Ink, ink media 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 ink, an ink media set, and a method for improving abrasion resistance.

Background Art

[0002] Among various color printing methods, the printing method using an inkjet printer (inkjet printing method) is one of the typical methods. In this method, small droplets of ink are generated and attached to a printing medium such as paper to perform printing. With the progress of inkjet technology, the 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 with poor ink absorbency, such as coated paper, are frequently used. In recent years, the demand for industrial inkjet printing has been increasing, and characteristics different from those in the past are being required. As one of such characteristics, there is a strong demand for improving the abrasion resistance of the ink attached to the printing medium. For example, when printing on coated paper using an inkjet printer and the resulting printed matter is scratched with a fingernail or the like, only the scratched portion is pressed and the surface becomes smooth. As a result, light is more strongly specularly reflected only at the scratched portion, causing glare. Since only the scratched portion glares, the appearance of the entire printed matter deteriorates, resulting in a decrease in print quality. Therefore, there is a strong demand for an ink with little change in glare of the coating film even when scratched with a fingernail or the like. As a method for suppressing the glare of the coating film, there are examples of applying a pretreatment agent to the coated paper before printing or applying an overcoat agent to the coated paper after printing. However, considering cost reduction of printing, improvement of printing speed, and enlargement of the apparatus due to an additional process, it is desirable to obtain the above-described 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 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] The present invention aims to provide an aqueous inkjet ink composition that exhibits minimal change in the glare of the coating even when scratched with fingernails or other marks, when used on printing media with poor ink absorption, particularly offset coated paper; an ink media set comprising the ink and printing media; and a method for improving the abrasion resistance thereof. [Means for solving the problem]

[0005] The inventors of the present invention have conducted extensive research to solve the above problems and 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 as a dispersant with a weight-average molecular weight of less than 50,000, at least one resin emulsion with a weight-average molecular weight of 50,000 or more, and a silane-modified silica sol with a particle size of 3 nm or more and less than 35 nm can solve the above problems and exhibits excellent storage stability of the ink, thus completing the present invention.

[0006] In other words, 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 used as a dispersant having a weight-average molecular weight of less than 50,000; at least one 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. 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 amount of solids in 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 an ink composition described in any one of items 1) to 3) and another ink composition. 5) Printed media printed using any one of the ink compositions described in item 1) to 3), or the ink composition set described in item 4). 6) An ink media set comprising an ink composition described in any one of items 1) to 3), or an ink composition set described in 4), and a printing media described in 5). 7) A method for improving abrasion resistance using an ink composition described in any one of items 1) to 3), or an ink composition set described in item 4). [Effects of the Invention]

[0007] The present invention provides an aqueous inkjet ink composition, an ink media set, and a method for improving abrasion resistance, which minimize changes in the glare of the coating even when scratched by fingernails or other marks, without the need to apply pretreatment agents or overcoats to ink-poor ink-absorbing printing media, particularly coated paper such as offset coated paper. [Modes for carrying out the invention]

[0008] In this specification, "CI" means "Color Index." Furthermore, in this specification, including in examples, "%" and "parts" are expressed on a mass basis unless otherwise specified. Furthermore, in this specification, the terms "alkylene," "propylene," and "alkyl" are used to encompass both linear and branched structures unless otherwise specified. Also, when values ​​are given as mass percent and include decimal points, the second decimal place is considered valid, and the second decimal place is rounded to one decimal place.

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

[0010] [Water-insoluble colorants 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, 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 solubility includes 0 g. In this specification, unless otherwise specified, "water-insoluble colorants selected from pigments, disperse dyes, and solvent dyes" may be abbreviated as "colorants." Colorants can be used in combination. When using colorants in combination, it is preferable to use two or more types if the ink is a color ink other than black ink, and to use three to five types if the ink is black ink. However, if the black ink contains carbon black as a coloring agent, it is preferable that there be two or one type of coloring agent. In this specification, "color ink" refers to colored inks other than black ink (for example, inks of various colors such as yellow, magenta, cyan, red, orange, brown, violet, blue, and green). Furthermore, among pigments, disperse dyes, and solvent dyes, pigments are preferred. Examples of pigments include inorganic pigments and organic pigments.

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

[0012] Preferred colorants for the above-mentioned black ink include, for example, carbon blacks such as thermal black, acetylene black, oil furnace black, gas furnace black, lamp black, gas black, and channel black. Specific examples of carbon blacks include, for example, the Raven series from Columbia Carbon; the Monarch series, Regal series, and Mogul series from Cabot; the ColorBlack series, Printex series, SpecIalBlack series, and Nerox series from Orion Engineered Carbons; and the MA series, MCF series, No. 25, No. 33, No. 40, No. 47, No. 52, No. 900, and No. 2300 from Mitsubishi Chemical Corporation.

[0013] Examples of the above-mentioned organic pigments include azo, disazo, phthalocyanine, quinacridone, isoindolinone, dioxazine, perylene, perinone, thioindigo, antholaquinone, and quinophthalone.

[0014] Examples of the organic pigment include known organic pigments. Examples of the known organic pigments include, for example, yellows such as C.I.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, 213; reds such as C.I.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, 207, 254, 255, 257, 260, 264, 269, 272; blues such as C.I.Pigment Blue 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 22, 25, 60, 66, 80; violets such as C.I.Pigment Violet 19, 23, 29, 37, 38, 50; oranges such as C.I.Pigment Orange 13, 16, 43, 68, 69, 71, 73; greens such as C.I.Pigment Green 7, 36, 54; blacks such as C.I.Pigment Black 1.

[0015] Examples of the disperse dyes include known disperse dyes. Among them, dyes selected from C.I.Dispers are preferred. Specific examples thereof include, for example, C.I.Dispers Yellow 9, 23, 33, 42, 49, 54, 58, 60, 64, 66, 71, 76, 79, 83, 86, 90, 93, 99, 114, 116, 119, 122, 126, 149, 160, 163, 165, 180, 183, 186, 198, 200, 211, 224, 226, 227, 231, 237, etc. of yellow; C.I.Dispers Red 60, 73, 88, 91, 92, 111, 127, 131, 143, 145, 146, 152, 153, 154, 167, 179, 191, 192, 206, 221, 258, 283, etc. of red; C.I.Dispers Orange 9, 25, 29, 30, 31, 32, 37, 38, 42, 44, 45, 53, 54, 55, 56, 61, 71, 73, 76, 80, 96, 97, etc. of orange; C.I.Dispers Violet 25, 27, 28, 54, 57, 60, 73, 77, 79, 79:1, etc. of violet; C.I.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, 368, etc. of blue disperse dyes of each color. Also, as the solvent dye, a dye selected from C.I.Solvent is preferred.

[0016] In the total mass of the above ink, the total content of the colorant is usually 1 to 30%, preferably 1 to 10%, more preferably 2 to 7%. Also, the average particle size of the colorant is usually 50 nm to 250 nm, preferably 60 nm to 200 nm. In this specification, the average particle size refers to the average particle size of the particles measured by the laser light scattering method.

[0017] [Resin as a dispersant] Examples of resins used as dispersants include copolymers composed of at least two monomers (preferably at least one of which is hydrophilic) selected from monomers in the group consisting of 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; fahric acid and its derivatives; vinyl acetate, vinyl alcohol, vinylpyrrolidone, acrylamide, and their derivatives. Examples of such copolymers include styrene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid-(meth)acrylic acid ester copolymer, (meth)acrylic acid ester-(meth)acrylic acid copolymer, polyethylene glycol (meth)acrylate-(meth)acrylic acid copolymer, and styrene-maleic acid copolymer. Among these, styrene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid-(meth)acrylic acid ester copolymer, (meth)acrylic acid ester-(meth)acrylic acid copolymer, and polyethylene glycol (meth)acrylate-(meth)acrylic acid copolymer are preferred; styrene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid-(meth)acrylic acid ester copolymer, and (meth)acrylic acid ester-(meth)acrylic acid copolymer are more preferred; (meth)acrylic acid ester-(meth)acrylic acid copolymer is even more preferred; and methacrylic acid ester-methacrylic acid copolymer is particularly preferred. In this specification, the term "(meth)acrylic" is used to include both "acrylic" and "methacrylic." The same applies to "(meth)acrylate," etc. Examples of copolymer types include block copolymers, random copolymers, graft copolymers, and / or salts thereof. Resins used as dispersants can be synthesized or obtained commercially. Specific examples of commercially available products include styrene-acrylic copolymers such as Johncryl 62, 67, 68, 678, and 687, all manufactured by Johnson Polymers; Movinyl S-100A (modified vinyl acetate copolymer manufactured by Hoechst Synthetic Co., Ltd.); and Julimer AT-210 (polyacrylic acid ester copolymer manufactured by Nippon Junyaku Co., Ltd.). As copolymers obtained by synthesis, the AB block polymer disclosed in International Publication No. 2013 / 115071 is a preferred example.

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

[0019] The resin used as a dispersant can be used either in a state mixed with the coloring agent, or in a state in which part or all of the surface of the coloring agent is coated with the resin as a dispersant. Furthermore, both of these states can be used in combination.

[0020] The above ink is preferably prepared by first preparing a dispersion containing a water-insoluble colorant and a resin as a dispersant, and then mixing it with other components. Known methods can be used to prepare the dispersion. One example is the phase inversion emulsification method. That is, the 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 coloring agent is added to the resulting emulsion and dispersed. By removing the organic solvent and some of the water from the resulting liquid under reduced pressure, the desired dispersion can be obtained. Dispersion processing can be carried out using, for example, a sand mill (bead mill), roll mill, ball mill, paint shaker, ultrasonic disperser, microfluidizer, etc. For example, when using a sand mill, beads with a particle size of about 0.01 mm to 1 mm can be used, and the dispersion processing can be carried out by appropriately setting the bead packing ratio. The dispersion obtained as described above can be subjected to operations such as filtration and / or centrifugation. This operation can standardize the particle size of the particles contained in the dispersion. If foaming occurs during the preparation of the dispersion, a very small amount of a known defoaming agent, such as a silicone-based or acetylene glycol-based agent, can be added. Other methods for preparing dispersions include acid precipitation, interfacial polymerization, in-situ polymerization, liquid curing coating, coacervation (phase separation), liquid drying, melt-dispersion-cooling, air suspension coating, and spray drying. Among these, phase inversion emulsification, acid precipitation, and interfacial polymerization are preferred.

[0021] The average particle size (D50) of the water-insoluble colorant in the dispersion is typically 300 nm or less, preferably 30 to 280 nm, more preferably 40 to 270 nm, and even more 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 an upper limit of 100 nm or less. Particle size can be measured using laser light scattering.

[0022] [Resin emulsion] The aforementioned resin emulsion preferably has a weight-average molecular weight (MW) of 50,000 or more and contains one or more selected from polymers and waxes. Examples of the polymers include urethane-based, polyester-based, acrylic-based, vinyl acetate-based, vinyl chloride-based, styrene-acrylic-based, acrylic-silicone-based, and styrene-butadiene-based polymers or emulsions containing them. Among these, polymers selected from urethane-based, acrylic-based, and styrene-butadiene-based polymers are preferred, with acrylic-based polymers being more preferred. The aforementioned polymer can be synthesized or purchased commercially. When synthesizing the polymer, polymers disclosed in, for example, International Publication No. 2015 / 147192, are preferred. Examples of commercially available products include Superflex 126, 130, 150, 170, 210, 420, 470, 820, 830, 890 (urethane resin emulsions manufactured by Daiichi Kogyo Seiyaku Co., Ltd.); Hydran HW-350, HW-178, HW-163, HW-171, AP-20, AP-30, WLS-201, WLS-210 (urethane resin emulsions manufactured by DIC Corporation); 0569, 0850Z, 2108 (styrene-butadiene resin emulsions manufactured by JSR Corporation); and AE980, AE981A, AE982, AE986B, AE104 (acrylic resin emulsions manufactured by E-Tech Co., Ltd.).

[0023] As the wax, a wax emulsion is preferred, and a water-based wax emulsion is more preferred. Natural waxes and synthetic waxes can be used as the wax. Examples of natural waxes include petroleum-based waxes such as paraffin wax and microcrystalline wax; lignite-based waxes such as montane wax; plant-based waxes such as carnauba wax and candelilla wax; and emulsions in which waxes such as beeswax and lanolin are dispersed in an aqueous medium.

[0024] Examples of the synthetic waxes mentioned above include polyalkylene wax (preferably poly C2-C4 alkylene wax), oxidized polyalkylene wax (preferably oxidized poly C2-C4 alkylene wax), and paraffin wax. Of these, one or more waxes selected from polyethylene wax, polypropylene wax, oxidized polyethylene wax, oxidized polypropylene wax, and paraffin wax are preferred, with oxidized polyethylene wax being more preferred. Furthermore, 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, 991; AQUACER 498, 515, 526, 531, 537, 539, 552, 1547; AQUAMAT 208, 263, 272; MINERPOL 221, etc. from Big Chemie Japan; Mitsui High Wax NL100, NL200, NL500, 4202E, 1105A, 2203A, NP550, NP055, NP505, etc. from Mitsui Chemicals, Inc.; KUE-100, 11 from Sanyo Chemical Co., Ltd.; and HYTECE-6500, 9015, 6400 from 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%, preferably 1.0% to 5%, from the viewpoint of ink fixation to paper, ink discharge performance, and ink storage stability.

[0027] [Silane-modified silica sol] The silane-modified silica sol mentioned above refers to a solution in which colloidal particles of silane-modified silica are dispersed in a liquid. From the viewpoint of storage stability of the ink composition, this silane-modified silica sol is preferably an aqueous or water-soluble organic solvent-based silane-modified silica sol. The silane-modified silica sol refers to a sol in which part or all of the surface of the silica particles is coated with silane. From the viewpoint of storage stability of the ink, it is particularly preferable that 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. Furthermore, the silane coating on the surface of the silica particles can be arbitrarily changed in terms of coating rate depending on the purpose to obtain a silane-modified silica sol. In addition, if the ink contains two or more of the above silane-modified silica sols, those with different coating rates may be used in combination, or the silane and silane derivatives used for the coating may be arbitrarily selected and used individually or in combination for processing. This is because the steric repulsion between substituents on the particle surface stabilizes the sol itself and thus stabilizes the ink. Furthermore, silane-treated and coated silane-modified silica sol can be obtained commercially, or it can be obtained by treating commercially available untreated silica sol with a silane coupling agent. Specific examples of commercially available silane-modified silica sols include, for example, the Levasil series manufactured by Nurion. On the other hand, specific examples of commercially available silica sols that have not undergone the above-mentioned silane treatment include, for example, the Snowtex series manufactured by Nissan Chemical Corporation, the SI series manufactured by JGC Catalysts & Chemicals Co., Ltd., the Silica Doll series manufactured by Nippon Chemical Industrial Co., Ltd., and the PL series manufactured by Fuso Chemical Industries, Ltd. Furthermore, 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 Corporation.

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

[0029] The aforementioned ink may contain, as needed, ink preparation agents such as organic solvents, surfactants, fungicides, preservatives, pH adjusters, rust inhibitors, defoamers, and water. These ink preparation agents may be used individually or in combination of two or more.

[0030] [Organic solvents] Organic solvents are not particularly limited, but examples include C1-C6 alkanols such as methanol, ethanol, propanol, texanol, isopropanol, butanol, isobutanol, tertiary butanol, or tertiary butanol; carboxylic acid amides such as N,N-dimethylformamide or N,N-dimethylacetamide; lactams such as 2-pyrrolidone, N-methyl-2-pyrrolidone, or N-methylpyrrolidine-2-one; cyclic ureas such as 1,3-dimethylimidazolidine-2-one or 1,3-dimethylhexahydropyrimido-2-one; ketones, keto alcohols, or carbonates such as acetone, 2-methyl-2-hydroxypentan-4-one, and ethylene carbonate; and cyclic ureas such as tetrahydrofuran and dioxane. Ethers; 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 with molecular weights of 400, 800, 1540 or higher), polypropylene glycol, thiodiglycol or dithiodiglycol, and other mono, oligo, or polyalkylene glycols or thioglycols having C2-C6 alkylene units; glycerin, diglycerin, hexane-1,2,6-triol, trimethylolpropane, and other C3-C9 polyols (triols);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 ( Examples include glycol ethers such as butyl carbitol, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, propylene glycol monopropyl ether, prolene glycol monobutyl ether, and dipropylene glycol monomethyl ether (preferably 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, and 2,4-diethyl-1,5-pentanediol; γ-butyrolactone or dimethyl sulfoxide; and others, with 1,2-hexanediol and texanol being preferred.

[0031] [Surfactants] Examples of surfactants include anionic, nonionic, silicone-based, and fluorine-based surfactants. Among these, silicone-based and fluorine-based surfactants are preferred, and silicone-based surfactants are more preferred from the viewpoint of safety for living organisms and the environment.

[0032] Examples of anionic surfactants include alkyl sulfocarboxylates, α-olefin sulfonates, polyoxyethylene alkyl ether acetates, polyoxyethylene alkyl ether sulfates, N-acyl amino acids or their salts, N-acyl methyl taurates, alkyl sulfates, polyoxyalkyl ether sulfates, alkyl sulfates, polyoxyethylene alkyl ether phosphates, rosinic acid soaps, castor oil sulfates, lauryl alcohol sulfates, alkylphenol type phosphates, alkyl type phosphates, alkylaryl sulfonates, diethyl sulfosaturates, diethylhexyl sulfosaturates, and dioctyl sulfosaturates.

[0033] 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-decine-4,7-diol, 3,6-dimethyl-4-octin-3,6-diol, and 3,5-dimethyl-1-hexyn-3-ol; and polyglycol ether-based surfactants. Examples of these commercially available products include Surfinol 104, 104PG50, 82, 420, 440, 465, 485, and Olfin STG from Nisshin Chemical Co., Ltd., and Emulgen A-60, A-90, and A-500 from Kao Corporation.

[0034] Examples of silicone-based surfactants include polyether-modified siloxanes and polyether-modified polydimethylsiloxanes. Examples include Dynol 960 and 980 from Air Products; Silface SAG001, SAG002, SAG003, SAG005, SAG503A, SAG008, SAG009, and SAG010 from Nisshin Chemical Co., Ltd.; and BYK-345, 347, 348, 349, 3455, LP-X23288, LP-X23289, and LP-X23347 from BYK Additives & Instruments; and TEGOTwin4000, TEGOWetKL245, 250, 260, 265, 270, and 280 from Evonic Tego Chemie.

[0035] Examples of fluorine-based surfactants include perfluoroalkyl sulfonic acid compounds, perfluoroalkyl carboxylic acid compounds, perfluoroalkyl phosphate ester compounds, perfluoroalkyl ethylene oxide adducts, and polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups in their side chains.

[0036] [Antifungal agent] Specific examples of antifungal agents include sodium dehydroacetate, sodium benzoate, sodium pyridinethion-1-oxide, ethyl p-hydroxybenzoate, 1,2-benzisothiazolin-3-one, and their salts.

[0037] [Preservatives] Examples of preservatives include compounds such as organosulfur, organonitrogen-sulfur, organohalogen, haloarylsulfone, iodopropagyl, haloalkylthio, nitrile, pyridine, 8-oxyquinoline, benzothiazole, isothiazolin, dithiol, pyridine oxide, nitropropane, organotin, phenol, quaternary ammonium salt, triazine, thiazine, anilide, adamantane, dithiocarbamate, brominated indanone, benzylbromoacetate, or inorganic salts. A specific example of an organic halogen compound is, for instance, sodium pentachlorophenol. A specific example of a pyridine oxide compound is sodium 2-pyridinethiol-1-oxide. Examples of isothiazolin 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 antiseptics and antifungal agents include anhydrous sodium acetate, sodium sorbate, or sodium benzoate, and products manufactured by Arch Chemical, such as 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 (ammonia water); alkali metal carbonates such as lithium carbonate, sodium carbonate, sodium bicarbonate, and potassium carbonate; alkali metal salts of organic acids such as sodium silicate and potassium acetate; and inorganic bases such as disodium phosphate.

[0039] [Rust inhibitor] Specific examples of rust inhibitors include, for example, acidic sulfites, sodium thiosulfate, ammonium thioglycolate, diisopropylammonium nitride, pentaerythritol tetranitrate, or dicyclohexylammonium nitride.

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

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

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

[0043] When using the above ink as an inkjet ink, it is preferable to use an ink with a low content of inorganic impurities such as metal cation chlorides (e.g., sodium chloride) and sulfates (e.g., sodium sulfate). Such inorganic impurities are often found in commercially available colorants. The guideline for the inorganic impurity content is approximately 1% by mass or less relative to the total mass of the colorant, and the lower limit should ideally be below the detection limit of analytical instruments, i.e., 0%. Methods for obtaining a colorant with few inorganic impurities include, for example, a method using a reverse osmosis membrane; a method in which the solid colorant is suspended and stirred in a mixed solvent of C1-C4 alcohol such as methanol and water, the colorant is filtered and separated, and then dried; or a method of exchanging and adsorbing inorganic impurities with an ion exchange resin; and other desalting treatments. Furthermore, when using the above ink as an inkjet ink, it is preferable to microfiltration the ink. When microfiltration is performed, a membrane filter and / or glass filter paper can be used. The pore size of the filter used for microfiltration is usually 0.5 μm to 20 μm, preferably 0.5 μm to 10 μm.

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

[0045] The above inkjet printing method involves ejecting droplets of ink in response to a print signal and adhering them to the printing medium to perform printing. There are no particular restrictions on the ink nozzles of the inkjet printer that eject the ink, and they can be appropriately selected according to the purpose. Inkjet printing methods include improving image quality by ejecting a large number of inks with a low colorant content in small volumes; improving image quality by using multiple inks with substantially the same hue but different colorant content; and improving the fixation of colorants to the printing medium by using a colorless, transparent ink in combination with an ink containing a colorant. The above-mentioned inks can also be used as inks containing colorants in these methods.

[0046] Inkjet printing can utilize known methods. Examples include charge control methods, drop-on-demand methods (also known as pressure pulse methods), acoustic inkjet methods, and thermal inkjet methods.

[0047] Of the printing media mentioned above, ink-poorly absorbent printing media are particularly preferred. Examples of ink-poorly absorbent printing media include media used in gravure printing and offset printing, art paper, coated paper, matte paper, and cast paper. Ink-poorly absorbent printing media refer to coated paper in which a white pigment is applied to the surface of the paper. Generally, smoothness of the paper surface is necessary to obtain a better printed image, but the surface of paper made only from pulp has considerable irregularities when viewed under a microscope. Therefore, ink-poorly absorbent printing media are made by dispersing fine particles of clay or calcium carbonate together with a binder in water and applying it to the surface of the paper to improve its smoothness. Examples of commercially available ink-poor printing media include OK Topcoat+ offset coated paper manufactured by Oji Paper Co., Ltd.

[0048] When printing on a printing medium using the inkjet printing method described above, for example, a container containing the ink (referred to as an ink tank, etc.) is loaded into a designated position in the inkjet printer, and the printing is performed on the printing medium using the printing method described above. The above inkjet printing method allows for full-color printing using an ink set of multiple inks selected from the above color inks. In this case, the containers containing each color ink are loaded into the designated positions in the inkjet printer as described above, and printing is performed on the printing medium using the above printing method.

[0049] Of the ingredients listed above, only one type may be used. Furthermore, multiple types may be selected and used in combination as needed. For all of the above, a combination of desirable elements is more desirable, and a combination of more desirable elements is even more desirable. The same applies to combinations of desirable elements and more desirable elements, and combinations of more desirable elements and even more desirable elements, 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 solids content in the dispersion was necessary, it was determined by the dry weight method using an MS-70 manufactured by A&D Company, Limited. The pigment solids content is a converted value calculated from the total amount of solids, with only the pigment solids content being considered. Each ink described in the examples is included in the above ink composition.

[0051] [Synthesis Example 1] Preparation of dispersion 1. The block copolymer of Synthesis Example 3 was prepared by replicating Synthesis Example 3 of International Publication No. 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 were dissolved in 20 parts of 2-butanone, and a solution of 0.36 parts of sodium hydroxide dissolved in 50 parts of deionized water was added. The mixture was stirred for 30 minutes to obtain an emulsion. 20 parts of Nerox 605 from ORION were added to the emulsion, and the mixture was dispersed in a sand grinder at 1500 rpm for 15 hours to obtain a liquid. 120 parts of deionized water were added to the obtained liquid, and the dispersion beads were filtered to obtain a filtrate. From the obtained filtrate, 2-butanone and a portion of the water were removed by vacuum distillation using an evaporator to obtain dispersion 1 with a pigment solid content of 12%.

[0052] [Synthesis Example 2] Preparation of acrylic resin emulsion 2. Water (100 parts), ammonium persulfate (0.3 parts), and reactive emulsifier (1 part) were added to a glass reaction vessel (capacity 3 liters) to obtain a solution. After replacing the air inside the reaction vessel with nitrogen, the temperature of the solution was raised to 70°C. To this solution, a solution consisting of water (120 parts), 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 over 3 hours. During the addition of the solution, the solution temperature was maintained at 70°C while introducing nitrogen, and the reaction was carried out. After the addition of the solution was completed, the reaction was continued at 70°C for another 2 hours to obtain a solution, and then cooled to 40°C to obtain the final solution. By adding triethanolamine (3.1 parts) to the obtained solution, an emulsion of acrylic resin 2 was obtained as a white suspension with a solid content of 25%. The obtained emulsion of acrylic resin 2 was designated as "A2". The resulting acrylic resin emulsion had an acid value of 13 KOH mg / g and a Tg of -10°C.

[0053] [Synthesis Example 3] Preparation of silane-modified silica sol 3 surface-treated with hydrophobic silane. In a glass reactor (capacity 3 liters) equipped with a stirrer, dropping funnel, and thermometer, 3.3 parts water and 80 parts Nissan Chemical Industries, Ltd.'s Snowtex 30 were added and mixed. To this solution, 0.7 parts Shin-Etsu Silicone's methyltrimethoxysilane KBM-13 were added dropwise over 0.5 hours. After the addition of the liquid was complete, the mixture was kept at a temperature of 60°C and stirred for 3 hours. After completing the reaction, the mixture was cooled to 25°C, and the silica concentration was adjusted with water to 30%, yielding 80 parts of silane-modified silica sol 3, which was surface-treated with hydrophobic silane. The particle size of silane-modified silica sol 3 was 12 nm. [Examples 1-8]: Ink preparation. After mixing the components listed in Table 1 below, the mixtures were filtered through a 3 μm membrane filter to obtain the inks for Examples 1 to 7 for evaluation testing.

[0054] [Comparative Examples 1-9]: Preparation of comparative inks. After mixing the components listed in Table 2 below, the mixture was filtered through a 3 μm membrane filter to obtain comparative examples 1 to 9.

[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: Manufactured by BYK, BYK-349. A2: Acrylic resin emulsion 2. (Classifies as a resin emulsion, solids content 25%) AQ515: Manufactured by BYK, AQUACER 515. (Resin emulsion, solids content 35%) CC151: Levasil CC151 manufactured by Nurion. (Similar to silane-modified silica sol, 15% solids content, particle size 5 nm) CC301: Levasil CC301 manufactured by Nurion. (Similar to silane-modified silica sol, 28% solids content, particle size 7 nm) CC401: Levasil CC401 manufactured by Nurion. (Similar to silane-modified silica sol, 37% solids content, particle size 12 nm) CC503: Levasil CC503 manufactured by Nurion. (Similar to silane-modified silica sol, 50% solids content, particle size 34 nm) S3: Silica sol 3 surface-treated with hydrophobic silane. (Similar to silane-modified silica sol, 30% solids content, 12 nm particle size.) ST30: Snowtex 30 manufactured by Nissan Chemical Corporation. (Comparable to the comparative example sol, solid content 30%) STXS: Snowtex XS manufactured by Nissan Chemical Corporation. (Comparable to the comparative example sol, solid content 20%) STC: Snowtex C, manufactured by Nissan Chemical Corporation. (Comparable to the comparative example sol, solid content 20%) ST50T: Snowtex 50T manufactured by Nissan Chemical Corporation. (Comparable to the comparative example sol, solid content 50%) ST30L: Snowtex 30L manufactured by Nissan Chemical Corporation. (Comparable to the comparative example sol, solid content 30%) SD40: Silica Doll 40 manufactured by Nippon Chemical Industrial Co., Ltd. (Comparable to the comparative example sol, solid content 40%). GXL(s): Proxel GXL(s) manufactured by Lonza. Particle size: The diameter of the particles in the sol. (Unit: nm) Dispersion volume: The amount of sol in the ink. (mass %) Binder content: Total resin emulsion content in the ink. (by mass) In Tables 1 and 2 below, hyphens indicate that the component is 0 parts, and that the particle size, dispersion amount, and binder amount do not contain the corresponding component and therefore cannot be represented numerically.

[0056] [Table 1]

[0057] [Table 2]

[0058] [Inkjet printing] Each ink from Examples 1-8 was combined with "OK Topcoat+", an offset coated paper manufactured by Oji Paper Co., Ltd., which is a printing medium with low ink absorption, to create an ink media set. Using the obtained ink media set, inkjet printing was performed using an inkjet printer in a single-pass (1-pass) method. The appropriate amount of ink ejected was 12 picoliters, and the head temperature was 32°C. A Kyocera 600dpi head was used as the print head. Inkjet printing was performed to obtain a 100% duty cycle image, and the printed image was then obtained. The obtained images were allowed to dry completely and then used as test pieces to perform the following abrasion test. Furthermore, ink media sets were created by combining each of the inks from Comparative Examples 1 to 9 with the "OK Top Coat+" mentioned above. Inkjet printing and the following abrasion tests 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 printed material obtained as described above was scratched with a fingernail, and then the difference in glare between the scratched and unscratched areas was observed when the printed material was held up to a fluorescent light. The evaluation criteria are as follows. A: All 10 observers determined that there was no change in shine or gloss on the scratched area. B: All 10 observers determined that there was a change in gloss or shine in the scratched area. C: When rubbing, the ink in the rubbed area peeled off the paper, making it impossible to observe the difference in glare. In the abrasion test results, those with a rating of B or lower are unsuitable for practical use because the abraded areas appear shiny, or the ink peels off the paper, making the abrasion marks visible and severely degrading the appearance of the printed material.

[0060] [Storage stability test] 100g of ink was placed in a polypropylene storage bottle (iBoy wide-mouth bottle, manufactured by AS ONE Corporation), sealed, and left in a 60°C environment for two weeks. After standing, the ink was filtered through a 3μm membrane filter (cellulose mixed ester type, manufactured by Advantec Toyo Co., Ltd.), and the presence or absence of residue on the filter and the rate of change in ink viscosity were evaluated. The evaluation criteria are as follows. The rate of change in viscosity was calculated using the following formula. Viscosity change rate = (Measurement value after storage - Measurement value immediately after preparation) / (Measurement value immediately after preparation) × 100%. A: No residue is generated at all, and the viscosity change rate is less than ±5%. B: There is slight residue generation, and the viscosity change rate is less than ±5%. C: There is slight residue generation, and the viscosity change rate is ±5% or more and less than ±10%. D: At least one of the following conditions is met: 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] The results in Table 3 show that the inks in each example exhibited excellent abrasion properties and storage stability, with all achieving a rating of B or higher. This indicates that they possess both excellent abrasion properties and storage stability. [Industrial applicability]

[0063] The ink of the present invention is extremely useful as an aqueous inkjet ink composition and ink media set that does not affect the glare of the coating even when scratched by fingernails or other marks, without the need to apply pretreatment agents or overcoats to printing media that do not absorb ink well, particularly coated paper such as offset coated paper.

Claims

1. An ink composition comprising 1 to 10% by mass of a water-insoluble colorant selected from the group consisting of pigments, disperse dyes, and solvent dyes; a resin used as a dispersant having a weight-average molecular weight of less than 50,000; at least one resin emulsion having a weight-average molecular weight of 50,000 or more; and 0.9 to 3.3% by mass of a silane-modified silica sol having a particle size of 3 nm or more and less than 35 nm, wherein the resin emulsion includes an acrylic resin emulsion and an oxidized polyethylene resin emulsion, and 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.

2. An ink composition set comprising the ink composition described in claim 1 and another ink composition.

3. A printing medium printed using the ink composition described in claim 1, or the ink composition set described in claim 2.

4. An ink media set comprising the ink composition according to claim 1, or the ink composition set according to claim 2, and the printing media according to claim 3.

5. A method for improving abrasion resistance using the ink composition described in claim 1, or the ink composition set described in claim 2.

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