Inkjet recording ink, inkjet recording ink container, inkjet recording device, image forming method, and image formed product

Abstract

To provide ink for inkjet recording which improves liquid dripping and discharge stability in horizontal discharge, and also has a color development property, an ink storage container for inkjet recording, an inkjet recording device, an image formation method, and an image formed object.SOLUTION: Ink for inkjet recording contains at least water, a pigment, a resin, and a water-soluble organic solvent, wherein a storage elastic modulus G' at 25°C when the ink for inkjet recording is concentrated so that a content of a solid content in the ink for inkjet recording is 10 mass% with respect to the total mass of ink is 0.50 Pa or more and 2.00 Pa or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to inkjet recording ink, inkjet recording ink container, inkjet recording apparatus, image forming method, and image formed product. [Background technology]

[0002] In recent years, inkjet printers have become remarkably popular due to their advantages such as low noise and low running costs, and color printers capable of printing on plain paper have also been actively introduced to the market. Accordingly, inks with multiple characteristics such as suppression of text smudging (feathering), color bleeding at color boundaries, and beading, as well as excellent image color reproduction, abrasion resistance, durability, lightfastness, image drying speed, double-sided printing capability, and ejection stability, are being selectively used depending on the application.

[0003] Ink used in inkjet recording methods generally contains a wetting agent consisting of a high-boiling point organic solvent. For example, inks containing organic solvents with high permeability to recording media have been proposed to suppress beading (see, for example, Patent Document 1), inks whose permeability to recording media is adjusted by controlling the viscosity of the ink by adjusting the organic solvent content (see, for example, Patent Document 2), and inks whose ink penetration rate into recording media is adjusted by the Bristow method (see, for example, Patent Document 3).

[0004] Furthermore, methods have been proposed to suppress beading by using inks containing glycol ethers or 1,2-alkanediols with 4 or more carbon atoms, thereby promoting the formation of a pseudo-crosslinked state between water-soluble resins and water-dispersible polymer particles during the evaporation, penetration, and diffusion processes after ink droplets have landed, and preventing the coalescence of ink droplets on the recording medium. (See, for example, Patent Document 4.) In addition, from the viewpoint of suppressing beading and obtaining good ink discharge performance, inks have been proposed in which the ratio of the storage modulus G' to the loss modulus G'' (G' / G'') and the absorption coefficient for low-permeability recording media according to the Bristow method are defined. (See, for example, Patent Document 5.) [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The present invention aims to provide an inkjet recording ink, an inkjet recording ink container, an inkjet recording apparatus, an image forming method, and an image formed product that improve liquid dripping and ejection stability during horizontal ejection, while also possessing excellent color development properties. [Means for solving the problem]

[0006] The inkjet recording ink of the present invention, as a means for solving the aforementioned problems, An inkjet recording ink comprising at least water, pigment, resin, and a water-soluble organic solvent, The inkjet recording ink is characterized in that, when the inkjet recording ink is concentrated so that the solid content is 10% by mass of the total ink mass, the storage modulus G' at 25°C is 0.50 Pa or more and 2.00 Pa or less. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an inkjet recording ink, an inkjet recording ink container, an inkjet recording apparatus, an image forming method, and an image formed product that improve liquid dripping and ejection stability during horizontal ejection, while also possessing color development properties. [Brief explanation of the drawing]

[0008] [Figure 1a] Figure 1a is an overall schematic side view of a liquid dispensing device according to one embodiment of the present invention. [Figure 1b] Figure 1b is an overall schematic plan view of a liquid dispensing device according to one embodiment of the present invention. [Modes for carrying out the invention]

[0009] (Inkjet recording ink) The inkjet recording ink of the present invention comprises at least water, a pigment, a resin, and a water-soluble organic solvent, wherein the storage modulus G' at 25°C when the inkjet recording ink is concentrated so that the solid content in the inkjet recording ink is 10% by mass of the total mass of the ink is 0.50 Pa or more and 2.00 Pa or less, and further comprises other components as necessary. In this invention, "inkjet recording ink" may be referred to simply as "ink."

[0010] Inkjet inks generally contain organic solvents with high boiling points, but depending on the amount of organic solvent used and the type of recording medium, problems such as beading and bleeding can occur. Furthermore, conventional inkjet recording inks were not sufficient in suppressing ink dripping that occurred when the ink was ejected horizontally, nor in ensuring good ejection stability.

[0011] As a result of diligent research, the inventors have found an inkjet recording ink containing at least water, pigment, resin, and a water-soluble organic solvent, wherein when the inkjet recording ink is concentrated so that the solid content is 10% by mass of the total ink mass, the storage modulus G' at 25°C is 0.50 Pa or more and 2.00 Pa or less, thereby suppressing dripping even when ejected horizontally, exhibiting sufficient ejection stability, and possessing color development properties.

[0012] Therefore, in the present invention, an inkjet recording ink comprising at least water, pigment, resin, and water-soluble organic solvent is provided, wherein the storage modulus G' at 25°C when the inkjet recording ink is concentrated so that the solid content in the inkjet recording ink is 10% by mass of the total mass of the ink is 0.50 Pa or more and 2.00 Pa or less, thereby improving liquid dripping and ejection stability during horizontal ejection, and also providing good color development.

[0013] [Pigments] The ink of the present invention contains a pigment. There are no particular restrictions on the aforementioned pigments, and they can be appropriately selected according to the purpose. Examples include yellow pigment, magenta pigment, cyan pigment, and black pigment.

[0014] Examples of the following examples of the yellow pigments include CI Pigment Yellow 1, CI Pigment Yellow 2, CI Pigment Yellow 3, CI Pigment Yellow 12, CI Pigment Yellow 13, CI Pigment Yellow 14, CI Pigment Yellow 16, CI Pigment Yellow 17, CI Pigment Yellow 73, CI Pigment Yellow 74, CI Pigment Yellow 75, CI Pigment Yellow 83, CI Pigment Yellow 93, CI Pigment Yellow 95, CI Pigment Yellow 97, CI Pigment Yellow 98, CI Pigment Yellow 110, CI Pigment Yellow 114, CI Pigment Yellow 120, CI Pigment Yellow 128, CI Pigment Yellow 129, CI Pigment Yellow 138, CI Pigment Yellow 150, CI Pigment Yellow 151, CI Pigment Yellow 154, CI Pigment Yellow 155, CI Pigment Yellow 180, and the like.

[0015] Specific examples of the aforementioned magenta pigments include CI Pigment Red 5, CI Pigment Red 7, CI Pigment Red 12, CI Pigment Red 18, CI Pigment Red 48(Ca), CI Pigment Red 48(Mn), CI Pigment Red 57(Ca), CI Pigment Red 57:1, CI Pigment Red 112, CI Pigment Red 122, CI Pigment Red 123, CI Pigment Red 168, CI Pigment Red 202, and CI Pigment Violet 19.

[0016] Specific examples of the aforementioned cyan pigments include CI Pigment Blue 1, CI Pigment Blue 2, CI Pigment Blue 3, CI Pigment Blue 15, CI Pigment Blue 15:3, CI Pigment Blue 15:4, CI Pigment Blue 16, CI Pigment Blue 22, CI Pigment Blue 60, CI Bat Blue 4, and CI Bat Blue 60.

[0017] Examples of the black pigment include carbon black (C.I. Pigment Black 7). As the carbon black, either appropriately synthesized carbon black or commercially available carbon black may be used. Examples of commercially available carbon black include #10, #20, #30, #33, #40, #44, #45, #45L, #95, #900, #1000, #2300, #2350, #2650, #4000B, MA8, MA11, MA77, MA100, MA220, MA230 (manufactured by Mitsubishi Chemical Corporation); Monarch 120, Monarch 700, Monarch 800, Monarch 880, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400, Mogul L, Regal 99R, Regal 250R, Regal 300R, Regal 330R, Regal 400R, Regal 500R, Regal 660R (manufactured by Cabot Corporation); Nipex 150, Printex A, Printex G, Printex U, Printex V, Printex 55, Printex 140U, Printex 140V, Special Black 4, Special Black 4A, Special Black 5, Special Black 6, Special Black 100, Special Black 250, Color Black FW1, Color Black FW2, Color Black FW2V, Color Black FW18, Color Black FW200, Color Black S150, Color Black S160, Color Black S170 (manufactured by Degussa Corporation), etc.

[0018] Among the above pigments, it is preferable to use a combination of C.I. Pigment Yellow 110 as the yellow pigment, C.I. Pigment Red 122 as the magenta pigment, C.I. Pigment Blue 15:3 as the cyan pigment, and C.I. Pigment Black 7 as the black pigment. By combining these pigments, an ink can be obtained that exhibits weather resistance, rub resistance, color development property, high chroma, and color reproducibility in the high-brightness red region, and furthermore, an ink in which clogging of the ink in the inkjet head hardly occurs can be obtained.

[0019] As the content of the pigment, from the viewpoint of obtaining a desired viscosity, it is preferably 1% by mass to 30% by mass, more preferably 7% by mass to 17% by mass, based on the total mass of the ink.

[0020] [Resin] The ink of the present invention contains a resin. There is no particular limitation on the resin, and it can be appropriately selected according to the purpose. For example, urethane resin, polyester resin, acrylic resin, vinyl acetate resin, styrene resin, butadiene resin, styrene-butadiene resin, vinyl chloride resin, styrene-acrylic resin, acrylic-silicone resin, etc. can be mentioned. Among these, from the viewpoint of obtaining a desired storage elastic modulus G', a thermoplastic resin is preferable, and a urethane resin and a styrene-acrylic resin are more preferable. Also, resin particles composed of these resins may be used.

[0021] The ink of the present invention can be obtained by mixing materials such as a pigment and an organic solvent described later in a state of a resin emulsion in which the resin particles are dispersed with water as a dispersion medium. As the resin particles, those synthesized appropriately may be used, or commercially available products may be used. The resin particles may be used alone or in combination of two or more kinds of resin particles.

[0022] There is no particular limitation on the volume average particle diameter of the resin particles, and it can be appropriately selected according to the purpose. However, from the viewpoint of obtaining good fixing property and high image hardness, it is preferably 10 nm to 1,000 nm, more preferably 10 nm to 200 nm, and particularly preferably 10 nm to 100 nm. The volume average particle diameter can be measured, for example, using a particle size analyzer (NanoTrack Wave-UT151; manufactured by Microtrac Bell Corporation).

[0023] As for the resin content, from the viewpoint of fixability, ink storage stability, and obtaining a desired storage modulus G', it is preferably 1% to 30% by mass, more preferably 5% to 20% by mass, and even more preferably 7% to 15% by mass, based on the total mass of the ink.

[0024] [Water-soluble organic solvents] The ink of the present invention contains a water-soluble organic solvent. The aforementioned water-soluble organic solvent is not particularly limited and can be appropriately selected depending on the purpose. Examples include polyhydric alcohols, ethers such as polyhydric alcohol alkyl ethers and polyhydric alcohol aryl ethers, nitrogen-containing heterocyclic compounds, amides, amines, and sulfur-containing compounds.

[0025] As the aforementioned water-soluble organic solvent, it is preferable to use a water-soluble organic solvent with a boiling point of 250°C or lower, from the viewpoint of not only functioning as a wetting agent but also obtaining good drying properties. As the aforementioned water-soluble organic solvent, from the viewpoint of improving quick-drying properties, saturated monohydric alcohols having 1 to 3 carbon atoms such as methyl alcohol, ethyl alcohol, n-propyl alcohol, and isopropyl alcohol can be suitably used. As the aforementioned water-soluble organic solvent, polyol compounds having 8 or more carbon atoms, glycol ether compounds, etc., can be suitably used from the viewpoint of improving ink permeability when paper is used as the recording medium.

[0026] Specific examples of the aforementioned water-soluble organic solvents include ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 3-methyl-1,3-butanediol, triethylene glycol, polyethylene glycol, polypropylene glycol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 2,4-pentanediol, 1,5-pentanediol, and 1,2-hexa Polyhydric alcohols such as diol, 1,6-hexanediol, 1,3-hexanediol, 2,5-hexanediol, 1,5-hexanediol, triethylene glycol, 1,2,6-hexanetriol, 2-ethyl-1,3-hexanediol, ethyl-1,2,4-butanetriol, 1,2,3-butanetriol, 2,2,4-trimethyl-1,3-pentanediol, petriol, etc.: ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, di Examples of polyhydric alcohol alkyl ethers include ethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, propylene glycol monoethyl ether, dipropylene glycol dimethyl ether, and diethylene glycol methyl ethyl ether; polyhydric alcohol aryl ethers include ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether; nitrogen-containing heterocyclic compounds include 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, ε-caprolactam, and γ-butyrolactone; amides include formamide, N-methylformamide, N,N-dimethylformamide, 3-methoxy-N,N-dimethylpropionamide, and 3-butoxy-N,N-dimethylpropionamide; amines include monoethanolamine, diethanolamine, and triethylamine; sulfur-containing compounds include dimethyl sulfoxide, sulfolane, and thiodiethanol; and propylene carbonate, ethylene carbonate, and ethanol.

[0027] From the viewpoint of obtaining an ink that exhibits good ink drying properties and ejection stability, the content of the water-soluble organic solvent is preferably 10% to 60% by mass, and more preferably 20% to 60% by mass, relative to the total mass of the ink.

[0028] [water] There are no particular restrictions on the water mentioned above, and it can be appropriately selected depending on the purpose. Examples include pure water such as ion-exchanged water, ultrafiltered water, reverse osmosis water, and distilled water, as well as ultrapure water.

[0029] [Other ingredients] Other components mentioned above include surfactants, dispersants, pH adjusters, preservatives and fungicides, rust inhibitors, antioxidants, UV absorbers, and corrosion inhibitors.

[0030] <Surfactants> The surfactant is not particularly limited and can be appropriately selected depending on the purpose. Examples include silicone-based surfactants, fluorine-based surfactants, acetylene glycol-based surfactants, nonionic surfactants, anionic surfactants, and amphoteric surfactants. These may be used individually or in combination of two or more.

[0031] -Silicone-based surfactants- The silicone-based surfactant is not particularly limited and can be appropriately selected depending on the purpose, but it is preferable that it does not decompose even at high pH (pH 10-11). Examples include side-chain modified polydimethylsiloxane, both-end modified polydimethylsiloxane, one-end modified polydimethylsiloxane, and both-end modified polydimethylsiloxane.

[0032] The side-chain modified polydimethylsiloxane, for example, is formed by introducing a modifying group into the Si side chain of a polydimethylsiloxane represented by the general formula (S-1). The aforementioned end-modified polydimethylsiloxane indicates, for example, the introduction of modifying groups at both ends of a polydimethylsiloxane represented by the general formula (S-1). The aforementioned one-ended modified polydimethylsiloxane indicates, for example, the introduction of a modifying group to one end of a polydimethylsiloxane represented by the general formula (S-1). The aforementioned side-chain end-modified polydimethylsiloxane indicates, for example, the introduction of modifying groups to the Si portion of the polydimethylsiloxane represented by the general formula (S-1) and to both ends.

[0033] [ka] General formula (S-1) (However, in general formula (S-1), m and n each represent an integer independently, and X represents a side chain.)

[0034] For example, the side-chain modified polydimethylsiloxane can be made into a polyether-modified silicone surfactant by introducing a polyalkylene oxide structure represented by general formula (S-2) to the Si side chain X of dimethylpolysiloxane represented by general formula (S-1).

[0035] [ka] General formula (S-2) (However, in general formula (S-2), a and b each represent independent integers, R represents an alkylene group, and R' represents an alkyl group.)

[0036] The modifying group is not particularly limited and can be appropriately selected depending on the purpose. Examples include a polyoxyethylene group, a polyoxyethylene polyoxypropylene group, and a polyalkylene oxide structure. Among these, the polyoxyethylene group and the polyoxyethylene polyoxypropylene group are preferred in that they exhibit low foaming properties and good wettability.

[0037] As the aforementioned silicone-based surfactant, a suitably synthesized one may be used, or a commercially available product may be used. Commercially available silicone-based surfactants include, for example, those from BIC Chemie Inc., Shin-Etsu Chemical Co., Ltd., Toray Dow Corning Silicone Co., Ltd., Nippon Emulsion Co., Ltd., and Kyoeisha Chemical Co., Ltd. As the polyether-modified silicone surfactant, commercially available products can be used, for example: KF-642, KF-643 (both from Shin-Etsu Chemical Co., Ltd.); DOWSIL FZ-2105, DOWSIL FZ-2154, DOWSIL FZ-2161, DOWSIL FZ-2162, DOWSIL FZ-2164 (all from Toray Dow Corning Silicone Co., Ltd.); TSF4440, TSF4452 (both from Momentive Performance Materials Japan LLC). These can be used individually or in combination of two or more types.

[0038] -Fluorine-based surfactants- The fluorine-based surfactant is not particularly limited and can be appropriately selected depending on the purpose. Examples include perfluoroalkyl phosphate compounds, perfluoroalkyl ethylene oxide adducts, and polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups in their side chains. Among these, polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups in their side chains are preferred because they have low foaming properties. The fluorine-based surfactant is more preferably a compound represented by general formula (F-1) and general formula (F-2).

[0039] [ka] In the compound represented by the general formula (F-1) above, m is preferably an integer between 0 and 10, and n is preferably an integer between 0 and 40, in order to impart water solubility. (However, in the general formula (F-1), m and n each represent an integer independently.)

[0040] [ka] In the compound represented by the above general formula (F-2), Y is H or CmF 2m+1 (m is an integer from 1 to 6), or CH2CH(OH)CH2-CmF 2m+1 (m is an integer between 4 and 6), or CmH 2m+1 (m is an integer between 1 and 19). n is an integer between 1 and 6. a is an integer between 4 and 14.

[0041] As the fluorine-based surfactant, compounds with 2 to 16 carbon atoms substituted with fluorine are preferred, and compounds with 4 to 16 carbon atoms substituted with fluorine are more preferred, in that they provide good water repellency and wettability.

[0042] The aforementioned fluorine-based surfactant may be one that has been synthesized as appropriate, or a commercially available product may be used. Examples of commercially available fluorine-based surfactants include Capstone FS-30, Capstone FS-31, Capstone FS-3100, Capstone FS-34, and Capstone FS-35 (all manufactured by Chemours): FT-110, FT-250, FT-251, FT-150, and FT-400SW (all manufactured by Neos Co., Ltd.): Polyfox PF-136A, Polyfox PF-156A, and Polyfox PF-151N (all manufactured by Omnova). Among these, Capstone FS-34 (manufactured by Chemours): FT-110, FT-250, FT-251, FT-150, and FT-400SW (all manufactured by Neos Co., Ltd.): Polyfox PF-151N (manufactured by Omnova) are preferred because they significantly improve print quality, especially color development, penetration into paper, wettability, and uniform dyeing.

[0043] -Acetylene glycol-based surfactant- The acetylene glycol-based surfactant is not particularly limited and can be appropriately selected depending on the purpose. Examples include acetylene glycol-based surfactants 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.

[0044] The acetylene glycol-based surfactant may be one that has been synthesized as appropriate, or a commercially available product may be used. Examples of commercially available acetylene glycol-based surfactants include Surfinol 104, Surfinol 465, and Surfinol 485 (all manufactured by Nisshin Chemical Industry Co., Ltd.). Among these, Surfinol 104 and Surfinol 465 are preferred from the viewpoint of exhibiting good print quality.

[0045] -Nonionic surfactant- The nonionic surfactant is not particularly limited and can be appropriately selected depending on the purpose. Examples include polyols, glycol ethers, polyoxyethylene alkyl ethers, polyoxyethylene alkyl esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene alkylphenyl ethers, polyoxyalkylene alkyl ethers, polyoxyethylene alkylamines, polyoxyethylene alkylamides, and acetylene glycols.

[0046] -Anionic surfactants- The anionic surfactant is not particularly limited and can be appropriately selected depending on the purpose. Examples include polyoxyethylene alkyl ether acetate, dodecylbenzene sulfonate, lauryl salt, salt of polyoxyethylene alkyl ether sulfate, sodium dialkyl sulfosuccinate, and sodium naphthalene sulfonate formalin condensate.

[0047] - Amphoteric surfactants - The aforementioned amphoteric surfactant is not particularly limited and can be appropriately selected depending on the purpose. Examples include laurylaminopropionate, lauryldimethylbetaine, stearyldimethylbetaine, and lauryldihydroxyethylbetaine.

[0048] The surfactant content is preferably 0.01% by mass or more and 5% by mass or less, and more preferably 0.03% by mass or more and 2% by mass or less, relative to the total mass of the ink. If the surfactant content is 0.01% by mass or more relative to the total mass of the ink, it is preferable because it prevents problems such as poor dot spreading after printing, a smaller dot diameter, poor filling of solid images, and a decrease in image density and saturation. When the amount of the surfactant is 5% by mass or less relative to the total mass of the ink, it is preferable because it makes foaming easier, preventing problems such as the flow path in the nozzle becoming blocked by foam and thus preventing ink from being dispensed.

[0049] <Dispersant> There are no particular restrictions on the dispersant, and it can be appropriately selected depending on the purpose, but one having the structure shown in the following general formula (1) is preferred. By having the structure of the general formula (1), the dispersant can be used to obtain an inkjet recording ink with a small average particle size and a small standard deviation in the particle size distribution.

[0050] [ka] General formula (1) In general formula (1), R represents an alkyl group, allyl group, or aralkyl group having 1 to 20 carbon atoms, and l represents an integer from 0 to 7. In general formula (1), n ​​is preferably 20 or more and 100 or less, and more preferably 30 or more and 50 or less. When n is 20 or more in general formula (1), the dispersion stability decreases, the average particle size becomes large, and the ink has a large standard deviation in the particle size distribution, which can solve the problem of not being able to obtain satisfactory saturation. Also, when n is 100 or less, the viscosity of the ink becomes high, which can solve the problem of difficulty in printing with an inkjet method. As the dispersant, a POE(n=40)β-naphthyl ether in which l is 0 and n is 40 is more preferred in the general (1) above.

[0051] <pH adjuster> The pH adjuster can stabilize the dispersion state and the ejection by keeping the ink alkaline. Generally, when the pH of the ink is 11 or more, the amount of dissolving the inkjet head and the ink supply unit is large, and problems such as ink deterioration, leakage, and ejection failure occur. As the timing of adding the pH adjuster, from the viewpoint that the dispersant may be destroyed depending on the type of the pH adjuster, it is preferable to add it when kneading and dispersing the pigment together with the dispersant in water.

[0052] The pH adjuster is not particularly limited and can be appropriately selected according to the purpose. However, those containing one or more of alcohol amines, alkali metal hydroxides, ammonium hydroxides, phosphonium hydroxides, and alkali metal carbonates are preferable. Specific examples of the alcohol amines include diethanolamine, triethanolamine, 2-amino-2-ethyl-1,3-propanediol, and the like. Specific examples of the alkali metal hydroxides include lithium hydroxide, sodium hydroxide, potassium hydroxide, and the like. Specific examples of the ammonium hydroxides include ammonium hydroxide, quaternary ammonium hydroxide, quaternary phosphonium hydroxide, and the like. Specific examples of the alkali metal carbonates include lithium carbonate, sodium carbonate, potassium carbonate, and the like. These may be used alone or in combination of two or more.

[0053] <Antiseptic and antifungal agent> The antiseptic and antifungal agent is not particularly limited and can be appropriately selected according to the purpose. For example, sodium dehydroacetate, sodium sorbate, sodium 2-pyridinethiol-1-oxide, sodium benzoate, sodium pentachlorophenol, and the like can be mentioned.

[0054] <Rust preventive> There are no particular restrictions on the rust inhibitor, and it can be appropriately selected depending on the purpose. Examples include acidic sulfites, sodium thiosulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite. These can be used individually or in combination of two or more types.

[0055] <Antioxidant> There are no particular restrictions on the antioxidants, and they can be appropriately selected depending on the purpose. Examples include phenolic antioxidants (including hindered phenolic antioxidants), amine antioxidants, sulfur-based antioxidants, and phosphorus-based antioxidants. These can be used individually or in combination of two or more types.

[0056] <UV absorber> There are no particular restrictions on the UV absorber, and it can be appropriately selected depending on the purpose. Examples include benzophenone-based UV absorbers, benzotriazole-based UV absorbers, salicylate-based UV absorbers, cyanoacrylate-based UV absorbers, and nickel complex salt-based UV absorbers. These can be used individually or in combination of two or more types.

[0057] <Crotting prevention agent> Coging is a malfunction in thermal print heads that use electric current to instantaneously heat the ink and eject it using the foaming force of the ink. It refers to the phenomenon where the ink components change when heated, and these altered substances adhere to the heater. When coging occurs, the heater does not heat properly, leading to problems such as weakened ejection force or no ink ejection at all. Therefore, to prevent coging, a coging inhibitor can be added to the ink used in this invention. The aforementioned coagulation inhibitor is not particularly limited and can be appropriately selected depending on the purpose. Examples include polyphosphate, polyaminocarboxylic acid, aldonic acid, hydroxycarboxylic acid, polyol phosphate ester, and salts thereof, or acids having an amino group and / or salts thereof, or ammonium salts of acids having a methyl group or a methylene group and a carboxyl group.

[0058] [Ink properties] <Storage modulus G'> The ink of the present invention has a storage modulus G' at 25°C of 0.50 Pa or more and 2.00 Pa or less when the ink is concentrated so that the solid content is 10% by mass of the total ink mass. Note that the "10% by mass" solid content includes an error range of ±0.2% by mass. The storage modulus G' at 25°C when the inkjet recording ink is concentrated so that the solid content is 10% by mass of the total ink mass is sometimes referred to as "storage modulus G'". The solid content in this invention includes resin and pigment particles, among others. Because the storage modulus G' is 0.50 Pa or higher, a less fluid gel can be created earlier (during printing, from the time until the ink droplet lands), which improves the effect of preventing ink droplet coalescence and suppresses beading. The storage modulus G' being 2.00 Pa or less eliminates the problem of reduced discharge stability due to ink solidification during concentration. The storage modulus G' can be controlled by the plasticizing force of the organic solvent on the resin. From the viewpoint of suppressing liquid dripping, the storage modulus G' is preferably 0.75 Pa or more and 1.50 Pa or less.

[0059] There are no particular restrictions on the method of concentrating the ink, and it can be appropriately selected depending on the purpose, for example, by evaporation. Examples of evaporation methods include placing the ink of the present invention in a container such as a beaker and heating it on a hot plate at 80°C while stirring.

[0060] There are no particular restrictions on the method for measuring the storage modulus G', but for example, the storage modulus G' can be determined by measuring and analyzing the ink concentrated by the concentration method using an AR2000 (manufactured by TA Instruments Inc.). The storage modulus G' can be measured under the following measurement conditions. -Measurement conditions- • Geometry: 40mm 1° cone plate • Geometry gap: 300 μm ·Measurement frequency: 1Hz ·Measurement temperature: 25℃ • Analysis software: TA DATA ANALYSIS (manufactured by TA Instruments Inc.) One method for measuring the solid content is to measure the mass of a container holding the ink during concentration over time and calculate the solid content from the change in mass. Furthermore, when the solid content approaches 10% by mass, the amount of solid content can be controlled by precisely measuring the mass of the ink and adjusting the concentration level.

[0061] <Viscosity> The viscosity of the ink at 25°C is preferably 1.0 mPa·s to 10 mPa·s, and more preferably 1.5 mPa·s to 8.0 mPa·s, from the standpoint of improving print density and character quality, as well as ensuring ejection stability. The viscosity can be measured, for example, using a rotational viscometer (RE-80L; manufactured by Toki Sangyo Co., Ltd.). The measurement conditions for the viscosity are 25°C, a standard cone rotor (1°34'×R24), a sample volume of 1.2 mL, a rotation speed of 50 rpm, and a measurement time of 3 minutes.

[0062] <Surface tension> The surface tension of the ink is preferably 30 mN / m or less, and more preferably 25 mN / m or less, at 25°C, in order to allow the ink to level nicely on the recording medium described later and shorten the ink drying time.

[0063] <Particle size> There are no particular restrictions on the particle size (median diameter) of the solid particles in the ink, and it can be appropriately selected according to the purpose. However, from the viewpoint of improving ejection stability and image quality such as image density, the particle size (median diameter) of the solid particles in the ink is preferably 20 nm or more and 1,000 nm or less, and more preferably 150 nm or more and 200 nm or less. The particle size of the solid particles in the ink can be measured using a particle size analyzer (NanoTrac Wave-UT151; manufactured by MicroTrac-Bell Co., Ltd.).

[0064] <ph> There are no particular restrictions on the pH of the ink, and it can be appropriately selected depending on the purpose. However, from the viewpoint of preventing corrosion of metal components that come into contact with the ink, a pH of 7 to 12 is preferred, and a pH of 8 to 11 is more preferred.

[0065] [Ink Set] The ink and processing solution of the present invention may be used in combination as an ink set.

[0066] <Processing solution> The aforementioned processing solution contains a flocculant and, if necessary, a water-soluble organic solvent, water, and other components. The water-soluble organic solvent, water, and other components can be the same as those used in the ink of the present invention.

[0067] -Agglutinant- The aforementioned coagulant is included in the ink of the present invention to coagulate the components contained in the ink (for example, colorants such as pigments). By forming an image using the ink containing the aforementioned coagulant, the image density can be improved. The aforementioned flocculant is not particularly limited as long as it flocculates the components contained in the ink of the present invention, and can be appropriately selected depending on the purpose, for example, metal salts. It is generally known that in ink, metal salts and colorants associate through electrostatic interaction to form pigment aggregates, which separates the pigment from the liquid phase and promotes its fixation to the recording medium. Therefore, by including a metal salt as a coagulant in the processing solution, beading can be suppressed even when using a recording medium with low ink absorption, and high-quality images can be formed.

[0068] There are no particular restrictions on the metal salts mentioned above, and they can be appropriately selected depending on the purpose. Examples include salts of titanium compounds, chromium compounds, copper compounds, cobalt compounds, strontium compounds, barium compounds, iron compounds, aluminum compounds, calcium compounds, magnesium compounds, zinc compounds, nickel compounds, etc. Among these, salts of calcium compounds, magnesium compounds, and nickel compounds are preferred because they can effectively aggregate colorants such as pigments, alkaline earth metal salts such as calcium and magnesium are more preferred, and magnesium salts are even more preferred. Furthermore, the metal salt is preferably ionic. These can be used individually or in combination of two or more.

[0069] The barium compound is not particularly limited and can be appropriately selected depending on the purpose; for example, barium sulfate is one such example. The aluminum compound is not particularly limited and can be appropriately selected depending on the purpose. Examples include aluminum silicate and aluminum hydroxide. The calcium compound is not particularly limited and can be appropriately selected depending on the purpose. Examples include calcium carbonate, calcium nitrate, calcium chloride, calcium acetate, calcium sulfate, and calcium silicate. The magnesium compound is not particularly limited and can be appropriately selected depending on the purpose. Examples include magnesium chloride, magnesium acetate, magnesium sulfate, magnesium nitrate, and magnesium silicate. The zinc compound is not particularly limited and can be appropriately selected depending on the purpose. Examples include zinc sulfide and zinc carbonate.

[0070] The content of the metal salt in the processing solution is preferably 0.85 mol / kg or more and 1.4 mol / kg or less. A metal salt content of 0.85 mol / kg or more suppresses beading even when using recording media with low ink absorption, enabling the formation of high-quality images. A metal salt content of 1.4 mol / kg or less improves the storage stability of the processing solution.

[0071] [Recording media] In this specification, "recording medium" refers to an object on which data is recorded using the ink of the present invention. The recording medium refers to a medium to which ink or the processing liquid can be temporarily attached. There are no particular limitations on the recording medium, and its shape, structure, material, etc. can be appropriately selected according to the purpose. Examples include plastic sheets based on polyethylene terephthalate, polycarbonate, polypropylene, polyethylene, polysulfone, ABS resin, polyvinyl chloride, etc.; recording mediums with a metal coating applied to a metal surface such as brass, iron, aluminum, SUS (stainless steel), copper, or a non-metallic substrate by methods such as vapor deposition; recording mediums with a paper substrate that has been treated with a water-repellent coating; and recording mediums made of so-called ceramic materials, which are inorganic materials fired at high temperatures. There are no particular restrictions on the size of the recording medium, and it can be selected as appropriate depending on the purpose. There are no particular restrictions on the direction in which the ink is ejected, and it can be appropriately selected according to the purpose, but it is preferable to eject it horizontally to the recording medium.

[0072] (Inkjet ink storage container) The inkjet recording ink container of the present invention comprises the ink of the present invention contained within the container, and further comprises other components as necessary. There are no particular restrictions on the material of the container, and it can be appropriately selected according to the purpose. Examples include polyethylene terephthalate. There are no particular restrictions on the shape, structure, or size of the container, and they can be appropriately selected according to the purpose.

[0073] [Inkjet recording device] In this specification, "inkjet recording apparatus" refers to a liquid dispensing apparatus capable of dispensing the ink of the present invention, the processing liquid, etc., onto the recording medium. In this specification, "inkjet recording method" refers to a method of recording using the inkjet recording apparatus. The inkjet recording method may include a processing liquid application step in which the processing liquid is applied to the recording medium before the ink of the present invention is applied, and an ink application step in which the ink of the present invention is applied to the recording medium to which the processing liquid has been applied. The inkjet recording device may be equipped with a head that ejects the ink of the present invention to perform recording.

[0074] An example of a liquid dispensing device will be described below with reference to Figures 1 and 2. However, the present invention is not limited to the embodiments shown below. Figure 1 is an overall schematic diagram of a liquid dispensing device according to one embodiment of the present invention, where Figure 1(a) is a side view of the liquid dispensing device and Figure 1(b) is a top view of the liquid dispensing device. The liquid ejection device 1000 is installed facing the object to be drawn on 100, which is an example of a recording medium. The carriage 1 is equipped with a head 300 for ejecting ink, which is an example of a liquid, toward the object to be drawn on 100. The Z-axis rail 103 holds the carriage 1 so that it can move in the Z-axis direction. The X-axis rail 101 holds the Z-axis rail 103 so that the Z-axis rail 103, which holds the carriage 1, can move in the X-axis direction. Furthermore, the Y-axis rail 102 holds the X-axis rail 101 so that the X-axis rail 101 can move in the Y-axis direction. Here, the X-axis is an example of a "first axis", the Y-axis is an example of a "second axis intersecting the first axis", and the Z-axis is an example of a "third axis intersecting the first and second axes". Also, the carriage 1 is an example of a "liquid discharge unit", and the head 300 is an example of a "liquid discharge head". The liquid dispensing device 1000 includes a Z-direction drive unit 92 that moves the carriage 1 along the Z-axis rail 103 in the Z-axis direction, and an X-direction drive unit 72 that moves the Z-axis rail 103 along the X-axis rail 101 in the X-axis direction. Furthermore, the liquid dispensing device 1000 includes a Y-direction drive unit 82 that moves the X-axis rail 101 along the Y-axis rail 102 in the Y-axis direction. The Z-direction drive unit 92 is an example of the "first drive means" and moves the carriage 1 in the direction of the Z-axis that intersects the X-axis and Y-axis. Note that the movement of the carriage 1 and head 300 in the Z-axis direction does not have to be parallel to the Z-axis direction, and may be oblique movement as long as it includes at least a component in the Z-axis direction. The carriage 1 is further equipped with another Z-direction drive unit 93. The Z-direction drive unit 93 is an example of a "second drive means" and moves the head 300 in the direction of the Z axis relative to the carriage 1. The liquid ejection device 1000 configured as described above ejects ink from the head 300 toward the object to be drawn 100 while moving the carriage 1 in the X, Y, and Z axis directions, thereby drawing on the object to be drawn 100. In Figure 1, the object to be drawn 100 is shown as a flat plate, but it may also be a surface that is nearly vertical or has a large radius of curvature, such as a car, truck, or aircraft.

[0075] <Image formation method and image formation product> The image formation method described above can be carried out by printing on the recording medium using the inkjet recording apparatus of the present invention. An image formed on the recording medium using the image forming method described above can be called an image-formed object. The recording medium in the image-forming product is preferably made of metal. [Examples]

[0076] The following describes embodiments of the present invention, but the present invention is not limited in any way to these embodiments.

[0077] (Preparation of pigment dispersion) <Preparation of Black Pigment Dispersion (A) (Black Pigment Surfactant Dispersion)> After premixing the following mixture of material (A), a bead mill disperser (UAM-015; manufactured by Kotobuki Kogyo Co., Ltd.) was used to disperse 0.03 mm zirconia beads (density 6.03 × 10⁻¹). -6 g / m 2 The particles were dispersed at a peripheral speed of 10 m / s and a liquid temperature of 30°C for 15 minutes, and then the coarse particles were centrifuged (8000 G, 20 minutes) using a centrifuge (Model-7700; manufactured by Kubota Shoji Co., Ltd.) to obtain a black pigment dispersion (A). -Material (A)- • CI Pigment Black 7 (NIPEX 150 (Carbon Black); manufactured by degussa) ... 200 parts by mass • Sodium naphthalene sulfonate formalin condensate (total content of naphthalene sulfonate dimer, trimer, and tetramer: 30%) (Demol N; manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) ... 50 parts by mass • Distilled water…750 parts by mass

[0078] The obtained black pigment dispersion (A) was diluted with water to a solid content of 0.1% by mass, and the particle size (median diameter) was measured using a particle size analyzer (NanoTrac Wave-UT151; manufactured by MicroTrac-Bell Co., Ltd.). The particle size (median diameter) of the black pigment was found to be 110 nm.

[0079] <Preparation of Black Pigment Dispersion (B) (Resin Polymer Coated Black Pigment Dispersion)> After thoroughly replacing the inside of a 1L flask equipped with a mechanical stirrer, thermometer, nitrogen gas inlet tube, reflux tube, and dropping funnel with nitrogen gas, the following material (B-1) was added and the temperature was raised to 65°C. -Material (B-1)- Styrene... 11.2g Acrylic acid... 2.8g • Lauryl methacrylate………12.0g Polyethylene glycol methacrylate... 4.0g • Styrene macromer (AS-6; manufactured by Toagosei Co., Ltd.) ... 4.0g • Mercaptoethanol………0.4g Next, the mixture of the following materials (B-2) was added dropwise to the flask over a period of 2.5 hours. -Material (B-2)- Styrene... 100.8g Acrylic acid... 25.2g • Lauryl methacrylate………108.0g Polyethylene glycol methacrylate...36.0g Hydroxyethyl methacrylate... 60.0g • Styrene macromer (AS-6; manufactured by Toagosei Co., Ltd.) ... 36.0g • Mercaptoethanol………3.6g • Azobisdimethylvaleronitrile………2.4g Methyl ethyl ketone...18g After the addition of the aforementioned mixture was complete, a mixed solution of 0.8 g of azobisdimethylvaleronitrile and 18 g of methyl ethyl ketone was added dropwise to the flask over 0.5 hours. Then, after aging at 65°C for 1 hour, 0.8 g of azobisdimethylvaleronitrile was added, and the mixture was aged for another hour. After aging, 364 g of methyl ethyl ketone was added to the flask to prepare 800 g of a polymer solution with a concentration of 50% by mass. Next, the following materials (B-3) were mixed and thoroughly stirred, then kneaded using a three-roll mill (BR series; manufactured by AIMEX) to obtain a paste. -Material (B-3)- • Obtained polymer solution: 28g • CI Pigment Black 7 (NIPEX 150 (Carbon Black); made by degussa) ... 26g • 1 mol / L potassium hydroxide solution………13.6 g Methyl ethyl ketone...20g • Ion-exchanged water………30g The resulting paste was added to 200g of deionized water and stirred thoroughly. Methyl ethyl ketone and water were then removed using an evaporator. After premixing, the mixture was dispersed using a bead mill disperser (UAM-015; manufactured by Kotobuki Kogyo Co., Ltd.) to 0.03mm zirconia beads (density 6.03 × 10⁻¹). -6 g / m 2 The particles were dispersed at a peripheral speed of 10 m / s and a liquid temperature of 30°C for 15 minutes. The coarse particles were then centrifuged using a centrifuge (Model-7700; manufactured by Kubota Shoji Co., Ltd.) at 8000 G for 20 minutes to obtain black pigment dispersion (B). The solid content of the obtained black pigment dispersion (B) was 20%. The obtained black pigment dispersion (B) was measured for particle size (median diameter) in the same manner as the black pigment dispersion (A), and the particle size (median diameter) of the black pigment was found to be 125 nm.

[0080] Preparation of Cyanide Pigment Dispersion (C) (Cyanide Pigment Surfactant Dispersion) In the preparation of the black pigment dispersion (A), a cyanide pigment dispersion (C) was obtained by the same method as in the preparation of the black pigment dispersion (A), except that material (A) was changed to the following material (C). The particle size (median diameter) of the obtained cyanide pigment dispersion (C) was measured in the same method as in the preparation of the black pigment dispersion (A), and the particle size (median diameter) of the cyanide pigment was found to be 80 nm. -Material (C)- • CI Pigment Blue 15:3 (Cyanine Blue A-385; manufactured by Dainichi Seika Kogyo Co., Ltd.) ... 200 parts by mass • Sodium di-2-ethylhexyl sulfosuccinate (CAS No. 577-11-7) (Paionin A-51-B; manufactured by Takemoto Oil Co., Ltd.) ... 2.5 parts by mass • Distilled water...742 parts by mass • Compound represented by the following general formula (1) (n=40) ... 56 parts by mass

[0081] [ka] General formula (1) In general formula (1), l is 0 and n is 40.

[0082] <Preparation of cyanide pigment dispersion (D) (cyanide pigment dispersion coated with resin polymer)> In the preparation of the black pigment dispersion (B), a cyanide pigment dispersion (D) was obtained by the same method as in the preparation of the black pigment dispersion (B), except that material (B-3) was changed to the following material (D). The solid content of the obtained cyanide pigment dispersion (D) was 20%. The particle size (median diameter) of the obtained cyanide pigment dispersion (D) was measured in the same method as in the preparation of the black pigment dispersion (A), and the particle size (median diameter) of the cyanide pigment was found to be 100 nm. -Material (D)- • Obtained polymer solution: 28g CI Pigment Blue 15:3 (Cyanine Blue A-385; manufactured by Dainichi Seika Kogyo Co., Ltd.) ... 26g • 1 mol / L potassium hydroxide solution………13.6 g Methyl ethyl ketone...20g • Ion-exchanged water………30g

[0083] <Preparation of Magenta Pigment Dispersion (E) (Magenta Pigment Surfactant Dispersion)> In the preparation of the black pigment dispersion (A), a magenta pigment dispersion (E) was obtained by the same method as in the preparation of the black pigment dispersion (A), except that material (A) was changed to the following material (E). The particle size (median diameter) of the obtained magenta pigment dispersion (E) was measured in the same method as in the preparation of the black pigment dispersion (A), and the particle size (median diameter) of the magenta pigment was found to be 120 nm. -Material (E)- • CI Pigment Red 122 (Chromophthal Jet Magenta DMQ; manufactured by Ciba Specialty Chemicals) ... 200 parts by mass • Distilled water………744 parts by mass • Compound represented by the following general formula (1) (n=40) ... 56 parts by mass

[0084] [ka] General formula (1) In general formula (1), l is 0 and n is 40.

[0085] <Magenta Pigment Dispersion (F) (Preparation of Magenta Pigment Dispersion with Resin Polymer Coating)> In the preparation of the black pigment dispersion (B), a magenta pigment dispersion (F) was obtained by the same method as in the preparation of the black pigment dispersion (B), except that material (B-3) was changed to the following material (F). The solid content of the obtained magenta pigment dispersion (F) was 20%. The particle size (median diameter) of the obtained magenta pigment dispersion (F) was measured in the same method as in the preparation of the black pigment dispersion (A), and the particle size (median diameter) of the magenta pigment was found to be 100 nm. -Material (F)- • Obtained polymer solution: 28g • CI Pigment Red 122 (Chromophthal Jet Magenta DMQ; manufactured by Ciba Specialty Chemicals) ... 26g • 1 mol / L potassium hydroxide solution………13.6 g Methyl ethyl ketone...20g • Ion-exchanged water………30g

[0086] <Preparation of Yellow Pigment Dispersion (G) (Yellow Pigment Surfactant Dispersion)> In the preparation of the black pigment dispersion (A), a yellow pigment dispersion (G) was obtained by the same method as in the preparation of the black pigment dispersion (A), except that material (A) was changed to the following material (G). The particle size (median diameter) of the obtained yellow pigment dispersion (G) was measured in the same method as in the preparation of the black pigment dispersion (A), and the particle size (median diameter) of the yellow pigment was found to be 90 nm. -Material (G)- • CI Pigment Yellow 110 (Corimax Yellow 3RL; manufactured by ZEYA CHEMICALS (HAIMEN) CO., LTD) ... 200 parts by mass • Distilled water………744 parts by mass • Compound represented by the following general formula (1) (n=40) ... 56 parts by mass

[0087] [ka] General formula (1) In general formula (1), l is 0 and n is 40.

[0088] <Preparation of yellow pigment dispersion (H) coated with resin polymer> In the preparation of the black pigment dispersion (B), a yellow pigment dispersion (H) was obtained by the same method as in the preparation of the black pigment dispersion (B), except that material (B-3) was changed to the following material (H). The solid content of the obtained yellow pigment dispersion (H) was 20%. The particle size (median diameter) of the obtained yellow pigment dispersion (H) was measured in the same method as in the preparation of the black pigment dispersion (A), and the particle size (median diameter) of the yellow pigment was found to be 100 nm. -Material (H)- • Obtained polymer solution: 28g CI Pigment Yellow 110 (Corimax Yellow 3RL; manufactured by ZEYA CHEMICALS (HAIMEN) CO., LTD) ... 26g • 1 mol / L potassium hydroxide solution………13.6 g Methyl ethyl ketone...20g • Ion-exchanged water………30g

[0089] <Examples 1-10, Comparative Examples 1-4> The obtained pigment dispersions, water-soluble organic solvents, surfactants, resins, preservatives, rust inhibitors, and pH adjusters were added as shown in Tables 1 and 2. After adding water to bring the total mass to 100, the mixture was stirred and mixed to obtain the inks of Examples 1 to 10 and Comparative Examples 1 to 4. The product names and manufacturers of the surfactants, resins, preservatives, rust inhibitors, and pH adjusters are as follows: -Product name and manufacturer- • Ethanol (manufactured by Nitto Chemical Co., Ltd.) as a water-soluble organic solvent. • 1,2-butanediol (manufactured by Shinko Organic Chemical Industry Co., Ltd.) as a water-soluble organic solvent. • Dipropylene glycol dimethyl ether (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a water-soluble organic solvent. • As a water-soluble organic solvent, diethylene glycol methyl ethyl ether (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) • Nonionic surfactant: Surfactant α (Triton HW-1000 (polyoxyalkylene alkyl ether); manufactured by Dow Chemical) • As a silicone-based surfactant, surfactant β (TEGO Wet 270; manufactured by Evonik) • As a fluorinated surfactant, surfactant γ (Capstone FS-34; manufactured by Chemours) • As a urethane resin, resin a (solid content 38%) (Superflex 460S; manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) • Styrene acrylic resin, specifically resin b (solids content 45%) (Joncryl J-450; manufactured by BASF) • 1,2-benzothiazolin-3-one (Proxel LV; manufactured by Lonza) as a preservative and rust inhibitor. • pH adjuster: 2-amino-2-ethyl-1,3-propanediol (manufactured by ACROS ORGANICS)

[0090] 50 mL each of the inks from Examples 1-10 and Comparative Examples 1-4 were placed in beakers and heated on an 80°C hot plate while stirring. The mass of the beakers containing the ink was measured over time, and the ink was concentrated to a solid content of 10% by mass based on the change in mass. The storage modulus G' of the concentrated ink was determined by measuring and analyzing it using an AR2000 (manufactured by TA Instruments Inc.). The results are shown in Table 1. The storage modulus G' can be measured under the following measurement conditions. -Measurement conditions- • Geometry: 40mm 1° cone plate • Geometry gap: 300 μm ·Measurement frequency: 1Hz ·Measurement temperature: 25℃ • Analysis software: TA DATA ANALYSIS (manufactured by TA Instruments Corporation)

[0091] The viscosity of the inks from Examples 1-10 and Comparative Examples 1-4 was measured. Viscosity was measured using a rotational viscometer (RE-80L; manufactured by Toki Sangyo Co., Ltd.) at 25°C, with a standard cone rotor (1°34'×R24), a sample volume of 1.2 mL, a rotation speed of 50 rpm, and a measurement time of 3 minutes. The results are shown in Table 1.

[0092] [Table 1]

[0093] [Table 2]

[0094] The inks from Examples 1-10 and Comparative Examples 1-4 were evaluated for "liquid dripping," "discharge stability," "YMCK image evaluation (image saturation and density)," and "storage stability." The results are shown in Tables 3 and 4.

[0095] <Liquid drip evaluation> The inks from Examples 1-10 and Comparative Examples 1-4 were loaded into a Ricoh Digital Painting NNV13 printer, which has the structure shown in Figures 1 and 2. A full-page A4 solid image (width: 13000mm x height: 3250mm) was printed on an aluminum composite board, Esco EA440HA-X2 (white), which was used as the printing test paper, at a temperature of 23°C and a humidity of 50% RH, using a recording density of 105.8 dpi and two passes. The ink adhesion amount was adjusted to 3.00 nL / dot, and the image 10 minutes after the end of printing was evaluated according to the following criteria. "○" and "△" indicate acceptable ranges. -Evaluation Criteria- ○: No liquid dripping occurred △: No liquid dripping occurred, but there was image unevenness (there was a liquid pool at the bottom of the image) ×: Liquid dripping occurred

[0096] <Evaluation of Discharge Stability> The inks of Examples 1 to 10 and Comparative Examples 1 to 4 were filled into NNV13 (manufactured by Ricoh Digital Painting) and set. For the aluminum composite board Esco EA440HA-X2 (white), which is the printing test paper, at a temperature of 23°C and a humidity of 50%RH, printing of a solid image (horizontal: 13000 mm × vertical: 3250 mm) was performed with a recording density of 105.8 dpi and 2 passes. The ink adhesion amount was adjusted to 3.00 nL / dot. After printing, a nozzle check pattern was printed, and the bending was evaluated according to the following criteria. Note that "○" and "△" are within the allowable range. -Evaluation Criteria- ○: No bending △: One or more bends and three or fewer bends ×: Four or more bends

[0097] <Evaluation of YMCK Images (Chroma and Density)> The inks of Examples 1 to 10 and Comparative Examples 1 to 4 were filled into NNV13 (manufactured by Ricoh Digital Painting) and set. For the aluminum composite board Esco EA440HA-X2 (white), which is the printing test paper, at a temperature of 23°C and a humidity of 50%RH, printing of a solid image (horizontal: 130,000 mm × vertical: 3250 mm) was performed with a recording density of 105.8 dpi and 2 passes. The optical density (OD) and chroma c * of the obtained solid image were measured with a spectrophotometer (X-Rite938) and evaluated according to the following criteria. Note that the image chroma c * (sharpness) refers to the distance from the origin on the chromaticity diagram when printing on the aluminum composite board Esco EA440HA-X2 (white), which is the printing test paper, performing colorimetry on the solid image of the image sample with a spectrophotometer (X-Rite938), and plotting it on the chromaticity diagram. More specifically, the a * value and b * This refers to the value derived from the given value by the following formula. JPEG0007830841000011.jpg1538

[0098] -Evaluation Criteria for Yellow Pigment Ink (Saturation)- ○: Saturation 55 or higher △: Saturation between 50 and 55 ×: Saturation less than 50 -Evaluation Criteria for Magenta Pigment Ink (Saturation)- ○: Saturation 55 or higher △: Saturation between 50 and 55 ×: Saturation less than 50 -Criteria for evaluating cyan pigment ink (saturation)- ○: Saturation 55 or higher △: Saturation between 50 and 55 ×: Saturation less than 50 -Evaluation Criteria for Black Pigment Ink (OD)- ○: k≧0.9 △: 0.9 > k ≥ 0.8 ×:0.8>k

[0099] <Evaluation of storage stability> The inks from Examples 1-10 and Comparative Examples 1-4 were placed in polyethylene containers, sealed, and stored at 70°C for two weeks. The viscosity was measured before and after storage, and the rate of change was calculated using the following formula. The obtained rate of change was evaluated based on the following evaluation criteria. For the viscosity measurement, a rotational viscometer (RE-80L; manufactured by Toki Sangyo Co., Ltd.) was used, and measurements were taken at 25°C under the following conditions: standard cone rotor (1°34'×R24), sample volume of 1.2 mL, rotation speed of 50 rpm, and for 3 minutes. -Evaluation Criteria- ○: Within 10% △: More than 10% and less than 30% ×: More than 30%

[0100] [Table 3]

[0101] [Table 4]

[0102] Examples of the present invention are as follows: <1> An inkjet recording ink comprising at least water, pigment, resin, and a water-soluble organic solvent, The inkjet recording ink is characterized in that, when the inkjet recording ink is concentrated so that the solid content is 10% by mass of the total ink mass, the storage modulus G' at 25°C is 0.50 Pa or more and 2.00 Pa or less. <2> The inkjet recording ink is ejected horizontally onto the recording medium, <1> This is the inkjet recording ink described in [the relevant document]. <3> The viscosity c (mPa·s) of the inkjet recording ink at 25°C is 1.0 ≤ c ≤ 10.0. <1> From the above <2> It is an inkjet recording ink as described in one of the following. <4> The pigment includes at least one selected from CI Pigment Yellow 110, CI Pigment Red 122, CI Pigment Blue 15:3, and CI Pigment Black 7. <1> From the above <3> It is an inkjet recording ink as described in one of the following. <5> The pigment content is 7% by mass or more and 17% by mass or less relative to the total mass of the ink. <1> From the above <4> It is an inkjet recording ink as described in one of the following. <6> The resin is a thermoplastic resin, <1> From the above <5> It is an inkjet recording ink as described in one of the following. <7> The resin content is 7% by mass or more and 15% by mass or less relative to the total mass of the ink. <1> From the above <6> It is an inkjet recording ink as described in one of the following. <8> The aforementioned <1> From the above <7> This is an inkjet recording ink container characterized by containing an inkjet recording ink as described in any of the above. <9> The aforementioned <1> From the above <7> This is an inkjet recording device characterized by having a head that ejects inkjet recording ink as described in any of the above to perform recording. <10> The aforementioned <9> This is an image forming method characterized by printing using the inkjet recording device described above. <11> The aforementioned <10> This is an image-formed product characterized by being printed using the image-forming method described above. <12> The recording medium is characterized by being made of metal. <11> This is the image formation described in [the document].

[0103] The aforementioned <1> From the above <7> Inkjet recording ink as described in any of the above, <8> The inkjet recording ink container described above, <9> The inkjet recording apparatus described above, <10> The image forming method described above, <11> From the above <12> According to the image forming product described in any of the above, the conventional problems can be solved and the objectives of the present invention can be achieved. [Explanation of symbols]

[0104] 1 carriage 72 X-direction drive unit 82 Y-direction drive unit 92 Z-direction drive unit 93 Another Z-direction drive unit 100 Object to be drawn 101 X-axis rail 102 Y-axis rail 103 Z-axis rail 300 heads 1000 liquid dispensing device [Prior art documents] [Patent Documents]

[0105] [Patent Document 1] Japanese Patent Publication No. 2011-063630 [Patent Document 2] Japanese Patent Publication No. 2008-101192 [Patent Document 3] Japanese Patent Publication No. 2004-174948 [Patent Document 4] Japanese Patent Publication No. 2010-047700 [Patent Document 5] Japanese Patent Publication No. 2017-165961< / ph>

Claims

1. An inkjet recording ink comprising at least water, pigment, resin, and a water-soluble organic solvent, The solid content in the inkjet recording ink is 10% by mass or less relative to the total mass of the inkjet recording ink. The aforementioned pigment includes at least one selected from C.I. Pigment Yellow 110, C.I. Pigment Red 122, C.I. Pigment Blue 15:3, and C.I. Pigment Black 7. The aforementioned resin is at least one selected from urethane resin and styrene acrylic resin. An inkjet recording ink characterized in that, when the inkjet recording ink is concentrated by heating the inkjet recording ink and evaporating the water and the water-soluble organic solvent so that the solid content in the inkjet recording ink is 10% by mass of the total mass of the inkjet recording ink, the storage modulus G' at 25°C is 0.50 Pa or more and 2.00 Pa or less.

2. The inkjet recording ink according to claim 1, wherein the inkjet recording ink is ejected horizontally onto a recording medium.

3. The inkjet recording ink according to any one of claims 1 to 2, wherein the viscosity c (mPa·s) of the inkjet recording ink at 25°C is 1.0 ≤ c ≤ 10.

0.

4. The inkjet recording ink according to any one of claims 1 to 3, wherein the water-soluble organic solvent is at least one selected from ethanol, 1,2-butanediol, dipropylene glycol dimethyl ether, and diethylene glycol methyl ethyl ether.

5. The inkjet recording ink according to any one of claims 1 to 4, wherein the content of the pigment dispersion containing the pigment is 7% by mass or more and 17% by mass or less with respect to the total mass of the inkjet recording ink.

6. The inkjet recording ink according to any one of claims 1 to 5, wherein the total content of the pigment and the resin solids is 9% by mass or less with respect to the total mass of the inkjet recording ink.

7. The inkjet recording ink according to any one of claims 1 to 6, wherein the content of the resin dispersion containing the resin is 7% by mass or more and 15% by mass or less with respect to the total mass of the inkjet recording ink.

8. An inkjet recording ink container characterized by containing the inkjet recording ink described in any one of claims 1 to 7.

9. An inkjet recording apparatus characterized by comprising a head that ejects inkjet recording ink according to any one of claims 1 to 7 to perform recording.

10. An image forming method characterized by printing using the inkjet recording apparatus described in claim 9.

11. An image-formed object characterized by being printed by the image-forming method described in claim 10.

12. The image-forming product according to claim 11, characterized in that the recording medium is made of metal.

Images