Aqueous inkjet ink and printed matter

Abstract

To provide an aqueous inkjet ink that, even when a low-absorbency print substrate such as coated paper is used, produces printed matter having no color bleeding due to coalescence of droplets and no white voids, having superior dot circularity of the droplets, and further having superior print density and color reproducibility, and that also demonstrates superior ejection stability.SOLUTION: An aqueous inkjet ink is provided which contains crosslinked-polymer particles (A) containing a pigment and a surfactant (B), wherein the crosslinked-polymer particles (A) include a crosslinked product of a compound (A-1) having a plurality of functional groups which reacts with a carboxy group and / or a carboxylate group and an uncrosslinked polymer (A-2), the surfactant (B) contains a polyoxyethylene alkyl ether compound (B-1) having a specific structure and a nonionic surfactant (B-2) having an HLB value of 1 to 10, wherein the ratio between the content of the compound (B-1) and the content of the nonionic surfactant (B-2) is defined.SELECTED DRAWING: None

Description

Technical Field

[0001] Embodiments of the present invention relate to an aqueous inkjet ink and a printed matter produced using the aqueous inkjet ink.

Background Art

[0002] The inkjet printing method is a recording method in which ink droplets are directly ejected from fine nozzles and adhered to a printing substrate to obtain characters and / or images. The inkjet printing method not only has the advantages of low noise of the apparatus and good operability, but also has many advantages such as easy full-colorization, low cost of the printing apparatus, and furthermore, it is possible to perform non-contact printing on various printing substrates. Therefore, it has become very popular. In particular, in recent years, it has been used not only for general household use in offices and homes, but also for commercial printing and industrial printing applications. Among them, the demand for inkjet inks (aqueous inkjet inks) containing water as a main component for the purpose of reducing the environmental impact and the burden on workers is increasing more and more.

[0003] Note that the above "image" also includes seamless images such as solid images and checkered images.

[0004] Aqueous inkjet inks have been developed for a long time using plain paper and special paper as printing substrates. In these applications, it is premised that the liquid component of the aqueous inkjet ink is absorbed into the printing substrate. Therefore, when the above aqueous inkjet ink is printed on a printing substrate with poor absorbability, such as those used in the above commercial printing and industrial printing applications, the image will bleed, and it is difficult to produce a printed matter that can withstand actual use.

[0005] For example, coated paper, which is a poorly absorbent printing substrate, has low absorbency for liquid components. Therefore, during printing, if the next droplet lands adjacent to the droplet of the water-based inkjet ink that has landed first before the first droplet dries, a phenomenon (beading) where adjacent droplets merge easily occurs. Beading causes color bleeding in printed materials. In addition, some poorly absorbent printing substrates such as coated paper have a low surface free energy. When printing on such a printing substrate, the water-based inkjet ink hardly wets and spreads on the surface of the printing substrate, which easily leads to the occurrence of white spots (a phenomenon where spots and / or streaks of areas where the water-based inkjet ink does not adhere occur on the printing substrate).

[0006] Furthermore, water, which is the main solvent of water-based inkjet ink, has a high surface tension and is difficult to wet and spread on the printing substrate, which easily causes deterioration of the printed image quality such as white spots and color bleeding. To improve the printed image quality, it is effective to lower the surface tension of the water-based inkjet ink. Generally, highly hydrophobic surfactants and organic solvents are used.

[0007] For example, Patent Document 1 discloses an inkjet recording ink composition containing three types of acetylene diol-based surfactants with different structures. According to Patent Document 1, it is said that an image with excellent printed image quality (color unevenness, aggregation, bleeding) and fixing properties (rub resistance) can be recorded at high speed on various printing substrates with different absorbencies. Also, Patent Document 2 discloses an aqueous ink composition containing a nonionic surfactant with an HLB value of 4 to 14. According to Patent Document 2, it is said that a printed material with excellent wetting and spreading properties, fineness, printing density, water resistance, and rubbing resistance (rub resistance), etc., and without aggregation can be obtained on an offset medium on which offset ink may be printed. Furthermore, Patent Document 3 discloses an inkjet recording method of recording on a printing substrate with low water absorption using an aqueous inkjet ink containing at least one acetylenediol surfactant selected from the group consisting of 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, and 2,5-dimethyl-3-hexyne-2,5-diol, and a nonionic surfactant. According to Patent Document 3, it is said that a printed matter without turbidity (such as white turbidity or oil floating) and with suppressed color unevenness can be obtained.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0009] On the other hand, the aqueous inkjet inks disclosed in Patent Documents 1 and 2 above have not been evaluated for ejection stability, which can be said to be an essential requirement for use in the inkjet printing method. Although details will be described later, depending on the materials used in combination, the effects of the above-mentioned highly hydrophobic materials may not be fully exhibited, and the ejection stability of the aqueous inkjet ink may also deteriorate.

[0010] In addition, when the present inventors reproduced and evaluated the aqueous inkjet ink specifically disclosed in the examples of Patent Document 3, it was confirmed that there was deterioration in whiteout and color bleeding, which had not been evaluated in Patent Document 3, and it was also found that the shape of the droplets of the aqueous inkjet ink became distorted (inferior dot roundness).

[0011] As described above, conventionally, there has been a situation where further improvement was necessary in order to obtain a printed matter that has no color bleeding due to the coalescence of droplets and no white spots, is excellent in the dot roundness of the droplets, and furthermore, has excellent ejection stability. Also, there has been no aqueous inkjet ink that can obtain a printed matter with good printing density and color reproducibility while solving these problems.

[0012] Therefore, one object of an embodiment of the present invention is to provide an aqueous inkjet ink that can obtain a printed matter that is excellent in printing image quality, i.e., has no color bleeding due to the coalescence of droplets and no white spots, is excellent in the dot roundness of the droplets, and furthermore, has good printing density and color reproducibility, and also has good ejection stability, even on a poorly absorbent printing substrate such as coated paper. Another object of an embodiment of the present invention is to provide an aqueous inkjet ink that is excellent in drying property in addition to the above-described effects.

[0013] In the present disclosure, the state of a printed matter that has no color bleeding due to the coalescence of droplets and no white spots and is excellent in the dot roundness of the droplets is also described as "excellent in printing image quality".

Means for Solving the Problems

[0014] The inventors of the present invention have conducted intensive studies to solve the above problems, and have found an aqueous inkjet ink having the following configuration, thereby completing the present invention.

[0015] That is, some embodiments of the present invention relate to an aqueous inkjet ink shown in the following [1] to [5], and a printed matter manufactured using the above aqueous inkjet ink shown in the following [6]. [1] An aqueous inkjet ink containing crosslinked polymer particles (A) containing a pigment and a surfactant (B), The crosslinked polymer particles (A) include a crosslinked reaction product of a compound (A-1) having a plurality of functional groups reactive with carboxyl groups and / or carboxylate groups in one molecule and an uncrosslinked polymer (A-2) having carboxyl groups and / or carboxylate groups. The surfactant (B) contains a compound (B-1) represented by the following general formula 1 and a nonionic surfactant (B-2) having an HLB value of 1 to 10. An aqueous inkjet ink, wherein the ratio of the content of the compound (B-1) to the content of the nonionic surfactant (B-2) is 1:1.2 to 1:20 by mass ratio. R 1 -(O-CH2-CH2) n -OH General formula 1 (In general formula 1, R 1 represents a linear or branched alkyl group having 10 to 25 carbon atoms, and n is an integer of 20 to 100.) [2] Further contains an organic solvent. The aqueous inkjet ink according to [1], wherein the organic solvent includes an alkanediol-based solvent having 5 to 8 carbon atoms and / or a (poly)alkylene glycol monoalkyl ether-based solvent having 5 to 9 carbon atoms. [3] The aqueous inkjet ink according to [2], wherein the organic solvent includes a (poly)propylene glycol monoalkyl ether-based solvent having 5 to 9 carbon atoms. [4] The aqueous inkjet ink according to any one of [1] to [3], wherein the acid value of the uncrosslinked polymer (A-2) is 60 to 180 mgKOH / g. [5] The aqueous inkjet ink according to any one of [1] to [4], wherein the nonionic surfactant (B-2) having an HLB value of 1 to 10 includes a gemini-type silicone-based surfactant and / or a both-end polyether-modified silicone-based surfactant (excluding those which are the gemini-type silicone-based surfactant). [6] A printed matter obtained by printing the aqueous inkjet ink according to any one of [1] to [5] above.

Advantages of the Invention

[0016] According to the present disclosure, even for a poorly absorbent printing substrate such as coated paper, there is no color mixing bleeding due to the coalescence of droplets and no white bleeding, the dot roundness of the droplets is excellent, and furthermore, a printed matter with good printing density and color reproducibility can be obtained, and it has become possible to provide an aqueous inkjet ink with good ejection stability. Further, according to the present invention, in addition to the above-described effects, it has become possible to provide an aqueous inkjet ink that is further excellent in drying property.

Embodiments for Carrying Out the Invention

[0017] Hereinafter, some preferred embodiments of the inkjet ink of the present disclosure (hereinafter, also simply referred to as "the ink of the present disclosure") will be described in detail. It should be noted that the present disclosure is not limited to the following embodiments, and also includes modified examples implemented within the scope of not changing the gist of the present disclosure.

[0018] As described above, poorly absorbent printing substrates such as coated paper have low surface energy and it is not easy to sufficiently wet and spread aqueous inkjet ink. Therefore, for example, even in a printed matter with a high printing rate, image defects such as white bleeding are likely to occur. Further, since the poorly absorbent printing substrate has low permeability of the liquid component into the interior, there is a risk that droplets of another ink land adjacent to the droplets of the aqueous inkjet ink that have landed first before the droplets of the previously landed aqueous inkjet ink are sufficiently dried, resulting in beading. Beading appears as color mixing bleeding and density unevenness, and thus is not preferable from the viewpoint of improving the print quality. Thus, in inkjet printing on a poorly absorbent printing substrate, in order to improve the print quality, it is necessary to sufficiently ensure the wettability and permeability of the aqueous inkjet ink.

[0019] Generally, in order to ensure the wettability and permeability of the ink, it is effective to lower the surface tension of the ink. Further, by adding a surfactant with high hydrophobicity to the ink, the surfactant is quickly oriented at the interface of the ink (gas-liquid interface and the interface between the printing substrate and the ink), and it becomes easy to impart wettability and permeability.

[0020] On the other hand, as a result of investigations by the present inventors, it has been found that a surfactant with high hydrophobicity adsorbs onto the free polymer dispersant present in the aqueous inkjet ink. A surfactant with high hydrophobicity has a property of easily affinity with another hydrophobic material, and it is considered that this is because it interacts with the hydrophobic group in the free polymer dispersant.

[0021] In general, a polymer dispersant used in aqueous inkjet ink has a hydrophilic group such as a carboxy group or a carboxylate group, and a hydrophobic group such as an aromatic ring structure or a long-chain alkyl group. The above hydrophilic group is introduced for the purpose of improving the affinity for water as the main component and stabilizing the dispersion state of the pigment due to the charge repulsion between the polymer dispersants. On the other hand, the above hydrophobic group functions as, for example, an adsorption group for the pigment. Therefore, it is extremely difficult to exclude the hydrophobic group from the polymer dispersant used in aqueous inkjet ink.

[0022] Thus, when a surfactant with high hydrophobicity adsorbs onto the free polymer dispersant, when the ink droplet lands on the printing substrate, the orientation of the surfactant at the interface is inhibited by the above free polymer dispersant, and it becomes difficult to obtain sufficient wettability and permeability. Also, although the detailed mechanism is unknown, when a large amount of the polymer dispersant adsorbed with a surfactant with high hydrophobicity is present in the ink, the ejection stability of the ink also tends to deteriorate.

[0023] Therefore, in order to obtain printed matter with excellent print quality on a poorly absorbent printing substrate such as coated paper, and further to improve the ejection stability of the ink, it is important to reduce the amount of the free polymer dispersant so as not to interfere with the orientation of the surfactant. Therefore, in the present embodiment, for example, from the viewpoint that the desorption of the polymer dispersant from the pigment can be suppressed even if the composition ratio of the ink components changes due to drying or the like, it is more preferable to use a polymer (crosslinked polymer) crosslinked with a crosslinking agent as the polymer dispersant. In particular, by using a crosslinking agent having a plurality of functional groups that react with carboxyl groups and carboxylate groups, which are generally present in the polymer dispersant, in one molecule, the above polymer dispersant can be crosslinked at a high density, and desorption from the pigment can be prevented. As a result, the surfactant can be quickly oriented at the interface of the ink, and the wettability and permeability of the ink can be improved. Furthermore, since the desorption of the polymer dispersant is prevented and the amount of the free polymer dispersant is reduced, the ejection stability of the ink is also improved.

[0024] However, as a drawback of crosslinking the polymer dispersant and reducing the amount of the free polymer dispersant, there may arise a problem that the surfactant having no adsorbing component may not be stably present in the ink. In this case, the surfactant may be non-uniformly localized at the ink interface, and the ink droplets may spread unevenly in terms of wetting, resulting in a printed image quality with poor roundness.

[0025] Also, generally, when a polymer is crosslinked with a crosslinking agent, functional groups having hydrophilicity such as hydroxyl groups, amino groups, and amide bonds are generated in the polymer dispersant due to the crosslinking reaction. As a result, the affinity between the polymer dispersant having the above functional groups and the surfactant having high hydrophobicity deteriorates, and there is also a concern that, for example, in printed matter, the surfactant and the crosslinked polymer (including pigment particles) may be localized and / or separated. In this case, there is a risk that the printing density and color reproducibility may decrease.

[0026] In order to solve the above problems, as a result of intensive studies by the present inventors, crosslinked polymer particles containing a pigment are used in combination with a compound (B-1) represented by the general formula 1 and a nonionic surfactant (B-2) having an HLB value of 1 to 10. Furthermore, by setting the ratio (mass ratio) of the content of the compound (B-1) to the content of the nonionic surfactant (B-2) to 1:1.2 to 1:20, even on a difficult-to-absorb printing substrate such as coated paper, the wettability and penetrability of the ink can be ensured. Moreover, it has become clear that a printed matter excellent in dot roundness, printing density, and color reproducibility can be obtained, leading to the present invention. Although the detailed mechanism by which these effects are achieved by the above configuration is not clear, for example, the following can be considered.

[0027] First, the surfactant (B-2) corresponds to the above-mentioned "surfactant with high hydrophobicity". The surfactant (B-2) has an HLB value in a suitable range and can impart excellent penetrability and wettability to aqueous inkjet ink even on a difficult-to-absorb printing substrate such as coated paper. On the other hand, as described above, the surfactant (B-2) has poor affinity with the crosslinked polymer having a hydrophilic functional group, and for example, by spreading unevenly on the printing substrate, there is a risk of obtaining a printed matter with poor dot roundness. Also, during the drying process after printing, as water preferentially volatilizes, the compatibility between the surfactant (B-2) and the crosslinked polymer decreases, and the surfactant (B-2) and the crosslinked polymer (including pigment particles) may localize and / or separate, resulting in a non-uniform ink film (dried ink film). In that case, the light incident on the ink film scatters on the surface of the ink film, and the printed matter may appear whitish (whitening), or the color reproducibility may be impaired.

[0028] On the one hand, in compound (B-1), a linear or branched alkyl chain having 10 to 25 carbon atoms functions as a hydrophobic moiety, and a polyethylene oxide chain having an added molar number of 20 to 100 functions as a hydrophilic moiety. Further, by using compound (B-1) and surfactant (B-2) in a suitable ratio, in the ink, the polyethylene oxide chain in compound (B-1) is hydrophilic with water, while the alkyl chain is preferably compatible with surfactant (B-2). As a result, the surfactant (B-2) emulsified in the ink of the present disclosure can be uniformly oriented without being localized at a part of the interface. It is considered that, in this way, a printed matter excellent in dot roundness can be obtained while suppressing white spots and color bleeding.

[0029] Also, in the drying process of the ink, even after water is preferentially volatilized, the alkyl chain in compound (B-1) is compatible with surfactant (B-2), and the polyethylene oxide chain is compatible with the crosslinked polymer, so that it is considered that a uniform ink film is formed without separation of each material. As a result, it becomes possible to obtain a printed matter excellent in printing density and color reproducibility.

[0030] As described above, in order to obtain an ink that has no color bleeding and white spots, is excellent in dot roundness, has good printing density and color reproducibility, and is further excellent in ejection stability, in addition to crosslinked polymer particles containing a pigment, compound (B-1) represented by General Formula 1 and surfactant (B-2) having an HLB value of 1 to 10 are used in combination, and their content ratio is preferably defined. The above mechanism is an inference and does not limit the present invention in any way. In the present disclosure, compound (B-1) and nonionic surfactant (B-2) are different. Specifically, compound (B-1) is a surfactant excluding a nonionic surfactant having an HLB value of 1 to 10.

[0031] Incidentally, the aqueous inkjet inks specifically disclosed in Patent Documents 1 and 2 described above differ from the present disclosure in that they do not use crosslinked polymer particles containing pigments. Further, Patent Documents 1 and 2 do not describe or suggest using a polymer having a crosslinked structure as a dispersion polymer and that the effect of a highly hydrophobic surfactant can be sufficiently exhibited by the polymer having the crosslinked structure, thereby improving the ejection stability of the aqueous inkjet ink. On the other hand, "acetylene glycol (A)", which is an essential component in Patent Document 3, corresponds to the nonionic surfactant (B-2) in the present disclosure, and a part of the "nonionic surfactant (B)" corresponds to the compound (B-1) in the present disclosure (see Claim 3 etc. of Patent Document 3). However, in Patent Document 3, the ratio represented by "nonionic surfactant (B) / acetylene glycol (A)" is defined to be 1 to 3, whereas in the present disclosure, the ratio of the content of the compound (B-1) to the content of the nonionic surfactant (B-2) is defined to be 1:1.2 to 1:20 by mass ratio (when expressed in the description method of Patent Document 3, "1 / 20 to 1 / 1.2 (5 / 6)"), and this is the difference between the two. Actually, Comparative Example 3 of Patent Document 3 discloses an example in which the above ratio is "0.3" (when expressed in the description method of the present disclosure, 1:3.3), and color unevenness and ejection stability are said to be below the practical level. On the other hand, in the present disclosure, by further defining the structure of the compound (B-1), it is possible to exhibit good quality even for the aqueous inkjet ink that is said to not obtain good quality in Patent Document 3.

[0032] Subsequently, the main components constituting the inkjet ink according to one embodiment will be described below.

[0033] <Crosslinked polymer particles (A) containing a pigment> The inkjet ink of the present embodiment contains crosslinked polymer particles (A) containing a pigment. The crosslinked polymer particles (A) containing the pigment include a crosslinked reaction product of a pigment and a compound (A-1) having a plurality of functional groups reactive with a carboxy group and / or a carboxylate group in one molecule and an uncrosslinked polymer (A-2). By the crosslinking treatment carried out for the production of the crosslinked reaction product, the uncrosslinked polymer (A-2) is crosslinked at a high density, and it becomes possible to suppress the desorption of the polymer dispersant in the ink of the present disclosure. As a result, the surfactant (B-2) can function effectively, and it becomes possible to improve the wettability and permeability of the ink.

[0034] The "crosslinked polymer particles containing a pigment" in the present disclosure refers to particles after a crosslinking treatment using a crosslinking agent (a compound used to chemically bond polymer molecules) has been performed on the polymer contained in the crosslinked polymer particle precursor. The "crosslinked polymer particle precursor" is a particle at the stage before the crosslinking treatment, and is, for example, an uncrosslinked polymer particle encapsulating a pigment, an uncrosslinked particle having a sea-island structure containing a polymer and a pigment and having a part of the pigment exposed on the surface of the particle, and at least a part of the surface. It refers to one or more particles selected from the group consisting of pigment particles to which a polymer is chemically adsorbed and / or bonded.

[0035] <<Pigment>> The pigment contained in the crosslinked polymer particles (A) containing a pigment may be either an organic pigment or an inorganic pigment. Further, an organic pigment and an inorganic pigment may be used in combination. Furthermore, the hue of the pigment to be used is not particularly limited, and for example, colored pigments such as yellow, green, cyan, blue, violet, magenta, red, orange, etc., and achromatic pigments such as white, black, etc. can be used.

[0036] When using inorganic pigments as pigments, examples of such inorganic pigments include titanium oxide, zinc white, zinc sulfide, lead white, calcium carbonate, precipitated barium sulfate, white carbon, alumina white, kaolin clay, talc, bentonite, carbon black, black iron oxide, cadmium red, red iron oxide, molybdenum red, molybdate orange, chrome vermilion, lead yellow, cadmium yellow, yellow iron oxide, titanium yellow, chromium oxide, viridian, titanium cobalt green, cobalt green, cobalt chromium green, victoria green, ultramarine, indigo, cobalt blue, cerulean blue, cobalt silica blue, cobalt zinc silica blue, manganese violet, cobalt violet, etc.

[0037] As the above carbon black, carbon black produced by the furnace method or the channel method can be used. Among them, these carbon blacks having a primary particle size of 11 to 40 nm, a specific surface area by the BET method of 50 to 400 m 2 / g, a volatile content of 0.5 to 10%, and a pH value of 2 to 10 are preferably suitable.

[0038] On the other hand, specific examples of organic pigments include azo pigments such as azo lake pigments, insoluble monoazo pigments, insoluble disazo pigments, and chelate azo pigments; polycyclic pigments such as phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, diketopyrrolopyrrole pigments, benzimidazolone pigments, and threne pigments; and the like.

[0039] Specifically, when exemplifying organic pigments that can be used as the above pigments according to the Color Index, examples of organic pigments that exhibit cyan or blue colors include C.I.Pigment Blue 1, 2, 3, 15:1, 15:3, 15:4, 15:6, 16, 21, 22, 60, 64, etc.

[0040] In addition, examples of organic pigments exhibiting magenta, red, or violet colors include C.I. Pigment Red 5, 7, 9, 12, 31, 48, 49, 52, 53, 57, 97, 112, 120, 122, 146, 147, 149, 150, 168, 170, 177, 178, 179, 184, 188, 202, 206, 207, 209, 238, 242, 254, 255, 264, 269, 282, C.I. Pigment Violet 19, 23, 29, 30, 32, 36, 37, 38, 40, 50, etc.

[0041] In addition, examples of organic pigments exhibiting yellow color include C.I. Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 20, 24, 74, 83, 86, 93, 94, 95, 109, 110, 117, 120, 125, 128, 129, 137, 138, 139, 147, 148, 150, 151, 154, 155, 166, 168, 180, 185, 213, etc.

[0042] In addition, examples of black pigments include aniline black (C.I. Pigment Black 1), perylene black (C.I. Pigment Black 31, 32), azomethine azo black, etc.

[0043] In addition, as pigments other than the above, C.I. Pigment Green 7, 10, 36, C.I. Pigment Brown 3, 5, 25, 26, C.I. Pigment Orange 2, 5, 7, 13, 14, 15, 16, 24, 34, 36, 38, 40, 43, 62, 63, 64, 71, etc. can be used.

[0044] The pigments listed above may be used alone or in combination of two or more. For example, a plurality of the pigments listed above can be used to form a black pigment composition. Also, the preferred content of the pigment is 0.1 to 20% by mass, more preferably 1 to 10% by mass, and still more preferably 2 to 7% by mass based on the total mass of the aqueous inkjet ink.

[0045] <<Compound (A-1)>> Compound (A-1) is a compound used as the above crosslinking agent, and is a compound having a plurality of functional groups that react with carboxyl groups and / or carboxylate groups present in the uncrosslinked polymer (A-2) in one molecule. As the above compound (A-1), an aziridine compound, an isocyanate compound, an epoxy compound, a carbodiimide compound, an oxetane compound, an oxazoline compound, etc. can be used. Among them, from the viewpoint that the crosslinking reaction of the polymer (A-2) can proceed in the vicinity of the pigment while maintaining the dispersion stability of the pigment, and the desorption of the polymer (A-2) accompanying the crosslinking reaction can be prevented, a printed matter without white spots can be obtained, and the ejection stability of the aqueous inkjet ink can also be improved. Therefore, it is preferable to use an epoxy compound as the compound (A-1), that is, the compound (A-1) is a compound having a plurality of epoxy groups in one molecule. Further, the compound (A-1) may be water-soluble or water-insoluble, but from the viewpoint that the crosslinking reaction can proceed more efficiently in a liquid medium mainly composed of water, the dissolution amount of the above compound (A-1) in 100 g of water at 25 °C is preferably 0.1 to 50 g / 100 gH2O, and more preferably 0.2 to 40 g / 100 gH2O. Even more preferably, it is 0.5 to 30 g / 100 gH2O.

[0046] As described above, it is preferable that the compound (A-1) is a compound having a plurality of epoxy groups in one molecule. Further, as the compound having a plurality of epoxy groups in one molecule, it is more preferable to use a compound having two or more glycidyl ether groups in one molecule. Furthermore, it is particularly preferable that the compound (A-1) is a polyglycidyl ether compound of a polyhydric alcohol having a hydrocarbon group with 3 to 8 carbon atoms.

[0047] When a compound having a plurality of epoxy groups in one molecule is used as the compound (A-1), the epoxy equivalent is preferably 90 to 300 g / eq., more preferably 100 to 200 g / eq., from the viewpoint that it can more efficiently undergo a crosslinking reaction with carboxyl groups and / or carboxylate groups present in the uncrosslinked polymer (A-2) in a liquid medium mainly composed of water.

[0048] Specific examples of the compound having two or more glycidyl ether groups in one molecule include cyclohexanedimethanol diglycidyl ether, polyethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, diethylene glycol diglycidyl ether, glycerol polyglycidyl ether, polyglycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, sorbitol polyglycidyl ether, pentaerythritol polyglycidyl ether, resorcinol diglycidyl ether, neopentyl glycol diglycidyl ether, bisphenol A type diglycidyl ether, hydrogenated bisphenol A type diglycidyl ether, and the like.

[0049] The compound (A-1) is preferably added so that the functional group content (mol%) represented by the following formula 2 is 50 to 150 mol%. The functional group content is more preferably 70 to 120 mol%, and particularly preferably 80 to 100 mol%.

[0050]

Number

[0051] For example, when a compound having a plurality of epoxy groups in one molecule and having an epoxy equivalent of EE (g / eq.) (corresponding to the compound (A-1)) is mixed with EW (g) and a polymer having an acid value of AV (mgKOH / g) (corresponding to the polymer (A-2)) of PW (g), the functional group content is represented by the following formula 2-2.

[0052] Functional group content (mol%) = 100×(EW / EE) / {PW×AV / (56.1×1000)} Formula 2-2

[0053] In the above Formula 2-2, "56.1" is the molecular weight of potassium hydroxide.

[0054] When the above functional group content is within the above range, the crosslinking of the polymer dispersant becomes densified, and the amount of the free polymer dispersant can be significantly reduced. On the other hand, in this case, the nonionic surfactant (B-2) cannot stably exist in the ink, the wetting spread of the ink droplets becomes non-uniform, or the amount of hydrophilic groups in the polymer dispersant increases, resulting in a deterioration in the affinity with the above nonionic surfactant (B-2), and there is a risk of a decrease in printing density and color reproducibility. However, the inkjet ink of the present disclosure contains the compound (B-1) as described above. And, since the nonionic surfactant (B-2) stabilized by the compound (B-1) can be quickly and uniformly oriented, an improvement in dot roundness in the printed matter, and further suppression of white spots and color bleeding can be realized. In addition, a decrease in printing density and color reproducibility can be prevented, and the ejection stability can also be improved.

[0055] <<Polymer (A-2)>> The uncrosslinked polymer (A-2) used in this embodiment has a carboxy group and / or a carboxylate group (COO - ) in its structure. Also, any polymer having a carboxy group and / or a carboxylate group can be used as the polymer (A-2). For example, the above polymer (A-2) may be a resin (dispersion resin) having a function of dispersing a pigment.

[0056] Examples of the types of polymers that can be used as the polymer (A-2) include acrylic, maleic, urethane, polyester, and the like. Further, from the viewpoint of strengthening the adsorption to the pigment and stabilizing the pigment dispersion even after the crosslinking reaction, it is preferable to use a polymer having an aromatic ring in the structure as the polymer (A-2).

[0057] In the present disclosure, the “acrylic polymer” refers to a polymer using at least one selected from the group consisting of acrylic acid, methacrylic acid, acrylic esters, and methacrylic esters as polymerizable monomers. In addition to the above-listed polymerizable monomers, a styrenic monomer may be further used as the polymerizable monomer constituting the acrylic polymer. However, a polymer containing (anhydrous) maleic acid (at least one selected from “maleic acid” and “maleic anhydride”) as a polymerizable monomer is excluded from the “acrylic polymer” in the present disclosure. The “maleic polymer” refers to a polymer using at least (anhydrous) maleic acid as a polymerizable monomer. The maleic polymer may be one in which an α-olefin, acrylic acid, methacrylic acid, acrylic ester, methacrylic ester, styrenic monomer, or the like is further used as the polymerizable monomer.

[0058] Polymer (A-2) preferably has at least a carboxylate group. This is because the charge repulsion due to the charge of the carboxylate group can stably disperse the crosslinked polymer particles containing the pigment. Further, the carboxylate group may be formed by neutralizing at least a part of the carboxyl groups present in the polymer in advance with a basic compound (neutralization treatment). Examples of the basic compound include ammonia; alkanolamines such as dimethylaminoethanol, diethanolamine, and triethanolamine; and alkali metal compounds such as lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide, disodium carbonate, sodium hydrogen carbonate, dipotassium carbonate, and sodium borate. Among these, from the viewpoint that the dispersion stability of the crosslinked polymer particles containing the pigment is good and pigment aggregation can be suppressed even in the drying process of the ink, resulting in a printed matter with excellent printing density and color reproducibility, alkali metal compounds can be preferably used, and sodium hydroxide and potassium hydroxide, which are hydroxides, can be particularly preferably used. The above-listed basic compounds may be used alone or in combination of two or more kinds.

[0059] As the polymer (A-2), for example, a polymer having only carboxyl groups (hereinafter referred to as polymer (A-2A)) may be used as it is, or a polymer obtained by neutralizing at least a part of the carboxyl groups in the polymer (A-2A) (neutralization treatment) may be used. In the latter case, when the amount of the basic compound used to neutralize the carboxyl groups in the polymer (A-2A) is expressed by the neutralization rate described below, the neutralization rate is preferably 10 to 200 mol%, more preferably 40 to 160 mol%, from the viewpoint of improving the dispersion stability of the pigment. Particularly preferably, it is 60 to 120 mol%. The above neutralization rate can be determined by the following formula 3.

[0060]

Equation

[0061] The "acid value of the polymer" also present in the above formula 3 can be measured by a conventional method. For example, about 1 g of the sample is precisely weighed into an Erlenmeyer flask, and 50 ml of a distilled water / dioxane mixture (mixing mass ratio: distilled water / dioxane = 1 / 9) is added and dissolved. Then, using a potentiometric titrator (the "Automatic Potentiometric Titrator AT-710M" manufactured by Kyoto Electronics Industry Co., Ltd.) for the above sample solution, titration is performed with a 0.1 mol / L potassium hydroxide-ethanol solution (titer F), and the amount (α (mL)) of the potassium hydroxide-ethanol solution required until the titration endpoint is measured. And the acid value (mgKOH / g) of the polymer can be calculated by the following formula 4.

[0062] Acid value (mgKOH / g) = {(5.611 × α × F) / S} Formula 4

[0063] In the above formula 4, S is the sampling amount (g) of the polymer as the sample, α is the amount (ml) of the 0.1 mol / L potassium hydroxide-ethanol solution used until the titration endpoint, and F is the titer of the 0.1 mol / L potassium hydroxide-ethanol solution.

[0064] The acid value of the polymer (A-2) that can be measured by the above-described method is preferably 60 to 180 mgKOH / g, more preferably 70 to 160 mgKOH / g, and particularly preferably 80 to 150 mgKOH / g, in terms of being able to improve the dispersion stability of the pigment, being able to improve the drying property of the aqueous inkjet ink, and being able to suppress the desorption of the polymer from the pigment even during drying after printing, so that a printed matter excellent in printing density and color reproducibility can be obtained.

[0065] The weight average molecular weight (Mw) of the polymer (A-2) is preferably from 5,000 to 100,000. By setting the weight average molecular weight to 5,000 or more, the dispersion stability can be made suitable, and by setting it to 100,000 or less, the ejection stability can be made good. More preferably, the weight average molecular weight is from 10,000 to 50,000, and still more preferably from 15,000 to 35,000.

[0066] The weight average molecular weight of the polymer can be measured by a conventional method. For example, a value measured as the weight average molecular weight in terms of polystyrene measured using a TSKgel column (manufactured by Tosoh Corporation) with a GPC equipped with an RI detector (Tosoh Corporation's "HLC-8120GPC") using THF as the eluent can be used.

[0067] The ratio of the content of the pigment to the content of the polymer (A-2) (pigment / polymer (A-2)) is preferably from 1 / 1 to 100 / 1 by mass ratio. By setting the above ratio to 1 / 1 or more, the viscosity of the ink can be suppressed within a suitable range as an inkjet ink, and by setting it to 100 / 1 or less, the dispersibility, as well as the dispersion stability and ejection stability after dispersion, can be made good. More preferably, the ratio of the contents of the pigment and the polymer (A-2) is from 2 / 1 to 50 / 1.

[0068] <Production of Aqueous Dispersion of Crosslinked Polymer Particles (A) Containing Pigment> As a method for producing an aqueous dispersion of crosslinked polymer particles (A) containing a pigment, for example, a method of sequentially performing a neutralization treatment step, a dispersion treatment step, and a crosslinking treatment step shown below can be mentioned. First, a polymer (A-2A) having only carboxy groups and a basic compound are mixed in an aqueous medium (a medium composed of a liquid containing at least water) to neutralize at least a part of the carboxy groups (neutralization treatment step). The polymer obtained after the neutralization treatment step is used as polymer (A-2) in the subsequent steps. Note that the polymer (polymer (A-2)) obtained after the neutralization treatment step is in the state of an aqueous solution (a solution containing an aqueous medium and components dispersed and / or dissolved in the aqueous medium). Next, a pigment is added to the aqueous solution of the polymer (A-2), and after mixing the two, a dispersion treatment is further performed (dispersion treatment step). By the dispersion treatment step, an aqueous dispersion of pigment particles (crosslinked polymer particle precursors) on the surface of which polymer (A-2) is chemically adsorbed is obtained. Thereafter, compound (A-1) is added to the aqueous dispersion of the crosslinked polymer particle precursors, and a crosslinking treatment is performed (crosslinking treatment step). By the crosslinking treatment step, an aqueous dispersion of crosslinked polymer particles (A) containing a pigment can be produced.

[0069] <<Dispersion treatment>> In the dispersion treatment of the pigment, it is preferable to pre-disperse (premix) the pigment and polymer (A-2) using a commonly used mixing and stirring device such as a disper, and then perform dispersion (main dispersion) using a conventionally known disperser. By performing pre-dispersion before the main dispersion, a pigment dispersion having a uniform particle size can be obtained. Also, as the disperser used for the main dispersion of the pigment, generally used dispersers can be arbitrarily used, and examples include a ball mill, a roll mill, a kneader, a sand mill, a bead mill, and a high-pressure homogenizer. Among these, from the viewpoint of being able to crush and refine coarse particles of the pigment, a bead mill can be preferably used. Examples of the bead mill include a super mill, a sand grinder, an agitator mill, a Glen mill, a dyno mill, a pearl mill, and a cobol mill (all are trade names), and any of them can be suitably used.

[0070] <<Crosslinking treatment>> In the crosslinking treatment, in an aqueous dispersion of crosslinkable polymer particles precursors, the polymer (A-2) adsorbed on the pigment is crosslinked by the compound (A-1). As a result, a crosslinked polymer is formed, and an aqueous dispersion of crosslinked polymer particles (A) containing the pigment can be obtained.

[0071] From the viewpoint of enabling the crosslinking reaction to proceed efficiently, the temperature of the crosslinking treatment is preferably 50 to 95°C, more preferably 70 to 85°C. Also, from the same viewpoint as above, the time of the crosslinking treatment is preferably 0.5 to 10 hours, more preferably 1 to 8 hours, and even more preferably 2 to 5 hours.

[0072] From the viewpoint of enabling the ink to be stably discharged from the nozzle, the average particle size of the crosslinked polymer particles (A) containing the pigment is preferably 60 to 200 nm, more preferably 70 to 175 nm, and particularly preferably 80 to 150 nm.

[0073] The above "average particle size" refers to the median diameter on a volume basis and can be measured by the dynamic light scattering method. For example, it can be measured using "NanoTrack UPA-EX150" manufactured by Microtrac Bell Corporation under an environment of 25°C.

[0074] The pH of the aqueous dispersion of the crosslinked polymer particles (A) containing the pigment is preferably 8 to 12. If the pH is 8 or more, the carboxy groups in the crosslinked polymer tend to become carboxylate groups, and due to suitable charge repulsion, it becomes possible to enhance the dispersion stability of the above crosslinked polymer particles (A). Also, the more preferable pH value is 9 to 11.

[0075] Incidentally, the pH of the aqueous dispersion can be measured by a conventional method. For example, it can be measured using a desktop pH meter "F-71" (manufactured by Horiba, Ltd.) using a pH electrode "6337-10D" (manufactured by Horiba, Ltd.) under an environment of 25°C.

[0076] <Surfactant (B)> The ink of the present embodiment contains, as the surfactant (B), the compound (B-1) represented by the above general formula 1 and a nonionic surfactant (B-2) having an HLB value of 1 to 10.

[0077] <<Compound (B-1)>> As described above, since the compound (B-1) is compatible with the crosslinked polymer and the nonionic surfactant (B-2), it is possible to obtain a printed matter excellent in dot roundness, printing density, and color reproducibility while suppressing white spots and bleeding of color mixture. In particular, from the viewpoint of obtaining a printed matter having excellent printing density and color reproducibility, n in the general formula 1 is an integer of 20 to 100, more preferably 25 to 65, and particularly preferably 25 to 50. Since the compound (B-1) contains a hydrophobic part and a hydrophilic part, it can preferably show compatibility with a surfactant (B-2) having high hydrophobicity in the ink.

[0078] Also, from the viewpoint of improving the affinity with the surfactant (B-2) described later and obtaining a printed matter excellent in dot roundness, R in the general formula 1 1 The group represented by is a linear or branched alkyl group having 10 to 25 carbon atoms, and more preferably a linear or branched alkyl group having 12 to 22 carbon atoms.

[0079] Furthermore, from the point that the surfactant (B-2) can be preferably stabilized in the aqueous inkjet ink, the suppression of white spots and bleeding of color mixture in the printed matter becomes easy, the point of obtaining a printed matter having excellent printing density and color reproducibility, and further, from the point of improving the ejection stability of the above aqueous inkjet ink, in the general formula 1, when the number of carbon atoms of the alkyl group represented by R 1 is CE, the value of n in the general formula 1 is preferably an integer included between CE × 1.30 and CE × 4.60 (however, when CE × 1.30 and CE × 4.60 are integers, those integers are also included), and particularly preferably an integer included between CE × 1.60 and CE × 3.50 (however, when CE × 1.60 and CE × 3.50 are integers, those integers are also included).

[0080] Also, the HLB value of compound (B-1) is preferably from 14.0 to 19.4, more preferably from 15.8 to 19.0, and particularly preferably from 16.6 to 18.2. If the HLB value of compound (B-1) is within the above range, it becomes easier to suppress white spots and bleeding of color mixing in printed matter, improve printing density and color reproducibility, and further improve the ejection stability of aqueous inkjet ink. The method for calculating the HLB value of compound (B-1) is the same as that for the nonionic surfactant (B-2) described later.

[0081] The above compound (B-1) may be obtained by synthesizing it by a conventionally known method, or a commercially available product may be used. Examples of commercially available products of compound (B-1) include the Emulgen series manufactured by Kao Corporation, the Nonion series manufactured by NOF Corporation, the EMALEX series manufactured by Nippon Emulsion Co., Ltd., the NIKKOL series manufactured by Nikko Chemicals Co., Ltd., the Emalmin series and Sun Nonic series manufactured by Sanyo Chemical Industries, Ltd., and the Braunon series and Fine Surf series manufactured by Aoki Yushi Industry Co., Ltd. However, commercially available products that can be used as compound (B-1) are not limited to these.

[0082] The content of compound (B-1) is preferably 0.01 to 2% by mass, more preferably 0.1 to 1% by mass, based on the total amount of the aqueous inkjet ink. By setting the content to 0.01% by mass or more, the effects of the above-described compound (B-1) can be exhibited, and by setting the content to 2% by mass or less, the drying property of the ink on a hardly absorbent printing substrate can be made suitable.

[0083] <<Nonionic surfactant (B-2)>> The surfactant (B-2) used in this embodiment has an HLB value of 1 to 10. The HLB (Hydrophile-Lipophile Balance) value is one of the parameters representing the hydrophilicity and hydrophobicity of a material. As methods for calculating the HLB value, various methods such as the Griffin method, the Davis method, and the Kawakami method are known. In the present disclosure, the HLB value is calculated using the Griffin method.

[0084] Generally, the Griffin method is used for nonionic materials. In the above Griffin method, the HLB value is determined by the following formula 5 using the molecular weight of the target material. Note that the smaller the HLB value, the higher the hydrophobicity of the material, and the larger the HLB value, the higher the hydrophilicity of the material.

[0085] HLB value = 20 × (sum of molecular weights of hydrophilic moieties) ÷ (molecular weight of the material) Formula 5

[0086] The nonionic surfactant (B-2) used in this embodiment is not particularly limited as long as it is a surfactant with an HLB value of 1 to 10. For example, acetylene diol-based surfactants, acetylene monoalcohol-based surfactants, silicone-based surfactants, fluorine-based surfactants, sorbitan fatty acid ester-based surfactants, glycerin fatty acid ester-based surfactants, polyoxyalkylene alkyl ether-based surfactants (excluding compounds corresponding to the general formula (1)), polyoxyalkylene alkylamine-based surfactants, etc. can be arbitrarily used. Further, these surfactants may be used alone or in combination of two or more. On the other hand, from the viewpoint of obtaining a printed matter with no white spots and no bleeding of color mixture and excellent dot roundness on a poorly absorbent printing substrate, among the above-listed surfactants, as the surfactant (B-2), it is preferable to use an acetylene diol-based surfactant and / or a silicone-based surfactant, and it is more preferable to use an acetylene diol-based surfactant and a silicone-based surfactant in combination.

[0087] Since acetylene diol-based surfactants are excellent in the orientation speed at the interface, the wettability and penetrability of the ink are improved, and it becomes easy to obtain a printed matter without white spots and bleeding of color mixture, so they can be preferably used. When using an acetylene diol-based surfactant as the nonionic surfactant (B-2), from the viewpoint that a printed matter having excellent print quality can be produced even for a poorly absorbent printing substrate, the HLB value is preferably 1 to 8, more preferably 1 to 4. Further, as specific examples of the acetylene diol-based surfactant having an HLB value of 1 to 4, for example, 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol, hexadeca-8-yne-7,10-diol, 4,7-dipropyl-deca-5-yne-4,7-diol, 6,9-dimethyl-tetradeca-7-yne-6,9-diol, 3,6-diisopropyl-2,7-dimethyloct-4-yne-3,6-diol, octadeca-9-yne-8,11-diol, 7,10-dimethylhexadeca-8-yne-7,10-diol, 5,8-dibutyldodeca-6-yne-5,8-diol, 4,7-diisobutyl-2,9-dimethyl-deca-5-yne-4,7-diol, 5,14-diethyl-8,11-dimethyloctadeca-9-yne-8,11-diol and the like can be mentioned. Among them, from the viewpoint that sufficient wettability and penetrability on a poorly absorbent printing substrate can be imparted to the ink and a printed matter having excellent print quality can be obtained, it is preferable to use one or more compounds selected from the group consisting of 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol, hexadeca-8-yne-7,10-diol, and 2,4,7,9-tetramethyl-5-decyne-4,7-diol. Note that only one kind of the above compounds may be used, or two or more kinds may be used in combination. Also, the above compounds may be those synthesized by a conventionally known method, or commercially available products may be used.

[0088] The blending amount of the acetylene diol-based surfactant is preferably 0.1 to 3% by mass, more preferably 0.5 to 2% by mass, and still more preferably 0.8 to 1.5% by mass in the total amount of the aqueous inkjet ink.

[0089] On the one hand, although the silicon-based surfactant has a slower orientation speed at the interface than the acetylene diol-based surfactant, it has a high ability to lower the surface tension and can be preferably used from the viewpoints of reducing the color mixing bleeding between dots and improving the dot roundness because it is uniformly oriented at the interface. In this embodiment, the HLB value of the silicon-based surfactant is also calculated using the Griffin method.

[0090] The blending amount of the silicon-based surfactant having an HLB value of 1 to 10 is preferably 0.1 to 5% by mass, more preferably 0.5 to 3% by mass, and still more preferably 0.8 to 2.5% by mass in the total amount of the ink.

[0091] Also, from the viewpoint of improving the compatibility with the crosslinked polymer and obtaining excellent printing image quality with less dot roundness and color mixing bleeding by uniformly wetting and spreading on the printing substrate, as the silicon-based surfactant having the above HLB value of 1 to 10, it is preferable to use a gemini-type silicon-based surfactant and / or a polyether-modified silicon-based surfactant (excluding those that are gemini-type silicon-based surfactants). More preferably, it is a gemini-type silicon-based surfactant and / or a both-end polyether-modified silicon-based surfactant.

[0092] <<Gemini-Type Silicon-Based Surfactant>> Generally, a gemini-type surfactant has a structure in which surfactants having a hydrophilic structure and a hydrophobic structure are linked by a linking group (spacer) or a covalent bond. Also, in the case of a gemini-type silicon-based surfactant, for example, a hydrophobic structure represented by a siloxane chain (—[SiR 1 R 2 —O]n—, where R 1 and R 2 are each an arbitrary organic group and n is an integer of 2 or more.) and a hydrophilic structure (for example, a polyether chain) have the following structure. · A structure in which the bonding points of the siloxane chain and the hydrophilic structure are present in the middle of the siloxane chain and the middle of the hydrophilic structure, respectively. · A structure in which a plurality of siloxane chains are bonded via a linking group or the like (for example, R in the structural formula of the siloxane chain 1 and / or R 2 at least a part of which is an organic chain containing a siloxane chain). · A structure in which, in a plurality of silicone-based surfactants each having a plurality of hydrophilic structures, a part of the hydrophilic structures is shared.

[0093] Gemini surfactants are excellent in the ability to lower the surface tension compared to general surfactants. Therefore, by using a Gemini-type silicone-based surfactant, a reduction in surface tension superior to that of general silicone-based surfactants can be achieved. As a result, the wettability of an aqueous inkjet ink containing a Gemini-type silicone-based surfactant can be significantly improved, and in addition to the above-mentioned improvement in color bleeding between dots and dot roundness, a printed matter without white spots and excellent in printing density and color reproducibility can be obtained.

[0094] Examples of commercially available Gemini-type silicone-based surfactants include TEGO Twin 4000, TEGO Twin 4100, TEGO Twin 4200 manufactured by Evonik Degussa, and KF-6100, KF-6104, KF-6105, KF-6106, KF-6115 manufactured by Shin-Etsu Chemical Co., Ltd., etc.

[0095] <<Polyether-modified silicone-based surfactant (excluding Gemini-type silicone-based surfactant)>> Examples of the above polyether-modified silicone-based surfactant (excluding those that are Gemini-type silicone-based surfactants) that can be used in the aqueous inkjet ink of the present embodiment include compounds having a structure represented by the following general formula 6.

[0096]

Chemical formula

[0097] In General Formula 6, p is an integer from 0 to 99, and q is an integer from 1 to 100. However, p + q is an integer from 1 to 100. Also, R 3 is a methyl group or has a structure represented by the following General Formula 7, and R 4 is an alkyl group having 1 to 6 carbon atoms or has a structure represented by the following General Formula 7. However, when R 3 is a methyl group, p is 0. Also, at least one of R 3 and R 4 has a structure represented by the following General Formula 7 (R 3 and R 4 may both have a structure represented by the following General Formula 7.).

[0098]

Chemical Formula

[0099] In General Formula 7, r is an integer from 1 to 6, s is an integer from 1 to 50, and t is an integer from 0 to 50. However, s + t is an integer from 1 to 100. Also, R 5 is any one of a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an acrylic group, or a methacrylic group. Note that the addition pattern of the ethylene oxide group and the propylene oxide group in [ ] may be either block or random.

[0100] The polyether-modified silicone-based surfactant represented by the above General Formula 6 can be preferably used in terms of improving dot-to-dot color mixing bleeding and white spots. Also, when R 4 in the above General Formula 6 has a structure represented by General Formula 7 and R 3 does not have a structure represented by General Formula 7 (also described as "both-terminal polyether-modified silicone-based surfactant" in the present disclosure), it is likely to be uniformly oriented at the interface. In addition to improving color mixing bleeding and white spots, the dot roundness is particularly improved, so it can be particularly preferably used in the present invention.

[0101] Examples of commercially available products of the above-mentioned polyether-modified silicone surfactants with both ends include BY16-201, SF8427 manufactured by Toray Dow Corning, BYK-331, BYK-333, BYK-UV3500, BYK-3420 manufactured by BYK Chemie, TEGO Glide 410, TEGO Glide 432, TEGO Glide435, TEGO Glide440, TEGO Glide450 manufactured by Evonik Degussa, Silface SWP-001, Silface SAG003, Silface SAG005 manufactured by Nissin Chemical Industry Co., Ltd., and the like.

[0102] In addition, R in the general formula 6 3 has a structure represented by the general formula 7, and examples of commercially available products of polyether-modified silicone surfactants (also described as "side-chain polyether-modified silicone surfactants" in the present disclosure) in which R 4 does not have a structure represented by the general formula 7 include SF8428, FZ-2162, 8032ADDITIVE, SH3749, FZ-77, L-7001, L-7002, FZ-2104, FZ-2110, F-2123, SH8400, SH3773M manufactured by Toray Dow Corning, BYK-345, BYK-346, BYK-347, BYK-348, BYK-349 manufactured by BYK Chemie, TEGO Wet 240, TEGO Wet 250, TEGO Wet 260, TEGO Wet 270, TEGO Wet 280 manufactured by Evonik Degussa, KF-351A, KF-352A, KF-353, KF-354L, KF355A, KF-615A, KF-640, KF-642, KF-643 manufactured by Shin-Etsu Chemical Co., Ltd., and the like.

[0103] The total content of gemini-type silicone surfactants and polyether-modified silicone surfactants (excluding those that are gemini-type silicone surfactants) is preferably 0.4 to 3% by mass, more preferably 0.5 to 2% by mass, in the total amount of the aqueous inkjet ink.

[0104] The ratio (compound (B-1): surfactant (B-2)) of the content of the compound (B-1) represented by the general formula 1 and the content of the nonionic surfactant (B-2) having an HLB value of 1 to 10 used in this embodiment is 1:1.2 to 1:20 by mass ratio. The above ratio is more preferably 1:2 to 1:15, and even more preferably 1:3 to 1:10. By blending at the above-mentioned suitable ratio, the nonionic surfactant (B-2) can be emulsified by the compound (B-1). As a result, the nonionic surfactant (B-2) can be uniformly oriented on the interface of the ink, and even on a poorly absorbent printing substrate, the ink can uniformly wet and spread, and the penetrability is also improved. And a printed matter excellent in dot roundness can be obtained while suppressing whiteout and color bleeding. In addition, by using the compound (B-1) and the surfactant (B-2) in combination at the above mixing ratio, even in the drying process of the ink after printing, the surfactant (B-2) and the crosslinked polymer can maintain a compatible state, and as a result of suppressing the separation of each material, a printed matter having excellent printing density and color reproducibility can be obtained even after drying. Further, by setting the ratio to the above-mentioned suitable ratio, it is possible to suppress the non-uniform orientation of the surfactant (B-2) at the nozzle end face of the inkjet head, and it becomes possible to obtain stable ejection performance.

[0105] <Organic solvent> The ink of this embodiment may contain an organic solvent. From the viewpoints of adjusting the wettability and penetrability of the ink on the printing substrate, controlling the printing image quality and drying property by the adjustment, ensuring and improving the ejection stability from the inkjet nozzle, etc., the following compounds are preferably selected as the organic solvent.

[0106] In the present disclosure, the "organic solvent" represents an organic compound that is liquid at 45°C.

[0107] From the viewpoint that even a poorly absorbent printing substrate can ensure wettability and penetrability and a printed matter having excellent printing image quality can be obtained, among organic solvents, it is preferable to select a compound that is liquid at 25°C and has a surface tension of 20 to 30 mN / m at 25°C.

[0108] In the present disclosure, the "surface tension at 25°C" refers to the surface tension measured by the Wilhelmy method (plate method, vertical plate method) in an environment of 25°C. Specifically, for example, it can be measured using a platinum plate in an environment of 25°C with a surface tensiometer (CBVP-Z manufactured by Kyowa Interface Science Co., Ltd.).

[0109] Also, from the viewpoint of having suitable compatibility with the above-described surfactant and being able to impart excellent wettability and penetrability to the ink even on a hardly absorbent printing substrate, and obtaining a printed matter without white spots and color bleeding, as the above organic solvent, it is preferable to include an alkanediol-based solvent having 5 to 8 carbon atoms and / or a (poly)alkylene glycol monoalkyl ether-based solvent having 5 to 9 carbon atoms.

[0110] In the present disclosure, the "(poly)alkylene glycol monoalkyl ether-based solvent" represents at least one solvent selected from the group consisting of an alkylene glycol monoalkyl ether-based solvent and a polyalkylene glycol monoalkyl ether-based solvent.

[0111] Examples of the alkanediol-based solvent having 5 to 8 carbon atoms include, but are not limited to, 1,5-pentanediol, 1,2-pentanediol, 3-methyl-1,5-pentanediol, 3-methyl-1,3-butanediol, 1,2-hexanediol, 1,6-hexanediol, 2-methyl-2,4-pentanediol, 1,2-octanediol, 2-ethylhexane-1,3-diol, etc.

[0112] In addition, examples of the (poly)alkylene glycol monoalkyl ether solvents having 5 to 9 carbon atoms include ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, etc., but are not limited thereto. Among these, from the viewpoint that an aqueous inkjet ink having excellent drying properties can be obtained even on a poorly absorbent printing substrate and a printed matter having excellent printing quality can be obtained, as the (poly)alkylene glycol monoalkyl ether solvent having 5 to 9 carbon atoms, a (poly)propylene glycol monoalkyl ether solvent can be preferably used.

[0113] Note that the above “(poly)propylene glycol monoalkyl ether” represents “propylene glycol monoalkyl ether” and / or “polypropylene glycol monoalkyl ether”.

[0114] The inkjet ink of this embodiment can also preferably use organic solvents other than the compounds exemplified above. For example, ethanol, isopropanol, 2-butanol, tert-butanol, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, ethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol diethyl ether, dipropylene glycol dimethyl ether, γ-butyrolactone, etc. can be mentioned.

[0115] In the inkjet ink of the present embodiment, as long as the print quality and drying property are not impaired, a high-boiling organic solvent can be used. From the viewpoint of obtaining an aqueous inkjet ink that has sufficient drying property even on a poorly absorbent printing substrate and can obtain a printed matter with suppressed color mixing bleeding, the content of a high-boiling organic solvent having a boiling point of 230°C or higher (and, for example, 400°C or lower) at 1 atm is preferably 15% by mass or less (0% by mass is also possible) in the total amount of the aqueous inkjet ink, and more preferably 10% by mass or less (0% by mass is also possible). In the present disclosure, "0% by mass" means that the target organic solvent is not contained.

[0116] Further, from the viewpoint of obtaining a printed matter that has no color mixing bleeding, is excellent in print density and color reproducibility, and also has good coating film resistance, the content of an ultra-high-boiling organic solvent having a boiling point of 270°C or higher (and, for example, 400°C or lower) at 1 atm is preferably 5% by mass or less (0% by mass is also possible) with respect to the total amount of the aqueous inkjet ink, more preferably 2.5% by mass or less (0% by mass is also possible), and particularly preferably 1% by mass or less (0% by mass is also possible).

[0117] Specific examples of the high-boiling organic solvents having a boiling point of 230°C or higher under 1 atm as described above include glycerin, 1,2,4-butanetriol, 1,2,6-hexanetriol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, triethylene glycol monomethyl ether, tetraethylene glycol dimethyl ether, 2-pyrrolidone, N-methyloxazolidinone, ε-caprolactone, and the like. Among the above-exemplified organic solvents, those corresponding to the ultra-high-boiling organic solvents having a boiling point of 270 or higher under 1 atm include glycerin, 1,2,4-butanetriol, 1,2,6-hexanetriol, triethylene glycol, tetraethylene glycol, tetraethylene glycol dimethyl ether, and the like.

[0118] In this embodiment, the boiling point under 1 atm can be measured, for example, using a thermal analyzer.

[0119] The organic solvent used in the ink of this embodiment preferably has a boiling point (weighted average value) of 100 to 230°C under 1 atm, more preferably 120 to 220°C, and particularly preferably 150 to 210°C under 1 atm. If the boiling point (weighted average value) is 100°C or higher, drying of the ink on the inkjet head can be suppressed, and ejection stability is improved. Further, if the boiling point (weighted average value) is 230°C or lower, drying failure does not occur even on a poorly absorbent printing substrate, and color bleeding due to the remaining organic solvent does not occur. As a result, it becomes possible to obtain a printed matter having excellent drying properties and printing image quality. Furthermore, if the boiling point (weighted average value) is 230°C or lower, the abrasion resistance is improved even in a printed matter on a poorly absorbent printing substrate such as coated paper. In addition, the remaining organic solvent does not deteriorate the compatibility state between the above-described surfactant and the crosslinked polymer, and the printing density and color reproducibility of the printed matter are improved.

[0120] In the present disclosure, the description of "boiling point (weighted average value) of organic solvent" refers to the boiling point of the organic solvent when there is only one type of organic solvent contained in the target composition, and when two or more types of organic solvents are contained, it refers to the weighted average value of the boiling points of the two or more types of organic solvents. Further, the weighted average value of the boiling points under 1 atm is a value obtained by adding up the multiplication values of the boiling points under 1 atm calculated for each organic solvent and the mass ratio to the total content of the organic solvents.

[0121] The total content of the organic solvents contained in the aqueous inkjet ink of the present embodiment is preferably 5 to 40% by mass based on the total amount of the aqueous inkjet ink. Among them, from the viewpoint that sufficient wettability and penetrability can be ensured even on a poorly absorbent printing substrate, a printed matter with excellent print quality can be obtained, and the drying property of the aqueous inkjet ink is also improved, the total content of the organic solvents contained in the aqueous inkjet ink of the present embodiment is more preferably 10 to 35% by mass based on the total amount of the aqueous inkjet ink, and particularly preferably 15 to 30% by mass.

[0122] <Binder resin> In the aqueous inkjet ink of the present embodiment, it is preferable to use a binder resin in order to improve the rubbing resistance of the printed matter and the ejection stability of the aqueous inkjet ink.

[0123] The "binder resin" in the present disclosure is a resin used to bind the ink film to the printing substrate, and the rubbing resistance and drying property of the ink film can be improved by the resin forming a film during the drying process and / or the resin molecules entangling with each other. From this viewpoint, for example, a resin mainly contained in the ink (specifically, a resin that occupies 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 70% by mass or more of the total amount of the resin contained in the ink) functions as a binder resin. Note that the crosslinked polymer constituting the crosslinked polymer particles (A) containing the above-described pigment may also serve as a binder resin.

[0124] As forms of the binder resin, water-soluble resins and resin particles are generally known. In the present disclosure, either one may be used alone, or both may be used in combination. Here, the above-mentioned "resin particles" are a form of a water-insoluble resin (a resin that is not a water-soluble resin), and refer to particles having an average particle diameter measured in the same manner as in the case of the crosslinked polymer particles (A) containing a pigment, which is 5 to 1000 nm.

[0125] When the aqueous inkjet ink of the present embodiment contains a binder resin, from the viewpoint of improving the compatibility with the above-described surfactant and obtaining a printed matter excellent in printing density and color reproducibility, and further from the viewpoint of improving the formation rate of the ink film in the drying process of the ink and obtaining a printed matter excellent in drying property and printing image quality, it is preferable to use a water-soluble resin.

[0126] The acid value of the above binder resin is preferably 1 to 50 mgKOH / g, and more preferably 2.5 to 40 mgKOH / g. By using a binder resin having the above acid value, it becomes possible to improve the formation rate of the ink film even on a hardly absorbent printing substrate, and a printed matter having excellent printing image quality and drying property can be obtained. Also, the control of the above acid value is effective from the viewpoint of improving the ejection stability of the aqueous inkjet ink.

[0127] The acid value of the binder resin can be measured using the same method as the acid value of the polymer (A-2) described above.

[0128] Further, the glass transition temperature of the binder resin is preferably 60 to 140°C, more preferably 70 to 135°C, and particularly preferably 80 to 130°C, from the viewpoints of improving the rubbing resistance and ejection stability of the printed matter.

[0129] The above glass transition temperature is a value measured using a DSC (differential scanning calorimeter), and can be measured, for example, as follows in accordance with JIS K 7121. Weigh approximately 2 mg of a dried resin sample on an aluminum pan, and set the aluminum pan as a test container in a holder inside a DSC measuring device (for example, "DSC-60Plus" manufactured by Shimadzu Corporation). Then, perform the measurement under a temperature increase condition of 5°C / min, and define the temperature of the intersection of the baseline on the low temperature side and the tangent line at the inflection point read from the obtained DSC chart as the glass transition temperature in the present disclosure.

[0130] <<Resin particles>> When using resin particles as the above binder resin, examples of the types of resins that can be used as the resin particles include acrylic, epoxy, urethane, styrene-butadiene, polyether, polyamide, polyester, vinyl chloride, or copolymers thereof (however, those containing a siloxane chain are excluded). Among them, from the perspective of being able to improve both the rubbing resistance and ejection stability of the printed matter, resin particles using at least one selected from the group consisting of acrylic, urethane, styrene-butadiene, and vinyl chloride are preferred, resin particles using at least one selected from the group consisting of acrylic and urethane are more preferred, and from the point of improving ejection stability, it is particularly preferred to use acrylic resin particles.

[0131] The above resin particles can be synthesized by a conventionally known method or commercially available products can be used. Also, there are no particular restrictions on its structure, and for example, resins having a random structure, block structure, comb structure, star structure, etc. can be used.

[0132] The content of resin particles in the total amount of the ink in this embodiment is preferably 1 to 10% by mass in terms of solid content, more preferably 2 to 8% by mass, and even more preferably 3 to 7% by mass. By setting the amount of resin particles within the above range, an aqueous inkjet ink excellent in the rubbing resistance and drying property of the printed matter can be obtained without reducing the storage stability and ejection stability.

[0133] <<Water-soluble resin>> On the other hand, when resin particles are used as the binder resin, examples of the types of resins that can be used as the water-soluble resin include acrylic, urethane, styrene-butadiene, vinyl chloride, maleic acid, polyester, etc. (however, those containing a siloxane chain are excluded). Among them, from the viewpoint of obtaining a printed matter excellent in abrasion resistance and print image quality, and further obtaining an ink excellent in drying property and ejection stability, it is preferable to use one or more resins selected from the group consisting of acrylic and urethane.

[0134] The water-soluble resin can be synthesized by a conventionally known method or a commercially available product can be used. Also, there is no particular limitation on its structure, and for example, resins having a random structure, block structure, comb structure, star structure, etc. can be used. Among them, from the viewpoint that the characteristics of the polymerizable monomers constituting the binder resin are sufficiently exhibited, it is preferable that the resin has a block structure or a comb structure. Note that each unit constituting the block structure and the comb structure may be formed from a single polymerizable monomer or may be a random copolymer of a plurality of types of polymerizable monomers.

[0135] The weight average molecular weight of the water-soluble resin used as the binder resin is preferably 5,000 to 50,000 from the viewpoint that the ejection stability from the inkjet nozzle can be ensured and a printed matter having excellent abrasion resistance can be obtained for various printing substrates, and more preferably 8,000 to 45,000 from the viewpoint of improving the compatible state with the above-described surfactant and obtaining a printed matter excellent in printing density and color reproducibility, and particularly preferably 10,000 to 40,000.

[0136] Note that the weight average molecular weight of the water-soluble resin can be measured in the same manner as the weight average molecular weight of the above-described polymer (A-2).

[0137] The content of the water-soluble resin with respect to the total amount of the ink is preferably 0.1 to 10% by mass in terms of solid content, more preferably 0.5 to 8% by mass, and still more preferably 1 to 5% by mass. By setting the amount of the water-soluble resin within the above range, an aqueous inkjet ink excellent in rubbing resistance and drying property of a printed matter can be obtained without deteriorating the dispersion stability and ejection stability.

[0138] <Water> The water contained in the aqueous inkjet ink of the present embodiment is preferably ion-exchanged water (deionized water), rather than general water containing various ions.

[0139] The content of the water contained in the ink of the present embodiment is preferably in the range of 20 to 90% by mass in the total mass of the ink.

[0140] <Other components> In addition to the above-described components, the ink of the present embodiment can be appropriately added with additives such as infrared absorbers, ultraviolet absorbers, and preservatives as necessary in order to obtain an ink having desired physical property values. The total amount of the blending amounts of these additives is preferably 0.01 to 10% by mass with respect to the total mass of the ink.

[0141] <Ink set> The ink of the present embodiment may be used alone, but can also be used as an ink set in which a plurality of colors are combined according to the application. The combination is not particularly limited, but a full-color image can be obtained by using three colors of cyan, yellow, and magenta. In addition, by adding black ink, the black color feeling can be improved and the visibility of characters and the like can be increased. Furthermore, it is also possible to improve the color reproducibility by adding colors such as orange and green. When printing on a printing substrate other than white, a clear image can be obtained by using white ink in combination.

[0142] <Method for preparing ink> As an example of a method for preparing the ink of the present embodiment containing the components as described above, the following method can be mentioned, but the method for preparing the ink of the present embodiment is not limited thereto.

[0143] First, a pigment dispersion is obtained by the method described above. Next, a binder resin, an organic solvent, a surfactant, and other components as described above are appropriately added to the pigment dispersion as necessary, stirred, and filtered as necessary to obtain the ink of the present disclosure.

[0144] Since the ink of the present embodiment is for inkjet recording, it is preferable to use a pigment having an optimal particle size distribution from the viewpoint of preventing nozzle clogging and the like. As a method for obtaining a pigment having a desired particle size distribution, the method of reducing the size of the grinding media of the disperser as mentioned above, the method of increasing the filling rate of the grinding media, the method of lengthening the processing time, the method of classifying with a filter or a centrifuge after grinding, and combinations of these methods can be mentioned. The average particle size of the ink can be measured by the same method as in the case of the average particle size of the crosslinked polymer particles (A) containing the pigment described above.

[0145] <Printing substrate> The ink of the present embodiment can be particularly preferably used for a poorly absorbent printing substrate. A poorly absorbent printing substrate is a printing substrate that does not absorb water or has a slow absorption rate. Specifically, it refers to a printing substrate having an absorption coefficient for water of 0 to 0.6 ml / m 2 msec 1 / 2 measured by the Bristow method (J.TAPPI paper pulp test method No. 51-87). The absorption coefficient can be measured, for example, by using an automatic scanning liquid absorber manufactured by Kumagai Riki Kogyo Co., Ltd. Specifically, using the above apparatus and water, the liquid absorption amount of water (ml / m 2 ) obtained during a contact time of 100 to 1000 milliseconds and the square root of the contact time (msec 1 / 2 ), the slope of the straight line obtained by the least squares method is taken as the absorption coefficient.

[0146] Specific examples of the poorly absorbent printing substrate include, for example, paper substrates such as coated paper, art paper, cast paper, lightly coated paper, synthetic paper, etc.; plastic substrates such as polycarbonate, rigid PVC, soft PVC, polystyrene, expanded polystyrene, PMMA, polypropylene, polyethylene, PET, etc.; metal substrates such as aluminum, stainless steel, etc.; glass, etc., but are not limited thereto. Note that the inkjet ink of the present embodiment can also be suitably used for printing substrates that are not poorly absorbent printing substrates, such as plain paper, fabric, wood, etc.

[0147] <Printing method> The inkjet ink of the present embodiment is used in a printing method (inkjet printing method) in which ink is ejected from the nozzles of an inkjet head and droplets of the ink are attached onto a printing substrate. Further, the ink attached onto the printing substrate preferably becomes a printed matter (a thing having at least a layer of an ink film on the printing substrate) after being dried by a drying method described later.

[0148] <<Drying method>> It is preferable that a printing apparatus (inkjet printer) in which the inkjet ink of the present embodiment is mounted and used in the above inkjet printing method is provided with a mechanism for drying the ink on the printing substrate. As the above drying method, any one of a method of directly contacting the ink with a heat source, a method of indirectly contacting the ink with a heat source, and a method of irradiating electromagnetic waves may be adopted, or a plurality of types may be used in combination. For example, by using the infrared drying method (a method of irradiating electromagnetic waves) and the hot air drying method (a method of directly contacting the ink with a heat source) in combination, the ink can be dried faster than when each is used alone. When adopting a hot air drying method, which is a method of directly contacting the ink with a heat source, from the viewpoint of preventing the bumping of the liquid components contained in the ink and obtaining a printed matter excellent in printing density, color reproducibility, and print image quality, it is preferable that the hot air temperature be 50 to 250°C. Further, when adopting a substrate heating method (a method of contacting the non-printing surface of the printing substrate with the heat source), which is a method of indirectly contacting the ink with the heat source, from the same viewpoint as in the case of the above-described hot air temperature, it is preferable that the temperature of the heat source be 35 to 100°C.

[0149] <Printed matter> According to some embodiments, it is possible to provide a printed matter obtained by printing the aqueous inkjet ink of the present embodiment described above on a printing substrate. This printed matter includes a printing substrate and an ink film formed by applying the aqueous inkjet ink of the present embodiment to the printing substrate. Since this printed matter forms an ink film with crosslinked polymer particles (A) and a surfactant (B), color mixing bleeding and white missing can be prevented, and it can be excellent in dot roundness and have good printing density and color reproducibility.

Examples

[0150] Hereinafter, the present disclosure will be described more specifically by way of examples and comparative examples. In the following description, "parts" and "%" represent "parts by mass" and "mass%" respectively unless otherwise specified.

[0151] <Manufacture of dispersion resin> All of the "dispersion resins" shown below correspond to the uncrosslinked polymer (A-2) described above. These dispersion resins are synthesized by the methods shown below and are the obtained ones.

[0152] <Production example of dispersion resin 1> 93.4 parts of methyl ethyl ketone was charged into a reaction vessel equipped with a gas inlet tube, a thermometer, a condenser, and a stirrer, and the vessel was purged with nitrogen gas. After heating the contents in the reaction vessel to 110°C, a mixture of 23 parts of acrylic acid, 47 parts of methyl methacrylate, and 30 parts of lauryl methacrylate, which are polymerizable monomers; and 6 parts of V-601 (manufactured by Fuji Film Wako Pure Chemical Corporation), which is a polymerization initiator, was dropped into the above reaction vessel over 2 hours. After the dropping was completed, the polymerization reaction was continued for 3 hours while maintaining the temperature of the contents in the reaction vessel at 110°C, then 0.6 part of V-601 was added, and the reaction was further continued at 110°C for 1 hour to obtain a dispersion resin 1 precursor having only a carboxy group as a hydrophilic group. The weight average molecular weight of the obtained dispersion resin 1 precursor was 18,000, and the acid value was 179 mgKOH / g. Thereafter, using the acid value of the above dispersion resin 1 precursor and Equation 3, the amount of potassium hydroxide required to make the neutralization rate 100% was calculated, and an aqueous potassium hydroxide solution having a concentration of 48 mass% containing an amount of potassium hydroxide equal to the obtained amount was added to convert the carboxy groups present in the dispersion resin 1 precursor into carboxylate groups (neutralization treatment). Then, after adding ion-exchanged water so that the solid content concentration became 20%, the solution was heated to 50°C and stirred for 1 hour while maintaining 50°C to obtain an aqueous solution of dispersion resin 1.

[0153] <Production Examples of Pigment Dispersion Resins 2 to 8> Except that the polymerizable monomers described in Table 1 were used as the polymerizable monomers, aqueous solutions of dispersion resins 2 to 8 (each having a solid content concentration of 20%) were obtained by the same raw materials and operations as in the case of dispersion resin 1.

[0154]

Table 1

[0155] Table 1 also describes the raw materials used in the above-described dispersion resin 1, as well as the weight average molecular weights and acid values of dispersion resins 1 to 8. The abbreviations described in Table 1 are as follows. ·St: Styrene · AA: Acrylic acid · MMA: Methyl methacrylate · LMA: Lauryl methacrylate

[0156] <Production Example of Dispersion Resin 9> Into a reaction vessel equipped with a gas introduction tube, thermometer, condenser, and stirrer, 26 parts of 1-octadecene, 18 parts of maleic anhydride, and 56 parts of N-phenylmaleimide, which are polymerizable monomers; and 100 parts of methyl ethyl ketone as a solvent were charged. After replacing with nitrogen gas, while stirring the contents in the reaction vessel, the contents were heated to 130°C. Next, while maintaining the temperature and stirring of the contents, 1.0 part of t-butylperoxy-2-ethylhexanoate, which is a radical polymerization initiator, was added dropwise over 2 hours. Then, while keeping the temperature of the contents at 130°C, stirring was continued for another 1 hour to carry out the polymerization reaction. Also, after the start of the polymerization reaction, the solid content concentration of the contents was measured at regular intervals, and the ratio (polymerization conversion rate) to the solid content concentration when it was assumed that all the charged polymerizable monomers had polymerized was calculated. And when the polymerization conversion rate reached 95% or more, the temperature in the reaction vessel was lowered to 60°C, and 33.0 parts of water (5 equivalents based on the charged amount of maleic anhydride) and 0.01 part of 1,8-diazabicyclo[5.4.0]undec-7-ene as a catalyst were added. Then, while stirring the contents in the reaction vessel, it was heated to 80°C, and after reaching 80°C, it was held at that temperature for 4 hours to ring-open maleic anhydride, thereby obtaining a precursor of dispersion resin 9 having only a carboxy group as a hydrophilic group. The weight average molecular weight of the obtained precursor of dispersion resin 9 was 20,000, and the acid value was 206 mgKOH / g. Thereafter, using the acid value of the above precursor of dispersion resin 9 and Equation 3, the amount of potassium hydroxide required to make the neutralization rate 100% was calculated, and by adding an aqueous potassium hydroxide solution with a concentration of 48 mass% containing an amount of potassium hydroxide equal to the obtained amount, the carboxy groups present in the precursor of dispersion resin 9 were converted into carboxylate groups (neutralization treatment). Then, after adding ion-exchanged water so that the solid content concentration became 20%, the solution was heated to 50°C and stirred for 1 hour while maintaining 50°C to obtain an aqueous solution of dispersion resin 9.

[0157] <Production Example of Dispersion Resin 10 - 25> Synthesis was carried out using the same raw materials and operations as in the case of dispersion resin 9, except that the types and amounts of the polymerizable monomers used were changed as described in Table 2, and aqueous solutions of dispersion resins 10 - 25 (each having a solid content concentration of 20%) were obtained.

[0158]

Table 2

[0159] In addition, Table 2 also describes the raw materials used in the above - mentioned dispersion resin 9, as well as the weight - average molecular weights and acid values of dispersion resins 9 - 25. Among the abbreviations described in Table 2, those not used in Table 1 are as follows. ·OctD: 1 - octadecene ·Manh: Maleic anhydride ·PMI: N - phenylmaleimide ·CMI: Cyclohexylmaleimide ·MI: Maleimide

[0160] <Production Example of Aqueous Dispersion of Cyan Pigment - Containing Cross - Linked Polymer Particle Precursor 1 (CB1)> 20 parts of LIONOL BLUE FG - 7351 (C.I.Pigment Blue 15:3 manufactured by Toyo Color Co., Ltd.) as a pigment, 25 parts of an aqueous solution of dispersion resin 1 (solid content concentration 20%), and 55 parts of ion - exchanged water were charged into a mixing container. After all the raw materials were charged and preliminary dispersion was carried out with a stirrer, fine dispersion was carried out using a 0.6 L dyno - mill filled with 1,800 g of zirconia beads with a diameter of 0.5 mm. After this fine dispersion, 33.3 parts of ion - exchanged water was added to the obtained mixture, and while heating the mixture at 60 °C, a part of the ion - exchanged water and methyl ethyl ketone were distilled off under reduced pressure. Then, by adjusting with ion - exchanged water so that the pigment concentration became 15%, an aqueous dispersion of cyan pigment - containing cross - linked polymer particle precursor 1 (CB1) was obtained.

[0161] <Production Example of Aqueous Dispersion of Cyan Pigment - Containing Cross - Linked Polymer Particles 1 (CP1)> 93.3 parts of an aqueous dispersion of cyan pigment-containing crosslinked polymer particle precursor 1 (CB1) obtained by the method described above, 1.4 parts of Denacol EX-321 (an epoxy compound manufactured by Nagase ChemteX Corporation, epoxy equivalent: 140 g / eq.), which is compound (A-1) (crosslinking agent) (the amount at which the functional group content shown in the above formula 2 is 90 mol%), and 5.3 parts of ion-exchanged water were put into a reaction vessel. Next, while stirring the contents in the reaction vessel, it was heated to 80°C, and after reaching 80°C, stirring was continued for 3 hours while maintaining the temperature to carry out a crosslinking reaction. Then, after cooling until the internal temperature of the reaction vessel reached room temperature (about 25°C), ion-exchanged water was added to adjust the solid content concentration, thereby obtaining an aqueous dispersion (pigment concentration 14%) of cyan pigment-containing crosslinked polymer particles 1 (CP1) in which the dispersion resin was crosslinked.

[0162] <Production Examples of Aqueous Dispersions of Cyan Pigment-Containing Crosslinked Polymer Particle Precursors 2 to 25 (CB2 to CB25)> Aqueous dispersions of cyan pigment-containing crosslinked polymer particle precursors 2 to 25 (CB2 to CB25) were obtained by the same raw materials and method as the aqueous dispersion of cyan pigment-containing crosslinked polymer particle precursor 1 (CB1), except that the dispersion resin was changed to dispersion resins 2 to 25 respectively. In all the aqueous dispersions, the pigment concentration was 15%.

[0163] <Production Examples of Aqueous Dispersions of Cyan Pigment-Containing Crosslinked Polymer Particles 2 to 46 (CP2 to CP46)> Aqueous dispersions of cyan pigment-containing crosslinked polymer particles 2 to 46 (CP2 to CP46) were obtained by the same method as the aqueous dispersion of cyan pigment-containing crosslinked polymer particles 1 (CP1), except that the types and amounts of the cyan pigment-containing crosslinked polymer particle precursors and compound (A-1) (crosslinking agent) used, and the amount of ion-exchanged water were changed as described in Table 3. In all the aqueous dispersions, the pigment concentration was 14%.

[0164]

Table 3

[0165] In addition, the abbreviation "V02" described in Table 3 and Tables 4 to 6 described later represents Carbodiite V-02 (carbodiimide compound, NCN equivalent: 590 (g / eq.)) manufactured by Nisshinbo Chemical Inc.

[0166] <Production Examples of Magenta Pigment-Containing Crosslinked Polymer Particles Precursors 1 to 25 (MB1 to MB25)> Aqueous dispersion of magenta pigment-containing crosslinked polymer particles precursor 1 (MB1) was obtained by the same raw materials and method as in the case of the aqueous dispersion of cyan pigment-containing crosslinked polymer particles precursor 1 (CB1), except that TOSHIKI RED 150TR (C.I. Pigment Red 150 manufactured by Tokyo Ink Co., Ltd.) was used as the pigment. The pigment concentration of the aqueous dispersion of magenta pigment-containing crosslinked polymer particles precursor 1 (MB1) is 15%. In addition, aqueous dispersions of magenta pigment-containing crosslinked polymer particles precursors 2 to 25 (MB2 to MB25) were obtained by the same raw materials and method as in the case of the aqueous dispersion of magenta pigment-containing crosslinked polymer particles precursor 1 (MB1), except that the dispersion resins were changed to dispersion resins 2 to 25 respectively. The pigment concentration is 15% for all the aqueous dispersions.

[0167] <Production Example of Magenta Pigment-Containing Crosslinked Polymer Particles 1 (MP1)> An aqueous dispersion of magenta pigment-containing crosslinked polymer particles 1 (MP1) was obtained by the same raw materials and method as in the case of the aqueous dispersion of cyan pigment-containing crosslinked polymer particles 1 (CP1), except that the aqueous dispersion of magenta pigment-containing crosslinked polymer particles precursor 1 (MB1) was used. The pigment concentration of the aqueous dispersion of magenta pigment-containing crosslinked polymer particles 1 (MP1) is 14%.

[0168] <Production Examples of Magenta Pigment-Containing Crosslinked Polymer Particles 2 to 46 (MP2 to MP46)> The amount of the magenta pigment-containing crosslinked polymer particle precursor, the crosslinking agent (compound (A-1)), and ion-exchanged water was changed as described in Table 4. Otherwise, aqueous dispersions of magenta pigment-containing crosslinked polymer particles 2 to 46 (MP2 to MP46) were obtained in the same manner as the aqueous dispersion of magenta pigment-containing crosslinked polymer particles 1 (MP1). In all the aqueous dispersions, the pigment concentration was 14%.

[0169]

Table 4

[0170] <Production Examples of Yellow Pigment-Containing Crosslinked Polymer Particles Precursors 1 to 25 (YB1 to YB25)> An aqueous dispersion of yellow pigment-containing crosslinked polymer particle precursor 1 (YB1) was obtained in the same raw materials and manner as the aqueous dispersion of cyan pigment-containing crosslinked polymer particle precursor 1 (CB1), except that FAST YELLOW 7413 (C.I. Pigment Yellow 74 manufactured by Sanyo Shikiso Co., Ltd.) was used as the pigment. The pigment concentration of the aqueous dispersion of yellow pigment-containing crosslinked polymer particle precursor 1 (YB1) was 15%. In addition, aqueous dispersions of yellow pigment-containing crosslinked polymer particle precursors 2 to 25 (YB2 to YB25) were obtained in the same raw materials and manner as the aqueous dispersion of yellow pigment-containing crosslinked polymer particle precursor 1 (YB1), except that the dispersion resins were changed to dispersion resins 2 to 25, respectively. In all the aqueous dispersions, the pigment concentration was 15%.

[0171] <Production Example of Yellow Pigment-Containing Crosslinked Polymer Particles 1 (YP1)> An aqueous dispersion of yellow pigment-containing crosslinked polymer particles 1 (YP1) was obtained in the same raw materials and manner as the aqueous dispersion of cyan pigment-containing crosslinked polymer particles 1 (CP1), except that the aqueous dispersion of yellow pigment-containing crosslinked polymer particle precursor 1 (YB1) was used. The pigment concentration of the aqueous dispersion of yellow pigment-containing crosslinked polymer particles 1 (YP1) was 14%.

[0172] <Production Examples of Yellow Pigment-Containing Crosslinked Polymer Particles 2 to 46 (YP2 to YP46)> The amounts of the yellow pigment-containing crosslinked polymer particle precursor, the crosslinking agent (compound (A-1)), and ion-exchanged water were changed as described in Table 5, and aqueous dispersions of yellow pigment-containing crosslinked polymer particles 2 to 46 (YP2 to YP46) were obtained in the same manner as the aqueous dispersion of yellow pigment-containing crosslinked polymer particles 1 (YP1). In all the aqueous dispersions, the pigment concentration was 14%.

[0173] [Table 5]

[0174] <Production Examples of Black Pigment-Containing Crosslinked Polymer Particles 1 to 25 (KB1 to KB25)> An aqueous dispersion of black pigment-containing crosslinked polymer particle precursor 1 (KB1) was obtained in the same raw materials and manner as the aqueous dispersion of cyan pigment-containing crosslinked polymer particle precursor 1 (CB1), except that PrinteX85 (carbon black manufactured by Orion Engineered Carbons) was used as the pigment. The pigment concentration of the aqueous dispersion of black pigment-containing crosslinked polymer particle precursor 1 (KB1) was 15%. In addition, aqueous dispersions of black pigment-containing crosslinked polymer particle precursors 2 to 25 (KB2 to KB25) were obtained in the same raw materials and manner as the aqueous dispersion of black pigment-containing crosslinked polymer particle precursor 1 (KB1), except that the dispersion resins were changed to dispersion resins 2 to 25, respectively. In all the aqueous dispersions, the pigment concentration was 15%.

[0175] <Production Example of Black Pigment-Containing Crosslinked Polymer Particles 1 (KP1)> An aqueous dispersion of black pigment-containing crosslinked polymer particles 1 (KP1) was obtained in the same raw materials and manner as the aqueous dispersion of cyan pigment-containing crosslinked polymer particles 1 (CP1), except that the aqueous dispersion of black pigment-containing crosslinked polymer particle precursor 1 (KB1) was used. The pigment concentration of the aqueous dispersion of black pigment-containing crosslinked polymer particles 1 (KP1) was 14%.

[0176] <Production Examples of Black Pigment-Containing Crosslinked Polymer Particles 2 to 46 (KP2 to KP46)> The amounts of the black pigment-containing crosslinked polymer particle precursor, the crosslinking agent (compound (A-1)), and ion-exchanged water were changed as described in Table 6, and aqueous dispersions of black pigment-containing crosslinked polymer particles 2 to 46 (KP2 to KP46) were obtained in the same manner as the aqueous dispersion of black pigment-containing crosslinked polymer particles 1 (KP1), except for the change. In all the aqueous dispersions, the pigment concentration was 14%.

[0177] [Table 6]

[0178] <Production Example of Binder Resin 1> 93.4 parts of butanol was charged into a reaction vessel equipped with a gas introduction tube, a thermometer, a condenser, and a stirrer, and replaced with nitrogen gas. After heating the contents in the reaction vessel to 110 °C, a mixture of 6 parts of acrylic acid, 64 parts of methyl methacrylate, 20 parts of 2-ethylhexyl acrylate, 10 parts of styrene, which are polymerizable monomers; and 6 parts of V-601 (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.), which is a polymerization initiator, was dropped into the above reaction vessel over 2 hours. After the dropping was completed, the polymerization reaction was continued for 3 hours while maintaining the contents in the reaction vessel at 110 °C, then 0.6 part of V-601 was added, and the reaction was further continued at 110 °C for 1 hour to obtain a solution of binder resin 1. Next, after cooling the solution of the binder resin 1 to room temperature, 7.1 parts of dimethylaminoethanol was added to neutralize the carboxy groups in the binder resin 1, and 100 parts of ion-exchanged water was further added. Then, the mixture was heated to 100 °C or higher, and after reaching 100 °C, the temperature was maintained to azeotrope butanol with water and distill off the butanol. Then, an aqueous solution of binder resin 1, which has a random structure and is a water-soluble resin, was obtained by adjusting with ion-exchanged water so that the solid content concentration became 40%. The weight average molecular weight of the obtained binder resin 1 was 19,000, and the acid value was 47 mgKOH / g.

[0179] <Production Examples of Binder Resins 2 to 10> An aqueous solution of binder resins 2 to 10, which have a random structure and are water-soluble resins, was obtained by the same raw materials and operations as in the case of binder resin 1, except that the types and amounts of the polymerizable monomers used were changed as described in Table 7. In all the aqueous solutions, the solid content concentration is 40%.

[0180]

Table 7

[0181] Among the abbreviations described in Table 7, those not used in Tables 1 to 2 are as follows. · MAA: Methacrylic acid · 2EHA: 2-Ethylhexyl acrylate · STMA: Stearyl methacrylate

[0182] <Production Example of Binder Resin 11> Binder resin 11 having an A-B block structure was produced using the method described in Example 21 of International Publication No. 2008 / 139980. Specifically, in the polymerization of the first block, acrylic acid was used as the polymerizable monomer, and the reaction was carried out at 80°C for 2 hours and then reprecipitated to obtain a first block copolymer with iodine added. Next, the above first block copolymer, and the polymerizable monomers styrene, methyl methacrylate, and 2-ethylhexyl acrylate were used in a mass ratio of 10:65.5:15, and the reaction was carried out at 80°C for 2.5 hours and then reprecipitated to replace the iodine addition site of the above first block with a second block composed of styrene, methyl methacrylate, and 2-ethylhexyl acrylate. Then, ion-exchanged water was added to the mixture and stirred well to completely dissolve the reaction product, thereby obtaining an aqueous solution (solid content concentration 40%) of binder resin 11 having an A-B block structure. The weight average molecular weight of the obtained binder resin 11 was 19,000, and the acid value was 37 mgKOH / g.

[0183] <Production Example of Binder Resin 12> A reaction vessel equipped with a thermometer, a condenser, a stirrer, and a dropping funnel was charged with 40 parts of ion-exchanged water and 0.2 part of Aqualon KH-10 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) as an emulsifier. On the other hand, 15 parts of 2-ethylhexyl acrylate, 69.5 parts of methyl methacrylate, 0.5 part of acrylic acid, 15 parts of styrene; 53 parts of ion-exchanged water; and 1.8 parts of Aqualon KH-10 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) as an emulsifier were charged into another mixing vessel equipped with a stirrer, and thoroughly stirred and mixed to form an emulsion. 5 parts of the above emulsion was taken and added to the above reaction vessel. After the addition, the mixture was heated until the internal temperature of the reaction vessel reached 60°C, and then the inside of the reaction vessel was thoroughly purged with nitrogen gas. Then, 3 parts of a 5% aqueous solution of potassium persulfate and 4 parts of a 1% aqueous solution of sodium metabisulfite were added to initiate the polymerization reaction. After the start of the polymerization reaction, while maintaining the internal temperature of the reaction vessel at 60°C, the remainder of the above emulsion, 2 parts of a 5% aqueous solution of potassium persulfate, and 6 parts of a 1% aqueous solution of sodium metabisulfite were added dropwise over 1.5 hours. After the completion of the dropwise addition, stirring was continued for another 2 hours. Then, after cooling the internal temperature of the reaction vessel to 30°C, diethylaminoethanol was added until the pH of the contents reached 8.5. And ion-exchanged water was added to adjust the solid content concentration to 40% to obtain an aqueous dispersion of the binder resin 12, which is resin particles. The acid value of the obtained binder resin 12 was 3 mgKOH / g.

[0184] <Production of Aqueous Inkjet Ink> The raw materials described in each column of Table 8 were charged into a mixing vessel equipped with a stirrer while stirring the contents in the mixing vessel. After all the raw materials were charged, the mixture was stirred until the contents were sufficiently uniform, and then filtered through a 0.8-μm membrane filter to remove coarse particles that could cause clogging of the inkjet head, thereby preparing an aqueous inkjet ink. In the preparation of aqueous inkjet ink, a set of aqueous inkjet inks consisting of four colors, cyan, magenta, yellow, and black, was prepared by using pigment-containing crosslinked polymer particles or pigment-containing crosslinked polymer particle precursors (cyan, magenta, yellow, black) that have the same number but different colors, respectively. Then, the prepared set of four-color inks (ink set) was used in the evaluations shown below.

[0185]

Table 8

[0186]

Table 8

[0187]

Table 8

[0188]

Table 8

[0189]

Table 8

[0190]

Table 8

[0191]

Table 8

[0192]

Table 8

[0193]

Table 8

[0194]

Table 8

[0195]

Table 8

[0196]

Table 8

[0197]

Table 8

[0198]

Table 8

[0199]

Table 8

[0200]

Table 8

[0201]

Table 8

[0202]

Table 8

[0203] The details of the abbreviations and product names described in Table 8 are as follows, respectively. · PG: Propylene glycol (boiling point at 1 atm: 188 °C, surface tension at 25 °C: 37 mN / m) · 1,2-BuD: 1,2-Butanediol (boiling point at 1 atm: 191 °C, surface tension at 25 °C: 32 mN / m) · 1,2-HexD: 1,2-Hexanediol (boiling point at 1 atm: 223 °C, surface tension at 25 °C: 27 mN / m) · 1,2-PenD: 1,2-Pentanediol (boiling point at 1 atm: 206 °C, surface tension at 25 °C: 28 mN / m) · 1,5-PenD: 1,5-Pentanediol (boiling point at 1 atm: 239 °C, surface tension at 25 °C: 42 mN / m) · HexG: 2-Methyl-2,4-pentanediol (boiling point at 1 atm: 197 °C, surface tension at 25 °C: 29 mN / m) · 1,2-OctD: 1,2-Octanediol (boiling point at 1 atm: 295 °C, surface tension at 25 °C: 20 mN / m) · PGM: Propylene glycol monomethyl ether (boiling point at 1 atm: 120 °C, surface tension at 25 °C: 27 mN / m) · PnP: Propylene glycol monopropyl ether (boiling point at 1 atm: 150 °C, surface tension at 25 °C: 26 mN / m) · PnB: Propylene glycol monobutyl ether (boiling point at 1 atm: 170 °C, surface tension at 25 °C: 26 mN / m) · DEG: Diethylene glycol (boiling point at 1 atm: 245 °C, surface tension at 25 °C: 45 mN / m) · DPG: Dipropylene glycol (boiling point at 1 atm: 232 °C, surface tension at 25 °C: 36 mN / m) · DPM: Dipropylene glycol monomethyl ether (boiling point at 1 atm: 190 °C, surface tension at 25 °C: 29 mN / m) · DPnP: Dipropylene glycol monopropyl ether (boiling point at 1 atm: 212 °C, surface tension at 25 °C: 26 mN / m) ·BDG: Diethylene glycol monobutyl ether (boiling point at 1 atm: 230 °C, surface tension at 25 °C: 28 mN / m) ·BEG: Ethylene glycol monobutyl ether (boiling point at 1 atm: 171 °C, surface tension at 25 °C: 27 mN / m) ·GLY: Glycerin (boiling point at 1 atm: 290 °C, surface tension at 25 °C: 65 mN / m) · Nonionic K-220: A compound in general formula (1) where R 1 is an alkyl group with 12 carbon atoms and n is 20 (CE × 1.67) (manufactured by NOF Corporation, solid content 100%, HLB = 16.5) · Nonionic B-250: A compound in general formula (1) where R 1 is an alkyl group with 22 carbon atoms and n is 50 (CE × 2.27) (manufactured by NOF Corporation, solid content 100%, HLB = 17.4) · Nonionic K-230: A compound in general formula (1) where R 1 is an alkyl group with 12 carbon atoms and n is 30 (CE × 2.50) (manufactured by NOF Corporation, solid content 100%, HLB = 17.5) · Emulgen 150: A compound in general formula (1) where R 1 is an alkyl group with 12 carbon atoms and n is 50 (CE × 4.17) (manufactured by Kao Corporation, solid content 100%, HLB = 18.4) · Nonionic K-2100W: A compound in general formula (1) where R 1 is an alkyl group with 12 carbon atoms and n is 100 (CE × 8.33) (manufactured by NOF Corporation, solid content 50%, HLB = 19.2) · Emulgen 1150S-60: A compound in general formula (1) where R 1 is an alkyl group with 11 carbon atoms and n is 50 (CE × 4.55) (manufactured by Kao Corporation, solid content 60%, HLB = 18.6) · Emalex 630: A compound in general formula (1) where R 1 is an alkyl group with 18 carbon atoms and n is 30 (CE × 1.67) (manufactured by Nippon Emulsion Co., Ltd., solid content 100%, HLB = 16.6) · Emalex 640: A compound in general formula (1) where R 1is an alkyl group having 18 carbon atoms, and n is 40 (CE × 2.22) (manufactured by Nippon Emulsion Co., Ltd., solid content 100%, HLB = 17.3) · Emalex 120: In general formula (1), R 1 is an alkyl group having 16 carbon atoms, and n is 20 (CE × 1.25) (manufactured by Nippon Emulsion Co., Ltd., solid content 100%, HLB = 15.7) · Emalex 125: In general formula (1), R 1 is an alkyl group having 16 carbon atoms, and n is 25 (CE × 1.56) (manufactured by Nippon Emulsion Co., Ltd., solid content 100%, HLB = 16.4) · Braunon EL-1540P: In general formula (1), R 1 is an alkyl group having 12 carbon atoms, and n is 40 (CE × 3.33) (manufactured by Aoki Yushi Kogyo Co., Ltd., solid content 100%, HLB = 18.1) · Emulgen 120: In general formula (1), R 1 is an alkyl group having 12 carbon atoms, and n is 12 (manufactured by Kao Corporation, solid content 100%, HLB = 14.8) · Tritol TMN-10: In general formula (1), R 1 is an alkyl group having 12 carbon atoms, and n is 11 (manufactured by The Dow Chemical Company, solid content 90%, HLB = 14.4) · Tritol TMN-6: In general formula (1), R 1 is an alkyl group having 12 carbon atoms, and n is 8 (manufactured by The Dow Chemical Company, solid content 90%, HLB = 13.1) · Surfynol 104: An acetylene diol-based surfactant manufactured by Evonik Japan Co., Ltd. (2,4,7,9-tetramethyl-5-decyne-4,7-diol, HLB = 3.0) · Surfynol DF110D: An acetylene diol-based surfactant manufactured by Evonik Japan Co., Ltd. (2,5,8,11-tetramethyl-6-dodecyne-5,8-diol, HLB = 2.7) · Surfynol 440: An acetylene diol-based surfactant manufactured by Evonik Japan Co., Ltd. (ethoxy compound of Surfynol 104, number of moles of ethylene oxide added 3.5, HLB = 8.1) · Surfynol 465: An acetylene diol - based surfactant manufactured by Evonik Japan Co., Ltd. (an ethoxylated compound of Surfynol 104, with 10 moles of ethylene oxide added, HLB = 13.2) · Dynol 604: An ethoxylated compound of 2,5,8,11 - tetramethyl - 6 - dodecyne - 5,8 - diol, with an average of 4 moles of ethylene oxide added, HLB = 8.0) · TEGO Wet 240: A side - chain polyether - modified silicone - based surfactant manufactured by Evonik Japan Co., Ltd. (HLB: 5 - 7, R in the above general formula 6 3 has the structure represented by the above general formula 7, and R 4 does not have the structure represented by general formula 7) · TEGO Wet 270: A side - chain polyether - modified silicone - based surfactant manufactured by Evonik Japan Co., Ltd. (HLB: 2 - 4, R in the above general formula 6 3 has the structure represented by the above general formula 7, and R 4 does not have the structure represented by general formula 7) · TEGO Glide 440: A both - ends polyether - modified silicone - based surfactant manufactured by Evonik Japan Co., Ltd. (HLB: 3 - 5, R in the above general formula 6 4 has the structure represented by the above general formula 7, and R 3 does not have the structure represented by general formula 7) · BYK333: A both - ends polyether - modified silicone - based surfactant manufactured by BYK Chemie GmbH (HLB: 10.3 - 12, R in the above general formula 6 4 has the structure represented by the above general formula 7, and R 3 does not have the structure represented by general formula 7) · TEGO Twin 4100: A gemini - type silicone - based surfactant manufactured by Evonik Japan Co., Ltd. (HLB: 0 - 2)

[0204] [Examples 1 - 161, Comparative Examples 1 - 18] Using the above aqueous inkjet ink (set), the following evaluations were carried out. Also, the evaluation results were as shown in Table 8 above.

[0205] [Evaluation 1: Evaluation of white - out] An inkjet ejection device equipped with four inkjet heads (KJ4B-1200) manufactured by Kyocera was installed in an environment of 25°C. Next, each ink constituting the ink set was filled into the inkjet head so that the printing order in the inkjet printing device was in the order of the colors black, cyan, magenta, and yellow. After that, a nozzle check pattern was printed, and after confirming that ink was being ejected normally from all nozzles, it was left as it was for 1 minute. After leaving it, using only one color of ink under the printing conditions of a frequency of 40 kHz, 1,200×1,200 dpi, and a drop volume of 3 pL, solid printing with a print rate of 100% was performed on the following printing substrates. Immediately after printing, the printing substrate with the ink printed on it was put into a 70°C air oven and dried for 1 minute to obtain a solid print. Then, the degree of whiteout of the solid print was visually and with a magnifying glass to evaluate the whiteout. Note that, as the printing substrates, two types were used: OK Top Coat + paper manufactured by Oji Paper Co., Ltd. and UPM Finesse Gloss paper manufactured by UPM, and evaluations were performed for each. Also, the evaluation criteria were as follows, and AA, A, and B evaluations were regarded as the practical usable range. Note that the solid prints were created with each of the four-color inkjet inks of cyan, magenta, yellow, and black, and the whiteout was evaluated for each solid print. Also, Table 8 shows the evaluation criteria for the color with the worst evaluation result for each printing substrate. AA: No whiteout was seen visually or with a magnifying glass. A: Slight whiteout was seen with a magnifying glass, but no whiteout was seen visually. B: Slight whiteout was seen visually. C: Obvious whiteout was seen visually.

[0206] <Evaluation 2: Evaluation of color mixing bleeding> Using the inkjet printing apparatus used in the above Evaluation 1, under the same printing conditions as in the above Evaluation 1 and using the same type of printing substrate, printing of an overlaid gradation image was performed using all the inks mounted on the inkjet printing apparatus. The above "overlaid gradation image" is an image in which, for one color of ink, an image with the printing rate continuously changed from 10% to 60% within a predetermined area is overlaid in the order of black, cyan, magenta, and yellow. Therefore, the total printing rate of the overlaid gradation image (the sum of the printing rates of each color) is 40% to 240%. However, the printing rate of each color is the same for each total printing rate (for example, when the total printing rate is 40%, the printing rate of each color is 10%, and when the total printing rate is 240%, the printing rate of each color is 60%). After printing the above overlaid gradation image, the printed substrate on which the ink was printed was put into a 70 °C air oven and dried for 1 minute to obtain an overlaid gradation printed matter. Then, the degree of color mixing bleeding in the overlaid gradation printed matter was visually and confirmed with a loupe to evaluate the color mixing bleeding. The evaluation criteria are as follows, and AA, A, and B evaluations were set as the practical use range. AA: No color mixing bleeding was observed in all areas with a total printing rate of 40% to 240%. A: No color mixing bleeding occurred in the area with a total printing rate of 200% or less, but color mixing bleeding was observed in the area with a total printing rate exceeding 200% and 240% or less. B: No color mixing bleeding occurred in the area with a total printing rate of 160% or less, but color mixing bleeding was observed in the area with a total printing rate exceeding 160% and 200% or less. C: No color mixing bleeding occurred in the area with a total printing rate of 120% or less, but color mixing bleeding was observed in the area with a total printing rate exceeding 120% and 160% or less. D: Color mixing bleeding was observed in the area with a total printing rate of 120% or less.

[0207] <Evaluation 3: Evaluation of Dot Roundness> Using the inkjet printing apparatus used in the above Evaluation 1, under the same printing conditions as in the above Evaluation 1 and using the same type of printing substrate, printing of a single-color gradation image was performed using only any one color of ink mounted on the inkjet printing apparatus. The above "single-color gradation image" is an image in which the printing rate is continuously changed from 5% to 60% within a predetermined area. After printing the above single-color gradation image, the printed substrate on which the ink was printed was put into a 70 °C air oven and dried for 1 minute to obtain a single-color gradation printed matter. Then, a portion with a printing rate of 10% in the single-color gradation printed matter was observed using an image quality analyzer ("PIAS-II" manufactured by Quality Engineering Associates), and the dot roundness was measured. The closer the roundness is to 1, the more circular the dots are, indicating a good dot shape. The evaluation criteria were as follows, and AA, A, and B evaluations were defined as the practical use range. AA: The roundness was 1 or more and 2 or less. A: The roundness was more than 2 and 3 or less. B: The roundness was more than 3 and 3.5 or less. C: The roundness was greater than 3.5.

[0208] <Evaluation 4: Evaluation of printing density> Using OK topcoat + paper as the printing substrate, the density of the solid prints of each color created in the above Evaluation 1 was measured with a spectrophotometer ("eXact Advance" manufactured by X-rite), and the printing density was evaluated. The measurement conditions were ISO status T as the density standard, a viewing angle of 2°, and a light source of D50. The evaluation criteria were as follows, and AA, A, and B evaluations were defined as the practical use range. AA: For all colors, the printing density was 0.3 or more higher than the printing density of the solid print of the same color created using the ink set of Comparative Example 1. A: In the color with the smallest difference in the printing density with respect to the solid print of the same color created using the ink set of Comparative Example 1, the value of the difference was 0.15 or more and less than 0.3. B: In the color where the difference with respect to the printing density of the solid print of the same color created using the ink set of Comparative Example 1 was the smallest, the value of the difference was 0 or more and less than 0.15 C: In the color where the difference with respect to the printing density of the solid print of the same color created using the ink set of Comparative Example 1 was the smallest, the value of the difference was less than 0 (that is, the printing density of the solid print of the same color created using the ink set of Comparative Example 1 was higher)

[0209] <Evaluation 5: Evaluation of Color Reproduction Range> Using the inkjet printing apparatus used in the above Evaluation 1, among the inks of three colors, cyan, magenta, and yellow, mounted on the inkjet printing apparatus, under the same printing conditions as in the above Evaluation 1, printing of a secondary color solid image was performed. Note that as the printing substrate, Oji Paper Co., Ltd.'s OK Top Coat + paper was used. Further, the above "secondary color solid image" is an image in which three solid images of a red solid image (a solid image using magenta ink with a solid image using yellow ink overlaid thereon), a blue solid image (a solid image using magenta ink overlaid on a solid image using cyan ink), and a green solid image (a solid image using yellow ink overlaid on a solid image using cyan ink) are arranged. After printing the above secondary color solid image, the OK Top Coat + paper printed with ink was put into a 70 °C air oven and dried for 1 minute to obtain a secondary color solid print. Then, the hue (a* value and b* value) of each solid portion of the secondary color solid print was measured with a spectrophotometer ("eXact Advance" manufactured by X-rite). Note that the measurement conditions for the hue were the same as in Evaluation 4. Then, using the chroma (C value) calculated by adding the square value of the a* value and the square value of the b* value and taking the square root thereof (√(a*2 + b*2)), the color reproduction range was evaluated. Note that a larger numerical value of the C value means a wider color reproduction range. The evaluation criteria were as follows, and AA, A, and B evaluations were set as the practical use range. AA: The C value of the red color was 95 or more, the C value of the blue color was 60 or more, and the C value of the green color was 80 or more A: Did not meet all of the above evaluation criteria AA, the following evaluation criterion B, and the following evaluation criterion C B: Did not meet the above evaluation criteria AA and the following evaluation criterion C, and met one or more of the requirements of "C value of red color is 85 or more and less than 90", "C value of blue color is 50 or more and less than 55", and "C value of green color is 70 or more and less than 75" C: Did not meet the above evaluation criterion AA, and met one or more of the requirements of "C value of red color is less than 85", "C value of blue color is less than 50", and "C value of green color is less than 70"

[0210] <Evaluation 6: Evaluation of Drying Property> Using the inkjet printing apparatus used in the above Evaluation 1, and using all the inks mounted on the inkjet printing apparatus, a double half-solid image was printed under the same printing conditions as in the above Evaluation 1. Note that Oji Paper Co., Ltd.'s OK Top Coat + paper was used as the printing substrate. The "double half-solid image" is an image in which an image printed on one side with a printing rate of 60% for one color of ink is overlaid in the order of black, cyan, magenta, and yellow. Therefore, the total printing rate of the double half-solid image is 240%. After printing the above double half-solid image, the OK Top Coat + paper printed with ink was put into a 70 °C air oven, taken out at regular intervals, and the drying property was evaluated by touching the printed matter with a finger. The evaluation criteria are as follows, and AA, A, and B evaluations were defined as the practical usable range. AA: When touched after 30 seconds of drying time, there was no tackiness and the printed matter was dry A: When touched after 1 minute of drying time, there was no tackiness and the printed matter was dry, but it was not dry at the 30-second mark B: When touched after 1 minute and 30 seconds of drying time, there was no tackiness and the printed matter was dry, but it was not dry at the 1-minute mark C: When touched after 1 minute and 30 seconds of drying time, there was tackiness and the printed matter was not dry

[0211] <Evaluation 7: Discharge Stability> Using the inkjet printing apparatus used in the above Evaluation 1, after filling the inks constituting the ink set into the inkjet heads respectively, a nozzle check pattern was printed, and it was confirmed that the ink was being ejected normally from all nozzles. Thereafter, using the ink mounted on the above inkjet printing apparatus, 100 solid images of A4 size were printed continuously. Then, after printing, the nozzle check pattern was printed again, and the ejection stability was evaluated by visually counting the number of clogged nozzles. Note that the above evaluation was performed under two types of head drive frequency conditions of 40 kHz and 64 kHz. The evaluation criteria were as follows, and AA, A, and B evaluations were regarded as the practically applicable range. Note that the evaluation was performed for each of the four colors constituting the ink set. Table 8 shows the evaluation criteria for the color with the worst evaluation result. AA: No clogging of nozzles A: 1 to 3 nozzles were clogged B: 4 to 9 nozzles were clogged C: 10 to 49 nozzles were clogged D: 50 or more nozzles were clogged

[0212] It was confirmed that the aqueous inkjet inks of Examples 1 to 161 having the composition of the aqueous inkjet ink of the present disclosure had quality at a practically usable level in all of the print image quality, print density, color reproducibility, and ejection stability on a hardly absorbent printing substrate.

[0213] Further, by comparing Examples 2, 3, and 4, it was confirmed that by setting the acid value of the dispersion resin (polymer (A-2)) to 180 mgKOH / g or less, preferably 160 mgKOH / g, more preferably 150 mgKOH / g or less, the printing density, color reproducibility, and drying property of the printed matter are improved. Similarly, by comparing Examples 29, 30, and 31, it was confirmed that by using in combination a binder resin having a specific acid value, specifically an acid value of 50 mgKOH / g or less (preferably 40 mgKOH / g or less), the dot bleeding, drying property, and ejection stability of the printed matter are improved. From these results, it was confirmed that the acid value of the resins (polymer (A-2) and binder resin) contained in the aqueous inkjet ink of the present disclosure affects the drying property, printing image quality, color reproducibility, and solution of printing image quality.

[0214] Furthermore, the aqueous inkjet inks of Examples 93, 94, 95, 97, 98, 99, 100, 113, 119, 120, 125, 130, 131, 135, 138, 151, 152, 156, 157, 160, and 161 use resins (polymers) having suitable acid values as the polymer (A-2) and the binder resin, and further, as the nonionic surfactant (B-2), a gemini-type silicone surfactant (TEGO Twin 4100) or a both-end polyether-modified silicone surfactant (TEGO Glide 440) is used. In these aqueous inkjet inks, all evaluations are at the "AA" level. From this result, it was confirmed that it is extremely suitable to use a silicone surfactant having a specific structure as the nonionic surfactant (B-2).

[0215] On the other hand, in Comparative Examples 1 and 4, which reproduced the compositions of the organic solvent and surfactant of the aqueous inkjet ink specifically disclosed in Examples 4 and 8 of Patent Document 3, respectively, the ratio of compound (B-1) to nonionic surfactant (B-2) was 2:1 or 1:1, which did not have the preferred blending ratio in the present disclosure. It is presumed that the balance of the affinity of the nonionic surfactant (B-2) was disrupted, resulting in a deterioration of the printed image quality. In Comparative Example 1, since a pigment-containing crosslinked polymer particle precursor was used, the dispersed resin desorbed from the pigment and liberated in the ink also inhibited the orientation of the surfactant, which is considered to have affected the degradation of the printed image quality. Furthermore, due to the presence of the dispersed resin adsorbed with a highly hydrophobic surfactant in the ink, ejection stability suitable for practical use could not be obtained. The same tendency was also observed in Comparative Examples 3 and 16 using non-crosslinked dispersed resin.

[0216] In addition, in Comparative Example 4, although Surfynol 104, an acetylene diol-based surfactant, was used as the nonionic surfactant (B-2), since it did not contain compound (B-1), Surfynol 104 could not be sufficiently emulsified, and the printed image quality and printing density on the printed matter did not become suitable for practical use.

[0217] In addition, in the aqueous inkjet inks of Comparative Examples 7 to 15, which are systems that do not contain compound (B-1) or nonionic surfactant (B-2) as surfactant (B), similar to Comparative Example 4, the printed image quality and printing density on the printed matter did not become suitable for practical use. Also, in Comparative Examples 2, 6, 17, and 18, although they contain compound (B-1) and nonionic surfactant (B-2) as surfactant (B), the ratio of compound (B-1) to nonionic surfactant (B-2) is outside the above-mentioned preferred range, and thus a printed image quality suitable for practical use could not be obtained.

[0218] Although the present disclosure has been described with reference to some of the above embodiments, the present disclosure is not limited by the above embodiments. Various changes can be made to the configuration and details of the present disclosure within the scope of the present disclosure. The disclosure of the present application is related to the subject matter described in Japanese Patent Application No. 2023-209883 filed on December 13, 2023, and all of the disclosure contents thereof are incorporated herein by reference.

Claims

1. An aqueous inkjet ink comprising (A) pigment-containing crosslinked polymer particles and (B) a surfactant, the crosslinked polymer particles (A) contain a crosslinked reaction product between a compound (A-1) having a plurality of functional groups in one molecule that react with a carboxy group and / or a carboxylate group, and an uncrosslinked polymer (A-2) having a carboxy group and / or a carboxylate group, The surfactant (B) contains a compound (B-1) represented by the following general formula 1 and a nonionic surfactant (B-2) having an HLB value of 1 to 10: The ratio of the content of the compound (B-1) to the content of the nonionic surfactant (B-2) is from 1:1.2 to 1:20 in terms of mass ratio. R 1 -(O-CH 2 -CH 2 ) n -OH General formula 1 (In general formula 1, R 1 represents a linear or branched alkyl group having 10 to 25 carbon atoms, and n is an integer of 20 to 100.

2. Further containing an organic solvent, 2. The water-based inkjet ink according to claim 1, wherein the organic solvent comprises an alkanediol-based solvent having 5 to 8 carbon atoms and / or a (poly)alkylene glycol monoalkyl ether-based solvent having 5 to 9 carbon atoms.

3. The aqueous inkjet ink according to claim 2, wherein the organic solvent comprises a (poly)propylene glycol monoalkyl ether solvent having 5 to 9 carbon atoms.

4. The aqueous inkjet ink according to claim 1 or 2, wherein the acid value of the uncrosslinked polymer (A-2) is 60 to 180 mgKOH / g.

5. 3. The aqueous inkjet ink according to claim 1, further comprising an organic solvent, the organic solvent comprising a (poly)propylene glycol monoalkyl ether solvent having 5 to 9 carbon atoms, and the acid value of the uncrosslinked polymer (A-2) is 60 to 180 mgKOH / g.

6. The aqueous inkjet ink according to claim 1 or 2, wherein the nonionic surfactant (B-2) having an HLB value of 1 to 10 comprises a gemini type silicon-based surfactant and / or a silicon-based surfactant modified at both ends with polyether (excluding the gemini type silicon-based surfactant).

7. 3. The aqueous inkjet ink according to claim 1, further comprising an organic solvent, the organic solvent comprising a (poly)propylene glycol monoalkyl ether solvent having 5 to 9 carbon atoms, and the nonionic surfactant (B-2) having an HLB value of 1 to 10 comprising a gemini type silicon-based surfactant and / or a silicon-based surfactant modified at both ends with polyether (excluding the gemini type silicon-based surfactant).

8. 3. The aqueous inkjet ink according to claim 1, further comprising an organic solvent, the organic solvent comprising a (poly)propylene glycol monoalkyl ether solvent having 5 to 9 carbon atoms, the uncrosslinked polymer (A-2) having an acid value of 60 to 180 mgKOH / g, and the nonionic surfactant (B-2) having an HLB value of 1 to 10 comprising a gemini type silicon-based surfactant and / or a both-end polyether-modified silicon-based surfactant (excluding the gemini type silicon-based surfactant).

9. A printed matter obtained by printing with the aqueous inkjet ink according to claim 1 or 2.

Images