Ink and inkjet recording method

Abstract

To provide an ink that can suppress the bleeding of inks between different inks. [Solution] An ink containing a water-insoluble colorant, water, and diethylene glycol mono(C4-C8) alkyl ether in an amount of 0.01% to less than 3% by mass.

Description

Technical Field

[0001] The present invention relates to an ink and an inkjet recording method using the ink.

Background Art

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

[0003] Among printing media, for non-ink-absorbent media and hard-to-ink-absorbent media (hereinafter sometimes referred to as "non- and hard-to-ink-absorbent media"), inks with good wet spreading on the media are desired. When the wet spreading on the media is good, the area that can be colored increases when the same amount of ink droplets is used (in other words, the dot diameter of the ink increases), so the consumption of the ink can be suppressed. However, non- and hard-to-ink-absorbent media are media with poor ink absorbency. Therefore, it is difficult for the ink to penetrate into the media, and compared with ink-absorbent media, the wet spreading of the ink is poor, so generally the dot diameter of the ink becomes small. For this reason, its improvement has been desired.

[0004] Furthermore, regarding the printed image quality, it is required that the granularity be as small as possible. Inks containing water-insoluble colorants are in a non-uniform state (not in a solution state but in a dispersion state) themselves. When solid printing is performed on a printing medium with such a non-uniform ink, the printed image may appear to have "grains" of light and dark scattered and may not look like a uniform image. Such a printed image is evaluated as "granularity is observed" and is one of the factors that significantly deteriorate the printing quality. Therefore, there is a strong demand for inks that can obtain printed images with as little granularity as possible.

[0005] Furthermore, when performing color printing, an ink set consisting of multiple colors is used. When performing color printing using such an ink set, it is known that bleeding may occur between the first and second colors when the landing positions of the first and second colors of ink are adjacent on the printing medium. This "bleeding between colors" is one of the factors that significantly deteriorates print quality. Therefore, it is necessary to eliminate this bleeding between colors. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2016-044188 [Patent Document 2] Japanese Patent Publication No. 2014-139004 [Patent Document 3] International Publication No. 2011 / 136000 [Overview of the project] [Problems that the invention aims to solve]

[0007] There is a demand for ink that produces high-quality images with minimal bleeding.

[0008] This invention has been made in view of the above circumstances, and aims to provide an ink that enables the provision of printed images with extremely good color bleeding, an inkjet recording method using the ink, a printing medium, and a printing medium set. [Means for solving the problem]

[0009] The inventors of this invention conducted extensive research to solve the above-mentioned problems and, as a result, discovered that a specific ink can solve the above-mentioned problems, thus completing the present invention.

[0010] In other words, the present invention relates to the following 1) to 8). 1) An ink containing a water-insoluble colorant, water, and diethylene glycol mono(C4-C8) alkyl ether in an amount of 0.01% to less than 3% by mass. 2) The ink according to 1), wherein the above-mentioned diethylene glycol mono(C4-C8) alkyl ether comprises at least diethylene glycol monohexyl ether. 3) The ink described in 1) contains 0.6% to 1.4% by mass of diethylene glycol mono(C4-C8) alkyl ether. 4) Furthermore, the ink described in 1) contains a polyoxyethylene compound. 5) Furthermore, the ink described in 1) contains an organic solvent. 6) An ink set comprising the ink described in claim 1 as the first ink and the ink described in 5) as the second ink. 7) A recording medium recorded with the ink described in 1). 8) An inkjet recording method comprising an ink application step of ejecting the ink described in 1) from an inkjet head and adhering it to a recording medium. [Effects of the Invention]

[0011] The present invention provides an ink, an inkjet printing method, a printing medium, and a printing medium set that enable the provision of printed images with extremely good color bleeding. [Modes for carrying out the invention]

[0012] The present invention will be described in detail below. In this specification, unless otherwise specified, "parts" and "%" in the examples and other descriptions shall all be expressed on a mass basis.

[0013] The above ink contains a water-insoluble colorant, water, and diethylene glycol mono(C4-C8) alkyl ether in an amount of 0.01% by mass or more and less than 3% by mass.

[0014] [Water-insoluble colorant] The above water-insoluble colorant is not particularly limited as long as it is a water-insoluble colorant. For example, known pigments, disperse dyes, solvent dyes, and water-insoluble resins colored with colorants such as dyes and pigments can be used. In this specification, the water-insoluble colorant means a colorant having a solubility of usually 5 g or less, preferably 3 g or less, more preferably 1 g or less, and still more preferably 0.5 g or less in 1 liter of water at 25°C. The lower limit of the solubility includes 0 g. Unless otherwise specified, the "water-insoluble colorant" may be abbreviated as "colorant" hereinafter. Among the above colorants, pigments are preferred. Examples of pigments include inorganic pigments, organic pigments, and extender pigments.

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

[0016] As the colorant contained in the black ink, carbon blacks such as thermal black, acetylene black, oil furnace black, gas furnace black, lamp black, gas black, and channel black are preferred. Specific examples of carbon black include, for example, the Raven series manufactured by Columbian Carbon; the Monarch series, Regal series, and Mogul series manufactured by Cabot; the ColorBlack series, Printex series, SpecialBlack series, and Nerox series manufactured by Orion Engineered Carbons; 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, etc.

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

[0018] Specific examples of organic pigments include, for example, yellows such as C.I.PigmentYellow 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, 213, etc.; reds such as C.I.PigmentRed 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, 272, etc.; blues such as C.I.PigmentBlue 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 22, 25, 60, 66, 80, etc.; violets such as C.I.PigmentViolet 19, 23, 29, 37, 38, 50, etc.; oranges such as C.I.PigmentOrange 13, 16, 43, 68, 69, 71, 73, etc.; greens such as C.I.PigmentGreen 7, 36, 54, etc.; blacks such as C.I.PigmentBlack 1, 7, etc.

[0019] Examples of extender pigments include, for example, silica, calcium carbonate, talc, clay, barium sulfate, and white carbon, etc. Extender pigments are often used in combination with other colorants.

[0020] Examples of disperse dyes include well-known disperse dyes. Among these, dyes selected from CIDispers are preferred. Specific examples include, for instance, CIDispers Yellow 9, 23, 33, 42, 49, 54, 58, 60, 64, 66, 71, 76, 79, 83, 86, 90, 93, 99, 114, 116, 119, 122, 126, 149, 160, 163, 165, 180, 183, 186, 198, 200, 211, 224, 226, 227, 231, 237, etc.; CIDispers Red 60, 73, 88, 91, 92, 111, 127, 131, 143, 145, 146, 152, 153, 154, 167, 179, 191, 192, 206, 221, 258, 283, etc.; CIDispers Orange Disperse dyes in various colors are listed, including orange (9, 25, 29, 30, 31, 32, 37, 38, 42, 44, 45, 53, 54, 55, 56, 61, 71, 73, 76, 80, 96, 97, etc.); violet (CIDispers Violet 25, 27, 28, 54, 57, 60, 73, 77, 79, 79:1, etc.); and blue (CIDispers 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.).

[0021] The content of the colorant relative to the total mass of the above ink is typically 1 to 30%, preferably 1 to 10%, and more preferably 2 to 8%. The average particle size of the colorant is typically 50 to 350 nm, preferably 60 to 300 nm. In this specification, the average particle size refers to the average particle size measured using the laser light scattering method.

[0022] The water mentioned above 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 water content in each ink is preferably 55% to 90% by mass, and more preferably 60% to 85% by mass.

[0023] [Diethylene glycol mono(C4-C8) alkyl ether] The above ink contains 0.01% by mass or more and less than 3% by mass of diethylene glycol mono(C4-C8) alkyl ether. The above C4-C8 refers to a group with 4 to 8 carbon atoms, preferably 5 to 7 carbon atoms, and more preferably 6 carbon atoms. Examples of the above diethylene glycol mono(C4-C8) alkyl ether include diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, diethylene glycol monooctyl ether, etc., and the above C4-C8 may be linear, branched, or cyclic. In this specification, unless otherwise specified, it refers to a linear group.

[0024] The above ink preferably contains at least diethylene glycol monohexyl ether as a diethylene glycol mono(C4-C8) alkyl ether, and more preferably consists solely of diethylene glycol monohexyl ether.

[0025] If the above ink contains diethylene glycol monohexyl ether, the content is preferably 0.01% by mass or more and less than 3% by mass, more preferably 0.1% by mass or more and less than 2.5% by mass, even more preferably 0.2% by mass or more and 2.0% by mass or less, particularly preferably more than 0.5% by mass and 1.5% by mass or less, and especially preferably 0.6% by mass or more and 1.4% by mass or less.

[0026] The above ink may also contain ink modifiers in addition to the above components. Examples of ink modifiers include organic solvents, resins, polymer dispersants, waxes, viscosity modifiers, surfactants, preservatives, fungicides, pH adjusters, chelating agents, rust inhibitors, water-soluble UV absorbers, antioxidants, and defoamers.

[0027] [Organic solvents] The organic solvent is not particularly limited as long as it is a solvent other than the diethylene glycol mono(C4-C8) alkyl ether mentioned above. Examples include C1-C6 alkanols having one hydroxyl group, such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, tertiary butanol, 3-methoxy-3-methyl-1-butanol, and 3-methoxy-1-butanol; amides such as N,N-dimethylformamide and N,N-dimethylacetamide; lactams such as 2-pyrrolidone, N-methyl-2-pyrrolidone, and N-methylpyrrolidine-2-one; cyclic ureas such as 1,3-dimethylimidazolidin-2-one and 1,3-dimethylhexahydropyrimido-2-one; acetone, 2-methyl-2-hydroxypentan-4-one, and ethylene carbonate Examples include ketones or keto alcohols such as tetrahydrofuran and cyclic ethers such as dioxane; 1,2-(C2-C3) alkanediols such as ethylene glycol, propylene glycol, and 1,3-propanediol; oligos or polyalkylene glycols or thioglycols having C2-C4 alkylene units such as diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, polyethylene glycol or polypropylene glycol with a molecular weight of 400 or more, thiodiglycol or dithiodiglycol; polyols (triols) such as glycerin, diglycerin, hexane-1,2,6-triol, and trimethylolpropane; γ-butyrolactone and dimethyl sulfoxide, glycol ethers, C4-C12 alkanediols, etc.

[0028] The above ink preferably contains a glycol ether and a C4-C12 alkanediol as organic solvents.

[0029] The glycol ether is not particularly limited, but alkyl ethers of di or tri C2-C6 alkylene glycols are preferred, and monoalkyl ethers of di or tri C2-C6 alkylene glycols are more preferred. Examples of the C2-C6 alkylene glycol portion include ethylene glycol, propylene glycol, and butylene glycol. Among these, ethylene glycol and propylene glycol are preferred, with propylene glycol being more preferred. Furthermore, as the glycol ether, phenyl ethers of di or tri C2-C6 alkylene glycols are also preferred, and in this case, the examples and preferred examples of the C2-C6 alkylene glycol portion may be the same as above. Specific examples include, for instance, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monopropyl ether, tripropylene glycol monobutyl ether, and diethylene glycol monophenyl ether.

[0030] The above C4-C12 alkanediol is not particularly limited, but 1,2-(C4-C12)alkanediol is preferred, and 1,2-(C6-C8)alkanediol is more preferred. Alkanediols with 7 or more C7 are generally considered to be poorly water-soluble. Specific examples include 1,2-heptanediol, 1,2-octanediol, 5-methyl-1,2-hexanediol, 4-methyl-1,2-hexanediol, and 4,4-dimethyl-1,2-pentanediol. Among these, 1,2-octanediol is preferred. Furthermore, alkanediols with 6 or fewer C6 are generally considered to be water-soluble. Specific examples include 1,2-hexanediol, 1,2-pentanediol, 1,2-butanediol, 4-methyl-1,2-pentanediol, and 3,3-dimethyl-1,2-butanediol.

[0031] The above organic solvents are preferably 3-methoxy-1-butanol, propylene glycol monobutyl ether, and diethylene glycol monophenyl ether, and it is preferable to combine any two of these, and more preferably to combine all three. Examples of combinations of two include 3-methoxy-1-butanol and propylene glycol monobutyl ether, 3-methoxy-1-butanol and diethylene glycol monophenyl ether, and propylene glycol monobutyl ether and diethylene glycol monophenyl ether.

[0032] The organic solvent contained in the above ink may be used alone or in combination of two or more types. The total content of the organic solvent relative to the total mass of the ink is preferably 0.1% to 25% by mass, more preferably 0.5% to 15% by mass, even more preferably 1% to 12% by mass, and particularly preferably 3% to 10% by mass.

[0033] If the above ink contains propylene glycol monobutyl ether, and A1 is the content of diethylene glycol mono(C4-C8) alkyl ether in the ink, and A2 is the content of propylene glycol monobutyl ether in the ink, then the value obtained by A1 / A2 is preferably 0.05 or more and less than 3, more preferably 0.07 or more and 2 or less, even more preferably 0.1 or more and less than 1, particularly preferably 0.1 or more and 0.5 or less, and extremely preferably 0.1 or more and 0.3 or less.

[0034] If the above ink contains 3-methoxy-1-butanol, and B2 is the amount of 3-methoxy-1-butanol contained in the ink, then the value obtained by A1 / B2 is preferably 0.01 or more and less than 3, more preferably 0.015 or more and 2 or less, even more preferably 0.02 or more and less than 1, particularly preferably 0.02 or more and 0.5 or less, and extremely preferably 0.03 or more and 0.2 or less.

[0035] If the above ink contains diethylene glycol monophenyl ether, and C2 is the content of diethylene glycol monophenyl ether in the ink, then the value obtained by A1 / C2 is preferably 1 or more and less than 30, more preferably 1.5 or more and 25 or less, even more preferably 2 or more and less than 20, and particularly preferably 2 or more and 15 or less.

[0036] [resin] The above resin is not particularly limited, but examples include one or more selected from condensation polymers such as polyurethane and polyester; and vinyl polymers such as (meth)acrylic resins, styrene resins, acrylic-styrene resins, butadiene resins, styrene-butadiene resins, vinyl chloride resins, vinyl acetate resins, and acrylic silicone resins. (Meth)acrylic resins are preferred as the above resin. The above-mentioned (meth)acrylic resins include, for example, copolymers composed of constituent monomers such as methacrylic acid, C1-C4 alkyl methacrylate, C6-C10 alkyl acrylate, and C2-C4 unsaturated alkyl methacrylate, and a reactive emulsifier having a radically polymerizable double bond in its molecule. Preferably, the resin is a resin fine particle described in Japanese Patent Application No. 2023-058989, or a resin having methacrylic acid, methyl methacrylate, allyl methacrylate, or 2-ethylhexyl acrylate as constituent monomers. Examples of copolymer types include block copolymers, random copolymers, and graft copolymers, with random copolymers being preferred. The polymer resin may also be in the form of a salt. The polymer resin can be synthesized by known methods.

[0037] Examples of C1-C4 alkyl methacrylates include those with a linear alkyl portion, such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, and n-butyl methacrylate; those with a branched alkyl portion, such as isopropyl methacrylate, isobutyl methacrylate, and t-butyl methacrylate; and those with a cyclic alkyl portion, such as cyclopropyl methacrylate and cyclobutyl methacrylate. Among these, those with a linear alkyl portion are preferred, C1-C3 alkyl methacrylates with a linear alkyl portion are more preferred, and methyl methacrylate is even more preferred. Examples of C6-C10 alkyl acrylates include those with a linear alkyl portion, such as hexyl acrylate, heptyl acrylate, octyl acrylate, nonyl acrylate, and decyl acrylate; those with a branched alkyl portion, such as isohexyl acrylate, isoheptyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, and isodecyl acrylate; and those with a cyclic alkyl portion, such as cyclohexyl acrylate, 4-t-butylcyclohexyl acrylate, cycloheptyl acrylate, cyclooctyl acrylate, cyclononyl acrylate, and cyclodecyl acrylate. Among these, those with a branched alkyl portion are preferred, C8 alkyl acrylate with a branched alkyl portion is more preferred, and 2-ethylhexyl acrylate is even more preferred. Examples of C2-C4 unsaturated alkyl methacrylates include vinyl methacrylate, allyl methacrylate, 2-butene methacrylate, 3-methyl-2-butene methacrylate, and 3-butene methacrylate, which are C2-C4 alkenyl methacrylates. Among these, C2-C4 alkenyl methacrylates are preferred, C3 alkenyl methacrylates are more preferred, and allyl methacrylates are even more preferred.

[0038] Reactive emulsifiers are emulsifiers that have a radically polymerizable double bond in their molecule. The number of radically polymerizable double bonds is usually one.

[0039] As the reactive emulsifier, an anionic type reactive emulsifier having an anionic group in its molecule is preferred. Such anionic type reactive emulsifiers are sometimes referred to as "reactive anionic surfactants." Examples of anionic groups include sulfonic acid groups, sulfonate groups, sulfate ester groups, phosphate groups, phosphate ester groups, nitrate ester groups, carboxyl groups, and salts thereof. Among these, sulfonic acid groups, sulfonate groups, sulfate ester groups, and salts thereof are preferred, and salts of sulfate ester groups are more preferred. Examples of salts include ammonium salts and alkali metal salts (e.g., sodium salts, potassium salts, etc.). It can be done.

[0040] Among reactive emulsifiers, ethylenically unsaturated monomers having a group selected from sulfonic acid groups, sulfonate groups, sulfate ester groups, phosphate groups, phosphate ester groups, and salts thereof are preferred.

[0041] Specific examples of reactive emulsifiers include polyoxyalkylene alkenyl ether sulfate ammonium, ether sulfate type ammonium, phosphate esters, bis(polyoxyethylene polycyclic phenyl ether) methacrylate sulfate, 2-sodium sulfoethyl methacrylate, alkoxy polyethylene glycol maleate, and salts thereof. Specific examples of reactive emulsifiers include sodium alkylallyl sulfosuccinate (Sanyo Chemical Industries, Ltd., Eleminor JS-20), dipotassium alkenylsuccinate (Kao Corporation, Latemul ASK), polyoxyethylene alkylpropenylphenyl ether sulfate (Daiichi Kogyo Seiyaku Co., Ltd., Aqualon HS-10), α-[1-[(allyloxy)methyl]-2-(nonylphenoxy)ethyl]-ω-polyoxyethylene sulfate (ADEKA Corporation, Adekaria Soap SE series such as Adekaria Soap SE-10N), and polyoxyethylene-1-(allyloxymethyl)alkyl ether sulfate ammonium salt (Daiichi Kogyo Seiyaku Co., Ltd., Aqualon KH-1025, etc.). Examples include the KH series), styrene sulfonates (manufactured by Tosoh Finechem Co., Ltd., spinomer NaSS), α-[2-[(allyloxy)-1-(alkyloxymethyl)]ethyl]-ω-polyoxyethylene sulfate (manufactured by ADEKA Corporation, Adekaria Soap SR series such as Adekaria Soap SR-1025), sulfate salts of polyoxyethylene polyoxybutylene (3-methyl-3-butenyl) ether (manufactured by Kao Corporation, Latemul PD-104), and ammonium salts of sulfated products of oxirane polyadducts of {C10-C14 branched chain alkanol and 1-(allyloxy)-2,3-epoxypropane}, mainly composed of [({α-[2-(allyloxy)-1-({C10-C14 alkyloxy}methyl)ethyl]-ω-hydroxypoly(n=1~100)(oxyethylene)}].Among these, the ammonium salt of the sulfated product of the reaction product of {C10-C14 branched chain alkanol and 1-(allyloxy)-2,3-epoxypropane}, mainly composed of {α-[2-(allyloxy)-1-({C10-C14 alkyloxy}methyl)ethyl]-ω-hydroxypoly(n=1~100)(oxyethylene)} is preferred.

[0042] A reactive emulsifier is used together with a monomer when synthesizing a resin. This allows for the production of a resin emulsion. When preparing each of the inks according to this embodiment, it is preferable to use such a resin emulsion.

[0043] There are no particular restrictions on the amount of reactive emulsifier used when synthesizing the resin. As a guideline for the amount used, it is usually 0.1 to 10% by mass, preferably 0.3 to 5% by mass, more preferably 0.5 to 3% by mass, and even more preferably 1 to 3% by mass, relative to the total mass of the four types of monomers mentioned above. By using the reactive emulsifier within the above range, it is possible to stably synthesize the resin, control the average particle size of the resin within a suitable range, and adjust the viscosity of the resin emulsion within a suitable range.

[0044] The average particle size of the resin is typically 10 to 500 nm, preferably 20 to 200 nm, and more preferably 40 to 120 nm. By setting the average particle size within this range, clogging of the inkjet head and re-aggregation of the resin tend to be suppressed.

[0045] In this embodiment, the lower limit of the resin content (in terms of solid content) in the total mass of each ink is typically 0.1% by mass, preferably 0.2% by mass, and more preferably 0.3% by mass, while the upper limit is typically 10% by mass, preferably 7% by mass, more preferably 6% by mass, and even more preferably 5% by mass.

[0046] The above-mentioned polymeric dispersant is not particularly limited as long as it is a polymer with a weight-average molecular weight of 2,500 or more that can disperse the above-mentioned water-insoluble colorant, and is not one of the components mentioned above. In this specification, the above-mentioned polymeric dispersant may be abbreviated as dispersant. Known polymer dispersants can be used as the polymer dispersant. Examples of polymer dispersants include copolymers composed of at least two monomers selected from monomers such as 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; fahric acid and its derivatives; vinyl acetate, vinyl alcohol, vinylpyrrolidone, acrylamide, and their derivatives (preferably at least one of which is a hydrophilic monomer). 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 copolymers, styrene-(meth)acrylic acid-(meth)acrylic acid ester copolymers, and (meth)acrylic acid ester-(meth)acrylic acid copolymers are preferred, (meth)acrylic acid ester-(meth)acrylic acid copolymers are more preferred, and methacrylic acid ester-methacrylic acid copolymers are even more preferred. Examples of copolymer types include block copolymers, random copolymers, and graft copolymers. These copolymers may also be in the form of salts.

[0047] Dispersants can be obtained commercially or synthesized.

[0048] 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 Resin Co., Ltd.); and Julimer AT-210 (polyacrylic acid ester copolymer manufactured by Toagosei Co., Ltd.).

[0049] Examples of dispersants obtained by synthesis include the AB block polymer disclosed in International Publication No. 2013 / 115071. The monomer constituting the A block of the AB block polymer disclosed in International Publication No. 2013 / 115071 is at least one monomer selected from (meth)acrylic acid and linear or branched C4 alkyl (meth)acrylate, with at least one monomer selected from methacrylic acid and n-butyl methacrylate being preferred, and more preferably a combination of these two monomers. The monomer constituting the B block of the AB block polymer disclosed in International Publication No. 2013 / 115071 is at least one monomer selected from benzyl methacrylate and benzyl acrylate, with benzyl methacrylate being preferred. Specific examples of AB block polymers include the block copolymers disclosed in Synthesis Examples 3 to 8 of International Publication No. 2013 / 115071.

[0050] The acid value of the dispersant is typically 90-200 mgKOH / g, preferably 100-150 mgKOH / g, and more preferably 100-120 mgKOH / g.

[0051] 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, with ammonia being more preferred. As a guideline for the amount of neutralizing agent to use, the degree of neutralization is usually 30-300%, preferably 50-200%, with 100% neutralization being defined as neutralization with a theoretical equivalent amount of the acid value of the dispersant.

[0052] The mass-average molecular weight of the dispersant is typically 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 permuration chromatography (GPC). Specifically, the measurement can be performed using an HLC-8320GPC (manufactured by Tosoh Corporation) as the GPC instrument, 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.

[0053] The PDI (mass-average molecular weight / number-average molecular weight) of the dispersant is preferably around 1.29 to 1.49. Within this range, the dispersibility and storage stability of the ink tend to be good.

[0054] The dispersant can be used in a mixed state with the colorant. Alternatively, it can be used with part or all of the surface of the colorant coated with the dispersant. Or, both of these states may be used in combination.

[0055] In the above ink, the ratio of the total mass of the colorant to the total mass of the dispersant is preferably 0.01 to 1.0, more preferably 0.05 to 0.6, and even more preferably 0.1 to 0.5, when Dy is the total mass of the colorant and Ds is the total mass of the dispersant.

[0056] As the above 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 candelilla wax; and emulsions in which waxes such as beeswax and lanolin, which are dispersed in an aqueous medium.

[0057] Examples of synthetic waxes 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 30 nm to 5 μm, and more preferably 50 nm to 1 μm, in order to prevent clogging of the inkjet head.

[0058] Examples of commercially available wax emulsions include AQUACER 515 and 1547 from BIC Chemie Japan, and the HYTEC E series from Toho Chemical Industry Co., Ltd., such as E-6500, E-9015, and E-6314.

[0059] The above ink may contain a viscosity modifier. In particular, industrial inkjet printers typically have a defined viscosity range for the ink that can be ejected, based on the specifications of the printer head (the head that ejects the ink). Therefore, a viscosity modifier can be added to the ink to adjust its 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; known substances can be used. Specific examples include the polymer dispersants mentioned above.

[0060] The above ink may contain a surfactant. There are no particular limitations on the surfactant, but examples include anionic, cationic, nonionic, silicone, and fluorine-based surfactants.

[0061] 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.

[0062] Examples of cationic surfactants include 2-vinylpyridine derivatives and poly-4-vinylpyridine derivatives.

[0063] Examples of silicone-based surfactants include polyether-modified siloxanes and polyether-modified polydimethylsiloxanes. Examples include Dynol 960 and 980 from Air Products Corporation; Silface SAG001, SAG002, SAG003, SAG005, SAG503A, SAG008, SAG009, and SAG010 from Nisshin Chemical Co., Ltd.; and BYK-345, 347, 348, 349, 3450, 3451, and 3455 from BYK Additives & Instruments; and TEGO Twin 4000, TEGO Wet KL 245, 250, 260, 265, 270, and 280 from Evonic Tego Chemie.

[0064] Examples of fluorinated 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. Specific examples of commercially available products include Capstone FS-30 and FS-31 (manufactured by Chemours).

[0065] Examples of the above-mentioned 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, benzylbromacetate, and inorganic salts. Specific examples of commercially available preservatives include Proxel GXL(S) and XL-2(S) manufactured by Arch Chemical.

[0066] Examples of the above-mentioned antifungal agents include sodium dehydroacetate, sodium benzoate, sodium pyridinethion-1-oxide, ethyl p-hydroxybenzoate, and 1,2-benzisothiazolin-3-one, as well as salts thereof.

[0067] Examples of the pH adjusting agents mentioned above include diethanolamine, triethanolamine, N-methyldiethanolamine, 2-methyl-2-amino-1-propanol; alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; ammonium hydroxide (ammonia water); or 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. The pH adjusting agent in the above ink is preferably 2-methyl-2-amino-1-propanol. When the above ink contains 2-methyl-2-amino-1-propanol, the content of 2-methyl-2-amino-1-propanol in the ink is preferably 0.1% by mass or more and 2% by mass or less, and more preferably 0.2% by mass or more and 1% by mass or less.

[0068] The pH of the above ink is typically 5 to 11, preferably 7 to 10. The surface tension of the ink is typically 20 to 60 mN / m, preferably 25 to 50 mN / m. The viscosity of the ink is typically 2.0 to 15 mPa·s, preferably 2.5 to 13 mPa·s, more preferably 3.0 to 12 mPa·s, and particularly preferably 3.5 to 11 mPa·s. The pH and surface tension of the ink can be adjusted by using pH adjusters, surfactants, organic solvents, etc.

[0069] Examples of the chelating agents mentioned above include disodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, sodium uracil diacetate, α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin.

[0070] Examples of the above-mentioned rust inhibitors include acidic sulfites, sodium thiosulfate, ammonium thioglycolate, diisopropylammonium nitride, pentaerythritol tetranitrate, and dicyclohexylammonium nitride.

[0071] Examples of the above-mentioned water-soluble ultraviolet absorbers include, for example, sulfonated benzophenone compounds, benzotriazol compounds, salicylic acid compounds, cinnamic acid compounds, and triazine compounds.

[0072] Examples of the above antioxidants include, for example, various organic and metal complex-based colorfastness inhibitors. Examples of the above organic colorfastness inhibitors include hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromans, alkoxyanilines, ascorbic acid, isoascorbic acid, chlorogenic acid, sulfur dioxide, catechins, dibutylhydroxytoluene, tocopherol, and butylhydroxyanisole.

[0073] The above-mentioned defoaming agents include acetylene-based defoaming agents such as the Surfinol 104 series (104A, 104E, 104H, 104PA, 104PG-50), Surfinol DF110D, Surfinol AD01, Surfinol MD-20, Surfinol 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, BY Examples of defoaming agents include silicone-based defoamers such as K-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 Bisfoam CS, Bisfoam ECC, and Bisfoam TDI-1; and fatty acid derivatives such as Bisfoam TS-10. The defoaming agent is preferably an acetylene-based or silicone-based defoamer, and more preferably Surfinol DF110D.

[0074] The above ink can be used in various printing applications. For example, it is suitable for writing instruments, various types of printing, information printing, textile printing, etc., and is particularly preferred for use in inkjet printing.

[0075] When preparing the above-mentioned ink, known manufacturing methods can be used. For example, one method involves preparing an ink by adding diethylene glycol mono(C4-C8) alkyl ether, water, and optionally an organic solvent, resin, and ink preparation agent to an aqueous dispersion prepared from the above-mentioned water-insoluble colorant and polymer dispersant, and then mixing the mixture.

[0076] The above ink can be prepared using conventionally known equipment, such as a ball mill, sand mill, attritor, basket mill, or roll mill. During preparation, it is preferable to remove coarse particles using a membrane filter or mesh filter.

[0077] Furthermore, it is preferable to microfilter 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.

[0078] An ink set containing multiple of the above-mentioned inks, an ink set containing the above-mentioned ink and other inks, or an ink set containing multiple of the above-mentioned inks and other inks are also included in the present invention.

[0079] <Inkjet Printing Method> The present invention also includes an inkjet printing method in which printing is performed by ejecting droplets of the above-mentioned ink, or each ink constituting the above-mentioned ink set, from an inkjet printer and adhering them to a printing medium.

[0080] Any known inkjet method can be used. Specific examples of inkjet methods include, for example, charge control methods, drop-on-demand (pressure pulse) methods, acoustic inkjet methods, and thermal inkjet methods, with the drop-on-demand method being preferred. In addition, inkjet methods also include methods that improve image quality by ejecting many small volumes of ink with a low pigment content, 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 and transparent ink.

[0081] <Print media> The present invention also includes printing media to which the above-mentioned ink, or each ink constituting the above-mentioned ink set, is attached. The printing media is not particularly limited as long as it is a material to which the above-mentioned ink can adhere, and examples include paper, film, cans, leather, cloth, and fibers. Printing media are broadly classified into non-permeable printing media such as films and cans to which ink does not penetrate, and permeable printing media to which ink does penetrate.

[0082] Regarding all of the above, combinations of preferred elements are more preferable, and combinations of preferred elements are even more preferable. The same applies to combinations of preferred elements and preferred elements, and combinations of preferred elements and even more preferable elements. Furthermore, unless otherwise specified, all of the above-mentioned components can be used individually or in combination of two or more elements.

[0083] The ink of the present invention has excellent ink-bleed prevention properties, and furthermore, the ink has excellent redispersibility, and the image obtained using the ink has excellent color development, quality, scratch resistance, lightfastness, water resistance, substrate drying properties, and peel resistance. [Examples]

[0084] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the examples, unless otherwise specified, "parts" means parts by mass and "%" means mass percent. When it was necessary to quantify the pigment solids content in the dispersion, it was determined by the dry weight method using the MS-70 manufactured by A&D Co., Ltd. The pigment solids content is a converted value calculated from the total amount of solids, with only the pigment solids content being considered.

[0085] The present invention will be described in detail below with reference to examples. The present invention is not limited to the following examples. The "water" used in the examples is "ion-exchanged water".

[0086] [Preparation Example 1] Preparation of Binder Resin 1 A binder sample (solid content concentration 40%) described in Synthesis Example 3 of Japanese Patent Application Publication No. 2024-146796 was prepared and used as Binder Resin 1.

[0087] [Preparation Example 2]: Preparation of a yellow pigment dispersion. 4.5 parts of BYKJET9151 (BYK Chemie Japan Co., Ltd.) were dissolved in 80.5 parts of deionized water and stirred for 1 hour. 15 parts of CIPigment Yellow 155 (Heubach GmbH, Inkjet Yellow 4G) were added to the resulting solution and dispersed in a sand grinder at 1500 rpm for 10 hours. 30 parts of deionized water were added dropwise to the resulting liquid, and the dispersion beads were removed by filtration to obtain yellow pigment dispersion 2 with a pigment solid content of 11.5%. [Preparation Example 3]: Preparation of Magenta Pigment Dispersion Magenta pigment dispersion 3 was obtained in the same manner as in Preparation Example 2, except that the added pigment was changed to CI Pigment Red 122 (Heubach, Inkjet Magenta E-02). [Preparation Example 4]: Preparation of cyanide pigment dispersion. Cyanide pigment dispersion 4 was obtained in the same manner as in Preparation Example 2, except that the added pigment was changed to CI Pigment Blue 15:4 (manufactured by Dainichi Seika Kogyo Co., Ltd., CHROMOFINE BLUE 4851). [Preparation Example 5]: Preparation of a black pigment dispersion. A black pigment dispersion 5 was obtained in the same manner as in Preparation Example 2, except that the added pigment was changed to CI Pigment Black 7 (NEROX 600, manufactured by Orion Engineered Carbons).

[0088] [Examples 1-12: Preparation of evaluation yellow ink Y1, evaluation magenta inks M1-M12, evaluation cyan ink C1, evaluation black ink Bk1, and Comparative Example 1: Preparation of evaluation magenta ink M13] The compositions Y1, M1-M13, C1, and Bk1 of each prepared ink are shown in Tables 1 and 2 below. Each abbreviation represents the following. A blank space indicates zero copies. PY155 as100: Yellow pigment dispersion obtained in Preparation Example 2 PR122 as100: Magenta pigment dispersion 3 obtained in Preparation Example 3 PB15:4 as100: Cyanide pigment dispersion obtained in Preparation Example 4 CB as100: Black pigment dispersion obtained in preparation example 5 Surfynol 440: Manufactured by Nisshin Chemical Co., Ltd. Surfynol DF-110D: Manufactured by Nisshin Chemical Co., Ltd. GENAPOL EP2544 (Polyoxyethylene polyoxypropylene alkyl ether, manufactured by Clariant) Emulgen A-60 (Polyoxyethylene (di)styrene-modified phenyl ether, manufactured by Kao Corporation) Binder resin 1 as100: Binder resin 1 prepared in Preparation Example 1 HITEC E-6314: Wax emulsion manufactured by Toho Chemical Industry Co., Ltd. In the tables above and below, "as100" indicates the set value by mass of the solid content of the water-insoluble colorant or binder resin 1 contained in the ink when 100 copies of the ink are prepared. It also indicates that the amounts of water-insoluble colorant and binder resin 1 are added to achieve the indicated value.

[0089] [Table 1]

[0090] [Table 2]

[0091] [evaluation] The inks prepared in Examples 1 to 12 above were combined in the combinations shown in Table 3 below, and the viscosity and color bleeding of the inks were evaluated as described later. Note that the ink in Comparative Example 1 had too high a viscosity, so printing evaluation was not possible.

[0092] [Table 3]

[0093] [Evaluation of ink viscosity] (1) Initial viscosity evaluation The initial viscosity at 32°C was measured for each of the evaluation inks immediately after preparation: evaluation yellow ink Y1, evaluation magenta inks M1-M12, evaluation cyan ink C1, and evaluation black ink Bk1. Initial viscosity was measured using an E-type viscometer TVE-35L (manufactured by Toki Sangyo Co., Ltd.) with a rotation speed setting of 100 (only the ink in Comparative Example 1 was set to 20 because its viscosity was too high to measure). The results were evaluated based on the following evaluation criteria A to F. The results are shown in Table 4 below. Ink with high initial viscosity can cause malfunctions such as printer nozzle clogging; therefore, a viscosity of 4.0 mPa·s to 8.0 mPa·s is preferable. Ink with an initial viscosity of 10.0 mPa·s or higher cannot be evaluated for print quality. A: The initial viscosity of the ink is less than 6.0 mPa·s. B: The initial viscosity of the ink is 6.0 mPa·s or more and less than 7.0 mPa·s. C: The initial viscosity of the ink is 7.0 mPa·s or more and less than 8.0 mPa·s. D: The initial viscosity of the ink is 8.0 mPa·s or more and less than 9.0 mPa·s. E: The initial viscosity of the ink is between 9.0 mPa·s and less than 10.0 mPa·s. F: The initial viscosity of the ink is 10.0 mPa·s or higher. (2) Evaluation of viscosity increase rate After ink preparation, the inks were stored at 25°C for more than one day. The viscosity of these inks was then measured using an E-type viscometer TVE-35L (manufactured by Toki Sangyo Co., Ltd.) with a rotation speed setting of 100 (only the ink for Comparative Example 1 was set to 20 because its viscosity was too high to measure), and evaluated based on the following evaluation criteria A to F. Based on the measured viscosity and the initial viscosity results mentioned above, the viscosity increase rate was calculated using the following formula (Z) and evaluated according to the following evaluation criteria A to F. The results are shown in Table 4 below. A lower rate of viscosity increase indicates superior storage stability and print stability of the ink. Viscosity increase rate (%) = (Measurement value after 1 day or more has passed since preparation - Measurement value immediately after preparation) / (Measurement value immediately after preparation) × 100 ...Equation (Z) A: The ink viscosity increase rate is less than 1.0%. B: Ink viscosity increase rate is 1.0% or more and less than 1.5% C: Ink viscosity increase rate is 1.5% or more but less than 2.0% D: Ink viscosity increase rate is 2.0% or more but less than 2.5% E: Ink viscosity increase rate is 2.5% or more but less than 3.0% F: Ink viscosity increase rate of 3.0% or more

[0094] [Evaluation of color bleeding] (1) Preparation of test specimens Using Y1 ink, M1-M12 inks, C1 ink, and Bk1 ink, a single linear image was printed at 100% coverage and a line width of 1 mm, perpendicular to a 7.5 mm wide 100% solid image recorded with each ink. The printed image was obtained by printing a line of 1 mm coverage with each ink of a different color, superimposed perpendicularly on top of the solid image. Printing was performed using a printing jig equipped with four Kyocera KJ4B inkjet heads, in the order of yellow, magenta, cyan, and black inks, under three conditions (combination of microdroplets and medium droplets), on Toyobo Co., Ltd.'s "Toyobo Ester Film E5102" as the printing medium. The four inkjet heads were installed in the printing evaluation device in the order of yellow ink, magenta ink, cyan ink, and black ink from the upstream side in the feeding direction of the printing medium. At this time, the spacing between each inkjet head filled with each ink was set to 20 mm. The obtained printed image was dried by leaving it on a heater for 3 seconds to obtain a test piece. The bleeding of the test specimens was judged visually. The bleeding in the secondary color area where two lines intersect is also called "inter-color bleeding." The printing speed was set to 50.0 m / min. (2) Evaluation of color bleeding between colors Color bleeding was evaluated by printing a solid 100% image in a straight line with a line width of 7.5 mm using primary ink (magenta or yellow ink), and then overlaying it with a single solid 100% image in a straight line with a line width of 1 mm using secondary ink (cyan or black ink). In the above-mentioned printed area, bleeding occurred under conditions where there was a large amount of primary ink and a small amount of secondary ink. The length of the vertical width of the mixed colors was measured using a handheld image quality analyzer PIAS2 manufactured by Quality Engineering Associates, and evaluated based on the following evaluation criteria A to F. The results are shown in Table 4 below. The smaller the width of the color bleeding between inks, the higher the resolution of the printing that can be achieved. A: The width of the smudged area is 1.50 mm or less. B: The width of the bleed is greater than 1.50 mm and less than or equal to 1.75 mm. C: The width of the bleed exceeds 1.75 mm and is 2.00 mm or less. D: The width of the bleed is greater than 2.00 mm and less than or equal to 2.25 mm. E: The width of the bleed exceeds 2.25 mm and is 2.50 mm or less. F: The width of the blurring exceeds 2.50 mm.

[0095] [Table 4]

[0096] As is clear from Table 4 above, the inks of the examples showed suppression of color bleeding, low initial viscosity immediately after ink preparation, and minimal viscosity change after ink preparation. [Industrial applicability]

[0097] The present invention makes it possible to provide an ink that can suppress the occurrence of bleeding between inks, and can be suitably used in printers that require higher resolution print quality.

Claims

1. An ink containing a water-insoluble colorant, water, and 0.01% to less than 3% by mass of diethylene glycol mono(C4-C8) alkyl ether.

2. The ink according to claim 1, wherein the above-mentioned diethylene glycol mono(C4-C8) alkyl ether comprises at least diethylene glycol monohexyl ether.

3. The ink according to claim 1, comprising 0.6% by mass or more and 1.4% by mass or less of diethylene glycol mono(C4-C8) alkyl ether.

4. The ink according to claim 1, further comprising a polyoxyethylene compound.

5. The ink according to claim 1, further comprising an organic solvent.

6. An ink set comprising the ink described in claim 1 as the first ink and the ink described in claim 5 as the second ink.

7. A recording medium recorded with the ink described in claim 1.

8. An inkjet recording method comprising an ink application step of ejecting the ink described in claim 1 from an inkjet head and adhering it to a recording medium.

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