Ink

Abstract

To provide an ink that exhibits excellent intermittent discharge and enables provision of a printed material having superior whiteness.SOLUTION: An ink comprises a pigment, a polyethyleneimine compound, and water, the ink containing 1 to 20 mass% of the pigment and 0.1 to 20 mass% of the polyethyleneimine compound.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an ink and an inkjet recording method. [Background technology]

[0002] Printing with an inkjet printer involves ejecting ink from a nozzle and depositing it on a recording material. Unlike conventional printing methods, this method does not require the use of plates, making it a printing method that is expected to be widely used as an on-demand printing method capable of handling small-lot, high-mix production. Because inkjet ink nozzles are extremely small, even the smallest coarse particles can clog the nozzles, necessitating extremely high levels of pigment dispersion stability. However, titanium dioxide has a higher specific gravity than organic pigments, and its particle size, required for achieving sufficient whiteness, is relatively large, making it extremely difficult to ensure pigment dispersion stability. Pigment dispersants are used to improve the dispersibility of titanium dioxide.

[0003] In recent years, there has been an increasing demand for printing on non-white recording media such as corrugated cardboard, paperboard, and resin film, rather than on conventional white recording media such as paper. Traditionally, flexographic printing methods have generally been used in the field of packaging containers, primarily made of corrugated cardboard. Particularly in recent years, interest in inkjet printing methods, which are capable of reproducing high-quality designs, has been growing in the field of packaging containers, primarily made of corrugated cardboard, from the perspective of increasing added value. In this case, it is desirable for the white image to be sufficiently white so as to conceal the recording medium. When printing on non-white recording media, a white ink is sometimes used to express the white color and enhance visibility, and color inks are then printed on top of it.

[0004] However, titanium oxide has a higher specific gravity than organic pigments and a relatively large particle size to achieve sufficient whiteness. Therefore, when used in low-viscosity inkjet recording inks, titanium oxide is prone to settling. As a result, titanium oxide settles and aggregates during storage, adversely affecting ejection, resulting in poor storage stability. Therefore, the ink must be redispersed using a mixer before being installed in a recording device. However, even if the ink is redispersed using a mixer, the aggregates do not completely disintegrate, adversely affecting ejection. In addition to storage, if the ink flow in the recording device temporarily stops due to a printing pause or other reason, titanium oxide settles or aggregates in the ink flow path, adversely affecting ejection. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-86954 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in view of the above circumstances, and has as its object to provide an ink that has excellent intermittent ejection properties and that can provide printed matter with excellent whiteness. [Means for solving the problem]

[0007] As a result of extensive research into solving the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by an ink containing a pigment, a polyethyleneimine compound, and water, wherein the content of the pigment in the ink is 1 to 20 mass % and the content of the polyethyleneimine compound in the ink is 0.1 to 20 mass %, and have thus completed the present invention.

[0008] That is, the present invention relates to the following 1) to 7). 1) An ink comprising a pigment, a polyethyleneimine compound, and water, wherein the content of the pigment in the ink is 1 to 20% by mass, and the content of the polyethyleneimine compound in the ink is 0.1 to 20% by mass. 2) The ink according to 1), further containing an organic solvent. 3) A recording medium recorded with the ink according to 1) or 2). 4) The recording medium according to 3), wherein the recording medium is a permeable recording medium. 5) 4) The recording medium according to 4), wherein the permeable recording medium is colored paper. 6) An inkjet recording method comprising an ink deposition step of ejecting the ink according to 1) or 2) from an inkjet head and depositing it onto a recording medium. 7) The inkjet recording method according to 6), wherein the inkjet head is provided with a circulation mechanism. [Effects of the Invention]

[0009] The present invention has made it possible to provide an ink that has excellent intermittent ejection properties and is capable of producing printed matter with excellent whiteness. DETAILED DESCRIPTION OF THE INVENTION

[0010] In this specification, including the examples, all "parts" and "%" are based on mass unless otherwise specified.

[0011] The ink of the present invention contains a pigment, a polyethyleneimine compound, and water, and the content of the pigment in the ink is 1 to 20% by mass, and the content of the polyethyleneimine compound in the ink is 0.1 to 20% by mass.

[0012] [Pigment] The ink contains a pigment. Examples of the pigment include inorganic pigments, organic pigments, extender pigments, and hollow particles.

[0013] 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 white ink and the pigment is an inorganic pigment, examples of the inorganic pigment contained in the white ink include oxides, nitrides, or oxynitrides of metals such as zinc, silicon, aluminum, titanium, strontium, and zirconium; and inorganic compounds such as glass and silica. Among these, titanium dioxide and zinc oxide are preferred. It is preferable that the ink is a white ink.

[0014] Examples of organic pigments include various pigments such as azo, disazo, phthalocyanine, quinacridone, isoindolinone, dioxazine, perylene, perinone, thioindigo, anthraquinone, and quinophthalone.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] The pigment content, relative to the total mass of the ink according to this embodiment, is 1 to 20 mass%, more preferably 2 to 20 mass%, even more preferably 5 to 20 mass%, particularly preferably 8 to 18 mass%, and extremely preferably 12 to 18 mass%.

[0020] 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.

[0021] 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.

[0022] [Polyethyleneimine compounds] The ink contains a polyethyleneimine compound. The polyethyleneimine compound refers to polyethyleneimine or a polyethyleneimine derivative. The polyethyleneimine may be a linear polyethyleneimine (including primary amines and secondary amines), a partially branched polyethyleneimine (including primary amines and secondary amines), or a completely branched dendrimer-type polyethyleneimine (including primary amines and tertiary amines). The polyethyleneimine derivative may be the above-mentioned polyethyleneimine substituted with alkylene oxide. Since substitution with alkylene oxide or the like is necessary, polyethyleneimine containing a primary amino group or a secondary amino group is preferred, and partially branched polyethyleneimine is more preferred. The alkylene oxide is preferably a straight chain or a branched chain, and examples thereof include ethylene oxide, trimethylene oxide, tetramethylene oxide, propylene oxide, ethylethylene oxide, pentamethylene oxide, hexamethylene oxide, heptamethylene oxide, and octamethylene oxide. It is preferable that the alkylene oxide is substituted with at least one selected from the group consisting of ethylene oxide and propylene oxide, and it is more preferable that the alkylene oxide is substituted with ethylene oxide. The primary amine refers to an amino group. Examples of the secondary amine include ethyleneimine, trimethyleneimine, tetramethyleneimine, propyleneimine, ethylethyleneimine, pentamethyleneimine, hexamethyleneimine, heptamethyleneimine, and octamethyleneimine. Examples of the tertiary amine include dimethylamino, diethylamino, methylethylamino, and dipropylamino. The alkylene oxide may be composed of a single repeating unit or a plurality of repeating units, and a plurality of types of alkylene oxide may be bonded in any order. Specific examples of the polyethyleneimine compound include polyethyleneimine, Epomin SP-006, Epomin SP-012, Epomin SP-018, Epomin SP-200, and Epomin P-1000 manufactured by Nippon Shokubai Co., Ltd., and polyethyleneimine ethoxylate manufactured by Nippon Shokubai Co., Ltd. Examples include PN-100, polyethyleneimine manufactured by BASF, and Lupasol G 20, and PN-100 is preferred in terms of ink ejection properties and color development properties. It is believed that the ink containing the polyethyleneimine compound prevents the ink from drying in the vicinity of the inkjet nozzle, thereby improving the ejection properties.

[0023] The content of the polyethyleneimine compound in the ink is 0.1 to 20% by mass, preferably 0.1 to 11% by mass, more preferably 0.1 to 10% by mass, even more preferably 0.5 to 8% by mass, particularly preferably 1.0 to 6% by mass, especially preferably 1.5 to 4% by mass, and extremely preferably 2 to 4% by mass.

[0024] [water] The ink 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.

[0025] 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.

[0026] 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, and is other than the polyethyleneimine compound. The polymer dispersant may be synthesized or commercially available, and examples thereof include copolymers composed of at least two monomers (preferably at least one of which is a hydrophilic monomer) selected from 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, faric acid and its derivatives, vinyl acetate, vinyl alcohol, vinylpyrrolidone, acrylamide, and derivatives thereof. 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. The types of copolymers include, for example, block copolymers, random copolymers, graft copolymers, and / or salts thereof, with block copolymers being preferred. Specific examples of commercially available products include JONCRYL 62 (weight average molecular weight 13,000, acid value 213), 67 (weight average molecular weight 12,500, acid value 213), 68 (weight average molecular weight 13,000, acid value 200), 586 (weight average molecular weight 4,600, acid value 108), 611 (weight average molecular weight 8,100, acid value 53), 678 (weight average molecular weight 8,600, acid value 215), 679 (weight average molecular weight 9,000, acid value 108), all manufactured by BASF. acid value 200), 680 (weight average molecular weight 4500, acid value 215), 682 (weight average molecular weight 1700, acid value 238), 683 (weight average molecular weight 8000, acid value 165), 690 (weight average molecular weight 16500, acid value 240), 693 (weight average molecular weight 6000, acid value 205), and 819 (weight average molecular weight 14500, acid value 75), etc. manufactured by Seiko PMC Corporation. NS-2092 (weight average molecular weight 9000, acid value 200), RS-1191 (weight average molecular weight 6500, acid value 280), VS-1047 (weight average molecular weight 10000, acid value 240), BS -1291 (weight average molecular weight 10,000, acid value 210), ZS-1417 (weight average molecular weight 14,000, acid value 156), US-1071 (weight average molecular weight 10,000, acid value 75), YS-1 styrene-acrylic copolymers such as styrene-acrylic copolymers 274 (weight average molecular weight 19,000, acid value 200), ZS-1074 (weight average molecular weight 14,000, acid value 210), X-1 (weight average molecular weight 18,000, acid value 110), VS-1259 (weight average molecular weight 25,000, acid value 164), and FS-2358 (weight average molecular weight 25,000, acid value 203); and DISPERBYK 2014, 2015, 2018, and 2019 manufactured by BYK Japan, with DISPERBYK 2018 being preferred. A specific example of a block copolymer obtained by synthesis preferably includes the AB block polymer disclosed in WO 2013 / 115071 Gazette.

[0027] The resin emulsion is not particularly limited as long as it is one other than the polyethyleneimine compound 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, 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, preventing the ink from wetting and 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.

[0028] 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 petroleum-based waxes such as paraffin wax and microcrystalline wax; lignite-based waxes such as montan wax; plant-based waxes such as carnauba wax and candelilla wax; and emulsions of animal and plant-based waxes such as beeswax and lanolin dispersed in an aqueous medium.

[0029] 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 50 nm to 5 μm, more preferably 100 nm to 1 μm, in order to prevent clogging of the inkjet head.

[0030] Commercially available wax emulsions include, for example, AQUACER manufactured by BYK Japan. 515 (acid value: 5), and HYTEC E-6500 (acid value: 10 to 20) manufactured by Toho Chemical Co., Ltd.

[0031] When the ink contains the resin emulsion, the content of the resin emulsion in the ink is preferably 0.2 to 10%, and more preferably 0.5 to 5%.

[0032] 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.

[0033] 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 20%.

[0034] 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. The viscosity modifier is not particularly limited as long as it is a substance that can adjust the viscosity of the ink, with the exception of the polyethyleneimine compound, and known substances can be used. Specific examples include the organic solvents, polymer dispersants, and resin emulsions listed above.

[0035] 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.

[0036] 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.

[0037] Examples of cationic surfactants include 2-vinylpyridine derivatives and poly(4-vinylpyridine) derivatives.

[0038] 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.

[0039] 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.

[0040] 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).

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] Examples of the chelating agent include disodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, sodium uracildiacetate, α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin.

[0046] Examples of the rust inhibitor include acid sulfite, sodium thiosulfate, ammonium thioglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite.

[0047] Examples of the water-soluble ultraviolet absorber include sulfonated benzophenone compounds, benzotriazole compounds, salicylic acid compounds, cinnamic acid compounds, and triazine compounds.

[0048] 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.

[0049] 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.

[0050] The ink of the present invention has excellent intermittent ejection properties, dispersion stability, inkjet ejection properties, color development improvement properties, storage stability, redispersibility, and ink circulation stability. Furthermore, images recorded with the ink of the present invention have excellent fastness properties, such as dot diameter, granularity, hue, dot shape (e.g., suppression of coffee stain), color development, abrasion resistance, heat abrasion resistance, light resistance, heat resistance, and oxidation gas (e.g., ozone gas) resistance. Furthermore, there is little coating unevenness during image formation, and the image forming properties are also excellent. Furthermore, images recorded with an ink set containing the ink of the present invention have excellent suppression of intercolor bleeding, intercolor bleeding stability, granularity in printed areas of secondary or higher colors, and solid uniformity in printed areas of secondary or higher colors.

[0051] 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.

[0052] The ink can be prepared by any known production 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 a polyethyleneimine compound, and mixing the mixture.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] The ink and ink set are preferably used in inkjet printing.

[0057] <Inkjet recording method> The inkjet recording method includes a step of ejecting droplets of the ink 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 deposition step of ejecting the ink from an inkjet and depositing it on a recording medium, which will be described later.

[0058] 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.

[0059] Inkjet heads with or without an ink circulation mechanism can be used. From the viewpoint of suppressing pigment particle sedimentation, inkjet heads with an internal circulation mechanism are preferred. An inkjet head with a circulation mechanism refers to, for example, a mechanism having multiple droplet ejection elements, a common flow path communicating with each of the droplet ejection elements via a supply path, and a common circulation path communicating with the droplet ejection elements via a return path, and an ink circulation device that supplies ink to the droplet ejection elements from the common flow path and circulates it in 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. Linehead-type industrial inkjet printers are known, which use an array of inkjet heads as a circulation mechanism. Therefore, the preferred range refers to the circulation flow rate per inkjet. Examples of inkjet heads equipped with a circulation mechanism include the SambaG3L manufactured by Fujifilm, the S series manufactured by Canon, and the KJ4B-EX1200 print head manufactured by Kyocera.

[0060] <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 can adhere, 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 transparent paper and colored paper, with colored paper being preferred. Examples of colored paper include plain paper, inkjet paper, art paper, coated paper, matte paper, cast paper, and liner paper.

[0061] The recording medium is preferably liner paper. Liner paper is paper that forms the outside of cardboard and is made primarily from recycled paper or kraft pulp. Liner paper is liner paper for cardboard as described in Japanese Industrial Standard JIS P3902:2011 "Corrugated cardboard liners." The recording method of this embodiment is applicable to recording not only the liner itself but also the liner after it has been processed into cardboard.

[0062] Furthermore, the object of recording using the recording method of this embodiment may be the liner paper on the surface of a cardboard sheet before processing, or, for example, the liner paper on the surface after it has been processed and / or formed into a cardboard box.

[0063] The liner paper may be non-white. As described above, liner paper is often made from recycled paper and is often not white. Such non-white liner paper tends to have poor whiteness in the image formed on its surface, but the recording method of this embodiment allows for the formation of an image with good color development.

[0064] The surface of the liner paper may be coated or surface-treated. Examples of surface treatments include water-repellent treatment, anti-fouling treatment, and coloring treatment. In particular, if the surface of the liner paper is water-repellent, it repels water-based liquids, and therefore inks, resulting in unevenness in the image. According to the recording method using the ink of this embodiment, good images can be formed even on liner paper treated as described above. The reason for this, as will be described in detail later, is believed to be due to the suppression of ink repelling due to the effects of the organic solvents, surfactants, and the like contained in the ink. Furthermore, in a preferred recording method using an aqueous treatment liquid according to the present invention, the coagulant contained in the aqueous treatment liquid thickens and solidifies the components in the ink, including the colorant, thereby further suppressing ink repelling and making unevenness less likely to occur. Therefore, it is believed that clear, good images can be obtained. Water-repellent treatment can be achieved by applying a water-repellent agent, and commercially available products, such as cardboard, containing water-repellent liner paper are also available. The liner paper is preferably cardboard liner paper.

[0065] 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]

[0066] 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 (purified water)."

[0067] [Example 1: Ink Preparation Example] The following components were mixed with sufficient stirring, and the resulting mixture was filtered through a mixed cellulose ester filter with a pore size of 5 μm, followed by degassing using a vacuum pump to obtain test ink 1. TF5760 WHITE (D2B) (white pigment dispersion: manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.) (pigment concentration: 60%) PN-100 (Polyethyleneimine Ethoxylate: Nippon Shokubai Co., Ltd.) (Solid content: 80%) Glycerin (manufactured by Junsei Chemical Co., Ltd.) Triethylene glycol (Mitsubishi Chemical Corporation) Surfynol 485 (nonionic surfactant: manufactured by Nissin Chemical Industry Co., Ltd.) Triethanolamine (Mitsui Chemicals, Inc.) (solid content: 90%)

[0068] [Examples 2 to 4, Comparative Example 1, and Preparation Examples of Each Ink] The inks of Examples 2 to 4 and Comparative Example 1 were obtained in the same manner as the ink of Example 1, except that the type and amount of titanium oxide dispersion liquid added were changed in the proportions shown in Table 1. Note that blank spaces indicate 0 parts.

[0069] [Table 1]

[0070] [Table 2]

[0071] [Evaluation of inkjet intermittent ejection] Each ink was used in a printer equipped with a Kyocera KJ4B-YH inkjet head (600 dpi x 600 dpi) to inkjet print on HEIKO fine black cut paper (Shimojima Co., Ltd.) at a droplet size of 12 pL and a speed of 25 m / min, obtaining an initial printed image. Inkjet printing was performed to obtain a 100% duty solid image. Immediately after printing the initial print image, the nozzle of the inkjet head was left uncapping for 5 minutes, and within 1 minute of leaving it, inkjet recording was performed again to obtain a print image. The area of ​​the print image after inkjet recording was measured in comparison with the initial print image, and evaluated according to the following criteria. ◎, ◯, △ are evaluated in order of good, and × is evaluated as bad. [Evaluation criteria] ◎: When the area of ​​the initial printed image is 100, the area of ​​the re-inked printed image is 80 or more ○: When the area of ​​the initial printed image is taken as 100, the area of ​​the printed image after inkjet recording is less than 80 and 70 or more △: When the area of ​​the initial printed image is taken as 100, the area of ​​the printed image after inkjet recording is less than 70 and 60 or more ×: When the area of ​​the initial printed image is taken as 100, the area of ​​the printed image after inkjet recording is less than 60

[0072] [Color development evaluation] The inks of Examples 1 to 4 were printed on liner paper (K ​​Liner, manufactured by Daio Paper Co., Ltd., basis weight 170 g / m) using a printer equipped with an inkjet head KJ4B-YH (600 dpi x 600 dpi) manufactured by Kyocera Corporation, at a droplet size of 12 pL and a speed of 25 m / min. 2 , L * Inkjet recording was performed on a brown liner with a CIE / L color temperature of 63 to prepare a test piece. Inkjet recording was performed to obtain a solid image with a duty of 100%. The colorimeter used was an eXact manufactured by X-Rite, and the CIE / L color temperature was * a * b * In the color system, L * The color measurement conditions were: observation light source D50, observation field of view 2°, and density Status E. The color measurement was performed six times on the prepared test piece, and the average value was used as the measurement result. L * A larger value is preferable because it indicates higher whiteness. The evaluation is in the order of ⊚, ◯, △, and × is poor. The evaluation results are shown in Table 2 above. [Evaluation criteria] ◎:L * is greater than 72 〇:L * is between 70 and 72 △:L * is between 68 and 70 ×:L * is under 68

[0073] From the results in Tables 1 and 2 above, it was found that the inks of the present invention have excellent intermittent ink ejection properties and also have the effect of showing high whiteness in printed matter produced using the ink. [Industrial Applicability]

[0074] The ink of the present invention is excellent in intermittent ejection properties and in the whiteness of printed matter produced using the ink.

Claims

1. An ink comprising a pigment, a polyethyleneimine compound, and water, wherein the content of the pigment in the ink is 1 to 20% by mass, and the content of the polyethyleneimine compound in the ink is 0.1 to 20% by mass.

2. The ink of claim 1 further comprising an organic solvent.

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

4. 4. The recording medium of claim 3, wherein the recording medium is a permeable recording medium.

5. 5. The recording medium according to claim 4, wherein the permeable recording medium is colored paper.

6. 3. An inkjet recording method comprising: an ink deposition step of ejecting the ink according to claim 1 from an inkjet head and depositing it on a recording medium.

7. 7. The ink-jet recording method according to claim 6, wherein the ink-jet head is provided with a circulation mechanism.

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