Colorant dispersions, inks, ink sets, and coatings

Abstract

To provide a colorant dispersion capable of making an ink jet ink that allows high-density printing onto uncoated paper free of an ink reception layer, and has high storage stability.SOLUTION: A colorant dispersion contains a dispersant, a colorant, and water. The dispersant is a polymer containing a colorant adsorption group-containing monomer unit, a maleic acid unit, and a maleimide unit or an N-substituted maleimide unit. The colorant adsorption group-containing monomer unit contains at least one of an α-olefin unit and a methacrylate monomer unit having an alkyl group.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a colorant dispersion for use in aqueous inkjet inks and the like, and to an ink, an ink set, and a coating material containing the same. [Background technology]

[0002] Among inkjet inks used in inkjet printing, inks that use pigments as colorants contain the pigments in a finely dispersed state. Paper is often the recording medium for inkjet printing. Paper can be broadly divided into coated paper, such as art paper and coated paper, and uncoated paper, such as foam paper and wood-free paper. However, while coated paper has a smooth recording surface, uncoated paper has a relatively uneven surface. As the ink absorption of the two types of paper differs significantly, an ink-receiving layer is typically formed on the surface to produce printed matter with high print density. To reduce costs, there has been a demand for inkjet inks for uncoated paper that do not have an ink-receiving layer. Normally, to increase print density, ink with finely dispersed colorants can be used, but the print density of uncoated paper, which easily absorbs ink, decreases if there is no ink-receiving layer, as the ink penetrates into the paper. In contrast, increasing the particle size of the dispersed colorants allows the colorants to remain on the surface of uncoated paper, increasing print density, but at the same time, the storage stability of the ink decreases.

[0003] Patent Document 1 discloses an ink that uses a random copolymer of styrene macromer / styrene / benzyl methacrylate / alkyleneoxy chain-containing methacrylate / methacrylic acid as a dispersant to increase print density. Patent Document 2 also discloses an ink that uses a block polymer as a dispersant, with the A block consisting of benzyl methacrylate and the B block consisting of methacrylic acid / butyl methacrylate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-108115 [Patent Document 2] Japanese Patent Publication No. 2020-125452 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0005] However, conventional inks have been unable to achieve both storage stability and high print density.

[0006] An object of the present invention is to provide a colorant dispersion that can be used to prepare an inkjet ink that is capable of producing high-density printing on uncoated paper that does not have an ink-receiving layer and has good storage stability. [Means for solving the problem]

[0007] The colorant dispersion of the present invention is a colorant dispersion containing a dispersant, a colorant, and water, the dispersant is a polymer containing a colorant-adsorptive-group-containing monomer unit, a maleic acid unit, and a maleimide unit or an N-substituted maleimide unit; The colorant-adsorptive-group-containing monomer unit contains at least one of an α-olefin unit and a (meth)acrylic acid ester monomer unit having an alkyl group. DETAILED DESCRIPTION OF THE INVENTION

[0008] First, the terms used in this specification are defined. "CI" means color index (CI). Monomer and monomeric substance are ethylenically unsaturated group-containing monomers. A (poly)alkyleneoxy group includes both a polyalkyleneoxy group and an alkyleneoxy group. Examples of alkyleneoxy groups include an ethyleneoxy group, a propyleneoxy group, and a butyleneoxy group. A monomer that has been polymerized to become a part of a polymer is called a monomer unit. A dispersant is a compound used to disperse a colorant that has been finely divided in advance.

[0009] The colorant dispersion of the present invention is a colorant dispersion containing a dispersant, a colorant, and water, the dispersant is a polymer containing a colorant-adsorptive-group-containing monomer unit, a maleic acid unit, and a maleimide unit or an N-substituted maleimide unit; The colorant-adsorptive-group-containing monomer unit contains at least one of an α-olefin unit and a (meth)acrylic acid ester monomer unit having an alkyl group. The colorant dispersion is preferably used for applications such as inkjet ink, flexographic printing ink, stationery, textile printing agents, and paints.

[0010] The dispersant contained in the colorant dispersion is characterized by containing colorant-adsorptive group-containing monomer units, maleic acid units, and maleimide units or N-substituted maleimide units. This improves storage stability and dramatically improves print density on both uncoated and coated paper while maintaining fine dispersion that enables inkjet ejection. We speculate that these effects are due to the repulsion between the two carboxyl groups derived from the maleic acid units and the phenomenon of chelating traces of metal ions, such as calcium ions, present in paper, which are significantly improved by the inclusion of maleimide units or N-substituted maleimide units. Furthermore, we believe that the dispersant's inclusion of a colorant-adsorbing group-containing monomer unit and a highly polar and hydrophobic maleimide or N-substituted maleimide unit significantly improves its adsorption to various pigment types. We speculate that this allows the dispersant to maintain excellent dispersibility for various pigment types while also achieving insolubilization through chelating with traces of metal ions present in paper, thereby allowing the colorant dispersion to remain on the paper surface during printing, thereby achieving high print density.

[0011] <Coloring agent> The colorant is a compound in the form of particles, and may be an aggregate. The colorant may be selected from organic pigments, inorganic pigments, and dyes.

[0012] Examples of organic pigments include azo pigments, diazo pigments, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, dioxazine pigments, perylene pigments, perinone pigments, thioindigo pigments, anthraquinone pigments, and quinophthalone pigments.

[0013] In terms of the color index of organic pigments, for example, CI Pigment Red 1, 2, 3, 4, 5, 6, 7, 9, 10, 14, 17, 22, 23, 31, 32, 38, 41, 48:1, 48:2, 48:3, 48:4, 49, 49:1, 49:2, 52:1, 52:2, 53:1, 57:1, 60:1, 63:1, 66, 67, 81:1, 81:2, 81:3, 83, 88, 90, 105, 112, 119, 122, 123, 144, 146, 147, 148, 149, 150, 155, 166, 168, 169, 170, 171, 172, 175, 176, 177, 178, 179, 184, 185, 187, 188, 190, 200, 202, 206, 207, 208, 209, 210, 216, 220, 224, 226, 242, 246, 254, 255, 264, 266, 269, 270, 272, 279, CIPigmentYellow1, 2, 3, 4, 5, 6, 10, 11, 12, 13, 14, 15, 16, 17, 18, 20, 24, 31, 32, 34, 35, 35:1, 36, 36:1, 37, 37:1, 40, 42, 43, 53, 55, 60, 61, 62, 63, 65, 73, 74, 77, 81, 83, 86, 93, 94, 95, 97, 98, 100, 101, 104, 106, 108, 109, 110, 113, 114, 115, 11 6, 117, 118, 119, 120, 123, 125, 126, 127, 128, 129, 137, 138, 139, 147, 148, 150, 151, 152, 153, 154, 155, 156, 161, 162, 164, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 179, 180, 181, 182, 185, 187, 188, 193, 194, 199, 213, 214, CIPigmentOrange2, 5, 13, 16, 17:1, 31, 34, 36, 38, 43, 46, 48, 49, 51, 52, 55, 59, 60, 61, 62, 64, 71, 73, CIPigmentGreen7, 10, 36, 37, 58, 59, 62, 63, CIPigmentBlue1, 2, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 22, 60, 64, 66, 79, 79, 80 CIPigmentViolet1, 19, 23, 27, 32, 37, 42 CIPigmentBrown 25, 28 CIPigment Black 1, 7 CI Pigment White 1, 2, 4, 5, 6, 7, 11, 12, 18, 19, 21, 22, 23, 26, 27, 28, etc.

[0014] Among these, CIPigmentRed31, 48:1, 48:2, 48:3, 48:4, 57:1, 122, 146, 147, 148, 150, 170, 176, 177, 184, 185, 202, 242, 254, 255, 264, 266, 269, CIPigmentYellow12, 13, 14, 17, 74, 83, 108, 109, 120, 150, 151, 154, 155, 180, 185, 213 CIPigmentOrange36,38,43,64,73 CIPigmentGreen7, 36, 37, 58, 62, 63, CIPigmentBlue15:1, 15:3, 15:6, 16, 22, 60, 66, CIPigmentViolet19, 23, 32, CIPigmentBrown25, CIPigment Black 1, 7 CI Pigment White 6 is preferred.

[0015] Examples of inorganic pigments include carbon black, metal oxides, metal complexes, and other inorganic pigments. Examples of carbon black include furnace black, thermal lamp black, acetylene black, and channel black. Examples of metal oxides include titanium oxide, iron oxide, iron hydroxide, zirconia, and alumina. Examples of other inorganic pigments include ultramarine, yellow lead, zinc sulfide, and cobalt blue.

[0016] The carbon black has an average primary particle diameter of 11 to 50 nm and a specific surface area according to the BET method of 50 to 400 m 2 Preferably, the carbon black has properties such as a pH of 2 to 10 and a viscosity of 100 / g. Commercially available carbon black products include, for example, Nos. 25, 30, 33, 40, 44, 45, 52, 850, 900, 950, 960, 970, 980, 1000, 2200B, 2300, 2350, and 2600; MA7, MA8, MA77, MA100, and MA230 (manufactured by Mitsubishi Chemical Corporation); RAVEN 760UP, 780UP, 860UP, 900P, 1000P, 1060UP, 1080UP, and 1255 (manufactured by Columbia Chemical Co., Ltd.). Examples include: REGAL 330R, 400R, 660R, MOGULL (manufactured by Cabot Corporation), Nipex 160IQ, 170IQ, 35, 75; PrinteX 30, 35, 40, 45, 55, 75, 80, 85, 90, 95, 300; SpecialBlack 350, 550; Nerox 305, 500, 505, 600, 605 (manufactured by Orion Engineered Carbons).

[0017] Examples of the titanium oxide include anatase and rutile types. Among these, the rutile type is preferred in terms of improving the hiding power of printed matter. Titanium oxide can be synthesized by the chlorine method, sulfuric acid method, etc., and the chlorine method is preferred in terms of improving whiteness.

[0018] It is preferable to suppress the activity of titanium oxide by treating the surface with an inorganic compound. After the inorganic compound treatment, it is preferable to further treat the surface with an organic compound. This improves the dispersion stability of titanium oxide. Examples of inorganic compounds include compounds of silicon, aluminum, zirconium, tin, antimony, and titanium, as well as hydrated oxides thereof. Examples of organic compounds include polyhydric alcohols, alkanolamines and derivatives thereof, higher fatty acids and metal salts thereof, and organometallic compounds.

[0019] The dye is preferably a disperse dye. Disperse dyes are dyes that sublimate when heated. Examples of disperse dyes include: CI Disperse Yellow 3, 7, 8, 23, 39, 51, 54, 60, 71, 86; CI Disperse Orange 1, 1:1, 5, 20, 25, 25:1, 33, 56, 76; CI Disperse Brown 2; CI Disperse Red 11, 50, 53, 55, 55:1, 59, 60, 65, 70, 75, 93, 146, 158, 190, 190:1, 207 239, 240, 343; CI Vat Red 41; CI Disperse Violet 8, 17, 23, 27, 28, 29, 36, 57; CI Disperse Blue 19, 26, 26:1, 35, 55, 56, 58, 60, 64, 64:1, 72, 72:1, 81, 81:1, 91, 95, 108, 131, 141, 145, 165, 359, 360, etc.

[0020] The colorants can be used alone or in combination of two or more.

[0021] The average primary particle diameter of the colorant is preferably 5 to 1,000 nm. The average primary particle diameter is the average value of approximately 20 particles randomly selected from an image magnified 2,000 to 100,000 times using a transmission electron microscope. When the particles are elliptical, the length of the vertical axis is used.

[0022] <Dispersant> The dispersant is a polymer containing a colorant-adsorptive group-containing monomer unit, a maleic acid unit, and a maleimide unit or an N-substituted maleimide unit. Examples of methods for synthesizing the dispersant include emulsion polymerization, solution polymerization, bulk polymerization, and suspension polymerization. Examples of polymerization methods include random polymerization, alternating copolymerization, and block polymerization. Examples of polymerization reactions include radical polymerization, anionic polymerization, and cationic polymerization. The dispersant described herein can be synthesized by appropriately combining these methods. In the present specification, a dispersant that undergoes random polymerization or alternating copolymerization in a solution using a radical polymerization initiator will be described below as an example.

[0023] The dispersant is preferably synthesized by copolymerizing a monomer mixture containing a colorant-adsorbing group-containing monomer, maleic acid, and maleimide or N-substituted maleimide, and a (meth)allyl monomer.

[0024] <Colorant adsorption group-containing monomer> The colorant-adsorbing group-containing monomer may be any monomer containing a structure that adsorbs to a colorant, and includes at least one of an α-olefin unit and a (meth)acrylic acid ester monomer unit having an alkyl group. Among these, α-olefins are preferred from the viewpoint of copolymerizability with maleic acid (anhydride) or (meth)allyl monomers and adsorption rate to the colorant surface.

[0025] The α-olefin is preferably an α-olefin having 6 to 50 carbon atoms, more preferably 8 to 30 carbon atoms, and even more preferably 12 to 28 carbon atoms. Examples of α-olefins include 1-hexene (6 carbon atoms), 1-heptene (7 carbon atoms), 1-octene (8 carbon atoms), 1-nonene (9 carbon atoms), 1-decene (10 carbon atoms), 1-dodecene (12 carbon atoms), 1-tetradecene (14 carbon atoms), 1-hexadecene (16 carbon atoms), 1-octadecene (18 carbon atoms), 1-eicosene (20 carbon atoms), 1-docosene (22 carbon atoms), 1-tetracosene (24 carbon atoms), 1-octacosene (28 carbon atoms), 1-triacontene (30 carbon atoms), 1-dotriacontene (32 carbon atoms), 1-tetratriacontene (34 carbon atoms), 1-hexatriacontene (36 carbon atoms), and 1-octatriacontene (38 carbon atoms).

[0026] The α-olefins can be used alone or in combination of two or more kinds.

[0027] The alkyl chain of the (meth)acrylic acid ester monomer having an alkyl group preferably has 6 to 50 carbon atoms, more preferably 8 to 30 carbon atoms, and even more preferably 10 to 24 carbon atoms. Examples of the (meth)acrylic acid ester monomer having an alkyl group include decyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, and behenyl (meth)acrylate.

[0028] The (meth)acrylic acid ester monomers having an alkyl group can be used alone or in combination of two or more kinds.

[0029] <Maleic acid> To form the maleic acid unit, at least one of maleic acid and maleic anhydride is used, with maleic anhydride being preferred from the viewpoint of excellent copolymerizability.

[0030] <Maleimide, N-substituted maleimide> The dispersant contains maleimide units and N-substituted maleimide units, along with colorant-adsorbing group-containing monomer units and maleic acid units, dramatically improving print density on both uncoated and coated paper while maintaining the storage stability of the colorant dispersion and the fine dispersion required for inkjet ejection. This effect is believed to be due to the repulsion between the two carboxyl groups derived from the maleic acid units and the chelation of trace metal ions, such as calcium ions, present in the paper, which is significantly enhanced by the inclusion of maleimide units or N-substituted maleimide units. Furthermore, the dispersant contains colorant-adsorbing group-containing monomer units and hydrophobic maleimide units or N-substituted maleimide units, which possess highly polar imide bonds. This significantly improves the adsorption rate for various pigment types. This allows the dispersant to maintain excellent dispersibility for various pigment types while also achieving insolubilization through chelation with trace metal ions present in the paper. This allows the colorant dispersion to remain on the paper surface during printing, achieving high print density. Furthermore, by changing the substituent of the N-substituted maleimide unit, it is possible to adjust the compatibility and the adsorption rate to the colorant. Among the substituents, hydrocarbon groups include, for example, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a s-butyl group, a t-butyl group, an amyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, a lauryl group, a myristyl group, a cetyl group, a stearyl group, an oleyl group, and the like; Examples of the cyclic hydrocarbon group include a cyclohexyl group; Examples of the aromatic group include a phenyl group, an o-tolyl group, a m-tolyl group, a p-tolyl group, a 2-ethylphenyl group, a 2-fluorophenyl group, an o-methoxyphenyl group, a m-hydroxyphenyl group, a p-hydroxyphenyl group, a p-carboxylphenyl group, and a benzyl group; From the viewpoints of storage stability and compatibility with the binder, cyclic hydrocarbon groups and aromatic groups are preferred, a cyclohexyl group or a phenyl group is more preferred, and a phenyl group is particularly preferred.

[0031] To form the maleimide unit or N-substituted maleimide unit, a commercially available monomer may be used, or it may be obtained by modifying maleic anhydride.

[0032] The maleimide or N-substituted maleimide units can be used alone or in combination of two or more kinds.

[0033] The N-substituted maleimide unit may be formed using an amine, which may be obtained by modifying maleic anhydride. Examples of amines include, but are not limited to, methylamine, ethylamine, propylamine, isopropylamine, butylamine, amylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, laurylamine, myristylamine, cetylamine, stearylamine, oleylamine, aniline, o-toluidine, 2-ethylaniline, 2-fluoroaniline, o-anisidine, m-toluidine, m-anisidine, m-phenetidine, p-toluidine, 2,3-dimethylaniline, 5-aminoindan, aspartic acid, glutamic acid, and γ-aminobutyric acid.

[0034] The amines can be used alone or in combination of two or more.

[0035] In this specification, the maleimide unit or N-substituted maleimide unit may be hydrolyzed in the aqueous pigment dispersion to become either an imide bond or an amide bond. These forms are also included in the maleimide unit or N-substituted maleimide unit.

[0036] <(Meth)allyl Monomer> The (meth)allyl monomer is a monomer containing a (meth)allyl group. The (meth)allyl monomer is not particularly limited, but is preferably a (meth)allyl ether monomer represented by the following general formula (1).

[0037] [ka]

[0038] In general formula (1), R1 represents a hydrogen atom or a methyl group. R2O represents an alkyleneoxy group, and two or more types of alkyleneoxy groups may be added randomly or in blocks. The alkyleneoxy group represented by R2O is preferably an alkyleneoxy group having 2 to 5 carbon atoms, for example, from the viewpoint of dispersion stability. Examples of the alkyleneoxy group having 2 to 5 carbon atoms include an ethyleneoxy group, a propyleneoxy group, a butyleneoxy group, and a tetramethyleneoxy group. Among these, from the viewpoint of dispersibility, a single addition of an ethyleneoxy group or a propyleneoxy group, or a block or random addition of an ethyleneoxy group and a propyleneoxy group is preferred, and a single addition of a propyleneoxy group or a block or random addition of an ethyleneoxy group and a propyleneoxy group is more preferred.

[0039] In general formula (1), m is the average number of moles of alkyleneoxy groups and is an integer of 0 or 1 to 100. From the viewpoint of copolymerizability of the monomer and the adsorption rate of the dispersant to the colorant, it is preferably 1 to 60, more preferably 3 to 50, and even more preferably 5 to 40.

[0040] In general formula (1), R3 represents a hydrogen atom, a linear or branched alkyl group, a saturated acyl group, or a phenyl group which may be substituted with an alkyl group. The linear or branched alkyl group may be, for example, a linear or branched alkyl group having 1 to 20 carbon atoms, with methyl, ethyl, isopropyl, etc. being preferred. The saturated acyl group may be a saturated acyl group having 1 to 10 carbon atoms, with a substituent derived from ethanoic acid, butanoic acid, propionic acid, or butyric acid being preferred. The phenyl group which may be substituted with an alkyl group may be, for example, a phenyl group, a naphthyl group, or p-methylphenyl. Among these, R3 is preferably a linear or branched alkyl group, which has a high dispersion stability. From this viewpoint, a methyl group is most preferred.

[0041] Examples of the (meth)allyl ether monomer represented by general formula (1) include alkyl (meth)allyl ethers such as methyl (meth)allyl ether and ethyl (meth)allyl ether; ring-containing (meth)allyl ethers such as phenyl (meth)allyl ether and cyclohexyl (meth)allyl ether; hydroxyalkyl (meth)allyl ethers such as 2-hydroxyethyl (meth)allyl ether and 4-hydroxybutyl (meth)allyl ether; and (meth)allyl esters such as (meth)allyl propionate, (meth)allyl hexanoate, and (meth)allyl cyclohexanepropionate. Furthermore, the (meth)allyl ether monomer represented by general formula (1) preferably has a (poly)alkyleneoxy group. Examples include (poly)alkyleneoxy group-containing (meth)allyl ethers such as polyalkylene glycol (meth)allyl ether, alkyleneoxy glycol (meth)allyl ether, and alkoxy polyalkylene glycol (meth)allyl ether. Among these, from the viewpoint of compatibility with the binder resin, it is preferable that it contains a (poly)alkyleneoxy group, and alkoxy polyalkylene glycol (meth)allyl ether is more preferable.

[0042] Examples of alkoxy polyalkylene glycol (meth)allyl ethers include methoxyethylene glycol (meth)allyl ether, methoxypolyethylene glycol (meth)allyl ether, methoxypropylene glycol (meth)allyl ether, methoxypolypropylene glycol (meth)allyl ether, ethoxyethylene glycol (meth)allyl ether, ethoxypolyethylene glycol (meth)allyl ether, ethoxypropylene glycol (meth)allyl ether, ethoxypolypropylene glycol (meth)allyl ether, propoxyethylene glycol (meth)allyl ether, propoxypolyethylene glycol (meth)allyl ether, propoxypropylene glycol (meth)allyl ether, propoxypolypropylene glycol (meth)allyl ether, etc. From the viewpoint of compatibility with the binder resin, methoxypolyethylene glycol (meth)allyl ether and methoxypolypropylene glycol (meth)allyl ether are more preferred, and methoxypolypropylene glycol (meth)allyl ether is even more preferred.

[0043] The (meth)allyl ethers can be used alone or in combination of two or more.

[0044] The dispersant may contain other monomer units other than the colorant-adsorptive group-containing monomer unit, maleic acid unit, maleimide unit or N-substituted maleimide unit, and (meth)allyl monomer unit. Examples of other monomer units include, but are not limited to, aromatic ring-containing monomers (excluding heterocyclic ring-containing monomers), alicyclic ring-containing monomers, heterocyclic ring-containing monomers (excluding aromatic ring-containing monomers), and other vinyl monomers.

[0045] Examples of aromatic ring-containing monomers include styrene, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, and styrene macromers.

[0046] Examples of the alicyclic ring-containing monomer include isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, 3,3,5-trimethylcyclohexyl (meth)acrylate, and 4-tert-butylcyclohexyl (meth)acrylate.

[0047] Examples of heterocycle-containing monomers include N-vinyl-2-pyrrolidone, N-vinylcaprolactam, N-vinylpyridine, N-vinylpyrimidine, N-vinylpiperidone, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-vinylpiperazine, and (meth)acryloylmorpholine.

[0048] The dispersant can be synthesized by adding a radical polymerization initiator and, if necessary, a chain transfer agent to a monomer mixture containing a colorant-adsorbing group-containing monomer, maleic anhydride, maleimide or N-substituted maleimide, and a (meth)allyl monomer, and polymerizing the mixture. The resulting dispersant is essentially an alternating polymer in which maleic anhydride is alternately arranged between randomly arranged colorant-adsorbing group-containing monomer units and (meth)allyl monomer units.

[0049] The content of the colorant-adsorptive group-containing monomer unit in the total monomer units of the dispersant is preferably 20 to 60 mol %, more preferably 25 to 55 mol %, and even more preferably 30 to 50 mol %. When an appropriate amount is contained, the dispersant becomes more easily adsorbed to the surface of the colorant, and storage stability is further improved.

[0050] The content of maleic acid units in the dispersant is preferably 5 to 60 mol %, more preferably 10 to 50 mol %, and even more preferably 15 to 40 mol % of all monomer units. When an appropriate amount is contained, the colorant dispersion can maintain its storage stability while increasing the print density on uncoated paper.

[0051] The content of maleimide units or N-substituted maleimide units is preferably 5 to 60 mol %, more preferably 10 to 50 mol %, and even more preferably 15 to 40 mol %, of all monomer units in the dispersant. When an appropriate amount is contained, the colorant dispersion can maintain its storage stability while increasing the print density on uncoated paper.

[0052] The content of (meth)allyl monomer units in the total monomer units of the dispersant is preferably 1 to 30 mol %, more preferably 1 to 20 mol %, and even more preferably 2 to 15 mol %. When an appropriate amount is contained, the compatibility of the dispersant with the binder resin and the like is improved, and the print density is further improved.

[0053] Examples of the radical polymerization initiator include azo compounds and peroxides. Examples of the azo compounds include azobisisobutyronitrile and azobis-2,4-dimethylvaleronitrile. Examples of the peroxides include cumene hydroperoxide, t-butyl hydroperoxide, benzoyl peroxide, diisopropyl peroxycarbonate, di-t-butyl peroxide, lauroyl peroxide, t-butyl peroxybenzoate, and t-butylperoxy-2-ethylhexanoate.

[0054] The radical polymerization initiators can be used alone or in combination of two or more.

[0055] Examples of organic solvents used in solution polymerization include, but are not limited to, ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, xylene, acetone, hexane, methyl ethyl ketone, and cyclohexanone. Two or more of these polymerization solvents may be mixed and used.

[0056] The organic solvents can be used alone or in combination of two or more kinds.

[0057] <Modified site caused by hydroxycarboxylic acid> The maleic acid units of the dispersant are preferably units having modified moieties with an oxycarboxylic acid having a divalent or trivalent carboxyl group. The ester bond moieties are preferably formed by an oxycarboxylic acid having a divalent or trivalent carboxyl group (hereinafter referred to as oxycarboxylic acid). Specifically, the ester bond moieties are formed by reacting an oxycarboxylic acid with the acid anhydride group in the maleic anhydride unit to form the ester bond moieties. The ester bond moieties are preferably formed at a ratio of 30 to 100% of 100 mol% of the acid anhydride groups. Esterification can impart divalent or trivalent carboxyl group moieties to the dispersant, thereby achieving excellent electrostatic repulsion and simultaneously chelating trace metal ions, such as calcium ions, present in paper with adjacent carboxyl groups. By chelating the metal ions, the dispersant becomes insolubilized, and the colorant dispersion remains largely on the surface of the paper without penetrating deep into the paper, dramatically improving print density. Furthermore, esterification improves compatibility with binder resins and the like, further improving print density.

[0058] A preferred method for obtaining the esterified dispersant is, for example, to polymerize a monomer mixture containing a colorant-adsorbing group-containing monomer, maleic anhydride, and maleimide or N-substituted maleimide, and a (meth)allyl monomer, followed by reacting with water or an oxycarboxylic acid having a divalent or trivalent carboxyl group.

[0059] Examples of oxycarboxylic acids having a divalent carboxyl group include aminocarboxylic acid chelating agents such as tartronic acid, malic acid, 4-hydroxyphthalic acid, and N,N-bis(carboxymethyl)ethanolamine.

[0060] An example of an oxycarboxylic acid having a trivalent carboxyl group is citric acid.

[0061] In particular, water or a carboxyl group-containing hydroxycarboxylic acid having a divalent or trivalent carboxyl group and a molecular weight of 80 to 350 is preferred, with water being more preferred. When the molecular weight of the hydroxycarboxylic acid having a divalent or trivalent carboxyl group is 80 to 350, the esterification reaction proceeds easily, resulting in a dispersant with an excellent balance of hydrophilicity and hydrophobicity, which tends to enhance the pigment dispersion stabilization effect. Furthermore, dispersants obtained by esterification with water exhibit significantly improved storage stability, fine dispersion properties that enable inkjet ejection, and print density. This is thought to be due to the fact that adjacent carboxyl groups derived from maleic acid are highly effective as dispersion sites and also have excellent reactivity with metal ions in paper.

[0062] The esterification reaction is carried out at 50 to 300°C, and may be carried out in the presence of a suitable solvent, if necessary. Furthermore, an esterification catalyst may be added as needed. The esterification catalyst is not particularly limited, and examples thereof include sulfuric acid, hydrogen chloride, p-toluenesulfonic acid, triethylamine, dimethylbenzylamine, tetrabutylammonium bromide, and 1,8-diazabicyclo[5.4.0]undecene-7. The esterification catalyst is preferably used in an amount of about 0.03 to 5% by mass per 100 parts by mass of the reactant.

[0063] The dispersant preferably has a low acid anhydride value. For example, the acid anhydride value is preferably 0 to 50 mgKOH / g, more preferably 0 to 30 mgKOH / g, and even more preferably 0 to 10 mgKOH / g. A moderate acid anhydride value further improves the dispersibility of the colorant.

[0064] The compounds used to form the ester bond site can be used alone or in combination of two or more types. Cut.

[0065] The acid value of the dispersant is preferably 35 to 400 mgKOH / g, more preferably 50 to 300 mgKOH / g, and even more preferably 65 to 200 mgKOH / g. A moderate acid value not only provides an excellent electrostatic repulsion effect, improves storage stability and fine dispersion, but also increases reactivity to trace amounts of metal ions in paper, improving print density.

[0066] The number average molecular weight of the dispersant is preferably 2,000 to 35,000, more preferably 3,000 to 15,000, and the polydispersity (Mw / Mn) is preferably 1.2 to 4.0. If the dispersant has an appropriate number average molecular weight and polydispersity, the adsorption rate to the colorant is improved, and the storage stability and fine dispersion properties are also improved.

[0067] <Colorant dispersion> The colorant dispersion of the present specification contains at least a dispersant, a basic compound, a colorant, and water, and preferably contains an appropriate component selected from a binder resin, a crosslinking agent, and the like.

[0068] <Basic compounds> The basic compound neutralizes the carboxyl groups derived from the dispersant, enabling stable dispersion of colorant particles. It is also used to adjust the pH of the colorant dispersion to about 7 to 10. Examples of the basic compound include organic amines such as ammonia, dimethylaminoethanol, diethanolamine, and triethanolamine; inorganic alkalis such as alkali metal hydroxides such as sodium hydroxide, lithium hydroxide, and potassium hydroxide; organic acids; and mineral acids.

[0069] From the viewpoint of dispersion stability of the colorant dispersion, the degree of neutralization of the dispersant is preferably 10 to 200 mol % of the carboxyl groups, and more preferably 40 to 160 mol %. Here, the degree of neutralization is obtained by dividing the molar equivalent of the basic compound by the molar amount of the carboxyl groups of the dispersant. It can be calculated using the following formula. {(weight (g) of basic compound / equivalent of basic compound) / [(acid value of dispersant (KOH mg / g) × weight of dispersant (g) / (56.1 × 1000)] × 100

[0070] The basic compounds can be used alone or in combination of two or more.

[0071] <Crosslinking agent> In the colorant dispersion, it is preferable to crosslink the dispersant with a crosslinking agent. The crosslinking agent is used to crosslink carboxyl groups derived from the dispersant in the colorant dispersion. The crosslinking agent is a compound having two or more functional groups (hereinafter referred to as reactive functional groups) capable of reacting with carboxyl groups. Crosslinking allows the dispersant to tightly coat the colorant, further improving the dispersion stability of the colorant dispersion. Examples of the reactive functional group include an isocyanate group, an aziridine group, a carbodiimide group, an oxetane group, an oxazoline group, and an epoxy group, more preferably an aziridine group, a carbodiimide group, and an epoxy group, and even more preferably an epoxy group. The addition of a crosslinking agent is also preferable from the viewpoint of improving the dispersion stability of the inkjet ink. Examples of crosslinking agents include an isocyanate compound, an aziridine compound, a carbodiimide compound, an oxetane compound, an oxazoline compound, and an epoxy compound.

[0072] Examples of the isocyanate compound include organic polyisocyanates and isocyanate-terminated prepolymers. 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-terminated prepolymer can be obtained by reacting an organic polyisocyanate or a modified product thereof with a low-molecular-weight polyol or the like.

[0073] Examples of the aziridine compound 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.

[0074] Examples of the carbodiimide compound include high-molecular-weight polycarbodiimides produced by decarboxylation condensation of diisocyanate compounds in the presence of a carbodiimidization catalyst, such as the Carbodilite series manufactured by Nisshinbo Industries, Inc.

[0075] Examples of oxetane 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.

[0076] Examples of the oxazoline compound include compounds in which two or more, preferably two to three, oxazoline groups are bonded to an aliphatic group or an aromatic group, more specifically bisoxazoline compounds such as 2,2'-bis(2-oxazoline), 1,3-phenylenebisoxazoline, and 1,3-benzobisoxazoline, and compounds having a terminal oxazoline group obtained by reacting such compounds with polybasic carboxylic acids.

[0077] Examples of epoxy 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, and hydrogenated bisphenol A diglycidyl ether.

[0078] Of these, ethylene glycol diglycidyl ether and trimethylolpropane polyglycidyl ether are preferred.

[0079] The crosslinking agents can be used alone or in combination of two or more.

[0080] From the viewpoints of ease of reaction and storage stability of the colorant dispersion, the molecular weight (formula weight or number average molecular weight Mn) of the crosslinking agent is preferably 100 to 2,000, more preferably 120 to 1,500, and particularly preferably 150 to 1,000. The number of reactive functional groups contained in the crosslinking agent is preferably 2 to 6, from the viewpoints of controlling the molecular weight of the dispersant after crosslinking and improving storage stability.

[0081] The crosslinking agent preferably has a suitable water solubility so that it can react efficiently with the carboxyl groups of the dispersant in water. The water solubility is preferably such that the amount of the crosslinking agent dissolved in 100 g of water at 25°C is 0.1 to 50 g, more preferably 0.2 to 40 g, and even more preferably 0.5 to 30 g.

[0082] The amount of the crosslinking agent used is preferably about 10 to 150 mol %, more preferably 20 to 120 mol %, and even more preferably 30 to 100 mol % in terms of reactive functional groups relative to 100 mol % of the carboxyl groups of the dispersant.

[0083] The nonvolatile content of the colorant dispersion is preferably adjusted with water to about 5 to 80% by mass.

[0084] The content of the colorant and dispersant is preferably 5 to 40% by mass, more preferably 10 to 30% by mass, based on 100% by mass of the colorant dispersion. When an appropriate amount is contained, storage stability is further improved.

[0085] The D50 average particle size (median size) of the colorant in the colorant dispersion is preferably 20 to 200 nm, more preferably 25 to 150 nm, even more preferably 30 to 130 nm, and particularly preferably 35 to 90 nm. Having an appropriate particle size improves ejection stability from the nozzle and further improves the storage stability of the colorant dispersion. The D50 average particle size is measured using a laser diffraction / scattering method.

[0086] <Production of Colorant Dispersion> Examples of methods for producing a colorant dispersion include, but are not limited to, the following: First, a colorant is added to an aqueous medium containing at least a dispersant, a basic compound, and water, and the mixture is mixed and stirred. After that, a dispersion treatment is carried out using a dispersing means described below, and if necessary, a centrifugation treatment is carried out to obtain a desired colorant dispersion.

[0087] The colorant is dispersed using a commonly used dispersing machine. Examples of the dispersing machine include a ball mill, a roll mill, a sand mill, a bead mill, and a Nanomizer. Among these, a bead mill is preferably used. Examples of such a dispersing machine include a Super Mill, a sand grinder, an agitator mill, a grain mill, a Dyno Mill, a Pearl Mill, and a Cobol Mill (all of which are trade names).

[0088] Furthermore, if a micronization treatment is performed before the dispersion treatment, the colorant can be dispersed finely. A particularly preferred method is to coat the colorant with a dispersant using a salt milling method to micronize it. The salt milling method includes, for example, kneading a water-soluble solvent, a water-soluble inorganic salt, a colorant, and a dispersant to coat the surface of the colorant with the dispersant, and then removing the water-soluble inorganic salt and water-soluble solvent. First, the water-soluble solvent, the water-soluble inorganic salt, the colorant, and the dispersant are kneaded to coat the surface of the colorant with the dispersant. The kneading process micronizes the colorant while coating its surface with the dispersant. Kneading using the salt milling method efficiently micronizes the colorant. Examples of kneading devices used in the salt milling method include a kneader, a two-roll mill, a three-roll mill, a ball mill, an attritor, a horizontal sand mill, a vertical sand mill, and / or an annular bead mill. Among these, a kneader is preferred in terms of its ability to efficiently coat the surface of the colorant. Kneading conditions can be adjusted appropriately depending on the type of colorant, the degree of micronization, and the like. It can also be heated or cooled as needed.

[0089] The water-soluble inorganic salt acts as a crushing aid, and the colorant is crushed by utilizing the high hardness of the water-soluble inorganic salt. Examples of the water-soluble inorganic salt include sodium chloride, potassium chloride, and sodium sulfate. From the viewpoint of cost, it is preferable to use sodium chloride (table salt).

[0090] The water-soluble solvent wets the colorant and the water-soluble inorganic salt. The water-soluble solvent is a compound that dissolves (is miscible with) water but does not dissolve the water-soluble inorganic salt. Examples of water-soluble solvents include glycols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, polyethylene glycol, and polypropylene glycol; diols such as butanediol, pentanediol, and hexanediol; glycol esters such as propylene glycol laurate; ethers such as diethylene glycol monoethyl, diethylene glycol monobutyl, and diethylene glycol monohexyl; glycol ethers such as cellosolves containing propylene glycol ether, dipropylene glycol ether, and triethylene glycol ether; alcohols such as methanol, ethanol, isopropyl alcohol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, butyl alcohol, and pentyl alcohol; sulfolane; lactones such as γ-butyrolactone; lactams such as N-(2-hydroxyethyl)pyrrolidone; and glycerin. Among these, glycols such as diethylene glycol and triethylene glycol are preferred.

[0091] The water-soluble solvents can be used alone or in combination of two or more kinds.

[0092] The amount of the water-soluble solvent used is preferably 5 to 1,000 parts by mass, and more preferably 50 to 500 parts by mass, per 100 parts by mass of the colorant. The amount of the water-soluble inorganic salt used is preferably 50 to 2,000 parts by mass, and more preferably 300 to 1,000 parts by mass, per 100 parts by mass of the colorant. The amount of the dispersant used is preferably 5 to 100 parts by mass, and more preferably 10 to 80 parts by mass, per 100 parts by mass of the colorant. Using an appropriate amount further improves storage stability and fine dispersion.

[0093] Next, the water-soluble inorganic salt and water-soluble solvent are removed from the resulting mixture containing the colorant. First, the mixture is removed from the kneading apparatus, and ion-exchanged water is added and stirred to obtain a suspension. The amount of ion-exchanged water used is preferably 10 to 10,000 times the mass of the mixture added to the kneading apparatus. The stirring temperature is preferably 25 to 90°C. Next, filtration is performed to obtain the colorant. These operations allow the water-soluble solvent and water-soluble inorganic salt to be removed. An additional step of removing ion-exchanged water may be performed. Water is preferably removed by drying. 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, or a method of drying under reduced pressure in the range of 25 to 80°C for about 12 to 60 hours. A spray dryer is preferably used for the drying. Furthermore, a pulverization process can be performed simultaneously with or after the drying process.

[0094] The colorant dispersion is preferably used in inks (inkjet inks, flexographic printing inks, etc.), paints, stationery, textile printing agents, etc. The ink is preferably an inkjet ink.

[0095] <Inkjet ink> The inkjet ink of this specification contains a colorant dispersion, water, and a water-soluble solvent. The inkjet ink of this specification uses water as a solvent (medium), but it is preferable to use a water-soluble solvent in combination to prevent the ink from drying. The water-soluble solvent has a lower surface tension than water, and therefore improves the penetration and wetting / spreading properties of the ink into the substrate after printing.

[0096] Examples of the water-soluble 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.

[0097] Examples of polyhydric alcohols include glycerin, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, tripropylene glycol, polypropylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 1,5-pentanediol, 1,2-hexanediol, 1,3-hexanediol, 1,4-hexanediol, 1,5-hexanediol, and 1, Examples include 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, and 2-ethyl-1,3-hexanediol. Among these, 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.

[0098] 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, propylene glycol monobutyl ether, etc. Examples of polyhydric alcohol aryl ethers include ethylene glycol monophenyl ether, diethylene glycol monophenyl ether, tetraethylene glycol chlorophenyl ether, ethylene glycol monobenzyl ether, ethylene glycol monoallyl ether, etc.

[0099] Examples of nitrogen-containing heterocyclic compounds include 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, ε-caprolactam, γ-butyrolactone, etc. Examples of amides include formamide, N-methylformamide, N,N-dimethylformamide, etc. Examples of amines include monoethanolamine, diethanolamine, triethanolamine, monoethylamine, diethylamine, triethylamine, etc. Examples of sulfur-containing compounds include dimethyl sulfoxide, sulfolane, thiodiethanol, etc.

[0100] The other water-soluble solvent is preferably a sugar. Examples of sugars include monosaccharides, disaccharides, oligosaccharides (including trisaccharides and tetrasaccharides), polysaccharides, etc. Examples of sugars include glucose, mannose, fructose, ribose, xylose, arabinose, galactose, maltose, cellobiose, lactose, sucrose, trehalose, maltotriose, etc. Here, polysaccharides refers to sugars in a broad sense, and includes substances that are widely present in nature, such as α-cyclodextrin and cellulose. Derivatives of these sugars include, for example, reducing sugars of the sugars (for example, sugar alcohols [general formula: HOCH2(CHOH) nExamples include sugar alcohols (represented by CHOH (where n is an integer of 2 to 5)), sugar oxides (for example, aldonic acid, uronic acid, etc.), amino acids, thioacids, etc. Among these, sugar alcohols are preferred, and maltitol and sorbitol are more preferred.

[0101] The water-soluble solvents can be used alone or in combination of two or more kinds.

[0102] The content of the water-soluble solvent in the inkjet ink is preferably 3 to 60% by mass, more preferably 3 to 50% by mass. The content of water in the inkjet ink is preferably 10 to 90% by mass, more preferably 30 to 80% by mass. The inclusion of an appropriate amount of water-soluble solvent improves the stability of ink ejection from the head.

[0103] Inkjet inks preferably contain a binder resin, which improves the water resistance, solvent resistance, abrasion resistance, gloss, etc. of the printed coating film. Examples of binder resins include (meth)acrylic resins, styrene-(meth)acrylic resins, polyurethane resins, styrene-butadiene resins, vinyl chloride resins, polyolefin resins, polyester resins, polyurethane resins, alkyd resins, fluororesins, and silicone-containing resins.

[0104] The content of the binder resin is preferably from 1 to 30% by mass, more preferably from 2 to 20% by mass, of the nonvolatile content of the coloring composition.

[0105] The binder resins can be used alone or in combination of two or more.

[0106] The inkjet ink of the present specification may contain additives as needed. Examples of additives include surfactants, antifoaming agents, waxes, preservatives, etc. The content of the additives in the inkjet ink is preferably 0.05 to 10% by mass, more preferably 0.2 to 5% by mass.

[0107] The inkjet ink of the present specification can be used in various inkjet printers. Examples of inkjet systems include continuous jet types such as charge control types and spray types, and on-demand types such as piezo types, thermal types, and electrostatic suction types.

[0108] <Flexographic printing ink> The flexographic printing ink of the present specification more preferably contains a colorant, a dispersant, and a binder resin. Examples of the binder resin include acrylic resin and urethane resin. The flexographic printing ink may also contain additives, a solvent, and a crosslinking agent.

[0109] (acrylic resin) Examples of acrylic resins include acrylic copolymers, acrylic acid-styrene copolymer resins, acrylic acid-maleic acid resins, acrylic acid-styrene-maleic acid resins, etc. The acrylic copolymer is a copolymer that uses two or more monomers of (meth)acrylic acid and (meth)acrylic acid esters.

[0110] The weight-average molecular weight of the acrylic resin is preferably in the range of 200,000 to 800,000. If the weight-average molecular weight is less than 200,000, the strength of the resin film may decrease, and the substrate adhesion, water rub resistance, scratch resistance, and blocking resistance of the laminate may decrease. On the other hand, if the weight-average molecular weight exceeds 800,000, the mobility of the molecular chain decreases, and therefore, under low-temperature drying conditions, fusion between the ink film layers may be insufficient, and the substrate adhesion and water rub resistance of the laminate may decrease. In addition, resolubility may also decrease.

[0111] The glass transition temperature (Tg) of the acrylic resin is preferably about −30° C. to 30° C. A suitable Tg further improves water friction resistance, blocking resistance, and adhesion to the substrate.

[0112] (urethane resin) Examples of urethane resins include polyurethane-urea resins in addition to polyurethane resins. From the viewpoint of film-forming properties, it is preferable that the urethane resin has an acid value. The weight-average molecular weight of the urethane resin is preferably 10,000 to 100,000. When the urethane resin has an appropriate molecular weight, adhesion to the substrate, water friction resistance, scratch resistance, and blocking resistance are further improved.

[0113] The acid value of the binder resin is preferably 20 to 180 mgKOH / g, more preferably 40 to 150 mgKOH / g. A suitable acid value improves resolubility during printing, adhesion to substrates, water abrasion resistance, and blocking resistance.

[0114] The amount of binder resin contained in flexographic printing ink is preferably 1 to 50% by mass based on 100% by mass of the flexographic printing ink. A moderate amount of binder resin improves the strength of the ink coating, and further improves adhesion to the substrate and water abrasion resistance.

[0115] Flexographic printing inks may contain additives as needed, such as leveling agents, wetting agents, water repellents, antifoaming agents, waxes, and crosslinking agents.

[0116] The solvent used in flexographic printing inks can be water or the water-soluble solvents mentioned above. The solvents can be used alone or in combination of two or more.

[0117] The content of the colorant is preferably an amount sufficient to ensure the concentration and coloring strength of the flexographic printing ink, i.e., 1 to 50% by mass of 100% by mass of the flexographic printing ink. The viscosity of the flexographic printing ink composition is preferably 10 mPa·s or more to prevent sedimentation of the colorant and ensure adequate dispersion, and 1000 mPa·s or less to ensure workability during ink production and printing. The above viscosity was measured at 25°C using a Tokimec B-type viscometer.

[0118] Flexographic printing ink can be prepared by mixing and dispersing the above-mentioned components. For example, an aqueous flexographic ink can be prepared by adding optional components such as wax and wetting agents to the colorant dispersion of the present invention and mixing and stirring them. Dispersion and stirring can be performed using, for example, a high-speed mixer, homogenizer, planetary mixer, trimix, kneader, extruder, horizontal sand mill, vertical sand mill and / or annular bead mill, paint shaker, ball mill, disperser equipped with an ultrasonic oscillator, two-roll mill, three-roll mill, etc.

[0119] <Ink set> The ink set of the present invention includes inks of two or more colors, at least one of which contains the colorant dispersion of the present invention. Examples of colors included in the ink set include cyan, yellow, magenta, black, orange, green, and white.

[0120] <Ink manufacturing method> The method for producing the ink of the present invention will be described below, although the method for producing the ink of the present invention is not limited to the following.

[0121] (adjustment) The colorant dispersion, water-soluble organic solvent, water, and optionally binder resin, surfactant, and other additives are added and stirred and mixed. If necessary, the mixture may be stirred and mixed while being heated in the range of 40 to 100°C.

[0122] (Removal of large particles) Coarse particles contained in the mixture are removed by filtration, centrifugation, or other methods to produce an ink. Any known method can be used as the filtration method. The filter pore size is not particularly limited as long as it can remove coarse particles and dust, but in the case of inkjet ink, it is preferably 0.3 to 5 μm, and more preferably 0.5 to 3 μm. When filtering, a single type of filter may be used, or multiple types may be used in combination.

[0123] <Method for manufacturing coated products> The coated article of the present invention preferably comprises a substrate and a printed layer formed from an ink or an ink set. Examples of the substrate include paper substrates such as fine paper, recycled paper, coated paper, art paper, cast paper, lightly coated paper, and synthetic paper, as well as polyvinyl chloride sheets, polyester films, polypropylene films, and polyethylene films. The substrate may also be a laminate of multiple materials. Among these, uncoated paper such as fine paper is preferred. The thickness of the substrate is about 20 to 300 μm, and the basis weight of the substrate is 30 to 300 g / m 2 That's about it. The thickness of the printed layer is preferably 0.01 to 5 μm, more preferably 0.1 to 4 μm, and even more preferably 0.5 to 3 μm. By keeping the thickness of the printed layer within this range, it is possible to obtain sufficient color development as a printed matter, while also allowing the solvent to evaporate sufficiently in the drying step during production of the printed layer, thereby forming a strong film. The printing layer may be formed using a printing machine suitable for each ink, such as an inkjet printer, a flexographic printer, a gravure printer, or an offset printer. After printing the ink, a drying step can be added as needed. Examples of the dryer used in the drying step include a hot air dryer and an infrared heater.

[0124] <Paint> In this specification, the paint preferably contains a colorant dispersion and a binder resin, and more preferably contains a crosslinking agent. The paint is preferably an aqueous paint containing a colorant dispersion and a binder resin. The ratio of the colorant dispersion to the binder resin varies depending on the desired application and is not particularly limited.

[0125] (binder resin) Examples of binder resins include acrylic resins, polyester resins, alkyd resins, fluororesins, urethane resins, and silicone-containing resins containing crosslinkable functional groups. Examples of crosslinking agents include melamine resins, urea resins, polyisocyanate compounds, blocked polyisocyanate compounds, epoxy compounds, carboxyl group-containing compounds, acid anhydrides, and alkoxysilane group-containing compounds. Among these, a combination of acrylic resins and melamine resins is preferred.

[0126] The coating material may further contain water, organic solvents, rheology control agents, pigment dispersants, anti-settling agents, curing catalysts, antifoaming agents, antioxidants, ultraviolet absorbers, surface conditioners, crosslinking agents, extender pigments, etc. as needed.

[0127] The paint can be prepared by mixing and dispersing the above materials.

[0128] The paint can be applied to a variety of substrates, including metal substrates such as iron, stainless steel, aluminum, and surface-treated materials thereof; cement-based substrates such as cement, lime, and gypsum; and plastic substrates such as polyvinyl chlorides, polyesters, polycarbonates, and acrylics.

[0129] The paint can be applied by, for example, brush coating, roller coating, spray coating, etc. After application, the coating is dried at room temperature or by heating to form a coating. The thickness of the coating is usually about 5 to 70 μm.

[0130] <Stationery> The stationery ink of this specification contains a colorant dispersion and can be used for applications such as writing instruments, recorders, and printers. The stationery preferably contains a binder. Depending on the application (e.g., ballpoint pen, marking pen, etc.), the stationery may optionally contain a water-soluble organic solvent, a thickener, a dispersant, a lubricant, an anti-rust agent, an antiseptic, an antibacterial agent, etc. The ratio of colorant to binder resin varies depending on the desired application and is not particularly limited.

[0131] Stationery is preferably prepared by preparing a high-concentration colorant dispersion, diluting it with water, and adding the binder resin and, if necessary, other additives. The method for dispersing the colorant dispersion is not particularly limited, and any of the known dispersion methods described above may be used. More preferred applications for stationery include thixotropic inks (e.g., gel inks for water-based ballpoint pens) and Newtonian inks (e.g., low-viscosity water-based ballpoint pen inks). Furthermore, the pH (25°C) of the stationery is preferably adjusted to 5 to 10, more preferably 6 to 9.5, using a pH adjuster or the like, from the viewpoints of usability, safety, the stability of the ink itself, and compatibility with the ink container.

[0132] The content of the colorant can be adjusted appropriately depending on the density of the lines drawn on the stationery, and is preferably about 0.1 to 40% by mass of the total amount of the ink composition for stationery.

[0133] <Textile printing agents> The printing agent of the present specification preferably contains a colorant dispersion, water, and a binder resin. The printing agent can record images such as letters, pictures, and designs on fabrics such as woven fabrics, nonwoven fabrics, and knitted fabrics. The ratio of the colorant to the binder resin varies depending on the desired application and is not particularly limited.

[0134] The binder resin may be any of the above-mentioned binder resins. The binder resin may be in the form of water-dispersed particles, a water-soluble resin, etc. Examples of the binder resin include urethane resin and acrylic resin.

[0135] After preparing a colorant dispersion, the printing agent can be prepared by further mixing water, a binder resin, and other necessary additives to suit the fiber to be colored, and suitable for a preferred processing method such as dip dyeing or printing. Screen-recording printing agents preferably contain additives such as preservatives, viscosity modifiers, pH adjusters, chelating agents, antioxidants, UV absorbers, flame retardants, and crosslinkers. The colorant concentration of the screen-recording printing agent is preferably 1 to 10% by mass. Dip-dyeing printing agents preferably contain additives such as preservatives, viscosity modifiers, pH adjusters, chelating agents, antioxidants, UV absorbers, flame retardants, and crosslinkers. The colorant concentration of the dip-dyeing printing agent is preferably in the range of 1 to 10% by mass. The viscosity of the dip-dyeing printing agent can be arbitrarily set within the range of 1 mPa·s to 100 mPa·s to suit the printing device. The printing agent for spray printing preferably contains additives such as a viscosity adjuster, a pH adjuster, a chelating agent, a plasticizer, an antioxidant, and an ultraviolet absorber. The colorant concentration of the printing agent for spray recording is preferably 1% by mass to 10% by mass. The viscosity of the printing agent for spray recording is set arbitrarily within the range of 1 mPa·s to 100 mPa·s depending on the device. The printing agent for inkjet recording preferably contains additives such as a preservative, a viscosity adjuster, a pH adjuster, a chelating agent, an antioxidant, an ultraviolet absorber, and a flame retardant. The colorant concentration of the printing agent for inkjet recording is preferably 1% by mass to 20% by mass. The additives are preferably added to the aqueous dispersion of the coating colorant together with the binder resin. Examples of preservatives include sodium benzoate, sodium pentachlorophenol, sodium 2-pyridinethiol-1-oxide, sodium sorbate, sodium dehydroacetate, 1,2-dibenzisothiazolin-3-one (Proxel GXL, Proxel XL-2, Proxel LV, Proxel AQ, Proxel BD20, and Proxel DL, manufactured by Arch Chemicals), etc. Specific examples of viscosity modifiers include mainly water-soluble natural or synthetic polymers such as carboxymethyl cellulose, sodium polyacrylate, polyvinylpyrrolidone, gum arabic, and starch.Examples of pH adjusters include collidine, imidazole, phosphoric acid, 3-(N-morpholino)propanesulfonic acid, tris(hydroxymethyl)aminomethane, and boric acid. Examples of chelating agents include ethylenediaminetetraacetic acid, ethylenediaminediacetic acid, nitrilotriacetic acid, 1,3-propanediaminetetraacetic acid, diethylenetriaminepentaacetic acid, N-hydroxyethylethylenediaminetriacetic acid, iminodiacetic acid, uramildiacetic acid, 1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid, malonic acid, succinic acid, glutaric acid, maleic acid, and salts thereof (including hydrates). Examples of antioxidants include hindered phenol compounds, hydroquinone compounds, phosphite compounds and their substitution products, copper halides, and alkali metal halides. Examples of UV absorbers include organic compound UV absorbers such as benzotriazoles and benzophenones; and inorganic compound UV absorbers such as titanium oxide and zinc oxide. When applying a printing agent to inkjet recording, its surface tension is preferably adjusted to 20 mN / m or more and 60 mN / m or less. More preferably, it is 20 mN / m or more and 45 mN / m or less, and even more preferably, it is 20 mN / m or more and 40 mN / m or less. If the surface tension is less than 20 mN / m, the liquid may overflow onto the nozzle surface, preventing normal printing. On the other hand, if the surface tension exceeds 60 mN / m, it tends to be easily repellent on non-absorbent substrates. Furthermore, the viscosity is preferably 1.2 mPa·s or more and 20.0 mPa·s or less, more preferably 2.0 mPa·s or more and less than 15.0 mPa·s, and even more preferably 3.0 mPa·s or more and less than 12.0 mPa·s. Within this viscosity range, excellent jetting properties can be achieved and good jetting properties can be maintained for a long period of time. The surface tension can be appropriately adjusted using the surfactant.

[0136] The printing agent of the present invention can be used for printing on fabrics, artificial leather, natural leather, etc. It is particularly excellent for printing on fabrics. The fabric is preferably a medium composed of fibers, and may be a woven fabric or a nonwoven fabric. Examples of materials include cotton, silk, wool, hemp, nylon, polyester, polyurethane, and rayon. [Example]

[0137] The present invention will be described in more detail below with reference to examples and comparative examples. It goes without saying that the present invention is not limited to the examples. Hereinafter, "parts" means "parts by mass" and "%" means "% by mass." In this specification, Examples 10, 14 and 15 are reference examples.

[0138] (Mass average molecular weight (Mw), number average molecular weight (Mn)) The mass average molecular weight (Mw) and number average molecular weight (Mn) are measured in terms of polystyrene using a TSK-GELSUPERHZM-N column (manufactured by Tosoh Corporation) at a column temperature of 40°C with a GPC (manufactured by Tosoh Corporation, HLC-8320GPC) equipped with an RI detector, using THF as the developing solvent at a flow rate of 0.35 ml / min.

[0139] (Dispersion degree) The dispersity can be calculated from the following formula: Dispersity = mass average molecular weight (Mw) / number average molecular weight (Mn)

[0140] (acid number) Accurately weigh approximately 1 g of sample into an Erlenmeyer flask and add distilled water / dioxane (weight ratio: distilled water / dioxane). Add 50 ml of a mixture of water and dioxane (1 / 9) and dissolve. A potential difference measuring device (Kyoto Electronics Manufacturing Co., Ltd., device name "potentiometric automatic titrator AT-710M") was used. Titrate with 0.1 mol / L potassium hydroxide ethanol solution (titer F). The amount of potassium hydroxide ethanol solution (α (mL)) required to reach the end point was measured. The acid value (mgKOH / g) of the dispersant in this state was calculated using the following formula. Acid value (mgKOH / g) = {(5.611 × α × F) / S} / (non-volatile content / 100) Where S: sample amount (g) α: Amount of 0.1 mol / L potassium hydroxide ethanol solution consumed (ml) F: Potency of 0.1 mol / L potassium hydroxide ethanol solution

[0141] The (meth)allyl monomers used in synthesizing the dispersants are shown in Table 1. The (meth)allyl monomers were obtained according to known synthesis methods such as those described in JP-A-01-000109.

[0142] [Table 1]

[0143] <Production of dispersants> (Production of Dispersant 1) A reaction vessel equipped with a gas inlet tube, thermometer, condenser, and stirrer was charged with 19.5 parts (35 mol%) of 1-octene as a pigment-adsorbing group-containing monomer, 19.5 parts (30 mol%) of maleic anhydride, 34.5 parts (30 mol%) of N-phenylmaleimide, 26.5 parts (5 mol%) of Monomer M4 as an allyl monomer, and 100 parts of methyl ethyl ketone as a solvent. After nitrogen substitution, the mixture was heated to 130°C and stirred. While stirring, 1.0 part of t-butylperoxy-2-ethylhexanoate as a radical polymerization initiator was added dropwise over 2 hours. The mixture was then stirred for another hour while maintaining the temperature at 130°C. After confirming that the polymerization conversion rate had reached 95-100%, the reaction temperature was lowered to 60°C, and 16.8 parts of water (5 equivalents relative to the amount of maleic anhydride charged) and 0.01 parts of diazabicycloundecene as a catalyst were added. The mixture was heated to 80°C with stirring and maintained for 4 hours to complete the reaction. The solvent was then completely removed by vacuum concentration. The resulting dispersant had a number-average molecular weight of 6,400 and an acid value of 203.2 mg KOH / g. Dimethylaminoethanol was then added to the resulting dispersant so that the degree of neutralization was 100% based on the acid value. Ion-exchanged water was then added so that the nonvolatile content was 30%. The mixture was stirred at 50°C for 1 hour to obtain Dispersant 1.

[0144] (Production of Dispersants 2 to 23) Dispersants 2 to 23 were obtained by synthesizing in the same manner as Dispersant 1, except that the raw materials and amounts charged for Dispersant 1 were changed as shown in Table 2. Dispersants 14 to 15 were prepared by modifying the acid anhydride group in the maleic anhydride unit using a compound shown in Table 2 in an amount of 1 equivalent relative to the amount of maleic anhydride charged. The blending amounts in Tables 2 to 4 are in mol %.

[0145] [Table 2-1]

[0146] [Table 2-2]

[0147] [Table 2-3]

[0148] The abbreviations in Tables 2-1 to 2-3 are as follows: HIDA: N-(2-hydroxyethyl)iminodiacetic acid

[0149] <Production of Colorant Dispersion> (Production of Colorant Dispersion Set 1) 20 parts of Printex 85 (carbon black, manufactured by Orion Engineered Carbons), 20 parts of Dispersant 1, and 60 parts of water were mixed and premixed using a stirrer. After premixing, a 0.6 L Dyno-Mill filled with 1,800 g of 0.5 mm diameter zirconia beads was used for main dispersion to obtain a black colorant dispersion. Colorant dispersion set 1 (K, C, M, Y) was obtained using the same method, except for changing the pigments as shown below. Cyan: Toyocolor Lionogen Blue FG-7358G (CIPigment Blue15:3) Magenta: TOSHIKI RED150TR (CI Pigment Red 150) manufactured by Tokyo Color Materials Co., Ltd. Yellow: Toyo Color LIONOL YELLOW TT1405G (CI Pigment Yellow 14)

[0150] (Production Examples of Colorant Dispersion Sets 2 to 23) Colorant Dispersion Sets 2 to 23 were obtained in the same manner as Colorant Dispersion Set 1, except that the dispersant used was changed according to Table 3.

[0151] [Table 3]

[0152] <Inkjet ink set manufacturing> (Inkjet ink set 1 production) A black inkjet ink was obtained by mixing 20.0 parts of the black colorant dispersion from the resulting Colorant Dispersion Set 1, 20.0 parts of propylene glycol, 5.0 parts of 1,2-hexanediol, 10.0 parts of Joncryl 780 as a binder resin, 43.9 parts of ion-exchanged water, 0.1 parts of Surfynol DF110D (manufactured by Air Products Japan Co., Ltd.) as an activator, 0.5 parts of BYK-349 (manufactured by BYK), 0.5 parts of triethanolamine as a pH adjuster, and Proxel GXL(s) (manufactured by Arch Chemical Co., Ltd.) as a preservative. Inkjet ink set 1 (K, C, M, Y) was obtained using the same method as Colorant Dispersion Set 1, except that the color of the colorant dispersion used was changed.

[0153] <Production of inkjet ink sets 2 to 23> Inkjet ink sets 2 to 23 were obtained in the same manner as inkjet ink set 1, except that the colorant dispersions used were changed according to Tables 4-1 to 4-3.

[0154] [Table 4-1]

[0155] [Table 4-2]

[0156] [Table 1]

[0157] The abbreviations in Tables 4-1 to 4-3 are as follows: 1,2-HD: 1,2-hexanediol PG: 1,2-propanediol SF DF110D: Surfynol DF110D (manufactured by Nissin Chemical Industry Co., Ltd.) TEA: Triethanolamine

[0158] <Manufacturing of coated products> (1 production of coated products) The resulting inkjet ink set 1 was loaded into an inkjet printer (Seiko Epson Corporation, model number: EM-930C, piezo type), and full-surface solid printing (fine mode) was performed on fine paper (Nippon Paper Industries Co., Ltd., NPi Form NEXT-IJ, 64 g / m²) and coated paper (Oji Paper Co., Ltd., OK Topcoat, 104.7 g / m²) using black ink, cyan ink, magenta ink, and yellow ink, respectively. After leaving the printer at 25°C and 50% relative humidity for 24 hours, Coated Product 1 was obtained.

[0159] <Production of coated products 2 to 23> Coated Materials 2 to 23 were obtained in the same manner as Coated Material 1, except that inkjet inks 2 to 23 were used.

[0160] <Examples 1 to 20 and Comparative Examples 1 to 3> The colorant dispersions, inkjet inks, and coatings produced above were subjected to the following evaluations 1 to 4.

[0161] <Evaluation 1: Storage stability evaluation> The storage stability of the resulting colorant dispersion set was evaluated using the black colorant dispersion as follows. The colorant dispersion was stored in a thermostatic chamber at 70°C to accelerate aging, and the change in viscosity of the colorant dispersion before and after aging was evaluated. Viscosity was measured using an E-type viscometer (TVE-20L, standard cone, manufactured by Toki Sangyo Co., Ltd.) at 25°C and a rotation speed of 50 rpm, and the value after 1 minute was recorded as the viscosity value. The evaluation criteria were as follows: A rating of 2 or higher was considered to be in the practical range. 5: Viscosity change rate after four weeks of storage is less than ±10% 4: Viscosity change rate after two weeks of storage is less than ±10% 3: Viscosity change rate after one week of storage is less than ±10% 2: Viscosity change rate after one week of storage is ±10-20% 1: Viscosity change rate after one week of storage is more than ±20%

[0162] <Evaluation 2: Coarse particle amount evaluation> The amount of coarse particles in the colorant dispersion was evaluated using the black colorant dispersion from the resulting colorant dispersion set as follows. Specifically, the time it took for a fixed amount of colorant dispersion to pass through a 25 mm diameter glass fiber filter (manufactured by GF / BGE Healthcare Life Sciences) was measured. If the amount of coarse particles was large, the filter would clog, resulting in a longer observed passing time. Furthermore, if the amount of coarse particles was even larger, the filter would become clogged and the entire amount of colorant dispersion would not be filtered. Generally, filters used in the ink supply path to inkjet heads are larger than 1 μm, and inkjet recording inks generally have lower colorant concentrations than colorant dispersions. Therefore, passing through the filter using this test method is sufficient. However, a faster filtration rate would improve the resolubility and disintegration of colorant particles, resulting in superior productivity. Specific evaluation conditions are as follows: A 15 mm diameter glass fiber filter was fed via a stopcock into a suction vessel equipped with a vacuum pump. A 25mm diameter filter holder (manufactured by ADVANTEC) with a funnel graduated in ml and a 25mm diameter glass fiber filter (manufactured by GF / BGE Healthcare Life Sciences) was placed on the vessel. The vacuum pump was operated using the cock to prevent the pressure inside the suction vessel from decreasing. 15g of colorant dispersion was weighed into the funnel. The pressure in the pump and suction vessel was opened, and the time it took for the entire amount of colorant dispersion to pass through the filter was measured. The pressure inside the suction vessel at this time was 0.05MPa to 0.07MPa. A rating of 2 or higher was considered to be within the practical range. 5. Filtration in less than 30 seconds 4: Filtration can be done in 30 seconds or more and less than 45 seconds 3: Filtration takes between 45 and 60 seconds 2: Filtration takes between 60 and 90 seconds 1: Cannot be filtered in less than 90 seconds

[0163] <Evaluation 3: Density evaluation of fine paper> The obtained inkjet ink was loaded into an inkjet printer (Seiko Epson Corporation, model number: EM-930C, piezo type), and printed on high-quality paper (Nippon Paper Industries Co., Ltd., NPi Form NEXT-IJ, 64 g / m 2 ) and a 100% solid image was printed using black ink, cyan ink, magenta ink, and yellow ink. The print was left for 24 hours at 25°C and 50% relative humidity, and the resulting test piece was then measured using an eXactAdvance densitometer manufactured by X-rite. The color measurement conditions were ISO status T, a viewing angle of 2°, and a light source D50, based on density. A higher numerical value for print density indicates higher print density. The evaluation criteria were as follows: A score of 2 or higher was considered to be in the usable range. 5: OD value: For each of the colors K, C, M, and Y, the density is higher than that of Comparative Example 3 by 0.3 or more. 4: OD value: For each of the colors K, C, M, and Y, the density is higher than that of Comparative Example 3 in the range of 0.2 or more and less than 0.3. 3: OD value: For each of the colors K, C, M, and Y, the density is higher than that of Comparative Example 3 in the range of 0.1 or more and less than 0.2. 2: OD value K, C, M, Y: Higher than the density of Comparative Example 3 in the range of less than 0.1 1: OD value for each color K, C, M, Y is equal to or lower than that of Comparative Example 3

[0164] <Evaluation 4: Coated Paper Density Evaluation> The obtained inkjet ink was loaded into an inkjet printer (Seiko Epson Corporation, model number: EM-930C, piezo type), and printed on coated paper (Oji Paper Co., Ltd. OK Topcoat, 104.7 g / m²). 2 ) and a 100% solid image was printed using black ink, cyan ink, magenta ink, and yellow ink. The print was left for 24 hours at 25°C and 50% relative humidity, and the resulting test piece was then measured using an eXactAdvance densitometer manufactured by X-rite. The color measurement conditions were ISO status T, a viewing angle of 2°, and a light source D50, based on density. A higher numerical value for print density indicates higher print density. The evaluation criteria were as follows: A score of 2 or higher was considered to be in the usable range. 5: OD value: For each of the colors K, C, M, and Y, the density is higher than that of Comparative Example 3 in the range of 0.7 or more. 4: OD value: For each of the colors K, C, M, and Y, the density is higher than that of Comparative Example 3 in the range of 0.5 or more and less than 0.7. 3: OD value: For each of the colors K, C, M, and Y, the density is higher than that of Comparative Example 3 in the range of 0.2 or more and less than 0.5. 2: OD value K, C, M, Y: Higher than the density of Comparative Example 3 in the range of less than 0.2 1: OD value K, C, M, Y are equal to or lower than the density of Comparative Example 2

[0165] The evaluation results of the examples and comparative examples are shown in Table 5 above.

[0166] [Table 5]

[0167] The results in Table 5 show that Examples 1 to 20 enable high-density printing on uncoated paper without an ink-receiving layer, and provide colorant dispersions that can be used to prepare inkjet inks with good storage stability.

Claims

1. A colorant dispersion comprising a dispersant, a colorant, and water, the dispersant is a polymer containing a colorant-adsorptive-group-containing monomer unit, a maleic acid unit, a (meth)allyl monomer unit, and a maleimide unit or an N-substituted maleimide unit, the colorant-adsorptive-group-containing monomer unit contains at least one of an α-olefin unit and a (meth)acrylic acid ester monomer unit having an alkyl group, The colorant dispersion, wherein the N-substituted maleimide unit is a unit having a ring structure at a substitution site.

2. 2. The colorant dispersion according to claim 1, wherein the maleic acid unit is a maleic acid unit modified with an oxycarboxylic acid having a divalent or trivalent carboxyl group.

3. The colorant dispersion according to claim 1 or 2, wherein the (meth)allyl monomer unit is a unit having an alkyleneoxy moiety.

4. An ink comprising the colorant dispersion according to any one of claims 1 to 3.

5. An ink set comprising the ink of claim 4.

6. A coated product comprising a substrate and a printed layer formed from the ink according to claim 4 or the ink set according to claim 5.

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