Aqueous ink, ink cartridge, and ink jet recording method

Abstract

To provide an aqueous ink that is suppressed from causing mist and is excellent in storage stability.SOLUTION: The aqueous ink is an aqueous ink to be ejected from a recording head of an ink jet system through action of thermal energy. The aqueous ink contains a first surfactant and a second surfactant. The first surfactant is a compound represented by the general formula (1) (where m and n each independently represent an integer equal to or greater than 1 and satisfy m+n≤10, and a represents an integer from 10 to 20 inclusive). The second surfactant is an acetylene glycol compound.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] In recent years, inkjet recording methods have made it possible to record high-definition images, such as those achieved by silver halide photography and offset printing. In addition, with the diversification of applications such as photo printing and graphic art printing, there is a demand for improved image quality in recording media having a coating layer, such as glossy paper. The method of ejecting ink from an inkjet recording head by the action of thermal energy (thermal inkjet method) is suitable for improving image quality, as it allows high-density recording.

[0003] In recent years, there has been a demand for inkjet recording methods to record images with higher resolution than ever before. Studies are being conducted to improve the image quality of recording media having a coating layer, such as glossy paper. For example, an ink capable of recording images with improved gloss has been proposed by using a low molecular weight surfactant to lower the surface tension of the ink and effectively increasing the ink's permeability into the recording medium (Patent Document 1). In addition, an ink capable of recording images with improved gloss has been proposed by using a silicone (polyorganosiloxane) surfactant to increase the wettability of the recording medium (Patent Document 2). In addition, there has been a proposal regarding a dye ink that uses an acetylene glycol surfactant to increase the wettability of the recording medium and improve defoaming properties (Patent Document 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2004-115649 A [Patent Document 2] JP 2006-233083 A [Patent Document 3] JP 2005-103457 A Summary of the Invention [Problem to be solved by the invention]

[0005] The present inventors have investigated a recording method that can improve the image quality of a recording medium having a coating layer, such as glossy paper, using a thermal inkjet system. As the ink, a low surface tension ink using a silicone surfactant was used, with reference to the description in the above-mentioned Patent Document 2. As a result, it was found that the silicone surfactant can improve the image quality, but it was also found that the following problems arise.

[0006] First, it was confirmed that when ink is stored for a long period of time, the surface tension of the ink increases over time due to the decomposition of the silicone surfactant. When ink whose surface tension has increased due to long-term storage is used for recording, a significant decrease in image quality was observed compared to when recording is performed using the ink before storage. In addition, when a silicone surfactant is used, although storage stability can be improved, a phenomenon was confirmed in which minute droplets (hereinafter referred to as mist) are generated during image recording and adhere to the recording head and recording device. The mist is a very small droplet compared to the main ink droplets for recording an image. If recording is continued in a state in which the mist is generated, the mist may adhere to various sensors in the recording device, causing a decrease in the sensitivity of the sensor or a malfunction. In addition, when the mist adheres to the recording medium, it also affects the image. In other words, when attempting to obtain good image quality using the thermal inkjet method, the suppression of mist generation and the improvement of the storage stability of the ink are issues, and further consideration is needed to solve these issues.

[0007] It is therefore an object of the present invention to provide an aqueous ink that suppresses the generation of mist and has excellent storage stability. It is also an object of the present invention to provide an ink cartridge and an ink-jet recording method that use the aqueous ink. [Means for solving the problem]

[0008] The above object is achieved by the present invention, which is described below. That is, according to the present invention, there is provided an aqueous ink that is ejected from an inkjet recording head by the action of thermal energy, the aqueous ink comprising a particulate component, a first surfactant, and a second surfactant, the particulate component being at least one selected from the group consisting of pigments and resin particles, the first surfactant being a compound represented by the following general formula (1), and the second surfactant being an acetylene glycol compound.

[0009] TIFF2024023137000001.tif32170 (In the general formula (1), m and n each independently represent an integer of 1 or more and m+n is 10 or less, and a represents an integer of 10 or more and 20 or less.) Effect of the Invention

[0010] According to the present invention, it is possible to provide an aqueous ink that suppresses the generation of mist and has excellent storage stability. Furthermore, according to the present invention, it is possible to provide an ink cartridge and an inkjet recording method that use the aqueous ink. [Brief description of the drawings]

[0011] [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

[0012] 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.

[0013] The present inventors have investigated low surface tension inks that use silicone surfactants as surfactants contained in aqueous inks in order to improve image quality on recording media having a coating layer, such as glossy paper. As a result, it has been confirmed that the surface tension of the ink increases over time when the ink is stored for a long period of time. This phenomenon is caused by the decomposition of the silicone surfactant in the ink. When ink whose surface tension has increased due to long-term storage is used for recording, a significant decrease in image quality is observed compared to when recording is performed using the ink before storage.

[0014] It is speculated that the reason why silicone surfactants decompose in aqueous inks is because the siloxane portion, which is the hydrophobic portion of the silicone surfactant, is easily hydrolyzed. It is also speculated that the reason why the surface tension of the ink increases due to the decomposition of the silicone surfactant is because when the silicone surfactant is hydrolyzed, the hydrophobic portion and the hydrophilic portion of the surfactant are separated, and the surfactant function is lost.

[0015] In the case of aqueous inkjet inks, silicone surfactants modified with polyether chains using a siloxane structure as a basic skeleton are widely used. This type of surfactant is roughly classified into one-end modified type, both-end modified type, ABn type, side chain modified type, and both-end modified type of side chain, according to the type of modification of the polyether chain to the siloxane structure (-Si-O-). The present inventors have conducted various studies on the structure of silicone surfactants capable of suppressing the increase in surface tension due to long-term storage of ink even when a silicone surfactant is used. As a result, it was found that among silicone surfactants, both-end modified type; ABn type (linear block copolymer); and side chain modified type in which the ethylene oxide chain end of the side chain is alkylated; can improve the storage stability of ink.

[0016] The reason why the silicone surfactants of both ends modified and ABn type were able to suppress the increase in surface tension is presumed to be that even if the siloxane skeleton is split by hydrolysis, the split molecules have hydrophobic and hydrophilic parts, so that the surfactant activity is not easily lost. The reason why the silicone surfactants of the side chain modified type, in which the ethylene oxide chain end of the side chain is alkylated, were able to suppress the increase in the surface tension of the ink is presumed to be as follows. One of the causes of the hydrolysis reaction of the siloxane skeleton of the silicone surfactant is the hydroxide ion contained in the ink. Another cause is the carboxylate ion generated by the oxidation of the hydroxyl group at the ethylene oxide chain end of the silicone surfactant. It is considered that the hydrolysis proceeds by the nucleophilic attack of the siloxane skeleton within or between molecules by this carboxylate ion. Therefore, it is presumed that the hydrolysis of the siloxane skeleton was suppressed by alkylating the ethylene oxide chain end, and therefore the increase in the surface tension of the ink was suppressed.

[0017] The present inventors have investigated the ejection characteristics of inks with improved storage stability by selecting a silicone-based surfactant using a thermal inkjet system. As a result, it was found that a large amount of mist is generated peculiarly when the above-mentioned silicone-based surfactant capable of improving the storage stability of the ink is used. The phenomenon of a large amount of mist generation does not occur when a silicone-based surfactant with a low effect of improving the storage stability of the ink is used or when an ejection system other than the thermal inkjet system is used.

[0018] Here, the mist in the inkjet method will be described. The inkjet method is broadly divided into a piezoelectric inkjet method and a thermal inkjet method. The piezoelectric inkjet method is a method in which a piezoelectric element is used to eject ink from the nozzles of a recording head. The thermal inkjet method is a method in which thermal energy is applied to ink to eject it from the nozzles of a recording head. In both the piezoelectric inkjet method and the thermal inkjet method, energy is applied to the liquid near the nozzles of the recording head, causing the ink to be ejected from the nozzles in the form of droplets.

[0019] Although it is preferable that one droplet is ejected for each application of ejection energy to the ink, the droplet may be split into several droplets due to various factors such as the physical properties of the ink, the shape of the ejection port, and the amount of ejection energy. Of these split droplets, the droplet with the largest volume (main droplet) adheres to the intended position on the recording medium. On the other hand, droplets with a small volume may adhere to an unintended position on the recording medium, lowering the image quality, or may adhere to the inside of the recording device without adhering to the recording medium, and may cause dirt or device failure. Split droplets that do not adhere to the intended position on the recording medium are called mist. It is known that the ink split phenomenon is less likely to occur when the surface tension of the ink is high in terms of ink physical properties, and more likely to occur when the surface tension of the ink is low. The surface tension referred to here refers to the surface tension (dynamic surface tension) on the time scale when the ink droplet is ejected from the ejection port of the recording head. The amount of mist is related to the ease with which droplets leave a trail when ejected, and it is known that the amount of mist is greater when the viscosity of the ink is high and tends to be less when the viscosity of the ink is low.

[0020] For example, acetylene glycol surfactants are quickly oriented to the gas-liquid interface. When an acetylene glycol surfactant is used in an ink, it is considered that the surfactant quickly orients on the surface of the droplets formed by ejection, lowering the surface tension of the droplets and making it easier for the droplets to break up. In contrast, a silicone surfactant is not oriented to the gas-liquid interface fast enough to lower the surface tension of the droplets formed by ejection, so it is considered that the droplets are less likely to break up. The surfactant molecules are detached from the micelles formed by the surfactant in the liquid and oriented to the gas-liquid interface, thereby lowering the tension of the gas-liquid interface. The orientation speed depends on the strength of the association of the micelles. In other words, it was expected that the silicone surfactant has a strong intermolecular association force, the surfactant molecules are less likely to detach from the formed micelles, and the orientation to the gas-liquid interface is slow, making it difficult for the droplets to break up. However, contrary to this expectation, it was found that a phenomenon of a specific increase in mist occurs when an ink using a silicone surfactant that can improve the storage stability of the ink is ejected by a thermal inkjet method. The inventors speculate that the cause of the large amount of mist is as follows.

[0021] First, the reason why mist increased when both-end modified or ABn type silicone surfactants were used is thought to be as follows. It is thought that ink containing both-end modified or ABn type silicone surfactants is likely to increase in ink viscosity due to evaporation at the nozzle of the recording head due to the molecular structure of the surfactant. Therefore, it is thought that mist is more likely to be generated because the droplets leave a trailing tail when ejected before being broken into spherical shapes.

[0022] Next, the reason why mist increased when using a silicone surfactant with alkylated ethylene oxide chain ends of the side chains of the side chain modified type is presumed to be as follows. It is expected that alkylating the ethylene oxide chain ends lowers the cloud point of the silicone surfactant. As a result, the micelles formed by the silicone surfactant become hydrophobic when heated in the thermal inkjet method, and these hydrophobic micelles immediately move to the gas-liquid interface, lowering the surface tension of the droplets, causing the droplets to break up, making it easier for mist to be generated.

[0023] Based on the above assumption, the present inventors further investigated a composition that can suppress mist when using a thermal inkjet method and maintain storage stability of the ink. As a result, they found an ink composition that uses a particulate component (pigment or resin particles), a compound represented by the general formula (1) described below, and an acetylene glycol compound in combination. With an ink of this composition, it is possible to suppress the generation of mist even when using a thermal inkjet method, and further achieve a high level of storage stability of the ink. Hereinafter, the compound represented by the general formula (1) is also referred to as the "first surfactant" and the acetylene glycol compound is also referred to as the "second surfactant."

[0024] The present inventors speculate as follows about the mechanism by which the ink contains a particulate component, a compound represented by general formula (1) (first surfactant), and an acetylene glycol compound (second surfactant), thereby suppressing mist and achieving storage stability of the ink. First, the ink contains a particulate component, a first surfactant, and a second surfactant, thereby achieving suppression of mist and storage stability of the ink. When a silicone-based surfactant of both ends modified or ABn type other than the first surfactant, which is a silicone-based surfactant of side chain modified type, is used in combination with the second surfactant, the generation of mist during ejection cannot be suppressed. In addition, when the first surfactant and the second surfactant are used but the particulate component is absent, when a dye is used instead of the pigment, which is the particulate component, or when a water-soluble resin is used instead of the resin particles, which is the particulate component, the generation of mist during ejection cannot be suppressed. From this, it is speculated that this effect is due to the specific action of the particulate component, the first surfactant, and the second surfactant.

[0025] It is known that when multiple types of nonionic surfactants are mixed in a liquid, they may form mixed micelles due to their structures and HLB (hydrophilic-lipophilic balance) relationships. It is believed that the above-mentioned effects were achieved by the first surfactant and the second surfactant forming mixed micelles and the coexistence of particulate components.

[0026] By forming mixed micelles, even if the cloud point of the first surfactant is lowered and hydrophobized by heating using the thermal inkjet method, it is considered that the hydrophobization of the surface of the mixed micelles is suppressed by the hydrophilic part of the second surfactant adjacent to the mixed micelles. On the other hand, since the mixed micelles contain not only the second surfactant but also the first surfactant that has been hydrophobized by heating using the thermal inkjet method, the inside of the mixed micelles is in a state where the hydrophobic part and the hydrophilic part are mixed. As a result, the hydrophobicity of the mixed micelles is reduced and they are less likely to move to the gas-liquid interface of the droplets, but since the hydrophobic part exists on the surface of the mixed micelles, they are considered to move to the gas-liquid interface of the droplets. Since the pigment and resin particles, which are particulate components, have hydrophobic parts on their particle surfaces, the hydrophobic part of the mixed micelles efficiently interact with the particulate components, restricting the movement of the mixed micelles to the gas-liquid interface. As a result, it is considered that the mixed micelles are less likely to exist at the gas-liquid interface of the droplets, making it less likely to reduce the surface tension of the droplets, thereby suppressing the generation of mist. In addition, the ink contains a first surfactant that has detached from the mixed micelles and exists in a monomolecular state. The first surfactant that has detached from the mixed micelles can become hydrophobic when heated by the thermal inkjet method, lowering the surface tension of the droplets and making it easier to generate mist. However, it is believed that the generation of mist can also be suppressed by the action of the particulate component adsorbing the hydrophobic first surfactant.

[0027] As described above, even if dyes or water-soluble resins are used instead of particulate components, the effect of suppressing mist generation cannot be obtained. The reason for this is considered to be as follows. Since dyes and resins do not have hydrophobic parts that are large enough to form particles like pigments and resin particles, their interaction with mixed micelles is weak, and it is considered that the movement of mixed micelles to the gas-liquid interface of the droplets cannot be suppressed, and the effect of suppressing mist generation cannot be obtained. In addition, it is expected that mist is easily generated when only the second surfactant is used as a surfactant in the ink. In contrast, it is presumed that the reason why the generation of mist can be suppressed by the configuration of the ink of the present invention is that the second surfactant is captured by the strong association force of the first surfactant, suppressing its separation from the mixed micelles.

[0028] The reason why inks using silicone surfactants other than the first surfactant were not effective in suppressing mist is presumed to be as follows. Silicone surfactants other than the first surfactant differ from the first surfactant in the chain length of the siloxane skeleton and the balance between the hydrophilic and hydrophobic parts. For this reason, silicone surfactants other than the first surfactant are less likely to form mixed micelles with the second surfactant, and some of the silicone surfactants other than the first surfactant exist as single molecules or form independent micelles rather than a mixture. It is presumed that this is why the generation of mist could not be suppressed.

[0029] It was also found that the above composition improves the storage stability of the ink. The reason for this is believed to be that hydroxide ions, which are one of the causes of hydrolysis of silicone surfactants, are captured by hydrogen bonding with the hydroxyl groups of the second surfactant in the mixed micelles. In addition, it is believed that the mixed micelles are adsorbed to the particulate components, suppressing nucleophilic attack on the siloxane skeleton inside the mixed micelles.

[0030] <Water-based ink> As described above, the ink is an aqueous ink that is ejected from an inkjet recording head by the action of thermal energy. The ink contains a particulate component (pigment or resin particles) and a surfactant. The surfactant includes a first surfactant and a second surfactant. The ink of the present invention does not need to be a so-called "curable ink." Therefore, the ink of the present invention does not need to contain a compound such as a polymerizable monomer that can be polymerized by the addition of external energy. Each component that constitutes the ink will be described in detail below.

[0031] (particulate component) The ink contains at least one kind selected from the group consisting of pigments and resin particles as a particulate component. It is more preferable that the ink contains at least a pigment as a particulate component. The content (mass%) of the particulate component in the ink is preferably 0.10% by mass or more and 10.00% by mass or less based on the total mass of the ink. The content (mass%) of the particulate component in the ink is preferably 0.01 times or more and 10.00 times or less in mass ratio to the total content (mass%) of the first surfactant and the second surfactant. In particular, the mass ratio is more preferably 0.10 times or more and 5.00 times or less, and even more preferably 0.10 times or more and 2.00 times or less.

[0032] [Pigments] When a pigment is used as the particulate component, the content (mass %) of the pigment in the ink is preferably 0.10% by mass or more and 10.00% by mass or less, and more preferably 0.50% by mass or more and 6.00% by mass or less, based on the total mass of the ink. Inks that do not contain a pigment as a particulate component can be used as clear inks that do not contain coloring materials, dye inks that contain dyes as coloring materials, and the like.

[0033] Specific examples of pigments include inorganic pigments such as carbon black and titanium oxide; and organic pigments such as azo, phthalocyanine, quinacridone, isoindolinone, imidazolone, diketopyrrolopyrrole, and dioxazine.

[0034] As pigments, when classified by dispersion method, resin-dispersed pigments using resin as a dispersant, self-dispersed pigments in which hydrophilic groups are bonded to the pigment particle surface, etc. can be used. In addition, resin-bonded pigments in which organic groups containing resin are chemically bonded to the pigment particle surface, and microcapsule pigments in which the pigment particle surface is coated with resin, etc. can be used. Pigments of any dispersion method can be used in the ink. Furthermore, it is also possible to use a combination of pigments with different dispersion methods. Among them, a method in which the pigment is dispersed by the action of a resin dispersant (for example, a water-soluble resin including a unit having an acid group and a unit not having an acid group) physically adsorbed on the pigment particle surface (resin-dispersed pigment) is preferred. The constituent units of the water-soluble resin used as the resin dispersant can be selected from the same ones as those listed as units forming the resin particles described later.

[0035] [Resin particles] When resin particles are used as the particulate component, the resin type forming the resin particles may be any resin with any structure as long as it can be used in aqueous ink. For example, acrylic resin, urethane resin, polyamide resin, polyester resin, polyvinyl alcohol resin, polyolefin resin, etc. can be mentioned. Resin particles formed of one or more of these can be contained in the ink. When resin particles are used as the particulate component, the content (mass%) of the resin particles in the ink is preferably 0.10% by mass or more and 5.00% by mass or less, and more preferably 0.10% by mass or more and 3.00% by mass or less, based on the total mass of the ink. Of these, it is even more preferable that it is 0.50% by mass or more and 2.00% by mass or less.

[0036] "Resin particles" refers to a resin that does not dissolve in the aqueous medium that constitutes the ink, specifically, a resin that can exist in the aqueous medium in a state in which it forms particles whose particle diameter can be measured by dynamic light scattering. On the other hand, "water-soluble resin" refers to a resin that can dissolve in the aqueous medium that constitutes the ink, specifically, a resin that can exist in the aqueous medium in a state in which it does not form particles whose particle diameter can be measured by dynamic light scattering. "Resin particles" can also be referred to as "water-dispersible resin (water-insoluble resin)".

[0037] Whether or not a certain resin is a "resin particle" can be determined according to the method shown below. First, a liquid (resin solid content: 10 mass%) containing a resin neutralized with an alkali (sodium hydroxide, potassium hydroxide, etc.) equivalent to the acid value is prepared. Next, the prepared liquid is diluted 10 times (volume basis) with pure water to prepare a sample solution. Then, when the particle size of the resin in the sample solution is measured by dynamic light scattering, if particles having a particle size are measured, the resin can be determined to be a "resin particle" (water-dispersible resin). On the other hand, if particles having a particle size are not measured, the resin can be determined to be not a "resin particle" (it is a "water-soluble resin"). As a particle size distribution measuring device using the dynamic light scattering method, a particle size analyzer (for example, the product name "UPA-EX150", manufactured by Nikkiso) can be used. The measurement conditions at this time can be, for example, SetZero: 30 seconds, number of measurements: 3 times, measurement time: 180 seconds, shape: spherical, refractive index: 1.59. Of course, the particle size distribution measuring device and the measuring conditions are not limited to those described above. The particle size is measured using a neutralized resin in order to confirm that particles are formed even if the resin is sufficiently neutralized to make it more difficult to form particles. Even under such conditions, the resin having a particle shape exists in the form of particles in the aqueous ink.

[0038] The resin particles are preferably those having a so-called core-shell structure, which has a core portion and a shell portion covering the core portion. In particular, it is preferable to use resin particles that are composed of a core formed only of units having no acid groups and a shell formed including units having acid groups, and that contain specific units. Specifically, it is preferable that at least one of the units forming the core and the units forming the shell contains a unit derived from a (meth)acrylic acid ester. By using resin particles with such a core-shell structure, the resin particles can easily maintain their shape in the droplets, so that the mixed micelles of the first surfactant and the second surfactant can be effectively adsorbed, and the effect of suppressing mist can be easily expressed. When the core is only a unit having no acid groups, in other words, when it does not contain a unit having an acid group, the hydrophilicity of the resin forming the core is reduced, and the resin particles can easily maintain their shape in the droplets ejected by the thermal inkjet method, and the effect of suppressing mist can be easily expressed. In addition, when the shell contains a unit having an acid group, the hydrophilicity of the resin particles is higher than when the shell is formed only of units having no acid groups, so that aggregation is less likely to occur, and the mixed micelles can be effectively adsorbed, and the effect of suppressing mist can be easily expressed. Furthermore, when at least one of the units forming the core and the units forming the shell contains a unit derived from a (meth)acrylic acid ester, aggregation of resin particles in the ink is easily suppressed, and storage stability can be further improved.

[0039] Examples of resin species that form resin particles with a core-shell structure include acrylic resins obtained by (co)polymerizing acrylic monomers such as (meth)acrylic acid and (meth)acrylic acid esters. In this specification, the term "unit" of a resin means a repeating unit derived from one monomer. In addition, "(meth)acrylic acid" refers to "acrylic acid, methacrylic acid", and "(meth)acrylate" refers to "acrylate, methacrylate".

[0040] Examples of monomers having no acid groups that become units having no acid groups by polymerization include monomers having hydroxy groups such as 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 3-methyl-5-hydroxypentyl (meth)acrylate; monomers having aromatic groups such as styrene, α-methylstyrene, and benzyl (meth)acrylate; and alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. One or more of the monomers having no acid groups can be used.

[0041] Examples of monomers having an acid group that become units having an acid group by polymerization include monomers having a carboxylic acid group such as (meth)acrylic acid, maleic acid, itaconic acid, and fumaric acid; monomers having a sulfonic acid group such as styrenesulfonic acid; monomers having a phosphonic acid group such as 2-ethyl phosphonate (meth)acrylic acid; and anhydrides and salts of these monomers. Examples of salts include alkali metal salts such as lithium, sodium, and potassium, ammonium salts, and organic ammonium salts. One or more types of monomers having an acid group can be used.

[0042] (Surfactant) The ink contains a first surfactant, that is, a compound represented by the following general formula (1). The compound represented by general formula (1) is a silicone-based surfactant having a structure in which an ethylene oxide chain with a methylated end is introduced into the side chain of a polydimethylsiloxane structure. The ink can contain one or more of the compounds represented by general formula (1) as the first surfactant.

[0043] TIFF2024023137000002.tif32170

[0044] In general formula (1), m and n each independently represent an integer of 1 or more and m+n is 10 or less, and a represents an integer of 10 or more and 20 or less. m and n each independently represent an integer of 1 or more and 9 or less, and preferably an integer of 1 or more and 8 or less, in the range satisfying m+n≦10. It is more preferable that m is an integer of 1 or more and 8 or less, and n is 1 or 2.

[0045] The weight average molecular weight (Mw) of the compound represented by the general formula (1) is preferably 800 to 12,000, more preferably 800 to 2,000, and even more preferably 1,000 to 1,500. The weight average molecular weight (Mw) can be measured by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as the mobile phase. The specific method for measuring the Mw of the compound represented by the general formula (1) is as follows, and the Mw of the surfactants S1 to S5 and S8 to S16 used in the examples described later was measured by the preferred measurement method described below. The measurement conditions, such as the filter, column, standard polystyrene sample, and its molecular weight, are not limited to those described below.

[0046] The weight average molecular weight (Mw) of the compound represented by the general formula (1) can be measured by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as the mobile phase. The measurement conditions such as the filter, column, standard polystyrene sample and its molecular weight are not limited to the following. First, the sample to be measured is placed in tetrahydrofuran (THF) and left to stand for several hours to dissolve, preparing a solution. Then, the solution is filtered through a solvent-resistant membrane filter with a pore size of 0.2 μm to obtain a sample solution. The concentration of the sample in the sample solution is adjusted so that the content of the silicone surfactant is 0.1% by mass to 0.3% by mass. An RI detector (Refractive Index Detector) is used for GPC. In addition, 10 3 ~2×10 6In order to accurately measure the molecular weight range, it is preferable to combine multiple commercially available polystyrene gel columns. For example, four Shodex LF-804 (Showa Denko) columns can be combined or an equivalent can be used. THF is passed through the column stabilized in a heat chamber at 40.0°C as the mobile phase at a flow rate of 1 mL / min, and about 0.1 mL of the above sample solution is injected. The weight-average molecular weight of the sample is determined using a molecular weight calibration curve prepared using standard polystyrene samples. The standard polystyrene samples are used for a molecular weight of 10 2 〜10 7 It is appropriate to use a standard polystyrene standard (eg, manufactured by Polymer Laboratories) and to use at least about 10 types of standard polystyrene samples.

[0047] The compound represented by general formula (1) can be obtained, for example, by an addition reaction between a compound represented by the following general formula (A) and a compound represented by the following general formula (B).

[0048] TIFF2024023137000003.tif29170 (In general formula (A), m and n are defined the same as m and n in general formula (1), respectively.)

[0049] TIFF2024023137000004.tif19170 (In general formula (B), a has the same meaning as a in general formula (1).)

[0050] The compound represented by the general formula (A) is a polysiloxane compound having n hydrogen atoms bonded to n Si atoms in the general formula (A). The compound represented by the general formula (B) is a methoxy-polyethylene glycol-allyl ether having an ethylene oxide unit and an allyloxy group (CH2=CH-CH2-O-) at one end and a methyl group (-CH3) at the other end.

[0051] The content (mass %) of the first surfactant in the ink is preferably 0.05% by mass or more and 4.00% by mass or less based on the total mass of the ink. The content (mass %) of the first surfactant in the ink is preferably 0.05% by mass or more, and more preferably 0.10% by mass or more, more preferably 2.00% by mass or less, and even more preferably 1.00% by mass or less.

[0052] The ink contains a second surfactant, that is, an acetylene glycol compound. The acetylene glycol compound is a compound in which a plurality of hydroxy groups are substituted on an acetylene skeleton, and an ethylene oxide chain may be present between the acetylene skeleton and the hydroxy group. As the second surfactant, a compound represented by the following general formula (2) is preferable. The ink can contain, as the second surfactant, one or more of acetylene glycol compounds such as the compound represented by general formula (2).

[0053] TIFF2024023137000005.tif54170 (In general formula (2), b and c each independently represent a positive integer.)

[0054] In general formula (2), b and c indicate the number of hydrophilic ethylene oxide groups (-CH2CH2O-) added, and each is independently a positive integer. b and c are each preferably an integer of 1 or more and 50 or less, and more preferably an integer of 1 or more and 20 or less. b+c is preferably 4 or more, and more preferably 6 or more. b+c is preferably 50 or less, and more preferably 20 or less.

[0055] The acetylene glycol compound (second surfactant) may be a commercially available product. Specific examples of the second surfactant include the following trade names: Acetylenol E60 and Acetylenol E100 (both manufactured by Kawaken Fine Chemicals); Surfynol 104, Surfynol 465, and Surfynol 485 (both manufactured by Nissin Chemical Industry Co., Ltd.).

[0056] The content (mass %) of the second surfactant in the ink is preferably 0.10% by mass to 3.00% by mass based on the total mass of the ink, more preferably 0.20% by mass to 3.00% by mass, and even more preferably 0.50% by mass to 2.50% by mass.

[0057] The content (mass %) of the first surfactant in the ink is preferably 0.05 times or more and 3.00 times or less, particularly preferably 0.05 times or more and 2.00 times or less, in terms of the mass ratio to the content (mass %) of the second surfactant. When the mass ratio is 0.05 times or more, mist is easily suppressed. This is considered to be because in the mixed micelles of the first surfactant and the second surfactant, the second surfactant is sufficiently captured by the strong association force of the first surfactant. From the viewpoint of easier suppression of mist, it is more preferable that the mass ratio is 0.10 times or more. On the other hand, when the mass ratio is 2.00 times or less, mist is easily suppressed and the storage stability of the ink is easily improved. This is considered to be because the first surfactant is prevented from forming micelles by itself.

[0058] (Other resins) The ink may contain other resins (water-soluble resins) in addition to the resin dispersant suitable for dispersing the pigment as a particulate component and the resin particles as a particulate component. The other resins may be resins of any structure that can be used in water-based inks. Examples of such resins include acrylic resins, urethane resins, polyamide resins, polyester resins, polyvinyl alcohol resins, and polyolefin resins. One or more of these may be contained in the ink.

[0059] Among them, the ink preferably contains a urethane resin, and more preferably contains a urethane resin having units derived from polyisocyanate, polyol without an acid group, and polyol with an acid group. The urethane bond or urea bond in the urethane resin interacts with the hydroxide ions in the ink through hydrogen bonding, weakening the reactivity of the hydroxide ions, which is thought to make the compound represented by general formula (1) less likely to decompose, and thus improve storage stability. The urethane resin may be a water-soluble urethane resin that dissolves in the aqueous medium constituting the ink, or a water-dispersible urethane resin that disperses in the aqueous medium constituting the ink. Among these, a water-soluble urethane resin is preferred.

[0060] Polyisocyanates are compounds that have two or more isocyanate groups in their molecular structure. Examples of polyisocyanates include aliphatic polyisocyanates and aromatic polyisocyanates.

[0061] Examples of the aliphatic polyisocyanate include polyisocyanates having a chain structure such as tetramethylene diisocyanate, dodecamethylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2-methylpentane-1,5-diisocyanate, and 3-methylpentane-1,5-diisocyanate; and polyisocyanates having a cyclic structure such as isophorone diisocyanate, hydrogenated xylylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate, methylcyclohexylene diisocyanate, and 1,3-bis(isocyanatemethyl)cyclohexane.

[0062] Examples of aromatic polyisocyanates include tolylene diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-dibenzyl diisocyanate, 1,5-naphthylene diisocyanate, xylylene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, α,α,α',α'-tetramethylxylylene diisocyanate, etc. These polyisocyanates can be used alone or in combination of two or more.

[0063] Examples of the polyol that does not have an acid group include polyether polyol, polyester polyol, and polycarbonate polyol. One or more of the polyols that do not have an acid group can be used. The number average molecular weight of the polyol that does not have an acid group is preferably 400 or more and 4,000 or less. In addition, the polyol that does not have an acid group is preferably polyether polyol.

[0064] Examples of polyether polyols include polyalkylene glycols and addition polymers of alkylene oxides with dihydric alcohols or polyhydric alcohols having trihydric or higher hydricity. Examples of polyalkylene glycols include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and ethylene glycol-propylene glycol copolymers. Examples of alkylene oxides include ethylene oxide, propylene oxide, butylene oxide, and α-olefin oxide. Examples of dihydric alcohols include hexamethylene glycol, tetramethylene glycol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, 1,4-butanediol, 4,4-dihydroxyphenylpropane, and 4,4-dihydroxyphenylmethane. Examples of polyhydric alcohols having trihydric or higher hydricity include glycerin, trimethylolpropane, 1,2,5-hexanetriol, 1,2,6-hexanetriol, and pentaerythritol.

[0065] Examples of the polyol having an acid group include polyols having an acid group such as a carboxylic acid group, a sulfonic acid group, a phosphoric acid group, and a phosphonic acid group. The acid group is preferably a carboxylic acid group. Examples of the polyol having a carboxylic acid group include dimethylol acetic acid, dimethylol propionic acid, and dimethylol butanoic acid. The acid group of the polyol having an acid group may be in the form of a salt. Examples of the cation forming the salt include ions of alkali metals such as lithium, sodium, and potassium; ammonium ions, and cations of organic amines such as dimethylamine. One or more types of polyols having an acid group can be used.

[0066] Furthermore, it is more preferable that the ratio of the units derived from the polyol having an acid group at the molecular end to the total units derived from the polyol having an acid group in the urethane resin is 30.0 mol % or less. The acid groups at the terminals are more likely to approach the compound represented by general formula (1) than the acid groups in the main chain of the urethane resin. Therefore, it is considered that by reducing the ratio of the units derived from the polyol having an acid group at the molecular end to 30.0 mol % or less, it is easier to suppress the decomposition of the compound represented by general formula (1) due to the acid groups. This makes it easier to further improve the storage stability of the ink. It is preferable that the ratio is 0.0 mol % or more.

[0067] The ratio of units derived from polyol having an acid group present at the molecular end to the total units derived from polyol having an acid group in the urethane resin can be verified by the method shown below. The urethane resin to be verified can be a urethane resin prepared for the preparation of the ink or a urethane resin appropriately extracted from the ink. First, the urethane resin is analyzed by pyrolysis gas chromatography to identify the types of polyisocyanate, polyol without an acid group, and polyol with an acid group. Next, the reaction product of the identified polyisocyanate and polyol with an acid group is dissolved in deuterated dimethyl sulfoxide (deuterated DMSO) and analyzed by carbon nuclear magnetic resonance spectroscopy ( 13 The compound is analyzed by C-NMR. This confirms the chemical shift of the carbonyl carbon (lower magnetic field side) in the unit derived from the polyol having an acid group at the molecular end. In addition, the chemical shift of the carbonyl carbon (higher magnetic field side) in the unit derived from the polyol having an acid group inside the molecule is confirmed.

[0068] Next, the ratio of the peak integrated value of the carbonyl carbon in the unit derived from the polyol having an acid group present at the molecular end to the total of the peak integrated values ​​of the carbonyl carbon in the unit derived from the polyol having an acid group is calculated. This makes it possible to obtain the ratio of the unit derived from the polyol having an acid group present at the molecular end to the total units derived from the polyol having an acid group in the urethane resin. For example, when dimethylolpropionic acid (DMPA) is used, the peak of the carbonyl carbon in the unit derived from the polyol having an acid group present at the molecular end is detected at about 176 ppm, although there is some deviation depending on the measurement conditions. In addition, the peak of the carbonyl carbon in the unit derived from the polyol having an acid group present inside the molecule is detected at about 175 ppm. Furthermore, when dimethylolbutanoic acid (DMBA) is used, the peak of the carbonyl carbon in the unit derived from the polyol having an acid group present at the molecular end is detected at about 175 ppm. And the peak of the carbonyl carbon in the unit derived from the polyol having an acid group present inside the molecule is detected at about 174 ppm. In addition, 13 By analyzing by C-NMR, the number of repeating units derived from the polyol can be determined, and the number average molecular weight of the polyol can be calculated.

[0069] In order to impart a crosslinked structure to the urethane resin, a chain extender having two or more functionalities can be used. Examples of the chain extender include trimethylolmelamine and its derivatives, dimethylolurea and its derivatives, dimethylolethylamine, diethanolmethylamine, dipropanolethylamine, dibutanolmethylamine, ethylenediamine, propylenediamine, diethylenetriamine, hexylenediamine, triethylenetetramine, tetraethylenepentamine, isophoronediamine, xylylenediamine, diphenylmethanediamine, hydrogenated diphenylmethanediamine, hydrazine, polyamidepolyamine, polyethylenepolyimine, trimethylolmelamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine. These chain extenders can be used alone or in combination of two or more.

[0070] The content (mass %) of other resins in the ink is preferably 0.10% by mass or more and 5.00% by mass or less, and more preferably 0.50% by mass or more and 5.00% by mass or less, based on the total mass of the ink. Of these, it is even more preferable that it is 1.00% by mass or more and 4.00% by mass or less. Of these, the content (mass %) of water-soluble urethane resins in the ink is preferably 0.40% by mass or more and 3.50% by mass or less, and more preferably 0.50% by mass or more and 3.00% by mass or less, based on the total mass of the ink.

[0071] (aqueous medium) The ink is an aqueous ink containing at least water as an aqueous medium. As the water, deionized water (ion-exchanged water) is preferably used. The content (mass%) of water in the ink is preferably 10.00% by mass or more and 90.00% by mass or less, and more preferably 50.00% by mass or more and 90.00% by mass or less, based on the total mass of the ink.

[0072] (Water-soluble organic solvent) The aqueous medium may further contain a water-soluble organic solvent. As the water-soluble organic solvent, monohydric alcohols, polyhydric alcohols, (poly)alkylene glycols, glycol ethers, nitrogen-containing polar solvents, sulfur-containing polar solvents, etc. can be used. One or more water-soluble organic solvents can be used.

[0073] Among the water-soluble organic solvents, it is preferable to use a first water-soluble organic solvent that is an alkanediol having a dielectric constant of 28.0 or less and a hydroxyl group at both ends of the hydrocarbon chain, and a second water-soluble organic solvent having a dielectric constant of 40.0 or more. By using an ink that further contains the above-mentioned first water-soluble organic solvent and second water-soluble organic solvent, it is easier to suppress the generation of mist. The reason for this is presumed to be as follows. It is presumed that a water-soluble organic solvent with a low dielectric constant is likely to interact with the polysiloxane portion of the first surfactant, and a water-soluble organic solvent with a high dielectric constant is likely to interact with the polyethylene oxide portion of the first surfactant, respectively, weakening the interaction between each portion. In addition, a first water-soluble organic solvent with hydrophilic groups at both ends of the alkyl chain is unlikely to cause steric hindrance with the first surfactant and is likely to come close to each other, so that the hydrophobic portion of the main chain is likely to interact with the polysiloxane portion. Therefore, the molecules of the first surfactant are less likely to gather together, and mixed micelles of the first surfactant and the second surfactant are more likely to be smoothly formed. As a result, it is thought that the mist suppression effect is enhanced.

[0074] As the first water-soluble organic solvent, for example, 1,5-pentanediol (27.0), 3-methyl-1,5-pentanediol (23.9), and 1,6-hexanediol (7.1) can be used, with the relative dielectric constant at 25°C shown in parentheses. One or more of the first water-soluble organic solvents can be used. The relative dielectric constant of the first water-soluble organic solvent is preferably 3.0 or more. As the second water-soluble organic solvent, for example, glycerin (42.3) and ethylene glycol (40.4) can be used, with the relative dielectric constant at 25°C shown in parentheses. One or more of the second water-soluble organic solvents can be used. The relative dielectric constant of the second water-soluble organic solvent is preferably 120.0 or less.

[0075] The relative dielectric constant of a water-soluble organic solvent can be measured using a dielectric constant meter (for example, trade name "BI-870" manufactured by BROOKHAVEN INSTRUMENTS CORPORATION) at a frequency of 10 kHz. The relative dielectric constant of a water-soluble organic solvent that is solid at 25°C is determined by measuring the relative dielectric constant of a 50% by mass aqueous solution and calculating the value from the following formula (I). Usually, the term "water-soluble organic solvent" refers to a liquid, but in the present invention, water-soluble organic solvents that are solid at 25°C (room temperature) are also included. ε sol =2 ε50% -ε water (I) ε sol : Dielectric constant of solid water-soluble organic solvent at 25℃ ε 50% : Relative dielectric constant of a 50% by mass aqueous solution of a solid water-soluble organic solvent at 25°C ε water : relative dielectric constant of water

[0076] Examples of water-soluble organic solvents that are generally used in aqueous inks and are solid at 25°C include 1,6-hexanediol, trimethylolpropane, ethylene urea, urea, and polyethylene glycol with a number-average molecular weight of 1,000. The reason for determining the relative dielectric constant of a water-soluble organic solvent that is solid at 25°C from the relative dielectric constant of a 50% by mass aqueous solution is as follows. Among water-soluble organic solvents that are solid at 25°C and can be used as components of aqueous inks, it is difficult to prepare a high-concentration aqueous solution of more than 50% by mass. On the other hand, in a low-concentration aqueous solution of 10% by mass or less, the relative dielectric constant of water becomes dominant, and it is not possible to obtain a reliable (effective) relative dielectric constant value of the water-soluble organic solvent. As a result of the inventors' investigation, it was found that the aqueous solution to be measured can be prepared from almost all of the water-soluble organic solvents that are solid at 25°C and can be used in inks, and the relative dielectric constant to be determined is consistent with the effect of the present invention. For these reasons, it was decided to use a 50% by mass aqueous solution. For water-soluble organic solvents that are solid at 25°C and cannot be prepared as a 50% aqueous solution due to their low solubility in water, use an aqueous solution of the saturated concentration and use the above ε sol For convenience, the value of the relative dielectric constant calculated in accordance with the case of determining

[0077] The content (mass%) of the water-soluble organic solvent in the ink is preferably 50.00% by mass or less, and more preferably 3.00% by mass or more and 30.00% by mass or less, based on the total mass of the ink. The content (mass%) of the first water-soluble organic solvent in the ink is more preferably 1.00% by mass or more and 10.00% by mass or less, based on the total mass of the ink. The content (mass%) of the second water-soluble organic solvent in the ink is more preferably 2.00% by mass or more and 25.00% by mass or less, based on the total mass of the ink.

[0078] (Other additives) In addition to the components described above, the ink may contain various additives, such as surfactants, pH adjusters, rust inhibitors, preservatives, antifungal agents, antioxidants, reduction inhibitors, evaporation promoters, and chelating agents, as necessary.

[0079] (Compound represented by general formula (3)) The ink preferably contains a compound represented by the following general formula (3).

[0080] TIFF2024023137000006.tif28170 (In general formula (3), o represents an integer of 1 or more and 10 or less.)

[0081] It is presumed that the compound represented by general formula (3) easily interacts with the polysiloxane moiety of the compound represented by general formula (1), and alleviates the decomposition of the polysiloxane moiety by hydroxide ions in the ink. Therefore, it is considered that the storage stability of the ink is further improved. In particular, it is preferable that o in general formula (3) is 1 or more, since the storage stability of the ink is further improved. On the other hand, it is preferable that o in general formula (3) is 10 or less, since the effect of suppressing mist can be sufficiently obtained. In addition, it is more preferable that the content (mass%) of the compound represented by general formula (3) is 0.01 times or less in terms of the mass ratio to the content (mass%) of the first surfactant, since the effect of suppressing mist can be sufficiently obtained. The above mass ratio is preferably 0.0005 times or more.

[0082] The content (mass %) of the compound represented by general formula (3) in the ink is preferably 0.040% by mass or less based on the total mass of the ink, more preferably 0.0001% by mass or more and 0.020% by mass or less, and even more preferably 0.0001% by mass or more and 0.010% by mass or less.

[0083] (Ink properties) The viscosity of the ink at 25°C is preferably from 1.0 mPa·s to 10.0 mPa·s, more preferably from 1.0 mPa·s to 5.0 mPa·s, and particularly preferably from 1.0 mPa·s to 3.0 mPa·s. The surface tension (static surface tension) of the ink at 25°C is preferably from 10.0 mN / m to 60.0 mN / m, more preferably from 20.0 mN / m to 60.0 mN / m, and particularly preferably from 30.0 mN / m to 50.0 mN / m. The pH of the ink at 25°C is preferably from 5.0 to 10.0, and more preferably from 7.0 to 9.5.

[0084] <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.

[0085] <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. The ink is ejected 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 known. In the present invention, it is sufficient to carry out a step of applying the ink to a recording medium, and it is not necessary to carry out other treatments (such as a step of applying a reaction liquid that reacts with the ink, a step of curing the image by irradiation with active energy rays, or a step of heating the image).

[0086] 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).

[0087] Any recording medium may be used as the target for recording using the ink of the present invention, but it is preferable to use a recording medium having ink permeability, such as plain paper or a recording medium having a coating layer (glossy paper or art paper). In particular, it is preferable to use a recording medium having a coating layer that allows at least a part of the pigment particles in the ink to be present on the surface of the recording medium or in its vicinity. Such a recording medium can be selected depending on the purpose of use of the recorded matter on which the image is recorded. For example, glossy paper suitable for obtaining an image having a glossy feel of photographic quality, and art paper that makes use of the texture of the base material (drawing paper, canvas, Japanese paper, etc.) to express paintings, photographs, and graphic images according to preference, etc., can be mentioned. Among them, it is particularly preferable to use so-called glossy paper, in which the surface of the coating layer has glossiness. EXAMPLES

[0088] 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.

[0089] <Resin analysis conditions> The acid value of the resin was measured by dissolving the resin in tetrahydrofuran and using a 0.5 mol / L ethanol solution of potassium hydroxide as a titration reagent with an automatic potentiometric titrator (product name "AT510", manufactured by Kyoto Electronics Co., Ltd.). The weight average molecular weight (Mw) and number average molecular weight (Mn) of the resin were measured by gel permeation chromatography (product name "Alliance GPC 2695", manufactured by Waters) equipped with a differential refractive index detector, using polystyrene as a standard substance and tetrahydrofuran as a solvent.

[0090] <Preparation of water-soluble resin> (Acrylic Resin 1) By a conventional method, 80.7 parts of styrene and 19.3 parts of acrylic acid were copolymerized to synthesize acrylic resin 1, which is a water-soluble resin having an acid value of 150 mgKOH / g and a weight average molecular weight of 8,000. The obtained acrylic resin 1 was dissolved in ion-exchanged water by adding potassium hydroxide in an amount equimolar to the acid value, to prepare an aqueous solution of acrylic resin 1 with an acrylic resin 1 content of 20.0%.

[0091] (Acrylic Resin 2) By a conventional method, 80.7 parts of styrene and 19.3 parts of acrylic acid were copolymerized to synthesize acrylic resin 2, which is a water-soluble resin having an acid value of 150 mgKOH / g and a number average molecular weight of 1,600. The obtained acrylic resin 2 was dissolved in ion-exchanged water by adding potassium hydroxide in an amount equimolar to the acid value, to prepare an aqueous solution of acrylic resin 2 with an acrylic resin 2 content of 20.0%.

[0092] <Preparation of pigment dispersion> (Pigment dispersion 1) A mixture of 15.0 parts of carbon black (pigment), 30.0 parts of an aqueous solution of acrylic resin 1, and 55.0 parts of water was placed in a sand grinder and subjected to a dispersion treatment for 1 hour. After that, a centrifugal separation treatment was performed to remove coarse particles, and pressure filtration was performed using a microfilter (manufactured by Fujifilm) with a pore size of 3.0 μm, and an appropriate amount of ion-exchanged water was added to obtain pigment dispersion 1. The pigment content in pigment dispersion 1 was 10.0%, and the resin content was 3.0%.

[0093] (Pigment dispersion 2) Pigment dispersion 2 was obtained in the same manner as in the preparation of pigment dispersion 1, except that the type of pigment was changed to CI Pigment Blue 15:3. The pigment content in pigment dispersion 2 was 10.0%, and the resin content was 3.0%.

[0094] (Pigment dispersion 3) Pigment dispersion 3 was obtained in the same manner as in the preparation of pigment dispersion 1, except that the type of pigment was changed to CI Pigment Red 122. The pigment content in pigment dispersion 3 was 10.0%, and the resin content was 3.0%.

[0095] (Pigment Dispersion 4) Pigment dispersion 4 was obtained in the same manner as in the preparation of pigment dispersion 1, except that the type of pigment was changed to CI Pigment Yellow 74. The pigment content in pigment dispersion 4 was 10.0%, and the resin content was 3.0%.

[0096] (Pigment Dispersion 5) A solution obtained by dissolving 2.5 g of concentrated hydrochloric acid in 5.5 g of water was cooled to 5°C, and 0.7 g of 4-aminophthalic acid was added in this state. The container containing this solution was placed in an ice bath, and while stirring to maintain the temperature of the solution at 10°C or less, 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 220 m 2 10.0 g of 1,2-dichlorophenyl ether (100% CO2 / g, DBP oil absorption 105 mL / 100 g) was added under stirring and stirred for another 15 minutes to obtain a slurry. The obtained slurry was filtered through filter paper (product name "Standard Filter Paper No. 2", Advantec), the particles were thoroughly washed with water, and dried in an oven at 110°C. The sodium ions were then replaced with potassium ions by ion exchange to obtain a self-dispersing pigment in which -C6H3-(COOK)2 groups were bonded to the particle surfaces of the carbon black. An appropriate amount of water was added to adjust the pigment content, and pigment dispersion 5 with a pigment content of 10.0% was obtained.

[0097] <Synthesis of resin particles> (Resin particles 1-5) 2.0 parts of n-hexadecane, 1.0 part of polymerization initiator (2,2'-azobis-(2-methylbutyronitrile)), and the core monomer (unit: part) shown in Table 1 were mixed and stirred for 30 minutes to obtain a mixture. The abbreviations of the monomers are nBA: n-butyl acrylate, St: styrene, and AA: acrylic acid. The obtained mixture was dropped into 229.5 parts of water in which 0.27 parts of sodium dodecyl sulfate was dissolved, and then stirred for 30 minutes to obtain a core monomer mixture. Then, using an ultrasonic homogenizer (trade name "S-150D Digital Sonifier", manufactured by Branson), ultrasonic waves were irradiated to the core monomer mixture under the conditions of output: 400 W, frequency: 20 kHz, and 3 hours to disperse the components. Then, the mixture was polymerized at 80°C for 4 hours under a nitrogen atmosphere to synthesize a resin, and a dispersion containing an acrylic resin that becomes the core of the resin particles was obtained.

[0098] Next, 200.0 parts of ion-exchanged water, 0.1 parts of potassium persulfate, 8.0 parts of sodium dodecyl sulfate, and the monomers of the shell part shown in Table 1 (unit: parts) were emulsified to obtain an emulsion of the monomers for the shell part. The abbreviations of the monomers are MMA: methyl methacrylate, nBA: n-butyl acrylate, St: styrene, AA: acrylic acid, and StSA: styrene sulfonic acid. 0.1 parts of potassium persulfate and 600.0 parts of ion-exchanged water were added to 240.0 parts of the dispersion containing the resin that will become the core part obtained above, and the temperature was raised to 75°C under a nitrogen atmosphere. 350.0 parts of the emulsion of the monomers for the shell part were dropped into this dispersion over 3 hours. Thereafter, the temperature was raised to 85°C, and the mixture was stirred for 2 hours to polymerize, and an acrylic resin that will become the shell part of the resin particles was synthesized. After that, the mixture was cooled to 25°C, and an appropriate amount of ion-exchanged water and potassium hydroxide in an amount equimolar to the acid value were added to obtain a liquid containing each resin particle, with a pH of 8.5 and a resin content of 10.0%. Resin particles 1 to 5 were all resin particles composed of a core and a shell.

[0099] TIFF2024023137000007.tif47170

[0100] (Resin particles 6) In a 300mL four-neck flask equipped with a stirring seal, a stirrer, a reflux condenser, a septum rubber, and a nitrogen inlet tube, 9.0 parts of styrene, 1.5 parts of acrylic acid, 0.1 parts of sodium dodecyl sulfate, and 100.0 parts of distilled water were placed and mixed. The flask was placed in a thermostatic bath at 70°C, and nitrogen gas was introduced into the flask while stirring the contents at 300 rpm, and nitrogen replacement was performed for 1 hour. Thereafter, polymerization was started by injecting potassium persulfate dissolved in 100.0 parts of distilled water into the flask using a syringe. The end of polymerization was confirmed by monitoring the molecular weight by gel permeation chromatography. After purification by ultrafiltration, an appropriate amount of ion-exchanged water and potassium hydroxide equimolar to the acid value were added to obtain a liquid containing resin particles 6 with a pH of 8.5 and a resin content of 10.0%. Resin particles 6 were single-layer resin particles composed of acrylic resin.

[0101] (Resin particles 7) Acrylic-silicone polymer microparticles were synthesized as resin particles 7 in accordance with the description of Preparation Example 10 of JP2017-019990A, and a liquid having a resin particle 7 content of 40.0% was obtained.

[0102] <Synthesis of urethane resin> A four-neck flask equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, and a reflux tube was prepared. Into this four-neck flask, polyisocyanate, polyol having no acid group, a part of dimethylolpropionic acid (amount used a), and 200.0 parts of methyl ethyl ketone, the types and amounts of which are shown in Table 2, were placed. Then, the mixture was reacted at 80°C for 6 hours under a nitrogen gas atmosphere. Next, a part of dimethylolpropionic acid (amount used b), ethylenediamine (chain extender), methanol (terminator), and 100.0 parts of methyl ethyl ketone, the types and amounts of which are shown in Table 2, were added. The residual rate of isocyanate groups was confirmed by FT-IR, and the reaction was continued at 80°C until the desired residual rate was reached, to obtain a reaction liquid. The obtained reaction liquid was cooled to 40°C, and then ion-exchanged water was added. While stirring at high speed with a homomixer, an appropriate amount of ion-exchanged water and potassium hydroxide in an amount equimolar to the acid value were added to obtain a liquid. Methyl ethyl ketone was distilled off from the obtained liquid by heating under reduced pressure, and liquids containing water-soluble urethane resins 1 to 7 with a urethane resin content of 20.0% were obtained. All of the obtained urethane resins 1 to 7 were water-soluble. The abbreviations in Table 2 are IPDI: isophorone diisocyanate, HDI: hexamethylene diisocyanate, MDI: diphenylmethane diisocyanate, PPG: polypropylene glycol with a number average molecular weight of 2,000, and PTMG: polytetramethylene glycol with a number average molecular weight of 2,000.

[0103] Hydrochloric acid was added to the liquid containing the urethane resin to precipitate the urethane resin. The dried resin was dissolved in deuterated DMSO to prepare a measurement sample. 13The prepared sample was analyzed by C-NMR (apparatus name "Avance500", manufactured by BRUKER Bio Spin). The ratio of the peak integrated value of the carbonyl carbon in the unit derived from the polyol having an acid group at the molecular end to the total peak integrated value of the carbonyl carbon in the unit derived from the polyol having an acid group was calculated. The value (ratio) calculated in this way was taken as the "ratio of the unit derived from the polyol having an acid group at the molecular end". For example, when dimethylolpropionic acid is used, the peak of the carbonyl carbon in the unit derived from the polyol having an acid group at the molecular end is detected at about 176 ppm, although there is some deviation depending on the measurement conditions. In addition, the peak of the carbonyl carbon in the unit derived from the polyol having an acid group inside the molecule is detected at about 175 ppm. The results are shown in Table 2 as "Ratio of terminal acid groups (mol%)".

[0104] TIFF2024023137000008.tif77170

[0105] <Preparation of surfactant> (Surfactants S1 to S5, S8 to S16) A polysiloxane compound and a polyoxyethylene compound were placed in a glass vessel equipped with a thermometer and a stirring means, and an addition reaction was carried out in the presence of a platinum catalyst to synthesize surfactants S1 to S5 and S8 to S16. The polysiloxane compound used was a compound represented by the following general formula (A-1), and in which m and n in general formula (A-1) are the numbers shown in Table 3. The polyoxyethylene compound used was a compound represented by the following general formula (B-1), and in which a, R1 and R2 in general formula (B-1) are the structures shown in Table 3. Each surfactant obtained by the above synthesis is a compound represented by the following general formula (1-1), and in which R3 in general formula (1-1) is the structure shown in Table 3. m, n, a, and R2 in general formula (1-1) correspond to m, n, a, and R2 in general formulas (A-1) and (B-1) that represent the structures of the compounds used in the synthesis, respectively. Table 3 also shows the weight average molecular weights of the synthesized surfactants.

[0106] TIFF2024023137000009.tif27170

[0107] TIFF2024023137000010.tif18170

[0108] TIFF2024023137000011.tif31170

[0109] TIFF2024023137000012.tif102170

[0110] (Surfactant S6) A polysiloxane compound represented by the following general formula (C) and a polyoxyethylene compound represented by the following general formula (D) were placed in a glass vessel equipped with a thermometer and a stirring means, and an addition reaction was carried out in the presence of a platinum catalyst to synthesize surfactant S6. Surfactant S6 has the structure of a silicone-based compound modified at both ends represented by general formula (4). d, p, R6, and R5 in general formula (4) correspond to d, p, R4, and R5 in general formulas (C) and (D) that represent the structures of the compounds used in the synthesis, respectively, where d=10, p=5, R6 is a propylene group, and R5 is a methyl group.

[0111] TIFF2024023137000013.tif31170

[0112] TIFF2024023137000014.tif20170

[0113] TIFF2024023137000015.tif33170

[0114] (Surfactant S7) A polysiloxane compound represented by the following general formula (E) and a polyoxyethylene compound represented by the following general formula (F) were placed in a glass vessel equipped with a thermometer and a stirring means, and an addition reaction was carried out in the presence of a platinum catalyst to synthesize surfactant S7. Surfactant S7 has an ABn-type silicone compound structure represented by general formula (5). e, q, R7, and R9 in general formula (5) correspond to e, q, R7, and R8 in general formulas (E) and (F) that represent the structures of the compounds used in the synthesis, respectively, with e=10, q=5, r=2, R7 being a methyl group, and R9 being a propylene group.

[0115] TIFF2024023137000016.tif30170

[0116] TIFF2024023137000017.tif23170

[0117] TIFF2024023137000018.tif31170

[0118] (Surfactant F1) A fluorochemical surfactant, trade name "Megafac F-410" (manufactured by DIC), was prepared and designated as surfactant F1.

[0119] (Surfactants C1-C7) Surfactants C1 to C6, which are acetylene glycol compounds, and surfactant C7, which is a polyoxyethylene alkyl ether, were prepared. Surfactants C1 to C3 and C5 are acetylene glycol compounds represented by the general formula (2). Surfactant C1: Trade name "Acetylenol E60" (b+c=6 in general formula (2), manufactured by Kawaken Fine Chemicals) Surfactant C2: Trade name "Acetylenol E40" (b+c=4 in general formula (2), manufactured by Kawaken Fine Chemicals) Surfactant C3: Trade name "Acetylenol E100" (b+c=10 in general formula (2), manufactured by Kawaken Fine Chemicals) Surfactant C4: Trade name "Surfynol 104" (b=c=0 in general formula (2), manufactured by Nissin Chemical Industry Co., Ltd.) Surfactant C5: Trade name "Olfine E1010" (b+c=10 in general formula (2), manufactured by Nissin Chemical Industry Co., Ltd.) Surfactant C6: Ethoxylated 2,4,7,9-tetramethyl-5-decyne-4,7-diol (b+c=50 in formula (2)) Surfactant C7: Polyoxyethylene cetyl ether (product name "NIKKOL BC-20", manufactured by Nikko Chemicals)

[0120] <Preparation of compounds> Siloxane compounds were synthesized by a conventional method to obtain compounds 1 to 6 represented by the above general formula (3) where o in general formula (3) is a number shown in Table 4 below.

[0121] TIFF2024023137000019.tif47170

[0122] <Ink Preparation> (Ink 1-67) Each component (unit: %) shown in the middle of Table 5 (Tables 5-1 to 5-9) was mixed and thoroughly stirred, and then pressure filtered through a microfilter (manufactured by Fujifilm) with a pore size of 3.0 μm to prepare each ink. The "pigment dispersion liquid," "liquid containing resin particles," "aqueous solution of urethane resin," "surfactant S," "surfactant C," and "compound" shown in the middle of Table 5 were those with the numbers shown in the upper part of Table 5. However, "-" in the upper part of Table 5 indicates that they were not used. The numbers in parentheses shown for the water-soluble organic solvents in the middle of Table 5 are the relative dielectric constants at 25°C. The amount of ion-exchanged water used was the remaining amount so that the total of the components was 100.00%. The lower part of Table 5 shows the properties of the ink, including the pigment content P (%), resin particle content R (%), and particulate component content C (%). Similarly, the content S (%) of the first surfactant (surfactants S1 to S5, S15, S16), the content A (%) of the second surfactant (surfactants C1 to C6), and the content T (%) of the surfactant (surfactants S1 to S16, F1, C1 to C7) are shown. Similarly, the content D (%) of the compound represented by general formula (3) (compounds 1, 3, 4, 6), the value of S / A (times), the value of C / T (times), and the value of D / S (times) are shown.

[0123] TIFF2024023137000020.tif203170

[0124] TIFF2024023137000021.tif205170

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[0130] TIFF2024023137000027.tif209170

[0131] TIFF2024023137000028.tif202170

[0132] (Ink 68) The components shown below were mixed and thoroughly stirred, and then pressure filtered through a microfilter (manufactured by Fujifilm) with a pore size of 3.0 μm to prepare Ink 68, which is an ink that does not contain a second surfactant. Pigment dispersion 1: 15.00% Acrylic resin 2 aqueous solution: 32.00% Dipropylene glycol: 3.00% 1,2-Hexanediol: 0.50% 1,2-Octanediol: 1.00% Surfactant S1: 0.10% Ion-exchanged water: 48.40%

[0133] (Ink 69) The components shown below were mixed and thoroughly stirred, and then pressure filtered through a microfilter (manufactured by Fujifilm) with a pore size of 3.0 μm to prepare Ink 69, which does not contain a second surfactant. Pigment dispersion 1: 15.00% Liquid containing resin particles 7: 8.75% 3-Ethyl-3-hydroxymethyloxetane: 30.00% Propylene glycol monomethyl ether: 10.00% 2-Ethyl-1,3-hexanediol: 2.00% 2,4,7,9-Tetramethyldecane-4,7-diol: 0.50% 2-Amino-2-ethyl-1,3-propanediol: 0.20% Surfactant S15: 2.00% Ion-exchanged water: 31.55%

[0134] (Ink 70) The components shown below were mixed and thoroughly stirred, and then pressure filtered through a microfilter (manufactured by Fujifilm) with a pore size of 3.0 μm to prepare Ink 70, which is an ink that does not contain the first surfactant. Pigment dispersion 1: 15.00% Glycerin: 10.00% Ethylene glycol: 20.00% Triethylene glycol monobutyl ether: 15.00% Surfactant C5: 0.60% Ion-exchanged water: 39.40%

[0135] (Ink 71) The components shown below were mixed and thoroughly stirred, and then pressure filtered through a microfilter (manufactured by Fujifilm) with a pore size of 3.0 μm to prepare Ink 71, an ink that does not contain a second surfactant. KF-353A is a side-chain type silicone oil (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.). Pigment dispersion 1: 15.00% Glycerin: 20.00% 1,2-Hexanediol: 10.00% Triethanolamine: 0.90% KF-353A: 0.10% Ion-exchanged water: 54.00%

[0136] (Ink 72) The components shown below were mixed and thoroughly stirred, and then pressure filtered through a microfilter (manufactured by Fujifilm) with a pore size of 3.0 μm to prepare Ink 72, an ink that does not contain particulate components. Cibafix Direct Black 19 (made by Ciba-Geigy Japan): 5.00% Glycerin: 15.00% Propylene glycol: 0.05% Polyethylene glycol (number average molecular weight 200): 10.00% Surfactant S16: 0.40% Surfactant C6: 0.50% ·Compound 6:0.0025% Ion-exchanged water: 69.0475%

[0137] <Evaluation> The inks thus prepared were used to carry out the following evaluations. The evaluation results are shown in Table 6.

[0138] (Storage stability) The surface tension (static surface tension) of the ink obtained above was measured. The surface tension of the ink was measured at 25°C using a Wilhelmy type surface tensiometer (product name "Automatic Surface Tensiometer CBVP-Z", manufactured by Kyowa Interface Science). Each ink was placed in an airtight container and stored in an oven at 70°C for one week. The surface tension of the ink before storage was subtracted from the surface tension of the ink after storage to calculate the storage stability of the ink according to the evaluation criteria shown below. A: The difference in surface tension was 1.0 mN / m or less. B: The difference in surface tension was greater than 1.0 mN / m and less than 2.0 mN / m. C: The difference in surface tension exceeded 2.0 mN / m.

[0139] (Mist suppression) Each of the prepared inks was filled into an ink cartridge, and the ink cartridge was set in an inkjet recording device (product name "TM-300", manufactured by Canon; indicated as "thermal" in the ejection method section in Table 6) that ejects ink from a recording head by the action of thermal energy. In this embodiment, the recording duty of a solid image recorded under the condition that four ink droplets with a mass of 4.0 ng ± 5% per droplet are applied to a unit area of ​​1 / 600 inch × 1 / 600 inch is defined as 100%. In Reference Examples 1 and 2, an inkjet recording device (product name "SC-T5255", manufactured by Seiko Epson; indicated as "piezo" in the ejection method section in Table 6) that ejects ink from a recording head using a piezoelectric element was used. Using the above inkjet recording device, a 36" x 48" solid image was recorded on thick coated paper (product name "Thick Coated Paper HG", manufactured by Canon) with a recording duty of 30%, and the mist suppression effect was evaluated according to the following evaluation criteria. If continuous recording is continued while mist is generated, a sensor inside the device detects an error and recording is stopped. For this reason, the greater the number of records that can be recorded normally, the greater the effect of suppressing mist generation. AA: Recording was performed normally even with over 50,000 recorded images. A: Recording stopped when the number of recorded images was between 40,000 and 50,000. B: Recording stopped when the number of recorded images was between 30,000 and 40,000. C: Recording stopped when the number of recorded images was less than 30,000.

[0140] TIFF2024023137000029.tif218170

[0141] The disclosure of this embodiment includes the following configurations and methods. (Configuration 1) A water-based ink that is ejected from an ink-jet recording head by the action of thermal energy, the aqueous ink contains a particulate component, a first surfactant, and a second surfactant; the particulate component is at least one selected from the group consisting of pigments and resin particles, The first surfactant is a compound represented by the following general formula (1): The aqueous ink, wherein the second surfactant is an acetylene glycol compound.

[0142] TIFF2024023137000030.tif32170 (In the general formula (1), m and n each independently represent an integer of 1 or more and m+n is 10 or less, and a represents an integer of 10 or more and 20 or less.)

[0143] (Configuration 2) An aqueous ink according to Configuration 1, wherein the content (mass %) of the first surfactant in the aqueous ink is 0.05 to 3.00 times the content (mass %) of the second surfactant in the aqueous ink. (Configuration 3) An aqueous ink according to configuration 1, wherein the content (mass %) of the first surfactant in the aqueous ink is 0.05 to 2.00 times the content (mass %) of the second surfactant in the aqueous ink. (Configuration 4) The water-based ink contains a first water-soluble organic solvent having a relative dielectric constant of 28.0 or less and a second water-soluble organic solvent having a relative dielectric constant of 40.0 or more, 4. The aqueous ink according to any one of claims 1 to 3, wherein the first water-soluble organic solvent is an alkanediol having hydroxy groups at both ends of a hydrocarbon chain. (Configuration 5) The water-based ink further contains a compound represented by the following general formula (3): 5. The aqueous ink according to any one of claims 1 to 4, wherein the content (mass%) of the compound represented by general formula (3) in the aqueous ink is 0.01 times or less in mass ratio to the content (mass%) of the first surfactant.

[0144] TIFF2024023137000031.tif28170 (In the general formula (3), o represents an integer of 1 or more and 10 or less.)

[0145] (Configuration 6) The aqueous ink according to any one of Configurations 1 to 5, wherein the particulate component contains a pigment. (Structure 7) The aqueous ink according to any one of Structures 1 to 6, wherein the particulate component contains the resin particles, the resin particles are composed of a core formed only of units not having an acid group and a shell formed containing units having an acid group, and at least one of the units forming the core and the units forming the shell contains a unit derived from a (meth)acrylic acid ester. (Configuration 8) The water-based ink further contains a urethane resin, 8. The aqueous ink according to any one of claims 1 to 7, wherein the urethane resin has units derived from a polyisocyanate, a polyol having no acid group, and a polyol having an acid group. (Configuration 9) The aqueous ink according to Configuration 8, wherein the proportion of units derived from the polyol having an acid group present at a molecular terminal in the urethane resin is 30.0 mol % or less of all units derived from the polyol having an acid group. (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 in which ink is ejected from an inkjet recording head by the action of thermal energy to record an image on a recording medium, 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 ink ejected from an inkjet recording head by the action of thermal energy, The aqueous ink contains particulate components, a first surfactant, and a second surfactant. The particulate component is at least one selected from the group consisting of pigments and resin particles. The first surfactant is a compound represented by the following general formula (1), An aqueous ink characterized in that the second surfactant is an acetylene glycol compound. (In the general formula (1) above, m and n each represent an integer that is 1 or greater and that satisfies the condition m + n is 10 or less, and a represents an integer between 10 and 20.)

2. The aqueous ink according to claim 1, wherein m in the general formula (1) is an integer between 1 and 8.

3. The aqueous ink according to claim 1, wherein n in the general formula (1) is 1 or 2.

4. The aqueous ink according to claim 1, wherein m in the general formula (1) is an integer between 1 and 8, and n is 1 or 2.

5. The aqueous ink according to claim 1, wherein the second surfactant is a compound represented by the following general formula (2). (In the general formula (2) above, b and c each represent independent positive integers.)

6. The aqueous ink according to claim 1, wherein the content (mass%) of the first surfactant in the aqueous ink is 0.05% by mass or more and 4.00% by mass or less, based on the total mass of the ink.

7. The aqueous ink according to claim 1, wherein the content (mass%) of the second surfactant in the aqueous ink is 0.10% by mass or more and 3.00% by mass or less, based on the total mass of the ink.

8. The aqueous ink according to claim 1, wherein the content (mass%) of the first surfactant in the aqueous ink is 0.05 times or more and 3.00 times or less by mass ratio to the content (mass%) of the second surfactant.

9. The aqueous ink according to claim 1, wherein the content (mass%) of the first surfactant in the aqueous ink is 0.05 times or more and 2.00 times or less by mass ratio to the content (mass%) of the second surfactant.

10. The aqueous ink contains a first water-soluble organic solvent having a relative permittivity of 28.0 or less, and a second water-soluble organic solvent having a relative permittivity of 40.0 or more. The aqueous ink according to claim 1, wherein the first water-soluble organic solvent is an alkanediol having hydroxyl groups at both ends of a hydrocarbon chain.

11. The aqueous ink further contains a compound represented by the following general formula (3): The aqueous ink according to claim 1, wherein the content (mass%) of the compound represented by the general formula (3) in the aqueous ink is 0.01 times or less in mass ratio to the content (mass%) of the first surfactant. (In the general formula (3) above, o represents an integer between 1 and 10.)

12. The aqueous ink according to claim 1, wherein the particulate component comprises a pigment.

13. The aqueous ink according to claim 1, wherein the particulate component comprises resin particles, the resin particles are composed of a core formed only of units without acid groups and a shell formed of units having acid groups, and at least one of the units forming the core and the units forming the shell comprises a unit derived from a (meth)acrylic acid ester.

14. The aforementioned water-based ink further contains a urethane resin, The aqueous ink according to claim 1, wherein the urethane resin comprises units derived from polyisocyanate, polyol without acid groups, and polyol having acid groups, respectively.

15. The aqueous ink according to claim 14, wherein the proportion of units derived from the polyol having acid groups located at the molecular ends of the urethane resin to the total number of units derived from the polyol having acid groups is 30.0 mol% or less.

16. An ink cartridge comprising ink and an ink storage section for storing the ink, An ink cartridge characterized in that the ink is the water-based ink described in any one of claims 1 to 15.

17. An inkjet recording method that records an image on a recording medium by ejecting ink from an inkjet recording head using the action of thermal energy, An inkjet recording method characterized in that the ink is an aqueous ink according to any one of claims 1 to 15.

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