Aqueous ink for inkjet recording

Abstract

To provide an aqueous ink for inkjet recording, which can afford printed matter having nearly equal image qualities in both gloss coated paper and matte coated paper.SOLUTION: Provided is an aqueous ink for inkjet recording, comprising a pigment, a glycol ether (A), a polyether-modified silicone (B), and an acetylene glycol-based surfactant (C). The glycol ether (A) has an HLB value (Davis method) of 6.0 to 7.5. The polyether-modified silicone (B) has [m / n] of 3.0 to 12.0, which is a ratio of the number m of repeating polyorganosiloxane units having no polyether group to the number n of repeating polyorganosiloxane units having polyether groups. A mass ratio of the content of the polyether-modified silicone (B) to the content of the acetylene glycol-based surfactant (C) is 1.5 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a water-based ink for ink-jet printing. [Background technology]

[0002] Inkjet recording is a method of printing characters and images by ejecting ink droplets directly from minute nozzles onto a recording medium. This method has many advantages, including the ease of full-color printing, low cost, the ability to use plain paper as a recording medium, and non-contact printing. In recent years, the spread of digital printing has expanded its use beyond consumer printing to commercial and industrial printing using low-absorbency coated paper, etc., and there has been an increasing demand for water-based inkjet inks with the aim of increasing printing speed, improving image quality, and reducing the environmental impact. In order to meet such demands, various water-based inks have been proposed, provided that they satisfy basic performance requirements such as ejection stability and storage stability.

[0003] Patent Document 1 discloses an ink that exhibits high image density and has excellent storage stability and ejection stability, the ink containing water, a pigment, an organic solvent, and a surfactant, wherein the surfactant contains a silicone surfactant and a dialkyl sulfosuccinate salt, and the organic solvent contains a glycol ether, and wherein, when the dynamic surface tension of the ink is measured at 23°C by the maximum bubble pressure method, the difference between the dynamic surface tension value at 15 msec and the dynamic surface tension value at 1500 msec is 4.0 mN / m or less, and the dynamic surface tension value at 15 msec is 31 mN / m or less. Furthermore, Patent Document 2 discloses an ink composition that can achieve print quality with less cissing and aggregation unevenness, excellent solid coverage, particularly on non-absorbent or low-absorbent recording media, can reduce nozzle clogging, and has excellent ink storage stability, and the ink composition contains at least a colorant, two or more polysiloxane surfactants with different water solubilities, and alkyl polyols having a boiling point in the range of 180 to 230°C at 1 atmospheric pressure, and is substantially free of alkyl polyols having a boiling point of 280°C or higher at 1 atmospheric pressure, and is capable of recording on non-absorbent or low-absorbent recording media. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2017-78158 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-41809 Summary of the Invention [Problem to be solved by the invention]

[0005] To achieve the desired color and texture, users use a variety of recording media with different surface properties. For coated paper, which is in high demand for high image quality and quality, gloss coated paper with an excellent glossy finish and matte coated paper with a matte finish are used. When ink jet recording is performed using pigment ink, it is advisable to change the recording conditions appropriately depending on the surface characteristics of the recording medium used, but this affects productivity. Therefore, there is a demand for a versatile water-based ink that can produce printed matter of substantially the same image quality regardless of the type of recording medium, such as gloss-coated paper, matte-coated paper, etc. However, when printing on coated paper with different surface conditions, the appearance of the printed matter varies due to differences in wetting properties, and this has not yet been sufficiently improved. An object of the present invention is to provide a water-based ink for ink-jet printing that can produce recorded images of substantially the same image quality on either gloss coated paper, which has a smooth surface and thus makes it difficult for the ink to wet and spread, or matte coated paper, which has an uneven surface and therefore makes it easy for the ink to wet and spread due to capillary action. [Means for solving the problem]

[0006] The present inventors have found that the above-mentioned problems can be solved by a water-based ink for inkjet printing, which contains a pigment, a glycol ether (A) having an HLB value calculated by the Davis method within a specific range, a polyether-modified silicone (B) having a specific structure, and an acetylene glycol-based surfactant (C), wherein the polyether-modified silicone (B) and the acetylene glycol-based surfactant (C) are contained in a specific ratio. The present invention relates to the following [1]. [1] A water-based ink for inkjet printing containing a pigment, a glycol ether (A), a polyether-modified silicone (B), and an acetylene glycol-based surfactant (C), wherein the glycol ether (A) has an HLB value of 6.0 or more and 7.5 or less, as calculated by the Davis method; the ratio [m / n] of the number of repeating polyorganosiloxane units m having no polyether group to the number of repeating polyorganosiloxane units n having a polyether group, in the polyether-modified silicone (B), is 3.0 or more and 12.0 or less; and the mass ratio of the content of the polyether-modified silicone (B) to the content of the acetylene glycol-based surfactant (C) [polyether-modified silicone (B) / acetylene glycol-based surfactant (C)] is 1.5 or less. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a water-based ink for ink-jet printing that can produce recorded images of substantially the same image quality on both gloss coated paper, which has a smooth surface and thus makes it difficult for the ink to wet and spread, and matte coated paper, which has an uneven surface and therefore makes it easy for the ink to wet and spread due to capillary action. DETAILED DESCRIPTION OF THE INVENTION

[0008] [Water-based ink for inkjet printing] The water-based ink for ink-jet printing of the present invention (hereinafter also referred to as "the ink of the present invention") is a water-based ink for ink-jet printing containing a pigment, a glycol ether (A), a polyether-modified silicone (B), and an acetylene glycol-based surfactant (C), in which the glycol ether (A) has an HLB value calculated by the Davis method of 6.0 or more and 7.5 or less, the ratio [m / n] of the number of repeating polyorganosiloxane units m having no polyether group to the number of repeating polyorganosiloxane units n having a polyether group in the polyether-modified silicone (B) is 3.0 or more and 12.0 or less, and the mass ratio of the content of the polyether-modified silicone (B) to the content of the acetylene glycol-based surfactant (C) [polyether-modified silicone (B) / acetylene glycol-based surfactant (C)] is 1.5 or less. In this specification, "recording" is a concept that includes printing and printing characters or images, and "recorded matter" is a concept that includes printed matter and printed matter on which characters or images are recorded. "Water-based" means that water accounts for the largest proportion of the medium contained in the ink.

[0009] The water-based ink for ink-jet printing of the present invention can produce printed matter of substantially the same image quality on both gloss coated paper, which has a smooth surface and therefore the ink does not wet or spread easily, and matte coated paper, which has an uneven surface and therefore the ink wets or spreads easily due to capillary action. The reason for this is not clear, but is thought to be as follows. The reason why water-based inks do not wet and spread easily on gloss-coated paper is thought to be because the surface of gloss-coated paper is smooth and has low surface free energy. On the other hand, matte-coated paper has the same low surface free energy as gloss-coated paper, but because the surface is uneven, water-based inks are thought to wet and spread easily by penetrating into these unevenness due to capillary action. Furthermore, in terms of liquid absorption, matte-coated paper absorbs organic solvents more easily than gloss-coated paper. Generally, in order for ink to wet and spread on a recording medium with low surface free energy, it is necessary to lower the surface tension of the ink. In the ink of the present invention, the glycol ether (A) and acetylene glycol surfactant (C), both of which have HLB values ​​of 6.0 to 7.5, are hydrophobic and are therefore believed to orient at the interface between the ink and the recording medium at an early stage after the ink is ejected from the head nozzle and lands on the recording medium. This rapidly reduces the surface tension near the interface, allowing the ink to wet the surface of gloss-coated paper, which has a low surface free energy. Furthermore, the ink of the present invention has a mass ratio of the polyether-modified silicone (B) content to the acetylene glycol-based surfactant (C) content [polyether-modified silicone (B) / acetylene glycol-based surfactant (C)] of 1.5 or less, allowing the ink to sufficiently wet the surface of gloss-coated paper, thereby enabling the ink dot diameter to be sufficiently large and preventing uneven printing. Furthermore, the ink of the present invention can suppress excessive wetting on matte coated paper by using a polyether-modified silicone (B) in which the ratio [m / n] of the repeat number m of polyorganosiloxane units without polyether groups to the repeat number n of polyorganosiloxane units with polyether groups is 3.0 or more and 12.0 or less. Although the reason for this is unclear, it is thought that when the ink lands on the recording medium and spreads in the capillaries, the polyether-modified silicone (B) orients at the interface between the ink and the recording medium, thereby suppressing the expansion of the ink dot diameter caused by the glycol ether (A) and the acetylene glycol surfactant (C). As a result, it is believed that it is possible to obtain prints of substantially the same image quality on either gloss coated paper or matte coated paper.

[0010] <Pigments> The pigment used in the present invention may be either an inorganic pigment or an organic pigment. Examples of inorganic pigments include carbon black and metal oxides, and carbon black is preferred for black inks. Examples of carbon black include furnace black, lamp black, acetylene black, and channel black. Examples of white inks include titanium dioxide, zinc oxide, silica, alumina, and metal oxides such as magnesium oxide. Examples of organic pigments include azo pigments, diazo pigments, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, dioxazine pigments, perylene pigments, perinone pigments, thioindigo pigments, anthraquinone pigments, and quinophthalone pigments. The hue is not particularly limited, and in the chromatic ink, any chromatic pigment such as yellow, magenta, cyan, red, blue, orange, or green can be used. The pigments can be used alone or in combination of two or more.

[0011] Suitable forms of the pigment include a pigment that can maintain a dispersed state without a dispersant, i.e., a self-dispersing pigment, pigment particles in which the pigment is dispersed with a low-molecular-weight or high-molecular-weight surfactant, and polymer particles containing the pigment. Among these, the form of polymer particles containing the pigment is preferred from the viewpoint of the dispersion stability and fixability of the pigment. Furthermore, the polymer of the polymer particles containing the pigment may be either a non-crosslinked polymer or a crosslinked polymer, but from the viewpoint of the dispersion stability and fixability of the pigment, a crosslinked polymer is preferred. In other words, the pigment is more preferably in the form of crosslinked polymer particles containing the pigment. Here, "pigment-containing polymer particles" (hereinafter also referred to as "pigment-containing polymer particles") means particles in which a polymer encapsulates a pigment, particles consisting of a polymer and a pigment with part of the pigment exposed on the surface, particles in which a polymer is adsorbed to part of the pigment, or a mixture thereof. Of these, particles in which a polymer encapsulates a pigment are more preferred.

[0012] [Pigment-containing polymer particles] The polymer constituting the pigment-containing polymer particles (hereinafter also referred to as "polymer a") may be either water-soluble or water-insoluble, as long as it has at least the pigment dispersibility to disperse the pigment in an aqueous medium, and is preferably a water-insoluble polymer. Here, "water-insoluble" means that when a polymer that has been dried at 105°C for 2 hours and has reached a constant weight is dissolved in 100 g of water at 25°C until saturation is reached, the amount of dissolution is 10 g or less. When the water-insoluble polymer is an anionic polymer, the amount of dissolution is the amount of dissolution when the anionic groups of the polymer are 100% neutralized with sodium hydroxide.

[0013] [Polymer a] Examples of polymer a include vinyl resins, polyester resins, polyurethane resins, etc. Among these, vinyl polymers obtained by addition polymerization of vinyl monomers are preferred from the viewpoint of improving the storage stability and ejection stability of the ink of the present invention. The vinyl polymer preferably contains (a-1) a structural unit derived from an ionic monomer, and further preferably contains (a-2) a structural unit derived from a hydrophobic monomer and / or (a-3) a nonionic monomer.

[0014] [(a-1) Ionic Monomer] The (a-1) ionic monomer is preferably an anionic monomer, and examples thereof include carboxylic acid monomers and sulfonic acid monomers, with carboxylic acid monomers being more preferred. The carboxylic acid monomer may be at least one selected from acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, and citraconic acid, with at least one selected from acrylic acid and methacrylic acid being more preferred.

[0015] [(a-2) Hydrophobic Monomer] (a-2) The term "hydrophobic" in the hydrophobic monomer means that when the monomer is dissolved in 100 g of ion-exchanged water at 25° C. until saturation, the amount of the dissolved monomer is less than 10 g. Specific examples of the (a-2) hydrophobic monomer include those described in paragraphs

[0020] to

[0022] of JP 2018-83938 A. Among these, alkyl(meth)acrylates having an alkyl group with 1 to 18 carbon atoms, particularly 1 to 10 carbon atoms, aromatic group-containing monomers having an aromatic group with 6 to 22 carbon atoms, and macromonomers having a polymerizable functional group at one end are preferred, with one or more selected from styrene, α-methylstyrene, and benzyl(meth)acrylate being more preferred. The macromonomer having a polymerizable functional group at one end is a compound having a number average molecular weight of 500 or more and 100,000 or less, preferably 1,000 or more and 10,000 or less, and the polymerizable functional group can be an acryloyloxy group or a methacryloyloxy group. The macromonomer is preferably an aromatic group-containing monomer-based macromonomer, and examples of the aromatic group-containing monomer constituting the macromonomer include the aromatic group-containing monomers described above. Specific examples of commercially available styrene-based macromonomers include AS-6(S), AN-6(S), and HS-6(S) manufactured by Toagosei Co., Ltd.

[0016] [(a-3) Nonionic Monomer] (a-3) The nonionic monomer is a monomer that has a high affinity with water or a water-soluble organic solvent, and is, for example, a monomer that contains a hydroxyl group or a polyalkylene glycol chain. Specific examples of the component (a-3) include those described in paragraph

[0018] of JP-A No. 2018-83938. Among these, one or more selected from methoxypolyethylene glycol (n = 1 to 30) (meth)acrylate and polypropylene glycol (n = 2 to 30) (meth)acrylate are preferred. The monomer components contained in each of the above components (a-1) to (a-3) can be used alone or in combination of two or more.

[0017] (Content of each structural unit in polymer a) The content of the structural units derived from components (a-1) to (a-3) in polymer a is as follows, from the viewpoints of the dispersion stability of the pigment, the storage stability of the ink of the present invention, and obtaining recorded materials of substantially the same image quality on both gloss coated paper and matte coated paper. The content of component (a-1) is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, still more preferably 20% by mass or more, even more preferably 25% by mass or more, and is preferably 70% by mass or less, more preferably 60% by mass or less, even more preferably 50% by mass or less. The content of component (a-2) is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, and preferably 95% by mass or less, more preferably 90% by mass or less, even more preferably 80% by mass or less, and even more preferably 75% by mass or less.

[0018] When the component (a-3) is contained, the content of the component (a-3) is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less, and still more preferably 5% by mass or less.

[0019] The mass ratio of [component (a-1) / component (a-2)] is preferably 0.1 or more, more preferably 0.3 or more, even more preferably 0.35 or more, still more preferably 0.38 or more, and is preferably 2 or less, more preferably 1.5 or less, even more preferably 1 or less, and still more preferably 0.8 or less. In the present invention, the content of the structural units derived from the components (a-1) to (a-3) in polymer a can be determined by measurement, or can be substituted by the charging ratio of the raw material monomers including the components (a-1) to (a-3) during the production of polymer a.

[0020] (Production of polymer a) Polymer a can be produced by copolymerizing the mixture of the above-mentioned monomers by a known polymerization method, preferably a solution polymerization method. There are no limitations on the solvent used in the solution polymerization method, but polar solvents such as water, lower aliphatic alcohols, ketones such as methyl ethyl ketone, ethers, and esters are preferred. During polymerization, a polymerization initiator such as an azo compound or a persulfate, or a polymerization chain transfer agent such as a mercaptan, can be used. The polymerization temperature varies depending on the type of polymerization initiator, monomer, and solvent used, but is preferably 30°C or higher, more preferably 50°C or higher, and preferably 95°C or lower, more preferably 80°C or lower. The polymer a is preferably neutralized with an alkali metal compound as described below.

[0021] From the viewpoint of dispersion stability of the pigment, the number average molecular weight of polymer a is preferably 4,000 or more, more preferably 6,000 or more, even more preferably 8,000 or more, and is preferably 150,000 or less, more preferably 100,000 or less, even more preferably 80,000 or less, still more preferably 50,000 or less, and even more preferably 30,000 or less. From the same viewpoint as above, the acid value of polymer a is preferably 50 mgKOH / g or more, more preferably 90 mgKOH / g or more, even more preferably 180 mgKOH / g or more, still more preferably 200 mgKOH / g or more, still more preferably 220 mgKOH / g or more, and preferably 400 mgKOH / g or less, more preferably 320 mgKOH / g or less, still more preferably 300 mgKOH / g or less, still more preferably 280 mgKOH / g or less. The number average molecular weight and acid value of the polymer can be measured by the method described in the Examples.

[0022] <Production of Pigment-Containing Polymer Particles> The pigment-containing crosslinked polymer particles can be efficiently produced by a method including the following steps 1 and 2. Step 1: Neutralizing at least a portion of the carboxy groups of polymer a with an alkali metal compound to obtain an aqueous dispersion of polymer a Step 2: A step of dispersing the aqueous dispersion of polymer a obtained in step 1 and a pigment to obtain an aqueous pigment dispersion of polymer particles containing the pigment dispersed in polymer a.

[0023] In the present invention, it is preferable to further crosslink the pigment aqueous dispersion obtained in step 2 with a crosslinking agent, if necessary. That is, in the present invention, the production of pigment-containing crosslinked polymer particles preferably further includes the following step 3 after step 2. Step 3: A step of adding a crosslinking agent to the pigment aqueous dispersion obtained in Step 2 and subjecting it to a crosslinking treatment to obtain a pigment aqueous dispersion of crosslinked polymer particles containing the pigment.

[0024] (Process 1) It is preferable that at least a portion of the carboxyl groups of polymer a be neutralized with an alkali metal compound, which is believed to increase the charge repulsion force that occurs after neutralization, thereby suppressing aggregation of pigment particles in aqueous inks and improving the dispersion stability of the pigment. The neutralization in step 1 is preferably carried out so that the pH is 7 or more and 11 or less. Examples of the alkali metal compound include one or more selected from alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, and cesium hydroxide, alkali metal carbonates such as disodium carbonate, sodium bicarbonate, and dipotassium carbonate, and alkali metal borate salts such as sodium borate, etc. Among these, preferred are alkali metal hydroxides, more preferred are one or more selected from sodium hydroxide and potassium hydroxide, and even more preferred is sodium hydroxide.

[0025] From the viewpoint of ensuring the dispersion stability of the pigment, the degree of neutralization of polymer a is preferably 15 mol % or more, more preferably 20 mol % or more, even more preferably 30 mol % or more, and is preferably 150 mol % or less, more preferably 100 mol % or less, even more preferably 80 mol % or less. Here, the degree of neutralization (mol %) is calculated by the following formula. Degree of neutralization (mol %) = [number of moles of alkali metal compound / number of moles of carboxyl groups in polymer (a)] × 100 In the present invention, when the alkali metal compound is used in excess of the number of moles of carboxy groups in the polymer (a), the degree of neutralization may exceed 100 mol %.

[0026] (Process 2) In the dispersion treatment in step 2, the pigment particles can be atomized to the desired particle size by main dispersion using shear stress alone, but from the viewpoint of obtaining a uniform aqueous pigment dispersion, it is preferable to pre-disperse the pigment mixture and then further perform main dispersion. As a disperser used for pre-dispersion, a commonly used mixing and stirring device such as an anchor blade or a disperser blade can be used. Examples of dispersing machines used for this dispersion include kneading machines such as a roll mill and a kneader, high-pressure homogenizers such as a microfluidizer, and media-type dispersing machines such as a paint shaker and a bead mill. Among these, it is preferable to use a high-pressure homogenizer from the viewpoint of reducing the particle size of the pigment. When the dispersion treatment is carried out using a high-pressure homogenizer, the average particle size of the pigment particles in the pigment aqueous dispersion can be adjusted by controlling the treatment pressure and the number of passes. From the viewpoints of productivity and economy, the treatment pressure is preferably 60 MPa or more and 300 MPa or less, and the number of passes is preferably 3 or more and 30 or less.

[0027] (Step 3) In step 3, polymer a dispersing the pigment is crosslinked by a crosslinking agent to form a crosslinked polymer, thereby obtaining a pigment aqueous dispersion in which particles of the crosslinked polymer containing the pigment are dispersed in an aqueous medium.

[0028] The crosslinking agent used in step 3 is preferably an epoxy compound, more preferably a compound having two or more epoxy groups in the molecule. The compound having two or more epoxy groups in the molecule is preferably a compound having two or more glycidyl ether groups in the molecule, more preferably a polyglycidyl ether compound of a polyhydric alcohol having a hydrocarbon group having from 3 to 8 carbon atoms. The epoxy equivalent of the compound having two or more epoxy groups in the molecule is preferably 90 or more, more preferably 100 or more, even more preferably 110 or more, and is preferably 300 or less, more preferably 200 or less, even more preferably 170 or less, from the viewpoint of more efficiently crosslinking with the carboxyl group of polymer a in a medium mainly composed of water. Specific examples of the compound having two or more epoxy groups in the molecule include one or more selected from polyglycidyl ethers such as cyclohexanedimethanol diglycidyl ether, polyethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, diethylene glycol diglycidyl ether, glycerol polyglycidyl ether, polyglycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, sorbitol polyglycidyl ether, pentaerythritol polyglycidyl ether, resorcinol diglycidyl ether, neopentyl glycol diglycidyl ether, and hydrogenated bisphenol A diglycidyl ether. Among these, one or more selected from cyclohexanedimethanol diglycidyl ether, 1,6-hexanediol diglycidyl ether, diethylene glycol diglycidyl ether, trimethylolpropane polyglycidyl ether, and pentaerythritol polyglycidyl ether are preferred.

[0029] In step 3, the temperature of the crosslinking treatment is preferably 50° C. or higher, more preferably 70° C. or higher, and preferably 95° C. or lower, more preferably 92° C. or lower, from the viewpoints of completing the crosslinking reaction and economy. The time of the crosslinking treatment is preferably 0.5 hours or higher, more preferably 1 hour or higher, and preferably 10 hours or lower, more preferably 6 hours or lower, from the same viewpoints as above.

[0030] The acid value of the polymer constituting the pigment-containing crosslinked polymer particles is preferably 50 mgKOH / g or more, more preferably 95 mgKOH / g or more, even more preferably 100 mgKOH / g or more, and is preferably 200 mgKOH / g or less, more preferably 210 mgKOH / g or less, even more preferably 160 mgKOH / g or less.

[0031] The crosslinking rate of polymer a is preferably 80 mol % or less, more preferably 70 mol % or less, and even more preferably 60 mol % or less. Here, when an epoxy compound is used as a crosslinking agent in step 3, the crosslinking rate (mol %) is calculated by "(mol number of epoxy groups of epoxy compound / mol number of carboxy groups of polymer a) x 100".

[0032] From the viewpoint of dispersion stability, the non-volatile component concentration (solid content concentration) of the resulting pigment water dispersion is preferably 10% by mass or more, more preferably 15% by mass or more, and preferably 45% by mass or less, more preferably 40% by mass or less. From the viewpoint of dispersion stability, the content of the pigment in the pigment water dispersion is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 12% by mass or more, and is preferably 45% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less. The average particle size of the pigment-containing polymer particles in the pigment water dispersion is preferably 50 nm or more, more preferably 70 nm or more, even more preferably 80 nm or more, and is preferably 350 nm or less, more preferably 250 nm or less, even more preferably 150 nm or less, from the viewpoint of reducing coarse particles and improving the ejection stability of the water-based ink. The average particle size of the pigment-containing polymer particles in the water-based ink is substantially the same as the average particle size in the pigment water dispersion. The solid content concentration and average particle size of the pigment water dispersion are measured by the method described in the examples.

[0033] <Pigment-free polymer particles> The ink of the present invention may contain polymer particles that do not contain a pigment, if necessary, from the viewpoint of improving the fixability of the ink of the present invention to a recording medium. Examples of the polymer constituting the pigment-free polymer particles (hereinafter also referred to as "polymer b") include (meth)acrylic resins, styrene resins, urethane resins, polyester resins, butadiene resins, vinyl chloride resins, etc. Among these, from the viewpoint of improving the hiding power of the ink of the present invention and the blocking resistance of the recorded matter, (meth)acrylic resins are preferred, and styrene-(meth)acrylic resins are more preferred. The polymer particles not containing a pigment are preferably used as an aqueous dispersion in which they are dispersed in water. The polymer b may be an appropriately synthesized product or a commercially available product. Furthermore, from the viewpoint of further improving the fixability of the ink of the present invention to a recording medium, it is preferable that polymer b has a crosslinked structure crosslinked with a crosslinking agent, i.e., be a crosslinked polymer particle containing no pigment. The crosslinked polymer particle containing no pigment is composed of a component derived from polymer b and a component derived from the crosslinking agent.

[0034] [Polymer b] The (meth)acrylic resin as the polymer (b) preferably has (b-1) a structural unit derived from a carboxy group-containing vinyl monomer and (b-2) a structural unit derived from a hydrophobic vinyl monomer. Examples of the component (b-1) include the same carboxylic acid monomers as those of the component (a-1). Among them, from the viewpoint of improving fixability to a recording medium and improving image fastness of a recorded product, one or more selected from acrylic acid and methacrylic acid are preferred, and acrylic acid is more preferred. As the component (b-2), the same alkyl (meth)acrylates and aromatic group-containing monomers as those of the component (a-2) are preferably used. Among them, styrene-based monomers are preferred, and one or more selected from styrene and α-methylstyrene are preferred, with styrene being more preferred. The monomer components contained in the above components (b-1) and (b-2) can be used alone or in combination of two or more.

[0035] [Content of each structural unit in polymer b] The content of the structural units derived from the components (b-1) and (b-2) in the polymer b is as follows, from the viewpoint of improving fixability to a recording medium. The content of the (b-1) component is preferably 15% by mass or more, more preferably 20% by mass or more, even more preferably 25% by mass or more, and is preferably 70% by mass or less, more preferably 60% by mass or less, even more preferably 50% by mass or less. The content of the (b-2) component is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, and preferably 85% by mass or less, more preferably 80% by mass or less, even more preferably 75% by mass or less.

[0036] The polymer b can be produced by copolymerizing a monomer mixture containing the components (b-1) and (b-2) by a known solution polymerization method or the like. The methods for producing, neutralizing, and crosslinking polymer b are the same as those for producing, neutralizing, and crosslinking polymer a described above, and therefore will not be described here.

[0037] From the viewpoint of improving fixation to a recording medium, the acid value of polymer b is preferably 180 mgKOH / g or more, more preferably 200 mgKOH / g or more, even more preferably 220 mgKOH / g or more, and is preferably 320 mgKOH / g or less, more preferably 300 mgKOH / g or less, even more preferably 280 mgKOH / g or less. The number average molecular weight of polymer b is preferably 4,000 or more, more preferably 6,000 or more, even more preferably 8,000 or more, and preferably 80,000 or less, more preferably 50,000 or less, even more preferably 30,000 or less. The acid value and number average molecular weight of polymer b can be measured in the same manner as in the case of polymer a.

[0038] From the viewpoint of improving fixation to a recording medium, the average particle size of the pigment-free polymer particles is preferably 60 nm or more, more preferably 80 nm or more, even more preferably 100 nm or more, and is preferably 200 nm or less, more preferably 160 nm or less, even more preferably 150 nm or less. The average particle size of the pigment-free polymer particles in the ink of the present invention after preparation of the ink of the present invention is substantially the same as the average particle size of the pigment-free polymer particles prepared before preparation of the water-based ink.

[0039] Polymer a and polymer b may be the same or different, i.e., polymer a and b may have different compositions (structures), or may be the same polymer including the composition (structure) and differ only in the presence or absence of a pigment. Polymer a and polymer b may also be commercially available products. Examples of commercially available dispersions of polymers a and b that can be used include Neocryl A1127 (anionic self-crosslinking waterborne acrylic resin) manufactured by DSM Neo Resins, Joncryl 390 (acrylic resin) manufactured by BASF, Joncryl PDX-7775 (styrene-acrylic resin) manufactured by BASF, and Vinyblan 700 (vinyl chloride-acrylic resin) manufactured by Nissin Chemical Industry Co., Ltd. When the polymer particles containing a pigment and the polymer particles not containing a pigment are both crosslinked polymer particles containing a pigment and crosslinked polymer particles not containing a pigment, it is preferable that the crosslinking agent is the same. Furthermore, when the polymer particles containing a pigment and the polymer particles not containing a pigment are both crosslinked polymer particles containing a pigment and crosslinked polymer particles not containing a pigment, it is preferable that polymer a and polymer b are the same, and further that the crosslinking agent is also the same.

[0040] <Glycol ether (A)> The glycol ether (A) contained in the ink of the present invention has an HLB value of 6.0 or more and 7.5 or less, as calculated by the Davis method. When the glycol ether (A) has an HLB value of 6.0 or more and 7.5 or less, it is possible to obtain printed matter of substantially the same image quality on both gloss coated paper and matte coated paper. The HLB value of the glycol ether (A) is preferably 6.2 or more, more preferably 6.8 or more, and preferably 7.3 or less, more preferably 7.0 or less, from the viewpoint of obtaining printed matter of approximately the same image quality on both gloss coated paper and matte coated paper.

[0041] In the present invention, the "HLB value" is a value that indicates the affinity of a compound for water and oil. The HLB value of the glycol ether in the present invention is calculated by the "Davis method" using the following formula: HLB value (Davis method) = 7 + Σ (number of hydrophilic groups) + Σ (number of lipophilic groups) Here, "Σ (number of hydrophilic groups)" indicates the total number of hydrophilic group groups contained in the compound, and "Σ (number of lipophilic groups)" indicates the total number of lipophilic group groups contained in the compound. The number of radicals is a value specific to the functional group (hydrophilic group and lipophilic group), and the number of radicals of the main functional groups is as follows: (Hydrophilic group) -(CH2CH2O)-:+0.330 -OH:+1.900 (Lipophilic group) -CH2-:-0.475 -CH3:-0.475 -(CH2(CH3)CH2O)-:-0.150

[0042] In the ink of the present invention, the glycol ether (A) is preferably a glycol ether represented by the following formula (1). R 1 O-(R 2 O) x -R 3 (1) (In the formula, R 1 represents a linear or branched alkyl group having 1 to 8 carbon atoms, and R2 O represents a linear or branched alkyleneoxy group having 2 to 6 carbon atoms; R 3 represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. x represents the average number of moles of alkylene oxide added, and x (R 2 O) may be the same or different from each other.

[0043] The glycol ether (A) is preferably at least one selected from propylene glycol mono-n-butyl ether (HLB value=6.9), propylene glycol monopropyl ether (HLB value=7.3), dipropylene glycol monopropyl ether (HLB value=7.2), ethylene glycol monobutyl ether (HLB value=7.3), ethylene glycol monoisobutyl ether (HLB value=7.3), ethylene glycol monohexyl ether (HLB value=6.4), propylene glycol monopropyl ether, ethylene glycol dimethyl ether (HLB value=6.4), diethylene glycol dimethyl ether (HLB value=6.7), triethylene glycol dimethyl ether (HLB value=7.0), and diethylene glycol methyl ethyl ether (HLB value=6.2).

[0044] <Organic solvents other than glycol ether (A) (other organic solvents)> The ink of the present invention preferably contains an organic solvent other than the glycol ether (A) (hereinafter also referred to as "other organic solvent"), to the extent that the effect of the present invention is not impaired. The other organic solvent is preferably one that is miscible with water in any ratio. The inclusion of the other solvent improves the stability of the glycol ether (A), the polyether-modified silicone (B), and the acetylene glycol surfactant (C) in water, thereby enabling the dot diameter of the ejected ink to be increased. Specific examples of other organic solvents include polyhydric alcohols, glycol ethers other than the glycol ether (A), and nitrogen-containing heterocyclic compounds. Among these, one or more selected from polyhydric alcohols and glycol ethers other than the glycol ether (A) are preferred, and polyhydric alcohols are more preferred. The boiling point of the other organic solvent is preferably 100°C or higher, more preferably 120°C or higher, even more preferably 140°C or higher, and preferably 260°C or lower, more preferably 250°C or lower, even more preferably 240°C or lower.

[0045] Preferred polyhydric alcohols include diols such as ethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, 1,2-butanediol, 1,4-butanediol, 3-methyl-1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 2-methyl-2,4-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 2-methyl-2,4-pentanediol, 1,2-octanediol, and 1,8-octanediol. Among these, preferred are at least one selected from propylene glycol, dipropylene glycol, 1,2-butanediol, 1,4-butanediol, and 1,2-hexanediol, more preferred are at least one selected from propylene glycol, dipropylene glycol, and 1,2-butanediol, and even more preferred is propylene glycol. When the ink of the present invention contains propylene glycol, the propylene glycol suppresses the evaporation of the glycol ether (A), thereby enhancing the effect of obtaining recorded images of substantially the same image quality on both gloss coated paper and matte coated paper.

[0046] Examples of glycol ethers other than the glycol ether (A) include glycol ethers having an HLB value of less than 6.0 or more than 7.5. Glycol ethers other than glycol ether (A) include ethylene glycol monomethyl ether (HLB value = 8.8), diethylene glycol monomethyl ether (HLB value = 9.1), triethylene glycol monomethyl ether (HLB value = 9.4), polyethylene glycol monomethyl ether, ethylene glycol monoisopropyl ether (HLB value = 7.8), diethylene glycol monoisopropyl ether (HLB value = 8.1), diethylene glycol monobutyl ether (HLB value = 7.7), triethylene glycol monobutyl ether (HLB value = 8.0), diethylene glycol monomethyl ether (HLB value = 8.1 ... Examples include cholesteryl monoisobutyl ether (HLB value = 7.7), diethylene glycol monobenzyl ether, propylene glycol methyl ether (HLB value = 8.3), dipropylene glycol monomethyl ether (HLB value = 8.1), and tripropylene glycol monomethyl ether (HLB value = 8.0). Of these, one or more selected from diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monoisobutyl ether, and dipropylene glycol methyl ether are preferred, and diethylene glycol monoisopropyl ether is more preferred.

[0047] <Polyether-modified silicone (B)> In the polyether-modified silicone (B) contained in the ink of the present invention, the ratio [m / n] of the repeat number m of polyorganosiloxane units without polyether groups to the repeat number n of polyorganosiloxane units with polyether groups is 3.0 or more and 12.0 or less. When [m / n] is 3.0 or more, the interfacial orientation is increased and wetting by the glycol ether (A) and the acetylene glycol surfactant (C) is improved, and when [m / n] is 12 or less, wetting by the glycol ether (A) and the acetylene glycol surfactant (C) is not significantly inhibited, preventing unevenness in the image. From the viewpoint of obtaining recorded materials of approximately the same image quality on both gloss coated paper and matte coated paper, the [m / n] of the polyether-modified silicone (B) is preferably 3.5 or more, more preferably 4.0 or more, even more preferably 6.0 or more, still more preferably 7.0 or more, and preferably 11.0 or less, more preferably 10.5 or less, even more preferably 10.0 or less, and still more preferably 9.0 or less.

[0048] The polyether-modified silicone (B) has a structure in which the hydrocarbon groups on the side chains and / or terminals of the silicone oil are substituted with polyether groups. The polyether groups are preferably polyethyleneoxy groups, polypropyleneoxy groups, or polyalkyleneoxy groups in which ethyleneoxy groups (EO) and propyleneoxy groups (PO) are added in a block or random fashion. Compounds in which polyether groups are grafted onto a silicone main chain, compounds in which silicone and polyether groups are bonded in a block fashion, etc. can be used.

[0049] The polyether-modified silicone (B) is preferably a polyether-modified silicone represented by the following formula (2).

[0050] [ka]

[0051] In the above formula (2), R 1 represents an alkyl group or a hydroxy group having 1 to 3 carbon atoms, and R 2 represents an alkanediyl group having 2 to 5 carbon atoms, and R 3 represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a hydroxy group, PO represents a propyleneoxy group, and EO represents an ethyleneoxy group. a, b, m, and n represent the average number of moles of each unit added, where a is 0 to 50, b is 1 to 50, m is 1 to 600, and n is 1 to 50. 1 may be the same or different. In the above formula (2), m represents the repeating number of the polyorganosiloxane unit not having a polyether group, and n represents the repeating number of the polyorganosiloxane unit having a polyether group.

[0052] In the above formula (2), R 1 is preferably an alkyl group having 1 to 3 carbon atoms, more preferably a methyl group. 2 is preferably an alkanediyl group having 3 or 4 carbon atoms, more preferably a trimethylene group. 3 is preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably a hydrogen atom, a methyl group or a butyl group. Furthermore, the propyleneoxy group represented by PO is preferably a propane-1,2-diyloxy group.

[0053] In the above formula (1), a is preferably 0 or more and 50 or less, more preferably 0 or more and 20 or less, even more preferably 0 or more and 10 or less, and even more preferably 0 or more and 7 or less. Furthermore, b is preferably 1 or more and 50 or less, more preferably 1 or more and 30 or less, even more preferably 5 or more and 25 or less, and even more preferably 10 or more and 18 or less. Furthermore, m is preferably 1 or more and 600 or less, more preferably 3-400, and even more preferably 5-300. Furthermore, n is preferably 1 or more and 50 or less, and more preferably 1 or more and 30 or less.

[0054] The ratio [m / n] of the repeat number m of the polyorganosiloxane unit not having a polyether group to the repeat number n of the polyorganosiloxane unit having a polyether group in the polyether-modified silicone (B) is 1 From the H-NMR measurement results, the peak area of ​​the proton (H) of the methylene group (CH2) directly bonded to the Si element is normalized to 2 (2H: fixed value), and the calculation can be performed using the following formula. In the following calculation formula, "modified Si element" refers to a Si element to which EO or PO is bonded via an alkanediyl group, and "unmodified Si element" refers to a Si element to which no EO or PO is bonded. [m / n] = {[peak area value of δ = 0 to 0.5 (ppm)] - [area value of methyl group protons directly bonded to modified Si element (area value = 3)]} / [area value of methyl group protons directly bonded to unmodified Si element (area value = 6)]

[0055] 1 Specifically, for the H-NMR measurement, 100 mg of polyether-modified silicone (B) is diluted with 2.0 mL of deuterated chloroform containing trimethylsilyl to prepare a measurement sample, which is measured using an NMR device (e.g., Agilent-NMR-vnmrs400, 400 MHz, manufactured by Varian) under the following measurement conditions: (Measurement conditions) Pulse width: 45 μs (45° pulse) Observation width: 6410Hz Waiting time: 10 seconds Number of times accumulated: 8 times Measurement temperature: room temperature More specifically, [m / n] can be calculated by the method described in the Examples. 1 H-NMR measurement is performed and the value is calculated using the above formula.

[0056] The method for synthesizing the polyether-modified silicone (B) is not particularly limited and can be appropriately selected depending on the purpose. For example, reference can be made to the descriptions in Japanese Patent Nos. 5101598, 5032325, and 5661229. Specifically, it can be synthesized by subjecting polyether (b1) (hereinafter also referred to as "component (b1)") and organohydrogensiloxane (b2) (hereinafter also referred to as "component (b2)") to a hydrosilylation reaction. The polyether of component (b1) is -(C n H 2n 0)-(n=2 to 4) represents a polyoxyalkylene copolymer. Examples of polyoxyalkylene copolymer units include oxyethylene units -(C2H4O)-, oxypropylene units -(C3H6O)-, oxybutylene units -(C4H8O)-, or mixtures thereof. The oxyalkylene units may be arranged in any manner to form either a block structure or a random copolymer structure, but preferably form a random copolymer group. The polyoxyalkylene preferably contains both oxyethylene units -(C2H4O)- and oxypropylene units -(C3H6O)- in a random copolymer.

[0057] The organohydrogensiloxane of component (b2) is an organopolysiloxane containing at least one silicon-bonded hydrogen (SiH) per molecule. Examples of the organopolysiloxane include (RSiO 0.5 ), (RSiO), (RSiO 1.5 ), (SiO2) (wherein R independently represents an organic group or a hydrocarbon group), and any number or combination of siloxy units. Organopolysiloxane (R3SiO 0.5 ), (RSiO), (RSiO 1.5 When R in (SiO2) is a methyl group, the siloxy units are designated as M units, D units, and T units, respectively, while (SiO2) siloxy units are designated as Q units. Organohydrogensiloxanes have a similar structure but have at least one SiH present on the siloxy unit. The methyl siloxy units in organohydrogensiloxanes are "MH" siloxy units (R2HSiO 0.5 ), "DH" siloxy unit (RHSiO), "TH" siloxy unit (HSiO 1.5 ) can be expressed as The organohydrogensiloxane can contain any number of M, MH, D, DH, T, TH, or Q siloxy units, provided that at least one siloxy unit contains SiH.

[0058] The component (b1) and the component (b2) are reacted by a hydrosilylation reaction. The hydrosilylation reaction is not particularly limited and can be appropriately selected depending on the purpose, but is preferably carried out in the presence of a hydrosilylation catalyst. The hydrosilylation catalyst is not particularly limited and can be appropriately selected depending on the purpose. Examples include platinum, rhodium, ruthenium, palladium, osmium, and iridium metals, organometallic compounds thereof, and combinations thereof. The content of the hydrosilylation catalyst is preferably 0.1 ppm to 1,000 ppm, and more preferably 1 ppm to 100 ppm, based on the weight of the component (b1) and the component (b2).

[0059] The hydrosilylation reaction can be carried out neat or in the presence of a solvent, but is preferably carried out in the presence of a solvent. Examples of solvents include alcohols such as methanol, ethanol, isopropanol, butanol, and n-propanol; ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as heptane, hexane, and octane; glycol ethers such as propylene glycol methyl ether, dipropylene glycol methyl ether, propylene glycol n-butyl ether, propylene glycol n-propyl ether, and ethylene glycol n-butyl ether; halogenated hydrocarbons such as dichloromethane, 1,1,1-trichloroethane, methylene chloride, and chloroform; dimethyl sulfoxide; dimethylformamide; acetonitrile; tetrahydrofuran; white spirits; mineral spirits; naphtha, etc. These may be used alone or in combination of two or more.

[0060] The amounts of component (b1) and component (b2) used in the hydrosilylation reaction are not particularly limited and can be adjusted appropriately depending on the purpose, and are expressed as the molar ratio of the total unsaturated groups in component (b1) to the SiH content in component (b2). The reaction is preferably carried out using a polyether unsaturated group amount of 20 mol% or less, and more preferably 10 mol% or less, of the SiH molar amount of the organohydrogensiloxane. The hydrosilylation reaction may be carried out in any suitable manner depending on the purpose, without any particular limitation. Examples of the method include a batch method, a semi-continuous method, and a continuous method. For example, the reaction may be carried out in a continuous method using a plug flow reactor.

[0061] Specific examples of the polyether-modified silicone (B) include PEG-9 dimethicone, PEG-9PEG-9 dimethicone, PEG-9 methyl ether dimethicone, PEG-10 dimethicone, PEG-11 methyl ether dimethicone, PEG / PPG-20 / 22 butyl ether dimethicone, PEG-32 methyl ether dimethicone, PEG-9 polydimethylsiloxyethyl dimethicone, and lauryl PEG-9 polydimethylsiloxyethyl dimethicone. Commercially available examples of polyether-modified silicone (B) include the BYK series manufactured by BYK Japan K.K., the KF series manufactured by Shin-Etsu Chemical Co., Ltd., the Silface SAG series manufactured by Nissin Chemical Industry Co., Ltd., the TEGO WET series manufactured by Evonik, and the DOWSIL series manufactured by Dow Toray Co., Ltd. In particular, from the viewpoints of kinematic viscosity, [m / n] ratio, and ability to obtain printed matter of approximately the same image quality on both gloss coated paper and matte coated paper, KF-352A, KF-353A, KF-355A, KF-615A, KF-642, KF-6011, and KF-6012 manufactured by Shin-Etsu Chemical Co., Ltd., Silface SAG-005 and SAG-008 manufactured by Nissin Chemical Industry Co., Ltd., and DOWSIL FZ-2123 manufactured by Dow Toray Industries, Inc. are particularly preferred.

[0062] In the ink of the present invention, the kinematic viscosity of the polyether-modified silicone (B) at 25°C is preferably 50 mm from the viewpoint of obtaining printed matter of substantially the same image quality on both gloss coated paper and matte coated paper. 2 / s or more, preferably 90 mm 2 / s or more, 300mm 2 / s or more, and preferably 1,500 mm 2 / s or less, preferably 1,000 mm 2 / s or less, more preferably 700 mm 2 / s or less. Specifically, preferably 50 mm 2 / s or more 1,500mm 2 / s or less, preferably 90 mm 2 / s or more 1,000mm 2 / s or less, more preferably 90 mm 2 / s or more 700mm 2 / s or less, and even more preferably 300 mm 2 / s or more 700mm 2 / s or less. The kinematic viscosity of polyether-modified silicone (B) is measured at 25°C using an Ubbelohte capillary viscometer as described in Method 1 of Viscosity Measurement, General Test Methods, in the Commentary on Cosmetic Raw Materials, Second Edition (pp. 1461-1463, 1984, Yakuji Nipposha).

[0063] <Acetylene glycol surfactant (C)> The ink of the present invention contains an acetylene glycol surfactant (C). Since the acetylene glycol surfactant (C) is a relatively low-molecular surfactant, its dynamic surface tension decreases shortly after the ink lands, and therefore its use together with the glycol ether (A) of the present invention is thought to optimize the change in surface tension over time, which is thought to suppress the expansion of the ink dot diameter and to enable the production of printed matter of approximately the same image quality on both gloss-coated and matte-coated paper.

[0064] Examples of the acetylene glycol surfactant (C) include acetylene glycols having 8 to 22 carbon atoms and ethylene adducts of the acetylene glycols, and one or more selected from 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, or 3,5-dimethyl-1-hexyne-3-ol, 2,4-dimethyl-5-hexyne-3-ol, and ethylene oxide adducts thereof are preferred, one or more selected from 2,4,7,9-tetramethyl-5-decyne-4,7-diol and ethylene oxide adducts thereof are more preferred, and 2,4,7,9-tetramethyl-5-decyne-4,7-diol is even more preferred.

[0065] The HLB value (Griffin method) of the acetylene glycol surfactant (C) is preferably 8 or less, more preferably 6 or less, even more preferably 5 or less, and is preferably 1 or more, more preferably 2 or more, even more preferably 3 or more, from the viewpoints of suppressing the solubility in water and enabling the ink droplets to quickly orient on the dot surface after landing on the recording medium and improving the wettability of the ink on the recording medium. Examples of commercially available acetylene glycol surfactants (C) include the Surfynol series manufactured by Air Products & Chemicals and the Acetylenol series manufactured by Kawaken Fine Chemicals Co., Ltd. In the present invention, the HLB value of the acetylene glycol surfactant (C) is determined by the Griffin method and is calculated using the following formula. HLB value (Griffin method) = 20 × (total formula weight of hydrophilic groups) / (molecular weight)

[0066] <Wax> The ink of the present invention may contain wax. It is believed that the wax easily aggregates with other dispersants as the ink wets and spreads, and is fixed on the recording medium, thereby suppressing ink bleeding. The wax may be either a natural wax or a synthetic wax. Examples of natural waxes include petroleum waxes such as paraffin wax and microcrystalline wax; vegetable waxes such as carnauba wax, candelilla wax and rice wax; and animal waxes such as lanolin and beeswax. Examples of synthetic waxes include synthetic hydrocarbon waxes such as polyolefin wax and Fischer-Tropsch wax, silicone waxes, and modified waxes such as paraffin wax derivatives, montan wax derivatives, and microcrystalline wax derivatives. The above waxes can be used alone or in combination of two or more.

[0067] Among the waxes mentioned above, one or more selected from paraffin wax and polyolefin wax are preferred, polyolefin wax which has a large molecular weight and tends to aggregate is more preferred, and polyethylene wax containing ethylene as the main component is even more preferred. Oxidized polyethylene wax can be obtained by adjusting high molecular weight polyethylene to a desired molecular weight by thermal decomposition or the like while introducing oxygen atoms or the like into the molecule, and can be used as polyethylene wax.

[0068] From the viewpoint of ink storage stability and obtaining printed images of substantially the same image quality on both gloss coated paper and matte coated paper, the melting point of the wax is preferably 80°C or higher, more preferably 85°C or higher, and is preferably 150°C or lower, more preferably 145°C or lower. The melting point of the wax is measured by the method described in the Examples.

[0069] The wax is preferably used as a wax emulsion dispersed in an aqueous medium. To ensure dispersibility, the wax emulsion preferably has an anionic or cationic surface charge, or is nonionic. Among these, nonionic wax emulsions are more preferred from the viewpoint of suppressing the influence on other dispersants and reducing the influence of other dispersants to achieve good ink performance. A nonionic wax emulsion can be obtained, for example, by mixing and emulsifying wax with a known nonionic surfactant.

[0070] The average particle size of the wax particles in the wax emulsion, particularly the average particle size of the paraffin wax particles and / or polyolefin wax particles, is preferably 300 nm or less, more preferably 250 nm or less, even more preferably 150 nm or less, from the viewpoint of wax dispersion stability and obtaining printed matter of substantially the same image quality on both gloss coated paper and matte coated paper, and is preferably 20 nm or more, preferably 40 nm or more. The average particle size of the wax particles can be measured by dynamic light scattering, for example, using a Microtrac particle size analyzer UPA manufactured by Nikkiso Co., Ltd. according to the method described in the Examples. The average particle size of the wax particles in the water-based ink is substantially the same as the average particle size of the wax particles in the wax emulsion.

[0071] [Production of the ink of the present invention] The ink of the present invention can be efficiently produced by mixing the pigment aqueous dispersion containing the pigment-containing polymer particles, glycol ether (A), polyether-modified silicone (B), acetylene glycol surfactant (C), and, if necessary, pigment-free polymer particles, other organic solvents, wax, water, and various additives. There are no particular limitations on the method for mixing the above components. Examples of the additives include fixing aids, humectants, wetting agents, penetrating agents, viscosity adjusters, antifoaming agents, preservatives, antifungal agents, and antirust agents. The fixing aid may be an emulsion containing water-insoluble polymer particles. Examples of the water-insoluble polymer particles include particles of condensation resins such as polyurethane and polyester; and vinyl resins such as (meth)acrylic resins, styrene resins, styrene-(meth)acrylic resins, butadiene resins, styrene-butadiene resins, vinyl chloride resins, vinyl acetate resins, and acrylic silicone resins.

[0072] The content of each component of the ink of the present invention and the ink properties are as follows, from the viewpoint of improving ejection stability and obtaining recorded images of substantially the same image quality on both gloss coated paper and matte coated paper.

[0073] (Pigment content) The content of the pigment in the ink of the present invention is preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 4% by mass or more, and is preferably 15% by mass or less, more preferably 10% by mass or less, even more preferably 8% by mass or less.

[0074] (polymer content) The polymer content in the ink of the present invention is preferably 0.5% by mass or more, more preferably 1% by mass or more, even more preferably 1.5% by mass or more, and preferably 10% by mass or less, more preferably 8% by mass or less, even more preferably 6% by mass or less.

[0075] (Content of pigment-containing polymer particles) When the pigment is in the form of pigment-containing polymer particles, the content of the pigment-containing polymer particles in the ink of the present invention, in terms of the total of the pigment and polymer, is preferably 2% by mass or more, more preferably 4% by mass or more, even more preferably 6% by mass or more, and is preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less.

[0076] When the ink of the present invention contains polymer particles that do not contain a pigment, the content of the polymer particles that do not contain a pigment in the ink of the present invention is preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 3% by mass or more, and preferably 15% by mass or less, more preferably 12% by mass or less, even more preferably 10% by mass or less.

[0077] (Glycol ether (A) content) The content of glycol ether (A) in the ink of the present invention is preferably 0.5% by mass, more preferably 1% by mass or more, even more preferably 1.5% by mass or more, still more preferably 2% by mass or more, and preferably 10% by mass or less, more preferably 8% by mass or less, even more preferably 6% by mass or less, and still more preferably 4% by mass or less.

[0078] (Content of other organic solvents) From the viewpoint of stably retaining the glycol ether (A), polyether-modified silicone (B), and acetylene glycol surfactant (C) in the ink, the content of other organic solvents in the ink of the present invention is preferably 5% by mass or more, more preferably 10% by mass or more, more preferably 15% by mass or more, and is preferably 30% by mass or less, more preferably 28% by mass or less, and even more preferably 25% by mass or less.

[0079] (Polyether-modified silicone (B) content) The content of polyether-modified silicone (B) in the ink of the present invention is preferably 0.005% by mass or more, more preferably 0.01% by mass or more, even more preferably 0.02% by mass or more, and still more preferably 0.1% by mass or more, and is preferably 0.9% by mass or less, more preferably 0.7% by mass or less, and even more preferably 0.5% by mass or less.

[0080] (Acetylenic glycol surfactant (C) content) The content of the acetylene glycol surfactant (C) in the ink of the present invention is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, even more preferably 0.3% by mass or more, and is preferably 1.5% by mass or less, more preferably 1.2% by mass or less, even more preferably 1% by mass or less.

[0081] (Wax content) When the ink of the present invention contains a wax, the content of the wax in the ink of the present invention is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, even more preferably 0.3% by mass or more, and preferably 1.5% by mass or less, more preferably 1.2% by mass or less, even more preferably 1% by mass or less.

[0082] (Water content) The water content in the ink of the present invention is preferably 35% by mass or more, more preferably 45% by mass or more, even more preferably 55% by mass or more, and preferably 95% by mass or less, more preferably 90% by mass or less, even more preferably 85% by mass or less.

[0083] (mass ratio of the content of polyether-modified silicone (B) to the content of acetylene glycol surfactant (C)) The mass ratio of the content of polyether-modified silicone (B) to the content of acetylene glycol-based surfactant (C) in the ink of the present invention [polyether-modified silicone (B) / acetylene glycol-based surfactant (C)] is preferably 0.01 or more, more preferably 0.02 or more, and even more preferably 0.08 or more, from the viewpoint of obtaining printed matter of approximately the same image quality on both gloss coated paper and matte coated paper, and from the same viewpoint as above, is 1.5 or less, preferably 1.0 or less, more preferably 0.7 or less, and even more preferably 0.5 or less.

[0084] (Mass ratio of polyether-modified silicone (B) content to glycol ether (A) content in the ink of the present invention) The mass ratio of the content of polyether-modified silicone (B) to the content of glycol ether (A) in the ink of the present invention [polyether-modified silicone (B) / glycol ether (A)] is preferably 0.001 or more, more preferably 0.01 or more, even more preferably 0.015 or more, and even more preferably 0.025 or more, from the viewpoints similar to those mentioned above, from the viewpoint of obtaining recorded materials of substantially the same image quality on both gloss coated paper and matte coated paper, and is preferably 0.2 or less, more preferably 0.15 or less, even more preferably 0.1 or less, and even more preferably 0.05 or less.

[0085] (mass ratio of the content of acetylene glycol surfactant (C) to the content of glycol ether (A)) The mass ratio of the acetylene glycol surfactant (C) content to the glycol ether (A) content in the ink of the present invention [acetylene glycol surfactant (C) / glycol ether (A)] is preferably 0.01 or more, more preferably 0.05 or more, even more preferably 0.1 or more, and even more preferably 0.15 or more, from the viewpoints similar to those mentioned above, from the viewpoint of obtaining printed matter of substantially the same image quality on both gloss coated paper and matte coated paper, and is preferably 1.0 or less, more preferably 0.8 or less, even more preferably 0.5 or less, and even more preferably 0.3 or less.

[0086] <Physical properties of the ink of the present invention> From the viewpoint of improving the storage stability of the ink, the viscosity of the ink of the present invention at 32°C is preferably 2 mPa s or more, more preferably 4 mPa s or more, and preferably 12 mPa s or less, more preferably 9 mPa s or less. The viscosity of the ink can be measured using an E-type viscometer. The pH of the ink of the present invention is preferably 7 or more, more preferably 7.5 or more, from the viewpoint of improving the storage stability of the ink, and is preferably 10 or less, more preferably 9.5 or less, from the viewpoint of component resistance and skin irritation.

[0087] The ink of the present invention can be loaded into a known ink jet recording apparatus and ejected as ink droplets onto a recording medium to obtain a recorded image or the like. Ink jet recording apparatuses include those of the piezo-driven type and those of the thermal-driven type, but it is more preferable to use water-based ink for ink jet printing of the piezo-driven type. Usable recording media include highly water-absorbent plain paper, low water-absorbent coated paper, art paper, and non-water-absorbent resin films such as polyester film and polypropylene film. By using the ink of the present invention, inkjet recordings of substantially the same image quality can be obtained on both gloss coated paper, which has a particularly smooth surface and thus the ink does not easily wet and spread, and matte coated paper, which has an uneven surface and therefore the ink easily wets and spreads due to capillary action. [Example]

[0088] In the following Production Examples, Examples and Comparative Examples, "parts" and "%" are "parts by mass" and "% by mass" unless otherwise specified. The methods for measuring each physical property are as follows.

[0089] (1) Measurement of polymer number average molecular weight The measurements were performed using gel permeation chromatography (GPC) on a Tosoh GPC system (HLC-8320GPC) with Tosoh columns (TSKgel SuperAWM-H, TSKgel SuperAW3000, TSKgel guard column Super AW-H) at a flow rate of 0.5 mL / min, using N,N-dimethylformamide containing phosphate and lithium bromide at concentrations of 60 mmol / L and 50 mmol / L, respectively, as the eluent. The measurements were performed using a monodisperse polystyrene kit (PStQuick B (F-550, F-80, F-10, F-1, A-1000) and PStQuick C (F-288, F-40, F-4, A-5000, A-500), both manufactured by Tosoh) with known molecular weights as standards. The measurement sample was prepared by mixing 0.1 g of polymer with 10 mL of the eluent in a glass vial, stirring at 25° C. for 10 hours, and filtering through a syringe filter (DISMIC-13HP, made of PTFE, 0.2 μm, manufactured by Advantec Co., Ltd.).

[0090] (2) Measurement of the acid value of the polymer The resin was dissolved in a titration solvent consisting of a mixture of toluene and acetone (2:1 by mass) in an automatic potentiometric titrator (Kyoto Electronics Manufacturing Co., Ltd., electric burette, model number: APB-610), and titrated with a 0.1 N potassium hydroxide / ethanol solution by potentiometric titration. The inflection point on the titration curve was taken as the endpoint. The acid value (mg KOH / g) was calculated from the titration volume of the potassium hydroxide solution up to the endpoint.

[0091] (3) Measurement of the average particle size of pigment-containing polymer particles Using a laser particle analysis system (Otsuka Electronics Co., Ltd., product name: ELS-8000), the average particle size of the pigment-containing polymer particles was measured from a pigment aqueous dispersion of the pigment-containing polymer particles by dynamic light scattering, and calculated by cumulant analysis. The measurement conditions were a temperature of 25°C, an angle of 90° between the incident light and the detector, and 100 accumulations, and the refractive index of water (1.333) was input as the refractive index of the dispersion solvent. For the measurement sample, the aqueous dispersion of the polymer particles was weighed into a screw tube (Maruem Co., Ltd., No. 5), and the solids concentration was 2 x 10 -4 Water was added to the mixture so that the concentration reached 5% by mass, and the mixture was stirred at 25°C for 1 hour using a magnetic stirrer.

[0092] (4) Measurement of solids concentration of pigment water dispersion 10.0 g of sodium sulfate, brought to a constant weight in a desiccator, was weighed out into a 30 mL polypropylene container (φ: 40 mm, height: 30 mm), and approximately 1.0 g of the sample was added and mixed. The mixture was then accurately weighed and kept at 105°C for 2 hours to remove volatiles. The mixture was then left in the desiccator for a further 15 minutes, and the mass was measured. The mass of the sample after volatile matter removal was taken as the solid content, and the solid content concentration was determined by dividing the mass by the mass of the added sample.

[0093] (5) Measurement of dynamic viscosity of polyether-modified silicone at 25°C Using an Ubbelohte capillary viscometer, the kinematic viscosity at 25°C was measured in accordance with Method 1 of the viscosity measurement method in the general testing method of the Cosmetic Ingredients Standards, Second Edition Commentary (pp. 1461-1463, 1984, Yakuji Nipposha).

[0094] (6) Calculation of [m / n] of polyether-modified silicone As described below, NMR measurement was carried out for each polyether-modified silicone, and [m / n] was calculated from the measurement results.

[0095] (6-1) 1 H-NMR measurement As a measurement sample, 100 mg of each polyether-modified silicone was diluted with 2.0 mL of trimethylsilyl-containing deuterated chloroform NMR-grade chloroform-d (99.8%, containing 0.05 vol% TMS, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and placed in a 5.0 mm diameter tube. 1 The solution was filled into a 1 H-NMR tube and measured using an Agilent-NMR-vnmrs400 (Varian, 400 MHz) under the following measurement conditions. (Measurement conditions) Pulse width: 45 μs (45° pulse) Observation width: 6410Hz Waiting time: 10 seconds Number of times accumulated: 8 times Measurement temperature: room temperature

[0096] For example, in the case of Silicone A, which will be described later, 1 The results of H-NMR (CDCl3, 400 MHz) measurement are as follows: δ(ppm); 0~0.5(50H, m), 0.50(2H, m), 1.15(17H, m), 1.55(2H, m), 3.30~3.80(92H, m). In addition, in the case of silicone A, 1 The chemical shift values ​​determined by H-NMR measurement are assigned as follows: δ = 0 to 0.5 (ppm); proton (H) of methyl group (CH3) directly bonded to Si element δ = 0.3 to 0.6 (ppm); proton (H) of methylene group (CH2) directly bonded to Si element δ = 1.5-1.7 (ppm); proton (H) of methylene group (CH2) directly bonded to (Si-CH2) δ = 3.0 to 3.8 (ppm); methylene group (CH2) of ethyleneoxy group (EO), methylene group (CH2) and CH group of propyleneoxy group (PO), and proton (H) directly bonded to oxygen atom of EO or PO

[0097] (6-2) Calculation of [m / n] The peak area value at δ = 0.3 to 0.6 (ppm) was normalized to 2 (2H: fixed value). As a result, the intramolecular ratio of Si elements directly bonded to EO or PO becomes 1, and the ratio of Si elements directly bonded to EO or PO and Si elements not directly bonded to EO or PO can be calculated. Since Si elements directly bonded to EO or PO correspond to polyorganosiloxane units having polyether groups, and Si elements not directly bonded to EO or PO correspond to polyorganosiloxane units not having polyether groups, [m / n] can be calculated by calculating the above ratio. Since there is one methyl group (CH3) directly bonded to a Si element to which EO or PO is directly bonded, as in the above formula (2), the area value of the proton of the methyl group (CH3) is 3. On the other hand, there are two methyl groups (CH3) directly bonded to a Si element to which EO or PO is not directly bonded, as in the above formula (2), so the area value of the proton of the methyl group (CH3) is 6. From the above, [m / n] was calculated using the following formula. [m / n] = {[peak area value of δ = 0 to 0.5 (ppm)] - [area value of methyl group protons directly bonded to modified Si element (area value = 3)]} / [area value of methyl group protons directly bonded to unmodified Si element (area value = 6)]

[0098] For example, in the case of Silicone A, [m / n] was calculated using the above formula as follows: [m / n] = {[peak area value of δ = 0 to 0.5 (ppm)] - [area value of methyl group protons directly bonded to modified Si element (area value = 3)]} / [area value of methyl group protons directly bonded to unmodified Si element (area value = 6)] = {50.0 - 3} / 6 = 7.8

[0099] (7) Measurement of wax melting point The melting point of the wax was measured using a measuring device conforming to JIS K 0064. Specifically, using a differential scanning calorimeter (Q20, manufactured by TA Instruments), the sample was heated to 200°C and then cooled to 0°C at a rate of 10°C / min. The sample was then heated at a rate of 10°C / min, and the calorific value was measured up to 200°C. The temperature of the peak with the largest peak area among the observed heat of fusion peaks was taken as the maximum peak temperature of melting, and this peak temperature was taken as the melting point.

[0100] (8) Measurement of the average particle size of wax particles in a wax emulsion The average particle size of wax particles in the wax emulsion was measured using a Nikkiso Microtrac particle size analyzer UPA at a laser wavelength of 780 nm, a laser output of 3 mW, and a sample concentration of 5 × 10 -3 The median value of the volume average particle size distribution (D 50 ) was taken as the average particle size of the wax particles in the wax emulsion.

[0101] Production Example 1 (Production of aqueous dispersion of pigment-containing polymer particles) (1) Production of water-insoluble polymers A monomer mixture was prepared by mixing 31 parts of acrylic acid and 69 parts of styrene. 10 parts of MEK, 0.2 parts of 2-mercaptoethanol (a polymerization chain transfer agent), and 10% of the monomer mixture were placed in a reaction vessel and mixed, followed by thorough nitrogen gas replacement. Meanwhile, a mixture of the remaining 90% of the monomer mixture, 0.13 parts of the polymerization chain transfer agent, 30 parts of MEK, and 1.1 parts of an azo-based radical polymerization initiator (2,2'-azobis(2,4-dimethylvaleronitrile), manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., product name: V-65) was placed in a dropping funnel. The monomer mixture in the reaction vessel was heated to 65°C under a nitrogen atmosphere while being stirred, and the mixture in the dropping funnel was added dropwise over 3 hours. After 2 hours at 65°C from the end of the dropping, a solution of 0.1 parts of the polymerization initiator in 2 parts of MEK was added, and the mixture was further aged at 65°C for 2 hours and then at 70°C for 2 hours, followed by drying under reduced pressure to obtain polymer (a) (number average molecular weight: 19,000, acid value: 240 mgKOH / g).

[0102] (2) Preparation of aqueous dispersion of pigment-containing polymer particles 33.3 parts of the polymer obtained in (1) above was mixed with 202 parts of ion-exchanged water, and 13.3 parts of a 5N aqueous sodium hydroxide solution (sodium hydroxide solid content: 16.9%) was further added to neutralize the mixture so that the ratio of the number of moles of sodium hydroxide to the number of moles of carboxyl groups in the polymer became 40% (neutralization degree: 40 mol%). The mixture was heated to 90°C using a warm bath and stirred for 1 hour to completely disperse the polymer in water, thereby obtaining a polymer dispersion. To this polymer dispersion, 100 parts of CI Pigment Black 7 (manufactured by Cabot Corporation) as a carbon black pigment was added to obtain a pigment mixture. The resulting pigment mixture was mixed for 1 hour at 7000 rpm and 20°C using a disperser blade, and the resulting dispersion was subjected to 15 passes of dispersion treatment at a pressure of 180 MPa using a Microfluidizer (manufactured by Microfluidics, product name: M-140K). Next, 120 parts of ion-exchanged water was added, and the mixture was dispersed 15 times using a Microfluidizer (Microfluidics, product name) at a pressure of 150 MPa. The resulting dispersion was placed in a 500 mL angle rotor and centrifuged at 3,660 rpm for 20 minutes using a high-speed refrigerated centrifuge (Hitachi Koki Co., Ltd., product name: himac CR22G, set temperature 20°C). The liquid layer was then recovered and filtered through a 5 μm membrane filter (Sartorius, product name: Minisart) to obtain a pigment aqueous dispersion. The solids concentration of the pigment aqueous dispersion at this time was 25%. (3) Preparation of an aqueous pigment dispersion of crosslinked polymer particles containing a pigment One hundred parts of the pigment aqueous dispersion obtained in (2) above was transferred to a screw-cap glass bottle, 34 parts of ion-exchanged water was added, and 2.2 parts of trimethylolpropane polyglycidyl ether (Nagase ChemteX Corporation, product name: Denacol EX-321LT, epoxy equivalent: 140, water solubility: 27%) was added as a water-insoluble crosslinker. The bottle was then sealed and heated at 70°C for 5 hours with stirring. The crosslinking treatment was carried out using an amount of crosslinker sufficient to react with 50% of the total carboxyl groups in the polymer (crosslinking rate: 50 mol%). After 5 hours, the dispersion was cooled to room temperature (25°C) and filtered using a 25 mL needleless syringe (Terumo Corporation) equipped with a 5 μm filter to obtain a pigment aqueous dispersion of crosslinked polymer particles containing the pigment (acid value: 120 mg KOH / g, solids concentration: 20%, pigment: 14.0%, polymer: 6.0%, average particle size: 100 nm).

[0103] Production Example 2-1 (Production of Polyether-Modified Silicone (B) (Production of Silicone A)) 993 g of methylhydrogenpolysiloxane represented by the following formula (3), average composition "CH2=CHCH2O(CH2CH2O) 11 835 g of allylated polyether represented by "H", 2610 g of ethyl alcohol, 0.14 g of a 2% solution of chloroplatinic acid in isopropanol, and 0.14 g of potassium acetate as a pH adjuster were weighed out and reacted for 5 hours with stirring at a reaction temperature of 80°C. Residual SiH was removed by adding hexene, and the reaction liquid was stripped and purified under reduced pressure and filtered.

[0104] [ka]

[0105] To the filtered polyether-modified silicone was added 63 g of 10-3 N hydrochloric acid and stirred at 90°C for 4 hours. After vacuum stripping, the mixture was purified and filtered to obtain silicone A as polyether-modified silicone (B). The kinematic viscosity of silicone A at 25°C was measured to be 425 mm 2 / s.

[0106] Production Examples 2-2 to 2-9 (Production of Polyether-Modified Silicone (B) (Production of Silicones B to I)) Silicones B to I were obtained as polyether-modified silicones (B) in the same manner as in Production Example 2-1, except that the types and amounts of methylhydrogenpolysiloxane and allylated polyether used were appropriately changed.

[0107] Silicones A to I obtained in Production Examples 2-1 to 2-9 are as follows. In addition, the following m, n, and R 1 , R 2 , R 3 , a and b are m, n, R in the above formula (2). 1 , R 2 , R 3 , a and b. Silicone A: [m / n] = 7.8, kinematic viscosity at 25°C = 425 mm 2 / s, R 1 =CH3, R 2 =C3H6,R 3 =H, a=0, b=11 Silicone B: [m / n] = 6.8, kinematic viscosity at 25°C = 95 mm 2 / s, R 1 =CH3, R 2 =C3H6,R 3 =CH3, a=0, b=12 Silicone C: [m / n] = 10.8, kinematic viscosity at 25°C = 172 mm 2 / s, R 1 =CH3, R 2 =C3H6,R 3 =CH3, a=6, b=18 Silicone D: [m / n] = 3.6, kinematic viscosity at 25°C = 134 mm 2 / s, R 1 =CH3, R 2 =C3H6,R 3 =CH3, a=0, b=16 Silicone E: [m / n] = 3.0, kinematic viscosity at 25°C = 142 mm 2 / s, R 1 =CH3, R 2 =C3H6,R 3 =CH3, a=0, b=16 Silicone F: [m / n] = 6.8, kinematic viscosity at 25°C = 950 mm 2 / s, R 1 =CH3, R 2 =C3H6,R 3 =C4H9, a=13, b=34 Silicone G: [m / n] = 11.2, kinematic viscosity at 25°C = 785 mm 2 / s, R 1 =CH3, R 2 =C3H6,R 3 =H, a=35, b=38 Silicone H: [m / n] = 2.9, kinematic viscosity at 25°C = 72 mm 2 / s, R 1 =CH3, R 2 =C3H6,R 3 =CH3, a=0, b=12 Silicone I: [m / n] = 15.3, kinematic viscosity at 25°C = 812 mm 2 / s, R 1 =CH3, R 2 =C3H6,R 3 =CH3, a=0, b=11

[0108] Example 1 (Production of Water-Based Ink 1) 37.5 parts of the pigment water dispersion of crosslinked polymer particles containing the pigment obtained in Production Example 1 [solid content: 7.5 parts (pigment: 5.25 parts, polymer: 2.25 parts)], silicone A as polyether-modified silicone 0.1 parts of propylene glycol mono-n-butyl ether (manufactured by Nippon Nyukazai Co., Ltd., trade name: BFG) 3.0 parts of propylene glycol (manufactured by AGC Corporation) 20.0 parts of propylene glycol (manufactured by AGC Corporation), 1.2 parts of an acetylene glycol surfactant (manufactured by Nissin Chemical Industry Co., Ltd., trade name: Surfynol 104PG50, HLB value (Griffin method): 4 (catalog value), active ingredient: 50% by mass), and ion-exchanged water were added to bring the total amount to 100 parts, and the mixture was stirred with a magnetic stirrer for 30 minutes. After that, the mixture was filtered using a syringe equipped with a 5 μm acetyl cellulose filter to obtain water-based ink 1 [solid content concentration: 8.2%, pigment-containing polymer particles 7.5% (pigment: 5.25%, polymer: 2.25%), average particle size: 95 nm].

[0109] Examples 2 to 20 and Comparative Examples 1 to 7 (Production of Water-Based Inks 2 to 20 and C1 to C7) In the same manner as in Example 1, water-based inks 2 to 20 and C1 to C7 were obtained according to the formulations shown in Table 1. The results are shown in Table 1. The amount of each component in Table 1 is the amount of solid content (active content).

[0110] The waxes in Table 1 are as follows: Polyethylene wax: Toho Chemical Industry Co., Ltd., product name: Hi-Tec E-6500, nonionic polyethylene wax emulsion, melting point: 140°C, average particle size: 60 nm, solid content: 35% by mass

[0111] <Measurement of dot diameter> An inkjet printer (ImageXpert, product name: Jetxpert) equipped with a Fujifilm Dimatix piezo-driven inkjet head (product name: Samba G3L) was filled with water-based ink. After adjusting the head voltage to 30 V, frequency to 20 kHz, push-pull drive waveform, and ink ejection volume to 2.0 pL, printing was performed at a resolution of 1200 x 1200 dpi on gloss-coated paper (Oji Paper, product name: OK Topcoat+) and matte-coated paper (GRAFICAS Y FORMULARIOS, product name: Fitnes Matt), with an image density of 6%. The resulting print was observed under an optical microscope, and the diameter of the ink dots was measured and recorded as the dot diameter. To print evenly on paper at a resolution of 1200 dpi, a dot diameter of 30 μm is required, but due to the impact accuracy of the inkjet head, a dot diameter of 30 μm may cause streaks (white spaces), etc. Therefore, a dot diameter of 31 μm or more was deemed acceptable.

[0112] <Measurement of the difference in line width between matte coated paper and gloss coated paper> The same gloss-coated paper and matte-coated paper as above were prepared, and an inkjet printer (manufactured by Tritec Corporation) equipped with a piezo-driven inkjet head, product name: KJ4B-600, manufactured by Kyocera Corporation, was filled with water-based ink, and a line five dots wide was printed on each of the gloss-coated paper and matte-coated paper. The resulting prints were observed under an optical microscope and the line widths were measured. The difference in line width was calculated by subtracting the line width of the gloss coated paper from the line width of the matte coated paper. The smaller this difference, the more equivalent the image quality of the gloss coated paper and matte coated paper. The difference in line width is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 35 μm or less.

[0113] [Table 1]

[0114] Table 1 shows that the water-based inks of Examples 1 to 20 have a smaller difference in line width between matte-coated paper and gloss-coated paper than the water-based ink of Comparative Example 1, which does not contain polyether-modified silicone, and Comparative Example 4, in which the [m / n] of the polyether-modified silicone (B) is less than 3.0. Furthermore, the water-based inks of Examples 1 to 20 have a larger dot diameter on gloss-coated paper than Comparative Example 2, in which the mass ratio [polyether-modified silicone (B) / acetylene glycol-based surfactant (C)] exceeds 1.5, Comparative Example 3, in which the acetylene glycol-based surfactant is not contained, Comparative Example 5, in which the [m / n] of the polyether-modified silicone (B) exceeds 12.0, and Comparative Example 6, in which the HLB value of the glycol ether (A) exceeds 7.5. Furthermore, it can be seen that when the HLB value of the glycol ether (A) is less than 6.0, as in Comparative Example 7, a repellency phenomenon occurs, resulting in uneven printing.

Claims

1. An inkjet water-based ink containing a pigment, a glycol ether (A), a polyether-modified silicone (B), and an acetylene glycol-based surfactant (C), The HLB value of glycol ether (A), calculated by the Davis method, is between 6.0 and 7.

5. The ratio [m / n] of the number of repeating polyorganosiloxane units without polyether groups m to the number of repeating polyorganosiloxane units with polyether groups n of the polyether-modified silicone (B) is 3.0 or more and 12.0 or less. A water-based inkjet ink having a mass ratio of polyether-modified silicone (B) content to acetylene glycol-based surfactant (C) content [polyether-modified silicone (B) / acetylene glycol-based surfactant (C)] of 1.5 or less.

2. The kinematic viscosity of polyether-modified silicone (B) at 25°C is 50 mm². 2 / s or more 1500mm 2 The water-based inkjet recording ink according to claim 1, wherein the value is less than or equal to / s.

3. The water-based inkjet recording ink according to claim 1 or 2, wherein the mass ratio of the content of polyether-modified silicone (B) to the content of glycol ether (A) [polyether-modified silicone (B) / glycol ether (A)] is 0.001 or more and 0.2 or less.

4. The water-based inkjet recording ink according to claim 1 or 2, wherein the pigment is in the form of polymer particles containing the pigment.

5. Furthermore, the water-based inkjet recording ink according to claim 1 or 2, further comprising an organic solvent other than glycol ether (A).