Ink composition for aqueous inkjet

Abstract

The present invention provides an ink composition for an aqueous inkjet. The ink composition has excellent storage stability, continuous discharge property, and blocking resistance and is capable of suppressing changes over time in the water repellency of the nozzle plate. The ink composition for an aqueous inkjet contains a pigment, an alkali-soluble resin, a water-soluble organic solvent, water, and a surfactant, and satisfies the following conditions (conditions 1) to (condition 3). (Condition 1) The water-soluble organic solvent has a water solubility of 500 g / L or more at 25°C. (Condition 2) The surfactant contains a surfactant represented by formula (I), and the content of the surfactant represented by formula (I) in the composition for an aqueous inkjet is 0.7 mass% or less. (Condition 3) The pH is 7.5-8.3. (In formula (I), R1 is a C1-15 linear or branched substituent containing a hydroxy group and / or an ether structure.)

Description

Aqueous inkjet ink composition

[0001] The present invention relates to an aqueous inkjet ink composition.

[0002] Aqueous inkjet ink compositions are used in a wide range of fields because they are highly safe and have a low environmental impact.

[0003] For example, Patent Document 1 discloses an aqueous inkjet ink composition containing at least water (A), a colorant (B), a water-soluble organic solvent component (C), a surfactant (D), and resin fine particles (E), wherein the aqueous inkjet ink composition further contains a water-soluble carbodiimide compound (F) as a crosslinking component, the surfactant (D) is a silicone surfactant, the resin fine particles (E) have, at least on their surfaces, functional groups that react with carbodiimide groups, and the mass ratio (E) / (F) of the resin fine particles (E) to the water-soluble carbodiimide compound (F) is 10 or more.

[0004] Japanese Patent Application Laid-Open No. 2018-070827

[0005] Conventional aqueous inkjet ink compositions (also simply referred to as ink compositions) have insufficient ejection properties, and in particular, when printing continuously, degradation of image quality due to streaks and the like (poor continuous ejection properties) can be observed.

[0006] Inkjet printers that eject aqueous inkjet ink compositions are equipped with a nozzle plate having a plurality of ejection ports as the portion from which the ink composition is ejected. The nozzle plate has a water-repellent layer on its surface to maintain the ejection properties of the ink composition. However, continued use of conventional ink compositions can result in a decrease in the water repellency of the nozzle plate (i.e., the water repellency decreases over time).

[0007] Furthermore, conventional ink compositions have had the problem that the dispersibility of the pigment decreases over storage time, causing the pigment to aggregate and making the nozzle plate more susceptible to clogging. Therefore, there is a demand for ink compositions that have the property of suppressing pigment aggregation even after storage time has elapsed (storage stability).

[0008] Furthermore, the ink composition is also required to have a property (blocking property) that prevents the printed ink composition from being easily transferred.

[0009] Conventional aqueous inkjet ink compositions have not been able to solve all of the above-mentioned problems, and there is still room for further improvement.

[0010] Therefore, an object of the present invention is to provide an aqueous inkjet ink composition that has excellent storage stability, continuous ejection properties, and blocking resistance, and that can suppress changes over time in the water repellency of a nozzle plate.

[0011] The present invention provides an aqueous inkjet ink composition that contains a pigment, an alkali-soluble resin, a water-soluble organic solvent, water, and a surfactant, and satisfies the following (Condition 1) to (Condition 3): (Condition 1) The water-soluble organic solvent has a water solubility of 500 g / L or more at 25°C. (Condition 2) The surfactant contains a surfactant represented by the following formula (I), and the content of the surfactant represented by the following formula (I) in the aqueous inkjet ink composition is 0.7 mass% or less. (Condition 3) The pH is 7.5 or more and 8.3 or less.

[0012] (In formula (I), R １ is a linear or branched substituent having 1 to 15 carbon atoms and containing a hydroxy group and / or an ether structure.

[0013] In the aqueous inkjet ink composition of the present invention, in the above formula (I), R １ Preferably, R contains a hydroxy group, and more preferably contains a hydroxy group and an ether structure. １ The number of carbon atoms in the group is preferably 2 to 11. The content of the surfactant represented by formula (I) in the aqueous inkjet ink composition is preferably 0.05 to 0.5% by mass.

[0014] The present invention can provide an aqueous inkjet ink composition that has excellent storage stability, continuous ejection properties, and blocking resistance, and that can suppress changes over time in the water repellency of a nozzle plate.

[0015] The aqueous inkjet ink composition of the present invention contains a pigment, an alkali-soluble resin, a water-soluble organic solvent, water, and a surfactant, and satisfies the following (Condition 1) to (Condition 3): (Condition 1) The water-soluble organic solvent has a water solubility of 500 g / L or more at 25°C. (Condition 2) The surfactant contains a surfactant represented by the following formula (I), and the content of the surfactant represented by the following formula (I) in the aqueous inkjet ink composition is 0.7 mass% or less. (Condition 3) The pH is 7.5 or more and 8.3 or less.

[0016] (In formula (I), R １ is a linear or branched substituent having 1 to 15 carbon atoms and containing a hydroxy group and / or an ether structure.

[0017] The aqueous inkjet ink composition of the present invention contains a pigment, an alkali-soluble resin, a water-soluble organic solvent having a water solubility of 500 g / L or more at 25°C, water, and a predetermined amount of a surfactant represented by formula (I) above. The aqueous inkjet ink composition has a pH of 7.5 or more and 8.3 or less, and therefore has excellent storage stability, continuous ejection properties, and blocking resistance, and can suppress changes over time in the water repellency of a nozzle plate.

[0018] (Pigment) The aqueous inkjet ink composition of the present invention contains a pigment.

[0019] As the pigment, any known pigment may be appropriately selected.

[0020] Examples of organic pigments include azo pigments (e.g., azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments, etc.), polycyclic pigments (e.g., phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, etc.), dye chelates (e.g., basic dye chelates, acid dye chelates, etc.), nitro pigments, nitroso pigments, and aniline black.

[0021] Examples of inorganic pigments include titanium oxide, zinc oxide, zinc sulfide, white lead, calcium carbonate, precipitated barium sulfate, white carbon, alumina white, kaolin clay, talc, bentonite, carbon black, black iron oxide, cadmium red, red iron oxide, molybdenum red, molybdate orange, chrome vermilion, yellow lead, cadmium yellow, yellow iron oxide, titanium yellow, chromium oxide, viridian, titanium cobalt green, cobalt green, cobalt chrome green, Victoria green, ultramarine, Prussian blue, cobalt blue, cerulean blue, cobalt silica blue, cobalt zinc silica blue, manganese violet, and cobalt violet.

[0022] The content of the pigment in the aqueous inkjet ink composition is preferably 1 to 20% by mass in terms of solid content, and more preferably 3 to 10% by mass in terms of solid content.

[0023] (Alkali-Soluble Resin) The aqueous inkjet ink composition of the present invention contains an alkali-soluble resin.

[0024] Examples of the alkali-soluble resin include acrylic resins copolymerized with acrylic acid or methacrylic acid and their alkyl esters, or styrene or the like as the main monomer component, styrene-acrylic resins, styrene-maleic acid resins, styrene-acrylic-maleic acid resins, polyurethane resins, polyester resins, etc. These alkali-soluble resins can be used alone or in combination of two or more.

[0025] The alkali-soluble resin is preferably a copolymer of styrene, alkyl (meth)acrylate, and (meth)acrylic acid, and more preferably an acrylic acid / n-butyl acrylate / benzyl methacrylate / styrene copolymer. Here, (meth)acrylate means acrylate and / or methacrylate, and (meth)acrylic acid means acrylic acid and / or methacrylic acid.

[0026] The alkali-soluble resin preferably has a weight-average molecular weight of 5,000 to 100,000, more preferably 10,000 to 50,000. In this specification, "weight-average molecular weight" refers to a weight-average molecular weight obtained by measurement using gel permeation chromatography (GPC). For example, chromatography can be performed using a Water 2690 (manufactured by Waters) GPC apparatus and a PLgel 5 μm MIXED-D (manufactured by Polymer Laboratories) column under the following conditions: tetrahydrofuran as a developing solvent, a column temperature of 25°C, a flow rate of 1 milliliter / minute, an RI detector, a sample injection concentration of 10 milligrams / milliliter, and an injection volume of 100 microliters, and the weight-average molecular weight can be determined as a polystyrene-equivalent.

[0027] From the viewpoints of storage stability and ejection property, the alkali-soluble resin preferably has an acid value of 100 mgKOH / g or more and 250 mgKOH / g or less, and more preferably 140 mgKOH / g or more and 230 mgKOH / g or less. In this specification, the term "acid value" refers to a theoretical acid value obtained by arithmetically calculating the number of milligrams of potassium hydroxide theoretically required to neutralize 1 g of the resin.

[0028] From the viewpoint of improving the blocking resistance and folding resistance of the printed matter, the alkali-soluble resin preferably has a glass transition temperature of 0°C or higher and 100°C or lower, more preferably 10°C or higher and 80°C or lower.

[0029] The content of the alkali-soluble resin is preferably 1 to 200 parts by mass, and more preferably 5 to 100 parts by mass, per 100 parts by mass of the pigment.

[0030] (Water-soluble organic solvent) The aqueous inkjet ink composition of the present invention contains a water-soluble organic solvent, which has a water solubility at 25°C of 500 g / L or more.

[0031]

[0033] From the viewpoint of providing suitable storage stability to the aqueous inkjet ink composition, the water-soluble organic solvent is preferably miscible with water at any ratio. The water solubility at 25°C can be measured by visually inspecting a mixture of water and the water-soluble solvent, but catalog values ​​may also be referenced.

[0032] The water-soluble organic solvent is preferably an alcohol or polyhydric alcohol solvent, and more preferably methanol, ethanol, propanol, ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, triethylene glycol, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, propylene glycol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, tripropylene glycol, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monopropyl ether, glycerin, or the like.

[0033] From the viewpoint of providing favorable continuous ejection properties and storage stability, the content of the water-soluble organic solvent in the aqueous inkjet ink composition is preferably 20% by mass or more, and more preferably 25% by mass or more, and is preferably 50% by mass or less.

[0034] (Water) The aqueous inkjet ink composition of the present invention contains water.

[0035] The water content in the aqueous inkjet ink composition is preferably about 15 to 70% by mass, from the viewpoint of providing favorable continuous ejection properties and storage stability.

[0036] (Surfactant) The aqueous inkjet ink composition of the present invention contains a surfactant represented by the following general formula (I).

[0037] (In formula (I), R １ is a linear or branched substituent having 1 to 15 carbon atoms and containing a hydroxy group and / or an ether structure.

[0038] In the above formula (I), R １ However, from the viewpoint of favorably imparting storage stability to the aqueous inkjet ink composition, it preferably contains a hydroxy group, and more preferably contains a hydroxy group and an ether structure.

[0039] In the above formula (I), R １ From the viewpoint of favorably imparting storage stability and continuous ejection properties to the aqueous inkjet ink composition, the carbon number of the alkyl group is preferably 2 to 11, and more preferably 4 to 11.

[0040] Specific examples of the surfactant represented by formula (I) above include 2-{[2-hydroxy-3-(octyloxy)propyl]sulfanyl}ethan-1-ol, 2,2′-thiodiethanol, 1-[(2-hydroxyethyl)thio]-2-propanol, etc. Among these, 2-{[2-hydroxy-3-(octyloxy)propyl]sulfanyl}ethan-1-ol is preferred from the viewpoint of suitably improving the storage stability and continuous ejection properties of the aqueous inkjet ink composition.

[0041] The content of the surfactant represented by formula (I) in the aqueous inkjet ink composition is 0.7% by mass or less. By ensuring that the content of the surfactant represented by formula (I) is within this range, it is possible to obtain an aqueous inkjet ink composition that is excellent in storage stability, continuous ejection property, and blocking resistance, and that can suppress changes over time in the water repellency of the nozzle plate.

[0042] The content of the surfactant represented by formula (I) in the aqueous inkjet ink composition is preferably 0.05% by mass or more, and more preferably 0.1% by mass or more, from the viewpoint of favorably imparting continuous dischargeability, and is preferably 0.5% by mass or less, from the viewpoint of favorably imparting blocking resistance.

[0043] From the viewpoint of further improving the jetting properties, the aqueous inkjet ink composition of the present invention preferably further contains a nonionic surfactant and / or anionic surfactant.

[0044] Examples of the nonionic surfactants include polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl esters, polyoxyethylene alkyl ethers, polyoxyethylene alkylamines, polyoxyethylene alkylamides, polyoxyethylene propylene block polymers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyether siloxane copolymers, and ethylene oxide adducts of acetylene alcohol.

[0045] Examples of the anionic surfactant include polyoxyethylene alkyl ether acetates, dodecylbenzenesulfonates, laurates, sodium sulfates, and salts of polyoxyethylene alkyl ether sulfates.

[0046] From the viewpoint of compatibility with the ink composition, the nonionic surfactants and anionic surfactants preferably have an HLB of 7 or more. The HLB can be calculated using the Griffin method according to the following formula, but catalog values ​​may also be referenced: HLB = 20 x [(molecular weight of the hydrophilic group contained in the surfactant) / (molecular weight of the surfactant)]

[0047] The content of the nonionic surfactant and / or anionic surfactant is preferably 0.1 to 1 mass %. The nonionic surfactant and / or anionic surfactant may be used alone or in combination of two or more thereof.

[0048] (Resin Emulsion) The aqueous inkjet ink composition of the present invention may contain a resin emulsion.

[0049] Examples of the resin emulsion include emulsions of polyethylene resin, polypropylene resin, urethane resin, acrylic resin, styrene resin, styrene-acrylic copolymer resin, butadiene resin, styrene-butadiene copolymer resin, vinyl acetate resin, vinyl acetate-acrylic copolymer resin, vinyl chloride resin, vinyl chloride-acrylic copolymer resin, fluoroolefin resin, polyester urethane resin, polyether polyurethane resin, polycarbonate urethane resin, and polyester resin, etc. Among these, emulsions of styrene-acrylic resin and polyurethane resin are preferred, and emulsions of polyester polyurethane resin are more preferred.

[0050] The resin emulsion preferably has a glass transition temperature of -40°C or higher and 100°C or lower, more preferably -35°C or higher and 80°C or lower. In this specification, the "glass transition temperature" may be measured using a thermal analysis device such as a differential scanning calorimeter (DSC), but when the following Wood's formula is applicable, it is preferably the theoretical glass transition temperature calculated by the following Wood's formula. Wood's formula: 1 / Tg=W １ / Tg １ +W ２ / Tg ２ +W ３ / Tg ３ +...+W ｎ / Tg ｎ (wherein Tg is the theoretical glass transition temperature of the resin; Tg １ ~Tg ｎ is the glass transition temperature of each homopolymer of monomers 1, 2, 3, . . . n constituting the resin copolymer; W １ ~W ｎ represents the polymerization fraction of each of the monomers 1, 2, 3, ..., n of the resin. However, the glass transition temperature in Wood's formula is an absolute temperature.)

[0051] The content of the resin emulsion in the aqueous inkjet ink composition is preferably 1.0% by mass or more, more preferably 1.5% by mass or more, in terms of solids. Furthermore, the content of the resin emulsion in the aqueous inkjet ink composition is preferably 3.5% by mass or less, in terms of solids. By having the content of the resin emulsion within the above range, it is possible to provide the aqueous inkjet ink composition with favorable storage stability and continuous ejection properties.

[0052] (Others) The aqueous inkjet ink composition of the present invention may contain various additives as needed. Specific examples include wax, silica, light stabilizers, surface treatment agents, antioxidants, antiaging agents, crosslinking accelerators, plasticizers, preservatives, pH adjusters, antifoaming agents, and moisturizing agents. These additives can be appropriately selected from known additives.

[0053] The content of the additives is, for example, about 0 to 10% by mass in terms of solid content in the aqueous inkjet ink composition.

[0054] (Method for producing aqueous inkjet ink composition) The method for producing the aqueous inkjet ink composition of the present invention is not particularly limited, and examples thereof include a method in which the above-mentioned components are added in order or simultaneously, and the mixture is mixed, stirred, and kneaded to produce an aqueous inkjet ink composition, and then the pH is adjusted to a predetermined range using a chelating resin or an ion exchange resin.

[0055] When the above components are mixed and stirred in order, for example, an aqueous resin varnish may be obtained by mixing an alkali-soluble resin, a basic compound, and water or a water-soluble organic solvent, and then a pigment may be mixed, stirred, and milled to prepare a pigment ink base, and then a resin emulsion, a surfactant, and, if necessary, water or a water-soluble organic solvent may be mixed and stirred to prepare an aqueous inkjet ink composition.

[0056] Examples of the basic compound used in preparing the aqueous resin varnish include ammonia, organic amines, and alkali metal hydroxides. Examples of the organic amines include alkylamines such as diethylamine, triethylamine, and ethylenediamine, and alkanolamines such as monoethanolamine, ethylethanolamine, diethylethanolamine, diethanolamine, and triethanolamine. Examples of the alkali metal hydroxides include sodium hydroxide and potassium hydroxide.

[0057] The method for the above-mentioned mixing, stirring, and milling is not particularly limited, and for example, mixing, stirring, and milling may be carried out by a known method using a bead mill, a ready mill, an ultrasonic homogenizer, a high-pressure homogenizer, a paint shaker, a ball mill, a roll mill, a sand mill, a sand grinder, a Dyno Mill, a Dispermat, an SC mill, a Nanomizer, or the like.

[0058] Examples of the ion exchange resin include acrylic acid type, methacrylic acid type, sulfonic acid type, trimethylammonium type, dimethylethanolammonium type, polyamine type, etc. Among these, methacrylic acid type and sulfonic acid type are preferred.

[0059] Examples of the chelating resin include iminodiacetic acid type, polyamine type, primary amine type, methylglucamine type, amidoxime type, isothiouronium type, thiol type, sulfonic acid type, phosphonic acid type, aminophosphate type, bispicolylamine type, and semithiocarbamic acid type chelating resins. Among these, iminodiacetic acid type is preferred.

[0060] By mixing with the ion exchange resin or chelating resin, the aqueous inkjet ink composition is adjusted so that the total amount of the basic compounds is 1.5 g / L or less, and the pH is within a predetermined range. The ion exchange resin and chelating resin can be removed, for example, using a sieve with an opening of 250 mesh.

[0061] The method for printing the aqueous inkjet ink composition of the present invention is not particularly limited, and it may be printed on the substrate using a known inkjet printing device.

[0062] (Physical Properties of Aqueous Inkjet Ink Composition) The aqueous inkjet ink composition of the present invention has a pH of 7.5 or more and 8.3 or less. From the viewpoint of providing favorable storage stability, the pH is preferably 7.6 or more, and more preferably 7.8 or more. Furthermore, from the viewpoint of favorably suppressing changes over time in the water repellency of the nozzle plate, the pH is preferably 8.2 or less, and more preferably 8.0 or less. In this specification, the pH was confirmed using a pH meter (B-712, manufactured by Horiba, Ltd.).

[0063] The aqueous inkjet ink composition of the present invention has excellent storage stability. In this specification, storage stability is evaluated by the following method.

[0064] The aqueous inkjet ink composition is placed in a glass bottle, and the viscosity at 25°C is measured using a viscometer (RE100L model, manufactured by Toki Sangyo Co., Ltd.). The bottle is then sealed and stored at 60°C for one month, and the viscosity (25°C) after storage is measured using the same viscometer. Storage stability is evaluated by calculating the viscosity change rate [[(viscosity after one month of storage - viscosity before storage) / (viscosity before storage)] x 100 (%)], and a viscosity change rate of less than 10% is evaluated as excellent storage stability, and a viscosity change rate of less than 5% is evaluated as extremely excellent storage stability.

[0065] The aqueous inkjet ink composition of the present invention has excellent continuous ejection properties. In this specification, the continuous ejection properties are evaluated by the following method.

[0066] The aqueous inkjet ink composition is loaded into the cartridge of an Epson PX105 printer, and 50 15 cm x 20 cm solid images are continuously printed on photo paper GL-101A450 (Canon Inc.). The 50 printed images are visually inspected, and images showing slight deterioration in image quality such as streaks but without affecting quality are rated as having excellent continuous dischargeability, and images showing good image quality and stable discharge are rated as having extremely excellent continuous dischargeability.

[0067] The aqueous inkjet ink composition of the present invention has excellent blocking resistance. In this specification, blocking resistance is evaluated by the following method.

[0068] The aqueous inkjet ink composition is printed on the treated surface of an OPP film (P2161, 25 μm, manufactured by Toyobo Co., Ltd.) using a 0.15 mm bar coater to prepare a coating film. Two sheets of the OPP film are stacked together so that the untreated side of the film is in contact with the prepared coating film, and a sufficient pressure (400 g / cm) is applied using a vice. ２ The mixture was left to stand for 24 hours at 40°C while adding the OPP film. Thereafter, the OPP film was peeled off and observed for paint transfer. Those in which there was resistance when peeling but no paint transfer was observed were rated as having excellent blocking resistance, and those in which there was no paint transfer and no resistance when peeling off were rated as having extremely excellent blocking resistance.

[0069] The aqueous inkjet ink composition of the present invention can suppress the change over time in the water repellency of a nozzle plate. In this specification, the change over time in the water repellency of a nozzle plate is evaluated by the following method.

[0070] A 2 cm x 2 cm silicon nozzle plate was immersed in the aqueous inkjet ink composition and stored for one month at 60° C. After storage, the water repellency of the nozzle plate was evaluated by measuring the contact angle of water with a contact angle meter (DM701, manufactured by Kyowa Interface Science Co., Ltd.). If the contact angle of water was 80° or more, it was evaluated that the change in the water repellency of the nozzle plate over time could be suppressed, and if it was 90° or more, it was evaluated that the change in the water repellency of the nozzle plate over time could be suitably suppressed.

[0071] The present specification discloses the following:

[0072] The present disclosure (1) provides an aqueous inkjet ink composition that includes a pigment, an alkali-soluble resin, a water-soluble organic solvent, water, and a surfactant, and that satisfies the following (Condition 1) to (Condition 3): (Condition 1) The water-soluble organic solvent has a water solubility of 500 g / L or more at 25°C. (Condition 2) The surfactant includes a surfactant represented by the following formula (I), and the content of the surfactant represented by the following formula (I) in the aqueous inkjet ink composition is 0.7 mass% or less. (Condition 3) The pH is 7.5 or more and 8.3 or less.

[0073] (In formula (I), R １ is a linear or branched substituent having 1 to 15 carbon atoms and containing a hydroxy group and / or an ether structure.

[0074] The present disclosure (2) relates to the above formula (I), R １ The aqueous inkjet ink composition according to the present disclosure (1), wherein R １ The aqueous inkjet ink composition according to the present disclosure (1) or (2), wherein R １ The aqueous inkjet ink composition according to any one of Disclosures (1) to (3), wherein the number of carbon atoms is 2 to 11. The aqueous inkjet ink composition according to Disclosure (5) is the aqueous inkjet ink composition according to any one of Disclosures (1) to (4), wherein the content of the surfactant represented by Formula (I) is 0.05 to 0.5% by mass in the aqueous inkjet ink composition.

[0075] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "%" means "% by mass" and "parts" means "parts by mass."

[0076] The materials used in the examples and comparative examples are as follows.

[0077] <Water-soluble organic solvent> Propylene glycol (water solubility of 500 g / L or more at 25°C, miscible with water at any ratio) Dipropylene glycol dimethyl ether (water solubility of 526 g / L at 25°C) Propylene carbonate (water solubility of 175 g / L at 25°C) The water solubility at 25°C was confirmed by the method described in this specification.

[0078] <Surfactants> (Surfactants satisfying formula (I)) 2-{[2-hydroxy-3-(octyloxy)propyl]sulfanyl}ethan-1-ol 2,2'-thiodiethanol 1-[(2-hydroxyethyl)thio]-2-propanol (Surfactants not satisfying formula (I)) 2-(methylthio)ethanol 2-(ethylthio)ethanol 2-(isopropylthio)ethanol 2-(isobutylthio)ethanol 2-(n-propylthio)ethanol (Other surfactants) Olfine E1004 (active ingredient 100%, HLB: 8, manufactured by Nissin Chemical Industry Co., Ltd.) Olfine E1010 (active ingredient 100%, HLB: 13, manufactured by Nissin Chemical Industry Co., Ltd.) The values ​​in the table indicate the solid content (solid content % by mass) of the aqueous inkjet ink composition.

[0079] <Resin emulsion> Neocryl A-1092 (solid content 48.5% by mass, styrene-acrylic emulsion, manufactured by DSM, glass transition temperature 6°C) Superflex 740 (solid content 40% by mass, polyester polyurethane emulsion, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., glass transition temperature -34°C) The values ​​in the table indicate the solid content (solid content %) in the aqueous inkjet ink composition.

[0080] <Water> Water (purified water)

[0081] <Chelate resin or ion exchange resin> Ion exchange resin 1: acrylic acid type ion exchange resin, Amberlite IRC76 (manufactured by DuPont) Ion exchange resin 2: sulfonic acid type ion exchange resin, Amberlite HPR1024H (manufactured by DuPont) Chelate resin 1: terminal H ＋ Iminodiacetic acid type chelating resin with carboxyl groups

[0082] <Preparation of aqueous resin varnish> 20 parts by mass of acrylic acid / n-butyl acrylate / benzyl methacrylate / styrene copolymer (alkali-soluble resin, weight average molecular weight 30,000, acid value 185 mgKOH / g, glass transition temperature 40°C) was dissolved in a mixed solution of 2.5 parts by mass of potassium hydroxide and 77.5 parts by mass of water to obtain an aqueous resin varnish with a solid content of 20% by mass.

[0083] <Preparation of aqueous black ink base> 23.7 parts by mass of aqueous resin varnish was mixed with 64.3 parts by mass of water to prepare a resin varnish for pigment dispersion. 12 parts by mass of carbon black (trade name Printex 90, manufactured by Orion Engineered Carbons) was further added to this varnish, stirred and mixed, and then milled in a wet circulation mill to prepare an aqueous black ink base (solid content 16.74% by mass).

[0084] <Preparation of aqueous yellow ink base> 23.7 parts by mass of the aqueous resin varnish was mixed with 64.3 parts by mass of water to prepare a resin varnish for pigment dispersion. 12 parts by mass of a yellow pigment (trade name Novapalm Yellow 4G01, manufactured by Clariant) was further added to this varnish, stirred and mixed, and then milled in a wet circulation mill to prepare an aqueous yellow ink base (solid content 16.74% by mass).

[0085] <Preparation of aqueous magenta ink base> 23.7 parts by mass of the aqueous resin varnish was mixed with 64.3 parts by mass of water to prepare a resin varnish for pigment dispersion. 12 parts by mass of magenta pigment (product name Inkjet Magenta E5B02, manufactured by Clariant) was further added to this varnish, stirred and mixed, and then milled in a wet circulation mill to prepare an aqueous magenta ink base (solid content 16.74% by mass).

[0086] <Preparation of aqueous cyan ink base> 23.7 parts by mass of the aqueous resin varnish was mixed with 64.3 parts by mass of water to prepare a resin varnish for pigment dispersion. 12 parts by mass of a cyan pigment (product name Heliogen Blue L7101F, manufactured by BASF) was further added to this varnish, stirred and mixed, and then milled in a wet circulation mill to prepare an aqueous cyan ink base (solid content 16.74% by mass).

[0087] <Preparation of aqueous inkjet ink compositions> (Examples 1 to 15, Comparative Examples 1 to 10) Each material was blended based on Tables 1 and 2, and stirred and mixed by a known method to prepare an aqueous inkjet ink composition. 100 g of the aqueous inkjet ink composition was then mixed with an ion exchange resin or chelating resin shown in Tables 1 and 2 by stirring for 30 minutes. The ion exchange resin or chelating resin was then removed (referred to as "treatment step" in the tables). In Comparative Example 9, the treatment step was not performed. The pH before and after the treatment step was confirmed using a pH meter (B-712, manufactured by Horiba, Ltd.).

[0088]

[0089]

[0090] <Storage Stability> The aqueous inkjet ink composition was placed in a glass bottle, and the viscosity at 25°C was measured using a viscometer (RE100L model, manufactured by Toki Sangyo Co., Ltd.). The bottle was then sealed and stored at 60°C for one month, and the viscosity (25°C) after storage was measured using the same viscometer. The viscosity change rate [[(viscosity after one month of storage - viscosity before storage) / (viscosity before storage)] x 100 (%)] was calculated and evaluated according to the following evaluation criteria. The results are shown in Tables 3 and 4. (Evaluation Criteria) ⊚: Viscosity change rate is less than 5% ◯: Viscosity change rate is 5% or more but less than 10% ×: Viscosity change rate is 10% or more

[0091] <Continuous Dischargeability> The aqueous inkjet ink composition was loaded into the cartridge of an Epson printer PX105, and 50 15 cm x 20 cm solid images were continuously printed on photo paper GL-101A450 (Canon). The 50 printed images were visually inspected and evaluated according to the following evaluation criteria. The results are shown in Tables 3 and 4. (Evaluation Criteria) ⊚: Good image quality and stable discharge was possible. ◯: Slight deterioration in image quality such as streaks was observed, but this did not affect quality. ×: Streaks or other deterioration in image quality was observed, and stable discharge was not possible.

[0092] <Blocking Resistance> The aqueous inkjet ink composition was printed on the treated surface of an OPP film (P2161, 25 μm, manufactured by Toyobo Co., Ltd.) using a 0.15 mm bar coater to prepare a coating film. Two sheets of the OPP film were stacked together so that the untreated side of the film was in contact with the prepared coating film, and a sufficient pressure (400 g / cm) was applied using a vice. ２ ) was added and the mixture was left to stand at 40°C for 24 hours. After that, the OPP film was peeled off and observed for paint transfer, and rated according to the following criteria. The results are shown in Tables 3 and 4. (Evaluation criteria) ⊚: No paint transfer was observed and there was no resistance when peeling. ◯: There was resistance when peeling, but no paint transfer was observed. ×: Paint transfer was observed.

[0093] <Change in water repellency of nozzle plate over time> A 2 cm x 2 cm silicon nozzle plate was immersed in an aqueous inkjet ink composition and stored at 60°C for one month. After storage, the water contact angle of the nozzle plate was measured using a contact angle meter (DM701, manufactured by Kyowa Interface Science Co., Ltd.) and evaluated according to the following evaluation criteria. In the tables, "change in water repellency of nozzle plate over time" is referred to as "change in water repellency over time". The results are shown in Tables 3 and 4. (Evaluation criteria) ⊚: 90° or more ◯: 80° or more, less than 90° ×: Less than 80°

[0094]

[0095]

[0096] From Tables 3 and 4, it was confirmed that the aqueous inkjet ink compositions of the examples were excellent in storage stability, continuous ejection property, and blocking resistance, and were able to suppress changes over time in the water repellency of the nozzle plate.

[0097] It is possible to provide an aqueous inkjet ink composition that has excellent storage stability, continuous ejection properties, and blocking resistance, and that can suppress changes over time in the water repellency of a nozzle plate.

Claims

1. An aqueous inkjet ink composition comprising a pigment, an alkali-soluble resin, a water-soluble organic solvent, water, and a surfactant, and satisfying the following (Condition 1) to (Condition 3): (Condition 1) The water-soluble organic solvent has a water solubility of 500 g / L or more at 25°C. (Condition 2) The surfactant comprises a surfactant represented by the following formula (I), and the content of the surfactant represented by the following formula (I) in the aqueous inkjet ink composition is 0.7 mass% or less. (Condition 3) The pH is 7.5 or more and 8.3 or less. (In formula (I), R １ is a linear or branched substituent having 1 to 15 carbon atoms and containing a hydroxy group and / or an ether structure.

2. In the formula (I), R １ The aqueous ink-jet ink composition of claim 1 , wherein comprises a hydroxy group.

3. In the formula (I), R １ The aqueous inkjet ink composition according to claim 1 or 2, wherein the alkyl group contains a hydroxy group and an ether structure.

4. In the formula (I), R １ 3. The aqueous inkjet ink composition according to claim 1, wherein the number of carbon atoms is 2 to 11.

5. The aqueous inkjet ink composition according to claim 1 or 2, wherein the content of the surfactant represented by formula (I) in the aqueous inkjet ink composition is 0.05% by mass or more and 0.5% by mass or less.

Images