Inkjet printing ink and method for producing printed matter

Abstract

To provide an aqueous pigment dispersion usable in the production of an inkjet printing ink which maintains excellent storage stability and can form a clear printed image with reduced color unevenness and superior water resistance.SOLUTION: The present invention provides an aqueous pigment dispersion which contains (A) a pigment, (B) a pigment dispersion resin that has an anionic group and a structure (X) represented by general formula (I) or (II), and (C) an aqueous medium. The pigment dispersion resin (B) contains 0.2 to 1.5 mmol / g of the anionic group relative to the total amount of the pigment dispersion resin (B)SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to aqueous pigment dispersions which can be used to make inks, including, for example, ink jet printing inks. [Background technology]

[0002] Inkjet recording is a method of recording in which ink droplets are ejected from extremely fine nozzles directly onto a recording material, causing the ink to adhere to the recording material, thereby obtaining characters and images. This method has the advantages of low noise and good operability of the equipment used, as well as the ease of producing colored printed matter. For this reason, inkjet recording is used not only as an output device in offices and homes, but also for industrial purposes.

[0003] In order to prevent clogging of ink ejection nozzles, inks used in the ink jet recording method are required to be less susceptible to sedimentation of pigments over time and to have excellent storage stability.

[0004] Known examples of inkjet printing inks with excellent storage stability include water-based inks obtained by dispersing a pigment in a water-soluble polymer having an anionic group and a water-insoluble polymer having an anionic group, and then crosslinking the polymers with a specific amount of a crosslinking agent (see, for example, Patent Document 1).

[0005] Meanwhile, as inkjet printing inks have begun to be used in the above-mentioned industrial applications, new performance that has not been achieved before is being required of inkjet printing inks. For example, white background is printed on the surface of cardboard in order to impart a good appearance, and various printing is increasingly being performed on the surface. When the printing is performed by the inkjet printing method, the inkjet printing ink is required to have the property of forming a clear printed image. However, conventional inkjet printing inks tend to be difficult to wet and spread on the surface of a layer that is difficult to absorb a solvent, such as the above-mentioned white background, and are easily repelled. Therefore, conventional inks may cause printing defects such as mottling in solid printed areas and granular unevenness (grainy feeling) due to dot combination.

[0006] The printing defects of the printed image can be suppressed to some extent by, for example, adjusting the viscosity, surface tension, etc. of the ink. However, ink whose surface tension, etc. has been adjusted to such an extent that printing defects can be suppressed to some extent may cause an increase in viscosity or an increase in particle size of pigments, etc., contained in the ink, when stored, for example, in a room temperature or high temperature environment.

[0007] As described above, there is a trade-off between improving printing defects in printed images and maintaining storage stability, and there has been a demand for the development of an inkjet printing ink that achieves both of these goals. A water-based ink for ink-jet printing, comprising: a pigment dispersed in a water-soluble polymer (x) having an anionic group and a water-insoluble polymer (y) having an anionic group, and then crosslinking the polymer with a crosslinking agent having a functional group capable of reacting with the anionic group, wherein the amount of crosslinking agent per gram of polymer is 0.8 to 3.0 mmol equivalent / g, and the amount of anionic group per gram of polymer after crosslinking is 1.5 to 3.0 mmol / g. A water-based ink for ink-jet printing, comprising: a pigment dispersed in a water-soluble polymer (x) having an anionic group and a water-insoluble polymer (y) having an anionic group, and then crosslinking the polymer with a crosslinking agent having a functional group capable of reacting with the anionic group, wherein the amount of crosslinking agent per gram of polymer is 0.8 to 3.0 mmol equivalent / g, and the amount of anionic group per gram of polymer after crosslinking is 1.5 to 3.0 mmol / g. The water-based ink for ink-jet printing is prepared by dispersing a pigment in a water-soluble polymer (x) having an anionic group and a water-insoluble polymer (y) having an anionic group, and then crosslinking the polymer with a crosslinking agent having a functional group capable of reacting with the anionic group, the amount of the crosslinking agent per gram of polymer being 0.8 to 3.0 mmol equivalents / g, and the amount of the anionic group per gram of polymer after the crosslinking treatment being 1.5 to 3.0 mmol / g. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2011-137102 A Summary of the Invention [Problem to be solved by the invention]

[0009] The problem to be solved by the present invention is to provide an aqueous pigment dispersion that can be used for producing an inkjet printing ink that maintains excellent storage stability and is capable of forming clear printed images with little color unevenness or the like. [Means for solving the problem]

[0010] The present inventors have solved the above-mentioned problems by providing an aqueous pigment dispersion containing a pigment (A), a pigment dispersing resin (B) having a structure (X) represented by the following general formula (I) and an anionic group, and an aqueous medium (C), wherein the pigment dispersing resin (B) has the anionic group in an amount of 0.2 to 1.5 mmol / g relative to the total amount of the pigment dispersing resin (B), and an inkjet printing ink using the aqueous pigment dispersion.

[0011] [ka] Effect of the Invention

[0012] According to the aqueous pigment dispersion of the present invention, it is possible to obtain an inkjet printing ink and a printed matter which maintain excellent storage stability and are capable of forming clear printed images with little color unevenness. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The aqueous pigment dispersion of the present invention is an aqueous pigment dispersion containing a pigment (A), a pigment dispersing resin (B) having a structure (X) represented by the following general formula (I) and an anionic group, and an aqueous medium (C), wherein the pigment dispersing resin (B) has the anionic group in an amount of 0.25 to 1.5 mmol / g based on the total amount of the pigment dispersing resin (B).

[0014] [ka]

[0015] First, the pigment (A) used in the aqueous pigment dispersion of the present invention will be described.

[0016] As the pigment (A), for example, organic pigments and inorganic pigments that are usually used in water-based gravure inks or water-based ink-jet inks can be used.

[0017] The pigment (A) may include one or both of an organic pigment and an inorganic pigment. In addition, the pigment (A) may be either a non-acid-treated pigment or an acid-treated pigment.

[0018] As the inorganic pigment, for example, iron oxide and carbon black produced by a contact method, a furnace method, a thermal method, or the like can be used.

[0019] Examples of organic pigments that can be used include azo pigments (azo lake, insoluble azo pigment, condensed azo pigment, chelate azo pigment, etc.), polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, etc.), lake pigments (for example, basic dye type chelates, acid dye type chelates, etc.), nitro pigments, nitroso pigments, and aniline black.

[0020] Examples of pigments (black pigments) that can be used in black inks include CI Pigment Black 1, 6, 7, 8, 10, 26, 27, and 28. Of these, CI Pigment Black 7 is preferably used. Specific examples of black pigments include No. 2300, No. 2200B, No. 900, No. 960, No. 980, No. 33, No. 40, No. 45, No. 45L, No. 52, HCF88, MA7, MA8, MA100, etc. manufactured by Mitsubishi Chemical Corporation; Raven 5750, Raven 5250, Raven 5000, Raven 3500, Raven 1255, Raven 700, etc. manufactured by Columbia Chemical Corporation; Regal 400R, Regal 330R, Regal 660R, Mogul L, Mogul 700, Monarch 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400, etc. manufactured by Cabot Corporation; and Color Black manufactured by Degussa. These include FW1, FW2, FW2V, FW18, FW200, S150, S160, S170, Printex 35, U, V, 1400U, Special Black 6, 5, 4, 4A, NIPEX150, NIPEX160, NIPEX170 and NIPEX180.

[0021] Specific examples of pigments (yellow pigments) that can be used in yellow inks include CI Pigment Yellow 1, 2, 12, 13, 14, 16, 17, 73, 74, 75, 83, 93, 95, 97, 98, 109, 110, 114, 120, 128, 129, 138, 150, 151, 154, 155, 174, 180, and 185.

[0022] Specific examples of pigments (magenta pigments) that can be used in magenta inks include CI Pigment Red 5, 7, 12, 48(Ca), 48(Mn), 57(Ca), 57:1, 112, 122, 123, 146, 176, 184, 185, 202, 209, 269, 282, and the like; CI Pigment Violet 19, and the like.

[0023] Specific examples of pigments (cyan pigments) that can be used in cyan inks include CI Pigment Blue 1, 2, 3, 15, 15:3, 15:4, 15:6, 16, 22, 60, 63, and 66. Of these, CI Pigment Blue 15:3 is preferably used.

[0024] Specific examples of pigments (white pigments) that can be used in white ink include alkaline earth metal sulfates, carbonates, finely powdered silicic acid, silicas such as synthetic silicates, calcium silicate, alumina, alumina hydrate, titanium oxide, zinc oxide, talc, clay, and the like.

[0025] The pigment (A) is preferably used in an amount of 10% by mass to 25% by mass, based on the total amount of the aqueous pigment dispersion, and is preferably used in an amount of 15% by mass to 20% by mass, in order to obtain an aqueous pigment dispersion that can suppress aggregation over time and has excellent storage stability.

[0026] Next, the pigment dispersing resin (B) used in the aqueous pigment dispersion of the present invention will be described. The pigment dispersing resin (B) used in the present invention is one having a structure (X) represented by the following general formula (I) and an anionic group, and has the anionic group in an amount of 0.25 to 1.5 mmol / g based on the total amount of the pigment dispersing resin (B).

[0027] [ka]

[0028] It is believed that the pigment dispersing resin (B) has the structure (X) and thereby forms a network structure on the surface of the pigment (A). As a result, excellent storage stability can be imparted to the aqueous pigment dispersion of the present invention containing the pigment dispersing resin (B) and to the ink using the same.

[0029] The structure (X) contained in the pigment dispersing resin (B) is, for example, a structure formed by a reaction between a carboxyl group and an epoxy group.

[0030] As the pigment dispersing resin (B) having the structure (X), for example, a reaction product of a compound (B1) having an anionic group including a carboxyl group and a compound (B2) having two or more epoxy groups can be used.

[0031] As the pigment dispersion resin (B), for example, a reaction product obtained by reacting the compound (B1) with the compound (B2) in advance can be used. The pigment dispersion resin (B) is preferably formed, for example, by producing an aqueous pigment dispersion containing the pigment (A), the compound (B1), an aqueous medium (C), etc., mixing the aqueous pigment dispersion with the compound (B2), and reacting the carboxyl group of the compound (B1) with the epoxy group of the compound (B2).

[0032] The degree of reaction between the carboxyl group of the compound (B1) and the epoxy group of the compound (B2) can be evaluated by the crosslinking rate. Here, the crosslinking rate refers to a value calculated by 100 x [the number of moles of epoxy groups in the compound (B2)] / [the number of moles of carboxyl groups in the compound (B1)]. As the aqueous pigment dispersion of the present invention, it is preferable to use a pigment dispersion resin (B) having a crosslinking rate in the range of 20% to 90%, more preferably a pigment dispersion resin (B) having a crosslinking rate in the range of 30% to 90%, and particularly preferable to use a pigment dispersion resin (B) having a crosslinking rate in the range of 45% to 85%, in order to maintain the dispersibility due to the neutralized carboxyl group and to exhibit the effect of improving storage stability.

[0033] The pigment dispersion resin (B) used has anionic groups in a range of 0.2 to 1.5 mmol / g based on the total amount of the pigment dispersion resin (B). By using a pigment dispersion resin (B) having anionic groups in this range, it is possible to obtain an aqueous pigment dispersion and an ink containing the same that have excellent storage stability. It is more preferable to use the amount of the anionic groups in a range of 0.25 to 1.2 mmol / g based on the total amount of the pigment dispersion resin (B) in order to further improve the storage stability of the aqueous pigment dispersion and ink.

[0034] When the reaction product of the compound (B1) and the compound (B2) is used as the pigment dispersion resin (B), a part of the anionic groups of the compound (B1) reacts with the epoxy groups of the compound (B2) and is consumed. Therefore, the amount of the anionic groups relative to the total amount of the pigment dispersion resin (B) refers to the amount of the anionic groups remaining in the reaction product of the compound (B1) and the compound (B2).

[0035] Examples of the compound (B1) include acrylic resins such as acrylic acid-acrylic acid ester copolymers, styrene-acrylic acid copolymers, styrene-methacrylic acid copolymers, styrene-methacrylic acid-acrylic acid ester copolymers, styrene-α-methylstyrene-acrylic acid copolymers, styrene-α-methylstyrene-acrylic acid-acrylic acid ester copolymers, styrene-acrylic resins such as styrene-maleic acid copolymers, styrene-maleic anhydride copolymers, vinylnaphthalene-acrylic acid copolymers, and salts of the resins. Examples of the compound (B1) include the Acrydic series from DIC Corporation and the Hi-Los-X series from Seiko PMC Corporation. Compounds exemplified as polymer (G) in the pamphlet of WO2018 / 190139 can also be used as the compound (B1).

[0036] Among these, it is preferable to use a styrene-acrylic acid copolymer or a styrene-methacrylic acid copolymer as the compound (B1) since the pigment (A) can be stably dispersed in the aqueous medium (C).

[0037] The compound (B1) preferably has an acid value of 250 mgKOH / g or less. The compound (B1) preferably has an acid value of 70 mgKOH / g to 190 mgKOH / g, and more preferably has an acid value of 100 mgKOH / g to 190 mgKOH / g, in order to prevent aggregation or precipitation of the pigment over time and obtain an aqueous pigment dispersion and ink with excellent storage stability.

[0038] The compound (B1) is preferably used in an amount of 20% by mass to 40% by mass, and more preferably 30% by mass to 40% by mass, based on the total amount of the pigment (A).

[0039] As the compound (B1), it is preferable to use one in which a part of the anionic groups has been neutralized with a neutralizing agent.

[0040] As the neutralizing agent, for example, it is preferable to use an alkali metal hydroxide in order to further increase the dispersion stability immediately after the production of the aqueous pigment dispersion of the present invention and the storage stability.

[0041] Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide, and cesium hydroxide, with sodium hydroxide and potassium hydroxide being preferred.

[0042] The neutralizing agent is preferably used in such a range that the neutralization rate calculated by the following formula exceeds 100%, in order to prevent precipitation or aggregation of the pigment (A) over time and to obtain an aqueous pigment dispersion with excellent storage stability. The neutralization rate refers to a value calculated based on the formula [100 x (molar equivalents of hydroxyl groups of alkali metal hydroxide / molar equivalents of anionic groups of compound (B1)].

[0043] As the compound (B2), a compound having two or more epoxy groups can be used. As the compound (B2), it is more preferable to use a compound having 2 to 4 epoxy groups in order to further improve the storage stability of the aqueous pigment dispersion and ink.

[0044] Examples of the compound (B2) include polyglycidyl ethers such as ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerin triglycidyl ether, glycerol polyglycidyl ether, polyglycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, sorbitol polyglycidyl ether, pentaerythritol polyglycidyl ether, resorcinol diglycidyl ether, and neopentyl glycol diglycidyl ether.

[0045] Among them, it is preferable to use a compound having an epoxy group and an oxyethylene structure as the compound (B2) in order to further improve the storage stability of the aqueous pigment dispersion. Specifically, it is preferable to use polyethylene glycol polyglycidyl ether or trimethylolpropane polyglycidyl ether as the compound (B2).

[0046] The compound (B2) is preferably used in an amount of 3.2 mmol / g or less, more preferably 2.7 mmol / g or less, and even more preferably 0.6 mmol / g or more and 2.4 mmol / g or less, based on the total amount of the compound (B1), in order to obtain an aqueous pigment dispersion having even better storage stability.

[0047] The compound (B2) preferably has a molecular weight in the range of 100 to 1000, and it is particularly preferable to use one in the range of 150 to 750 in order to obtain an aqueous pigment dispersion and ink having even better storage stability.

[0048] Next, the aqueous medium (C) of the present invention will be described. The aqueous medium (C) is, for example, water, and specifically, pure water or ultrapure water such as ion-exchanged water, ultrafiltered water, reverse osmosis water, distilled water, etc. can be used. The aqueous medium (C) is preferably used in an amount of 35% by mass to 75% by mass, more preferably 45% by mass to 65% by mass, based on the total amount of the aqueous pigment dispersion.

[0049] The aqueous pigment dispersion of the present invention can contain, as necessary, a preservative, a viscosity adjuster, a pH adjuster, a chelating agent, a plasticizer, an antioxidant, an ultraviolet absorber, etc. The chelating agent can reduce the content of metal ions derived from the pigment contained in the aqueous pigment dispersion.

[0050] Next, a method for producing the aqueous pigment dispersion of the present invention will be described. The aqueous pigment dispersion of the present invention can be produced, for example, through a process including: step 1 of mixing the pigment (A), the compound (B1), and the aqueous medium (C) to produce a dispersion in which the pigment (A) is dispersed in the aqueous medium (C) by the compound (B1); and step 2 of mixing the dispersion obtained in step 1 with the compound (B2) to react anionic groups, such as carboxyl groups, contained in the compound (B1) contained in the dispersion with functional groups, such as epoxy groups, contained in the compound (B2), to form a pigment dispersing resin (B).

[0051] The step 1 is, for example, a step of treating a mixture of the pigment (A), the compound (B2) and the aqueous medium (C) using a disperser.

[0052] Examples of the dispersing machine that can be used include kneading dispersing machines with high-speed stirring blades, such as an Intensive Mixer (manufactured by Nippon Eirich Co., Ltd.) and a Butterfly Mixer (Inoue Seisakusho Co., Ltd.), and media-type wet dispersing machines, such as an SC Mill (Nippon Coke and Engineering Co., Ltd.) and a Nano Mill (Asada Iron Works Co., Ltd.).

[0053] Among them, it is preferable to use the kneading disperser having the high-speed stirring blade as the disperser in order to prevent the ink jet dischargeability of the ink from being deteriorated due to the influence of beads, etc. used in the media-type wet disperser. Furthermore, the kneading disperser having the high-speed stirring blade can raise the temperature of the contents of the disperser to near 100°C, as compared with the media-type wet disperser, and as a result, it is possible to increase the ease with which the compound (B1) is adsorbed to the pigment (A).

[0054] On the other hand, when the media-type wet disperser is used, the step 1 may include a step 1-1 of producing a mixture containing the pigment (A) and the aqueous medium (C) by mixing the pigment (A), the compound (B2) and the aqueous medium (C) and pre-dispersing the mixture using a stirrer or the like, and a step 1-2 of treating the mixture obtained in the step 1-1 with the media-type wet disperser. With this step, the dispersibility of the pigment (A) and the like contained in the aqueous pigment dispersion can be confirmed during the process.

[0055] The neutralization of the compound (B1) is preferably carried out during or after the completion of the step 1. Specifically, the neutralization can be carried out by supplying and mixing the neutralizing agent to the mixture during the step 1 or the dispersion obtained after the completion of the step 1.

[0056] Furthermore, it is preferable to subject the dispersion obtained in step 1 to a centrifugation treatment as necessary before carrying out step 2 in order to remove coarse particles and reduce the amount of sediment contained in the dispersion obtained in step 1, the aqueous pigment dispersion, or the ink.

[0057] Next, step 2 will be described. Step 2 is a step of forming a pigment dispersing resin (B) that coats or adsorbs on the surface of the pigment (A) by reacting an anionic group such as a carboxyl group of the compound (B1) with a functional group such as an epoxy group of the compound (B2). The reaction is preferably carried out at a temperature in the range of 60 to 70°C in order to obtain an aqueous pigment dispersion having even better storage stability.

[0058] As described above, the compound (B2) is preferably supplied to the dispersion obtained after completion of step 1. However, the compound (B2) may be supplied to a mixture of the pigment (A), the compound (B1), and the aqueous medium (C) during step 1.

[0059] The aqueous pigment dispersion obtained through steps 1 and 2 is preferably subjected to a centrifugation treatment as necessary in order to remove coarse particles and reduce the amount of sediment contained in the dispersion obtained in step 1, the aqueous pigment dispersion, and the ink.

[0060] The aqueous pigment dispersion obtained by the above method can be used to produce inks such as inkjet printing inks, as described below. However, since the aqueous pigment dispersion obtained by the above method tends to have a slightly high pH, ​​if there is a discrepancy with the pH expected for the ink, it is preferable to adjust the pH of the aqueous pigment dispersion to a lower value in advance in order to increase the freedom of ink design. As a method for adjusting the pH of the aqueous pigment dispersion, a method of treating the aqueous pigment dispersion with an ion exchange resin can be mentioned. Specifically, a method of mixing a weakly acidic cation exchange resin such as Amberlite IRC76 manufactured by Organo Corporation with the aqueous pigment dispersion and then removing the cation exchange resin can be mentioned.

[0061] The aqueous pigment dispersion of the present invention obtained by the above method can be used, for example, for the production of inks, particularly for the production of inkjet printing inks. The inkjet printing ink can be produced, for example, by supplying and mixing an aqueous medium, a binder, a surfactant, and the like, as necessary, to the aqueous pigment dispersion. When the aqueous pigment dispersion is mixed with an aqueous medium, a binder, a surfactant, and the like as necessary, a dispersing machine such as a bead mill, an ultrasonic homogenizer, a high-pressure homogenizer, a paint shaker, a ball mill, a roll mill, a sand mill, a sand grinder, a Dyno Mill, a Dispermat, an SC Mill, or a Nanomizer can be used.

[0062] The inkjet printing ink may contain other additives, such as binders, surfactants, waxes, wetting agents (drying inhibitors), penetrants, preservatives, viscosity adjusters, pH adjusters, chelating agents, plasticizers, antioxidants, and ultraviolet absorbers, as necessary.

[0063] As the binder, for example, an acid-modified polypropylene resin can be used. As the acid-modified polypropylene resin, a resin obtained by modifying polypropylene with one or more acidic compounds can be used, and it is preferable to use one having a polypropylene-derived skeleton (polypropylene skeleton) and a functional group derived from an acidic compound. If the inkjet printing ink contains the acid-modified polypropylene resin, it is possible to suppress the occurrence of mottling or white streaks in the printed matter even when the ink is printed on a recording medium that does not absorb or does not easily absorb the solvent in the ink.

[0064] The acid-modified polypropylene resin may be a commercially available product. Preferred commercially available products include Auroren (registered trademark) AE-301 and AE-502 manufactured by Nippon Paper Industries Co., Ltd. The oxidized polyethylene wax may be, for example, a polyethylene wax that has been subjected to an oxidation treatment, and specifically, a wax having a skeleton derived from polyethylene (polyethylene skeleton) may be used.

[0065] As the surfactant, for example, anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, etc. can be used.

[0066] As the surfactant, it is preferable to use one or more types selected from the group consisting of anionic surfactants and nonionic surfactants, from the viewpoint of easily suppressing the occurrence of streak-like printing defects.

[0067] Examples of the anionic surfactant include alkylbenzenesulfonates, alkylphenylsulfonates, alkylnaphthalenesulfonates, higher fatty acid salts, sulfate salts of higher fatty acid esters, sulfonates of higher fatty acid esters, sulfate salts and sulfonates of higher alcohol ethers, higher alkyl sulfosuccinates, polyoxyethylene alkyl ether carboxylates, polyoxyethylene alkyl ether sulfates, alkyl phosphates, and polyoxyethylene alkyl ether phosphates. Specific examples of these include dodecylbenzenesulfonates, isopropylnaphthalenesulfonates, monobutylphenylphenol monosulfonates, monobutylbiphenylsulfonates, and dibutylphenylphenol disulfonates.

[0068] Examples of the nonionic surfactant include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters, glycerin fatty acid esters, polyoxyethylene glycerin fatty acid esters, polyglycerin fatty acid esters, sucrose fatty acid esters, polyoxyethylene alkylamines, polyoxyethylene fatty acid amides, fatty acid alkylol amides, alkyl alkanol amides, acetylene glycol, oxyethylene adducts of acetylene glycol, and polyethylene glycol polypropylene glycol block copolymers. Among these, polyoxyethylene nonylphenyl ethers, polyoxyethylene octylphenyl ethers, polyoxyethylene dodecylphenyl ethers, polyoxyethylene alkyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, fatty acid alkylol amides, acetylene glycol, oxyethylene adducts of acetylene glycol, and polyethylene glycol polypropylene glycol block copolymers are preferred.

[0069] As the nonionic surfactant, the inkjet printing ink preferably contains an acetylene-based surfactant from the viewpoint of easily suppressing the occurrence of streaky printing defects. The acetylene-based surfactant is a surfactant having an acetylene structure in the molecule. From the viewpoint of easily suppressing the occurrence of streaky printing defects, the acetylene-based surfactant preferably contains one or more types selected from the group consisting of acetylene glycol and oxyethylene adducts of acetylene glycol.

[0070] From the viewpoint of easily suppressing the occurrence of streak-like printing defects, the content of the acetylene-based surfactant is preferably 80 to 100 mass%, more preferably 85 to 99.9 mass%, even more preferably 90 to 99.5 mass%, and particularly preferably 95 to 99.3 mass%, relative to the total amount of surfactants.

[0071] Other surfactants that can be used include silicone surfactants such as polysiloxane oxyethylene adducts; fluorine-based surfactants such as perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, and oxyethylene perfluoroalkyl ethers; and biosurfactants such as spiculisporic acid, rhamnolipid, and lysolecithin.

[0072] The content of the surfactant is preferably from 0.1 to 2% by mass, more preferably from 0.5 to 2% by mass, and even more preferably from 0.8 to 1.6% by mass, based on the total amount of the inkjet printing ink. An inkjet printing ink containing such a surfactant content has good wettability of the ejected droplets on the surface of a substrate, tends to have sufficient wetting and spreading on the substrate, and tends to be effective in preventing the occurrence of streak-like printing defects.

[0073] The use of a surfactant makes it easy to prevent the occurrence of streaky printing defects, since the inkjet printing ink discharged from the discharge port of the inkjet head easily wets and spreads on the surface after landing on the printed material, etc. Furthermore, the use of a surfactant makes it easy to improve the leveling property of the inkjet printing ink by, for example, lowering the surface tension of the inkjet printing ink.

[0074] As the wax, for example, oxidized polyethylene wax can be used.

[0075] When the inkjet printing ink contains the oxidized polyethylene wax, it is possible to obtain a printed matter having excellent image fastness.

[0076] As the oxidized polyethylene wax, it is preferable to use an oxidized polyethylene wax in a state of being dissolved or dispersed in a solvent in order to obtain a printed matter having excellent image fastness.

[0077] The oxidized polyethylene wax may be a commercially available product, and preferred commercially available products include AQUACER 515 and AQUACER 1547 manufactured by BYK.

[0078] The wetting agent can be used for the purpose of preventing the inkjet printing ink from drying in the ejection nozzle of the inkjet head. As the wetting agent, it is preferable to use one that is miscible with water and has an effect of preventing the ejection port of the inkjet head from being clogged, and examples of the wetting agent include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol with a molecular weight of 2000 or less, propylene glycol, dipropylene glycol, tripropylene glycol, isopropylene glycol, isobutylene glycol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, mesoerythritol, pentaerythritol, and glycerin.

[0079] As the wetting agent, a solid wetting agent can also be used. Examples of such wetting agents include urea and urea derivatives. Examples of urea derivatives include ethylene urea, propylene urea, diethyl urea, thiourea, N,N-dimethyl urea, hydroxyethyl urea, hydroxybutyl urea, ethylene thiourea, and diethyl thiourea. These can be used alone or in combination of two or more. From the viewpoint of easily obtaining a printed matter with excellent setting properties, it is preferable to use at least one selected from the group consisting of urea, ethylene urea, and 2-hydroxyethyl urea.

[0080] The content of the humectant is 3 to 50% by mass relative to the total amount of the inkjet printing ink, which makes it possible to easily dry the ink on the recording medium while preventing the inkjet printing ink from sticking inside the inkjet head.

[0081] Examples of the penetrating agent include lower alcohols such as ethanol and isopropyl alcohol; and glycol monoethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl butyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monopropyl ether, and tripropylene glycol monobutyl ether.

[0082] In the inkjet printing ink obtained by the above method, the pigment (A) is preferably used in the range of 1% by mass to 15% by mass, and more preferably in the range of 2% by mass to 10% by mass, based on the total amount of the inkjet printing ink, in order to obtain printed matter having high print density, being less susceptible to streaks, excellent image fastness, and excellent dispersion stability.

[0083] The pH of the inkjet printing ink is preferably 7.0 or more, more preferably 7.5 or more, and even more preferably 8.0 or more, in order to improve the storage stability and ejection stability of the ink, and to improve the wet spread, print density, and abrasion resistance when printed on a poorly ink-absorbing or non-ink-absorbing recording medium. The upper limit of the pH of the aqueous ink composition is preferably 11.0 or less, more preferably 10.5 or less, and even more preferably 10.0 or less, in order to suppress deterioration of the members (e.g., ink ejection port, ink flow path, etc.) constituting the ink application or ejection device, and to reduce the effect when the ink adheres to the skin. From these viewpoints, the pH of the inkjet printing ink is preferably 7.0 to 11.0. The above pH is measured at 25°C.

[0084] The viscosity of the inkjet printing ink is preferably 2 mPa·s or more and less than 10 mPa·s at 32°C. When the viscosity of the inkjet printing ink is in this range, when the inkjet printing ink is used in an inkjet recording method, the deviation of the landing position on the recording medium caused by the flight deflection tends to be reduced, and the occurrence of streaks in the printed matter tends to be effectively prevented. In addition, an inkjet printing ink having a viscosity in this range tends to have excellent storage stability and ejection stability in an inkjet recording method. The viscosity of the inkjet printing ink at 32°C is preferably 3 mPa·s or more, more preferably 4 mPa·s or more. The viscosity of the aqueous ink composition at 32°C is preferably 8 mPa·s or less, more preferably 7 mPa·s or less. The above viscosity is, for example, a value measured under the following conditions using a cone-plate type rotational viscometer equivalent to an E-type viscometer.

[0085] Measurement equipment: TVE-25 type viscometer (Toki Sangyo Co., Ltd., TVE-25 L) Calibration standard solution: JS20 Measurement temperature: 32℃ Rotation speed: 10~100rpm Injection volume: 1200μL

[0086] The surface tension of the inkjet printing ink is, for example, 20 to 40 mN / m at 25°C. When the surface tension of the aqueous ink composition is within this range, when used in an inkjet recording method, the wettability of the discharged droplets on the surface of the recording medium tends to be good, and the ink tends to spread sufficiently after landing. The surface tension of the inkjet printing ink at 25°C is preferably 25 mN / m or more, more preferably 27 mN / m or more. The surface tension of the aqueous ink composition at 25°C is preferably 35 mN / m or less, more preferably 32 mN / m or less.

[0087] A printed matter obtained using the inkjet printing ink of the present invention has, for example, a recording medium and a coating film of the inkjet printing ink printed on the surface of the recording medium. The ink coating film formed on the surface of the recording medium is, for example, a dried product of the inkjet printing ink, and contains the solid content of the inkjet printing ink (for example, the pigment (A) and the pigment dispersant (B), etc.).

[0088] The recording medium is, for example, a poorly ink-absorbent or non-ink-absorbent recording medium. Even if the recording medium is a poorly ink-absorbent or non-ink-absorbent recording medium, the printed matter has sufficient image fastness.

[0089] The printed matter can be obtained, for example, by printing an inkjet printing ink onto the surface of a recording medium using an inkjet recording method. Specifically, the printed matter can be obtained by ejecting the inkjet printing ink onto a recording medium using an inkjet recording method in which the distance from a surface (x) having ink ejection ports of an inkjet head to a position (y) where a perpendicular line to the surface (x) intersects with the recording medium is 1 mm or more. EXAMPLES

[0090] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0091] <Preparation of aqueous pigment dispersion> Comparative Example 1 150 g of the black pigment (carbon black "#960" (product name) manufactured by Mitsubishi Chemical Corporation), 60 g of a styrene-acrylic acid copolymer (weight average molecular weight 18,000, glass transition temperature 52°C, acid value 110 mgKOH / g) as a pigment dispersant X, 30 g of propylene glycol, and 15.5 g of a 34 mass% aqueous potassium hydroxide solution were charged into a 1.0 L intensive mixer (manufactured by Nippon Airich Co., Ltd.), and a kneaded product was formed while gradually adding ion-exchanged water, and then the product was kneaded for 60 minutes with a rotor peripheral speed of 2.94 m / s and a pan peripheral speed of 1 m / s. Next, 266 g of warm ion-exchanged water was gradually added to the kneaded material in the container of the intensive mixer while continuing to stir, and then 30 g of propylene glycol, 0.75 g of ACTICIDE B20, and up to 197 g of ion-exchanged water were added and mixed to give a pigment concentration of 20 mass%, thereby obtaining an aqueous pigment dispersion 1K having a pigment concentration of 20 mass%.

[0092] Example 1 The aqueous pigment dispersion 1K obtained in Comparative Example 1 was diluted with ion-exchanged water to a solid content concentration of 20% by mass to obtain an aqueous pigment dispersion 500 g, to which 4.61 g of a crosslinking agent (product name: Denacol EX-512, epoxy equivalent 168, solubility rate of 10 g of crosslinking agent in 90 g of ion-exchanged water is about 100% by mass (25°C), manufactured by Nagase ChemteX Corporation) was added, and the mixture was stirred for 5 hours at 60 to 70°C. After stirring, the mixture was cooled to obtain an aqueous pigment dispersion 11K (pigment concentration: 13.9% by mass).

[0093] Comparative Example 2 As a cyan pigment, "FASTOGEN BLUE SBG-SD" (product name) manufactured by DIC Corporation was prepared. The cyan pigment was used instead of the black pigment, the amount of pigment dispersant X used was 45 g, the amount of 34 mass% potassium hydroxide aqueous solution used was 11.6 g, and 60 g of propylene glycol was initially added and not added after the kneaded product was formed. The process was the same as in Comparative Example 1, and aqueous pigment dispersion 2C (pigment concentration: 20 mass%) was prepared.

[0094] Example 2 The aqueous pigment dispersion 2C obtained in Comparative Example 2 was diluted with ion-exchanged water to a solid content concentration of 20% by mass to obtain an aqueous pigment dispersion 500 g, to which 3.73 g of a crosslinking agent (product name: Denacol EX-512, epoxy equivalent 168, solubility rate of 10 g of crosslinking agent in 90 g of ion-exchanged water is about 100% by mass (25°C), manufactured by Nagase ChemteX Corporation) was added, and the mixture was stirred for 5 hours at 60 to 70°C. After stirring, the mixture was cooled to obtain an aqueous pigment dispersion 12C (pigment concentration: 15% by mass).

[0095] Comparative Example 3 As a magenta pigment, "FASTOGEN SUPER MAGENTA RY" (product name) manufactured by DIC Corporation was prepared. Aqueous pigment dispersion 3M (pigment concentration: 20% by mass) was prepared in the same manner as in Comparative Example 2, except that the magenta pigment was used instead of the cyan pigment.

[0096] Example 3 The aqueous pigment dispersion 3M obtained in Comparative Example 3 was diluted with ion-exchanged water to a solid content concentration of 20% by mass to obtain an aqueous pigment dispersion of 500 g, to which 6.12 g of a crosslinking agent (product name: Denacol EX-512, epoxy equivalent 168, solubility rate of 10 g of crosslinking agent in 90 g of ion-exchanged water is about 100% by mass (25°C), manufactured by Nagase ChemteX Corporation) was added, and the mixture was stirred for 5 hours at 60 to 70°C. After stirring, the mixture was cooled to obtain an aqueous pigment dispersion 13M (pigment concentration: 14.9% by mass).

[0097] Comparative Example 4 As a yellow pigment, Clariant's "Ink Jet Yellow 4GC" (product name) was prepared. Aqueous pigment dispersion 4Y (pigment concentration: 20% by mass) was prepared in the same manner as in Comparative Example 2, except that the yellow pigment was used instead of the cyan pigment.

[0098] Example 4 The aqueous pigment dispersion 4Y obtained in Comparative Example 4 was diluted with ion-exchanged water to a solid content concentration of 20% by mass to obtain an aqueous pigment dispersion 500 g, to which 3.73 g of a crosslinking agent (product name: Denacol EX-512, epoxy equivalent 168, solubility rate of 10 g of crosslinking agent in 90 g of ion-exchanged water is about 100% by mass (25°C), manufactured by Nagase ChemteX Corporation) was added, and the mixture was stirred for 5 hours at 60 to 70°C. After stirring, the mixture was cooled to obtain an aqueous pigment dispersion 14Y (pigment concentration: 15% by mass).

[0099] (Preparation Example 1) 1200g of isopropyl alcohol was charged into the reaction vessel of an automatic polymerization reaction apparatus (polymerization tester DSL-2AS type, manufactured by Todoroki Sangyo Co., Ltd.) having a reaction vessel equipped with a stirring device, a dropping device, a temperature sensor, and a reflux device having a nitrogen introduction device at the top, and the inside of the reaction vessel was replaced with nitrogen while stirring. After the temperature inside the reaction vessel was raised to 80°C while maintaining a nitrogen atmosphere, a mixture of 75g of 2-hydroxyethyl methacrylate, 260.8g of methacrylic acid, 400g of styrene, 234.2g of benzyl methacrylate, 30g of glycidyl methacrylate, and 80g of "Perbutyl (registered trademark) O" (active ingredient peroxy 2-ethylhexanoate t-butyl, manufactured by Nippon Oil & Fats Co., Ltd.) was dropped over 4 hours from the dropping device. After the dropwise addition was completed, the reaction was continued at the same temperature for a further 15 hours, and then a portion of the isopropyl alcohol was distilled off under reduced pressure to adjust the non-volatile content to 42.5 mass %, thereby obtaining pigment dispersant Y, which is a (meth)acrylic acid ester resin solution having an acid value of 165 (weight average molecular weight: 5,000, glass transition temperature: 66°C, acid value: 165).

[0100] Next, a portion of the isopropyl alcohol was distilled off under reduced pressure from the pigment dispersant Y to adjust the non-volatile content to 90 mass %, thereby obtaining pigment dispersant Z, which is a (meth)acrylic acid ester resin solution having an acid value of 165 (weight average molecular weight: 5,000, glass transition temperature: 66°C, acid value: 165).

[0101] Comparative Example 5 Aqueous pigment dispersion 5K (pigment concentration: 20% by mass) was prepared in the same manner as in Comparative Example 1, except that pigment dispersant Z was used instead of pigment dispersant X, and the amount of 34% by mass potassium hydroxide aqueous solution was changed to 23.6 g.

[0102] Example 5 The aqueous pigment dispersion 5K obtained in Comparative Example 5 was diluted with ion-exchanged water to a solid content concentration of 20 mass %, and 6.91 g of a crosslinking agent (product name: Denacol EX-512, epoxy equivalent 168, manufactured by Nagase ChemteX Corporation) was added to 500 g of the aqueous pigment dispersion, followed by stirring for 5 hours at 60 to 70° C. After stirring, the mixture was cooled to obtain an aqueous pigment dispersion 15K (pigment concentration: 13.6 mass %).

[0103] Comparative Example 6 Aqueous pigment dispersion 6C (pigment concentration: 20% by mass) was prepared in the same manner as in Comparative Example 2, except that pigment dispersant Z was used instead of pigment dispersant X, and the amount of 34% by mass potassium hydroxide aqueous solution was changed to 17.7 g.

[0104] Example 6 The aqueous pigment dispersion 6C obtained in Comparative Example 6 was diluted with ion-exchanged water to a solid content concentration of 20% by mass to obtain an aqueous pigment dispersion 500 g, to which 5.61 g of a crosslinking agent (product name: Denacol EX-512, epoxy equivalent 168, solubility rate of 10 g of crosslinking agent in 90 g of ion-exchanged water is about 100% by mass (25°C), manufactured by Nagase ChemteX Corporation) was added, and the mixture was stirred for 5 hours at 60 to 70°C. After stirring, the mixture was cooled to obtain an aqueous pigment dispersion 16C (pigment concentration: 14.8% by mass).

[0105] Comparative Example 7 Aqueous pigment dispersion 7M (pigment concentration: 20% by mass) was prepared in the same manner as in Comparative Example 3, except that pigment dispersant Z was used instead of pigment dispersant X, and the amount of 34% by mass potassium hydroxide aqueous solution was changed to 17.7 g.

[0106] Example 7 The aqueous pigment dispersion 7M obtained in Comparative Example 7 was diluted with ion-exchanged water to a solid content concentration of 20% by mass to obtain an aqueous pigment dispersion 500g, to which 9.19g of a crosslinking agent (product name: Denacol EX-512, epoxy equivalent 168, solubility rate of 10g of crosslinking agent in 90g of ion-exchanged water is about 100% by mass (25°C), manufactured by Nagase ChemteX Corporation) was added, and the mixture was stirred for 5 hours at 60 to 70°C. After stirring, the mixture was cooled to obtain an aqueous pigment dispersion 17M (pigment concentration: 14.7% by mass).

[0107] Comparative Example 8 Aqueous pigment dispersion 8Y (pigment concentration: 20% by mass) was prepared in the same manner as in Comparative Example 4, except that pigment dispersant Z was used instead of pigment dispersant X, and the amount of 34% by mass potassium hydroxide aqueous solution was changed to 17.7 g.

[0108] Example 8 The aqueous pigment dispersion 8Y obtained in Comparative Example 8 was diluted with ion-exchanged water to a solid content concentration of 20% by mass to obtain an aqueous pigment dispersion of 500 g, to which 5.61 g of a crosslinking agent (product name: Denacol EX-512, epoxy equivalent 168, solubility rate of 10 g of crosslinking agent in 90 g of ion-exchanged water is about 100% by mass (25°C), manufactured by Nagase ChemteX Corporation) was added, and the mixture was stirred for 5 hours at 60 to 70°C. After stirring, the mixture was cooled to obtain an aqueous pigment dispersion 18Y (pigment concentration: 14.8% by mass).

[0109] <Preparing the wax> As the wax, the following oxidized polyethylene wax was prepared. AQUACER515: BYK, product name, high density oxidized polyethylene wax emulsion, melting point (Tm2) 135℃ AQUACER1547: BYK, product name, high density oxidized polyethylene wax emulsion, melting point (Tm2) 125℃

[0110] Example 9 2.0g of ion-exchanged water, 12.0g of propylene glycol, 12.0g of glycerin, 0.2g of triethanolamine, 0.1g of TegoWET (manufactured by Evonik, silicone-based surfactant), 0.1g of ACTICIDE B20 (manufactured by Thor Japan, preservative), and 5.6g of ethylene urea were mixed, and after the ethylene urea was dissolved, 1.2g of propylene glycol and 1.0g of SURFYNOL 420 (manufactured by Evonik, acetylene-based surfactant) were mixed (Mixture A). Next, 3.3g of Auroren (registered trademark) AE-301 (manufactured by Nippon Paper Industries Co., Ltd., acid-modified polypropylene), 5.0g of ion-exchanged water, 2.9g of AQUACER515 (manufactured by BYK, high-density oxidized polyethylene wax emulsion), and 5.0g of ion-exchanged water were mixed in this order (Mixture B). Mixture B was mixed with 40.3 g of the aqueous pigment dispersion 11K obtained in Example 1, and then mixture A was mixed therewith. The container was washed with 9.3 g of ion-exchanged water, and the mixture was stirred to obtain an aqueous pigment ink. Example 10 2.0g of ion-exchanged water, 12.0g of propylene glycol, 12.0g of glycerin, 0.2g of triethanolamine, 0.1g of TegoWET (manufactured by Evonik, silicone-based surfactant), 0.1g of ACTICIDE B20 (manufactured by Thor Japan, preservative), and 5.6g of ethylene urea were mixed, and after the ethylene urea was dissolved, 9.1g of propylene glycol and 1.0g of SURFYNOL 420 (manufactured by Evonik, acetylene-based surfactant) were mixed (mixture A). Next, 3.3g of Auroren (registered trademark) AE-301 (manufactured by Nippon Paper Industries Co., Ltd., acid-modified polypropylene), 5.0g of ion-exchanged water, 2.9g of AQUACER515 (manufactured by BYK, high-density oxidized polyethylene wax emulsion), and 5.0g of ion-exchanged water were mixed in this order (mixture B). 28.7 g of the aqueous pigment dispersion 12C obtained in Example 2 was mixed into mixture B, and then mixture A was mixed therein. The container was washed with 13.0 g of ion-exchanged water, and the mixture was stirred to obtain an aqueous pigment ink.

[0111] Example 11 2.0g of ion-exchanged water, 12.0g of propylene glycol, 12.0g of glycerin, 0.2g of triethanolamine, 0.1g of TegoWET (manufactured by Evonik, silicone-based surfactant), 0.1g of ACTICIDE B20 (manufactured by Thor Japan, preservative), and 5.6g of ethylene urea were mixed, and after the ethylene urea was dissolved, 2.6g of propylene glycol and 1.1g of SURFYNOL 420 (manufactured by Evonik, acetylene-based surfactant) were mixed (Mixture A). Next, 3.3g of Auroren (registered trademark) AE-301 (manufactured by Nippon Paper Industries Co., Ltd., acid-modified polypropylene), 5.0g of ion-exchanged water, 2.9g of AQUACER515 (manufactured by BYK, high-density oxidized polyethylene wax emulsion), and 5.0g of ion-exchanged water were mixed in this order (Mixture B). Mixture B was mixed with 40.3 g of the aqueous pigment dispersion 13M obtained in Example 3, and then mixture A was mixed therewith. The container was washed with 7.8 g of ion-exchanged water, and the mixture was stirred to obtain an aqueous pigment ink.

[0112] Example 12 2.0g of ion-exchanged water, 12.0g of propylene glycol, 12.0g of glycerin, 0.2g of triethanolamine, 0.1g of TegoWET280 (manufactured by Evonik, silicone-based surfactant), 0.1g of ACTICIDE B20 (manufactured by Thor Japan, preservative), and 5.6g of ethylene urea were mixed, and after the ethylene urea was dissolved, 11.6g of propylene glycol and 1.0g of SURFYNOL 420 (manufactured by Evonik, acetylene-based surfactant) were mixed (Mixture A). Next, 3.3g of Auroren (registered trademark) AE-301 (manufactured by Nippon Paper Industries Co., Ltd., acid-modified polypropylene), 5.0g of ion-exchanged water, 2.9g of AQUACER515 (manufactured by BYK, high-density oxidized polyethylene wax emulsion), and 5.0g of ion-exchanged water were mixed in this order (Mixture B). Mixture B was mixed with 22 g of the aqueous pigment dispersion 14Y obtained in Example 4, and then mixed with mixture A. The container was washed with 17.2 g of ion-exchanged water, and the mixture was stirred to obtain an aqueous pigment ink.

[0113] Example 13 2.0g of ion-exchanged water, 12.0g of propylene glycol, 12.0g of glycerin, 0.2g of triethanolamine, 0.1g of TegoWET (manufactured by Evonik, silicone-based surfactant), 0.1g of ACTICIDE B20 (manufactured by Thor Japan, preservative), and 5.6g of ethylene urea were mixed, and after the ethylene urea was dissolved, 1.2g of propylene glycol and 1.0g of SURFYNOL 420 (manufactured by Evonik, acetylene-based surfactant) were mixed (Mixture A). Next, 3.3g of Auroren (registered trademark) AE-301 (manufactured by Nippon Paper Industries Co., Ltd., acid-modified polypropylene), 5.0g of ion-exchanged water, 2.9g of AQUACER515 (manufactured by BYK, high-density oxidized polyethylene wax emulsion), and 5.0g of ion-exchanged water were mixed in this order (Mixture B). Mixture B was mixed with 41.1 g of the aqueous pigment dispersion 15K obtained in Example 5, and then mixture A was mixed therewith. The container was washed with 8.5 g of ion-exchanged water, and the mixture was stirred to obtain an aqueous pigment ink.

[0114] Example 14 2.0g of ion-exchanged water, 12.0g of propylene glycol, 12.0g of glycerin, 0.2g of triethanolamine, 0.1g of TegoWET280 (manufactured by Evonik, silicone-based surfactant), 0.1g of ACTICIDE B20 (manufactured by Thor Japan, preservative), and 5.6g of ethylene urea were mixed, and after the ethylene urea was dissolved, 9.1g of propylene glycol and 1.0g of SURFYNOL 420 (manufactured by Evonik, acetylene-based surfactant) were mixed (Mixture A). Next, 3.3g of Auroren (registered trademark) AE-301 (manufactured by Nippon Paper Industries Co., Ltd., acid-modified polypropylene), 5.0g of ion-exchanged water, 2.9g of AQUACER515 (manufactured by BYK, high-density oxidized polyethylene wax emulsion), and 5.0g of ion-exchanged water were mixed in this order (Mixture B). 29.1 g of the aqueous pigment dispersion 16C obtained in Example 6 was mixed into mixture B, and then mixture A was mixed therein. The container was washed with 12.6 g of ion-exchanged water, and the mixture was stirred to obtain an aqueous pigment ink.

[0115] Example 15 2.0g of ion-exchanged water, 12.0g of propylene glycol, 12.0g of glycerin, 0.2g of triethanolamine, 0.1g of TegoWET280 (manufactured by Evonik, silicone-based surfactant), 0.1g of ACTICIDE B20 (manufactured by Thor Japan, preservative), and 5.6g of ethylene urea were mixed, and after the ethylene urea was dissolved, 2.6g of propylene glycol and 1.1g of SURFYNOL 420 (manufactured by Evonik, acetylene-based surfactant) were mixed (Mixture A). Next, 3.3g of Auroren (registered trademark) AE-301 (manufactured by Nippon Paper Industries Co., Ltd., acid-modified polypropylene), 5.0g of ion-exchanged water, 2.9g of AQUACER515 (manufactured by BYK, high-density oxidized polyethylene wax emulsion), and 5.0g of ion-exchanged water were mixed in this order (Mixture B). Mixture B was mixed with 40.9 g of the aqueous pigment dispersion 17M obtained in Example 7, and then mixture A was mixed therewith. The container was washed with 7.2 g of ion-exchanged water, and the mixture was stirred to obtain an aqueous pigment ink.

[0116] (Example 16) 2.0g of ion-exchanged water, 12.0g of propylene glycol, 12.0g of glycerin, 0.2g of triethanolamine, 0.1g of TegoWET280 (manufactured by Evonik, silicone-based surfactant), 0.1g of ACTICIDE B20 (manufactured by Thor Japan, preservative), and 5.6g of ethylene urea were mixed, and after the ethylene urea was dissolved, 11.6g of propylene glycol and 1.0g of SURFYNOL 420 (manufactured by Evonik, acetylene-based surfactant) were mixed (Mixture A). Next, 3.3g of Auroren (registered trademark) AE-301 (manufactured by Nippon Paper Industries Co., Ltd., acid-modified polypropylene), 5.0g of ion-exchanged water, 2.9g of AQUACER515 (manufactured by BYK, high-density oxidized polyethylene wax emulsion), and 5.0g of ion-exchanged water were mixed in this order (Mixture B). 22.3 g of the aqueous pigment dispersion 18Y obtained in Example 8 was mixed into mixture B, and then mixture A was mixed therein. The container was washed with 16.9 g of ion-exchanged water, and the mixture was stirred to obtain an aqueous pigment ink.

[0117] Comparative Example 9 2.0g of ion-exchanged water, 12.0g of propylene glycol, 12.0g of glycerin, 0.2g of triethanolamine, 0.1g of TegoWET280 (manufactured by Evonik, silicone-based surfactant), 0.1g of ACTICIDE B20 (manufactured by Thor Japan, preservative), and 5.6g of ethylene urea were mixed, and after the ethylene urea was dissolved, 1.2g of propylene glycol and 1.0g of SURFYNOL 420 (manufactured by Evonik, acetylene-based surfactant) were mixed (Mixture A). Next, 3.3g of Auroren (registered trademark) AE-301 (manufactured by Nippon Paper Industries Co., Ltd., acid-modified polypropylene), 5.0g of ion-exchanged water, 2.9g of AQUACER515 (manufactured by BYK, high-density oxidized polyethylene wax emulsion), and 5.0g of ion-exchanged water were mixed in this order (Mixture B). Mixture B was mixed with 28.0 g of the aqueous pigment dispersion 1K obtained in Comparative Example 1, and then mixture A was mixed therewith. The container was washed with 21.6 g of ion-exchanged water, and the mixture was stirred to obtain an aqueous pigment ink.

[0118] Comparative Example 10 2.0g of ion-exchanged water, 12.0g of propylene glycol, 12.0g of glycerin, 0.2g of triethanolamine, 0.1g of TegoWET280 (manufactured by Evonik, silicone-based surfactant), 0.1g of ACTICIDE B20 (manufactured by Thor Japan, preservative), and 5.6g of ethylene urea were mixed, and after the ethylene urea was dissolved, 9.1g of propylene glycol and 1.0g of SURFYNOL 420 (manufactured by Evonik, acetylene-based surfactant) were mixed (Mixture A). Next, 3.3g of Auroren (registered trademark) AE-301 (manufactured by Nippon Paper Industries Co., Ltd., acid-modified polypropylene), 5.0g of ion-exchanged water, 2.9g of AQUACER515 (manufactured by BYK, high-density oxidized polyethylene wax emulsion), and 5.0g of ion-exchanged water were mixed in this order (Mixture B). Mixture B was mixed with 21.5 g of the aqueous pigment dispersion 2C obtained in Comparative Example 2, and then mixed with mixture A. The container was washed with 20.2 g of ion-exchanged water, and the mixture was stirred to obtain an aqueous pigment ink.

[0119] Comparative Example 11 2.0g of ion-exchanged water, 12.0g of propylene glycol, 12.0g of glycerin, 0.2g of triethanolamine, 0.1g of TegoWET280 (manufactured by Evonik, silicone-based surfactant), 0.1g of ACTICIDE B20 (manufactured by Thor Japan, preservative), and 5.6g of ethylene urea were mixed, and after the ethylene urea was dissolved, 2.6g of propylene glycol and 1.1g of SURFYNOL 420 (manufactured by Evonik, acetylene-based surfactant) were mixed (Mixture A). Next, 3.3g of Auroren (registered trademark) AE-301 (manufactured by Nippon Paper Industries Co., Ltd., acid-modified polypropylene), 5.0g of ion-exchanged water, 2.9g of AQUACER515 (manufactured by BYK, high-density oxidized polyethylene wax emulsion), and 5.0g of ion-exchanged water were mixed in this order (Mixture B). Mixture B was mixed with 30.0 g of the aqueous pigment dispersion 3M obtained in Comparative Example 3, and then mixture A was mixed therewith. The container was washed with 18.1 g of ion-exchanged water, and the mixture was stirred to obtain an aqueous pigment ink.

[0120] Comparative Example 12 2.0g of ion-exchanged water, 12.0g of propylene glycol, 12.0g of glycerin, 0.2g of triethanolamine, 0.1g of TegoWET280 (manufactured by Evonik, silicone-based surfactant), 0.1g of ACTICIDE B20 (manufactured by Thor Japan, preservative), and 5.6g of ethylene urea were mixed, and after the ethylene urea was dissolved, 11.6g of propylene glycol and 1.0g of SURFYNOL 420 (manufactured by Evonik, acetylene-based surfactant) were mixed (Mixture A). Next, 3.3g of Auroren (registered trademark) AE-301 (manufactured by Nippon Paper Industries Co., Ltd., acid-modified polypropylene), 5.0g of ion-exchanged water, 2.9g of AQUACER515 (manufactured by BYK, high-density oxidized polyethylene wax emulsion), and 5.0g of ion-exchanged water were mixed in this order (Mixture B). Mixture B was mixed with 16.5 g of the aqueous pigment dispersion 4Y obtained in Comparative Example 4, and then mixed with mixture A. The container was washed with 22.7 g of ion-exchanged water, and the mixture was stirred to obtain an aqueous pigment ink.

[0121] Comparative Example 13 2.0g of ion-exchanged water, 12.0g of propylene glycol, 12.0g of glycerin, 0.2g of triethanolamine, 0.1g of TegoWET280 (manufactured by Evonik, silicone-based surfactant), 0.1g of ACTICIDE B20 (manufactured by Thor Japan, preservative), and 5.6g of ethylene urea were mixed, and after the ethylene urea was dissolved, 1.2g of propylene glycol and 1.0g of SURFYNOL 420 (manufactured by Evonik, acetylene-based surfactant) were mixed (Mixture A). Next, 3.3g of Auroren (registered trademark) AE-301 (manufactured by Nippon Paper Industries Co., Ltd., acid-modified polypropylene), 5.0g of ion-exchanged water, 2.9g of AQUACER515 (manufactured by BYK, high-density oxidized polyethylene wax emulsion), and 5.0g of ion-exchanged water were mixed in this order (Mixture B). Mixture B was mixed with 28.0 g of the aqueous pigment dispersion 5K obtained in Comparative Example 5, and then mixture A was mixed therewith. The container was washed with 21.6 g of ion-exchanged water, and the mixture was stirred to obtain an aqueous pigment ink.

[0122] Comparative Example 14 2.0g of ion-exchanged water, 12.0g of propylene glycol, 12.0g of glycerin, 0.2g of triethanolamine, 0.1g of TegoWET280 (manufactured by Evonik, silicone-based surfactant), 0.1g of ACTICIDE B20 (manufactured by Thor Japan, preservative), and 5.6g of ethylene urea were mixed, and after the ethylene urea was dissolved, 9.1g of propylene glycol and 1.0g of SURFYNOL 420 (manufactured by Evonik, acetylene-based surfactant) were mixed (Mixture A). Next, 3.3g of Auroren (registered trademark) AE-301 (manufactured by Nippon Paper Industries Co., Ltd., acid-modified polypropylene), 5.0g of ion-exchanged water, 2.9g of AQUACER515 (manufactured by BYK, high-density oxidized polyethylene wax emulsion), and 5.0g of ion-exchanged water were mixed in this order (Mixture B). Mixture B was mixed with 21.5 g of the aqueous pigment dispersion 6C obtained in Comparative Example 6, and then mixed with mixture A. The container was washed with 20.2 g of ion-exchanged water, and the mixture was stirred to obtain an aqueous pigment ink.

[0123] Comparative Example 15 2.0g of ion-exchanged water, 12.0g of propylene glycol, 12.0g of glycerin, 0.2g of triethanolamine, 0.1g of TegoWET280 (manufactured by Evonik, silicone-based surfactant), 0.1g of ACTICIDE B20 (manufactured by Thor Japan, preservative), and 5.6g of ethylene urea were mixed, and after the ethylene urea was dissolved, 2.6g of propylene glycol and 1.1g of SURFYNOL 420 (manufactured by Evonik, acetylene-based surfactant) were mixed (Mixture A). Next, 3.3g of Auroren (registered trademark) AE-301 (manufactured by Nippon Paper Industries Co., Ltd., acid-modified polypropylene), 5.0g of ion-exchanged water, 2.9g of AQUACER515 (manufactured by BYK, high-density oxidized polyethylene wax emulsion), and 5.0g of ion-exchanged water were mixed in this order (Mixture B). Mixture B was mixed with 30.0 g of the aqueous pigment dispersion 7M obtained in Comparative Example 7, and then mixture A was mixed therewith. The container was washed with 18.1 g of ion-exchanged water, and the mixture was stirred to obtain an aqueous pigment ink.

[0124] Comparative Example 16 2.0g of ion-exchanged water, 12.0g of propylene glycol, 12.0g of glycerin, 0.2g of triethanolamine, 0.1g of TegoWET280 (manufactured by Evonik, silicone-based surfactant), 0.1g of ACTICIDE B20 (manufactured by Thor Japan, preservative), and 5.6g of ethylene urea were mixed, and after the ethylene urea was dissolved, 11.6g of propylene glycol and 1.0g of SURFYNOL 420 (manufactured by Evonik, acetylene-based surfactant) were mixed (Mixture A). Next, 3.3g of Auroren (registered trademark) AE-301 (manufactured by Nippon Paper Industries Co., Ltd., acid-modified polypropylene), 5.0g of ion-exchanged water, 2.9g of AQUACER515 (manufactured by BYK, high-density oxidized polyethylene wax emulsion), and 5.0g of ion-exchanged water were mixed in this order (Mixture B). Mixture B was mixed with 16.5 g of the aqueous pigment dispersion 8Y obtained in Comparative Example 8, and then mixed with mixture A. The container was washed with 22.7 g of ion-exchanged water, and the mixture was stirred to obtain an aqueous pigment ink.

[0125] (Example 17) An aqueous pigment dispersion 21M (pigment concentration: 14.9% by mass) was obtained in the same manner as in Example 3, except that 6.67 g of a crosslinking agent (trade name: Denacol EX-521, epoxy equivalent 183, solubility of 10 g of crosslinking agent in 90 g of ion-exchanged water is approximately 100% by mass (25° C.), manufactured by Nagase ChemteX Corporation) was used instead of 6.12 g of the crosslinking agent (trade name: Denacol EX-512, epoxy equivalent 168, solubility of 10 g of crosslinking agent in 90 g of ion-exchanged water is approximately 100% by mass (25° C.), manufactured by Nagase ChemteX Corporation). Moreover, an aqueous pigment ink with a non-volatile content of 6% by mass was obtained in the same manner as in Example 11, except that 40.2 g of Aqueous Pigment Dispersion 21M was used instead of Aqueous Pigment Dispersion 13M.

[0126] (Example 18) An aqueous pigment dispersion 22M (pigment concentration: 15.0% by mass) was obtained in the same manner as in Example 3, except that 5.14 g of a crosslinking agent (trade name: Denacol EX-313, epoxy equivalent 144, solubility of 10 g of crosslinking agent in 90 g of ion-exchanged water is approximately 90% by mass (25° C.), manufactured by Nagase ChemteX Corporation) was used instead of 6.12 g of the crosslinking agent (trade name: Denacol EX-512, epoxy equivalent 168, solubility of 10 g of crosslinking agent in 90 g of ion-exchanged water is approximately 100% by mass (25° C.), manufactured by Nagase ChemteX Corporation). Moreover, an aqueous pigment ink with a non-volatile content of 6.0% by mass was obtained in the same manner as in Example 11, except that 40.1 g of Aqueous Pigment Dispersion 22M was used instead of Aqueous Pigment Dispersion 13M.

[0127] (Example 19) An aqueous pigment dispersion 23M (pigment concentration: 15.0% by mass) was obtained in the same manner as in Example 3, except that 4.45 g of a crosslinking agent (trade name: Denacol EX-850, epoxy equivalent 122, solubility of 10 g of crosslinking agent in 90 g of ion-exchanged water is approximately 100% by mass (25° C.), manufactured by Nagase ChemteX Corporation) was used instead of 6.12 g of the crosslinking agent (trade name: Denacol EX-512, epoxy equivalent 168, solubility of 10 g of crosslinking agent in 90 g of ion-exchanged water is approximately 100% by mass (25° C.), manufactured by Nagase ChemteX Corporation). Moreover, an aqueous pigment ink with a non-volatile content of 6.0% by mass was obtained in the same manner as in Example 11, except that 40.1 g of Aqueous Pigment Dispersion 23M was used instead of Aqueous Pigment Dispersion 13M.

[0128] (Example 20) An aqueous pigment dispersion 24M (pigment concentration: 15.0% by mass) was obtained in the same manner as in Example 3, except that 5.47 g of a crosslinking agent (trade name: Denacol EX-851, epoxy equivalent 150, solubility of 10 g of crosslinking agent in 90 g of ion-exchanged water is approximately 99% by mass (25° C.), manufactured by Nagase ChemteX Corporation) was used instead of 6.12 g of the crosslinking agent (trade name: Denacol EX-512, epoxy equivalent 168, solubility of 10 g of crosslinking agent in 90 g of ion-exchanged water is approximately 100% by mass (25° C.), manufactured by Nagase ChemteX Corporation). Furthermore, an aqueous pigment ink with a non-volatile content of 6.0% by mass was obtained in the same manner as in Example 11, except that 40.1 g of Aqueous Pigment Dispersion 24M was used instead of Aqueous Pigment Dispersion 13M.

[0129] Example 21 An aqueous pigment dispersion 25M (pigment concentration: 14.9% by mass) was obtained in the same manner as in Example 3, except that 6.74 g of a crosslinking agent (trade name: Denacol EX-821, epoxy equivalent 185, solubility of 10 g of crosslinking agent in 90 g of ion-exchanged water is approximately 100% by mass (25° C.), manufactured by Nagase ChemteX Corporation) was used instead of 6.12 g of the crosslinking agent (trade name: Denacol EX-512, epoxy equivalent 168, solubility of 10 g of crosslinking agent in 90 g of ion-exchanged water is approximately 100% by mass (25° C.), manufactured by Nagase ChemteX Corporation). Moreover, an aqueous pigment ink having a nonvolatile content of 6.0% by mass was obtained in the same manner as in Example 11, except that 40.2 g of Aqueous Pigment Dispersion 25M was used instead of Aqueous Pigment Dispersion 13M.

[0130] Example 22 An aqueous pigment dispersion 26M (pigment concentration: 14.8% by mass) was obtained in the same manner as in Example 3, except that 9.77 g of a crosslinking agent (trade name: Denacol EX-830, epoxy equivalent: 268, solubility of 10 g of crosslinking agent in 90 g of ion-exchanged water is approximately 100% by mass (25° C.), manufactured by Nagase ChemteX Corporation) was used instead of 6.12 g of the crosslinking agent (trade name: Denacol EX-512, epoxy equivalent: 168, solubility of 10 g of crosslinking agent in 90 g of ion-exchanged water is approximately 100% by mass (25° C.), manufactured by Nagase ChemteX Corporation). Moreover, an aqueous pigment ink having a non-volatile content of 6.0% by mass was obtained in the same manner as in Example 11, except that 40.5 g of Aqueous Pigment Dispersion 26M was used instead of Aqueous Pigment Dispersion 13M.

[0131] Example 23 An aqueous pigment dispersion 27M (pigment concentration: 14.8% by mass) was obtained in the same manner as in Example 3, except that 10.35 g of a crosslinking agent (trade name: Denacol EX-832, epoxy equivalent: 284, solubility of 10 g of crosslinking agent in 90 g of ion-exchanged water is approximately 100% by mass (25° C.), manufactured by Nagase ChemteX Corporation) was used instead of 6.12 g of the crosslinking agent (trade name: Denacol EX-512, epoxy equivalent: 168, solubility of 10 g of crosslinking agent in 90 g of ion-exchanged water is approximately 100% by mass (25° C.), manufactured by Nagase ChemteX Corporation). Furthermore, an aqueous pigment ink with a non-volatile content of 6.0% by mass was obtained in the same manner as in Example 11, except that 40.5 g of Aqueous Pigment Dispersion 27M was used instead of Aqueous Pigment Dispersion 13M.

[0132] (Example 24) An aqueous pigment dispersion 28M (pigment concentration: 14.7% by mass) was obtained in the same manner as in Example 3, except that 13.56 g of a crosslinking agent (trade name: Denacol EX-841, epoxy equivalent: 372, solubility of 10 g of crosslinking agent in 90 g of ion-exchanged water is approximately 100% by mass (25° C.), manufactured by Nagase ChemteX Corporation) was used in place of 6.12 g of the crosslinking agent (trade name: Denacol EX-512, epoxy equivalent: 168, solubility of 10 g of crosslinking agent in 90 g of ion-exchanged water is approximately 100% by mass (25° C.), manufactured by Nagase ChemteX Corporation). Furthermore, an aqueous pigment ink with a non-volatile content of 6.0% by mass was obtained in the same manner as in Example 11, except that 40.8 g of Aqueous Pigment Dispersion 28M was used instead of Aqueous Pigment Dispersion 13M.

[0133] (Example 25) An aqueous pigment dispersion 29M (pigment concentration: 14.9% by mass) was obtained in the same manner as in Example 3, except that 6.49 g of a crosslinking agent (trade name: Denacol EX-920, epoxy equivalent 178, solubility of 10 g of crosslinking agent in 90 g of ion-exchanged water is approximately 100% by mass (25° C.), manufactured by Nagase ChemteX Corporation) was used instead of 6.12 g of the crosslinking agent (trade name: Denacol EX-512, epoxy equivalent 168, solubility of 10 g of crosslinking agent in 90 g of ion-exchanged water is approximately 100% by mass (25° C.), manufactured by Nagase ChemteX Corporation). Furthermore, an aqueous pigment ink with a non-volatile content of 6.0% by mass was obtained in the same manner as in Example 11, except that 40.2 g of Aqueous Pigment Dispersion 29M was used instead of Aqueous Pigment Dispersion 13M.

[0134] <Characteristics evaluation> The properties of the aqueous pigment dispersions and aqueous pigment inks obtained in the examples and comparative examples were evaluated by the methods described below.

[0135] [Evaluation of storage stability] The viscosity V0 at each temperature of the aqueous pigment dispersion (25° C.) and the aqueous pigment ink (32° C.) immediately after production obtained in the examples and comparative examples was measured by the following method.

[0136] Next, the aqueous pigment dispersion and the aqueous pigment ink were each filled into a plastic bottle and stored in a thermostatic chamber at 60° C. One week after the start of the storage, the viscosity V1 at each temperature of the aqueous pigment dispersion (25° C.) and the aqueous pigment ink (32° C.) was measured by the following method. Next, two weeks after the start of the storage, the viscosity V1 at each temperature of the aqueous pigment dispersion (25° C.) and the aqueous pigment ink (32° C.) was measured by the following method.

[0137] Based on the viscosities V0 and V1 and the following formula, the rate of change and the range of viscosity change of the aqueous pigment dispersion and the aqueous pigment ink one week and two weeks after the start of storage were calculated, respectively, and the storage stability of the aqueous pigment dispersion and the aqueous pigment ink was evaluated based on the rate of change. Viscosity change rate = [(viscosity V1 - viscosity V0) / (viscosity V0)] x 100 Viscosity change range = Viscosity V1 - Viscosity V0

[0138] Evaluation criteria for storage stability of aqueous pigment dispersions 3: After one week and two weeks of storage, the viscosity change rate of the aqueous pigment dispersion was less than 10%, and the range of viscosity change was less than ±0.5 mPa·s. 2: After one week of storage, the viscosity change rate of the aqueous pigment dispersion was less than 10% and the viscosity change range was less than ±0.5 mPa s, but after two weeks of storage, the viscosity change rate of the aqueous pigment dispersion was less than 10% or the viscosity change range was less than ±0.5 mPa s. 1: After one week of storage, the viscosity change rate of the aqueous pigment dispersion was 10% or more, or the viscosity change range was ±0.5 mPa s or more.

[0139] Evaluation criteria for storage stability of water-based pigment ink 3: The viscosity of the aqueous pigment ink immediately after production was less than 10 MPa·s, and the viscosity change rate of the aqueous pigment ink after one week of storage was less than 10%, and the viscosity change rate of the aqueous pigment ink after two weeks of storage was less than 10%. 2: The viscosity of the aqueous pigment ink immediately after production was less than 10 MPa·s, and the viscosity change rate of the aqueous pigment ink after one week of storage was less than 10%, and the viscosity change rate of the aqueous pigment ink after two weeks of storage was 10% or more. 1: The viscosity of the aqueous pigment ink immediately after production was less than 10 MPa·s, and the viscosity change rate of the aqueous pigment ink after one week of storage was 10% or more. 0: The viscosity of the water-based pigment ink immediately after production was 10 MPa·s or more.

[0140] The viscosity of the aqueous pigment dispersion and the aqueous pigment ink was measured using a cone-plate type rotational viscometer, which is an E-type viscometer, under the following conditions. Measurement equipment: TVE-25 type viscometer (Toki Sangyo Co., Ltd., TVE-25 L) Calibration standard solution: JS20 Measurement temperature: 32℃ Rotation speed: 10~100rpm Injection volume: 1200μL

[0141] [Evaluation of mottling in printed matter] The aqueous pigment inks obtained in the examples and comparative examples were filled into an inkjet head KJ4B-YH manufactured by Kyocera Corporation, and 50% solid printing was performed on OK Topcoat+ (manufactured by Oji Paper Co., Ltd., basis weight 104.7 g / m2), a recording medium with poor ink absorption. Next, the printed surface was heated for 1 second from a position about 8 cm above the printed surface with a 9 kW near infrared heater and dried to obtain a printed matter.

[0142] The printed surface of the print was subjected to a numerical analysis using a quality evaluation device "PIAS-II" manufactured by Quality Engineering Associates. Specifically, the mottle value (mottle) of the printed surface of the print was measured for each color. The suppression of mottle was evaluated based on the mottle value of the printed surface of each color, K (black), C (cyan), M (magenta) and Y (yellow), and the evaluation criteria listed in Table 1. Specifically, an ink evaluated as 3 in the evaluation criteria can be evaluated as being capable of obtaining a printed material in which mottle is sufficiently suppressed. On the other hand, an ink evaluated as 0 in the evaluation criteria was evaluated as being unable to be ejected from the inkjet head and therefore unable to obtain a printed material.

[0143] [Table 1]

[0144] [Evaluation of graininess of printed matter] The aqueous pigment inks obtained in the examples and comparative examples were filled into an inkjet head KJ4B-YH manufactured by Kyocera Corporation, and 50% solid printing was performed on OK Topcoat+ (manufactured by Oji Paper Co., Ltd., basis weight 104.7 g / m2), a recording medium with poor ink absorption. Next, the printed surface was heated for 1 second from a position about 8 cm above the printed surface with a 9 kW near infrared heater and dried to obtain a printed matter.

[0145] The printed surface of the print was subjected to a numerical analysis using the image quality evaluation device "PIAS-II" manufactured by Quality Engineering Associates, Inc. Specifically, the graininess value of the printed surface of the print was measured, and the suppression of graininess was evaluated based on the following criteria. Evaluation criteria 5: Graininess value is less than 2 4: Graininess value is between 2 and 3 3: Graininess value is 3 or more but less than 4 2: Graininess value is 4 or more and less than 5 1: Graininess value is 5 or more 0: Unable to print

[0146] [Table 2]

[0147] [Table 3]

[0148] [Table 4]

[0149] [Table 5]

[0150] [Table 6]

[0151]

Table 7

Claims

1. An inkjet printing ink comprising an aqueous pigment dispersion and an acid-modified polypropylene resin, the aqueous pigment dispersion contains a pigment (A), a pigment dispersing resin (B) having a structure (X) represented by the following general formula (I) and an anionic group, and an aqueous medium (C), the pigment dispersing resin (B) is a reaction product of a compound (B1) having an anionic group and a compound (B2) having two or more epoxy groups, the pigment dispersing resin (B) has the anionic group in an amount of 0.2 to 1.5 mmol / g based on the total amount of the pigment dispersing resin (B); An ink-jet printing ink, characterized in that the compound (B1) having an anionic group is a styrene-acrylic resin. 【Chemistry 1】

2. 2. The ink-jet printing ink according to claim 1, wherein the anionic group is a carboxyl group neutralized with an alkali metal hydroxide.

3. 3. The inkjet printing ink according to claim 2, wherein the compound (B1) has an acid value of 250 mg KOH / g or less.

4. 4. The ink-jet printing ink according to claim 2, wherein a crosslinking rate between the carboxyl group of said compound (B1) and the epoxy group of said compound (B2) is in the range of 45% to 85%.

5. The inkjet printing ink according to claim 1 or 2, wherein the compound (B2) is used in an amount of 3.2 mmol / g or less based on the total amount of the compound (B1).

6. 3. The ink-jet printing ink according to claim 1, wherein the compound (B2) has an oxyethylene structure.

7. An ink jet printing ink according to claim 1 or 2, further comprising an oxidized polyethylene wax.

8. An ink jet printing ink according to claim 1 or 2, further comprising a surfactant.

9. 9. The inkjet printing ink according to claim 8, wherein the surfactant comprises a silicone-based surfactant and / or an acetylene-based surfactant.

10. A method for producing a printed matter, comprising printing a recording medium by an inkjet printing method using the inkjet printing ink according to claim 1 or 2.

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