JP2024008101A - Aqueous ink, ink cartridge, and inkjet recording method - Google Patents

Abstract

To provide an aqueous ink for inkjet recording that enables the recording of an image with superior scratch resistance and exhibits a superior ability to restore the ink fixation.SOLUTION: An aqueous ink for inkjet recording includes a pigment, resin particles, and a water-soluble resin. The resin particles are composed of at least one first resin selected from the group consisting of polyethylene, oxidized polyethylene, Fischer-Tropsch wax, microcrystalline wax, paraffin wax, ozokerite, and ceresin. The water-soluble resin is a second resin with crystallinity, such as polyester or ethylene-acrylic acid copolymers.SELECTED DRAWING: None

Description

The present invention relates to an aqueous ink, an ink cartridge, and an inkjet recording method.

BACKGROUND ART Water-based inks for inkjet use containing pigments as coloring materials are widely used in order to impart fastness such as weather resistance and water resistance to recorded images. In recent years, inks using pigments (pigment inks) have been used in the fields of signage and graphic art, which are recorded using commercial and large-format inkjet recording devices. In these fields, it is required not only to improve quality but also to be able to record images with scratch resistance to prevent scratching or peeling during the recording process, post-recording processing process, logistics, and exhibition environment. There is.

Further, pigment ink tends to aggregate and stick within minute ink channels formed inside a recording head used in an inkjet recording method, and the ejection state tends to become unstable. Furthermore, if the ink is left for a long time after recording, even if a recovery operation is performed, the ink ejection state is difficult to return to its original state, and non-ejection or ejection skewing is likely to occur. For this reason, there is a demand for ink that is less likely to stick.

Since the pigment exists as a solid on the surface of the recording medium, it is difficult to improve the scratch resistance of the image unless the pigment is protected by some method. In order to improve the scratch resistance of recorded images, an ink containing wax particles formed of a chain hydrocarbon such as polyethylene and a recording method using this ink have been proposed (Patent Document 1). Furthermore, an ink set has been proposed that combines an ink containing resin particles formed from a chain hydrocarbon such as polyolefin and a primer containing an aggregation promoter that promotes aggregation of the ink (Patent Document 2). ).

JP 2019-202419 Publication JP2020-176218A

The present inventors investigated the fixation recovery properties of inks containing resin particles formed from chain hydrocarbons proposed in Patent Documents 1 and 2. Specifically, after ink was ejected from an inkjet recording head, the ink was left to stand for a long time, and then a suction recovery operation was performed. As a result, it was found that the sticking of ink was not resolved and it was difficult to restore the initial normal ejection state. That is, it has been found that when an image is recorded using the inks proposed in Patent Documents 1 and 2 after an inkjet recording apparatus has been left unused for a long time, ink non-ejection or ejection distortion is likely to occur.

Therefore, an object of the present invention is to provide an aqueous inkjet ink that can record images with excellent scratch resistance and has excellent fixation recovery properties. Another object of the present invention is to provide an ink cartridge and an inkjet recording method using this aqueous ink.

That is, according to the present invention, there is provided a water-based inkjet ink containing a pigment, resin particles, and a water-soluble resin, wherein the resin particles include polyethylene, oxidized polyethylene, Fischer-Tropsch wax, microcrystalline wax, paraffin wax, Provided is a water-based ink formed of at least one first resin selected from the group consisting of ozokerite and ceresin, wherein the water-soluble resin is a second resin having crystallinity. .

According to the present invention, it is possible to provide an aqueous inkjet ink that can record images with excellent scratch resistance and has excellent fixation recovery properties. Further, according to the present invention, it is possible to provide an ink cartridge and an inkjet recording method using this aqueous ink.

1 is a cross-sectional view schematically showing an embodiment of an ink cartridge of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram schematically showing 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.

Hereinafter, the present invention will be further explained in detail by citing preferred embodiments. In the present invention, when a compound is a salt, the salt is dissociated into ions and exists in the ink, but for convenience, it is expressed as "containing a salt." Furthermore, water-based ink for inkjet is sometimes simply referred to as "ink." Physical property values are values at room temperature (25° C.) unless otherwise specified.

First, the present inventors studied inks containing waxes with different characteristics in order to improve the scratch resistance of images. As a result, the fixation recovery of ink tends to decrease regardless of the type of wax, but the scratch resistance of images recorded with ink containing resin particles formed from wax, which is a chain hydrocarbon, decreases. It turned out to be good. Furthermore, among the chain hydrocarbons, paraffin wax, microcrystalline wax, ozokerite, ceresin, Fischer-Tropsch wax, polyethylene, and oxidized polyethylene were found to be preferable. The resin particles tend to remain in the image (in the pigment layer to be formed). Further, resin particles substantially formed of linear and branched hydrocarbons have high crystallinity, and the crystal molecules interact strongly with each other. Therefore, it is thought that the strength of the image is improved and the scratch resistance is increased.

On the other hand, when resin particles made of polypropylene wax are used, the interaction between crystal molecules tends to be too strong, resulting in images that are hard and brittle, making it difficult to improve scratch resistance. Understood. Furthermore, animal-derived waxes such as beeswax, spermaceti, and shellac wax; plant-derived waxes such as carnauba wax, wood wax, rice wax, and candelilla wax; and mineral-derived waxes such as montan wax were also investigated. As a result, it was found that while these waxes have hydrocarbon chains, they also have ester bonds and carboxylic acid groups, so intermolecular interactions are weak, making it difficult to improve the scratch resistance of images. In other words, in order to improve the scratch resistance of images, it is necessary to select a wax with appropriate intermolecular interactions, and it has been found that a specific type of chain hydrocarbon wax is suitable. .

Next, the present inventors investigated the fixation recovery properties of ink containing resin particles formed of chain hydrocarbons. As a result, it was found that the fixation recovery property of the ink was particularly reduced due to the resin particles formed of chain hydrocarbons. The resin particles aggregate due to the intermolecular interaction of the crystalline components constituting the resin particles to form aggregates, and the aggregates accumulate and become fixed due to water evaporation. If such a phenomenon occurs in the vicinity of the ejection port that has been left unused for a long time, it is thought that the ejection port is likely to become clogged, leading to non-ejection or skewed ejection of ink.

The present inventors have studied the combined use of additives such as surfactants and resin dispersants that can be stably adsorbed to resin particles in order to weaken intermolecular interactions and suppress agglomeration of resin particles. As a result, it was discovered that the fixation recovery property of the ink can be improved by containing a crystalline water-soluble resin together with the above-mentioned specific wax, leading to the present invention.

A water-soluble resin having crystallinity is dissolved in an aqueous ink whose main liquid medium is water. Therefore, the crystalline portion in the water-soluble resin is diffused into the liquid medium at the molecular level. The crystalline portion in the water-soluble resin diffused into the ink selectively and firmly adsorbs to the surface of the resin particle through intermolecular interaction with the resin particle having a crystal component. The water-soluble resin is difficult to be released from the surface of the strongly adsorbed resin particles, weakens the intermolecular interaction between the resin particles, and suppresses aggregation, so it is thought that the fixation recovery property of the ink is improved.

In addition, when using an ink containing resin particles formed from a water-soluble resin having crystallinity and a chain hydrocarbon, compared to using an ink containing resin particles without containing a water-soluble resin, It was found that the scratch resistance of the image was further improved. When the water evaporates on the recording medium while the water-soluble resin remains interposed between the resin particles, the cohesive force of the resin particles increases due to the interaction between the crystal parts in the water-soluble resin, and the scratch resistance of the image increases. This is thought to improve performance.

Note that even if resin particles made of the above waxes derived from animals, plants, and minerals are combined with a water-soluble resin having crystallinity, it is difficult to improve the fixation recovery property of the ink. This is because resin particles made of the above-mentioned animal-derived waxes have few sites where water-soluble resin can be adsorbed, and it is difficult to have water-soluble resin stably exist around the resin particles. it is conceivable that.

<Ink>
The aqueous ink of the present invention is an inkjet ink containing a pigment, resin particles, and a water-soluble resin. The resin particles are made of at least one first resin selected from the group consisting of polyethylene, oxidized polyethylene, Fischer-Tropsch wax, microcrystalline wax, paraffin wax, ozokerite, and ceresin. The water-soluble resin is a second resin having crystallinity. Each component constituting the ink will be described in detail below.

(pigment)
The ink contains pigment. Examples of pigment dispersion methods include resin-dispersed pigments dispersed with a resin dispersant, pigments dispersed with a surfactant, and microcapsule pigments in which at least a portion of the pigment particle surface is coated with a resin or the like. can. In addition, there are self-dispersing pigments in which functional groups containing hydrophilic groups such as anionic groups are bonded to the surface of pigment particles, and pigments in which organic groups containing polymers are chemically bonded to the surface of pigment particles (resin bonding). A type of self-dispersing pigment) can also be used. Further, pigments having different dispersion methods may be used in combination.

As the pigment, inorganic pigments, organic pigments, etc. can be used. Specific examples of pigments include inorganic pigments such as carbon black and titanium oxide; organic pigments such as azo, phthalocyanine, quinacridone, isoindolinone, imidazolone, diketopyrrolopyrrole, and dioxazine. The pigment content (mass%) in the ink is preferably 0.1% by mass or more and 15.0% by mass or less, and 1.0% by mass or more and 10.0% by mass or less, based on the total mass of the ink. It is more preferable that

As the resin dispersant, it is preferable to use one that can disperse the pigment in an aqueous medium by the action of an anionic group. As the resin dispersant, resins such as those described below, especially water-soluble resins, can be used. The pigment content (mass %) in the ink is preferably 0.3 times or more and 10.0 times or less relative to the resin dispersant content (mass %).

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

(resin particles)
The ink contains resin particles made of a first resin. The first resin is at least one selected from the group consisting of polyethylene, polyethylene oxide, Fischer-Tropsch wax, microcrystalline wax, paraffin wax, ozokerite, and ceresin. The first resin is a resin that can be dispersed in an aqueous medium and exist in the aqueous medium in a state having a particle size.

Whether a certain resin is a resin particle (water-dispersible resin) or a water-soluble resin can be determined according to the method shown below. First, a liquid (resin solid content: 10% by mass) containing a resin neutralized with an alkali equivalent to an acid value (sodium hydroxide, potassium hydroxide, etc.) is prepared. Next, the prepared liquid is diluted 10 times (by volume) 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 particles with the same particle size are measured, the resin is determined to be "resin particles (water-dispersible resin)". can be judged. On the other hand, when the particle size of the resin in the sample solution is measured by dynamic light scattering and no particles having the same particle size are detected, the resin can be determined to be a "water-soluble resin."

As a particle size distribution measuring device using a dynamic light scattering method, a particle size analyzer (for example, trade name "UPA-EX150", manufactured by Nikkiso Co., Ltd.) or the like can be used. The measurement conditions at this time can be, for example, Set Zero: 30 seconds, number of measurements: 3 times, measurement time: 180 seconds, shape: spherical, and refractive index: 1.59. Of course, the particle size distribution measuring device and measurement conditions used are not limited to those described above. The purpose of measuring the particle diameter of the neutralized resin is to confirm that particles are being formed even if the resin is sufficiently neutralized and becomes more difficult to form particles. Even under such conditions, the resin having a particle shape exists in a particle state even in the aqueous ink.

Preferably, the first resin is polyethylene oxide. Unoxidized polyethylene may have too high crystallinity, and an excessive amount of the second resin tends to exist between the polyethylenes. As a result, the polyethylene, which has the effect of improving the scratch resistance, becomes more likely to be covered with the second resin, and the effect of improving the scratch resistance of the image may be slightly reduced. In addition, the first resin other than oxidized polyethylene has relatively low crystallinity, making it difficult for the second resin to exist between the first resins, and the effect of improving scratch resistance may be slightly reduced.

The first resin does not need to have an acid value, but preferably has an acid value. Since a resin without an acid value does not repel charges, the resin particles tend to come close to each other. Therefore, when moisture evaporates on the recording medium, it becomes difficult for the second resin to exist between the resin particles, and the effect of improving scratch resistance may be slightly reduced. The acid value of the first resin is preferably 40 mgKOH/g or less. When the acid value of the first resin exceeds 40 mgKOH/g, charge repulsion with the second resin is likely to occur. For this reason, the second resin is less likely to be interposed between the resin particles, and the effect of improving scratch resistance may be slightly reduced. The acid value of the first resin is preferably 0 mgKOH/g or more, more preferably 5 mgKOH/g or more.

The acid values of the first resin and the second resin described below can both be measured and calculated by a titration method. Specifically, first, a sample in which a resin is dispersed or dissolved in water is prepared. Next, using a potentiometric automatic titrator, potentiometric titration is performed using a methyl glycol chitosan solution (a 200/N titrant is used in the examples described later) to calculate the number of anionic functional groups per gram of resin. Thereafter, the acid value (mgKOH/g) of the resin can be calculated by converting the calculated number of anionic functional groups into the mass of potassium hydroxide (KOH). As the automatic potentiometric titrator, for example, the product name "AT510" (manufactured by Kyoto Electronics Industry Co., Ltd.) can be used.

The weight average molecular weight of the first resin is preferably 2,000 or more and 40,000 or less. When the weight average molecular weight of the first resin is less than 2,000, the resin becomes soft and weak, and the effect of improving scratch resistance may be reduced. On the other hand, if the weight average molecular weight of the first resin exceeds 40,000, the resin becomes hard and brittle, and the effect of improving scratch resistance may decrease. Furthermore, when resin particles are produced by an emulsification method, the resin becomes difficult to deform, which may make it difficult to prepare the resin particles.

The content (% by mass) of the first resin in the ink is preferably from 0.01% by mass to 5.0% by mass, based on the total mass of the ink. When the content of the first resin is less than 0.01% by mass, the scratch resistance improving component is reduced, so the scratch resistance may be slightly reduced. On the other hand, if the content of the first resin is more than 5.0% by mass, the first resin tends to be excessive, and the effect of improving the fixation recovery property of the ink may be slightly reduced. The content (% by mass) of the first resin in the ink is preferably 0.1% by mass or more and 1.0% by mass or less based on the total mass of the ink.

The melting point of the first resin is preferably 40°C or more and 140°C or less. If the melting point of the first resin is less than 40° C., the resin becomes soft and weak, so that the effect of improving scratch resistance may be slightly reduced. On the other hand, if the melting point of the first resin exceeds 140° C., the resin becomes hard and brittle, and the effect of improving scratch resistance may be slightly reduced. Moreover, when producing resin particles by emulsification, the resin becomes difficult to deform, which may make it difficult to prepare the resin particles. It is more preferable that the first resin has a melting point of 110° C. or higher. If the melting point of the first resin is less than 110°C, the crystallinity will be low, so the effect of improving scratch resistance may be slightly reduced.

The volume-based cumulative 50% particle diameter (D ₅₀ ) of the resin particles formed of the first resin is preferably 30 nm or more and 300 nm or less. If the _D50 of the resin particles is less than 30 nm, the resin particles tend to enter the gaps between the pigment particles in the recording medium to which the ink has been applied, so that the effect of improving scratch resistance may be reduced. On the other hand, if the _D50 of the resin particles exceeds 300 nm, the resin particles may easily separate and float in the ink.

(Water-soluble resin)
The ink contains a water-soluble resin. The water-soluble resin is a second resin having crystallinity. The second resin is not particularly limited as long as it is a water-soluble resin having crystallinity. Examples of the second resin include polyester, α-olefin-maleic anhydride copolymer, ethylene-acrylic acid copolymer, water-soluble nylon, and polyvinyl alcohol.

Whether or not a resin "has crystallinity" can be determined by the "R&B softening point" measured in accordance with JIS K 6863:1994. That is, a resin having an R&B softening point equal to or higher than the glass transition temperature can be determined to "have crystallinity." The glass transition temperature of the resin can be measured using a differential scanning calorimeter (for example, trade name "DSC2500" (manufactured by TA Instruments Japan)).

Polyesters are usually condensates of polycarboxylic acids and polyols. When the polyester contains a unit derived from an aromatic compound as a constituent unit, the crystallinity of the polyester is improved. Moreover, the water solubility of the polyester is improved by including a unit derived from a sulfonic acid or a unit derived from a carboxylic acid different from a dicarboxylic acid. Specifically, polyesters containing units derived from dimethyl isophthalate, dimethyl terephthalate, dimethyl 2,6-naphthalene dicarboxylate, etc. have more preferable crystallinity. Further, polyesters containing units derived from trimellitic anhydride, dimethyl sodium 5-sulfoisophthalate, etc. have more preferable water solubility.

The α-olefin-maleic anhydride copolymer has improved crystallinity when the α-olefin has a long hydrocarbon chain. Further, the α-olefin-maleic anhydride copolymer has improved water solubility when the proportion of units derived from maleic anhydride is high. Specifically, an α-olefin-maleic anhydride copolymer in which the α-olefin has a hydrocarbon number of 12 or more and an acid value of 100 mgKOH/g or more has more preferable crystallinity and water solubility.

The ethylene-acrylic acid copolymer is preferably a binary copolymer of ethylene and acrylic acid. Since the ethylene-acrylic acid copolymer has a unit derived from ethylene (ethylene skeleton), it has high crystallinity, is easily adsorbed to resin particles, and can further improve the fixation recovery property of the ink.

The water solubility of the ethylene-acrylic acid copolymer improves when the proportion of units derived from acrylic acid is high. On the other hand, an ethylene-acrylic acid copolymer further having a unit derived from a (meth)acrylic acid ester tends to have lower crystallinity and water solubility. Specifically, an ethylene-acrylic acid copolymer that is composed only of units derived from ethylene and units derived from acrylic acid and has an acid value of 20 mgKOH/g or more has more preferable crystallinity and water solubility. have

The second resin is preferably at least one of polyester and ethylene-acrylic acid copolymer. Since resins that do not have ester bonds in their main chains have strong hydrogen bonds, the resins interact strongly with each other and become difficult to adsorb onto resin particles, which may reduce the effect of improving fixation recovery.

The second resin is preferably a polyester having a naphthalene skeleton. Since polyester having a naphthalene skeleton has high crystallinity, it is easily adsorbed to resin particles and can further improve the fixation recovery property of the ink.

The second resin does not need to have an acid value, but preferably has an acid value. Resins that do not have an acid value may be difficult to prevent intermolecular interactions between resin particles, and the effect of improving ink fixation recovery may be reduced. The acid value of the second resin is preferably 40 mgKOH/g or less. If the acid value of the second resin exceeds 40 mgKOH/g, the adsorption force to the resin particles tends to decrease due to charge repulsion, and the effect of improving the fixation recovery property of the ink may decrease. The acid value of the second resin is preferably 0 mgKOH/g or more, more preferably 5 mgKOH/g or more.

The difference between the acid value of the first resin and the acid value of the second resin is preferably 15 mgKOH/g or less. If the difference in acid value between the two resins exceeds 15 mgKOH/g, the charge density on the surface of the resin particles will be uneven, and the dispersibility may become unstable and agglomeration may occur. As a result, the effect of improving ink fixation recovery properties may be reduced. The difference between the acid value of the first resin and the acid value of the second resin may be 0 mgKOH/g, and is preferably 1 mgKOH/g or more.

The content (mass%) of the second resin in the ink is preferably 0.001% by mass or more and 5.0% by mass or less, and 0.1% by mass or more and 1.0% by mass, based on the total mass of the ink. % or less is more preferable. The content (mass %) of the second resin in the ink is preferably 1.0 times or more and 3.0 times or less relative to the content (mass %) of the first resin. When the above mass ratio is less than 1.0 times, the amount of the second resin adsorbed to the resin particles decreases, and the effect of improving the fixation recovery property of the ink may decrease. On the other hand, if the above mass ratio is more than 3.0 times, the amount of the second resin becomes excessive, and the resin particles exhibiting scratch resistance are likely to be covered with the second resin, improving the scratch resistance of the image. The effect may be slightly reduced.

The softening point of the second resin is preferably 40°C or more and 200°C or less. If the softening point of the second resin is less than 40° C., the crystallinity of the second resin decreases, making it difficult to adsorb onto the resin particles, and the effect of improving the fixation recovery property of the ink may be slightly decreased. On the other hand, if the softening point of the second resin exceeds 200° C., the resin becomes hard and brittle, so that the effect of improving the scratch resistance of the image may be slightly reduced. The softening point of the second resin is the aforementioned "R&B softening point" measured in accordance with JIS K 6863:1994.

The softening point of the second resin is preferably higher than the melting point of the first resin forming the resin particles. If the softening point of the second resin is lower than the melting point of the first resin, the crystallinity of the second resin may be lower than that of the first resin. For this reason, the second resin may become difficult to adsorb to the resin particles, and the effect of improving ink fixation recovery may be reduced.

The weight average molecular weight of the second resin is preferably 2,000 or more and 30,000 or less. If the weight average molecular weight of the second resin is less than 2,000, the crystallinity of the second resin decreases, making it difficult to adsorb onto resin particles, and the effect of improving the fixation recovery property of the ink may decrease. On the other hand, if the weight average molecular weight of the second resin exceeds 30,000, the resin becomes hard and brittle, and the effect of improving scratch resistance may be reduced.

(aqueous medium)
The ink is an aqueous ink containing at least water as an aqueous medium. As water, it is preferable to use deionized water or ion-exchanged water. The water content (mass%) in the ink is preferably 50.0% by mass or more and 95.0% by mass or less, based on the total mass of the ink. The ink can further contain a water-soluble organic solvent as an aqueous medium. As water, it is preferable to use deionized water or ion-exchanged water. The water content (mass%) in the ink is preferably 50.0% by mass or more and 95.0% by mass or less, based on the total mass of the ink. Further, as the water-soluble organic solvent, any one commonly used for ink can be used. Examples include alcohols, (poly)alkylene glycols, glycol ethers, nitrogen-containing compounds, and sulfur-containing compounds. The content (mass%) of the water-soluble organic solvent in the ink is preferably 3.0% by mass or more and 50.0% by mass or less, based on the total mass of the ink.

(Other additives)
In addition to the above ingredients, the ink may also contain water-soluble organic compounds that are solid at room temperature, such as polyhydric alcohols such as trimethylolpropane and trimethylolethane, and urea derivatives such as urea and ethylene urea. You may. Furthermore, the ink may contain surfactants, pH adjusters, rust inhibitors, preservatives, antifungal agents, antioxidants, reduction inhibitors, evaporation accelerators, chelating agents, and other resins, etc., as necessary. It may contain various additives.

(Physical properties of ink)
Since the ink is a water-based ink applied to the inkjet method, it is preferable to appropriately control its physical property values. Specifically, the surface tension of the ink at 25° C., measured by a plate method, is preferably 20 mN/m or more and 60 mN/m or less, and more preferably 25 mN/m or more and 45 mN/m or less. Further, the viscosity of the ink at 25° C. is preferably 1.0 mPa·s or more and 10.0 mPa·s or less, and more preferably 1.0 mPa·s or more and 5.0 mPa·s or less. Further, the pH of the ink at 25° C. is preferably 7.0 or more and 10.0 or less.

<Ink cartridge>
The ink cartridge of the present invention includes ink and an ink storage portion that stores the ink. The ink contained in this ink storage portion is the water-based ink of the present invention described above. FIG. 1 is a cross-sectional view schematically showing an embodiment of an ink cartridge of the present invention. As shown in FIG. 1, an ink supply port 12 for supplying ink to the recording head is provided on the bottom surface of the ink cartridge. The inside of the ink cartridge serves as an ink storage section for storing ink. The ink storage section includes an ink storage chamber 14 and an absorbent storage chamber 16, which communicate with each other via a communication port 18. Further, the absorbent storage chamber 16 communicates with the ink supply port 12 . The ink storage chamber 14 stores liquid ink 20, and the absorbent storage chamber 16 stores absorbers 22 and 24 that hold the ink in an impregnated state. The ink storage section may have a configuration in which the entire amount of ink contained therein is retained by an absorber without having an ink storage chamber that stores liquid ink. Further, the ink accommodating portion may have a form that does not include an absorber and stores the entire amount of ink in a liquid state. Furthermore, the ink cartridge may be configured to include an ink storage section and a recording head.

<Inkjet recording method>
The inkjet recording method of the present invention is a method of recording an image on a recording medium by ejecting the aqueous ink of the present invention described above from an inkjet recording head. Examples of methods for ejecting ink include a method of applying mechanical energy to the ink and a method of applying thermal energy to the ink. In the present invention, it is particularly preferable to adopt a method of ejecting ink by applying thermal energy to the ink. Other than using the ink of the present invention, the steps of the inkjet recording method may be those known in the art.

FIG. 2 is a diagram schematically 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 the head cartridge. It is. The inkjet recording apparatus is provided with a conveying means (not shown) for conveying the 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 such that an ink cartridge 42 is set therein. While the head cartridge 36 is transported 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).

Preferably, the recording head is provided with an ink temperature control means for heating the ink to be ejected. By discharging the heated ink, the fixation recovery property of the ink can be further improved. The temperature of the ink ejected from the recording head is preferably 40° C. or higher. If the temperature of the ink to be ejected is less than 40°C, the Brownian motion of the resin particles in the ink after water evaporates will be weakened, making it difficult for the resin particles to diffuse into the liquid medium, so the effect of improving the fixation recovery of the ink will be reduced. It may decrease. The temperature of the ink ejected from the recording head is preferably 70°C or lower, more preferably 60°C or lower. Examples of the ink temperature control means include a heater for adjusting the ink temperature and a heater for discharging ink, which are arranged so as to be in contact with the recording head. In order to heat the ink with the ink ejection heater, for example, it is sufficient to repeatedly apply a current to an extent that the ink is not ejected. The temperature of the ink can be read by a temperature sensor provided in the print head.

It is preferable to eject ink from the recording head at a temperature that is 40° C. or more lower than the melting point of the first resin forming the resin particles in the ink. If the difference between the temperature of the ink to be ejected and the melting point of the first resin is less than 40° C., the molecules will move more easily and the resin particles will be more likely to deform. For this reason, the surface condition of the resin particles changes, the surface area increases, and they become more likely to aggregate, which may reduce the effect of improving the fixation recovery property of the ink. The difference between the melting point of the first resin forming the resin particles and the temperature of the ink ejected from the recording head is preferably 100° C. or less.

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples in any way unless it exceeds the gist thereof. Regarding component amounts, "parts" and "%" are based on mass unless otherwise specified.

<Preparation of pigment dispersion>
(Pigment dispersion liquid 1)
C. I. A mixture was obtained by mixing 12.0 parts of Pigment Blue 15:3 (trade name "Hostaperm Blue B2G" manufactured by Clariant), 24.0 parts of an aqueous solution of a resin dispersant, and 64.0 parts of ion-exchanged water. The aqueous solution of the resin dispersant was obtained by neutralizing a styrene-acrylic acid copolymer with an acid value of 250 mgKOH/g and a weight average molecular weight of 8,000 with a 10.0% aqueous sodium hydroxide solution. An aqueous solution containing 20.0% was used. The resulting mixture was placed in a batch type vertical sand mill (manufactured by Imex), filled with 85 parts of 0.3 mm zirconia beads, and dispersed for 3 hours while cooling with water. Thereafter, non-dispersed matter containing coarse particles was removed by centrifugation. Furthermore, pressure filtration was performed using a cellulose acetate filter (manufactured by Advantech) with a pore size of 3.0 μm to prepare a pigment dispersion liquid 1 having a pigment content of 10.0% and a resin content of 4.0%.

(Pigment dispersion liquid 2)
The type of pigment is C. I. Pigment dispersion 2 was prepared in the same manner as in the case of pigment dispersion 1, except that the pigment was changed to Pigment Yellow 74 (trade name "Hansa yellow 5GXB", manufactured by Clariant). The pigment content in Pigment Dispersion 2 was 10.0%, and the resin content was 4.0%.

(Pigment dispersion liquid 3)
The type of pigment is C. I. Pigment Red 202 and C.I. I. Pigment Violet 19 solid solution (trade name "CROMOPHTAL JET MAGENTA 2BC", manufactured by Ciba Specialty Chemicals). Pigment dispersion liquid 3 was prepared in the same manner as in the case of pigment dispersion liquid 1 described above except for this. The pigment content in Pigment Dispersion 3 was 10.0%, and the resin content was 4.0%.

(Pigment dispersion liquid 4)
Pigment dispersion 4 was prepared in the same manner as in the case of pigment dispersion 1, except that the type of pigment was changed to carbon black (trade name "Black Pearls 880", manufactured by Cabot). The pigment content in Pigment Dispersion 4 was 10.0%, and the resin content was 4.0%.

<Preparation of polyethylene oxide>
(Polyethylene oxide 1-6)
An autoclave with an internal capacity of 2.0 L was equipped with a thermometer, a stirring device, a temperature controller, a pressure gauge, a gas inlet pipe, and a gas exhaust pipe. 500 parts of polyethylene powder was placed in an autoclave and heated until the internal temperature reached 140°C to melt the polyethylene powder. The melt was stirred at 250 rpm and air and oxygen were introduced into the melt at a rate of 1.2 L/min and 0.18 L/min, respectively. Air and oxygen were introduced under the conditions of an internal pressure of 0.69 MPa, a temperature of 140°C, and a stirring speed of 250 rpm, and the reaction was carried out by changing the oxidation treatment time in the range of 2 to 12 hours to produce oxidized polyethylenes 1 to 1 with different acid values and melting points. I got 6. Table 1 shows the acid values and melting points of polyethylene oxides 1 to 6 obtained.

<Preparation of resin particle dispersion>
(Resin particle dispersion 1 to 17)
An autoclave equipped with emulsification equipment having an internal capacity of 2.0 L and equipped with a thermometer, a stirring device, a temperature controller, a pressure gauge, a gas inlet pipe, and a gas exhaust pipe was prepared. 360 parts of the first resin of the type shown in Table 2, 60 parts of polyoxyethylene oleyl ether, 33.6 parts of 48% potassium hydroxide aqueous solution, and 873.2 parts of ion-exchanged water are placed in an autoclave, which is purged with nitrogen and sealed. did. As the polyoxyethylene oleyl ether, the trade name "NIKKOL BO-20V" (manufactured by Nikko Chemicals) was used. While stirring the contents, the temperature was raised to a temperature 20° C. higher than the melting point of the first resin, and the mixture was stirred at that temperature for 3 hours. After cooling to 40° C., water was added for dilution to obtain resin particle dispersions 1 to 17 having a resin particle (first resin) content of 20.0%. Details of the first resin used are shown below.
・Fischer-Tropsch wax 1: Product name “Sasolwax H1”, manufactured by Sasol ・Fischer-Tropsch wax 2: Product name “Sasolwax C80M”, manufactured by Sasol ・Fischer-Tropsch wax 3: Product name “Sasolwax C80”, manufactured by Sasol ・Microcrystalline wax: Product name: "Hi-Mic-1070", made by Nippon Seizan - Paraffin wax: product name: "Paraffin Wax-115", made by Nippon Seizan - Ceresin: product name: "Purified Ceresin N", made by Nikko Rica - Ozokerite: product name "Ozokerite Wax Psstilles SP-1021P", manufactured by Strahl and Pitsch - Montan wax: product name "LICOWAX KST", manufactured by Clariant Chemicals - Carnauba wax: product name "Carnauba wax", manufactured by Toyochem - Shellac wax: product name "Shellac", Koyo Chemical Co., Ltd.

(Resin particle dispersion liquid 18)
An autoclave equipped with emulsification equipment having an internal capacity of 2.0 L and equipped with a thermometer, a stirring device, a temperature controller, a pressure gauge, a gas inlet pipe, and a gas exhaust pipe was prepared. 180 parts of polyethylene oxide 1, 180 parts of water-soluble polyester (trade name "Plus Coat Z687", manufactured by Gooh Chemical Industry Co., Ltd., solid content 25%), and 873.2 parts of ion-exchanged water were placed in an autoclave and heated to 150°C while stirring. The temperature was raised and the reaction was carried out for 3 hours. The water-soluble polyester has an acid value of 4 mgKOH/g, a glass transition temperature of 110°C, and a softening point of 185°C. After cooling to 40° C., water was added for dilution to obtain a resin particle dispersion 18 containing 20.0% of resin particles having a core-shell structure (first resin). These resin particles have a core made of polyethylene oxide 1 and a shell made of water-soluble polyester that covers the core, and the ratio of the core to the resin particles is 80.0%, and the ratio of the shell to the resin particles is 20.0%. .0%.

(Resin particle dispersion liquid 19)
A polyester emulsion (trade name "Elytel KT-0507", manufactured by Unitika) was diluted by adding water to obtain a resin particle dispersion 19 having a resin particle content of 20.0%. The acid value of the resin constituting the resin particles was 5 mgKOH/g, and the melting point was 65°C.

(Resin particle dispersion 20)
In a flask equipped with a stirring device, nitrogen inlet tube, reflux condenser, and thermometer, 18.0 parts of butyl methacrylate, 0.35 parts of methacrylic acid, 2.0 parts of polymerization initiator, and 2.0 parts of n-hexadecane were added. and stirred for 30 minutes while introducing nitrogen gas. 2,2'-azobis(2-methylbutylnitrile) was used as a polymerization initiator. 78.0 parts of a 6.0% aqueous solution of polyoxyethylene cetyl ether (trade name "NIKKOL BC-20", manufactured by Nikko Chemicals) was added dropwise and stirred for 30 minutes to obtain a mixture. The mixture was emulsified by irradiating ultrasonic waves for 3 hours using an ultrasonic irradiator, and then polymerized at 80° C. for 4 hours in a nitrogen atmosphere. After cooling to 5° C. and filtering, an appropriate amount of pure water was added to obtain a resin particle dispersion 20 having a resin particle content of 20.0%. The acid value of the resin constituting the resin particles was 10 mgKOH/g, and no melting point was observed.

(Resin particle dispersion liquid 21)
A polyurethane emulsion (trade name "Rethermin D-1060", manufactured by Dainichiseika Chemical Industry Co., Ltd.) was diluted by adding water to obtain a resin particle dispersion 21 having a resin particle content of 20.0%. The acid value of the resin constituting the resin particles was 12 mgKOH/g, and no melting point was observed.

<Preparation of water-soluble polyester>
(Water-soluble polyester 1-4)
A stainless steel separable flask equipped with a thermometer, a K-tube, a stirrer, and a gas introduction tube was prepared. Each component of the type and amount (unit: part) shown in Table 3 and 0.1 part of titanium tetrabutoxide (manufactured by Tokyo Kasei Kogyo, first class) were placed in a separable flask, and the mantle was placed under stirring under normal pressure and nitrogen atmosphere. It was heated to 160°C with a heater. Thereafter, the temperature was gradually raised to 260° C. over 4 hours to perform a transesterification reaction. While stirring, the pressure was gradually reduced from normal pressure to 0.5 mmHg at 250° C., and stirring was continued in this state for 2 hours to allow the polycondensation reaction to proceed. Nitrogen was introduced into the separable flask and the temperature was returned to normal pressure and temperature to obtain water-soluble polyesters 1 to 4. Table 3 shows the acid values, glass transition temperatures, and softening points of the water-soluble polyesters 1 to 4 obtained.

<Preparation of liquid containing resin>
(Liquids containing resin 1 to 12, 14, 15)
20 parts of the second resin of the type shown in Table 4 and 80 parts of ion-exchanged water were mixed, heated at 80 to 90°C and stirred for 2 hours, and liquid 1 containing a resin with a resin content of 20.0% was prepared. ~12, 14, and 15 were obtained. Details of the second resin used are shown below. The obtained resin-containing liquids are all resin aqueous solutions in which the resin is dissolved.
・Water-soluble polyester A: Product name "Plus Coat Z-687", manufactured by Gooo Kagaku Kogyo ・Water-soluble polyester B: Product name "Plus Coat Z-760", manufactured by Gooo Kagaku Kogyo ・Water-soluble polyester C: Product name "Plus Coat Z-730'', manufactured by Goio Kagaku Kogyo ・Water-soluble polyester D: product name ``Plus Coat Z-446'', manufactured by Goio Kagaku Kogyo ・Water-soluble polyester E: product name ``Plus Coat RZ-105'', manufactured by Gooo Kagaku Kogyo・Water-soluble polyester F: Product name "Plus Coat Z-221", manufactured by Gooo Kagaku Kogyo ・Water-soluble polyester G: Product name "Plus Coat Z-561", manufactured by Gooo Kagaku Kogyo ・Ethylene-acrylic acid copolymer: Product Name: "Poly(ethylene-co-acrylic acid)", manufactured by Sigma-Aldrich Water-soluble nylon: Product name: "AQ Nylon T-70", manufactured by Toray Polyvinyl alcohol: Product name: "Poly(vinyl alcohol)", Tokyo Kasei industrial

(Liquid containing resin 13)
A flask equipped with a stirring device, a nitrogen inlet tube, a reflux condenser, and a thermometer was prepared. 258 parts of an α-olefin having an average number of carbon atoms of 17 was placed in a flask, and after the flask was sufficiently purged with nitrogen gas, it was heated to 190° C. and stirred. 44 parts of maleic anhydride and 2.27 parts of di-t-butyl peroxide were simultaneously dropped into the flask over 2 hours for polymerization. After aging at 190° C. for 1 hour, the mixture was cooled to obtain 300 parts of an α-olefin-maleic anhydride copolymer. 20 parts of the obtained pulverized α-olefin-maleic anhydride copolymer was placed in a flask. An aqueous sodium hydroxide solution obtained by dissolving 4.90 parts of sodium hydroxide in 80 parts of distilled water was added, and the mixture was stirred at 90°C for 8 hours. After cooling to room temperature, an appropriate amount of distilled water was added to obtain a resin-containing liquid 13 with a resin content of 20.0%. The obtained resin-containing liquid 13 is an aqueous resin solution in which the resin is dissolved.

(Liquid 16 containing resin)
A flask equipped with a stirrer, a reflux condenser, and a nitrogen gas introduction tube was prepared. After putting 100.0 parts of ethylene glycol monobutyl ether into a flask and introducing nitrogen gas, the flask was stirred and heated to 110°C. A mixture of 39.5 parts of styrene, 40.0 parts of methyl methacrylate, and 20.5 parts of acrylic acid was mixed with a solution of 1.3 parts of t-butyl peroxide (polymerization initiator) in ethylene glycol monobutyl ether over a period of 3 hours. dripped. After aging for 2 hours, ethylene glycol monobutyl ether was removed under reduced pressure to obtain a solid water-soluble acrylic resin. Potassium hydroxide in an amount equivalent to the acid value and an appropriate amount of ion-exchanged water are added to the obtained water-soluble acrylic resin, and the mixture is neutralized and dissolved at 80°C to obtain a resin-containing liquid 16 with a resin content of 20.0%. I got it. The obtained resin-containing liquid 16 is an aqueous resin solution in which the resin is dissolved.

(Liquid containing resin 17)
A flask equipped with a stirrer, a thermometer, a nitrogen gas introduction tube, and a reflux tube was prepared. 41.7 parts of isophorone diisocyanate, 40.1 parts of polypropylene glycol (number average molecular weight 2,000), 13.2 parts of dimethylolpropionic acid, and 200.0 parts of methyl ethyl ketone were placed in a flask, and the mixture was heated at 80°C under a nitrogen gas atmosphere. The mixture was allowed to react for 6 hours. Then, 0.6 parts of ethylenediamine, 2.0 parts of methanol, 2.4 parts of dimethylolpropionic acid, and 100.0 parts of methyl ethyl ketone were added. The residual rate of isocyanate groups was confirmed by FT-IR, and the reaction was carried out at 80°C until the desired residual rate was reached to obtain a reaction solution. After cooling the obtained reaction solution to 40° C., ion-exchanged water was added, and while stirring at high speed with a homomixer, an aqueous potassium hydroxide solution was added to obtain a liquid. After methyl ethyl ketone was distilled off from the obtained liquid by heating under reduced pressure, an appropriate amount of ion-exchanged water was added to obtain a resin-containing liquid 17 with a resin content of 20.0%. The resulting resin-containing liquid 17 is an aqueous resin solution in which the resin is dissolved.

(Liquid containing resin 18)
A flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas introduction tube was prepared. 100.0 parts of polyethylene and 100.0 parts of diethylene glycol monoethyl ether acetate were placed in a flask. The mixture was heated and stirred under a nitrogen atmosphere to an internal temperature of 170°C, and 10.0 parts of benzyl acrylate, 5.0 parts of acrylic acid, and 0.4 parts of di-t-butyl peroxide were added. After reacting at 170° C. for 30 minutes, equal amounts of benzyl acrylate, acrylic acid, and di-t-butyl peroxide were further added. Similarly, benzyl acrylate, acrylic acid, and di-t-butyl peroxide were added every 30 minutes for a total of five times. After cooling to 50° C., the pressure was reduced using an aspirator for 1 hour to remove the solvent, unreacted monomers, di-t-butyl peroxide, and decomposed products of di-t-butyl peroxide. After aging for 2 hours, ethylene glycol monobutyl ether was distilled off under reduced pressure to obtain a resin. Potassium hydroxide in an amount equivalent to the acid value and an appropriate amount of ion-exchanged water were added to the obtained resin, and the mixture was heated to 80° C. to dissolve it. As a result, a resin-containing liquid 18 having a resin content of 20.0% was obtained. The resulting resin-containing liquid 18 is an aqueous resin solution in which the resin is dissolved.

(Liquid containing resin 19)
A polyester emulsion (trade name "Elytel KT-0507", manufactured by Unitika, 25% emulsion) was diluted with water to obtain a resin-containing liquid 19 with a resin content of 20.0%. The obtained resin-containing liquid 18 is a resin dispersion containing dispersed resin (resin particles).

<Preparation of ink>
Each component (unit: %) shown in the middle row of Tables 5-1 to 5-4 was mixed, thoroughly stirred, and filtered under pressure using a microfilter (manufactured by Fujifilm) with a pore size of 3.0 μm. was prepared. In Tables 5-1 to 5-4, "Acetylenol E100" is the trade name of a nonionic surfactant manufactured by Kawaken Fine Chemicals. The properties of the ink are shown in the lower rows of Tables 5-1 to 5-4. The pH of all the prepared inks was within the range of 8.5 to 9.0.

<Evaluation>
Each ink obtained above was filled into an ink cartridge and set in an inkjet recording device (a modified model of the product name "PIXUS PRO 10-S" (manufactured by Canon)) equipped with a recording head that ejects ink using thermal energy. . In this inkjet recording apparatus, a sub-heater was provided as a mechanism for heating the ink in the bubbling chamber of the recording head so as to surround the ejection port array, in addition to the recording element (heater). This inkjet recording device has a resolution of 600 dpi x 600 dpi, and prints an image under conditions of applying 8 ink droplets of 4.0 ng to a unit area of 1/600 inch x 1/600 inch at a recording duty of 100%. Define it as . In the present invention, in the evaluation criteria for each item below, "AA", "A", and "B" were defined as acceptable levels, and "C" was defined as unacceptable level. The evaluation results are shown in Table 6.

(Abrasion resistance)
A solid image (200 mm x 200 mm) with a recording duty of 100% was recorded on a recording medium (trade name: "Canon Photo Paper Glossy Gold GL-101", manufactured by Canon) to obtain a recorded matter. After 24 hours of recording, using an abrasion tester (manufactured by Imoto Seisakusho), which is a JIS L 0849-compliant Gakushin type tester, the solid image was tested for friction under the conditions of 30 reciprocations and 60 reciprocations with a load of 500g. The test was conducted. The solid image after the test was visually observed, and the scratch resistance of the image was evaluated according to the evaluation criteria shown below.
AA: No scratch marks were produced on the image even after 60 reciprocations.
A: Even after 30 reciprocations, no scratch marks were produced on the image, but after 60 reciprocations, slight scratch marks were generated to the extent that the white background of the recording medium was not visible.
C: Scratch marks appeared on the image after 60 reciprocations, and the white background of the recording medium was also visible.

(Adhesion recovery)
A recovery operation (cleaning) was performed on the inkjet recording apparatus, and the power cable was pulled out while the carriage was in operation, so that the recording head was not capped. In this state, the inkjet recording apparatus was left in an environment with a temperature of 30° C. and a relative humidity of 10% for 14 days. Thereafter, a recovery operation (cleaning) of the inkjet recording apparatus was performed, and then a nozzle check pattern was recorded. The recorded nozzle check pattern was visually observed, and the ink fixation recovery property was evaluated according to the evaluation criteria shown below. Among those whose fixation recovery properties were rated "B", those whose performance was relatively poor were rated "B'".
AA: After one or two recovery operations, it became possible to record normally.
A: After 3 to 5 recovery operations, it became possible to record normally.
B: Normal recording became possible after 6 to 10 recovery operations.
C: After performing the recovery operation 11 times, it was not possible to record normally.

The disclosure of this embodiment includes the following configuration and method.
(Structure 1) A water-based ink for inkjet containing a pigment, resin particles, and a water-soluble resin,
The resin particles are formed of at least one first resin selected from the group consisting of polyethylene, oxidized polyethylene, Fischer-Tropsch wax, microcrystalline wax, paraffin wax, ozokerite, and ceresin,
A water-based ink, wherein the water-soluble resin is a second resin having crystallinity.
(Structure 2) The aqueous ink according to Structure 1, wherein the first resin is polyethylene oxide.
(Structure 3) The aqueous ink according to Structure 1 or 2, wherein the second resin is at least one of polyester and ethylene-acrylic acid copolymer.
(Structure 4) The aqueous ink according to any one of Structures 1 to 3, wherein the first resin has an acid value of 40 mgKOH/g or less.
(Structure 5) The aqueous ink according to any one of Structures 1 to 4, wherein the second resin has an acid value of 40 mgKOH/g or less.
(Structure 6) The aqueous ink according to any one of Structures 1 to 5, wherein the difference between the acid value of the first resin and the acid value of the second resin is 15 mgKOH/g or less.
(Configuration 7) Configurations 1 to 6, wherein the content (mass%) of the second resin is 1.0 times or more and 3.0 times or less as a mass ratio to the content (mass%) of the first resin. The water-based ink according to any one of the items.
(Structure 8) The water-based ink according to any one of Structures 1 to 7, wherein the second resin has a softening point equal to or higher than the melting point of the first resin.
(Structure 9) The aqueous ink according to any one of Structures 1 to 8, wherein the second resin is polyester having a naphthalene skeleton.
(Structure 10) An ink cartridge including ink and an ink storage section that stores the ink,
An ink cartridge, wherein the ink is the water-based ink according to any one of Structures 1 to 9.
(Method 1) An inkjet recording method in which an image is recorded on a recording medium by ejecting ink from an inkjet recording head, the method comprising:
An inkjet recording method, wherein the ink is the water-based ink according to any one of Structures 1 to 9.
(Method 2) The inkjet recording method according to Method 1, wherein the aqueous ink at a temperature of 40° C. or higher is ejected from the recording head.
(Method 3) The inkjet recording method according to method 1 or 2, wherein the aqueous ink at a temperature lower than the melting point of the first resin by 40° C. or more is ejected from the recording head.

Claims (13)

A water-based ink for inkjet containing a pigment, resin particles, and a water-soluble resin,
The resin particles are formed of at least one first resin selected from the group consisting of polyethylene, oxidized polyethylene, Fischer-Tropsch wax, microcrystalline wax, paraffin wax, ozokerite, and ceresin,
A water-based ink, wherein the water-soluble resin is a second resin having crystallinity. The aqueous ink according to claim 1, wherein the first resin is polyethylene oxide. The aqueous ink according to claim 1 or 2, wherein the second resin is at least one of polyester and ethylene-acrylic acid copolymer. The aqueous ink according to claim 1 or 2, wherein the first resin has an acid value of 40 mgKOH/g or less. The aqueous ink according to claim 1 or 2, wherein the second resin has an acid value of 40 mgKOH/g or less. The aqueous ink according to claim 1 or 2, wherein the difference between the acid value of the first resin and the acid value of the second resin is 15 mgKOH/g or less. The aqueous resin according to claim 1 or 2, wherein the content (mass%) of the second resin is 1.0 times or more and 3.0 times or less as a mass ratio with respect to the content (mass%) of the first resin. ink. The aqueous ink according to claim 1 or 2, wherein the second resin has a softening point equal to or higher than the melting point of the first resin. The aqueous ink according to claim 1 or 2, wherein the second resin is a polyester having a naphthalene skeleton. An ink cartridge comprising ink and an ink accommodating portion accommodating the ink, the ink cartridge comprising:
An ink cartridge, wherein the ink is the aqueous ink according to claim 1 or 2. An inkjet recording method that records an image on a recording medium by ejecting ink from an inkjet recording head, the method comprising:
An inkjet recording method, wherein the ink is the aqueous ink according to claim 1 or 2. The inkjet recording method according to claim 11, wherein the aqueous ink at a temperature of 40° C. or higher is ejected from the recording head. The inkjet recording method according to claim 11, wherein the aqueous ink is ejected from the recording head at a temperature that is 40° C. or more lower than the melting point of the first resin.

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