Ink, inkjet printing method, and printing media

Abstract

To provide an ink that is excellent in wet spreading on ink non-absorptive or low-absorptive media, does not deteriorate blur between colors regardless of the storage period, and offers a very low level of granularity in printed images, an inkjet printing method using the ink, and printed media on which the ink is adhered.SOLUTION: An ink contains a water-insoluble coloring agent, a dispersant, a nonionic surfactant represented by the following formula (1) and having a HLB value of 5.0 to 13.0, and water. (In formula (1), R represents a C6-C20 linear or branched hydrocarbon group, EO represents an ethyleneoxy group, and PO represents a propyleneoxy group, with EO and PO arranged in any order. m is the number of ethyleneoxy groups, n represents the number of propyleneoxy groups, and m is 1 to 20 and n is 0 to 5.)SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an aqueous ink, an inkjet printing method using the ink, and a print medium having the ink adhered thereon.

Background Art

[0002] Among various color printing methods, a typical representative printing method using an inkjet printer is a method that generates small droplets of ink and causes the droplets to adhere to a print medium such as paper to perform printing. In recent years, demand for industrial applications has increased, and inks capable of printing on various print media are required.

[0003] Among print media, for non-ink-absorbing media and poorly ink-absorbing media (hereinafter sometimes referred to as "non-poorly ink-absorbing media"), inks with good wettability and spreading on the media are desired. This is because when wettability and spreading on the medium is good, the colorable area becomes larger when the same amount of ink droplets is used (in other words, the dot diameter of the ink becomes larger), so that the ink consumption can be reduced. However, non-poorly ink-absorbing media are media having poor ink absorbability. For this reason, ink is less likely to penetrate into the medium, and compared with ink-absorbing media, wettability and spreading of ink is poor, so the dot diameter of ink generally becomes smaller. For this reason, improvement thereof has been desired. Further, when performing color printing, an ink set consisting of a plurality of colors is used. When performing color printing using such an ink set, when the landing position of ink of a first color and the landing position of ink of a second color are adjacent to each other on a print medium, it is known that bleeding may occur between the first color and the second color. This "inter-color bleeding" is one of the factors that significantly degrade print quality. Therefore, elimination of this inter-color bleeding has been demanded, and ink sets for solving this problem have also been proposed. However, it has become clear that this problem of color bleeding involves even more complex factors. Specifically, in the initial stages of printing, it is possible to print using both the first and second color inks, both of which are recently manufactured (in other words, new). Therefore, by selecting and using an ink set that takes color bleeding into consideration, it is possible to produce high-quality prints without color bleeding. However, as printing continues, the consumption rate of each ink color will vary. Therefore, inks with high consumption rates will be replaced with new ink when they run out. On the other hand, inks with low consumption rates will continue to be used until the initial ink runs out (in other words, new and old inks will be used concurrently). As a result, there may be a difference of several months to a year in the storage period of inks with high and low consumption rates. When printing using inks with such different storage periods, even though there is no significant change in the storage stability of each ink itself (various physical properties such as ejection performance, average particle size, viscosity, and pH), color bleeding between colors may worsen, resulting in a decrease in print quality, and a solution to this problem is desired. Furthermore, in terms of print quality, there is a requirement for inks to have as little graininess as possible. Inks containing water-insoluble colorants are in a non-uniform state (not a solution, but a dispersion). When solid printing is performed on printing media with such non-uniform ink, the printed image may appear to have scattered "grains" of varying shades, resulting in an uneven image. Such printed images are evaluated as having "graininess" and are one of the factors that significantly degrade print quality. For this reason, there is a strong demand for inks that produce printed images with as little graininess as possible.

[0004] Patent documents 1 to 5 describe water-based inkjet inks and inkjet recording methods using them. [Patent Document 1] Japanese Patent Publication No. 2016-044188 [Patent Document 2] Japanese Patent Publication No. 2014-139004 [Patent Document 3] Japanese Patent Publication No. 2007-162006 [Patent Document 4] International Publication No. 2011 / 136000 [Patent Document 5] Japanese Patent Publication No. 2014-210876 [Overview of the project] [Problems that the invention aims to solve]

[0005] The objective is to provide an ink that spreads well on non-absorbent or poorly absorbent media, prevents worsening of color bleeding regardless of storage period, and enables the production of printed images with extremely low graininess; an inkjet printing method using this ink; and a printing media to which this ink is attached. [Means for solving the problem]

[0006] The inventors of the present invention conducted extensive research to solve the above-mentioned problems and, as a result, found that the above-mentioned problems can be solved by the inventions described in [1] to [9] below, and thus completed the present invention.

[0007] In other words, the present invention relates to the following [1] to [9]. [1] An ink containing a water-insoluble colorant, a dispersant, a nonionic surfactant represented by the following formula (1) with an HLB value of 5.0 to 13.0, and water.

[0008] [ka]

[0009] (In formula (1), R represents a C6-C20 straight-chain or branched-chain hydrocarbon group. EO represents an ethylene oxy group, and PO represents a propylene oxy group. The order of EO and PO is arbitrary. m represents the number of ethyleneoxy groups, and n represents the number of propyleneoxy groups. m ranges from 1 to 20, and n ranges from 0 to 5. Furthermore, the HLB value mentioned above is calculated as follows. [How to calculate HLB value] Dissolve 0.5 g of nonionic surfactant in 10 mL of ethanol to obtain a solution. Stir the obtained solution at 25°C, and add a 2% by mass aqueous phenol solution dropwise until the solution becomes cloudy, which is the endpoint. When the amount of 2% by mass aqueous phenol solution used to reach the endpoint is Q (mL), calculate the HLB value using the following formula (2).

[0010] [ka]

[0011] [2] Furthermore, the ink according to [1] above, comprising at least one selected from glycol ethers and C4-C12 alkanediols. [3] Furthermore, the ink described in [1] or [2] above, which contains a binder. [4] The ink according to [3] above, wherein the binder comprises at least one selected from wax and (meth)acrylic acid polymers. [5] The ink according to [4] above, wherein the wax is one or more selected from polyalkylene wax, oxidized polyalkylene wax, and paraffin wax. [6] The ink according to [4] or [5] above, wherein the wax is oxidized polyethylene wax. [7] The ink according to [4] above, wherein the (meth)acrylic acid polymer is a (meth)acrylic acid polymer composed of four types of monomers: C1-C4 alkyl methacrylate, C6-C10 alkyl acrylate, methacrylic acid, and allyl methacrylate. [8] An inkjet printing method, wherein printing is performed by ejecting droplets of the ink according to any one of the above [1] to [7] from an inkjet printer and allowing the droplets to adhere to a print medium. [9] A print medium having the ink according to any one of the above [1] to [7] adhered thereto.

Effects of the Invention

[0012] According to the present invention, there are provided: an ink that exhibits good wetting and spreading on non-ink-absorbent and poorly ink-absorbent media, does not cause deterioration of inter-color bleeding regardless of storage period, and enables provision of printed images with extremely low graininess; an inkjet printing method using the ink; and a print medium having the ink adhered thereto, which has a printed image with good wetting and spreading of the ink, no inter-color bleeding, and extremely low graininess.

Mode for Carrying Out the Invention

[0013] In the present specification, unless otherwise specified, both "parts" and "%", including those used in examples and the like, are described based on mass. In the present specification, for example, when a "unit" is described only for one limit of the upper and lower range such as "X~Y%", it means that the unit of the upper and lower limits of the range is the same, that is, it means "X%~Y%".

[0014] [Water-insoluble colorant] The colorant described above is not particularly limited as long as it is a water-insoluble colorant. For example, known pigments, disperse dyes, solvent dyes, and water-insoluble resins colored with colorants such as dyes and pigments can be used. In the present specification, a water-insoluble colorant means a colorant whose solubility in 1 liter of water at 25°C is usually 5 g or less, preferably 3 g or less, more preferably 1 g or less, still more preferably 0.5 g or less. The lower limit of solubility includes 0 g. Unless otherwise specified, "water-insoluble colorant" is hereinafter referred to as "colorant". Among the above colorants, pigments are preferred. Examples of pigments include inorganic pigments, organic pigments, and extender pigments.

[0015] Examples of inorganic pigments include carbon black, titanium dioxide, metal oxides, hydroxides, sulfides, ferrocyanides, and metal chlorides.

[0016] Preferred colorants for black ink include carbon blacks such as thermal black, acetylene black, oil furnace black, gas furnace black, lamp black, gas black, and channel black. Specific examples of carbon blacks include, for example, the Raven series from Columbia Carbon; the Monarch series, Regal series, and Mogul series from Cabot; the 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.

[0017] Examples of organic pigments include azo, diazo, phthalocyanine, quinacridone, isoindolinone, dioxazine, perylene, perinone, thioindigo, antholaquinone, and quinophthalone.

[0018] Specific examples of organic pigments include, for example, 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, 180, 185, 193, 199, 202, 213, etc.; CIPigment Red 5, 7, 12, 48, 48:1, 57, 88, 112, 122, 123, 146, 149, 150, 166, 168, 177, 178, 179, 184, 185, 202, 206, 20 Examples of pigments include red (7, 254, 255, 257, 260, 264, 272, etc.), blue (CIPigment Blue 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 22, 25, 60, 66, 80, etc.), violet (CIPigment Violet 19, 23, 29, 37, 38, 50, etc.), orange (CIPigment Orange 13, 16, 43, 68, 69, 71, 73, etc.), green (CIPigment Green 7, 36, 54, etc.), and black (CIPigment Black 1, etc.).

[0019] 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.

[0020] Examples of disperse dyes include well-known disperse dyes. Among these, dyes selected from CIDispers are preferred. Specific examples include, for instance, CID Dispers 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, etc.; CID Dispers Red 60, 73, 88, 91, 92, 111, 127, 131, 143, 145, 146, 152, 153, 154, 167, 179, 191, 192, 206, 221, 258, 283, etc.; CID Examples of disperse dyes include orange (CIDispers Orange 9, 25, 29, 30, 31, 32, 37, 38, 42, 44, 45, 53, 54, 55, 56, 61, 71, 73, 76, 80, 96, 97, etc.), violet (CIDispers Violet 25, 27, 28, 54, 57, 60, 73, 77, 79, 79:1, etc.), and blue (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, 368, etc.).

[0021] The content of the colorant relative to the total mass of the above ink is usually 1 to 30%, preferably 1 to 10%, and more preferably 2 to 7%. Furthermore, the average particle size of the colorant is typically 50 to 250 nm, preferably 60 to 200 nm. In this specification, average particle size refers to the average particle size measured using the laser light scattering method.

[0022] [Dispersant] The dispersant used is not particularly limited, and any known dispersant can be used. The dispersant is used to disperse water-insoluble colorants in the ink. Generally, polymer dispersants such as resins are used as dispersants. Examples of such resins include polymers derived from polyvinyl alcohol, cellulose derivatives, polyethylene oxide, polypropylene oxide, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, itaconic acid monoester, maleic acid, maleic acid monoester, fumaric acid, fumaric acid monoester, vinylsulfonic acid, sulfoethyl methacrylate, sulfopropyl methacrylate, ionic monomers such as α,β-unsaturated monomers of sulfonated vinylnaphthalene, styrene, styrene derivatives, vinylnaphthalene, vinylnaphthalene derivatives, aliphatic alcohol esters of α,β-ethylenically unsaturated carboxylic acids, acrylonitrile, vinylidene chloride, vinyl acetate, vinyl chloride, acrylamide, methacrylamide, hydroxyethyl methacrylate, hydroxypropyl methacrylate, glycidyl methacrylate, N-butoxymethylacrylamide, and the like.

[0023] The dispersants mentioned above include the same ones as those disclosed in International Publication No. 2013 / 115071, including preferred ones. The same applies to the method for producing the AB block polymer. One example of a dispersant (AB block polymer) disclosed in International Publication No. 2013 / 115071 is a polymer A in which the monomers constituting the polymer A are selected from (meth)acrylic acid and one or more monomers selected from linear or branched C4 alkyl (meth)acrylates, and the monomers constituting the polymer B are benzyl methacrylate and / or benzyl acrylate. In this specification, the terms "(meth)acrylic" and "(meth)acrylate" are used to include both "acrylic, methacrylic" and "acrylate, methacrylate," respectively. The monomers constituting block A are preferably one or more monomers selected from methacrylic acid and n-butyl methacrylate, and it is particularly preferable to use these two monomers in combination. The monomer constituting block B is preferably benzyl methacrylate. A specific example of this is the block copolymer disclosed in Synthesis Examples 3-8 of the aforementioned International Publication No. 2013 / 115071.

[0024] As a styrene-(meth)acrylic polymer, the Joncryl series manufactured by BASF is preferred.

[0025] The acid value of the dispersant is typically 90-200 mgKOH / g, preferably 100-150 mgKOH / g, and more preferably 100-120 mgKOH / g. The mass-average molecular weight of the dispersant is typically 10,000 to 60,000, preferably 10,000 to 40,000, more preferably 15,000 to 30,000, and even more preferably 20,000 to 25,000. The PDI (mass-average molecular weight / number-average molecular weight) of the dispersant is approximately 1.29 to 1.49. By setting the range as described above, good dispersibility and storage stability can be achieved. Examples of neutralizing agents include ammonia, alkali metal hydroxides, alkaline earth metal hydroxides, aliphatic amine compounds, and alkanolamine compounds. Ammonia and alkali metal hydroxides are preferred, with ammonia being particularly preferred. The amount of neutralizing agent used is not particularly limited. As a guideline, the degree of neutralization is usually 30-300%, more preferably 50-200%, with 100% neutralization being defined as neutralization with a theoretical equivalent amount of the acid value of the dispersant.

[0026] The above-mentioned dispersant can be used in a mixed state with a water-insoluble colorant. It can also be used by coating the surface of the water-insoluble colorant with the dispersant. Both of these can also be used in combination. In this specification, "coating" means both a state in which the entire surface of the water-insoluble colorant is covered with the dispersant, and a state in which a portion of the surface of the water-insoluble colorant is covered with the dispersant. When using a dispersant, the ratio of the total mass of the dispersant to the total mass of the water-insoluble colorant is usually 0.1 to 1.0, preferably 0.1 to 0.6, and more preferably 0.2 to 0.5.

[0027] [Nonionic surfactant] The above ink contains a nonionic surfactant represented by formula (1). The HLB value of the nonionic surfactant is typically 5.0 to 13.0, preferably 5.5 to 12.5, more preferably 6.0 to 12.0, even more preferably 6.0 to 11.4, and particularly preferably 6.3 to 11.1. The HLB value of the surfactant is calculated as described in the [Method for Calculating HLB Value] above, and the result is rounded to the first decimal place.

[0028] Among the nonionic surfactants represented by formula (1), those having a linear alkyl group as R include Newcol 2303 manufactured by Nippon Emulsifier Co., Ltd., and GENAPOLE P2564 and EP2584 manufactured by Clariant. Furthermore, commercially available products containing a branched alkyl group as R include Newcol NT-3 from Nippon Emulsifier Co., Ltd.; Lutensol XL40 and 70 from BASF; BYKDYNWET800N and LPX7113 from BIC Chemie; Softanol 50 and 70 from Nippon Shokubai Co., Ltd.; Newcol 2303 from Nippon Emulsifier Co., Ltd., which has no PO group and only an EO group; and Emulmin 40, 110, and 240 from Sanyo Chemical Industries, Ltd. Table 1 below shows a compound represented by formula (1) and an example of its HLB value. In Table 1 below, "HLB" refers to the HLB value, "BR" in the "Type of R" column means that R is a branched chain, and "ST" means that R is a straight chain.

[0029] [Table 1]

[0030] [Glycol ethers and C4-C12 alkanediols] The above ink contains at least one selected from glycol ethers and C4-C12 alkanediols. This tends to improve the wetting and drying of the ink on non-absorbent and poorly absorbent media. The total content of these in the total mass of the ink composition is usually 0.1 to 30%, preferably 0.2 to 20%, more preferably 0.5 to 10%, even more preferably 2 to 8%, and particularly preferably 4 to 6%.

[0031] The glycol ether is not particularly limited, but alkyl ethers of di or tri C2-C4 alkylene glycols are preferred, and monoalkyl ethers of di or tri C2-C4 alkylene glycols are more preferred. Examples of the C2-C4 alkylene glycol portion include ethylene glycol, propylene glycol, and butylene glycol. Of these, ethylene glycol and propylene glycol are preferred, and propylene glycol is more preferred. The range of carbon atoms in the alkyl ether portion is typically C1-C6, preferably C1-C5, more preferably C2-C4, even more preferably C3-C4, and particularly preferably C4. Specific examples include, for instance, 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, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monopropyl ether, and tripropylene glycol monobutyl ether. Among these, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, dipropylene glycol monopropyl ether, or dipropylene glycol monobutyl ether are preferred.

[0032] The above C4-C12 alkanediol is not particularly limited, but 1,2-(C4-C12)alkanediols are preferred, and 1,2-(C6-C8)alkanediols are more preferred. Alkanediols with a carbon atom or higher are generally considered to have poor water solubility. Specific examples include 1,2-heptanediol, 1,2-octanediol, 5-methyl-1,2-hexanediol, 4-methyl-1,2-hexanediol, and 4,4-dimethyl-1,2-pentanediol. Among these, 1,2-octanediol is preferred. Furthermore, alkanediols with a carbon atom of 6 or less are generally considered to be water-soluble. Specific examples include 1,2-hexanediol, 1,2-pentanediol, 1,2-butanediol, 4-methyl-1,2-pentanediol, and 3,3-dimethyl-1,2-butanediol. While all of these can be used, 1,2-hexanediol is preferred among them due to its lower odor.

[0033] [Ink preparation agent] The above ink may further contain ink preparations in addition to the components described above. Examples of ink preparations include binders, organic solvents, non-nonionic surfactants, preservatives, fungicides, pH adjusters, chelating agents, rust inhibitors, water-soluble UV absorbers, and antioxidants. The total content of ink preparations, excluding the binder and organic solvent, is typically 0-30%, preferably 0.1-20%, and more preferably 0.5-10%, relative to the total mass of the ink.

[0034] [binder] The binder is preferably at least one selected from wax and (meth)acrylic acid polymers. The inclusion of a binder improves abrasion resistance. The binder is preferably used in emulsion form, with aqueous emulsions being more preferable. The average particle size of the binder is preferably 50 nm to 5 μm, and more preferably 100 nm to 1 μm, in order to prevent clogging of the inkjet head. When the above ink contains a binder, the binder content relative to the total mass of the ink is typically 0.1 to 14%, preferably 0.5 to 12%, more preferably 2 to 10%, and even more preferably 3 to 8%, in terms of solid content. With such a content, good abrasion resistance can be achieved.

[0035] [wax] Natural waxes and synthetic waxes can be used as the wax. Examples of natural waxes include petroleum-based waxes such as paraffin wax and microcrystalline wax; lignite-based waxes such as montane wax; plant-based waxes such as carnauba wax and candelilla wax; and animal and plant-based waxes such as beeswax and lanolin. These waxes are dispersed in an aqueous medium to form emulsions. Examples of synthetic waxes include polyalkylene wax (preferably poly C2-C4 alkylene wax), oxidized polyalkylene wax (preferably oxidized poly C2-C4 alkylene wax), and paraffin wax. Of these, one or more waxes selected from polyethylene wax, polypropylene wax, oxidized polyethylene wax, oxidized polypropylene wax, and paraffin wax are preferred, with oxidized polyethylene wax being more preferred. 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, etc. from BIC Chemie; Mitsui High Wax NL100, NL200, NL500, 4202E, 1105A, 2203A, NP550, NP055, NP505, etc. from Mitsui Chemicals, Inc.; and KUE-100, 11, etc. from Sanyo Chemical Co., Ltd. Among these, AQUACER 515, 531, 537, 539, and 1547 are preferred; AQUACER 515, 531, 537, and 1547 are more preferred.

[0036] [(meth)acrylic acid-based polymers] The (meth)acrylic acid polymer used as a binder is a different polymer from the dispersant mentioned above. Preferably, it is a (meth)acrylic acid polymer composed of four monomers: C1-C4 alkyl methacrylate, C6-C10 alkyl acrylate, methacrylic acid, and allyl methacrylate. The above C1-C4 alkyl methacrylate is preferably linear or branched in its alkyl portion, with linear being more preferred. In terms of the number of carbon atoms, C1-C3 alkyl methacrylate is preferred, C1-C2 alkyl methacrylate is more preferred, and methyl methacrylate is even more preferred. The above C6-C10 alkyl acrylates are preferably linear or branched in the alkyl portion; branched is more preferred. In terms of the number of carbon atoms, C7-C9 alkyl acrylates are preferred, C8 alkyl acrylates are more preferred, and 2-ethylhexyl acrylate is even more preferred. The ratios of the four monomers in (meth)acrylic acid polymers—C1-C4 alkyl methacrylate, C6-C10 alkyl acrylate, methacrylic acid, and allyl methacrylate—are typically 40-60%, 38-58%, 1-10%, and 1-5% by mass, respectively; preferably 45-55%, 52-42%, 2-4%, and 1-3%. It is preferable that the total of these monomers be within this range. The acid value (in mgKOH / g) of (meth)acrylic acid polymers is typically -10 to 35, preferably -5 to 30, and more preferably 0 to 25. Similarly, the glass transition temperature (Tg) is typically -20 to 30°C, preferably -15 to 25°C, and more preferably -10 to 20°C.

[0037] [Organic solvents] Examples of organic solvents include C1-C6 alkanols having one hydroxyl group, such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, tertiary butanol; 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-dimethylimidazolidine-2-one and 1,3-dimethylhexahydropyrimido-2-one; ketones or keto alcohols such as acetone, 2-methyl-2-hydroxypentan-4-one and ethylene carbonate; tetrahydrofuran, and Examples include cyclic ethers such as dioxane; 1,2-(C2-C3) alkanediols such as ethylene glycol, propylene glycol, and 1,3-propanediol; oligos or polyalkylene glycols or thioglycols having C2-C4 alkylene units, such as diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, polyethylene glycol or polypropylene glycol with a molecular weight of 400 or more, thiodiglycol or dithiodiglycol; polyols (triols) such as glycerin, diglycerin, hexane-1,2,6-triol, and trimethylolpropane; γ-butyrolactone, and dimethyl sulfoxide. Among these, 1,2-(C2-C3) alkanediols and oligos or polyalkylene glycols having C2-C4 alkylene units are preferred, and 1,2-(C2-C3) alkanediols are more preferred. When the above ink contains an organic solvent, the total content of the organic solvent relative to the total mass of the ink is usually 1 to 50%, preferably 5 to 45%, more preferably 10 to 40%, even more preferably 15 to 35%, and particularly preferably 20 to 30%.

[0038] [Surfactants] Examples of surfactants include anionic, cationic, amphoteric, silicone-based, and fluorine-based surfactants.

[0039] 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 sulfosaturates, diethylhexyl sulfosaturates, and dioctyl sulfosaturates.

[0040] Examples of cationic surfactants include 2-vinylpyridine derivatives and poly-4-vinylpyridine derivatives.

[0041] Examples of amphoteric surfactants include lauryldimethylaminoacetic acid betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, coconut oil fatty acid amidopropyl dimethylaminoacetic acid betaine, polyoctyl polyaminoethylglycine, and imidazoline derivatives.

[0042] Examples of silicone-based surfactants include polyether-modified siloxanes and polyether-modified polydimethylsiloxanes. Examples include Dynol 960 and 980 from Air Products Corporation; Silface SAG001, SAG002, SAG003, SAG005, SAG503A, SAG008, SAG009, and SAG010 from Nisshin Chemical Co., Ltd.; and BYK-345, 347, 348, 349, 3455, LP-X23288, LP-X23289, and LP-X23347 from BIC Chemie Corporation; and TEGOTwin4000, TEGOWetKL245, 250, 260, 265, 270, and 280 from Evonic Tego Chemie Corporation.

[0043] Examples of fluorine-based 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.

[0044] [Preservatives] 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, or inorganic salts. Examples of commercially available preservatives include Proxel GXL(S) and XL-2(S) manufactured by Arch Chemical Co., Ltd.

[0045] [Antifungal agent] Examples of fungicides include sodium dehydroacetate, sodium benzoate, sodium pyridinethion-1-oxide, p-hydroxybenzoate ethyl ester, 1,2-benzisothiazolin-3-one, and their salts.

[0046] [pH adjuster] Any substance can be used as a pH adjuster, as long as it can adjust the pH of the prepared ink composition to between 5 and 11 without adversely affecting it. Specific examples 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); or 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.

[0047] [Chelating agent] Examples of chelating agents include disodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, and sodium uracildiacetate.

[0048] [Rust inhibitor] Examples of rust inhibitors include acidic sulfites, sodium thiosulfate, ammonium thioglycolate, diisopropylammonium nitride, pentaerythritol tetranitrate, and dicyclohexylammonium nitride.

[0049] [Water-soluble UV absorber] Examples of water-soluble ultraviolet absorbers include sulfonated benzophenone compounds, benzotriazol compounds, salicylic acid compounds, cinnamic acid compounds, and triazine compounds.

[0050] [Antioxidant] Examples of antioxidants include various organic and metal complex-based colorfastness inhibitors. Examples of the above-mentioned organic colorfastness inhibitors include hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromans, alkoxyanilines, and heterocyclic compounds. [water] The above ink contains the above components and, if necessary, an ink preparation agent, with the remainder being water. The water used for the ink should preferably be deionized water, distilled water, or other water with a low content of impurities such as metal ions.

[0051] The pH of the above ink is typically 7 to 11, preferably 8 to 10. The surface tension of the ink is typically 10-50 mN / m, preferably 20-40 mN / m. The viscosity of the ink is typically 2-30 mPa·s, preferably 3-20 mPa·s. The pH and surface tension of the above ink can be adjusted by using pH adjusters, surfactants, water-soluble organic solvents, etc.

[0052] The above ink can be used in various printing applications. For example, it is suitable for writing instruments, various types of printing, information printing, textile printing, etc., and is particularly preferred for use in inkjet printing.

[0053] When the above ink is used for inkjet printing, printing can be performed by ejecting droplets of the ink in accordance with a print signal and adhering them to the printing medium. There are no particular restrictions on the ink nozzles of the inkjet printer, the inkjet method, etc., and they can be appropriately selected according to the purpose. When performing inkjet printing, printing can be carried out as described above by loading the container containing the above-mentioned ink into the designated position in the inkjet printer. The above inkjet printing method can also be used in combination with inks containing colorants selected from yellow, blue, red, green, violet, and orange pigments or dyes, as needed, to enable full-color printing. Industrial inkjet printers, in order to achieve high printing speeds, are configured as line-head type inkjet printers, and single-pass printing is also preferred. With the above ink, even under such printing conditions, it is possible to obtain printed images with good color reproduction and excellent scratch resistance.

[0054] Any known inkjet method can be used. Specific examples of inkjet methods include charge control methods, drop-on-demand (pressure pulse) methods, acoustic inkjet methods, and thermal inkjet methods. Furthermore, this includes methods that improve image quality by ejecting many small volumes of ink with a low colorant content; methods that improve image quality by using multiple inks with essentially the same hue but different concentrations of colorant; and methods that improve the fixation of colorant by using colorless, transparent ink.

[0055] The above-mentioned printing media refers to materials to which the above-mentioned ink can adhere. Examples of printing media include paper, film, fibers and cloth (cellulose, nylon, wool, etc.), leather, and substrates for color filters. Printing media can be broadly classified into those with an ink-receiving layer and those without. Printing media with an ink-receiving layer are commonly referred to as inkjet paper, inkjet film, glossy paper, etc. Representative examples of commercially available products include Canon Inc.'s Professional Photo Paper, Super Photo Paper, Glossy Gold and Matte Photo Paper; Seiko Epson Corporation's Photo Paper Crispia (High Gloss), Photo Paper (Glossy), and Photo Matte Paper; Hewlett-Packard Japan Ltd.'s Advanced Photo Paper (Glossy); and Fujifilm Corporation's Gakusai Photo Finish Pro, among others. Printing media without an ink-receiving layer include various types of paper such as coated paper and art paper used for gravure printing and offset printing; and cast-coated paper used for label printing. The above ink can be suitably used on printing media without an ink-receiving layer. When using printing media that does not have an ink-receiving layer, it is also preferable to perform surface modification treatment on the printing media in order to improve the fixation of colorants, etc. Examples of surface modification treatments mentioned above include known methods such as corona discharge treatment, plasma treatment, and flame treatment.

[0056] For all of the 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, etc. Furthermore, unless otherwise specified, all of the above ingredients can be used individually or in combination of two or more. [Examples]

[0057] The present invention will be described in detail below with reference to examples, but the present invention is not limited in any way by the following examples. Furthermore, when it was necessary to measure the amount of coloring agent (solid content) contained in various liquids, the dry weight method was used with the MS-70 manufactured by A&D Co., Ltd. to calculate the converted value of coloring agent only. Furthermore, the equipment used for measurements in "(A) Evaluation of color bleeding," "(B) Evaluation of granularity," and "(C) Evaluation of dot diameter" was the PIAS-II print image evaluation system manufactured by QEA Corporation.

[0058] [How to calculate HLB value] The HLB values ​​of the compounds were calculated as follows. An example of the calculation for Lutensol XL40 is provided below. 500 mg of "Lutensol XL40," the compound represented by formula (1), was dissolved in 10 mL of ethanol under stirring to obtain a visually clear solution. A 2% aqueous phenol solution was added dropwise to this solution using a 25 mL burette. As the 2% aqueous phenol solution was added, the liquid in the beaker became cloudy and did not return to clear. The amount of 2% aqueous phenol solution added at this time, Q, was 7.8 mL. Using "Q = 7.8," the HLB value was calculated using formula (2) above (HLB value = 0.89 × 7.8 + 1.11 = 8.052). By rounding to two decimal places, the HLB value of the compound represented by formula (1) was calculated to be 8.1. The HLB values ​​for the 12 compounds listed in Table 1 above were calculated in the same manner as for Lutensol XL40.

[0059] [Preparation Example 1]: Preparation of a dispersion of coloring agents (Dp1). A block copolymer (block copolymer A) was obtained by replicating Synthesis Example 3 of International Publication No. 2013 / 115071. The obtained block copolymer (4.8 parts) was dissolved in 20 parts of 2-butanone to obtain a homogeneous solution. A solution of sodium hydroxide (0.35 parts) dissolved in water (58.8 parts) was added to this solution and stirred for 1 hour to obtain a liquid. CIPigment Blue 15:4 (hereinafter referred to as "PB15:4", 16 parts) was added to this liquid and dispersed in a sand grinder under conditions of 1500 rpm for 15 hours to obtain a liquid. After adding water (100 parts) dropwise to the obtained liquid, the liquid was filtered to obtain a filtrate. From the obtained filtrate, 2-butanone and a portion of the water were removed under reduced pressure using an evaporator to obtain a cyanide dispersion with a colorant content of 11.9%. The obtained dispersion was designated "Dp1".

[0060] [Preparation Example 2]: Preparation of a dispersion of coloring agents (Dp2). A magenta dispersion with a colorant content of 12.1% was obtained in the same manner as in Preparation Example 1, except that CIPigmentRed122 (hereinafter referred to as "PR122," 20 parts) was used instead of PB15:4. The obtained dispersion was designated "Dp2."

[0061] [Preparation Example 3]: Preparation of (meth)acrylic acid-based polymer emulsion (Bd2). 60 parts of deionized water were mixed with 0.3 parts of polyoxyethylene dodecyl ether and 0.3 parts of ammonium persulfate, and heated to 70°C under a nitrogen atmosphere to obtain a solution. To this solution, a mixture of 70 parts of deionized water, 10 parts of polyoxyethylene dodecyl ether, 51 parts of methyl methacrylate, 47 parts of 2-ethylhexyl acrylate, 2 parts of methacrylic acid, and 1 part of allyl methacrylate was added dropwise over 3 hours. After the addition was complete, the mixture was stirred for a further 2 hours while maintaining the temperature of the solution at 70°C. After cooling the solution to 40°C, 150 parts of polyoxyethylene dodecyl ether were added to obtain a (meth)acrylic acid-based polymer emulsion. This polymer emulsion was designated "Bd1". The acid value of the (meth)acrylic acid polymer in Bd1 was 13 mg KOH / g, the Tg was 1.2°C, and the solids content was 33.5%.

[0062] [Preparation Example 4]: Preparation of (meth)acrylic acid-based polymer emulsion (Bd3). A (meth)acrylic acid-based polymer emulsion was obtained in the same manner as in Preparation Example 3, except that methyl methacrylate was changed to 52 parts and 2-ethylhexyl acrylate to 45 parts, and 1 part allyl methacrylate was used instead of 1 part acrylic acid. This polymer emulsion was designated "Bd2". The acid value of the (meth)acrylic acid-based polymer in Bd2 was 13 mg KOH / g, the Tg was 15°C, and the solids content was 25%.

[0063] [Preparation Example 5]: Ink preparation. The dispersions "Dp1" and "Dp2" obtained above were mixed with the components listed in Tables 2 to 5 below, and then filtered through a 3 μm membrane filter to obtain the inks for the evaluation test examples and comparative examples. The colorant content relative to the total mass of the ink was adjusted to 5.5% for all inks. The inks listed in Tables 2 and 3 are both cyan inks. The inks listed in Tables 4 and 5 are both magenta inks.

[0064] The abbreviations in Tables 2 to 5 below have the following meanings. Dp1: Cyanide dispersion obtained in Preparation Example 1. Dp2: Magenta dispersion obtained in Preparation Example 2. PG: Propylene glycol. 12HD: 1,2-Hexanediol. DPnB: Dipropylene glycol-n-butyl ether. TEA: Triethanolamine. 12030: SOFTANOL EP 12030. NT3: Newcol NT-3. 2564: GENAPOL EP 2564. 2303: Newcol 2303. XL40: Lutensol XL40. 800N: BYK-DYNWET 800N. 2584: GENAPOL EP 2584. 7113:BYK-LP X 7113. XL70: Lutensol FT XL 70. XL100: Lutensol XL 100. 1008: Newcol 1008. 2308HE: Newcol 2308-HE. 349:BYK-349. Bd1: Aquacer 515. Bd2: (meth)acrylic acid-based polymer emulsion obtained in Preparation Example 3. Bd3: (meth)acrylic acid-based polymer emulsion obtained in Preparation Example 4.

[0065] [Table 2]

[0066] [Table 3]

[0067] [Table 4]

[0068] [Table 5]

[0069] [Preparation of Ink Set 1 (Set of C1 and M1 Ink)] The M1 ink prepared as described above was divided into two equal parts. One part of the M1 ink was stored at room temperature with the C1 ink for four weeks, while the other part of the M1 ink was stored in a 60°C constant temperature bath for four weeks to perform an accelerated test. In both cases, the C1 ink and M1 ink stored at room temperature were combined to prepare ink set 1, which was also stored at room temperature. On the other hand, two types of ink sets 1 were obtained by combining C1 ink, which was stored at room temperature, with M1 ink, which underwent accelerated testing, and preparing an ink set 1 that underwent accelerated testing.

[0070] [Preparation of ink sets 2-13 and comparison ink sets 1-10] Except for using the inks listed in Tables 8 and 9 below instead of the C1 and M1 inks used in the preparation of Ink Set 1 above, two types of example ink sets 2 to 13 and comparative example ink sets 1 to 6 were prepared in the same manner as Ink Set 1 above: one stored at room temperature and the other subjected to accelerated testing.

[0071] [Preparation of test specimen 1] Using the cyan inks shown in Tables 2 and 3 obtained as described above, 100% solid images were printed. Printing was performed using a printing jig equipped with a Kyocera KJ4B inkjet head, at a frequency of 10 kHz and three levels (0, 5, 12 pL), with Oji Paper's "OK Topcoat+" as the printing medium. Each test piece 1 was prepared by drying the printed image for 3 seconds under an IR heater set to 100°C. Using the obtained test piece 1, the following "(A) Evaluation of granularity" was performed.

[0072] [(A) Evaluation of granularity] The cyanide concentration of test piece 2 obtained as described above was measured to two decimal places with a tile size of 42.3 μm, and evaluated according to the following four-level evaluation criteria. A lower value for granularity indicates less granularity and better print quality. The measured values ​​and evaluation results for granularity are shown in Tables 6 and 7 below. [Evaluation Criteria] D: 0.81 or more. C:0.51~0.80. B: 0.21~0.50. A: 0.20 or less.

[0073] [Preparation of Test Specimen 2] Using the cyan inks shown in Tables 2 and 3 obtained as described above, solid images with 5% coverage were printed. Printing was performed using a printing jig equipped with a Kyocera KJ4B inkjet head, at a frequency of 10 kHz and a binary (medium drop) setting, with Oji Paper's "OK Topcoat+" as the printing medium. Each test piece 2 was prepared by drying the printed image under an IR heater set to 100°C for 3 seconds. The obtained test pieces 2 were used to perform the "(B) Evaluation of Wetting Spreadability" described below.

[0074] [(B) Evaluation of wetting properties] The dot diameter of test piece 2 obtained as described above was measured to one decimal place, and the value was rounded to the nearest whole number. Using the dot diameter of the comparative cyan ink "cC7," which does not contain nonionic surfactants, as a reference, including the above formula (1), the dot diameter expansion ratio was calculated using the following formula (3) as an indicator of wetting spreadability on the printing media, and evaluated according to the following four evaluation criteria. A higher dot diameter expansion ratio indicates better wetting spreadability. The dot diameter, expansion ratio, and evaluation results are shown in Tables 6 and 7 below. Furthermore, when calculating the magnification of the dot diameter, the value obtained by rounding the measured dot diameter to the first decimal place was used. [Dot diameter magnification]

[0075] [ka]

[0076] (In formula (3), "C ink" refers to the cyan inks of the examples with ink numbers C1-C13; and "cC ink" refers to the comparative cyan inks with ink numbers cC1-cC6 and cC8-cC10.) [Evaluation Criteria] D: 1% or less. C: 2-7%. B: 8-13%. A: 14% or more.

[0077] [Preparation of test specimen 3] Using the cyan inks shown in Tables 2 and 3 obtained as described above, 100% solid images were printed. Printing was performed using a printing jig equipped with a Kyocera Corporation inkjet head, KJ4B, at a frequency of 10 kHz and three levels (microdroplet, medium droplet), with Oji Paper Co., Ltd.'s "OK Topcoat+" as the printing medium. Each test piece 3 was prepared by drying the printed image for 3 seconds under an IR heater set to 100°C. The obtained test pieces 3 were used to perform the "(C) Evaluation of abrasion resistance" described below.

[0078] [(C) Evaluation of abrasion resistance] Test specimen 3, obtained as described above, was rubbed back and forth 20 times under a 900g load using a Gakushin-type color friction fastness tester manufactured by Yasuda Seisakusho Co., Ltd. Unprinted "OK Topcoat+" was used as the receptor (the material to be rubbed). The degree of degradation of the solid image was evaluated visually according to the following three evaluation criteria. The evaluation results are shown in Tables 6 and 7 below. In Tables 6 and 7 below, "(A)", "(B)", and "(C)" refer to the evaluation results for "(A) Granularity Evaluation", "(B) Wetting Spread Evaluation", and "(C) Abrasion Resistance Evaluation", respectively. [Evaluation Criteria] A: Almost no damage was found in the printed images. B: A small scratch was found on the printed image. C: A very large scratch was found on the printed image.

[0079] [Table 6]

[0080] [Table 7]

[0081] [Preparation of test specimen 4] Using the two ink sets 1 obtained as described above, a single linear magenta image with 100% M1 ink and a line width of 0.5 mm was printed on top of a solid image of 100% C1 ink, thereby obtaining printed images. Printing was performed using a printing jig equipped with a Kyocera Corporation inkjet head, KJ4B, at a frequency of 10 kHz and binary (medium drop) conditions, with Oji Paper Co., Ltd.'s "OK Topcoat+" as the printing medium. The obtained printed images were dried for 3 seconds under an IR heater set to 100°C to obtain two types of test pieces 4. Except for using two types of ink sets 1, and using two types of ink sets 2 to 13 for the examples and two types of ink sets 1 to 10 for the comparative examples, two types of test pieces 4 corresponding to each ink set were obtained in the same manner as described above. Using the two types of test pieces 4 obtained, the following "(D) Evaluation of color bleeding" was performed.

[0082] [(D) Evaluation of color bleeding] The line widths of the magenta images of the two types of test pieces 4 obtained as described above were measured. From the obtained measurements, the line width ratio was calculated by dividing the line width of the ink set that underwent accelerated testing by the line width of the ink set that was stored at room temperature, and evaluated according to the following four evaluation criteria. A smaller line width ratio indicates that color bleeding does not worsen regardless of the storage period, and therefore indicates superior color bleeding performance. The evaluation results are shown in Tables 8 and 9 below. Note that "(D)" in Tables 8 and 9 below means the result of "(D) Evaluation of color bleeding". [Evaluation Criteria] D: Ratio 101% or more. C: Ratio 51~100%. B: Ratio 26~50%. A: The ratio is 25% or less.

[0083] [Table 8]

[0084] [Table 9]

[0085] As is clear from Tables 6 and 7 above, the results of "(A) evaluation of granularity" and "(B) evaluation of wetting spreadability" for the inks of each example were all A and B. On the other hand, with the exception of the cC6 ink, the inks of each comparative example were found to be "C" or lower in at least one evaluation result, and were clearly inferior to each example. The cC6 ink showed good results in terms of granularity and wetting spread, comparable to the inks in each example. However, the comparative example ink set 6, which used cC6 ink as cyan ink, showed a remarkably poor result of "D" in "(D) Evaluation of color bleeding." In other words, it became clear that the cC6 ink is an ink whose color bleeding deteriorates significantly with storage time. Furthermore, the ink of C11 had good wetting spread (rated "A") and granularity (rated "B"). However, when the abrasion resistance of this ink was evaluated, it received a result of "C". However, the inks of Examples C12 and C13, which had a binder added to this ink, showed improved abrasion resistance up to "A". This confirmed that the above ink, when further containing a binder, produces printed materials with good wetting spread, granularity, color bleeding, and abrasion resistance.

[0086] [Preparation Example 6]: Preparation of a dispersion of coloring agents (Dp3). A yellow dispersion with a coloring agent content of 12.1% was obtained in the same manner as in Preparation Example 1, except that CIPigmentYellow74 (hereinafter referred to as "PY74," 20 parts) was used instead of PB15:4. The obtained dispersion was designated "Dp3."

[0087] [Preparation Example 7]: Preparation of a dispersion of colorants (Dp4). A black dispersion with a coloring agent content of 12.1% was obtained in the same manner as in Preparation Example 1, except that carbon black manufactured by Orion Co., Ltd. (product name NEROX305, 20 parts) was used instead of PB15:4. The obtained dispersion was designated as "Dp2".

[0088] [Preparation Example 8]: Ink preparation. The dispersions "Dp3" and "Dp4" obtained above were mixed with the components listed in Table 10 below, and then filtered through a 3 μm membrane filter to obtain inks for the example and comparative example for evaluation testing. The colorant content relative to the total mass of the ink was adjusted to 5.5% for all inks. In Table 10, Y1 and Y2 are the yellow inks of the example; K1 and K2 are the black inks of the example; cY1 to cY3 are the yellow inks for comparison; and cK1 to cK3 are the yellow inks for comparison.

[0089] [Table 10]

[0090] Except for using the magenta inks listed in Table 11, the yellow inks listed in Table 12, and the black inks listed in Table 13 below instead of cyan ink, test specimens were prepared in the same manner as above, and then the above-mentioned [(A) evaluation of granularity] and [(B) evaluation of wetting spread] were performed. The test results are shown in Tables 11 to 13 below. The standard inks for each color, which do not contain nonionic surfactants, are as follows. Magenta ink: cM6. Yellow ink: cY1. Black ink: cK1.

[0091] [Table 11]

[0092] [Table 12]

[0093] [Table 13]

[0094] Tables 11 to 13 confirm that magenta, yellow, and black inks, which differ in the color and type of coloring agent, exhibit similar trends to cyan ink.

[0095] Except for using yellow ink and magenta ink, or black ink and magenta ink, as described in Table 14 below, instead of C1 ink and M1 ink, ink sets 14 to 17 for two different examples and comparative ink sets 11 to 16 were prepared in the same manner as in "[Preparation of Ink Set 1 (Set of C1 Ink and M1 Ink)]" above. Test specimens were prepared using these ink sets in the same manner as above, and [(D) Evaluation of Color Bleeding] was performed. The test results are shown in Table 14 below.

[0096] [Table 14]

[0097] Table 14 confirms that the same trend was observed in each ink set, including yellow ink and magenta ink, and black ink and magenta ink, which differ in the color and type of colorants, as in cyan ink and magenta ink. [Industrial applicability]

[0098] The present invention provides an ink that exhibits good wetting and spreading properties on non-ink-absorbing and poorly absorbent media, prevents deterioration of color bleeding regardless of storage period, and enables the provision of printed images with extremely low graininess; an inkjet printing method using this ink; and a printing media to which this ink is attached. For this reason, the ink of the present invention is extremely useful as a printing ink for various purposes, particularly as an inkjet printing ink.

Claims

1. An ink for poorly absorbent media, comprising a water-insoluble colorant, a dispersant, a nonionic surfactant represented by the following formula (1) having an HLB value of 5.0 to 8.2, and water, and further comprising at least one selected from diC2-C4 alkylene glycol monoC3-C4 alkyl ether and 1,2-(C6-C8) alkanediol, and wax. 【Chemistry 1】 (In formula (1), R represents a C6-C20 straight-chain or branched-chain hydrocarbon group. EO represents an ethyleneoxy group, and PO represents a propyleneoxy group. The order of EO and PO is arbitrary. m represents the number of ethyleneoxy groups, and n represents the number of propyleneoxy groups. m ranges from 1 to 20, and n ranges from 0 to 5. (However, the case where n is 0 is excluded.) Furthermore, the above HLB value is calculated as follows. [How to calculate HLB value] Dissolve 0.5 g of nonionic surfactant in 10 mL of ethanol to obtain a solution. Stir the obtained solution at 25°C, and add a 2% by mass aqueous phenol solution dropwise until the solution becomes cloudy, at which point the endpoint is reached. When the amount of 2% by mass aqueous phenol solution used to reach the endpoint is Q (mL), calculate the HLB value using the following formula (2). 【Chemistry 2】

2. The ink for poorly absorbent media according to claim 1, wherein the wax is one or more selected from polyalkylene wax, oxidized polyalkylene wax, and paraffin wax.

3. The ink for poorly absorbent media according to claim 1 or 2, wherein the wax is oxidized polyethylene wax.

4. An inkjet printing method that involves ejecting droplets of ink for poorly absorbent media described in any one of claims 1 to 3 from an inkjet printer and adhering them to a printing medium for printing.

5. A printing medium to which the ink for poorly absorbent media described in any one of claims 1 to 3 is attached.

Images