Ink

Abstract

The problem to be solved by the present invention is to provide an ink having abrasion resistance such that the printed surface does not peel off or wear even when, for example, the printed surfaces come into contact with each other or with other objects during the printing process of a fiber product (e.g., cloth) or a recording medium (e.g., ordinary paper, etc.) or during the use of the printed matter, and having ejection stability such that the ink nozzle of the inkjet recording device is not clogged or the ink ejection direction is abnormal. The inventors solved this problem by an ink in which a specific polymer (B) is dispersed in water (C) via a specific polymer (A), and the specific polymer (A) has a carboxyl group or a functional group in which the carboxyl group is neutralized by some basic compound.

Description

Technical Field

[0001] The present invention relates to an ink which can be used in various printing methods including, for example, an inkjet printing method. Background Art

[0002] It is known that ink containing, for example, a pigment can be used when printing images of text, pictures, patterns, etc. on recording media including cloth (such as woven fabrics, nonwoven fabrics, and knitted fabrics), plain paper, and coated paper.

[0003] Regarding the above-mentioned ink, generally, there is known an ink obtained by mixing a binder resin and other additives into an aqueous pigment dispersion containing a high concentration of pigment, and the aforementioned ink is diluted with water as needed. For example, there is known a printing ink having a polyurethane resin as a binder resin for printing on cloth (see, for example, Patent Document 1).

[0004] As a printing method of ink on a recording medium, a method using an inkjet recording device is known, for example. The aforementioned printing method using an inkjet recording device has the advantages that it is not necessary to form a printing plate for each picture or pattern to be printed, and the cost and delivery time of small-batch printing can be reduced, and therefore the aforementioned method is studied for use in the production of fiber products such as cloth and curtains.

[0005] Generally, in textile products, during the printing process or use, the printed surfaces may come into contact with each other or with other articles, or may be washed with a washing liquid.

[0006] However, in the prior art, when the above-mentioned contact occurs repeatedly, the aforementioned printed surface may peel off or wear over time, resulting in a poor appearance.

[0007] When using ordinary paper or coated paper as recording medium, the above-mentioned problems such as wear also occur. For example, when the printing surface and the conveying roller contact each other inside the printer, the printing surface may be worn, resulting in poor appearance of the printed product.

[0008] In addition, in order to form a clear and highly colored image or the like on plain paper, coated paper, textile products, or the like, there can be mentioned a method of increasing the concentration of a pigment contained in ink.

[0009] However, there is a problem that ink having a high pigment concentration is prone to cause nozzle clogging or abnormal ink ejection direction when ejected by an inkjet printing method.

[0010] Reference List

[0011] Patent Literature

[0012] PTL 1: JP-A-2016-199643 Summary of the invention

[0013] Technical issues

[0014] The problem to be solved by the present invention is to provide an ink having abrasion resistance to the extent that the printing surface will not peel off or wear even when, for example, the printing surfaces come into contact with each other or with other objects during printing on fiber products (such as cloth) or recording media (such as ordinary paper), or during the use of printed materials, and the ink has ejection stability to the extent that it will not cause clogging of the ink nozzle of the inkjet recording device or abnormality in the ink ejection direction.

[0015] In addition, another problem to be solved by the present invention is to provide an ink that can form a printed image, etc. having wash fastness, which is a wash fastness to the extent that the image, etc. will not be removed from a recording medium (such as cloth) even when washed with water, warm water or in a liquid containing a detergent, and the ink also has excellent abrasion resistance and ejection stability.

[0016] Technical Solution

[0017] The inventors of the present invention solved this problem through an ink, in which a polymer (B) is dispersed in water (C) through a polymer (A), the polymer (B) has more than 50% by mass of a structural unit represented by the following general formula (2), and the polymer (A) has a carboxyl group or a functional group in which the carboxyl group is neutralized by some basic compound, and a structural unit represented by the following general formula (1).

[0018] [Chemistry 1]

[0019]

[0020] (M in the general formula (1) represents a hydrogen atom or an alkali metal.)

[0021] [Chemistry 2]

[0022]

[0023] (R in general formula (2) 1 represents a hydrogen atom or a methyl group. )

[0024] Advantageous Effects of the Invention

[0025] The ink of the present invention can be used to produce printed products with excellent wear resistance and wash resistance. In addition, since the ink has a degree of ejection stability that does not cause clogging of the ink nozzle of the inkjet recording device or abnormal ink ejection direction, the aforementioned ink can be suitably used for inkjet printing on recording media such as cloth. DETAILED DESCRIPTION

[0026] The ink of the present invention is an ink in which a polymer (B) is dispersed in water (C) via a polymer (A), the aforementioned polymer (B) having 50% by mass or more of a structural unit represented by the following general formula (2), and the aforementioned polymer (A) having a carboxyl group or a functional group in which the carboxyl group is neutralized by some basic compound, and a structural unit represented by the following general formula (1).

[0027] [Chemistry 3]

[0028]

[0029] (M in the general formula (1) represents a hydrogen atom or an alkali metal.)

[0030] [Chemistry 4]

[0031]

[0032] (R in general formula (2) 1 represents a hydrogen atom or a methyl group. )

[0033] By using the ink of the present invention, even when the drying time after printing is short, a printed product having excellent wear resistance can be produced while maintaining good ejection stability of the ink, and having high colorability when printed on a recording medium (e.g., plain paper). In addition, the printed product obtained using the ink of the present invention not only has excellent wear resistance when the drying time after printing is short as described above, but also has further excellent wear resistance due to sufficient drying.

[0034] The polymer (A) is used to stably disperse the polymer (B) in the water (C). Therefore, unlike the pigment dispersing resin described below, the polymer (A) does not substantially contribute to the improvement of the dispersibility of the pigment in the water (C) described below.

[0035] Polymer (A) and polymer (B) exist in the form of particles in water (C). Specifically, the particles of polymer (A) exist on the surface of the particles of polymer (B), thereby forming a dispersion (X). Polymer (A) may be in a state of being adsorbed on the surface of the particles of polymer (B). In addition, polymer (A) may be in a state of forming a film on the surface of the particles of polymer (B).

[0036] In view of preventing deterioration of ink ejection stability due to increased ink viscosity, in particular, preventing kogation of a thermal inkjet print head (a phenomenon in which components contained in the ink are adsorbed on a heating component in the print head and hinder the generation of bubbles, which is a driving force for ink ejection), the dispersed particle size of the dispersion (X) is preferably in the range of 20 nm to 1000 nm, more preferably in the range of 200 nm to 600 nm, and particularly preferably in the range of 240 nm to 500 nm. The volume average particle size refers to a value measured by a dynamic light scattering method.

[0037] The dispersion (X) containing polymer (A) and polymer (B) plays the role of so-called binder resin. Binder resin is generally used for the purpose of improving the wear resistance of printed matter. As a binder resin, a binder resin with a volume average particle size of about 5nm to 20nm is conventionally used. However, as mentioned above, a binder resin with a very small volume average particle size tends to increase the dynamic viscosity of the ink, and as a result, the ejection stability of the ink may be reduced. In order to prevent the increase in the dynamic viscosity of the ink and maintain good ejection stability of the ink, a method of using an emulsified resin with a relatively large particle size as a binder resin can be mentioned. However, emulsified resins are often produced by an emulsion polymerization method using an emulsifier, so the emulsified resin contains an emulsifier. The emulsifier may cause the above-mentioned scaling.

[0038] In the present invention, by using an ink in which the polymer (B) is dispersed in water (C) via the polymer (A), the dispersed particle size of the dispersion (X) is controlled to be larger than the conventional particle size, so that good ink ejection stability can be maintained and a printed product having excellent abrasion resistance can be produced. In addition, since the ink of the present invention can reduce the amount of emulsifier used as described above, the ink has the effect of not easily causing scumming even when applied to the thermal inkjet printing method.

[0039] The ink of the present invention does not exclude the use of an emulsifier as described above. However, in view of taking into account both excellent wear resistance and ejection stability and suppressing the occurrence of scale formation, the content of the aforementioned emulsifier is preferably in the range of 0% to 1% by mass, more preferably in the range of 0% to 0.5% by mass, further more preferably in the range of 0% to 0.01% by mass, and particularly preferably 0% by mass, based on the total amount of the ink of the present invention.

[0040] As polymer (A), a polymer having a carboxyl group or a functional group in which the carboxyl group is neutralized by some basic compound and a structural unit represented by the following general formula (1) is used. The functional group -SO3M in the structural unit represented by general formula (1) represents a sulfonic acid group or a sulfonic acid alkali metal salt group.

[0041] [Chemistry 5]

[0042]

[0043] (M in the general formula (1) represents a hydrogen atom or an alkali metal.)

[0044] For example, a polymer obtained by radical polymerization of a monomer having a polymerizable unsaturated double bond can be used as the polymer (A).

[0045] As the monomer, a vinyl monomer having a carboxyl group for introducing a carboxyl group into the polymer (A) and a vinyl monomer for introducing a structure represented by the general formula (1) into the polymer (A) may be used in combination, and other vinyl monomers may be used as needed.

[0046] As the vinyl monomer having a carboxyl group, for example, acrylic acid, methacrylic acid, β-carboxyethyl (meth) acrylate, 2-(meth) acryloyl propionic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, itaconic acid half ester, maleic acid half ester, β-(meth) acryloyloxyethyl hydrogen succinate, β-(methyl) hydroxyethyl hydrogen phthalate, salts thereof, and acid anhydrides such as maleic anhydride can be used alone or in combination of two or more thereof. Among them, acrylic acid and methacrylic acid are preferably used in view of obtaining a printed product having excellent wear resistance and high colorability when printed on a recording medium (such as plain paper, etc.).

[0047] In view of obtaining an ink capable of producing a printed matter having both superior abrasion resistance and colorability, the vinyl monomer having a carboxyl group is preferably used in an amount within a range of 1% to 80% by mass, more preferably within a range of 5% to 70% by mass, and preferably within a range of 10% to 50% by mass, based on the total amount of monomers used in the production of the polymer (A).

[0048] In addition, as the vinyl monomer for introducing the structural unit represented by the general formula (1) into the polymer (A), for example, styrene sulfonic acid, alkali metal salts of styrene sulfonic acid, etc. can be used. As the alkali metal salt of styrene sulfonic acid, sodium styrene sulfonate, lithium styrene sulfonate, etc. can be used. Among them, sodium styrene sulfonate is particularly preferably used in view of obtaining an ink capable of producing a printed matter having excellent abrasion resistance.

[0049] In view of obtaining an ink capable of producing printed materials having both superior abrasion resistance and colorability, the vinyl monomer used to introduce the structural unit represented by the general formula (1) into the polymer (A) is preferably used in the range of 1% by mass to 90% by mass, and preferably in the range of 40% by mass to 90% by mass, based on the total amount of monomers used in the production of the polymer (A).

[0050] As other monomers that can be used for producing the polymer (A), for example, a monomer having a phosphorus atom can be used.

[0051] Examples of the monomer having a phosphorus atom include 2-(meth)acryloyloxyethyl acid phosphate (e.g., "Light Ester P-1M" and "Light Acrylate P-1A" manufactured by Kyoeisha Chemical Co., Ltd., etc.); bis(2-(meth)acryloyloxyethyl) acid phosphate; phosphate esters of polyalkylene glycol mono(meth)acrylates, such as phosphate esters of polyethylene glycol monomethacrylate (e.g., "Sipomer PAM100" and "Sipomer PAM4000" manufactured by Rhodia Nicca, Ltd., etc.), phosphate esters of polyethylene glycol monoacrylate (e.g., "Sipomer PAM5000" manufactured by Rhodia Nicca, Ltd., etc.), phosphate esters of polypropylene glycol monomethacrylate (e.g., "Sipomer PAM200" manufactured by Rhodia Nicca, Ltd., etc.), and phosphate esters of polypropylene glycol monoacrylate (e.g., "Sipomer PAM4000" manufactured by Rhodia Nicca, Ltd., etc.). "Sipomer PAM300" manufactured by Nicca, Ltd., etc.); alkylene (meth)acrylate phosphates such as methylene (meth)acrylate phosphate, trimethylene (meth)acrylate phosphate, propylene (meth)acrylate phosphate, tetramethylene (meth)acrylate phosphate, etc.

[0052] In addition, examples of other monomers include (meth)acrylates such as methyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, phenyl (meth)acrylate, and benzyl (meth)acrylate; vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, and vinyl versatate; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, pentyl vinyl ether, and hexyl vinyl ether; vinyl nitriles such as (meth)acrylonitrile, and the like; vinyl having an aromatic ring; The present invention also includes vinyl monomers such as styrene, α-methylstyrene, vinyl toluene, vinyl anisole, α-halogenated styrene, vinyl naphthalene and divinyl styrene; vinyl monomers containing glycidyl groups, such as glycidyl (meth)acrylate and allyl glycidyl ether; vinyl monomers containing hydroxyl groups, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, polyethylene glycol mono(meth)acrylate and glycerol mono(meth)acrylate; vinyl monomers containing hydroxymethylamide groups or alkoxylates thereof, such as N-hydroxymethyl (meth)acrylamide, N-isopropoxymethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide and N-isobutoxymethyl (meth)acrylamide; vinyl monomers containing amide groups, such as (meth)acrylamide, N-monoalkyl (meth)acrylamide and N,N-dialkyl (meth)acrylamide, etc. These can be used alone or in combination of two or more.

[0053] The polymer (A) can be prepared, for example, by supplying the above-mentioned vinyl monomer mixture all at once or in batches in the presence of water (C) or, if necessary, a polymerization initiator or a chain transfer agent, and subjecting the mixture to radical polymerization.

[0054] Examples of polymerization initiators include persulfates such as potassium persulfate, sodium persulfate, and ammonium persulfate, peroxides such as benzoyl peroxide, cumene hydroperoxide, and tert-butyl hydroperoxide, hydrogen peroxide, a redox polymerization initiator formed by combining the above peroxides and a reducing agent, and azo initiators such as 4,4'-azobis(4-cyanovaleric acid) and 2,2'-azobis(2-amidinopropane) dihydrochloride. Examples of reducing agents include ascorbic acid, isoascorbic acid, sodium isoascorbate, metal salts of formaldehyde sulfoxylate, sodium thiosulfate, and sodium bisulfite.

[0055] Among them, ammonium persulfate is preferably used as the polymerization initiator in view of improving the production efficiency of the polymer (A).

[0056] Examples of the chain transfer agent include thiomalic acid, thioglycerol, and the like, and they may be used alone or in combination of two or more. Thiomalic acid is preferably used in view of obtaining an ink capable of producing a printed matter having excellent dispersion stability and excellent colorability.

[0057] The production of the polymer (A) is usually preferably performed at a temperature of 30 to 100° C. for 1 to 40 hours. In order to rapidly polymerize the vinyl monomer, the polymer (A) is preferably produced in the presence of an inert gas such as nitrogen.

[0058] If necessary, the polymer (A) may be neutralized by mixing some basic compound as a neutralizing agent after the polymerization of the monomers.

[0059] Examples of the basic compound include alkali metal compounds such as sodium hydroxide and potassium hydroxide; alkaline earth metal compounds such as calcium hydroxide and calcium carbonate; ammonia; organic amines such as monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monopropylamine, dimethylpropylamine, monoethanolamine, diethanolamine, dimethylethanolamine, triethanolamine, ethylenediamine, and diethylenetriamine, etc. These may be used alone or in combination of two or more, and in view of obtaining an ink capable of producing a printed matter having excellent dispersion stability and excellent colorability, ammonia or aqueous ammonia is preferably used.

[0060] The composition in which the polymer (A) is dissolved or dispersed in water (C) can be produced by the above-mentioned method.

[0061] As the polymer (A) obtained by the above method, a polymer having a weight average molecular weight of 1,000 to 20,000 is preferably used, and in view of obtaining an ink capable of producing a printed matter having both more excellent abrasion resistance and colorability, a polymer having a weight average molecular weight of 3,000 to 15,000 is preferably used.

[0062] Next, the polymer (B) contained in the ink of the present invention will be described.

[0063] As the polymer (B), a polymer having 50% by mass or more of a structural unit represented by the following general formula (2) based on the total amount of the polymer (B) is used. As a result, the printed matter obtained by using the ink of the present invention can be imparted with excellent wear resistance. In particular, the wash resistance of the printed matter obtained by printing on cloth using the ink of the present invention can be improved.

[0064] In view of obtaining a printed matter having more excellent washing fastness and abrasion resistance, polymer (B) preferably contains the structure represented by the following general formula (2) in the range of 50 mass % to 90 mass %, more preferably in the range of 60 mass % to 80 mass %, and preferably in the range of 60 mass % to 75 mass %, based on the total amount of polymer (B).

[0065] [Chemistry 6]

[0066]

[0067] (R in general formula (2) 1 represents a hydrogen atom or a methyl group. )

[0068] Examples of the polymer (B) include various polymers such as acrylic polymer (b), polyurethane and polyester. Among them, acrylic polymer (b) is preferably used as the polymer (B).

[0069] As the acrylic polymer (b), a polymer of a (meth)acrylic acid monomer or other vinyl monomers can be used.

[0070] As the (meth)acrylic monomer, ethyl (meth)acrylate is preferably used in view of introducing the structural unit represented by the general formula (2) into the polymer (B).

[0071] As the (meth)acrylic acid monomer, in addition to ethyl (meth)acrylate, other vinyl monomers may be used as needed, and examples thereof include (meth)acrylic acid esters such as methyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, phenyl (meth)acrylate and benzyl (meth)acrylate, and vinyl monomers having a hydroxyl group such as 2-hydroxyethyl (meth)acrylate.

[0072] The acrylic polymer (b) can be produced by polymerizing a mixture of vinyl monomers containing ethyl (meth)acrylate.

[0073] On the other hand, the ink of the present invention is an ink in which the polymer (B) is dispersed in water (C) via the polymer (A). Therefore, in view of obtaining an ink capable of producing a printed matter having excellent dispersion stability and excellent abrasion resistance, it is preferred to produce the polymer (B) in the presence of the polymer (A).

[0074] Specifically, examples of the method for producing the polymer (B) include a method in which a (meth)acrylic acid monomer or the like contained in the acrylic polymer (b) is supplied all at once or in batches to a composition in which the polymer (A) is dissolved or dispersed in water (C), and the mixture is polymerized.

[0075] According to the above method, a composition in which the polymer (B) is dispersed in the water (C) via the polymer (A) can be obtained, and the composition can be used for the ink of the present invention.

[0076] In addition, considering obtaining an ink capable of producing printed materials with more excellent abrasion resistance, the ink of the present invention preferably contains a total amount of polymer (A) and polymer (B) in the range of 0.1 mass % to 30 mass %, based on the total amount of the ink, more preferably in the range of 0.1 mass % to 20 mass %, and particularly preferably in the range of 0.5 mass % to 10 mass %.

[0077] In the ink of the present invention obtained by the above method, considering obtaining an ink capable of producing printed materials with more excellent abrasion resistance, the mass ratio of polymer (A) to polymer (B) [polymer (A) / polymer (B)] is preferably in the range of 1 / 100 to 30 / 100, and more preferably in the range of 1 / 100 to 20 / 100.

[0078] As water (C), pure water such as ion exchange water, ultrafiltration water, water treated with a reverse osmosis membrane, and distilled water or ultrapure water can be used. In addition, as water, water sterilized by ultraviolet irradiation or by adding hydrogen peroxide or the like is preferably used because the generation of fungi or bacteria can be prevented when the ink of the present invention is stored for a long time.

[0079] Based on the total amount of the ink of the present invention, water (C) is preferably contained in the range of 40 mass % to 95 mass %, and more preferably in the range of 50 mass % to 90 mass %, in view of obtaining an ink capable of producing a printed matter having more excellent abrasion resistance and colorability.

[0080] The ink of the present invention may contain other components as necessary in addition to the polymer (A), the polymer (B) and the water (C).

[0081] Examples of the aforementioned other components include coloring materials such as pigments and dyes, pigment dispersion resins, binder resins other than polymer (A) and polymer (B), solvents other than water (C), wetting agents, lubricants, alkaline agents, pH regulators, surfactants, preservatives, chelating agents, plasticizers, antioxidants, waxes, ultraviolet light absorbers, etc. Wherein, as other components, as binder resins other than polymer (A) and polymer (B), it is preferred to use vinyl copolymers with anionic groups, such as polyester resins with anionic groups, epoxy resins with anionic groups, polyurethane resins with anionic groups, acrylic resins with anionic groups, maleic acid resins with anionic groups, styrene resins with anionic groups, and polyvinyl acetate resins with anionic groups. Wherein, considering obtaining inks capable of producing printed products with more excellent wear resistance and wash resistance, it is particularly preferred to use polyurethane resins with anionic groups.

[0082] As the pigment, for example, an organic pigment or an inorganic pigment may be used alone or in combination of two or more.

[0083] Examples of organic pigments include quinacridone pigments, quinacridonequinone pigments, di Oxazine pigments, phthalocyanine pigments, phthalocyanine pigments, isoindolinone pigments, methane / azomethine pigments, azo pigments, disazo pigments, anthrapymidin pigments, anthraquinone pigments, indanthrone pigments, vat yellow pigments, perylene pigments, diketopyrrolopyrrole pigments, pyrene pigments, quinophthalone pigments, anthraquinone pigments, thioindigo pigments, benzimidazolone pigments, azo lake pigments, insoluble azo pigments, condensed azo pigments, etc.

[0084] Examples of inorganic pigments include titanium dioxide, zinc oxide, iron oxide, chromium oxide, iron black, cobalt blue, aluminum oxide white, iron oxide yellow, viridian, zinc sulfide, lithobon, cadmium yellow, vermilion, cadmium red, chrome yellow, molybdate orange, zinc chromate, strontium chromate, white carbon, clay, talc, ultramarine, precipitated barium sulfate, barite powder, calcium carbonate, lead white, dark blue, manganese violet, carbon black, aluminum powder, pearlescent pigments, and the like.

[0085] As the pigment, a pigment that is self-dispersible in water may also be used.

[0086] In view of obtaining an ink having excellent storage stability and excellent ejection stability when applied to an inkjet printing method, the pigment is preferably used in a range of 0.1 mass % to 20 mass %, and more preferably in a range of 1 mass % to 10 mass %, based on the total amount of the ink.

[0087] When a pigment is used as a coloring material, a pigment dispersing resin is preferably used to stably disperse the pigment in water (C). Unlike polymer (A) or polymer (B), the aforementioned pigment dispersing resin imparts dispersion stability of the pigment in water (C) by adsorbing around pigment particles.

[0088] As the pigment dispersion resin, for example, a pigment dispersion resin having an anionic group can be used. Examples of the anionic group include a carboxyl group, a sulfonic acid group, a phosphoric acid group, and the like.

[0089] In view of obtaining an ink having a high degree of freedom in structural design while maintaining the stability of the ink of the present invention and being able to form a printed product with excellent colorability when printed on plain paper, it is particularly preferred to use a resin having a hydrophobic structural unit and a hydrophilic structural unit derived from an anionic group as the pigment dispersing resin having an anionic group.

[0090] As the resin having a hydrophobic structural unit derived from an anionic group and a hydrophilic structural unit, for example, the aforementioned pigment dispersion resin may use a resin having a structural unit derived from styrene and a structural unit derived from acrylic acid.

[0091] As the resin having a hydrophobic structural unit and a hydrophilic structural unit derived from an anionic group, in consideration of balancing pigment dispersibility, ink stability and high printing density, a resin having an acid value in the range of 60 mg to 300 mg KOH / g is preferably used, and a resin in the range of 100 mg to 250 mg KOH / g is suitable.

[0092] In view of balancing the pigment dispersibility in water (C), ink stability, abrasion resistance, high printing density and further ejection performance, as the resin having a hydrophobic structural unit and a hydrophilic structural unit derived from an anionic group, it is preferred to use a resin having a weight average molecular weight in the range of 3,000 to 50,000, more preferably in the range of 4,000 to 40,000, further more preferably in the range of 5,000 to 30,000, and particularly preferably in the range of 5,000 to 20,000.

[0093] In consideration of maintaining excellent ejection stability without deteriorating the resin due to the heating influence of the thermal jetting method even when the ink of the present invention is applied to a thermal-jet inkjet printing method, as the resin having a hydrophobic structural unit and a hydrophilic structural unit derived from an anionic group, a resin having a glass transition temperature in the range of 30°C to 150°C, more preferably a resin in the range of 70°C to 150°C is preferably used.

[0094] The resin having a hydrophobic structural unit and a hydrophilic structural unit derived from an anionic group is preferably a resin that can be made water-dispersible by neutralizing the anionic group, and is preferably a resin that has the ability to form stable water-dispersible particles under the action of some basic compounds as a neutralizing agent without using a dispersion stabilizer such as an emulsifier.

[0095] When a resin having an anionic group is used as the pigment dispersing resin, an inorganic basic compound or an organic basic compound can be used as the basic compound capable of neutralizing the anionic group. In view of obtaining an ink having more excellent storage stability, an inorganic basic compound is preferably used as the basic compound.

[0096] As the inorganic alkaline compound, alkali metal hydroxides, ammonium hydroxide, etc. can be used, and in view of imparting more excellent dispersion stability to the pigment, alkali metal hydroxides such as potassium hydroxide and sodium hydroxide, etc. are preferably used. In view of improving miscibility, an aqueous solution in which an inorganic alkaline compound has been previously dissolved or dispersed in water at a concentration of 10% to 60% by mass can be used.

[0097] In addition, examples of the organic basic compound include amines such as methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, diethanolamine and triethanolamine. These amines are generally in a liquid state and can therefore be used directly.

[0098] In view of improving the dispersibility in water (C) and ensuring good dispersion stability and stability for long-term storage, it is preferred to adjust the content of the basic compound so that the neutralization rate of the resin having anionic groups is preferably 50% or more, more preferably 70% or more. The upper limit of the neutralization rate is not particularly limited; however, it is preferably 200% or less, more preferably 120% or less, so that the ink is substantially stable and does not gel even if stored for a long time. Here, the aforementioned neutralization rate refers to the value calculated by the following formula.

[0099] Neutralization rate (%) = [{mass of basic compound (g) × 56.11 × 1000} / {acid value of pigment dispersion resin (mg KOH / g) × equivalent of basic compound × mass of pigment dispersion resin (g)}] × 100

[0100] More specifically, as the pigment dispersing resin, for example, vinyl copolymers having anionic groups such as polyester resins having anionic groups, epoxy resins having anionic groups, polyurethane resins having anionic groups, acrylic resins having anionic groups, maleic acid resins having anionic groups, styrene resins having anionic groups and polyvinyl acetate resins having anionic groups can be used.

[0101] Examples of the pigment dispersing resin include poly(meth)acrylic acid, vinyl acetate-acrylate copolymers, acrylic acid-alkyl acrylate copolymers, styrene-(meth)acrylic acid copolymers, styrene-(meth)acrylic acid-alkyl acrylate copolymers, styrene-maleic acid copolymers, vinyl acetate-maleic acid copolymers, vinyl acetate-crotonic acid copolymers, and vinyl acetate-acrylic acid copolymers.

[0102] Examples of the wetting agent include ethers of polyols such as ethylene glycol and glycerol, ethers of polyols such as ethylene glycol monoethyl ether and ethylene glycol monobutyl ether; polyoxyalkylene adducts of glycerol; nitrogen-containing heterocyclic compounds such as N-methyl-2-pyrrolidone and γ-butyrolactone; amides such as N,N-dimethylformamide; organic amines such as triethylamine, sulfur-containing compounds such as dimethyl sulfoxide, propylene carbonate, ethylene carbonate, etc., and they can be used alone or in combination of two or more.

[0103] As the wetting agent, in order to uniformly disperse the pigment and the pigment dispersion resin, it is preferred to use a wetting agent having a high boiling point, and more preferably to use a polyhydric alcohol such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, glycerol, and polyethylene oxide adducts of glycerol.

[0104] The aforementioned wetting agent is preferably used in the range of 10% by mass to 1000% by mass, more preferably in the range of 30% by mass to 200% by mass, based on the total amount of the pigment.

[0105] When an ink containing a pigment and a pigment dispersing resin is used as the ink of the present invention, as a production method of the ink of the present invention, for example, there can be mentioned a production method of a mixed aqueous pigment dispersion obtained by previously mixing a pigment, a pigment dispersing resin and water (C) with a composition containing a polymer (A), a polymer (B) and water (C).

[0106] The aqueous pigment dispersion can be produced, for example, by performing the following steps: step [1] kneading a composition containing a pigment, a pigment dispersing resin and some basic compound or a wetting agent as required; and step [2] diluting and dispersing the kneaded product obtained in step [1] in water (C).

[0107] By appropriately selecting the pigment dispersing resin in steps [1] and [2], the affinity of the pigment dispersing resin to the pigment becomes very good, the dispersion stability of the aqueous pigment dispersion is improved, and the gloss, durability, waterproofness, etc. of the printed product formed by printing the ink obtained using the aforementioned pigment dispersion on a recording medium can be improved.

[0108] In step [1], for example, an apparatus such as a roll mill, a Henschel mixer, a pressure kneader, and a planetary mixer can be used. An apparatus having a hermetically sealed stirring tank and stirring blades, such as a Henschel mixer, a pressure kneader, and a planetary mixer is preferably used because the solid content ratio of the composition in step [1] can be kept constant and a kneaded product having a good dispersion state can be obtained. A planetary mixer is preferably used because kneading treatment can be performed in a wide viscosity range.

[0109] Furthermore, step [2] is a step of diluting and dispersing the kneaded product obtained in step [1] in water (C).

[0110] In order to prevent ink nozzle clogging when the ink of the present invention is applied to an inkjet printing method, the aqueous pigment dispersion obtained by the above method is preferably centrifuged or filtered to remove coarse particles or aggregated particles derived from the pigment raw material, etc.

[0111] As the ink of the present invention, there may be mentioned a method of mixing the aqueous pigment dispersion obtained by the above method with a composition in which the polymer (B) is dispersed in water (C) via the polymer (A) and stirring for 30 to 90 minutes.

[0112] As the ink of the present invention obtained by the above method, for example, it is preferable to use an ink having a viscosity in the range of 1 mPa·sec to 10 mPa·sec. In particular, when the ink of the present invention is ejected by the inkjet printing method described later, it is more preferable to use an ink having a viscosity in the range of 1 mPa·sec to 6 mPa·sec.

[0113] The ink of the present invention can be used for printing on recording media.

[0114] Examples of the recording medium include coated paper having an ink absorbing layer that easily absorbs an ink solvent and fixes a pigment or the like on the surface, coated paper having a layer that does not easily absorb an ink solvent, plain paper, cloth, and the like.

[0115] By the way, when using an inkjet printer capable of double-sided printing to print on a recording medium, the single-sided print printed on one side (front) of the recording medium is usually dried for a certain period of time, and then turned over by the conveying roller and turning mechanism inside the printer to print the other side (back) of the single-sided print. When the single-sided print is turned over, the printed surface may be scratched due to the contact between the conveying roller and the like and the printed surface of the single-sided print, resulting in a decrease in printing quality. In particular, when double-sided printing is performed on coated paper, which is less likely to absorb solvents in ink than ordinary paper, the printing quality may decrease.

[0116] However, the ink of the present invention is excellent in abrasion resistance even in double-sided printing on coated paper or plain paper, and therefore is less likely to be scratched, and can effectively prevent a decrease in colorability when printing on plain paper.

[0117] The ink of the present invention can be suitably used for printing using cloth as a recording medium. Since the polymer (B) dispersed in water (C) via the polymer (A) contained in the ink of the present invention has a high affinity with fibers constituting the cloth, the ink is not easily removed from the cloth even when the printed matter is washed with water, warm water or a washing liquid, and a printed image with a high color density can be maintained even after washing.

[0118] As described above, the printed matter printed using the ink of the present invention can have both excellent abrasion resistance and high colorability.

[0119] Although the ink of the present invention may be suitable for use in various printing methods, the ink may be particularly suitable for printing by an inkjet printing method.

[0120] Examples of inkjet printing methods include continuous jet type (charge modulation type, spray type, etc.), on-demand type (piezoelectric method, heating method, electrostatic suction method, etc.), etc., and the ink of the present invention is suitable for printing by thermal inkjet printing method. When applied to these various inkjet methods, this aqueous ink for inkjet recording can basically be extremely stably jetted, and can also achieve excellent scratch resistance and abrasion resistance of the formed image.

[0121] Example

[0122] [Synthesis example 1]

[0123] 138 parts by mass of deionized water were placed in a reaction container equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, a thermometer, and a dropping funnel, and the temperature was raised to 80° C. while blowing nitrogen into the reaction container.

[0124] Next, 4.51 parts by mass of methacrylic acid, 5.63 parts by mass of sodium styrenesulfonate, and 0.15 parts by mass of thiomalic acid were added and heated to 80° C., and then 5 parts by mass of a 10% by mass ammonium persulfate aqueous solution was added to initiate polymerization.

[0125] After the temperature in the polymerization vessel was maintained at 80° C. for 1 hour, the content in the polymerization vessel was cooled to 40° C. or less and mixed with aqueous ammonia to obtain an aqueous solution (I-1) of the polymer (A-1).

[0126] Then, 100 parts by mass of a mixture for forming a polymer (B-1) containing 65 parts by mass of ethyl acrylate, 5 parts by mass of methyl methacrylate and 30 parts by mass of 2-hydroxyethyl methacrylate and 5 parts by mass of a 10% by mass aqueous solution of ammonium persulfate were added dropwise to an aqueous solution (I-1) of a polymer (A-1) adjusted to 80° C. over 4 hours and kept for 1 hour to perform polymerization.

[0127] After the above 1 hour, the content in the reaction container was cooled to 40° C. or lower.

[0128] After cooling, ammonia water was supplied to the reaction vessel to adjust the pH of the content to 7, and the reaction vessel was mixed for 1 hour to obtain a dispersion (II-1) having a non-volatile content of 40% by mass, in which polymer (B-1) was dispersed in water by polymer (A-1). The volume average particle size of the dispersed elements contained in the dispersion (II-1) was 470 nm.

[0129] The volume average particle size was calculated using NANOTRAC WAVE II manufactured by MicrotracBEL Corp. First, the dispersion was diluted 1000 times with ion exchange water. Then, about 4 ml of the diluted dispersion was placed in a small chamber, and the volume average particle size (MV) was measured by detecting the scattered light of the laser using NANOTRAC WAVE II manufactured by MicrotracBEL Corp. at 25°C. The volume average particle size was measured three times to calculate the average value (integer). The value obtained by rounding off the decimal point of the average value was used as the value of the volume average particle size (unit: nm).

[0130] [Synthesis example 2]

[0131] Except that the amount of methacrylic acid is changed from 4.51 mass parts to 1.03 mass parts, the amount of ethyl acrylate is changed from 65 mass parts to 68 mass parts, the amount of methyl methacrylate is changed from 5 mass parts to 12 mass parts, and the amount of 2-hydroxyethyl methacrylate is changed from 30 mass parts to 20 mass parts, a dispersion (II-2) in which the polymer (B-2) is dispersed in water through the polymer (A-2) and the non-volatile component content is 40 mass % is obtained by the same method as in Synthesis Example 1. The volume average particle diameter of the dispersed elements contained in the dispersion (II-2) is 320nm.

[0132] [Synthesis example 3]

[0133] Except that the amount of methacrylic acid is changed from 4.51 mass parts to 1.03 mass parts, the amount of ethyl acrylate is changed from 65 mass parts to 71 mass parts, the amount of methyl methacrylate is changed from 5 mass parts to 19 mass parts, and the amount of 2-hydroxyethyl methacrylate is changed from 30 mass parts to 10 mass parts, a dispersion (II-3) in which the polymer (B-3) is dispersed in water through the polymer (A-3) and the non-volatile content is 40 mass % is obtained by the same method as in Synthesis Example 1. The volume average particle diameter of the dispersed elements contained in the dispersion (II-3) is 290nm.

[0134] [Synthesis Example 4]

[0135] A dispersion (II-4) having a nonvolatile content of 40% by mass in which the polymer (B-4) was dispersed in water via the polymer (A-4) was obtained by the same method as in Synthesis Example 1, except that the amount of methacrylic acid was changed from 4.51 parts by mass to 1.03 parts by mass and a potassium hydroxide aqueous solution was used instead of ammonia water to adjust the pH to 7. The volume average particle diameter of the dispersed elements contained in the dispersion (II-4) was 440 nm.

[0136] [Synthesis example 5]

[0137] Except that the amount of ethyl acrylate was changed from 65 parts by mass to 40 parts by mass and the amount of methyl methacrylate was changed from 5 parts by mass to 30 parts by mass, a dispersion (II-5) having a non-volatile content of 40% by mass in which polymer (B-5) was dispersed in water through polymer (A-5) was obtained by the same method as in Synthesis Example 1. The volume average particle diameter of the dispersed elements contained in the dispersion (II-5) was 390 nm.

[0138] [Synthesis example 6]

[0139] Except that the amount of methacrylic acid was changed from 4.51 parts by mass to 1.03 parts by mass, the amount of ethyl acrylate was changed from 65 parts by mass to 47 parts by mass, and the amount of methyl methacrylate was changed from 5 parts by mass to 23 parts by mass, a dispersion (II-6) having a non-volatile content of 40% by mass in which the polymer (B-6) was dispersed in water via the polymer (A-6) was obtained by the same method as in Synthesis Example 1. The volume average particle diameter of the dispersed elements contained in the dispersion (II-6) was 350 nm.

[0140] [Table 1]

[0141]

[0142] [Synthesis Example 7]

[0143] 250.0 parts by mass of polytetramethylene ether glycol (average molecular weight 1000) and 181.7 parts by mass of hydrogenated 4,4'-diphenylmethane diisocyanate (H12MDI) were placed in a four-necked flask equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen inlet tube, and reacted at 100°C for 2 hours after sufficient stirring. Then, the mixture was cooled to 50°C, 59.3 parts by mass of 2,2-dimethylolpropionic acid (DMPA), 122.8 parts by mass of methyl ethyl ketone (MEK) and 0.18 parts by mass of dibutyltin dilaurate were added and reacted at 75°C for 15 hours. After the reaction, the mixture was cooled to 50°C or less, 204.6 parts by mass of MEK was added and stirred for 1 hour while cooling to 40°C or less to obtain a MEK solution of a polyurethane polymer (A-7). 94.4 parts by mass of a 25% by mass potassium hydroxide aqueous solution was added to the obtained MEK solution of the polyurethane polymer (A-7), and the mixture was stirred for 30 minutes to neutralize the acidic groups. Then, ion exchange water was slowly added under strong stirring, and after the polyurethane was emulsified, MEK was distilled by vacuum distillation to obtain a dispersion (II-7) of the polymer (A-7) having a non-volatile content of 40% by mass and an acid value of 50 mgKOH / g. The volume average particle size of the dispersed elements contained in the dispersion (II-7) was 15 nm.

[0144] [Synthesis example 8]

[0145] Except that the usage amount of H12MDI becomes 111.0 mass parts by 181.7 mass parts, the usage amount of DMPA becomes 23.2 mass parts by 59.3 mass parts and the usage amount of 25 mass % potassium hydroxide aqueous solution becomes 36.8 mass parts by 94.4 mass parts, by the method same as Synthesis Example 7, obtain the dispersion (II-8) of the polymer (A-8) with non-volatile content of 40 mass %, acid number of 25mgKOH / g. The volume average particle diameter of the dispersed elements contained in the dispersion (II-8) is 5nm.

[0146] [Example 1]

[0147] 500 parts by mass of JONCRYL PDX-6137A (manufactured by BASF SE, a styrene acrylic resin aqueous solution having a weight average molecular weight of 16,000, an acid value of 220 to 250, a glass transition point of 100° C., a pH of 7.8, and a nonvolatile content of about 29% by mass) as a pigment dispersion resin and 5000 parts by mass of a magenta pigment (FASTOGEN Super Magenta RY manufactured by DIC Corporation) were placed in a planetary mixer having a capacity of 50 L (manufactured by INOUE MFG., INC.), and the jacket was heated.

[0148] After the temperature of the contents in the planetary mixer reached 60° C., the contents were stirred and mixed under the conditions of a rotation speed of 80 rpm and a revolution speed of 25 rpm.

[0149] 5 minutes after the start of stirring, 3700 parts by mass of triethylene glycol were added.

[0150] Thereafter, a kneaded product was obtained by continuing mixing until 120 minutes had passed, wherein the timing was started when the current value of the planetary mixer showed a maximum current value.

[0151] Next, 10,000 parts by mass of ion-exchanged water were added to the kneaded product at 60° C. over 2 hours to obtain a liquid mixture. The mass ratio of the styrene acrylic resin to the magenta pigment contained in the liquid mixture was 0.29.

[0152] Next, ion exchange water and triethylene glycol were added to the liquid mixture to obtain a magenta aqueous pigment dispersion having a magenta pigment concentration of 14.5% by mass and a triethylene glycol concentration of 100% by mass relative to the magenta pigment.

[0153] Then, 5.6 parts by mass of 2-pyrrolidone (manufactured by BASF SE), 5.6 parts by mass of triethylene glycol monobutyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.), 2.1 parts by mass of purified glycerol (manufactured by Kao Corporation), 0.3 parts by mass of SURFYNOL 440 (nonionic surfactant, manufactured by Evonik Japan) and ion exchanged water were placed in a plastic container and stirred for 1 hour. Then, 1.7 parts by mass of dispersion (II-1) were added to the solution. The solution was further added to another plastic container with 14.5 parts by mass of a magenta aqueous pigment dispersion and stirred for 1 hour.

[0154] The pH of the mixture was then adjusted to within the range of 9 to 9.8 using a 5 mass % potassium hydroxide aqueous solution and filtered through a filter having a pore size of 5 to 10 μm to obtain a total of 70 parts by mass of aqueous ink M1 (3 mass % magenta pigment concentration).

[0155] [Example 2]

[0156] Aqueous ink M2 was obtained by the same method as in Example 1, except that dispersion (II-2) was used instead of dispersion (II-1).

[0157] [Example 3]

[0158] Aqueous ink M3 was obtained by the same method as in Example 1, except that dispersion (II-3) was used instead of dispersion (II-1).

[0159] [Example 4]

[0160] Aqueous ink M4 was obtained by the same method as in Example 1, except that dispersion (II-4) was used instead of dispersion (II-1).

[0161] [Comparative Example 1]

[0162] Aqueous ink M11 was obtained by the same method as in Example 1, except that dispersion (II-5) was used instead of dispersion (II-1).

[0163] [Comparative Example 2]

[0164] Aqueous ink M12 was obtained by the same method as in Example 1, except that dispersion (II-6) was used instead of dispersion (II-1).

[0165] [Comparative Example 3]

[0166] Aqueous ink M13 was obtained by the same method as in Example 1, except that HYDRAN WLS-210 manufactured by DIC Corporation was used instead of dispersion (II-1).

[0167] [Comparative Example 4]

[0168] Aqueous ink M14 was obtained by the same method as in Example 1, except that dispersion (II-7) was used instead of dispersion (II-1).

[0169] [Comparative Example 5]

[0170] Aqueous ink M15 was obtained by the same method as in Example 1, except that dispersion (II-8) was used instead of dispersion (II-1).

[0171] [Comparative Example 6]

[0172] Aqueous ink M16 was obtained by the same method as in Example 1, except that ion-exchanged water was used instead of dispersion (II-1).

[0173] [Table 2]

[0174] Example 1 Example 2 Example 3 Example 4 Ink M1 M2 M3 M4 Polymer (A) A-1 A-2 A-3 A-4 Polymer (B) B-1 B-2 B-3 B-4 Dispersion II-1 II-2 II-3 II-4

[0175] [Table 3]

[0176]

[0177] <Abrasion resistance>

[0178] The inks obtained in Examples and Comparative Examples were applied to brochure & leaflet paper (double-sided glossy paper) manufactured by HP using a No. 3 wire bar coater, and dried in an environment at 25° C. for 60 seconds to obtain printed paper.

[0179] Next, the printed paper was placed and attached to the friction area of ​​an abrasion tester (RT-300S manufactured by Daiei KagakuSeiki MFG. Co., Ltd.) via a plastic tape, and the surface of the printed paper was rubbed back and forth with a friction pin covered with another brochure & leaflet paper under a load of 200 g.

[0180] Next, the rubbed surface of the printed paper is scanned and converted into image data, and the number of pixels in the color residual part is calculated. The entire area of ​​the reference image is counted as 100 pixels, and it is determined that the more pixels there are in the color residual part, the better the wear resistance.

[0181] A: The number of pixels of the residual color portion is greater than 60.

[0182] B: The number of pixels of the residual color portion is 40 or more and 60 or less.

[0183] C: The number of pixels of the residual color portion is 20 or more and 40 or less.

[0184] D: The number of pixels of the residual color portion is less than 20.

[0185] <Stability of inkjet capability>

[0186] The ink obtained in Comparative Example 6 was filled in an ink cartridge. Next, the ink was printed on an OHP sheet for inkjet (a sheet having a layer for absorbing ink on the film surface) at a printing concentration of 100% using a commercially available thermal inkjet printer to obtain a printed product. After the printed product was left to dry in an environment at 25° C. for 1 hour, the maximum absorbance (Abs0) of the printed product was measured using an ultraviolet and visible spectrophotometer (JASCO Corporation V-660 model), using the unprinted portion of the OHP sheet as a reference.

[0187] Next, the inks obtained in the examples and comparative examples 1 to 5 were filled into ink cartridges.

[0188] Then, the ink was printed on an OHP sheet for inkjet at a printing concentration of 100% using a commercially available thermal-inkjet printer to obtain printed products. After the printed products were left to dry in an environment at 25° C. for 1 hour, the maximum absorbance (Abs1) of the printed products was measured using an ultraviolet and visible spectrophotometer (JASCO Corporation V-660 model), using the unprinted portion of the OHP sheet as a reference.

[0189] The ejection performance of the ink was evaluated according to the following criteria based on the value obtained from the formula [maximum absorbance (Abs1) / maximum absorbance (Abs0)]×100.

[0190] A: The value of the above formula is 70 or more.

[0191] B: The value of the above formula is 60 or more and less than 70.

[0192] C: The value of the above formula is 50 or more and less than 60.

[0193] D: The value of the above formula is less than 50.

[0194] <Optical Density on Plain Paper>

[0195] The ink obtained in Comparative Example 6 was applied to commercially available plain paper using a No. 3 wire bar coater, dried at 25°C for 1 hour, and then the optical density (OD0) of the printed area as a reference was measured using an integrating sphere spectrophotometer X-Rite (X-Rite, Inc.).

[0196] Next, the inks obtained in Examples and Comparative Examples 1 to 5 were applied to commercially available plain paper using a No. 3 wire bar coater and dried for 1 hour, and then the optical density (OD1) of the printed area was measured using an integrating sphere spectrophotometer X-Rite.

[0197] The colorability of the printed matter was evaluated according to the following criteria based on the value obtained from the formula [optical density (OD1) / optical density (OD0)]×100.

[0198] A: The value of the above formula is 90 or more.

[0199] B: The value of the above formula is 85 or more and less than 90.

[0200] C: The value of the above formula is 80 or more and less than 85.

[0201] D: The value of the above formula is less than 80.

[0202] <Washability>

[0203] A 5 cm×5 cm square cotton cloth was immersed in the ink obtained in Examples and Comparative Examples and dried at 150° C. for 5 minutes to obtain a test sample. Then, the optical density (OD0) of the test sample was measured using an integrating sphere spectrophotometer X-Rite.

[0204] Next, based on JIS L0844:2011, the test sample was immersed in a washing liquid at 50°C for 30 minutes, and then the washing liquid and the test sample were stirred with a food mixer for 1 minute. The sample was washed with water and dried at room temperature. Then, the optical density (OD1) of the test sample was measured using an integrating sphere spectrophotometer X-Rite.

[0205] The washing fastness of the printed matter was evaluated according to the following criteria based on the value obtained from the formula [optical density (OD1) / optical density (OD0)]×100.

[0206] A: The value of the above formula is 70 or more.

[0207] B: The value of the above formula is 60 or more and less than 70.

[0208] C: The value of the above formula is 50 or more and less than 60.

[0209] D: The value of the above formula is less than 50.

[0210] [Table 4]

[0211] Example 1 Example 2 Example 3 Example 4 Abrasion resistance A A A B Stability of inkjet capability A A B A Optical density on plain paper A A B A Washability A A A B

[0212] [Table 5]

[0213] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Abrasion resistance C C A B C D Stability of inkjet capability C C D C C A Optical density on plain paper A A D C C A Washability C C A D D D

Claims

1. An ink comprising a dispersion (X) as a binder resin, wherein the dispersion (X) comprises a polymer (B) dispersed in water (C) via a polymer (A), the polymer (B) comprising 50% by mass or more of a structural unit represented by the following general formula (2), the polymer (A) comprising a carboxyl group or a functional group in which the carboxyl group is neutralized by a basic compound, and a structural unit represented by the following general formula (1), In the general formula (1), M represents a hydrogen atom or an alkali metal, R in the general formula (2) 1 represents a hydrogen atom or a methyl group. 2 . The ink according to claim 1 , further comprising a pigment and a pigment dispersing resin.

3. The ink according to claim 1 or 2, wherein The polymer (A) is a polymer of a monomer mixture containing a monomer having a carboxyl group or an anhydride thereof and an alkali metal salt of styrenesulfonic acid.

4. The ink according to claim 1 or 2, wherein The polymer (A) has a weight average molecular weight in the range of 1,000 to 20,000.

5. The ink according to claim 1 or 2, wherein The mass ratio of the polymer (A) to the polymer (B), that is, polymer (A) / polymer (B) is in the range of 1 / 100 to 30 / 100.

6. The ink according to claim 1 or 2, wherein The polymer (A) and the polymer (B) are contained in a total amount within a range of 0.1% by mass to 30% by mass based on the total amount of the ink.

7. The ink according to claim 1 or 2, wherein The dispersion of the polymer (B) in water (C) having a volume average particle size of 20 nm to 1000 nm.

8. The ink according to claim 1 or 2, further comprising a pigment and a pigment dispersing resin for dispersing the pigment in the water (C).

9. The ink according to claim 1 or 2, for printing in an inkjet printing process.

10. The ink according to claim 9, wherein The inkjet printing method is a thermal inkjet printing method.

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