Inkjet inks, inkjet recording methods, ink sets, ink media sets, and printing media

Abstract

To provide ink for various types of recording, particularly for inkjet which has excellent compatibility, wettability and ejection properties of a printed matter, and a printed matter using the ink for inkjet.SOLUTION: Ink for inkjet is provided, containing a coloring agent including at least either one selected from the group consisting of pigment and disperse dye, an organic compound other than the coloring agent, and water, where the content ratio of the water is 60 to 90 mass% for the total mass of ink, and the organic compound satisfies specific conditions. A dynamic surface tension value X of the ink at 25°C and surface lifetime 10 msec by a maximum bubble pressure technique is 32.0 mN / m or more, and the dynamic surface tension value X and a static surface tension value Y of the ink at 25°C satisfy the relation of 0.05≤(X-Y) / Y≤0.25.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to inkjet ink, inkjet recording method, ink set, ink media set, and printing media. [Background technology]

[0002] Inkjet printing, one of the most representative color recording methods, works by generating tiny droplets of ink and depositing them onto printing media such as paper. In recent years, demand for inks that can print on a variety of media has increased in commercial and industrial applications.

[0003] In the commercial sector, such as catalogs and brochures, printing media with lower ink absorption than plain paper, such as coated paper and art paper (hereinafter also referred to as "low-ink-absorbing media"), are often used. In the industrial sector, such as outdoor signage and flexible food packaging, non-ink-absorbing printing media, such as polyvinyl chloride film, PET (polyethylene terephthalate) film, and polyolefin film (hereinafter also referred to as "non-ink-absorbing media"), are often used.

[0004] For media that do not absorb ink well or do not absorb ink at all, development has progressed on solvent-based inks using organic solvents as the main solvent, and curable inks containing polymerizable monomers. However, these inks have many safety concerns regarding the natural environment and human health. Therefore, in recent years, the development of water-based inks using water as the main solvent has become increasingly popular.

[0005] Water-based inks generally have poor wetting properties on media that do not absorb ink well or do not absorb ink at all. To improve wettability, a large amount of organic solvent is needed. However, inks with a high solvent content suffer from reduced drying properties on these media. Therefore, methods have been employed to lower surface tension by using silicone-based surfactants instead of large amounts of organic solvents. While low surface tension inks improve wettability on the aforementioned media, they have the drawback of reduced ejection performance due to poor liquid cohesion and satellite formation during ejection by the inkjet head.

[0006] Patent Document 1 reports that by using multiple surfactants with different HLB values, including silicone-based surfactants, an ink capable of forming good images on ink-poorly absorbing media can be obtained. However, the ink in Patent Document 1 had insufficient ejection properties. Patent Document 2 reports that by controlling the balance between the dynamic and static surface tension of the ink, good ejection stability can be achieved and good images can be obtained on general-purpose paper media. However, the ink in Patent Document 2 had insufficient wettability on ink-poorly absorbing media and ink-non-absorbing media.

[0007] As described above, no water-based ink has yet been proposed that satisfies both the wettability and ejection properties. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2016-125057 [Patent Document 2] Japanese Patent Publication No. 2017-119415 [Overview of the initiative] [Problems that the invention aims to solve]

[0009] The present invention aims to provide an inkjet ink that exhibits good wettability even on non-ink-absorbing media and also has excellent ejection properties, an inkjet recording method using the inkjet ink, an ink set comprising the inkjet ink, an ink media set comprising the inkjet ink or the ink set and a printing medium, and a printing medium to which each inkjet ink of the inkjet ink or the ink set is attached. [Means for solving the problem]

[0010] The present inventors have conducted extensive research to solve the above problems and have found a coloring agent comprising at least one selected from the group consisting of pigments and disperse dyes, an organic compound excluding the coloring agent, and water. An inkjet ink wherein the water content is 60 to 90% by mass relative to the total mass of the ink, and the organic compound satisfies the following condition (A): The dynamic surface tension value X of the aforementioned ink at 25°C and a surface life of 10 msec using the maximum foam pressure method is 32.0 mN / m or more. An inkjet ink wherein the dynamic surface tension value X and the static surface tension value Y of the ink at 25°C satisfy the relationship 0.05 ≤ (XY) / Y ≤ 0.25. (A) Compound a: At least one compound selected from the compounds represented by the following formula (1) and the compounds represented by the following formula (2); Compound b: At least one compound selected from the compounds represented by the following formula (3) and the compounds represented by the following formula (4); Compound c: At least one compound selected from the group consisting of C4-C5 alkanediols, compounds represented by the following formula (5), and compounds represented by the following formula (6); We discovered that an ink containing [the specified ingredient] can solve the above problems, and thus completed the present invention.

[0011] In other words, the present invention relates to the following 1) to 9). 1) A colorant comprising at least one selected from the group consisting of pigments and disperse dyes, an organic compound other than the colorant, and water, An inkjet ink, wherein the content of said water is 60 to 90% by mass relative to the total mass of the ink, and said organic compound satisfies the following condition (A), wherein a dynamic surface tension value X of said ink at 25°C and a surface lifetime of 10 msec measured by the maximum bubble pressure method is 32.0 mN / m or more, and said dynamic surface tension value X and a static surface tension value Y of said ink at 25°C satisfy the relationship 0.05 ≤ (X-Y) / Y ≤ 0.25. An inkjet ink. (A) Compound a: at least one compound selected from the group consisting of a compound represented by the following formula (1) and a compound represented by the following formula (2); Compound b: at least one compound selected from the group consisting of a compound represented by the following formula (3) and a compound represented by the following formula (4); Compound c: at least one compound selected from the group consisting of C4-C5 alkanediols, a compound represented by the following formula (5), and a compound represented by the following formula (6); comprising the above.

[0012]

Chemical Formula

[0013] (In formula (1), R 1 represents a linear or branched C5-C10 hydrocarbon group.)

[0014]

Chemical Formula

[0015] (In formula (2), R 2 represents a linear or branched C6-C7 hydrocarbon group, and n1 represents 1 or 2.)

[0016]

Chemical Formula

[0017] (In formula (3), R 3 (This represents a linear or branched C7-C12 hydrocarbon group.)

[0018] [ka]

[0019] (In formula (4), R 4 (where n2 represents a phenyl group or a benzyl group, and n2 represents 1 or 2.)

[0020] [ka]

[0021] (In formula (5), R 5 (This represents a hydrogen atom or a methyl group.)

[0022] [ka]

[0023] (In formula (6), R 6 (where n3 represents a linear or branched C1-C4 hydrocarbon group, and n3 represents 1 or 2.) 2) The inkjet ink according to 1), wherein the dynamic surface tension value X is 34.0 mN / m or more. 3) The inkjet ink according to 1) or 2), wherein the dynamic surface tension value X and the static surface tension value Y satisfy the relationship 0.10 ≤ (XY) / Y ≤ 0.20. 4) An inkjet recording method that involves ejecting droplets of inkjet ink described in any one of items 1) to 3) from an inkjet head and recording them on a printing medium. 5) The inkjet recording method according to 4), wherein the printing medium is an ink-poorly absorbent or ink-non-absorbent printing medium. 6) The inkjet recording method according to 4), wherein the inkjet head is an inkjet head including a circulation mechanism. 7) An ink set comprising an inkjet ink described in any one of items 1) to 3), and another inkjet ink different from the said inkjet ink. 8) An ink media set comprising at least one selected from the group consisting of inkjet inks described in any one of items 1) to 3), and ink sets described in item 7), and a printing medium. 9) A printing medium to which at least one of the inkjet inks selected from the group consisting of the inkjet inks described in any one of items 1) to 3) and the inkjet inks included in the ink set described in item 7) is attached. [Effects of the Invention]

[0024] The present invention provides an inkjet ink with excellent compatibility, wettability of printed materials, and ejection properties. [Modes for carrying out the invention]

[0025] The following describes in detail specific embodiments to which the present invention is applied. In this specification, "CI" means "Color Index." Furthermore, in this specification, the terms "alkylene," "propylene," and "alkyl" are used to encompass both linear and branched structures unless otherwise specified.

[0026] <Inkjet ink> The inkjet ink according to this embodiment (hereinafter also simply referred to as "ink") contains a colorant selected from the group consisting of pigments and disperse dyes, an organic compound excluding the colorant, and water. The components contained in the ink according to this embodiment will be described in detail below. Note that each of the components described below may be used individually or in combination of two or more.

[0027] <Colorants containing at least one selected from the group consisting of pigments and disperse dyes> A colorant comprising at least one selected from the group consisting of pigments and disperse dyes is defined as comprising at least one selected from the group consisting of pigments and disperse dyes, and may be abbreviated as "colorant" in this specification.

[0028] Examples of the above-mentioned pigments include inorganic pigments, organic pigments, extender pigments, and hollow particles. Examples of inorganic pigments include carbon black, metal oxides, metal hydroxides, metal sulfides, metal ferrocyanides, and metal chlorides.

[0029] In this embodiment, if the ink is black ink and the colorant is an inorganic pigment, the inorganic pigment contained in the black ink is preferably carbon black such as thermal black, acetylene black, oil furnace black, gas furnace black, lamp black, gas black, or channel black. Specific examples of carbon black include, for example, the Raven series from Columbia Carbon; the Monarch series, Regal series, and Mogul series from Cabot; the HiBlack series, ColorBlack series, Printex series, SpecialBlack series, and Nerox series from Orion Engineered Carbons; and the MA series, MCF series, No. 25, No. 33, No. 40, No. 47, No. 52, No. 900, and No. 2300 from Mitsubishi Chemical Corporation.

[0030] In this embodiment, if the ink is a white ink and the colorant is an inorganic pigment, examples of inorganic pigments contained in the white ink include oxides, nitrides, or oxidized nitrides of metals such as zinc, silicon, aluminum, titanium, strontium, and zirconium; inorganic compounds such as glass and silica; and among these, titanium dioxide and zinc oxide are preferred.

[0031] Examples of organic pigments include azo, disazo, phthalocyanine, quinacridone, isoindolinone, dioxazine, perylene, perinone, thioindigo, antholaquinone, and quinophthalone.

[0032] Examples of organic pigments include, for instance, yellow pigments such as CIPigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 24, 55, 73, 74, 75, 83, 93, 94, 95, 97, 98, 108, 114, 128, 129, 138, 139, 150, 151, 154, 155, 180, 185, 193, 199, 202, 213; and CIPigment Red Red pigments such as 5, 7, 12, 48, 48:1, 57, 88, 112, 122, 123, 146, 149, 150, 166, 168, 177, 178, 179, 184, 185, 202, 206, 207, 254, 255, 257, 260, 264, 269, 272; Blue pigments such as CIPigment Blue 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 22, 25, 60, 66, 80; Violet pigments such as CIPigment Violet 19, 23, 29, 37, 38, 50; Orange pigments such as CIPigment Orange 13, 16, 43, 68, 69, 71, 73; Green Examples include green pigments such as 7, 36, and 54; and black pigments such as CIPigment Black 1. Among these, CIPigment Blue 15:4 is preferred.

[0033] Examples of extender pigments include silica, calcium carbonate, talc, clay, barium sulfate, and white carbon. Extender pigments are often used in combination with other colorants.

[0034] As hollow particles, known hollow particles described in, for example, U.S. Patent No. 4,880,465, Japanese Patent Publication No. 3,562,754, Japanese Patent Publication No. 6,026,234, Japanese Patent Publication No. 5,459,460, Japanese Patent Application Publication No. 2003-268694, Japanese Patent Publication No. 4902,216, etc., can be used, and it is particularly preferable to use them as a white pigment.

[0035] As for disperse dyes, dyes selected from CIDispers, for example, are preferred. Specific examples include, for instance, yellow dyes such as CIDispers Yellow 9, 23, 33, 42, 49, 54, 58, 60, 64, 66, 71, 76, 79, 83, 86, 90, 93, 99, 114, 116, 119, 122, 126, 149, 160, 163, 165, 180, 183, 186, 198, 200, 211, 224, 226, 227, 231, 237; red dyes such as CIDispers Red 60, 73, 88, 91, 92, 111, 127, 131, 143, 145, 146, 152, 153, 154, 167, 179, 191, 192, 206, 221, 258, 283; and CIDispers Orange Examples include orange dyes such as 9, 25, 29, 30, 31, 32, 37, 38, 42, 44, 45, 53, 54, 55, 56, 61, 71, 73, 76, 80, 96, and 97; violet dyes such as CIDispers Violet 25, 27, 28, 54, 57, 60, 73, 77, 79, and 79:1; and blue dyes such as CIDispers Blue 27, 56, 60, 79:1, 87, 143, 165, 165:1, 165:2, 181, 185, 197, 202, 225, 257, 266, 267, 281, 341, 353, 354, 358, 364, 365, and 368.

[0036] The average particle size of the colorant is preferably 30 to 300 nm, and more preferably 50 to 250 nm. In this specification, the average particle size refers to the average particle size measured using the laser light scattering method.

[0037] The colorant content is preferably 1 to 30% by mass, more preferably 1 to 10% by mass, and even more preferably 2 to 8% by mass, relative to the total mass of the ink according to this embodiment.

[0038] The above coloring agent may further contain other dyes besides the above pigment and the above disperse dye. Other dyes mentioned above include, for example, solvent dyes, direct dyes, acid dyes, and reactive dyes.

[0039] If the above inkjet ink contains multiple types of colorants, the mixing ratio of each colorant can be arbitrarily set according to the purpose. Furthermore, if the ink contains other dyes in addition to the colorants, the mixing ratio of the total amount of colorants to the total amount of other dyes can also be set to any arbitrary ratio.

[0040] <Organic compounds excluding the aforementioned colorants> The organic compounds other than the aforementioned colorants are organic compounds other than the aforementioned colorants and satisfy the following condition (A). (A) Compound a: At least one compound selected from the compound represented by formula (1) and the compound represented by formula (2) above; Compound b: At least one compound selected from the compound represented by formula (3) and the compound represented by formula (4) above; Compound c: At least one compound selected from the group consisting of C4-C5 alkanediols, compounds represented by formula (5) above, and compounds represented by formula (6) above; Includes.

[0041] [ka]

[0042] [ka]

[0043] [ka]

[0044] [ka]

[0045] [ka]

[0046] [ka]

[0047] In the above equation (1), R 1 R represents a linear or branched C5-C10 hydrocarbon group. Examples of C5-C10 hydrocarbon groups include n-pentyl group, isopentyl group, neopentyl group, sec-pentyl group, tert-pentyl group, 2-methylbutyl group, 1-ethylpropyl group, 1,2-dimethylpropyl group, n-hexyl group, isohexyl group, neohexyl group, sec-hexyl group, tert-hexyl group, 2-methylpentyl group, 3-methylpentyl group, 2,2-dimethylbutyl group, 2-ethylbutyl group, n-heptyl group, isoheptyl group, sec-heptyl group, tert-heptyl group, n-octyl group, isooctyl group, n-nonyl group, isononyl group, sec-nonyl group, n-decyl group, etc. 1 Preferably, it is a linear or branched C5-C7 hydrocarbon group.

[0048] In the above formula (2), R2 represents a linear or branched C6-C7 hydrocarbon group. Examples of the C6-C7 hydrocarbon group include an n-hexyl group, an isohexyl group, a neohexyl group, a sec-hexyl group, a tert-hexyl group, a 2-methylpentyl group, a 3-methylpentyl group, a 2,2-dimethylbutyl group, a 2-ethylbutyl group, an n-heptyl group, an isoheptyl group, a sec-heptyl group, a tert-heptyl group, etc. R 2 is preferably a linear or branched C6 hydrocarbon group. In the above formula (2), n1 represents 1 or 2, and is preferably 2.

[0049] In the above formula (3), R 3 represents a linear or branched C7-C12 hydrocarbon group. Examples of the C7-C12 hydrocarbon group include an n-heptylene group, a 1-methylhexylene group, a 2-methylhexylene group, a 3-methylhexylene group, a 1,5-dimethylpentylene group, a 2,4-dimethylpentylene group, an n-octylene group, a 1-methylheptylene group, a 2-methylheptylene group, a 3-methylheptylene group, a 4-methylheptylene group, a 1,6-dimethylhexylene group, a 2,5-dimethylhexylene group, a 2-ethylpentylene group, a 2-ethyl-1-propylpropylene group, an n-nonylene group, a 1-methyloctylene group, a 2-methyloctylene group, a 3-methyloctylene group, a 4-methyloctylene group, a 1,7-dimethylheptylene group, a 2,6-dimethylheptylene group, a 3,5-dimethylheptylene group, a 2-butyl-2-ethylpropylene group, an n-decylene group, an n-undecylene group, an n-dodecylene group, etc. R 3 is preferably a linear or branched C7-C9 hydrocarbon group.

[0050] In the above formula (4), R 4 represents a phenyl group or a benzyl group, and is preferably a phenyl group. In the above formula (4), n2 represents 1 or 2, and is preferably 2.

[0051] In the above formula (5), R 5 represents a hydrogen atom or a methyl group, and is preferably a hydrogen atom.

[0052] In the above formula (6), R 6 R represents a linear or branched C1-C4 hydrocarbon group. Examples of C1-C4 hydrocarbon groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl groups. 6 The C3-C4 hydrocarbon group is preferably a linear or branched C3-C4 hydrocarbon group. In formula (6) above, n3 represents 1 or 2, and is preferably 2.

[0053] Examples of compound a include 1,2-heptanediol, 1,2-octanediol, 1,2-nonanediol, 1,2-decanediol, 1,2-undecanediol, 1,2-dodecanediol, diethylene glycol monohexyl ether, diethylene glycol monoheptyl ether, ethylene glycol monohexyl ether, and ethylene glycol monoheptyl ether, with 1,2-nonanediol, diethylene glycol monohexyl ether, and ethylene glycol monohexyl ether being preferred. All of the above compound a are highly hydrophobic compounds and have the property of easily oriented on the ink surface after the ink lands on the printing medium. This property is thought to reduce the surface tension of the ink and promote the wetting and spreading of the ink on the printing medium, thereby exhibiting excellent wettability.

[0054] Examples of compound b include 1,7-heptanediol, 1,8-octanediol, 2-ethyl-1,3-hexanediol, 1,9-nonanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, diethylene glycol monophenyl ether, and diethylene glycol monobenzyl ether, with 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 2-butyl-2-ethyl-1,3-propanediol, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, diethylene glycol monophenyl ether, and diethylene glycol monobenzyl ether being preferred. Compound b has the property of easily oriented at the interface between the ink and the printing medium after the ink has landed on the printing medium. This property is thought to reduce the interfacial tension generated at the interface between the ink and the printing medium, thereby promoting the wetting and spreading of the ink on the printing medium, and resulting in excellent wettability.

[0055] Examples of compound c include 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 1,5-pentanediol, 3-methoxy-3-methyl-1-butanol, 3-methoxy-1-butanol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, and diethylene glycol monobutyl ether, with 1,4-butanediol, 1,5-pentanediol, 3-methoxy-3-methyl-1-butanol, 3-methoxy-1-butanol, ethylene glycol monobutyl ether, and diethylene glycol monobutyl ether being preferred. Compound c is a compound with a balanced combination of hydrophilicity and hydrophobicity, and is soluble in water and compounds a and b contained in the ink. This property makes it possible to stably dissolve compounds a and b even in inks where water makes up the majority of the total mass of the ink, thus preventing the ink from undergoing phase separation.

[0056] When the total content of compound a in 100 parts by mass of the above ink is (a) parts by mass, the total content of compound b is (b) parts by mass, and the total content of compound c is (c) parts by mass, it is preferable that the relationships (a) ≤ (c) and 0.1 ≤ (c) / (b) ≤ 50 are satisfied. The value of (c) / (b) is preferably greater than 1 and 50 or less, more preferably greater than 1 and less than 50, even more preferably 5 to 30, particularly preferably 6 to 20, and extremely preferably 7 to 19. The total content of compound a in 100 parts by mass of the ink according to this embodiment is preferably 0.1 to 10 parts by mass, more preferably 0.1 to 7 parts by mass, even more preferably 0.1 to 5 parts by mass, and particularly preferably 0.2 to 1.0 parts by mass. Furthermore, the total content of compound b in 100 parts by mass of the ink according to this embodiment is preferably 0.05 to 10 parts by mass, more preferably 0.05 to 8 parts by mass, and even more preferably 0.05 to 6 parts by mass. Furthermore, the total content of compound c in 100 parts by mass of ink according to this embodiment is preferably 1 to 20 parts by mass, more preferably 1 to 15 parts by mass, and even more preferably 1 to 10 parts by mass. In particular, by setting the value of (c) / (b) to 0.1 to 50, compound b dissolves stably in the ink without phase separation, and the ink tends to exhibit sufficient wettability.

[0057] <Water> As for the water, water with a low content of impurities such as metal ions is preferred, i.e., ion-exchanged water, distilled water, etc. The water content is 60 to 90% by mass, and preferably 70 to 90% by mass, relative to the total mass of the ink according to this embodiment.

[0058] The dynamic surface tension value X of the ink at 25°C and a surface life of 10 msec using the maximum foam pressure method is 32.0 mN / m or more, preferably 34.0 mN / m or more, and more preferably 35.0 mN / m or more and 45.0 mN / m or less. The dynamic surface tension value X at a surface life of 10 msec using the above maximum bubble pressure method can be measured and calculated, for example, using a bubble pressure type dynamic surface tension meter BP100 (manufactured by KRUSS). Furthermore, it is preferable that the dynamic surface tension value X and the static surface tension value Y of the ink at 25°C satisfy the relationship 0.05 ≤ (XY) / Y ≤ 0.25 and the relationship 0.10 ≤ (XY) / Y ≤ 0.20. The static surface tension value Y mentioned above can be measured and calculated, for example, using an automatic surface tension meter DY-300 (manufactured by Kyowa Interface Science Co., Ltd.).

[0059] The ink according to this embodiment may optionally contain ink preparations such as dispersants, organic solvents, surfactants, fungicides, preservatives, pH adjusters, chelating reagents, rust inhibitors, defoamers, water-soluble ultraviolet absorbers, antioxidants, and resin emulsions. The content of each ink preparation can be arbitrarily set depending on the intended use of the ink.

[0060] Examples of dispersants include copolymers composed of at least two monomers selected from monomers such as styrene and its derivatives; vinylnaphthalene and its derivatives; aliphatic alcohol esters of α,β-ethylenically unsaturated carboxylic acids; (meth)acrylic acid and its derivatives; maleic acid and its derivatives; itaconic acid and its derivatives; fahric acid and its derivatives; vinyl acetate, vinyl alcohol, vinylpyrrolidone, acrylamide, and their derivatives (preferably at least one of which is a hydrophilic monomer). Examples of hydrophilic monomers include monomers that retain a carboxyl group after polymerization, such as acrylic acid and methacrylic acid.

[0061] Examples of such copolymers include styrene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid-(meth)acrylic acid ester copolymer, (meth)acrylic acid ester-(meth)acrylic acid copolymer, polyethylene glycol (meth)acrylate-(meth)acrylic acid copolymer, and styrene-maleic acid copolymer. Among these, styrene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid-(meth)acrylic acid ester copolymer, (meth)acrylic acid ester-(meth)acrylic acid copolymer, and polyethylene glycol (meth)acrylate-(meth)acrylic acid copolymer are preferred, styrene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid-(meth)acrylic acid ester copolymer, and (meth)acrylic acid ester-(meth)acrylic acid copolymer are more preferred, (meth)acrylic acid ester-(meth)acrylic acid copolymer is even more preferred, and methacrylic acid ester-methacrylic acid copolymer is particularly preferred. Examples of copolymer types include block copolymers, random copolymers, and graft copolymers. These copolymers may also be in the form of salts. In this specification, the term "(meth)acrylic" is used to include both "acrylic" and "methacrylic." The same applies to "(meth)acrylate," etc.

[0062] Dispersants can be synthesized or obtained commercially. Examples of dispersants obtained by synthesis include the AB block polymer disclosed in International Publication No. 2013 / 115071. The monomer constituting the A block of the AB block polymer disclosed in International Publication No. 2013 / 115071 is at least one monomer selected from (meth)acrylic acid and linear or branched C4 alkyl (meth)acrylate, with at least one monomer selected from methacrylic acid and n-butyl methacrylate being preferred, and more preferably a combination of these two monomers. The monomer constituting the B block of the AB block polymer disclosed in International Publication No. 2013 / 115071 is at least one monomer selected from benzyl methacrylate and benzyl acrylate, with benzyl methacrylate being preferred. Specific examples of AB block polymers include the block copolymers disclosed in Synthesis Examples 3 to 8 of International Publication No. 2013 / 115071.

[0063] Examples of commercially available dispersants include Joncyrl 62, 67, 68, 678, and 687 (styrene-acrylic copolymers manufactured by BASF); Aron AC-10SL (polyacrylic acid manufactured by Toagosei Co., Ltd.); and BYKJET 9151, 9152, 9170, and 9171 (wetting dispersants manufactured by BYK Chemie Japan Co., Ltd.).

[0064] The mass-average molecular weight (MW) of the dispersant is preferably 3,000 to 50,000, and more preferably 7,000 to 25,000. The mass-average molecular weight of the dispersant can be measured by gel permuration chromatography (GPC). Specifically, the measurement can be performed using an HLC-8320GPC (manufactured by Tosoh Corporation) as the GPC instrument, two TSK gel Super Multipore HZ-H columns (manufactured by Tosoh Corporation, inner diameter 4.6 mm × 15 cm), tetrahydrofuran as the eluent, and TSK Standard (manufactured by Tosoh Corporation) as the standard sample.

[0065] The acid value of the dispersant is preferably 50 to 300 mg KOH / g, more preferably 80 to 275 mg KOH / g, and even more preferably 80 to 250 mg KOH / g.

[0066] The dispersant can be used in a mixed state with the colorant. Alternatively, it can be used with part or all of the surface of the colorant coated with the dispersant. Or, both of these states may be used in combination.

[0067] When the ink according to this embodiment contains a dispersant, the ratio of the total mass of the dispersant to the total mass of the colorant is preferably 0.01 to 1.0, more preferably 0.05 to 0.6, and even more preferably 0.1 to 0.5.

[0068] Examples of organic solvents include C1-C6 alkanols such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, derbutanol, and terbutanol; carboxylic acid amides such as N,N-dimethylformamide and N,N-dimethylacetamide; lactams such as 2-pyrrolidone, N-methyl-2-pyrrolidone, and N-methylpyrrolidine-2-one; cyclic ureas such as 1,3-dimethylimidazolidin-2-one or 1,3-dimethylhexahydropyrimido-2-one; acetone, 2-methyl-2- Ketones, keto alcohols, or carbonates such as hydroxypentan-4-one and ethylene carbonate; cyclic ethers such as tetrahydrofuran and dioxane; ethylene glycol, diethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, polyethylene glycol (preferably with a molecular weight of 400, 800, 1540, or higher), polypropylene glycol, thiodiglycol, dithiodiglycol Examples include mono, oligo, or polyalkylene glycols or thioglycols having C2-C6 alkylene units such as 1,2-H,6-H,3

[0069] Examples of surfactants include anionic, nonionic, silicone, and fluorine-based surfactants. Among these, surfactants selected from silicone-based and fluorine-based surfactants are preferred, and silicone-based surfactants are more preferred from the viewpoint of safety for living organisms and the environment.

[0070] Examples of anionic surfactants include alkyl sulfocarboxylates, α-olefin sulfonates, polyoxyethylene alkyl ether acetates, polyoxyethylene alkyl ether sulfates, N-acyl amino acids or their salts, N-acyl methyl taurates, alkyl sulfates, polyoxyalkyl ether sulfates, alkyl sulfates, polyoxyethylene alkyl ether phosphates, rosinic acid soaps, castor oil sulfates, lauryl alcohol sulfates, alkylphenol type phosphates, alkyl type phosphates, alkylaryl sulfonates, diethyl sulfosulfate, diethylhexyl sulfosulfate, and dioctyl sulfosulfate.

[0071] Nonionic surfactants include, for example, ether-based surfactants such as polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, polyoxyethylene alkyl ether, and polyoxyethylene distyrenated phenyl ether (e.g., Emulgen A-60, A-90, A-500 manufactured by Kao Corporation); polyoxyethylene oleate ester, polyoxyethylene distearate ester, sorbitan laurate, and sorbitan monostearate. Examples include ester-based compounds such as sorbitan monooleate, sorbitan sesquioleate, polyoxyethylene monooleate, and polyoxyethylene stearate; acetylene glycol (or acetylene alcohol)-based compounds such as 2,4,7,9-tetramethyl-5-decine-4,7-diol, 3,6-dimethyl-4-octin-3,6-diol, and 3,5-dimethyl-1-hexyn-3-ol (for example, Surfinol 104, 104PG50, 82, 420, 440, 465, 485; Olfin STG; etc., manufactured by Evonik Japan Co., Ltd.); and polyglycol ether-based compounds.

[0072] Examples of silicone-based surfactants include polyether-modified siloxanes and polyether-modified polydimethylsiloxanes. Examples include Dynol 960 and 980 from Air Products Inc.; Silface SAG001, SAG002, SAG003, SAG005, SAG503A, SAG008, SAG009, and SAG010 from Nisshin Chemical Industry Co., Ltd.; BYK-345, 347, 348, 349, 3450 (also known as BYKLPX 23289), 3451 (also known as BYKLPX 23347), 3455, LP-X23288, and LP G20726 from BIC Chemie Japan Inc.; and TEGO® Twin 4000, TEGO® Wet KL 245, 250, 260, 265, 270, and 280 from Evonic Tego Chemie Inc.

[0073] Examples of fluorinated surfactants include perfluoroalkyl sulfonic acid compounds, perfluoroalkyl carboxylic acid compounds, perfluoroalkyl phosphate ester compounds, perfluoroalkyl ethylene oxide adducts, and polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups in their side chains. Examples of commercially available products include Capstone FS-30 and FS-31 manufactured by Chemors.

[0074] Examples of antifungal agents include sodium dehydroacetate, sodium benzoate, sodium pyridinethion-1-oxide, ethyl p-hydroxybenzoate, 1,2-benzisothiazolin-3-one, and their salts.

[0075] Examples of preservatives include compounds such as organic sulfur, organic nitrogen sulfur, organic halogen, haloaryl sulfone, iodopropagyl, haloalkylthio, nitrile, pyridine, 8-oxyquinoline, benzothiazole, isothiazolin, dithiol, pyridine oxide, nitropropane, organotin, phenol, quaternary ammonium salt, triazine, thiazine, anilide, adamantane, dithiocarbamate, brominated indanone, benzyl bromacetate, and inorganic salts. Specific examples of organic halogen compounds include, for example, sodium pentachlorophenol. Specific examples of pyridine oxide compounds include, for example, sodium 2-pyridinethiol-1-oxide. Specific examples of isothiazolin compounds include, for example, 1,2-benzisothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one magnesium chloride, 5-chloro-2-methyl-4-isothiazolin-3-one calcium chloride, and 2-methyl-4-isothiazolin-3-one calcium chloride. Specific examples of other preservatives and fungicides include, for example, anhydrous sodium acetate, sodium sorbate, sodium benzoate, and Arch Chemical's trade names Proxel GXL(S), Proxel LV, and Proxel XL-2(S).

[0076] Examples of pH adjusting agents include alkanolamines such as diethanolamine, triethanolamine, and N-methyldiethanolamine; alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; ammonium hydroxide (ammonia water); alkali metal carbonates such as lithium carbonate, sodium carbonate, sodium bicarbonate, and potassium carbonate; alkali metal salts of organic acids such as sodium silicate and potassium acetate; and inorganic bases such as disodium phosphate.

[0077] Examples of chelating reagents include disodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, and sodium uracildiacetate.

[0078] Examples of rust inhibitors include acidic sulfites, sodium thiosulfate, ammonium thioglycolate, diisopropylammonium nitride, pentaerythritol tetranitrate, and dicyclohexylammonium nitride.

[0079] Examples of defoaming agents include silicone-based, silica mineral oil-based, olefin-based, and acetylene-based compounds. Examples of commercially available defoaming agents include Surfinol DF37, DF58, DF110D, DF220, MD-20, and Olfin SK-14, manufactured by Shin-Etsu Chemical Co., Ltd.

[0080] Examples of water-soluble ultraviolet absorbers include sulfonated benzophenone compounds, benzotriazol compounds, salicylic acid compounds, cinnamic acid compounds, and triazine compounds.

[0081] As antioxidants, for example, various organic and metal complex-based colorfastness inhibitors can be used. Examples of organic colorfastness inhibitors include hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromans, alkoxyanilines, and heterocyclic compounds.

[0082] The ink according to this embodiment may contain a resin emulsion to improve the ink's fixation to the printing medium. The inclusion of a resin emulsion in the ink according to this embodiment tends to improve the image fastness of the printed image on the printing medium, such as water resistance, scratch resistance, and alcohol resistance. At least one of polymer emulsions and wax emulsions is preferred as the resin emulsion.

[0083] Examples of polymer emulsions include emulsions containing urethane-based, polyester-based, acrylic-based, vinyl acetate-based, vinyl chloride-based, styrene-acrylic-based, acrylic-silicone-based, and styrene-butadiene-based polymers. Among these, emulsions of polymers selected from urethane-based, acrylic-based, and styrene-butadiene-based polymers are preferred.

[0084] Examples of commercially available polymer emulsions include: Superflex 420, 470, 890 (urethane resin emulsions manufactured by Daiichi Kogyo Seiyaku Co., Ltd.); Hydran HW-350, HW-178, HW-163, HW-171, AP-20, AP-30, WLS-201, WLS-210 (urethane resin emulsions manufactured by DIC Corporation); 0569, 0850Z, 2108 (styrene-butadiene resin emulsions manufactured by JSR Corporation); AE980, AE981A, AE982, AE986B, AE104 (acrylic resin emulsions manufactured by E-Tech Co., Ltd.); NeoCryl A-1105, A-1125, A-1127 (acrylic resin emulsions manufactured by DSM Coating Resin Co., Ltd.); NeoCryl A-655 (DSM Coating Examples include styrene-acrylic resin emulsion manufactured by Resin Corporation.

[0085] As the wax emulsion, an emulsion in which natural wax or synthetic wax is dispersed in an aqueous medium can be used.

[0086] Examples of natural wax emulsions include emulsions of various waxes such as: petroleum-based waxes like paraffin wax and microcrystalline wax; lignite-based waxes like montane wax; plant-based waxes like carnauba wax and candelilla wax; and animal and plant-based waxes like beeswax and lanolin.

[0087] Examples of synthetic wax emulsions include polyalkylene wax (preferably poly C2-C4 alkylene wax), oxidized polyalkylene wax (preferably oxidized poly C2-C4 alkylene wax), and paraffin wax emulsions. Among these, emulsions of waxes selected from polyethylene wax, polypropylene wax, oxidized polyethylene wax, oxidized polypropylene wax, and paraffin wax are preferred.

[0088] The average particle size of the wax is preferably 50 nm to 5 μm, and more preferably 100 nm to 1 μm, in order to prevent clogging of the inkjet head.

[0089] Examples of commercially available wax emulsions include CERAFLOUR 925, 929, 950, 991, AQUACER 498, 515, 526, 531, 537, 539, 552, 1547, AQUAMAT 208, 263, 272; MINERPOL 221 (all manufactured by Big Chemie Japan Co., Ltd.); Mitsui High Wax NL100, NL200, NL500, 4202E, 1105A, 2203A, NP550, NP055, NP505 (all manufactured by Mitsui Chemicals, Inc.); KUE-100, 11 (all manufactured by Sanyo Chemical Industries, Ltd.); HYTEC P-5300, E-6500, 9015, 6400 (all manufactured by Toho Chemical Industry Co., Ltd.).

[0090] When the ink according to this embodiment contains a resin emulsion, its solid content is preferably 1 to 20% by mass, and more preferably 3 to 15% by mass. A solid content of 1% by mass or more of the resin emulsion tends to result in good adhesion to the printing medium. Furthermore, a solid content of 20% by mass or less of the resin emulsion tends to result in good ink discharge and storage stability.

[0091] The method for preparing the ink according to this embodiment is not particularly limited, and known preparation methods can be employed. For example, one method is to prepare a dispersion containing a colorant and a dispersant, and then add water, organic compounds such as compounds a to c mentioned above, and an ink preparation agent as needed to this dispersion and mix.

[0092] Methods for preparing the dispersion include, for example, phase inversion emulsification, acid precipitation, interfacial polymerization, in-situ polymerization, liquid curing coating, coacervation (phase separation), liquid drying, melt-dispersion-cooling, air suspension coating, and spray drying. Among these, phase inversion emulsification, acid precipitation, and interfacial polymerization are preferred, with phase inversion emulsification being more preferred.

[0093] When preparing a dispersion by the phase inversion emulsification method, for example, a dispersant is dissolved in an organic solvent such as 2-butanone, and an aqueous solution of a neutralizing agent is added to prepare an emulsion. A coloring agent is added to the resulting emulsion and the dispersion treatment is performed. By removing the organic solvent and some of the water from the liquid obtained in this way under reduced pressure, the desired dispersion can be obtained.

[0094] Dispersion can be performed using a sand mill (bead mill), roll mill, ball mill, paint shaker, ultrasonic disperser, microfluidizer, etc. For example, when using a sand mill, beads with a particle size of about 0.01 to 1 mm can be used, and the bead packing ratio can be appropriately set to perform the dispersion. The particle size of the particles contained in the dispersion can be made uniform by performing operations such as filtration and centrifugation on the dispersion obtained in the above manner. If foaming occurs during the preparation of the dispersion, a very small amount of a known antifoaming agent such as a silicone-based or acetylene glycol-based agent can be added.

[0095] In this embodiment, it is preferable that the ink contains a low amount of inorganic impurities such as metal cation chlorides (e.g., sodium chloride) and metal sulfates (e.g., sodium sulfate). Such inorganic impurities are often found in commercially available colorants. The guideline for the inorganic impurity content is approximately 1% by mass or less relative to the total mass of the colorant, and the lower limit is below the detection limit of analytical instruments, i.e., ideally 0% by mass. Methods for obtaining a colorant with low levels of inorganic impurities include, for example, using a reverse osmosis membrane; suspending and stirring the solid colorant in a mixed solvent of C1-C4 alcohol such as methanol and water, filtering and separating the colorant, and drying it; and exchanging and adsorbing inorganic impurities with an ion exchange resin.

[0096] The ink according to this embodiment is preferably microfiltered. A membrane filter, glass filter paper, or the like can be used for microfiltration. The pore size of the filter when performing microfiltration is usually 0.5 to 20 μm, preferably 0.5 to 10 μm.

[0097] The ink according to this embodiment exhibits excellent storage stability, redispersibility, color development, and saturation. Furthermore, printed images recorded using the ink according to this embodiment exhibit excellent fastness in various aspects, such as lightfastness, heat resistance, and oxidation gas resistance (e.g., ozone gas resistance). In addition, the ink according to this embodiment exhibits excellent image formation performance with minimal coating unevenness during image formation.

[0098] Examples of ink sets according to this embodiment include sets of the inks according to this embodiment described above, or sets comprising the inks according to this embodiment described above and other inks different from those inks. The other inks are not particularly limited as long as their composition differs from that of the inks according to this embodiment, but it is preferable that they differ in hue from that of the inks according to this embodiment.

[0099] Furthermore, the printing media according to this embodiment has at least one selected from the group consisting of the ink or inkjet ink included in the ink set according to this embodiment described above attached to it.

[0100] Furthermore, the ink media set according to this embodiment comprises the ink or ink set according to this embodiment described above, and a printing medium.

[0101] The printing media is not particularly limited, but ink-poorly absorbent or ink-non-absorbent printing media are preferred, and ink-non-absorbent printing media are more preferred. Examples of ink-poorly absorbent printing media include plain paper without an ink-receiving layer, media used in gravure printing and offset printing, art paper, coated paper, matte paper, and cast paper. Examples of ink-non-absorbent printing media include PET (polyethylene terephthalate) film, PP (polypropylene) film, vinyl chloride sheet, glass, and rubber.

[0102] The inkjet recording method according to this embodiment involves ejecting the ink droplets described above from the inkjet head and recording them on a printing medium. There are no particular restrictions on the ink nozzles of the inkjet printer that eject the ink, and they can be appropriately selected according to the purpose.

[0103] The inkjet recording method according to this embodiment also includes methods for improving image quality by ejecting a large number of inks with a low colorant content in a small volume; methods for improving image quality by using multiple inks with substantially the same hue but different colorant content in the ink; and methods for improving the fixation of colorants to printing media by using a colorless transparent ink and an ink containing a colorant in combination.

[0104] Known inkjet recording methods can be employed. Examples include charge control methods, drop-on-demand methods (also called pressure pulse methods), acoustic inkjet methods, and thermal inkjet methods. Furthermore, the inkjet recording method may be either a multi-pass method or a single-pass method (one-pass printing method). In industrial inkjet printers, single-pass printing using a line-head type inkjet printer is also preferred for the purpose of increasing printing speed. In recent years, circulating heads that have a mechanism to prevent ink drying near the nozzle by circulating the ink to the vicinity of the nozzle (i.e., a circulation mechanism) have been actively developed. The ink according to this embodiment can also be suitably used in such circulating heads.

[0105] When recording to a printable medium, for example, an ink-containing container (ink tank) is loaded into the designated position in the inkjet printer, and the data is recorded to the printable medium using the printing method described above. Furthermore, full-color printing can be achieved by loading containers containing each color of ink into the designated positions in the inkjet printer and recording the data to the printable medium using the printing method described above.

[0106] Furthermore, when using printing media that does not have an ink-receiving layer, surface modification treatment is also preferably performed. Examples of surface modification treatments include corona discharge treatment, plasma treatment, and flame treatment. It is generally known that the effect of surface modification treatment decreases over time. For this reason, it is preferable to perform the surface modification treatment process and the inkjet recording process consecutively, and it is even more preferable to perform the surface modification treatment process immediately before the inkjet recording process.

[0107] For all the matters mentioned above, a combination of desirable items is more desirable, and a combination of more desirable items is even more desirable. The same applies to combinations of desirable items and more desirable items, and combinations of more desirable items and even more desirable items, and so on. [Examples]

[0108] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples. In this text, "parts" and "%" refer to mass unless otherwise specified. In the examples, when it is necessary to quantify the pigment solids content in the dispersion, it was determined by the dry weight method using MS-70 manufactured by A&D Co., Ltd. The pigment solids content is a converted value calculated from the total amount of solids, with only the pigment solids content being considered. The inks described in the examples are included in the above-mentioned inkjet inks.

[0109] [Preparation Example 1] Preparation of Cyanide Dispersion 1 A block copolymer described in Synthesis Example 3 of International Publication No. 2013 / 115071 was prepared, and 6 parts of the obtained polymer dispersant were dissolved in 30 parts of 2-butanone to obtain a homogeneous solution. To this solution, a solution of 0.68 parts of 28% aqueous ammonia dissolved in 53 parts of deionized water was added, and the mixture was stirred for 1 hour to prepare an emulsion solution in which the polymer dispersant was dissolved. 20 parts of CIPigment Blue 15:4 (manufactured by Dainichi Seika Kogyo Co., Ltd., CHROMOFINE BLUE 4851) was added, and the mixture was dispersed in a sand grinder at 1500 rpm for 15 hours. 100 parts of deionized water were added dropwise to the obtained solution, and after filtering to remove the dispersion beads, 2-butanone and a portion of the water were removed by vacuum distillation in an evaporator to obtain cyanide dispersion 1 with a pigment solid content of 12%. [Preparation Example 2] Preparation of Cyanide Dispersion 2 BYKJET 9151 (manufactured by Bic Chemie Japan Co., Ltd.) (8 parts) was dissolved in ion-exchanged water (72 parts) and stirred for 1 hour. CIPigment Blue 15:4 (manufactured by Dainichi Seika Kogyo Co., Ltd., CHROMOFINE BLUE 4851) (20 parts) was added to the resulting solution and the mixture was dispersed in a sand grinder at 1500 rpm for 15 hours. Ion-exchanged water (70 parts) was added dropwise to the resulting liquid, and the dispersion beads were removed by filtration to obtain cyanide dispersion 2 with a pigment solid content of 11.6%. [Preparation Example 3] Preparation of Cyanide Dispersion 3 Joncyrl 68 (BASF, mass-average molecular weight: 13000) (9 parts) and triethanolamine (6 parts) were dissolved in deionized water (75 parts) and stirred for 1 hour. CIPigment Blue 15:4 (Dainichi Seika Kogyo Co., Ltd., CHROMOFINE BLUE 4851) (30 parts) was added to the resulting solution and the mixture was dispersed in a sand grinder at 1500 rpm for 15 hours. Deionized water (40 parts) was added dropwise to the resulting liquid, and the dispersion beads were removed by filtration to obtain cyanide dispersion 3 with a pigment solid content of 18.7%.

[0110] [Example 1] The cyanide dispersion 1 obtained above was mixed with the components listed in Table 1 below, and then filtered through a 3 μm membrane filter to obtain the ink for Example 1 for evaluation testing. The colorant content in the total mass of the ink was adjusted to 4.5%. [Examples 2-21, Comparative Examples 1-7] Inks for Examples 2-21 and Comparative Examples 1-7 were obtained in the same manner as in Example 1, except that the type of cyanide dispersion to be added, the type of resin emulsion, and the compositions of compounds a, b, and c were as shown in Tables 1-2 below. The abbreviations in Tables 1 and 2 represent the following, respectively. A-1127: NeoCryl A-1127 (Acrylic resin emulsion, manufactured by DSMCoating Resin Ltd., solids content 44.0%) AQ-515: AQUACER 515 (Polyethylene wax emulsion, manufactured by BIC Chemie Japan Co., Ltd., solids content 34.6%)

[0111] [Table 1]

[0112] [Table 2]

[0113] [Compatibility evaluation] For each composition of Examples 1-21 and Comparative Examples 1-7, a mixture containing only the materials other than the colorants (cyan dispersions 1-3) was prepared, and the compatibility of the mixture was evaluated. The results are shown in Tables 3-4 below. If the compatibility is insufficient, the uniformity of the ink will decrease and the wettability effect will not be fully realized, so it is practically preferable that the evaluation criterion below is A. In Tables 3 and 4 below, a hyphen "-" indicates that the ink materials were not mixed, and therefore evaluation as an ink composition was not possible. (Compatibility evaluation criteria) A: A state that is uniform and completely mixed. B: There are no oil droplets on the surface of the liquid, but it is suspended and not completely dissolved. C: Oil droplets are floating on the surface of the mixture, indicating that it is not completely dissolved. D: The components in the mixture have separated and are not dissolved at all. [Contact angle evaluation] Using PET film (Toyobo Co., Ltd., E5102) as the substrate, the contact angles between each ink obtained above and the PET film were measured. A DM-501Hi contact angle meter (Kyowa Interface Science Co., Ltd.) was used, with a droplet volume of 2 μL, and the measurement time was 10 seconds after ink placement, at 25°C. The contact angle was evaluated on a four-point scale from A to D, as shown below. A lower contact angle indicates that the ink is wetting and spreading well on the film, and an evaluation of B or higher is preferable for practical use. (Contact angle evaluation criteria) A: Contact angle ≦15° B:15°<contact angle≦20° C:20°<contact angle≦30° D:30°<contact angle [Inkjet Printing Evaluation Test] When the inks from examples 1 to 21 described above were used to form images on paper and PET film, respectively, using an inkjet head KJ4B-1200 (manufactured by Kyocera Corporation), all of them showed good ink ejection and good image formation.

[0114] [Table 3]

[0115] [Table 4]

[0116] From the results in Tables 3 and 4 above, the ink of the example is at least superior in wettability compared to the ink of the comparative example, and its compatibility is equal to or better than that of the comparative example. In other words, the ink of the example is an excellent ink that combines compatibility, wettability, and ejection properties. [Industrial applicability]

[0117] The ink of the present invention is extremely useful as an ink for various recording purposes, particularly for inkjet recording, because it has excellent compatibility, wettability of printed materials, and ejection properties.

Claims

1. A colorant comprising at least one selected from the group consisting of pigments and disperse dyes, an organic compound excluding the colorant, and water, An inkjet ink wherein the water content is 60 to 90% by mass relative to the total mass of the ink, and the organic compound satisfies the following condition (A): The dynamic surface tension value X of the aforementioned ink at 25°C and with a surface life of 10 msec using the maximum foam pressure method is 32.0 mN / m or more. An inkjet ink wherein the dynamic surface tension value X and the static surface tension value Y of the ink at 25°C satisfy the relationship 0.05 ≤ (X - Y) / Y ≤ 0.

25. (A) Compound a: At least one compound selected from the compound represented by the following formula (1) and the compound represented by the following formula (2); Compound b: At least one compound selected from the compounds represented by the following formula (3) and the compounds represented by the following formula (4); Compound c: At least one compound selected from the group consisting of C4-C5 alkanediols, compounds represented by the following formula (5), and compounds represented by the following formula (6); Includes. 【Chemistry 1】 (In formula (1), R １ (This represents a linear or branched C5-C10 hydrocarbon group.) 【Chemistry 2】 (In formula (2), R ２ (where n1 represents a linear or branched C6-C7 hydrocarbon group, and n1 represents 1 or 2.) 【Transformation 3】 (In formula (3), R ３ (This represents a linear or branched C7-C12 hydrocarbon group.) 【Chemistry 4】 (In formula (4), R ４ (where n2 represents a phenyl group or a benzyl group, and n2 represents 1 or 2.) 【Transformation 5】 (In formula (5), R ５ (This represents a hydrogen atom or a methyl group.) 【Transformation 6】 (In formula (6), R ６ (where n3 represents a linear or branched C1-C4 hydrocarbon group, and n3 represents 1 or 2.)

2. The inkjet ink according to claim 1, wherein the dynamic surface tension value X is 34.0 mN / m or more.

3. The inkjet ink according to claim 1 or 2, wherein the dynamic surface tension value X and the static surface tension value Y satisfy the relationship 0.10 ≤ (X - Y) / Y ≤ 0.

20.

4. An inkjet recording method comprising ejecting droplets of inkjet ink according to claim 1 or 2 from an inkjet head and recording them on a printing medium.

5. The inkjet recording method according to claim 4, wherein the printing medium is an ink-poorly absorbent or ink-non-absorbent printing medium.

6. The inkjet recording method according to claim 4, wherein the inkjet head is an inkjet head including a circulation mechanism.

7. An ink set comprising the inkjet ink described in claim 1 or 2, and another inkjet ink different from the said inkjet ink.

8. An ink media set comprising at least one selected from the group consisting of the inkjet ink described in claim 1 or 2 and the ink set described in claim 7, and a printing medium.

9. A printing medium to which at least one selected from the group consisting of the inkjet ink described in claim 1 or 2, and the inkjet ink included in the ink set described in claim 7, is attached.

Images