Ink for inkjet, inkjet recording method, ink set, ink medium set, and printing medium

Abstract

Provided are an ink and the like, the ink being an inkjet ink containing a colorant, an organic compound other than the colorant, and water, the organic compound including a compound a such as diethylene glycol monohexyl ether, a compound b such as 1,8-octanediol, and a compound c such as 1,5-pentanediol, wherein, when the total content of the compound a in 100 parts by mass of the ink is set as (a) parts by mass, the total content of the compound b is set as (b) parts by mass, and the total content of the compound c is set as (c) parts by mass, the following relationships are satisfied: (a) ≤ (c), and 0.1 ≤ (c) / (b) ≤ 50. Also provided are an inkjet recording method using the ink, an ink set and an ink medium set provided with the ink, and a print medium having the ink attached thereto.

Description

TECHNICAL FIELD

[0001] The present application relates to an ink for inkjet, an inkjet recording method, an ink set, an ink medium set, and a print medium. BACKGROUND

[0002] As one of representative methods among various color recording methods, a recording method based on an inkjet printer (inkjet recording method) is a method of generating droplets of ink, and causing them to adhere to a print medium such as paper, thereby performing recording. In recent years, the demand is rising in commercial use, industrial use, and ink capable of printing on various print media is required.

[0003] In the commercial field of catalogues, brochures, and the like, a print medium (hereinafter, also referred to as "ink difficultly-absorbing medium") such as art paper, and bristol board, which has a lower ink-absorbing property than ordinary paper, is often used. In addition, in the industrial field of outdoor signboards, food soft packaging, and the like, a print medium (hereinafter, also referred to as "ink non-absorbing medium") such as vinyl chloride film, PET (polyethylene terephthalate) film, and polyolefin film, which has a non-ink-absorbing property, is often used.

[0004] For the ink difficultly-absorbing medium and the ink non-absorbing medium, development of a solvent ink using an organic solvent as a main solvent, a curable ink containing a polymerizable monomer, and the like has been performed. However, these inks have many problems in safety to the natural environment and the human body. Therefore, in recent years, development of an aqueous ink using water as a main solvent has been gradually popularized.

[0005] The aqueous ink generally has a property of being difficult to spread on the ink difficultly-absorbing medium and the ink non-absorbing medium. In addition, in order to fix the aqueous ink to the print medium, it is necessary to dry the water and the organic solvent in the ink.

[0006] In Patent Literature 1, it is reported that by using water as a main solvent and using three or more kinds of organic solvents different in water-octanol partition coefficient, an ink showing a good wetting property on the ink non-absorbing medium can be obtained. However, the drying property of the ink of Patent Literature 1 is not sufficient. In addition, in Patent Literature 2, it is reported that by using an ink composition in which the glass transition temperature, the particle diameter, and the solid content rate of a resin added are improved, a good drying property is shown even on the ink non-absorbing medium. However, the wetting property of the ink of Patent Literature 2 on the ink non-absorbing medium is not sufficient.

[0007] In water-based inks, organic solvents and surfactants are often used to improve wettability. The more of these materials added, the better the wettability, but the worse the drying performance. On the other hand, if drying performance is excessively improved, the ink droplets begin to dry immediately upon landing on the printing medium, and the ink is fixed before it has fully saturated and spread, sometimes resulting in poor image quality. As mentioned above, in water-based inks, wettability and drying performance are opposite properties, and no ink has yet been proposed that satisfies both of these requirements.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Application Publication No. 2020-125382

[0011] Patent Document 2: Japanese Patent Application Publication No. 2020-55943 Summary of the Invention

[0012] The problem that the invention aims to solve

[0013] The objective of this invention is to provide an inkjet ink that exhibits good wettability and excellent drying properties even on non-absorbent ink media, an inkjet recording method using the inkjet ink, an ink group comprising the inkjet ink, an ink medium group comprising the inkjet ink or ink group and a printing medium, and a printing medium having each inkjet ink comprising the inkjet ink or ink group attached thereto.

[0014] Methods for solving problems

[0015] The specific means used to solve the above problems include the following implementation methods. 1)

[0017] Inkjet ink contains a colorant, an organic compound other than the aforementioned colorant, and water, wherein the aforementioned organic compound satisfies any one of the following conditions (A) to (C).

[0018] (A)

[0019] The ink contains compounds a, b, and c. When the total content of compound a in 100 parts by mass of the ink is set as (a) parts by mass, the total content of compound b is set as (b) parts by mass, and the total content of compound c is set as (c) parts by mass, the following relationships are satisfied: (a) ≤ (c) and 0.1 ≤ (c) / (b) ≤ 50.

[0020] Compound a: selected from at least one of the compounds represented by formula (1) below and the compounds represented by formula (2) below;

[0021] Compound b: at least one compound selected from the compounds represented by formula (3) below and the compounds represented by formula (4) below; and

[0022] Compound c: at least one compound selected from the group consisting of C4-C5 alkane diols, compounds represented by formula (5) below, and compounds represented by formula (6) below;

[0023] (B)

[0024] The ink contains compounds a, b, and c. When the total content of compound a in 100 parts by mass of the ink is set as (a) parts by mass and the total content of compound c is set as (c) parts by mass, (a) is greater than 0.4 and satisfies the relationship (a) > (c).

[0025] Compound a: selected from at least one of the compounds represented by formula (1) below and the compounds represented by formula (2) below;

[0026] Compound b: at least one compound selected from the compounds represented by formula (3) below and the compounds represented by formula (4) below; and

[0027] Compound c: at least one compound selected from the group consisting of C4-C5 alkane diols, compounds represented by formula (5) below, and compounds represented by formula (6) below;

[0028] (C)

[0029] Contains 1,5-pentanediol and R in the following formula (1) 1 When the content of 1,5-pentanediol in 100 parts by mass of the aforementioned inkjet ink is set as (e) parts by mass, and the total content of the aforementioned compound d is set as (d) parts by mass, (d) is greater than 0.3 and satisfies the relationship 1 < (e) / (d) ≤ 50.

[0030] [Chemical Formula 1]

[0031]

[0032] (In equation (1), R) 1 This refers to a straight-chain or branched C5-C10 hydrocarbon group.

[0033] [Chemical Formula 2]

[0034]

[0035] (In equation (2), R) 2 This indicates a straight-chain or branched C6-C7 hydrocarbon group, where n1 represents 1 or 2.

[0036] [Chemical Formula 3]

[0037] HO-R 3 -OH (3)

[0038] (In equation (3), R) 3 This indicates a straight-chain or branched C7-C12 hydrocarbon group.

[0039] [Chemical Formula 4]

[0040]

[0041] (In equation (4), R) 4 (n represents phenyl or benzyl, n2 represents 1 or 2.)

[0042] [Chemical Formula 5]

[0043]

[0044] (In equation (5), R) 5 (This indicates a hydrogen atom or a methyl group.)

[0045] [Chemical Formula 6]

[0046]

[0047] (In equation (6), R) 6 This indicates a straight-chain or branched C1-C4 hydrocarbon group, where n3 represents 1 or 2. 2)

[0049] The ink for inkjet printing as described in 1), wherein the aforementioned organic compound satisfies the aforementioned condition (A) and satisfies the relationship 1 < (c) / (b) ≤ 50. 3)

[0051] The inkjet ink as described in 1) or 2), wherein the aforementioned colorant comprises at least one selected from pigments and disperse dyes. 4)

[0053] An inkjet recording method wherein droplets of ink for inkjet printing, as described in any one of 1) to 3), are ejected from an inkjet head and recorded on a printing medium. 5)

[0055] As described in 4), the inkjet recording method, wherein the aforementioned printing medium is a printing medium with non-absorbent or non-absorbent ink. 6)

[0057] As described in 4) or 5), the inkjet recording method wherein the aforementioned inkjet head is a printhead with a circulation mechanism. 7)

[0059] The ink group includes any one of 1) to 3) inkjet ink and other inkjet inks different from the inkjet ink. 8)

[0061] An ink media group comprising any one of 1) to 3) inkjet ink or the ink group described in 7) and a printing medium. 9)

[0063] A printing medium, wherein the inkjet ink described in any one of 1) to 3) is attached, or each inkjet ink contained in the ink group described in 7).

[0064] Invention Effects

[0065] According to the present invention, inkjet inks that exhibit good wettability and excellent drying properties even on non-absorbent ink media can be provided; an inkjet recording method using the inkjet ink; an ink group comprising the inkjet ink; an ink medium group comprising the inkjet ink or ink group and a printing medium; and a printing medium having each inkjet ink comprising the inkjet ink or ink group attached thereto. Detailed Implementation

[0066] The following is a detailed description of specific embodiments in which the present invention is applied.

[0067] In this manual, "CI" refers to "Color Index".

[0068] In addition, unless otherwise specified, the terms "alkylene", "propylene", and "alkyl" are used in this specification to mean both linear and branched structures.

[0069] Inkjet inks

[0070] The inkjet ink (hereinafter, also simply referred to as "ink") according to this embodiment contains a colorant, an organic compound other than the colorant, and water. The components contained in the ink according to this embodiment will be described in detail below. It should be noted that each component described below may be used individually or in combination of two or more.

[0071] [Coloring agent]

[0072] As a coloring agent, known coloring agents such as pigments, disperse dyes, and solvent dyes can be used. Among them, it is preferable to include at least one selected from pigments and disperse dyes, and more preferably, it includes pigments.

[0073] As pigments, examples include inorganic pigments, organic pigments, extender pigments, and hollow particles.

[0074] Examples of inorganic pigments include carbon black, metal oxides, metal hydroxides, metal sulfides, metal ferrocyanides, and metal chlorides.

[0075] In this embodiment, when the ink is a black ink and the colorant is an inorganic pigment, the inorganic pigment contained in the black ink is preferably a thermal cracking carbon black, acetylene black, oil furnace carbon black, gas furnace carbon black, lampblack, gas black, or channel black. Specific examples of carbon black include the Raven series manufactured by Columbia Carbon Co., Ltd.; the Monarch, Regal, and Mogul series manufactured by Cabot Corporation; the HiBlack, ColorBlack, Printex, SpecialBlack, and Nerox series manufactured by Orion Engineered Carbons Co., Ltd.; and the MA, MCF, No. 25, No. 33, No. 40, No. 47, No. 52, No. 900, and No. 2300 series manufactured by Mitsubishi Chemical Corporation; and so on.

[0076] In this embodiment, when the ink is white ink and the colorant is an inorganic pigment, examples of inorganic pigments included in the white ink include oxides, nitrides, or nitrides of metals such as zinc, silicon, aluminum, titanium, strontium, and zirconium; inorganic compounds such as glass and silicon dioxide; and so on. Among these, titanium dioxide and zinc oxide are preferred.

[0077] Examples of organic pigments include azo, diazo, phthalocyanine, quinacridone, isoindolineone, dioxazine, perylene, violet ketone, thioindigo, anthraquinone, quinoline ketone, and many others.

[0078] Specific examples of organic pigments include CI pigments such as 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, and 213; and CI pigments such as Red 5, 7, 12, 48, 48, 1, 57, 88, 112, 122, 123, 146, 149, 150, 166, 168, 177, and 178. Red pigments such as 179, 184, 185, 202, 206, 207, 254, 255, 257, 260, 264, 269, and 272; CI pigments Blue 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 22, 25, 60, 66, and 80; CI pigments Violet 19, 23, 29, 37, 38, and 50; CI pigments Orange 13, 16, 43, 68, 69, 71, and 73; CI pigments Green 7, 36, and 54; CI pigment Black 1; and so on. Among these, CI pigment Blue 15:4 is preferred.

[0079] Examples of extender pigments include silica, calcium carbonate, talc, clay, barium sulfate, and silica. Extender pigments are mostly used in combination with other colorants.

[0080] Hollow particles, for example, can be used as known hollow particles described in U.S. Patent No. 4,880,465, Japanese Patent No. 3,562,754, Japanese Patent No. 6,026,234, Japanese Patent No. 5,459,460, Japanese Unexamined Patent Application Publication No. 2003-268,694, Japanese Patent No. 4,902,216, etc., and are particularly preferred for use as white pigments.

[0081] As a disperse dye, a dye selected, for example, from CI disperse dyes (CIDispers) is preferred. Specific examples include CI Disperse 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, and other yellow dyes; CI Disperse Red 60, 73, 88, 91, 92, 111, 127, 131, 143, 145, 146, 152, 153, 154, 167, 179, 191, 192, 206, 221, 258, etc. Red dyes such as 283; orange dyes such as CI disperse orange 9, 25, 29, 30, 31, 32, 37, 38, 42, 44, 45, 53, 54, 55, 56, 61, 71, 73, 76, 80, 96, 97; purple dyes such as CI disperse violet 25, 27, 28, 54, 57, 60, 73, 77, 79, 79:1; blue dyes such as CI disperse 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, 368; and so on.

[0082] As a solvent dye, a dye selected, for example, from CI solvent dyes (CISolvent) is preferred.

[0083] The average particle size of the colorant is preferably 30–300 nm, more preferably 50–250 nm. In this specification, the term "average particle size" refers to the average particle size measured using laser scattering.

[0084] The content of colorant 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 involved in this embodiment.

[0085] [Organic compounds]

[0086] Organic compounds satisfy any one of the following conditions (A) to (C).

[0087] (A)

[0088] The ink contains compounds a, b, and c. When the total content of compound a in 100 parts by mass of the ink involved in this embodiment is set as (a) parts by mass, the total content of compound b is set as (b) parts by mass, and the total content of compound c is set as (c) parts by mass, the relationships (a) ≤ (c) and 0.1 ≤ (c) / (b) ≤ 50 are satisfied.

[0089] Compound a: selected from at least one of the compounds represented by formula (1) below and the compounds represented by formula (2) below;

[0090] Compound b: at least one compound selected from the compounds represented by formula (3) below and the compounds represented by formula (4) below; and

[0091] Compound c: at least one compound selected from the group consisting of C4-C5 alkane diols, compounds represented by formula (5) below, and compounds represented by formula (6) below;

[0092] (B)

[0093] The ink contains compounds a, b, and c. When the total content of compound a in 100 parts by mass of the ink involved in this embodiment is set as (a) parts by mass and the total content of compound c is set as (c) parts by mass, (a) is greater than 0.4 and satisfies the relationship (a) > (c).

[0094] Compound a: selected from at least one of the compounds represented by formula (1) below and the compounds represented by formula (2) below;

[0095] Compound b: at least one compound selected from the compounds represented by formula (3) below and the compounds represented by formula (4) below; and

[0096] Compound c: at least one compound selected from the group consisting of C4-C5 alkane diols, compounds represented by formula (5) below, and compounds represented by formula (6) below;

[0097] (C)

[0098] Contains 1,5-pentanediol and R in the following formula (1) 1 When the content of 1,5-pentanediol in 100 parts by mass of the ink involved in this embodiment is set as (e) parts by mass, and the total content of compound d is set as (d) parts by mass, (d) is greater than 0.3 and satisfies the relationship 1 < (e) / (d) ≤ 50.

[0099] [Chemical Formula 7]

[0100]

[0101] [Chemical Formula 8]

[0102]

[0103] [Chemical Formula 9]

[0104] HO-R 3 -OH (3)

[0105] [Chemical Formula 10]

[0106]

[0107] [Chemical Formula 11]

[0108]

[0109] [Chemical Formula 12]

[0110]

[0111] In equation (1) above, R 1 This refers to a C5-C10 hydrocarbon group that is either straight-chain or branched. Examples of C5-C10 hydrocarbon groups include n-pentyl, isopentyl, neopentyl, sec-pentyl, tert-pentyl, 2-methylbutyl, 1-ethylpropyl, 1,2-dimethylpropyl, n-hexyl, isohexyl, neohexyl, sec-hexyl, tert-hexyl, 2-methylpentyl, 3-methylpentyl, 2,2-dimethylbutyl, 2-ethylbutyl, n-heptyl, isoheptyl, sec-heptyl, tert-heptyl, n-octyl, isooctyl, n-nonyl, isononyl, sec-nonyl, n-decyl, etc. As R 1 Preferably, it consists of straight-chain or branched C5-C7 hydrocarbon groups.

[0112] In equation (2) above, R 2 This refers to a straight-chain or branched C6-C7 hydrocarbon group. Examples of C6-C7 hydrocarbon groups include n-hexyl, isohexyl, neohexyl, secondary hexyl, tert-hexyl, 2-methylpentyl, 3-methylpentyl, 2,2-dimethylbutyl, 2-ethylbutyl, n-heptyl, isoheptyl, secondary hexyl, and tert-heptyl. As R... 2 Preferably, it is a C6 hydrocarbon group that is straight-chain or branched. In the above formula (2), n1 represents 1 or 2, preferably 2.

[0113] In equation (3) above, R 3This refers to a C7-C12 hydrocarbon group that is either straight-chain or branched. Examples of C7-C12 hydrocarbon groups include n-heptyl, 1-methylhexane, 2-methylhexane, 3-methylhexane, 1,5-dimethylpentane, 2,4-dimethylpentane, n-octyl, 1-methylheptyl, 2-methylheptyl, 3-methylheptyl, 4-methylheptyl, 1,6-dimethylhexane, 2,5-dimethylhexane, 2-ethylpentane, 2-ethyl-1-propylpropane, n-nonyl, 1-methyloctyl, 2-methyloctyl, 3-methyloctyl, 4-methyloctyl, 1,7-dimethylheptyl, 2,6-dimethylheptyl, 3,5-dimethylheptyl, 2-butyl-2-ethylpropane, n-decyl, n-undecyl, n-dodecyl, etc. As R 3 Preferably, it is a straight-chain or branched C7-C9 hydrocarbon group.

[0114] In equation (4) above, R 4 It represents phenyl or benzyl, preferably phenyl. In the above formula (4), n2 represents 1 or 2, preferably 2.

[0115] In equation (5) above, R 5 It represents a hydrogen atom or a methyl group, preferably a hydrogen atom.

[0116] In equation (6) above, R 6 This refers to a C1-C4 hydrocarbon group, which can be either straight-chain or branched. Examples of C1-C4 hydrocarbon groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl. As R... 6 Preferably, it is a C3-C4 hydrocarbon group that is straight-chain or branched. In addition, in the above formula (6), n3 represents 1 or 2, preferably 2.

[0117] Examples of compounds a mentioned above 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 compounds a are highly hydrophobic compounds, possessing the property of readily orienting on the ink surface after the ink has settled on the printing medium. It is believed that this property reduces the surface tension of the ink, promotes the wetting and spreading of the ink on the printing medium, and thus exhibits excellent wetting properties.

[0118] Examples of the compound b described above 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 exhibits the property of readily orienting at the interface between the ink and the printing medium after the ink has settled onto the printing medium. It is believed that this property reduces the interfacial tension at the interface between the ink and the printing medium, promotes the wetting and spreading of the ink on the printing medium, and thus exhibits excellent wetting properties.

[0119] Examples of the compound c mentioned above 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, diethylene glycol monobutyl ether, etc., preferably 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. Compound c is a compound that achieves a balance between hydrophilicity and hydrophobicity, and is soluble in water, compounds a, b, and d contained in the ink. It is believed that due to this property, even in water-based inks where water constitutes a large portion of the total ink mass, compounds a, b, and d can be stably dissolved, preventing phase separation of the ink.

[0120] Examples of compounds d mentioned above include 1,2-heptadecyl alcohol and 1,2-octanediol. These compounds d are all highly hydrophobic and possess the property of readily orienting themselves on both the ink surface and at the ink-printing medium interface after the ink has settled onto the printing medium. It is believed that this property reduces the surface tension of the ink and also reduces the interfacial tension at the ink-printing medium interface, promoting the wetting and spreading of the ink on the printing medium, thereby exhibiting excellent wetting properties.

[0121] The aforementioned condition (A) is as follows: the organic compound contains compounds a to c. When the total content of compound a in 100 parts by mass of the ink according to this embodiment is set as (a) parts by mass, the total content of compound b is set as (b) parts by mass, and the total content of compound c is set as (c) parts by mass, the relationship (a) ≤ (c) and 0.1 ≤ (c) / (b) ≤ 50 is satisfied. When the organic compound satisfies the aforementioned condition (A), the value of (c) / (b) is preferably greater than 1 and less than 50, more preferably greater than 1 and less than 50, further preferably 5 to 30, especially preferably 6 to 20, and extremely preferably 7 to 19. When the organic compound satisfies the aforementioned condition (A), 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, further preferably 0.1 to 5 parts by mass, and especially preferably 0.2 to 1.0 parts by mass. Furthermore, the total content of compound b in 100 parts by weight of the ink according to this embodiment is preferably 0.05 to 10 parts by weight, more preferably 0.05 to 8 parts by weight, and even more preferably 0.05 to 6 parts by weight. Additionally, the total content of compound c in 100 parts by weight of the ink according to this embodiment is preferably 1 to 20 parts by weight, more preferably 1 to 15 parts by weight, and even more preferably 1 to 10 parts by weight.

[0122] By ensuring that the organic compound meets the above condition (A), it is possible to achieve both drying properties and wettability to both non-absorbent and non-absorbent media while ensuring ink compatibility. In particular, by setting the value of (c) / (b) above to 0.1 to 50, there is a tendency for compound b to dissolve stably in the ink without phase separation, and for the ink to exhibit sufficient wettability.

[0123] The aforementioned condition (B) is as follows: the organic compound contains compounds a to c. When the total content of compound a in 100 parts by mass of the ink according to this embodiment is set as (a) parts by mass, and the total content of compound c is set as (c) parts by mass, (a) is greater than 0.4, and the relationship (a) > (c) is satisfied. When the organic compound satisfies the aforementioned condition (B), the total content of compound a in 100 parts by mass of the ink according to this embodiment is preferably greater than 0.4 parts by mass and less than 4 parts by mass, more preferably 0.5 to 4 parts by mass, and even more preferably 0.5 to 2 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 5 parts by mass, more preferably 0.05 to 3 parts by mass, and even more preferably 0.05 to 2 parts by mass. Furthermore, the total content of compound c in 100 parts by mass of the ink according to this embodiment is preferably 0.1 to 3.5 parts by mass, more preferably 0.1 to 3 parts by mass, and even more preferably 0.1 to 2 parts by mass.

[0124] By ensuring that the organic compound meets the above condition (B), it is possible to achieve both drying properties and wettability to both non-absorbent and non-absorbent media while maintaining ink compatibility. In particular, by setting (a) to 0.4 or less, there is a tendency for compound a to dissolve stably in the ink without phase separation, and for the ink to exhibit sufficient drying properties.

[0125] The aforementioned condition (C) is as follows: the organic compound contains 1,5-pentanediol and the aforementioned compound d. When the content of 1,5-pentanediol in 100 parts by mass of the ink according to this embodiment is set as (e) parts by mass, and the total content of compound d is set as (d) parts by mass, (d) is greater than 0.3, and satisfies the relationship 1 < (e) / (d) ≤ 50. When the organic compound satisfies the aforementioned condition (C), the value of (e) / (d) is preferably 2 to 30, more preferably 5 to 20. When the organic compound satisfies the aforementioned condition (C), the content of 1,5-pentanediol in 100 parts by mass of the ink according to this embodiment is preferably greater than 0.3 parts by mass and less than 20 parts by mass, more preferably 0.5 to 10 parts by mass, and even more preferably 1 to 7 parts by mass. In addition, the total content of the aforementioned compound d in 100 parts by mass of the ink according to this embodiment is preferably 0.3 to 5 parts by mass, more preferably 0.3 to 3 parts by mass, and even more preferably 0.4 to 2 parts by mass.

[0126] By ensuring the organic compound meets the aforementioned condition (C), it is possible to achieve both drying properties and wettability to both non-absorbent and non-absorbent media while maintaining ink compatibility. Specifically, by setting the value of (e) / (d) above to greater than 1, compound d tends to dissolve stably in the ink without phase separation; and by setting the value of (e) / (d) below 50, the ink tends to exhibit sufficient wettability. Furthermore, by setting (d) above 0.3, the ink tends to exhibit sufficient wettability; and by setting (d) below 4, compound d tends to dissolve stably in the ink without phase separation, and the ink exhibits sufficient drying properties.

[0127] [water]

[0128] The preferred water is water with low content of impurities such as metal ions, i.e., ion-exchanged water, distilled water, etc.

[0129] The water content is preferably 50-90% by mass, more preferably 60-90% by mass, and even more preferably 70-90% by mass, relative to the total mass of the ink involved in this embodiment.

[0130] [Other ingredients]

[0131] The ink described in this embodiment may contain dispersants, organic solvents, surfactants, mildew inhibitors, preservatives, pH adjusters, chelating agents, rust inhibitors, defoamers, water-soluble ultraviolet absorbers, antioxidants, resin emulsions, and other ink modifiers as needed. The content of each ink modifier can be arbitrarily set according to the intended use of the ink.

[0132] (Dispersant)

[0133] Examples of dispersants include copolymers composed of at least two monomers selected from the following (preferably at least one of which is hydrophilic): styrene and its derivatives; vinylnaphthalene and its derivatives; aliphatic alcohol esters of α,β-olefinically unsaturated carboxylic acids; (meth)acrylic acid and its derivatives; maleic acid and its derivatives; itaconic acid and its derivatives; fumaric acid and its derivatives; vinyl acetate, vinyl alcohol, vinylpyrrolidone, acrylamide, and their derivatives; etc. Examples of hydrophilic monomers include acrylic acid, methacrylic acid, and other monomers that retain a carboxyl group after polymerization.

[0134] Examples of such copolymers include styrene-(meth)acrylic acid copolymers, styrene-(meth)acrylic acid-(meth)acrylate copolymers, (meth)acrylate-(meth)acrylic acid copolymers, polyethylene glycol (meth)acrylate-(meth)acrylic acid copolymers, and styrene-maleic acid copolymers. Among these, styrene-(meth)acrylic acid copolymers, styrene-(meth)acrylic acid-(meth)acrylate copolymers, (meth)acrylate-(meth)acrylic acid copolymers, and polyethylene glycol (meth)acrylate-(meth)acrylic acid copolymers are preferred; styrene-(meth)acrylic acid copolymers, styrene-(meth)acrylic acid-(meth)acrylate copolymers, and (meth)acrylate-(meth)acrylic acid copolymers are more preferred; (meth)acrylate-(meth)acrylic acid copolymers are even more preferred; and methacrylate-methacrylic acid copolymers are particularly preferred. Examples of copolymer types include block copolymers, random copolymers, and graft copolymers. These copolymers may also be in the form of salts.

[0135] It should be noted that in this specification, the term "(meth)propylene-" is used to include both "propylene-" and "methpropylene-". The same applies to "(meth)acrylate", etc.

[0136] Dispersants can be synthesized or obtained in the form of commercially available products.

[0137] As a dispersant obtained through synthesis, for example, the AB block polymer disclosed in International Publication No. 2013 / 115071 can be cited. 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)acrylates, preferably at least one monomer selected from methacrylic acid and n-butyl methacrylate, more preferably both monomers. Furthermore, 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, preferably benzyl methacrylate. As specific examples of AB block polymers, the block copolymers disclosed in Synthesis Examples 3 to 8 of International Publication No. 2013 / 115071 can be cited.

[0138] Examples of dispersants available commercially, such as Joncyrl 62, 67, 68, 678, 687 (styrene-acrylic copolymers manufactured by BASF); AronAC-10SL (polyacrylic acid manufactured by Toa Synthetic Co., Ltd.); BYKJET 9151, 9152, 9170, 9171 (wetting and dispersing agents manufactured by BYK Corporation); and so on.

[0139] The mass-average molecular weight (MW) of the dispersant is preferably 3,000 to 50,000, more preferably 7,000 to 25,000. The mass-average molecular weight of the dispersant can be determined by gel permeation chromatography (GPC). Specifically, an HLC-8320GPC (manufactured by TOSOH Corporation) can be used as the GPC apparatus, two TSK gel Super MultIpore HZ-H (manufactured by TOSOH Corporation, inner diameter 4.6 mm × 15 cm) columns can be used, tetrahydrofuran can be used as the eluent, and TSK Standard (manufactured by TOSOH Corporation) can be used as the standard sample for determination.

[0140] The acid value of the dispersant is preferably 50-300 mg KOH / g, more preferably 80-275 mg KOH / g, and even more preferably 80-250 mg KOH / g.

[0141] The dispersant can be used in a state where it is mixed with the colorant. Alternatively, it can be used in a state where part or all of the surface of the colorant is coated with the dispersant. Or, both states can be used in combination.

[0142] 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.

[0143] (Organic solvents)

[0144] Examples of organic solvents include, for example, C1-C6 alkanols such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol, and tert-butanol; carboxylic amides such as N,N-dimethylformamide and N,N-dimethylacetamide; lactams such as 2-pyrrolidone, N-methyl-2-pyrrolidone, and N-methylpyrrolidone-2-one; and 1,3-dimethylimidazolidine-2-one or 1,3-dimethylhexahydropyrimidine. Cyclic ureas such as 2-ketones; ketones, ketols, or carbonates such as acetone, 2-methyl-2-hydroxypentane-4-one, and ethylene carbonate; cyclic ethers such as tetrahydrofuran and dioxane; ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, triethylene glycol, tetraethylene glycol, dipropylene glycol, polyethylene glycol (preferably polyethylene glycol with a molecular weight of 400, 800, 1540, or higher), and polypropylene glycol. Mono- or oligomeric alkylene glycols or thioglycols with C2-C6 alkylene units, such as glycols, thiodiethylene glycol, and dithiodiethylene glycol; C3-C9 polyols (triols) such as glycerol, diglycerol, hexane-1,2,6-triol, and trimethylolpropane; ethylene glycol monoallyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, propylene glycol monopropyl ether, and propylene glycol monobutyl ether. Dipropylene glycol monopropyl ether, dipropylene glycol monomethyl ether, and other glycol ethers (preferably C7-C10 triethylene glycol ethers, or C4-C13 mono, di, or tripropylene glycol ethers); 1,2-hexanediol, 1,6-hexanediol, 2-methyl-2,4-pentanediol, and other C6-C9 alkane diols (excluding compounds contained in formulas (1) and (3) above); γ-butyrolactone; dimethyl sulfoxide; etc.

[0145] (surfactant)

[0146] Examples of surfactants include anionic, nonionic, silicone, and fluorinated surfactants. Among these, surfactants selected from silicone and fluorinated surfactants are preferred, and from the viewpoint of safety to organisms and the environment, silicone surfactants are more preferred.

[0147] Examples of anionic surfactants include alkyl sulfonyl carboxylates, α-olefin sulfonates, polyoxyethylene alkyl ether acetates, polyoxyethylene alkyl ether sulfates, N-acyl amino acids or their salts, N-acylmethyl taurate, alkyl sulfate polyoxyalkyl ether sulfates, alkyl sulfate polyoxyethylene alkyl ether phosphates, rosin soap, castor oil sulfates, lauryl sulfates, alkylphenol phosphates, alkyl phosphates, alkyl aryl sulfonates, diethyl sulfosuccinate, diethylhexyl sulfosuccinate, and dioctyl sulfosuccinate.

[0148] Examples of 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 styrene phenyl ether (e.g., EMULGEN A-60, A-90, A-500 manufactured by Kao Corporation); ester-based surfactants such as polyoxyethylene oleate, polyoxyethylene distearate, sorbitan laurate, sorbitan monostearate, sorbitan monooleate, sorbitan sesquioleate, polyoxyethylene monooleate, and polyoxyethylene stearate; and alkynyl diol (or alkynyl alcohol)-based surfactants such as 2,4,7,9-tetramethyl-5-decyn-4,7-diol, 3,6-dimethyl-4-octyyn-3,6-diol, and 3,5-dimethyl-1-hexyn-3-ol (e.g., Evonik Japan). SURFYNOL 104, 104PG50, 82, 420, 440, 465, 485; OLFINE STG; etc., manufactured by Ltd.; polydiol ethers; etc.

[0149] Examples of organosilicon surfactants include, for example, polyether-modified siloxanes and polyether-modified polydimethylsiloxanes. Examples include Dynol 960 and 980 manufactured by Air Products; Silface SAG001, SAG002, SAG003, SAG005, SAG503A, SAG008, SAG009, and SAG010 manufactured by Nissin Chemical Industries, Ltd.; BYK-345, 347, 348, 349, 3450 (alias: BYKLP X 23289), 3451 (alias: BYKLPX 23347), 3455, LP-X23288, and LP G20726 manufactured by BYK Corporation; TEGO Twin 4000, TEG O WetKL 245, 250, 260, 265, 270, and 280 manufactured by Evonic Tego Chemie; and so on.

[0150] Examples of fluorinated surfactants include, for example, perfluoroalkyl sulfonic acid compounds, perfluoroalkyl carboxylic acid compounds, perfluoroalkyl phosphate compounds, perfluoroalkyl ethylene oxide adducts, and polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups in the side chain. Commercially available examples include, for instance, Capstone FS-30 and FS-31 manufactured by Chemours.

[0151] (Anti-mold agent)

[0152] Examples of antifungal agents include sodium dehydroacetate, sodium benzoate, sodium pyrithione sodium-1-oxide, ethyl p-hydroxybenzoate, 1,2-benzisothiazolin-3-one and its salts.

[0153] (preservative)

[0154] Examples of preservatives include compounds of the following types: organosulfur, organonitrogen-sulfur, organohalogen, halogenated aryl sulfone, iodopropynyl, halogenated alkyl sulfone, nitrile, pyridine, 8-hydroxyquinoline, benzothiazole, isothiazolinyl, dithiol, pyridine oxide, nitrobenzene, organotin, phenol, quaternary ammonium salt, triazine, thiazine, acetanilide, adamantane, dithiocarbamate, indanone bromide, benzyl bromoacetate, and inorganic salts. Specific examples of organohalogen compounds include sodium pentachlorophenate. Specific examples of pyridine oxide compounds include sodium 2-mercaptopyridine-1-oxide. Specific examples of isothiazolinone compounds include 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 anhydrous sodium acetate, sodium sorbate, sodium benzoate, and Proxel GXL(S), Proxel LV, and Proxel XL-2(S) manufactured by Arch Chemicals.

[0155] (pH adjuster)

[0156] Examples of pH adjusters include, for example, alkanolamines such as diethanolamine, triethanolamine, and N-methyldiethanolamine; hydroxides of alkali metals such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; ammonium hydroxide (ammonia); carbonates of alkali metals such as lithium carbonate, sodium carbonate, sodium bicarbonate, and potassium carbonate; alkali metal salts of organic acids such as sodium silicate and potassium acetate; inorganic bases such as disodium phosphate; and so on.

[0157] (chelating agent)

[0158] Examples of chelating agents include disodium ethylenediaminetetraacetate, sodium hypotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, and sodium uracil diacetate.

[0159] (Rust inhibitor)

[0160] Examples of rust inhibitors include acidic sulfites, sodium thiosulfate, ammonium mercaptoacetate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite.

[0161] (Defoamer)

[0162] Examples of defoamers include compounds based on organosilicon, silica-mineral oil, olefins, and acetylene. Commercially available defoamers include, for example, SURFYNOL DF37, DF58, DF110D, DF220, MD-20, and OLFINE SK-14 manufactured by Shin-Etsu Chemical Co., Ltd.

[0163] (Water-soluble UV absorber)

[0164] Examples of water-soluble ultraviolet absorbers include sulfonated benzophenone compounds, benzotriazole compounds, salicylic acid compounds, cinnamic acid compounds, and triazine compounds.

[0165] (Antioxidants)

[0166] As antioxidants, various organic and metal complex-based anti-fading agents can be used, for example. Examples of organic anti-fading agents include hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromophores, alkoxyanilines, and heterocyclic compounds.

[0167] (Resin Emulsion)

[0168] The ink according to this embodiment may contain a resin emulsion to improve the ink's fixing properties on the printing medium. By containing a resin emulsion in the ink according to this embodiment, there is a tendency to improve the image adhesion, such as water resistance, rub resistance, and alcohol resistance, of the image printed onto the printing medium. As the resin emulsion, at least one selected from polymer emulsions and wax emulsions is preferred.

[0169] Examples of polymer emulsions include those containing polymers of various types, such as urethane, polyester, acrylic, vinyl acetate, vinyl chloride, styrene-acrylic, acrylic-silicone, and styrene-butadiene. Among these, emulsions containing polymers selected from urethane, acrylic, and styrene-butadiene types are preferred.

[0170] Commercially available polymer emulsions include, for example, SUPER FLEX 420, 470, and 890 (all of which are urethane resin emulsions manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.); HYDRAN HW-350, HW-178, HW-163, HW-171, AP-20, AP-30, WLS-201, and WLS-210 (all of which are urethane resin emulsions manufactured by DIC Co., Ltd.); 0569, 0850Z, and 2108 (all of which are styrene-butadiene resin emulsions manufactured by JSR Co., Ltd.); AE980, AE981A, AE982, AE986B, and AE104 (all of which are acrylic resin emulsions manufactured by E-TEC Co., Ltd.); and NeoCryl A-1105, A-1125, and A-1127 (all of which are DSM Coating). Acrylic resin emulsion manufactured by Resin; NeoCryl A-655 (styrene-acrylic resin emulsion manufactured by DSM Coating Resin); etc.

[0171] As a wax emulsion, an emulsion obtained by dispersing natural or synthetic wax in an aqueous medium can be used.

[0172] Natural wax emulsions include, for example, petroleum-based waxes such as paraffin wax and microcrystalline wax; lignite-based waxes such as lignite wax; plant-based waxes such as carnauba wax and candelilla wax; and animal and plant-based waxes such as beeswax and lanolin.

[0173] Examples of synthetic wax emulsions include emulsions of polyalkylene wax (preferably polyC2-C4 alkylene wax), oxidized polyalkylene wax (preferably oxidized polyC2-C4 alkylene wax), and paraffin wax. Among these, emulsions of waxes selected from polyethylene wax, polypropylene wax, oxidized polyethylene wax, oxidized polypropylene wax, and paraffin wax are preferred.

[0174] To prevent inkjet head clogging, the average particle size of the wax is preferably 50 nm to 5 μm, more preferably 100 nm to 1 μm.

[0175] Commercially available wax emulsions include, for example, CERAFLOUR 925, 929, 950, 991, AQUACER 498, 515, 526, 531, 537, 539, 552, 1547, AQUAMAT 208, 263, 272; MINERPOL 221 (all manufactured by BYK); Mitsui Hi-WAX NL100, NL200, NL500, 4202E, 1105A, 2203A, NP550, NP055, NP505 (all manufactured by Mitsui Chemicals Co., Ltd.); KUE-100, 11 (all manufactured by Sanyo Chemical Industry Co., Ltd.); HYTEC P-5300, E-6500, 9015, 6400 (all manufactured by Toho Chemical Industry Co., Ltd.); and so on.

[0176] In the case of the ink according to this embodiment containing a resin emulsion, the content of the resin emulsion, based on its solid components, is preferably 1 to 20% by mass, more preferably 3 to 15% by mass. By making the content of the resin emulsion, based on its solid components, more than 1% by mass, there is a tendency to exhibit good fixing properties for printing media. In addition, by making the content of the resin emulsion, based on its solid components, less than 20% by mass, there is a tendency to improve the ink's ejectibility and storage stability.

[0177] [Ink preparation methods, etc.]

[0178] There are no particular limitations on the method for preparing the ink according to this embodiment, and known preparation methods can be used. As an example, for instance, the following method can be used: preparing a dispersion containing a colorant and a dispersant, adding water, organic compounds such as compounds a to c, and an ink modifier to the dispersion, and mixing them.

[0179] Examples of methods for preparing dispersions include phase inversion emulsification, acid precipitation, interfacial polymerization, in-situ polymerization, liquid-based solidification coating, coagulation (phase separation), liquid-based drying, melt dispersion cooling, gas suspension coating, and spray drying. Among these, phase inversion emulsification, acid precipitation, and interfacial polymerization are preferred, with phase inversion emulsification being more preferred.

[0180] In the case of preparing a dispersion using a 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 colorant is added to the obtained emulsion, and dispersion treatment is performed. From the liquid obtained as described above, the organic solvent and a portion of water are removed by distillation under reduced pressure, thereby obtaining the desired dispersion.

[0181] Dispersion processing can be performed using sand mills (bead mills), roller mills, ball mills, paint shakers, ultrasonic dispersers, microfluidic homogenizers, etc. For example, when using a sand mill, beads with a particle size of approximately 0.01–1 mm can be used, and the bead filling rate can be appropriately set for dispersion processing. The dispersion obtained as described above can be subjected to operations such as filtration and centrifugation to ensure that the particle size contained in the dispersion is uniform. If foaming occurs during the preparation of the dispersion, a trace amount of a known defoamer such as an organosilicon-based or acetylenic diol-based agent can be added.

[0182] For the inks involved in this embodiment, it is preferable to have a low content of inorganic impurities such as chlorides of metal cations (e.g., sodium chloride) and sulfates of metals (e.g., sodium sulfate). Such inorganic impurities are often found in commercially available colorants. Ideally, the content of inorganic impurities should be about 1% by mass or less relative to the total mass of the colorant, with the lower limit being below the detection limit of the analytical device, i.e., 0% by mass. Methods for obtaining colorants with low inorganic impurity content include, for example, using a reverse osmosis membrane; suspending and stirring the solid colorant in a mixed solvent of C1-C4 alcohols such as methanol and water, filtering and separating the colorant, and then drying it; using an ion exchange resin to exchange and adsorb inorganic impurities; and so on.

[0183] The ink involved in this embodiment is preferably pre-microfiltered. Microfiltration can be performed using membrane filters, glass filter paper, etc. The pore size of the filter or the like used for microfiltration is typically 0.5–20 μm, preferably 0.5–10 μm.

[0184] The ink described in this embodiment exhibits excellent storage stability, redispersibility, color development, and chroma. Furthermore, printed images recorded using the ink described in this embodiment demonstrate excellent lightfastness, heat resistance, and resistance to oxidizing gases (e.g., ozone gas resistance). Additionally, the ink described in this embodiment exhibits minimal uneven coating during image formation and excellent image formation properties.

[0185] <Ink Group, Ink Media Group>

[0186] The ink group involved in this embodiment includes the ink involved in this embodiment as described above, and other inks different from the ink involved in this embodiment. As for the other inks, there are no particular limitations as long as they are inks that constitute different structures from the ink involved in this embodiment, but inks with different hues from the ink involved in this embodiment are preferred.

[0187] In addition, the ink group involved in this embodiment includes the ink or ink group involved in this embodiment described above, and the printing medium.

[0188] There are no particular limitations on the printing medium, but a printing medium with poor ink absorption or non-absorbent ink is preferred, and a printing medium with non-absorbent ink is more preferred. Examples of printing media with poor ink absorption include ordinary paper without an ink-receiving layer, media used in gravure printing, offset printing, art paper, coated paper, matte paper, and cast-coated paper. Examples of printing media with non-absorbent ink include PET (polyethylene terephthalate) film, PP (polypropylene) film, vinyl chloride sheet, glass, and rubber.

[0189] <Inkjet Recording Methods>

[0190] The inkjet recording method described in this embodiment is a method for ejecting ink droplets from an inkjet head and recording them on a printing medium. There are no particular limitations on the ink nozzles or the like used in the inkjet printer for ejecting ink; they can be appropriately selected depending on the purpose.

[0191] The inkjet recording method involved in this embodiment also includes the following methods: a method of improving image quality by ejecting a large quantity of ink with a low content of colorant in the ink in a small volume; a method of improving image quality by using multiple inks with substantially the same hue but different contents of colorant in the ink; a method of improving the fixing property of colorant onto the printing medium by using colorless transparent ink and ink containing colorant together; and so on.

[0192] As an inkjet recording method, known methods can be employed. Examples include charge control, on-demand inkjet (also known as pressure pulse), acoustic inkjet, and thermal inkjet. Furthermore, the inkjet recording method can be either multi-pass or single-pass (1-pass printing). In industrial inkjet printers, single-pass printing using linear printheads is preferred for achieving high printing speeds. Additionally, in recent years, circulating printheads with mechanisms that prevent ink drying near the nozzles by circulating ink to the nozzle area are being actively developed. The ink described in this embodiment can also be suitably used in such circulating printheads.

[0193] When recording onto printing media, for example, a container containing ink (ink can) is filled into a designated position on an inkjet printer, and the above-described printing method is used to record onto the printing media. It should be noted that by filling containers containing inks of various colors into designated positions on an inkjet printer and using the above-described printing method to record onto the printing media, full-color printing can also be achieved.

[0194] It should be noted that when using printing media without an ink-receiving layer, it is also preferable to perform a surface modification treatment. 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. Therefore, it is preferable to perform the surface modification treatment step and the inkjet recording step consecutively, and more preferably to perform the surface modification treatment step just before the inkjet recording step.

[0195] Regarding all the above-mentioned matters, the combination of preferred items is more preferred, and the combination of more preferred items is even more preferred. The same applies to combinations of preferred items and more preferred items, and combinations of more preferred items and even more preferred items.

[0196] Example

[0197] The present invention will be described in more detail below through embodiments, but the present invention is not limited to the embodiments.

[0198] In the embodiments, unless otherwise specified, "parts" refers to parts by mass and "%" refers to percentage by mass. Furthermore, when it is necessary to quantify the solid pigment component in the dispersion, it is determined by the dry weight method using MS-70 manufactured by A&D Co., Ltd. The solid pigment component is a converted value obtained by calculating the solid pigment component solely from the total amount of solid components.

[0199] <Preparation Example 1: Preparation of Cyan Dispersion 1>

[0200] Additional experiments were conducted on Synthesis Example 3 of International Publication No. 2013 / 115071, thereby obtaining a block copolymer. The obtained block copolymer had an acid value of 105 mg KOH / g and a mass-average molecular weight of 25,000. The obtained block copolymer (6 parts) was dissolved in 2-butanone (30 parts) to prepare a homogeneous solution. A liquid obtained by dissolving 28% ammonia solution (0.68 parts) in deionized water (53 parts) was added to this liquid, and the mixture was stirred for 1 hour to obtain an emulsion. CI Pigment Blue 15:4 (manufactured by Dainishi Chemical Industry Co., Ltd., CHRO MOFINE BLUE 4851) (20 parts) was added to this emulsion, and the mixture was dispersed in a sand mill at 1500 rpm for 15 hours. Add 100 parts of ion-exchanged water to the obtained liquid, filter to remove the dispersing beads, and then use an evaporator to remove 2-butanone and a portion of the water by distillation under reduced pressure to obtain a cyan dispersion 1 with a pigment solid content of 12%.

[0201] <Preparation Example 2: Preparation of Cyan Dispersion 2>

[0202] BYKJET 9151 (manufactured by BYK Corporation) (8 parts) was dissolved in ion-exchanged water (72 parts) and stirred for 1 hour. Chromofine Blue 15:4 (manufactured by Daihisei Kagaku Co., Ltd., Chromofine Blue 4851) (20 parts) was added to the resulting solution, and the mixture was dispersed in a sand mill 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, thus obtaining a cyan dispersion 2 with a pigment solid content of 11.6%.

[0203] <Preparation Example 3: Preparation of Cyan Dispersion 3>

[0204] Joncyrl 68 (manufactured by BASF, mass average molecular weight: 13000) (9 parts) and triethanolamine (6 parts) were dissolved in deionized water (75 parts) and stirred for 1 hour. CI Pigment Blue 15:4 (manufactured by Dainishi Chemical Co., Ltd., Chrom ofine Blue 4851) (30 parts) was added to the resulting solution, and the mixture was dispersed in a sand mill 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, thus obtaining a cyan dispersion 3 with a pigment solid content of 18.7%.

[0205] <Examples 1-27 and Comparative Examples 1-12>

[0206] The cyan dispersions 1-3 obtained in Preparation Examples 1-3 were mixed with the components listed in Tables 1-3 below, and then filtered using a membrane filter with a pore size of 3 μm to obtain the inks of Examples 1-27 and Comparative Examples 1-12. The ink content was adjusted so that the total mass of the ink contained 3.5% of the colorant. The values ​​in the component columns of Tables 1-3 indicate the amount (parts) of that component used; "-" indicates that the component was not used.

[0207] Details of the resin emulsions in Tables 1-3 are as follows.

[0208] A-1127: NeoCryl A-1127 (acrylic resin emulsion, manufactured by DSM Coating Resin, solid content 44.0%)

[0209] P5300: HYTEC P-5300 (polypropylene wax emulsion, manufactured by Toho Chemical Industry Co., Ltd., solid content 30.5%)

[0210] AQ-515: AQUACER 515 (polyethylene wax emulsion, manufactured by BYK, solid content 34.6%)

[0211] [Table 1]

[0212]

[0213] [Table 2]

[0214]

[0215] [Table 3]

[0216]

[0217] <Evaluation>

[0218] [Compatibility Assessment]

[0219] A mixture containing all materials except the cyan dispersion from the compositions of Examples 1-27 and Comparative Examples 1-12 was prepared, and the compatibility of the mixture was evaluated. The results are shown in Tables 4-6 below. If the compatibility is insufficient, the uniformity of the ink will decrease, and the wetting effect cannot be fully utilized. Therefore, in practical applications, the following evaluation criterion A is preferred.

[0220] -Compatibility Evaluation Criteria-

[0221] A: A state of uniform and complete mixing

[0222] B: A state in which there are no oil droplets on the liquid surface, but the liquid is suspended and not completely dissolved.

[0223] C: The mixture contains oil droplets that are not completely dissolved and are floating on the surface.

[0224] D: The components in the mixture are separated and completely undissolved.

[0225] [Contact Angle Measurement]

[0226] Using PET film (manufactured by Toyobo Co., Ltd., E5102) as the substrate, the contact angles between the inks obtained above and the PET film were measured, and evaluated according to the following evaluation criteria. Specifically, a DM-501Hi (manufactured by Kyowa Interface Science Co., Ltd.) was used as a contact angle meter, with a droplet volume of 2 μL, and the contact angle was measured 10 seconds after the ink fell at 25°C. The results are shown in Tables 4 to 6 below. The lower the contact angle value, the better the ink wets and spreads on the PET film; therefore, an evaluation criterion of B or higher is preferred in practical applications. In Table 6 below, "-" indicates that the ink cannot be evaluated as an ink because the ink materials are not mixed.

[0227] -Contact Angle Evaluation Criteria-

[0228] A: Contact angle ≤15°

[0229] B: 15° < contact angle ≤ 20°

[0230] C: 20° < contact angle ≤ 30°

[0231] D: 30° < Contact Angle

[0232] [Desiccation Evaluation]

[0233] Using PET film (manufactured by Toyobo Co., Ltd., E5102) as the substrate, 20 μL of each of the inks obtained in this paper were added dropwise using a micropipette and allowed to stand at 70°C. Every 5 minutes, the film was removed, and another new PET film was gently overlapped on top of the PET film containing the ink droplets. After standing for 10 seconds, the film was peeled off. At this point, it was confirmed whether the ink had transferred to the overlapping PET film. The drying time was defined as the time at which no further transfer occurred, and the film was evaluated according to the following evaluation criteria. The results are shown in Tables 4-6 below. In practical applications, an evaluation criterion of B or higher is preferred. In Table 6 below, "-" indicates that the ink cannot be evaluated as ink because the ink materials are not mixed.

[0234] -Dryness Evaluation Criteria-

[0235] A: Drying time ≤ 15 minutes

[0236] B: 15 minutes < Drying time ≤ 30 minutes

[0237] C: 30 minutes < drying time ≤ 60 minutes

[0238] D: 60 minutes <drying time

[0239] [Table 4]

[0240]

[0241] [Table 5]

[0242]

[0243] [Table 6]

[0244]

[0245] As shown in Tables 4-6 above, compared with the inks of Comparative Examples 1-12, the inks of Examples 1-27 exhibit excellent wettability on PET films, and are also equivalent or better in terms of compatibility and drying properties. These results indicate that the inks of Examples 1-27 are excellent inks that combine compatibility, wettability, and drying properties.

Claims

1. An inkjet ink comprising a colorant, an organic compound other than the colorant, and water, wherein the organic compound satisfies either (A) or (B) below, and the colorant comprises at least one selected from pigments and disperse dyes. （A） The inkjet ink contains compounds a, b, and c. When the total content of compound a in 100 parts by mass of the inkjet ink is set as (a) parts by mass, the total content of compound b is set as (b) parts by mass, and the total content of compound c is set as (c) parts by mass, the following relationships are satisfied: (a) ≤ (c) and 0.1 ≤ (c) / (b) ≤ 50. Compound a: selected from at least one of the compounds represented by formula (1) below and the compounds represented by formula (2) below; Compound b: selected from at least one compound represented by formula (3) below and formula (4) below; and Compound c: at least one compound selected from the group consisting of C4-C5 alkane diols, compounds represented by formula (5) below, and compounds represented by formula (6) below; （B） The inkjet ink contains compounds a, b, and c. When the total content of compound a in 100 parts by mass of the inkjet ink is defined as (a) parts by mass, and the total content of compound c is defined as (c) parts by mass, (a) is greater than 0.4, and the relationship (a) > (c) is satisfied. Compound a: selected from at least one of the compounds represented by formula (1) below and the compounds represented by formula (2) below; Compound b: selected from at least one compound represented by formula (3) below and formula (4) below; and Compound c: at least one compound selected from the group consisting of C4-C5 alkane diols, compounds represented by formula (5) below, and compounds represented by formula (6) below; [Chemical Formula 1] In equation (1), R 1 Indicates a straight-chain or branched C5-C10 hydrocarbon group. [Chemical Formula 2] In equation (2), R 2 This indicates a straight-chain or branched C6-C7 hydrocarbon group, where n1 represents 1 or 2. [Chemical Formula 3] In equation (3), R 3 It represents a straight-chain C7-C12 hydrocarbon group. [Chemical Formula 4] In equation (4), R 4 n represents phenyl or benzyl, and n2 represents 1 or 2. [Chemical Formula 5] In equation (5), R 5 Indicates a hydrogen atom or a methyl group. [Chemical Formula 6] In equation (6), R 6 It represents a straight-chain or branched C1-C4 hydrocarbon group, and n3 represents 1 or 2.

2. The ink for inkjet printing as described in claim 1, wherein, The organic compound satisfies condition (A) and also satisfies the relationship 1 < (c) / (b) ≤ 50.

3. Inkjet recording method, among which, The ink droplets of the inkjet ink as described in claim 1 or 2 are ejected from the inkjet head and recorded on the printing medium.

4. The inkjet recording method as described in claim 3, wherein, The printing medium is a printing medium with ink that is difficult to absorb or has non-absorbent ink.

5. The inkjet recording method as described in claim 3 or 4, wherein, The inkjet head is a printhead equipped with a circulation mechanism.

6. An ink group comprising the inkjet ink as described in claim 1 or 2, and other inkjet inks different from the inkjet ink.

7. An ink media assembly comprising the inkjet ink as described in claim 1 or 2 or the ink assembly as described in claim 6, and a printing medium.

8. Printing media, of which, The inkjet ink of claim 1 or 2, or each inkjet ink of the ink group of claim 6, is attached.

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