Water-based ink composition and method for manufacturing inkjet printed materials

Abstract

The present invention provides an ink that excels in solid color filling, which leads to improved color development of printed materials, and suppression of satellite formation, which leads to improved print quality, while simultaneously improving the conflicting properties of storage stability, and printed materials using this ink. [Solution] This is an aqueous ink composition containing a pigment, a nonionic surfactant, a penetrant, and a water-soluble organic solvent (excluding those with a ClogP greater than 0 and less than or equal to 2). The nonionic surfactant comprises at least one acetylene glycol-based surfactant and at least one polyoxyethylene styrene-phenyl ether-based surfactant. To provide a water-based ink composition in which the weighted average HLB value of the penetrating agent and the nonionic surfactant is in the range of 5.8 to 9.7.

Description

TECHNICAL FIELD

[0001] The present invention relates to an aqueous ink composition and a method for producing an inkjet printed matter.

BACKGROUND ART

[0002] A recording method using an inkjet printer, which is one of the representative methods among color recording methods, performs recording by generating fine ink droplets and depositing them onto a recording medium such as paper. In recent years, demand for commercial and industrial applications has increased, and compatibility with various recording media is required.

[0003] In commercial fields such as catalogs and pamphlets, recording media with lower ink absorbency than plain paper, such as coated paper and art paper (hereinafter sometimes referred to as "low-absorbency media"), are often used. In industrial fields, applications include outdoor signage and flexible food packaging, for which non-ink-absorbent recording media (hereinafter sometimes referred to as "non-absorbent media") such as plastic films of vinyl chloride, PET, and polyolefin types are mainly used.

[0004] For the above low-absorbency media and non-absorbent media, development of solvent-based inks containing an organic solvent as a main component, UV inks containing a polymerizable monomer, and the like has been progressing. However, these inks have many safety issues for the environment and the human body, such as VOCs and skin sensitization. On the other hand, aqueous inks, which have water as the main component and offer high safety and cleanability, have been actively developed in recent years. However, aqueous inks generally have the property of being difficult to wet and spread on the aforementioned recording media, and when sufficient wetting and spreading cannot be achieved, solid images suffer from poor filling, causing printing defects such as white streaks.

[0005] Water-based inks generally use organic solvents or surfactants to improve wettability and fill in solid areas. However, while adding more of these materials improves wettability, it also makes the dispensed ink droplets more prone to separation, leading to the formation of satellites. This also affects storage stability. The occurrence of satellites leads to a deterioration of dot shape on the recorded image, resulting in a decrease in image quality. It can also lead to mist generation, potentially contaminating the inkjet head. To solve this problem, there is a strong demand for inks that improve solid dot filling while being less prone to satellite formation. However, no ink has yet been proposed that satisfies the performance requirements for suppressing the aforementioned solid fill and satellite formation, while also possessing high storage stability. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-125382 [Patent Document 2] Japanese Patent Publication No. 2020-55943 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] The present invention aims to provide an ink that excels in solid color filling, which leads to improved color development of printed materials, and suppression of satellite formation, which leads to improved print quality, while simultaneously improving the conflicting properties of storage stability, as well as printed materials using this ink. [Means for solving the problem]

[0008] As a result of diligent research, the inventors have found that an aqueous ink composition containing a pigment, a nonionic surfactant, a penetrating agent, and a water-soluble organic solvent (excluding those with a ClogP greater than 0 and 2 or less), wherein the nonionic surfactant comprises at least one acetylene glycol-based surfactant and at least one polyoxyethylene styrene-phenyl ether-based surfactant, and the weighted average HLB value of the penetrating agent and the nonionic surfactant is in the range of 5.8 to 9.7, can solve the above problems, and have completed the present invention. In other words, the present invention relates to the following 1) to 8). 1) This is an aqueous ink composition containing a pigment, a nonionic surfactant, a penetrant, and a water-soluble organic solvent (excluding those with a ClogP greater than 0 and less than or equal to 2). The nonionic surfactant comprises at least one acetylene glycol-based surfactant and at least one polyoxyethylene styrene-phenyl ether-based surfactant. A water-based ink composition in which the weighted average HLB values ​​of the penetrating agent and the nonionic surfactant are in the range of 5.8 to 9.7. 2) The aqueous ink composition according to 1), wherein the content of the penetrating agent is greater than 3.0% by mass and less than or equal to 5.0% by mass relative to the total amount of ink. 3) The aqueous ink composition according to 1), wherein the weighted average HLB values ​​of the nonionic surfactant and the penetrating agent are in the range of 7.4 to 8.9. 4) The aqueous ink composition according to 1), wherein the total content of the nonionic surfactant is 0.8% by mass or more and 2.3% by mass or less based on the total amount of ink. 5) The aqueous ink composition according to 1), wherein the weight ratio (A / B) of the acetylene glycol surfactant (A) to the polyoxyethylene styrene-phenyl ether surfactant (B) in the nonionic surfactant is 0.15 or more and 0.7 or less. 6) An inkjet recording method that ejects droplets of inkjet ink described in 1) or 2) from an inkjet head and records them onto a recording medium. 7) The inkjet recording method according to 6), wherein the inkjet head is a head equipped with a circulation mechanism. 8) Printed media printed using the inkjet ink described in 1) or 2), or the inkjet ink set described in 9). [Effects of the Invention]

[0009] The present invention provides an aqueous inkjet ink composition that exhibits excellent solid filling properties in poorly absorbent and non-absorbent media, as well as superior suppression of satellite formation and excellent storage stability. [Modes for carrying out the invention]

[0010] The present invention will be described in detail below. In this specification, "CI" means "Color Index." Furthermore, in this specification, including in examples, "%" and "parts" are expressed on a mass basis unless otherwise specified. Furthermore, in this specification, the terms "alkylene," "propylene," and "alkyl" are used to encompass both linear and branched structures unless otherwise specified. Inkjet ink may be abbreviated as ink or water-based ink. In addition, the above-mentioned poorly absorbent media, non-absorbent media, printing media, and recording media described later may be abbreviated as media.

[0011] The above inkjet ink is an aqueous ink composition containing a pigment, a nonionic surfactant, a penetrating agent, and a water-soluble organic solvent (excluding those with a ClogP greater than 0 and 2 or less), wherein the nonionic surfactant contains at least one acetylene glycol-based surfactant and at least one polyoxyethylene styrene-phenyl ether-based surfactant, and the weighted average HLB value of the penetrating agent and the nonionic surfactant is in the range of 5.8 to 9.7.

[0012] [Pigments] Examples of known pigments, disperse dyes, and solvent dyes can be used as the above-mentioned pigments. Among the above-mentioned pigments, disperse dyes, and solvent dyes, it is preferable to include at least one selected from the group consisting of pigments and disperse dyes, and it is more preferable to include pigments. Examples of pigments include inorganic pigments, organic pigments, extender pigments, and hollow particles.

[0013] Examples of the inorganic pigments mentioned above include carbon black, metal oxides, hydroxides, sulfides, ferrocyanides, and metal chlorides.

[0014] If the above ink is black ink and the above pigment is the above inorganic pigment, then the inorganic pigment contained in the black ink is preferably carbon black such as thermal black, acetylene black, oil furnace black, gas furnace black, lamp black, gas black, and channel black. Specific examples of carbon black include, for example, the Raven series from Columbia Carbon; the Monarch series, Regal series, and Mogul series from Cabot; the HiBlack series, ColorBlack series, Printex series, SpecialBlack series, and Nerox series from Orion Engineered Carbons; and the MA series, MCF series, No. 25, No. 33, No. 40, No. 47, No. 52, No. 900, and No. 2300 from Mitsubishi Chemical Corporation. When the above ink is a white ink and the above pigment is the above inorganic pigment, examples of the inorganic pigment contained in the white ink include oxides, nitrides, and oxynitrides of metals such as zinc, silicon, aluminum, titanium, strontium, and zirconium; and various inorganic compounds such as various types of glass and silica, among which titanium dioxide and zinc oxide are preferred.

[0015] Examples of the above organic pigment include various pigments such as azo, disazo, phthalocyanine, quinacridone, isoindolinone, dioxazine, perylene, perinone, thioindigo, anthraquinone, and quinophthalone.

[0016] Examples of the above organic pigment include yellows such as C.I. Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 24, 55, 73, 74, 75, 83, 93, 94, 95, 97, 98, 108, 114, 128, 129, 138, 139, 150, 151, 154, 155, 180, 185, 193, 199, 202, 213; reds such as C.I. Pigment Red 5, 7, 12, 48, 48:1, 57, 88, 112, 122, 123, 146, 149, 150, 166, 168, 177, 178, 179, 184, 185, 202, 206, 207, 254, 255, 257, 260, 264, 269, 272; blues such as C.I. Pigment Blue 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 22, 25, 60, 66, 80; violets such as C.I. Pigment Violet 19, 23, 29, 37, 38, 50; oranges such as C.I. Pigment Orange 13, 16, 43, 68, 69, 71, 73; greens such as C.I. Pigment Green 7, 36, 54; and black pigments of respective colors such as C.I. Pigment Black 1. The above organic pigment is preferably C.I. Pigment Blue 15:4.

[0017] Examples of the extender pigments mentioned above include silica, calcium carbonate, talc, clay, barium sulfate, and white carbon. Extender pigments are often used in combination with other colorants.

[0018] As the hollow particles mentioned above, known hollow particles described in, for example, U.S. Patent No. 4,880,465, Japanese Patent No. 3,562,754, Japanese Patent No. 6026234, Japanese Patent No. 5459460, Japanese Patent Application Publication No. 2003-268694, Japanese Patent No. 4902216, etc., can be used, and it is particularly preferable to use them as a white pigment.

[0019] Examples of the above-mentioned disperse dyes include known disperse dyes or known oil-soluble dyes. Among the known disperse dyes, CIDispers-based disperse dyes are preferred. Specific examples include, for instance, CIDispers Yellow 9, 23, 33, 42, 49, 54, 58, 60, 64, 66, 71, 76, 79, 83, 86, 90, 93, 99, 114, 116, 119, 122, 126, 149, 160, 163, 165, 180, 183, 186, 198, 200, 211, 224, 226, 227, 231, 237, etc.; CIDispers Red 60, 73, 88, 91, 92, 111, 127, 131, 143, 145, 146, 152, 153, 154, 167, 179, 191, 192, 206, 221, 258, 283, etc.; CIDispers Orange Disperse dyes in various colors include orange (9, 25, 29, 30, 31, 32, 37, 38, 42, 44, 45, 53, 54, 55, 56, 61, 71, 73, 76, 80, 96, 97, etc.), violet (CIDispers Violet 25, 27, 28, 54, 57, 60, 73, 77, 79, 79:1, etc.), and blue (CIDispers Blue 27, 56, 60, 79:1, 87, 143, 165, 165:1, 165:2, 181, 185, 197, 202, 225, 257, 266, 267, 281, 341, 353, 354, 358, 364, 365, 368, etc.). Among the known solvent dyes mentioned above, CISolvent-based disperse dyes are preferred.

[0020] The total content of the water-insoluble colorant in the total mass of the above ink is preferably 0.1 to 30% by mass, more preferably 0.1 to 10% by mass, and particularly preferably 0.5 to 8% by mass. Furthermore, the average particle size of the colorant in the ink is preferably 30 nm to 300 nm, and more preferably 50 nm to 250 nm. In this specification, the average particle size refers to the average particle size measured using the laser light scattering method.

[0021] [Surfactants] Examples of the surfactants mentioned above include nonionic, anionic, silicone, and fluorine-based surfactants. Among these, nonionic surfactants are preferred.

[0022] [Nonionic surfactants] Nonionic surfactants include ether-based surfactants such as polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, polyoxyethylene alkyl ether, polyoxyethylene styrene phenyl ether (e.g., Emulgen® A-60, A-90, A-500 from Kao Corporation, and Braunon® DSP-9, DSP-12.5, TSP-7.5, KTSP-16, TSP-50 from Aoki Oil & Fat Co., Ltd.), and polyoxyethylene-β-naphthyl ether (e.g., Braunon® BN-3, BN-10, BN-25 from Aoki Oil & Fat Co., Ltd.); polyoxyethylene oleate ester, polyoxyethylene distearate ester, sorbitan laurate, sorbitan monostearate ester; and ether-based surfactants such as polyoxyethylene oleate ester, polyoxyethylene distearate ester, sorbitan laurate, and sorbitan monostearate ester. Examples include esters such as areates, sorbitan monooleate, sorbitan sesquioleate, polyoxyethylene monooleate, and polyoxyethylene stearate; acetylene glycol (or acetylene alcohol) 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® 104, 104PG50, 82, 420, 440, 465, 485, and Olfin STG from Evonik Japan Co., Ltd.); and polyglycol ether compounds. Of the nonionic surfactants mentioned above, it is preferable to use ether-based surfactants such as polyoxyethylene styrene-phenyl ether (e.g., Emulgen® A-60, A-90, A-500 manufactured by Kao Corporation), ether-based surfactants such as polyoxyethylene-β-naphthyl ether (e.g., Brownon® BN-3, BN-10, BN-25 manufactured by Aoki Oil & Fat Co., Ltd.), or acetylene glycol (or acetylene alcohol)-based surfactants (e.g., Surfinol® 104, 104PG50, 82, 420, 440, 465, 485, Olfin STG, etc. manufactured by Evonik Japan Co., Ltd.). It is even more preferable to use one or more ether-based surfactants such as polyoxyethylene styrene-phenyl ether and one or more acetylene glycol (or acetylene alcohol)-based surfactants in combination. By using these nonionic surfactants, it is possible to obtain an ink that has good filling properties and excellent suppression of satellite formation. The total content of nonionic surfactants in the total mass of the above ink is typically 0.1% to 5.5% by mass, preferably 0.1% to 3% by mass, and more preferably 0.8% to 2.3% by mass. By including a penetrating agent within this range, an ink can be obtained that has good solid filling and excellent suppression of satellite formation.

[0023] The weight ratio (A / B) of the polyoxyethylene styrene-phenyl ether surfactant (A) to the acetylene glycol surfactant (B) in the above nonionic surfactant is calculated from the weights of the polyoxyethylene styrene-phenyl ether surfactant (A) and the acetylene glycol surfactant (B) contained in the aqueous ink composition. The weight ratio (A / B) of the polyoxyethylene styrene-phenyl ether-based surfactant acetylene glycol-based (A) and the acetylene glycol-based surfactant (B) is typically 0.02 to 10, preferably 0.1 to 2.3, and more preferably 0.15 to 0.7. By including a penetrating agent within this range, an ink can be obtained that exhibits good filling and excellent suppression of satellite formation.

[0024] Examples of the above-mentioned 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.

[0025] 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, 3455, LP-X23288, and LP G20726 from BYK Additives & Instruments; and TEGO Twin 4000, TEGO Wet KL 245, 250, 260, 265, 270, and 280 from Evonic Tego Chemie.

[0026] 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).

[0027] [Penetrating agent] The ink may further contain, as a penetrating agent, at least one organic solvent selected from glycol ethers and C4-C9 alkanediols, having a water-octanol partition coefficient of 0.00 or more and less than 2.00. This tends to improve the wetting and drying of the ink on non-absorbent and poorly absorbent media. Penetrating agents having a ClogP within the above numerical range include, for example, 1,2-pentanediol (-0.00), ethylene glycol monoallyl ether (0.03), isopropyl alcohol (0.07), isopropyl glycol (0.09), diethylene glycol ethyl methyl ether (0.13), dipropylene glycol dimethyl ether (0.36), 3-methoxy-3-methyl-1-butanol (0.42), diethylene glycol methyl isopropyl ether (0.44), butyl triglyceride (0.49), diethylene glycol monoethyl ether acetate (0.50), diethylene glycol diethyl ether (0.52), 1,2-hexanediol (0.53), dipropylene glycol monoisopropyl ether (0.53), and diethylene glycol mono Examples include isobutyl ether (0.54), propylene glycol methyl ether acetate (0.60), propylpropylene glycol (0.62), butyl diglycol (0.67), dipropylene glycol n-propyl ether (0.75), 2,2-diethyl-1,3-propanediol (0.82), 2,2,4-trimethyl-1,3-pentanediol (1.00), 2-ethyl-1,3-hexanediol (1.26), 1,2-octanediol (1.58), hexyl diglycol (1.72), and 1-heptanol (1.88). Of these, it is preferable to contain 1,2-hexanediol (0.53), 1,2-octanediol (1.58), and 1-heptanol (1.88), and it is more preferable to contain 1,2-hexanediol (0.53). By using these penetrating agents, it is possible to obtain an ink that provides excellent solid filling and also effectively suppresses the formation of satellites. When the above ink contains a penetrating agent, the total content of the penetrating agent in the total mass of the ink is usually 0.1 to 30%, preferably 0.2 to 20%, and more preferably 0.5 to 10%. By including the penetrating agent within this range, it is possible to obtain an ink that maintains good storage stability, has good solid filling, and is also excellent in suppressing the formation of satellites.

[0028] [Viscosity modifier] The aforementioned ink may further contain a viscosity modifier. Industrial inkjet printers typically have a defined viscosity range for the ink they can eject, 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, and known substances can be used. Specific examples include, for example, water-soluble organic solvents (this does not include the "organic solvents" mentioned above as penetrating agents), sugars, etc. Among these, water-soluble organic solvents with a ClogP value of usually less than 0.00, preferably -0.05 or less, and more preferably -0.08 or less are mentioned. The lower limit of the ClogP value of the water-soluble organic solvent is not particularly limited, but is usually -4.00 or higher, preferably -3.00 or higher, more preferably -2.00 or higher, and even more preferably -1.50 or higher. Examples of such water-soluble organic solvents include 2-methyl-2,4-pentanediol (-0.02), tripropylene glycol monomethyl ether (-0.03), isopropyl diglycol (-0.08), dipropylene glycol monomethyl ether (-0.16), ethanol (-0.24), 3-methyl-1,5-pentanediol (-0.24), diethylene glycol dimethyl ether (-0.26), propylene glycol monomethyl ether (-0.30), 3-methyl-1,3-butanediol (-0.33), trimethylolpropane (-0.39), N-methyl-2-pyrrolidone (-0.40), 1,2-butanediol (-0.53), and 3-ethyl-3-hydroxymethyl Examples include thioxetane (-0.58), 1,5-pentanediol (-0.64), 2-methyl-1,3-propanediol (-0.64), dipropylene glycol (-0.69), 1,3-butanediol (-0.73), methyl diglycol (-0.78), methyl triglycol (-0.96), 2-pyrrolidone (-0.97), propylene glycol (-1.06), 1,4-butanediol (-1.16), diethylene glycol (-1.30), ethylene glycol (-1.37), triethylene glycol (-1.48), glycerin (-1.54), diglycerin (-2.96), glycereth-3 (-3.49) and glycereth-20 (-5.42) manufactured by Aoki Oil & Fat Industry Co., Ltd.

[0029] The above ink contains water. The water contained in the ink should preferably be 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.

[0030] [Weighted average HLB] The weighted average HLB in the aforementioned aqueous ink composition is the weighted average of the HLB (Hydrophile-lipophile balance value) values ​​calculated by the Griffin method (Griffin, WC.: Classification of surface active agents by HLB, J. Soc., Cosmet., Chem., 1, 1949) for penetrating agents and surfactants. The calculation method involves calculating the average value weighted according to the amount of each compound added. For example, the weighted average HLB value for an ink containing 0.3 parts of Emulgen A60, 1 part of SF485, and 4 parts of 1,2-hexanediol is (12.8 × 0.3 + 17 × 1 + 5.8 × 4) / (0.3 + 1 + 4) = 8.3. By controlling this value, it is possible to adjust the balance between storage stability, solid filling, and satellite suppression. The weighted average HLB in the aforementioned aqueous ink composition is typically 4.6 to 14, preferably 5.5 to 10.4, and more preferably 5.8 to 9.7. By adjusting the balance of penetrants and surfactants within this range, it is possible to obtain an ink that maintains good storage stability, provides excellent solid filling, and also suppresses satellite formation.

[0031] The above ink may contain, in addition to the above pigment, the above nonionic surfactant, the above penetrating agent, the above viscosity modifier, and the above water, an ink preparation agent. The ink preparation agent may not contain any of the above pigment, the above nonionic surfactant, the above penetrating agent, the above viscosity modifier, or the above water, and may contain, as needed, an ink preparation agent such as a dispersant, a fungicide, a preservative, a pH adjuster, a chelating agent, a rust inhibitor, an antifoaming agent, a water-soluble ultraviolet absorber, an antioxidant, a resin emulsion, or a wax. One or more of any type of ink preparation agent may be used, or multiple types may be used one by one, or multiple types may be used in combination. The amount of the above ink preparation agent in the above ink, or the amounts between each ink preparation agent if multiple ink preparation agents are included in the above ink, can be arbitrarily set according to the purpose of the ink, such as its intended use.

[0032] [Dispersant] Commercially available dispersants can be used as the dispersant mentioned above. Commercially available dispersants are sold by companies such as BASF, Bic Chemie, EVONIC, and Toagosei Co., Ltd., and can be used. Specific examples of commercially available products include polyacrylic acid such as Aron AC-10SL manufactured by Toagosei Co., Ltd. The above-mentioned dispersants can also be synthesized. Preferred dispersants obtained by synthesis include, for example, the AB block polymer disclosed in International Publication No. 2013 / 115071. The hydrophilic monomers mentioned above refer to monomers such as acrylic acid and methacrylic acid, in which a carboxyl group remains after polymerization.

[0033] The weight-average molecular weight (MW) of the above dispersant is not particularly limited, but is preferably 3,000 to 50,000, and more preferably 7,000 to 25,000. The acid value is also not particularly limited, but is preferably 50 to 300 KOH mg / g, more preferably 80 to 275 KOH mg / g, and more preferably 80 to 250 KOH mg / g.

[0034] The above-mentioned dispersant can be used either in a state mixed with the water-insoluble colorant, or in a state in which part or all of the surface of the water-insoluble colorant is coated with the dispersant. It can also be used in the presence of a mixture of these multiple states.

[0035] [Antifungal agent] Specific examples of fungicides include sodium dehydroacetate, sodium benzoate, sodium pyridinethion-1-oxide, p-hydroxybenzoate ethyl ester, 1,2-benzisothiazolin-3-one, and their salts.

[0036] [Preservatives] Examples of 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, benzylbromoacetate, or inorganic salts. A specific example of an organic halogen compound is, for instance, sodium pentachlorophenol. A specific example of a pyridine oxide compound is sodium 2-pyridinethiol-1-oxide. Examples of isothiazolin compounds include 1,2-benzisothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one magnesium chloride, 5-chloro-2-methyl-4-isothiazolin-3-one calcium chloride, and 2-methyl-4-isothiazolin-3-one calcium chloride. Other specific examples of antiseptics and antifungal agents include anhydrous sodium acetate, sodium sorbate, or sodium benzoate, and products manufactured by Arch Chemical, such as Proxel GXL(S), Proxel LV, and Proxel XL-2(S).

[0037] [pH adjuster] Specific examples of pH adjusters include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; ammonium hydroxide (ammonia water); 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.

[0038] [Chelating reagent] Specific examples of chelating reagents include, for example, disodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, or sodium uracildiacetate.

[0039] [Rust inhibitor] Specific examples of rust inhibitors include, for example, acidic sulfites, sodium thiosulfate, ammonium thioglycolate, diisopropylammonium nitride, pentaerythritol tetranitrate, or dicyclohexylammonium nitride.

[0040] [Antifoaming agent] Examples of defoaming agents include silicone-based, silica mineral oil-based, olefin-based, and acetylene-based agents. Examples of commercially available defoaming agents include Surfinol DF37, DF58, DF110D, DF220, MD-20, and olefin SK-14, all manufactured by Shin-Etsu Chemical Co., Ltd.

[0041] [Water-soluble UV absorber] Examples of water-soluble ultraviolet absorbers include, for example, sulfonated benzophenone compounds, benzotriazol compounds, salicylic acid compounds, cinnamic acid compounds, or triazine compounds.

[0042] [Antioxidant] Examples of antioxidants include various organic and metal complex-based colorfastness inhibitors. Examples of the above-mentioned organic colorfastness inhibitors include hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromans, alkoxyanilines, or heterocyclic compounds.

[0043] [Resin emulsion] The above ink may further contain a resin emulsion to improve the ink's fixation to the recording medium. Adding a resin emulsion to the ink can improve the image fastness of the printed image on the medium, such as its water resistance, scratch resistance, and alcohol resistance. There are no particular limitations on the resin emulsion, but it is preferable to use one or more selected from the group consisting of polymers and waxes. However, dispersants such as pigments and disperse dyes are not included in the binder. Examples of the polymers 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, polymers selected from urethane-based, acrylic-based, and styrene-butadiene-based polymers are preferred. Examples of commercially available products include Superflex 420, 470, and 890 (urethane resin emulsions manufactured by Daiichi Kogyo Seiyaku Co., Ltd.); Hydran HW-350, HW-178, HW-163, HW-171, AP-20, AP-30, WLS-201, and WLS-210 (urethane resin emulsions manufactured by DIC Corporation); 0569, 0850Z, and 2108 (styrene-butadiene resin emulsions manufactured by JSR Corporation); and AE980, AE981A, AE982, AE986B, and AE104 (acrylic resin emulsions manufactured by E-Tech Co., Ltd.).

[0044] [wax] As the above-mentioned wax, a wax emulsion is preferred, and a water-based wax emulsion is more preferred. As the wax, natural waxes and synthetic waxes can be used. Examples of natural waxes include petroleum-based waxes such as paraffin wax and microcrystalline wax; lignite-based waxes such as montane wax; plant-based waxes such as carnauba wax and candelilla wax; and emulsions in which waxes such as beeswax and lanolin are dispersed in an aqueous medium.

[0045] Examples of synthetic waxes include polyalkylene wax (preferably poly C2-C4 alkylene wax), oxidized polyalkylene wax (preferably oxidized poly C2-C4 alkylene wax), and paraffin wax. Of these, one or more waxes selected from polyethylene wax, polypropylene wax, oxidized polyethylene wax, oxidized polypropylene wax, and paraffin wax are preferred. Furthermore, the average particle size of the wax is preferably 50 nm to 5 μm, and more preferably 100 nm to 1 μm, in order to prevent clogging of the inkjet head.

[0046] Furthermore, the above wax can also be an emulsified wax, or "wax emulsion." Examples of commercially available wax emulsions include CERAFLOUR 925, 929, 950, 991; AQUACER 498, 515, 526, 531, 537, 539, 552, 1547; AQUAMAT 208, 263, 272; MINERPOL 221, etc., manufactured by BIC Chemie Japan; Mitsui High Wax NL100, NL200, NL500, 4202E, 1105A, 2203A, NP550, NP055, NP505, etc., manufactured by Mitsui Chemicals, Inc.; KUE-100, 11, manufactured by Sanyo Chemical Co., Ltd.; and HYTEC E-6500, 9015, 6400, etc., manufactured by Toho Chemical Co., Ltd.

[0047] The total content of the resin emulsion relative to the total mass of the ink is preferably in the range of 1% to 20%, and more preferably in the range of 3% to 15%. When the total content of the resin emulsion is 1% or more, the ink exhibits good adhesion to the printing medium. Furthermore, when the total content of the resin emulsion is 20% or less, the ink has good discharge properties and storage stability.

[0048] When preparing the above-mentioned ink, known manufacturing methods can be used. For example, one method involves preparing a dispersion consisting of a colorant and an organic compound, and then adding water and, if necessary, an ink preparing agent to this dispersion and mixing to prepare the ink. A known method can be used to prepare the dispersion. One example is the phase inversion emulsification method. That is, a dispersant is dissolved in a solvent such as 2-butanone, and an aqueous solution of a neutralizing agent is added to prepare an emulsion. A coloring agent is added to the obtained emulsion and a dispersion treatment is performed. By removing the solvent and some of the water from the liquid obtained in this way under reduced pressure, the desired dispersion can be obtained. Dispersion processing can be carried out using, for example, a sand mill (bead mill), roll mill, ball mill, paint shaker, ultrasonic disperser, microfluidizer, etc. For example, when using a sand mill, beads with a particle size of about 0.01 mm to 1 mm can be used, and the dispersion processing can be carried out by appropriately setting the bead packing ratio. The dispersion obtained as described above can be subjected to operations such as filtration and / or centrifugation. This operation can standardize the particle size of the particles contained in the dispersion. If foaming occurs during the preparation of the dispersion, a very small amount of a known defoaming agent, such as a silicone-based or acetylene glycol-based agent, can be added. Other methods for preparing dispersions include acid precipitation, interfacial polymerization, in-situ polymerization, liquid curing coating, coacervation (phase separation), liquid drying, melt-dispersion-cooling, air suspension coating, and spray drying. Of the above-mentioned dispersion preparation methods, phase inversion emulsification, acid precipitation, and interfacial polymerization are preferred.

[0049] The inks described above are preferably those with low levels of inorganic impurities such as metal cation chlorides (e.g., sodium chloride) and sulfates (e.g., sodium sulfate). Such inorganic impurities are often found in commercially available colorants. The guideline for the inorganic impurity content is approximately 1% by mass or less relative to the total mass of the colorant, and the lower limit should ideally be below the detection limit of the analytical instrument, i.e., 0%. Methods for obtaining a colorant with few inorganic impurities include, for example, a method using a reverse osmosis membrane; a method in which the solid colorant is suspended and stirred in a mixed solvent of C1-C4 alcohol such as methanol and water, the colorant is filtered and separated, and then dried; or a method of exchanging and adsorbing inorganic impurities with an ion exchange resin; and other desalting treatments. 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.

[0050] [Ink Set] An ink set containing two or more of the above-mentioned inks is also included in the present invention. Furthermore, an ink set containing the above-mentioned inks and other inks is also included in the present invention. The other inks mentioned above are not particularly limited as long as their composition differs from the above inks, but it is preferable that they differ in hue from the above inks.

[0051] The present invention also includes an inkjet ink media set comprising a printing medium printed using the above ink or the above ink set, any one selected from the group consisting of the above inkjet ink or the above inkjet ink set, and the above printing medium, and a method for suppressing solid fill, satellite formation, and improving storage stability using any of the above ink, the above ink set, the above printing medium, or the above ink media set.

[0052] [Inkjet recording method] The method used for inkjet printing described above is a method of printing by ejecting droplets of ink in accordance with a print signal and adhering them to a printing medium (hereinafter sometimes referred to as the recording method). There are no particular restrictions on the ink nozzles of the inkjet printer that eject the ink, and they can be appropriately selected according to the purpose. Inkjet printing methods include improving image quality by ejecting a large number of inks with a low colorant content in small volumes; improving image quality by using multiple inks with substantially the same hue but different colorant content; and improving the fixation of colorants to the printing medium by using a colorless, transparent ink in combination with an ink containing a colorant. The above-mentioned inks can also be used as inks containing colorants in these methods.

[0053] When performing the above inkjet printing method, known methods can be used. Examples include charge control methods, drop-on-demand methods (also called pressure pulse methods), acoustic inkjet methods, and thermal inkjet methods. It is also possible to use multi-pass methods, single-pass methods (one-pass printing methods), etc.

[0054] Furthermore, recording media to which the above-mentioned ink has been attached by, for example, the above-mentioned recording method, are also included in the scope of the present invention. There are no particular restrictions on the recording media, but poorly absorbent recording media are preferred, and non-absorbent recording media are particularly preferred. Examples of poorly absorbent recording media include plain paper without an ink-receiving layer, media used in gravure printing and offset printing, art paper, coated paper, matte paper, cast paper, etc. Examples of non-absorbent recording media include PET (polyethylene terephthalate), PP (polypropylene), vinyl chloride sheets, glass, rubber, etc. When using recording media that does not have an ink-receiving layer, surface modification treatment is also preferably performed. As the surface modification treatment, known surface modification treatments selected from corona discharge treatment, plasma treatment, and flame treatment are preferred. It is generally known that the effect of the surface modification treatment decreases over time. For this reason, it is preferable to perform the surface modification treatment process and the inkjet recording process consecutively, and it is preferable to perform the surface modification treatment process immediately before the inkjet recording process.

[0055] When recording on a recording medium using the inkjet recording method described above, for example, a container containing the above-described ink can be set in a predetermined position on an inkjet printer, and the data can be recorded on the recording medium using the above-described recording method. The above inkjet recording method can also be used in combination with the ink of the present invention and, if necessary, with inks of various colors such as green, blue (or violet), and red (or orange). Each color of ink is poured into its respective container, and each container can be loaded into a designated position in an inkjet printer, similar to the containers containing the aforementioned inks, and used for inkjet recording. Industrial inkjet printers, in order to achieve high printing speeds, often utilize a line-head type inkjet printer configuration, and single-pass printing is also preferred. Furthermore, in recent years, circulating heads, which have a mechanism to prevent ink drying near the nozzles by circulating the ink to the vicinity of the nozzles, have been actively developed. The above-mentioned ink is also suitable for use with such heads. With the above-mentioned ink, it is possible to obtain an ink that exhibits excellent solid filling, suppression of satellite formation, and storage stability even under such printing conditions. The present invention also includes an inkjet recording method in which droplets of inkjet ink are ejected from an inkjet head and recorded on a recording medium, an inkjet recording method in which the recording medium is poorly absorbent or non-absorbent, and an inkjet recording method in which the inkjet head is equipped with a circulation mechanism.

[0056] Of the ingredients listed above, only one type may be used. Furthermore, multiple types may be selected and used in combination as needed. For all of the above, a combination of desirable elements is more desirable, and a combination of more desirable elements is even more desirable. The same applies to combinations of desirable elements and more desirable elements, and combinations of more desirable elements and even more desirable elements, etc.

[0057] The ink of the present invention exhibits excellent solid filling, suppression of satellite formation, storage stability, drying properties, resolubility, wettability, redispersibility, color development, and saturation. Furthermore, images recorded with the ink of the present invention exhibit excellent durability in various aspects, such as lightfastness, heat resistance, and resistance to oxidizing gases (e.g., ozone gas). In addition, it exhibits excellent sharp image formation with minimal coating unevenness during image formation. [Examples]

[0058] The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto. In this text, "parts" and "%" refer to mass unless otherwise specified. When it is necessary to quantify the pigment solids content in the dispersion, it was calculated as a converted value of only the pigment solids content using the dry weight method with MS-70 manufactured by A&D Co., Ltd.

[0059] [How to calculate HLB value] The HLB values ​​of the compounds were calculated according to the Griffin method (Griffin, WC.: Classification of surface active agents by HLB, J. Soc., Cosmet., Chem., 1, 1949). According to this method, 1,2-hexanediol has an HLB value of 5.8, Surfinol 485 has an HLB value of 17 (catalog value), Surfinol 440 has an HLB value of 13 (catalog value), and Surfinol 420 has an HLB value of 4 (catalog value).

[0060] [Method for calculating HLB value weighted average] The HLB-weighted average was calculated by weighting the HLB values ​​of each compound according to their respective addition amounts. For example, the HLB-weighted average for an ink containing 0.3 parts of Emulgen A60, 1 part of SF485, and 4 parts of 1,2-hexanediol is (12.8 × 0.3 + 17 × 1 + 5.8 × 4) / (0.3 + 1 + 4) = 8.3.

[0061] [Method for measuring particle size] For particle size measurement, a nanotrac WAVE II dynamic light scattering particle size distribution analyzer manufactured by Microtrac-Bell Co., Ltd. was used. The pigment concentration was adjusted with water so that it fell within the detection window, and then the measurement was performed.

[0062] [Method for measuring viscosity] Viscosity was measured at 35°C using an E-type viscometer "TV-25" (manufactured by Toki Sangyo Co., Ltd., using a standard cone rotor 1°34′×R24, rotation speed 50 rpm).

[0063] [Preparation Example]: Preparation of a colored dispersion A block copolymer (dispersant) was obtained by replicating Synthesis Example 3 of International Publication No. 2013 / 115071. The obtained block copolymer (6 parts) was dissolved in 20 parts methyl ethyl ketone to obtain a homogeneous solution. A mixture of sodium hydroxide (0.45 parts) dissolved in water (53.55 parts) was added to this solution, and then carbon black (Orion Engineered Carbons, Nerox 605) (20 parts) was added. The mixture was dispersed in a sand grinder at 1500 rpm for 15 hours to obtain a liquid. After adding water (100 parts) to the obtained liquid, aggregates and other contaminants were removed by filtration using glass filter paper GA-100 to obtain a filtrate. The obtained filtrate was subjected to vacuum distillation of the methyl ethyl ketone and a portion of the water using an evaporator, so that the pigment content in the filtrate was 12.0%, thereby obtaining a black dispersion.

[0064] [Preparation Example]: Ink Preparation Each ink for evaluation testing was obtained by mixing the components shown in Tables 1 and 2 below and then filtering them through a 3 μm membrane filter. Blank spaces indicate 0 copies.

[0065] The abbreviations in the table below have the following meanings. A60 (HLB: 12.8): Emulgen A60 (manufactured by Kao Corporation) SF485 (HLB: 17): Surfinol 485 (manufactured by Nisshin Chemical Industry Co., Ltd.) SF440 (HLB:13): Surfinol 440 (manufactured by Nisshin Chemical Industry Co., Ltd.) SF420 (HLB:4): Surfinol 420 (manufactured by Nisshin Chemical Industry Co., Ltd.) 12HD(HLB:5.8):1,2-Hexanediol (manufactured by Tokyo Chemical Industry Co., Ltd.) PG: Propylene glycol (manufactured by Tokyo Chemical Industry Co., Ltd.) TEA: Triethanolamine (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0066] [Table 1]

[0067] [Table 2]

[0068] [Inkjet recording] Tone-gradation printing was performed in 5% increments using the aqueous ink compositions of each example and comparative example to obtain printed images. Printing was performed using a printing jig equipped with a 1200 dpi inkjet head manufactured by Kyocera Corporation, under the conditions of a frequency of 20 kHz, tri-level settings, and a print gap of 1 mm. The printing medium used was "OK Topcoat+" manufactured by Oji Paper Co., Ltd. Test pieces were obtained by drying the obtained printed images in a constant temperature bath set to 70°C for 2 minutes.

[0069] [Evaluation of fullness] The 100% concentration portion of the obtained test specimens was evaluated visually using a five-level scale from A+ to D. The evaluation results are shown in Tables 3 and 4 below. A+, A, and B indicate a good evaluation, while C and D indicate a poor evaluation. —Evaluation Criteria— A+: Fewer than 10 white streaks A: The solid areas are not completely filled in, but there are about 10 to 30 white streaks. B: There are more than 30 white streaks, but they are not very noticeable. C: White streaks are noticeable in the solid areas. D: The white streaks in the solid areas are unusually prominent.

[0070] [Satellite Evaluation] For the 5% concentration portion of the obtained test specimens, the number of dots with a Boxratio of 0.9 or higher and 1.1 or lower was counted using the PIAS-II print image evaluation system manufactured by QEA. The evaluation results are shown in Tables 3 and 4 below. A+, A, and B indicate good evaluation, while C and D indicate poor evaluation. —Evaluation Criteria— A+: Count exceeds 100 A: The count is 50 or more, and less than 100. B: The count is less than 50, but no dispensing is observed. C: The count is less than 50, and partial droplets are observed. D: The count is less than 50, and most of the dots are droplets.

[0071] [Storage stability evaluation] The D50 particle size and viscosity at 35°C of the resin-dispersed pigments in each water-based ink, stored at 60°C for two weeks, were measured and compared with the values ​​at the time of preparation. The evaluation results are shown in Tables 3-4 below. A+, A, and B indicate a good evaluation, while C and D indicate a poor evaluation. —Evaluation Criteria— A+: Change rate is less than 5% A: Rate of change is 5% or more, but less than 10%. B: Rate of change is 10% or more, but less than 15% C: Rate of change is 15% or more, but less than 20%. D: Change rate of 20% or more

[0072] [Table 3]

[0073] [Table 4]

[0074] The results shown in Tables 3-4 indicate that the aqueous ink compositions in the examples exhibit good solid coverage, satellite formation suppression, and storage stability. In other words, the inks in the examples are excellent aqueous ink compositions that combine solid coverage, suppression of satellite formation, and storage stability. [Industrial applicability]

[0075] The ink of the present invention possesses excellent solid filling, suppression of satellite formation, and storage stability, making it extremely useful as a water-based ink composition for various recording applications, particularly for inkjet recording.

Claims

1. This is an aqueous ink composition containing a pigment, a nonionic surfactant, a penetrant, and a water-soluble organic solvent (excluding those with a ClogP value greater than 0 and less than or equal to 2). The nonionic surfactant comprises at least one acetylene glycol-based surfactant and at least one polyoxyethylene styrene-phenyl ether-based surfactant. A water-based ink composition in which the weighted average HLB values ​​of the penetrating agent and the nonionic surfactant are in the range of 5.8 to 9.

7.

2. The aqueous ink composition according to claim 1, wherein the content of the penetrating agent is more than 3.0% by mass and 5.0% by mass or less with respect to the total amount of ink.

3. The aqueous ink composition according to claim 1, wherein the weighted average HLB values ​​of the nonionic surfactant and the penetrating agent are in the range of 7.0 to 8.

6.

4. The aqueous ink composition according to claim 1, wherein the total content of the nonionic surfactant is 0.8% by mass or more and 2.3% by mass or less based on the total amount of ink.

5. The aqueous ink composition according to claim 1, wherein the weight ratio (A / B) of the polyoxyethylene styrene-phenyl ether surfactant (A) to the acetylene glycol surfactant (B) in the nonionic surfactant is 0.15 or more and 0.7 or less.

6. An inkjet recording method for recording ink droplets of inkjet ink according to claim 1 or 2 onto a recording medium by ejecting them from an inkjet head.

7. The inkjet recording method according to claim 6, wherein the inkjet head is a head equipped with a circulation mechanism.

8. A printing medium printed using the inkjet ink described in claim 1 or 2, or the inkjet ink set described in claim 9.

Images