inkjet ink

Abstract

This invention provides an inkjet ink that can produce high-quality records on both gloss coated paper, which has a smooth surface and is resistant to ink spreading, and matte coated paper, which has an uneven surface and is resistant to ink spreading due to capillary action, as well as a method for manufacturing the same and a printing method using the inkjet ink. [Solution] An inkjet ink comprising crosslinked resin particles as a fixing resin, a pigment, an organic solvent, and water, wherein the crosslinked resin particles include a crosslinked structure consisting of a structure derived from a carboxyl group in an acrylic resin (A) and a structure derived from a polyfunctional epoxy compound, and the acrylic resin (A) includes constituent units derived from (meth)acrylic acid (a-1) and constituent units derived from cycloalkyl (meth)acrylate (a-2), an inkjet ink, a method for producing the same, and a printing method using the inkjet ink.

Description

Technical Field

[0001] The present invention relates to an inkjet ink, a method for producing the same, and a printing method using the inkjet ink.

Background Art

[0002] The inkjet recording method is a recording method in which ink droplets are directly ejected from fine nozzles and adhered to a recording medium to obtain characters and images. This method has many advantages such as being easy to achieve full color, inexpensive, capable of using plain paper as a recording medium, and non-contact with the printed material, and thus has become extremely popular. In recent years, due to the spread of digital printing, it has been increasingly used not only for consumer printing but also for commercial printing and industrial printing using low-absorbency coated paper and the like. The demand for inkjet inks is increasing more and more for the purpose of speeding up the printing speed, improving the image quality, and further reducing the environmental impact. In order to meet such demands, various inkjet inks have been proposed on the premise of satisfying basic performances such as ejection stability and storage stability.

[0003] For example, Patent Document 1 discloses an aqueous pigment dispersion excellent in the adhesion of an ink coating film of a printed matter (tape peeling resistance) to a substrate when used for printing on a resin film and excellent in intermittent ejection property, and an aqueous ink containing the aqueous pigment dispersion. The aqueous pigment dispersion is an aqueous pigment dispersion in which the pigment is dispersed by a crosslinked polymer A, and the crosslinked polymer A includes a structure derived from a water-dispersible polymer A' and a structure derived from a water-insoluble polyfunctional epoxy crosslinking agent, and the water-dispersible polymer A' is a vinyl resin containing a structural unit derived from cycloalkyl (meth)acrylate (a-1).

[0004] Furthermore, Patent Document 2 discloses an aqueous inkjet ink containing resin particles, for the purpose of providing an aqueous ink that can record images with excellent fixability and scratch resistance, wherein the resin particles have a first layer and a second layer in that order from the inside outwards, the first layer is formed of a first resin in which the proportion of units derived from cyclic aliphatic group-containing ethylenically unsaturated monomers is 10% by mass or less, the tetrahydrofuran insoluble fraction of the second layer is 15% by mass or more, and the second layer is formed of a second resin having units derived from cyclic aliphatic group-containing ethylenically unsaturated monomers and units derived from ionic group-containing ethylenically unsaturated monomers, and the proportion of units derived from the ionic group-containing ethylenically unsaturated monomers in the second resin is 3% by mass or more and 70% by mass or less. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2024-95001 [Patent Document 2] Japanese Patent Publication No. 2017-210604 [Overview of the project] [Problems that the invention aims to solve]

[0006] Users of inkjet recording systems sometimes use various recording media with different surface characteristics, such as glossy coated paper and matte coated paper, to achieve their desired color and texture. However, because glossy coated paper and matte coated paper have different surface conditions, to the best of the inventor's knowledge, there is no inkjet ink that produces excellent image quality on both glossy and matte coated paper.

[0007] For example, the aqueous ink for inkjet printing using the aqueous pigment dispersion described in Patent Document 1 has the problem of bleeding when printed on matte coated paper. Also, the aqueous ink described in Patent Document 2 has the problem that the ink does not spread sufficiently when printed on gloss coated paper.

[0008] The present invention aims to provide an inkjet ink that can produce high-quality records on both gloss coated paper, which has a smooth surface and is resistant to ink spreading, and matte coated paper, which has an uneven surface and is resistant to ink spreading due to capillary action. [Means for solving the problem]

[0009] The present inventors have found that the above problem can be solved by providing an inkjet ink containing crosslinked resin particles as a fixing resin, a pigment, an organic solvent, and water, wherein the crosslinked resin particles include a crosslinked structure consisting of a structure derived from a carboxyl group in an acrylic resin (A) and a structure derived from a polyfunctional epoxy compound, the acrylic resin (A) includes constituent units derived from (meth)acrylic acid (a-1) and constituent units derived from cycloalkyl (meth)acrylate (a-2), and the mass ratio of constituent units derived from (a-1) to constituent units derived from cycloalkyl (meth)acrylate (a-2) in the acrylic resin (A) is greater than 0.22 and less than or equal to 1.

[0010] In other words, the present invention provides the following [1] to [3]. [1] An inkjet ink comprising crosslinked resin particles as a fixing resin, a pigment, an organic solvent, and water, The crosslinked resin particles include a crosslinked structure consisting of a structure derived from a carboxyl group in the acrylic resin (A) and a structure derived from a polyfunctional epoxy compound. The acrylic resin (A) comprises constituent units derived from (meth)acrylic acid (a-1) and constituent units derived from cycloalkyl (meth)acrylate (a-2), The mass ratio ((a-1) derived from constituent units / (a-2) derived from constituent units) of the acrylic resin (A) is greater than 0.22 and less than or equal to 1. Inkjet ink.

[0011] [2] An inkjet printing method for printing on a printing substrate using the inkjet ink described in [1]. [3] A method for manufacturing an inkjet ink, comprising the step of mixing crosslinked resin particles as a fixing resin, a pigment, an organic solvent, and water, The crosslinked resin particles are obtained by reacting carboxyl groups in acrylic resin (A) with epoxy groups in a polyfunctional epoxy compound. The acrylic resin (A) comprises constituent units derived from (meth)acrylic acid (a-1) and constituent units derived from cycloalkyl (meth)acrylate (a-2), The mass ratio ((a-1) derived from constituent units / (a-2) derived from constituent units) of the acrylic resin (A) is greater than 0.22 and less than or equal to 1. A method for manufacturing inkjet ink. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide an inkjet ink that can produce high-quality records on both gloss coated paper, which has a smooth surface and is difficult for ink to spread, and matte coated paper, which has an uneven surface and is easily wetted and spread by capillary action, as well as a method for manufacturing the same, and a printing method using the inkjet ink. [Modes for carrying out the invention]

[0013] [Inkjet ink] The inkjet ink of the present invention (hereinafter also simply referred to as "ink") contains crosslinked resin particles as a fixing resin, a pigment, an organic solvent, and water. In the present invention, the crosslinked resin particles include a crosslinked structure composed of a structure derived from a carboxy group in an acrylic resin (A) and a structure derived from a polyfunctional epoxy compound, and the acrylic resin (A) includes a structural unit derived from (meth)acrylic acid (a-1) and a structural unit derived from cycloalkyl (meth)acrylate (a-2), and the mass ratio of the structural unit derived from (meth)acrylic acid (a-1) to the structural unit derived from cycloalkyl (meth)acrylate (a-2) in the acrylic resin (A) ((structural unit derived from (a-1)) / (structural unit derived from (a-2))) is more than 0.22 and 1 or less.

[0014] An inkjet ink is an ink used for inkjet printing, and the inkjet ink of the present invention is preferably an aqueous inkjet ink in which water occupies the largest proportion by mass in the contained medium.

[0015] The definitions of various terms in this specification are shown below. "Printing" is a concept including printing and typing for recording characters and images, and "printed matter" is a concept including printed matter and typed matter on which characters and images are recorded. "(Meth)acrylic acid" means at least one selected from the group consisting of acrylic acid and methacrylic acid. "(Meth)acrylate" means at least one selected from the group consisting of acrylate and methacrylate.

[0016] According to the inkjet ink of the present invention, high-quality recorded matter can be obtained on both glossy coated paper with a smooth surface and difficult ink wetting and spreading, and matte coated paper with uneven surface and easy ink wetting and spreading by capillary action. The reason is not necessarily clear, but it is considered as follows. Since the surface of the gloss-coated paper is smooth and has a low surface free energy, it is considered that ink hardly wets and spreads on the gloss-coated paper, the dot diameter of the ink becomes small, and printing unevenness occurs. On the other hand, the matte-coated paper is the same as the gloss-coated paper in that the surface free energy is low, but due to the unevenness on the surface, it is considered that the ink enters the unevenness by capillary action, and the ink wets and spreads excessively, causing bleeding.

[0017] The crosslinked resin particles contained in the ink of the present invention have a crosslinked structure in which the resin particles as the fixing resin contain a crosslinked structure. Therefore, compared with resin particles having no crosslinked structure, the fusion of resin particles is suppressed, and it is considered that the ink immediately after landing on the paper surface of the gloss-coated paper maintains a low viscosity and the dot diameter of the ink can be sufficiently expanded on the gloss-coated paper.

[0018] In addition, the acrylic resin (A) contained in the crosslinked resin particles contained in the ink of the present invention contains a structural unit derived from cycloalkyl (meth)acrylate. Due to the presence of this cycloalkyl (meth)acrylate group, the ink thickens as it dries on the paper surface, making it difficult to enter the unevenness on the matte-coated paper surface, and it is considered that excessive wetting and spreading of the ink on the matte-coated paper can be suppressed. On the other hand, when the resin dispersing the pigment contains a cycloalkyl (meth)acrylate group, the resin containing the cycloalkyl (meth)acrylate group is immobilized on the pigment surface, reducing the resin component contributing to thickening during drying, and it is considered that it is inferior in suppressing excessive wetting and spreading of the ink on the matte-coated paper.

[0019] <Crosslinked resin particles as the fixing resin> The crosslinked resin particles as the fixing resin contained in the inkjet ink of the present invention contain a crosslinked structure composed of a structure derived from a carboxy group in the acrylic resin (A) and a structure derived from a polyfunctional epoxy compound.

[0020] (Acrylic resin (A)) The acrylic resin (A) contains a structural unit derived from (meth)acrylic acid (a-1) and a structural unit derived from cycloalkyl (meth)acrylate (a-2). The acrylic resin (A) may be either a water-soluble resin or a water-insoluble resin. Here, the "water-soluble" and "water-insoluble" nature of the acrylic resin (A) is determined by the amount of resin that has been dried at 105°C for 2 hours to reach a constant weight, and then dissolved in 100g of water at 25°C until saturated. If the amount dissolved exceeds 10g, it is determined to be "water-soluble," and if it is 10g or less, it is determined to be "water-insoluble." Furthermore, if the anionic groups of the acrylic resin (A) are neutralized by a neutralizing agent as described later, the determination is made by the amount of dissolution measured under conditions in which the neutralizing agent is present under conditions in which the mass ratio of the acrylic resin (A) to the neutralizing agent is the same as that in the inkjet ink of the present invention.

[0021] [Constituent units derived from (meth)acrylic acid (a-1)] The acrylic resin (A) contains constituent units derived from (meth)acrylic acid (a-1) from the viewpoint of forming a crosslinked structure by reacting with a polyfunctional epoxy compound, and from the viewpoint of obtaining high-quality recordings on gloss-coated paper and matte-coated paper. (Meth)acrylic acid (a-1) is preferably one or more selected from the group consisting of acrylic acid and methacrylic acid, and more preferably acrylic acid.

[0022] The content of constituent units derived from (meth)acrylic acid (a-1) in the acrylic resin (A) is preferably 15% by mass or more, more preferably 20% by mass or more, and even more preferably 23% by mass or more, of the total constituent units of the acrylic resin (A), from the viewpoint of forming a crosslinked structure by reacting with a polyfunctional epoxy compound, and from the viewpoint of obtaining high-quality recordings on gloss-coated paper and matte-coated paper. Furthermore, from the same viewpoint as above, it is preferably 45% by mass or less, more preferably 42% by mass or less, and even more preferably 40% by mass or less. From the same viewpoint as above, the content of constituent units derived from (meth)acrylic acid (a-1) in the acrylic resin (A) is preferably 15% by mass or more and 45% by mass or less, more preferably 20% by mass or more and 42% by mass or less, and even more preferably 23% by mass or more and 40% by mass or less, of the total constituent units of the acrylic resin (A).

[0023] [Constituent units derived from cycloalkyl (meth)acrylate (a-2)] In the constituent units derived from cycloalkyl (meth)acrylate (a-2), the number of carbon atoms in the cycloalkyl group is preferably 4 or more, more preferably 5 or more, from the viewpoint of obtaining high-quality recordings on gloss-coated paper and matte-coated paper, as well as from the viewpoint of availability and economic efficiency, and from the same viewpoint as above, preferably 12 or less, more preferably 8 or less, and even more preferably 7 or less. From the same viewpoint as above, in the constituent units derived from cycloalkyl (meth)acrylate (a-2), the number of carbon atoms in the cycloalkyl group is preferably 4 or more and 12 or less, more preferably 4 or more and 8 or less, and even more preferably 5 or more and 7 or less.

[0024] From the viewpoint of availability and economic efficiency, the constituent units derived from cycloalkyl (meth)acrylate (a-2) are preferably constituent units derived from cycloalkyl acrylate, more preferably one or more selected from the group consisting of constituent units derived from cyclopentyl acrylate, constituent units derived from cyclohexyl acrylate, and constituent units derived from cycloheptyl acrylate, and even more preferably cyclohexyl acrylate.

[0025] From the viewpoint of obtaining high-quality recordings on gloss-coated paper and matte-coated paper, the content of constituent units derived from cycloalkyl (meth)acrylate (a-2) in the acrylic resin (A) is preferably 40% by mass or more, more preferably 45% by mass or more, and even more preferably 50% by mass or more, of the total constituent units of the acrylic resin (A), and from the same viewpoint as above, preferably 70% by mass or less, more preferably 65% ​​by mass or less, and even more preferably 60% by mass or less. From the same viewpoint as above, the content of constituent units derived from cycloalkyl (meth)acrylate (a-2) in the acrylic resin (A) is preferably 40% by mass or more and 70% by mass or less, more preferably 45% by mass or more and 65% by mass or less, and even more preferably 50% by mass or more and 60% by mass or less, of the total constituent units of the acrylic resin (A).

[0026] From the viewpoint of obtaining high-quality recordings in gloss-coated paper and matte-coated paper, the mass ratio of constituent units derived from (a-1) to constituent units derived from (a-2) in the acrylic resin (A) (the mass ratio of [constituent units derived from (a-1) / constituent units derived from (a-2)]) is greater than 0.22, more preferably 0.25 or higher, even more preferably 0.30 or higher, even more preferably 0.40 or higher, and even more preferably 0.45 or higher. Also, from the same viewpoint as above, the mass ratio of constituent units derived from (a-1) to constituent units derived from (a-2) in the acrylic resin (A) (the mass ratio of [constituent units derived from (a-1) / constituent units derived from (a-2)]) is 1.00 or less, preferably 0.95 or less, more preferably 0.90 or less, even more preferably 0.80 or less, even more preferably 0.70 or lower, and even more preferably 0.60 or lower. From the same viewpoint as described above, the mass ratio of constituent units derived from (a-1) to constituent units derived from (a-2) in the acrylic resin (A) (mass ratio of [constituent units derived from (a-1) / constituent units derived from (a-2)]) is greater than 0.22 and less than or equal to 1.00, more preferably 0.25 or more and less than or equal to 0.95, even more preferably 0.30 or more and less than or equal to 0.90, even more preferably 0.40 or more and less than or equal to 0.80, and even more preferably 0.45 or more and less than or equal to 0.70. From the viewpoint of ease of wetting and spreading on gloss coated paper, the mass ratio of constituent units derived from (a-1) to constituent units derived from (a-2) in the acrylic resin (A) (mass ratio of [constituent units derived from (a-1) / constituent units derived from (a-2)]) is preferably 0.67 or more and less than or equal to 0.8. The mass ratio of constituent units derived from (a-1) to constituent units derived from (a-2) in the acrylic resin (A) (the mass ratio of [constituent units derived from (a-1) / constituent units derived from (a-2)]) is preferably 0.45 or more and 0.70 or less from the viewpoint of suppressing wetting and spreading on matte paper.

[0027] [Constituent units derived from hydrophobic monomer (a-3)] The acrylic resin (A) preferably further contains constituent units derived from a hydrophobic monomer (a-3) from the viewpoint of improving the adsorption of the crosslinked resin to the pigment and obtaining high-quality recordings on gloss-coated paper and matte-coated paper. The constituent units derived from the hydrophobic monomer (a-3) are preferably one or more selected from the group consisting of alkyl (meth)acrylates and aromatic group-containing (meth)acrylates.

[0028] As for alkyl (meth)acrylates, alkyl (meth)acrylates having an alkyl group with 1 to 22 carbon atoms are preferred from the viewpoint of improving the adsorption of the crosslinked resin to the pigment, obtaining high-quality recordings on gloss-coated and matte-coated paper, as well as from the viewpoint of availability and economic efficiency. As for aromatic group-containing (meth)acrylates, from a similar viewpoint, aromatic group-containing (meth)acrylates having 6 to 22 carbon atoms are preferred.

[0029] Among these, as hydrophobic monomers (a-3), monomers with a glass transition temperature (Tg) of 30°C or less when made into a homopolymer are preferred, monomers with a glass transition temperature (Tg) of 20°C or less are more preferred, and monomers with a glass transition temperature (Tg) of 10°C or less are even more preferred. Furthermore, the glass transition temperature (Tg) of each monomer homopolymer can be determined using the values ​​listed in, for example, the Polymer Handbook Third Edition (Wiley-Interscience 1989).

[0030] As alkyl (meth)acrylates having an alkyl group with 1 to 22 carbon atoms, for example, one or more selected from the group consisting of methyl acrylate (Tg: 8°C), ethyl acrylate (Tg: -20°C), propyl acrylate (Tg: 3°C), isopropyl acrylate (Tg: -3°C), butyl acrylate (Tg: -55°C), isobutyl acrylate (Tg: -33°C), hexyl acrylate (Tg: -57°C), 2-ethylhexyl acrylate (Tg: -70°C), octyl acrylate (Tg: -65°C), and dodecyl acrylate (Tg: -3°C) are preferred. Among these, from the viewpoint of obtaining high-quality recordings on gloss-coated paper and matte-coated paper, one or more selected from the group consisting of methyl acrylate, ethyl acrylate, butyl acrylate, and isobutyl acrylate is more preferred, and butyl acrylate is even more preferred.

[0031] As the aromatic group-containing (meth)acrylate having 6 to 22 carbon atoms, one or more selected from the group consisting of benzyl acrylate (Tg: 6°C), phenoxyethyl acrylate (Tg: -22°C), and phenoxydiethylene glycol acrylate (Tg: -25°C) are preferred. Among these, benzyl acrylate is more preferred from the viewpoint of obtaining high-quality recordings on gloss-coated paper and matte-coated paper. The numbers in parentheses above indicate the glass transition temperature (Tg) when each monomer is formed into a single polymer.

[0032] If the acrylic resin (A) further contains constituent units derived from hydrophobic monomer (a-3), the content of constituent units derived from hydrophobic monomer (a-3) in the acrylic resin (A) is preferably 4% by mass or more, more preferably 4.5% by mass or more, even more preferably 5% by mass or more, even more preferably 6% by mass or more, even more preferably 9% by mass or more, even more preferably 10% by mass or more, and even more preferably 15% by mass or more, and from the same viewpoint as above, preferably 35% by mass or less, more preferably 30% by mass or less, even more preferably 25% by mass or less, even more preferably 21% by mass or less, and even more preferably 20% by mass or less. From the same viewpoint as described above, when the acrylic resin (A) further contains constituent units derived from hydrophobic monomer (a-3), the content of constituent units derived from hydrophobic monomer (a-3) in the acrylic resin (A) is preferably 4% by mass or more and 35% by mass or less, more preferably 4.5% by mass or more and 30% by mass or less, more preferably 5% by mass or more and 30% by mass or less, even more preferably 5% by mass or more and 25% by mass or less, even more preferably 6% by mass or more and 21% by mass or less, and even more preferably 9% by mass or more and 20% by mass or less. When the acrylic resin (A) further contains constituent units derived from hydrophobic monomer (a-3), the content of constituent units derived from hydrophobic monomer (a-3) in the acrylic resin (A) is preferably 4.5% by mass or more and 8% by mass or less from the viewpoint of ease of wetting and spreading on gloss coated paper. If the acrylic resin (A) further contains constituent units derived from the hydrophobic monomer (a-3), the content of constituent units derived from the hydrophobic monomer (a-3) in the acrylic resin (A) is preferably 9% by mass or more and 20% by mass or less, from the viewpoint of suppressing wetting and spreading on matte paper.

[0033] The acrylic resin (A) may contain constituent units derived from other monomers other than the monomers (a-1) to (a-3), as long as it does not impede the effects of the present invention. Examples of other monomers include ionic monomers, hydrophobic monomers, and nonionic monomers other than the monomers (a-1) to (a-3). From the viewpoint of obtaining high-quality recordings on gloss coated paper and matte coated paper, the mass ratio of the constituent units derived from the hydrophobic monomer (a-3) to the constituent units derived from (meth)acrylic acid (a-1) (constituent units derived from (a-3) / constituent units derived from (a-1)) is preferably 0.1 or more, more preferably 0.15 or more, even more preferably 0.20 or more, even more preferably 0.25 or more, even more preferably 0.30 or more, and from the same viewpoint as above, preferably 2.0 or less, more preferably 1.5 or less, even more preferably 1.0 or less, and even more preferably 0.8 or less. From the same viewpoint as above, the mass ratio of the constituent units derived from the hydrophobic monomer (a-3) to the constituent units derived from (meth)acrylic acid (a-1) (constituent units derived from (a-3) / constituent units derived from (a-1)) is preferably 0.1 or more and 2.0 or less, more preferably 0.15 or more and 1.5 or less, and even more preferably 0.20 or more and 1.00 or less. The mass ratio of the constituent units derived from the hydrophobic monomer (a-3) to the constituent units derived from the (meth)acrylic acid (a-1) (constituent units derived from (a-3) / constituent units derived from (a-1)) is preferably 0.13 or more and 0.2 or less from the viewpoint of ease of wetting and spreading on gloss coated paper. The mass ratio of the constituent units derived from the hydrophobic monomer (a-3) to the constituent units derived from the (meth)acrylic acid (a-1) (constituent units derived from (a-3) / constituent units derived from (a-1)) is preferably 0.1 or more and 0.8 or less from the viewpoint of suppressing wetting and spreading on matte paper.

[0034] From the viewpoint of obtaining high-quality recordings on gloss coated paper and matte coated paper, the mass ratio of the constituent units derived from the hydrophobic monomer (a-3) to the constituent units derived from the cycloalkyl (meth)acrylate (a-2) (constituent units derived from (a-3) / constituent units derived from (a-2)) is preferably 0.1 or more, more preferably 0.13 or more, even more preferably 0.15 or more, even more preferably 0.2 or more, even more preferably 0.3 or more, and from the same viewpoint as above, preferably 1.0 or less, more preferably 0.5 or less, and even more preferably 0.4 or less. From the same viewpoint as above, the mass ratio of the constituent units derived from the hydrophobic monomer (a-3) to the constituent units derived from the cycloalkyl (meth)acrylate (a-2) (constituent units derived from (a-3) / constituent units derived from (a-2)) is preferably 0.1 or more and 1.0 or less, more preferably 0.13 or more and 0.5 or less, and even more preferably 0.15 or more and 0.4 or less. The mass ratio of the constituent units derived from the hydrophobic monomer (a-3) to the constituent units derived from the cycloalkyl (meth)acrylate (a-2) ((a-3) derived constituent units / (a-2) derived constituent units) is preferably 0.1 to 0.4 from the viewpoint of ease of wetting and spreading on gloss coated paper. The mass ratio of the constituent units derived from the hydrophobic monomer (a-3) to the constituent units derived from the cycloalkyl (meth)acrylate (a-2) ((a-3) derived constituent units / (a-2) derived constituent units) is preferably 0.1 to 0.4 from the viewpoint of suppressing wetting and spreading on matte paper.

[0035] (Manufacturing of acrylic resin (A)) Acrylic resin (A) may be synthesized as appropriate or a commercially available product may be used. Acrylic resin (A) can be produced by copolymerizing raw material monomers, including the monomers (a-1) to (a-3), etc., using a known polymerization method. Solution polymerization is preferred as the polymerization method.

[0036] There are no restrictions on the solvent used in solution polymerization, but polar solvents such as aliphatic alcohols, ketones, ethers, and esters are preferred, and methanol, ethanol, acetone, and methyl ethyl ketone are more preferred.

[0037] Polymerization initiators and polymerization chain transfer agents can be used during polymerization. Examples of polymerization initiators include persulfates such as ammonium persulfate and potassium persulfate; and azo compounds such as water-soluble azo polymerization initiators and polymer azo polymerization initiators. Examples of polymerization chain transfer agents include thiols and mercaptans.

[0038] 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 more preferably 95°C or lower, and more preferably 80°C or lower.

[0039] The acrylic resin (A) is preferably used as an aqueous dispersion dispersed in an aqueous medium, and may contain a dispersant such as a surfactant as needed.

[0040] (Physical properties of acrylic resin (A)) The acid value of the acrylic resin (A) is preferably 100 mg KOH / g or more, more preferably 110 mg KOH / g or more, even more preferably 120 mg KOH / g or more, even more preferably 150 mg KOH / g or more, and even more preferably 190 mg KOH / g or more, and from the same viewpoint as above, preferably 350 mg KOH / g or less, more preferably 330 mg KOH / g or less, even more preferably 310 mg KOH / g or less, and even more preferably 290 mg KOH / g or less. From the same viewpoint as described above, the acid value of the acrylic resin (A) is preferably 100 mg KOH / g or more and 350 mg KOH / g or less, more preferably 110 mg KOH / g or more and 330 mg KOH / g or less, even more preferably 120 mg KOH / g or more and 310 mg KOH / g or less, even more preferably 150 mg KOH / g or more and 290 mg KOH / g or less, and even more preferably 190 mg KOH / g or more and 290 mg KOH / g or less.

[0041] The weight-average molecular weight of the acrylic resin (A) is preferably 5,000 or more, more preferably 8,000 or more, and even more preferably 10,000 or more, from the viewpoint of obtaining high-quality recordings on gloss-coated paper and matte-coated paper, and from the same viewpoint as above, preferably 100,000 or less, more preferably 50,000 or less, and even more preferably 30,000 or less. From the same viewpoint as above, the weight-average molecular weight of the acrylic resin (A) is preferably 5,000 or more and 100,000 or less, more preferably 8,000 or more and 50,000 or less, and even more preferably 10,000 or more and 30,000 or less.

[0042] The acid value of acrylic resin (A) is calculated from the mass ratio of its constituent monomers. The weight-average molecular weight of acrylic resin (A) is measured by the method described in the examples.

[0043] (Polyfunctional epoxy compound) The polyfunctional epoxy compound is preferably a polyfunctional epoxy compound having two or more epoxy groups in the molecule, more preferably a polyglycidyl ether compound of a polyhydric alcohol having hydrocarbon groups with 3 to 8 carbon atoms, even more preferably one or more selected from the group consisting of trimethylolpropane polyglycidyl ether, pentaerythritol polyglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,4-cyclohexanedimethanol diglycidyl ether, and diethylene glycol diglycidyl ether, and even more preferably trimethylolpropane polyglycidyl ether.

[0044] The epoxy group equivalent of the polyfunctional epoxy compound is preferably 90 or more, more preferably 100 or more, even more preferably 110 or more, and preferably 300 or less, more preferably 200 or less, and even more preferably 170 or less. The epoxy group equivalent of the polyfunctional epoxy compound is preferably 90 or more and 300 or less, more preferably 100 or more and 200 or less, and even more preferably 110 or more and 170 or less.

[0045] From the viewpoint of obtaining high-quality recordings on gloss-coated paper and matte-coated paper, the mass ratio of the constituent units derived from the hydrophobic monomer (a-3) to the constituent units derived from the polyfunctional epoxy compound (constituent units derived from (a-3) / constituent units derived from the polyfunctional epoxy compound) is preferably 0.1 or more, more preferably 0.14 or more, even more preferably 0.2 or more, even more preferably 0.4 or more, even more preferably 0.6 or more, and from the same viewpoint as above, preferably 2.0 or less, more preferably 1.4 or less, even more preferably 1 or less, even more preferably 0.9 or less, and even more preferably 0.8 or less. From the same viewpoint as above, the mass ratio of the constituent units derived from the hydrophobic monomer (a-3) to the constituent units derived from the polyfunctional epoxy compound (constituent units derived from (a-3) / constituent units derived from the polyfunctional epoxy compound) is preferably 0.1 or more and 2.0 or less, more preferably 0.14 or more and 1.4 or less, even more preferably 0.2 or more and 0.9 or less. The mass ratio of the constituent units derived from the hydrophobic monomer (a-3) to the constituent units derived from the polyfunctional epoxy compound ((a-3)-derived constituent units / polyfunctional epoxy compound-derived constituent units) is preferably 0.4 to 0.8 from the viewpoint of ease of wetting and spreading on gloss coated paper. The mass ratio of the constituent units derived from the hydrophobic monomer (a-3) to the constituent units derived from the polyfunctional epoxy compound ((a-3)-derived constituent units / polyfunctional epoxy compound-derived constituent units) is preferably 0.1 to 1 from the viewpoint of suppressing wetting and spreading on matte paper.

[0046] From the viewpoint of obtaining high-quality recordings on gloss-coated and matte-coated paper, the mass ratio of the constituent units derived from the cycloalkyl (meth)acrylate (a-2) to the constituent units derived from the polyfunctional epoxy compound (constituent units derived from (a-2) / constituent units derived from the polyfunctional epoxy compound) is preferably 1.0 or more, more preferably 1.2 or more, even more preferably 1.3 or more, even more preferably 1.5 or more, even more preferably 1.7 or more, and from the same viewpoint as above, preferably 6.0 or less, more preferably 4.0 or less, and even more preferably 2.0 or less. From the same viewpoint as above, the mass ratio of the constituent units derived from the cycloalkyl (meth)acrylate (a-2) to the constituent units derived from the polyfunctional epoxy compound (constituent units derived from (a-2) / constituent units derived from the polyfunctional epoxy compound) is preferably 1.0 or more and 6.0 or less, more preferably 1.2 or more and 4.0 or less, and even more preferably 1.3 or more and 2.0 or less. The mass ratio of the constituent units derived from the cycloalkyl (meth)acrylate (a-2) to the constituent units derived from the polyfunctional epoxy compound ((a-2)-derived constituent units / polyfunctional epoxy compound-derived constituent units) is preferably 1.2 to 2 from the viewpoint of ease of wetting and spreading on gloss coated paper. The mass ratio of the constituent units derived from the cycloalkyl (meth)acrylate (a-2) to the constituent units derived from the polyfunctional epoxy compound ((a-2)-derived constituent units / polyfunctional epoxy compound-derived constituent units) is preferably 1.2 to 2.0 from the viewpoint of suppressing wetting and spreading on matte paper.

[0047] (Manufacturing of cross-linked resin particles) Crosslinked resin particles can be efficiently manufactured by a method comprising the following steps 1 and 2. Crosslinked resin particles manufactured by the method comprising steps 1 and 2 have a crosslinked structure on the surface of the crosslinked resin particles, which consists of a structure derived from carboxyl groups in the acrylic resin (A) and a structure derived from a polyfunctional epoxy compound. Step 1: A step to obtain an aqueous dispersion of acrylic resin (A) by neutralizing at least a portion of the carboxyl groups of acrylic resin (A) with an alkali metal compound. Step 2: A step to obtain an aqueous dispersion of crosslinked resin particles by adding a polyfunctional epoxy compound to the aqueous dispersion of acrylic resin (A) obtained in Step 1, and reacting the carboxyl groups in the acrylic resin (A) with the epoxy groups in the polyfunctional epoxy compound.

[0048] (Process 1) It is preferable that at least a portion of the carboxyl groups of the acrylic resin (A) are neutralized using a neutralizing agent. This is thought to increase the charge repulsion force that emerges after neutralization, thereby suppressing aggregation of crosslinked resin particles in the ink and improving the dispersion stability of the crosslinked resin particles.

[0049] In step 1, neutralization is preferably performed so that the pH is between 7 and 11.

[0050] Examples of the neutralizing agent include one or more selected from alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, and cesium hydroxide; alkali metal salts of carbonic acid such as disodium carbonate, sodium bicarbonate, and dipotassium carbonate; alkali metal salts of boric acid such as sodium borate; and bases such as organic amines. Of these, from the viewpoint of availability and economic efficiency, it is preferable to select one or more from the group consisting of alkali metal hydroxides and organic amines, more preferably one or more selected from sodium hydroxide, potassium hydroxide, and organic amines, and even more preferably sodium hydroxide and organic amines.

[0051] Suitable examples of the aforementioned organic amines include alkylamines, alkanolamines, aminoalkanediols, alkoxyamines, and heterocyclic amines. Among these, alkanolamines are more preferred. Preferably, one or more alkanolamines are selected from the group consisting of N-methyldiethanolamine, N-ethyldiethanolamine, N,N-dimethylethanolamine, and N,N-diethylethanolamine, with N,N-dimethylethanolamine being more preferred.

[0052] From the viewpoint of ensuring the dispersion stability of the acrylic resin (A), the degree of neutralization of the acrylic resin (A) is preferably 15 mol% or more, more preferably 20 mol% or more, and even more preferably 25 mol% or more. From the viewpoint of the productivity of crosslinked resin particles, it is preferably 50 mol% or less, more preferably 40 mol% or less, and even more preferably 35 mol% or less. From the same viewpoint as above, the degree of neutralization of the acrylic resin (A) is preferably 15 mol% or more and 50 mol% or less, more preferably 20 mol% or more and 40 mol% or less, and even more preferably 25 mol% or more and 35 mol% or less.

[0053] The degree of neutralization (mol%) is calculated using the following formula. Degree of neutralization (mol %) = [Number of moles of alkali metal compound / Number of moles of carboxyl groups in acrylic resin (A)] × 100

[0054] In this invention, if an excess of alkali metal compound is used compared to the number of moles of carboxyl groups in the acrylic resin (A), the degree of neutralization may exceed 100 mol%.

[0055] (Process 2) In step 2, the temperature at which the carboxyl groups in the acrylic resin (A) react with the epoxy groups in the polyfunctional epoxy compound is preferably 50°C or higher, more preferably 70°C or higher, and preferably 95°C or lower, more preferably 90°C or lower, from the viewpoint of completing the crosslinking reaction and economic efficiency. Also, from the same viewpoint as above, the crosslinking treatment time is preferably 1 hour or more, more preferably 3 hours or more, and preferably 10 hours or less, more preferably 8 hours or less.

[0056] From the viewpoint of obtaining high-quality recordings on gloss-coated and matte-coated paper, the amount of polyfunctional epoxy compound used is such that the degree of crosslinking of the resulting crosslinked resin particles is preferably 10 mol% or more, more preferably 15 mol% or more, even more preferably 20 mol% or more, even more preferably 30 mol% or more, even more preferably 40 mol% or more, and even more preferably 50 mol% or more. From the same viewpoint as above, the amount of polyfunctional epoxy compound used is such that the degree of crosslinking of the resulting crosslinked resin particles is preferably 80 mol% or less, more preferably 75 mol% or less, even more preferably 70 mol% or less, even more preferably 65 mol% or less, and even more preferably 60 mol% or less. From the same viewpoint as above, the amount of polyfunctional epoxy compound used is such that the degree of crosslinking of the resulting crosslinked resin particles is preferably 10 mol% to 80 mol%, more preferably 15 mol% to 75 mol%, even more preferably 20 mol% to 70 mol%, and even more preferably 30 mol% to 65 mol%. From the viewpoint of ease of wetting and spreading on gloss-coated paper, the amount of polyfunctional epoxy compound used is preferably such that the degree of crosslinking of the resulting crosslinked resin particles is 50 mol% to 80 mol%. From the viewpoint of suppressing wetting and spreading on matte paper, the amount of polyfunctional epoxy compound used is preferably such that the degree of crosslinking of the resulting crosslinked resin particles is 40 mol% to 60 mol%.

[0057] In step 2, the degree of crosslinking (mol%) of the crosslinked resin particles may be the theoretical degree of crosslinking calculated by the following formula, which may be used as the degree of crosslinking of the pigment-containing polymer. However, if the theoretical degree of crosslinking exceeds 100 mol%, the degree of crosslinking shall be 100 mol%. Degree of crosslinking of crosslinked resin particles (mol%) = [Amount of polyfunctional epoxy compound added / {Equivalent amount of polyfunctional epoxy compound (g / eq.) × Number of moles of carboxylic acid in acrylic resin (A) contained in the crosslinked resin particles}] × 100

[0058] From the viewpoint of obtaining high-quality recordings on gloss-coated and matte-coated paper, the acid value of the cross-linked resin particles is preferably 35 mgKOH / g or more, more preferably 40 mgKOH / g or more, even more preferably 50 mgKOH / g or more, and even more preferably 60 mgKOH / g or more. Furthermore, from the same viewpoint as above, it is preferably 220 mgKOH / g or less, more preferably 190 mgKOH / g or less, even more preferably 155 mgKOH / g or less, even more preferably 130 mgKOH / g or less, even more preferably 110 mgKOH / g or less, even more preferably 90 mgKOH / g or less, and even more preferably 85 mgKOH / g or less. From the same viewpoint as described above, the acid value of the crosslinked resin particles is 35 mg KOH / g or more and 220 mg KOH / g or less, more preferably 40 mg KOH / g or more and 190 mg KOH / g or less, even more preferably 40 mg KOH / g or more and 155 mg KOH / g or less, even more preferably 40 mg KOH / g or more and 130 mg KOH / g or less, and even more preferably 50 mg KOH / g or more and 110 mg KOH / g or less. From the viewpoint of ease of wetting and spreading on gloss coated paper, the acid value of the crosslinked resin particles is preferably 40 mg KOH / g or more and 85 mg KOH / g or less. From the viewpoint of suppressing wetting and spreading on matte paper, the acid value of the crosslinked resin particles is preferably 60 mg KOH / g or more and 85 mg KOH / g or less.

[0059] In the present invention, the acid value of the crosslinked resin particles is the acid value of the resin constituting the crosslinked resin particles, and is calculated from the acid value of the acrylic resin (A) before crosslinking, the degree of crosslinking, and the amount of polyfunctional epoxy compound added.

[0060] From the viewpoint of obtaining high-quality recordings on gloss-coated paper and matte-coated paper, the content of cross-linked resin particles in the inkjet ink is preferably 2.5% by mass or more, more preferably 3.0% by mass or more, even more preferably 3.5% by mass or more, and even more preferably 4.0% by mass or more, and from the same viewpoint as above, preferably 10% by mass or less, more preferably 8% by mass or less, and even more preferably 6% by mass or less. From the same viewpoint as above, the content of the cross-linked resin particles in the inkjet ink is preferably 2.5% by mass or more and 10% by mass or less, more preferably 3.0% by mass or more and 8% by mass or less, even more preferably 3.5% by mass or more and 8% by mass or less, and even more preferably 4.0% by mass or more and 6% by mass or less.

[0061] <Pigments> (Pigment) The pigment contained in the inkjet ink of the present invention may be either an inorganic pigment or an organic pigment. Examples of inorganic pigments include carbon black and metal oxides, with carbon black being preferred for black inks. Examples of carbon black include furnace black, lamp black, acetylene black, and channel black. Examples of white pigments include titanium dioxide, zinc oxide, silica, alumina, and magnesium oxide.

[0062] 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.

[0063] For achromatic inks, achromatic pigments such as white, black, and gray can be used, while for chromatic inks, chromatic pigments such as yellow, magenta, cyan, red, blue, orange, and green can be used. The aforementioned pigments can be used individually or in combination of two or more types.

[0064] Preferred forms of pigments include pigments that can maintain a dispersed state without a dispersant, i.e., self-dispersing pigments; pigment particles in which the pigment is dispersed with a low-molecular-weight or high-molecular-weight surfactant; and resin particles containing the pigment. Of these, the form of resin particles containing the pigment is preferred from the viewpoint of dispersion stability and fixation of the pigment. Furthermore, the resin in the resin particles containing the pigment may be an uncrosslinked resin or a crosslinked resin.

[0065] Here, "pigment-containing resin particles" (hereinafter also referred to as "pigment-containing resin particles") means particles in which the resin encapsulates the pigment, particles in which a portion of the pigment is exposed on the surface of particles composed of resin and pigment, particles in which the resin is adsorbed onto a portion of the pigment, or mixtures thereof. Among these, particles in which the resin encapsulates the pigment are more preferred.

[0066] [Pigment-containing resin particles] The pigment-dispersing resin constituting the pigment-containing resin particles may be any resin having the ability to disperse pigments in an aqueous medium, and may be water-soluble or water-insoluble, but a water-insoluble resin is preferred.

[0067] Here, "water-insoluble" means that when a resin that has been dried at 105°C for 2 hours and reached a constant weight is dissolved in 100g of water at 25°C until saturation is reached, the amount that dissolves is 10g or less. If the water-insoluble resin is an anionic resin, the amount that dissolves is the amount that dissolves when the anionic groups of the resin are 100% neutralized with sodium hydroxide.

[0068] [Resin for pigment dispersion] Examples of resins for pigment dispersion include vinyl resins, polyester resins, and polyurethane resins. Among these, vinyl resins (B) obtained by addition polymerization of vinyl monomers are preferred from the viewpoint of storage stability and ejection stability of inkjet inks.

[0069] The vinyl resin (B) preferably contains (b-1) structural units derived from ionic monomers and (b-2) structural units derived from hydrophobic monomers, and may further contain (b-3) structural units derived from nonionic monomers.

[0070] [(b-1) Ionic monomers] (b-1) As ionic monomers, anionic monomers are preferred, including carboxylic acid monomers and sulfonic acid monomers, with carboxylic acid monomers being more preferred.

[0071] Examples of carboxylic acid monomers include one or more selected from acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, and citraconic acid, but one or more selected from acrylic acid and methacrylic acid are more preferred, and acrylic acid is even more preferred.

[0072] [(b-2) Hydrophobic monomers] (b-2) The term "hydrophobic" in "hydrophobic monomer" means that when the monomer is dissolved in 100g of deionized water at 25°C until saturated, the amount dissolved is less than 10g.

[0073] (b-2) Specific examples of hydrophobic monomers include those described in paragraphs

[0020] to

[0022] of Japanese Patent Publication No. 2018-83938. 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, macromonomers having a polymerizable functional group at one end are preferred, one or more selected from styrene, α-methylstyrene, benzyl (meth)acrylate, cyclohexyl acrylate, and butyl acrylate are more preferred, and styrene is even more preferred.

[0074] Macromonomers having a polymerizable functional group at one end are compounds with a number-average molecular weight of 500 to 100,000, preferably 1,000 to 10,000, and examples of polymerizable functional groups include acryloyloxy groups or methacryloyloxy groups.

[0075] As macromonomers, aromatic group-containing monomer-based macromonomers are preferred, and examples of aromatic group-containing monomers that constitute them include the aforementioned aromatic group-containing monomers.

[0076] Specific examples of commercially available styrene-based macromonomers include AS-6(S), AN-6(S), and HS-6(S) manufactured by Toagosei Co., Ltd.

[0077] [(b-3) Nonionic monomers] (b-3) Nonionic monomers are monomers that have a high affinity for water and water-soluble organic solvents, such as monomers containing hydroxyl groups or polyalkylene glycol chains.

[0078] (b-3) Specific examples of the component include those described in paragraph

[0018] of Japanese Patent Publication No. 2018-83938. Among these, one or more selected from methoxypolyethylene glycol (n=1~30) (meth)acrylate and polypropylene glycol (n=2~30) (meth)acrylate are preferred. The above components (b-1) to (b-3) can each be used by using the monomer components contained in each component individually or by mixing two or more of them.

[0079] (Content of each constituent unit in the pigment dispersion resin) The content of constituent units derived from components (b-1) to (b-3) in the pigment dispersion resin is as follows, from the viewpoint of pigment dispersion stability and the storage stability and ejection stability of inkjet ink. The content of component (b-1) is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, and preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less. The content of component (b-1) is preferably 10% by mass or more and 50% by mass or less, more preferably 15% by mass or more and 45% by mass or less, and even more preferably 20% by mass or more and 40% by mass or less.

[0080] The content of component (b-2) is preferably 50% by mass or more, more preferably 55% by mass or more, even more preferably 60% by mass or more, and preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less. The content of component (b-2) is preferably 50% by mass or more and 90% by mass or less, more preferably 55% by mass or more and 85% by mass or less, and even more preferably 60% by mass or more and 80% by mass or less.

[0081] If component (b-3) is present, the content of component (b-3) is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less, and even more preferably 5% by mass or less.

[0082] The mass ratio of [(b-1) component / (b-2) component] is preferably 0.4 or more, more preferably 0.5 or more, even more preferably 0.6 or more, and preferably 2 or less, more preferably 1.5 or less, and even more preferably 1 or less. The mass ratio of [(b-1) component / (b-2) component] is preferably 0.4 or more and 2 or less, more preferably 0.5 or more and 1.5 or less, and even more preferably 0.6 or more and 1 or less.

[0083] In the present invention, the content of constituent units derived from components (b-1) to (b-3) in the pigment dispersion resin can be determined by measurement, or it can be substituted by the charging ratio of raw material monomers containing components (b-1) to (b-3) during the production of the pigment dispersion resin.

[0084] (Manufacturing of resins for pigment dispersion) The pigment dispersion resin can be produced by copolymerizing the monomer mixture using a known polymerization method. Solution polymerization is preferred as the polymerization method. There are no restrictions on the solvent used in solution polymerization, but polar solvents such as water, lower aliphatic alcohols, ketones such as methyl ethyl ketone, ethers, and esters are preferred.

[0085] During polymerization, polymerization initiators such as azo compounds and persulfates, and polymerization chain transfer agents such as mercaptans 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 resin for pigment dispersion is preferably neutralized with an alkali metal compound, as described later.

[0086] The weight-average molecular weight of the pigment dispersion resin is preferably 4,000 or more, more preferably 6,000 or more, even more preferably 8,000 or more, and preferably 150,000 or less, more preferably 100,000 or less, even more preferably 80,000 or less, even more preferably 50,000 or less, and even more preferably 30,000 or less, from the viewpoint of the dispersion stability of the pigment. From the same viewpoint as above, the weight-average molecular weight of the pigment dispersion resin is preferably 4,000 or more and 150,000 or less, more preferably 6,000 or more and 100,000 or less, even more preferably 8,000 or more and 80,000 or less, even more preferably 8,000 or more and 50,000 or less, and even more preferably 8,000 or more and 30,000 or less.

[0087] From the same viewpoint as above, the acid value of the pigment dispersion resin is preferably 50 mg KOH / g or more, more preferably 90 mg KOH / g or more, even more preferably 180 mg KOH / g or more, even more preferably 200 mg KOH / g or more, even more preferably 220 mg KOH / g or more, and preferably 400 mg KOH / g or less, more preferably 320 mg KOH / g or less, even more preferably 300 mg KOH / g or less, and even more preferably 280 mg KOH / g or less. From the same viewpoint as above, the acid value of the pigment dispersion resin is preferably 50 mg KOH / g or more and 400 mg KOH / g or less, more preferably 90 mg KOH / g or more and 320 mg KOH / g or less, even more preferably 180 mg KOH / g or more and 300 mg KOH / g or less, even more preferably 200 mg KOH / g or more and 280 mg KOH / g or less, and even more preferably 220 mg KOH / g or more and 280 mg KOH / g or less.

[0088] The weight-average molecular weight and acid value of the pigment dispersion resin can be measured by the method described in the examples.

[0089] <Manufacturing of pigment-containing resin particles> Resin particles containing pigments can be efficiently manufactured by a method comprising the following steps I and II. Step I: A step to obtain an aqueous dispersion of the pigment dispersion resin by neutralizing at least a portion of the carboxyl groups of the pigment dispersion resin with an alkali metal compound. Step II: A step to obtain an aqueous pigment dispersion of resin particles containing pigment dispersed in pigment dispersion resin, by dispersing the aqueous dispersion of pigment resin obtained in Step I with the pigment.

[0090] Furthermore, in the production of pigment-containing resin particles, the process may optionally include a step III in which the aqueous pigment dispersion obtained in step II is crosslinked with a crosslinking agent.

[0091] (Process I) It is preferable that at least a portion of the carboxyl groups in the pigment dispersion resin are neutralized using an alkali metal compound. This is thought to increase the charge repulsion force that emerges after neutralization, thereby suppressing the aggregation of pigment particles in inkjet inks and improving the dispersion stability of the pigment. In step I, neutralization is preferably performed so that the pH is between 7 and 11.

[0092] Examples of alkali metal compounds include one or more selected from alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, and cesium hydroxide; alkali metal salts of carbonic acid such as disodium carbonate, sodium bicarbonate, and dipotassium carbonate; and alkali metal salts of boric acid such as sodium borate. Among these, from the viewpoint of availability and economic efficiency, alkali metal hydroxides are preferred, more preferably one or more selected from sodium hydroxide and potassium hydroxide, and even more preferably sodium hydroxide.

[0093] From the viewpoint of ensuring the dispersion stability of the pigment, the degree of neutralization of the pigment dispersion resin is preferably 20 mol% or more, more preferably 25 mol% or more, and even more preferably 30 mol% or more. From the viewpoint of crosslinking the pigment dispersion resin with the crosslinking agent, it is preferably 60 mol% or less, more preferably 55 mol% or less, and even more preferably 50 mol% or less. From the same viewpoint as above, the degree of neutralization of the pigment dispersion resin is preferably 20 mol% or more and 60 mol% or less, more preferably 25 mol% or more and 55 mol% or less, and even more preferably 30 mol% or more and 50 mol% or less.

[0094] The degree of neutralization (mol%) is calculated using the following formula. Degree of neutralization (mol %) = [Number of moles of alkali metal compound / Number of moles of carboxyl groups in pigment dispersion resin] × 100 In this invention, if an excess of alkali metal compound is used compared to the number of moles of carboxyl groups in the pigment dispersion resin, the degree of neutralization may exceed 100 mol%.

[0095] (Process II) In step II, the dispersion treatment can be performed solely by shear stress to finely atomize the pigment particles to the desired particle size. However, from the viewpoint of obtaining a uniform aqueous pigment dispersion, it is preferable to pre-disperse the pigment mixture before further pre-dispersion. For pre-dispersion, commonly used mixing and stirring devices such as anchor blades and disperser blades can be used.

[0096] Dispersion machines used for this dispersion include kneaders such as roll mills and kneaders, high-pressure homogenizers such as microfluidizers, and media-type dispersants such as paint shakers and bead mills. Among these, it is preferable to use a high-pressure homogenizer from the viewpoint of reducing the particle size of the pigment.

[0097] When performing dispersion processing using a high-pressure homogenizer, the average particle size of pigment-containing resin particles in the aqueous pigment dispersion can be adjusted by controlling the processing pressure and the number of passes.

[0098] From the viewpoint of productivity and economic efficiency, the processing pressure is preferably 60 MPa to 300 MPa, and the number of passes is preferably 3 to 30.

[0099] (Process III) In step III, the pigment dispersion resin containing the pigment is crosslinked with a crosslinking agent to form a crosslinked resin, and a pigment aqueous dispersion can be obtained in which particles of the crosslinked resin containing the pigment are dispersed in an aqueous medium.

[0100] The crosslinking agent used in step III is preferably an epoxy compound, and more preferably a compound having two or more epoxy groups in its molecule. For compounds having two or more epoxy groups in the molecule, the same applies as for the polyfunctional epoxy compounds described above. Furthermore, the preferred range of epoxy equivalents for compounds having two or more epoxy groups in the molecule is also the same as for the polyfunctional epoxy compounds described above.

[0101] When the pigment dispersion resin is crosslinked with a crosslinking agent, the degree of crosslinking of the particles of the crosslinked pigment dispersion resin is preferably 35 mol% or more, more preferably 40 mol% or more, and even more preferably 45 mol% or more, from the viewpoint of storage stability and ejection stability of the inkjet ink, and also preferably 65 mol% or less, more preferably 60 mol% or less, and even more preferably 55 mol% or less, from the same viewpoint as above. From the same viewpoint as above, the degree of crosslinking of the particles of the crosslinked pigment dispersion resin is preferably 35 mol% or more and 65 mol% or less, more preferably 40 mol% or more and 60 mol% or less, and even more preferably 45 mol% or more and 55 mol% or less.

[0102] Here, in step III, the degree of crosslinking (mol%) of the particles of the crosslinked pigment dispersion resin may be the theoretical degree of crosslinking calculated by the following formula. However, if the theoretical degree of crosslinking exceeds 100 mol%, the degree of crosslinking shall be 100 mol%. The degree of crosslinking (mol%) of particles of crosslinked pigment dispersion resin = [Amount of crosslinking agent added / {Equivalent amount of functional groups of crosslinking agent (g / eq.) × Number of moles of carboxylic acid in the pigment dispersion resin contained in the pigment-containing resin particles}] × 100

[0103] From the viewpoint of dispersion stability, the concentration of nonvolatile components (solids) in the aqueous dispersion of pigment-containing resin particles obtained is preferably 10% by mass or more, more preferably 15% by mass or more, and preferably 30% by mass or less, more preferably 25% by mass or less. From the same viewpoint as above, the concentration of nonvolatile components (solids) in the aqueous dispersion of pigment-containing resin particles obtained is preferably 10% by mass or more and 30% by mass or less, more preferably 15% by mass or more and 25% by mass or less.

[0104] From the viewpoint of dispersion stability, the pigment content in the aqueous dispersion of pigment-containing resin particles is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 12% by mass or more, and preferably 25% by mass or less, more preferably 20% by mass or less, and even more preferably 18% by mass or less. From the same viewpoint as above, the pigment content in the aqueous dispersion of pigment-containing resin particles is preferably 5% by mass or more and 25% by mass or less, more preferably 10% by mass or more and 20% by mass or less, and even more preferably 12% by mass or more and 18% by mass or less.

[0105] The average particle size of pigment-containing resin particles in an aqueous dispersion of pigment-containing resin particles is preferably 50 nm or more, more preferably 70 nm or more, even more preferably 80 nm or more, and preferably 350 nm or less, more preferably 250 nm or less, and even more preferably 150 nm or less, from the viewpoint of reducing coarse particles and improving the ejection stability of inkjet ink. The average particle size of pigment-containing resin particles in inkjet ink is substantially the same as the average particle size in an aqueous dispersion of pigment-containing resin particles. From the same viewpoint as above, the average particle size of pigment-containing resin particles in an aqueous dispersion of pigment-containing resin particles is preferably 50 nm or more and 350 nm or less, more preferably 70 nm or more and 250 nm or less, and even more preferably 80 nm or more and 150 nm or less. The solid content concentration and average particle size of the aqueous dispersion of pigment-containing resin particles are measured by the method described in the examples.

[0106] From the viewpoint of storage stability and ejection stability of the inkjet ink, the pigment content in the inkjet ink is preferably 2% by mass or more, more preferably 3% by mass or more, and even more preferably 3.5% by mass or more, and from the viewpoint of dispersion stability, it is preferably 8% by mass or less, more preferably 6% by mass or less, and even more preferably 5% by mass or less. From the same viewpoint as above, the pigment content in the inkjet ink is preferably 2% by mass or more and 8% by mass or less, more preferably 3% by mass or more and 6% by mass or less, and even more preferably 3.5% by mass or more and 5% by mass or less.

[0107] From the viewpoint of obtaining high-quality recordings on gloss-coated paper and matte-coated paper, the mass ratio of the crosslinked resin particles to the pigment-containing resin particles, or the ratio of crosslinked resin particles to pigment-containing resin particles, is preferably 0.1 or more, more preferably 0.2 or more, even more preferably 0.5 or more, even more preferably 0.7 or more, even more preferably 0.8 or more, even more preferably 0.9 or more, and from the same viewpoint as above, preferably 2.0 or less, more preferably 1.5 or less, even more preferably 1.2 or less, and even more preferably 1.0 or less. From the same viewpoint as above, the mass ratio of the crosslinked resin particles to the pigment-containing resin particles is preferably 0.1 or more and 2.0 or less, more preferably 0.2 or more and 1.5 or less, and even more preferably 0.5 or more and 1.2 or less.

[0108] When the pigment is in the form of resin particles containing the pigment, the content of the pigment-containing resin particles in the inkjet ink is preferably 3% by mass or more, more preferably 4% by mass or more, and even more preferably 4.5% by mass or more, from the viewpoint of storage stability and ejection stability of the inkjet ink, and preferably 10% by mass or less, more preferably 8% by mass or less, and even more preferably 6% by mass or less, from the viewpoint of dispersion stability. From the same viewpoint as above, the content of the pigment-containing resin particles in the inkjet ink is preferably 3% by mass or more and 10% by mass or less, more preferably 4% by mass or more and 8% by mass or less, and even more preferably 4.5% by mass or more and 6% by mass or less.

[0109] <Organic solvents> The organic solvent contained in the inkjet ink of the present invention contains glycol ether.

[0110] Examples of glycol ethers include (poly)alkylene glycol monoalkyl ethers such as monoalkylene glycol monoalkyl ethers, dialkylene glycol monoalkyl ethers, and trialkylene glycol monoalkyl ethers; and (poly)alkylene glycol dialkyl ethers such as monoalkylene glycol dialkyl ethers and dialkylene glycol dialkyl ethers.

[0111] The alkylene oxide group of the glycol ether can be one or more selected from the group consisting of ethylene oxide groups and propylene oxide groups, with the ethylene oxide group being more preferred. Glycol ethers preferably have at least one hydrocarbon group having 2 to 8 carbon atoms.

[0112] As for glycol ethers, those having an octanol-water partition coefficient logP value (hereinafter also simply referred to as "logP") of 0 or greater are preferred from the viewpoint of storage stability and ejection stability of inkjet inks.

[0113] Examples of glycol ethers with an octanol-water partition coefficient logP value of 0 or greater include (poly)alkylene glycol monoalkyl ethers. Among these, ethylene glycol monoisopropyl ether (logP: 0.23), ethylene glycol monoallyl ether (logP: 0.26), ethylene glycol monobutyl ether (logP: 0.81), and diethylene glycol monoisopropyl ether are examples. Preferably, one or more selected from the group consisting of (logP:0.07), diethylene glycol monoisobutyl ether (logP:0.64), diethylene glycol mono-n-butyl ether (logP:0.67), diethylene glycol ethyl methyl ether (logP:0.12), diethylene glycol diethyl ether (logP:0.45), propylene glycol monopropyl ether (logP:0.71), propylene glycol monobutyl ether (logP:1.13), dipropylene glycol monopropyl ether (logP:0.88), and dipropylene glycol monoisobutyl ether (logP:1.29) are mentioned, with diethylene glycol monoisobutyl ether or diethylene glycol monoisopropyl ether being more preferred, and diethylene glycol monoisopropyl ether being even more preferred.

[0114] From the viewpoint of storage stability and ejection stability of the inkjet ink, the glycol ether content in the inkjet ink of the present invention is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 4% by mass or more, and from the same viewpoint as above, preferably 20% by mass or less, more preferably 10% by mass or less, more preferably 8% by mass or less, and even more preferably 6% by mass or less. From the same viewpoint as above, the glycol ether compound content in the inkjet ink is preferably 1% by mass or more and 20% by mass or less, more preferably 3% by mass or more and 10% by mass or less, even more preferably 4% by mass or more and 8% by mass or less, and even more preferably 4% by mass or more and 6% by mass or less.

[0115] The mass ratio of the glycol ether compound to the crosslinked resin particles is preferably 0.5 or more, more preferably 0.7 or more, and even more preferably 0.9 or more, from the viewpoint of storage stability and ejection stability of the inkjet ink, and from the same viewpoint, preferably 3.0 or less, more preferably 2.5 or less, and even more preferably 2.0 or less. From the same viewpoint, the mass ratio of the glycol ether compound to the crosslinked resin particles is preferably 0.5 or more and 3.0 or less, more preferably 0.7 or more and 2.5 or less, and even more preferably 0.9 or more and 2.0 or less.

[0116] The organic solvent preferably further contains a water-soluble organic solvent. In the present invention, a water-soluble organic solvent is an organic solvent that can be mixed with water in any proportion.

[0117] Examples of water-soluble organic solvents include polyhydric alcohols, nitrogen-containing heterocyclic compounds such as 2-pyrrolidone, and alkanolamines. Among these, one or more selected from the group consisting of polyhydric alcohols are preferred from the viewpoint of storage stability and ejection stability of inkjet inks.

[0118] Water-soluble organic solvents can be used individually or in combination of two or more.

[0119] As for polyhydric alcohols, from the viewpoint of storage stability and ejection stability of inkjet inks, one or more selected from the group consisting of propylene glycol (1,2-propanediol), alkanediols having 2 to 6 carbon atoms such as 1,2-hexanediol, diethylene glycol, and glycerin are preferred, with propylene glycol being more preferred.

[0120] From the viewpoint of storage stability and ejection stability of the inkjet ink, the content of the water-soluble organic solvent in the inkjet ink of the present invention is preferably 10% by mass or more, more preferably 20% by mass or more, and from the same viewpoint, preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less. From the same viewpoint, the content of the water-soluble organic solvent in the inkjet ink of the present invention is preferably 10% by mass or more and 50% by mass or less, more preferably 20% by mass or more and 40% by mass or less, and even more preferably 20% by mass or more and 30% by mass or less.

[0121] <Water> The inkjet ink of the present invention contains water. As the water used in the inkjet ink according to the present invention, pure water or ion-exchanged water is preferred from the viewpoint of preventing the contamination of unintended substances.

[0122] From the viewpoint of storage stability and ejection stability of the inkjet ink, the water content in the inkjet ink is preferably 50% by mass or more, more preferably 55% by mass or more, and even more preferably 60% by mass or more, and from the same viewpoint as above, preferably 80% by mass or less, more preferably 75% by mass or less, and even more preferably 70% by mass or less. From the same viewpoint as above, the water content in the inkjet ink is preferably 50% by mass or more and 80% by mass or less, more preferably 55% by mass or more and 75% by mass or less, and even more preferably 60% by mass or more and 70% by mass or less.

[0123] The inkjet ink of the present invention may contain various additives commonly used in inkjet inks, such as surfactants, humectants, wetting agents, viscosity modifiers, defoamers, preservatives, fungicides, and rust inhibitors.

[0124] As the surfactant, nonionic surfactants are preferred, and one or more selected from the group consisting of acetylene glycol-based surfactants, ether-based surfactants, and silicone-based surfactants are more preferred.

[0125] Examples of acetylene glycol-based surfactants include acetylene diols such as 2,4,7,9-tetramethyl-5-decine-4,7-diol, 3,6-dimethyl-4-octin-3,6-diol, 3,5-dimethyl-1-hexyn-3-ol, and 2,4-dimethyl-5-hexyn-3-ol, as well as ethylene oxide adducts of these acetylene diols, from the viewpoint of wettability to resin films and defoaming properties.

[0126] Examples of commercially available acetylene glycol-based surfactants include the "Surfinol" series and "Orfin" series manufactured by Nisshin Chemical Industry Co., Ltd.

[0127] As the ether-based surfactant, polyoxyalkylene alkyl ether type surfactants are preferred. Examples of commercially available ether-based surfactants include the "Emulgen" series manufactured by Kao Corporation.

[0128] As the silicone-based surfactant, polyether-modified silicone is preferred. Examples of commercially available silicone-based surfactants include the KF series from Shin-Etsu Chemical Co., Ltd. (KF-353, KF-355A, KF-642, KF-6011, etc.), the Silface SAG series from Nisshin Chemical Industry Co., Ltd., and the BYK series from Big Chemie Japan Co., Ltd.

[0129] When the inkjet ink of the present invention contains a surfactant, the surfactant content in the ink is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 1% by mass or more, and preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less.

[0130] [Inkjet ink manufacturing method] The inkjet ink of the present invention can be efficiently manufactured by blending the above-mentioned pigment, organic solvent, fixing resin, and water, and optionally surfactants, other additives, etc., and mixing the mixture. There are no particular restrictions on the mixing method, but stirring is preferred.

[0131] The amount of each component blended in the inkjet ink manufacturing method of the present invention can be considered as the content of each component in the inkjet ink of the present invention.

[0132] Specifically, the method for manufacturing inkjet ink according to the present invention is: A method for manufacturing inkjet ink, comprising the step of mixing crosslinked resin particles as a fixing resin, a pigment, an organic solvent, and water, The crosslinked resin particles are obtained by reacting carboxyl groups in acrylic resin (A) with epoxy groups in a polyfunctional epoxy compound. The acrylic resin (A) comprises constituent units derived from (meth)acrylic acid (a-1) and constituent units derived from cycloalkyl (meth)acrylate (a-2), The mass ratio ((a-1) derived from constituent units / (a-2) derived from constituent units) of the acrylic resin (A) is greater than 0.22 and less than or equal to 1.

[0133] In the method for producing inkjet ink of the present invention, the acid value of the acrylic resin (A) is preferably 100 mg KOH / g or more, more preferably 110 mg KOH / g or more, even more preferably 120 mg KOH / g or more, even more preferably 150 mg KOH / g or more, and even more preferably 190 mg KOH / g or more, and from the viewpoint of obtaining high-quality recordings on gloss coated paper and matte coated paper, and also preferably 350 mg KOH / g or less, more preferably 330 mg KOH / g or less, even more preferably 310 mg KOH / g or less, and even more preferably 290 mg KOH / g or less.

[0134] In the method for producing inkjet ink of the present invention, it is preferable to react the carboxyl groups in the acrylic resin (A) with the epoxy groups in the polyfunctional epoxy compound such that the degree of crosslinking of the crosslinked resin particles is 10 mol% or more and 80 mol% or less, preferably 15 mol% or more and 75 mol% or less, more preferably 20 mol% or more and 70 mol% or less, and even more preferably 30 mol% or more and 65 mol% or less.

[0135] (Physical properties of inkjet inks) The viscosity of the inkjet ink of the present invention at 32°C is preferably 2 mPa·s or more, more preferably 3 mPa·s or more, and even more preferably 3.5 mPa·s or more, from the viewpoint of obtaining high-quality recordings on gloss-coated paper and matte-coated paper, and from the same viewpoint as above, preferably 10 mPa·s or less, more preferably 8 mPa·s or less, and even more preferably 6 mPa·s or less. From the same viewpoint as above, the viscosity of the inkjet ink of the present invention at 32°C is preferably 2 mPa·s or more and 10 mPa·s or less, more preferably 3 mPa·s or more and 8 mPa·s or less, and even more preferably 3.5 mPa·s or more and 6 mPa·s or less.

[0136] The pH of the inkjet ink of the present invention is preferably 7.0 or higher, more preferably 7.2 or higher, and even more preferably 7.5 or higher. Furthermore, from the viewpoint of material resistance and skin irritation, the pH is preferably 11.0 or lower, more preferably 10.0 or lower, and even more preferably 9.0 or lower. From the same viewpoint as above, the pH of the inkjet ink of the present invention is preferably 7.0 or higher and 11.0 or lower, more preferably 7.2 or higher and 10.0 or lower, and even more preferably 7.5 or higher and 9.0 or lower.

[0137] The viscosity and pH of inkjet ink at 32°C can be measured by conventional methods.

[0138] [Inkjet printing method] The inkjet ink of the present invention can be loaded into a known inkjet printing apparatus and ejected as ink droplets onto a printing substrate such as gloss coated paper or matte coated paper to print images and the like. Piezoelectric, thermal, or electrostatic ink ejection methods can all be used for ejecting the ink droplets.

[0139] As printing substrates used in printing with the inkjet ink of the present invention, low-water-absorbent coated paper, particularly gloss coated paper, matte coated paper, and non-water-absorbent resin films can also be used.

[0140] In printing substrates, "low liquid absorption" is a concept that includes both low liquid absorption and non-liquid absorption, where the amount of water absorbed by the resin film substrate during a 100 m / s contact time with pure water is 0 g / m². 2 More than 10g / m 2 This means the following:

[0141] Examples of resin films include transparent synthetic resin films, such as polyester films like polyethylene terephthalate film; vinyl chloride film; polyolefin films like polypropylene film and polyethylene film; and polyamide films like nylon film. These resin films may be stretched films such as biaxially oriented films and uniaxially oriented films, or unstretched films.

[0142] Among these, the inkjet ink of the present invention can produce high-quality records on gloss-coated paper and matte-coated paper; therefore, one or more types of paper selected from gloss-coated paper and matte-coated paper are preferred as the printing substrate.

[0143] [Use as inkjet ink] The use of the present invention is the use of a composition containing crosslinked resin particles as a fixing resin, a pigment, an organic solvent, and water, wherein the crosslinked resin particles are obtained by reacting carboxyl groups in an acrylic resin (A) with epoxy groups in a polyfunctional epoxy compound, and the acrylic resin (A) contains constituent units derived from (meth)acrylic acid (a-1) and constituent units derived from cycloalkyl (meth)acrylate (a-2), and the mass ratio of constituent units derived from (a-1) to constituent units derived from (a-2) is greater than 0.22 and less than or equal to 1, preferably 0.25 or more and less than or equal to 0.95, more preferably 0.30 or more and less than or equal to 0.90, and even more preferably 0.40 or more and less than or equal to 0.80, and is used as an inkjet ink.

[0144] Furthermore, the use of the present invention is the use of a composition containing crosslinked resin particles as a fixing resin, a pigment, an organic solvent, and water as an inkjet ink. The crosslinked resin particles include a crosslinked structure consisting of a structure derived from a carboxyl group in the acrylic resin (A) and a structure derived from a polyfunctional epoxy compound. The acrylic resin (A) comprises constituent units derived from (meth)acrylic acid (a-1) and constituent units derived from cycloalkyl (meth)acrylate (a-2), The mass ratio of the constituent units derived from (a-1) to the constituent units derived from (a-2) is greater than 0.22 and less than or equal to 1, preferably 0.25 or more and less than or equal to 0.95, more preferably 0.30 or more and less than or equal to 0.90, and even more preferably 0.40 or more and less than or equal to 0.80. It is intended for use as an inkjet ink.

[0145] The present invention also includes the following embodiments.

[0146] <1> An inkjet ink containing crosslinked resin particles as a fixing resin, a pigment, an organic solvent, and water, The crosslinked resin particles include a crosslinked structure consisting of a structure derived from a carboxyl group in the acrylic resin (A) and a structure derived from a polyfunctional epoxy compound. The acrylic resin (A) comprises constituent units derived from (meth)acrylic acid (a-1) and constituent units derived from cycloalkyl (meth)acrylate (a-2), The mass ratio ((a-1) derived from constituent units / (a-2) derived from constituent units) of the acrylic resin (A) is greater than 0.22 and less than or equal to 1. Inkjet ink.

[0147] <2> The constituent unit derived from cycloalkyl (meth)acrylate (a-2) is a constituent unit derived from cycloalkyl acrylate, <1> The inkjet inks listed above.

[0148] <3> The constituent unit derived from the cycloalkyl acrylate is one or more selected from the group consisting of constituent units derived from cyclopentyl acrylate, constituent units derived from cyclohexyl acrylate, and constituent units derived from cycloheptyl acrylate. <1> or <2> The inkjet inks listed above.

[0149] <4> The acrylic resin (A) further comprises one or more constituent units selected from the group consisting of a hydrophobic monomer (a-3), preferably alkyl (meth)acrylate and aromatic group-containing (meth)acrylate, and more preferably alkyl (meth)acrylate having an alkyl group having 1 to 22 carbon atoms and aromatic group-containing (meth)acrylate having 6 to 22 carbon atoms. <1> ~ <3> Inkjet ink as described in one of the following.

[0150] <5> The mass ratio of the constituent units derived from the hydrophobic monomer (a-3) to the constituent units derived from the (meth)acrylic acid (a-1) (constituent units derived from (a-3) / constituent units derived from (a-1)) is 0.1 or more and 2.0 or less, preferably 0.13 or more and 1.5 or less, more preferably 0.15 or more and 1.00 or less. <4> The inkjet inks listed above.

[0151] <6> The mass ratio of the constituent units derived from the hydrophobic monomer (a-3) to the constituent units derived from the polyfunctional epoxy compound (constituent units derived from (a-3) / constituent units derived from the polyfunctional epoxy compound) is 0.1 or more and 2.0 or less, preferably 0.14 or more and 1.4 or less, more preferably 0.2 or more and 0.9 or less. <4> or <5> The inkjet inks listed above.

[0152] <7> The mass ratio of the constituent units derived from the cycloalkyl (meth)acrylate (a-2) to the constituent units derived from the polyfunctional epoxy compound (constituent units derived from (a-2) / constituent units derived from the polyfunctional epoxy compound) is 1.0 or more and 6.0 or less, preferably 1.1 or more and 5.0 or less, more preferably 1.2 or more and 3.0 or less. <4> ~ <6> Inkjet ink as described in one of the following.

[0153] <8> The content of the constituent units derived from the hydrophobic monomer (a-3) in the acrylic resin (A) is 4% by mass or more and 35% by mass or less, preferably 4.5% by mass or more and 30% by mass or less, more preferably 5% by mass or more and 35% by mass or less, even more preferably 5% by mass or more and 25% by mass or less, and even more preferably 6% by mass or more and 21% by mass or less. <4> ~ <7> Inkjet ink as described in one of the following.

[0154] <9> The mass ratio of the constituent units derived from the hydrophobic monomer (a-3) to the constituent units derived from the cycloalkyl (meth)acrylate (a-2) (constituent units derived from (a-3) / constituent units derived from (a-2)) is preferably 0.1 to 1.0, more preferably 0.13 to 0.5, and even more preferably 0.15 to 0.4.

[0155] <10> The content of the constituent units derived from the cycloalkyl (meth)acrylate (a-2) in the acrylic resin (A) is 40% by mass or more and 70% by mass or less, preferably 45% by mass or more and 65% by mass or less, more preferably 50% by mass or more and 60% by mass or less. <1> ~ <9> Inkjet ink as described in one of the following.

[0156] <11> The content of the crosslinked resin particles in the inkjet ink is 2.5% by mass or more and 10% by mass or less, preferably 3.0% by mass or more and 8% by mass or less, more preferably 3.5% by mass or more and 8% by mass or less, and even more preferably 4.0% by mass or more and 6% by mass or less. <1> ~ <10> Inkjet ink as described in one of the following.

[0157] <12> The acid value of the crosslinked resin particles is 35 mg KOH / g or more and 220 mg KOH / g or less, preferably 40 mg KOH / g or more and 190 mg KOH / g or less, more preferably 40 mg KOH / g or more and 155 mg KOH / g or less, even more preferably 40 mg KOH / g or more and 130 mg KOH / g or less, and even more preferably 50 mg KOH / g or more and 110 mg KOH / g or less. <1> ~ <11> Inkjet ink as described in one of the following.

[0158] <13> An inkjet ink containing crosslinked resin particles as a fixing resin, a pigment, an organic solvent, and water, The crosslinked resin particles include a crosslinked structure consisting of a structure derived from a carboxyl group in the acrylic resin (A) and a structure derived from a polyfunctional epoxy compound. The acrylic resin (A) comprises constituent units derived from acrylic acid (a-1) and constituent units derived from cyclohexyl acrylate (a-2). The mass ratio ((a-1) derived constituent units / (a-2) derived constituent units) of the acrylic resin (A) to the acrylic acid (a-1) is 0.45 or more and 0.6 or less. The content of the constituent units derived from the cyclohexyl acrylate (a-2) is 45% by mass or more and 65% by mass or less of the constituent units of the acrylic resin (A). The acrylic resin (A) contains constituent units derived from butyl acrylate (a-3), The content of the constituent units derived from the butyl acrylate (a-3) is 15% by mass or more and 21% by mass or less of the constituent units of the acrylic resin (A). The mass ratio of the constituent units derived from the butyl acrylate (a-3) to the constituent units derived from the acrylic acid (a-1) (constituent units derived from (a-3) / constituent units derived from (a-1)) is 0.5 or more and 1 or less. The polyfunctional epoxy compound is trimethylolpropane polyglycidyl ether, The mass ratio of the butyl acrylate (a-3) to the trimethylolpropane polyglycidyl ether (butyl acrylate / trimethylolpropane polyglycidyl ether) is 0.6 or more and 0.8 or less. The mass ratio of the cyclohexyl acrylate (a-2) to the trimethylolpropane polyglycidyl ether (cyclohexyl acrylate / trimethylolpropane polyglycidyl ether) is 1.7 or more and 2 or less. The amount of trimethylolpropane polyglycidyl ether is such that the degree of crosslinking of the resulting crosslinked resin particles is 50 mol% or more and 65 mol% or less. The acid value of the crosslinked resin particles is 50 mg KOH / g or more and 90 mg KOH / g or less. The content of cross-linked resin particles in the inkjet ink is 4% by mass or more and 6% by mass or less. The aforementioned <1> The inkjet inks listed above.

[0159] <14> An inkjet ink containing crosslinked resin particles as a fixing resin, a pigment, an organic solvent, and water, The crosslinked resin particles include a crosslinked structure consisting of a structure derived from a carboxyl group in the acrylic resin (A) and a structure derived from a polyfunctional epoxy compound. The acrylic resin (A) comprises constituent units derived from acrylic acid (a-1) and constituent units derived from cyclohexyl acrylate (a-2). The mass ratio of constituent units derived from acrylic acid (a-1) and constituent units derived from cyclohexyl acrylate (a-2) in the acrylic resin (A) is 0.67 or more and 0.8 or less. The content of the constituent units derived from the cyclohexyl acrylate (a-2) is 45% by mass or more and 65% by mass or less of the constituent units of the acrylic resin (A). The acrylic resin (A) contains constituent units derived from butyl acrylate (a-3), The content of the constituent units derived from the butyl acrylate (a-3) is 4.5% by mass or more and 8% by mass or less of the constituent units of the acrylic resin (A). The mass ratio of the constituent units derived from the butyl acrylate (a-3) to the constituent units derived from the acrylic acid (a-1) (constituent units derived from (a-3) / constituent units derived from (a-1)) is 0.13 or more and 0.2 or less. The polyfunctional epoxy compound is trimethylolpropane polyglycidyl ether, The mass ratio (butyl acrylate / trimethylolpropane polyglycidyl ether) of the butyl acrylate (a-3) to the trimethylolpropane polyglycidyl ether is 0.4 or more and 0.8 or less. The mass ratio of the cyclohexyl acrylate (a-2) to the trimethylolpropane polyglycidyl ether (cyclohexyl acrylate / trimethylolpropane polyglycidyl ether) is 1.2 or more and 2 or less. The amount of trimethylolpropane polyglycidyl ether is such that the degree of crosslinking of the resulting crosslinked resin particles is 50 mol% or more and 80 mol% or less. The acid value of the crosslinked resin particles is 35 mg KOH / g or more and 50 mg KOH / g or less. The content of cross-linked resin particles in the inkjet ink is 4% by mass or more and 6% by mass or less. The aforementioned <1> The inkjet inks listed above.

[0160] <15> An inkjet ink containing crosslinked resin particles as a fixing resin, a pigment, an organic solvent, and water, The crosslinked resin particles include a crosslinked structure consisting of a structure derived from a carboxyl group in the acrylic resin (A) and a structure derived from a polyfunctional epoxy compound. The acrylic resin (A) comprises constituent units derived from acrylic acid (a-1) and constituent units derived from cyclohexyl acrylate (a-2). The mass ratio of constituent units derived from acrylic acid (a-1) to constituent units derived from cyclohexyl acrylate (a-2) in the acrylic resin (A) is 0.25 or more and 0.35 or less. The content of the constituent units derived from the cyclohexyl acrylate (a-2) is 45% by mass or more and 65% by mass or less of the constituent units of the acrylic resin (A). The acrylic resin (A) contains constituent units derived from butyl acrylate (a-3), The content of the constituent units derived from butyl acrylate (a-3) is 25% by mass or more and 30% by mass or less of the constituent units of the acrylic resin (A). The mass ratio of the constituent units derived from the butyl acrylate (a-3) to the constituent units derived from the acrylic acid (a-1) (constituent units derived from (a-3) / constituent units derived from (a-1)) is 1.5 or more and 2 or less. The polyfunctional epoxy compound is trimethylolpropane polyglycidyl ether, The mass ratio (butyl acrylate / trimethylolpropane polyglycidyl ether) of the butyl acrylate (a-3) to the trimethylolpropane polyglycidyl ether is 1 or more and 2 or less. The mass ratio of the cyclohexyl acrylate (a-2) to the trimethylolpropane polyglycidyl ether (cyclohexyl acrylate / trimethylolpropane polyglycidyl ether) is 3 or more and 6 or less. The amount of trimethylolpropane polyglycidyl ether is such that the degree of crosslinking of the resulting crosslinked resin particles is 10 mol% or more and 30 mol% or less. The acid value of the crosslinked resin particles is 100 mg KOH / g or more and 155 mg KOH / g or less. The content of cross-linked resin particles in the inkjet ink is 4% by mass or more and 6% by mass or less. The aforementioned <1> The inkjet inks listed above.

[0161] <16> An inkjet ink containing crosslinked resin particles as a fixing resin, a pigment, an organic solvent, and water, The crosslinked resin particles include a crosslinked structure consisting of a structure derived from a carboxyl group in the acrylic resin (A) and a structure derived from a polyfunctional epoxy compound. The acrylic resin (A) comprises constituent units derived from acrylic acid (a-1) and constituent units derived from cyclohexyl acrylate (a-2). The mass ratio ((a-1) derived constituent units / (a-2) derived constituent units) of the acrylic resin (A) to the acrylic acid (a-1) is 0.45 or more and 0.6 or less. The content of the constituent units derived from the cyclohexyl acrylate (a-2) is 45% by mass or more and 65% by mass or less of the constituent units of the acrylic resin (A). The acrylic resin (A) contains constituent units derived from butyl acrylate (a-3), The content of the constituent units derived from the butyl acrylate (a-3) is 15% by mass or more and 21% by mass or less of the constituent units of the acrylic resin (A). The mass ratio of the constituent units derived from the butyl acrylate (a-3) to the constituent units derived from the acrylic acid (a-1) (constituent units derived from (a-3) / constituent units derived from (a-1)) is 0.5 or more and 1 or less. The polyfunctional epoxy compound is trimethylolpropane polyglycidyl ether, The mass ratio of the butyl acrylate (a-3) to the trimethylolpropane polyglycidyl ether (butyl acrylate / trimethylolpropane polyglycidyl ether) is 0.6 or more and 0.8 or less. The mass ratio of the cyclohexyl acrylate (a-2) to the trimethylolpropane polyglycidyl ether (cyclohexyl acrylate / trimethylolpropane polyglycidyl ether) is 1.7 or more and 2 or less. The amount of trimethylolpropane polyglycidyl ether is such that the degree of crosslinking of the resulting crosslinked resin particles is 50 mol% or more and 65 mol% or less. The acid value of the crosslinked resin particles is 50 mg KOH / g or more and 90 mg KOH / g or less. The content of cross-linked resin particles in the inkjet ink is 4% by mass or more and 6% by mass or less. The mass ratio of the crosslinked resin particles to the resin particles containing the pigment, where the ratio of crosslinked resin particles to pigment-containing resin particles is 0.8 or more and 1.2 or less, The aforementioned organic solvent contains diethylene glycol monoisopropyl ether, The content of the diethylene glycol monoisopropyl ether in the inkjet ink is 4% by mass or more and 6% by mass or less. The mass ratio of the diethylene glycol monoisopropyl ether to the crosslinked resin particles is 0.7 or more and 1.5 or less. The aforementioned pigment is in the form of resin particles containing the pigment, hereinafter referred to as pigment-containing resin particles. The pigment dispersion resin constituting the pigment-containing resin particles is a vinyl resin (B), The vinyl resin (B) contains (b-1) constituent units derived from acrylic acid and (b-2) constituent units derived from styrene, In the pigment dispersion resin, (b-1) the constituent units derived from acrylic acid are 20% by mass or more and 40% by mass or less, and (b-2) the constituent units derived from styrene are 60% by mass or more and 80% by mass or less. The mass ratio of the constituent units derived from (b-1) acrylic acid and (b-2) styrene is 0.4 or more and 2 or less. The weight-average molecular weight of the aforementioned pigment dispersion resin is 8,000 or more and 30,000 or less. The acid value of the aforementioned pigment dispersion resin is 220 mg KOH / g or more and 280 mg KOH / g or less. The aforementioned organic solvent further contains propylene glycol, The propylene glycol content in the inkjet ink is 10% by mass or more and 50% by mass or less. It contains acetylene glycol-based surfactants and ether-based surfactants as surfactants. The acetylene glycol-based surfactant is 2,4,7,9-tetramethyl-5-decine-4,7-diol, The ether-based surfactant is an ethylene oxide adduct of lauryl alcohol, The content of the surfactant in the inkjet ink is 1% by mass or more and 4% by mass. The aforementioned <1> The inkjet inks listed above.

[0162] <17> An inkjet ink containing crosslinked resin particles as a fixing resin, a pigment, an organic solvent, and water, The crosslinked resin particles include a crosslinked structure consisting of a structure derived from a carboxyl group in the acrylic resin (A) and a structure derived from a polyfunctional epoxy compound. The acrylic resin (A) comprises constituent units derived from acrylic acid (a-1) and constituent units derived from cyclohexyl acrylate (a-2). The mass ratio of constituent units derived from acrylic acid (a-1) and constituent units derived from cyclohexyl acrylate (a-2) in the acrylic resin (A) is 0.67 or more and 0.8 or less. The content of the constituent units derived from the cyclohexyl acrylate (a-2) is 45% by mass or more and 65% by mass or less of the constituent units of the acrylic resin (A). The acrylic resin (A) contains constituent units derived from butyl acrylate (a-3), The content of the constituent units derived from the butyl acrylate (a-3) is 4.5% by mass or more and 8% by mass or less of the constituent units of the acrylic resin (A). The mass ratio of the constituent units derived from the butyl acrylate (a-3) to the constituent units derived from the acrylic acid (a-1) (constituent units derived from (a-3) / constituent units derived from (a-1)) is 0.13 or more and 0.2 or less. The polyfunctional epoxy compound is trimethylolpropane polyglycidyl ether, The mass ratio (butyl acrylate / trimethylolpropane polyglycidyl ether) of the butyl acrylate (a-3) to the trimethylolpropane polyglycidyl ether is 0.4 or more and 0.8 or less. The mass ratio of the cyclohexyl acrylate (a-2) to the trimethylolpropane polyglycidyl ether (cyclohexyl acrylate / trimethylolpropane polyglycidyl ether) is 1.2 or more and 2 or less. The amount of trimethylolpropane polyglycidyl ether is such that the degree of crosslinking of the resulting crosslinked resin particles is 50 mol% or more and 80 mol% or less. The acid value of the crosslinked resin particles is 35 mg KOH / g or more and 50 mg KOH / g or less. The content of cross-linked resin particles in the inkjet ink is 4% by mass or more and 6% by mass or less. The mass ratio of the crosslinked resin particles to the resin particles containing the pigment, where the ratio of crosslinked resin particles to pigment-containing resin particles is 0.8 or more and 1.2 or less, The aforementioned organic solvent contains diethylene glycol monoisopropyl ether, The content of the diethylene glycol monoisopropyl ether in the inkjet ink is 4% by mass or more and 6% by mass or less. The mass ratio of the diethylene glycol monoisopropyl ether to the crosslinked resin particles is 0.7 or more and 1.5 or less. The aforementioned pigment is in the form of resin particles containing the pigment, hereinafter referred to as pigment-containing resin particles. The pigment dispersion resin constituting the pigment-containing resin particles is a vinyl resin (B), The vinyl resin (B) contains (b-1) constituent units derived from acrylic acid and (b-2) constituent units derived from styrene, In the pigment dispersion resin, (b-1) the constituent units derived from acrylic acid are 20% by mass or more and 40% by mass or less, and (b-2) the constituent units derived from styrene are 60% by mass or more and 80% by mass or less. The mass ratio of the constituent units derived from (b-1) acrylic acid and (b-2) styrene is 0.4 or more and 2 or less. The weight-average molecular weight of the aforementioned pigment dispersion resin is 8,000 or more and 30,000 or less. The acid value of the aforementioned pigment dispersion resin is 220 mg KOH / g or more and 280 mg KOH / g or less. The aforementioned organic solvent further contains propylene glycol, The propylene glycol content in the inkjet ink is 10% by mass or more and 50% by mass or less. It contains acetylene glycol-based surfactants and ether-based surfactants as surfactants. The acetylene glycol-based surfactant is 2,4,7,9-tetramethyl-5-decine-4,7-diol, The ether-based surfactant is an ethylene oxide adduct of lauryl alcohol, The content of the surfactant in the inkjet ink is 1% by mass or more and 4% by mass. The aforementioned <1> The inkjet inks listed above.

[0163] <18> An inkjet ink containing crosslinked resin particles as a fixing resin, a pigment, an organic solvent, and water, The crosslinked resin particles include a crosslinked structure consisting of a structure derived from a carboxyl group in the acrylic resin (A) and a structure derived from a polyfunctional epoxy compound. The acrylic resin (A) comprises constituent units derived from acrylic acid (a-1) and constituent units derived from cyclohexyl acrylate (a-2). The mass ratio of constituent units derived from acrylic acid (a-1) to constituent units derived from cyclohexyl acrylate (a-2) in the acrylic resin (A) is 0.25 or more and 0.35 or less. The content of the constituent units derived from the cyclohexyl acrylate (a-2) is 45% by mass or more and 65% by mass or less of the constituent units of the acrylic resin (A). The acrylic resin (A) contains constituent units derived from butyl acrylate (a-3), The content of the constituent units derived from butyl acrylate (a-3) is 25% by mass or more and 30% by mass or less of the constituent units of the acrylic resin (A). The mass ratio of the constituent units derived from the butyl acrylate (a-3) to the constituent units derived from the acrylic acid (a-1) (constituent units derived from (a-3) / constituent units derived from (a-1)) is 1.5 or more and 2 or less. The polyfunctional epoxy compound is trimethylolpropane polyglycidyl ether, The mass ratio (butyl acrylate / trimethylolpropane polyglycidyl ether) of the butyl acrylate (a-3) to the trimethylolpropane polyglycidyl ether is 1 or more and 2 or less. The mass ratio of the cyclohexyl acrylate (a-2) to the trimethylolpropane polyglycidyl ether (cyclohexyl acrylate / trimethylolpropane polyglycidyl ether) is 3 or more and 6 or less. The amount of trimethylolpropane polyglycidyl ether is such that the degree of crosslinking of the resulting crosslinked resin particles is 10 mol% or more and 30 mol% or less. The acid value of the crosslinked resin particles is 100 mg KOH / g or more and 155 mg KOH / g or less. The content of cross-linked resin particles in the inkjet ink is 4% by mass or more and 6% by mass or less. The mass ratio of the crosslinked resin particles to the resin particles containing the pigment, where the ratio of crosslinked resin particles to pigment-containing resin particles is 0.8 or more and 1.2 or less, The aforementioned organic solvent contains diethylene glycol monoisopropyl ether, The content of the diethylene glycol monoisopropyl ether in the inkjet ink is 4% by mass or more and 6% by mass or less. The mass ratio of the diethylene glycol monoisopropyl ether to the crosslinked resin particles is 0.7 or more and 1.5 or less. The aforementioned pigment is in the form of resin particles containing the pigment, hereinafter referred to as pigment-containing resin particles. The pigment dispersion resin constituting the pigment-containing resin particles is a vinyl resin (B), The vinyl resin (B) contains (b-1) constituent units derived from acrylic acid and (b-2) constituent units derived from styrene, In the pigment dispersion resin, (b-1) the constituent units derived from acrylic acid are 20% by mass or more and 40% by mass or less, and (b-2) the constituent units derived from styrene are 60% by mass or more and 80% by mass or less. The mass ratio of the constituent units derived from (b-1) acrylic acid and (b-2) styrene is 0.4 or more and 2 or less. The weight-average molecular weight of the aforementioned pigment dispersion resin is 8,000 or more and 30,000 or less. The acid value of the aforementioned pigment dispersion resin is 220 mg KOH / g or more and 280 mg KOH / g or less. The aforementioned organic solvent further contains propylene glycol, The propylene glycol content in the inkjet ink is 10% by mass or more and 50% by mass or less. It contains acetylene glycol-based surfactants and ether-based surfactants as surfactants. The acetylene glycol-based surfactant is 2,4,7,9-tetramethyl-5-decine-4,7-diol, The ether-based surfactant is an ethylene oxide adduct of lauryl alcohol, The content of the surfactant in the inkjet ink is 1% by mass or more and 4% by mass. The aforementioned <1> The inkjet inks listed above.

[0164] <19> The aforementioned <1> ~ <18> An inkjet printing method that prints on a printing substrate using an inkjet ink described in any of the above.

[0165] <20> The aforementioned <19> An inkjet printing method as described above, wherein the printing substrate is one or more selected from gloss coated paper and matte coated paper.

[0166] <21> The aforementioned <19> An inkjet printing method as described above, wherein the printing substrate is gloss coated paper.

[0167] <22> The aforementioned <19> An inkjet printing method as described above, wherein the printing substrate is matte coated paper.

[0168] <23> A method for manufacturing inkjet ink, comprising the step of mixing crosslinked resin particles as a fixing resin, a pigment, an organic solvent, and water, The crosslinked resin particles are obtained by reacting carboxyl groups in acrylic resin (A) with epoxy groups in a polyfunctional epoxy compound. The acrylic resin (A) comprises constituent units derived from (meth)acrylic acid (a-1) and constituent units derived from cycloalkyl (meth)acrylate (a-2), The mass ratio ((a-1) derived from constituent units / (a-2) derived from constituent units) of the acrylic resin (A) is greater than 0.22 and less than or equal to 1. A method for manufacturing inkjet ink.

[0169] <24> The acid value of the acrylic resin (A) is 100 mg KOH / g or more and 350 mg KOH / g or less. <23> The method for manufacturing inkjet ink as described above.

[0170] <25> The carboxyl groups in the acrylic resin (A) and the epoxy groups in the polyfunctional epoxy compound are reacted such that the degree of crosslinking of the crosslinked resin particles is 10 mol% or more and 80 mol% or less. <23> or <24> The method for manufacturing inkjet ink as described above.

[0171] <26> The use of a composition containing crosslinked resin particles as a fixing resin, a pigment, an organic solvent, and water as an inkjet ink, The crosslinked resin particles include a crosslinked structure consisting of a structure derived from a carboxyl group in the acrylic resin (A) and a structure derived from a polyfunctional epoxy compound. The acrylic resin (A) comprises constituent units derived from (meth)acrylic acid (a-1) and constituent units derived from cycloalkyl (meth)acrylate (a-2), The mass ratio of the constituent units derived from (a-1) to the constituent units derived from (a-2) is greater than 0.22 and less than or equal to 1. For use as inkjet ink.

[0172] <27> The use of a composition containing crosslinked resin particles as a fixing resin, a pigment, an organic solvent, and water as an inkjet ink, The crosslinked resin particles include a crosslinked structure consisting of a structure derived from a carboxyl group in the acrylic resin (A) and a structure derived from a polyfunctional epoxy compound. The acrylic resin (A) comprises constituent units derived from acrylic acid (a-1) and constituent units derived from cyclohexyl acrylate (a-2). The mass ratio ((a-1) derived constituent units / (a-2) derived constituent units) of the acrylic resin (A) to the acrylic acid (a-1) is 0.45 or more and 0.6 or less. The content of the constituent units derived from the cyclohexyl acrylate (a-2) is 45% by mass or more and 65% by mass or less of the constituent units of the acrylic resin (A). The acrylic resin (A) contains constituent units derived from butyl acrylate (a-3), The content of the constituent units derived from the butyl acrylate (a-3) is 15% by mass or more and 21% by mass or less of the constituent units of the acrylic resin (A). The mass ratio of the constituent units derived from the butyl acrylate (a-3) to the constituent units derived from the acrylic acid (a-1) (constituent units derived from (a-3) / constituent units derived from (a-1)) is 0.5 or more and 1 or less. The polyfunctional epoxy compound is trimethylolpropane polyglycidyl ether, The mass ratio of the butyl acrylate (a-3) to the trimethylolpropane polyglycidyl ether (butyl acrylate / trimethylolpropane polyglycidyl ether) is 0.6 or more and 0.8 or less. The mass ratio of the cyclohexyl acrylate (a-2) to the trimethylolpropane polyglycidyl ether (cyclohexyl acrylate / trimethylolpropane polyglycidyl ether) is 1.7 or more and 2 or less. The amount of trimethylolpropane polyglycidyl ether is such that the degree of crosslinking of the resulting crosslinked resin particles is 50 mol% or more and 65 mol% or less. The acid value of the crosslinked resin particles is 50 mg KOH / g or more and 90 mg KOH / g or less. The content of cross-linked resin particles in the inkjet ink is 4% by mass or more and 6% by mass or less. The mass ratio of the crosslinked resin particles to the resin particles containing the pigment, where the ratio of crosslinked resin particles to pigment-containing resin particles is 0.8 or more and 1.2 or less, The aforementioned organic solvent contains diethylene glycol monoisopropyl ether, The content of the diethylene glycol monoisopropyl ether in the inkjet ink is 4% by mass or more and 6% by mass or less. The mass ratio of the diethylene glycol monoisopropyl ether to the crosslinked resin particles is 0.7 or more and 1.5 or less. The aforementioned pigment is in the form of resin particles containing the pigment, hereinafter referred to as pigment-containing resin particles. The pigment dispersion resin constituting the pigment-containing resin particles is a vinyl resin (B), The vinyl resin (B) contains (b-1) constituent units derived from acrylic acid and (b-2) constituent units derived from styrene, In the pigment dispersion resin, (b-1) the constituent units derived from acrylic acid are 20% by mass or more and 40% by mass or less, and (b-2) the constituent units derived from styrene are 60% by mass or more and 80% by mass or less. The mass ratio of the constituent units derived from (b-1) acrylic acid and (b-2) styrene is 0.4 or more and 2 or less. The weight-average molecular weight of the aforementioned pigment dispersion resin is 8,000 or more and 30,000 or less. The acid value of the aforementioned pigment dispersion resin is 220 mg KOH / g or more and 280 mg KOH / g or less. The aforementioned organic solvent further contains propylene glycol, The propylene glycol content in the inkjet ink is 10% by mass or more and 50% by mass or less. It contains acetylene glycol-based surfactants and ether-based surfactants as surfactants. The acetylene glycol-based surfactant is 2,4,7,9-tetramethyl-5-decine-4,7-diol, The ether-based surfactant is an ethylene oxide adduct of lauryl alcohol, The content of the surfactant in the inkjet ink is 1% by mass or more and 4% by mass. The aforementioned <26> Use as an inkjet ink as described above.

[0173] <28> The use of a composition containing crosslinked resin particles as a fixing resin, a pigment, an organic solvent, and water as an inkjet ink, The crosslinked resin particles include a crosslinked structure consisting of a structure derived from a carboxyl group in the acrylic resin (A) and a structure derived from a polyfunctional epoxy compound. The acrylic resin (A) comprises constituent units derived from acrylic acid (a-1) and constituent units derived from cyclohexyl acrylate (a-2). The mass ratio of constituent units derived from acrylic acid (a-1) and constituent units derived from cyclohexyl acrylate (a-2) in the acrylic resin (A) is 0.67 or more and 0.8 or less. The content of the constituent units derived from the cyclohexyl acrylate (a-2) is 45% by mass or more and 65% by mass or less of the constituent units of the acrylic resin (A). The acrylic resin (A) contains constituent units derived from butyl acrylate (a-3), The content of the constituent units derived from the butyl acrylate (a-3) is 4.5% by mass or more and 8% by mass or less of the constituent units of the acrylic resin (A). The mass ratio of the constituent units derived from the butyl acrylate (a-3) to the constituent units derived from the acrylic acid (a-1) (constituent units derived from (a-3) / constituent units derived from (a-1)) is 0.13 or more and 0.2 or less. The polyfunctional epoxy compound is trimethylolpropane polyglycidyl ether, The mass ratio (butyl acrylate / trimethylolpropane polyglycidyl ether) of the butyl acrylate (a-3) to the trimethylolpropane polyglycidyl ether is 0.4 or more and 0.8 or less. The mass ratio of the cyclohexyl acrylate (a-2) to the trimethylolpropane polyglycidyl ether (cyclohexyl acrylate / trimethylolpropane polyglycidyl ether) is 1.2 or more and 2 or less. The amount of trimethylolpropane polyglycidyl ether is such that the degree of crosslinking of the resulting crosslinked resin particles is 50 mol% or more and 80 mol% or less. The acid value of the crosslinked resin particles is 35 mg KOH / g or more and 50 mg KOH / g or less. The content of cross-linked resin particles in the inkjet ink is 4% by mass or more and 6% by mass or less. The mass ratio of the crosslinked resin particles to the resin particles containing the pigment, where the ratio of crosslinked resin particles to pigment-containing resin particles is 0.8 or more and 1.2 or less, The aforementioned organic solvent contains diethylene glycol monoisopropyl ether, The content of the diethylene glycol monoisopropyl ether in the inkjet ink is 4% by mass or more and 6% by mass or less. The mass ratio of the diethylene glycol monoisopropyl ether to the crosslinked resin particles is 0.7 or more and 1.5 or less. The aforementioned pigment is in the form of resin particles containing the pigment, hereinafter referred to as pigment-containing resin particles. The pigment dispersion resin constituting the pigment-containing resin particles is a vinyl resin (B), The vinyl resin (B) contains (b-1) constituent units derived from acrylic acid and (b-2) constituent units derived from styrene, In the pigment dispersion resin, (b-1) the constituent units derived from acrylic acid are 20% by mass or more and 40% by mass or less, and (b-2) the constituent units derived from styrene are 60% by mass or more and 80% by mass or less. The mass ratio of the constituent units derived from (b-1) acrylic acid and (b-2) styrene is 0.4 or more and 2 or less. The weight-average molecular weight of the aforementioned pigment dispersion resin is 8,000 or more and 30,000 or less. The acid value of the aforementioned pigment dispersion resin is 220 mg KOH / g or more and 280 mg KOH / g or less. The aforementioned organic solvent further contains propylene glycol, The propylene glycol content in the inkjet ink is 10% by mass or more and 50% by mass or less. It contains acetylene glycol-based surfactants and ether-based surfactants as surfactants. The acetylene glycol-based surfactant is 2,4,7,9-tetramethyl-5-decine-4,7-diol, The ether-based surfactant is an ethylene oxide adduct of lauryl alcohol, The content of the surfactant in the inkjet ink is 1% by mass or more and 4% by mass. The aforementioned <26> Use as an inkjet ink as described above.

[0174] <29> The use of a composition containing crosslinked resin particles as a fixing resin, a pigment, an organic solvent, and water as an inkjet ink, The crosslinked resin particles include a crosslinked structure consisting of a structure derived from a carboxyl group in the acrylic resin (A) and a structure derived from a polyfunctional epoxy compound. The acrylic resin (A) comprises constituent units derived from acrylic acid (a-1) and constituent units derived from cyclohexyl acrylate (a-2). The mass ratio of constituent units derived from acrylic acid (a-1) to constituent units derived from cyclohexyl acrylate (a-2) in the acrylic resin (A) is 0.25 or more and 0.35 or less. The content of the constituent units derived from the cyclohexyl acrylate (a-2) is 45% by mass or more and 65% by mass or less of the constituent units of the acrylic resin (A). The acrylic resin (A) contains constituent units derived from butyl acrylate (a-3), The content of the constituent units derived from butyl acrylate (a-3) is 25% by mass or more and 30% by mass or less of the constituent units of the acrylic resin (A). The mass ratio of the constituent units derived from the butyl acrylate (a-3) to the constituent units derived from the acrylic acid (a-1) (constituent units derived from (a-3) / constituent units derived from (a-1)) is 1.5 or more and 2 or less. The polyfunctional epoxy compound is trimethylolpropane polyglycidyl ether, The mass ratio (butyl acrylate / trimethylolpropane polyglycidyl ether) of the butyl acrylate (a-3) to the trimethylolpropane polyglycidyl ether is 1 or more and 2 or less. The mass ratio of the cyclohexyl acrylate (a-2) to the trimethylolpropane polyglycidyl ether (cyclohexyl acrylate / trimethylolpropane polyglycidyl ether) is 3 or more and 6 or less. The amount of trimethylolpropane polyglycidyl ether is such that the degree of crosslinking of the resulting crosslinked resin particles is 10 mol% or more and 30 mol% or less. The acid value of the crosslinked resin particles is 100 mg KOH / g or more and 155 mg KOH / g or less. The content of cross-linked resin particles in the inkjet ink is 4% by mass or more and 6% by mass or less. The mass ratio of the crosslinked resin particles to the resin particles containing the pigment, where the ratio of crosslinked resin particles to pigment-containing resin particles is 0.8 or more and 1.2 or less, The aforementioned organic solvent contains diethylene glycol monoisopropyl ether, The content of the diethylene glycol monoisopropyl ether in the inkjet ink is 4% by mass or more and 6% by mass or less. The mass ratio of the diethylene glycol monoisopropyl ether to the crosslinked resin particles is 0.7 or more and 1.5 or less. The aforementioned pigment is in the form of resin particles containing the pigment, hereinafter referred to as pigment-containing resin particles. The pigment dispersion resin constituting the pigment-containing resin particles is a vinyl resin (B), The vinyl resin (B) contains (b-1) constituent units derived from acrylic acid and (b-2) constituent units derived from styrene, In the pigment dispersion resin, (b-1) the constituent units derived from acrylic acid are 20% by mass or more and 40% by mass or less, and (b-2) the constituent units derived from styrene are 60% by mass or more and 80% by mass or less. The mass ratio of the constituent units derived from (b-1) acrylic acid and (b-2) styrene is 0.4 or more and 2 or less. The weight-average molecular weight of the aforementioned pigment dispersion resin is 8,000 or more and 30,000 or less. The acid value of the aforementioned pigment dispersion resin is 220 mg KOH / g or more and 280 mg KOH / g or less. The aforementioned organic solvent further contains propylene glycol, The propylene glycol content in the inkjet ink is 10% by mass or more and 50% by mass or less. It contains acetylene glycol-based surfactants and ether-based surfactants as surfactants. The acetylene glycol-based surfactant is 2,4,7,9-tetramethyl-5-decine-4,7-diol, The ether-based surfactant is an ethylene oxide adduct of lauryl alcohol, The content of the surfactant in the inkjet ink is 1% by mass or more and 4% by mass. The aforementioned <26> Use as an inkjet ink as described above.

[0175] [Examples] In the following manufacturing examples, embodiments, and comparative examples, "parts" and "%" refer to "parts by mass" and "mass%" unless otherwise specified. The measurement and calculation methods for each physical property are as follows.

[0176] (1) Measurement of the weight-average molecular weight of the resin The results were obtained by gel permeation chromatography. The measurement conditions are as follows: GPC instrument: Tosoh Corporation "HLC-8320GPC" Columns: Tosoh Corporation products "TSKgel SuperAWM-H", "TSKgel SuperAW3000", "TSK gel guardcolumn Super AW-H" Eluent: A solution prepared by dissolving phosphoric acid and lithium bromide in N,N-dimethylformamide at concentrations of 60 mmol / L and 50 mmol / L, respectively. Flow rate: 0.5mL / min Standard material: Monodisperse polystyrene kits with known molecular weight [PStQuick B (F-550, F-80, F-10, F-1, A-1000), PStQuick C (F-288, F-40, F-4, A-5000, A-500)] (all manufactured by Tosoh Corporation) Measurement sample: 0.1 g of resin was mixed with 10 mL of the eluent in a glass vial, stirred with a magnetic stirrer at 25°C for 10 hours, and filtered through a syringe filter "DISMIC-13HP" (PTFE, 0.2 μm, manufactured by Advantec Co., Ltd.).

[0177] (2) Measurement of the average particle size of pigment-containing resin particles and crosslinked resin particles Cumulant analysis was performed using the laser particle analysis system "ELS-8000" (manufactured by Otsuka Electronics Co., Ltd.), and the resulting average cumulant particle size was used as the average particle size of the pigment-containing acrylic resin particles. The measurement sample contained particles with a concentration of 5 × 10⁻⁶ -3 A dispersion solution diluted with water to a concentration of % (converted to solid content) was used. The measurement conditions were a temperature of 25°C, an angle of 90° between the incident light and the detector, and 100 cumulative measurements. The refractive index of water (1.333) was input as the refractive index of the dispersion solvent, and the resulting cumulant average particle size was taken as the average particle size of the pigment-containing polymer particles.

[0178] (3) Measurement of the acid value of acrylic resins and vinyl resins The resin was dissolved in a titrant solvent prepared by mixing toluene and acetone (2:1) in a potentiometric automatic titrator (manufactured by Kyoto Electronics Industry Co., Ltd., electric burette, model number: APB-610), and titrated with a 0.1 N potassium hydroxide / ethanol solution by potentiometric titration method. The inflection point on the titration curve was taken as the end point. The acid value (mgKOH / g) was calculated from the titration volume up to the end point of the potassium hydroxide solution.

[0179] (4) Calculation of the crosslinking degree of crosslinked resin particles The crosslinking degree of the crosslinked resin particles was determined by calculation from the mass and epoxy equivalent of the crosslinking agent, and the mass and acid value of the acrylic resin, assuming that all the epoxy groups in the crosslinking agent reacted with the carboxyl groups of the acrylic resin.

[0180] (5) Calculation of the acid value of crosslinked resin particles The acid value of the crosslinked resin particles was determined from the acid value of the acrylic resin before crosslinking or the acrylic resin vinyl-based resin before crosslinking, the crosslinking degree and mass of the crosslinked resin particles.

[0181] (6) Measurement of the solid content concentration of the aqueous dispersion of crosslinked resin particles and the aqueous dispersion of pigment-containing resin particles 10.0 g of sodium sulfate, which had been made constant in a desiccator, was precisely weighed into a 30 mL polypropylene container (φ: 40 mm, height: 30 mm). Approximately 1.0 g of the sample was added thereto, mixed, and then precisely weighed. It was maintained at 105 °C for 2 hours to remove the volatile components, and then left in the desiccator for an additional 15 minutes, and the mass was precisely weighed. The mass of the sample after removing the volatile components was taken as the solid content, and divided by the mass of the added sample to obtain the solid content concentration. <\

[0182] (7) Measurement of the viscosity of the inkjet ink The viscosity of the inkjet ink at 32 °C was measured using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd., "TV-25", standard cone rotor 1°34’×R24, rotation speed 50 rpm).

[0183] (8) Measurement of the pH of the inkjet ink The pH of inkjet ink at 25°C was measured using a benchtop pH meter (Horiba, Ltd. "F-71") equipped with a pH electrode (Horiba, Ltd. "6337-10D").

[0184] <Manufacturing of aqueous dispersions of cross-linked resin particles> (Manufacturing of acrylic resin (A)) Manufacturing Example I-1: Manufacturing of Acrylic Resin A1 A monomer mixture was prepared by mixing 25.7 parts of acrylic acid, 55.0 parts of cyclohexyl acrylate, 19.3 parts of butyl acrylate, and 100 parts of methyl ethyl ketone (hereinafter referred to as "MEK").

[0185] Furthermore, a polymerization initiator solution was prepared by mixing 1.1 parts of 2,2'-azobis-(2,4-dimethylvaleronitrile) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., trade name: V-65) and 12.7 parts of MEK as polymerization initiators. In a reaction vessel equipped with a stirrer, reflux condenser, and two dropping funnels, 10% of the monomer mixture was added as an initial charge, and the vessel was thoroughly purged with nitrogen gas. In one dropping funnel, a mixture of the remaining 90% of the monomer mixture and 1.2 parts of 2-mercaptoethanol as a polymerization chain transfer agent was prepared. In the other dropping funnel, 80% of the polymerization initiator solution was added.

[0186] Under a nitrogen atmosphere, the contents of the reaction vessel were stirred while the temperature was raised to 65°C. The mixture from two dropping funnels and the polymerization initiator solution were then continuously added dropwise to the reaction vessel over 3 hours. After the addition was complete, the reaction was carried out at 65°C for 2 hours. Subsequently, the remaining 20% ​​of the polymerization initiator solution was added, and the reaction was carried out again at 65°C for 2 hours. After raising the temperature to 70°C, the reaction was carried out for another 2 hours. After cooling to room temperature, MEK was removed by vacuum drying to obtain acrylic resin A1 (acid value: 200 mg KOH / g, weight-average molecular weight: 21,000).

[0187] Manufacturing Examples I-2 to I-10: Manufacturing of Acrylic Resins A2 to A10 Acrylic resins A2 to A10 were produced in the same manner as in Production Example I-1, except that the monomer mixture was modified as shown in Table 1. The acid value and weight-average molecular weight of acrylic resins A2 to A10 are shown in Table 1.

[0188] [Table 1]

[0189] (Manufacturing of aqueous dispersions of cross-linked resin particles) Manufacturing Example I-11: Production of Aqueous Dispersion I-11 of Crosslinked Resin Particles (Process 1) 40.0 parts of acrylic resin A1 were dissolved in 60.0 parts of MEK, and 10.1 parts of a 5N sodium hydroxide aqueous solution (16.9% sodium hydroxide solids, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., for volumetric titration) were added to achieve a neutralization degree of acrylic resin A1 of 30 mol%. Then, 200.0 parts of water were added over 1 hour. After the addition was complete, the MEK was removed using an evaporator, and deionized water was added to obtain an aqueous dispersion of acrylic resin A1 with a solid content concentration of 20% by mass.

[0190] (Process 2) 200.0 parts of the aqueous dispersion of acrylic resin A1 obtained in step 1 were mixed with 12.0 parts of trimethylolpropane polyglycidyl ether (manufactured by Nagase ChemteX Corporation, trade name: Denacol EX-321LT, epoxy equivalent: 140) as a crosslinking agent. The mixture was then heated at 80°C for 5 hours with stirring to react the carboxyl groups in acrylic resin A1 with the epoxy groups in trimethylolpropane polyglycidyl ether. The reaction solution was then cooled to 25°C and filtered through a 5 μm pore size filter (acetylcellulose membrane, outer diameter: 2.5 cm, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.). Ion-exchanged water was added to achieve a solid content concentration of 20% by mass to obtain aqueous dispersion of crosslinked resin particles I-11. The degree of crosslinking of the crosslinked resin particles in aqueous dispersion of crosslinked resin particles I-11 was 60.0 mol%, the acid value was 61.6 mgKOH / g, and the average particle size was 99 nm.

[0191] Production Examples I-12 to I-25: Production of Aqueous Dispersions of Crosslinked Resin Particles I-12 to I-25 Aqueous dispersions of crosslinked resin particles I-12 to I-25 were produced in the same manner as in Production Example I-11, except that the type of acrylic resin (A) and the amounts of 5N aqueous sodium hydroxide solution and trimethylolpropane polyglycidyl ether were changed as shown in Table 2. The crosslinking degree, acid value, and average particle diameter of the crosslinked resin particles in the aqueous dispersions of crosslinked resin particles I-12 to I-25 are shown in Table 2.

[0192] Production Example I-26: Production of Aqueous Dispersion of Acrylic Resin (A) I-26 An aqueous dispersion of acrylic resin A1 I-26 was produced in the same manner as in Production Example I-11, except that Step 2 was not carried out. The acid value and average particle diameter of acrylic resin A1 in the aqueous dispersion of acrylic resin A1 I-26 are shown in Table 2.

[0193] [Table 2]

[0194] <Production of Aqueous Dispersion of Pigment-Containing Resin Particles> Production Example II-1: Aqueous Dispersion of Pigment-Containing Resin Particles II-1 (Production of Vinyl Resin B1) A vinyl resin B1 as a resin for pigment dispersion was produced in the same manner as in Production Example I-1, except that the monomer mixture was changed as shown in Table 3. The acid value and weight average molecular weight of vinyl resin B1 are shown in Table 3.

[0195] (Production of Aqueous Dispersion of Pigment-Containing Resin Particles II-1) (Step I) 25 parts of the obtained vinyl resin B1 was dissolved in 78.6 parts of MEK, and 10.1 parts of a 5N aqueous sodium hydroxide solution (sodium hydroxide solid content 16.9%, manufactured by Fuji Film Wako Pure Chemical Industries, Ltd., for volumetric titration) was added thereto so that the neutralization degree of vinyl resin B1 became 40 mol%, to obtain an aqueous dispersion of neutralized vinyl resin B1.

[0196] (Step II) To the aqueous dispersion of vinyl resin B1 obtained in step I, 400.0 parts of deionized water and 100.0 parts of carbon black pigment (CI Pigment Black 7, manufactured by Orion Engineered Carbons, trade name: NIPex 180IQ) were added, and the mixture was stirred for 60 minutes at 20°C with a disperser (manufactured by Asada Iron Works Co., Ltd., trade name: Ultra Disperser) rotating the disperser blades at 7000 rpm.

[0197] Next, the mixture was subjected to a 15-pass dispersion treatment at a pressure of 150 MPa using a microfluidizer (Microfluidics, high-pressure homogenizer, product name: M-140K) to obtain a dispersion. 250.0 parts of deionized water were added to the obtained dispersion, and after stirring, MEK was completely removed under reduced pressure at 60°C, and some of the water was further removed. The liquid phase of the obtained dispersion was recovered using a centrifuge and filtered through a cellulose acetate membrane filter with a pore size of 5 μm to obtain an aqueous dispersion (solid content concentration 25% by mass) in which the pigment was dispersed in vinyl resin B1.

[0198] (Process III) 100.0 parts of the aqueous dispersion in which the pigment obtained in step II was dispersed in vinyl resin B1 were placed in a screw-top glass bottle, 31.0 parts of deionized water were added, and 1.5 parts of trimethylolpropane polyglycidyl ether (manufactured by Nagase ChemteX Corporation, trade name: Denacol EX-321LT, epoxy equivalent: 140) were added as a crosslinking agent to achieve a degree of crosslinking of 50 mol%, the bottle was sealed tightly, and the mixture was heated at 70°C for 5 hours while stirring with a stirrer. After that, the dispersion was cooled to room temperature (25°C), filtered through a cellulose acetate membrane filter with a pore size of 5 μm, and an aqueous dispersion of pigment-containing resin particles II-1 was obtained (solid content concentration 20% by mass, carbon black content 15.7%, pigment dispersion resin content 4.3%, average particle size of pigment-containing resin particles 107 nm).

[0199] Manufacturing Example II-2: Aqueous dispersion of pigment-containing resin particles II-2 Aqueous dispersion of pigment-containing resin particles II-2 was obtained in the same manner as in Production Example II-1, except that the formulation during manufacturing was changed as shown in Table 3.

[0200] [Table 3]

[0201] [Manufacturing of inkjet inks] Example 1 Aqueous dispersion of cross-linked resin particles I-11 (solid content concentration 20% by mass) 25.0 parts (breakdown: resin 5.0 parts, water 20.0 parts), Aqueous dispersion of pigment-containing resin particles II-1 (solid content concentration 20% by mass) 25.5 parts (breakdown: carbon black 4.0 parts, vinyl resin B1 1.1 parts, water 20.4 parts), Propylene glycol (manufactured by Fujifilm Wako Pure Chemical Industries Ltd.) 20.0 parts of reagent, 5.0 parts of diethylene glycol monoisopropyl ether (manufactured by Nippon Emulsifier Co., Ltd.), 2.0 parts of Surfinol 104PG-50 (manufactured by Nisshin Chemical Industry Co., Ltd., 50% by mass solution of 2,4,7,9-tetramethyl-5-decine-4,7-diol in propylene glycol), 0.5 parts of Emulgen 120 (manufactured by Kao Corporation, 100% of the active ingredient of the ethylene oxide adduct of lauryl alcohol), and 1N sodium hydroxide aqueous solution (manufactured by Fujifilm Wako Pure Chemical Industries Ltd., for volumetric analysis) were mixed to achieve an ink pH of 8.5. Deionized water was then added to bring the total volume to 100 parts, and the mixture was filtered through a cellulose acetate membrane filter with a pore size of 5 μm to obtain inkjet ink 1. The dot diameter was evaluated when printing on gloss coated paper using the obtained inkjet ink 1, and the line width was evaluated when printing on matte coated paper.

[0202] [Inkjet ink evaluation] <Measurement of dot diameter when printing on gloss coated paper> In an environment with a temperature of 25±1℃ and a relative humidity of 30±5%, inkjet ink 1 was loaded into a printing evaluation device (manufactured by Trytech Co., Ltd.) equipped with an inkjet recording head (Kyocera Corporation, "KJ4B-HD06MHG-STDV", piezo line head). The head voltage was set to 26V, the drive frequency to 10kHz, the head temperature to 32℃, the ejection droplet volume to 7pL, the resolution to 600×600dpi, the number of pre-ejection flushes to 200, and the negative pressure to -4.0kPa. Gloss coated paper "OK ​​Topcoat+" (manufactured by Oji Paper Co., Ltd., product name, water absorption 4.9g / m²) was used. 2 Using a press, the print medium was fixed to the transport table under reduced pressure, with its longitudinal direction and transport direction being the same. A print command was transferred to the print evaluation device, and a print pattern with a 2cm square area (image area for dot diameter measurement) with a duty cycle of 30% was printed in a single pass to obtain a printed material.

[0203] The dot diameter of the ink in printed materials was measured using the "PIAS-II" handheld image evaluation system manufactured by Quality Engineering Associates Inc., under conditions of a threshold of 50%, a minimum dot diameter of 40 μm, and a maximum dot diameter of 500 μm. The larger the dot diameter, the more the graininess of the printed image can be reduced, and the fewer streaks there are when printing solid areas. A dot diameter of 51 μm or more is practically acceptable, but 55 μm or more is preferable.

[0204] <Measuring line width when printed on matte coated paper> Using the same settings as described above for "<Measurement of dot diameter when printing on gloss coated paper>", matte coated paper (GRAFICAS Y FORMULARIOS, product name: Fitnesse Matt) was used and fixed to the transport table under reduced pressure, with the longitudinal direction of the printing medium and the transport direction being the same. A print command was transferred to the print evaluation device, and a line with a width of 5 dots was printed. The line width of the printed material was measured using the "PIAS-II" handheld image evaluation system manufactured by Quality Engineering Associates Inc.

[0205] If the line width is too small, streaks will appear during solid printing, and if it is too large, bleeding will occur. Therefore, a line width of 280 μm to 360 μm is practically acceptable, preferably 290 μm to 350 μm, and more preferably 300 μm to 310 μm.

[0206] Examples 2-13 and Comparative Examples 1-5 Inkjet inks 2-13 and C1-C5 were manufactured in the same manner as in Example 1, except that the ink formulations were changed as shown in Table 4. The resulting inkjet inks were then measured for dot diameter when printed on gloss coated paper and line width when printed on matte coated paper, in the same manner as in Example 1. The results are shown in Table 4.

[0207] [Table 4]

[0208] Table 4 shows that the inkjet ink of the example exhibits superior wetting and spreading properties on gloss-coated paper and moderate wetting and spreading properties on matte-coated paper compared to the inkjet ink of the comparative example.

[0209] The inkjet ink of the present invention makes it possible to obtain high-quality recordings on both gloss-coated paper, which has a smooth surface and is resistant to ink spreading, and matte-coated paper, which has an uneven surface and is resistant to ink spreading due to capillary action. Therefore, the inkjet ink of the present invention can be suitably used for printing on various recording media with different surface characteristics.

Claims

1. An inkjet ink containing crosslinked resin particles as a fixing resin, a pigment, an organic solvent, and water, The crosslinked resin particles include a crosslinked structure consisting of a structure derived from a carboxyl group in the acrylic resin (A) and a structure derived from a polyfunctional epoxy compound. The acrylic resin (A) comprises a constituent unit derived from (meth)acrylic acid (a-1) and a constituent unit derived from cycloalkyl (meth)acrylate (a-2), The mass ratio ((a-1) derived from constituent units / (a-2) derived from constituent units) of the acrylic resin (A) is greater than 0.22 and less than or equal to 1. Inkjet ink.

2. The inkjet ink according to claim 1, wherein the constituent unit derived from cycloalkyl (meth)acrylate (a-2) is a constituent unit derived from cycloalkyl acrylate.

3. The inkjet ink according to claim 2, wherein the constituent unit derived from cycloalkyl acrylate is one or more selected from the group consisting of constituent units derived from cyclopentyl acrylate, constituent units derived from cyclohexyl acrylate, and constituent units derived from cycloheptyl acrylate.

4. The inkjet ink according to claim 1, wherein the acrylic resin (A) further comprises a constituent unit derived from a hydrophobic monomer (a-3).

5. The inkjet ink according to claim 4, wherein the mass ratio of constituent units derived from the hydrophobic monomer (a-3) to constituent units derived from the (meth)acrylic acid (a-1) (constituent units derived from (a-3) / constituent units derived from (a-1)) is 0.1 or more and 2.0 or less.

6. The inkjet ink according to claim 4, wherein the mass ratio of constituent units derived from the hydrophobic monomer (a-3) to constituent units derived from the polyfunctional epoxy compound (constituent units derived from (a-3) / constituent units derived from the polyfunctional epoxy compound) is 0.1 or more and 2.0 or less.

7. The inkjet ink according to claim 4, wherein the mass ratio of constituent units derived from the cycloalkyl (meth)acrylate (a-2) to constituent units derived from the polyfunctional epoxy compound (constituent units derived from (a-2) / constituent units derived from the polyfunctional epoxy compound) is 1.0 or more and 6.0 or less.

8. The inkjet ink according to claim 4, wherein the content of constituent units derived from the hydrophobic monomer (a-3) in the acrylic resin (A) is 5% by mass or more and 35% by mass or less.

9. The inkjet ink according to claim 4, wherein the mass ratio of the constituent units derived from the hydrophobic monomer (a-3) to the constituent units derived from the cycloalkyl (meth)acrylate (a-2) (constituent units derived from (a-3) / constituent units derived from (a-2)) is 0.1 or more and 1.0 or less.

10. The inkjet ink according to claim 1, wherein the content of the constituent units derived from the cycloalkyl (meth)acrylate (a-2) in the acrylic resin (A) is 40% by mass or more and 70% by mass or less.

11. The inkjet ink according to claim 1, wherein the content of the crosslinked resin particles in the inkjet ink is 2.5% by mass or more and 10% by mass or less.

12. The inkjet ink according to claim 1, wherein the acid value of the crosslinked resin particles is 35 mg KOH / g or more and 220 mg KOH / g or less.

13. The inkjet ink according to claim 1, wherein the mass ratio of the crosslinked resin particles to the pigment-containing resin particles is 0.1 or more and 2.0 or less.

14. The inkjet ink according to claim 1, wherein the organic solvent contains a glycol ether compound.

15. The inkjet ink according to claim 14, wherein the content of the glycol ether compound in the inkjet ink is 1% by mass or more and 20% by mass or less.

16. The inkjet ink according to claim 14, wherein the mass ratio of the glycol ether compound to the crosslinked resin particles is 0.5 or more and 3.0 or less.

17. The inkjet ink according to claim 1, wherein the pigment is in the form of resin particles containing the pigment.

18. An inkjet printing method comprising printing on a printing substrate using the inkjet ink described in claim 1.

19. An inkjet printing method according to claim 18, wherein the printing substrate is one or more selected from gloss coated paper and matte coated paper.

20. A method for manufacturing inkjet ink, comprising the step of mixing crosslinked resin particles as a fixing resin, a pigment, an organic solvent, and water, The crosslinked resin particles are obtained by reacting carboxyl groups in acrylic resin (A) with epoxy groups in a polyfunctional epoxy compound. The acrylic resin (A) comprises a constituent unit derived from (meth)acrylic acid (a-1) and a constituent unit derived from cycloalkyl (meth)acrylate (a-2), The mass ratio ((a-1) derived from constituent units / (a-2) derived from constituent units) of the acrylic resin (A) is greater than 0.22 and less than or equal to 1. A method for manufacturing inkjet ink.

21. The method for producing an inkjet ink according to claim 20, wherein the acid value of the acrylic resin (A) is 100 mg KOH / g or more and 350 mg KOH / g or less.

22. A method for producing an inkjet ink according to claim 20, wherein the carboxyl groups in the acrylic resin (A) and the epoxy groups in the polyfunctional epoxy compound are reacted such that the degree of crosslinking of the crosslinked resin particles is 10 mol% or more and 80 mol% or less.

23. The use of a composition containing crosslinked resin particles as a fixing resin, a pigment, an organic solvent, and water as an inkjet ink, The crosslinked resin particles include a crosslinked structure consisting of a structure derived from a carboxyl group in the acrylic resin (A) and a structure derived from a polyfunctional epoxy compound. The acrylic resin (A) comprises a constituent unit derived from (meth)acrylic acid (a-1) and a constituent unit derived from cycloalkyl (meth)acrylate (a-2), The mass ratio of the constituent units derived from (a-1) to the constituent units derived from (a-2) is greater than 0.22 and less than or equal to 1. For use as inkjet ink.

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