Inkjet ink composition and recording method

Abstract

To provide an ink jet ink composition that gives a recorded material having a high color development property while having excellent ejection stability.SOLUTION: An ink jet ink composition includes a color material having a ligand, an inorganic compound, and a pH adjuster, and the color material forms a complex with the inorganic compound through the ligand.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an inkjet ink composition and a recording method.

Background Art

[0002] The inkjet recording method can record high-definition images with a relatively simple device and has been rapidly developing in various fields. Among them, various studies have been made on obtaining more stable and high-quality recordings.

[0003] For example, Patent Document 1 discloses a dye solution and a mordant solution for vegetable dyeing that can be stably ejected by the inkjet method. These dye solution and mordant solution are ejected by the inkjet method and supplied to the same location of a cellulose-based carrier to dye by causing deposition, immobilization, and color development of the pigment. Further, the dye solution contains water as the main solvent, alcohol for adjusting the drying rate, and pigment molecules extracted from natural products, has a surface tension of 20 mN / m or more and 75 mN / m or less, and a viscosity of 0.5 mPa·s or more and 40 mPa·s or less. On the other hand, the mordant solution contains polyvalent metal ions for forming a complex with pigment molecules extracted from natural products, water as the main solvent, and alcohol as a solvent for adjusting the drying rate, has a surface tension of 20 mN / m or more and 75 mN / m or less, and a viscosity of 0.5 mPa·s or more and 40 mPa·s or less.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, since the dye solution and the mordant solution described in Patent Document 1 are separate, they are complicated. Therefore, there has been a demand for an inkjet ink composition that is excellent in color developability and has good ejection stability without adopting the complicated configuration of separately preparing the dye solution and the mordant solution.

Means for Solving the Problems

[0006] As a result of intensive studies to solve the above problems, the present inventors have found that by using an inkjet ink composition containing a colorant having a ligand, an inorganic compound, and a pH adjuster, and the colorant forms a complex with the inorganic compound by the ligand, while solving the above problems, it is excellent in various properties in an ink composition for recording by an inkjet method, and thus completed the present invention.

[0007] That is, the present invention is an inkjet ink composition containing a colorant having a ligand, an inorganic compound, and a pH adjuster, and the colorant forms a complex with the inorganic compound by the ligand.

Modes for Carrying Out the Invention

[0008] Hereinafter, modes for carrying out the present invention (hereinafter referred to as "the present embodiment") will be described in detail. The following present embodiment is an exemplification for explaining the present invention, and is not intended to limit the present invention to the following contents. The present invention can be appropriately modified and implemented within the scope of its gist.

[0009] Inkjet Ink Composition The inkjet ink composition of the present embodiment (hereinafter, also simply referred to as "ink composition") contains a coloring material having a ligand, an inorganic compound, and a pH adjuster. Further, the coloring material forms a complex with the inorganic compound by the above ligand. The reasons why the ink composition of the present embodiment is excellent in various characteristics in the ink composition for recording by the inkjet method are considered as follows. However, the reasons are not limited to this. That is, in the case of a conventional ink composition, especially when it contains a natural pigment as a coloring material, the color development property of the obtained recording may not be sufficiently obtained due to insufficient chemical structure stability. Also, there may be cases where the ejection stability is not excellent. On the other hand, in the ink composition of the present embodiment, the ligand contained in the coloring material coordinates with the inorganic compound to form a complex, and since the chemical structure of the coloring material is stable, an ink composition excellent in the color development property of the obtained recording can be obtained. Furthermore, since the chemical structure of the coloring material is stable, the ink composition of the present embodiment is excellent not only in color development property but also in reliability other than that and in ejection stability.

[0010] In this specification, the "inkjet ink composition" means an ink composition for recording (printing) on a recording medium using the inkjet method. The "recording" means an object in which an ink composition is recorded on a recording medium to form an image.

[0011] Coloring material having a ligand The ink composition of the present embodiment contains a coloring material having a ligand. In this specification, the "coloring material having a ligand" means a coloring material that forms a complex with an inorganic compound by the ligand and imparts color development property to the recording.

[0012] The type of the coloring material having a ligand is not particularly limited, and examples thereof include coloring materials derived from natural products and chemically synthesized coloring materials. The coloring material of the present embodiment can be appropriately selected from these various coloring materials having a ligand and used, but it is preferably included a coloring material derived from a natural product.

[0013] The coloring materials derived from natural substances are not particularly limited. For example, anthraquinone-based coloring materials such as cochineal (carminic acid, ligands: OH (hydroxo), C=O (carbonyl)), lac (laccaic acid, ligands: OH (hydroxo), C=O (carbonyl)), flavonoid compounds such as safflower red (carthamin, ligands: OH (hydroxo), C=O (carbonyl)), iridoid glycosides such as gardenia red, grape peel (malvidin-3-glucoside, ligands: OH (hydroxo), OCH3 (methoxy)), anthocyanin-based coloring materials such as butterfly pea (pelargonidin, cyanidin, delphinidin, ligands: OH (hydroxo), O (oxocation)), and turmeric-based coloring materials such as curcumin (ligands: OH (hydroxo), OCH3 (methoxy), C=O (carbonyl)) can be mentioned. Among these, cochineal and curcumin are preferred.

[0014] The coloring materials having ligands may be used alone or in combination of two or more. The coloring materials having ligands are preferably 1.0 to 15% by mass, more preferably 2.0 to 10.0% by mass, and even more preferably 3.0 to 8.0% by mass based on the total amount of the ink composition. When the content of the coloring material having ligands is within the above range, the color development property of the recording material is excellent and the ejection stability tends to be better.

[0015] The ink composition of this embodiment can contain coloring materials other than the coloring materials having ligands (for example, pigments and dyes).

[0016] By including a coloring material that forms a complex with an inorganic compound by a ligand, the ink composition of this embodiment exhibits excellent color development properties applicable to various inks such as white ink, black ink, yellow ink, magenta ink, cyan ink, and further special inks such as violet ink, brown ink, orange ink, red ink, green ink, etc.

[0017] Inorganic compound The ink composition of the present embodiment contains an inorganic compound that forms a complex with a ligand of a coloring material. In this specification, the "inorganic compound" means a compound containing a metal.

[0018] The type of the inorganic compound is not particularly limited, and examples thereof include salts that ionize in water to form metal ions or ions containing a metal. As the inorganic compound of the present embodiment, various inorganic compounds that form a complex with a ligand of a coloring material can be appropriately selected and used from among these. However, in the ink composition, it is preferable that the inorganic compound contains an oxonium ion of a metal or a metal ion.

[0019] Specific examples of the above metal include metals of Group 13 such as aluminum, including metals of Group 8 such as iron, or metals of Group 11 such as copper, silver, and gold, and metals of Group 14 such as tin and lead. When the metal is a metal of Group 13 or Group 14, it is preferable that the inorganic compound contains sodium stannate and aluminum potassium sulfate. When the metal is a metal of Group 8 or Group 11, it is preferable that the inorganic compound contains copper(II) sulfate or iron(II) sulfate.

[0020] The inorganic compound may be used alone or in combination of two or more. The inorganic compound is preferably 0.001 to 5.0% by mass, more preferably 0.01 to 1.0% by mass, and still more preferably 0.05 to 0.2% by mass based on the total amount of the ink composition. When the content of the inorganic compound is within the above range, the color developability of the recorded matter is excellent, and the ejection stability tends to be better.

[0021] The inorganic compound may be used alone or in combination of two or more. The inorganic compound is preferably 0.001 to 5.0% by mass, more preferably 0.01 to 1.0% by mass, and still more preferably 0.05 to 0.2% by mass based on the total amount of the ink composition. When the content of the inorganic compound is within the above range, the color developability of the recorded matter is excellent, and the ejection stability tends to be better.

[0022] The content ratio of the dye having a ligand for the inorganic compound (dye / inorganic compound) is preferably 5 to 200, more preferably 20 to 120, and even more preferably 40 to 80 on a mass basis. By the content ratio being within the above range, the color developability of the recording material is excellent, and the ejection stability tends to be better.

[0023] pH adjuster The ink composition of the present embodiment contains a pH adjuster for adjusting the pH of the ink composition. By including a pH adjuster, it promotes the formation of a complex between the ligand of the coloring material and the inorganic compound, and the recording material has excellent color developability and better ejection stability.

[0024] The type of the pH adjuster is not particularly limited, and examples thereof include acids such as citric acid and acetic acid, and bases such as triethanolamine. The pH adjuster of the present embodiment can be appropriately selected from these various pH adjusters that promote the formation of a complex between the ligand of the coloring material and the inorganic compound and used.

[0025] When the metal in the inorganic compound is a Group 13 or Group 14 metal, the pH adjuster preferably contains triethanolamine or citric acid. When the metal is a Group 8 or Group 11 metal, the pH adjuster preferably contains acetic acid.

[0026] The pH of the ink composition is not particularly limited, but when the metal in the inorganic compound is a Group 13 or Group 14 metal, it is preferably 6.0 to 10.0, more preferably 6.5 to 9.5, and even more preferably 7.0 to 9.0. When the metal in the inorganic compound is a Group 8 or Group 11 metal, the pH of the ink composition is preferably 3.0 to 7.0, more preferably 3.5 to 6.0, and even more preferably 4.0 to 5.0. By the pH of the ink composition being within the above range, the color developability of the recording material is excellent, and the ejection stability tends to be better.

[0027] Water-soluble organic solvent The ink composition of this embodiment preferably contains a water-soluble organic solvent. As used herein, "water-soluble" means the property of being able to be used together with water and at least a part of it being dissolved in water.

[0028] The type of the water-soluble organic solvent is not particularly limited, and examples thereof include monoalcohols, alkyl polyols, glycol ethers, cyclic nitrogen compounds, and aprotic polar solvents. The organic solvent of this embodiment can appropriately select and use various water-soluble organic solvents from among these organic solvents, but preferably contains an alkyl polyol.

[0029] The monoalcohol is not particularly limited, and examples thereof include methanol, ethanol, n-propyl alcohol, iso-propyl alcohol, n-butanol, 2-butanol, tert-butanol, iso-butanol, n-pentanol, 2-pentanol, 3-pentanol, and tert-pentanol.

[0030] The alkyl polyol is not particularly limited, and examples thereof include glycerin, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol (1,2-propanediol), dipropylene glycol, 1,3-propylene glycol (1,3-propanediol), isobutylene glycol (2-methyl-1,2-propanediol), 1,2-butanediol, 1,3-butylene glycol (1,3-butanediol), 1,4-butanediol, 2-butene-1,4-diol, 1,2-pentanediol, 1,5-pentanediol, 2-methyl-2,4-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 2-ethyl-1,3-hexanediol, 1,7-heptanediol, and 1,8-octanediol. Among these, glycerin and 1,3-butylene glycol are preferred.

[0031] The glycol ethers are not particularly limited. For example, diethylene glycol mono-n-propyl ether, ethylene glycol mono-iso-propyl ether, diethylene glycol mono-iso-propyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol mono-t-butyl ether, diethylene glycol mono-n-butyl ether, triethylene glycol monobutyl ether, diethylene glycol mono-t-butyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-t-butyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-iso-propyl ether, propylene glycol mono-n-butyl ether, dipropylene glycol mono-n-butyl ether, dipropylene glycol mono-n-propyl ether, and dipropylene glycol mono-iso-propyl ether can be mentioned.

[0032] The aprotic polar solvents are not particularly limited. For example, cyclic ketone compounds, chain ketone compounds, and chain nitrogen compounds can be mentioned. Further, as the cyclic nitrogen compounds and aprotic polar solvents, solvents such as pyrrolidones, imidazolidinones, sulfoxides, lactones, amide ethers, and imidazoles can be mentioned as typical examples. The pyrrolidones are not particularly limited as long as they have a pyrrolidone skeleton. For example, 2-pyrrolidone, N-alkyl-2-pyrrolidone, and 1-alkyl-2-pyrrolidone can be mentioned. Examples of the imidazolidinones include 1,3-dimethyl-2-imidazolidinone. Examples of the sulfoxides include dimethyl sulfoxide. Examples of the lactones include γ-butyrolactone. Examples of the imidazoles include imidazole, 1-methylimidazole, 2-methylimidazole, and 1,2-dimethylimidazole.

[0033] The water-soluble organic solvent may be used alone or in combination of two or more. The content of the water-soluble organic solvent is preferably 1.0 to 70% by mass, more preferably 5.0 to 50% by mass, and still more preferably 10 to 30% by mass with respect to the total amount of the ink composition. When the content of the water-soluble organic solvent is within the above range, the ejection stability tends to be better.

[0034] Surfactant The ink composition preferably contains a surfactant. In the present specification, the "surfactant" means a substance that promotes the penetration of the ink composition into the recording medium.

[0035] The surfactant is not particularly limited, and examples thereof include acetylene glycol-based surfactants, alkyl ether-based surfactants, fluorine-based surfactants, and silicone-based surfactants.

[0036] The acetylene glycol-based surfactant is not particularly limited, and one or more selected from 2,4,7,9-tetramethyl-5-decyne-4,7-diol and alkylene oxide adducts of 2,4,7,9-tetramethyl-5-decyne-4,7-diol, and 2,4-dimethyl-5-decyne-4-ol and alkylene oxide adducts of 2,4-dimethyl-5-decyne-4-ol are preferred. Commercially available products of acetylene glycol-based surfactants are not particularly limited, and examples thereof include Olfin E1010, PD-002W, PD-005, EXP4200, EXP4300, WE-003, etc. (trade names, manufactured by Nissin Chemical Industry Co., Ltd.), Surfynol 104E, 104PG50, 420, 465, 485, 61, 82, DF110D, DF37, DF75, MD-20, etc. (trade names, manufactured by Evonik Industries AG).

[0037] As the alkyl ether surfactant, although not particularly limited, one or more selected from polyoxyethylene 2-ethylhexyl ether, polyoxyethylene oleyl ether, polyoxyethylene tridecyl ether, polyoxyethylene castor oil ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene alkyl ether, and polyoxyalkylene tridecyl ether are preferred. As commercially available products of alkyl ether surfactants, although not particularly limited, for example, Newcol 1006, 1008, 1020 (trade names of products manufactured by Nippon Emulsion Co., Ltd.), Neugen DL-0415, ET-116B, ET-106A, DH-0300, YX-400, EA-160 (trade names of products manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), Emulgen 430, 1108 (trade names of products manufactured by Kao Corporation) can be mentioned.

[0038] As the fluorosurfactant, although not particularly limited, for example, perfluoroalkyl sulfonate, perfluoroalkyl carboxylate, perfluoroalkyl phosphate ester, perfluoroalkyl ethylene oxide adduct, perfluoroalkyl betaine, and perfluoroalkyl amine oxide compound can be mentioned. As commercially available products of fluorosurfactants, although not particularly limited, for example, S-144, S-145 (above trade names, manufactured by Asahi Glass Co., Ltd.); FC-170C, FC-430, Fluorad-FC4430 (above trade names, manufactured by Sumitomo 3M Limited); FSO, FSO-100, FSN, FSN-100, FS-300 (above trade names, manufactured by Dupont); FT-250, 251 (above trade names, manufactured by Neos Co., Ltd.) can be mentioned.

[0039] The silicone-based surfactant is not particularly limited, and examples thereof include polysiloxane-based compounds and polyether-modified organosiloxanes. Commercially available products of silicone-based surfactants are not particularly limited, and specifically include SAG503A (trade name, manufactured by Nissin Chemical Industry Co., Ltd.), BYK-306, BYK-307, BYK-333, BYK-341, BYK-345, BYK-346, BYK-347, BYK-348, BYK-349 (the above trade names, manufactured by BYK-Chemie), KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-945, KF-640, KF-642, KF-643, KF-6020, X-22-4515, KF-6011, KF-6012, KF-6015, KF-6017 (the above trade names, manufactured by Shin-Etsu Chemical Co., Ltd.), etc.

[0040] Among the above-mentioned surfactants, acetylene glycol-based surfactants are preferred.

[0041] The surfactant may be used alone or in combination of two or more. The content of the surfactant is preferably 0.05 to 2.5% by mass, more preferably 0.1 to 1.5% by mass, and still more preferably 0.3 to 1.0% by mass based on the total amount of the ink composition. When the content of the surfactant is within the above range, the ejection stability tends to be better.

[0042] Water The ink composition of this embodiment contains water. Examples of water include pure water such as ion-exchanged water, ultrafiltration water, reverse osmosis permeated water, and distilled water, and those with ionic impurities removed as much as possible such as ultrapure water. Also, when using water sterilized by ultraviolet irradiation or addition of hydrogen peroxide, etc., the generation of mold and bacteria can be prevented when storing the condensate for a long time. Thereby, the storage stability tends to be further improved.

[0043] The water content is preferably 10 to 95% by mass, more preferably 40 to 90% by mass, and still more preferably 60 to 85% by mass with respect to the total amount of the ink composition. When the water content is within the above range, the ejection stability tends to be better.

[0044] The ink composition can also appropriately contain various additives such as a dispersant for a coloring material, resin particles, a dissolution aid, a viscosity modifier, an antioxidant, a fungicide and preservative, a mildew-proof agent, a corrosion inhibitor, etc. as components other than the above-described components.

[0045] Recording method The recording method of this embodiment includes a step of attaching the above-described ink composition onto a recording medium (hereinafter referred to as the "attachment step"). In the attachment step, more specifically, the ink composition is ejected onto the recording medium by an inkjet method to obtain a recorded matter. Examples of this recording medium include an absorbent recording medium or a non-absorbent recording medium. The recording method of this embodiment can be widely applied to recording media having various absorption performances, from a non-absorbent recording medium in which penetration of a water-soluble ink composition is difficult to an absorbent recording medium in which penetration of a water-soluble ink composition is easy, but it is preferably applied to an absorbent recording medium.

[0046] Specific examples of the absorbent recording medium include plain paper such as electrophotographic paper with high ink permeability, inkjet paper (inkjet dedicated paper provided with an ink absorption layer composed of silica particles or alumina particles, or an ink absorption layer composed of a hydrophilic polymer such as polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP)), art paper, coated paper, and cast paper used for general offset printing with relatively low ink permeability.

[0047] As non-absorbent recording media, specifically, films and plates of plastics such as polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate (PET), plates of metals such as iron, silver, copper, aluminum, and metal plates and plastic films manufactured by vapor deposition of these various metals, plates of alloys such as stainless steel and cast iron can be mentioned.

[0048] This embodiment may include a heating step of heating the recording medium before recording, during recording, a part of after recording, and all in order to promote drying of the ink composition. As a means for heating, there is no particular limitation as long as it is a device whose temperature can be controlled, and examples include a radiation heating type sheathed heater, an infrared heater, a contact heating type sheet heater, and a method using electromagnetic waves. The heating temperature is preferably 40 to 80°C as the surface temperature of the recording medium to be recorded. Further, a blowing step by a fan or the like may be further included.

[0049] The recording method of this embodiment may include known steps of a conventional inkjet recording method in addition to the above steps.

Examples

[0050] Hereinafter, the present embodiment will be described more specifically with reference to examples and comparative examples, but the present embodiment is not limited by the following examples and comparative examples as long as the gist thereof is not exceeded.

[0051] The materials used in the ink composition in the following examples and comparative examples are as follows. 〔Colorant〕 Cochineal (natural pigment, ligands: OH (hydroxy), C=O (carbonyl), "Carmine Red DX" manufactured by Kiriya Chemical Co., Ltd.) Curcumin (natural pigment, ligands: OH (hydroxy), OCH3 (methoxy), C=O (carbonyl), curcumin raw powder manufactured by Kiriya Chemical Co., Ltd., abbreviated as "curcumin" in the table.) Beni-koji red (natural pigment, no ligand, "Monascus Red AL" manufactured by Kiriya Chemical Co., Ltd.) Yellow No. 4 (synthetic pigment, no ligand, manufactured by Kiriya Chemical Co., Ltd.) [Inorganic compound] Sodium stannate (oxonium ion of a Group 14 metal, sodium stannate trihydrate, CAS RN: 12209-98-2, manufactured by Fujifilm Wako Pure Chemical Corporation, denoted as "Na stannate" in the table.) Potassium aluminum sulfate (metal cation of a Group 13 metal, potassium aluminum sulfate dodecahydrate, CAS RN: 7784-24-9, manufactured by Fujifilm Wako Pure Chemical Corporation, denoted as "KAl sulfate" in the table.) Copper(II) sulfate (metal cation of Group 11, iron(II) sulfate heptahydrate, CAS RN: 7782-63-0, manufactured by Fujifilm Wako Pure Chemical Corporation) Iron(II) sulfate (metal cation of Group 8, copper(II) sulfate pentahydrate, CAS RN: 7758-99-8, manufactured by Fujifilm Wako Pure Chemical Corporation) [pH adjuster] Triethanolamine (abbreviated as "TEA" in the table.) Citrate buffer (citric acid - sodium citrate, abbreviated as "citric acid" in the table.) Acetate buffer (acetic acid - sodium acetate, abbreviated as "acetic acid" in the table.) [Water-soluble organic solvent] Glycerin 1,3-Butylene glycol [Surfactant] Orfin E1010 (trade name of Air Products) [Water] Pure water

[0052] [Preparation of ink composition] Each material was mixed in the composition shown in Table 1 below and stirred well to obtain each ink composition. In Table 1 below, the numerical values represent the solid content, the unit is mass%, and the total is 100.0 mass%.

[0053] [Table 1]

[0054] [Color development (Abs.)] Each ink composition was diluted with water so that the colorant concentration became 0.001%, and measured in the range of 400 - 800 nm using a spectrophotometer ("U-39000H type" manufactured by Hitachi High-Tech Sciences Corporation). The color development property (Abs.) was evaluated according to the following evaluation criteria from the Abs. value of the maximum absorption wavelength in the range of 400 - 800 nm. (Evaluation Criteria) A: Abs. 0.8 or more B: Abs. 0.6 or more and less than 0.8 C: Abs. 0.4 or more and less than 0.6 D: Abs. less than 0.4

[0055] [Color Development Property (OD)] Using an inkjet recording apparatus ("PX-S840" manufactured by Seiko Epson Corporation), each ink composition was filled into the ink cartridge of the inkjet recording apparatus, and printed on plain woven cotton with A4 - 100% Duty solid printing. The OD of the printed matter was measured using a colorimeter ("FD-7" manufactured by Konica Minolta: fluorescence spectral densitometer), and the color development property (OD) was evaluated according to the following evaluation criteria. (Evaluation Criteria) A: OD 1.0 or more B: OD 0.8 or more and less than 1.0 C: OD 0.6 or more and less than 0.8 D: OD less than 0.6

[0056] [Discharge Stability] Using an inkjet recording apparatus ("PX-S840" manufactured by Seiko Epson Corporation), each ink composition was filled into the ink cartridge of the inkjet recording apparatus, and printed on plain paper with A4 - 100% Duty solid printing for 50 consecutive sheets. After printing, the discharge stability was evaluated according to the following evaluation criteria from the number of nozzles from which the ink composition was discharged. (Evaluation Criteria) AA: Less than 5 nozzles dropped A: 5 or more and less than 10 nozzles dropped B: 10 or more and less than 20 nozzles dropped C: 20 or more and less than 30 nozzles dropped D: 30 or more nozzles dropped

[0057]

Table 2

Claims

1. A coloring material having a ligand, an inorganic compound, a pH adjuster, and comprising the coloring material forms a complex with the inorganic compound by the ligand, the coloring material is derived from a natural product and contains cochineal or curcumin, an inkjet ink composition.

2. The inkjet ink composition according to claim 1, wherein the inorganic compound contains a metal oxonium ion or a metal ion.

3. The inkjet ink composition according to claim 1 or 2, wherein the content ratio of the coloring material to the inorganic compound (coloring material / inorganic compound) is 20 to 120 on a mass basis.

4. A coloring material having a ligand, an inorganic compound, a pH adjuster, and comprising the inorganic compound contains sodium stannate or aluminum potassium sulfate, an inkjet ink composition.

5. The inkjet ink composition according to claim 4, wherein the pH adjuster contains triethanolamine or citric acid.

6. The inkjet ink composition according to claim 4 or 5, wherein the pH is 6.5 to 9.

5.

7. A coloring material having a ligand, an inorganic compound, a pH adjuster, and comprising the inorganic compound contains a Group 8 or Group 11 metal, the pH adjuster contains acetic acid, an inkjet ink composition.

8. The inkjet ink composition according to claim 7, wherein the inorganic compound contains copper (II) sulfate or iron (II) sulfate.

9. The inkjet ink composition according to claim 7 or 8, wherein the pH is 4.0 to 5.

0.

10. A recording method comprising an attaching step of attaching the inkjet ink composition according to any one of claims 1 to 9 onto a recording medium. ​

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