Aqueous inkjet ink and printed matter

Abstract

To provide an aqueous inkjet ink capable of producing a printed matter excellent in water resistance and scratch resistance and having high discharge stability at the same time. The aqueous inkjet ink contains water, diols, a binder resin, and a wax. The diols include a diol (A) having an SP value of from10.0 to less than 12.0 and containing a branched alkylene group, and a diol (B) having an SP value of from 12.0 to 15.0. The difference between the boiling point of the diol (A) at 1 atm and the boiling point of the diol (B) at 1 atm is 30°C or less.

Description

Water-based inkjet inks and printed materials

[0001] SUMMARY OF THE INVENTION An embodiment of the present invention relates to an aqueous inkjet ink and a printed matter produced using the aqueous inkjet ink.

[0002] Unlike plate-based printing methods such as gravure printing and offset printing, digital printing methods do not require plates, and therefore have advantages such as smaller printing equipment and reduced printing costs. Inkjet printing, one type of digital printing method, records characters and / or images by ejecting ink from the nozzles of an inkjet head and depositing it on a printing substrate. In addition to the characteristics of digital printing methods described above, inkjet printing methods also have other advantages such as low noise during printing, inexpensive printing equipment, and ease of colorization.

[0003] In this disclosure, a printing substrate on which characters and / or images are recorded is collectively referred to as a “printed matter.” The “image” also includes a solid image and a seamless image such as a checkerboard pattern image.

[0004] Inks used in inkjet printing methods (also referred to as "inkjet inks" in this disclosure) are classified into solvent-based, water-based, ultraviolet-curable, and other types depending on their composition. Meanwhile, in recent years, there has been an accelerating trend toward restricting the use of raw materials that are harmful to humans and the environment. Accordingly, there has been an increasing demand for water-based inkjet inks (also referred to simply as "water-based inkjet inks" in this disclosure) rather than solvent-based inkjet inks and ultraviolet-curable inkjet inks that use these raw materials.

[0005] In recent years, with the advancement of inkjet head performance, inkjet printing has been increasingly adopted for industrial applications. In particular, in the commercial printing and packaging (label and package) printing markets, the replacement of conventional plate-based printing with inkjet printing is being actively considered, as the advantages of inkjet printing described above can be effectively utilized and it is highly suitable for printing a wide variety of products in small lots.

[0006] In the packaging printing market, lamination, in which a transparent film (laminating film) is attached to a printed surface (the surface to which ink is applied), is commonly used to protect the printed surface from friction, water penetration, and the like. However, in recent years, there has been a trend toward eliminating laminating films from the perspective of resource conservation and environmental protection. In order to respond to this trend, it is necessary to impart various resistances (abrasion resistance, water resistance, solvent resistance, etc.) to printed materials so that printed characters and / or images are not damaged even without the laminating film.

[0007]

[0003] One method for improving various resistances of printed matter produced using aqueous inkjet inks is to promote film formation of the binder resin contained in the aqueous inkjet ink and increase the strength of the film itself. Patent Document 1 discloses an ink containing at least one of an amide compound and an oxetane compound having a specific structure and two or more types of resin particles. Patent Document 1 also describes that the presence of at least one of the amide compound and the oxetane compound results in a favorable mixing of the two or more types of resin particles during the process of drying the ink on the printing substrate, and that as a result, even printed matter on a non-permeable substrate has excellent abrasion resistance and solvent resistance.

[0008] Patent Document 2 discloses an inkjet recording ink containing two types of resin particles with different volume average particle diameters and heat distortion temperatures, one of which is a urethane resin. It also describes that the combined use of these resin particles can prevent nozzle clogging and smooth the printed surface. Furthermore, it also describes that the ink described in Patent Document 2 can contain wax particles as third resin particles, and that the wax particles can impart slip properties to the surface of the printed material and improve its abrasion resistance (see paragraphs 0054-0055).

[0009] JP 2016-169370 A JP 2013-144730 A

[0010] In the technology disclosed in Patent Document 1, the presence of a compound that has high affinity with resin particles and promotes the mixing of the resin particles increases the risk of ink adhesion near the nozzles of an inkjet head. The inventors have confirmed through their studies that the use of such a compound can impair ejection stability depending on the printing conditions. However, the examples in Patent Document 1 do not evaluate ejection stability, and it is difficult to say that the ejection stability has been adequately examined.

[0011] In the technology disclosed in Patent Document 2, depending on the properties of the raw materials used in combination with the wax particles, the wax may swell and / or aggregate in the ink, impairing ejection stability. Furthermore, the raw materials may inhibit the orientation of the wax on the printed surface, potentially preventing sufficient improvement in abrasion resistance. In fact, among the inks specifically disclosed in the examples of Patent Document 2, there are examples in which nozzle clogging, i.e., ejection stability, is poor, and abrasion resistance is poor, despite the inks containing wax particles. Furthermore, Patent Document 2 does not specifically describe a method for improving the water resistance of printed matter.

[0012] As described above, it can be said that sufficient research has not yet been conducted into obtaining an aqueous inkjet ink that can produce printed materials with excellent water resistance and abrasion resistance and that also has high ejection stability.

[0013] The embodiments of the present invention have been made to solve the above-mentioned problems, and one of the objects thereof is to provide an aqueous inkjet ink that can produce printed matter that is excellent in water resistance and abrasion resistance, and that also has high ejection stability.

[0014] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by an aqueous inkjet ink having the following composition.

[0015] That is, some embodiments of the present invention relate to aqueous inkjet inks as shown in [1] to [5] below, and a method for producing printed matter using the aqueous inkjet ink as shown in [6] below. [1] An aqueous inkjet ink containing water, diols, a binder resin, and a wax, wherein the diols include diols (A) having an SP value of 10.0 or more but less than 12.0 and containing a branched alkylene group, and diols (B) having an SP value of 12.0 or more and 15.0 or less, and wherein the difference between the boiling points of the diols (A) and the diols (B) at 1 atmosphere is 30°C or less. [2] The aqueous inkjet ink according to [1], wherein the wax includes a polyolefin wax having a melting point of 100°C or more and 170°C or less at 1 atmosphere. [3] The aqueous inkjet ink according to [2], wherein the value expressed by R / W is 15 or less, where W (g) is the content of the wax contained in 100 g of the aqueous inkjet ink and R (g) is the content of the binder resin contained in 100 g of the aqueous inkjet ink. [4] The aqueous inkjet ink according to [1] or [2], further comprising a glycol monoether (C) having a terminal alkyl group with 2 to 4 carbon atoms. [5] The aqueous inkjet ink according to [2], further comprising a glycol monoether (C) having a terminal alkyl group with 2 to 4 carbon atoms, wherein the value expressed by R / W is 15 or less, where W (g) is the content of the wax contained in 100 g of the aqueous inkjet ink and R (g) is the content of the binder resin contained in 100 g of the aqueous inkjet ink. [6] A printed matter obtained by printing the aqueous inkjet ink according to any one of [1] to [5] on a printing substrate.

[0016] The aqueous inkjet ink according to one embodiment of the present invention can produce printed matter that is excellent in abrasion resistance and water resistance, and at the same time, can have high ejection stability.

[0017]

[0033] An aqueous inkjet ink according to one embodiment of the present invention (hereinafter referred to as "the aqueous inkjet ink of this embodiment" or simply "the ink") will be described below. Note that the present invention is not limited to the embodiment described below, and includes modified embodiments that can be implemented without changing the essential parts of the present invention.

[0018] The aqueous inkjet ink of this embodiment having the above-described configuration can produce printed matter with excellent water resistance and abrasion resistance. Furthermore, the ejection properties do not deteriorate, even when printing is resumed after a long pause. While the mechanism behind this is unclear, the inventors speculate as follows. However, the present invention is not limited by this speculation.

[0019] As described above, adding a binder resin to ink is widely known as a means of improving the abrasion resistance and water resistance of printed matter. Furthermore, in order to impart good abrasion resistance and water resistance to printed matter, the binder resin must be sufficiently formed into a film. Therefore, in this embodiment, a diol (A) having an SP value of 10.0 or more and less than 12.0 and a branched alkylene group is used together with the binder resin. The diol (A) is water-soluble due to the presence of multiple hydroxyl groups, but its low SP value and the presence of the branched alkylene group ensure affinity with the resin component. As a result, after the water, the main component, evaporates from the ink droplets after printing, the binder resin is softened by the diol (A), thereby achieving efficient film formation and uniformity of the film, thereby improving the abrasion resistance and water resistance of the printed matter.

[0020] On the other hand, depending on the properties of the binder resin (e.g., glass transition temperature and mass average molecular weight), it may not be possible to impart sufficient abrasion resistance to the printed matter. In such cases, as described in Patent Document 2, the addition of wax is known as a means of improving abrasion resistance. Wax oriented on the surface of a dried ink film (ink film) melts by heating and / or pressure, imparting slip properties to the film and improving abrasion resistance. In this embodiment, it is more preferable to use a wax with a melting point of 100 to 170°C. By using a wax with such a melting point, the wax will not melt even in a stationary environment. Furthermore, slip properties are exhibited under typical usage conditions, such as when the printed matter is touched with a finger, resulting in a particularly excellent effect in improving abrasion resistance.

[0021] However, since the diols (A) have an affinity with wax, which is a type of resin component, when the diols (A) and wax are used together, the wax may become unstable in the ink. As a result, for example, aggregation or precipitation of the wax may occur in the inkjet head, which may cause deterioration of ejection stability. Furthermore, after printing, the orientation of the wax on the film surface may be hindered, which may prevent good abrasion resistance from being obtained.

[0022] Therefore, the present inventors conducted extensive research and found that by using a diol (B) having an SP value of 12.0 or more in combination with the diol (A) and further setting the difference between the boiling points of the diol (A) and the diol (B) to 30°C or less, aggregation, precipitation, etc. of the wax within the inkjet head described above is suppressed, resulting in good ejection stability, even after a long period of inactivity, and further enabling the production of printed matter with good scratch resistance. While the details of the reason for this are unclear, it is believed that diols (B) having a high SP value of 12.0 or more have good affinity with water and the diol (A), but have poorer affinity with resin components than the diol (A). As a result, it is believed that the diol (B) inhibits the affinity between the diol (A) and the wax within the inkjet head, thereby preventing aggregation and precipitation of the wax and improving ejection stability. Furthermore, since the boiling point of the diols (B) is almost the same as that of the diols (A), it is thought that, even after the water, which is the main component, evaporates within the ink droplets after printing, the diols (B) and the diols (A) remain in the ink droplets together. As a result, similar to the behavior within the inkjet head described above, the wax and the diols (A) remain in a state of low affinity within the ink droplets. As a result, the orientation of the wax on the film surface is less likely to be inhibited by the diols (A), and improved abrasion resistance can be achieved.

[0023] As described above, in order to solve the above-mentioned problems, an aqueous inkjet ink having the above-mentioned configuration is provided. More specifically, this embodiment is based on the discovery that in an aqueous inkjet ink that combines water, a diol (A), a binder resin, and a wax, the use of a diol (B) is sufficient to avoid impairing the effect of the wax.

[0024] The aqueous inkjet ink specifically disclosed in Patent Document 1 differs from the aqueous inkjet ink of the present embodiment in that it does not contain wax, and the aqueous inkjet ink specifically disclosed in Patent Document 2 differs from the aqueous inkjet ink of the present embodiment in that it has an SP value of 10.0 or more and less than 12.0 and does not contain a diol (A) having a branched alkylene group.

[0025] Next, each component constituting the aqueous inkjet ink of one embodiment will be described in detail below.

[0026] <Diols> The aqueous inkjet ink of this embodiment contains diols. As described above, the diols include diol (A) having an SP value of 10.0 or more and less than 12.0 and containing a branched alkylene group, and diol (B) having an SP value of 12.0 or more and 15.0 or less.

[0027] In the present disclosure, diols having a ring structure (alicyclic structure, aromatic ring structure) are not included in the above diols. Furthermore, the above "branched alkylene group" refers to an alkylene group having only alkyl groups as branched structures.

[0028] In the present disclosure, "SP value" is an abbreviation for "Solubility Parameter." Known methods for determining the SP value include a method of calculating it from the physical properties of a compound, a method of calculating it from the molecular structure, and a method of actually measuring it experimentally. In the present disclosure, the SP value used is a value calculated by Fedor's estimation method, which is represented by the following formula 1:

[0029] Equation 1: (SP value) = (ΣEcoh / ΣV) １／２

[0030] In the above formula 1, Ecoh represents the cohesive energy determined for each functional group, and V represents the molar volume determined for each functional group. The Ecoh and V are described in R. F. Fedors, "Polymer Engineering & Science" (Vol. 14, No. 2, 1974, pp. 147-154).

[0031] In the present disclosure, the unit of the SP value is (cal / cm ３ ) １／２ Use.

[0032] <<Diols (A) Having an SP Value of 10.0 or More and Less than 12.0 and Containing a Branched Alkylene Group>> In the aqueous inkjet ink of this embodiment, examples of the diols (A) that can be used include 2-ethyl-1,3-hexanediol (11.1, 244°C), 2,5-dimethyl-2,5-hexanediol (10.8, 214°C), 2-methyl-2,5-hexanediol (11.2, 231°C), hexylene glycol (2-methyl-2,4-pentanediol; 11.5, 197°C), 2-methyl-1,3-pentanediol (11.6, 218°C), 3-methyl-1,5-pentanediol (11.8, 250°C), and 2,3-dimethyl-2,3-butanediol (11.3, 174°C). These compounds may be used alone or in combination of two or more. The values ​​in the parentheses above are the SP values ​​of each compound (unit: (cal / cm ３ ) １／２ ), and the boiling point at 1 atmosphere.

[0033] Among these, it is preferable to use a compound having 6 carbon atoms as the diol (A) because it has good affinity with both water and the binder resin component, which facilitates efficient film formation and uniform film formation, thereby improving the scratch resistance and water resistance of printed matter. Among these, it is particularly preferable to use hexylene glycol because it has excellent drying properties and provides particularly good water resistance to printed matter.

[0034] Furthermore, the SP value of the diols (A) is preferably 10.5 or more and less than 12.0, particularly preferably 11.2 or more and less than 12.0, in view of having good affinity with both water and the binder resin component and being able to improve the scratch resistance and water resistance of printed matter.

[0035] The diol (A) may be solid or liquid at 25°C, but is more preferably a water-soluble organic solvent that is liquid at 25°C.

[0036] Furthermore, since ejection stability is improved regardless of the conditions of use, and printed matter having excellent abrasion resistance and water resistance can be obtained, the content of the diol (A) is preferably from 0.5 to 19 mass%, more preferably from 1.2 to 16 mass%, and particularly preferably from 2 to 12 mass%, of the total amount of the aqueous inkjet ink.

[0037] In addition, the content of the diol (A) is preferably 10 to 49 mass%, more preferably 15 to 42 mass%, and particularly preferably 20 to 35 mass%, of the total amount of water-soluble organic solvents contained in the aqueous inkjet ink. In the present disclosure, the total amount of water-soluble organic solvents does not include the content of the diols (A) and diols (B) that are not water-soluble organic solvents. The same applies hereinafter.

[0038] <<Diols (B) having an SP value of 12.0 or more>> In the aqueous inkjet ink of this embodiment, examples of the diols (B) include 1,2-propanediol (propylene glycol) (13.5, 188°C), 1,3-propanediol (13.7, 214°C), 1,2-butanediol (12.8, 193°C), 1,3-butanediol (12.8, 208°C), 1,4-butanediol (12.9, 230°C), 2,3-butanediol (12.5, 183°C), 1,2-pentanediol ( Examples of compounds that can be used include 1,5-pentanediol (12.4, 239°C), 2,2-dimethyl-1,3-propanediol (12.1, 210°C), 2-methyl-1,3-propanediol (12.8, 213°C), 3-methyl-1,3-butanediol (12.6, 203°C), ethylene glycol (14.8, 197°C), diethylene glycol (13.0, 244°C), and triethylene glycol (12.1, 287°C). These compounds may be used alone or in combination of two or more. The numerical values ​​in the parentheses above are the SP values ​​of each compound (unit: (cal / cm ３ ) １／２ ), and the boiling point at 1 atmosphere.

[0039] Among these, from the viewpoint that the affinity with the diol (A) is moderately increased, the affinity between the diol (A) and the wax is inhibited, and the discharge stability is improved, the SP value of the diol (B) is set to 12.0 to 14.0 (cal / cm ３ ) １／２ It is preferable that the viscosity is 12.5 to 13.5 (cal / cm ３ ) １／２ It is particularly preferable that the diol (B) is one or more of these compounds. Taking into consideration affinity with water, it is also preferable to use a compound having 3 to 4 carbon atoms. Of the compounds listed above, examples of compounds that satisfy these requirements include one or more selected from the group consisting of 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 2-methyl-1,3-propanediol, and diethylene glycol. In the aqueous inkjet ink of this embodiment, it is preferable to use one or more of these compounds as the diol (B).

[0040] The diol (B) may be a solid or a liquid at 25°C, but is more preferably a water-soluble organic solvent that is a liquid at 25°C.

[0041] Furthermore, from the viewpoint of achieving both moisture retention (ejection stability) in the inkjet nozzle and drying properties and water resistance of the printed matter, the content of the diol (B) is preferably from 1 to 30 mass %, more preferably from 4 to 25 mass %, and particularly preferably from 6 to 20 mass %, of the total amount of the aqueous inkjet ink.

[0042] Additionally, the content of the diol (B) is preferably from 51 to 99 mass %, more preferably from 55 to 95 mass %, and particularly preferably from 60 to 90 mass %, of the total amount of the water-soluble organic solvent contained in the aqueous inkjet ink.

[0043] Furthermore, from the viewpoint that the effect of the diol (B) in inhibiting the affinity between the diol (A) and the wax can be suitably exhibited and the abrasion resistance of the printed matter can be improved while improving the discharge stability, the ratio of the content of the diol (B) to the content of the diol (A) (diol (B) / diol (A)) is preferably 1 to 5, more preferably 1.5 to 4.5, and particularly preferably 2 to 4, in terms of mass.

[0044] As described above, by keeping the difference between the boiling points of the diols (A) and (B) at 30°C or less, wax aggregation during the ink drying process can be suppressed. Furthermore, the orientation of the wax on the film surface is less likely to be inhibited by the diols (A), enabling the production of printed matter with good scratch resistance. From the viewpoint that both the diols (A) and (B) are more likely to remain in the ink droplets on the printing substrate and the above-mentioned effects are more likely to be favorably exhibited, it is considered that the smaller the boiling point difference, the better. Specifically, the difference between the boiling points of the diols (A) and (B) at 1 atmosphere is preferably 20°C or less, and particularly preferably 15°C or less. For example, this boiling point difference may be 0 to 10°C.

[0045] When two or more diols (A) are contained in the aqueous inkjet ink, the difference in boiling point is calculated using the weighted average of the boiling points of the two or more diols (A). The same applies to the diol (B). However, the "weighted average of the boiling points" is a value obtained by adding together the product of the boiling point calculated for each compound and the mass proportion of the water-soluble organic solvent relative to the total content.

[0046] <Water-soluble organic solvent> The aqueous inkjet ink of this embodiment may contain a water-soluble organic solvent. In this disclosure, the term "water-soluble organic solvent" refers to an organic compound that has a solubility in water at 25°C of 1% by mass or more and is liquid at 25°C. Among the compounds contained in the diols (A) and diols (B) described above, compounds that satisfy the above conditions are also included in the "water-soluble organic solvent" in this disclosure.

[0047] <<Other Diols>> For example, the aqueous inkjet ink of this embodiment may use, as the water-soluble organic solvent, diols other than the above-mentioned diols (A) and (B) (referred to as “other diols” in the present disclosure). Examples of such other diols include 1,2-hexanediol and 1,2-heptanediol.

[0048] <<Glycol monoethers (C) having a terminal alkyl group with 2 to 4 carbon atoms>> The aqueous inkjet ink of this embodiment may also contain, as a water-soluble organic solvent, glycol monoethers (C) having a terminal alkyl group with 2 to 4 carbon atoms. The inclusion of glycol monoethers (C) in the inkjet ink of this embodiment, together with the diols (A) described above, can further soften the binder resin, promoting more efficient film formation and more uniform film formation, thereby further improving the abrasion resistance and water resistance of printed matter. Furthermore, when the aqueous inkjet ink of this embodiment contains a surfactant, for example, the glycol monoethers (C) suppress the orientation of the surfactant within the inkjet head, thereby further improving ejection stability, particularly ejection stability after a short pause.

[0049] Examples of the glycol monoethers (C) include propylene glycol monopropyl ether, propylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, dipropylene glycol monopropyl ether, and dipropylene glycol monobutyl ether. When the inkjet ink of this embodiment contains glycol monoethers (C), it is preferable to use one or more selected from the group consisting of propylene glycol monobutyl ether, diethylene glycol monoethyl ether, and diethylene glycol monobutyl ether, among the compounds listed above. These compounds are particularly favorable in terms of their affinity with binder resins, and their use in combination with the diols (A) further improves the abrasion resistance and water resistance of printed materials, making them suitable for use. More preferred are propylene glycol monopropyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, and combinations thereof.

[0050] From the viewpoint of obtaining an aqueous inkjet ink that is excellent in all of the abrasion resistance and water resistance of the printed matter, as well as the ejection stability, the content of the glycol monoethers (C) is preferably from 0.1 to 15 mass%, more preferably from 0.5 to 12 mass%, and particularly preferably from 1 to 10 mass%, of the total amount of the aqueous inkjet ink.

[0051] Furthermore, from the viewpoint of suppressing wax aggregation and achieving both abrasion resistance of the printed matter and ejection stability during printing, when the aqueous inkjet ink of this embodiment contains glycol monoethers (C), the total content of the diols (A) (however, only compounds that fall under the category of water-soluble organic solvents) and the glycol monoethers (C), which exert similar effects, is preferably 10% by mass or more and less than 50% by mass, and particularly preferably 10% by mass or more and 40% by mass or less, of the total amount of water-soluble organic solvents contained in the aqueous inkjet ink.

[0052] Furthermore, from the viewpoint of improving the abrasion resistance of printed matter and the ejection stability during printing due to the same effects as those described above, when the aqueous inkjet ink of this embodiment contains glycol monoethers (C), the total content of the diols (A) and the glycol monoethers (C) is preferably 10% by mass or more and less than 50% by mass, and particularly preferably 10% by mass or more and 40% by mass or less, relative to the total content of the water-soluble organic solvent, the compound of the diols (A) that is not a water-soluble organic solvent, and the compound of the diols (B) that is not a water-soluble organic solvent.

[0053] Other Water-Soluble Organic Solvents In addition to the compounds listed above, the aqueous inkjet ink of this embodiment can use, as water-soluble organic solvents, alkanetriols (having 3 to 6 carbon atoms); polyoxyalkylene glycols (having oxyethylene or oxypropylene oxyalkylene groups each having 2 to 4 carbon atoms); glycol monoethers having a terminal alkyl group with 1 carbon atom; glycol diethers (having two terminal alkyl groups each having 1 to 4 carbon atoms); lactams (having 5 to 7 atoms constituting the lactam ring; and an alkyl group having 1 to 2 carbon atoms, a hydroxyalkyl group having 1 to 2 carbon atoms, or a vinyl group may be bonded to a nitrogen atom and / or a carbon atom constituting the lactam ring); alkanolamines (having 1 amino group, 1 to 3 hydroxyl groups, and 3 to 9 carbon atoms); and the like. These water-soluble organic solvents may be used alone or in combination of two or more.

[0054] Furthermore, when the aqueous inkjet ink of this embodiment contains another water-soluble organic solvent, it is preferable to use a water-soluble organic solvent having a static surface tension of 29 to 50 mN / m at 25° C. By using a water-soluble organic solvent having this surface tension, it is possible to maintain an appropriate surface tension for ejection as an inkjet ink, and also to ensure good ejection stability, for example, even after a long period of inactivity.

[0055] On the other hand, in order to simultaneously improve the water resistance and abrasion resistance of the printed matter, as well as the ejection stability, it is preferable that the total content of the diols (A), the diols (B), and the glycol monoethers (C) is a certain amount or more. Specifically, when the aqueous inkjet ink of this embodiment contains the glycol monoethers (C), the total content of the diols (A), the diols (B), and the glycol monoethers (C) is preferably 70 to 100% by mass, and particularly preferably 85 to 100% by mass, of the total content of the water-soluble organic solvent, the compound of the diols (A) that is not a water-soluble organic solvent, and the compound of the diols (B) that is not a water-soluble organic solvent. Furthermore, when the aqueous inkjet ink of this embodiment does not contain glycol monoethers (C), for the same reasons as above, the total content of the diols (A) and the diols (B) is preferably 70 to 100 mass %, and particularly preferably 85 to 100 mass %, relative to the total content of the water-soluble organic solvent, the compound of the diols (A) that is not a water-soluble organic solvent, and the compound of the diols (B) that is not a water-soluble organic solvent.

[0056] When the aqueous inkjet ink of the present embodiment contains a water-soluble organic solvent other than the diols (A), the diols (B), and the glycol monoethers (C), it is preferable that the aqueous inkjet ink contains the above-mentioned other diols and / or polyoxyalkylene glycols.

[0057] The total content of water-soluble organic solvents contained in the aqueous inkjet ink of this embodiment is preferably 5 to 50 mass %, more preferably 9 to 40 mass %, even more preferably 12 to 35 mass %, and particularly preferably 15 to 30 mass % of the total amount of the aqueous inkjet ink. By keeping the total content of water-soluble organic solvents within the above range, it is possible to maintain an appropriate viscosity for ejection as an aqueous inkjet ink and to ensure good ejection stability, even after, for example, long-term suspension. Note that the total content of water-soluble organic solvents also includes the content of compounds from the above-mentioned diols (A) and diols (B) that meet the above-mentioned requirements for water-soluble organic solvents.

[0058] Furthermore, since the water resistance and abrasion resistance of the printed matter, as well as the ejection stability, can be improved at the same time, the total content of the water-soluble organic solvent, the compound which is a diol (A) but is not a water-soluble organic solvent, and the compound which is a diol (B) but is not a water-soluble organic solvent is preferably 5 to 50 mass %, more preferably 9 to 40 mass %, even more preferably 12 to 35 mass %, and particularly preferably 15 to 30 mass %, of the total amount of the aqueous inkjet ink.

[0059] In order to suitably soften the binder resin and improve the scratch resistance and water resistance of the printed matter, the content of the diols (A) relative to the total content of the water-soluble organic solvent, the diols (A) which are not water-soluble organic solvents, and the diols (B) which are not water-soluble organic solvents is preferably 10 to 49% by mass, more preferably 15 to 42% by mass, and particularly preferably 20 to 35% by mass.

[0060] Furthermore, from the viewpoints of suppressing aggregation and precipitation of wax, improving discharge stability, and also improving abrasion resistance, the content of the diol (B) relative to the total content of the water-soluble organic solvent, the compound which is the diol (A) but is not a water-soluble organic solvent, and the compound which is the diol (B) but is not a water-soluble organic solvent is preferably 50 to 99% by mass, more preferably 55 to 95% by mass, and particularly preferably 60 to 90% by mass.

[0061] Furthermore, in the aqueous inkjet ink of this embodiment, the content of the water-soluble organic solvent having a boiling point of 250°C or higher at 1 atmospheric pressure is preferably 1% by mass or less (or may be 0% by mass) of the total amount of the aqueous inkjet ink. By not including a water-soluble organic solvent having a boiling point of 250°C or higher, or by keeping the amount of the water-soluble organic solvent within the above range, good ejection stability can be achieved, for example, even after a long period of inactivity.

[0062] For the same reason, that is, from the viewpoint of improving ejection stability, it is preferable that the total content of water-soluble organic solvents having a boiling point of 250°C or higher at 1 atmospheric pressure, diols (A) which are not water-soluble organic solvents and have a boiling point of 250°C or higher at 1 atmospheric pressure, and diols (B) which are not water-soluble organic solvents and have a boiling point of 250°C or higher at 1 atmospheric pressure is 1% by mass or less (or may be 0% by mass) of the total amount of the aqueous inkjet ink.

[0063] Furthermore, when the aqueous inkjet ink of this embodiment contains a water-soluble organic solvent, the water-soluble organic solvent preferably has a boiling point (weighted average) at 1 atmosphere of 120 to 215° C., particularly preferably 150 to 200° C. By adjusting the boiling point (weighted average) within the above range, it is possible to achieve both ejection stability and the abrasion resistance and water resistance of the printed matter.

[0064] For the same reason, that is, from the viewpoint of achieving both ejection stability and the scratch resistance and water resistance of the printed matter, the weighted average boiling points at 1 atmospheric pressure of the water-soluble organic solvent, the compound which is a diol (A) but is not a water-soluble organic solvent, and the compound which is a diol (B) but is not a water-soluble organic solvent are preferably 120 to 215°C, and particularly preferably 150 to 200°C.

[0065] In the present disclosure, the expression "boiling point (weighted average value) of the water-soluble organic solvent" refers to the boiling point of the water-soluble organic solvent when the target composition contains only one type of water-soluble organic solvent, and refers to the weighted average value of the boiling points of the two or more water-soluble organic solvents when the target composition contains two or more types of water-soluble organic solvents. In addition, when calculating the boiling point (weighted average value) of the water-soluble organic solvent, compounds of the above-mentioned diols (A) and diols (B) that meet the requirements of a water-soluble organic solvent are also included.

[0066] <Binder Resin> The aqueous inkjet ink of this embodiment contains a binder resin because it can impart water resistance and abrasion resistance to printed matter, and further because the viscosity of the aqueous inkjet ink printed on a poorly permeable substrate or a non-permeable substrate increases as it dries at a speed on the order of microseconds, thereby suppressing bleeding (a phenomenon in which aqueous inkjet inks of different colors mix together) and beading (a phenomenon in which droplets of the aqueous inkjet ink attract each other and coalesce) and thereby producing printed matter with excellent print quality.

[0067] In this disclosure, the term "binder resin" refers to a resin used to bind an ink film to a printing substrate. For example, the resin contained in the aqueous inkjet ink of this embodiment may account for 50% by mass of the total resin content of the binder resin of this disclosure. Furthermore, the term "resin" refers to a compound formed by polymerizing multiple polymerizable monomers and having a mass average molecular weight of 1,000 or more.

[0068] In the present disclosure, the mass average molecular weight of a compound is measured by a method conforming to JIS K 7252, and is expressed in terms of polystyrene. Specific examples of measurement conditions are shown below. Apparatus used: Tosoh Corporation's "HLC-8320GPC" Columns used: TSKgel (registered trademark) SuperMultiporeHZ-M (3 columns) Column temperature: 40°C Developing solvent: tetrahydrofuran Flow rate: 0.6 mL / min Sample solution concentration: 0.1% by mass Sample solution injection volume: 10 μL

[0069] Generally, water-soluble resins and resin particles are known as the forms of resins used in aqueous inkjet inks. The binder resin contained in the aqueous inkjet ink of this embodiment may be a water-soluble resin or resin particles. Furthermore, a combination of a water-soluble resin and resin particles may be used.

[0070] In this disclosure, a resin having a solubility of 1 g or more in 100 g of water at 25° C. is referred to as a "water-soluble resin," and a resin having a solubility of less than 1 g is referred to as a "water-insoluble resin." Furthermore, among the water-insoluble resins, a resin that is dispersed in water in the form of particles and has a volume-based median diameter (also referred to as "D50" in this disclosure) of 10 to 1,000 nm is referred to as a "resin particle."

[0071] D50 in the present disclosure is a value measured using a dynamic light scattering particle size distribution measuring device such as Microtrac-Bell's "Nanotrac UPA-EX150" using water as a dispersion medium in an environment of 25°C.

[0072] Examples of types of binder resins that can be used in the aqueous inkjet ink of this embodiment include acrylic resins (excluding the acrylic-silicone copolymers described below), styrene resins, styrene-maleic (anhydride) resins, olefin-maleic (anhydride) resins, urethane resins (excluding the urethane-silicone copolymers described below), polyester resins, vinyl chloride resins, vinyl chloride-vinyl acetate resins, polyolefin resins, polyvinyl alcohol resins, etc. These resins may be used alone or in combination of two or more.

[0073] Among the above, it is preferable to use one or more resins selected from the group consisting of acrylic resins (excluding the acrylic-silicone copolymers described below), urethane resins (excluding the urethane-silicone copolymers described below), and polyester resins, as this will result in printed matter with excellent water resistance and abrasion resistance, and it is more preferable to use at least an acrylic resin (excluding the acrylic-silicone copolymers described below).

[0074] In the present disclosure, "acrylic resin" refers to a resin using one or more polymerizable monomers selected from the group consisting of acrylic acid, methacrylic acid, acrylic acid esters, and methacrylic acid esters (however, a styrene-based monomer may also be used as a polymerizable monomer). Furthermore, "maleic acid (anhydride)" refers to at least one polymerizable monomer selected from "maleic acid" and "maleic anhydride."

[0075] The content of the binder resin in the aqueous inkjet ink of this embodiment is preferably 1 to 25 mass %, more preferably 2 to 20 mass %, and particularly preferably 5 to 18 mass %, of the total amount of the aqueous inkjet ink.

[0076] <Wax> The inkjet ink of this embodiment contains wax. In this disclosure, "wax" refers to a non-volatile organic compound that is solid at room temperature (25°C) and becomes liquid when heated. For example, it refers to a compound that has a melting point of 40 to 200°C and melts without decomposition in a temperature environment above that melting point. From the viewpoint of improving the abrasion resistance of printed matter, the melting point of the wax is preferably 100 to 170°C, and more preferably 110 to 150°C. Note that in this disclosure, the melting point of the wax is the value measured under 1 atmosphere. Furthermore, from the viewpoint of the abrasion resistance of printed matter, the melting point of the wax is more preferably 100 to 160°C, even more preferably 110 to 150°C, and even more preferably 110 to 137°C.

[0077] Furthermore, the term "non-volatile organic compound" in the present disclosure refers to an organic compound that leaves a "non-volatile residue" when dried according to a method conforming to JIS K 5601 under conditions of a test temperature of 140°C, a heating time of 30 minutes, and a sample weight of 1±0.2 g.

[0078] The wax may be a water-soluble or water-insoluble compound, but is preferably a water-insoluble compound. Furthermore, it is preferable to use a resin as the wax, and it is particularly preferable to use a resin in the form of resin fine particles.

[0079] On the other hand, waxes that can be used in the aqueous inkjet ink of this embodiment can be classified by chemical structure to include hydrocarbon waxes, ester waxes (for example, fatty acid esters), silicone waxes (for example, acrylic resins (acrylic-silicone copolymers) having a silicone chain (siloxane chain) structure, urethane resins (urethane-silicone copolymers) having a silicone chain structure, and fatty acid esters having a silicone chain structure), polyalkylene glycol waxes (for example, polyethylene glycols having a mass-average molecular weight of 600 or more, polypropylene glycols having a mass-average molecular weight of 10,000 or more, and polyethylene glycol-polypropylene glycol copolymers having a mass-average molecular weight of 6,000 or more). Among acrylic resins having a silicone chain structure, those having a glass transition temperature of 50°C or higher are generally unlikely to satisfy the above-mentioned melting point condition, and therefore do not qualify as waxes in this embodiment.

[0080] Furthermore, waxes that can be used in the aqueous inkjet ink of this embodiment can be classified based on their method of acquisition into natural waxes, synthetic waxes, and semi-synthetic waxes. Examples of natural waxes include petroleum-based waxes such as paraffin wax, microcrystalline wax, and petrolatum; plant-based waxes such as carnauba wax, candelilla wax, and rice wax; animal-based waxes such as lanolin and beeswax; and mineral-based waxes such as montan wax and ceresin. Examples of synthetic waxes include polyolefin-based waxes (polyethylene wax, polypropylene wax, etc.), Fischer-Tropsch wax, acrylic-silicone copolymers, urethane-silicone copolymers, polyethylene glycol, polypropylene glycol, and polyethylene glycol-polypropylene glycol copolymers. Examples of semi-synthetic waxes include paraffin wax derivatives, montan wax derivatives, and microcrystalline wax derivatives. The waxes listed above can be used alone or in combination of two or more in the aqueous inkjet ink.

[0081] Among the above, hydrocarbon waxes and / or silicone waxes are preferred, with hydrocarbon waxes being more preferred, since they can produce printed matter with excellent abrasion resistance and print quality on various printing substrates. Examples of hydrocarbon waxes include natural waxes such as paraffin wax and microcrystalline wax, as well as synthetic waxes such as polyolefin wax and Fischer-Tropsch wax. Polyolefin waxes are more preferred as the hydrocarbon waxes. By including polyolefin wax, the binder resin and the polyolefin wax each form microscopic clusters, which suppresses uneven distribution of the components contained in the aqueous inkjet ink as the ink dries, thereby improving beading. Furthermore, the clusters function to prevent localized drying and viscosity increase near the inkjet nozzle, thereby improving ejection stability.

[0082] Examples of polyolefin waxes include polyethylene waxes and polypropylene waxes. Among them, polyethylene waxes are preferred in terms of improving the ejection stability and the scratch resistance of printed matter. The polyolefin waxes may be used alone or in combination of two or more.

[0083] The polyolefin wax is preferably a soft polyolefin having a mass average molecular weight of 500 to 10,000, and more preferably 600 to 8,000.

[0084] When resin microparticles are used as the wax, their D50 is preferably 5 to 300 nm, more preferably 30 to 250 nm, and particularly preferably 40 to 200 nm. If the wax has a D50 of 5 nm or more, the scratch resistance of the printed matter is improved, and if it is 300 nm or less, not only is the ejection stability improved but also printed matter with excellent print quality can be obtained regardless of the printing substrate. The D50 of the wax can be measured using the same method as for the D50 of the resin microparticles described above.

[0085] Wax in the form of resin microparticles can be produced, for example, by mixing a resin that is solid at room temperature and that has been heated and melted, with hot water and an emulsifier. Commercially available waxes can also be used, including, for example, AQUACER-507, 513, 515, 526, 531, 533, 535, 537, 539, 552, 840, 593, 1547, and HORDAMER PE 02 and PE 03 manufactured by BYK-Chemie; NOPCOT PEM-17 manufactured by San Nopco; JONCRYLWAX4, WAX26, WAX28, and WAX120 manufactured by BASF; HI-TECH E series and HI-TECH P series manufactured by Toho Chemical Industry Co., Ltd.; and CHALINE FE230N and FE502 manufactured by Shin-Etsu Chemical Co., Ltd.

[0086] In order to achieve both good jetting stability and good abrasion resistance of the printed matter, and to obtain a highly dense printed matter without beading, the wax content is preferably 0.2 to 8% by mass, more preferably 0.3 to 5% by mass, and particularly preferably 0.5 to 4% by mass, of the total mass of the aqueous inkjet ink. For the same reasons, when the wax content of the total mass of the aqueous inkjet ink is W (% by mass) and the binder resin content is R (% by mass), the value expressed by R / W is preferably 1 to 15, particularly preferably 3 to 13. By having R / W of 22 or less, preferably 15 or less, the abrasion resistance of the printed matter can be further improved. By having R / W of 0.9 or more, preferably 1 or more, the water resistance of the printed matter can be further improved. R / W is more preferably 1 to 15, even more preferably 2 to 14, and even more preferably 5 to 13. Within these ranges, the abrasion resistance, water resistance, and jetting stability of the printed matter can be further improved.

[0087] As mentioned above, in the present disclosure, wax and binder resin can be distinguished by their melting points. That is, the wax in the present disclosure is a compound that is solid at room temperature (25°C) and has a melting point of 40 to 200°C. The melting point of wax is preferably 100 to 170°C, and particularly preferably 110 to 150°C. On the other hand, the binder resin in the present disclosure is, for example, a compound that is solid at room temperature (25°C) and has a melting point greater than 200°C, or a compound that is solid at room temperature (25°C) and has no melting point. Specifically, the binder resin is a resin that decomposes without melting when heated, or an amorphous resin.

[0088] Furthermore, by optimizing the ratio of the content of the diols (A) to the content of the wax, it is possible to suppress destabilization of the wax and easily achieve both ejection stability and abrasion resistance of the printed matter. Therefore, the ratio of the content of the diols (A) to the content of the wax (diols (A) / wax) is preferably 2 to 12, and particularly preferably 3 to 10, in terms of mass.

[0089] <Colorant> The aqueous inkjet ink of this embodiment may contain a colorant. Conventionally known dyes and pigments can be used as the colorant. Among these, it is preferable to use a pigment, because it can produce printed matter with high density or hiding power and excellent lightfastness, waterfastness, etc., and it dries and thickens appropriately after landing on the printing substrate, suppressing color mixing between aqueous inkjet ink colors and resulting in good print quality.

[0090] As the pigment, any conventionally known organic or inorganic pigment can be used, and for example, pigments represented by the following color index names can be used: red pigments, such as C.I. Pigment Red 52, 5, 7, 9, 12, 17, 22, 23, 31, 48:1, 48:2, 48:3, 48:4, 49:1, 49:2, 57:1, 57:2, 112, 122, 123, 146, 147, 149, 150, 166, 168, 170, 171, 175, 176, 177, 178, 184, 188, 202, 207, 209, 254, 255, 260, 264, 266, 269, and 282; violet pigments, such as C.I. As orange pigments, C.I. Pigment Violet 19, 23, 29, 32, 36, 37, 42, 50; as orange pigments, C.I. Pigment Orange 1, 2, 3, 5, 7, 13, 14, 15, 16, 22, 34, 36, 38, 40, 43, 47, 48, 49, 51, 52, 53, 60, 61, 62, 64, 65, 66, 69, 71, 73; as blue pigments, C.I. Pigment Blue 15, 15:3, 15:4, 15:6, 16, 60, 64, 79; as green pigments, C.I. Pigment Green 7, 10, 36, 48; as yellow pigments, C.I. C.I. Pigment Yellow 1, 2, 3, 5, 12, 13, 14, 16, 17, 24, 73, 74, 83, 87, 93, 94, 95, 97, 98, 109, 110, 111, 112, 120, 126, 127, 128, 129, 137, 138, 139, 147, 150, 151, 154, 155, 166, 167, 168, 170, 180, 185, 213; as black pigments, C.I. Pigment Black 1, 7, 11; and as white pigments, C.I. Pigment White 4, 5, 6, 21, etc. These pigments may be used alone or in combination of two or more. Furthermore, a solid solution consisting of two or more of the pigments listed above can also be used as a pigment.

[0091] The content of the pigment contained in the aqueous inkjet ink of this embodiment is adjusted depending on the intended use of the printed matter produced using the aqueous inkjet ink, but is preferably 0.5 to 30 mass% of the total amount of the aqueous inkjet ink. Furthermore, except for white aqueous inkjet inks (aqueous white inks), the content of the pigment is more preferably 1 to 15 mass%, and particularly preferably 1.5 to 10 mass%, in order to obtain printed matters with high density without deteriorating the jetting stability of the aqueous inkjet ink. On the other hand, in the case of aqueous white inks, the content of the pigment is more preferably 5 to 25 mass%, and particularly preferably 10 to 20 mass%, in order to obtain printed matters with high hiding power without deteriorating the jetting stability of the aqueous white ink.

[0092] <Pigment Dispersion Resin> When the aqueous inkjet ink of this embodiment contains a pigment, a resin used for dispersing pigments (pigment dispersion resin) can be used. By selecting and considering the composition and mass average molecular weight of the polymerizable monomers that make up the pigment dispersion resin, the covering ability and charge of the pigment dispersion resin can be easily adjusted, making it possible to impart dispersion stability to even fine pigments, and further making it possible to obtain printed matter that is excellent in ejection stability, color development, and color reproducibility.

[0093] The type of pigment dispersion resin is not particularly limited, and resins that can be used include acrylic resins (excluding the above-mentioned acrylic-silicone copolymers), styrene resins, styrene-maleic (anhydride) resins, olefin-maleic (anhydride) resins, urethane resins (excluding the above-mentioned urethane-silicone copolymers), polyester resins, vinyl chloride resins, vinyl chloride-vinyl acetate resins, polyolefin resins, polyvinyl alcohol resins, etc. Among these, it is preferable to use one or more resins selected from the group consisting of acrylic resins, urethane resins, polyester-based resins, and polyolefin-based resins, in terms of ejection stability, wide range of material selectivity, ease of synthesis, etc.

[0094] The pigment dispersion resin may be synthesized by a known method or may be a commercially available product. There are no particular limitations on its structure; for example, resins having a random structure, a block structure, a comb structure, a star structure, or the like can be used. Furthermore, either a water-soluble resin or a water-insoluble resin may be selected as the pigment dispersion resin. An example of a water-insoluble pigment dispersion resin is resin fine particles containing a pigment. Furthermore, when an aqueous inkjet ink contains a water-soluble resin, whether the water-soluble resin is a pigment dispersion resin can be confirmed by a method conforming to JIS K 5101-1-4.

[0095] Specifically, the primary particle diameter is 15 to 25 nm, and the nitrogen adsorption specific surface area is 120 to 260 m ２ / g, DBP absorption (granular) 40-80 cm ３ 600 g of carbon black (100 g / 100 g), 300 g of the target water-soluble resin, and 2,100 g of water are thoroughly mixed (premixed), and then dispersed for 4 hours using a 0.6 L bead mill (e.g., a "Dyno Mill" manufactured by Shinmaru Enterprises) filled with 1,800 parts of grinding beads (e.g., zirconia beads with a diameter of 0.5 mm). After dispersion, the viscosity of the resulting carbon black dispersion at 25°C is measured using an E-type viscometer (e.g., a "TVE25L" type viscometer" manufactured by Toki Sangyo Co., Ltd.). The carbon black dispersion is then stored in a constant-temperature, air-blowing incubator set at 70°C for one week, and the viscosity is measured again. If the viscosity of the dispersion immediately after dispersion is 100 mPa·s or less and the absolute value of the viscosity change rate of the carbon black dispersion before and after storage is 10% or less, the water-soluble resin is determined to be a pigment dispersion resin.

[0096] Furthermore, regardless of whether the pigment dispersing resin is a water-soluble resin or a water-insoluble resin, the pigment dispersing resin may also function as the binder resin described above.

[0097] When a water-soluble resin is used as the pigment dispersion resin, its acid value is preferably 100 to 450 mgKOH / g or less, and more preferably 120 to 400 mgKOH / g. By setting the acid value within the above range, it is possible to maintain the dispersion stability of the pigment, and stable ejection from the inkjet head is possible regardless of the use conditions. Furthermore, this is preferable in that the solubility of the pigment dispersion resin in water can be ensured and the interaction between the pigment dispersion resins can be favorable, thereby reducing the viscosity of the pigment dispersion and achieving good ejection properties from the inkjet head.

[0098] On the other hand, when a water-insoluble resin is used as the pigment dispersing resin, its acid value is preferably 0 to 100 mgKOH / g, more preferably 5 to 90 mgKOH / g, and even more preferably 10 to 80 mgKOH / g. When the acid value is within the above range, printed matter having excellent drying properties and good print quality can be obtained.

[0099] The acid value of the resin can be measured using a known device. The acid value of the resin in the present disclosure is a value measured by potentiometric titration in accordance with JIS K 2501. A specific example of the measurement method is a method in which a resin is dissolved in a toluene-ethanol mixed solvent using an AT-610 manufactured by Kyoto Electronics Manufacturing Co., Ltd., and then titrated with a potassium hydroxide solution, and the acid value is calculated from the titration amount up to the endpoint.

[0100] In the aqueous inkjet ink of this embodiment, from the viewpoint of improving the adsorption ability to the pigment and ensuring dispersion stability and ejection stability, it is preferable to introduce an aromatic group into the pigment dispersing resin. Examples of the aromatic group include, but are not limited to, a phenyl group, a naphthyl group, an anthryl group, a tolyl group, a xylyl group, a mesityl group, and an anisyl group. Among these, a phenyl group, a naphthyl group, and a tolyl group are preferable from the viewpoint of ensuring sufficient dispersion stability.

[0101] From the viewpoint of improving the dispersion stability and ejection stability of the pigment, as well as the print quality and drying properties of the printed matter, the amount of the aromatic ring-containing monomer incorporated is preferably 5 to 75 mass %, more preferably 5 to 65 mass %, and even more preferably 10 to 50 mass %, relative to the total amount of monomers constituting the pigment dispersion resin.

[0102] <Surfactant> The aqueous inkjet ink of this embodiment may contain a surfactant. Examples of the surfactant that can be used include acetylene diol surfactants, acetylene monool surfactants, siloxane surfactants (excluding the above-mentioned acrylic-silicone copolymers (having a glass transition temperature of less than 50°C), urethane-silicone copolymers, and fatty acid esters having a silicone chain structure), fluorine-containing surfactants, and polyoxyalkylene monoalkyl ether surfactants (excluding those having a terminal alkyl group with 1 to 4 carbon atoms). These surfactants may be used alone or in combination of two or more.

[0103] In particular, it is preferable to use one or more surfactants selected from the group consisting of acetylene diol surfactants and siloxane surfactants as the surfactant, because this can significantly reduce the surface tension of the aqueous inkjet ink of this embodiment in a very short time, thereby improving the print quality of printed matter, and also because this surfactant has good wettability even for printing substrates with relatively high interfacial free energy.

[0104] Examples of commercially available acetylene diols that can be suitably used include Surfynol (registered trademark) 61, 104E, 104H, 104A, 104BC, 104DPM, 104PA, 104PG-50, 420, 440, 2502, SE, SE-F, DF-110D, Dynol (registered trademark) 604, 607 (manufactured by Evonik Japan K.K.), Olfine (registered trademark) E1004, PD-001, PD-002W, PD-004 (manufactured by Nissin Chemical Industry Co., Ltd.), etc. Among these, it is preferable to use Surfynol 440 and / or Surfynol 2502 because of their excellent discharge stability.

[0105] Examples of commercially available siloxane surfactants that can be suitably used include TEGO (registered trademark) Wet 270, TEGO Wet 280, TEGO Twin 4000, TEGO Twin 4100, TEGO Glide 410, TEGO Glide 432, TEGO Glide 435, TEGO Glide 440, and TEGO Glide 450 manufactured by Evonik Japan Co., Ltd.; and the Silface SAG series manufactured by Nissin Chemical Industry Co., Ltd. Among these, one or more commercially available products selected from the group consisting of TEGO Wet 270, TEGO Wet 280, TEGO Twin 4000, and TEGO Twin 4100 can be preferably used.

[0106] <Water> The aqueous inkjet ink of this embodiment contains water. It is preferable to use ion-exchanged water (deionized water) as the water contained in the ink, rather than ordinary water containing various ions. The water content is preferably 45 to 75% by mass, and particularly preferably 50 to 70% by mass, based on the total amount of the aqueous inkjet ink. Because water has a low boiling point, it tends to volatilize preferentially, for example, at the nozzle end face of the inkjet head, resulting in a high solids concentration at the gas-liquid interface. This can lead to film formation of the binder resin, non-uniform surfactant distribution, and thickening of the aqueous inkjet ink, potentially resulting in poor ejection stability. By limiting the water content within the above range, good ejection stability is achieved, even after extended periods of inactivity.

[0107] <Other Components> The aqueous inkjet ink of this embodiment may contain, in addition to the components described above, a pH adjuster and / or other additives. Examples of the other additives include a crosslinking agent, a preservative, an ultraviolet absorber, and an infrared absorber. Each of these components may be one or more of conventionally known compounds.

[0108] <Method for Producing Aqueous Inkjet Ink> The aqueous inkjet ink of this embodiment can be produced by a conventionally known method. For example, when a water-insoluble colorant (water-insoluble colorant) is used as the colorant, the water-insoluble colorant is dispersed in a medium containing at least water (aqueous medium) to produce a water-insoluble colorant dispersion. On the other hand, when a water-soluble colorant (water-soluble colorant) is used as the colorant, the water-soluble colorant is dissolved in a water-based medium to produce an aqueous colorant solution. Then, water, diols (A), diols (B), a binder resin, wax, and, if necessary, a water-soluble organic solvent other than the diols (A) and diols (B), a surfactant, etc. are added to the water-insoluble colorant dispersion and / or the aqueous water-soluble colorant solution, followed by thorough stirring and mixing, followed by removal of coarse particles by techniques such as filtration and centrifugation. However, the method for producing the aqueous inkjet ink of this embodiment is not limited to the above-described method.

[0109] <Characteristics of Aqueous Inkjet Ink> The aqueous inkjet ink of this embodiment preferably has a viscosity at 25°C of 3 to 15 mPa·s. Within this viscosity range, droplets of the aqueous inkjet ink can be stably ejected not only from inkjet heads with ejection frequencies of approximately 4 to 10 kHz, but also from inkjet heads with high ejection frequencies of approximately 20 to 70 kHz. In particular, when the viscosity of the aqueous inkjet ink of this embodiment at 25°C is 4 to 10 mPa·s, the aqueous inkjet ink can be stably ejected even when an inkjet head with a design resolution of 600 dpi or higher is used. In this disclosure, the viscosity is measured at 25°C using a cone-plate rotational viscometer (E-type viscometer, cone angle 1°34') such as the TVE25L viscometer manufactured by Toki Sangyo Co., Ltd.

[0110] Furthermore, in order to obtain an aqueous inkjet ink that is excellent in ejection stability and print quality of printed matter, the aqueous inkjet ink of this embodiment preferably has a static surface tension of 18 to 35 mN / m, and particularly preferably 21 to 32 mN / m, at 25° C. In the present disclosure, the static surface tension is a value measured in an environment of 25° C. using the Wilhelmy method (plate method) with an "Automatic Surface Tensiometer CBVP-Z" manufactured by Kyowa Interface Science Co., Ltd.

[0111] Furthermore, when the aqueous inkjet ink of this embodiment contains a water-insoluble colorant, in order to achieve both high levels of ejection stability and high levels of density or hiding power in the printed matter, the volume-based median diameter (D50) of the water-insoluble colorant is preferably 30 to 450 nm, more preferably 50 to 400 nm, and particularly preferably 70 to 350 nm. The D50 of the water-insoluble colorant can be measured by the same method as for the D50 of the resin fine particles described above.

[0112] <Aqueous Inkjet Ink Set> Although only one aqueous inkjet ink of this embodiment may be used alone, two or more aqueous inkjet inks may also be combined to form an aqueous inkjet ink set. Examples of such aqueous inkjet ink sets include a four-color aqueous inkjet ink set (process color ink set) consisting of a cyan aqueous inkjet ink (aqueous cyan ink), a magenta aqueous inkjet ink (aqueous magenta ink), a yellow aqueous inkjet ink (aqueous yellow ink), and a black aqueous inkjet ink (aqueous black ink); and a five-color aqueous inkjet ink set obtained by adding an aqueous white ink to the process color ink set. It is preferable that all of the aqueous inkjet inks constituting the aqueous inkjet ink set satisfy the requirements of this embodiment described above.

[0113] <Ink-Pretreatment Liquid Set> The aqueous inkjet ink of this embodiment and the aqueous inkjet ink set described above can also be used in a form combined with a pretreatment liquid containing an aggregating agent (in the form of an ink-pretreatment liquid set). By applying a pretreatment liquid containing an aggregating agent to a printing substrate before printing with the aqueous inkjet ink, it is possible to form a layer (ink aggregation layer) that intentionally aggregates solid components contained in the aqueous inkjet ink. Then, by landing the aqueous inkjet ink on this ink aggregation layer, it is possible to prevent coalescence and color mixing of droplets of the aqueous inkjet ink, and significantly improve the print quality of the printed matter.

[0114] As the flocculant, for example, a water-soluble inorganic or organic salt containing a polyvalent metal ion, and a resin having a cationic group in which the cationic group equivalent is greater than the anionic group equivalent can be used.

[0115] <Inkjet Printing Method> The aqueous inkjet ink of this embodiment is used in the inkjet printing method described above. That is, the aqueous inkjet ink of this embodiment is ejected onto a printing substrate from an inkjet head having fine nozzles (ejection step). In addition, the aqueous inkjet ink ejected onto the printing substrate is preferably dried by a drying mechanism (drying step).

[0116] <<Discharge Process>> In the discharge process, the inkjet head can be operated in two ways: a shuttle (scan) method, in which the inkjet head is scanned back and forth in a direction perpendicular to the transport direction of the printing substrate while discharging and recording the aqueous inkjet ink, and a single-pass method, in which the inkjet head is scanned back and forth in a direction perpendicular to the transport direction of the printing substrate while discharging and recording the aqueous inkjet ink as the printing substrate passes below a fixedly disposed inkjet head. The inkjet head equipped with the aqueous inkjet ink of this embodiment may be either a shuttle method or a single-pass method. Of these, the single-pass method is preferably selected because it reduces deviation in the landing position of droplets of the aqueous inkjet ink, improving the print quality of the printed matter, and further enables high-speed printing and provides high productivity as an alternative to plate-based printing.

[0117] The method of ejection from the inkjet head can also be selected from any known methods, such as a piezoelectric method that utilizes the volume change of a piezoelectric element, a thermal method that ejects aqueous inkjet ink by bubbles generated by heating a heater, and a valve method that ejects pressurized aqueous inkjet ink by opening and closing a nozzle cover (valve) with a solenoid.

[0118] The volume of droplets of the aqueous inkjet ink ejected from the inkjet head is preferably 0.5 to 20 picoliters, and particularly preferably 0.5 to 15 picoliters, from the viewpoints of reducing the drying load, improving print quality, etc. Furthermore, from the viewpoint of improving print quality, it is preferable to adjust the printing conditions (specifically, the driving frequency and number of inkjet heads installed, and the printing speed) so that the recording resolution of the printed matter is 600 dpi or higher, and it is particularly preferable to adjust the printing conditions so that the resolution is 1200 dpi or higher.

[0119] <<Drying Step>> Examples of drying methods employed in the drying mechanism used in the drying step include heat drying, hot air drying, infrared drying (for example, infrared with a wavelength of 700 to 2500 nm), microwave drying, and drum drying. In the drying step, one or more of these methods can be selected and used as desired. Furthermore, when two or more of the above drying methods are used, the methods may be used separately (for example, consecutively) or simultaneously. For example, by using heat drying and hot air drying in combination, the ink can be dried more quickly than when each method is used alone.

[0120] In particular, from the viewpoint of preventing bumping of the liquid components in the aqueous inkjet ink and obtaining printed matter with excellent print quality, when a heat drying method is employed, it is preferable that the drying temperature be 35 to 100° C., and when a hot air drying method is employed, it is preferable that the hot air temperature be 50 to 250° C. From the same viewpoint, when an infrared drying method is employed, it is preferable that 50% or more of the integrated value of the total output of the irradiated infrared rays be in the wavelength region of 700 to 2200 nm.

[0121] <Printing substrate> The printing substrate on which the aqueous inkjet ink of this embodiment is printed is not particularly limited. However, by using the aqueous inkjet ink of this embodiment on a poorly permeable substrate or a non-permeable substrate, which are generally considered to be prone to bleeding and beading, and even in high-speed printing, it is possible to obtain a printed product having print quality equivalent to that of a printed product produced by a plate-based printing method.

[0122] In the present disclosure, the permeability of a printing substrate is determined by the amount of water absorption measured by a dynamic scanning absorptivity meter. Specifically, the amount of pure water absorption measured by the following method for a contact time of 100 msec is 1 g / m ２ A printing substrate with a density of less than 1 g / m is called an "impermeable substrate." ２ 6g / m or more ２ A printing substrate with a permeability of less than 6 g / m is called a "hard-to-penetrate substrate." ２ A printing substrate that satisfies the above criteria is referred to as a "permeable substrate." The water absorption of a printing substrate can be measured using a dynamic scanning absorptivity meter (for example, the "KM500win" manufactured by Kumagai Riki Kogyo Co., Ltd.) set under the following conditions, using a printing substrate approximately 15 to 20 cm square as a sample, in an environment of 23°C and 50% RH. Measurement method: Spiral scanning Measurement start radius: 20 mm Measurement end radius: 60 mm Contact time: 10 to 1,000 msec Number of sampling points: 19 (measured at approximately equal intervals relative to the square root of the contact time) Scanning interval: 7 mm Rotating table speed switching angle: 86.3 degrees Headbox conditions: width 5 mm, slit width 1 mm

[0123] Examples of impermeable substrates and poorly permeable substrates include plastic films and sheets such as polyvinyl chloride sheets, polyethylene terephthalate (PET) films, polypropylene films, polyethylene films, polyethylene sheets, nylon films, nylon sheets, polystyrene films, polystyrene sheets, and polyvinyl alcohol films; coated papers such as coated paper, art paper, and cast paper; metals such as aluminum, iron, stainless steel, and titanium; and glass.

[0124] The printing substrates listed above may have a smooth or uneven surface. The printing substrates may be transparent, translucent, or opaque. Furthermore, the printing substrates may be in the form of rolls or sheets. Additionally, two or more of the printing substrates listed above may be bonded together and used as the printing substrate. A release adhesive layer or the like may be provided on the side opposite the printed surface, or an adhesive layer or the like may be provided on the printed surface after printing.

[0125] It is also preferable to subject the printing surface of the printing substrates listed above to surface modification such as corona treatment or plasma treatment, since this improves the wettability of the aqueous inkjet ink of this embodiment, and results in a printed product with excellent print quality and drying properties, and with a uniform printed surface, which also has good abrasion resistance and adhesion to the substrate.

[0126] The aqueous inkjet ink of this embodiment has excellent water resistance and abrasion resistance even without lamination, and therefore can be used for commercial printed materials, printed packaging, and the like. For example, it can be used for labels, packages, and the like. In these applications, the printing substrate may be a plastic film. For example, since the ink film can be bound to the printing substrate by the binder resin, it can be used to print on polyethylene sheets, polypropylene sheets, and the like.

[0127] <Printed Material> According to some embodiments, it is possible to provide a printed material obtained by printing the aqueous inkjet ink of the present embodiment described above onto a printing substrate. This printed material comprises a printing substrate and an ink film formed by applying the aqueous inkjet ink of the present embodiment to the printing substrate. This printed material can have good abrasion resistance and water resistance because the ink film is formed by the binder resin and the ink film is given slip properties by the wax. Preferably, the wax is oriented on the surface of the ink film, which gives it slip properties and further enhances abrasion resistance.

[0128] The present invention will be described in more detail below with reference to examples and comparative examples. In the following description, "parts" and "%" are by mass unless otherwise specified.

[0129] <Production of binder resin> An aqueous solution of acrylic resin (solid content 30%) was produced using the same raw materials and method as binder resin 28 produced in the example of JP 2020-180178 A, and used as a binder resin.

[0130] The above-mentioned "aqueous solution" refers to a solution containing an aqueous solvent and components dispersed and / or dissolved in the aqueous solvent.

[0131] <Preparation of Pigment Dispersion> (Preparation of Black Pigment Dispersion) 15 parts of carbon black ("PrinteX85" manufactured by Orion Engineered Carbons), 3 parts of a styrene-acrylic resin (a random polymer of styrene / acrylic acid / behenyl acrylate = 45 / 30 / 25 (mass ratio), in which all acid groups had been neutralized with dimethylaminoethanol, acid value 230 mgKOH / g, mass average molecular weight 20,000), and 82 parts of water were charged into a mixing vessel equipped with a stirrer, and premixing was carried out for 1 hour. Subsequently, using a "Dyno Mill" (volume 0.6 L) manufactured by Shinmaru Enterprises Inc. filled with 1,800 g of zirconia beads with a diameter of 0.5 mm, circulation dispersion was carried out until the 50% diameter of the carbon black reached approximately 100 nm, thereby producing a black pigment dispersion. Here, the 50% diameter is the particle diameter at which the integrated value reaches 50% in the volume-based particle size distribution measured by dynamic light scattering. The same applies hereinafter.

[0132] (Preparation of Cyan Pigment Dispersion, Magenta Pigment Dispersion, and Yellow Pigment Dispersion) Cyan pigment dispersion, magenta pigment dispersion, and yellow pigment dispersion were prepared using the same materials and method as for the black pigment dispersion, except that the following pigments were used as pigments and circulatory dispersion was carried out until the 50% diameters shown below were reached. Cyan pigment dispersion: LIONOL BLUE 7358G (C.I. Pigment Blue 15:3) manufactured by Toyocolor Co., Ltd., 50% diameter = 150 nm Magenta pigment dispersion: TOSHKI RED 150TR (C.I. Pigment Red 150) manufactured by Tokyo Shikizai Kogyo Co., Ltd., 50% diameter = 200 nm Yellow pigment dispersion: LIONOL YELLOW TT1405G (C.I. Pigment Yellow 14) manufactured by Toyocolor Co., Ltd., 50% diameter = 150 nm

[0133] <Production of Aqueous Inkjet Ink Sets> Using the pigment dispersions produced by the above method, each raw material was added to a mixing vessel equipped with a stirrer so as to obtain the formulation shown in each column of Table 1. After addition, the mixture was heated to approximately 50°C and then mixed for an additional hour. The mixture was then cooled to room temperature (approximately 25°C) and filtered through a membrane filter with a pore size of 1.2 μm to produce aqueous inkjet inks 1 to 108. In producing the aqueous inkjet inks, the above black pigment dispersion, cyan pigment dispersion, magenta pigment dispersion, and yellow pigment dispersion were used as the pigment dispersions, and the aqueous inkjet inks were produced with the same configuration except for the type of pigment dispersion. This produced aqueous inkjet ink sets consisting of black (aqueous black ink), cyan (aqueous cyan ink), magenta (aqueous magenta ink), and yellow (aqueous yellow ink), respectively.

[0134] In addition, when producing the aqueous inkjet ink, each raw material was added while stirring the mixture in the mixing vessel. Furthermore, each raw material was added in the order listed in the top row of each column in Table 1. However, if a component was not included, that component was skipped and the next component was added. Furthermore, for components containing two or more raw materials, the order of addition within that component was arbitrary.

[0135]

[0136]

[0137]

[0138]

[0139]

[0140]

[0141]

[0142]

[0143]

[0144] Details of the product names listed in Table 1 are as follows. The units of boiling point and melting point listed in Table 1 are °C, and the unit of SP value is (cal / cm ３ ) １／２In Table 1, "Nv" represents the solid content concentration (unit: mass %).・Surfynol 104 (acetylene diol surfactant manufactured by Evonik) ・Surfynol 440 (acetylene diol surfactant manufactured by Evonik) ・Surfynol 2502 (acetylene diol surfactant manufactured by Evonik) ・TEGO Wet 280 (polyether modified siloxane surfactant manufactured by Evonik) ・TEGO Wet 270 (polyether modified siloxane surfactant manufactured by Evonik) ・TEGO Twin 4100 (polyether modified siloxane surfactant manufactured by Evonik) ・Hitec E-4A (oxidized polyethylene wax manufactured by Toho Chemical Industry, solids content 35%) ・Hitec E-6400 (oxidized polyethylene wax manufactured by Toho Chemical Industry, solids content 35%) ・AQUACER 515 (oxidized high-density polyethylene wax manufactured by BYK-Chemie KK, solids content 35%) ・AQUACER 531 (oxidized high-density polyethylene wax manufactured by BYK, solids content 35%), HORDAMER PE 03 (polyethylene wax manufactured by BYK, solids content 35%), AQUACER 593 (polypropylene wax manufactured by BYK, solids content 30%), and Proxel GXL: 1,2-benzisothiazol-3-one in dipropylene glycol and water solution (1,2-benzisothiazol-3-one:dipropylene glycol:water = 2:6:2 mixture, preservative manufactured by Arch Chemicals).

[0145] <Preparation of Printed Material> An inkjet ejection device equipped with four Kyocera KJ4B-1200 inkjet heads (design resolution 1200 dpi, nozzle diameter 20 μm) arranged in the conveyance direction of the printing substrate was placed in a 25°C environment, and aqueous black ink, aqueous cyan ink, aqueous magenta ink, and aqueous yellow ink were filled in this order from the upstream inkjet head. Furthermore, a biaxially oriented polypropylene film "OPU-1" (thickness 20 μm) manufactured by Mitsui Chemicals Tohcello was fixed on the conveyor. The conveyor was then driven at a speed of 50 m / min, and as the film substrate passed below the installation section of the inkjet heads, aqueous inkjet inks were ejected at a drop volume of 2 pL each, printing an image. The printed printing substrate was then immediately placed in a 70°C air oven and dried for 3 minutes to produce a printed material.

[0146] In addition, the printed image was a solid print (5 cm width and 30 cm length for each color) of aqueous cyan ink, aqueous magenta ink, aqueous yellow ink, and aqueous black ink at a printing rate of 100% so that they did not overlap each other, and an image (colored solid image) was used in which the solid image areas were arranged adjacent to each other in the order of cyan, magenta, yellow, and black.

[0147] [Examples 1 to 91, Comparative Examples 1 to 17] After printing colored solid images on polypropylene films by the above-described method, the following evaluations were carried out using these printed materials. The evaluation results are shown in Table 1.

[0148] <Evaluation 1: Evaluation of Abrasion Resistance> From the print of the colored solid image prepared by the above method, the cyan ink printed portion, magenta ink printed portion, yellow ink printed portion, and black ink printed portion were cut out and placed as test pieces in a Tester Sangyo Co., Ltd. AB-301 Gakushin-type abrasion fastness tester. Next, a test attachment white cotton cloth (Kanakin No. 3) was attached to a friction element (weight: 200 g), and the friction element was subjected to a predetermined number of vibrations while varying the load applied. After the abrasion test, the condition of the surface of the print and the degree of coloring of the cotton cloth were visually confirmed to evaluate abrasion resistance. The evaluation criteria were as follows, with ◎, ○, and △ being considered usable. Table 1 lists the results for the color that received the worst evaluation among the four colors evaluated. ◎: Even after shaking the friction element 50 times with a 300g weight placed on it (500g in total), there were no abrasion marks on the printed surface and no discoloration on the cotton cloth. ○: Even after shaking the friction element 25 times with a 300g weight placed on it (500g in total), there were no abrasion marks on the printed surface and no discoloration on the cotton cloth, but after shaking the friction element 50 times under the same load conditions, there were abrasion marks on the printed surface and / or discoloration on the cotton cloth. △: After shaking the friction element 25 times without a weight placed on it (200g load), there were no abrasion marks on the printed surface and no discoloration on the cotton cloth, but after shaking the friction element 25 times with a 300g weight placed on it (500g in total), there were abrasion marks on the printed surface and / or discoloration on the cotton cloth. ×: After shaking the friction element 25 times without placing a weight (200 g load), scratches were observed on the printed surface and / or coloring of the cotton cloth was observed.

[0149] <Evaluation 2: Evaluation of Water Resistance> As in Evaluation 1, test pieces were cut out for each color from the printed matter with a colored solid image and placed in a Tester Sangyo Co., Ltd. AB-301 Gakushin-type abrasion fastness tester. A test attachment white cotton cloth (Kanakin No. 3) thoroughly moistened with ion-exchanged water was attached to the abrader (weight: 200 g). The abrader was subjected to various loads and shaken several times. The abrasion resistance was then evaluated by visually observing the condition of the surface of the printed matter and the degree of coloring of the cotton cloth. The evaluation criteria were as follows, with ◎, ◎-, ○, and △ being considered usable. Table 1 lists the evaluation results for the color with the lowest evaluation among the four colors. ◎: Even after a 300g weight was placed on the frictional element (500g in total) and the element was shaken 20 times, there were no abrasion marks on the printed surface and no discoloration on the cotton cloth. ◎-: Even after a 300g weight was placed on the frictional element (500g in total) and the element was shaken 10 times, there were no abrasion marks on the printed surface and no discoloration on the cotton cloth, but after shaking 20 times under the same load conditions, there were abrasion marks on the printed surface and / or discoloration on the cotton cloth. ○: Even after a 300g weight was placed on the frictional element (500g in total) and the element was shaken 5 times, there were no abrasion marks on the printed surface and no discoloration on the cotton cloth, but after shaking 10 times under the same load conditions, there were abrasion marks on the printed surface and / or discoloration on the cotton cloth. △: After shaking the friction element five times without placing a weight (load 200 g), there were no scratches on the printed surface and no discoloration of the cotton cloth was observed. However, after shaking the friction element five times with a 300 g weight (total 500 g), scratches on the printed surface and / or discoloration of the cotton cloth were observed. ×: After shaking the friction element five times without placing a weight (load 200 g), scratches on the printed surface and / or discoloration of the cotton cloth were observed.

[0150] <Evaluation 3: Evaluation of Discharge Stability> The inkjet printing device used to produce the printed matter was filled with each of the aqueous inkjet inks listed in Table 1. Next, a nozzle check pattern was printed, and after confirming that there were no clogged nozzles, the device was left in a 25°C environment for 10 minutes. Thereafter, a nozzle check pattern was printed again, and the number of clogged nozzles was visually counted to evaluate discharge stability. The evaluation criteria were as follows, with ⊚ and ∘ indicating that the ink was usable. The above evaluation was carried out for each of the aqueous inkjet inks constituting the aqueous inkjet ink set. Table 1 also lists the evaluation result of the color that received the lowest rating out of the four colors. ⊚: No clogged nozzles at all ⊚: 1 to 9 clogged nozzles Δ: 10 to 49 clogged nozzles ×: 50 or more clogged nozzles

[0151] As is clear from Table 1, an aqueous inkjet ink containing a diol (A) having an SP value of 10.0 or more but less than 12.0 and containing a branched alkylene group, a diol (B) having an SP value of 12.0 or more but less than 15.0, a binder resin, and a wax, in which the difference in boiling point between the diol (A) and the diol (B) is 30°C or less, can produce printed matter that is excellent in water resistance and abrasion resistance, while also having high ejection stability. In particular, by setting the difference in boiling point between the diol (A) and the diol (B) to 30°C or less, it is possible to cause both the diol (A) and the diol (B) to remain within the aqueous inkjet ink droplets on the printing substrate, preventing aggregation of the wax and promoting softening and reorientation of the binder resin, which is thought to make it possible to obtain printed matter that is excellent in abrasion resistance and water resistance. Furthermore, it has been revealed that when multiple types of diols (A) and / or multiple types of diols (B) are used, the same effect can be obtained by calculating the weighted average value of the boiling points of the multiple types of diols (A) and / or multiple types of diols (B) and adjusting the difference in the boiling points (weighted average values) to 30°C or less.

[0152] Although the present invention has been described with reference to the above-mentioned several embodiments, the present invention is not limited to these several embodiments. Various modifications can be made to the configuration and details of the present invention within the scope of the present invention.

[0153] The disclosure of this application is related to the subject matter described in Japanese Patent Application No. 2023-198147, filed November 22, 2023, the entire disclosure of which is incorporated herein by reference.

Claims

1. An aqueous inkjet ink containing water, diols, a binder resin, and a wax, wherein the diols include diols (A) having an SP value of 10.0 or more and less than 12.0 and containing a branched alkylene group, and diols (B) having an SP value of 12.0 or more and 15.0 or less, and the difference between the boiling point of the diols (A) at 1 atmospheric pressure and the boiling point of the diols (B) at 1 atmospheric pressure is 30°C or less.

2. The aqueous ink-jet ink according to claim 1, wherein the wax comprises a polyolefin wax having a melting point of 100° C. or higher and 170° C. or lower at one atmospheric pressure.

3. The aqueous inkjet ink according to claim 2, wherein the content of the wax contained in 100 g of the aqueous inkjet ink is W (g) and the content of the binder resin contained in 100 g of the aqueous inkjet ink is R (g), and the value expressed by R / W is 15 or less.

4. The water-based inkjet ink according to claim 1 or 2, further comprising (C) a glycol monoether having a terminal alkyl group with 2 to 4 carbon atoms.

5. The aqueous inkjet ink according to claim 2, further comprising glycol monoethers (C) having a terminal alkyl group with 2 to 4 carbon atoms, wherein the content of the wax contained in 100 g of the aqueous inkjet ink is W (g) and the content of the binder resin contained in 100 g of the aqueous inkjet ink is R (g), and the value expressed as R / W is 15 or less.

6. A printed matter obtained by printing the aqueous inkjet ink according to claim 1 or 2 onto a printing substrate.

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