Ink, inkjet recording method, and recording medium.

Abstract

To provide an ink composition that offers excellent handling properties in dispersion slurry form, superior storage stability of the dispersion and ink, and enables the provision of printed materials with excellent print density. [Solution] An ink comprising carbon black and a lignin compound, satisfying at least one of the following conditions. Condition 1: The BET specific surface area of ​​the carbon black is 118 m². 2 It exceeds / g Condition 2: The primary particle size of the carbon black is less than 22 nm. Condition 3: The amount of oil absorbed by the carbon black exceeds 66cc / 100g.

Description

[Technical Field]

[0001] This invention relates to ink, an inkjet recording method, and a recording medium. [Background technology]

[0002] Inkjet printing, one of the most representative printing methods, works by generating tiny droplets of ink and depositing them onto a recording medium such as paper. In recent years, the demand for inkjet printing for industrial applications has also been increasing. In industrial inkjet printing using paper as the recording medium, recording media without an ink-receiving layer, such as plain paper, art paper, and coated paper, are typically used. Recording media without an ink-receiving layer can absorb less ink compared to recording media with an ink-receiving layer. For this reason, improving print density on recording media without an ink-receiving layer is difficult, and this poses a significant problem. Among the various colors, black is the most frequently used ink for printing documentary images, including text. Furthermore, high print density is required for these documentary images. Water-insoluble carbon black is commonly used as the colorant for black ink. Various methods are being tried to improve the print density of black ink. For example, the print density can be improved to some extent by increasing the carbon black content in the ink. However, increasing the carbon black content has a limited effect on improving print density and may negatively affect the inkjet ejection stability. Alternatively, print density can be improved by surface-modifying the carbon black to make it self-dispersible. However, when using this method, the self-dispersing carbon black disperses easily in water, reducing the water resistance of the printed material. Another method is to use carbon black with a small particle size. However, carbon black with a small particle size is bulky and difficult to handle when dispersed into a slurry. Dispersions and inks of carbon black with a small particle size tend to re-aggregate over time, making it difficult to ensure storage stability. To address the above issues, there is a need for inks that offer excellent handling during dispersion slurry formation, storage stability of the dispersion and ink, and superior print density. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2011-153189 [Patent Document 2] Japanese Patent Publication No. 2023-154903 [Patent Document 3] Japanese Patent Publication No. 2024-119166 [Overview of the project] [Problems that the invention aims to solve]

[0004] This invention has been made in view of the above circumstances, and aims to provide an ink that is excellent in handling when dispersed into a slurry, in storage stability of the dispersion and ink, and in print density. [Means for solving the problem]

[0005] The inventors of the present invention conducted extensive research to solve the above-mentioned problems and, as a result, discovered that an ink containing carbon black and a lignin compound, satisfying at least one of the following conditions, can solve the above-mentioned problems, thus completing the present invention. Condition 1: The BET specific surface area of ​​the carbon black is 118 m². 2 It exceeds / g Condition 2: The primary particle size of the carbon black is less than 22 nm. Condition 3: The amount of oil absorbed by the carbon black exceeds 66cc / 100g.

[0006] In other words, the present invention relates to the following 1) to 4). 1) An ink comprising carbon black and a lignin compound, satisfying at least one of the following conditions. Condition 1: The BET specific surface area of ​​the carbon black is 118 m². 2 It exceeds / g Condition 2: The primary particle size of the carbon black is less than 22 nm. Condition 3: The amount of oil absorbed by the carbon black exceeds 66cc / 100g. 2) The ink described in 1) above, which satisfies at least two of the above conditions 1 to 3. 3) The ink according to 1) or 2) above, wherein the lignin compound comprises a lignin sulfonate. 4) A recording medium to which the ink described in 1) or 2) above has adhered. [Effects of the Invention]

[0007] The present invention provides an ink that offers excellent handling properties during dispersion slurry formation, superior storage stability of the dispersion and ink, and excellent print density. [Modes for carrying out the invention]

[0008] In this specification, unless otherwise specified, "parts" and "%" in the examples and other descriptions shall all be expressed on a mass basis.

[0009] The present invention will be described in detail below. The above ink contains carbon black and a lignin compound and satisfies at least one of the following conditions. Condition 1: The BET specific surface area of ​​the carbon black is 118 m². 2 It exceeds / g Condition 2: The primary particle size of the carbon black is less than 22 nm. Condition 3: The amount of oil absorbed by the carbon black exceeds 66cc / 100g.

[0010] [Carbon Black] Specific examples of the above carbon black include, for example, PRINTEX L6, HIBLACK 600L, 890, COLOUR BLACK S170, SPECIAL BLACK 6 manufactured by Orion Engineered Carbons; MA600, #950, #2600, #2650B, etc. manufactured by Mitsubishi Chemical Corporation.

[0011] The BET specific surface area of the carbon black under the above condition 1 is preferably more than 118m 2 / g and 600m 2 / g or less, more preferably 150m 2 / g or more and 580m 2 / g or less, even more preferably 200m 2 / g or more and 560m 2 / g or less. The BET specific surface area of the above carbon black can be determined by adsorbing nitrogen on the surface of the carbon black.

[0012] The primary particle size of the carbon black under the above condition 2 is preferably 10 nm or more and 22 nm or less, more preferably 11 nm or more and 20 nm or less, and even more preferably 12 nm or more and 18 nm or less. The primary particle size of the above carbon black can be determined by the arithmetic mean diameter measured by an electron microscope.

[0013] The oil absorption of the carbon black under the above condition 3 is preferably 66cc / 100g or more and 165cc / 100g or less, more preferably 70cc / 100g or more and 160cc / 100g or less, and even more preferably 80cc / 100g or more and 155cc / 100g or less. The oil absorption of the above carbon black can be determined by adding paraffin oil or the like to a predetermined amount of carbon black, and measuring the drop amount of paraffin oil when the maximum viscosity is reached.

[0014] The ink of the present invention satisfies any one of the above conditions 1 to 3, but it is preferable that it satisfies any two of them, it is more preferable that it satisfies at least two of conditions 1 and 2, and it is most preferable that it satisfies all of conditions 1 to 3.

[0015] [Lignin compounds] The lignin compound mentioned above is not particularly limited as long as it has a lignin skeleton in its chemical structure, but examples include lignin and lignin derivatives. Examples of lignin derivatives include ligninsulfonic acid, ligninsulfonates, Kraft lignin, and soda lignin. All of these can be obtained from black liquor during pulp production, with ligninsulfonic acid obtained from the sulfurous acid process, Kraft lignin from the Kraft process, and soda lignin from the soda process. However, the methods for obtaining these lignins are not limited to these. Lignin derivatives are preferred as the lignin compound contained in the above ink, and ligninsulfonates are more preferred. Specific examples of the lignin sulfonates mentioned above include, for example, sodium lignin sulfonate, potassium lignin sulfonate, calcium lignin sulfonate, magnesium lignin sulfonate, and ammonium lignin sulfonate. Furthermore, the lignin sulfonates may be partially desulfonated. The sulfonation rate of the above lignin sulfonate is preferably 30% or more and less than 100%, more preferably 50% or more and less than 100%, and even more preferably 70% or more and less than 100%. The lignin sulfonate may be a preparation made by a known method, or a commercially available product may be used. Examples of commercially available lignin sulfonates include Sun Extract P321, P252, SCP, M-100, SCL, Vanirex N, NP, DP from Nippon Paper Industries; and Vanisperse CB, Ultrazine NA, Ufoxane 3A from Borregaard. The above lignin compounds may be used individually or in combination of two or more.

[0016] The above ink may also contain ink modifiers in addition to the above components. Examples of ink modifiers include polymer dispersants, water, organic solvents, waxes, resin emulsions, viscosity modifiers, surfactants, preservatives, fungicides, pH adjusters, chelating agents, rust inhibitors, water-soluble UV absorbers, antioxidants, and defoamers.

[0017] The above ink preferably contains one or more polymeric dispersants to disperse the colorant. In this specification, the polymeric dispersant may be abbreviated as "dispersant". Another aspect of the present invention involves using a self-dispersing colorant as a coloring agent to achieve dispersion without the use of a dispersant. The dispersant is not particularly limited, and known dispersants such as polymeric dispersants can be used. Examples of polymeric dispersants other than the binder and wax mentioned above include copolymers composed of at least two monomers selected from monomers such as styrene and its derivatives; vinylnaphthalene and its derivatives; aliphatic alcohol esters of α,β-ethylenically unsaturated carboxylic acids; (meth)acrylic acid and its derivatives; maleic acid and its derivatives; itaconic acid and its derivatives; fahric acid and its derivatives; vinyl acetate, vinyl alcohol, vinylpyrrolidone, acrylamide, and their derivatives (preferably at least one of which is a hydrophilic monomer). Examples of such copolymers include styrene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid-(meth)acrylic acid ester copolymer, (meth)acrylic acid ester-(meth)acrylic acid copolymer, polyethylene glycol (meth)acrylate-(meth)acrylic acid copolymer, and styrene-maleic acid copolymer. Among these, styrene-(meth)acrylic acid copolymers, styrene-(meth)acrylic acid-(meth)acrylic acid ester copolymers, and (meth)acrylic acid ester-(meth)acrylic acid copolymers are preferred, (meth)acrylic acid ester-(meth)acrylic acid copolymers are more preferred, and methacrylic acid ester-methacrylic acid copolymers are even more preferred. Examples of copolymer types include block copolymers, random copolymers, and graft copolymers. These copolymers may also be in the form of salts. From the viewpoint of ensuring the stability of the pigment dispersion and ink, block copolymers and graft copolymers are preferred, and block copolymers are more preferred.

[0018] Dispersants can be obtained commercially or synthesized.

[0019] Examples of commercially available dispersants include Joncyrl 62, 67, 68, 678, and 687 (styrene-acrylic copolymers manufactured by BASF); Movinyl S-100A (modified vinyl acetate copolymer manufactured by Japan Coating Resin Co., Ltd.); and Julimer AT-210 (polyacrylic acid ester copolymer manufactured by Toagosei Co., Ltd.).

[0020] Examples of dispersants obtained by synthesis include the AB block polymer disclosed in International Publication No. 2013 / 115071. The monomer constituting the A block of the AB block polymer disclosed in International Publication No. 2013 / 115071 is at least one monomer selected from (meth)acrylic acid and linear or branched C4 alkyl (meth)acrylate, with at least one monomer selected from methacrylic acid and n-butyl methacrylate being preferred, and more preferably a combination of these two monomers. The monomer constituting the B block of the AB block polymer disclosed in International Publication No. 2013 / 115071 is at least one monomer selected from benzyl methacrylate and benzyl acrylate, with benzyl methacrylate being preferred. Specific examples of AB block polymers include the block copolymers disclosed in Synthesis Examples 3 to 8 of International Publication No. 2013 / 115071.

[0021] The acid value of the dispersant is typically 90-200 mgKOH / g, preferably 100-150 mgKOH / g, and more preferably 100-120 mgKOH / g.

[0022] A neutralizing agent may be used to uniformly disperse the dispersant in water. Examples of neutralizing agents include ammonia, alkali metal hydroxides, alkaline earth metal hydroxides, aliphatic amine compounds, and alkanolamine compounds. Among these, ammonia and alkali metal hydroxides are preferred, with ammonia being more preferred. As a guideline for the amount of neutralizing agent to use, the degree of neutralization is usually 30-300%, preferably 50-200%, with 100% neutralization being defined as neutralization with a theoretical equivalent amount of the acid value of the dispersant.

[0023] The mass-average molecular weight of the dispersant is typically 10,000 to 60,000, preferably 10,000 to 40,000, more preferably 15,000 to 30,000, and even more preferably 20,000 to 25,000. The mass-average molecular weight of the dispersant can be measured by gel permuration chromatography (GPC). Specifically, the measurement can be performed using an HLC-8320GPC (manufactured by Tosoh Corporation) as the GPC instrument, two TSK gel Super Multipore HZ-H columns (manufactured by Tosoh Corporation, inner diameter 4.6 mm × 15 cm), tetrahydrofuran as the eluent, and TSK Standard (manufactured by Tosoh Corporation) as the standard sample.

[0024] The PDI (mass-average molecular weight / number-average molecular weight) of the dispersant is preferably around 1.29 to 1.49. Within this range, the dispersibility and storage stability of the ink tend to be good.

[0025] The dispersant can be used in a mixed state with the colorant. Alternatively, it can be used with part or all of the surface of the colorant coated with the dispersant. Or, both of these states may be used in combination.

[0026] In the above ink, the ratio of the total mass of the colorant to the total mass of the lignin compound and dispersant is preferably 0.01 to 1.0, more preferably 0.05 to 0.6, and even more preferably 0.1 to 0.5, when Dy is the total mass of the colorant and Ds is the total mass of the lignin compound and dispersant.

[0027] The above ink may contain water. The water mentioned above is preferably water with a low content of impurities such as metal ions, i.e., ion-exchanged water, distilled water, etc. Such water can be prepared by known methods. The water content in the ink is preferably 55% to 90% by mass, and more preferably 60% to 85% by mass.

[0028] The above inks may contain organic solvents. Examples of the aforementioned organic solvents include C1-C6 alkanols such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, derbutanol, or terbutanol; carboxylic acid amides such as N,N-dimethylformamide or N,N-dimethylacetamide; lactams such as 2-pyrrolidone, N-methyl-2-pyrrolidone, or N-methylpyrrolidine-2-one; cyclic ureas such as 1,3-dimethylimidazolidin-2-one or 1,3-dimethylhexahydropyrimido-2-one; acetone, 2-methyl-2-hydroxypentane -4-one, ketones or keto alcohols such as ethylene carbonate; cyclic ethers such as tetrahydrofuran and dioxane; ethylene glycol, diethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butylene glycol, 1,4-butylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, polyethylene glycol (preferably with a molecular weight of 400, 800, 1540 or higher), polypropylene glycol, thiodiglycol or Glycol ethers such as mono, oligo, or polyalkylene glycols or thioglycols having C2-C6 alkylene units such as dithiodiglycol; C3-C9 polyols (triols) such as glycerin, diglycerin, hexane-1,2,6-triol, and trimethylolpropane; glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoallyl ether, ethylene glycol monoisopropyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether (butyl carbitol), triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, propylene glycol monopropyl ether, prolene glycol monobutyl ether, and dipropylene glycol monomethyl ether (preferably glycol ethers selected from the group consisting of C3-C10 mono, di, or triethylene glycol ethers and C4-C13 mono, di, or tripropylene glycol ethers);Examples include C5-C9 alkanediols such as 1,2-pentanediol, 1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 2-methyl-2,4-pentanediol, 2-ethyl-1,3-hexanediol, and 2,4-diethyl-1,5-pentanediol; γ-butyrolactone or dimethyl sulfoxide; etc. These organic solvents may be used individually or in combination of two or more. Of the above, it is preferable to use at least one selected from the group consisting of glycol ethers and / or alkanediols. The total content of organic solvents in the total mass of ink is typically 1-60%, preferably 2-50%, more preferably 3-45%, and even more preferably 4-30%.

[0029] The above inks may contain wax. As the above wax, a wax emulsion is preferred, and a water-based wax emulsion is more preferred. Natural waxes and synthetic waxes can be used as the wax. Of these, synthetic waxes are preferred. Examples of synthetic waxes include polyethylene wax, with oxidized polyethylene wax being preferred, and polyethylene wax emulsion being more preferred. The average particle size of the wax is preferably 40 nm to 5 μm, and more preferably 40 nm to 1 μm, in order to prevent clogging of the inkjet head.

[0030] Examples of commercially available polyethylene wax emulsions include AQUACER 515(45) and 1547 from BIC Chemie, and the HYTEC E series from Toho Chemical Industry Co., Ltd., such as E-6500(40), E-9015(45), and E-6314(85). The numbers in parentheses after each wax name represent the average particle size (in nm) of each wax. The wax content relative to the total mass of the above ink is typically 0.1 to 10%, preferably 0.2 to 8%, more preferably 0.4 to 5%, even more preferably 0.6 to 3%, and particularly preferably 0.8 to 1.2%. By setting the wax content to 0.1 to 10%, the abrasion resistance of the printed material can be improved. In the above ink, it is preferable to use AQUACER 515 as the wax.

[0031] The above-mentioned resin emulsion is not particularly limited as long as it is not the above-mentioned wax or polymer dispersant. The resin emulsion described above is preferably one with an acid value of less than 10 mg KOH / g. By including a resin emulsion with an acid value of less than 10 mg KOH / g in the ink composition, the ink viscosity can be kept within a suitable range, and printed images with extremely low granularity can be achieved. Resin emulsions with an acid value exceeding 10 mg KOH / g cause a large increase in ink viscosity when water evaporates, which suppresses the wetting and spreading of the ink after it lands on the media, making it impossible to obtain uniform solid print quality. The resin emulsion preferably contains one or more selected from polymers and waxes. The method for preparing the resin emulsion is not particularly limited. Examples include a method of mechanically micronizing and dispersing the resin in an aqueous medium; a method of preparing the resin emulsion by emulsion polymerization, dispersion polymerization, suspension polymerization, etc. Emulsion polymerization can be carried out using an emulsifier or without soap. An example of a method for preparing the resin emulsion is the method disclosed in Production Example 1 of Japanese Patent Publication No. 2000-336292. The resin content of the resin emulsion is preferably 20 to 50%. Examples of resin emulsions include urethane-based, polyester-based, acrylic-based, vinyl acetate-based, vinyl chloride-based, styrene-acrylic-based, acrylic-silicone-based, and styrene-butadiene-based polymers or emulsions containing them. Among these, resin emulsions selected from urethane-based, acrylic-based, and styrene-butadiene-based are preferred, with acrylic-based resin emulsions being more preferred. Examples of commercially available products include Sanyo Chemical Industries' U-Coat UX-320 (acid value: 10), Taisei Fine Chemicals' WBR-016U (acid value: 7) and WBR-2101 (acid value: 10), all of which are urethane polymers; Toyobo's Byronal MD-1480 (acid value: 3), Byronal MD-1985 (acid value: 2), and Byronal MD-2000 (acid value: 2), all of which are polyester polymers; and Nisshin Chemical Industry's Vinibran 715 (acid value: 8) and Vinibran 985 (acid value: 5), all of which are vinyl acetate polymers.

[0032] When the above ink contains the above resin emulsion, the content of the resin emulsion in the ink composition is preferably 0.2 to 10%, and more preferably 0.5 to 8%.

[0033] The above ink may contain a viscosity modifier. In particular, industrial inkjet printers typically have a defined viscosity range for the ink that can be ejected, based on the specifications of the printer head (the head that ejects the ink). Therefore, a viscosity modifier can be added to the ink to adjust its viscosity to an appropriate range. The viscosity modifier is not particularly limited as long as it is a substance that can adjust the viscosity of the ink; known substances can be used. Specific examples include the organic solvents, polymer dispersants, and resin emulsions mentioned above.

[0034] The above ink may contain a surfactant. While there are no particular limitations on the surfactant, examples include anionic, cationic, nonionic, silicone, and fluorine-based surfactants. Cationic and nonionic surfactants are preferred.

[0035] Examples of anionic surfactants include alkyl sulfocarboxylates, α-olefin sulfonates, polyoxyethylene alkyl ether acetates, polyoxyethylene alkyl ether sulfates, N-acyl amino acids or their salts, N-acyl methyl taurates, alkyl sulfates, polyoxyalkyl ether sulfates, alkyl sulfates, polyoxyethylene alkyl ether phosphates, rosinic acid soaps, castor oil sulfates, lauryl alcohol sulfates, alkylphenol type phosphates, alkyl type phosphates, alkylaryl sulfonates, diethyl sulfosaturates, diethylhexyl sulfosaturates, and dioctyl sulfosaturates.

[0036] Examples of cationic surfactants include 2-vinylpyridine derivatives and poly-4-vinylpyridine derivatives.

[0037] Nonionic surfactants include polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene alkyl ethers with 4 to 18 carbon atoms (e.g., polyoxyethylene butyl ether, polyoxyethylene lauryl ether, polyoxyethylene oleyl ether, polyoxyethylene 2-ethylhexyl ether), and polyoxyethylene (di)styrene-modified phenyl ether (e.g., Emulgen manufactured by Kao Corporation). Ether-based compounds such as A-60, A-90, A-500, and DSP-9, DSP-12.5, TSP-7.5, KTSP-16, TSP-50 from Aoki Oil Co., Ltd.; ester-based compounds such as polyoxyethylene oleate, polyoxyethylene distearate, sorbitan laurate, sorbitan monostearate, sorbitan monooleate, sorbitan sesquioleate, polyoxyethylene monooleate, and polyoxyethylene stearate; acetylene glycol (or acetylene alcohol)-based compounds such as 2,4,7,9-tetramethyl-5-decine-4,7-diol, 3,6-dimethyl-4-octin-3,6-diol, and 3,5-dimethyl-1-hexyn-3-ol (for example, Surfinol 420, 440, 465, 485, and Orphine from Evonik Japan Co., Ltd.). Examples include STG, E1004, E1040, etc.; and polyglycol ether-based compounds.

[0038] Examples of silicone-based surfactants include polyether-modified siloxanes and polyether-modified polydimethylsiloxanes. Examples include Dynol 960 and 980 from Air Products Corporation; Silface SAG001, SAG002, SAG003, SAG005, SAG503A, SAG008, SAG009, and SAG010 from Nisshin Chemical Co., Ltd.; and BYK-345, 347, 348, 349, 3450, 3451, and 3455 from BYK Additives & Instruments; and TEGO Twin 4000, TEGO Wet KL 245, 250, 260, 265, 270, and 280 from Evonic Tego Chemie.

[0039] Examples of fluorinated surfactants include perfluoroalkyl sulfonic acid compounds, perfluoroalkyl carboxylic acid compounds, perfluoroalkyl phosphate ester compounds, perfluoroalkyl ethylene oxide adducts, and polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups in their side chains. Specific examples of commercially available products include Capstone FS-30 and FS-31 (manufactured by Chemours).

[0040] Examples of the above-mentioned preservatives include compounds such as organosulfur, organonitrogen-sulfur, organohalogen, haloarylsulfone, iodopropagyl, haloalkylthio, nitrile, pyridine, 8-oxyquinoline, benzothiazole, isothiazolin, dithiol, pyridine oxide, nitropropane, organotin, phenol, quaternary ammonium salt, triazine, thiazine, anilide, adamantane, dithiocarbamate, brominated indanone, benzylbromacetate, and inorganic salts. Specific examples of commercially available preservatives include Proxel GXL(S) and XL-2(S) manufactured by Arch Chemical.

[0041] Examples of the above-mentioned antifungal agents include sodium dehydroacetate, sodium benzoate, sodium pyridinethion-1-oxide, ethyl p-hydroxybenzoate, and 1,2-benzisothiazolin-3-one, as well as salts thereof.

[0042] Examples of the pH adjusting agents mentioned above include alkanolamines such as diethanolamine, triethanolamine, and N-methyldiethanolamine; alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; ammonium hydroxide (ammonia water); or alkali metal carbonates such as lithium carbonate, sodium carbonate, sodium bicarbonate, and potassium carbonate; alkali metal salts of organic acids such as sodium silicate and potassium acetate; and inorganic bases such as disodium phosphate.

[0043] The pH of the above ink is typically 5 to 11, preferably 6 to 9. The surface tension of the ink is typically 20 to 60 mN / m, preferably 25 to 50 mN / m. The viscosity of the ink is typically 2 to 30 mPa·s, preferably 3 to 15 mPa·s. The pH and surface tension of the ink can be adjusted by using pH adjusters, surfactants, and organic solvents.

[0044] Examples of the chelating agents mentioned above include disodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, sodium uracil diacetate, α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin.

[0045] Examples of the above-mentioned rust inhibitors include acidic sulfites, sodium thiosulfate, ammonium thioglycolate, diisopropylammonium nitride, pentaerythritol tetranitrate, and dicyclohexylammonium nitride.

[0046] Examples of the above-mentioned water-soluble ultraviolet absorbers include, for example, sulfonated benzophenone compounds, benzotriazol compounds, salicylic acid compounds, cinnamic acid compounds, and triazine compounds.

[0047] Examples of the above antioxidants include, for example, various organic and metal complex-based colorfastness inhibitors. Examples of the above organic colorfastness inhibitors include hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromans, alkoxyanilines, ascorbic acid, isoascorbic acid, chlorogenic acid, sulfur dioxide, catechins, dibutylhydroxytoluene, tocopherol, and butylhydroxyanisole.

[0048] The above-mentioned defoaming agents include acetylene-based defoaming agents such as the Surfinol 104 series (104A, 104E, 104H, 104PA, 104PG-50), Surfinol DF110D, Surfinol AD01, Surfinol MD-20, Surfinol DF-58, BYK-017, BYK-018, BYK-019, BYK-021, BYK-022, BYK-023, BYK-024, BYK-025, BYK-028, BYK-044, BYK-092, BYK-1610, BYK-1611, BY Examples of defoaming agents include silicone-based defoamers such as K-1615, BYK-1617, BYK-1650, BYK1679, BYK-1719, BYK-1723, BYK-1724, BYK-1730, BYK-1770, BYK-1781, BYK-1786, and BYK-1789; mineral oil-based defoamers such as BYK-035, BYK-037, BYK-038, and BYK-1630; higher alcohol derivatives such as Bisform CS, Bisform ECC, and Bisform TDI-1; and fatty acid derivatives such as Bisform TS-10. The defoaming agent is preferably an acetylene-based or silicone-based defoamer, and preferably DF-58.

[0049] The above ink can be used in various printing applications. For example, it is suitable for writing instruments, various types of printing, information printing, textile printing, etc., and is particularly preferred for use in inkjet printing.

[0050] When preparing the above-mentioned ink, known manufacturing methods can be used. For example, one method involves preparing an ink by adding water and, if necessary, an ink preparing agent to an aqueous dispersion prepared from a pigment dispersion and a resin emulsion and mixing the mixture.

[0051] The above ink can be prepared using conventionally known equipment, such as a ball mill, sand mill, attritor, basket mill, or roll mill. During preparation, it is preferable to remove coarse particles using a membrane filter or mesh filter.

[0052] Furthermore, it is preferable to microfilter the ink. When microfiltration is performed, a membrane filter and / or glass filter paper can be used. The pore size of the filter used for microfiltration is usually 0.5 μm to 20 μm, preferably 0.5 μm to 10 μm.

[0053] An ink set containing at least the above-mentioned inks is also included in the present invention. Examples of the above-mentioned ink sets include an ink set containing two or more of the above-mentioned inks, an ink set containing one or more of the above-mentioned inks and one or more of other inks. The other inks other than the above-mentioned inks are not particularly limited as long as their composition is different from the above-mentioned inks, but it is preferable that they have a different hue from the above-mentioned inks. Furthermore, recording media to which the above-mentioned ink or the ink contained in the above-mentioned ink set is attached is also included in the present invention. The recording media mentioned above is not particularly limited as long as it is a material to which the ink can adhere. Examples include paper, film, cans, leather, cloth, and textiles. Printing media are broadly classified into non-permeable printing media such as films and cans that do not absorb ink, and permeable printing media that do absorb ink.

[0054] Regarding all of the above, combinations of preferred elements are more preferable, and combinations of preferred elements are even more preferable. The same applies to combinations of preferred elements and preferred elements, and combinations of preferred elements and even more preferable elements. Furthermore, unless otherwise specified, all of the above-mentioned components can be used individually or in combination of two or more elements.

[0055] The above inks excel in pigment wettability during dispersion, handling properties, dispersion stability over time, ink stability (viscosity), print density, gloss, character quality, and barcode quality. [Examples]

[0056] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The "water" used in the examples is deionized water. Furthermore, the reactive emulsifier used in the examples is an ammonium salt of the sulfated ester of the oxirane polyadduct of the reaction product of {C10-C14 branched chain alkanol and 1-(allyloxy)-2,3-epoxypropane}, with {α-[2-(allyloxy)-1-({C10-C14 alkyloxy}methyl)ethyl]-ω-hydroxypoly(n=1~100)(oxyethylene)} as the main component.

[0057] [Preparation Example 1]: Preparation of an aqueous solution of lignin compound 20 parts of sodium ligninsulfonate (manufactured by Borregaard AS, Vaniseprese CB) were dissolved in 80 parts of water to obtain a 20 wt% aqueous solution of lignin compounds.

[0058] [Preparation Example 2]: Preparation of carbon black dispersion 1. A block copolymer was prepared as described in Synthesis Example 3 of International Publication No. 2013 / 115071. The obtained block copolymer (4.5 parts) was dissolved in 20 parts of methyl ethyl ketone to obtain a homogeneous solution. To this solution, a mixture of sodium hydroxide (0.4 parts) dissolved in water (52.6 parts) was added, followed by the addition of 7.5 parts of a 20 wt% aqueous solution of lignin compound to obtain a homogeneous resin solution. Carbon black A (HIBLACK 890, Orion Engineered Carbons, primary particle size 15 nm, BET specific surface area 270 m²) was added to this resin solution. 2 (15 parts of a substance with an oil absorption capacity of 98cc / 100g) were added and dispersed in a sand grinder at 1500 rpm for 15 hours to obtain the liquid. After adding water (100 parts) to the obtained liquid, the liquid was filtered using glass filter paper GA-100 to remove aggregates and other contaminants, and a filtrate was obtained. The obtained filtrate was then subjected to vacuum distillation using an evaporator to remove methyl ethyl ketone and a portion of the water from the filtrate, so that the pigment content in the filtrate was 10.0%, thereby obtaining carbon black dispersion 1. The obtained carbon black dispersion was designated as "DP1".

[0059] [Preparation Example 3]: Preparation of carbon black dispersion 2. Preparation Example 2: Carbon Black B instead of Carbon Black A (Orion Engineered Carbons, HIBLACK 600L, primary particle size 16nm, BET specific surface area 235m²) 2 Carbon black dispersion 2 (DP2) was obtained in the same manner as in Preparation Example 2, except that a ratio of 72cc / 100g was used. The pigment concentration of DP2 was also adjusted to 10.0%.

[0060] [Preparation Example 4: Preparation of Polymer Emulsion] In a glass reaction vessel (capacity 3 L), water (100 parts), ammonium persulfate (0.3 parts), and reactive emulsifier (1 part) were added to obtain a solution. After replacing the air inside the reaction vessel with nitrogen, the temperature of the solution was raised to 70°C. To this solution, a solution consisting of water (120 parts), reactive emulsifier (0.9 parts), methacrylic acid (2 parts), methyl methacrylate (37 parts), 2-ethylhexyl acrylate (59 parts), and allyl methacrylate (2 parts) was added dropwise over 3 hours. During the addition of the solution, the temperature of the solution was maintained at 70°C while introducing nitrogen. After the addition of the solution was completed, the reaction was continued at 70°C for another 2 hours, and then cooled to 40°C. By adding triethanolamine (3.1 parts) to the obtained solution, an emulsion of polymer resin 1 was obtained as a white suspension with a solid content of 25%. The obtained emulsion of polymer resin 1 was designated "PEM1". The resulting polymer resin 1 had an acid value of 13 KOH mg / g and a glass transition temperature of -10°C.

[0061] [Preparation Example 5: Ink Preparation] The dispersions "DP1," "DP2," and "PEM1" obtained above were mixed with the components listed in Table 1 below to obtain inks. These inks were then filtered through a 3 μm membrane filter to obtain inks 1 and 2 for evaluation testing. The numerical values ​​in the component column in Table 1 represent the amount (parts) of that component used. In Table 1, a blank space represents 0 parts. The abbreviations used in Table 1 are as follows: DP1: Carbon black dispersion obtained in Preparation Example 2 DP2: Carbon black dispersion obtained in Preparation Example 3 PEM1: Polymer emulsion obtained in Preparation Example 4 PG: Propylene glycol 12HD:1,2-Hexanediol BYK-349 (Silicone-based surfactant manufactured by Big Chemie Japan Co., Ltd.) AQUACER 515 (Polyethylene wax emulsion manufactured by BIC Chemie Japan, 35% solids content)

[0062] [Table 1]

[0063] [Handling test for dispersed slurry] In Preparation Examples 2 and 3, the time it took for each carbon black to completely settle after being added to the resin solution was measured. The handling properties of the dispersed slurry were evaluated according to the following criteria. The evaluation results are shown in Table 2. [Evaluation Criteria] A: The time it takes for the carbon black to completely sink into the resin solution is less than 5 minutes. B: The time required for the carbon black to completely sink in the resin solution is between 5 and 8 minutes. C: The time it takes for the carbon black to completely sink in the resin solution is more than 8 minutes.

[0064] [Dispersion stability test over time] The carbon black dispersions obtained in Preparation Examples 2-3 were used to measure the particle size D50% before and after storage at 60°C for one week. The particle size D50% was measured using a Nanotrac Wave from Microtrac. The stability of the dispersion over time was evaluated using the absolute value of the rate of change in particle size D50% according to the following criteria. The evaluation results are shown in Table 2. The absolute value of the percentage change in particle size D50 can be calculated from (|Particle size D50 after 1 week of storage at 60°C - Particle size D50 before 1 week of storage at 60°C| ÷ Particle size D50 before 1 week of storage at 60°C). [Evaluation Criteria] A: The absolute value of the rate of change in particle size D by 50% is less than 2%. B: The change rate of particle size D50% is between 2% and less than 5%. C: The change rate of particle size D50% is between 5% and 10%. D: The rate of change in particle size D by 50% exceeds 10%.

[0065] [Ink long-term stability test] The viscosity of the ink obtained in Preparation Example 5 was measured before and after storage at 60°C for one week. Viscosity was measured using a TV-35 E-type viscometer manufactured by Toki Sangyo Co., Ltd. The long-term stability of the ink was evaluated by the absolute value of the rate of change in viscosity according to the following criteria. The evaluation results are shown in Table 2. The absolute value of the viscosity change rate can be calculated from (|Viscosity after 1 week of storage at 60°C - Viscosity before 1 week of storage at 60°C| ÷ Viscosity before 1 week of storage at 60°C). [Evaluation Criteria] A: The absolute value of the rate of change in viscosity is less than 4%. B: The absolute value of the rate of change in viscosity is between 4% and 8%. C: The absolute value of the rate of change in viscosity exceeds 8%.

[0066] [Bar coater coating test] The ink obtained in Preparation Example 5 was coated using a PI-1210 automatic coating machine manufactured by Tester Industries Co., Ltd., under the conditions of bar coater No. 3, coating speed of 200 mm / sec, and coating length of 180 mm, with Oji Paper's OK Topcoat+ at 127.9 g / m². 2 The coating was applied to coated paper, and a recorded image was obtained. This was used as a test piece, and the print density was measured. The colorimetric measurements of each test specimen were performed using an X-rite eXact colorimeter. The measurement conditions were: density standard ISO status T, field of view 2°, and light source D50.

[0067] [Print density test] Using each test specimen obtained as described above, the Dk value (OD value) was measured and evaluated according to the evaluation criteria below. The evaluation results are shown in Table 2. A higher OD value indicates better color development and superior quality. [Evaluation Criteria] A: OD value is 2.40 or higher. B: OD value is 2.20 or higher, and less than 2.40. C:OD value is 2.10 or higher, and less than 2.20. D:OD value is less than 2.10.

[0068] [Table 2]

[0069] From the results in Table 2 above, it was found that the dispersion and ink composition of the present invention are significantly superior to the prior art in terms of dispersion slurry handling, and also possess high dispersion and ink stability, as well as high print density. [Industrial applicability]

[0070] The ink composition of the present invention offers excellent handling properties in dispersion slurry form, superior storage stability of the dispersion and ink, and enables the provision of printed materials with excellent print density.

Claims

1. An ink comprising carbon black and a lignin compound, satisfying at least one of the following conditions. Condition 1: The BET specific surface area of ​​the carbon black is 118 m². ２ It exceeds / g. Condition 2: The primary particle size of the carbon black is less than 22 nm. Condition 3: The amount of oil absorbed by the carbon black exceeds 66 cc / 100 g.

2. The ink according to claim 1, satisfying at least two of the above conditions 1 to 3.

3. The ink according to claim 1 or 2, wherein the lignin compound comprises a lignin sulfonate.

4. A recording medium to which the ink described in claim 1 or 2 is attached.

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