Ink, ink medium set, and method for improving scratch resistance

Abstract

To provide an ink which exhibits little change in glare of the coated film even when scratch marks, such as those made by a nail, occur upon use in an ink-hardly-absorbable printing medium, particularly in coated paper such as offset coated paper, and which is excellent in storage stability; an ink medium set comprising the ink and the printing medium; and a method for improving the scratch resistance thereof.SOLUTION: An ink composition contains a water-insoluble coloring agent selected from the group consisting of a pigment, a dispersion dye and a solvent dye, a resin as a dispersion agent having a weight average molecular weight of less than 50,000, at least one or more resin emulsions having a weight average molecular weight of 50,000 or more, and a silane-modified silica sol having a particle size of 3 nm or more and less than 35 nm.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to inks, ink media sets and methods for improving rub resistance. [Background technology]

[0002] Among various color printing methods, the printing method using an inkjet printer (inkjet printing method) is one of the most representative methods. In this method, small droplets of ink are generated and deposited on a printing medium such as paper to print. With the advancement of inkjet technology, inkjet printing method has come to be used even in the field of high-definition printing that has been realized by silver halide photography and offset printing. In such fields, printing media that do not absorb ink well, such as coated paper, are often used as the printing media. In addition, the demand for industrial inkjet printing has increased in recent years, and new properties are now required, one of which is the strong demand for improved abrasion resistance of the ink adhered to the print media. For example, when a coated paper is printed using an inkjet printer and the resulting print is scratched with a fingernail or the like, the coating film is pressed only at the scratched area, making the surface smooth. As a result, light is more strongly mirror-reflected only at the scratched area, causing glare. The glare only at the scratched area makes the overall appearance of the print worse, resulting in a decrease in print quality. Therefore, there is a strong demand for an ink that causes little change in the glare of the coating film even when scratched with a fingernail or the like. Methods for suppressing the glare of the coating film include applying a pretreatment agent to the coated paper before printing, and applying an overcoat agent to the coated paper after printing. However, in consideration of reducing printing costs, improving printing speed, and increasing the size of the equipment due to the addition of processes, it is desirable to obtain the above-mentioned abrasion resistance without using a pretreatment agent or an overcoat agent. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5273434 [Patent Document 2] Patent No. 4679322 [Patent Document 3] WO2016 / 035787 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention aims to provide an aqueous ink composition for inkjet printing that, when used on a printing medium having poor ink absorption, particularly offset coated paper, exhibits little change in glare of the coating film even if scratches caused by a fingernail or the like are left on the ink composition; an ink media set of the ink and the printing medium; and a method for improving the abrasion resistance of the ink composition. [Means for solving the problem]

[0005] Means for Solving the Problems The present inventors have conducted intensive research to solve the above problems, and as a result have found that an ink composition comprising a water-insoluble colorant selected from the group consisting of pigments, disperse dyes, and solvent dyes, a resin serving as a dispersant having a weight-average molecular weight of less than 50,000, at least one type of resin emulsion having a weight-average molecular weight of 50,000 or more, and a silane-modified silica sol having a particle size of 3 nm or more and less than 35 nm, can solve the above problems and has excellent ink storage stability, thereby completing the present invention.

[0006] That is, the present invention relates to the following 1) to 7). 1) An ink composition comprising: a water-insoluble colorant selected from the group consisting of pigments, disperse dyes, and solvent dyes; a resin having a weight-average molecular weight of less than 50,000 as a dispersant; at least one type of resin emulsion having a weight-average molecular weight of 50,000 or more; and a silane-modified silica sol having a particle diameter of 3 nm or more and less than 35 nm. 2) The ink composition according to 1), wherein the resin emulsion comprises an acrylic resin emulsion and an oxidized polyethylene resin emulsion. 3) The ink composition according to 1) or 2), wherein the total solid content of the resin emulsion in the ink composition is 0.6% by mass or more and 6.0% by mass or less. 4) An ink composition set comprising the ink composition according to any one of 1) to 3) above and another ink composition. 5) A print medium printed using the ink composition according to any one of 1) to 3) or the ink composition set according to 4). 6) An ink media set comprising the ink composition according to any one of 1) to 3) or the ink composition set according to 4) and the print medium according to 5). 7) A method for improving abrasion resistance, comprising using the ink composition according to any one of 1) to 3) or the ink composition set according to 4). Effect of the Invention

[0007] The present invention has provided an aqueous ink composition for inkjet printing, an ink media set, and a method for improving abrasion resistance, which are capable of reducing the change in glare of the coating film even when scratched by a fingernail or the like, without the need to apply a pretreatment agent or overcoat agent to printing media with poor ink absorption, particularly coated paper such as offset coated paper. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] In this specification, "CI" means "Color Index." In addition, in this specification, including the examples, "%" and "parts" are all based on mass unless otherwise specified. In this specification, the terms "alkylene", "propylene" and "alkyl" are used to mean both straight-chain and branched-chain structures unless otherwise specified. In addition, when a value is given in mass% and has a decimal point, the value is rounded off to the nearest decimal place and is written to the nearest decimal place.

[0009] The ink composition includes a water-insoluble colorant selected from the group consisting of pigments, disperse dyes, and solvent dyes, a resin having a weight-average molecular weight of less than 50,000 as a dispersant, at least one type of resin emulsion having a weight-average molecular weight of 50,000 or more, and a silane-modified silica sol having a particle size of 3 nm or more and less than 35 nm. In this specification, the ink composition may be abbreviated to ink.

[0010] [Water-insoluble colorant selected from the group consisting of pigments, disperse dyes, and solvent dyes] The water-insoluble colorant selected from the group consisting of pigments, disperse dyes, and solvent dyes is not particularly limited as long as it is a water-insoluble colorant selected from pigments, disperse dyes, and solvent dyes. For example, known pigments, disperse dyes, and solvent dyes can be used. In this specification, the 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. In this specification, unless otherwise specified, "a water-insoluble colorant selected from a pigment, a disperse dye, and a solvent dye" may be abbreviated to "colorant". The colorants can be used in combination. When using a combination of colorants, it is preferable to use two or more types when the ink is a color ink other than a black ink, and to use three to five types when the ink is a black ink. However, when the black ink contains carbon black as a colorant, the number of types of the colorant is preferably 2 or 1. In this specification, color ink refers to colored ink other than black ink (e.g., ink of each color such as yellow, magenta, cyan, red, orange, brown, violet, blue, and green). Among the pigments, disperse dyes, and solvent dyes, the pigments are preferred. Examples of the pigments include inorganic pigments and organic pigments.

[0011] Examples of the inorganic pigment include carbon black, metal oxides, hydroxides, sulfides, ferrocyanides, and metal chlorides.

[0012] 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, 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.

[0013] Examples of the organic pigment include various pigments such as azo, disazo, phthalocyanine, quinacridone, isoindolinone, dioxazine, perylene, perinone, thioindigo, anthraquinone, and quinophthalone.

[0014] Examples of the organic pigment include known organic pigments. Examples of known 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; Red: 5, 7, 12, 48, 48:1, 57, 88, 112, 122, 123, 146, 149, 150, 166, 168, 177, 178, 179, 184, 185, 202, 206, 207, 254, 255, 257, 260, 264, 269, 272, etc.; CI Pigment Blue: 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 22, 25, 60, 66, 80, etc.; CI Pigment Violet: 19, 23, 29, 37, 38, 50, etc.; CI Pigment Orange: 13, 16, 43, 68, 69, 71, 73, etc.; CI Pigment Examples of pigments include green pigments such as Green 7, 36, and 54; and black pigments such as CI Pigment Black 1.

[0015] 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 CIDispers Yellow 9, 23, 33, 42, 49, 54, 58, 60, 64, 66, 71, 76, 79, 83, 86, 90, 93, 99, 114, 116, 119, 122, 126, 149, 160, 163, 165, 180, 183, 186, 198, 200, 211, 224, 226, 227, 231, and 237; reds such as CIDispers Red 60, 73, 88, 91, 92, 111, 127, 131, 143, 145, 146, 152, 153, 154, 167, 179, 191, 192, 206, 221, 258, and 283; Examples of disperse dyes include oranges such as 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. As the solvent dye, a dye selected from CISolvent is preferable.

[0016] The total content of the colorants in 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 nm to 250 nm, and preferably 60 nm to 200 nm. In this specification, the average particle size refers to the average particle size of particles measured using a laser light scattering method.

[0017] [Resin as a dispersant] Examples of the resin as the dispersant include copolymers composed of at least two monomers (preferably at least one of which is a hydrophilic monomer) selected from the group consisting of monomers such as styrene and its derivatives, vinylnaphthalene and its derivatives, aliphatic alcohol esters of α,β-ethylenically unsaturated carboxylic acids, acrylic acid and its derivatives, maleic acid and its derivatives, itaconic acid and its derivatives, faric acid and its derivatives, vinyl acetate, vinyl alcohol, vinylpyrrolidone, acrylamide, and their derivatives. Examples of such copolymers include styrene-(meth)acrylic acid copolymers, styrene-(meth)acrylic acid-(meth)acrylic acid ester copolymers, (meth)acrylic acid ester-(meth)acrylic acid copolymers, polyethylene glycol (meth)acrylate-(meth)acrylic acid copolymers, and styrene-maleic acid copolymers. Among these, styrene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid-(meth)acrylic acid ester copolymer, (meth)acrylic acid ester-(meth)acrylic acid copolymer, polyethylene glycol (meth)acrylate-(meth)acrylic acid copolymer are preferred; styrene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid-(meth)acrylic acid ester copolymer, (meth)acrylic acid ester-(meth)acrylic acid copolymer are more preferred; (meth)acrylic acid ester-(meth)acrylic acid copolymer is even more preferred; and methacrylic acid ester-methacrylic acid copolymer is particularly preferred. In this specification, the term "(meth)acrylic" is used to mean both "acrylic" and "methacrylic". The same applies to "(meth)acrylate" and the like. Examples of types of copolymers include block copolymers, random copolymers, and graft copolymers, and / or salts thereof. Resins as dispersants can be synthesized or obtained as commercial products. Specific examples of commercial products include styrene-acrylic copolymers such as JONCRYL 62, 67, 68, 678, and 687, all manufactured by Johnson Polymer Co.; Movinyl S-100A (modified vinyl acetate copolymer manufactured by Hoechst Chemical Co.); and JURIMER AT-210 (polyacrylic acid ester copolymer manufactured by Nippon Junyaku Co., Ltd.). Preferred examples of copolymers obtained by synthesis include the AB block polymers disclosed in WO 2013 / 115071 Gazette.

[0018] The weight average molecular weight (MW) of the resin as the dispersant is less than 50,000, preferably 3,000 or more and less than 50,000, and more preferably 7,000 to 25,000. The acid value of the resin as the dispersant is preferably 50 to 300 KOHmg / g, more preferably 80 to 275 KOHmg / g, and particularly preferably 80 to 250 KOHmg / g.

[0019] The resin as a dispersant can be used either in a state where it is mixed with a colorant, or in a state where a part or the whole of the surface of the colorant is coated with the resin as a dispersant. It is also possible to use both of these states together.

[0020] The ink is preferably prepared by preparing a dispersion containing a water-insoluble colorant and a resin as a dispersant, and then mixing it with other components. A known method can be used to prepare the dispersion. One example is the phase inversion emulsification method. That is, a resin as a dispersant is dissolved in an organic solvent such as 2-butanone, and an aqueous solution of a neutralizing agent is added to prepare an emulsion. A colorant is added to the resulting emulsion and a dispersion treatment is carried out, and the organic solvent and a portion of the water are distilled off under reduced pressure from the thus obtained liquid to obtain the desired dispersion liquid. The dispersion treatment can be carried out using, for example, a sand mill (bead mill), a roll mill, a ball mill, a paint shaker, an ultrasonic disperser, a microfluidizer, etc. When using a sand mill as an example, beads having a particle diameter of about 0.01 mm to 1 mm are used, and the dispersion treatment can be carried out by appropriately setting the filling rate of the beads. The dispersion obtained as described above can be subjected to a procedure such as filtration and / or centrifugation, etc. By this procedure, the particle diameter of the particles contained in the dispersion can be made uniform. If foaming occurs during preparation of the dispersion, a very small amount of a known antifoaming agent such as a silicone type or acetylene glycol type can be added. Other methods for preparing the dispersion liquid include an acid precipitation method, an interfacial polymerization method, an in-situ polymerization method, a liquid hardening coating method, a coacervation (phase separation) method, a liquid drying method, a melt dispersion cooling method, an air suspension coating method, a spray drying method, etc. Among these, the phase inversion emulsification method, the acid precipitation method, and the interfacial polymerization method are preferred.

[0021] The average particle size (D50) of the water-insoluble colorant in the dispersion is usually 300 nm or less, preferably 30 to 280 nm, more preferably 40 to 270 nm, and further preferably 50 to 250 nm. Similarly, D90 is usually 400 nm or less, preferably 350 nm or less, and more preferably 300 nm or less. The lower limit is preferably 100 nm or more. Similarly, D10 is usually 10 nm or more, preferably 20 nm or more, more preferably 30 nm or more, with the upper limit being 100 nm or less. Particle size can be measured using laser light scattering.

[0022] [Resin emulsion] The resin emulsion preferably has a weight average molecular weight (MW) of 50,000 or more and contains one or more types selected from polymers and waxes. Examples of the polymer include urethane-based, polyester-based, acrylic-based, vinyl acetate-based, vinyl chloride-based, styrene-acrylic-based, acrylic-silicone-based, and styrene-butadiene-based polymers, and emulsions containing the same. Among these, urethane-based, acrylic-based, and styrene-butadiene-based polymers are preferred, and acrylic polymers are more preferred. The polymer can be synthesized or purchased commercially. When synthesizing the polymer, for example, the polymer disclosed in WO 2015 / 147192 Gazette is preferred. Examples of commercially available products include Superflex 126, 130, 150, 170, 210, 420, 470, 820, 830, and 890 (urethane-based resin emulsions manufactured by Daiichi Kogyo Seiyaku Co., Ltd.); Hydran HW-350, HW-178, HW-163, HW-171, AP-20, AP-30, WLS-201, and WLS-210 (urethane-based resin emulsions manufactured by DIC Corporation); 0569, 0850Z, and 2108 (styrene-butadiene-based resin emulsions manufactured by JSR Corporation); and AE980, AE981A, AE982, AE986B, and AE104 (acrylic resin emulsions manufactured by E-Tech Co., Ltd.).

[0023] The wax is preferably a wax emulsion, more preferably a water-based wax emulsion. The wax may be a natural wax or a synthetic wax. 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.

[0024] Examples of the synthetic wax include polyalkylene wax (preferably poly C2-C4 alkylene wax), oxidized polyalkylene wax (preferably poly C2-C4 alkylene wax), and paraffin wax. Among them, 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. The average particle size of the wax is preferably 50 nm to 5 μm, and more preferably 100 nm to 1 μm, in order to prevent clogging of the inkjet head.

[0025] Examples of commercially available waxes include CERAFLOUR 925, 929, 950, and 991 manufactured by BYK Japan; 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.; KUE-100 and 11 manufactured by Sanyo Chemical Co., Ltd.; and HYTECE-6500, 9015, and 6400 manufactured by Toho Chemical Co., Ltd.

[0026] The total content of the resin emulsion relative to the total mass of the ink is usually 0.6% to 6.0%, and preferably 1.0% to 5%, from the viewpoints of the fixability of the ink to paper, the ejection property of the ink, and the storage stability of the ink.

[0027] [Silane-modified silica sol] The silane-modified silica sol refers to a sol in which colloidal particles of silane-modified silica are dispersed in a liquid. From the viewpoint of storage stability of the ink composition, the silane-modified silica sol is preferably a water-based or water-soluble organic solvent-based silane-modified silica sol. The silane-modified silica sol refers to a sol in which a part or all of the surface of silica particles is coated with silane, and from the viewpoint of storage stability of the ink, a part or all of the silanol groups on the surface of the silica particles are treated and coated with silane or a silane derivative such as a general silane coupling agent is particularly preferable. In addition, the silane coating on the surface of the silica particles can be obtained as a silane-modified silica sol whose coverage rate is arbitrarily changed according to the purpose. In addition, when the ink contains two or more kinds of the silane-modified silica sol, those with different coverage rates may be used in combination, or the silane and silane derivative used for the coating may be arbitrarily selected and used alone or in combination for treatment. This is because the sol itself is highly stabilized by the steric repulsion between the substituents on the surface of the particles, and the ink is also stabilized. The silane-modified silica sol that has been treated and coated with silane may be available as a commercial product, or may be obtained by treating a commercially available silica sol that has not been treated with silane with a silane coupling agent, etc. Specific examples of the commercially available silane-modified silica sol include the Levasil series manufactured by Nouryon. On the other hand, specific examples of commercially available silica sols that are not silane-treated include the Snowtex series manufactured by Nissan Chemical Industries, Ltd., the SI series manufactured by JGC Catalysts and Chemicals, Ltd., the Silicadol series manufactured by Nippon Chemical Industry Co., Ltd., and the PL series manufactured by Fuso Chemical Industry Co., Ltd. In addition, examples of water-soluble organic solvent-based silica sols include methanol silica sol, IPA-ST, EG-ST, NPC-ST-30, PGM-ST, and NMP-ST manufactured by Nissan Chemical Industries, Ltd.

[0028] The particle size of the silane-modified silica sol is from 3 nm to less than 35 nm, more preferably from 5 nm to less than 20 nm, from the viewpoint of preventing the scratch marks from glittering. The content of the silane-modified silica sol in the ink composition is preferably from 0.2 mass% to 5.0 mass%, more preferably from 0.5 mass% to 4.0 mass%, even more preferably from 0.8 mass% to 3.5 mass%, and particularly preferably from 0.9 mass% to 3.3 mass%, from the viewpoint of preventing the scratch marks from glittering and from the viewpoint of storage stability.

[0029] The ink may contain ink preparation agents, such as organic solvents, surfactants, antifungal agents, preservatives, pH adjusters, rust inhibitors, antifoaming agents, water, etc., as necessary. These ink preparation agents may be used alone or in combination of two or more.

[0030] [Organic solvents] The organic solvent is not particularly limited, and examples thereof include C1-C6 alkanols such as methanol, ethanol, propanol, texanol, isopropanol, butanol, isobutanol, secondary butanol, and tertiary butanol; carboxylic acid 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, ketoalcohols, and carbonates such as acetone, 2-methyl-2-hydroxypentan-4-one, and ethylene carbonate; and cyclic ureas such as tetrahydrofuran and dioxane. ethers; mono-, oligo- or polyalkylene glycols or thioglycols having C2-C6 alkylene units, such as ethylene glycol, diethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butylene glycol, 1,4-butylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, polyethylene glycol (preferably having a molecular weight of 400, 800, 1540 or more), polypropylene glycol, thiodiglycol or dithiodiglycol; C3-C9 polyols (triols), such as glycerin, diglycerin, hexane-1,2,6-triol, trimethylolpropane;Ethylene glycol monomethyl ether, Ethylene glycol monoethyl ether, Ethylene glycol monoallyl ether, Ethylene glycol monoisopropyl ether, Diethylene glycol monomethyl ether, Diethylene glycol monoethyl ether, Diethylene glycol monobutyl ether ( butyl carbitol), triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether and other glycol ethers (preferably glycol ethers selected from the group consisting of C3-C10 mono-, di- or triethylene glycol ethers, and C4-C13 mono-, di- or tripropylene glycol ethers); C5-C9 alkanediols such as 1,2-pentanediol, 1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 2-methyl-2,4-pentanediol, 2-ethyl-1,3-hexanediol, 2,4-diethyl-1,5-pentanediol; γ-butyrolactone or dimethyl sulfoxide; and the like, with 1,2-hexanediol and texanol being preferred.

[0031] [Surfactants] The surfactant may be anionic, nonionic, silicone-based, or fluorine-based surfactant. Among these, surfactants selected from silicone-based and fluorine-based surfactants are preferred, and silicone-based surfactants are more preferred from the viewpoint of safety to living organisms and the environment.

[0032] 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.

[0033] Examples of nonionic surfactants include ether-based surfactants such as polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, polyoxyethylene alkyl ether, and polyoxyethylene distyrenated phenyl ether (for example, Emulgen A-60, A-90, and A-500 manufactured by Kao Corporation); ester-based surfactants such as polyoxyethylene oleate, polyoxyethylene distearate, sorbitan laurate, sorbitan monostearate, sorbitan monooleate, sorbitan sesquioleate, polyoxyethylene monooleate, and polyoxyethylene stearate; acetylene glycol (alcohol)-based surfactants such as 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, and 3,5-dimethyl-1-hexyne-3-ol; and polyglycol ether-based surfactants. Examples of commercially available products of these include Surfynol 104, 104PG50, 82, 420, 440, 465, 485, and Olfin STG manufactured by Nissin Chemical Co., Ltd.; and Emulgen A-60, A-90, and A-500 manufactured by Kao Corporation.

[0034] 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 Co., Ltd.; and BYK-345, 347, 348, 349, 3455, LP-X23288, LP-X23289, and LP-X23347 manufactured by BYK Additives & Instruments; and TEGOTwin4000, TEGOWetKL245, 250, 260, 265, 270, and 280 manufactured by EvonicTegoChemie.

[0035] 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.

[0036] [Anti-mold agent] Specific examples of antifungal agents include sodium dehydroacetate, sodium benzoate, sodium pyridinethione-1-oxide, p-hydroxybenzoic acid ethyl ester, 1,2-benzisothiazolin-3-one and salts thereof.

[0037] [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, or inorganic salt compounds. A specific example of the organic halogen compound is sodium pentachlorophenol. A specific example of the pyridine oxide compound is sodium 2-pyridinethiol-1-oxide. Examples of isothiazoline compounds include 1,2-benzisothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one magnesium chloride, 5-chloro-2-methyl-4-isothiazolin-3-one calcium chloride, and 2-methyl-4-isothiazolin-3-one calcium chloride. Other specific examples of antiseptic and antifungal agents include anhydrous sodium acetate, sodium sorbate, sodium benzoate, and products of Arch Chemical Co. under the trade names Proxel GXL(S), Proxel LV, and Proxel XL-2(S).

[0038] [pH adjuster] Specific examples of pH adjusters 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 bicarbonate, and potassium carbonate; alkali metal salts of organic acids such as sodium silicate and potassium acetate; and inorganic bases such as disodium phosphate.

[0039] [Rust inhibitor] Specific examples of the rust inhibitor include acid sulfite, sodium thiosulfate, ammonium thioglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite.

[0040] [Antifoaming agent] Examples of the defoaming agent include silicone-based, silica mineral oil-based, olefin-based, acetylene-based, etc. Examples of commercially available defoaming agents include Surfynol DF37, DF58, DF110D, DF220, MD-20, Olefin SK-14, etc., all manufactured by Shin-Etsu Chemical Co., Ltd.

[0041] [water] The ink is an aqueous ink containing water. The water contained in the ink is preferably water containing a small amount of impurities such as metal ions, i.e., ion-exchanged water, distilled water, etc. Such water can be prepared by a known method.

[0042] When preparing the ink, a known method for producing a dispersion ink can be used. One example of such a method is to prepare an ink by preparing an aqueous dispersion from a colorant and a resin as a dispersant, and then adding and mixing water, various organic solvents, and, if necessary, ink preparation agents to this dispersion.

[0043] When the ink is used as an inkjet ink, it is preferable to use an ink having a low content of inorganic impurities such as chlorides (e.g., sodium chloride) and sulfates (e.g., sodium sulfate) of metal cations. Such inorganic impurities are often contained in commercially available colorants. The guideline for the content of inorganic impurities is approximately 1% by mass or less relative to the total mass of the colorant, and the lower limit is below the detection limit of analytical equipment, i.e., 0%, is ideal. Examples of methods for obtaining a colorant with reduced inorganic impurities include desalination treatments such as a method using a reverse osmosis membrane; a method in which a solid colorant is suspended and stirred in a mixed solvent of a C1-C4 alcohol such as methanol and water, and the colored body is separated by filtration and dried; and a method in which inorganic impurities are exchanged and adsorbed by an ion exchange resin. When the ink is used as an inkjet ink, it is preferable to microfilter the ink. When microfiltering, a membrane filter and / or glass filter paper can be used. The pore size of the filter used for microfiltering is usually 0.5 μm to 20 μm, preferably 0.5 μm to 10 μm.

[0044] The ink can be used in various printing fields. For example, it is suitable for applications such as writing, printing, information printing, textile printing, etc. It is particularly preferable to use the ink for inkjet printing.

[0045] The inkjet printing method is a method of printing by ejecting droplets of the ink in response to a printing signal and depositing them on a printing medium. There are no particular limitations on the ink nozzles of the inkjet printer that eject the ink, and they can be appropriately selected depending on the purpose. Inkjet printing methods include a method of improving image quality by ejecting a large number of inks with a low content of colorant in a small volume, a method of improving image quality by using multiple inks with substantially the same hue but different content of colorant in the ink, and a method of improving fixation of the colorant to the printing medium by using a colorless transparent ink in combination with an ink containing a colorant, etc. The above ink can be used as an ink containing a colorant in these methods as well.

[0046] The inkjet printing method may be any known method, such as a charge control method, a drop-on-demand method (also called a pressure pulse method), an acoustic inkjet method, a thermal inkjet method, and the like.

[0047] The printing media mentioned above is particularly preferably a printing media that is poorly ink-absorbent. Examples of printing media that are poorly ink-absorbent include media used in gravure printing and offset printing, art paper, coated paper, matte paper, cast paper, and the like. The poorly ink-absorbent printing media refers to coated paper with a white pigment applied to the surface of the paper. Generally, to obtain a better printed image, the paper surface needs to be smooth, but the surface of paper made only from pulp has considerable unevenness when viewed under a microscope. Therefore, poorly ink-absorbent printing media is made by dispersing fine particles of clay or calcium carbonate in water together with a binder and applying the dispersion to the surface of the paper to improve its smoothness. An example of a commercially available printing medium with poor ink absorption is offset coated paper OK Topcoat+ manufactured by Oji Paper Co., Ltd.

[0048] When printing on a print medium using the inkjet printing method, for example, a container containing the ink (called an ink tank or the like) is loaded into a predetermined position of an inkjet printer, and printing is performed on the print medium using the printing method. The inkjet printing method can be used to print in full color by using an ink set of a plurality of inks selected from the color inks described above. In this case, containers containing inks of each color are loaded in predetermined positions of the inkjet printer in the same manner as described above, and printing is performed on a print medium by the printing method described above.

[0049] All of the above-mentioned components can be used alone, or multiple components can be used in combination as necessary. For all of the above, 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. EXAMPLES

[0050] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples. Furthermore, all operations such as synthesis reactions were carried out under stirring unless otherwise specified. In the examples, when quantitative determination of the pigment solid content in the dispersion was required, it was determined by the dry weight method using MS-70 manufactured by A&D Co., Ltd. The pigment solid content is a converted value calculated from the total amount of solids, i.e., the pigment solid content alone. Each ink described in the examples is included in the above ink composition.

[0051] [Synthesis Example 1] Preparation of Dispersion 1. A block copolymer of Synthesis Example 3 was prepared by re-examining Synthesis Example 3 of WO 2013 / 115071. The acid value of the obtained block copolymer was 105 mgKOH / g and Mw was 25000. 6.6 parts of the obtained block copolymer was dissolved in 20 parts of 2-butanone, and a solution obtained by dissolving 0.36 parts of sodium hydroxide in 50 parts of ion-exchanged water was added thereto and stirred for 30 minutes to obtain an emulsion. Nerox 605 (20 parts) manufactured by ORION was added to the obtained emulsion, and a dispersion treatment was performed for 15 hours under a condition of 1500 rpm with a sand grinder to obtain a liquid. 120 parts of ion-exchanged water was added to the obtained liquid, and the dispersion beads were filtered and separated to obtain a filtrate. 2-butanone and a part of the water were distilled off from the obtained filtrate under reduced pressure with an evaporator to obtain a dispersion liquid 1 having a pigment solid content of 12%.

[0052] [Synthesis Example 2] Preparation of acrylic resin emulsion 2. A liquid was obtained by adding water (100 parts), ammonium persulfate (0.3 parts), and a reactive emulsifier (1 part) to a glass reaction vessel (capacity 3 liters). After replacing the air inside the reaction vessel with nitrogen, the temperature of the liquid was raised to 70°C. A liquid consisting of water (120 parts), a reactive emulsifier (0.9 parts), methacrylic acid (2 parts), methyl methacrylate (37 parts), 2-ethylhexyl acrylate (59 parts), and allyl methacrylate (2 parts) was added dropwise to this liquid over 3 hours. During the dropwise addition of the liquid, the liquid temperature was maintained at 70°C while introducing nitrogen, and the reaction was carried out. After the dropwise addition of the liquid was completed, the reaction was further carried out at 70°C for 2 hours to obtain a liquid, and then the liquid was cooled to 40°C to obtain a liquid. Triethanolamine (3.1 parts) was added to the obtained liquid to obtain an emulsion of acrylic resin 2 as a white suspension with a solid content of 25%. The obtained emulsion of acrylic resin 2 is called "A2". The resulting acrylic resin 2 emulsion had an acid value of 13 KOHmg / g and a Tg of -10°C.

[0053] [Synthesis Example 3] Preparation of silane-modified silica sol 3 surface-treated with hydrophobic silane. Water (3.3 parts) and Nissan Chemical's Snowtex 30 (80 parts) were added and mixed in a glass reactor (capacity 3 liters) equipped with a stirrer, a dropping funnel and a thermometer. Methyltrimethoxysilane KBM-13 (0.7 parts) manufactured by Shin-Etsu Silicone Co., Ltd. was added dropwise to this solution over 0.5 hours. After the dropwise addition of the liquid was completed, the liquid temperature was maintained at 60°C while stirring for 3 hours. The reaction was completed and the mixture was cooled to 25°C, and the silica concentration was adjusted to 30% with water, thereby obtaining 80 parts of silane-modified silica sol 3 surface-treated with hydrophobic silane. The particle size of the silane-modified silica sol 3 was 12 nm. [Examples 1 to 8]: Preparation of inks. The components shown in Table 1 below were mixed and then filtered through a 3 μm membrane filter to obtain inks of Examples 1 to 7 for evaluation tests.

[0054] [Comparative Examples 1 to 9]: Preparation of comparative inks. The components shown in Table 2 below were mixed and then filtered through a 3 μm membrane filter to obtain inks of Comparative Examples 1 to 9 for comparison.

[0055] The abbreviations in Tables 1 and 2 have the following meanings: DP1: Dispersion 1. 12HD: 1,2-hexanediol. PG: 1,2-propylene glycol. TEX: Texanol TEA: Triethanolamine. BYK349: BYK-349, manufactured by BYK. A2: Acrylic resin emulsion 2. (corresponding to resin emulsion, solid content 25%) AQ515: BYK AQUACER515 (corresponding to resin emulsion, solid content 35%) CC151: Levasil CC151 manufactured by Nouryon. (Silane-modified silica sol, solid content 15%, particle size 5 nm) CC301: Levasil CC301 manufactured by Nouryon. (Silane-modified silica sol, solid content 28%, particle size 7 nm) CC401: Levasil CC401 manufactured by Nouryon. (Silane-modified silica sol, solid content 37%, particle size 12 nm) CC503: Levasil CC503 manufactured by Nouryon. (Silane-modified silica sol, solid content 50%, particle size 34 nm) S3: Silica sol 3 surface-treated with hydrophobic silane. (corresponding to silane-modified silica sol, solid content 30%, particle size 12 nm) ST30: Snowtex 30 manufactured by Nissan Chemical Co., Ltd. (corresponding to the comparative sol, solid content 30%) STXS: Snowtex XS manufactured by Nissan Chemical Co., Ltd. (corresponding to the comparative sol, solid content 20%) STC: Snowtex C manufactured by Nissan Chemical Co., Ltd. (corresponding to the comparative sol, solid content 20%) ST50T: Snowtex 50T manufactured by Nissan Chemical Co., Ltd. (corresponding to the comparative sol, solid content 50%) ST30L: Snowtex 30L manufactured by Nissan Chemical Co., Ltd. (corresponding to the comparative sol, solid content 30%) SD40: Silicadol 40 manufactured by Nippon Chemical Industry Co., Ltd. (corresponding to the comparative sol, solid content 40%) GXL(s): Proxel GXL(s), manufactured by Lonza. Particle size: Sol particle size (unit: nm) Dispersion amount: Amount of sol in the ink (mass%) Binder content: The total content of resin emulsion in the ink (mass%) In Tables 1 and 2 below, a hyphen indicates that the component is 0 part, and a numerical value cannot be listed for particle size, amount of dispersion, and amount of binder because the corresponding component is not included.

[0056] [Table 1]

[0057] [Table 2]

[0058] [Inkjet printing] Each ink of Examples 1 to 8 was combined with "OK Topcoat+", an offset coated paper manufactured by Oji Paper Co., Ltd., which is a printing medium with poor ink absorption, to prepare an ink media set. Using the obtained ink media set, inkjet printing was performed by a single pass (1 pass) method using an inkjet printer. The amount of ink droplets ejected was 12 picoliters, and the head temperature was 32°C. A Kyocera 600 dpi head was used as the head. Inkjet printing was carried out so as to obtain a 100% duty image, and a printed image was obtained. The resulting image was allowed to dry completely and then used as a test piece for the following abrasion test. In addition, each ink of Comparative Examples 1 to 9 was combined with the above-mentioned "OK Topcoat+" to prepare an ink-media set. Ink-jet printing and the following abrasion test were performed in the same manner as above, except that the ink-media sets of Comparative Examples 1 to 9 were used instead of the ink-media sets of Examples 1 to 8.

[0059] [Abrasion test] The print obtained as described above was scratched in a line with a fingernail, and then the print was held up to a fluorescent lamp to observe the difference in glare between the scratched area and the non-scratched area. The evaluation criteria were as follows: A: All 10 observers judged that there was no glare or change in gloss in the rubbed area. B: All 10 observers judged that there was a glitter or change in gloss in the rubbed area. C: The ink in the rubbed area peeled off from the paper during rubbing, and no difference in glare could be observed. As a result of the abrasion test, those that received a rating of B or lower were deemed unsuitable for practical use because the abraded areas appeared shiny or the ink in the abraded areas peeled off from the paper, making the abrasion marks obvious and significantly impairing the appearance of the printed matter.

[0060] [Storage stability test] 100 g of ink was placed in a polypropylene storage bottle (Eyeboy wide-mouth bottle, AS ONE Corporation), and the bottle was closed and left for 2 weeks in an environment at 60°C. After leaving the bottle, the ink was filtered through a 3 μm membrane filter (cellulose mixed ester type, ADVANTEC TOYO CO., LTD.), and the presence or absence of residue on the filter and the rate of change in the ink viscosity were judged. The evaluation criteria were as follows. The rate of change in viscosity was calculated using the following formula. Viscosity change rate = (measured value after storage - measured value immediately after preparation) / (measured value immediately after preparation) x 100%. A: No residue is generated and the viscosity change rate is less than ±5%. B: A small amount of residue is generated, and the viscosity change rate is less than ±5%. C: A small amount of residue is generated, and the viscosity change rate is ±5% or more and less than ±10%. D: At least one of the following conditions is satisfied: a large amount of residue is generated, or the viscosity change rate is ±10% or more. The evaluation results are shown in Table 3 below.

[0061] [Table 3]

[0062] From the results in Table 3, it is clear that the inks of the examples have excellent abrasion resistance and also have storage stability rated at B or higher, and thus have both excellent abrasion resistance and storage stability. [Industrial Applicability]

[0063] The ink of the present invention is extremely useful as an aqueous ink composition for inkjet printing, and an ink media set, which are capable of preventing a large change in the glare of the coating film even when scratched by a fingernail or the like, without the need for a pretreatment agent or overcoat agent on printing media having poor ink absorption, particularly coated paper such as offset coated paper.

Claims

1. An ink composition comprising: a water-insoluble colorant selected from the group consisting of pigments, disperse dyes, and solvent dyes; a resin having a weight average molecular weight of less than 50,000 as a dispersant; at least one type of resin emulsion having a weight average molecular weight of 50,000 or more; and a silane-modified silica sol having a particle diameter of 3 nm or more and less than 35 nm.

2. 2. The ink composition of claim 1, wherein the resin emulsion comprises an acrylic resin emulsion and an oxidized polyethylene resin emulsion.

3. The ink composition according to claim 1 or 2, wherein the total solid content of the resin emulsion in the ink composition is 0.6% by mass or more and 6.0% by mass or less.

4. An ink composition set comprising the ink composition according to any one of claims 1 to 3 and another ink composition.

5. A print medium printed using the ink composition according to any one of claims 1 to 3 or the ink composition set according to claim 4.

6. An ink media set comprising the ink composition according to any one of claims 1 to 3 or the ink composition set according to claim 4 and the print medium according to claim 5.

7. A method for improving rub resistance, comprising using the ink composition according to any one of claims 1 to 3 or the ink composition set according to claim 4.

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