Water-based ink, ink cartridge, and ink-jet recording method

Abstract

To provide a water-based ink for inkjet capable of recording an image having excellent abrasion resistance and color development.SOLUTION: There is provided a water-based ink for inkjet which comprises a pigment, wax, a dispersant for dispersing wax, a phosphate ester type surfactant and an amine compound, wherein the pigment is a pigment dispersed by the action of at least one selected from the group consisting of a carboxylic acid group and a sulfonic acid group, the phosphate ester type surfactant contains an aliphatic alcohol alkoxylate moiety and the cumulative 50% particle diameter by volume of the wax is 0.10 times or more and 2.0 times or less in ratio to the cumulative 50% particle diameter by volume of the pigment.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] Inkjet recording methods are widely used not only for printing documents at home and in offices, but also for commercial printing and industrial printing. In particular, large-format inkjet printers suitable for printing posters and advertisements have become widespread in recent years. For such applications, inks containing pigments as coloring materials (pigment inks) are widely used for the purpose of recording images with improved fastness such as gas resistance, light resistance, and water resistance.

[0003] However, it is known that images recorded with pigment inks generally have inferior color development compared to images recorded with inks containing dyes as coloring materials (dye inks). Also, unlike dye inks, in which the dyes as coloring materials penetrate into the interior of the recording medium, pigment inks, in which the pigments as coloring materials accumulate on the surface of the recording medium, can easily cause the image to be scratched or peeled off due to external forces. Therefore, when recording images for posters or advertisements, it is required not only to improve the image quality but also to improve the abrasion resistance of the image.

[0004] In order to meet these demands, various inks have been proposed in recent years. For example, inks containing wax such as polyolefins made of chain hydrocarbons have been proposed to record images with improved abrasion resistance (Patent Documents 1 to 3). The inks proposed in Patent Documents 1 to 3 contain wax to impart slipperiness to the surface of the recorded image, reduce frictional resistance, and improve the abrasion resistance of the image. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2019-202419 A [Patent Document 2] JP 2015-168805 A [Patent Document 3] U.S. Pat. No. 1,082,9658 Summary of the Invention [Problem to be solved by the invention]

[0006] The present inventors have studied the characteristics of images recorded with the inks proposed in Patent Documents 1 to 3. As a result, it has been found that when the inks proposed in Patent Documents 1 and 2 are used, the abrasion resistance of the image is improved to a certain extent, but is not sufficient. In addition, it has been found that when the ink proposed in Patent Document 3 is used, the abrasion resistance of the image is good, but the color development of the image is low, and there is room for improvement. In order to improve the color development of the image, further studies have been carried out by adding a water-soluble acrylic resin or a water-soluble urethane resin with low coagulation to the ink, but the color development of the image could not be improved.

[0007] It is therefore an object of the present invention to provide an inkjet water-based ink capable of recording images having excellent abrasion resistance and color development, and an ink cartridge and an inkjet recording method using the inkjet water-based ink. [Means for solving the problem]

[0008] That is, according to the present invention, there is provided an aqueous inkjet ink containing a pigment, a wax, a dispersant for dispersing the wax, a phosphate ester surfactant, and an amine compound, wherein the pigment is a pigment that is dispersed by the action of at least one group selected from the group consisting of a carboxylic acid group and a sulfonic acid group, the phosphate ester surfactant contains an aliphatic alcohol alkoxylate moiety, and the volume-based cumulative 50% particle diameter of the wax is 0.10 to 2.0 times the volume-based cumulative 50% particle diameter of the pigment. Effect of the Invention

[0009] According to the present invention, it is possible to provide an inkjet water-based ink capable of recording images having excellent abrasion resistance and color development. 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]

[0010] [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

[0011] The present invention will be described in more detail below with reference to preferred embodiments. In the present invention, when the compound is a salt, the salt is present in the ink in the form of dissociation into ions, but for convenience, it is expressed as "containing a salt." In addition, water-based 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.

[0012] The present inventors analyzed the inside of a recorded image to investigate the reason why the color development of an image cannot be obtained even when the inks having the configurations proposed in Patent Documents 1 to 3 are used. As a result, it was found that the wax increases the number of voids formed inside the image, and the scattering of incident light increases, thereby decreasing the color development of the image. It was also found that when a wax with a small particle size is used to suppress the voids inside the image, the voids are reduced and the color development of the image is improved, but the scratch resistance of the image is reduced. This is believed to be because the wax with a small particle size is likely to sink into the lower layer of the image, and the surface of the image cannot be sufficiently protected. From the above study results, it was found that it is difficult to achieve both scratch resistance and color development at a high level for an image recorded with an ink containing a pigment as a coloring material.

[0013] Therefore, when the present inventors studied the composition of an ink using a pigment as a coloring material, which can record an image with excellent abrasion resistance and color development, they first focused on using a wax with a small particle size and leaving the wax on the surface of the image while suppressing the generation of voids. Specifically, they studied surfactants and additives that control the cohesive force of the wax in order to cause the wax to aggregate on the surface of the image. As a result, they found the following. That is, the ratio of the cumulative 50% particle size of the wax based on volume to the cumulative 50% particle size of the pigment based on volume is 0.10 times or more and 2.0 times or less. Furthermore, a phosphate ester type surfactant containing an aliphatic alcohol alkoxylate moiety (hereinafter also simply referred to as "phosphate ester type surfactant") and an amine compound are contained. In this case, they found that the abrasion resistance and color development of the image are good.

[0014] Since the aliphatic structure of the aliphatic alcohol alkoxylate portion of the phosphate ester surfactant is similar to the skeleton of the wax, the phosphate ester surfactant selectively adsorbs to the surface of the wax. Therefore, when an ink containing wax and a phosphate ester surfactant is used, the wax is more likely to remain on the surface of the image, and the scratch resistance of the image is improved. The phosphate ester surfactant adsorbed to the wax is protonated more quickly than the pigment dispersed by the action of the carboxylic acid group or sulfonic acid group. The pKa of the phosphate group is higher than the pKa of the carboxylic acid group or sulfonic acid group, and the phosphate group is more likely to accept protons. Therefore, when the intermolecular distance between the acid group and the proton approaches due to the evaporation or penetration of the liquid component during image recording, the phosphate group is more likely to be protonated than the carboxylic acid group or sulfonic acid group. When the phosphate ester surfactant is protonated, it loses its electrostatic repulsive force and its affinity with the liquid component of the ink decreases, so the fluidity of the wax is lost. As a result, the wax that cannot ride the flow of the ink penetrating into the recording medium is more likely to remain on the surface of the image.

[0015] However, it was found that the color development of the image was not achieved despite the use of a wax with a small particle size. When the phosphate group of the phosphate ester surfactant is protonated, the cohesive force of the wax becomes stronger. Since the protonation of the pigment proceeds slowly, the cohesive force of the wax is stronger than that of the pigment. Therefore, the cohesion of the wax proceeds relatively quickly relative to the pigment, and an aggregate of the wax is formed. Since the particle size of the wax aggregate formed is large, it is considered that the voids inside the image increase, and the color development of the image is reduced.

[0016] Next, the present inventors investigated the addition of a buffer solution to an ink containing a wax and a phosphate ester type surfactant in order to suppress the cohesive force of the wax in order to improve the color development of the image. A buffer solution is a liquid whose pH hardly changes (has a buffering effect) even when the surrounding environment changes. As the buffer solution, boric acid-potassium chloride-sodium hydroxide buffer solution and sodium bicarbonate-sodium hydroxide buffer solution, which are general-purpose buffer solutions, were used. As a result, it was found that the color development of the image was improved when any of the buffer solutions was added, but the scratch resistance of the image was reduced. The addition of a buffer solution produces a buffering effect, so that the phosphate ester type surfactant is easily ionized and maintained in a negatively charged state as a whole molecule. Then, even when the ink droplets are applied to a recording medium and the evaporation and penetration of the liquid components proceed, the pH of the ink is unlikely to change due to the buffering effect, so that the protonation of the dispersant and the phosphate ester type surfactant for dispersing the wax is unlikely to proceed. As a result, the electrostatic repulsion becomes stronger, the cohesive force of the wax becomes weaker, and it becomes difficult for coagulation to form, so that it is believed that the voids inside the image are reduced and the color development of the image is improved. On the other hand, since the image is recorded in a state in which the protonation of the dispersant for dispersing the wax and the phosphate ester surfactant does not easily proceed, the wax is less likely to remain on the surface of the image and easily penetrates into the inside of the image, so that it is believed that the scratch resistance of the image is reduced.

[0017] As a result of further investigation, the present inventors found that adding an amine compound to an ink containing a wax and a phosphate ester surfactant improves both the abrasion resistance and color development of the image. In an ink containing an amine compound, the phosphate ester surfactant is more likely to dissociate and become negatively charged than in an ink not containing an amine compound. Therefore, immediately after the ink droplets are applied to the recording medium, the electrostatic repulsive force acts stronger, the cohesive force of the wax is weakened, and wax aggregates are less likely to form. Furthermore, it is believed that the hydration of the alcohol alkoxylate moiety of the phosphate ester surfactant makes it more difficult for wax aggregates to form. Thereafter, when the amine compound and the phosphate ester surfactant approach each other due to evaporation or penetration of the liquid medium, the amine compound and the phosphate ester surfactant form a poorly soluble salt.

[0018] From the viewpoint of pKa, amine compounds are more likely to form salts with phosphoric acid groups than with carboxylic acid groups or sulfonic acid groups. Therefore, amine compounds are more likely to form salts with phosphate ester surfactants than pigments. The poorly soluble salts formed by amine compounds and phosphate ester surfactants have a negative charge neutralized, so they cannot exert electrostatic repulsion and their affinity with the liquid medium is reduced. Therefore, it is considered that the cohesive force of the wax increases rapidly with the formation of the poorly soluble salts. As a result, the wax is less likely to sink into the image and is more likely to remain on the surface of the image. In addition, since phosphates have a lower solubility than carboxylates and sulfonates, it is considered that amine compounds are more likely to reduce the affinity between the wax and the liquid components than pigments. Furthermore, as the liquid components evaporate and penetrate, the pigments are also protonated, and the cohesive force of the pigments is also becoming stronger. Therefore, the difference in cohesive force between the wax and the pigment becomes smaller. As a result, both the cohesion of the pigments and the cohesion of the wax progress, and the pigments enter between the waxes, making it difficult to form cohesion of only the wax. It is believed that this makes it difficult for voids to form in the image, improving the color development of the image, and also allows the wax to remain on the surface of the image, improving the scratch resistance of the image.

[0019] The volume-based cumulative 50% particle size of the wax must be 0.10 to 2.0 times the volume-based cumulative 50% particle size of the pigment. If the ratio is less than 0.10, the wax is likely to sink into the image and is difficult to spread due to crushing. This makes it difficult to release external forces, and the image does not have abrasion resistance. On the other hand, if the ratio is more than 2.0, voids are likely to form inside the image, and the wax is likely to scatter light, resulting in the image not being able to have color development.

[0020] <Ink> The ink of the present invention is a water-based ink for inkjet recording, which contains a pigment, a wax, a dispersant for dispersing the wax, a phosphate ester surfactant, and an amine compound. The components constituting the ink of the present invention and the physical properties of the ink are described in detail below.

[0021] (Pigments) The ink contains a pigment as a coloring material. The content (mass %) of the pigment in the ink is preferably 0.50% by mass or more and 15.00% by mass or less, and more preferably 0.50% by mass or more and 10.00% by mass or less, based on the total mass of the ink.

[0022] Specific examples of pigments 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, and dioxazine pigments.

[0023] Pigments can be classified according to the dispersion method, such as resin-dispersed pigments that use a resin as a dispersant, and self-dispersed pigments in which hydrophilic groups are bonded to the pigment particle surface. Other examples include 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. It is not necessary to use resin particles dyed with a colorant as the coloring material.

[0024] The pigment used in the ink of the present invention is a pigment that is dispersed by the action of at least one group selected from the group consisting of a carboxylic acid group and a sulfonic acid group.

[0025] The resin (resin dispersant) for dispersing the pigment in the aqueous medium has at least one of a carboxylic acid group and a sulfonic acid group. In particular, the pigment is preferably a resin-dispersed pigment dispersed by a resin (resin dispersant) having a carboxylic acid group. The resin dispersant having a sulfonic acid group may be difficult to adsorb to the pigment due to its somewhat high hydrophilicity, and the pigment's cohesive force may be easily strengthened, and the color development of the image may not be sufficient. In addition, if the resin dispersant having a sulfonic acid group is difficult to adsorb to the pigment, the adsorption sites on the pigment particle surface increase and the phosphate ester surfactant is easily adsorbed to the pigment. As a result, it becomes difficult to obtain a difference between the cohesive force of the pigment and the cohesive force of the wax, and the abrasion resistance of the image may not be sufficient. In addition, if the pigment is a self-dispersing pigment dispersed by a carboxylic acid group, the abrasion resistance and color development of the image may not be sufficient. The content (mass%) of the pigment in the ink is preferably 0.30 times or more and 10.0 times or less in mass ratio to the content (mass%) of the resin dispersant.

[0026] The resin dispersant is preferably a resin having a hydrophilic unit and a hydrophobic unit as constituent units, and is preferably an acrylic resin having at least an acrylic component such as a unit derived from (meth)acrylic acid or a unit derived from (meth)acrylic ester, and is more preferably a water-soluble acrylic resin. In particular, a water-soluble acrylic resin in the form of a random copolymer is preferred.

[0027] The hydrophilic unit is a unit having a hydrophilic group such as an acid group or a hydroxy group. The hydrophilic unit can be formed, for example, by polymerizing a monomer having a hydrophilic group. Specific examples of the monomer having a hydrophilic group include acidic monomers having a carboxy group such as (meth)acrylic acid, itaconic acid, maleic acid, and fumaric acid, acidic monomers having a sulfonic acid group such as styrenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, and 3-sulfopropyl (meth)acrylate, and anionic monomers such as anhydrides and salts of these acidic monomers; monomers having a hydroxy 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. Examples of cations constituting the salt of anionic monomers include ions of lithium, sodium, potassium, ammonium, and organic ammonium. The acid value of the resin is preferably 50 mgKOH / g or more and 200 mgKOH / g or less.

[0028] The self-dispersing pigment is a pigment having at least one of a carboxylic acid group and a sulfonic acid group bonded directly or via another atomic group (-R-) to the particle surface of the pigment. The carboxylic acid group and the sulfonic acid group may be either an acid type or a salt type, and when they are salt types, they may be either partially dissociated or completely dissociated. When the carboxylic acid group and the sulfonic acid group are salt types, 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. The group may also be a combination of these groups.

[0029] The volume-based cumulative 50% particle diameter of the pigment is preferably 40 nm or more and 400 nm or less, and more preferably 45 nm or more and 350 nm or less. 50 "Volume-based cumulative 50% particle diameter (D )" is the diameter of the particle that is 50% of the total volume of the measured particles when accumulated from the small particle diameter side in the particle diameter accumulation curve. 50 The particle size distribution of the particles can be measured by a particle size distribution analyzer using a dynamic light scattering method. The measurement method will be described in detail later.

[0030] (wax) The ink contains wax and a dispersant for dispersing the wax. The wax may be a composition containing components other than the wax, or may be the wax itself. The wax may be dispersed as wax particles by a dispersant such as a surfactant or a resin. In this specification, "wax particles" refers to particles formed of wax. The wax may be used alone or in combination of two or more kinds. Examples of the wax include natural wax and synthetic wax.

[0031] In the narrow sense, wax is an ester of a water-insoluble higher monohydric or dihydric alcohol and a fatty acid, and includes animal waxes and vegetable waxes, but does not include oils and fats. In the broad sense, wax includes high-melting-point fats, mineral waxes, petroleum waxes, and blends and modified products of various waxes. In the recording method of the present invention, any wax in the broad sense can be used without particular restrictions. Wax in the broad sense can be classified into natural waxes, synthetic waxes, blends thereof (blended waxes), and modified products thereof (modified waxes).

[0032] Examples of natural waxes include animal and vegetable waxes, plant waxes, mineral waxes, and petroleum waxes. Examples of animal and vegetable waxes include lanolin, beeswax, whale wax, and privet wax. Examples of plant waxes include carnauba wax, candelilla wax, rice wax, Japan wax, olicury wax, sugarcane wax, and palm wax. Examples of mineral waxes include montan wax, ozokerite, ceresin, and lignite wax. Examples of petroleum waxes include paraffin wax, microcrystalline wax, and petrolatum.

[0033] Examples of synthetic waxes include synthetic hydrocarbon waxes, modified waxes, and hydrogenated waxes. Examples of synthetic hydrocarbon waxes include polyolefin waxes and Fischer-Tropsch waxes. Modified waxes are those obtained by subjecting the above-mentioned various waxes to modification treatments such as oxidation, hydrogenation, alcohol modification, acrylic modification, and urethane modification. Specific examples of modified waxes include paraffin wax derivatives, montan wax derivatives, and microcrystalline wax derivatives. Examples of hydrogenated waxes include castor wax and opal wax.

[0034] The wax is preferably at least one wax selected from the group consisting of polyethylene wax, Fischer-Tropsch wax, microcrystalline wax, paraffin wax, ozokerite, and ceresin. These waxes may be modified or blended. These waxes tend to be highly crystalline waxes because they do not contain an ester moiety or a carboxyl moiety in their skeletons. By using a highly crystalline wax, when an external force is applied, the crystal interface slides and spreads, making it easier to release the force, and an image with excellent abrasion resistance can be recorded.

[0035] The volume-based cumulative 50% particle diameter of the wax must be 0.10 to 2.0 times the volume-based cumulative 50% particle diameter of the pigment. Of these, it is preferably 0.20 to 1.5 times. In this specification, when simply referring to "average particle diameter," it is meant to refer to the volume-based cumulative 50% particle diameter (D 50 The "50% cumulative particle size by volume" of wax is the diameter of the particle that is 50% of the total volume of the measured particles when calculated from the small particle size side in the particle size accumulation curve. This "50% cumulative particle size by volume (D 50 ) can be measured using a particle size distribution measuring device using a dynamic light scattering method. A particle size analyzer (for example, the product name "UPA-EX150" manufactured by Nikkiso) can be used as a particle size distribution measuring device using a dynamic light scattering method. The measurement conditions at this time can be, for example, SetZero: 30 seconds, number of measurements: 3, measurement time: 180 seconds, shape: spherical, refractive index: 1.59. Of course, the particle size distribution measuring device used and the measurement conditions are not limited to those described above. The cumulative 50% particle size based on volume of the wax is preferably 20 nm or more and 200 nm or less, and more preferably 30 nm or more and 150 nm or less.

[0036] The total content (mass%) of the wax and the dispersant for dispersing the wax in the ink is preferably 0.005 to 0.20 times, more preferably 0.01 to 0.05 times, in terms of mass ratio to the pigment content (mass%). If the mass ratio is less than 0.005 times, the total content of the wax and the dispersant for dispersing the wax relative to the pigment is relatively small, and the wax is less likely to protect the pigment, so that the scratch resistance of the image may not be sufficient. On the other hand, if the mass ratio is more than 0.20 times, the wax may easily scatter incident light, and the color development of the image may not be sufficient. The total content (mass%) of the wax and the dispersant for dispersing the wax in the ink is preferably 0.010 to 1.50 mass%, more preferably 0.030 to 1.00 mass%, based on the total mass of the ink.

[0037] (Phosphate ester surfactant) The ink contains a phosphate ester surfactant containing an aliphatic alcohol alkoxylate moiety. The aliphatic alcohol alkoxylate moiety means a moiety in which a polyalkylene oxide is bonded to an aliphatic hydrocarbon. Examples of the polyalkylene oxide include polyethylene oxide, polypropylene oxide, and polybutylene oxide. Among them, polyethylene oxide or polypropylene oxide is preferable, and polyethylene oxide is more preferable. The phosphate group in the phosphate ester surfactant may be either an acid type or a salt type, and in the case of a salt type, it may be either a partially dissociated state or a completely dissociated state. When the phosphate group is a salt type, examples of the cation serving as the counter ion include an alkali metal cation, ammonium, and organic ammonium. The phosphate ester moiety may be either a monoester or a diester, or a mixture thereof. The content (mass%) of the phosphate ester surfactant in the ink is preferably 0.10% by mass to 5.00% by mass, more preferably 0.10% by mass to 2.00% by mass. The total content (mass %) of the surfactants in the ink is preferably from 0.10 to 5.00% by mass, and more preferably from 0.10 to 2.50% by mass.

[0038] The phosphate ester surfactant is preferably a compound represented by the following general formula (1): 1 The chain hydrocarbon group represented by the formula (1) may be either a straight chain or a branched chain. In particular, in consideration of adsorption to wax, a straight chain is preferable. Also, it is preferable that the chain has no substituent. Furthermore, the chain hydrocarbon group may be a saturated chain hydrocarbon group or an unsaturated chain hydrocarbon group having a double bond or a triple bond. In the following general formula (1), R 1If the number of carbon atoms in the chain hydrocarbon group represented by the formula (1) is less than 12, or if a is more than 10, the hydrophilicity may be excessively increased, making it difficult for the wax to remain on the surface of the image, and the scratch resistance of the image may not be sufficient. 1 If the number of carbon atoms in the chain hydrocarbon group represented by the formula (I) exceeds 24, the hydrophobicity may increase excessively. As a result, the wax particles may come close to each other, which may lead to voids being formed in the image, and the image may not exhibit sufficient color development.

[0039] TIFF0007669454000001.tif34170 (In the above general formula (1), R 1 represents a chain hydrocarbon group having 12 to 24 carbon atoms, and a represents an integer of 1 to 10.

[0040] The phosphate ester surfactant is more preferably a compound represented by the following general formula (2). When the phosphate ester surfactant represented by the following general formula (2) is used, the scratch resistance of the image can be further improved from the viewpoint of hydrophilicity, and the color development of the image can be further improved from the viewpoint of hydrophobicity. In addition, the structure represented by the following general formula (2) has a bent structure because it contains a double bond, and is more flexible than saturated hydrocarbons with a straight chain structure that does not bend. Therefore, the phosphate ester surfactant represented by the following general formula (2) is easily adsorbed by wax, and can suppress the cohesive force of the wax from becoming excessively strong. Therefore, by using the phosphate ester surfactant represented by the following general formula (2), the generation of voids in the image is further suppressed, and the wax is more likely to remain on the surface of the image, and the scratch resistance and color development of the image can be further improved. In the general formula (2), it is particularly preferable that a is 3 or more and 5 or less.

[0041] TIFF0007669454000002.tif30170 (in the general formula (2), a represents an integer of 1 or more and 10 or less)

[0042] (Amine compounds) The ink contains an amine compound. Examples of the amine compound include trishydroxymethylaminomethane, monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine, triisopropanolamine, N-methylethanol, N-dimethylethanol, dicyclohexylamine, dimethylcyclohexylamine, triethylamine, 3-[N,N-bis(hydroxyethyl)amino]-2-hydroxypropanesulfonic acid, 2-hydroxy-3-[4-(2-hydroxyethyl)-1-piperazinyl]propanesulfonic acid, N,N-bis(2-hydroxyethyl)glycine, and N-tris(hydroxymethyl)methyl-3-aminopropanesulfonic acid. Among them, the amine compound is preferably an alkanolamine. Examples of the alkanolamine include trishydroxymethylaminomethane, monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine, triisopropanolamine, N-methylethanol, and N-Dimethylethanol Lu Amine compounds that do not contain hydroxyl groups in the molecule have a slightly low hydrophilicity. Therefore, when an amine compound that does not contain hydroxyl groups in the molecule is used, the cohesive force of the wax may become strong, which may cause voids to easily occur in the image, and the color development of the image may not be sufficient.

[0043] It is more preferable that the amine compound is triethanolamine. Primary and secondary alkanolamines have high basicity and easily extract protons from the surface of the recording medium. When the protons from the surface of the recording medium are extracted by the alkanolamine, the aggregation speed of the pigment that aggregates by reacting with the protons decreases, and the cohesive force of the wax tends to be stronger than the cohesive force of the pigment. As a result, wax aggregates are formed, voids tend to occur in the image, and the color development of the image may not be sufficient. If the alkanol group is a trialkanol group with a longer chain than the triethanol group, the carbon chain is long, so the hydrophobicity is high and the cohesive force of the wax may be strong. For this reason, the wax tends to aggregate and voids tend to occur in the image, and the color development of the image may not be sufficient. On the other hand, when triethanolamine is used as the amine compound, voids are less likely to occur in the image compared to when other amine compounds are used. Then, the wax tends to remain on the surface of the image, and the scratch resistance and color development of the image can be further improved.

[0044] The content (mol%) of the amine compound in the ink is preferably 1.0 times or more and 5.0 times or less, more preferably 1.5 times or more and 3.0 times or less, in terms of the molar ratio to the content (mol%) of the phosphate ester surfactant. If the molar ratio is less than 1.0 times, the phosphate ester surfactant is less likely to have a negative charge, and the cohesive force of the phosphate ester surfactant is likely to be strong. As a result, voids may be easily generated in the image, and the color development of the image may not be sufficient. On the other hand, if the molar ratio is more than 5.0 times, the amine compound is likely to be always present near the phosphate ester surfactant. Therefore, the rate of formation of a poorly soluble salt by the amine compound and the phosphate ester surfactant is high, and the cohesive force of the wax is likely to be strong immediately after recording. As a result, the cohesive force of the wax is likely to be excessively strong compared to the cohesive force of the pigment, and the pigment is less likely to enter between the wax particles. As a result, wax aggregates are easily formed, and voids may be easily generated in the image, and the color development of the image may not be sufficient. The content (mass %) of the amine compound in the ink is preferably from 0.10% to 1.50% by mass, and more preferably from 0.20% to 1.00% by mass, based on the total mass of the ink.

[0045] (aqueous medium) The ink of the present invention is an aqueous ink containing an aqueous medium which is water or a mixed solvent of water and 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. As the water-soluble organic solvent, any of those usable for inkjet inks, such as alcohols, glycols, (poly)alkylene glycols, nitrogen-containing compounds, and sulfur-containing compounds, can be used. The content (mass%) of the water-soluble organic solvent in the ink is preferably 3.00 mass% or more and 50.00 mass% or less based on the total mass of the ink. If the content of the water-soluble organic solvent is outside the above range, the reliability of the inkjet ink, such as adhesion resistance, may be slightly reduced.

[0046] (Other Ingredients) In addition to the above-mentioned components, the ink may contain, as necessary, water-soluble organic compounds that are solid at 25° C., such as polyhydric alcohols, such as trimethylolpropane and trimethylolethane, and urea derivatives, such as urea and ethyleneurea. Furthermore, the ink may contain, as necessary, various additives, such as surfactants other than phosphate ester-type surfactants, pH adjusters, defoamers, rust inhibitors, preservatives, antifungal agents, antioxidants, reduction inhibitors, and chelating agents.

[0047] (Ink properties) The ink of the present invention is an aqueous ink applied to the inkjet method. Therefore, from the viewpoint of reliability, it is preferable to appropriately control the physical property values. The viscosity of the ink at 25°C is preferably 1.0 mPa·s to 10.0 mPa·s, more preferably 1.0 mPa·s to 5.0 mPa·s, and particularly preferably 1.0 mPa·s to 3.0 mPa·s. The surface tension of the ink at 25°C is preferably 10 mN / m to 60 mN / m, more preferably 20 mN / m to 60 mN / m, and particularly preferably 30 mN / m to 50 mN / m. The pH of the ink at 25°C is preferably 5.0 to 10.0, and more preferably 7.0 to 9.5.

[0048] <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.

[0049] <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.

[0050] 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

[0051] 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.

[0052] <Method of measuring physical properties> (Cumulative 50% particle size of pigment and wax by volume D 50 ) The pigment dispersion and the wax particle (particles formed from wax) dispersion were each diluted with pure water to prepare samples. Using a particle size analyzer that uses dynamic light scattering, the cumulative 50% particle diameter (DP) of the particles in the prepared samples was measured. 50 ), cumulative 50% particle size of wax (DW 50 ) were measured. The measurement conditions were: SetZero: 30 seconds, number of measurements: 3, measurement time: 180 seconds, shape: spherical, refractive index: 1.50. The particle size analyzer using the dynamic light scattering method was the Nanotrac UPA-EX150 (manufactured by Nikkiso).

[0053] (Acid value of resin) The resin was dispersed or dissolved in water to prepare a sample. The prepared sample was titrated with methyl glycol chitosan 200 / N titrant (manufactured by Fujifilm) using an automatic potentiometric titrator to calculate the number of anionic functional groups per 1 g of resin. The calculated number of anionic functional groups was converted to KOH mass to obtain the acid value of the resin (mgKOH / g). The automatic potentiometric titrator used was the product name "AT510" (manufactured by Kyoto Electronics Manufacturing Co., Ltd.).

[0054] <Synthesis of copolymer> (styrene-acrylic acid copolymer) A four-neck flask equipped with a stirrer, a reflux condenser, and a nitrogen gas inlet tube was prepared. 100.00 parts of ethylene glycol monobutyl ether was placed in the prepared flask, and nitrogen gas was introduced and heated to 110°C while stirring. A mixture of 39.50 parts of styrene, 40.00 parts of methyl methacrylate, and 21.00 parts of acrylic acid, and an ethylene glycol monobutyl ether solution of 1.30 parts of t-butyl peroxide (polymerization initiator) were each added dropwise over 3 hours. After aging for 2 hours, the ethylene glycol monobutyl ether was removed under reduced pressure to obtain a solid styrene-acrylic acid copolymer. To the obtained styrene-acrylic acid copolymer, potassium hydroxide equivalent to the acid value and an appropriate amount of ion-exchanged water were added, and the mixture was heated to 80°C to neutralize and dissolve. As a result, an aqueous solution of styrene-acrylic acid copolymer with a resin (solid content) content of 20.00% was obtained. The acid value of the obtained styrene-acrylic acid copolymer was 170 mgKOH / g, and the weight average molecular weight was 8,000. The amount of acrylic acid used was appropriately changed to obtain aqueous solutions of styrene-acrylic acid copolymers having acid values ​​of 50 mgKOH / g and 200 mgKOH / g, respectively.

[0055] (styrene-styrene sulfonic acid copolymer) Except for using styrene sulfonic acid instead of acrylic acid, an aqueous solution of styrene-styrene sulfonic acid copolymer with a resin (solid content) content of 20.00% was obtained in the same manner as in the case of the above-mentioned styrene-acrylic acid copolymer. The acid value of the obtained styrene-styrene sulfonic acid copolymer was 170 mg KOH / g, and the weight average molecular weight was 8,000. In addition, the amount of styrene sulfonic acid used was appropriately changed to obtain aqueous solutions of styrene-styrene sulfonic acid copolymer with acid values ​​of 50 mg KOH / g and 200 mg KOH / g.

[0056] (Styrene-2-methacryloyloxyethylphosphonic acid copolymer) Instead of acrylic acid, 2-methacryloyloxyethyl phosphonic acid was used. Otherwise, an aqueous solution of styrene-2-methacryloyloxyethyl phosphonic acid copolymer with a resin (solid content) content of 20.00% was obtained in the same manner as in the case of the above-mentioned styrene-acrylic acid copolymer. As the 2-methacryloyloxyethyl phosphonic acid, a product name "Light Ester P-1M" (manufactured by Kyoeisha Chemical Co., Ltd.) was used. The acid value of the obtained styrene-2-methacryloyloxyethyl phosphonic acid copolymer was 170 mgKOH / g, and the weight average molecular weight was 8,000.

[0057] <Production of pigment dispersion> (Pigment dispersion 1) A mixture was obtained by mixing 12.00 parts of pigment, 24.00 parts of an aqueous solution of a resin dispersant, and 64.00 parts of ion-exchanged water. Carbon black (trade name "Black Pearls 880", manufactured by Cabot) was used as the pigment. As the aqueous solution of the resin dispersant, an aqueous solution containing 20.00% of resin (solid content) was used, which was obtained by neutralizing a styrene-acrylic acid copolymer having an acid value of 170 mgKOH / g and a weight average molecular weight of 8,000 with a 10.0% aqueous solution of sodium hydroxide. The obtained mixture was placed in a batch-type vertical sand mill (manufactured by Imex), filled with 85 parts of zirconia beads of 0.3 mm, and dispersed while cooling with water. The dispersion time and dispersion pressure were appropriately adjusted so as to obtain the average particle diameter described later. Thereafter, the mixture was centrifuged to remove non-dispersed matter including coarse particles. The mixture was then filtered under pressure using a cellulose acetate filter (manufactured by Advantec) with a pore size of 3.0 μm to obtain Pigment Dispersion 1 having a pigment content of 10.00% and a resin content of 4.00%. The average particle diameter (DP 50 ) was 65 nm.

[0058] (Pigment dispersion 2) Pigment dispersion 2 was obtained in the same manner as for pigment dispersion 1 described above, except that CI Pigment Blue 15:3 (product name "Hostaperm Blue B2G", manufactured by Clariant) was used as the pigment. The pigment content in pigment dispersion 2 was 10.00%, and the resin content was 4.00%. In addition, the average particle diameter (DP 50 ) was 120 nm.

[0059] (Pigment dispersion 3) Pigment dispersion 3 was obtained in the same manner as in the case of pigment dispersion 1 described above, except that a solid solution of CI Pigment Red 202 and CI Pigment Violet 19 was used as the pigment. As the solid solution of CI Pigment Red 202 and CI Pigment Violet 19, a product named "CROMOPHTAL JET MAGENTA 2BC" (manufactured by Ciba Specialty Chemicals) was used. The pigment content in pigment dispersion 3 was 10.00%, and the resin content was 4.00%. The average particle diameter (DP 50 ) was 120 nm.

[0060] (Pigment Dispersion 4) Pigment dispersion 4 was obtained in the same manner as for pigment dispersion 1 described above, except that CI Pigment Yellow 74 (product name "Hansa yellow 5GXB", manufactured by Clariant) was used as the pigment. The pigment content in pigment dispersion 4 was 10.00%, and the resin content was 4.00%. In addition, the average particle diameter (DP 50 ) was 120 nm.

[0061] (Pigment Dispersion 5) As the aqueous solution of the resin dispersant, an aqueous solution with a resin (solid content) content of 20.00% was used, which was obtained by neutralizing a styrene-acrylic acid copolymer with an acid value of 50 mgKOH / g and a weight average molecular weight of 8,000 with a 10.0% aqueous sodium hydroxide solution. Except for this, Pigment Dispersion Liquid 5 was obtained in the same manner as in the case of the above-mentioned Pigment Dispersion Liquid 1. The pigment content in Pigment Dispersion Liquid 5 was 10.00%, and the resin content was 4.00%. In addition, the average particle diameter (DP 50 ) was 65 nm.

[0062] (Pigment Dispersion 6) As the aqueous solution of the resin dispersant, an aqueous solution with a resin (solid content) content of 20.00% was used, which was obtained by neutralizing a styrene-acrylic acid copolymer with an acid value of 200 mgKOH / g and a weight average molecular weight of 8,000 with a 10.0% aqueous sodium hydroxide solution. Except for this, pigment dispersion 6 was obtained in the same manner as in the case of pigment dispersion 1 described above. The pigment content in pigment dispersion 6 was 10.00%, and the resin content was 4.00%. In addition, the average particle diameter (DP 50 ) was 65 nm.

[0063] (Pigment Dispersion 7) A solution obtained by dissolving 5.0 g of concentrated hydrochloric acid in 5.5 g of water was cooled to 5°C, and in this state, 1.6 g of 4-aminophthalic acid (treatment agent) was added. The container containing this solution was placed in an ice bath, and while stirring to maintain the temperature of the solution below 10°C, a solution obtained by dissolving 0.9 g of sodium nitrite in 9.0 g of 5°C ion-exchanged water was added. After stirring for 15 minutes, carbon black (specific surface area 260 m 2 6.0 g of 100% ethanol (1.0 g / g) was added under stirring, and further stirred for 15 minutes to obtain a slurry. The obtained slurry was filtered through filter paper (product name "Standard Filter Paper No. 2", manufactured by Advantec), and the particles were thoroughly washed with water and dried in an oven at 110°C. Sodium ions were then replaced with potassium ions by ion exchange to form -C on the surface of the pigment particles. 6 H 3 -(COOK) 2 A self-dispersing pigment having a DP group bonded thereto was obtained. An appropriate amount of ion-exchanged water was added to adjust the pigment content, and Pigment Dispersion Liquid 7 having a pigment content of 10.00% was obtained. The average particle diameter (DP 50 ) was 85 nm.

[0064] (Pigment Dispersion 8) As the aqueous solution of the resin dispersant, an aqueous solution with a resin (solid content) content of 20.00% was used, which was obtained by neutralizing a styrene-styrene sulfonic acid copolymer with an acid value of 170 mgKOH / g and a weight average molecular weight of 8,000 with a 10.0% aqueous sodium hydroxide solution. Except for this, Pigment Dispersion Liquid 8 was obtained in the same manner as in the case of the above-mentioned Pigment Dispersion Liquid 1. The pigment content in Pigment Dispersion Liquid 8 was 10.00%, and the resin content was 4.00%. In addition, the average particle diameter (DP 50 ) was 65 nm.

[0065] (Pigment Dispersion 9) As the aqueous solution of the resin dispersant, an aqueous solution with a resin (solid content) content of 20.00% was used, which was obtained by neutralizing a styrene-styrene sulfonic acid copolymer with an acid value of 50 mgKOH / g and a weight average molecular weight of 8,000 with a 10.0% aqueous sodium hydroxide solution. Except for this, Pigment Dispersion Liquid 9 was obtained in the same manner as in the case of the above-mentioned Pigment Dispersion Liquid 1. The pigment content in Pigment Dispersion Liquid 9 was 10.00%, and the resin content was 4.00%. In addition, the average particle diameter (DP 50 ) was 65 nm.

[0066] (Pigment Dispersion 10) As the aqueous solution of the resin dispersant, an aqueous solution with a resin (solid content) content of 20.00% was used, which was obtained by neutralizing a styrene-styrene sulfonic acid copolymer with an acid value of 200 mgKOH / g and a weight average molecular weight of 8,000 with a 10.0% aqueous sodium hydroxide solution. Except for this, Pigment Dispersion 10 was obtained in the same manner as in the case of Pigment Dispersion 1 described above. The pigment content in Pigment Dispersion 10 was 10.00%, and the resin content was 4.00%. In addition, the average particle diameter (DP 50 ) was 65 nm.

[0067] (Pigment Dispersion 11-14) Pigment dispersions 11 to 14 were obtained in the same manner as for the above-mentioned pigment dispersion 1, except that the dispersion time and dispersion pressure using the batch-type vertical sand mill were appropriately changed. The pigment content in each of the pigment dispersions 11 to 14 was 10.00%, and the resin content in each of the pigment dispersions 11 to 14 was 4.00%. The average particle diameter (DP 50 ) were 50 nm, 48 nm, 300 nm, and 330 nm, respectively.

[0068] (Pigment Dispersion 15) As the aqueous solution of resin dispersant, an aqueous solution with a resin (solid content) content of 20.00% was used, which was obtained by neutralizing a styrene-2-methacryloyloxyethylphosphonic acid copolymer with an acid value of 170 mgKOH / g and a weight average molecular weight of 8,000 with a 10.0% aqueous sodium hydroxide solution. Except for this, Pigment Dispersion 15 was obtained in the same manner as in the case of Pigment Dispersion 1 described above. The pigment content in Pigment Dispersion 15 was 10.00%, and the resin content was 4.00%. In addition, the average particle diameter (DP 50 ) was 65 nm.

[0069] <Production of aqueous dispersion of wax particles> (Water dispersion of wax particles 1, 7, and 8) A four-neck flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube was prepared. 225 g of ion-exchanged water and 50 g of polyethylene wax were placed in this four-neck flask, and the polyethylene wax was melted and stirred while maintaining the temperature at 90 to 95°C. 25 g of a liquid containing an ethylene-acrylic resin was added, and a dispersion treatment was carried out for 15 minutes using an ultrasonic homogenizer while maintaining the temperature at 90 to 95°C, and then the mixture was cooled to room temperature to obtain a dispersion. Ion-exchanged water was added to the obtained dispersion to adjust the content of wax and its dispersant (solid content) to 10.00%, and an aqueous dispersion of wax particles 1 was obtained. The average particle diameter (DW) of the wax in the obtained aqueous dispersion was 50 ) was 40 nm. Aqueous dispersions of wax particles 7 and 8 were obtained in the same manner as in the production of the aqueous dispersion of wax particles 1, except that the time of the dispersion treatment was appropriately changed so as to obtain the average particle diameter shown in Table 1.

[0070] (Water dispersion of wax particles 2-6, 9-11) Except for using the type of wax shown in Table 1, the content of wax and its dispersant (solid content) was adjusted to 10.00% in the same manner as in the case of the aqueous dispersion of wax particles 1 described above, to obtain aqueous dispersions of wax particles 2 to 6 and 9 to 11. The average particle diameter (DW) of the wax in the obtained aqueous dispersions was 50 ) is shown in Table 1. The average particle size of the wax (DW 50 ) was adjusted by changing the time of dispersion treatment using an ultrasonic homogenizer.

[0071] TIFF0007669454000003.tif112170

[0072] <Production of Aqueous Dispersion of Acrylic Resin Particles> In a flask equipped with a stirrer, a nitrogen inlet tube, a reflux condenser, and a thermometer, 18.00 parts of butyl methacrylate, 0.35 parts of methacrylic acid, 2.00 parts of a polymerization initiator, and 2.00 parts of n-hexadecane were placed, and the mixture was stirred for 30 minutes while introducing nitrogen gas. 2,2'-azobis(2-methylbutylnitrile) was used as the polymerization initiator. Next, 78.00 parts of a 6.0% aqueous solution of polyoxyethylene cetyl ether (trade name "NIKKOL BC-20", manufactured by Nikko Chemicals) was dropped, and the mixture was stirred for 30 minutes to obtain a mixture. After emulsifying the mixture by irradiating it with ultrasonic waves for 3 hours using an ultrasonic irradiation machine, a polymerization reaction was carried out at 80°C for 4 hours under a nitrogen atmosphere. After cooling to 25°C and filtering, an appropriate amount of pure water was added to obtain an aqueous dispersion of acrylic resin particles with a resin particle content of 20.00% by mass.

[0073] <Production of Fatty Alcohol Alkoxylate> Into a flask equipped with a stirrer, nitrogen inlet tube, reflux condenser, and thermometer, the type and amount of aliphatic alcohol shown in Table 2 and 1.8 mmol of potassium hydroxide catalyst were placed. While stirring at 110 to 120°C, the amount of ethylene oxide (Tokyo Chemical Industry Co., Ltd.) shown in Table 2 was added. The reaction mixture was neutralized and then filtered to obtain aliphatic alcohol alkoxylates 1 to 13. The carbon numbers of the aliphatic moieties and the number of moles of ethylene oxide (EO) added (number of repeating units) of the obtained aliphatic alcohol alkoxylates 1 to 13 are shown on the right side of Table 2.

[0074] TIFF0007669454000004.tif111170

[0075] <Production of phosphate ester surfactants> A flask equipped with a stirrer, nitrogen inlet tube, reflux condenser, and thermometer was charged with strong phosphoric acid (manufactured by Rasa Kogyo) and N,N-dimethylformamide, and stirred at 60°C. alcohol After the alkoxylate or aliphatic alcohol was added dropwise, the temperature was raised to 80°C and reaction was carried out for 12 hours. Saturated saline was then added and the mixture was stirred at 60°C for 12 hours to hydrolyze the pyrophosphate, thereby obtaining phosphate surfactants 1 to 14. The carbon numbers of the aliphatic moieties and the number of moles of ethylene oxide added (number of repeating units) of the obtained phosphate surfactants 1 to 14 are shown on the right side of Table 3. Phosphate surfactant 8 is a phosphate surfactant that does not contain an aliphatic alcohol alkoxylate moiety.

[0076] TIFF0007669454000005.tif118170

[0077] <Production of sulfate ester surfactants> In a flask equipped with a stirrer, a nitrogen inlet tube, a reflux condenser, and a thermometer, the aliphatic alcohol alkoxylate 1 was placed under a nitrogen atmosphere. After 90% sulfuric acid was added dropwise, the mixture was stirred at 80°C for 2 hours. The temperature was then raised to 120°C and the mixture was reacted for 5 hours to obtain a sulfate ester type surfactant. The number of carbon atoms in the aliphatic portion was 18, and the number of moles of ethylene oxide added was 3.

[0078] <Ink Preparation> (Ink 1-58) Each component (unit: %) shown in the middle of Tables 4-1 to 4-6 was mixed and thoroughly stirred, and then pressure filtered with a polypropylene filter (manufactured by Advantec) with a pore size of 1.0 μm to prepare each ink. The ink properties are shown in the lower part of Tables 4-1 to 4-6. The pH of each prepared ink was adjusted to within the range of 8.5 to 9.0 using a 0.5 mol / L aqueous sulfuric acid solution. In Tables 4-1 to 4-6, "Acetylenol E60" is the trade name of a nonionic acetylene glycol surfactant (manufactured by Kawaken Fine Chemicals), and "Proxel GXL" is the trade name of a preservative (manufactured by Arch Chemicals). The numerical value attached to the amine compound is the molecular weight of the amine compound.

[0079] TIFF0007669454000006.tif230170

[0080] TIFF0007669454000007.tif232170

[0081] TIFF0007669454000008.tif231170

[0082] TIFF0007669454000009.tif232170

[0083] TIFF0007669454000010.tif231170

[0084] TIFF0007669454000011.tif255166

[0085] (Ink 59) A cyan ink, Ink 59, was prepared according to the preparation method of Example 1 described in Patent Document 2. The average particle diameter (DW 50 ) is 160 nm, and the average particle diameter of the pigment (DP 50 The average wax particle diameter (DW50 ) / Average Pigment Particle Size (DP 50 ) was 1.33. Ink 59 does not contain a phosphate ester type surfactant.

[0086] (Ink 60) A black ink, ink 60, was prepared according to the preparation method of Example 1 described in Patent Document 3. The average particle diameter (DW 50 ) / Average Pigment Particle Size (DP 50 ) is the average particle diameter of the wax in ink 1 (DW 50 ) / Average Pigment Particle Size (DP 50 ) This ink 60 does not contain an amine compound.

[0087] <Evaluation> Each prepared ink was filled into an ink cartridge, and the ink cartridge was set in an inkjet recording device (product name "PIXUS PRO-10S" (manufactured by Canon)) equipped with a recording head that ejects ink by thermal energy. In this embodiment, the recording duty of an image recorded under the condition that one ink droplet of 30 ng per droplet is applied to a unit area of ​​1 / 600 inch x 1 / 600 inch is defined as 100%. In the present invention, the evaluation criteria for each item shown below are "AA", "A", and "B" as acceptable levels, and "C" as unacceptable level. The evaluation results are shown in Table 6.

[0088] (Abrasion resistance) Using the above-mentioned inkjet recording device, a solid image (200 mm x 200 mm) with a recording duty of 100% was recorded on a recording medium (product name "Canon Photo Paper Glossy Gold GL-101", manufactured by Canon). The recorded image was dried at 25°C for 24 hours, and then a friction test was carried out using a Gakushin type tester (product name "AB-301 Gakushin type friction fastness tester", manufactured by Tester Sangyo) conforming to JIS L 0849:2013, with a load of 500 g and 30 or 60 reciprocations. The image after the friction test was visually observed, and the abrasion resistance of the image was evaluated according to the following evaluation criteria. AA: There were no scratches on the image even after 60 round trips. A: There were no scratches on the image after 30 strokes, but there were scratches after 60 strokes. B: After 30 round trips, there were scratches on the image, but the white background of the recording medium underneath the image was not visible. C: After 30 round trips, there were scratches on the image and the white background of the recording medium underneath the image was visible.

[0089] (Color development) Using the above-mentioned inkjet recording device, 15 types of solid images were recorded on a recording medium (product name "Canon Photo Paper Glossy Gold GL-101", manufactured by Canon) with the recording duty changed in 10% increments between 0% and 140%. After the recorded images were dried at 25°C for 24 hours, the optical density of the images was measured using a fluorescence spectrodensitometer (product name "FD-7", manufactured by Konica Minolta). The measurement conditions were a light source D50 and a viewing angle of 2°. The image with the maximum optical density among the 15 types of solid images was evaluated, and the color development of the image was evaluated according to the evaluation criteria shown in Table 5.

[0090] TIFF0007669454000012.tif49170

[0091] TIFF0007669454000013.tif222170

[0092] The abrasion resistance and color development of the image of Example 41 were evaluated as "AA" like Example 1, but Example 1 was superior.

[0093] The disclosure of this embodiment includes the following configurations and methods. (Configuration 1) A water-based inkjet ink containing a pigment, a wax, a dispersant for dispersing the wax, a phosphate ester type surfactant, and an amine compound, the pigment is dispersed by the action of at least one group selected from the group consisting of a carboxylic acid group and a sulfonic acid group, the phosphate ester surfactant contains an aliphatic alcohol alkoxylate moiety, and the volume-based cumulative 50% particle diameter of the wax is 0.10 to 2.0 times the volume-based cumulative 50% particle diameter of the pigment. (Configuration 2) The aqueous ink according to Configuration 1, wherein the total content (mass %) of the wax and the dispersant for dispersing the wax is 0.005 to 0.20 times the mass content (mass %) of the pigment. (Configuration 3) The aqueous ink according to configuration 1 or 2, wherein the content (mol %) of the amine compound is 1.0 to 5.0 times the content (mol %) of the phosphate ester surfactant in terms of a molar ratio. (Configuration 4) The aqueous ink according to any one of Configurations 1 to 3, wherein the pigment is a resin-dispersed pigment dispersed by a resin having a carboxylic acid group. (Configuration 5) The aqueous ink according to any one of configurations 1 to 4, wherein the wax is at least one wax selected from the group consisting of polyethylene wax, Fischer-Tropsch wax, microcrystalline wax, paraffin wax, ozokerite, and ceresin. (Configuration 6) The aqueous ink according to any one of Configurations 1 to 5, wherein the amine compound is an alkanolamine. (Configuration 7) The aqueous ink according to any one of Configurations 1 to 6, wherein the phosphate ester surfactant is a compound represented by the following general formula (1): TIFF0007669454000014.tif34170 (In the above general formula (1), R 1 represents a chain hydrocarbon group having 12 to 24 carbon atoms, and a represents an integer of 1 to 10. (Configuration 8) The aqueous ink according to any one of Configurations 1 to 7, wherein the phosphate ester surfactant is a compound represented by the following general formula (2): TIFF0007669454000015.tif30170 (in the general formula (2), a represents an integer of 1 or more and 10 or less) (Configuration 9) The aqueous ink according to any one of Configurations 1 to 8, wherein the amine compound is triethanolamine. (Configuration 10) An ink cartridge including an ink and an ink storage section for storing the ink, 10. An ink cartridge, wherein the ink is the aqueous ink described in any one of configurations 1 to 9. (Method 1) An inkjet recording method for recording an image on a recording medium by ejecting ink from an inkjet recording head, 10. An ink-jet recording method, wherein the ink is the aqueous ink described in any one of configurations 1 to 9.

Claims

1. A water-based inkjet ink containing a pigment, a wax, a dispersant for dispersing the wax, a phosphate ester surfactant, and an amine compound, the pigment is dispersed by the action of at least one group selected from the group consisting of a carboxylic acid group and a sulfonic acid group, The phosphate ester surfactant contains an aliphatic alcohol alkoxylate moiety, The aqueous ink according to claim 1, wherein the cumulative 50% volumetric particle size of the wax is 0.10 to 2.0 times the cumulative 50% volumetric particle size of the pigment.

2. 2. The water-based ink according to claim 1, wherein a total content (mass %) of the wax and the dispersant for dispersing the wax is 0.005 to 0.20 times, in terms of mass ratio, relative to a content (mass %) of the pigment.

3. 2. The aqueous ink according to claim 1, wherein the content (mol %) of the amine compound is 1.0 to 5.0 times the content (mol %) of the phosphate ester surfactant in terms of a molar ratio.

4. 2. The water-based ink according to claim 1, wherein the pigment is a resin-dispersed pigment dispersed by a resin having a carboxylic acid group.

5. 2. The water-based ink according to claim 1, wherein the wax is at least one wax selected from the group consisting of polyethylene wax, Fischer-Tropsch wax, microcrystalline wax, paraffin wax, ozokerite, and ceresin.

6. 2. The aqueous ink of claim 1, wherein the amine compound is an alkanolamine.

7. 2. The aqueous ink according to claim 1, wherein the phosphate ester surfactant is a compound represented by the following general formula (1): (In the general formula (1), R １ represents a chain hydrocarbon group having 12 to 24 carbon atoms, and a represents an integer of 1 to 10.

8. 2. The aqueous ink according to claim 1, wherein the phosphate ester surfactant is a compound represented by the following general formula (2): (In the general formula (2), a represents an integer of 1 or more and 10 or less).

9. 2. The water-based ink according to claim 1, wherein the amine compound is triethanolamine.

10. An ink cartridge including an ink and an ink storage section for storing the ink, 10. An ink cartridge, wherein the ink is a water-based ink as claimed in claim 1.

11. An inkjet recording method for recording an image on a recording medium by ejecting ink from an inkjet recording head, comprising:

10. An ink-jet recording method, wherein the ink is a water-based ink according to claim 1.

Images