Ink set

Abstract

To solve the problem, provided is an ink set, which is an ink set having a pretreatment liquid and an ink composition, characterized in that the pretreatment liquid contains an organic acid having a boiling point of 120°C or lower at 1 atm, and the ink composition contains a pigment, an alkali-soluble resin or a crosslinked product thereof having an acid value of 200 mgKOH / g or more, which accounts for 1.8% by mass or more of the ink composition, and further contains a water-dispersible resin and water.

Description

Technical Field

[0001] This invention relates to an ink assembly consisting of a pretreatment liquid and an ink composition. Background Technology

[0002] As described in Patent Document 1, a pretreatment solution for inkjet printing containing water-insoluble resin particles, organic acids such as malonic acid, a crosslinking agent, and water is known. Images obtained using this pretreatment solution do not bleed ink, exhibit excellent adhesion, and have excellent lamination strength. From the perspective of achieving such effects, this is a pretreatment solution and ink composition intended for printing used in lamination. In such applications, the printing section exists within the laminated product, not on the outermost layer, during printing. Therefore, the invention described in Patent Document 1 does not attempt to improve the wear resistance or other effects of the printing section.

[0003] Patent Document 2 describes a method of printing using inkjet printing ink after treating the surface of the object to be printed with an acidic pretreatment solution. It also describes the use of various acids to make the pretreatment solution acidic. However, the printed patterns obtained through this method are limited to images and the like, where there is no penetration.

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2019-177510

[0006] Patent Document 2: Japanese Patent Application Publication No. 2005-001259 Summary of the Invention

[0007] The problem to be solved by the present invention is to provide an ink set that can produce excellent image quality even when an acidic environment is present, such as near the ink nozzle, wherein the acidic environment is generated when a volatile acid is used in the pretreatment solution.

[0008] The inventors conducted in-depth research to solve the above-mentioned problems and found that the above-mentioned problems could be solved by setting specific components, thus completing the present invention.

[0009] That is, the present invention is as follows.

[0010] (1) An ink assembly comprising a pretreatment liquid and an ink composition, characterized in that,

[0011] The pretreatment solution contains organic acids with a boiling point below 120°C at 1 atmosphere.

[0012] The ink composition contains pigments, an alkali-soluble resin or its crosslinked product comprising 1.8% or more by mass of an acid value of 200 mg KOH / g or more, and further contains a water-dispersible resin and water.

[0013] (2) The ink group according to (1) is characterized in that the ink composition contains 10.0 to 30.0% by mass of the water-dispersible resin, based on the solid content.

[0014] (3) The ink group according to (1) or (2) is characterized in that the water-dispersible resin is an acrylic resin and / or a styrene-acrylic resin with an acid value of less than 15 mg KOH / g.

[0015] (4) The ink group according to any one of (1) to (3) is characterized in that it is for inkjet printing.

[0016] (5) The ink group according to any one of (1) to (4) is characterized in that it is for printing and dyeing.

[0017] (6) The ink group according to any one of (1) to (5) is characterized in that the alkali-soluble resin with an acid value of 200 mg KOH / g or more is a substance in which, based on the mass ratio of the constituent monomers, the alkyl ester of styrene / free radical polymerizable unsaturated carboxylic acid with 8 or more carbon atoms is 35 to 55 / 25 to 35 / 15 to 35, or an alkyl ester of (meth)acrylic acid with less than 8 carbon atoms is 50 to 70 / 13 to 25 / 15 to 25.

[0018] According to the ink group of the present invention, the printing or image exhibits excellent scratch resistance, and even in the presence of volatile organic acids, the flight path of the ink composition ejected from the nozzle remains undisturbed, thus achieving the effect of forming excellent image quality (acid resistance). Detailed Implementation

[0019] The ink kit of the present invention comprises a pretreatment liquid and an ink composition, which will be described in turn below. The ink composition may be an inkjet ink composition or an ink composition for printing and dyeing.

[0020] The glass transition temperature and weight-average molecular weight of the resins mentioned in this specification are defined as follows.

[0021] <Glass transition temperature>

[0022] Regarding the glass transition temperature of the resin in this invention, when the resin is an acrylic copolymer resin, it is the theoretical glass transition temperature obtained by the following Wood formula.

[0023] Wood formula: 1 / Tg=W1 / Tg1+W2 / Tg2+W3 / Tg3+·····+Wx / Tgx

[0024] [In the formula, Tg1~Tgx represent the glass transition temperatures of the homopolymers of monomers 1, 2, 3...x constituting the resin, W1~Wx represent the polymerization fractions of monomers 1, 2, 3...x, and Tg represents the theoretical glass transition temperature. The glass transition temperature in Wood's formula is an absolute temperature.]

[0025] Regarding the glass transition temperature of a resin, when the resin is not an acrylic copolymer, it is the theoretical glass transition temperature obtained through thermal analysis. As a method of thermal analysis, according to Japanese Industrial Standard JIS K7121 (Method for Determination of Conversion Temperature of Plastics), as an example, the glass transition temperature can be determined using a Perkin Elmer Pyris1 DSC at a heating rate of 20°C / min and a nitrogen flow rate of 20 mL / min.

[0026] <Weight-average molecular weight>

[0027] The weight-average molecular weight of the resin in this invention can be determined by gel permeation chromatography (GPC). As an example, a Waters 2690 (manufactured by Waters Corporation) can be used as the GPC apparatus, with a PL gel 5 μm, MIXED-D (manufactured by Polymer Laboratories) column, tetrahydrofuran as the developing solvent, and chromatographic analysis performed under the following conditions: column temperature 25°C, flow rate 1 mL / min, RI detector, sample injection concentration 10 mg / mL, and injection volume 100 μl. The result is used to calculate the weight-average molecular weight of polystyrene.

[0028] <Pretreatment solution>

[0029] The pretreatment solution in this invention contains an organic acid with a boiling point below 120°C at 1 atmosphere, and may further contain a surfactant.

[0030] (Organic acids with a boiling point below 120°C at 1 atmosphere)

[0031] For the organic acids used in the pretreatment solution that have a boiling point of less than 120°C at 1 atmosphere, formic acid (boiling point of 100.8°C at 1 atmosphere) and / or acetic acid (boiling point of 118°C at 1 atmosphere) can be used.

[0032] The organic acid in the pretreatment solution preferably contains 5.0% by mass or more, more preferably 8.0% by mass or more. Furthermore, it is preferable to contain 30.0% by mass or less, more preferably 25.0% by mass or less. If the content of the organic acid is too low, the fixation of the resin in the ink composition printed on it may take time. Conversely, if the content is excessive, the organic acid may evaporate after printing, and it may take time for the free acid in the print or image to disappear.

[0033] (surfactant)

[0034] The pretreatment solution may or may not contain surfactants. Anionic and nonionic surfactants are preferred as optional surfactants. When cationic or amphoteric surfactants are included, there is a possibility of forming salts with organic acids that have a boiling point below 120°C at 1 atmosphere.

[0035] The surfactant content, for example, relative to the whole pretreatment solution, is 0 to 1.0% by mass, preferably 0.01 to 1.0% by mass, more preferably 0.1 to 0.7% by mass.

[0036] As anionic surfactants, phosphate surfactants, alkenyl succinic acid surfactants, alkali metal salts of alkylbenzene sulfonic acid, taurine surfactants, and alkali metal salts of polyoxyethylene alkylphenyl sulfate can be used.

[0037] As a phosphate surfactant, a phosphate ester surfactant is preferred, and PLYSURF AL, PLYSURF DB-01, PLYSURF A219B, PLYSURF A208B, and PLYSURF 212C (Daiichi Kogyo Pharmaceutical Co., Ltd.) can be used simultaneously. It can also be used with alkenyl succinic acid surfactants and / or taurine surfactants.

[0038] Alkenyl succinic acid or its salts can be used as alkenyl succinic acid (Starlight PMC) or dipotassium alkenyl succinate (Kao Corporation).

[0039] Sodium dodecylbenzenesulfonate, etc., can be used as an alkali metal salt of alkylbenzene sulfonates.

[0040] As a taurine-based surfactant, it may contain N-acyl taurate (Nikko Chemical Co., Ltd.), LMT (sodium N-methyl lauroyl taurate), MMT (sodium N-methyl myristoyl taurate), PMT (sodium N-methyl palmitoyl taurate), and SMT (sodium N-methyl stearyl taurate).

[0041] Sodium nonylphenyl sulfate, etc., can be used as an alkali metal salt of polyoxyethylene alkylphenyl sulfate.

[0042] As a nonionic surfactant, one or more of the following can be selected: silicone surfactants, fluorinated surfactants, and acetylene surfactants.

[0043] Examples of silicone surfactants include BYK-347, BYK-377, and BYK-3455 (BYK Chemicals Japan).

[0044] Examples of fluorinated surfactants include F-410, F-444, F-553 (manufactured by DIC), FS-65, FS-34, FS-35, FS-31, and FS-30 (manufactured by DuPont).

[0045] Examples of acetylene surfactants include SURFYNOL 104E, SURFYNOL 104H, SURFYNOL 104A, SURFYNOL 104BC, SURFYNOL 104DPM, SURFYNOL 104PA, SURFYNOL 104PG-50, SURFYNOL 420, SURFYNOL 440, SURFYNOL 465 (EVONIK), DYNOL 607, DYNOL 609, OLFINE E1004, OLFINE E1010, OLFINE E1020, OLFINE PD-001, OLFINE PD-002W, OLFINE PD-004, OLFINE PD-005, OLFINE EXP.4001, OLFINE EXP.4200, and OLFINE... One or more of the products sold under trade names such as EXP.4123 and OLFINEEXP.4300 (Nikshin Chemical Industry Co., Ltd.).

[0046] (solvent)

[0047] The pretreatment solution used in this invention can be water alone, or a mixture of water and a water-soluble organic solvent.

[0048] Examples of water-soluble organic solvents include monohydric alcohols, polyhydric alcohols, lower alkyl ethers of polyhydric alcohols, ketones, ethers, esters, and nitrogen-containing compounds. These can be used individually or in combination of two or more.

[0049] Examples of the aforementioned monohydric alcohols include methanol, ethanol, n-propanol, n-butanol, isobutanol, n-pentanol, n-hexanol, n-heptanol, n-octanol, n-nonanol, n-decanol or their isomers, cyclopentanol, cyclohexanol, etc., with alcohols having 1 to 6 carbon atoms in the alkyl group being preferred.

[0050] As the aforementioned polyols, ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,5-pentanediol, neopentanediol, 1,2-hexanediol, 1,6-hexanediol, 1,2-cyclohexanediol, heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, glycerol, pentaerythritol, diethylene glycol, dipropylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, polypropylene glycol, thiodiglycol, etc.

[0051] As lower alkyl ethers of the aforementioned polyols, ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, ethylene glycol monoethyl ether, ethylene glycol diethyl ether, ethylene glycol monopropyl ether, ethylene glycol isopropyl ether, ethylene glycol monobutyl ether, ethylene glycol isobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol n-propyl ether, propylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-n-butyl ether, etc., can be used.

[0052] The content of the aforementioned water-soluble organic solvent is preferably set to a very small amount, or it may be omitted.

[0053] However, the content during preparation is preferably 0 to 10.0% by mass in the pretreatment solution, and more preferably 0 to 5.0% by mass. A content exceeding 10.0% by mass will result in poor drying or reduced resistance to clumping.

[0054] (Other ingredients)

[0055] The pretreatment solution in this invention may or may not contain water-soluble polyvalent metal salts as other components.

[0056] As a water-soluble polyvalent metal salt, it is an organic acid or inorganic acid salt of a polyvalent metal with a solubility of 1 g / 100 mL or more relative to 100 mL of water at 20°C, preferably 2 g / 100 mL or more, and more preferably 20 g / 100 mL or more.

[0057] Water-soluble polyvalent metal salts can be complex salts containing polyvalent metals or hydrates.

[0058] As a multivalent metal, it can be one or more selected from magnesium, calcium, strontium, zinc, copper, iron and aluminum.

[0059] Organic acids used to form water-soluble polyvalent metal salts include, for example, one or more fatty acids represented by RCOOH (where R is an organic group with 1 to 30 carbon atoms). Examples of such organic acids include formic acid, acetic acid, propionic acid, octanoic acid, lauric acid, myristic acid, pentadecanoic acid, palmitic acid, heptadecanoic acid, stearic acid, 12-hydroxystearic acid, ricinoleic acid, oleic acid, trans-11-octadecenoic acid, linoleic acid, linolenic acid, arachidic acid, docosanoic acid, tetracosanoic acid, hexacosanoic acid, linoleic acid, beeswax acid, lactic acid, citric acid, gluconic acid, malic acid, tartaric acid, succinic acid, malonic acid, glutaric acid, maleic acid, fumaric acid, penteneric acid, benzoic acid, ascorbic acid, etc.

[0060] As inorganic acids, examples include one or more selected from nitric acid, sulfuric acid, hydrogen chloride (hydrochloric acid), hydrogen bromide, hydrogen iodide, chloric acid, bromic acid, carbonic acid, and phosphoric acid.

[0061] As for water-soluble polyvalent metal salts that are polyvalent metal salts of organic acids, examples include one or more selected from zinc acetate, calcium acetate, strontium acetate, magnesium acetate, zinc formate, calcium formate, strontium formate, copper formate (II), magnesium formate, calcium benzoate, magnesium benzoate, zinc benzoate, calcium lactate, magnesium lactate, aluminum lactate, ferric lactate (II), copper lactate, calcium ascorbate, magnesium ascorbate, calcium propionate, magnesium propionate, calcium gluconate, magnesium gluconate, zinc gluconate, copper gluconate, zinc citrate, copper citrate, and their hydrates.

[0062] Furthermore, water-soluble polyvalent metal salts that are polyvalent metal salts of inorganic acids may be selected from one or more of the following: zinc chloride, aluminum chloride, calcium chloride, strontium chloride, ferric chloride, copper(II) chloride, nickel chloride, magnesium chloride, manganese(II) chloride, zinc bromide, calcium bromide, strontium bromide, ferric bromide(II), copper(II) bromide, magnesium bromide, zinc iodide, calcium iodide, magnesium iodide, aluminum nitrate, calcium nitrate, strontium nitrate, ferric nitrate(III), copper(II) nitrate, magnesium nitrate, zinc sulfate, aluminum sulfate, ferric sulfate(II), ferric sulfate(III), copper sulfate, magnesium sulfate, potassium aluminum sulfate, calcium dihydrogen phosphate, calcium bicarbonate, and their hydrates.

[0063] The amount of water-soluble polyvalent metal salts can be adjusted appropriately according to the type of salt or the purpose of preparation, and there are no particular limitations.

[0064] The lower limit of the content of water-soluble polyvalent metal salts, for example in the pretreatment solution, is 0.1% by mass or more, preferably 0.5% by mass or more, and more preferably 1% by mass or more, in terms of solid content. Furthermore, the upper limit of the content of water-soluble polyvalent metal salts, for example in the pretreatment solution, is 20% by mass or less, preferably 15% by mass or less, and more preferably 10% by mass or less, in terms of solid content.

[0065] The content of water-soluble polyvalent metal salts, for example in the pretreatment solution, is 0.1 to 20% by mass, preferably 0.5 to 15% by mass, and more preferably 1 to 10% by mass, in terms of solid content.

[0066] <Ink Composition>

[0067] (pigment)

[0068] By containing pigments of various hues in the ink composition of the present invention, ink compositions of various colors can be obtained.

[0069] As such a pigment, pigments previously used in common ink compositions can be used without particular restrictions.

[0070] Furthermore, examples of organic pigments include dye lake pigments, azo, benzimidazolone, phthalocyanine, quinacridone, anthraquinone, dioxazine, indigo, thioindigo, perylene, violet ketone, diketopyrrolopyrrole, isoindolinone, nitro, nitroso, anthraquinone, yellow anthrone, quinophthalone, pinanthrone, and indigoanthraquinone pigments. Examples of inorganic pigments include carbon black, titanium dioxide, iron oxide red, graphite, iron black, chromium oxide green, and aluminum hydroxide.

[0071] In addition, the following pigments can be listed as specific examples of pigments.

[0072] Examples of yellow pigments include CI pigment yellow 1, 2, 3, 12, 13, 14, 16, 17, 42, 73, 74, 75, 81, 83, 87, 93, 95, 97, 98, 108, 109, 114, 120, 128, 129, 138, 139, 150, 151, 155, 166, 180, 184, 185, and 213, with CI pigment yellow 150, 155, 180, and 213 being preferred examples.

[0073] Examples of magenta pigments include CI Pigment Red 5, 7, 12, 22, 38, 48:1, 48:2, 48:4, 49:1, 53:1, 57, 57:1, 63:1, 101, 102, 112, 122, 123, 144, 146, 149, 168, 177, 178, 179, 180, 184, 185, 190, 202, 209, 224, 242, 254, 255, 270, and CI Pigment Violet 19, with CI Pigment Red 122, 202, and CI Pigment Violet 19 being preferred examples.

[0074] Examples of cyan pigments include CI Pigment Blue 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 18, 22, 27, 29, 60, etc., with CI Pigment Blue 15:4 being a preferred example.

[0075] Examples of black pigments used in black ink compositions include carbon black (CI Pigment Black 7).

[0076] As white pigments used in white ink compositions, examples include titanium oxide and aluminum oxide, with titanium oxide that has been surface-treated with various materials such as aluminum oxide and silicon dioxide being preferred.

[0077] The pigment content in the ink composition is preferably 1.0 to 20.0% by mass relative to the total mass of the ink composition. If the pigment content is less than 1% by mass, there is a tendency for the image quality of the resulting printed matter to decrease. On the other hand, if it exceeds 20% by mass, there is a tendency for it to have an adverse effect on the viscosity characteristics of the ink composition.

[0078] (Pigment dispersant)

[0079] The ink composition of the present invention may also contain pigment dispersants as needed.

[0080] Pigment dispersants are used to improve the dispersibility of pigments and the storage stability of the ink compositions of the present invention. Conventionally used dispersants can be used without particular limitation, with polymeric dispersants being preferred. Examples of such pigment dispersants include carbodiimide dispersants, polyester amine dispersants, fatty acid amine dispersants, modified polyacrylate dispersants, modified polyurethane dispersants, multi-chain polymeric nonionic dispersants, and polymeric ionic surfactants. These pigment dispersants can be used alone or in combination of two or more.

[0081] Regarding the aforementioned pigment dispersant, when the total amount of pigment used is 100 parts by weight, it is preferable to contain 1 to 200 parts by weight. When the content of the pigment dispersant is less than 1 part by weight, the pigment dispersion and the storage stability of the ink composition of the present invention may sometimes decrease. On the other hand, more than 200 parts by weight of pigment dispersant may be contained, but sometimes there is no difference in effect. A more preferred lower limit for the content of pigment dispersant is 5 parts by weight, and a more preferred upper limit is 60 parts by weight.

[0082] (Alkali-soluble resins or their crosslinks with an acid value of 200 mg KOH / g or higher)

[0083] Examples of alkali-soluble resins or their crosslinks with an acid value of 200 mg KOH / g or higher include acrylic copolymer resins, maleic acid copolymer resins, polyester resins obtained through polycondensation reactions, and polyurethane resins or their crosslinks. Regarding the materials used to synthesize this alkali-soluble resin, for example, as disclosed in Japanese Patent Application Publication No. 2000-94825, acrylic copolymer resins, maleic acid copolymer resins, polyester resins, and polyurethane resins that can be obtained using the materials described in that publication can be used. Furthermore, resins obtained from materials other than those used can also be used. The alkali-soluble resin can be used alone or in combination of two or more types.

[0084] The content of the alkali-soluble resin relative to 100 parts by weight of the pigment is preferably 5.0 parts by weight or more, more preferably 15.0 parts by weight or more, from the viewpoint of improving the dispersibility of the pigment. The content of the alkali-soluble resin relative to 100 parts by weight of the pigment is preferably 100.0 parts by weight or less, more preferably 80.0 parts by weight or less, and even more preferably 60.0 parts by weight or less, from the viewpoint of reducing the viscosity of the ink composition.

[0085] As an acrylic copolymer resin, it can be a substance obtained by polymerizing a mixture of monomers containing anionic groups and other copolymerizable monomers in a solvent in the presence of a common free radical initiator (e.g., benzoyl peroxide, tert-butyl peroxide, azobisisobutyronitrile, etc.).

[0086] As monomers containing anionic groups, examples include monomers having at least one anionic group selected from carboxyl, sulfonic acid, and phosphonic acid groups, with monomers having carboxyl groups being particularly preferred.

[0087] Examples of monomers containing a carboxyl group include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, 2-carboxyethyl methacrylate, 2-carboxypropyl methacrylate, maleic anhydride, fumaric anhydride, and maleic half-ester. Examples of monomers containing a sulfonic acid group include ethanesulfonate methacrylate. Examples of monomers containing a phosphonic acid group include ethyl phosphonate methacrylate.

[0088] From the viewpoint of improving the adsorption of pigments, monomers containing hydrophobic groups are preferred as other monomers that can be copolymerized with the monomers containing anionic groups.

[0089] As monomers containing the hydrophobic group, examples include alkyl esters of free radical polymerizable unsaturated carboxylic acids having 8 or more carbon atoms (e.g., 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, 2-hydroxystearyl (meth)acrylate, etc.), alkyl vinyl ethers having 8 or more carbon atoms (e.g., dodecyl vinyl ether, etc.), and vinyl esters of fatty acids having 8 or more carbon atoms (e.g., vinyl 2-ethylhexanoate, vinyl laurate, vinyl stearate, etc.); monomers containing alicyclic hydrocarbon groups include cyclohexyl (meth)acrylate, etc.; and monomers containing aromatic hydrocarbon groups include styrene monomers such as benzyl (meth)acrylate, styrene, α-methylstyrene, and vinyltoluene, etc. The monomers containing the hydrophobic group can be used alone or in combination of two or more.

[0090] From the viewpoint of inhibiting the aggregation of alkali-soluble resins in aqueous media, monomers containing hydrophilic groups can be used as other monomers that can be copolymerized with the monomers containing anionic groups.

[0091] As monomers containing hydrophilic groups, examples of monomers having (poly)oxyalkylene chains include esters of mono-terminated alkyl-capped (poly)alkylene glycols and free radical polymerizable unsaturated carboxylic acids such as (meth)acrylic acid, or epoxy ethylene adducts and / or epoxy propylene adducts of free radical polymerizable unsaturated carboxylic acids such as (meth)acrylic acid; as monomers containing basic groups, examples include vinylpyrrolidones such as 1-vinyl-2-pyrrolidone and 1-vinyl-3-pyrrolidone, vinylpyridines such as 2-vinylpyridine, 4-vinylpyridine, 5-methyl-2-vinylpyridine, and 5-ethyl-2-vinylpyridine, 1-vinylimidazole, 1- The monomers include ethylene imidazoles such as ethylene-2-methylimidazolium, ethylene piperidines such as 3-ethylenepiperidine and N-methyl-3-ethylenepiperidine, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, tert-butylaminoethyl methacrylate, methacrylamide, N-methanol(meth)acrylamide, N-butoxymethyl(meth)acrylamide, N-methoxy(meth)acrylamide, N-ethoxy(meth)acrylamide, N-dimethylacrylamide, N-propylacrylamide, and other nitrogen-containing derivatives of (meth)acrylic acid; monomers with hydroxyl groups include, for example, hydroxyethyl methacrylate, hydroxypropyl methacrylate, and other hydroxyalkyl esters of (meth)acrylic acid; monomers with epoxy groups include, for example, glycidyl methacrylate. The monomers containing hydrophilic groups can be used alone or in combination of two or more.

[0092] Other copolymerizable monomers besides those containing hydrophobic and hydrophilic groups include, for example, alkyl esters of (meth)acrylic acid with fewer than 8 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, and cyclohexyl (meth)acrylate. These other copolymerizable monomers besides those containing hydrophobic and hydrophilic groups can be used alone or in combination of two or more.

[0093] For alkali-soluble resins, the preferred ratio by mass of the constituent monomers is styrene / alkyl ester of free radical polymerizable unsaturated carboxylic acid with 8 or more carbon atoms / (meth)acrylic acid = 35-55 / 25-35 / 15-35, more preferably styrene / laurate acrylate / acrylic acid = 35-55 / 25-35 / 15-35.

[0094] Furthermore, the preferred alkyl ester / acrylic acid / methacrylic acid ratio is 50-70 / 13-25 / 15-25, and more preferably cyclohexyl acrylate / acrylic acid / methacrylic acid ratio is 50-70 / 13-25 / 15-25.

[0095] From the viewpoint of suppressing pigment aggregation by moderately cross-linking the alkali-soluble resin, a cross-linking agent with two or more functions can be used, or it can be left uncross-linked.

[0096] The crosslinking agent with two or more functional groups is required to react with the functional groups of the alkali-soluble resin. Examples of such reactive functional groups include epoxy, hydroxyl, isocyanate, amino, and acridine groups. Furthermore, crosslinking agents that are dispersed, emulsified, or soluble in water, or those that can be dispersed, emulsified, and / or soluble in water, are particularly preferred. The crosslinking agent with two or more functional groups can be used alone or in combination.

[0097] Regarding the acid value of the alkali-soluble resin, from the viewpoint of improving its reactivity with the organic acids contained in the pretreatment solution, it is preferably 200 mg KOH / g or higher, more preferably 210 mg KOH / g or higher, and even more preferably 220 mg KOH / g or higher. Furthermore, regarding the acid value of the alkali-soluble resin, from the viewpoint of improving the water resistance of the printed matter, it is preferably 300 mg KOH / g or lower, more preferably 250 mg KOH / g or lower, and even more preferably 240 mg KOH / g or lower. Additionally, the acid value is the theoretical acid value, calculated arithmetically based on the composition of the monomers used to synthesize the alkali-soluble resin, representing the number of mg of potassium hydroxide theoretically required to neutralize 1 g of the alkali-soluble resin.

[0098] From the viewpoint of improving the resistance of printed materials to caking, the glass transition temperature of the alkali-soluble resin is preferably 0°C or higher, more preferably 20°C or higher, and even more preferably 40°C or higher. From the viewpoint of improving the resistance of printed materials to folding, the glass transition temperature of the alkali-soluble resin is preferably 100°C or lower, more preferably 80°C or lower, and even more preferably 60°C or lower.

[0099] From the viewpoint of improving the water resistance of printed materials, the weight-average molecular weight of the alkali-soluble resin is 5,000 or more, more preferably 8,000 or more, and even more preferably 13,000 or more. From the viewpoint of improving solubility in aqueous media, the weight-average molecular weight of the alkali-soluble resin is 50,000 or less, preferably 30,000 or less, and more preferably 20,000 or less.

[0100] (Water-dispersible resin)

[0101] As a water-dispersible resin, one or more selected from acrylic resin emulsions, styrene acrylic resin emulsions, polyurethane resin emulsions, and polyolefin resin emulsions may be used.

[0102] From the viewpoint of improving print quality and scratch resistance, the proportion of the solid component of the water-dispersible resin in the ink composition of the present invention is preferably 10.0% by mass or more, more preferably 13.0% by mass or more, and from the viewpoint of improving print quality, preferably 30.0% by mass or less, more preferably 25.0% by mass or less.

[0103] Furthermore, from the viewpoint of improving print quality and scratch resistance, the proportion of the solid component of the water-dispersible resin relative to the total amount of resin and pigment in the ink composition of the present invention is preferably 30.0% by mass or more, more preferably 40.0% by mass or more, further preferably 50.0% by mass or more, and most preferably 60.0% by mass. Moreover, from the viewpoint of improving print quality, it is preferably 93.0% by mass or less, more preferably 90.0% by mass or less.

[0104] Furthermore, from the viewpoint of improving acid resistance, the acid value of the water-dispersible resin is preferably below 20 mg KOH / g, more preferably below 10 mg KOH / g, even more preferably below 5 mg KOH / g, and most preferably below 1 mg KOH / g, and can be 0 mg KOH / g. Additionally, the acid value is the theoretical acid value, calculated arithmetically based on the composition of the monomers used to synthesize the alkali-soluble resin, representing the theoretical number of mg of potassium hydroxide required to neutralize 1 g of alkali-soluble resin.

[0105] Acrylic resin emulsions are polymers composed of one or more monomers selected from the following monomers.

[0106] Examples include (meth)acrylates, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, methoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, glycidyl (meth)acrylate, allyl (meth)acrylate, ethylene glycol di(meth)acrylate, and diethylene glycol di(meth)acrylate. Furthermore, the term "(meth)acrylate" is a general term for acrylates and methacrylates. In addition to the above, the following vinyl unsaturated monomers may also be used in combination: acrylonitrile, vinyl acetate, vinyl propionate, styrene, acrylic acid, methacrylic acid, (meth)acrylamide, N-methylene(meth)acrylamide, and N-methoxymethyl(meth)acrylamide.

[0107] Styrene-acrylic resin emulsions are emulsions obtained by dispersing styrene-acrylic resins in water. They can be manufactured through emulsification polymerization, dispersion polymerization, suspension polymerization, pulverization or solution / bulk polymerization, followed by post-emulsification.

[0108] Detailed information about this method and the stabilizer is described in “Emulsion Polymerization and Emulsion Polymers” (PA Lovell, MS El-Aasser, John Wiley & Sons Ltd., England, 1977, included in this specification by reference).

[0109] Commercially available styrene-acrylic resin emulsions include M6963 (manufactured by Japan Coating Resin), J-450, J-734, J-7600, J-352, J-390, J-7100, J-741, J-74J, J-511, J-840, J-775, HRC-1645, HPD-71, PDX-6102B, JDX-5050 (styrene-acrylic resin emulsion, manufactured by BASF), and UC-3900 (styrene-acrylic resin emulsion, manufactured by Toa Synthetic Co., Ltd.).

[0110] The polyurethane resin emulsion is an emulsion obtained by dispersing polyurethane resin in water. It can be anionic, cationic, or nonionic, with anionic and nonionic resins being preferred. Furthermore, examples of the polyurethane resin include polyether polyurethane resins, polyester polyurethane resins, polyester and polyether polyurethane resins, and polycarbonate polyurethane resins. The polyurethane resin emulsion can be used alone or in combination of two or more types.

[0111] Commercially available examples of the aforementioned polyurethane resin emulsions include, for example, "SUPER FLEXSTAR 210" (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd., anionic polyester polyurethane resin), "SUPER FLEXSTAR 130" (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd., anionic polyether polyurethane resin), "SUPER FLEXSTAR 500M" (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd., nonionic polyester polyurethane resin), "SUPER FLEXSTAR 460" (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd., anionic polycarbonate polyurethane resin), "Impranil DLP1380" (manufactured by Sumitomo Covestro Urethane Co., Ltd., anionic polyester polyurethane resin), and "BAYBOND PU407" (manufactured by Sumitomo Covestro Urethane Co., Ltd., anionic / nonionic polyester polyurethane resin). 420NS (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd., anionic polycarbonate polyurethane resin), SF460, SF460S, SF420, SF110, SF300, SF361 (polyurethane resin emulsion, manufactured by Unicar Corporation of Japan), W-6020, W-5025, W-5661, W-6010 (polyurethane resin emulsion, manufactured by Mitsui Chemicals Co., Ltd.), R967, acid value 19 mg KOH / g (trade name "NeoRez R-967", polyether polyurethane emulsion (solid content concentration 40% by mass), manufactured by DSM Neoresins Co., Ltd.), etc.

[0112] The polyolefin resin emulsion is an emulsion in which a polyolefin resin is dispersed in water. Examples of the polyolefin resin include polyethylene resin, polypropylene resin, polybutene resin, and polyolefin resins obtained by copolymerizing two or more of ethylene, propylene, and butene. Furthermore, the polyolefin resin may be a modified polyolefin resin in which amino, carboxyl, hydroxyl, acryloyl, or other polymer chains are introduced relative to the polyolefin chain; an oxidized polyolefin resin in which a portion of the polyolefin chain has been oxidized; or a halogenated polyolefin resin in which a portion has been treated with halogens. The polyolefin resin emulsion may be used alone or in combination of two or more types.

[0113] Commercially available examples of the aforementioned polyolefin resin emulsions include "CHEMIPEARL S100" (Mitsui Chemicals Co., Ltd., polyethylene resin emulsion), "CHEMIPEARL XEP800H" (Mitsui Chemicals Co., Ltd., polypropylene resin emulsion), and "ARROWBASE TC-4010" (UNITIKA Co., Ltd., polypropylene resin emulsion).

[0114] In addition to the acrylic resin emulsions, styrene-acrylic resin emulsions, polyurethane resin emulsions, and polyolefin resin emulsions mentioned above, other known resin emulsions such as AP4710 (acrylic-silicone resin emulsion, manufactured by Showa Polymer Co., Ltd.) used in the ink compositions may be used without impairing the effects of the present invention. Examples of such other resin emulsions include, for instance, polyvinyl acetate resin emulsions and polyvinyl chloride resin emulsions.

[0115] From the viewpoint of improving coating resistance such as scratch resistance, the styrene-acrylic resin emulsion and / or the polyurethane resin emulsion in the resin emulsion are preferably 70% or more by mass, more preferably 80% or more by mass, further preferably 90% or more by mass, and most preferably 95% or more by mass.

[0116] (surfactant)

[0117] In order to optimize the printing or dyeing process, the ink composition of the present invention may contain any surfactant. When further preparing an inkjet ink composition, depending on the inkjet head used, in order to improve the ejection stability, surfactants such as silicone surfactants used in conventional ink compositions are preferably used as surfactants.

[0118] Specific examples of silicone surfactants include polyether-modified silicone oil, polyester-modified polydimethylsiloxane, and polyester-modified methylalkyl polysiloxane. These can be used alone or in combination of two or more.

[0119] The surfactant content in the ink composition of the present invention is preferably 0.005 to 1.0% by mass. When it is below 0.005% by mass, the surface tension of the ink composition of the present invention increases, and the ejection stability from the inkjet head decreases. On the other hand, when it exceeds 1.0% by mass, the foaming in the ink composition increases and the ejection stability decreases.

[0120] (additive)

[0121] In the ink composition of this invention, various additives may be added as needed to express various functionalities. Specifically, examples include surface conditioners, light stabilizers, surface treatment agents, antioxidants, anti-aging agents, crosslinking promoters, polymerization inhibitors, plasticizers, preservatives, pH adjusters, defoamers, and humectants. Furthermore, a non-curing resin that functions as a color developer may or may not be formulated. Additionally, a solvent may or may not be present.

[0122] <Alkaline compounds>

[0123] From the viewpoint of dissolving alkali-soluble resins, the ink composition of this invention may also contain an alkaline compound. Examples of such alkaline compounds include inorganic alkaline compounds such as sodium hydroxide and potassium hydroxide; and organic alkaline compounds such as ammonia, methylamine, ethylamine, monoethanolamine, N,N-dimethylethanolamine, N,N-diethylethanolamine, N,N-dibutylethanolamine, diethanolamine, N-methyldiethanolamine, triethanolamine, morpholine, N-methylmorpholine, and N-ethylmorpholine. These alkaline compounds may be used alone or in combination of two or more.

[0124] The proportion of the alkaline compound in the ink composition of the present invention is only required to be an amount that allows the alkali-soluble resin to dissolve in the medium. Generally, from the viewpoint of improving the dispersion stability of the alkali-soluble resin, it is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and from the viewpoint of improving the water resistance of the printed matter, it is preferably 1% by mass or less, more preferably 0.5% by mass or less.

[0125] The ink composition of the present invention may be further supplemented with known additives such as resins, pigment dispersants, mildew inhibitors, rust inhibitors, thickeners, antioxidants, ultraviolet absorbers, shelf-enhancing agents, defoamers, and pH adjusters, depending on the purpose.

[0126] <Preparation method of pretreatment solution>

[0127] The pretreatment solution in this invention can be prepared by adding a specified amount of organic acid and a surfactant as needed to water in any order.

[0128] <Preparation Method of Ink Composition>

[0129] There are no particular limitations on the preparation (manufacturing) method of the ink composition in this invention; the above-mentioned components may be added sequentially or simultaneously and mixed. For example, the method described in (1) or (2) below may be used.

[0130] (1) A method for preparing an ink composition, wherein, in the presence of the alkaline compound, an aqueous resin varnish obtained by dissolving an alkali-soluble resin in water, pigments, pigment dispersants as needed, etc., are mixed, and a pigment dispersion (ink matrix) is prepared using various dispersers, such as ball mills, vertical ball mills (Attritor), roller mills, sand mills, stirred mills, etc., and the remaining materials are further added to prepare the ink composition.

[0131] (2) A method for preparing an ink composition, wherein after dispersing the pigment by the above method, an alkali-soluble resin is precipitated onto the pigment surface by acid precipitation or ion exchange method as described in Japanese Republished Patent No. WO2005 / 116147, to obtain a resin-coated pigment, the obtained resin-coated pigment is then neutralized with an alkaline compound, and then redispersed in water using various dispersers (high-speed stirring devices, etc.), and other materials are further added to prepare the ink composition.

[0132] The initial viscosity of the ink composition of the present invention after manufacturing is 2.0 to 15.0 mPa·s, preferably in the range of 3.0 to 12.0 mPa·s. The viscosity can be measured, for example, by an E-type viscometer (trade name "RE100L type viscometer", manufactured by Toki Sangyo Co., Ltd.).

[0133] (Printing method based on the ink group of the present invention)

[0134] The printing method based on the ink group of the present invention consists of the following two steps: a step of coating a pretreatment liquid onto the surface of a printing substrate such as printing paper or resin film, and a printing step of printing with an ink composition.

[0135] The process of applying the pretreatment solution can be carried out by inkjet printing or by other well-known methods.

[0136] Regarding these two processes, the printing process using the ink composition can be carried out in a wet-on-wet manner before the pretreatment solution for coating has dried, or in a dry-on-wet manner after the pretreatment solution for coating has dried.

[0137] Example

[0138] <Pretreatment solution>

[0139] Pretreatment solution 1 (prepared by mixing 20 parts by weight of acetic acid, 0.2 parts by weight of SURFYNOL 440 (acetylene glycol surfactant, HLB8, manufactured by EVONIK) and purified water to form 100 parts by weight of the substance).

[0140] Pretreatment solution 2 (the acetic acid in pretreatment solution 1 is set to 10 parts by mass).

[0141] Pretreatment solution 3 (a substance in which acetic acid in pretreatment solution 1 is replaced with lactic acid (an organic acid with a boiling point exceeding 120°C at 1 atmosphere)).

[0142] <Pigment>

[0143] JR-809 (trade name "JR-809", titanium dioxide treated with silica and alumina, average particle size 0.23μm, DBP oil absorption 24ml / 100g, manufactured by TAYCA)

[0144] PF-690 (trade name "PF-690", titanium dioxide treated with silica, alumina and organic matter, average particle size 0.21μm, DBP oil absorption 16ml / 100g, manufactured by Ishihara Sangyo Co., Ltd.)

[0145] HB890 (trade name "HIBLACK 890", average primary particle size 15nm, DBP oil absorption 95ml / 100g, pH 8.0, manufactured by Orion Engineered Carbons)

[0146] PB15:3 (Pigment Blue 15:3)

[0147] PR122 (Pigment Red 122)

[0148] PY14 (Pigment Yellow 14)

[0149] <Alkali-soluble resin>

[0150] Alkali-soluble resin 1 (a copolymer of cyclohexyl acrylate / acrylic acid / methacrylic acid = 65 / 16 / 19 with a weight average molecular weight of 15000 and an acid value of 235 mgKOH / g)

[0151] Alkali-soluble resin 2 (a copolymer of cyclohexyl acrylate / acrylic acid / methacrylic acid = 65 / 16 / 19 with a weight-average molecular weight of 9500 and an acid value of 235 mgKOH / g)

[0152] Alkali-soluble resin 3 (a copolymer of styrene / laurate acrylate / acrylic acid = 51 / 30 / 19 with a weight-average molecular weight of 15800 and an acid value of 144 mgKOH / g)

[0153] Alkali-soluble resin 4 (a copolymer of styrene / laurate acrylate / acrylic acid of 40 / 30 / 30 with a weight average molecular weight of 30,000 and an acid value of 220 mgKOH / g)

[0154] Alkali-soluble resin 5 (a copolymer of styrene / laurate acrylate / acrylic acid with a weight average molecular weight of 32,000 and an acid value of 188 mgKOH / g, consisting of 45 / 30 / 25).

[0155] <Alkali-soluble resin varnish>

[0156] 25 parts by weight of alkali-soluble resin 1 are mixed with sodium hydroxide and purified water with a neutralization equivalent of 100% by weight to prepare 100 parts by weight. The mixture is heated and stirred at 90°C to dissolve the resin, thus preparing alkali-soluble resin varnish 1.

[0157] Similarly, 25 parts by weight of each of alkali-soluble resin 2 to 5 are mixed with sodium hydroxide and purified water, each with a neutralization equivalent of 100% relative to the alkali-soluble resin, to prepare 100 parts by weight. The mixture is then heated and stirred at 90°C to dissolve the alkali-soluble resin varnish 2 to 5.

[0158] <Water-based color ink base>

[0159] As shown in Table 1, 50 parts by weight of JR-809, 40 parts by weight of alkali-soluble resin varnish 2 and 10 parts by weight of refined water were stirred and mixed, and then kneaded using a wet circulating mill to prepare water-based white ink matrix 1.

[0160] Similarly, as shown in Table 1, after mixing each pigment, each alkali-soluble resin varnish and refined water, the mixture was kneaded using a wet circulating mill to prepare water-based ink bases of various colors.

[0161] <Water-dispersible resins>

[0162] M6963 (trade name "M6963", styrene-acrylic emulsion (solid content concentration 45% by mass), acid value less than 10 mg KOH / g, manufactured by Japan Coating Resin Co., Ltd.)

[0163] R967 (trade name "NeoRez R-967", polyether polyurethane emulsion (solids concentration 40% by mass), acid value 19 mg KOH / g, manufactured by DSM Neoresins)

[0164] <Solvent>

[0165] Glycerol

[0166] Propylene glycol

[0167] <Additives>

[0168] E1010 (trade name "OLFINE E-1010", acetylene glycol surfactant, HLB13, manufactured by Nissin Chemical Industry Co., Ltd.)

[0169] <Ink Composition>

[0170] As shown in Table 2, the components were stirred and mixed to obtain the ink compositions of each example and comparative example. "Alkali-soluble resin varnish 2 (added later)" is a composition in which alkali-soluble resin varnish 2 is further added to the temporarily obtained ink composition.

[0171] [Table 1]

[0172] Water-based white ink base 1 2 3 4 Water-based black ink matrix 1 Water-based blue ink matrix 1 Water-based red ink matrix 1 Water-based yellow ink base 1 JR-809 50 50 50 PF-690 50 HB890 20 PB15:3 20 PR122 20 PY14 20 Alkali-soluble resin varnish 1 40 Alkali-soluble resin varnish 2 40 Alkali-soluble resin varnish 3 40 Alkali-soluble resin varnish 4 40 Alkali-soluble resin varnish 5 30 35 30 30 water 10 10 10 10 50 45 50 50 total 100 100 100 100 100 100 100 100

[0173] [Table 2]

[0174]

[0175] <Evaluation Methods>

[0176] (Image quality)

[0177] The pretreatment solutions of the examples and comparative examples were impregnated at a rate of 10g per A4 size in 100% white cotton fabric and then heated and dried to obtain printing media. Even after heating and drying, the acids contained in the pretreatment solutions remained in the printing media. In the presence of volatile organic acids, the flight path of the ink composition ejected from the nozzle generally tends to be irregular; when such flight paths are not irregular, an effect that can achieve excellent image quality can be achieved.

[0178] Using an evaluation printer equipped with a printhead manufactured by SPECTRA and the ink compositions of the examples and comparative examples, solid images were printed relative to the printing medium, followed by printing nozzle check images, and the printing medium was exchanged. Then, the printing of images and the exchange of printing media for printing nozzle check images were repeated 19 times.

[0179] The printing of the nozzle inspection image is achieved by printing a test image preset on the printer side using a dedicated printer-side program.

[0180] ○: Even when printing on media with more than 20 sheets, the print nozzles should be checked to ensure that the image is ejected from all nozzles.

[0181] ×: After printing begins, within the first 20 sheets of printing media, check the print nozzles for any instances of nozzles not ejecting or ejecting incorrectly during the nozzle inspection image.

[0182] (Coating resistance)

[0183] According to the drying conditions of Japanese Industrial Standard JIS L0849, the test was conducted using a Type II testing machine (200g load repeatedly rubbed against a 100mm length 100 times), and the fading grayscale level was used for evaluation.

[0184] ○: Level 4-5 ~ Level 5

[0185] △: Level 3-4 to Level 4

[0186] ×: Level 3 and below

[0187] According to Examples 1 to 10 of the present invention, images with excellent image quality and coating durability can be formed. However, the image quality is particularly poor in Comparative Example 1, which uses only an alkali-soluble resin with an acid value of less than 200 mg KOH / g, and in Comparative Example 3, which has a low content of alkali-soluble resin varnish in the ink composition.

[0188] Furthermore, according to Comparative Example 2, which used an organic acid with a boiling point exceeding 120°C at 1 atmosphere, poor image quality and coating durability were obtained.

Claims

1. An ink set for inkjet printing, comprising a pretreatment solution and an ink composition, characterized in that, The pretreatment solution contains organic acids with a boiling point below 120°C at 1 atmosphere. The ink composition contains pigments, an alkali-soluble resin or its crosslinking thereof accounting for more than 1.8% by mass of the ink composition and having an acid value of more than 200 mg KOH / g, and further contains a water-dispersible resin accounting for 10.0 to 30.0% by mass of the ink composition and having an acid value of less than 20 mg KOH / g, and water.

2. The ink assembly according to claim 1, characterized in that, The water-dispersible resin is an acrylic resin and / or a styrene-acrylic resin with an acid value of less than 15 mg KOH / g.

3. The ink set according to claim 1 or 2, characterized in that, For use in printing and dyeing.

4. The ink set according to claim 1 or 2, characterized in that, Alkali-soluble resins with an acid value of 200 mg KOH / g or higher, which, based on the mass ratio of the constituent monomers, are alkyl esters of styrene / free radical polymerizable unsaturated carboxylic acids with 8 or more carbon atoms / (meth)acrylic acid = 35~55 / 25~35 / 15~35, or alkyl esters of (meth)acrylic acid with less than 8 carbon atoms / acrylic acid / methacrylic acid = 50~70 / 13~25 / 15~25.

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