Aqueous ink, ink cartridge, and inkjet recording method

Abstract

To provide an aqueous ink for inkjet that enables recording of an image with superior image clarity.SOLUTION: An aqueous ink for inkjet includes a pigment, a resin, and an additive. The additive is at least one selected from the group consisting of a compound represented by general formula (1) and a compound represented by general formula (2), with its content being 10 ppm or more and 1,200 ppm or less relative to the total ink mass. (R1-R4 independently represent a hydrogen atom or a methyl group. n represents an integer of 1 to 15. L represents a C5 to 20 alkylene group or a C6 to 12 arylene group. a and b independently represent 0 or 1).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a water-based ink, an ink cartridge, and an ink-jet recording method. [Background technology]

[0002] 2. Description of the Related Art In recent years, inks containing pigments as coloring materials (pigment inks) have been widely used as inks for use in inkjet recording methods because they tend to increase the fastness of recorded images. In fields such as photography and graphic arts, there is a demand for inks that can print images with higher resolution and superior gloss.

[0003] When a pigment ink is used, the image clarity of an image recorded on a recording medium having a glossy surface, such as glossy paper, is generally lower than when a dye ink containing a dye is used. This is thought to be due to the fact that the pigment is a particulate material. Here, "image clarity" refers to the characteristic that indicates the sharpness of the image projected on the surface of the image. When image clarity is low, the image appears blurry, and when image clarity is high, the image appears sharp.

[0004] Improvements in various inkjet suitability of pigment inks have been studied so far, such as by selecting the materials to be added. For example, an inkjet ink containing an ether compound having a (poly)alkylene oxide chain has been proposed (Patent Document 1). Also, an inkjet ink containing an alkanediol having 6 to 10 carbon atoms has been proposed (Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 11-217528 [Patent Document 2] JP 2020-189961 A Summary of the Invention [Problem to be solved by the invention]

[0006] The present inventors have investigated the image clarity of images recorded using the inks proposed in Patent Documents 1 and 2. As a result, they have found that the image clarity of images recorded using these inks is not particularly good, and there is room for further improvement.

[0007] It is therefore an object of the present invention to provide a water-based ink for inkjet use capable of recording images with excellent image clarity. It is also an object of the present invention to provide an ink cartridge and an inkjet recording method using this water-based ink. [Means for solving the problem]

[0008] That is, according to the present invention, there is provided an aqueous ink for inkjet recording, comprising a pigment, a resin, and an additive, wherein the additive is at least one selected from the group consisting of a compound represented by the following general formula (1) and a compound represented by the following general formula (2), and the content of the additive is 10 ppm or more and 1,200 ppm or less based on the total mass of the ink.

[0009] TIFF2024022548000001.tif36170 (In the general formula (1), R1, R2, R3, and R4 each independently represent a hydrogen atom or a methyl group. n represents an integer of 1 to 15.)

[0010] TIFF2024022548000002.tif36170 (In the general formula (2), R1 and R2 each independently represent a hydrogen atom or a methyl group. L represents an alkylene group having 5 to 20 carbon atoms or an arylene group having 6 to 12 carbon atoms; a and b each independently represent 0 or 1. Effect of the Invention

[0011] According to the present invention, it is possible to provide a water-based ink for inkjet use capable of recording images with excellent image clarity. Furthermore, according to the present invention, it is possible to provide an ink cartridge and an inkjet recording method using the water-based ink. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a cross-sectional view illustrating an embodiment of an ink cartridge of the present invention. [Diagram 2] 1A and 1B are diagrams illustrating an example of an inkjet recording apparatus used in the inkjet recording method of the present invention, in which (a) is a perspective view of the main part of the inkjet recording apparatus, and (b) is a perspective view of a head cartridge. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present invention will be described in more detail below with reference to preferred embodiments. In the present invention, a "unit" of a resin means the smallest repeating unit constituting a resin, and a structure formed by (co)polymerization of one monomer. In addition, an aqueous ink for inkjet printing may be simply referred to as "ink." Physical property values ​​are values ​​at room temperature (25°C) unless otherwise specified. When "(meth)acrylic acid" or "(meth)acrylate" is written, it means "acrylic acid, methacrylic acid" and "acrylate, methacrylate", respectively.

[0014] The present inventors have conducted various studies on improving the image clarity by incorporating an additive into the ink. As a result, they have found that the image clarity of the recorded image can be improved by using at least one compound selected from the group consisting of a compound represented by the following general formula (1) and a compound represented by the following general formula (2) as an additive. Hereinafter, the compound represented by the following general formula (1) will also be simply referred to as "compound A". Furthermore, the compound represented by the following general formula (2) will also be simply referred to as "compound B".

[0015] TIFF2024022548000003.tif36170 (In the general formula (1), R1, R2, R3, and R4 each independently represent a hydrogen atom or a methyl group. n represents an integer of 1 to 15.)

[0016] TIFF2024022548000004.tif36170 (In the general formula (2), R1 and R2 each independently represent a hydrogen atom or a methyl group. L represents an alkylene group having 5 to 20 carbon atoms or an arylene group having 6 to 12 carbon atoms; a and b each independently represent 0 or 1.

[0017] Compound A has, in order from both ends of its molecular chain, a hydrophobic olefin moiety, a carbonyl group, and a hydrophilic 2-hydroxyethoxy moiety, and further has a hydrophilic (poly)alkylene oxide moiety in the center of its molecular chain.

[0018] Compound B has, in order from both ends of its molecular chain, a hydrophobic olefin moiety, a carbonyl group, and a hydrophilic 2-hydroxyethoxy moiety, and further has a hydrophobic alkylene group or arylene group in the center of its molecular chain.

[0019] The present inventors speculate as follows about the mechanism by which the image clarity of a recorded image is improved by including at least one of the additives, Compound A and Compound B (hereinafter, also simply referred to as "additive"). Aqueous inks containing a pigment as a coloring material usually further contain a resin having a hydrophobic unit derived from a monomer having an aromatic group and a hydrophilic unit derived from a monomer having a carboxylic acid group. The hydrophobic unit interacts with the hydrophobic pigment particle surface by at least one of van der Waals forces, π-π interactions, and hydrophobic interactions. As a result, the resin adsorbed on the pigment particle surface remains in the vicinity thereof and covers the pigment particle surface. On the other hand, the hydrophilic unit spreads the resin three-dimensionally in the aqueous medium due to its high affinity with water, which is the main component of the aqueous medium, and generates a repulsive force due to steric hindrance. This suppresses the aggregation of the pigment, and improves the dispersion stability of the pigment in the ink.

[0020] Since the resin molecules are three-dimensionally bulky, it is difficult to sufficiently cover the pigment particle surface with the resin. Therefore, even if the resin and the pigment coexist, it is considered that there are some parts where the pigment particle surface is exposed without the resin adsorbed. However, in the ink, the action of the hydrophilic unit of the resin suppresses the aggregation of the pigment and maintains the dispersion stability of the pigment. However, when the ink is applied to the recording medium, the aqueous medium in the ink evaporates or penetrates into the recording medium, the ink is concentrated, and the pigment begins to aggregate. Since the pigment aggregates, the distance between the pigment particles becomes very close, so that the exposed pigment particle surfaces without the resin adsorbed strongly interact with each other, promoting the aggregation of the pigment. As a result, it is considered that the pigment is likely to be biased on the surface of the recorded image, and the image clarity is reduced. In order to improve the image clarity, it is important to suppress the rapid and excessive aggregation of the pigment during image recording and to deposit the pigment on the recording medium without bias. For this purpose, it is considered effective to reduce the exposed pigment particle surface without the resin adsorbed.

[0021] When the ink contains the above additives, the hydrophobic olefin moieties at both ends are effectively adsorbed to the pigment particle surface, reducing the exposure of the pigment particle surface. These additives have a smaller molecular size and are not sterically bulky compared to resins, so they have a high adsorption density to the pigment particle surface and can effectively adsorb to and cover the pigment particle surface. In other words, it is believed that the inclusion of the above additives complements the coverage of the pigment particle surface by the resin and reduces the exposure of the pigment particle surface.

[0022] The 2-hydroxyethoxy moiety in the additive molecule has a high affinity with water, the main component of aqueous media, and is therefore believed to suppress pigment aggregation in the ink and improve the dispersion stability of the pigment. In addition, compound A has a hydrophilic (poly)alkylene oxide moiety in its molecule, so by including compound A in the ink, it is possible to suppress pigment aggregation and improve the dispersion stability of the pigment.

[0023] On the other hand, the molecule of compound B contains a hydrophobic alkylene group or arylene group represented by "L" in general formula (2). Therefore, compound B can adsorb the central alkylene group or arylene group as well as the hydrophobic olefin moieties at both ends to the pigment particle surface. Therefore, by including compound B in the ink, it becomes possible to more effectively cover the pigment particle surface, suppressing pigment aggregation and improving the pigment dispersion stability. By improving the pigment dispersion stability, rapid aggregation of the pigment during image recording is suppressed, improving the image clarity.

[0024] The content (ppm) of the additives in the ink is 10 ppm or more and 1,200 ppm or less based on the total weight of the ink. If the content of the additives is less than 10 ppm, the amount of the additives covering the pigment particle surface is too small, and the image clarity cannot be improved. On the other hand, if the content of the additives is more than 1,200 ppm, the additives tend to aggregate with each other, inhibiting the adsorption of the additives to the pigment particle surface, and there is a shortage of additives that can be adsorbed to the pigment particle surface. For this reason, when an image is recorded on a recording medium, it is not possible to suppress rapid and excessive aggregation of the pigment, and it is not possible to improve the image clarity.

[0025] <Water-based ink> The ink of the present invention is a water-based ink for inkjet use, containing a pigment, a resin, and specific additives. The ink of the present invention does not need to be a so-called "curable ink". Therefore, the ink of the present invention does not need to contain, in addition to the additives, compounds such as polymerizable monomers that can be polymerized by the addition of external energy such as heat or light. The components constituting the ink of the present invention and the physical properties of the ink are described in detail below.

[0026] (Pigments) The ink contains a pigment as a coloring material. The content (mass %) of the pigment in the ink is preferably from 0.10% to 15.00% by mass, and more preferably from 1.00% to 10.00% by mass, based on the total mass of the ink.

[0027] Specific examples of the pigment include inorganic pigments such as carbon black and titanium oxide; and organic pigments such as azo pigments, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, imidazolone pigments, diketopyrrolopyrrole pigments, dioxazine pigments, perinone pigments, and perylene pigments. Among them, the pigment is preferably at least one selected from the group consisting of quinacridone pigments, diketopyrrolopyrrole pigments, perinone pigments, and perylene pigments. These pigments tend to aggregate, but by including the additives described above, aggregation can be effectively suppressed, and image clarity can be further improved.

[0028] Examples of quinacridone pigments include CI Pigment Violet 19 (unsubstituted quinacridone), CI Pigment Red 122 (2,9-dimethylquinacridone), and CI Pigment Red 202 (2,9-dichloroquinacridone). As the quinacridone pigment, a quinacridone solid solution pigment formed of two or more quinacridone pigments can also be used. As the quinacridone solid solution pigment, a solid solution pigment of CI Pigment Red 202 and CI Pigment Violet 19; a solid solution pigment of CI Pigment Red 122 and CI Pigment Violet 19; are preferred.

[0029] Diketopyrrolopyrrole pigments include CI Pigment Orange 71, 73, etc.; CI Pigment Red 254, 255, 264, etc. Perinone pigments include CI Pigment Orange 43, etc. Perylene pigments include CI Pigment Red 149, 179, etc.

[0030] Pigments can be classified according to the dispersion method, and include resin-dispersed pigments using a resin as a dispersant and self-dispersed pigments in which hydrophilic groups are bonded to the pigment particle surface. Also, resin-bonded pigments in which an organic group containing a resin is chemically bonded to the pigment particle surface, and microcapsule pigments in which the pigment particle surface is coated with a resin, etc. can be used. Among them, it is preferable to use a resin-dispersed pigment in which a resin is physically adsorbed onto the pigment particle surface as a dispersant, rather than a resin-bonded pigment or a microcapsule pigment. The resin used as a dispersant is preferably non-crosslinked. Pigments with different dispersion methods may be combined.

[0031] As the resin dispersant for dispersing the pigment in the aqueous medium, it is preferable to use one that can disperse the pigment in the aqueous medium by the action of anionic groups. As the resin dispersant, a resin as described below, particularly a water-soluble resin, can be used. The content (mass%) of the pigment in the ink is preferably 0.30 times or more and 10.00 times or less in mass ratio to the content (mass%) of the resin dispersant.

[0032] As the self-dispersing pigment, an anionic group such as a carboxylic acid group, a sulfonic acid group, or a phosphonic acid group can be used, which is bonded to the particle surface of the pigment directly or via another atomic group (-R-). The anionic group may be either an acid type or a salt type, and when it is a salt type, it may be either a partially dissociated state or a completely dissociated state. When the anionic group is a salt type, examples of the cation that serves as the counter ion include an alkali metal cation, ammonium, and organic ammonium. Specific examples of the other atomic group (-R-) include a linear or branched alkylene group having 1 to 12 carbon atoms; an arylene group such as a phenylene group or a naphthylene group; a carbonyl group; an imino group; an amide group; a sulfonyl group; an ester group; and an ether group. In addition, it may be a group that is a combination of these groups.

[0033] (resin) The ink contains a resin. The content (mass%) of the resin in the ink is preferably 0.10% by mass or more and 5.00% by mass or less based on the total mass of the ink. Also, it is more preferable that it is 0.30% by mass or more and 2.00% by mass or less, and particularly preferably 0.50% by mass or more and 1.50% by mass or less. In other words, the content (ppm) of the resin in the ink is preferably 1,000 ppm or more and 50,000 ppm or less based on the total mass of the ink, and more preferably 3,000 ppm or more and 20,000 ppm or less. And it is particularly preferable that it is 5,000 ppm or more and 15,000 ppm or less.

[0034] The resin can be added to the ink (i) to stabilize the dispersion state of the pigment, that is, as a resin dispersant for the pigment or as an auxiliary thereof. Also, the resin can be added (ii) to improve various properties of the recorded image. Examples of the form of the resin include block copolymers, random copolymers, graft copolymers, and combinations thereof. The resin may be a water-soluble resin that can be dissolved in an aqueous medium, or may be resin particles that are dispersed in an aqueous medium. The resin particles do not need to encapsulate a colorant.

[0035] In this specification, "a resin is water-soluble" means that when the resin is neutralized with an alkali equivalent to the acid value, it exists in an aqueous medium in a state in which it does not form particles whose particle size can be measured by dynamic light scattering. Whether or not a resin is water-soluble can be determined according to the following method. First, a liquid (resin solid content: 10 mass%) containing a resin neutralized with an alkali (sodium hydroxide, potassium hydroxide, etc.) equivalent to the acid value is prepared. Next, the prepared liquid is diluted 10 times (volume basis) with pure water to prepare a sample solution. When the particle size of the resin in the sample solution is measured by dynamic light scattering, if no particles having a particle size are measured, the resin can be determined to be water-soluble. The measurement conditions in this case can be, for example, as follows. [Measurement conditions] SetZero: 30 seconds Number of measurements: 3 Measurement time: 180 seconds

[0036] As the particle size distribution measuring device, a particle size analyzer using a dynamic light scattering method (for example, the product name "UPA-EX150" manufactured by Nikkiso Co., Ltd.) can be used. Of course, the particle size distribution measuring device and the measurement conditions to be used are not limited to those described above.

[0037] The content of the resin in the ink (mass%) is preferably 0.15 to 0.50 times, more preferably 0.20 to 0.40 times, in terms of mass ratio to the content of the pigment (mass%). If the mass ratio is less than 0.15, the pigment dispersion state becomes unstable, and the ink storage stability may not be sufficient. On the other hand, if the mass ratio is more than 0.50, the excess resin may be easily aggregated, and the ink storage stability may not be sufficient.

[0038] The content (ppm) of the resin in the ink is preferably 20 to 1,000 times the mass ratio of the content (ppm) of the additive. By making the mass ratio 20 or more, the surface of the pigment particles can be more effectively covered with the resin and the additive, so that the effect of improving the image clarity can be further enhanced. On the other hand, by making the mass ratio 1,000 or less, it is possible to suppress the decrease in the adsorption action of the additive due to the excess resin, so that the effect of improving the image clarity can be further enhanced.

[0039] The weight average molecular weight of the resin is preferably 1,000 to 30,000, more preferably 6,000 to 15,000. The weight average molecular weight of the resin is a value measured by gel permeation chromatography (GPC) in terms of polystyrene. The weight average molecular weight of the resin can be measured as follows. First, the eluent to which the resin has been added is left to stand at 25°C for 24 hours to prepare a sample solution containing 0.5% by mass of resin. Next, the prepared sample solution is pressure-filtered through a solvent-resistant membrane filter (pore size: 0.45 μm), and then measurement is performed by GPC. A molecular weight calibration curve can be used to calculate the weight average molecular weight.

[0040] The acid value of the resin is preferably from 80 mgKOH / g to 250 mgKOH / g, and more preferably from 110 mgKOH / g to 160 mgKOH / g. The acid value of the resin can be measured by a titration method in accordance with JIS K 0070:1992.

[0041] Examples of the resin include acrylic resins, methacrylic resins, urethane resins, urea resins, and polyester resins. Among them, the resin is more preferably at least one selected from the group consisting of acrylic resins and methacrylic resins (hereinafter collectively referred to as "(meth)acrylic resins"). In other words, the resin preferably contains at least one selected from the group consisting of units derived from acrylic acid and units derived from methacrylic acid.

[0042] The (meth)acrylic resin preferably has a hydrophilic unit and a hydrophobic unit as constituent units. The carbonyl groups present in large amounts in the molecules of the (meth)acrylic resin strongly interact with the carbonyl groups in the molecules of the additive. Therefore, when the (meth)acrylic resin and the additive are adsorbed onto the surface of the pigment particles, the resin and the additive are close to each other, the adsorption density is increased, and the coverage of the pigment particle surface is increased. This can further improve the clarity of the image.

[0043] The hydrophilic unit is a unit having a hydrophilic group such as an acidic group, a hydroxyl group, and an ethylene oxide group. The hydrophilic unit can be formed, for example, by polymerizing a hydrophilic monomer having a hydrophilic group. Examples of the hydrophilic monomer having a hydrophilic group include acidic monomers having a carboxylic acid group such as (meth)acrylic acid, itaconic acid, maleic acid, and fumaric acid; anionic monomers such as anhydrides and salts of these acidic monomers; monomers having a hydroxyl group such as 2-hydroxyethyl (meth)acrylate and 3-hydroxypropyl (meth)acrylate; and monomers having an ethylene oxide group such as methoxy (mono, di, tri, and poly)ethylene glycol (meth)acrylate. Among them, from the viewpoint of hydrophilicity, it is preferable to use an acidic monomer having a carboxylic acid group, a salt of an acidic monomer having a carboxylic acid group, and an acid anhydride. Examples of the cation constituting the salt of the acidic monomer include ions of lithium, sodium, potassium, ammonium, and organic ammonium.

[0044] The hydrophobic unit is a unit that does not have a hydrophilic group such as an acidic group, a hydroxyl group, or an ethylene oxide group. The hydrophobic unit can be formed, for example, by polymerizing a hydrophobic monomer that does not have a hydrophilic group. Examples of the hydrophobic monomer include monomers having an aromatic ring such as styrene, α-methylstyrene, and benzyl (meth)acrylate; and (meth)acrylic acid ester monomers such as ethyl (meth)acrylate, methyl (meth)acrylate, (iso)propyl (meth)acrylate, (n-, iso-, and t-)butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate.

[0045] The resin can be contained in the ink as a dispersant for dispersing the pigment in the ink, or as an additive resin used together with a self-dispersing pigment. The resin used as a dispersant is preferably an acrylic resin having a hydrophilic unit derived from (meth)acrylic acid and a hydrophobic unit derived from a monomer having an aliphatic group or an aromatic ring. Furthermore, an acrylic resin having a hydrophilic unit derived from (meth)acrylic acid and a hydrophobic unit derived from at least one monomer selected from the group consisting of styrene and α-methylstyrene is preferable. These resins are particularly likely to interact with the pigment, and therefore can be suitably used as a resin dispersant for dispersing the pigment.

[0046] In addition, other resins than the above may be added to the ink as long as the image clarity is not impaired. The content (mass %) of the other resins in the ink is preferably 0.1 mass % or more and 5.0 mass % or less based on the total mass of the ink.

[0047] (Additives) The ink contains at least one additive selected from the group consisting of the compound represented by the general formula (1) and the compound represented by the general formula (2).

[0048] TIFF2024022548000005.tif36170 (In the general formula (1), R1, R2, R3, and R4 each independently represent a hydrogen atom or a methyl group. n represents an integer of 1 to 15.)

[0049] TIFF2024022548000006.tif36170 (In the general formula (2), R1 and R2 each independently represent a hydrogen atom or a methyl group. L represents an alkylene group having 5 to 20 carbon atoms or an arylene group having 6 to 12 carbon atoms; a and b each independently represent 0 or 1.

[0050] In the general formula (1), R1, R2, R3, and R4 each independently represent a hydrogen atom or a methyl group. When R3 and R4 are alkyl groups having 2 or more carbon atoms, the hydrophilicity of the alkylene oxide moiety is reduced, hindering its function, and image clarity cannot be obtained. Furthermore, n represents an integer of 1 to 15. When n is more than 15, the viscosity of the ink increases. Therefore, when recording an image, the leveling property is not sufficiently obtained, and as a result of the pigment being biased, image clarity cannot be obtained. As in the compounds A12 to A15 described later, n R3s and n R4s may be the same or different.

[0051] In general formula (2), R1 and R2 each independently represent a hydrogen atom or a methyl group. If R1 and R2 are not a hydrogen atom or a methyl group, it is believed that the hydrophobic olefin moiety is prevented from adsorbing to the pigment. As a result, image clarity is not obtained. L represents an alkylene group having 5 to 20 carbon atoms or an arylene group having 6 to 12 carbon atoms. If L is an alkylene group having more than 20 carbon atoms or an arylene group having more than 12 carbon atoms, the hydrophobicity becomes too high, the additive cannot exist stably in the aqueous ink, the above-mentioned action is weakened, and image clarity is not obtained. a and b each independently represent 0 or 1.

[0052] Examples of the alkylene group having 5 to 20 carbon atoms include an n-pentane-1,2-diyl group, an n-pentane-1,5-diyl group, an n-pentane-2,4-diyl group, a 2,2-dimethylpropane-1,3-diyl group, an n-hexane-1,2-diyl group, an n-hexane-1,6-diyl group, an n-hexane-2,5-diyl group, a 3-methylpentane-1,5-diyl group, a cyclohexane-1,2-diyl group, a cyclohexane-1,3-diyl group, a cyclohexane-1,4-diyl group, an n-heptane-1,2-diyl group, an n-heptane-1,7-diyl group, a 2-methyl-2-propylpropane-1,3-diyl group, an n-octane-1,2-diyl group, an n-octane-1,8-diyl group, a 1,4-dimethylcyclohexane-α, Examples of the arylene group having 6 to 12 carbon atoms include 1,2-phenylene group, 1,3-phenylene group, 1,4-phenylene group, 2,2'-biphenylene group, 3,3'-biphenylene group, 4,4'-biphenylene group, 1,3-naphthylene group, 1,4-naphthylene group, 1,5-naphthylene group, 2,3-naphthylene group, 2,6-naphthylene group, and 2,7-naphthylene group. The number of carbon atoms of the alkylene group is preferably 5 to 15.

[0053] The content (ppm) of the additive in the ink is 10 ppm or more and 1,200 ppm or less, preferably 50 ppm or more and 1,000 ppm or less, based on the total mass of the ink. By making the content of the additive 10 ppm or more, as described above, it is possible to make the additive act more effectively on the surface of the pigment particles, and the effect of improving the image clarity can be further enhanced. On the other hand, by making the content of the additive 1,200 ppm or less, it is possible to further suppress the aggregation of the additives, as described above, and the effect of improving the image clarity can be further enhanced.

[0054] Compound A can be synthesized according to a conventional method described in, for example, JP 2017-179006 A. Specifically, compound A can be obtained by heating and reacting (meth)acrylic acid with a bifunctional epoxy compound having glycidyl ether groups at both ends in the presence of a phase transfer catalyst and a polymerization inhibitor. Specific examples of compound A (compounds A01 to A20) are shown in Table 1.

[0055] TIFF2024022548000007.tif187170

[0056] Compound B can be synthesized according to a conventional method described in, for example, JP 2017-179006 A. Specifically, compound B can be obtained by heating and reacting (meth)acrylic acid with a bifunctional epoxy compound having glycidyl ether groups at both ends in the presence of a phase transfer catalyst and a polymerization inhibitor. Specific examples of compound B (compounds B01 to 16) are shown in Table 2.

[0057] TIFF2024022548000008.tif174170

[0058] (aqueous medium) The ink is an aqueous ink containing water as the aqueous medium. The aqueous medium may further contain a water-soluble organic solvent. As the water, deionized water (ion-exchanged water) is preferably used. The content (mass %) of water in the ink is preferably 50.00 mass % or more and 95.00 mass % or less based on the total mass of the ink.

[0059] The water-soluble organic solvent is not particularly limited as long as it is water-soluble. For example, alcohol, polyhydric alcohol, polyglycol, glycol ether, nitrogen-containing polar solvent, sulfur-containing polar solvent, etc. can be used as the water-soluble organic solvent. The content (mass%) of the water-soluble organic solvent in the ink is preferably 5.00 mass% or more and 90.00 mass% or less, and more preferably 10.00 mass% or more and 50.00 mass% or less, based on the total mass of the ink.

[0060] (Other additives) In addition to the above-mentioned additives (compound A and compound B), the ink may further contain other additives as necessary. Examples of the other additives include surfactants, pH adjusters, rust inhibitors, preservatives, antifungal agents, antioxidants, reduction inhibitors, evaporation promoters, and chelating agents. Among them, it is preferable to contain a surfactant in the ink. The content (mass %) of the surfactant in the ink is preferably 0.10% by mass or more and 5.00% by mass or less, and more preferably 0.10% by mass or more and 2.00% by mass or less, based on the total mass of the ink. Examples of the surfactant include anionic surfactants, cationic surfactants, and nonionic surfactants.

[0061] (Ink properties) Since the ink is applied to the inkjet method, it is preferable to appropriately control the physical properties of the ink. The surface tension of the ink at 25°C is preferably 10 mN / m or more and 60 mN / m or less, and more preferably 20 mN / m or more and 40 mN / m or less. The viscosity of the ink at 25°C is preferably 1.0 mPa·s or more and 10.0 mPa·s or less. The pH of the ink at 25°C is preferably 5.0 or more and 10.0 or less, and more preferably 6.0 or more and 9.0 or less. The pH of the ink at 25°C is particularly preferably 6.0 or more and 8.5 or less.

[0062] <Ink cartridges> The ink cartridge of the present invention includes ink and an ink storage section that stores the ink. The ink stored in the ink storage section is the water-based ink of the present invention described above. FIG. 1 is a cross-sectional view that shows a schematic diagram of an embodiment of the ink cartridge of the present invention. As shown in FIG. 1, an ink supply port 12 for supplying ink to a recording head is provided on the bottom surface of the ink cartridge. The inside of the ink cartridge is an ink storage section for storing ink. The ink storage section is composed of an ink storage chamber 14 and an absorber storage chamber 16, which are communicated with each other via a communication port 18. The absorber storage chamber 16 is also communicated with the ink supply port 12. The ink storage chamber 14 stores liquid ink 20, and the absorber storage chamber 16 stores absorbers 22 and 24 that hold the ink in an impregnated state. The ink storage section may not have an ink storage chamber that stores liquid ink, and may be in a form in which the entire amount of ink stored is held by the absorber. The ink storage section may also be in a form in which the entire amount of ink stored is stored in a liquid state, without having an absorber. Furthermore, the ink cartridge may be configured to have an ink container and a recording head.

[0063] <Inkjet recording method> The inkjet recording method of the present invention is a method of ejecting the above-described aqueous ink of the present invention from an inkjet recording head to record an image on a recording medium. Methods for ejecting the ink include a method of imparting mechanical energy to the ink and a method of imparting thermal energy to the ink. In the present invention, it is particularly preferable to adopt a method of ejecting the ink by imparting thermal energy to the ink. Other than using the ink of the present invention, the steps of the inkjet recording method may be known.

[0064] FIG. 2 is a diagram showing an example of an inkjet recording device used in the inkjet recording method of the present invention, in which (a) is a perspective view of the main part of the inkjet recording device, and (b) is a perspective view of a head cartridge. The inkjet recording device is provided with a conveying means (not shown) for conveying a recording medium 32, and a carriage shaft 34. A head cartridge 36 can be mounted on the carriage shaft 34. The head cartridge 36 includes recording heads 38 and 40, and is configured so that an ink cartridge 42 is set thereon. While the head cartridge 36 is conveyed in the main scanning direction along the carriage shaft 34, ink (not shown) is ejected from the recording heads 38 and 40 toward the recording medium 32. Then, an image is recorded on the recording medium 32 by conveying the recording medium 32 in the sub-scanning direction by a conveying means (not shown). EXAMPLES

[0065] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples without departing from the gist of the invention. "Parts" and "%" used to describe the amounts of components are based on mass unless otherwise specified.

[0066] <Method of resin analysis> (Weight average molecular weight and number average molecular weight) The weight average molecular weight (Mw) and number average molecular weight (Mn) of the resin are both values ​​calculated as polystyrene by gel permeation chromatography (GPC). The specific measurement conditions for GPC are shown below. Measurement equipment: Molecular weight measurement equipment (product name "Waters ALLIANCE e2695", manufactured by Waters) Column: Asahipak "GF-1G 7B" (guard column), "GF-310 HQ", and "GF-510 HQ" (all trade names, manufactured by Showa Denko) connected in series Eluent: 20mmol / L lithium bromide in N,N-dimethylformamide ·Flow rate: 0.6mL / min Sample injection volume: 0.100mL Oven temperature: 40℃ Detector: Refractive index (RI) detector (product name "Wyatt Optilab rex Refractive Index Detector", manufactured by Wyatt Technology)

[0067] The molecular weight was calculated using a molecular weight calibration curve prepared using a molecular weight standard (product name "EasiCal Type PS-2 polystyrene", manufactured by Agilent Technology).

[0068] (Acid value) The acid value of the resin was measured by a titration method conforming to JIS K 0070:1992. 0.5 to 2.0 g of precisely weighed resin was used as the sample to be measured. The sample was placed in a 50.0 mL beaker, and 25.0 mL of a mixture of tetrahydrofuran and ethanol (volume ratio = 2:1) was added to dissolve the sample. Titration was performed by potentiometric titration using an ethanol solution of 0.1 mol / L potassium hydroxide as the titrant, and the amount of titrant used was defined as S (mL). In addition, a blank not containing the sample was titrated in the same manner, and the amount of titrant used was defined as B (mL). An automatic titration device (trade name "COM-2500", manufactured by Hiranuma Sangyo Co., Ltd.) was used as the measuring device. Using the obtained S (mL) and B (mL), the acid value of the resin was calculated from the following formula (X). In the following formula (X), "f" represents the factor (potency) of the potassium hydroxide ethanol solution, and "M" represents the precisely weighed weight (g) of the sample. Acid value (mgKOH / g)={(SB)×f×5.61} / M ···(X)

[0069] <Resin manufacturing> 200.0 parts of methyl ethyl ketone was placed in a flask equipped with a stirrer, a nitrogen inlet tube, a reflux condenser, and a thermometer, and the temperature was raised to 78°C while stirring under a nitrogen atmosphere. A polymerization initiator solution was prepared by dissolving the amount of polymerization initiator (2,2'-azobis(2-methylbutyronitrile)) shown in Table 3 in 20.0 parts of methyl ethyl ketone. The types and amounts of monomers and polymerization initiator solutions shown in Table 3 were each dropped into a flask maintained at 78°C over 2 hours. After dropping, the mixture was stirred at 78°C for 4 hours to polymerize. The pressure was reduced to remove methyl ethyl ketone, and the resin was taken out. The resin was added to 10 times the amount (mass ratio) of methanol to precipitate, and then collected and dried. Potassium hydroxide 0.9 times (molar basis) the acid value of the resin and an appropriate amount of ion-exchanged water were added to obtain liquids 1 to 5 containing resin with a resin content of 20.0%. The abbreviations in Table 3 are St: styrene, nBA: n-butyl acrylate, MMA: methyl methacrylate, CHMA: cyclohexyl methacrylate, AA: acrylic acid, MAA: methacrylic acid, and MAn: maleic anhydride. Table 3 shows the weight average molecular weight, number average molecular weight, dispersity (weight average molecular weight / number average molecular weight), and acid value of the resin.

[0070] TIFF2024022548000009.tif58170

[0071] <Synthesis of additives> The additives were synthesized under the conditions shown below. The structures of the compounds obtained in Synthesis Examples 1 to 15 are as shown in Tables 1 and 2.

[0072] (Synthesis Example 1) The following reagents and solvent were placed in a 100 mL three-neck flask equipped with a thermometer and a condenser and stirred to obtain a reaction solution. Ethylene glycol diglycidyl ether (product name "Denacol EX-810", Nagase ChemteX): 20.9 g (0.12 mol) Tetrabutylammonium bromide: 1.93g (6.0mmol) 4-Methoxyphenol: 30mg (0.24mmol) Toluene: 30mL

[0073] The resulting reaction solution was heated to 110°C while stirring, and 19.0g (0.264mol) of acrylic acid was added dropwise over 45 minutes. After reacting for 1 hour, 20mL of ethyl acetate was added and extracted to obtain an organic layer. The resulting organic layer was washed three times with 35mL of saturated aqueous sodium bicarbonate solution, and then washed once with 35mL of saturated saline to remove unreacted acrylic acid. 5g of anhydrous sodium sulfate was added to the organic layer, which was then dried and filtered to obtain a filtrate. The filtrate obtained was concentrated using a rotary evaporator to obtain 32.2g of compound A01, which was a colorless and transparent liquid (yield 84%). Compound A01 was analyzed and identified using a matrix-assisted laser desorption ionization time-of-flight mass spectrometer (MALDI-TOF MS). The results are shown below. [MALDI-TOF MS analysis results] Actual value: m / z=318.08 Calculated value: C 14 H 22 O8=318.13

[0074] (Synthesis Example 2) Instead of ethylene glycol diglycidyl ether, 26.2 g (0.12 mol) of polyethylene glycol (n=2) diglycidyl ether (trade name "Denacol EX-850", Nagase ChemteX) was used. Otherwise, the procedure was the same as in the above-mentioned Synthesis Example 1, and 36.0 g of compound A02, which was a colorless and transparent liquid, was obtained (yield 83%). The results of analysis and identification of compound A02 using MALDI-TOF MS are shown below. [MALDI-TOF MS analysis results] Actual value: m / z=362.10 Calculated value: C 16 H 26 O9=362.16

[0075] (Synthesis Example 3) The following reagents and solvent were placed in a 100 mL three-neck flask equipped with a thermometer and a condenser and stirred to obtain a reaction solution. Polyethylene glycol (n=9) diglycidyl ether (product name "Denacol EX-830", Nagase ChemteX): 31.6 g (60 mmol) Tetrabutylammonium bromide: 0.967g (3.0mmol) 4-Methoxyphenol: 15mg (0.12mmol) Toluene: 45mL

[0076] The resulting reaction solution was heated to 110°C while stirring, and 9.51g (0.132mol) of acrylic acid was added dropwise over 45 minutes. After reacting for 2 hours, 30mL of ethyl acetate was added and extracted to obtain an organic layer. The resulting organic layer was washed three times with 40mL of saturated aqueous sodium bicarbonate solution, and then washed once with 40mL of saturated saline to remove unreacted acrylic acid. 5g of anhydrous sodium sulfate was added to the organic layer, which was then dried and filtered to obtain a filtrate. The filtrate obtained was concentrated using a rotary evaporator to obtain 31.7g of waxy compound A03 (yield 79%). The results of analysis and identification of compound A03 using MALDI-TOF MS are shown below. [MALDI-TOF MS analysis results] Actual value: m / z=670.22 Calculated value: C 30 H 54 O 16 =670.34

[0077] (Synthesis Example 4) Instead of polyethylene glycol (n=9) diglycidyl ether, 46.1 g (60 mmol) of polypropylene glycol (n=11) diglycidyl ether (trade name "Denacol EX-931", Nagase Chemtex) was used. Otherwise, the procedure was the same as in the above-mentioned Synthesis Example 3 to obtain 40.3 g of waxy compound A10 (74% yield). The results of analysis and identification of compound A10 using MALDI-TOF MS are shown below. [MALDI-TOF MS analysis results] Actual value: m / z=912.48 Calculated value: C 45 H 84 O18 =912.57

[0078] (Synthesis Example 5) Except for using 22.7 g (0.264 mol) of methacrylic acid instead of acrylic acid, the same procedure as in Synthesis Example 1 was followed to obtain 33.8 g of compound A17, which was a colorless, transparent liquid (yield 81%). The results of analysis and identification of compound A17 using MALDI-TOF MS are shown below. [MALDI-TOF MS analysis results] Actual value: m / z=346.09 Calculated value: C 16 H 26 O9=346.16

[0079] (Synthesis Example 6) The following reagents and solvent were placed in a 100 mL three-neck flask equipped with a thermometer and a condenser and stirred to obtain a reaction solution. 1,6-Hexanediol diglycidyl ether (product name "Denacol EX-212", Nagase ChemteX): 46.1 g (0.20 mol) Tetrabutylammonium bromide: 3.24g (10.0mmol) 4-Methoxyphenol: 50mg (0.40mmol) Toluene: 50 mL

[0080] The resulting reaction solution was heated to 110°C while stirring, and 30.3g (0.42mol) of acrylic acid was added dropwise over 45 minutes. After reacting for 1 hour, 40mL of ethyl acetate was added and extracted to obtain an organic layer. The resulting organic layer was washed three times with 50mL of saturated aqueous sodium bicarbonate solution, and then washed once with 50mL of saturated saline to remove unreacted acrylic acid. 5g of anhydrous sodium sulfate was added to the organic layer, which was then dried and filtered to obtain a filtrate. The filtrate obtained was concentrated using a rotary evaporator to obtain 59.0g of compound B01, which was a colorless and transparent liquid (yield 79%). The results of analysis and identification of compound B01 using MALDI-TOF MS are shown below. [MALDI-TOF MS analysis results] Actual value: m / z=374.09 Calculated value: C 18 H 30 O8=374.19

[0081] (Synthesis Example 7) Instead of 1,6-hexanediol diglycidyl ether, 44.5 g (0.20 mol) of resorcinol diglycidyl ether (trade name "Denacol EX-201", Nagase ChemteX) was used. Otherwise, the procedure was the same as in Synthesis Example 6 above, and 60.0 g of compound B08, a colorless and transparent liquid, was obtained (yield 82%). The results of analysis and identification of compound B08 using MALDI-TOF MS are shown below. [MALDI-TOF MS analysis results] Actual value: m / z=366.04 Calculated value: C 18 H 22 O8=366.13

[0082] (Synthesis Example 8) Instead of 1,6-hexanediol diglycidyl ether, 56.9 g (0.20 mol) of phthalic acid diglycidyl ester (trade name "Denacol EX-722", Nagase Chemtex) was used. Otherwise, the procedure was the same as in the above-mentioned Synthesis Example 6, and 68.1 g of compound B12, which was a colorless and transparent liquid, was obtained (yield 80%). The results of analysis and identification of compound B12 using MALDI-TOF MS are shown below. [MALDI-TOF MS analysis results] Actual value: m / z=428.07 Calculated value: C 20 H 28 O 10 =428.17

[0083] (Synthesis Example 9) Instead of 1,6-hexanediol diglycidyl ether, 55.7 g (0.20 mol) of phthalic acid diglycidyl ester (trade name "Denacol EX-721", Nagase Chemtex) was used. Otherwise, the procedure was the same as in the above-mentioned Synthesis Example 6, and 66.3 g of compound B14, which was a colorless and transparent liquid, was obtained (yield 79%). The results of analysis and identification of compound B14 using MALDI-TOF MS are shown below. [MALDI-TOF MS analysis results] Actual value: m / z=422.04 Calculated value: C 20 H 22 O 10 =422.12

[0084] (Synthesis Example 10) Instead of 1,6-hexanediol diglycidyl ether, 43.3 g (0.20 mol) of neopentyl glycol diglycidyl ether (trade name "Denacol EX-211", Nagase ChemteX) was used. Furthermore, instead of acrylic acid, 36.2 g (0.42 mol) of methacrylic acid was used. Except for these, the same procedure as in Synthesis Example 6 above was followed to obtain 65.0 g of compound B16, which is a colorless and transparent liquid (yield 84%). The results of analysis and identification of compound B16 using MALDI-TOF MS are shown below. [MALDI-TOF MS analysis results] Actual value: m / z=388.12 Calculated value: C 19 H 32 O8=388.21

[0085] (Synthesis Example 11) Polyethylene glycol (n=15), epichlorohydrin, and potassium hydroxide were prepared. Using these compounds, polyethylene glycol (n=15) diglycidyl ether was synthesized in water by the Williamson ether synthesis method in the presence of benzyltrimethylammonium chloride catalyst. Then, 47.5 g (60 mmol) of polyethylene glycol (n=15) diglycidyl ether was used instead of polyethylene glycol (n=9) diglycidyl ether. The rest was the same as in Synthesis Example 4 described above, and 34.9 g of compound A05 was obtained (yield 62%). The results of analysis and identification of compound A05 using MALDI-TOF MS are shown below. [MALDI-TOF MS analysis results] Actual value: m / z=934.40 Calculated value: C 42 H 78 O 22 =934.50

[0086] (Synthesis Example 12) 2,3-butanediol diglycidyl ether was synthesized in the same manner as in Synthesis Example 11, except that 2,3-butanediol was used instead of polyethylene glycol (n=15). Then, 30.3 g of compound A16 was obtained (73% yield) in the same manner as in Synthesis Example 1, except that 24.3 g (0.12 mol) of 2,3-butanediol diglycidyl ether was used instead of ethylene glycol diglycidyl ether. The results of analysis and identification of compound A16 using MALDI-TOF MS are shown below. [MALDI-TOF MS analysis results] Actual value: m / z=346.09 Calculated value: C 16 H 26 O8=346.16

[0087] (Synthesis Example 13) 1,8-octanediol diglycidyl ether was synthesized in the same manner as in Synthesis Example 11, except that 1,8-octanediol was used instead of polyethylene glycol (n=15). 47.7 g (0.20 mol) of 1,8-octanediol diglycidyl ether was used instead of 1,6-hexanediol diglycidyl ether. 64.4 g of compound B02 was obtained (yield 80%) in the same manner as in Synthesis Example 6, except that. The results of analysis and identification of compound B02 using MALDI-TOF MS are shown below. [MALDI-TOF MS analysis results] Actual value: m / z=402.14 Calculated value: C 20 H 34 O8=402.23

[0088] (Synthesis Example 14) Instead of 1,6-hexanediol diglycidyl ether, 70.5 g (0.20 mol) of 4,4'-isopropylidenedicyclohexane diglycidyl ether (trade name "Denacol EX-252", Nagase Chemtex) was used. Otherwise, the procedure was the same as in the above-mentioned Synthesis Example 6, and 75.5 g of compound B06, which was a colorless and transparent liquid, was obtained (76% yield). The results of analysis and identification of compound B06 using MALDI-TOF MS are shown below. [MALDI-TOF MS analysis results] Actual value: m / z=496.20 Calculated value: C 27 H 44 O8=496.30

[0089] (Synthesis Example 15) 3,3'-biphenol diglycidyl ether was synthesized in the same manner as in Synthesis Example 11 above, except that 3,3'-biphenol was used instead of polyethylene glycol (n=15). Then, 6.0 g (20 mmol) of 3,3'-biphenol diglycidyl ether was used instead of 1,6-hexanediol diglycidyl ether. Otherwise, the synthesis scale was reduced to one tenth as in Synthesis Example 6 above, and 5.5 g of compound B09 was obtained (yield 62%). The results of analysis and identification of compound B09 using MALDI-TOF MS are shown below. [MALDI-TOF MS analysis results] Actual value: m / z=442.55 Calculated value: C 24 H 26 O8=442.46

[0090] <Production of pigment dispersion> (Pigment Dispersion 1-15) After mixing the components shown in Table 4, a high-pressure homogenizer (product name "Starburst", manufactured by Sugino Machine) was used to perform a dispersion treatment under conditions of a treatment pressure of 200 MPa and 40 passes. After centrifuging for 5 minutes at a rotation speed of 12,000 rpm to remove coarse particles, the mixture was filtered under pressure using a polypropylene filter (manufactured by F-Tech) with a pore size of 1.0 μm. An appropriate amount of ion-exchanged water was added as necessary to obtain pigment dispersions 1 to 15.

[0091] TIFF2024022548000010.tif142170

[0092] (Pigment Dispersion 16) A commercially available pigment dispersion (product name "Cab-O-Jet 400", manufactured by Cabot) was heated and concentrated to half its volume to obtain pigment dispersion 16, which has a self-dispersing pigment content of 30.0%. Pigment dispersion 16 is an aqueous dispersion (pigment content: 15.0%) of a self-dispersing pigment in which atomic groups containing anionic groups are bonded to the particle surfaces of the pigment (carbon black).

[0093] <Ink Preparation> The components shown below were mixed and thoroughly stirred, then pressure filtered through a microfilter (manufactured by Sartorius) with a pore size of 1.2 μm to prepare each ink. "Acetylenol E100" shown below is the trade name of a nonionic surfactant manufactured by Kawaken Fine Chemicals. Pigment dispersions of the types shown in Tables 5-1 and 5-2: The amount (parts) shown in Tables 5-1 and 5-2 Additives of the types shown in Tables 5-1 and 5-2: Amounts (ppm) shown in Tables 5-1 and 5-2 Glycerin: 5.00 parts Triethylene glycol: 10.00 parts Acetylenol E100: 0.10 parts 1,2-Hexanediol: 2.00 parts Ion exchange water: the remaining amount that makes the total of all ingredients 100.00 parts

[0094] In Table 5-2, "Comparative Compound 1" used in Comparative Example 4 is the same compound as "Ether Compound 1" described in the Example of Patent Document 1 (JP Patent Publication No. 11-217528). "Comparative Compound 2" used in Comparative Example 5 is 1,8-octanediol. "Comparative Compound 3" used in Comparative Example 6 is the same compound as "(3) Polyoxyethylene Allyl Glycidyl Nonyl Phenyl Ether" described in the Example of JP Patent Publication No. 2008-184546. The structures of Comparative Compounds 1 to 3 are shown below.

[0095] TIFF2024022548000011.tif76170

[0096] <Evaluation> The following evaluation was performed for each ink. In the evaluation criteria shown below, "A" and "B" were considered to be acceptable levels, and "C" was considered to be unacceptable. The evaluation results are shown on the right side of Tables 5-1 and 5-2. In Tables 5-1 and 5-2, "Additive content A" is the total content (ppm) of the compound represented by general formula (1) and the compound represented by general formula (2).

[0097] (Image clarity) Each ink was filled into an ink cartridge, and the ink was mounted on an inkjet recording device (trade name "PIXUS Pro 9500", manufactured by Canon) that ejects ink from a recording head by the action of thermal energy. In this embodiment, the recording duty of a solid image recorded under the condition that 28 ng of ink is applied to a unit area of ​​1 / 600 inch x 1 / 600 inch is defined as 100%. Using the above inkjet recording device, a solid image with a recording duty of 100% was recorded on the entire surface of an A4-sized recording medium (photo paper, trade name "Canon Photo Paper Gloss Gold GL-101", manufactured by Canon). After drying the image at 25°C for 24 hours, two fluorescent lamps arranged in parallel at 10 cm intervals were used as an observation light source, and the image was irradiated with fluorescent light at an angle of 45 degrees from a distance of 2 m (illumination angle 45 degrees). The shape of a fluorescent lamp was projected onto the image, and the shape of the fluorescent lamp projected onto the image was visually observed from an angle of 45 degrees (observation angle of 45 degrees), and the image clarity was evaluated according to the evaluation criteria shown below. A: The boundary between the two projected fluorescent lights was clearly visible, and there was no blurring at the edges. B: The boundary between the two projected fluorescent lights was clear, but the edges were blurred. C: I couldn't see the boundary between the two projected fluorescent lights.

[0098] TIFF2024022548000012.tif250170

[0099] TIFF2024022548000013.tif255170

[0100] The evaluation result of the image clarity of Example 45 was "B", the same as Examples 29, 32 to 34, 39, and 41 to 43, but Example 45 was inferior. The evaluation result of the image clarity of Example 46 was "B", the same as Examples 35, 38, 40, and 44, but Example 46 was inferior. In Comparative Example 3, the pigment aggregated during the ink preparation, so "poor" was entered in the evaluation result column for image clarity.

Claims

1. An aqueous inkjet ink containing pigments, resins, and additives, The aforementioned additive is at least one selected from the group consisting of compounds represented by the following general formula (1) and compounds represented by the following general formula (2). A water-based ink characterized in that the content of the aforementioned additive is 10 ppm or more and 1,200 ppm or less, based on the total mass of the ink. (In the above general formula (1), R １ , R ２ , R ３ , and R ４ Each of these independently represents either a hydrogen atom or a methyl group. (n represents an integer from 1 to 15.) (In the above general formula (2), R １ and R ２ Each of these independently represents either a hydrogen atom or a methyl group. L represents an alkylene group with 5 to 20 carbon atoms or an arylene group with 6 to 12 carbon atoms. (a and b each independently represent 0 or 1.)

2. The content of the resin (ppm) is, in terms of its mass ratio to the content of the additive (ppm), The aqueous ink according to claim 1, wherein the dilution ratio is 20 times or more and 1,000 times or less.

3. The aqueous ink according to claim 1 or 2, wherein the resin is at least one selected from the group consisting of acrylic resins and methacrylic resins.

4. The aqueous ink according to claim 1 or 2, wherein the pigment is at least one selected from the group consisting of quinacridone pigment, diketopyrrolopyrrole pigment, perinone pigment, and perylene pigment.

5. The aqueous ink according to claim 1 or 2, wherein the resin content (ppm) is 1,000 ppm or more and 50,000 ppm or less, based on the total mass of the ink.

6. An ink cartridge comprising ink and an ink storage section for storing the ink, An ink cartridge characterized in that the ink is the aqueous ink described in claim 1 or 2.

7. An inkjet recording method that records an image on a recording medium by ejecting ink from an inkjet recording head, An inkjet recording method characterized in that the ink is the aqueous ink described in claim 1 or 2.

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