Ink, inkjet printing method and printed 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 a water-based ink, an ink-jet printing method using the ink, and a print medium having the ink deposited thereon. [Background technology]

[0002] Among various color printing methods, the printing method using an inkjet printer, which is one of the most representative methods, generates small droplets of ink and deposits them on a printing medium such as paper to perform printing. In recent years, demand for inkjet printers for industrial use has increased, and there is a demand for inks that can be used for printing on a variety of printing media.

[0003] Among printing media, inks that wet and spread well on the media are required for non-ink-absorbent media and poorly ink-absorbent media (hereinafter sometimes referred to as "non-ink / poorly ink-absorbent media"). If the ink spreads well on the media, the area that can be colored using the same amount of ink droplets is larger (in other words, the ink dot diameter becomes larger), and the amount of ink consumed can be reduced. However, non-ink / poorly ink-absorbent media is a media that has poor ink absorption. For this reason, the ink does not soak into the media easily, and compared to ink-absorbent media, the ink does not wet and spread well, so the ink dot diameter generally becomes smaller. For this reason, improvements are required. Furthermore, when color printing is performed, an ink set consisting of multiple colors is used. It is known that when color printing is performed using such an ink set, bleeding between the first color and the second color may occur when the landing positions of the ink of the first color and the ink of the second color are adjacent to each other on the printing medium. This "bleeding between colors" is one of the factors that significantly deteriorates print quality. For this reason, there is a demand to eliminate this bleeding between colors, and ink sets have been proposed to solve this problem. However, it has become clear that the problem of inter-color bleeding involves more complex factors. That is, in the early stages of printing, printing can be performed using a combination of a first color ink and a second color ink, both of which have only recently been manufactured (in other words, both are new). Therefore, by selecting and using an ink set that takes inter-color bleeding into consideration, it is possible to perform high-quality printing without inter-color bleeding. However, when printing is continued, the consumption of each ink varies depending on the type of ink. For this reason, when an ink with a high consumption runs out, it is replaced with a new ink. On the other hand, for an ink with a low consumption, the ink that was initially used continues to be used until it runs out (in other words, the new ink and the old ink are used together). For this reason, there may be a difference of several months to a year in the storage period between an ink with a high consumption and an ink with a low consumption. In this way, when printing is performed using inks with different storage periods in combination, bleeding between colors may worsen and the print image quality may deteriorate, even though there is no significant change in the storage stability of each ink itself (various physical properties such as ejection property, average particle size, viscosity, and pH), and a solution to this problem is desired. Furthermore, print quality requires that graininess be as minimal as possible. Inks that contain water-insoluble colorants are in a non-uniform state (not in a solution state, but in a dispersion state). When solid printing is performed on print media using ink in such a non-uniform state, the printed image may appear to have scattered "grains" of various shades, and may not appear to be a uniform image. Such printed images are evaluated as having "graininess," which is one of the factors that significantly deteriorate print quality. For this reason, there is a strong demand for inks that can 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 the same. [Patent Document 1] JP 2016-044188 A [Patent Document 2] JP 2014-139004 A [Patent Document 3] JP 2007-162006 A [Patent Document 4] International Publication No. 2011 / 136000 [Patent Document 5] JP 2014-210876 A Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention provides an ink that has good wetting and spreading properties on non- or poorly ink-absorbent media, does not cause bleeding between colors regardless of storage period, and enables the provision of printed images with extremely little graininess, an inkjet printing method using the ink, and a printing medium to which the ink is attached. [Means for solving the problem]

[0006] As a result of extensive research aimed at solving the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by the inventions described in [1] to [9] below, and have completed the present invention.

[0007] That is, 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) and having an HLB value of 5.0 to 13.0, and water.

[0008] [ka]

[0009] (In formula (1), R represents a C6-C20 linear or branched 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, where m is an integer of 1 to 20 and n is an integer of 0 to 5. The HLB value is calculated as follows. [How to calculate HLB value] A solution is obtained by dissolving 0.5 g of a nonionic surfactant in 10 mL of ethanol. The resulting solution is stirred at 25°C, and a 2% by mass aqueous solution of phenol is dropped into the solution. The end point is when the solution becomes turbid. When the amount of 2% by mass aqueous solution of phenol required to reach the end point is Q (mL), the HLB value is calculated using the following formula (2).

[0010] [ka]

[0011] [2] The ink according to the above item [1], further comprising at least one selected from glycol ethers and C4-C12 alkanediols. [3] The ink according to the above item [1] or [2] further contains a binder. [4] The ink according to the above item [3], wherein the binder contains at least one selected from the group consisting of wax and (meth)acrylic acid-based polymers. [5] The ink according to [4] above, wherein the wax is one or more selected from the group consisting of polyalkylene wax, polyalkylene oxide wax, and paraffin wax. [6] The ink according to [4] or [5] above, wherein the wax is an oxidized polyethylene wax. [7] The ink according to [4] above, wherein the (meth)acrylic acid-based polymer is a (meth)acrylic acid-based 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 in which droplets of the ink according to any one of the above items [1] to [7] are ejected from an inkjet printer and deposited on a printing medium, thereby carrying out printing. [9] A print medium having the ink according to any one of the above items [1] to [7] adhered thereto. Effect of the Invention

[0012] The present invention has made it possible to provide an ink that wets and spreads well on non- or poorly ink-absorbent media, does not deteriorate in inter-color bleeding regardless of storage period, and enables the provision of printed images with extremely little graininess; an inkjet printing method using the ink; and a printing medium to which the ink is applied, having printed images with excellent ink wettability, no inter-color bleeding, and extremely little graininess. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] In this specification, including the examples, all "parts" and "%" are based on mass unless otherwise specified. In this specification, when a "unit" is written at only one of the upper and lower limits of a range, such as "X to Y%", this means that the units at the upper and lower limits of the range are the same, i.e., "X% to Y%".

[0014] [Water-insoluble colorants] The colorant 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 this 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, and even more preferably 0.5 g or less. The lower limit of the solubility includes 0 g. Unless otherwise specified, the "water-insoluble colorant" will hereinafter be referred to as the "colorant." Among the above colorants, pigments are preferred, and examples of the pigments include inorganic pigments, organic pigments, and extender pigments.

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

[0016] The colorant contained in the black ink is preferably carbon black such as thermal black, acetylene black, oil furnace black, gas furnace black, lamp black, gas black, and channel black. Specific examples of carbon black include the Raven series manufactured by Columbia Carbon Corporation, the Monarch series, Regal series, and Mogul series manufactured by Cabot Corporation, the ColorBlack series, Printex series, SpecIalBlack series, and Nerox series manufactured by Orion Engineered Carbons, and the MA series, MCF series, No. 25, No. 33, No. 40, No. 47, No. 52, No. 900, and No. 2300 manufactured by Mitsubishi Chemical Corporation.

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

[0018] Specific examples of organic pigments include yellow such as CI Pigment 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, and 213; and CI Pigment 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, CI Pigment Blue 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 22, 25, 60, 66, 80, etc.; violet, CI Pigment Violet 19, 23, 29, 37, 38, 50, etc.; orange, CI Pigment Orange 13, 16, 43, 68, 69, 71, 73, etc.; green, CI Pigment Green 7, 36, 54, etc.; and black, such as CI Pigment Black 1, etc.

[0019] Examples of the extender pigment include silica, calcium carbonate, talc, clay, barium sulfate, white carbon, etc. The extender pigment is often used in combination with other colorants.

[0020] The disperse dye may be any known disperse dye, of which dyes selected from CI Dispers are preferred. Specific examples thereof include yellows such as CIDispersYellow 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, and 237; reds such as CIDispersRed 60, 73, 88, 91, 92, 111, 127, 131, 143, 145, 146, 152, 153, 154, 167, 179, 191, 192, 206, 221, 258, and 283; and CID Examples of disperse dyes include oranges such as CI Dispers Orange 9, 25, 29, 30, 31, 32, 37, 38, 42, 44, 45, 53, 54, 55, 56, 61, 71, 73, 76, 80, 96, and 97; violets such as CI Dispers Violet 25, 27, 28, 54, 57, 60, 73, 77, 79, and 79:1; and blues such as CI Dispers Blue 27, 56, 60, 79:1, 87, 143, 165, 165:1, 165:2, 181, 185, 197, 202, 225, 257, 266, 267, 281, 341, 353, 354, 358, 364, 365, and 368.

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

[0022] [Dispersant] The dispersant is not particularly limited, and any known dispersant can be used. The dispersant is used for the purpose of dispersing the water-insoluble colorant in the ink. Generally, a polymer dispersant such as a resin is used as the dispersant. 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 monoesters, maleic acid, maleic acid monoesters, fumaric acid, fumaric acid monoesters, vinyl sulfonic acid, sulfoethyl methacrylate, sulfopropyl methacrylate, α,β-unsaturated monomers such as sulfonated vinyl naphthalene, styrene, styrene derivatives, vinyl naphthalene, vinyl naphthalene 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, and N-butoxymethyl acrylamide.

[0023] The dispersant may be the same as the AB block polymer disclosed in WO 2013 / 115071, including preferred ones. The same also applies to the production method of the AB block polymer. In one example of a dispersant (AB block polymer) disclosed in WO 2013 / 115071, for example, the monomer constituting the above-mentioned A polymer is one or more monomers selected from (meth)acrylic acid and linear or branched C4 alkyl (meth)acrylate, and the monomer constituting the B polymer is benzyl methacrylate and / or benzyl acrylate. Note that in this specification, the terms "(meth)acrylic" and "(meth)acrylate" are used to mean both "acrylic, methacrylic" and "acrylate, methacrylate", respectively. The monomer constituting the A block is 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 the B block is preferably benzyl methacrylate. Specific examples thereof include the block copolymers disclosed in Synthesis Examples 3 to 8 of WO 2013 / 115071.

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

[0025] The acid value of the dispersant is usually from 90 to 200 mgKOH / g, preferably from 100 to 150 mgKOH / g, and more preferably from 100 to 120 mgKOH / g. The mass average molecular weight of the dispersant is usually 10,000 to 60,000, preferably 10,000 to 40,000, more preferably 15,000 to 30,000, and further preferably 20,000 to 25,000. The PDI (mass average molecular weight / number average molecular weight) of the dispersant is about 1.29 to 1.49. By setting the content within the above range, the dispersibility and storage stability can be improved. Examples of the neutralizing agent include ammonia, hydroxides of alkali metals, hydroxides of alkaline earth metals, aliphatic amine compounds, and alkanolamine compounds. Ammonia and hydroxides of alkali metals are preferred, and ammonia is particularly preferred. The amount of the neutralizing agent used is not particularly limited. As a guideline, the neutralization degree is usually 30 to 300%, more preferably 50 to 200%, assuming that the neutralization degree is 100% when neutralized with the theoretical equivalent of the acid value of the dispersant.

[0026] The above-mentioned dispersant can be used in a state of being mixed with a water-insoluble colorant. It can also be used in a state in which the surface of the water-insoluble colorant is coated with the dispersant. It can also be used in combination of these. 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 only a part of the surface of the water-insoluble colorant is covered with the dispersant. When a dispersant is used, 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 surfactants] The ink contains a nonionic surfactant represented by formula (1). The HLB value of the nonionic surfactant is usually 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 above [Method of calculating HLB value], and the value is rounded off to one decimal place to indicate the HLB value.

[0028] Among the nonionic surfactants represented by formula (1), those having a straight-chain alkyl group as R include Newcol 2303 manufactured by Nippon Nyukazai Co., Ltd.; GENAPOLE P2564 and EP2584 manufactured by Clariant, and the like. In addition, examples of commercially available products having a branched alkyl group as R include Newcol NT-3 manufactured by Nippon Nyukazai Co., Ltd.; Lutensol XL 40 and 70 manufactured by BASF; BYK DYNWET 800N and LPX 7113 manufactured by BYK-Chemie; Softanol 50 and 70 manufactured by Nippon Shokubai Co., Ltd.; Newcol 2303 manufactured by Nippon Nyukazai Co., Ltd. which has no PO group and only EO group; and Emulmin 40, 110, and 240 manufactured by Sanyo Chemical Industry Co., Ltd. Table 1 below shows an example of a compound represented by formula (1) and its HLB value. In Table 1 below, "HLB" means the HLB value, and in the "Type of R" column, "BR" 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 ink contains at least one selected from glycol ether and C4-C12 alkanediol. This tends to improve the wetting and spreading of the ink on non- or poorly ink-absorbing media, and the drying of the ink. 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 is preferably an alkyl ether of di- or tri-C2-C4 alkylene glycol, and more preferably a monoalkyl ether of di- or tri-C2-C4 alkylene glycol. The C2-C4 alkylene glycol moiety includes ethylene glycol, propylene glycol, and butylene glycol, of which ethylene glycol and propylene glycol are preferred, and propylene glycol is more preferred. The carbon number of the alkyl in the alkyl ether moiety is usually in the range of C1-C6, preferably C1-C5, more preferably C2-C4, further preferably C3-C4, and particularly preferably C4. Specific examples thereof include 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. Of these, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, dipropylene glycol monopropyl ether, and dipropylene glycol monobutyl ether are preferred.

[0032] The C4-C12 alkanediol is not particularly limited, but is preferably a 1,2-(C4-C12) alkanediol, more preferably a 1,2-(C6-C8) alkanediol. Alkanediols having C7 or more are generally considered to be poorly water-soluble. Specific examples thereof 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. In addition, alkanediols of C6 or less are generally considered to be water-soluble. Specific examples thereof include 1,2-hexanediol, 1,2-pentanediol, 1,2-butanediol, 4-methyl-1,2-pentanediol, 3,3-dimethyl-1,2-butanediol, etc. Although any of these can be used, 1,2-hexanediol is more preferable among these because it has less odor.

[0033] [Ink preparations] The ink may further contain ink preparation agents in addition to the above-mentioned components, such as binders, organic solvents, non-nonionic surfactants, preservatives, antifungal agents, pH adjusters, chelating agents, rust inhibitors, water-soluble ultraviolet absorbers, and antioxidants. The total content of ink preparation agents excluding the binder and the organic solvent is usually about 0 to 30%, preferably about 0.1 to 20%, and more preferably about 0.5 to 10%, based on the total mass of the ink.

[0034] [binder] The binder is preferably at least one selected from wax and (meth)acrylic acid-based polymers. By including a binder, the scratch resistance can be improved. The binder is preferably used in the form of an emulsion, and among these, a water-based emulsion is 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 ink contains a binder, the content of the binder relative to the total mass of the ink is usually 0.1 to 14%, preferably 0.5 to 12%, more preferably 2 to 10%, and even more preferably 3 to 8%, calculated as a solid content. At such a content, it is possible to improve the scratch resistance.

[0035] [wax] As the wax, natural wax and synthetic wax can be used. Examples of natural waxes include petroleum-based waxes such as paraffin wax and microcrystalline wax; lignite-based waxes such as montan wax; vegetable waxes such as carnauba wax and candelilla wax; and animal and vegetable waxes such as beeswax and lanolin, etc., dispersed in an aqueous medium. Examples of synthetic waxes include polyalkylene waxes (preferably poly C2-C4 alkylene waxes), oxidized polyalkylene waxes (preferably poly C2-C4 alkylene waxes), and paraffin waxes. Among the above, one or more waxes selected from polyethylene wax, polypropylene wax, oxidized polyethylene wax, oxidized polypropylene wax, and paraffin wax are preferred, and oxidized polyethylene wax is more preferred. Examples of commercially available wax emulsions include CERAFLOUR 925, 929, 950, and 991 manufactured by BYK-Chemie; AQUACER 498, 515, 526, 531, 537, 539, 552, and 1547; AQUAMAT 208, 263, and 272; and MINERPOL 221, manufactured by Mitsui Chemicals, Inc.; Mitsui Hiwax NL100, NL200, NL500, 4202E, 1105A, 2203A, NP550, NP055, and NP505, manufactured by Mitsui Chemicals, Inc.; and KUE-100 and 11, manufactured by Sanyo Chemical Co., Ltd. Of these, AQUACER 515, 531, 537, 539, and 1547 are preferred; AQUACER 515, 531, 537, and 1547 are more preferred.

[0036] [(Meth)acrylic acid polymer] The (meth)acrylic acid-based polymer used as the binder is a polymer different from the dispersant described above. It is preferable that the (meth)acrylic acid-based polymer is composed of four types of monomers, namely, C1-C4 alkyl methacrylate, C6-C10 alkyl acrylate, methacrylic acid, and allyl methacrylate. The C1-C4 alkyl methacrylate preferably has an alkyl moiety that is linear or branched, more preferably linear. As for the range of carbon numbers, C1-C3 alkyl methacrylate is preferred, C1-C2 alkyl methacrylate is more preferred, and methyl methacrylate is even more preferred. The C6-C10 alkyl acrylate has an alkyl moiety that is preferably linear or branched, more preferably branched. As for the range of carbon numbers, C7-C9 alkyl acrylate is preferred, C8 alkyl acrylate is more preferred, and 2-ethylhexyl acrylate is even more preferred. The ratios of the four monomers of C1-C4 alkyl methacrylate, C6-C10 alkyl acrylate, methacrylic acid, and allyl methacrylate in the (meth)acrylic acid-based polymer are usually 40-60%, 38-58%, 1-10%, and 1-5%, respectively, based on mass, and preferably 45-55%, 52-42%, 2-4%, and 1-3%. It is preferable that the total of these monomers is 100%. The acid value (unit: mgKOH / g) of the (meth)acrylic acid-based polymer is usually -10 to 35, preferably -5 to 30, and more preferably 0 to 25. Similarly, the glass transition temperature (Tg) is usually from -20 to 30°C, preferably from -15 to 25°C, and more preferably from -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, secondary butanol, and tertiary butanol; amides, such as N,N-dimethylformamide and N,N-dimethylacetamide; lactams, such as 2-pyrrolidone, N-methyl-2-pyrrolidone, and N-methylpyrrolidin-2-one; cyclic ureas, such as 1,3-dimethylimidazolidin-2-one and 1,3-dimethylhexahydropyrimid-2-one; ketones or ketoalcohols, such as acetone, 2-methyl-2-hydroxypentan-4-one, and ethylene carbonate; tetrahydrofuran, and Examples of suitable alkane diols include cyclic ethers such as dioxane, 1,2-(C2-C3) alkane diols such as ethylene glycol, propylene glycol, and 1,3-propane diol, oligo- 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 having 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 dimethylsulfoxide. Among these, 1,2-(C2-C3) alkane diols and oligo- or polyalkylene glycols having C2-C4 alkylene units are preferred, and 1,2-(C2-C3) alkane diols are more preferred. When the 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] The surfactant may be anionic, cationic, amphoteric, silicone-based, or fluorine-based surfactant.

[0039] Examples of anionic surfactants include alkyl sulfocarboxylates, α-olefin sulfonates, polyoxyethylene alkyl ether acetates, polyoxyethylene alkyl ether sulfates, N-acylamino acids or salts thereof, N-acylmethyltaurines, alkyl sulfates, polyoxyalkyl ether sulfates, alkyl sulfates, polyoxyethylene alkyl ether phosphates, rosin acid soaps, castor oil sulfates, lauryl alcohol sulfates, alkylphenol phosphates, alkyl phosphates, alkylarylsulfonates, diethylsulfosuccinates, diethylhexylsulfosuccinates, and dioctylsulfosuccinates.

[0040] Examples of the cationic surfactant include 2-vinylpyridine derivatives and poly(4-vinylpyridine) derivatives.

[0041] Examples of amphoteric surfactants include lauryl dimethylaminoacetate betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazolinium betaine, coconut oil fatty acid amidopropyl dimethylaminoacetate betaine, polyoctyl polyaminoethyl glycine, and imidazoline derivatives.

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

[0043] Examples of fluorine-based surfactants include perfluoroalkyl sulfonic acid compounds, perfluoroalkyl carboxylic acid compounds, perfluoroalkyl phosphate compounds, perfluoroalkyl ethylene oxide adducts, and polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups on the side chains.

[0044] [Preservatives] Examples of preservatives include organic sulfur, organic nitrogen sulfur, organic halogen, haloarylsulfone, iodopropargyl, haloalkylthio, nitrile, pyridine, 8-oxyquinoline, benzothiazole, isothiazolinone, dithiol, pyridine oxide, nitropropane, organic tin, phenol, quaternary ammonium salt, triazine, thiazine, anilide, adamantane, dithiocarbamate, brominated indanone, benzyl bromoacetate, and inorganic salt compounds. Specific examples of commercially available preservatives include Proxel GXL(S) and XL-2(S) manufactured by Arch Chemical Company.

[0045] [Anti-mold agent] Examples of the antifungal agent include sodium dehydroacetate, sodium benzoate, sodium pyridinethione-1-oxide, p-hydroxybenzoic acid ethyl ester, 1,2-benzisothiazolin-3-one and salts thereof.

[0046] [pH adjuster] As the pH adjuster, any substance can be used as long as it can adjust the pH of the ink composition to 5 to 11 without adversely affecting the ink composition to be prepared. Specific examples of such an acid include alkanolamines such as diethanolamine, triethanolamine, and N-methyldiethanolamine; alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; ammonium hydroxide (aqueous ammonia); alkali metal carbonates such as lithium carbonate, sodium carbonate, sodium hydrogen carbonate, 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 agents] Examples of chelating agents include disodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, and sodium uracildiacetate.

[0048] [Rust inhibitor] Examples of the rust inhibitor include acid sulfite, sodium thiosulfate, ammonium thioglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite.

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

[0050] [Antioxidants] Examples of the antioxidant include various organic and metal complex-based anti-fading agents. Examples of the organic anti-fading agents include hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromans, alkoxyanilines, and heterocycles. [water] The ink contains the above-mentioned components and, if necessary, ink preparation agents, with the remainder being water. The water used in the ink is preferably ion-exchanged water, distilled water, or the like, which has a low content of impurities such as metal ions.

[0051] The pH of the ink is usually 7-11, and preferably 8-10. The surface tension of the ink is usually 10 to 50 mN / m, preferably 20 to 40 mN / m. The viscosity of the ink is usually 2 to 30 mPa·s, preferably 3 to 20 mPa·s. The pH and surface tension of the ink can be adjusted by using a pH adjuster, a surfactant, a water-soluble organic solvent, or the like.

[0052] The ink can be used in various printing applications, such as writing instruments, various printing applications, information printing, textile printing, and the like, and is particularly preferably used in inkjet printing.

[0053] When the ink is used for inkjet printing, droplets of the ink are ejected in response to a printing signal and deposited on a printing medium, thereby performing printing. There are no particular limitations on the ink nozzle of the inkjet printer, the inkjet method, etc., and these can be appropriately selected depending on the purpose. When inkjet printing is to be performed, a container containing the ink is loaded into a predetermined position of the inkjet printer, and printing can be performed as described above. The 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, if necessary, to produce full-color printing. For the purpose of increasing the printing speed, industrial inkjet printers are preferably configured as line head inkjet printers and are also preferably used for single pass printing. With the above ink, even under such printing conditions, it is possible to obtain printed images with good color development and excellent abrasion resistance.

[0054] As the inkjet method, a known method can be used, and specific examples of the inkjet method include a charge control method, a drop-on-demand (pressure pulse) method, an acoustic inkjet method, and a thermal inkjet method. Other examples include a method of improving image quality by ejecting a large number of inks with a small content of colorant in a small volume; a method of improving image quality by using multiple inks of substantially the same hue but with different concentrations of colorant; and a method of improving the fixation of colorant by using colorless and transparent ink.

[0055] The printing medium refers to a material to which the ink can adhere. Examples of the printing medium include paper, film, fibers and cloth (cellulose, nylon, wool, etc.), leather, and color filter substrates. Print media can be broadly divided into those that have an ink-receiving layer and those that do not. Print media having an ink-receiving layer are usually called inkjet paper, inkjet film, glossy paper, etc. Representative commercially available products include Professional Photo Paper, Super Photo Paper, Gloss Gold, and Matte Photo Paper manufactured by Canon Inc.; Photo Paper Crispia (high gloss), Photo Paper (gloss), and Photo Matte Paper manufactured by Seiko Epson Corporation; Advanced Photo Paper (gloss) manufactured by Hewlett-Packard Japan; and Gasai Photo Finishing Pro manufactured by Fujifilm Corporation. Examples of print media that do not have an ink-receiving layer include various papers such as coated paper and art paper used in applications such as gravure printing and offset printing, cast coated paper used for label printing, etc. The ink can be suitably used on print media that do not have an ink-receiving layer. When a printing medium having no ink receiving layer is used, it is preferable to subject the printing medium to a surface modification treatment in order to improve the fixation of the colorant, etc. The above surface modification treatment may be a known method such as a corona discharge treatment, a plasma treatment, or a flame treatment.

[0056] For all of the above items, combinations of preferred items are more preferred, and combinations of more preferred items are even more preferred. The same applies to combinations of preferred items and more preferred items, combinations of more preferred items and even more preferred items, etc. Moreover, unless otherwise specified, all of the above-mentioned components can be used alone or in combination of two or more kinds. EXAMPLES

[0057] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples in any way. In addition, when it was necessary to measure the content (solids) of colorant contained in various liquids, the content was calculated as the equivalent value of only the colorant by the dry weight method using an MS-70 manufactured by A&D Co., Ltd. The equipment used for the measurements in "(A) Evaluation of intercolor bleeding", "(B) Evaluation of graininess", and "(C) Evaluation of dot diameter" was a print image evaluation equipment, PIAS-II, manufactured by QEA.

[0058] [How to calculate HLB value] The HLB value of a compound was calculated as follows. As an example, the calculation example for Lutensol XL40 will be described. 500 mg of "Lutensol XL40" as the compound represented by formula (1) was dissolved in 10 mL of ethanol under stirring to obtain a solution that was visually transparent. 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 transparency. The amount of the 2% aqueous phenol solution added at this time, Q, was 7.8 mL. The HLB value was calculated using the above formula (2) assuming "Q = 7.8" (HLB value = 0.89 x 7.8 + 1.11 = 8.052), and the HLB value of the compound represented by formula (1) was calculated to be 8.1 by rounding off the second decimal place. The HLB values ​​of the 12 compounds listed in Table 1 above were calculated in the same manner as for Lutensol XL40.

[0059] [Preparation Example 1]: Preparation of colorant dispersion (Dp1). A block copolymer (block copolymer A) was obtained by re-examining Synthesis Example 3 of WO 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 liquid, and the mixture was stirred for 1 hour to obtain a liquid. CI Pigment Blue 15:4 (hereinafter referred to as "PB15:4", 16 parts) was added to this liquid, and a dispersion treatment was performed in a sand grinder under the condition of 1500 rpm to obtain a liquid. Water (100 parts) was added dropwise to the obtained liquid, and the liquid was filtered to obtain a filtrate. From the obtained filtrate, 2-butanone and a part of the water were distilled off under reduced pressure using an evaporator to obtain a cyan dispersion with a colorant content of 11.9%. The obtained dispersion was designated "Dp1".

[0060] [Preparation Example 2]: Preparation of colorant dispersion (Dp2). A magenta dispersion liquid with a colorant content of 12.1% was obtained in the same manner as in Preparation Example 1, except that CI Pigment Red 122 (hereinafter referred to as "PR122", 20 parts) was used instead of PB15:4. The obtained dispersion liquid is designated "Dp2".

[0061] [Preparation Example 3]: Preparation of (meth)acrylic acid-based polymer emulsion (Bd2). 0.3 parts of polyoxyethylene dodecyl ether and 0.3 parts of ammonium persulfate were added to 60 parts of ion-exchanged water, and heated to 70°C under a nitrogen atmosphere to obtain a liquid. A mixture of 70 parts of ion-exchanged 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 to this liquid over 3 hours. After the dropwise addition was completed, the liquid was stirred for another 2 hours while maintaining the temperature at 70°C. After cooling the liquid to 40°C, 150 parts of polyoxyethylene dodecyl ether was added to obtain a (meth)acrylic acid-based polymer emulsion. This polymer emulsion is referred to as "Bd1." The (meth)acrylic acid polymer in Bd1 had an acid value of 13 mgKOH / g, a Tg of 1.2°C, and a solid content of 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, 2-ethylhexyl acrylate was changed to 45 parts, and 1 part of allyl methacrylate was used instead of 1 part of acrylic acid. This polymer emulsion is called "Bd2". The acid value of the (meth)acrylic acid-based polymer in Bd2 was 13 mgKOH / g, Tg was 15°C, and the solid content was 25%.

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

[0064] The abbreviations in Tables 2 to 5 below have the following meanings. Dp1: Cyan 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 Ink and M1 Ink)] The M1 ink prepared as described above was divided into two halves, and one half of the M1 ink was stored together with the C1 ink at room temperature for four weeks, while the other half was stored in a thermostatic chamber at 60° C. for four weeks to carry out an accelerated test. The C1 ink and M1 ink, both of which had been stored at room temperature, were combined to prepare ink set 1, which had been stored at room temperature. Meanwhile, two types of ink sets 1 were obtained by combining the C1 ink stored at room temperature and the M1 ink that had been subjected to the accelerated test to prepare ink set 1 that had been subjected to the accelerated test.

[0070] [Preparation of Ink Sets 2 to 13 and Comparative Ink Sets 1 to 10] Ink sets 2 to 13 as examples and ink sets 1 to 6 as comparative examples were prepared in the same manner as in the preparation of ink set 1 above, except that the inks listed in Tables 8 and 9 below were used instead of the C1 ink and M1 ink used in the preparation of ink set 1 above. Two types of ink sets, one stored at room temperature and one subjected to an accelerated test, were prepared in the same manner as in the preparation of ink set 1 above.

[0071] [Preparation of test piece 1] Using each of the cyan inks shown in Tables 2 and 3 obtained as described above, a 100% solid image was printed. The printing was performed using a printing tool equipped with an inkjet head, KJ4B, manufactured by Kyocera Corporation, under conditions of a frequency of 10 kHz and three values ​​(0, 5, 12 pL), and using "OK Topcoat+" manufactured by Oji Paper Co., Ltd. as the printing medium. The printed image was dried for 3 seconds under an IR heater set at 100°C to prepare each test piece 1. The obtained test piece 1 was used to carry out the "(A) Evaluation of granularity" described below.

[0072] [(A) Graininess evaluation] The graininess of the cyan density of test piece 2 obtained as described above was measured to two decimal places with a tile size set to 42.3 μm, and evaluated according to the following four-level evaluation criteria. The smaller the graininess value, the less graininess there is, and the better the print quality. The measured graininess values ​​and evaluation results 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 piece 2] Using each of the cyan inks shown in Tables 2 and 3 obtained as described above, a 5% solid image was printed. The printing was performed using a printing tool equipped with an inkjet head, KJ4B, manufactured by Kyocera Corporation, under conditions of a frequency of 10 kHz and binary (medium droplets), and using "OK Topcoat+" manufactured by Oji Paper Co., Ltd. as the printing medium. The printed image was dried for 3 seconds under an IR heater set at 100°C to prepare each test piece 2. The obtained test pieces 2 were used to perform the "(B) Evaluation of wetting and spreading property" described below.

[0074] [(B) Evaluation of Wetting and Spreading Properties] The dot diameter of the test piece 2 obtained as described above was measured to the first decimal place, and the dot diameter was determined by rounding off the first decimal place. The dot diameter of the comparative cyan ink "cC7" containing no nonionic surfactant was used as a standard, including the above formula (1), and the dot diameter expansion rate was calculated using the following formula (3) as an index of wet spreadability on the printing medium, and evaluated according to the following four-level evaluation criteria. A larger value for the dot diameter expansion rate means better wet spreadability. The dot diameter, expansion rate, and evaluation results are shown in Tables 6 and 7 below. In addition, when calculating the dot diameter enlargement rate, the measured dot diameter was rounded to one decimal place. [Dot diameter expansion rate]

[0075] [ka]

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

[0077] [Preparation of test piece 3] Using each of the cyan inks shown in Tables 2 and 3 obtained as described above, a 100% solid image was printed. The printing was performed using a printing tool equipped with an inkjet head, KJ4B, manufactured by Kyocera Corporation, under conditions of a frequency of 10 kHz and three values ​​(fine droplets, medium droplets), and using "OK Topcoat+" manufactured by Oji Paper Co., Ltd. as the printing medium. The printed image was dried for 3 seconds under an IR heater set at 100°C to prepare each test piece 3. The obtained test pieces 3 were used to perform the "(C) Evaluation of abrasion resistance" described below.

[0078] [(C) Evaluation of abrasion resistance] The test piece 3 obtained as described above was rubbed back and forth 20 times under a load of 900 g using a Gakushin type dye rub fastness tester manufactured by Yasuda Seisakusho Co., Ltd. An unprinted "OK Topcoat+" was used as the receptor (what was rubbed). The deterioration of the solid image was visually evaluated according to the following three-level evaluation criteria. The evaluation results are shown in Tables 6 and 7 below. In addition, "(A)", "(B)" and "(C)" in Tables 6 and 7 below mean the evaluation results of "(A) Evaluation of graininess", "(B) Evaluation of wet spreadability" and "(C) Evaluation of rub resistance", respectively. [Evaluation Criteria] A: Almost no scratches were found on the printed image. B: Slight scratches were found on the printed image. C: Very large scratches were found on the printed image.

[0079] [Table 6]

[0080] [Table 7]

[0081] [Preparation of test piece 4] Using the two types of ink sets 1 obtained as described above, one linear magenta image with a line width of 0.5 mm was printed using 100% M1 ink so as to overlap a solid image of 100% C1 ink, to obtain a printed image. The printing was performed using a printing tool equipped with an inkjet head, KJ4B, manufactured by Kyocera Corporation, under conditions of a frequency of 10 kHz and binary (medium droplets), and using "OK Topcoat+" manufactured by Oji Paper Co., Ltd. as the printing medium. The obtained printed image was dried for 3 seconds under an IR heater set at 100°C to obtain two types of test pieces 4. Except for using two types of ink sets 2 to 13 of the examples and two types of ink sets 1 to 10 of the comparative examples instead of the two types of ink sets 1, two types of test pieces 4 corresponding to each ink set were obtained in the same manner as above. The two types of test pieces 4 thus obtained were used to carry out the "(D) Evaluation of intercolor bleeding" described below.

[0082] [(D) Evaluation of inter-color bleeding] The line width of the magenta image of each of the two types of test pieces 4 obtained as described above was measured. Of the measured values ​​obtained, the line width of the ink set that underwent the accelerated test was divided by the line width of the ink set stored at room temperature to calculate the line width ratio, which was then evaluated according to the following four-level evaluation criteria. A smaller line width ratio indicates that inter-color bleeding does not worsen regardless of the storage period, and therefore indicates excellent inter-color bleeding performance. The evaluation results are shown in Tables 8 and 9 below. Note that "(D)" in Tables 8 and 9 below refers to the results of "(D) Evaluation of inter-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 graininess" and "(B) Evaluation of wetting and spreading" for the inks of each Example were both A and B. On the other hand, with the exception of ink cC6, the inks of each Comparative Example were found to have at least one evaluation result of "C" or lower, and were clearly inferior to the respective Examples. The cC6 ink showed good results in terms of graininess and wet spreadability, equivalent to the inks of the other examples. However, the comparative ink set 6, which used the cC6 ink as the cyan ink, showed a significantly poor result of "D" in "(D) Evaluation of intercolor bleeding." In other words, it became clear that the cC6 ink is an ink whose intercolor bleeding deteriorates significantly depending on the storage period. In addition, the ink C11 has good wettability and spreadability, with a grade of "A" and graininess, with a grade of "B." When the ink was evaluated for abrasion resistance, it received a grade of "C." However, the inks of Examples C12 and C13, which contained binders, improved in abrasion resistance to an "A." This confirmed that the ink further containing a binder can provide printed matter with good wetting and spreading properties, graininess, intercolor bleeding, and abrasion resistance.

[0086] [Preparation Example 6]: Preparation of colorant dispersion (Dp3). A yellow dispersion with a colorant content of 12.1% was obtained in the same manner as in Preparation Example 1, except that CI Pigment Yellow 74 (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 colorant dispersion (Dp4). A black dispersion having a colorant content of 12.1% was obtained in the same manner as in Preparation Example 1, except that Orion carbon black (trade name NEROX305, 20 parts) was used instead of PB15:4. The obtained dispersion is designated as "Dp2".

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

[0089] [Table 10]

[0090] Test pieces were prepared in the same manner as above, except that the magenta inks listed in Table 11, the yellow inks listed in Table 12, and the black inks listed in Table 13 were used instead of the cyan ink, and then the above-mentioned [(A) Evaluation of graininess] and [(B) Evaluation of wetting and spreading properties] were carried out. The test results are shown in Tables 11 to 13 below. The inks that do not contain a nonionic surfactant and are used as the standard for the dot diameter of each color are as follows. Magenta ink: cM6. Yellow ink: cY1. Black ink: cK1.

[0091] [Table 11]

[0092] [Table 12]

[0093] [Table 13]

[0094] From Tables 11 to 13, it was confirmed that the magenta, yellow, and black inks, which have different colors and types of colorants, also exhibited the same tendency as the cyan ink.

[0095] Except for using the yellow ink and magenta ink, or the black ink and magenta ink shown in Table 14 below instead of C1 ink and M1 ink, two types of example ink sets 14 to 17 and comparative ink sets 11 to 16 were prepared in the same manner as described above under "Preparation of ink set 1 (set of C1 ink and M1 ink)". Test pieces were prepared using these ink sets in the same manner as described above, and [(D) Evaluation of inter-color bleeding] was performed. The test results are shown in Table 14 below.

[0096] [Table 14]

[0097] From Table 14, it was confirmed that the ink sets of yellow ink and magenta ink, and black ink and magenta ink, which have different colors and types of colorants, also showed the same trends as those of cyan ink and magenta ink. [Industrial Applicability]

[0098] The present invention provides an ink that has good wetting and spreading properties on non- or poorly ink-absorbent media, does not cause inter-color bleeding regardless of storage period, and enables the provision of printed images with extremely little graininess, an inkjet printing method using the ink, and a printing medium to which the ink is applied. Therefore, the ink of the present invention is extremely useful as a variety of printing inks, particularly as an inkjet printing ink.

Claims

1. The ink comprises a water-insoluble colorant, a dispersant, a nonionic surfactant represented by the following formula (1) and having an HLB value of 5.0 to 13.0, and water, and further comprises at least one selected from the group consisting of dipropylene glycol-n-butyl ether and 1,2-hexanediol, wherein the dispersant is a block copolymer. 【Chemistry 1】 (In formula (1), R represents a C6-C20 linear or branched 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, where m is 1 to 20 and n is 0 to 5, except for the case where n is 0. The HLB value is calculated as follows. [Method of calculating HLB value] A solution is obtained by dissolving 0.5 g of a nonionic surfactant in 10 mL of ethanol. The obtained solution is stirred at 25° C., and a 2% by weight aqueous phenol solution is dropped into the solution. The end point is when the solution becomes turbid. When the amount of 2% by weight aqueous phenol solution required to reach the end point is Q (mL), the HLB value is calculated by the following formula (2). 【Chemistry 2】

2. 2. The ink according to claim 1, further comprising at least one selected from the group consisting of glycol ethers and C4-C12 alkanediols.

3. The ink according to claim 1 or 2, further comprising a binder.

4. The ink according to claim 3 , wherein the binder comprises at least one selected from the group consisting of wax and (meth)acrylic acid-based polymers.

5. The wax is a polyalkylene wax, a polyalkylene oxide wax, or a paraffin wax. The ink according to claim 4, wherein the wax is one or more selected from the group consisting of phenyl wax and phenyl wax.

6. 6. An ink according to claim 4 or 5, wherein the wax is an oxidized polyethylene wax.

7. The ink according to claim 4, wherein the (meth)acrylic acid-based polymer is a (meth)acrylic acid-based polymer composed of four types of monomers: C1-C4 alkyl methacrylate, C6-C10 alkyl acrylate, methacrylic acid, and allyl methacrylate.

8. 8. An inkjet printing method comprising ejecting droplets of the ink according to claim 1 from an inkjet printer and depositing the droplets on a printing medium to perform printing.

9. A print medium having the ink according to any one of claims 1 to 7 deposited thereon.

Images