diethylaminopropyl(meth)acrylamide.

The (meth)acrylic acid ester unit is formed from the following monomers: linear or branched alkyl (meth)acrylates such as, for example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, tertiary butyl (meth)acrylate, isoamyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cetyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, isomyristyl (meth)acrylate, stearyl (meth)acrylate, and isostearyl (meth)acrylate;
cyclic alkyl (meth)acrylates such as cyclohexyl (meth)acrylate, tertiary butyl cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, and isobornyl (meth)acrylate;
(meth)acrylates having a heterocycle, such as tetrahydrofurfuryl (meth)acrylate and 3-methyl-3-oxetanyl (meth)acrylate;
(meth)acrylates having an aromatic ring, such as benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, paracumylphenoxyethyl (meth)acrylate, paracumylphenoxypolyethylene glycol (meth)acrylate, and nonylphenoxypolyethylene glycol (meth)acrylate;
Fluoroalkyl (meth)acrylates such as trifluoroethyl (meth)acrylate, octafluoropentyl (meth)acrylate, perfluorooctylethyl (meth)acrylate, and tetrafluoropropyl (meth)acrylate;
(Meth)acryloxy-modified polydimethylsiloxanes (silicone macromers);
(poly)alkylene glycol monoalkyl ether (meth)acrylates such as 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, 2-methoxypropyl (meth)acrylate, diethylene glycol monomethyl ether (meth)acrylate, diethylene glycol monoethyl ether (meth)acrylate, triethylene glycol monomethyl ether (meth)acrylate, triethylene glycol monoethyl ether (meth)acrylate, diethylene glycol mono-2-ethylhexyl ether (meth)acrylate, dipropylene glycol monomethyl ether (meth)acrylate, tripropylene glycol mono(meth)acrylate, polyethylene glycol monolauryl ether (meth)acrylate, and polyethylene glycol monostearyl ether (meth)acrylate;
The vinyl monomer unit is formed from the following monomers: for example, N-substituted (meth)acrylamides such as (meth)acrylamide, dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, diacetone(meth)acrylamide, and acryloylmorpholine;
Nitriles such as (meth)acrylonitrile;
Styrenes such as styrene and α-methylstyrene;
Vinyl ethers such as ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, and isobutyl vinyl ether;
vinyl acetate, vinyl propionate, and other fatty acid vinyl compounds;

[Resin not containing α-olefin units in the main chain]
As the resin not containing an α-olefin unit in the main chain, any conventionally known resin can be used. For example, the A-B block polymer described in JP-A-2012-36251 and the water-insoluble polymer described in JP-A-2018-65997 can be used, but the resin is not limited thereto.

The acid group-containing resin (B) can be used alone or in combination of two or more types.

The acid group-containing resin (B) is preferably a resin having a melting point. The melting point of the acid group-containing resin (B) is preferably less than 100°C. More preferably, it is 90°C or lower. More preferably, it is 80°C or lower. If it is 100°C or higher, water may evaporate rapidly during dispersion in an aqueous medium, making it difficult to prepare a dispersion.

<Basic Compound (E)>
The basic compound (E) is a compound capable of neutralizing the acid group-containing resin (B). The basic compound (E) is not limited as long as it is a compound that is soluble in the aqueous medium (C). Examples of the basic compound (E) include inorganic bases and organic bases.
Examples of inorganic bases include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; alkali metal salts of silicic acid such as sodium orthosilicate, sodium metasilicate, and sodium sesquisilicate; alkali metal salts of phosphoric acid such as trisodium phosphate; alkali metal salts of carbonate such as disodium carbonate, sodium hydrogen carbonate, and dipotassium carbonate; alkali metal salts of boric acid such as sodium borate; ammonia;
Examples of the organic base include alkylamines such as methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, and triethylamine; alkanolamines such as aminoethanol, methylaminoethanol, dimethylaminoethanol, ethylaminoethanol, diethylaminoethanol, diethanolamine, and triethanolamine; and amines having a nonionic group such as methoxypoly(oxyethylene/oxypropylene)-2-propylamine.

The basic compound (E) can be used alone or in combination of two or more.

<Neutralization value>
The neutralization value of the acid group-containing resin (B) is 0.5 or more and less than 1.0, and the neutralization value can be calculated from the following formula (1). By setting the neutralization value within the above range, the dispersion stability of the colorant is not easily impaired, and the filterability of the water-based colorant dispersion is improved. The neutralization value is preferably 0.6 or more and 0.95 or less, more preferably 0.65 or more and 0.9 or less.
(1) Neutralization value = molar equivalent number of basic functional groups of basic compound (E) / molar equivalent number of acidic functional groups of acid group-containing resin (B)

<Crosslinking Agent (D)>
The crosslinking agent (D) crosslinks with the acid group of the acid group-containing resin (B). This makes it difficult for the dispersion stability of the colorant to be impaired, and improves the filterability of the aqueous colorant dispersion. The crosslinking agent (D) is a compound having two or more functional groups (hereinafter referred to as reactive functional groups) that can react with the acid group.
Examples of the reactive functional group include an isocyanate group, an aziridinyl group, a carbodiimide group, an oxetanyl group, an oxazoline group, and an epoxy group. The weight average molecular weight or formula weight of the crosslinking agent is preferably 100 to 2,000, more preferably 120 to 1,500, and even more preferably 150 to 1,000.

The isocyanate group-containing compound is, for example, an organic polyisocyanate or an isocyanate group-terminated prepolymer. Examples of the organic polyisocyanate include aliphatic diisocyanates such as hexamethylene diisocyanate and 2,2,4-trimethylhexamethylene diisocyanate; aromatic diisocyanates such as tolylene-2,4-diisocyanate and phenylene diisocyanate; alicyclic diisocyanates; aromatic triisocyanates; and modified products thereof such as urethane modified products. The isocyanate group-terminated prepolymer can be obtained by reacting an organic polyisocyanate or a modified product thereof with a low molecular weight polyol or the like. The isocyanate group-containing compound is preferably a compound having three isocyanate groups.

Examples of aziridinyl group-containing compounds include N,N'-diphenylmethane-4,4'-bis(1-aziridinecarboxite), N,N'-toluene-2,4-bis(1-aziridinecarboxite), bisisophthaloyl-1-(2-methylaziridine), tri-1-aziridinylphosphine oxide, N,N'-hexamethylene-1,6-bis(1-aziridinecarboxite), 2,2'-bishydroxymethylbutanol-tris[3-(1-aziridinyl)propionate], trimethylolpropane tri-β-aziridinylpropionate, tetramethylolmethane tri-β-aziridinylpropionate, tris-2,4,6-(1-aziridinyl)-1,3,5-triazine, and 4,4'-bis(ethyleneiminocarbonylamino)diphenylmethane.

An example of a carbodiimide group-containing compound is a high molecular weight polycarbodiimide produced by subjecting a diisocyanate compound to a decarboxylation condensation reaction in the presence of a carbodiimide catalyst. Commercially available high molecular weight polycarbodiimides include the Carbodilite series manufactured by Nisshinbo Industries, Inc.

Examples of oxetanyl group-containing compounds include 4,4'-(3-ethyloxetan-3-ylmethyloxymethyl)biphenyl (OXBP), 3-ethyl-3-hydroxymethyloxetane (EHO), 1,4-bis[{(3-ethyl-3-oxetanyl)methoxy}methyl]benzene (XDO), di[1-ethyl(3-oxetanyl)]methyl ether (DOX), di[1-ethyl(3-oxetanyl)]methyl ether (DOE), 1,6-bis[(3-ethyl-3-oxetanyl)methoxy]hexane (HDB), 9,9-bis[2-methyl-4-{2-(3-oxetanyl)}butoxyphenyl]fluorene, and 9,9-bis[4-[2-{2-(3-oxetanyl)}butoxy]ethoxyphenyl]fluorene.

Examples of oxazoline group-containing compounds include compounds in which two or more, preferably two to three, oxazoline groups are bonded to an aliphatic or aromatic group, bisoxazoline compounds such as 2,2-bis(2-oxazoline), 1,3-phenylenebisoxazoline, and 1,3-benzobisoxazoline, and compounds containing terminal oxazoline groups obtained by reacting such compounds with polybasic carboxylic acids.

Examples of epoxy group-containing compounds include polyglycidyl ethers such as ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerin triglycidyl ether, glycerol polyglycidyl ether, polyglycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, sorbitol polyglycidyl ether, pentaerythritol polyglycidyl ether, resorcinol diglycidyl ether, neopentyl glycol diglycidyl ether, diglycidyl orthophthalate, and hydrogenated bisphenol A diglycidyl ether.

Among these, epoxy group-containing compounds are preferred, and ethylene glycol diglycidyl ether, trimethylolpropane polyglycidyl ether, glycerol polyglycidyl ether, polyglycerol polyglycidyl ether, neopentyl glycol diglycidyl ether, diglycidyl orthophthalate, sorbitol polyglycidyl ether, resorcinol diglycidyl ether, and hydrogenated bisphenol A diglycidyl ether are preferred, with trimethylolpropane polyglycidyl ether being more preferred. From the standpoint of crosslinking efficiency, it is preferred that the crosslinking agent (D) dissolves moderately in the aqueous medium (C). The solubility is such that when the crosslinking agent is dissolved in 100 g of water at 25°C, the amount dissolved is preferably 0.1 to 50 g, more preferably 0.2 to 40 g, and even more preferably 0.5 to 30 g.

<Crosslinking value>
The crosslinking value of the acid group-containing resin (B) is 0.7 or more and 1.5 or less. The crosslinking value can be calculated from the following formula (2). By setting the crosslinking value within this range, the dischargeability and solid filling when made into an inkjet recording ink are improved. The crosslinking value is preferably 0.8 or more and 1.3 or less, more preferably 0.9 or more and 1.1 or less.
(2) Crosslinking value = molar equivalent number of crosslinking functional groups of crosslinking agent (D) / molar equivalent number of acidic functional groups of acid group-containing resin (B)

By ensuring that the acid group-containing resin (B) satisfies the respective ranges of neutralization value and crosslinking value, the dispersion stability of the colorant (A) is not easily compromised even when there is a change in temperature, and an inkjet recording ink capable of continuous printing can be produced. The inventor considers the reason for this as follows.

First, the neutralization value will be considered. When the neutralization value is 1.0 or more, almost all carboxylic acids become carboxylates and can react with the crosslinking agent. However, when two carboxylates are present at very close adjacent positions, one crosslinking agent may react with the two adjacent carboxylates. Or, one crosslinking agent may react with two carboxylates present at close positions in the resin molecule. As a result, crosslinking between resin molecules does not proceed efficiently, and the resin coating on the colorant particle surface becomes incomplete, which is considered to result in a decrease in particle size distribution stability due to aggregation of colorant particles, a decrease in filterability, and further deterioration in ejection properties and solid filling properties when used as an ink for inkjet recording. On the other hand, when the neutralization value is less than 1.0, the probability of the presence of carboxylates present at adjacent or close positions in the resin molecule is reduced, and the probability of crosslinking with carboxylates present at more distant positions can be relatively increased.
On the other hand, when the neutralization value is less than 0.5, the number of moles of carboxylates that can react with the crosslinking agent is less than half the number of moles of all carboxy groups, which is thought to result in insufficient crosslinking and in incomplete resin treatment of the colorant particle surfaces, leading to a decrease in particle size distribution stability and filterability due to aggregation of colorant particles.
In other words, by setting the neutralization value to be 0.5 or more and less than 1.0, crosslinking between resin molecules can be efficiently carried out while ensuring the number of moles of carboxylate capable of crosslinking reaction, and as a result, the particle size distribution stability and filterability become good even under harsh conditions such as storage at fluctuating temperatures.

Next, the crosslinking value will be considered. It is presumed that the acid group-containing resin (B) is likely to be present on the particle surface of the colorant (A), and therefore suppresses aggregation of the colorant (A), thereby improving stability during storage at fluctuating temperatures.
On the other hand, when the aqueous colorant dispersion is used in inkjet recording inks and the like, in addition to the colorant (A) and the acid group-containing resin (B), substances with different polarities, such as additives including surfactants, solvents, and dye derivatives, are added according to the desired properties. Therefore, in many cases, the monomer composition of the acid group-containing resin (B) optimized to be present on the particle surface of the colorant (A) is not necessarily the same as the monomer composition that provides good physical properties in compositions such as inkjet recording inks.
Here, by reacting the acid group-containing resin (B) with the crosslinking agent (D), for example, one or more functional groups of the crosslinking agent (D) react with the acid group-containing resin (B), and the remaining functional groups may generate new functional groups having polarity such as hydroxyl groups or amino groups by hydrolysis or the addition of a nucleophilic solvent or reagent such as an alcohol. In this case, the polarity of the acid group-containing resin (B) can be changed while the crosslinking reaction is proceeding, improving the compatibility with various substances contained in the inkjet recording ink, and this is preferable because the dischargeability is improved in terms of solid filling (particularly color unevenness).
By adding a crosslinking agent so that the crosslinking value is 0.7 or more, not only can the crosslinking reaction proceed, but also an appropriate amount of substituents having various polarities can be produced, and by setting the crosslinking value to 1.5 or less, crosslinking between resin molecules proceeds efficiently, resulting in improved color unevenness and ejection properties.

The preferred relationship between the neutralization value and the crosslinking value is that the following formula (3) is preferably 0.6 or more and 1.0 or less, and more preferably 0.7 or more and 1.0 or less.

(3) Neutralization Value/Crosslinking Value When the neutralization value and the crosslinking value satisfy the above-mentioned relationship, the crosslinking reaction between the molecules of the acid group-containing resin (B) proceeds ideally, thereby covering the particle surfaces of the colorant (A). The dispersion stability of the colorant is unlikely to be impaired even when there is a temperature change, and an aqueous colorant dispersion that can be used to prepare an inkjet recording ink that enables continuous printing can be prepared.

<Aqueous medium (C)>
The aqueous medium (C) includes water and water-soluble organic solvents that are miscible with water.
Examples of the water-soluble organic solvent include polyhydric alcohols, polyhydric alcohol alkyl ethers, polyhydric alcohol aryl ethers, nitrogen-containing heterocyclic compounds, amides, amines, sulfur-containing compounds, propylene carbonate, ethylene carbonate, and other water-soluble solvents.

[water]
The water may be ordinary tap water, but is preferably ion-exchanged water, distilled water, or purified water. The total amount of metal ions contained in the water is preferably 10 ppm or less, more preferably 1 ppm or less, and even more preferably 100 ppb or less. In particular, divalent metal ions such as calcium and magnesium crosslink with the acid group of the acid group-containing resin (B), so that it is preferable to suppress them as much as possible. This makes it difficult for nozzle clogging to occur in inkjet recording inks that use aqueous colorant dispersions.

[Water-soluble organic solvent]
Examples of polyhydric alcohols include glycerin, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, 1,2-propanediol, 1,3-propanediol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,3-pentanediol, and 1,4-pentanediol. Diol, 1,5-pentanediol, 1,2-hexanediol, 1,3-hexanediol, 1,4-hexanediol, 1,5-hexanediol, 1,6-hexanediol, 3-methyl-1,3-butanediol, trimethylolethane, trimethylolpropane, 1,2,6-hexanetriol, 1,2,4-butanetriol, 1,2,3-butanetriol, petriol, 2-ethyl-2-methyl-1,3-propanediol, 3,3-dimethyl-1,2-butanediol, 2,2-diethyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2,4-dimethyl-2,4-pentanediol, 2,5-dimethyl-2,5-hexanediol, 5-hexene-1,2-diol, 2-ethyl-1,3-hexanediol, and the like.

Examples of polyhydric alcohol alkyl ethers include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, propylene glycol monoethyl ether, and propylene glycol monobutyl ether.

Examples of polyhydric alcohol aryl ethers include ethylene glycol monophenyl ether, diethylene glycol monophenyl ether, tetraethylene glycol chlorophenyl ether, ethylene glycol monobenzyl ether, and ethylene glycol monoallyl ether.

Examples of nitrogen-containing heterocyclic compounds include 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, ε-caprolactam, and γ-butyrolactone.

Examples of amides include formamide, N-methylformamide, and N,N-dimethylformamide.

Examples of amines include monoethanolamine, diethanolamine, triethanolamine, monoethylamine, diethylamine, triethylamine, etc.

Examples of sulfur-containing compounds include dimethyl sulfoxide, sulfolane, thiodiethanol, etc.

As the other water-soluble solvent, sugar is preferable. Examples of sugars include monosaccharides, disaccharides, oligosaccharides (including trisaccharides and tetrasaccharides), polysaccharides, etc. Specific examples include glucose, mannose, fructose, ribose, xylose, arabinose, galactose, maltose, cellobiose, lactose, sucrose, trehalose, maltotriose, etc. In addition, polysaccharides means sugar in a broad sense, and includes substances widely present in nature such as α-cyclodextrin and cellulose. In addition, derivatives of these sugars include reduced sugars of sugars (for example, sugar alcohols [represented by the general formula: HOCH ₂ (CHOH) n CH ₂ OH (where n = an integer of 2 to 5)]), oxidized sugars (for example, aldonic acid, uronic acid, etc.), amino acids, thioacids, etc. Among these, sugar alcohols are preferable, and maltitol and sorbitol are more preferable.

Of these, glycerin, ethylene glycol, propylene glycol, diethylene glycol monobutyl ether, 2-ethyl-1,3-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,2-propanediol, 1,2-butanediol, 1,3-butanediol, 1,2-pentanediol, 1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, and 1,2-heptanediol are preferred.

The aqueous medium (C) may be used alone or in combination of two or more.

<Method of producing water-based colorant dispersion>
The method for producing the aqueous colorant dispersion of the present invention includes the following steps 1 to 3, and the acid group-containing resin (B) satisfies the following (1) neutralization value and (2) crosslinking value:
Step 1: A step of mixing a colorant (A) with an acid group-containing resin (B) having an acid value of 1 to 300 mgKOH/g. Step 2: A step of adding an aqueous medium (C) and a basic compound (E) to the mixture obtained in step 1 to neutralize it. Step 3: A step of adding a crosslinking agent (D) to the mixture obtained in step 2 to perform a crosslinking treatment. The neutralization value of the acid group-containing resin (B) is 0.5 or more and less than 1.0, and the crosslinking value is 0.7 or more and 1.5 or less. (1) Neutralization value = number of molar equivalents of basic functional groups of the basic compound (E) / number of molar equivalents of acidic functional groups of the acid group-containing resin (B). (2) Crosslinking value = number of molar equivalents of crosslinking functional groups of the crosslinking agent (D) / number of molar equivalents of acidic functional groups of the acid group-containing resin (B).

The production of the water-based colorant dispersion is preferably carried out by, for example, adding at least a water-soluble inorganic salt (X) and a water-soluble organic solvent (Y) to the colorant (A) and the acid group-containing resin (B), and then grinding and kneading the colorant (A) to coat the acid group-containing resin (B). This is particularly effective when the colorant (A) is an organic pigment. The method of coating the organic pigment by grinding and kneading is not particularly limited and any method can be applied, but a kneading process by so-called salt milling is preferred. Note that dye particles may also be applied.
First, a step of mixing the colorant (A), the acid group-containing resin (B), the water-soluble inorganic salt (X) and the water-soluble organic solvent (Y) in a kneader (salt milling treatment) is carried out. After the mixing step, it is preferable to carry out a step of washing and removing the water-soluble inorganic salt (X) and the water-soluble organic solvent (Y) (washing treatment).

Salt milling is a process in which a mixture of an organic pigment, a water-soluble inorganic salt (X), and a water-soluble organic solvent (Y) is mechanically kneaded while being heated using a batch or continuous kneader such as a kneader, a two-roll mill, a three-roll mill, a ball mill, an attritor, a sand mill, or a planetary mixer, and then the water-soluble inorganic salt (X) and the water-soluble organic solvent (Y) are removed by washing with water. The water-soluble inorganic salt (X) acts as a crushing aid, and the high hardness of the inorganic salt is utilized during salt milling to crush the pigment. By optimizing the conditions for salt milling the pigment, it is possible to obtain a pigment with a very fine primary particle size, a narrow distribution range, and a sharp particle size distribution.

(Water-soluble inorganic salt (X))
Examples of the water-soluble inorganic salt (X) include sodium chloride, barium chloride, potassium chloride, sodium sulfate, etc. Sodium chloride (table salt) is preferred from the viewpoint of cost. From the viewpoints of both treatment efficiency and production efficiency, the water-soluble inorganic salt (X) is preferably used in an amount of 50 to 2,000 parts by mass, more preferably 300 to 1,000 parts by mass, per 100 parts by mass of the colorant (A).

(Water-soluble organic solvent (Y))
Any solvent can be used as the water-soluble organic solvent (Y) as long as it is soluble and miscible with water. Specific examples include glycerin, ethylene glycol, propanediol, butanediol, pentanediol, hexanediol, diethylene glycol, dipropylene glycol, periethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, dipropylene glycol monomethyl ether, 2-ethyl-1,3-hexanediol, 2,4-diethyl-1,5-pentanediol, monoacetin), diacetin, triacetin, tripropionin, tributyrin, and 2-butyl-2-ethyl-1,3-propanediol. The water-soluble organic solvent (Y) can be used alone or in combination of two or more kinds. The amount of the water-soluble organic solvent (Y) used is preferably 5 to 1,000 parts by mass, more preferably 50 to 500 parts by mass, per 100 parts by mass of the colorant (A).

In the washing process, the mixture containing the colorant (A), the acid group-containing resin (B), the water-soluble inorganic salt (X), and the water-soluble organic solvent (Y) is removed from the grinding kneader, ion-exchanged water is added, and the mixture is stirred to obtain a suspension. The amount of ion-exchanged water added is not particularly limited as long as it is an amount sufficient to obtain a suspension. For example, 10 to 10,000 times the weight of ion-exchanged water is added and mixed and stirred. Heating may be performed as necessary. The mixing and stirring conditions are not particularly limited, but it is preferable to perform the process at a temperature of 25 to 90°C. The filtrate is then removed by an operation such as filtration, thereby removing the water-soluble inorganic salt (X) and the water-soluble organic solvent (Y) used in the grinding kneader.

After the washing process, a step of removing water may be carried out. A suitable method is, for example, a method of carrying out a drying process. Drying conditions include, for example, a method of drying at normal pressure in the range of 80 to 120°C for about 12 to 48 hours, and a method of drying at reduced pressure in the range of 25 to 80°C for about 12 to 60 hours. The drying process is not particularly limited, but may also include a method using a spray dryer. A crushing process may be carried out simultaneously with or after the drying process.

Next, a basic compound (E) and an aqueous medium (C) in appropriate amounts relative to the acid value of the acid group-containing resin (B) in the mixture after the washing treatment are added and dissolved, and a process of stirring while heating is performed. Further, a crosslinking agent (D) is added and further stirred to perform a crosslinking treatment process.
By these steps, the crosslinking reaction proceeds uniformly in the system, and an aqueous colorant dispersion can be prepared. As the stirring method, a known method can be used, for example, a high-speed mixer, a homogenizer, a planetary mixer, a trimix, a kneader, an extruder, a horizontal sand mill, a vertical sand mill and/or an annular bead mill, a paint shaker, a ball mill, a disperser equipped with an ultrasonic oscillator, a high-pressure disperser, a two-roll mill, a three-roll mill, etc. can be mentioned.

The crosslinking treatment conditions are as follows: temperature is preferably 40°C to 95°C, more preferably 60°C to 90°C. Treatment time is preferably 0.5 hours to 12 hours, more preferably 1 hour to 6 hours.

After the reaction of the crosslinking agent (D) is complete, if pH adjustment is necessary, any acid or basic compound (E) can be used to adjust the pH to the desired level. Specific examples of acids include inorganic acids such as phosphoric acid, hydrochloric acid, sulfuric acid, and nitric acid, and organic acids such as acetic acid and citric acid. Centrifugation and filtration can also be added. An aqueous medium (C) can also be added to adjust the non-volatile content.

The pH of the aqueous colorant dispersion after pH adjustment is preferably 7 to 10, more preferably 8 to 10, and even more preferably 8 to 9.5.

It is preferable to filter the obtained aqueous colorant dispersion. By filtering, coarse particles can be removed, and the ink will have good ejection properties when used as an ink for inkjet recording. Any conventional method can be used for filtering.

<Other additives>
The aqueous colorant dispersion of the present invention may contain additives according to the purpose. Examples of the additives include surfactants, antiseptics and antifungals, chelating agents, rust inhibitors, antioxidants, ultraviolet absorbers, oxygen absorbers, and light stabilizers.

[Surfactant]
The surfactant may be an anionic surfactant, a cationic surfactant, a nonionic surfactant, an amphoteric surfactant, etc., which may be used alone or in combination of two or more thereof.

(Anionic Surfactant)
Examples of the anionic surfactant include fatty acid salts, alkyl sulfate salts, alkylaryl sulfonates, alkylnaphthalenesulfonates, dialkylsulfonates, dialkylsulfosuccinates, alkyldiaryletherdisulfonates, alkylphosphate salts, polyoxyethylene alkylether sulfate salts, polyoxyethylene alkylarylether sulfate salts, polyoxyethylene alkylether acetate salts, alkylbenzenesulfonates (e.g., NH ₄ , Na, Ca, etc.), alkyldiphenyletherdisulfonates (e.g., NH ₄ , Na, Ca, etc.), naphthalenesulfonic acid formalin condensates and their salts, dialkylsuccinatesulfonic acid Na salts, polyoxyethylene alkylphosphate salts, glycerol borate fatty acid esters, polyoxyethylene glycerol fatty acid esters, polyoxyethylene polycyclic phenylether sulfate salts (e.g., NH ₄ , Na, etc.), laurate, polyoxyethylene alkyl ether sulfate, oleate, perfluoroalkyl sulfonic acid, perfluoroalkyl sulfonate, perfluoroalkyl carboxylic acid, perfluoroalkyl carboxylate, perfluoroalkyl phosphate, salt of perfluoroalkyl phosphate, polyoxyalkylene ether polymer having perfluoroalkyl ether group in the side chain, sulfate ester salt of polyoxyalkylene ether polymer having perfluoroalkyl ether group in the side chain, salt of polyoxyalkylene ether polymer having perfluoroalkyl ether group in the side chain, etc. Examples of counter ions in the salts of these fluorine-based surfactants include Li, Na, K, _NH4 , _{NH3CH2CH2OH , NH2 ( CH2CH2OH} ) ₂ , NH _{( CH2CH2OH} )3 _, etc.

(Cationic Surfactant)
Examples of the cationic surfactant include alkylamine salts, quaternary ammonium salts, alkylpyridinium salts, and alkylimidazolium salts.

(Nonionic surfactant)
Examples of the nonionic surfactant include polyoxyethylene alkyl ethers, polyoxyalkylene alkyl ethers, polyoxyethylene alkylaryl ethers, polyoxyethylene oxypropylene block copolymers, polyoxyethylene polycyclic phenyl ethers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters, glycerin fatty acid esters, polyoxyethylene alkylphenyl ethers, polyoxyethylene alkylamines, polyoxyethylene alkylamides, polyoxyethylene fatty acid esters, acetylene glycols, polyoxyethylene alkylamines, fluorine-based, silicone-based, etc. In particular, examples of the acetylene glycol-based surfactants include 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, 3,5-dimethyl-1-hexyne-3-ol, etc. Commercially available acetylene glycol surfactants include, for example, Surfynol 104, 82, 465, 485, TG, and DF110D manufactured by Air Products, Inc. (USA).

Fluorine-based surfactants can also be used. For example, Surflon S-111, S-112, S-113, S-121, S-131, S-132, S-141, S-145 (all manufactured by Asahi Glass Co., Ltd.), Fullard FC-93, FC-95, FC-98, FC-129, FC-135, FC-170C, FC-430, FC-431 (all manufactured by Sumitomo 3M Limited), Megafac F-470, F1405, F -474 (all manufactured by DIC), Zonyl TBS, FSP, FSA, FSN-100, FSN, FSO-100, FSO, FS-300, UR (all manufactured by DuPont), FT-110, FT-250, FT-251, FT-400S, FT-150, FT-400SW (all manufactured by Neos), PF-151N (manufactured by Omnova), etc.

(Zwitterionic surfactant)
Examples of amphoteric surfactants include alkyl betaines, alkyl amine oxides, phosphatidylcholines, etc. Examples of amphoteric surfactants include lauryl aminopropionate, lauryl dimethyl betaine, stearyl dimethyl betaine, lauryl dihydroxyethyl betaine, lauryl dimethyl amine oxide, myristyl dimethyl amine oxide, stearyl dimethyl amine oxide, dihydroxyethyl lauryl amine oxide, polyoxyethylene coconut oil alkyl dimethyl amine oxide, dimethyl alkyl (coconut) betaine, dimethyl lauryl betaine, etc.

[Anti-septic and anti-fungal agent]
Examples of antiseptic and antifungal agents include sodium dehydroacetate, sodium sorbate, sodium 2-pyridinethiol-1-oxide, sodium benzoate, sodium pentachlorophenol, methylisothiazolinone, and benzisothiazolinone.

[Chelating Agent]
Examples of the chelating agent include sodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, and sodium uramildiacetate.

[anti-rust]
Examples of the rust inhibitor include acid sulfite, sodium thiosulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, dicyclohexylammonium nitrite, and benzotriazole.

[Antioxidant]
Examples of the antioxidant include phenol-based antioxidants (including hindered phenol-based antioxidants), amine-based antioxidants, sulfur-based antioxidants, and phosphorus-based antioxidants.
Examples of the phenolic antioxidant include butylated hydroxyanisole, 2,6-di-tert-butyl-4-ethylphenol, stearyl-β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,2-methylenebis(4-methyl-6-tert-butylphenol), 2,2-methylenebis(4-ethyl-6-tert-butylphenol), 4,4-butylidenebis(3-methyl-6-tert-butylphenol), 3,9-bis[1,1-dimethyl-2-[β-(3- tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]2,4,8,10-tetrakis[5,5]undecane, 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, tetrakis[methylene-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate]methane, and the like.
Examples of the amine-based antioxidant include phenyl-β-naphthylamine, α-naphthylamine, N,N-di-sec-butyl-p-phenylenediamine, phenothiazine, N,N-diphenyl-p-phenylenediamine, 2,6-di-tert-butyl-p-cresol, 2,6-di-tert-butylphenol, 2,4-dimethyl-6-tert-butyl-phenol, butylhydroxyanisole, 2,2-methylenebis(4 4,4-butylidenebis(3-methyl-6-tert-butylphenol), 4,4-thiobis(3-methyl-6-tert-butylphenol), tetrakis[methylene-3(3,5-di-tert-butyl-4-dihydroxyphenyl)propionate]methane, 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, and the like.
Examples of the sulfur-based antioxidant include dilauryl 3,3-thiodipropionate, distearyl thiodipropionate, lauryl stearyl thiodipropionate, dimyristyl-3,3-thiodipropionate, distearyl-β,β-thiodipropionate, 2-mercaptobenzimidazole, and dilauryl sulfide.
Examples of the phosphorus-based antioxidant include triphenyl phosphite, octadecyl phosphite, triisodecyl phosphite, trilauryl trithiophosphite, and trinonylphenyl phosphite.

[Ultraviolet absorber]
Examples of the ultraviolet absorber include benzophenone-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, salicylate-based ultraviolet absorbers, cyanoacrylate-based ultraviolet absorbers, and nickel complex salt-based ultraviolet absorbers.
Examples of the benzophenone-based ultraviolet absorbers include 2-hydroxy-4-n-octoxybenzophenone, 2-hydroxy-4-n-dodecyloxybenzophenone, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, and 2,2,4,4-tetrahydroxybenzophenone.
Examples of benzotriazole-based ultraviolet absorbers include 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-4'-octoxyphenyl)benzotriazole, and 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole.
Examples of the salicylate-based ultraviolet absorbers include phenyl salicylate, p-tert-butylphenyl salicylate, and p-octylphenyl salicylate.
Examples of cyanoacrylate ultraviolet absorbers include ethyl-2-cyano-3,3'-diphenylacrylate, methyl-2-cyano-3-methyl-3-(p-methoxyphenyl)acrylate, and butyl-2-cyano-3-methyl-3-(p-methoxyphenyl)acrylate.
Examples of nickel complex salt-based ultraviolet absorbers include nickel bis(octylphenyl) sulfide, 2,2-thiobis(4-tert-octylferrate)-n-butylamine nickel(II), 2,2-thiobis(4-tert-octylferrate)-2-ethylhexylamine nickel(II), and 2,2-thiobis(4-tert-octylferrate)triethanolamine nickel(II).

The aqueous colorant dispersion of the present invention can be used for various applications, such as inkjet recording ink, toner for developing electrostatic images, paint, and flexographic ink. Among these, inkjet recording ink is preferred.

<Inkjet recording ink>
The inkjet recording ink of the present invention contains a water-based colorant dispersion. The inkjet recording ink can contain a water-soluble solvent that is miscible with water as an optional component. Examples of the water-soluble solvent include glycol ethers and diols. These solvents penetrate very quickly into substrates, and penetrate quickly into low-absorbency or non-absorbency substrates such as coated paper, art paper, polyvinyl chloride sheets, films, and fabrics. Therefore, drying during printing is fast, and accurate printing can be achieved. In addition, since the boiling point is high, the function as a wetting agent is sufficient.

Examples of glycol ethers include 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, and tripropylene glycol monomethyl ether.
Examples of diols include 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. Among these, propylene glycol, (poly)alkylene glycol monoalkyl ether, and alkanediol having 3 to 6 carbon atoms are preferred. Examples of (poly)alkylene glycol monoalkyl ether include diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, and triethylene glycol monomethyl ether. Among these, diethylene glycol monobutyl ether is preferred. Examples of alkanediol having 3 to 6 carbon atoms include 1,2-propanediol, 1,2-butanediol, 1,3-butanediol, 1,2-hexanediol, and 2-methyl-2,4-pentanediol. Of these, 1,2-hexanediol is preferred.

Depending on the type of substrate to be printed on, water-soluble nitrogen-containing heterocyclic compounds such as 2-pyrrolidone, N-methylpyrrolidone, N-ethylpyrrolidone, N-methyloxazolidinone, and N-ethyloxazolidinone can be added to improve the solubility of the substrate.

Water-soluble solvents can be used alone or in combination of two or more types.

The content of the water-soluble solvent in the inkjet recording ink is preferably 3 to 60% by mass, more preferably 3 to 50% by mass. The content of water in the inkjet recording ink is preferably 10 to 90% by mass, more preferably 30 to 80% by mass.

The inkjet recording ink of the present invention can contain a binder resin. In terms of the type of binder resin, examples include acrylic resin, olefin resin, ester resin, ether resin, and urethane resin. In terms of solubility in water, examples of the binder resin include water-soluble resin and water-insoluble resin. Water-insoluble resin includes emulsion.

The content of the binder resin is preferably 2 to 30% by mass, and more preferably 3 to 20% by mass, based on 100% by mass of the non-volatile content of the inkjet recording ink.

The inkjet recording ink of the present invention may contain other additives that are known in the art.

It is preferable to filter the ink for inkjet recording. This improves the ejection properties from the inkjet printer. Any conventionally known method can be used for filtering.

The inkjet recording ink of this specification can be suitably used in various inkjet printers. There are no particular limitations on the inkjet system that can be used, but examples include charge control type, continuous jet type such as spray type, piezo type, thermal type, electrostatic suction type, etc.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" means parts by mass, and "%" means % by mass. NV means nonvolatile content. In the following examples, examples 1 to 32, 33, 38 to 40, 44, 56, 58, 119, 125, 127, 133 to 135, 144, 149 to 151, 158, 159, 164 to 166, 170, 182, 184, 245, and 251 are all reference examples.

The abbreviations and product names in the examples have the following meanings.
BzMA: benzyl methacrylate BzA: benzyl acrylate St: styrene AS-6: styrene macromer manufactured by Toagosei Co., Ltd. (number average molecular weight 6,000)
CHMA: Cyclohexyl methacrylate BHMA: Behenyl methacrylate LA: Lauryl acrylate AM-90G: Methoxy polyethylene glycol #400 acrylate manufactured by Shin-Nakamura Chemical Co., Ltd. AMP-20GY: Phenoxy polyethylene glycol acrylate manufactured by Shin-Nakamura Chemical Co., Ltd. MAA: Methacrylic acid AA: Acrylic acid MMA: Methyl methacrylate VSA: Vinyl sulfonic acid MR-200: 2-methacryloyloxyethyl acid phosphate manufactured by Daihachi Chemical Industry Co., Ltd. αMS: α-methylstyrene STA: Stearyl acrylate NaOH: Sodium hydroxide KOH: Potassium hydroxide LiOH: Lithium hydroxide NH ₃ : Ammonia M-230G: Methoxy polyethylene glycol #1000 methacrylate manufactured by Shin-Nakamura Chemical Co., Ltd. Blemmer PP-800: Polypropylene glycol monomethacrylate manufactured by NOF Corporation Unilube PKA-5013: NOF Corporation polyethylene glycol-polypropylene glycol-allyl ether (number average molecular weight 2,000)
PEG400: polyethylene glycol (number average molecular weight 400) manufactured by Tokyo Ohka Kogyo Co., Ltd.
PEG6000: polyethylene glycol (number average molecular weight 8,300) manufactured by Tokyo Ohka Kogyo Co., Ltd.
Jeffamine M-2005: polyethylene glycol-polypropylene glycol-monoamine manufactured by HUNTSMAN BDG: diethylene glycol monobutyl ether PG: propylene glycol MEK: methyl ethyl ketone Denacol EX-211: aliphatic epoxy crosslinking agent, manufactured by Nagase ChemteX Corporation, non-volatile content 100%, epoxy equivalent 138 g/eq, bifunctional Denacol EX-252: aliphatic epoxy crosslinking agent, manufactured by Nagase ChemteX Corporation, non-volatile content 100%, epoxy equivalent 213 g/eq, bifunctional Denacol EX-313: aliphatic epoxy crosslinking agent, manufactured by Nagase ChemteX Corporation, non-volatile content 100%, epoxy equivalent 141 g/eq, bi- to tri-functional Denacol EX-321: Aliphatic epoxy crosslinking agent, manufactured by Nagase ChemteX Corporation, non-volatile content 100%, epoxy equivalent 140 g/eq, 2-3 functional Denacol EX-512: Aliphatic epoxy crosslinking agent, manufactured by Nagase ChemteX Corporation, non-volatile content 100%, epoxy equivalent 168 g/eq, 4 or more functional Denacol EX-614B: Aliphatic epoxy crosslinking agent, manufactured by Nagase ChemteX Corporation, non-volatile content 100%, epoxy equivalent 173 g/eq, 4 or more functional Denacol EX-201: Aromatic epoxy crosslinking agent, manufactured by Nagase ChemteX Corporation, non-volatile content 100%, epoxy equivalent 117 g/eq, 2 functional Denacol EX-721: Aromatic epoxy crosslinking agent, manufactured by Nagase ChemteX Corporation, non-volatile content 100%, epoxy equivalent 154 g/eq, 2 functional Takelac W-6110: Polyurethane emulsion (NV 32%) manufactured by Mitsui Chemicals
Takelac W-6061: Polyurethane emulsion (NV 30%) manufactured by Mitsui Chemicals
Takelac W-5030: Polyurethane emulsion (NV 30%) manufactured by Mitsui Chemicals
Vylonal MD-2000: Polyester emulsion (NV 40%) manufactured by Toyobo Co., Ltd.
Joncryl 780: Polyacrylic emulsion (NV 48%) manufactured by BASF
Joncryl HPD96: Acrylic resin (NV 34%) manufactured by BASF
Chemipearl W400S: Olefin wax (NV 40%) manufactured by Mitsui Chemicals
Surfynol DF110D: acetylene-based surfactant manufactured by Evonik Industries. Surfynol 465: acetylene-based surfactant manufactured by Evonik Industries. BYK-348: silicon-based surfactant manufactured by BYK-Chemie. Proxel GXL: preservative manufactured by Lonza. Neosintol BC-493: preservative manufactured by Sumika Environmental Science.

The physical properties were determined according to the following methods:

(Number average molecular weight (Mn))
The measurements were performed by gel permeation chromatography (GPC) equipped with an RI detector. The equipment used was an HLC-8220GPC (manufactured by Tosoh Corporation), and two separation columns were connected in series. Both columns contained "TSK-GEL Two "SUPER HZM-N" columns were connected in series, and measurements were performed at an oven temperature of 40°C, a THF solution as the eluent, and a flow rate of 0.35 ml/min. The sample was dissolved in a solvent consisting of 1% of the above eluent. The molecular weight is a polystyrene equivalent value.

(Acid value)
The number of moles of acid groups contained in 1 g of resin was calculated from the monomer composition. The theoretical value of the acid value (mgKOH/g) was calculated assuming that the number of moles of acid groups was equal to the number of moles of potassium hydroxide (molecular weight 56.1) required for neutralization. It is known that the maleic anhydride units contained in the acid group-containing resin (B-60) in Table 3 described below are easily hydrolyzed to maleic acid in an aqueous medium, particularly in water. Therefore, it is considered that the maleic anhydride units exist as maleic acid, not as maleic anhydride, in the pigment dispersion of the present invention. Therefore, the acid value of the resin containing maleic anhydride was calculated assuming that the maleic anhydride was hydrolyzed to maleic acid.

(Non-volatile content)
The non-volatile content was determined by precisely weighing 0.5 g of the measurement object and placing it in a dryer at 180° C. for 20 minutes, and then measuring the loss on drying.

<Synthesis of Acid Group-Containing Resin (B)>
[A-B block polymer]

Synthesis of Acid Group-Containing Resin (B-1) (Synthesis of Polymer Block A)
A 1-liter separable flask reactor equipped with a stirrer, reflux condenser, thermometer and nitrogen inlet tube was charged with 295.68 parts of diethylene glycol dimethyl ether (hereinafter referred to as diglyme), 3.03 parts of iodine, 7 parts of azobis (methoxydimethylvaleronitrile) (hereinafter referred to as V-70), 0.66 parts of di-t-butylhydroxytoluene (hereinafter referred to as BHT), 35 parts (20 mol%) of BzMA, 21 parts (20 mol%) of AS-6, and 24 parts (10 mol%) of AMP-20GY, which were added and heated to 40°C while flowing nitrogen, and polymerized for 6.5 hours, and then 2 parts of V-70 were added. Then, 1 hour, 2 hours, and 3 hours later, 2 parts of V-70 were added, and the reaction was continued for another 2 hours. The polymerization conversion rate was confirmed to be 95% or more by sampling, and the reaction was terminated, to obtain a polymer block A. The polymerization conversion calculated from the non-volatile content was 95%, and the number average molecular weight (Mn) was 4,000.

(Synthesis of block polymer)
A mixture of 49 parts (49 mol%) of MMA, 1 part (1 mol%) of MAA, and 0.45 parts of V-70 was added to the reaction solution and polymerized for 4.5 hours to synthesize a B block. The polymerization rate calculated from the non-volatile content by sampling was 97.6%. This B polymer block was not polymerized with the constituent monomers of the A polymer block.

Next, 147.8 parts of BDG was added, and a mixture of 1 part of sodium hydroxide and 129.3 parts of ion-exchanged water was added, and the mixture was allowed to react at 50°C for 2 hours to decompose the iodine at the polymer terminals, yielding an acid group-containing resin (B-1) (number average molecular weight (Mn): 6,000, acid value 4 mgKOH/g).

Synthesis of Acid Group-Containing Resins (B-2) to (B-19) Acid group-containing resins (B-2) to (B-19) were obtained in the same manner as for the acid group-containing resin (B-1), except that the monomer composition and number average molecular weight were changed as shown in Table 1. The molecular weight was appropriately adjusted by changing the amount of V-70 added. The composition ratios in Table 1 indicate molar ratios.

[Random Polymerization]
Synthesis of Acid Group-Containing Resin (B-20) 2 parts (2 mol%) of MAA, 44 parts (25 mol%) of BzMA, 16 parts (15 mol%) of AS-6, 48 parts (48 mol%) of MMA, and 24 parts (10 mol%) of AMP-20GY were mixed to prepare a monomer mixture. 20 parts of MEK, 0.3 parts of 2-mercaptoethanol (chain transfer agent), and 10% of the monomer mixture were placed in a reaction vessel and mixed, followed by thorough nitrogen gas replacement.
Meanwhile, a mixture of the remaining 90% of the monomer mixture, 0.27 parts of the chain transfer agent, 60 parts of MEK, and 2.2 parts of an azo-based radical polymerization initiator (manufactured by Wako Pure Chemical Industries, Ltd., product name: V-65, 2,2'-azobis(2,4-dimethylvaleronitrile)) was placed in a dropping funnel, and the monomer mixture in the reaction vessel was heated to 65°C while being stirred under a nitrogen atmosphere, and the mixture in the dropping funnel was dropped over 3 hours. After 2 hours had elapsed at 65°C from the end of the dropping, a solution in which 0.3 parts of the polymerization initiator was dissolved in 5 parts of MEK was added, and the mixture was further aged at 65°C for 2 hours and at 70°C for 2 hours, to obtain an acid group-containing resin (B-20) (number average molecular weight (Mn): 11,700, acid value 8 mgKOH/g).

Synthesis of Acid Group-Containing Resins (B-21) to (B-34) Acid group-containing resins (B-21) to (B-34) were obtained in the same manner as for acid group-containing resin (B-20), except that the monomer composition was changed as shown in Table 2. The molecular weight was appropriately adjusted by changing the amount of V-65 added. The composition ratios in Table 2 are in parts by mass.

[Resin containing α-olefin units in the main chain]
Synthesis of acid group-containing resin (B-35) In a reaction vessel equipped with a gas inlet tube, a thermometer, a condenser, and a stirrer, 49.0 parts (50 mol%) of maleic anhydride as a monomer mixture, 500 parts (25 mol%) of Unilube PKA-5013, 49.1 parts (25 mol%) of 1-tetradecene as an α-olefin, 10 parts of xylene, and 0.2 parts of octyl thioglycolate as a chain transfer agent were charged, substituted with nitrogen, and heated to 110 ° C. with stirring. A mixture of 1.0 part of t-butylperoxy-2-ethylhexanoate and 20 parts of xylene was added dropwise thereto as a radical polymerization initiator over 2 hours. Thereafter, the mixture was stirred and reacted for 4 hours while maintaining the temperature at 110 ° C. After cooling to 85° C., 4619 parts (55 mol %) of PEG 6000 and 0.2 parts of diazabicycloundecene as a catalyst were added, and the mixture was stirred for 6 hours while maintaining the temperature at 85° C. to react and ring-open the maleic anhydride and half-esterify it. The solvent of the obtained product was completely removed by concentration under reduced pressure, and an acid group-containing resin (B-35) (number average molecular weight (Mn): 8,200, acid value 6 mgKOH/g) was obtained.

・Acid group-containing resin (B-36) to (B-60)
Except for changing the raw materials and compositions as shown in Table 3, acid group-containing resins (B-36) to (B-60) were obtained in the same manner as for the acid group-containing resin (B-35).

<Production of Colorant Composition>
[Production Example 1]
- Production of colorant composition (1) 35.0 parts of C.I. Pigment Red 122 (DIC Corporation "FASTOGEN Super Magenta RG") (hereinafter referred to as PR122) as colorant (A), 10 parts of (B-1) as acid group-containing resin (B) as nonvolatile matter, 175.0 parts of sodium chloride as water-soluble inorganic salt (X), and 30.0 parts of diethylene glycol as water-soluble organic solvent (Y) were charged into a stainless steel 1 gallon kneader (Inoue Seisakusho Co., Ltd.) and kneaded at 80 ° C. for 3 hours.
The obtained kneaded product was poured into 2,000 parts of ion-exchanged water of pH 5.6, stirred, filtered and washed with water, and then poured into 2,000 parts of ion-exchanged water adjusted to pH 1.0 by adding an appropriate amount of 98% sulfuric acid aqueous solution, stirred, filtered and washed with water to remove sodium chloride and diethylene glycol, thereby obtaining a colorant composition (1) containing the colorant (A), the acid group-containing resin (B) and water. The non-volatile content was 30%.

[Production Examples 2 to 96]
Production of Colorant Compositions (2) to (102) Colorant compositions (2) to (102) were obtained in the same manner as in Production Example 1, except that the colorant (A) and the acid group-containing resin (B) were changed as shown in Table 4.

<Production of Water-Based Colorant Dispersion>
[Example 1]
- Production of Water-Based Colorant Dispersion (1) 20 parts of the colorant composition (1) calculated as nonvolatile content and 40 parts of ion-exchanged water as the water-based medium (C) were mixed and stirred, and a 10% aqueous solution of potassium hydroxide was added as the basic compound (E) in an appropriate amount so that the neutralization value would be 0.8 based on the acid value of the acid group-containing resin (B-1) contained in the colorant composition (1). The mixture was stirred using a disper so as to make the system uniform, and dispersed for 1 hour using a high-pressure homogenizer (Econizer Lab 02, manufactured by Sanmaru Machinery Co., Ltd.).
After dispersion, an appropriate amount of Denacol EX321 was added as a crosslinking agent (D) so that the crosslinking value became 0.9, and the mixture was stirred at 85° C. for 5 hours using a disper to carry out a crosslinking reaction.
After stirring, 0.03 parts of Proxel GXL as a preservative and an appropriate amount of ion-exchanged water so that the non-volatile content becomes 25% were added to obtain a water-based colorant dispersion (1).

[Examples 2 to 100, 104 to 125, Comparative Examples 1 to 6]
Production of Water-Based Colorant Dispersions (2) to (102), (106) to (127), and (129) to (132) Water-based colorant dispersions (2) to (102), (106) to (127), and (129) to (132) were obtained in the same manner as in Example 1, except that the materials to be added, the neutralization value, and the crosslinking value were changed as shown in Table 5.

[Example 101]
- Preparation of Water-based Colorant Dispersion (103) A water-based colorant dispersion (103) was obtained in the same manner as in Example 37, except that a mixed solvent of 32 parts of ion-exchanged water and 8 parts of diethylene glycol monobutyl ether was used as the water-based medium (C).

[Example 102]
- Production of Water-based Colorant Dispersion (104) A water-based colorant dispersion (104) was obtained in the same manner as in Example 37, except that a mixed solvent of 30 parts of ion-exchanged water and 10 parts of propylene glycol was used as the water-based medium (C).

[Example 103]
- Production of Water-based Colorant Dispersion (105) A water-based colorant dispersion (105) was obtained in the same manner as in Example 37, except that a mixed solvent of 35 parts of ion-exchanged water and 5 parts of glycerin was used as the water-based medium (C).

[Example 125]
- Preparation of Water-based Colorant Dispersion (128) After dispersion with a high-pressure homogenizer, a water-based colorant dispersion (128) was obtained in the same manner as in Example 37, except that the pH was adjusted to 8.5 by adding a 1 M aqueous phosphoric acid solution.

<Evaluation of particle size distribution stability under temperature fluctuation storage>
The aqueous colorant dispersion was diluted with ion-exchanged water, and the volume average particle diameter was measured using Nanotrac Wave (manufactured by Microtrac Bell), and _D10B , _D50B , and _D90B were obtained as particle size distributions. Next, each aqueous colorant dispersion was placed in a sealed container and stored at 5°C for 60 days, then at 25°C for 60 days, and then at 50°C for 60 days. After a temperature fluctuation storage test was performed for 180 days, the aqueous colorant dispersion was removed from the sealed container, and the volume average particle diameter was measured in the same manner to obtain _{D10A, D50A, and D90A. For D10A , D50A , and D90A} after the temperature fluctuation storage and _D10B , _D50B , and _D90B before the temperature fluctuation storage, calculations were performed according to the following formula to obtain the particle size distribution change rates _D10C , _D50C , and _D90C . The evaluation criteria are as follows.
Particle size distribution change rate D10 _C = D10 _A / D10 _B
Particle size distribution change rate D50 _C = D50 _A / D50 _B
Particle size distribution change rate _D90C = _D90A / _D90B
◎: The particle size distribution change rates _D10C , _D50C , and _D90C are all less than ±5% (excellent)
○: At least one of the particle size distribution change rates _D10C , _D50C , and _D90C is ±5% or more and less than ±10% (good)
△: At least one of the particle size distribution change rates _D10C , _D50C , and _D90C is ±10% or more and less than ±15% (no problem in practical use)
×: Any one or more of the particle size distribution change rates _D10C , _D50C , and _D90C is ±15% or more (bad)

<Evaluation of filterability under temperature fluctuation storage>
The filterability under temperature fluctuation storage was evaluated using samples after temperature fluctuation storage in the above-mentioned evaluation of particle size distribution stability under temperature fluctuation storage. 50 g of each water-based colorant dispersion was subjected to a pressure of 0.05 MPa s for a certain period of time using a 1.0 μm disk filter TITAN3-PTFE manufactured by Tomsic, and the amount of liquid passing through the filter during that time was evaluated. The evaluation criteria were as follows.
◎：All quantity passed (excellent)
○: Passage amount is 45g or more and less than 50g (good)
△: The passing amount is 40g or more and less than 45g (no problem in practical use)
×: Passage amount is less than 40 g (bad)

The composition, parameters, and evaluation results are summarized in Tables 5-1 to 5-4. In the tables, water means ion-exchanged water. The name of the crosslinking agent is the product name of Denacol manufactured by Nagase ChemteX Corporation.

The abbreviations for colorant (A) in the table are as follows.
PR31: C.I. Pigment Red 31
PR122: C.I. Pigment Red 122
PR146: C.I. Pigment Red 146
PR147: C.I. Pigment Red 147
PR150: C.I. Pigment Red 150
PR176: C.I. Pigment Red 176
PR177: C.I. Pigment Red 177
PR179: C.I. Pigment Red 179
PR184: C.I. Pigment Red 184
PR185: C.I. Pigment Red 185
PR202: C.I. Pigment Red 202
PR242: C.I. Pigment Red 242
PR254: C.I. Pigment Red 254
PR269: C.I. Pigment Red 269
PR291: C.I. Pigment Red 291
PG7: C.I. Pigment Green 7
PG36: C.I. Pigment Green 36
PG58: C.I. Pigment Green 58
PG59: C.I. Pigment Green 59
PG62: C.I. Pigment Green 62
PG63: C.I. Pigment Green 63
PB15:1...C.I. Pigment Blue 15:1
PB15:3...C.I. Pigment Blue 15:3
PB15:4...C.I. Pigment Blue 15:4
PB15:6...C.I. Pigment Blue 15:6
PV19...C.I. Pigment Violet 19
PV23: C.I. Pigment Violet 23
PY12: C.I. Pigment Yellow 12
PY13: C.I. Pigment Yellow 13
PY14: C.I. Pigment Yellow 14
PY74: C.I. Pigment Yellow 74
PY138: C.I. Pigment Yellow 138
PY155: C.I. Pigment Yellow 155
PY174: C.I. Pigment Yellow 174
PY185: C.I. Pigment Yellow 185
PY213: C.I. Pigment Yellow 213
PO34: C.I. Pigment Orange 34
PO38: C.I. Pigment Orange 38
PO43: C.I. Pigment Orange 43
PO62: C.I. Pigment Orange 62
PO64: C.I. Pigment Orange 64
PO71: C.I. Pigment Orange 71
PO73: C.I. Pigment Orange 73

The results in Tables 5-1 to 5-4 show that the aqueous colorant dispersion of the present invention has excellent particle size distribution stability and filterability when stored at fluctuating temperatures. In particular, aqueous colorant compositions containing α-olefin units in the structure of the acid group-containing resin (B) and having neutralization and crosslinking values within specific ranges have excellent particle size distribution stability when stored in coarse particles and at fluctuating temperatures.

<Production of Inkjet Recording Ink>
[Example 127]
- Production of Inkjet Recording Ink (1) 33 parts of the aqueous colorant dispersion (1), 5 parts of BDG, 15 parts of 1,2-propanediol, 8.8 parts of Joncryl HPD96, 1.25 parts of Chemipearl W400S, 0.5 parts of Surfynol DF110D, 1 part of BYK-348, 0.1 part of triethanolamine, 0.15 parts of Proxel GXL, and 35.2 parts of ion-exchanged water were mixed and filtered through a 0.5 μm membrane filter to prepare an inkjet recording ink (1).

[Examples 128 to 252, Comparative Examples 7 to 12]
Production of Inkjet Recording Inks (2) to (128), (134) to (137) Inkjet recording inks (2) to (128), (134) to (137) were produced in the same manner as in Example 126, except that the aqueous colorant dispersions used were changed as shown in Table 6.

[Example 253]
- Production of Inkjet Recording Ink (129) 33 parts of the aqueous colorant dispersion (39), 5 parts of 1,2-hexanediol, 15 parts of 1,2-butanediol, 9.4 parts of Takelac W-6110, 1.25 parts of Chemipearl W400S, 0.5 parts of Surfynol DF110D, 1 part of BYK-348, 0.1 parts of triethanolamine, 0.15 parts of Neosynthol BC-493, and 34.6 parts of ion-exchanged water were mixed and filtered through a 0.5 μm membrane filter to prepare an inkjet recording ink (129).

[Example 254]
- Production of Inkjet Recording Ink (130) 33 parts of the aqueous colorant dispersion (39), 5 parts of BDG, 15 parts of 1,2-butanediol, 6.25 parts of Joncry780, 0.5 parts of Surfynol DF110D, 1 part of BYK-348, 0.1 parts of triethanolamine, 0.15 parts of Proxel GXL, and 39 parts of ion-exchanged water were mixed and filtered through a 0.5 μm membrane filter to prepare an inkjet recording ink (130).

[Example 255]
- Production of Inkjet Recording Ink (131) 33 parts of the aqueous colorant dispersion (39), 5 parts of diethylene glycol monoisobutyl ether, 15 parts of 1,2-butanediol, 10 parts of Takelac W-5030, 0.5 parts of Surfynol 465, 1 part of BYK-348, 0.1 parts of triethanolamine, 0.15 parts of Proxel GXL, and 35.25 parts of ion-exchanged water were mixed and filtered through a 0.5 μm membrane filter to prepare an inkjet recording ink (131).

[Example 256]
- Production of Inkjet Recording Ink (132) 33 parts of the aqueous colorant dispersion (39), 5 parts of diethylene glycol monoisobutyl ether, 15 parts of 1,2-propanediol, 10 parts of Takelac W-6061, 0.5 parts of Surfynol 465, 1 part of BYK-348, 0.1 parts of triethanolamine, 0.15 parts of Neosynthol BC-493, and 35.25 parts of ion-exchanged water were mixed and filtered through a 0.5 μm membrane filter to prepare an inkjet recording ink (132).

[Example 257]
- Production of Inkjet Recording Ink (133) 33 parts of the aqueous colorant dispersion (39), 5 parts of 1,2-hexanediol, 15 parts of 1,2-propanediol, 7.5 parts of Vylonal MD-2000, 1.25 parts of Chemipearl W400S, 0.5 parts of Surfynol DF110D, 1 part of BYK-348, 0.1 parts of triethanolamine, 0.15 parts of Neosynthol BC-493, and 37.75 parts of ion-exchanged water were mixed and filtered through a 0.5 μm membrane filter to prepare an inkjet recording ink (133).

<Viscosity stability>
The viscosity of the prepared inkjet recording ink was measured using a cone-plate type viscometer TV-22 manufactured by Toki Sangyo Co., Ltd., and was recorded as the initial viscosity _Vb . This inkjet recording ink was placed in a 20 mL glass sample tube, stored at 70°C for one week, and then cooled to room temperature and measured in the same manner as the initial viscosity, and was recorded as the aged viscosity V _a . The aged viscosity value was divided by the initial viscosity value to calculate the value V _a /V _b , and the viscosity stability was evaluated according to the following criteria.
◎: Value of V _a /V _b is less than 105% (excellent)
○: Value of V _a /V _b is 105% or more and less than 110% (good)
△: Value of _Va / _Vb is 110% or more and less than 115% (no problem in practical use)
×: Value of _Va / _Vb is 115% or more (bad)

<Continuous ejection>
Each inkjet recording ink was filled into a commercially available inkjet printer equipped with an inkjet head having a piezoelectric element in an environment of 25°C, and solid printing was continuously performed on coated paper (OK Topcoat N manufactured by Oji Paper Co., Ltd., basis weight 104.7 g/ ^m2 ) with a printing rate of 100%, and then a nozzle check pattern was printed to check for the presence or absence of nozzle clogs and evaluation was performed. The evaluation criteria are as follows.
◎: No missing nozzles even after printing for over an hour (Excellent)
○: No missing nozzles even after printing for 10 minutes or more but less than 1 hour (good)
△: No missing nozzles even after printing for 1 minute or more but less than 10 minutes (no practical problems)
×: Nozzle missing occurred in less than 1 minute (defective)

＜Filled in＞
The image area of the evaluation print obtained on the coated paper with a printing rate of 100% was visually observed for color unevenness and white streaks. The evaluation criteria were as follows:
◎: No uneven color or white streaks (Excellent)
○: No white streaks, but slight color unevenness (good)
△: There is some uneven coloring and white streaks (no practical problems).
×: Many streaks are present (poor)

The results are summarized in Table 6.

From the results in the above table, the inkjet recording ink using the aqueous colorant dispersion of the present invention has good continuous dischargeability and solid filling. In particular, the aqueous colorant composition containing α-olefin units in the structure of the acid group-containing resin (B) and having a neutralization value and crosslinking value within a specific range had particularly good continuous dischargeability and solid filling. In addition, the solid filling was evaluated on coated paper as well as fine paper, coated paper, OPP film, polyethylene terephthalate film, and fabric. Inkjet recording inks (1) to (128) were good on fine paper, inkjet recording ink (129) was good on OPP film and fabric, inkjet recording ink (130) was good on polyethylene terephthalate film, inkjet recording ink (131) was good on polyethylene terephthalate film and fabric, inkjet recording ink (132) was good on fabric, and inkjet recording ink (133) was good on fine paper and OPP film. Furthermore, when the clarity and coloring power of each coating were evaluated, both were found to be excellent.

Claims (4)

An aqueous colorant dispersion comprising a colorant (A), an acid group-containing resin (B), an aqueous medium (C), a crosslinking agent (D), and a basic compound (E), wherein the acid group-containing resin (B) is a polymer containing an α-olefin unit in its main chain, and the aqueous colorant dispersion satisfies the following:
The acid value of the acid group-containing resin (B) is 34 to 175 mgKOH/g.
The neutralization value of the acid group-containing resin (B) is 0.5 or more and 0.95 or less.
The crosslinking value of the acid group-containing resin (B) is 0.7 or more and 1.3 or less.
The acid group of the acid group-containing resin (B) is a carboxy group.
The acid group-containing resin (B) has a number average molecular weight (Mn) of 50,000 or less.
Here, the neutralization value and the crosslinking value are calculated from the following (1) and (2).
(1) Neutralization value = number of molar equivalents of basic functional groups of basic compound (E) / number of molar equivalents of acidic functional groups of acid group-containing resin (B) (2) Crosslinking value = number of molar equivalents of crosslinking functional groups of crosslinking agent (D) / number of molar equivalents of acidic functional groups of acid group-containing resin (B) 2. The aqueous colorant dispersion according to claim 1 , wherein the acid group-containing resin (B) is a polymer containing an α-olefin unit and a maleic acid unit, and the maleic acid unit contains at least one of a maleic anhydride unit and a maleic acid ester unit. An ink for ink-jet recording, comprising the aqueous colorant dispersion according to claim 1 or 2 . A method for producing an aqueous colorant dispersion, comprising the following steps 1 to 3, in which the acid group-containing resin (B) is a polymer containing an α-olefin unit in its main chain, and the following is satisfied:
Step 1: A step of mixing a colorant (A) and an acid group-containing resin (B). Step 2: A step of adding an aqueous medium (C) and a basic compound (E) to the mixture obtained in step 1 to neutralize it. Step 3: A step of adding a crosslinking agent (D) to the mixture obtained in step 2 to perform a crosslinking treatment. The acid value of the acid group-containing resin (B) is 34 to 175 mg KOH/g.
The neutralization value of the acid group-containing resin (B) is 0.5 or more and 0.95 or less.
The crosslinking value of the acid group-containing resin (B) is 0.7 or more and 1.3 or less.
The acid group of the acid group-containing resin (B) is a carboxy group.
The acid group-containing resin (B) has a number average molecular weight (Mn) of 50,000 or less.
Here, the neutralization value and the crosslinking value are calculated from the following (1) and (2).
(1) Neutralization value = number of molar equivalents of basic functional groups of basic compound (E) / number of molar equivalents of acidic functional groups of acid group-containing resin (B) (2) Crosslinking value = number of molar equivalents of crosslinking functional groups of crosslinking agent (D) / number of molar equivalents of acidic functional groups of acid group-containing resin (B)