Pigment composition and ink using same

Abstract

The present invention addresses the problem of providing a pigment composition and an ink (and, in particular, an aqueous ink) that have excellent coloring power and glossiness in printed matter and can suppress the thickening that occurs over time when an azo lake pigment is used as a pigment.　This pigment composition includes a bivalent metal lake azo pigment and 0.1–20 weight% of a bivalent metal salt of a mono- or dicarboxylic acid compound. The bivalent metal of the bivalent metal salt is preferably an alkali earth metal ion. The mono- or dicarboxylic acid compound is preferably a C4–20 mono- or dicarboxylic acid compound.

Description

[Technical field]

[0001] The present invention relates to a pigment composition and an ink (particularly a water-based ink) using the same. [Background technology]

[0002] Pigment compositions containing pigments such as azo pigments have long been used mainly for coloring inks, paints, toners, rubber and plastics, dope coloring of synthetic fibers, pigment printing, and coloring miscellaneous goods. Among them, the printing application of inks and the like is important. Printing is performed by making a printing plate, applying printing ink to the surface of the plate, and transferring it to paper, film, cloth, etc. There are lithographic, intaglio, relief, and screen printing plates, and there are printing methods such as offset printing, gravure printing, and flexographic printing depending on the shape of the plate. Among them, flexographic printing is a letterpress printing method that uses a plate made of elastic materials such as rubber and resin, and because the plate has elasticity, it has the characteristic of being able to flexibly handle paper with poor smoothness such as thick paper and cardboard, plastic film, cloth, etc. In addition, flexographic printing has been attracting attention in recent years because it is possible to print at high speed and can use environmentally friendly water-based ink.

[0003] Flexographic inks used in flexographic printing are required to have low viscosity and not increase in viscosity over time. Generally, carmine 6B pigment is used as a red pigment in water-based flexographic inks from the standpoint of hue and cost, but the ink increases in viscosity over time when such pigments are used alone. Therefore, improvements in viscosity stability are required. To date, surface treatments using resins or metal salts, lake formation using different metals, and the use of extender pigments and other additives have been considered for viscosity stabilization (see Patent Documents 1-5 below). However, there are cases where any of these methods are not effective enough in stabilizing viscosity. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 3-157457 [Patent Document 2] Japanese Patent Application Publication No. 5-43829 [Patent Document 3] Japanese Patent Application Publication No. 6-1851 [Patent Document 4] Japanese Patent Application Publication No. 6-1852 [Patent Document 5] JP 2004-67893 A DISCLOSURE OF THEINVENTION [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a pigment composition and an ink (particularly a water-based ink) that can suppress thickening over time when an azo lake pigment is used as a pigment and that has excellent coloring power and gloss in printed matter. [Means for solving the problem]

[0006] The present inventors conducted a detailed study on the mechanism of thickening that occurs in inks (especially water-based inks) that use azo lake pigments as pigments. As a result, they speculated that the thickening of inks that use azo lake pigments occurs because divalent lake metals such as calcium are gradually eluted in the ink system, forming unstable pigment particle surfaces that have lost the lake metal, which causes aggregation between pigment particles.

[0007] Therefore, the present inventors have conducted extensive research and found that by blending a divalent metal salt such as a carboxylic acid compound with an azo lake pigment, it is possible to supply divalent metal ions to the ink system, prevent the elution of the lake metal from the pigment particle surface, and suppress the aggregation of pigment particles and the resulting thickening of the ink. It is presumed that the carboxylic acid compound, which corresponds to the anion portion of the divalent metal salt, coordinates with the pigment particle surface to suppress the aggregation of pigment particles, and suppresses the thickening of the ink in cooperation with the supplied divalent metal ion. In other words, the present inventors considered that both the structure of the anion portion (the number of carboxyl groups) and the type of the cation portion (the valence of the metal ion) are important for suppressing the thickening of the ink over time.

[0008] That is, the present invention is "Item 1. A pigment composition comprising a divalent metal lake azo pigment and 0.1 to 20% by weight of a divalent metal salt of a mono- or dicarboxylic acid compound. Item 2. The pigment composition according to Item 1, wherein the divalent metal of the divalent metal salt is an alkaline earth metal ion. Item 3. The pigment composition according to item 1 or 2, wherein the mono- or dicarboxylic acid compound is a mono- or dicarboxylic acid compound having 4 to 20 carbon atoms. Item 4. The pigment composition according to any one of Items 1 to 3, wherein the mono- or dicarboxylic acid compound is at least one selected from the group consisting of tartaric acid, hexanoic acid, sorbic acid, octanoic acid, stearic acid, and dodecanedioic acid. Item 5. The pigment composition according to any one of Items 1 to 4, wherein the divalent metal lake azo pigment is CI Pigment Red 57:1 or 57:3. Item 6. An ink comprising the pigment composition according to any one of items 1 to 5. Item 7. A water-based ink obtained by mixing the pigment composition according to any one of items 1 to 5 with a water-based resin. Effect of the Invention

[0009] The pigment composition of the present invention can suppress thickening over time and has excellent coloring power and gloss in printed matter, and is therefore suitable for inks (particularly water-based inks). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present invention will be described in detail below.

[0011] [Pigment composition] The pigment composition of the present invention contains a divalent metal lake azo pigment and 0.1 to 20% by weight of a divalent metal salt of a mono- or dicarboxylic acid compound. Hereinafter, the divalent metal salt of the mono- or dicarboxylic acid compound may be simply referred to as an "additive."

[0012] (Divalent metal lake azo pigment) The divalent metal lake azo pigment is an azo pigment having an azo group (-N=N-) in the molecule laked with at least one divalent metal such as calcium, barium, strontium, manganese, etc. Examples of the divalent metal lake azo pigment include CI Pigment Red 57:1, 57:3, 48:1, 48:2, 48:3, 48:4, 49:1, 49:2, 49:3, 52:1, 53:1, 60:1, 64:1, 51, 58:2, 50:1, 63:1, 63:2, 63:3, 54, CI Pigment Orange 17, 18, and 19. Among them, CI Pigment Red 57:1 or 57:3 is preferred as the divalent metal lake azo pigment. The divalent metal lake azo pigments may be used alone or in combination of two or more.

[0013] The primary particle size of the divalent metal lake azo pigment is, for example, 0.01 to 1.0 μm, and preferably 0.1 to 0.6 μm. The specific surface area of ​​the divalent metal lake azo pigment is, for example, 10 to 150 m 2 / g, preferably 20 to 100m 2 When the primary particle size and the specific surface area are within the above ranges, the coloring power and dispersibility are excellent.

[0014] (Additives) Examples of the monocarboxylic acid compound in the additive include saturated fatty acids such as propanoic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, and heptadecanoic acid, unsaturated fatty acids such as sorbic acid, oleic acid, linoleic acid, linolenic acid, and arachidonic acid, and aromatic carboxylic acids such as benzoic acid and salicylic acid. Examples of the dicarboxylic acid compound include saturated fatty acids such as ethanedioic acid, propanedioic acid, butanedioic acid, pentanedioic acid, hexanedioic acid, and dodecanedioic acid, unsaturated fatty acids such as fumaric acid and maleic acid, hydroxy acids such as tartaric acid and malic acid, and aromatic carboxylic acids such as phthalic acid, isophthalic acid, and terephthalic acid. These mono- or dicarboxylic acid compounds preferably have 4 to 20 carbon atoms. Particularly preferred examples of these mono- or dicarboxylic acid compounds are tartaric acid, hexanoic acid, sorbic acid, octanoic acid, stearic acid, and dodecanedioic acid.

[0015] Examples of the divalent metal salt in the additive include calcium, magnesium, barium, strontium, manganese, zinc, cobalt, chromium, iron, and copper. Among them, the divalent metal salt is particularly preferably an alkaline earth metal (ion) such as calcium, barium, or strontium.

[0016] Therefore, the above-mentioned additives are particularly preferably calcium tartrate, strontium tartrate, barium tartrate, calcium hexanoate, calcium sorbate, calcium stearate, and calcium dodecanedioate. The above-mentioned additives may be used alone or in combination of two or more.

[0017] The content of the additive is 0.1 to 20% by weight, preferably 0.2 to 15% by weight, and more preferably 0.3 to 10% by weight, based on 100% by weight of the pigment composition. The content of the additive is, for example, 0.05 to 20 parts by weight, preferably 0.1 to 18 parts by weight, and more preferably 0.3 to 15 parts by weight, based on 100 parts by weight of the divalent metal lake azo pigment. The greater the amount of the additive, the greater the thickening suppression effect, but if the amount is too large, it leads to a decrease in the coloring power and gloss of the ink. Therefore, it is preferable to set the amount within the above range from the viewpoint of the balance between the thickening suppression effect and the coloring power and gloss.

[0018] The pigment composition of the present invention may contain an organic pigment (dye) other than the above-mentioned divalent metal lake azo pigment, which is generally used as a colorant in applications such as inks. Examples of such organic pigments (dyes) include insoluble azo, condensed azo, quinophthalone, isoindolinone, isoindoline, azomethine, anthraquinone, xanthene, diketopyrrolopyrrole, perylene, perinone, quinacridone, indigoid, dioxazine, and phthalocyanine. Since the pigment composition of the present invention contains a divalent metal lake azo pigment, it is preferable to contain a yellow or red organic pigment (dye) for color matching.

[0019] The pigment composition of the present invention may contain components other than the divalent metal lake azo pigment, additives, and organic pigments (dyes) other than the divalent metal lake azo pigment (hereinafter, these may be referred to as "other components") within the scope of not impairing the effects of the present invention. Examples of the other components include pigment derivatives, inorganic pigments, dispersants (surfactants), rosin, etc.

[0020] Examples of the pigment derivatives include sulfonic acid pigment derivatives, amino group-containing pigment derivatives, and phthalimidomethyl group-containing pigment derivatives. Examples of the inorganic pigments include calcium carbonate, magnesium carbonate, precipitated barium sulfate, kaolin, clay, alumina white, and white carbon. Examples of the dispersants (surfactants) include anionic compounds, cationic compounds, nonionic compounds, and polymer compounds.

[0021] When other components are contained, the content thereof is, for example, 0.1 to 10% by weight, preferably 0.2 to 5% by weight, based on 100% by weight of the pigment composition. Therefore, when other components are contained, the total content of the divalent metal lake azo pigment and additives in the pigment composition of the present invention is, for example, 90 to 99.9% by weight, preferably 95 to 99.8% by weight, based on 100% by weight of the pigment composition.

[0022] [Method of producing pigment composition] An example of a method for producing the pigment composition of the present invention is shown below. The pigment composition of the present invention can be obtained, for example, through 1) synthesis of a divalent metal lake azo pigment and 2) addition of a divalent metal salt of a mono- or dicarboxylic acid compound.

[0023] First, in 1), an azo pigment can be synthesized by coupling a diazo component made of an aromatic amine diazonium salt with a coupler component made of an aromatic compound other than the aromatic amine constituting the diazonium salt. The aromatic amine diazonium salt, which is the diazo component, can be obtained by acidifying an aromatic amine with hydrochloric acid and adding an aqueous solution of sodium nitrite. The coupling between the diazo component and the coupler component is carried out under alkaline conditions using sodium hydroxide or the like. The soluble azo (dye) obtained after coupling is insolubilized by adding an aqueous solution of a divalent metal salt such as calcium, barium, or strontium to obtain a divalent metal lake azo pigment. If necessary, the pigment obtained may be filtered, washed, or the like. In 1) the synthesis of a divalent metal lake azo pigment, a commercially available divalent metal lake azo pigment may be used as it is, rather than synthesizing it by a coupling reaction as described above.

[0024] Next, in 2), a divalent metal salt of a mono- or dicarboxylic acid compound is added to the divalent metal lake azo pigment obtained in 1). The amount of this additive is 0.1 to 20% by weight, preferably 0.2 to 15% by weight, and more preferably 0.3 to 10% by weight, based on 100% by weight of the pigment composition. Stirring may be performed during addition to ensure uniformity.

[0025] The pigment composition obtained through the above 1) and 2) may be subjected to general pigmentation treatments such as particle size adjustment, pH adjustment, filtration, alcohol washing, water washing, drying, and pulverization, as necessary. The particle size may be adjusted by heating, stirring, and aging the azo pigment in water and / or an organic solvent under normal pressure or pressure, or by a known method such as an acid paste method, an acid slurry method, a dry milling method, a solvent method, or a solvent milling method. In addition, the pigment particle surface may be treated with a pigment derivative such as a sulfonic acid pigment derivative, an amino group-containing pigment derivative, or a phthalimidomethyl group-containing pigment derivative, a polymer such as a dispersant, a surfactant, rosin, or the like.

[0026] [Ink] The ink of the present invention contains the pigment composition of the present invention. The ink of the present invention can be used for various applications such as offset printing, gravure printing, flexographic printing, screen printing, and printing by the inkjet method. That is, the ink of the present invention can be used as, for example, an offset ink, a gravure ink, a flexographic ink, a screen ink, or an inkjet ink. The ink of the present invention contains components suitable for each ink in addition to the pigment composition of the present invention, as described below.

[0027] Offset ink refers to ink used in various printing methods that combine lithographic printing (lithographic printing that uses dampening water and waterless lithographic printing that does not use dampening water), letterpress printing, intaglio printing, and stencil printing, as well as the transfer (offset) method, in which the ink on a plate is transferred to an intermediate transfer material such as a blanket and then printed on the target material.

[0028] Lithographic offset ink contains, in addition to the azo pigment of the present invention, components such as resin varnish, organic solvent, oils and fats such as animal and vegetable oils, and auxiliaries (drying inhibitors, driers, abrasion resistance improvers, etc.). Lithographic offset ink is produced by appropriately mixing these components and grinding and dispersing them using a roll mill or the like. Inks that can be used in lithographic offset printing methods usually have a relatively high viscosity of 5 to 100 Pa s.

[0029] Examples of the resin used in the resin varnish include rosin-modified phenolic resin, petroleum resin, petroleum resin-modified rosin-modified phenolic resin, alkyd resin, rosin ester, vegetable oil-modified rosin-modified phenolic resin, vegetable oil-modified rosin ester, polyester, and acrylic resin. Examples of the organic solvent include typical solvents used in inks, such as hydrocarbons, alcohols, esters, and ketones.

[0030] Liquid inks used as gravure inks and flexographic inks are roughly divided into organic solvent-based liquid inks, which contain an organic solvent as the main solvent, and water-based liquid inks, which contain water as the main solvent. The ink of the present invention can be applied to both organic solvent-based liquid inks and water-based liquid inks.

[0031] The liquid ink contains, in addition to the pigment composition of the present invention, for example, a binder resin, a solvent, and a dispersant. When the main component of the solvent is an organic solvent, the liquid ink is an organic solvent-based liquid ink, and when the main component of the solvent is a water-miscible organic solvent or an aqueous solvent such as water, the liquid ink is an aqueous liquid ink.

[0032] Liquid ink is obtained by dispersing a mixture of pigment and binder resin in a disperser to obtain a pigment dispersion, then adding resin, solvent, and additives such as leveling agents as necessary to the obtained pigment dispersion, and stirring and mixing. The ink viscosity of liquid ink is preferably in the range of 10 mPa·s or more to prevent pigment sedimentation and to disperse the pigment appropriately, and 1000 mPa·s or less to ensure workability during ink production and printing.

[0033] The binder resin is not particularly limited, and examples of the binder resin that can be used in general liquid inks include polyurethane resins, acrylic resins, vinyl chloride-vinyl acetate copolymer resins, vinyl chloride-acrylic copolymer resins, chlorinated polyolefin resins, modified polyolefin resins, cellulose, cellulose derivatives, polyamide resins, ethylene-vinyl acetate copolymer resins, vinyl acetate resins, styrene resins, dammar resins, styrene-maleic acid copolymer resins, polyester resins, alkyd resins, polyvinyl chloride resins, rosin resins, rosin-modified maleic acid resins, terpene resins, phenol-modified terpene resins, ketone resins, cyclized rubber, chlorinated rubber, butyral, polyacetal resins, petroleum resins, and modified resins thereof.

[0034] Examples of the organic solvent include aromatic hydrocarbon organic solvents such as toluene, xylene, Solvesso #100, and Solvesso #150; aliphatic hydrocarbon organic solvents such as hexane, methylcyclohexane, heptane, octane, and decane; and esters such as methyl acetate, ethyl acetate, isopropyl acetate, normal propyl acetate, butyl acetate, amyl acetate, ethyl formate, and butyl propionate. Examples of the water-miscible organic solvent include alcohols such as methanol, ethanol, propanol, butanol, and isopropyl alcohol; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; and glycol ethers such as ethylene glycol (mono, di)methyl ether, ethylene glycol (mono, di)ethyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, monobutyl ether, diethylene glycol (mono, di)methyl ether, diethylene glycol (mono, di)ethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, triethylene glycol (mono, di)methyl ether, propylene glycol (mono, di)methyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, and dipropylene glycol (mono, di)methyl ether.

[0035] The ink of the present invention uses the pigment composition of the present invention, but may also use organic pigments or inorganic pigments that are used in general inks as colorants in combination therewith, within the scope that does not affect the effects of the present invention.

[0036] Examples of the organic pigments include phthalocyanine pigments, halogenated phthalocyanine pigments, anthraquinone pigments, anthranthrone pigments, dianthraquinonyl pigments, anthrapyrimidine pigments, perylene pigments, perinone pigments, quinacridone pigments, thioindigo pigments, dioxazine pigments, isoindolinone pigments, quinophthalone pigments, insoluble azo pigments, condensed azo pigments, azomethine pigments, flavanthrone pigments, diketopyrrolopyrrole pigments, isoindoline pigments, indanthrone pigments, carbon black pigments, etc. Examples of the inorganic pigments include white pigments such as titanium oxide, zinc oxide, zinc sulfide, barium sulfate, calcium carbonate, chromium oxide, silica, lithopone, antimony white, and gypsum.

[0037] Examples of inorganic pigments other than the white pigment include aluminum particles, mica, bronze powder, chrome vermilion, yellow lead, cadmium yellow, cadmium red, ultramarine, Prussian blue, iron oxide red, yellow iron oxide, iron black, and zircon.

[0038] The ink of the present invention may further contain various additives, such as wax, a chelating crosslinking agent, an extender pigment, a leveling agent, an antifoaming agent, a plasticizer, an infrared absorbing agent, an ultraviolet absorbing agent, an aromatic agent, and a flame retardant, if necessary.

[0039] When the ink of the present invention is an inkjet ink, in addition to the pigment composition of the present invention, the ink may contain the above organic pigments and inorganic pigments, dyes (anionic azo, phthalocyanine, azo-based metal complex salts, etc.), resins (acrylic block copolymers, thermoplastic resins such as acrylic, maleic acid, rosin, epoxy, silicone, butyral, etc.), solvents (water, ketone, alcohol, ethyl acetate, etc.), penetrants (alcohol, glycol ether, etc.), drying inhibitors (glycerin, glycol, etc.), pH adjusters (alcoholamine, NaOH, etc.), surfactants (nonionic, cationic, anionic, etc.), conductive agents, plasticizers, antioxidants, ultraviolet absorbers, preservatives, antifungal agents, etc. The inkjet ink may be a water-based ink or an oil-based ink. The inkjet ink may be either a piezo type or a thermal type.

[0040] [Water-based ink] The water-based ink of the present invention is a preferred embodiment of the ink of the present invention, and contains a mixture of the pigment composition of the present invention and a water-based resin. The water-based ink of the present invention can be used for various applications such as printing, as with the ink of the present invention, but is particularly suitable for flexographic printing. In other words, it is particularly preferred that the water-based ink is a water-based flexographic ink. Since the water-based ink of the present invention contains the pigment composition of the present invention, it is possible to suppress thickening over time, and the printed matter is excellent in coloring power and gloss.

[0041] Generally, water-based inks contain a colorant such as the pigment composition of the present invention, a water-based resin for constituting a vehicle (water-based varnish), an auxiliary, a solvent, etc. Important roles of the vehicle include dispersing the colorant, imparting printability and coating film properties to the printed matter, etc., but ultimately, the vehicle's role is to transfer and fix the ink, which is a coloring material, to the printed material.

[0042] The aqueous resin may be any resin generally used for printing purposes, such as water-soluble acrylic resin, styrene-acrylic resin, styrene-maleic acid-acrylic acid resin, styrene-maleic acid resin, etc. The acrylic resin is, for example, a resin containing an acid component such as acrylic acid or methacrylic acid, an acrylic acid ester, a methacrylic acid ester, or a copolymer thereof. The styrene-acrylic resin is, for example, a resin containing an acid component such as styrene and acrylic acid or methacrylic acid, a resin containing styrene and an acrylic acid ester or a methacrylic acid ester, or a copolymer thereof. The styrene-maleic acid-acrylic acid resin is, for example, a resin containing an acid component such as styrene, maleic acid, acrylic acid, or methacrylic acid, a resin containing styrene and maleic acid or a maleic acid half ester, an acrylic acid ester, or a methacrylic acid ester, or a copolymer thereof. The styrene-maleic acid is a resin containing styrene and maleic acid or a maleic acid half ester, or the like. The aqueous resin may be either an emulsion type resin or a colloidal dispersion type resin.

[0043] The above-mentioned water-based resin, alkali-soluble resin, water, etc. are heated to dissolve the resin in water, thereby forming a vehicle (water-based varnish). In the alkali-soluble resin, the functional group in the resin, a carboxyl group (-COOH group), is neutralized with an alkali component. Then, a colorant such as the pigment composition of the present invention is dissolved in the vehicle (water-based varnish), and the pigment is dispersed through grinding and adjustment, and an auxiliary such as a defoamer, a pigment dispersant, and a surfactant, and a solvent such as water, a lower alcohol, or a glycol-based solvent are added to form a water-based ink. If necessary, a water-solubilizing agent such as ammonia water or an organic amine, an auxiliary such as an alcohol, an emulsifier, etc. may be added. EXAMPLES

[0044] The present invention will be described in more detail below with reference to examples and comparative examples. In the following examples and comparative examples, "parts" and "%" represent "parts by weight" and "% by weight" unless otherwise specified.

[0045] Pigment composition 1-15 was produced by the method of Production Example 1-15 below, and was further used as the water-based ink of Example 1-15. Pigment composition 16-21 was produced by the method of Production Example 16-21 below, and was further used as the water-based ink of Comparative Example 1-6. The water-based inks thus obtained were evaluated for viscosity, coloring strength, and gloss by the following methods. The evaluation results of each water-based ink are shown in Table 1 below.

[0046] <Production Example 1: Pigment Composition 1> 50 parts of 4-aminotoluene-3-sulfonic acid and 2.6 parts of 2-aminonaphthalene-1-sulfonic acid were dispersed in 170 parts of water, and then 32 parts of 35% hydrochloric acid was added, and 49 parts of 40% aqueous sodium nitrite solution was added dropwise while maintaining the temperature below 5°C, to obtain a diazonium salt suspension. Next, 54 parts of 2-hydroxy-3-naphthoic acid were dispersed in 521 parts of water, and then 111 parts of 25% aqueous sodium hydroxide solution was added to dissolve the mixture, and the mixture was cooled to below 5°C. The above diazo liquid was added dropwise to this coupler solution while stirring, to cause a coupling reaction. After the reaction was completed, 116 parts of a 10% aqueous rosin soda solution was added, and the mixture was stirred for 20 minutes, and 113 parts of a 35% aqueous calcium chloride solution was added, and the mixture was stirred for 90 minutes. After stirring, 135 parts of a 23% aqueous solution of strontium chloride was added and stirred for 60 minutes, and the temperature was raised to 80°C and further stirred for 60 minutes to obtain a suspension of an azo pigment (CI Pigment Red 57:3) laked with Ca and Sr in water. This suspension was filtered, washed with water, dried overnight at 110°C, and then pulverized to obtain 137 parts of azo pigment powder. 0.14 parts (0.1% blending ratio) of calcium tartrate tetrahydrate was blended with the obtained azo pigment powder as an additive to obtain a red pigment composition 1.

[0047] <Production Example 2: Pigment Composition 2> Pigment composition 2 was obtained in the same manner as in Production Example 1, except that 0.14 parts of calcium tartrate tetrahydrate was changed to 0.41 parts of calcium tartrate tetrahydrate (0.3% blending ratio).

[0048] <Production Example 3: Pigment Composition 3> Pigment composition 3 was obtained in the same manner as in Production Example 1, except that 0.14 parts of calcium tartrate tetrahydrate was changed to 0.69 parts of calcium tartrate tetrahydrate (0.5% blending ratio).

[0049] <Production Example 4: Pigment Composition 4> Pigment composition 4 was obtained in the same manner as in Production Example 1, except that 0.14 parts of calcium tartrate tetrahydrate was changed to 1.37 parts of calcium tartrate tetrahydrate (blending ratio: 1.0%).

[0050] <Production Example 5: Pigment Composition 5> Pigment composition 5 was obtained by carrying out the same procedure as in Production Example 1, except that 0.14 parts of calcium tartrate tetrahydrate was changed to 2.74 parts of calcium tartrate tetrahydrate (blending ratio: 2.0%).

[0051] <Production Example 6: Pigment Composition 6> Pigment composition 6 was obtained by carrying out the same procedure as in Production Example 1, except that 0.14 parts of calcium tartrate tetrahydrate was changed to 4.11 parts of calcium tartrate tetrahydrate (blending ratio: 3.0%).

[0052] <Production Example 7: Pigment Composition 7> Pigment composition 7 was obtained by carrying out the same procedure as in Production Example 1, except that 0.14 parts of calcium tartrate tetrahydrate was changed to 13.71 parts of calcium tartrate tetrahydrate (blending ratio: 10.0%).

[0053] <Production Example 8: Pigment Composition 8> Pigment composition 8 was obtained by carrying out the same procedure as in Production Example 1, except that 0.14 parts of calcium tartrate tetrahydrate was changed to 27.43 parts of calcium tartrate tetrahydrate (blending ratio 20.0%).

[0054] <Production Example 9: Pigment Composition 9> Pigment composition 9 was obtained by carrying out the same procedure as in Production Example 1, except that 0.14 parts of calcium tartrate tetrahydrate was changed to 2.74 parts of strontium tartrate (blending ratio 2.0%).

[0055] <Production Example 10: Pigment Composition 10> Pigment composition 10 was obtained by carrying out the same procedure as in Production Example 1, except that 0.14 parts of calcium tartrate tetrahydrate was changed to 2.74 parts of barium tartrate (blending ratio 2.0%).

[0056] <Production Example 11: Pigment Composition 11> Pigment composition 11 was obtained by carrying out the same procedure as in Production Example 1, except that 0.14 parts of calcium tartrate tetrahydrate was changed to 2.74 parts of calcium hexanoate (blending ratio 2.0%).

[0057] <Production Example 12: Pigment Composition 12> Pigment composition 12 was obtained by carrying out the same procedure as in Production Example 1, except that 0.14 parts of calcium tartrate tetrahydrate was changed to 2.74 parts of calcium sorbate (blending ratio 2.0%).

[0058] <Production Example 13: Pigment Composition 13> Pigment composition 13 was obtained by carrying out the same procedure as in Production Example 1, except that 0.14 parts of calcium tartrate tetrahydrate was changed to 2.74 parts of calcium octanoate (blending ratio 2.0%).

[0059] <Production Example 14: Pigment Composition 14> Pigment composition 14 was obtained by carrying out the same procedure as in Production Example 1, except that 0.14 parts of calcium tartrate tetrahydrate was changed to 2.74 parts of calcium stearate (blending ratio 2.0%).

[0060] <Production Example 15: Pigment Composition 15> Pigment composition 15 was obtained by carrying out the same procedure as in Production Example 1, except that 0.14 parts of calcium tartrate tetrahydrate was changed to 2.74 parts of calcium dodecanedioate (blending ratio: 2.0%).

[0061] <Example 1-15: Water-based ink> 34.75 parts of the pigment composition 1-15 obtained above, 56.00 parts of water-based varnish, 0.46 parts of an activator, and 150 parts of glass beads (diameter 2 mm) were placed in a glass container and dispersed for 60 minutes with a disperser to obtain water-based inks. These were named Examples 1-15, respectively.

[0062] <Production Example 16: Pigment Composition 16> Pigment composition 16 was prepared by the same procedure as in Production Example 1 except that 0.14 parts of calcium tartrate tetrahydrate was not added.

[0063] <Production Example 17: Pigment Composition 17> Pigment composition 17 was obtained by carrying out the same procedure as in Production Example 1, except that 0.14 parts of calcium tartrate tetrahydrate was changed to 2.74 parts of tartaric acid (blending ratio 2.0%).

[0064] <Production Example 18: Pigment Composition 18> Pigment composition 18 was obtained by carrying out the same procedure as in Production Example 1, except that 0.14 parts of calcium tartrate tetrahydrate was changed to 41.14 parts of calcium tartrate tetrahydrate (blending ratio 30.0%).

[0065] <Production Example 19: Pigment Composition 19> Pigment composition 19 was obtained by carrying out the same procedure as in Production Example 1, except that 0.14 parts of calcium tartrate tetrahydrate was changed to 2.74 parts of sodium tartrate dihydrate (blending ratio: 2.0%).

[0066] <Production Example 20: Pigment Composition 20> Pigment composition 20 was obtained by carrying out the same procedure as in Production Example 1, except that 0.14 parts of calcium tartrate tetrahydrate was changed to 2.74 parts of potassium tartrate pentahydrate (blending ratio 2.0%).

[0067] <Production Example 21: Pigment Composition 21> Pigment composition 21 was obtained by carrying out the same procedure as in Production Example 1, except that 0.14 parts of calcium tartrate tetrahydrate was changed to 2.74 parts of calcium citrate tetrahydrate (blending ratio: 2.0%).

[0068] <Comparative Example 1-6: Water-based ink> 34.75 parts of the pigment composition 16-21 obtained above, 56.00 parts of water-based varnish, 0.46 parts of an activator, and 150 parts of glass beads (diameter 2 mm) were placed in a glass container and dispersed for 60 minutes with a disperser to obtain water-based inks. These were designated as Comparative Examples 1-6.

[0069] <Evaluation: Viscosity test> Immediately after preparation, 30 parts of the aqueous ink was weighed out and cooled to 20°C, after which the viscosity was measured using a B-type viscometer, and this was taken as the initial viscosity. Next, this aqueous ink was stored at 50°C for 7 days, after which the viscosity was similarly measured, and this was taken as the viscosity over time. For both the initial viscosity and the viscosity over time, a relative value was recorded when the initial viscosity of Comparative Example 1, which serves as a reference, was taken as 100%. <Evaluation: Tinting strength> Two parts of the aqueous ink immediately after preparation and 24 parts of the titanium oxide pigment ink were mixed to obtain a light-colored ink. The light-colored ink obtained was spread on a test paper, and the coloring strength of the spread was measured using Datacolor 650 manufactured by Datacolor. The coloring strength is expressed as a relative value when the coloring strength of the reference Comparative Example 1 is set to 100%. <Evaluation: Gloss value> 10 parts of the aqueous ink immediately after preparation and 22.5 parts of the aqueous varnish for dilution were mixed to obtain a diluted ink. The diluted ink obtained was spread on a test film, and the gloss value of the spread was measured using MULTI GLOSS 268Plus manufactured by Konica Minolta. The gloss value is expressed as a relative value when the gloss value of the reference Comparative Example 1 is set to 100%.

[0070] [Table 1] *Water of hydration for additives is omitted.

[0071] As shown in Table 1 above, in Examples 1-15, by blending specific amounts of additives, it is possible to suppress the increase in viscosity over time while maintaining coloring power and gloss.

[0072] The details of what can be seen from the results of this example are as follows. In the case of using a carboxylic acid compound without a metal ion in the counter as an additive as in Comparative Example 2, the effect of suppressing thickening was weak and the gloss of the ink was reduced. This is believed to be the result of the pH of the ink increasing due to the addition of an unneutralized carboxylic acid compound, which adversely affected dispersion. As can be seen from Comparative Examples 4 and 5, when the cation part of the additive was a monovalent metal ion such as sodium, thickening was rather caused. From this result, it can be said that divalent metal ions are necessary to suppress aggregation. In addition, as can be seen from Comparative Example 6, thickening was also caused when a carboxylic acid compound having three carboxy groups was selected as the anion part. This is thought to be because the three carboxy groups formed complex aggregates having a crosslinked structure with the metal ion, pigment particles, and resin in the ink system, and it can be assumed that the same phenomenon occurs when the carboxy groups are four or more. Therefore, it can be said that an additive having two or less carboxy groups is desirable as the anion part. Furthermore, as can be seen from Comparative Example 3, the thickening suppression effect of the additive in the present invention is greater as the amount of the additive is larger, but if the amount of the additive is too large, it leads to a decrease in the coloring power and gloss of the ink. Therefore, it can be said that an effective blending ratio of the additive is 0.1 to 20.0% by weight (a more effective range is 0.3 to 10.0% by weight).

Claims

1. A pigment composition comprising a divalent metal lake azo pigment and 0.1 to 20% by weight of a divalent metal salt of a mono- or dicarboxylic acid compound, The pigment composition, wherein the divalent metal salt of the mono- or dicarboxylic acid compound is selected from the group consisting of calcium tartrate, strontium tartrate, barium tartrate, calcium hexanoate, and calcium sorbate.

2. A pigment composition as described in claim 1, wherein the divalent metal salt is calcium tartrate, strontium tartrate or barium tartrate.

3. The divalent metal lake azo pigment is C.I. Pigment Red 57: 1, 57: 3, 48: 1, 48: 2, 48: 3, 48: 4, 49: 1, 49: 2, 49: 3, 52: 1, 53: 1, 60: 1, 64: 1, 51, 58: 2, 50: 1, 63: 1, 63: 2, 63: 3, 54, C.I. Pigment Orange 17, 18, 19. The pigment composition according to claim 1 or 2, which is selected from the group consisting of.

4. The pigment composition according to claim 3, wherein the divalent metal lake azo pigment is C.I. Pigment Red 57:1 or 57:

3.

5. An ink comprising the pigment composition according to any one of claims 1 to 4.

6. 5. A water-based ink comprising the pigment composition according to claim 1 and a water-based resin.

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