Ink composition

Abstract

To provide an ink composition for inkjet printing that allows provision of printed matter having superior mechanical stability and superior scratch resistance.SOLUTION: An ink composition for a recording head having an ink circulation mechanism comprises a pigment, montan wax, and water.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an ink composition. [Background technology]

[0002] Printing using an inkjet printer recording device involves ejecting ink from a nozzle and depositing it on a recording material. Unlike conventional printing methods, this method does not use plates, making it a printing method that is expected to be used in a wide range of fields as an on-demand printing method that can handle small-lot, high-mix production. In recent years, inkjet printing has been expanding from personal and office use to industrial printing. In particular, in the field of packaging applications such as corrugated cardboard, folding cartons, labels, and packaging film, interest in inkjet printing methods that can reproduce high-quality designs has been growing from the perspective of adding value. Such packaging applications require printed materials with properties that can withstand actual use, and therefore, inks with excellent abrasion resistance are required. Generally, various resins are added to ink to make it resistant to abrasion, and it is known that the more resin added, the better the abrasion resistance. However, adding a large amount of resin makes the ink more prone to drying, which can lead to problems such as ink sticking on the head nozzle surface and reduced ejection reliability. Meanwhile, in recent years, circulation heads have been actively developed that have a mechanism for preventing ink from drying out near the nozzles by circulating the ink up to the nozzles. In printing devices with such ink circulation mechanisms, when ink is circulated for a long period of time, precipitates may form due to the shear forces applied when passing through the device's filters or when being pumped. If such precipitates form, the filters in the head may become clogged, ultimately shortening the head life of the inkjet head (for example, resulting in poor ejection). Therefore, inks with excellent mechanical stability are required. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-2309 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an inkjet ink composition that makes it possible to provide printed matter that has excellent mechanical stability and excellent abrasion resistance. [Means for solving the problem]

[0005] As a result of extensive research aimed at solving the above-mentioned problems, the present inventors have found that an ink composition for a recording head equipped with an ink circulation mechanism, which contains a pigment, montan wax, and water, can solve the above-mentioned problems, and have thus completed the present invention.

[0006] That is, the present invention relates to the following 1) to 4). 1) An ink composition for a recording head having an ink circulation mechanism, comprising a pigment, montan wax, and water. 2) 1) The ink composition according to 1), wherein the content of the montan wax in the ink composition is 0.1% by mass or more and 5% by mass or less. 3) A recording medium recorded with the ink composition according to 1) or 2). 4) An inkjet recording method comprising: an ink composition depositing step of ejecting the ink composition according to 1) or 2) from an inkjet head and depositing it onto a recording medium. [Effects of the Invention]

[0007] The present invention has made it possible to provide an ink composition that can provide printed matter that has excellent mechanical stability and abrasion resistance. DETAILED DESCRIPTION OF THE INVENTION

[0008] In this specification, including the examples, "parts" and "%" are all based on mass unless otherwise specified. Furthermore, in this specification, the ink composition may be abbreviated as "ink."

[0009] The ink composition of the present invention is an ink composition for use in a recording head equipped with an ink circulation mechanism, and contains a pigment, montan wax, and water.

[0010] [Pigment] The ink composition includes a pigment. Examples of the pigment include inorganic pigments, organic pigments, extender pigments, and hollow particles.

[0011] Examples of inorganic pigments include carbon black, metal oxides, metal hydroxides, metal sulfides, metal ferrocyanides, and metal chlorides. When the ink according to this embodiment is a black ink and the pigment is inorganic, the inorganic pigment 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, channel black, etc. 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 HiBlack series, 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. When the ink according to this embodiment is a white ink and the pigment is an inorganic pigment, examples of the inorganic pigment contained in the white ink include oxides, nitrides, and oxynitrides of metals such as zinc, silicon, aluminum, titanium, strontium, and zirconium; inorganic compounds such as glass and silica; etc. Among these, titanium dioxide and zinc oxide are preferred.

[0012] Examples of organic pigments include various pigments such as azo, disazo, phthalocyanine, quinacridone, isoindolinone, dioxazine, perylene, perinone, thioindigo, anthraquinone, and quinophthalone.

[0013] Specific examples of organic pigments include yellow pigments 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, 155, 180, 185, 193, 199, 202, and 213; Red pigments such as 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, and 272; blue pigments such as CI Pigment Blue 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 22, 25, 60, 66, and 80; violet pigments such as CI Pigment Violet 19, 23, 29, 37, 38, and 50; orange pigments such as CI Pigment Orange 13, 16, 43, 68, 69, 71, and 73; and CI Pigment Green green pigments such as CI Pigment Black 1, CI Pigment Blue 15:4, etc., and black pigments such as CI Pigment Black 1. Of these, CI Pigment Blue 15:4 is preferred.

[0014] Examples of extender pigments include silica, calcium carbonate, talc, clay, barium sulfate, white carbon, etc. Extender pigments are often used in combination with other colorants.

[0015] As the hollow particles, known hollow particles described in, for example, U.S. Pat. No. 4,880,465, Japanese Patent No. 3,562,754, Japanese Patent No. 6,026,234, Japanese Patent No. 5,459,460, JP-A-2003-268694, Japanese Patent No. 4,902,216, etc. can be used, and they are particularly preferably used as white pigments.

[0016] The average particle size of the pigment is preferably 30 to 300 nm, more preferably 50 to 250 nm. In this specification, the average particle size refers to the average particle size of particles measured using a laser light scattering method.

[0017] The pigment content is preferably 1 to 30 mass %, more preferably 1 to 10 mass %, and even more preferably 2 to 8 mass %, relative to the total mass of the ink according to this embodiment.

[0018] The ink may further contain other dyes in addition to the pigments. Examples of the other dyes include solvent dyes, direct dyes, acid dyes, and reactive dyes.

[0019] When the ink contains multiple pigments, the blending ratio of the pigments can be set arbitrarily depending on the purpose. When the ink contains other dyes in addition to the pigments, the blending ratio of the total amount of the pigments to the total amount of the other dyes can also be set arbitrarily.

[0020] [Montan Wax] The ink contains montan wax. Montan wax generally refers to a wax made from montan wax extracted from brown coal. The "montan wax" contained in the ink of the present invention includes the above-mentioned montan wax, a "montan ester wax" obtained by further oxidizing the above-mentioned montan wax and then esterifying it, a "montan saponified wax" obtained by further oxidizing the above-mentioned montan wax and then partially saponifying it, and a "montan adduct wax" obtained by adding ethylene oxide or the like to the above-mentioned montan wax. The above-mentioned montan wax may be a wax emulsion, and it is preferable that the montan wax contained in the ink contains montan ester wax, and it is more preferable that the ink contains only montan ester wax. Specific examples of the montan ester wax include Licowax E, Licowax KPS, Licowax KSL, Licowax WE4, and Licowax WE40 manufactured by Clariant Chemicals Co., Ltd., and examples of wax emulsions include AQUACER 541 manufactured by BYK Japan Co., Ltd.

[0021] The content of the montan wax in the ink is preferably 0.1% by mass or more and 5% by mass or less, more preferably 0.2% by mass or more and 4% by mass or less, even more preferably 0.4% by mass or more and 3% by mass or less, and particularly preferably 0.5% by mass or more and 2% by mass or less.

[0022] [water] The ink composition contains water. The water is preferably 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. The content of water in the ink is preferably 55% to 90% by mass, more preferably 60% to 85% by mass.

[0023] The ink may further contain ink preparation agents in addition to the above components, such as polymer dispersants, resin emulsions, organic solvents, viscosity modifiers, surfactants, preservatives, antifungal agents, pH adjusters, chelating agents, rust inhibitors, water-soluble ultraviolet absorbers, antioxidants, and antifoaming agents.

[0024] The polymer dispersant is not particularly limited as long as it is a polymer capable of dispersing the pigment and has a weight-average molecular weight of 2,500 or more, other than the montan wax. In this specification, the polymer dispersant may be abbreviated as "dispersant." Known polymer dispersants can be used as the polymer dispersant. Examples of polymer dispersants other than the montan wax include copolymers composed of at least two monomers (preferably at least one of which is a hydrophilic monomer) selected from the following monomers: styrene and its derivatives; vinylnaphthalene and its derivatives; aliphatic alcohol esters of α,β-ethylenically unsaturated carboxylic acids; (meth)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, and (meth)acrylic acid ester-(meth)acrylic acid copolymer are preferred, (meth)acrylic acid ester-(meth)acrylic acid copolymer is more preferred, and methacrylic acid ester-methacrylic acid copolymer is even more preferred. Examples of the copolymer include block copolymers, random copolymers, and graft copolymers. These copolymers may be in the form of a salt.

[0025] Dispersants can be commercially available or synthesized.

[0026] Examples of commercially available dispersants include Joncyrl 62, 67, 68, 678, and 687 (styrene-acrylic copolymers manufactured by BASF); Movinyl S-100A (modified vinyl acetate copolymer manufactured by Japan Coating Resins Co., Ltd.); and Jurymer AT-210 (polyacrylic acid ester copolymer manufactured by Toa Gosei Co., Ltd.).

[0027] Examples of dispersants obtained by synthesis include the AB block polymer disclosed in WO 2013 / 115071. The monomer constituting the A block of the AB block polymer disclosed in WO 2013 / 115071 is at least one monomer selected from (meth)acrylic acid and linear or branched C4 alkyl (meth)acrylates, preferably at least one monomer selected from methacrylic acid and n-butyl methacrylate, and more preferably a combination of these two monomers. Furthermore, the monomer constituting the B block of the AB block polymer disclosed in WO 2013 / 115071 is at least one monomer selected from benzyl methacrylate and benzyl acrylate, preferably benzyl methacrylate. Specific examples of AB block polymers include the block copolymers disclosed in Synthesis Examples 3 to 8 of WO 2013 / 115071.

[0028] The acid value of the dispersant is usually 90 to 200 mgKOH / g, preferably 100 to 150 mgKOH / g, and more preferably 100 to 120 mgKOH / g.

[0029] A neutralizing agent may be used to uniformly disperse the dispersant in water. Examples of neutralizing agents include ammonia, alkali metal hydroxides, alkaline earth metal hydroxides, aliphatic amine compounds, and alkanolamine compounds. Among these, ammonia and alkali metal hydroxides are preferred, and ammonia is more preferred. The amount of neutralizing agent used is typically 30 to 300% neutralization, preferably 50 to 200%, with 100% neutralization being defined as neutralization with the theoretical equivalent of the acid value of the dispersant.

[0030] The mass-average molecular weight of the dispersant is usually 10,000 to 60,000, preferably 10,000 to 40,000, more preferably 15,000 to 30,000, and even more preferably 20,000 to 25,000. The mass-average molecular weight of the dispersant can be measured by gel permeation chromatography (GPC). Specifically, the measurement can be performed using an HLC-8320GPC (manufactured by Tosoh Corporation) as the GPC device, two TSK gel Super Multipore HZ-H columns (manufactured by Tosoh Corporation, inner diameter 4.6 mm × 15 cm), tetrahydrofuran as the eluent, and TSK Standard (manufactured by Tosoh Corporation) as the standard sample.

[0031] The PDI (mass average molecular weight / number average molecular weight) of the dispersant is preferably about 1.29 to 1.49. By setting the PDI within this range, the dispersibility and storage stability of the ink tend to be improved.

[0032] The dispersant can be used in a state where it is mixed with the colorant, or in a state where the surface of the colorant is partially or entirely coated with the dispersant, or both of these states can be used in combination.

[0033] In the ink, the ratio of the total mass of colorants to the total mass of dispersants, calculated as Dy / Ds, where Dy is the total mass of colorants and Ds is the total mass of dispersants, is preferably 0.01 to 1.0, more preferably 0.05 to 0.6, and even more preferably 0.1 to 0.5.

[0034] The resin emulsion is not particularly limited as long as it contains a material other than the montan wax and the polymer dispersant. The resin emulsion preferably has an acid value of less than 10 mgKOH / g. By including a resin emulsion with an acid value of less than 10 mgKOH / g in the ink composition, the ink viscosity can be kept within a suitable range, resulting in a printed image with minimal graininess. Resin emulsions with an acid value exceeding 10 mgKOH / g significantly increase the ink viscosity upon evaporation of water, which inhibits the ink from spreading after landing on the media, making it difficult to achieve uniform solid print quality. The resin emulsion preferably contains one or more selected from polymers and waxes. The method for preparing the resin emulsion is not particularly limited. Examples include a method of mechanically micronizing and dispersing a resin in an aqueous medium; and a method of preparing a resin emulsion by emulsion polymerization, dispersion polymerization, suspension polymerization, or the like. Emulsion polymerization can be carried out using an emulsifier or in a soap-free manner. Examples of methods for preparing the resin emulsion include the method disclosed in Production Example 1 of JP-A No. 2000-336292. The resin content of the resin emulsion is preferably 20 to 50%. Examples of resin emulsions 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 the same. Among these, resin emulsions selected from urethane-based, acrylic-based, and styrene-butadiene-based are preferred, and acrylic resin emulsions are more preferred. Examples of commercially available products include urethane polymers such as U-coat UX-320 (acid value: 10) manufactured by Sanyo Chemical Industry Co., Ltd., and WBR-016U (acid value: 7) and WBR-2101 (acid value: 10) manufactured by Taisei Fine Chemical Co., Ltd., polyester polymers such as Vylonal MD-1480 (acid value: 3), Vylonal MD-1985 (acid value: 2), and Vylonal MD-2000 (acid value: 2) manufactured by Toyobo Co., Ltd., and vinyl acetate polymers such as Vinyblan 715 (acid value: 8) and Vinyblan 985 (acid value: 5) manufactured by Nissin Chemical Industry Co., Ltd.

[0035] The wax is preferably a wax emulsion, more preferably an aqueous wax emulsion. The wax may be a natural wax or a synthetic wax. Examples of natural waxes include emulsions in which petroleum-based waxes such as paraffin wax and microcrystalline wax; plant-based waxes such as carnauba wax and candelilla wax; and plant-based waxes such as beeswax and lanolin are dispersed in an aqueous medium.

[0036] Examples of synthetic waxes include polyalkylene waxes (preferably poly C2-C4 alkylene waxes), oxidized polyalkylene waxes (preferably poly C2-C4 alkylene waxes), and paraffin waxes. Among these, 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 30 nm to 5 μm, more preferably 50 nm to 1 μm, in order to prevent clogging of the inkjet head.

[0037] Examples of commercially available wax emulsions include AQUACER 515 and 1547 manufactured by BYK Japan; and HYTEC E series manufactured by Toho Chemical Industry Co., Ltd., such as E-6500, E-9015, and E-6314.

[0038] When the ink contains the resin emulsion, the content of the resin emulsion in the ink composition is preferably 0.2 to 10%, and more preferably 0.5 to 5%.

[0039] The ink may contain an organic solvent to adjust the ink's permeability to the medium, viscosity, drying property, defoaming property, etc. The organic solvent contained is not particularly limited, and examples thereof include carboxylic acid amides such as N,N-dimethylformamide or N,N-dimethylacetamide; lactams such as 2-pyrrolidone, N-methyl-2-pyrrolidone, or N-methylpyrrolidin-2-one; cyclic ureas such as 1,3-dimethylimidazolidin-2-one or 1,3-dimethylhexahydropyrimid-2-one; ketones, ketoalcohols, or carbonates such as acetone, 2-methyl-2-hydroxypentan-4-one, or ethylene carbonate; cyclic ethers such as tetrahydrofuran or dioxane; ethylene glycol, di ... Oligo- or polyalkylene glycols or thioglycols having C2-C6 alkylene units, such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butylene glycol, 1,4-butylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, thiodiglycol, or dithiodiglycol; C3-C9 polyols (triols), such as glycerin, diglycerin, hexane-1,2,6-triol, and 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), diethylene glycol monobutyl ether, diethylene glycol monopentyl ether, diethylene glycol monohexyl ether, diethylene glycol monophenyl ether, triethylene glycol monomethyl ether, triethylene glycol monobutyl ether, propylene glycol monopropyl ether, Examples of suitable alkyl ethers include glycol ethers such as ethylene 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); C3-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 the like. The organic solvent is preferably triethylene glycol, propylene glycol, glycerin, 1,4-butylene glycol, 1,2-hexanediol, or the like, and more preferably triethylene glycol or glycerin.

[0040] When the ink contains the organic solvent, the total amount of the organic solvent in the total amount of the ink is preferably 0.1 to 40%, more preferably 0.2 to 35%, even more preferably 1 to 30%, and particularly preferably 2 to 25%.

[0041] The ink may contain a viscosity modifier. In particular, the viscosity range of ink that can be ejected from industrial inkjet printers is usually determined based on the specifications of the printer head (the head that ejects the ink) installed in the printer. Therefore, a viscosity modifier can be added to the ink to adjust the viscosity to an appropriate range. Viscosity modifiers are not particularly limited as long as they are substances that can adjust the viscosity of the ink, with the exception of the carnauba wax mentioned above, and known substances can be used. Specific examples include the organic solvents, polymer dispersants, and resin emulsions mentioned above.

[0042] The ink may contain a surfactant. The surfactant is not particularly limited, but examples thereof include anionic, cationic, nonionic, silicon-based, and fluorine-based surfactants. Cationic and nonionic surfactants are preferably used as the surfactant.

[0043] 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-acylmethyl taurines, alkyl sulfates, polyoxyalkyl ether sulfates, alkyl sulfates, polyoxyethylene alkyl ether phosphates, rosin acid soaps, castor oil sulfates, lauryl alcohol sulfates, alkylphenol phosphates, alkyl phosphates, alkylaryl sulfonates, diethyl sulfosuccinates, diethylhexyl sulfosuccinates, and dioctyl sulfosuccinates.

[0044] Examples of cationic surfactants include 2-vinylpyridine derivatives and poly(4-vinylpyridine) derivatives.

[0045] Examples of nonionic surfactants include polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene alkyl ethers having 4 to 18 carbon atoms (e.g., polyoxyethylene butyl ether, polyoxyethylene lauryl ether, polyoxyethylene oleyl ether, polyoxyethylene 2-ethylhexyl ether), polyoxyethylene (di)styrenated phenyl ether (e.g., Emulgen manufactured by Kao Corporation), and polyoxyethylene (di)styrenated phenyl ether (e.g., Emulgen manufactured by Kao Corporation). ether-based surfactants such as A-60, A-90, A-500, and DSP-9, DSP-12.5, TSP-7.5, KTSP-16, and TSP-50 manufactured by Aoki Oil Co., Ltd.; ester-based surfactants such as polyoxyethylene oleate, polyoxyethylene distearate, sorbitan laurate, sorbitan monostearate, sorbitan monooleate, sorbitan sesquioleate, polyoxyethylene monooleate, and polyoxyethylene stearate; acetylene glycol (or acetylene 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-hexyn-3-ol (for example, Surfynol 420, 440, 465, and 485 manufactured by Evonik Japan Co., Ltd., and Olfine); STG, E1004, E1040, etc.); polyglycol ethers, etc.

[0046] Examples of silicone surfactants include polyether-modified siloxanes and polyether-modified polydimethylsiloxanes, such as Dynol 960 and 980 manufactured by Air Products Co., Ltd., Silface SAG001, SAG002, SAG003, SAG005, SAG503A, SAG008, SAG009, and SAG010 manufactured by Nissin Chemical Industry Co., Ltd., and BYK-345, 347, 348, 349, 3450, 3451, and 3455 manufactured by BYK Additives & Instruments, and TEGO Twin 4000, TEGO Wet KL 245, 250, 260, 265, 270, and 280 manufactured by Evonic Tego Chemie.

[0047] 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 on the side chains. Specific examples of commercially available surfactants include Capstone FS-30 and FS-31 (manufactured by Chemours).

[0048] Examples of the preservatives include organic sulfur compounds, organic nitrogen sulfur compounds, organic halogen compounds, haloarylsulfone compounds, iodopropargyl compounds, haloalkylthio compounds, nitrile compounds, pyridine compounds, 8-oxyquinolines, benzothiazole compounds, isothiazolinone compounds, dithiols, pyridine oxide compounds, nitropropane compounds, organic tin compounds, phenol compounds, quaternary ammonium salt compounds, triazine compounds, thiazine compounds, anilides, adamantane compounds, dithiocarbamates, brominated indanone compounds, benzyl bromoacetate compounds, and inorganic salt compounds. Specific examples of commercially available preservatives include Proxel GXL(S) and XL-2(S) manufactured by Arch Chemicals.

[0049] Examples of the antifungal agent include sodium dehydroacetate, sodium benzoate, sodium pyridinethione-1-oxide, p-hydroxybenzoic acid ethyl ester, and 1,2-benzisothiazolin-3-one, as well as salts thereof.

[0050] Examples of the pH adjuster 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.

[0051] The pH of the ink is usually 5 to 11, preferably 6 to 9. The surface tension of the ink is usually 20 to 60 mN / m, preferably 25 to 50 mN / m. The viscosity of the ink is usually 2 to 30 mPa s, preferably 3 to 15 mPa s. The pH and surface tension of the ink can be adjusted by using a pH adjuster, a surfactant, an organic solvent, etc.

[0052] Examples of the chelating agent include disodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, sodium uracildiacetate, α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin.

[0053] Examples of the rust inhibitor include acid sulfite, sodium thiosulfate, ammonium thioglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite.

[0054] Examples of the water-soluble ultraviolet absorber include sulfonated benzophenone compounds, benzotriazole compounds, salicylic acid compounds, cinnamic acid compounds, and triazine compounds.

[0055] Examples of the antioxidant include various organic and metal complex anti-fading agents, such as hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromans, alkoxyanilines, ascorbic acid, isoascorbic acid, chlorogenic acid, sulfur dioxide, catechins, dibutylhydroxytoluene, tocopherol, and butylhydroxyanisole.

[0056] Examples of the defoaming agents include acetylene-based defoaming agents such as the Surfynol 104 series (104A, 104E, 104H, 104PA, 104PG-50), Surfynol DF110D, Surfynol AD01, and Surfynol MD-20; Surfynol DF-58, BYK-017, BYK-018, BYK-019, BYK-021, BYK-022, BYK-023, BYK-024, BYK-025, BYK-028, BYK-044, BYK-092, BYK-1610, BYK-1611, and BYK-1622; Examples of suitable defoaming agents include silicone-based defoamers such as BYK-1615, BYK-1617, BYK-1650, BYK1679, BYK-1719, BYK-1723, BYK-1724, BYK-1730, BYK-1770, BYK-1781, BYK-1786, and BYK-1789, mineral oil-based defoamers such as BYK-035, BYK-037, BYK-038, and BYK-1630, higher alcohol derivatives such as Bisform CS, Bisform ECC, and Bisform TDI-1, and fatty acid derivatives such as Bisform TS-10. The defoaming agent is preferably an acetylene-based defoaming agent or a silicone-based defoaming agent.

[0057] The ink of the present invention has good stability against pressure fluctuations and the like applied to the ink (mechanical stability), and is excellent in ink circulation stability and ejection stability. Furthermore, images recorded with the ink of the present invention are excellent in abrasion resistance, drying properties, color development, gloss, granularity, and image quality.

[0058] The ink can be used in various printing applications, such as writing instruments, various printing applications, information printing, and textile printing, and is particularly preferably used in inkjet printing.

[0059] The ink can be prepared by any known method, including, for example, a method of preparing the ink by adding water and, if necessary, ink preparation agents to an aqueous dispersion prepared from a pigment and montan wax, and mixing the mixture.

[0060] The ink can be prepared using a conventionally known apparatus, such as a ball mill, a sand mill, an attritor, a basket mill, a roll mill, etc. During preparation, it is preferable to remove coarse particles using a membrane filter, a mesh filter, etc.

[0061] The ink is preferably microfiltered. When microfiltering, 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.

[0062] The present invention also includes an ink set containing at least the above ink. Examples of the ink set include an ink set containing two or more of the above inks, an ink set containing one or more of the above inks and one or more of other inks other than the above inks, etc. The other inks other than the above inks are not particularly limited as long as they have a different composition from the above inks, but it is preferable that they have a different hue from the above inks.

[0063] The ink and ink set are preferably used in inkjet printing.

[0064] <Inkjet recording method> The inkjet recording method includes a step of ejecting droplets of the ink composition onto a recording medium to form an image. The step of forming an image can be carried out using an inkjet system. The present invention also includes an inkjet recording method comprising an ink composition depositing step of ejecting the ink from an inkjet and depositing it onto a recording medium, which will be described later.

[0065] Known inkjet methods can be used. Specific examples of inkjet methods include charge control methods, drop-on-demand (pressure pulse) methods, acoustic inkjet methods, and thermal inkjet methods, with the drop-on-demand method being preferred. Inkjet methods also include methods that improve image quality by ejecting a large number of inks with a low pigment content in a small volume, methods that improve image quality by using multiple inks with substantially the same hue but different pigment concentrations, and methods that improve pigment fixation by using colorless, transparent ink.

[0066] The ink composition is for use in a head having an ink circulation mechanism. An inkjet head having an ink circulation mechanism refers to a mechanism having, for example, a plurality of droplet ejection elements, a common flow path communicating with each of the plurality of droplet ejection elements via a supply path, and a common circulation path communicating with the plurality of droplet ejection elements via a return path, and is equipped with an ink circulation device in which the ink composition is supplied from the common flow path to the plurality of droplet ejection elements and circulated through the common circulation path. There are no particular restrictions on the ink circulation flow rate, but a rate of 10 mL / min to 1000 mL / min is preferred, and a rate of 20 mL / min to 500 mL / min is more preferred. A line head type industrial inkjet printer is known as a mechanism in which multiple inkjet heads are arranged in a line, and since multiple inkjet heads are arranged as a circulation mechanism, the preferred range refers to the circulation flow rate per unit inkjet. Examples of inkjet heads equipped with a circulation mechanism include the SambaGL3 manufactured by Fujifilm, the S series manufactured by Canon, and the KJ4B-EX1200 print head manufactured by Kyocera.

[0067] <Recording Media> The present invention also includes recording media recorded using the ink. The recording media are not particularly limited as long as they are materials to which the ink composition can be attached, and examples include paper, film, cans, leather, cloth, and fibers. Recording media are broadly classified into non-permeable recording media, such as films and cans, which do not allow ink to penetrate, and permeable recording media, which allow ink to penetrate, with permeable recording media being more preferred. Examples of permeable recording media include plain paper, inkjet paper, art paper, coated paper, matte paper, cast paper, and liner paper.

[0068] <Ink recording medium set> The ink recording medium set is a set comprising the ink composition or ink set of the present invention and the above-mentioned recording medium.

[0069] For all of the above items, combinations of preferred items are more preferred, and combinations of more preferred items are even more preferred. The same applies to combinations of preferred items and more preferred items, and combinations of more preferred items and even more preferred items. Unless otherwise specified, all of the above-mentioned components can be used singly or in combination of two or more. [Example]

[0070] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The "water" used in the examples is "ion-exchanged water."

[0071] [Preparation Example 1]: Preparation of dispersion. A block copolymer was prepared as described in Synthesis Example 3 of WO 2013 / 115071. The resulting block copolymer (6 parts) was dissolved in 20 parts of methyl ethyl ketone to obtain a homogeneous solution. A mixture of sodium hydroxide (0.45 parts) and water (53.55 parts) was added to the resulting solution, followed by 20 parts of CI Pigment Blue 15:4 (Chromofine Blue 4851, manufactured by Dainichiseika Color & Chemicals Co., Ltd.). The mixture was dispersed in a sand grinder at 1500 rpm for 15 hours to obtain a liquid. Water (100 parts) was added to the resulting solution, and the solution was filtered through a GA-100 glass filter to remove aggregates and obtain a filtrate. The methyl ethyl ketone and a portion of the water in the filtrate were distilled under reduced pressure using an evaporator to obtain a cyan dispersion with a pigment content of 12.0%. The resulting pigment dispersion was designated "DP1."

[0072] [Example 1 and Comparative Example 1]: Preparation of ink. The dispersion "DP1" obtained above was mixed with each of the components listed in Table 1 below to obtain inks, which were then filtered through a 3 μm membrane filter to obtain the inks of Example 1 for evaluation tests and Comparative Example 1 for comparison. The numerical value in the column for each component in Table 1 indicates the amount (parts) of that component used, and "-" means that that component was not used. The abbreviations in Table 1 are as follows: DP1: Pigment dispersion obtained in Preparation Example 1 glycerin triethylene glycol SF440 (nonionic surfactant SF440: manufactured by Nissin Chemical Co., Ltd.) AQUACER 541 (Montan ester wax emulsion: BYK Japan, solid content 30%) E-6700 (Polyethylene wax emulsion: manufactured by Toho Chemical Industry Co., Ltd., solid content 35%)

[0073] [Table 1]

[0074] [Evaluation of mechanical stability] For the ink of Example 1, a circulation path was created by connecting a diaphragm pump (manufactured by KNF), a metal filter (filtration accuracy 15 μm), and a pressure gauge, and the ink was circulated and fed for 5,000 cycles in a water bath at 32°C. Furthermore, the ink circulation was carried out in the same manner as above, except that the ink of Comparative Example 1 was used instead of the ink of Example 1. The pressure transition from the beginning of circulation to the end of circulation was evaluated according to the following criteria, and the evaluation results are shown in Table 1. In terms of practical use, it is desirable that the evaluation be B or higher in the following criteria. [Evaluation criteria] A: The pressure at the end of the cycle is less than +15kPa of the initial value. B: The pressure at the end of circulation is between +15kPa and +30kPa of the initial value C: The pressure at the end of circulation is between +30kPa and +60kPa of the initial value D: The pressure at the end of circulation is 60 kPa or more higher than the initial value.

[0075] [Table 2]

[0076] [Abrasion resistance evaluation] Inkjet printing was performed using the ink of Example 1 and an inkjet printer using a single-pass (1-pass) method. The volume of ink droplets ejected was 12 picoliters, and the head temperature was 32°C. A Kyocera 600 dpi head was used. The media used was offset coated paper "OK ​​Topcoat+" manufactured by Oji Paper Co., Ltd. Inkjet printing was performed to obtain a 100% duty image, resulting in a printed image. After the obtained image was completely dried, it was used as a test piece and subjected to a scratch resistance test. The scratch resistance of the test piece was evaluated using a No. 428 Gakushin-type abrasion tester (friction tester type II) manufactured by Yasuda Seiki Seisakusho. Specifically, the inkjet-recorded portion of the test piece was rubbed 10 times under a load of 500 g, and the degree of image deterioration was evaluated using the following four-point evaluation criteria. In the following criteria, a rating of A is practically desirable. [Evaluation criteria] A: No scratches were found in the recorded images. B: Slight scratches were observed on the recorded image. C: Scratches were found on the recorded image. D: Scratches were observed on the recorded image, and the scratches were very large.

[0077] The results in Tables 1 and 2 above show that the ink compositions of the examples of the present invention have excellent mechanical stability, and also provide high abrasion resistance to printed matter produced using the ink. [Industrial Applicability]

[0078] The ink composition of the present invention makes it possible to provide printed matter that has excellent mechanical stability and abrasion resistance.

Claims

1. An ink composition for a recording head having an ink circulation mechanism, comprising a pigment, montan wax, and water.

2. 2. The ink composition according to claim 1, wherein the content of the montan wax in the ink composition is 0.1% by mass or more and 5% by mass or less.

3. A recording medium recorded with the ink composition according to claim 1 or 2.

4. An ink jet recording method comprising: an ink composition depositing step of ejecting the ink composition according to claim 1 or 2 from an ink jet head and depositing it on a recording medium.

Images