Aqueous inkjet ink and printed matter

Abstract

To provide an aqueous inkjet ink by which a printed matter having excellent water resistance and scratch resistance can be created, and which is simultaneously equipped with high discharge stability.SOLUTION: Aqueous inkjet ink contains water, diols, binder resin and wax, where the diols contain diols (A) which have SP value of 10.0 or more and less than 12.0 and contain branched alkylene group, and diols (B) which have SP value of 12.0 or more and 15.0 or less, and a difference between the boiling point of the diols (A) under 1 atmospheric pressure and the boiling point of the diols (B) under 1 atmospheric pressure is 30°C or less. Preferably, the wax contains polyolefin-based wax having the melting point under 1 atmospheric pressure of 100°C or more and 170°C or less.SELECTED DRAWING: None

Description

Technical Field

[0001] Embodiments of the present invention relate to an aqueous inkjet ink and a printed matter produced using the aqueous inkjet ink.

Background Art

[0002] Unlike the plate printing methods represented by the gravure printing method and the offset printing method, the digital printing method does not require a plate, and thus has advantages such as miniaturization of the printing apparatus and reduction of printing costs. Further, in an inkjet printing method which is a kind of digital printing method, ink is ejected from nozzles of an inkjet head and adhered to a printing substrate, thereby recording characters and / or images. In addition to the features of the digital printing method described above, the inkjet printing method also has advantages such as low noise during printing, low cost of the printing apparatus, and easy colorization.

[0003] In the present disclosure, a printing substrate on which characters and / or images are recorded is collectively referred to as a "printed matter". Further, the above "image" includes seamless images such as solid images and checkered images.

[0004] Inks used in the inkjet printing method (also referred to as "inkjet inks" in the present disclosure) are classified into solvent-based, water-based, ultraviolet curable, etc. according to their composition. On the other hand, in recent years, the movement to regulate the use of raw materials harmful to humans and the environment has been accelerating. Along with this, there is an increasing demand for water-based inkjet inks (also simply referred to as "aqueous inkjet inks" in the present disclosure) instead of solvent-based inkjet inks and ultraviolet curable inkjet inks that use these raw materials.

[0005] In recent years, with the improvement of the performance of inkjet heads, the industrial application of the inkjet printing method has been advanced. In particular, in the commercial printing market and the packaging (label / package) printing market, in addition to being able to effectively utilize the advantages of the above-mentioned inkjet printing method, it is highly suitable for printing in small lots and with many varieties. Therefore, the replacement from the conventional plate printing method to the inkjet printing method is being actively considered.

[0006] In the above-mentioned packaging printing market, in order to protect the printed surface from friction, immersion in water, etc., laminating the printed surface (the surface to which ink is applied) with a transparent film (laminate film) is generally performed. However, in recent years, there has also been a movement to eliminate laminate films from the perspective of resource conservation and environmental protection. In order to respond to such a movement, it is required to impart various resistances (scratch resistance, water resistance, solvent resistance, etc.) to printed matter so that the printed characters and / or images do not disappear even without the above-mentioned laminate film.

[0007] As a means of improving the various resistances of printed matter produced using water-based inkjet ink, there is a method of promoting the film formation of the binder resin contained in the water-based inkjet ink and increasing 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 kinds of resin particles. Further, Patent Document 1 describes that due to the presence of at least one of the above-mentioned amide compound and oxetane compound, a state in which the above two or more kinds of resin particles are preferably mixed can be obtained in the process of the ink drying on the printing substrate, and as a result, even a printed matter on a non-permeable substrate has excellent scratch resistance and solvent resistance.

[0008] Patent Document 2 also discloses an ink for inkjet recording that contains two types of resin particles having different volume average particle diameters and heat distortion temperatures, and furthermore, one of the two types of resin particles is a urethane resin. It is also described that by using the resin particles in combination, it is possible to prevent clogging of the nozzles and smooth the printed surface. Furthermore, the ink described in Patent Document 2 can contain wax particles as the third resin particles, and it has been shown that the wax particles can impart slipperiness to the surface of the printed matter and enhance its abrasion resistance (see paragraph numbers 0054 to 0055).

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0010] In the technology disclosed in Patent Document 1, the presence of a compound that has a high affinity for resin particles and promotes the mixing of the resin particles with each other also increases the risk of ink sticking in the vicinity of the nozzles of the inkjet head. As a result of investigations by the present inventors, it was confirmed that by using such a compound, the ejection stability may be impaired depending on the printing conditions and the like. On the other hand, in the examples of Patent Document 1 and the like, the ejection stability has not been evaluated, and it is difficult to say that the ejection stability has been sufficiently investigated.

[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, which may impair the ejection stability. Also, depending on the above raw materials, the orientation of the wax on the printing surface may be inhibited, and thus it may not be possible to obtain a sufficient effect of improving the abrasion resistance. In fact, among the inks specifically disclosed in the examples of Patent Document 2, there are examples where, despite containing wax particles, the clogging property of the nozzles, that is, the ejection stability is poor, and examples where the abrasion resistance is poor. Furthermore, Patent Document 2 does not specifically describe a method for enhancing the water resistance of printed matter.

[0012] As described above, it can be said that the study for obtaining an aqueous inkjet ink that can produce a printed matter excellent in water resistance and abrasion resistance and at the same time has high ejection stability has not yet been sufficiently carried out.

[0013] Embodiments of the present invention have been made to solve the above-described problems, and one of the objects is to provide an aqueous inkjet ink that can produce a printed matter excellent in water resistance and abrasion resistance and at the same time has high ejection stability.

Means for Solving the Problems

[0014] As a result of intensive studies by the present inventors, it has been found that the above-described problems can be solved by an aqueous inkjet ink having the following configuration.

[0015] That is, some embodiments of the present invention relate to an aqueous inkjet ink shown in the following [1] to [5], and a method for manufacturing a printed matter using the above aqueous inkjet ink shown in [6] below. [1] An aqueous inkjet ink containing water, diols, a binder resin, and 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, An aqueous inkjet ink in which the difference between the boiling point of the diols (A) under 1 atm and the boiling point of the diols (B) under 1 atm is 30°C or less. [2] The aqueous inkjet ink according to [1], wherein the wax contains a polyolefin wax having a melting point of 100°C or higher and 170°C or lower under 1 atm. [3] The aqueous inkjet ink according to [2], wherein when 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), the value represented by R / W is 15 or less. [4] The aqueous inkjet ink according to [1] or [2], further containing glycol monoethers (C) having 2 to 4 carbon atoms in the terminal alkyl group. [5] Further containing glycol monoethers (C) having 2 to 4 carbon atoms in the terminal alkyl group, [5] The aqueous inkjet ink according to [2], wherein when 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), the value represented by R / W is 15 or less. [6] A printed matter obtained by printing the aqueous inkjet ink according to any one of [1] to [5] on a printing substrate.

Advantages of the Invention

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

Modes for Carrying Out the Invention

[0017] The following describes an aqueous inkjet ink according to an embodiment of the present invention (hereinafter referred to as "the aqueous inkjet ink of the present embodiment" or simply "ink"). The present invention is not limited to the embodiments described below, and also includes forms that can be implemented with modifications without changing the essential part of the present invention.

[0018] The aqueous inkjet ink of the present embodiment having the above-described configuration can provide a printed matter excellent in water resistance and rubbing resistance. Also, for example, even when printing is resumed after a long pause, the ejection property does not deteriorate. Although the mechanism is not clear, the present inventors presume as follows. However, the present invention is not limited by the following presumption.

[0019] As described above, it is widely known that adding a binder resin to the ink is a means of improving the rubbing resistance and water resistance of the printed matter. Also, in order to impart good rubbing resistance and water resistance to the printed matter, it is necessary to sufficiently form a film of the binder resin. Therefore, in the present embodiment, diols (A) having an SP value of 10.0 or more and less than 12.0 and having a branched alkylene group are used together with the binder resin. The diols (A) have water solubility due to the presence of a plurality of hydroxyl groups, and can also ensure affinity with the resin component due to the low SP value and the presence of the branched alkylene group. As a result, in the ink droplets after printing, after the main component water has volatilized, the binder resin is softened by the diols (A), thereby enabling efficiency improvement of film formation and uniformity of the film, and improving the rubbing 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), sufficient abrasion resistance may not be imparted to the printed matter. In such a case, as described in Patent Document 2 above, the addition of wax as a means for improving abrasion resistance is known. Wax oriented on the surface of the dried ink film (ink film) melts by heating and / or pressurization, thereby imparting slipperiness to the film and improving abrasion resistance. In the present embodiment, it is more preferable to use a wax having a melting point of 100 to 170°C. By using such a wax, the wax does not melt in a static environment or the like. Further, slipperiness is exhibited under general use conditions such as when the printed matter is touched by a finger, and the effect of improving abrasion resistance is particularly excellent.

[0021] However, since the above-described diols (A) also affinity with wax which is a kind of resin component, when the above-described diols (A) and wax are used in combination, the wax may be destabilized in the ink. As a result, for example, aggregation, precipitation, etc. of wax may occur in the inkjet head, which may cause deterioration of ejection stability. Also after printing, the orientation of the wax on the film surface described above may be hindered, and there is a possibility that good abrasion resistance cannot be obtained.

[0022] As a result of intensive studies by the present inventors, by using diols (B) having an SP value of 12.0 or more together with the above-mentioned diols (A), and further making the difference between the boiling point of diols (A) and the boiling point of diols (B) 30°C or less, aggregation, precipitation, etc. of wax in the above-mentioned inkjet head are suppressed. For example, even after a long pause, the ejection stability becomes good. Furthermore, it has been found that it is possible to produce a printed matter having good abrasion resistance. Although the details of the reason are not clear, diols (B) having a high SP value of 12.0 or more are highly compatible with water and diols (A), but are considered to be inferior in affinity with the resin component compared with the diols (A). As a result, in the inkjet head, it is considered that diols (B) inhibit the affinity between diols (A) and wax, thereby preventing the aggregation and precipitation of the wax and improving the ejection stability. In addition, since the boiling point of diols (B) is almost the same as that of diols (A), it is considered that after water, which is the main component, evaporates in the ink droplet after printing, diols (B) remain in the droplet together with the diols (A). As a result, similar to the behavior in the above-mentioned inkjet head, in the ink droplet as well, a state where wax and diols (A) are less likely to be compatible is maintained. As a result, the orientation of the wax on the film surface is less likely to be inhibited by the diols (A), and improvement in 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. Specifically, in the present embodiment, in an aqueous inkjet ink combining water, diols (A), a binder resin, and wax, it has been found that diols (B) may be used in order not to impair the effects of the wax.

[0024] Incidentally, the water-based inkjet ink specifically disclosed in Patent Document 1 is different from the water-based inkjet ink of the present embodiment in that it does not contain wax. Further, the water-based inkjet ink specifically disclosed in Patent Document 2 is different from the water-based inkjet ink of the present embodiment in that its SP value is 10.0 or more and less than 12.0 and it does not contain diols (A) having a branched alkylene group.

[0025] Subsequently, each component constituting the water-based inkjet ink according to one embodiment will be described in detail below.

[0026] <Diols> The water-based inkjet ink of the present embodiment contains diols. Further, as described above, 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.

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

[0028] The "SP value" in the present disclosure is an abbreviation for "Solubility Parameter". As a method for obtaining the SP value, a method of calculating from physical property values of a compound, a method of calculating from a molecular structure, a method of actually measuring by experiment, etc. are known. In the present disclosure, as the above SP value, a value calculated by Fedor's estimation method represented by the following formula 1 is used.

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

[0030] In the above formula (1), Ecoh represents the cohesive energy defined for each functional group, and V represents the molar molecular volume defined for each functional group. The above 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, as the unit of the SP value, (cal / cm 3 ) 1 / 2 is used.

[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 the present embodiment, as the diols (A), 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), 2,3-dimethyl-2,3-butanediol (11.3, 174 °C), etc. can be used. These compounds may be used alone or in combination of two or more. The numerical values in the parentheses above are the SP values (unit: (cal / cm 3 ) 1 / 2 ) and the boiling points under 1 atm.

[0033] Among them, since it is easy to be compatible with both water and the binder resin component, the efficiency of film formation and the uniformity of the film are facilitated, and the abrasion resistance and water resistance of the printed matter are improved. Therefore, as the diols (A), it is preferable to use a compound having 6 carbon atoms. Among them, from the viewpoint of excellent drying property and particularly good water resistance of the printed matter, it is particularly preferable to use hexylene glycol.

[0034] Also, from the viewpoint of being easily compatible with both water and the binder resin component and improving the rubbing resistance and water resistance of the printed matter, the SP value of the diols (A) is preferably 10.5 or more and less than 12.0, and particularly preferably 11.2 or more and less than 12.0.

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

[0036] Furthermore, from the viewpoint of improving the discharge stability regardless of the use conditions and obtaining a printed matter excellent in rubbing resistance and water resistance, the content of the diols (A) is preferably 0.5 to 19% by mass, more preferably 1.2 to 16% by mass, and particularly preferably 2 to 12% by mass in the total amount of the aqueous inkjet ink.

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

[0038] ≪Diols (B) with an SP value of 12.0 or more≫ In the aqueous inkjet ink of the present embodiment, as the diols (B), 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 (12.2, 206 °C), 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), triethylene glycol (12.1, 287 °C), etc. can be used. These compounds may be used alone or in combination of two or more. The numerical values in the parentheses above are the SP values (unit: (cal / cm 3 ) 1 / 2 ) and the boiling points under 1 atm.

[0039] Among them, from the viewpoint that the affinity with the diols (A) is moderately increased, the affinity between the diols (A) and the wax is inhibited, and the ejection stability is improved, the SP value of the diols (B) is 12.0 to 14.0 (cal / cm 3 ) 1 / 2 is preferably, and particularly preferably 12.5 to 13.5 (cal / cm 3 ) 1 / 2 . Also, considering the affinity with water, it is preferable to use a compound having 3 to 4 carbon atoms. Among the compounds listed above, as the compounds satisfying these requirements, for example, 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 can be mentioned. In the aqueous inkjet ink of the present embodiment, it is preferable to use one or more of these compounds as the diols (B).

[0040] The diols (B) may be solid or liquid at 25°C, but are more preferably water-soluble organic solvents that are liquid at 25°C.

[0041] Also, from the perspective of achieving both moisture retention (discharge stability) at the inkjet nozzle and drying and water resistance of the printed matter, the content of the above diols (B) is preferably 1 to 30% by mass, more preferably 4 to 25% by mass, and particularly preferably 6 to 20% by mass in the total amount of the aqueous inkjet ink.

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

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

[0044] As described above, by setting the difference between the boiling points of the diols (A) and the diols (B) to 30°C or less, aggregation of the wax can be suppressed during the ink drying process. In addition, since the orientation of the wax on the film surface is less likely to be inhibited by the diols (A), it becomes possible to produce a printed matter having good abrasion resistance. From the viewpoint that both the diols (A) and the diols (B) are likely to remain in the ink droplets on the printing substrate and the above-described effects are more likely to be preferably exhibited, it is considered that the smaller the difference in the boiling points, the better. Specifically, the difference between the boiling point of the diols (A) at 1 atm and the boiling point of the diols (B) at 1 atm is preferably 20°C or less, and particularly preferably 15°C or less. For example, this difference in boiling points may be 0 to 10°C.

[0045] When two or more types of diols (A) are contained in the aqueous inkjet ink, the difference in the boiling points shall be calculated using the weighted average value of the boiling points of the two or more types of diols (A). The same applies to the diols (B). However, the "weighted average value of the boiling points" is a value obtained by adding up the multiplication values of the boiling point and the mass ratio with respect to the total content of the water-soluble organic solvent, calculated for each compound.

[0046] <Water-soluble organic solvent> The aqueous inkjet ink of the present embodiment may contain a water-soluble organic solvent. In the present disclosure, the "water-soluble organic solvent" represents an organic compound having a solubility in water at 25°C of 1 mass% or more and being liquid at 25°C. In addition, among the compounds contained in the above-described diols (A) and diols (B), the compounds satisfying the above conditions shall also be included in the "water-soluble organic solvent" in the present disclosure.

[0047] ≪Other diols≫ For example, as the water-soluble organic solvent of the aqueous inkjet ink of the present embodiment, diols that do not correspond to the above diols (A) and the above diols (B) (referred to as "other diols" in the present disclosure) can be used. Examples of the other diols include 1,2-hexanediol and 1,2-heptanediol.

[0048] ≪Glycol monoethers (C) in which the number of carbon atoms of the terminal alkyl group is 2 to 4≫ In addition, the aqueous inkjet ink of the present embodiment may contain glycol monoethers (C) in which the number of carbon atoms of the terminal alkyl group is 2 to 4 as the water-soluble organic solvent. By including the glycol monoethers (C) in the inkjet ink of the present embodiment, together with the above-mentioned diols (A), the binder resin can be softened more, and the efficiency of film formation and the uniformity of the film are promoted, so that the abrasion resistance and water resistance of the printed matter are further improved. Further, when the aqueous inkjet ink of the present embodiment contains a surfactant, for example, the orientation of the surfactant in the inkjet head is suppressed by the glycol monoethers (C), so that the ejection stability, particularly the ejection stability after a short pause, is further improved.

[0049] As the glycol monoethers (C), for example, propylene glycol monopropyl ether, propylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, etc. may be mentioned. When the inkjet ink of the present embodiment contains glycol monoethers (C), among the above-listed compounds, 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. These compounds have particularly good affinity with the binder resin, and can be preferably used because the rub resistance and water resistance of the printed matter are further improved when used in combination with diols (A). More preferably, it is propylene glycol monopropyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, or a combination thereof.

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

[0051] Furthermore, from the viewpoint of suppressing the aggregation of wax and achieving both the rub resistance of the printed matter and the ejection stability during printing, when the aqueous inkjet ink of the present embodiment contains glycol monoethers (C), the total content of the above diols (A) (however, only the compounds corresponding to the water-soluble organic solvents) and the above glycol monoethers (C) having a similar effect 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 in the total amount of the water-soluble organic solvents contained in the aqueous inkjet ink.

[0052] Further, from the viewpoint of improving the rubbing resistance of the printed matter and the ejection stability during printing due to the same effects as described above, when the aqueous inkjet ink of the present embodiment contains glycol monoethers (C), the total content of the above diols (A) and the above 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, with respect to the total content of the water-soluble organic solvent, the compound which is a diol (A) and not a water-soluble organic solvent, and the compound which is a diol (B) and not a water-soluble organic solvent.

[0053] ≪Other Water-Soluble Organic Solvents≫ In the aqueous inkjet ink of the present embodiment, in addition to the compounds listed above, as the water-soluble organic solvent, alkanetriols (however, those having 3 to 6 carbon atoms); polyoxyalkylene glycols (however, the oxyalkylene group is an oxyethylene group or an oxypropylene group, and the number of the oxyalkylene groups is 2 to 4); glycol monoethers having a terminal alkyl group with 1 carbon atom; glycol diethers (however, those having 1 to 4 carbon atoms for each of the two terminal alkyl groups); lactams (however, those having 5 to 7 atoms constituting the lactam ring. Further, a C1-C2 alkyl group, a C1-C2 hydroxyalkyl group, or a vinyl group may be bonded to the nitrogen atom and / or carbon atom constituting the lactam ring); alkanolamines (however, those having 1 amino group, 1 to 3 hydroxyl groups, and 3 to 9 carbon atoms); etc. can be used. These water-soluble organic solvents may be used alone or in combination of two or more.

[0054] In addition, when the aqueous inkjet ink of the present embodiment contains other water-soluble organic solvents, it is preferable to use a water-soluble organic solvent having a static surface tension of 29 to 50 mN / m at 25°C as the other water-soluble organic solvent. By using the water-soluble organic solvent having the above surface tension, it is possible to maintain an appropriate surface tension for ejection as inkjet ink, and the ejection stability can be made good even after a long-term pause, for example.

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

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

[0057] The total content of the water-soluble organic solvent contained in the aqueous inkjet ink of the present embodiment is preferably 5 to 50% by mass, more preferably 9 to 40% by mass, still more preferably 12 to 35% by mass, and particularly preferably 15 to 30% by mass in the total amount of the aqueous inkjet ink. By setting the total content of the water-soluble organic solvent within the above range, an appropriate viscosity for ejection as an aqueous inkjet ink can be maintained, and the ejection stability can be made good even after a long-term pause, for example. Note that the total content of the water-soluble organic solvent includes the content of the compound corresponding to the requirements of the above-described water-soluble organic solvent among the above-described diols (A) and diols (B).

[0058] Further, since the water resistance, rubbing resistance, and ejection stability of the printed matter can be improved simultaneously, the total content of the water-soluble organic solvent, the compound which is a diol (A) but not a water-soluble organic solvent, and the compound which is a diol (B) but not a water-soluble organic solvent is preferably 5 to 50% by mass, more preferably 9 to 40% by mass, still more preferably 12 to 35% by mass, and particularly preferably 15 to 30% by mass in the total amount of the aqueous inkjet ink.

[0059] Note that from the viewpoint that the binder resin is preferably softened and the rubbing resistance and water resistance of the printed matter are improved, the content of the above-described diols (A) with respect to the total of the content of the water-soluble organic solvent, the compound which is a diol (A) but not a water-soluble organic solvent, and the compound which is a diol (B) but not a water-soluble organic solvent is preferably 10 to 49% by mass, more preferably 15 to 42% by mass, and particularly preferably 20 to 35% by mass.

[0060] In addition, from the viewpoints of suppressing the aggregation and precipitation of wax, improving the ejection stability, and also improving the abrasion resistance, the content of the diol compound (B) that is not a water-soluble organic solvent with respect to the total content of the water-soluble organic solvent, the diol compound (A) that is not a water-soluble organic solvent, and the diol compound (B) that 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 the present embodiment, the content of the water-soluble organic solvent having a boiling point of 250°C or higher under 1 atm is preferably 1% by mass or less (it may be 0% by mass) in the total amount of the aqueous inkjet ink. By not containing a water-soluble organic solvent having a boiling point of 250°C or higher or, even if containing, setting the blending amount within the above range, for example, even after a long-term pause, the ejection stability becomes good.

[0062] For the same reason, that is, from the viewpoint of improving the ejection stability, the total content of the water-soluble organic solvent having a boiling point of 250°C or higher under 1 atm, the diol compound (A) that is not a water-soluble organic solvent and has a boiling point of 250°C or higher under 1 atm, and the diol compound (B) that is not a water-soluble organic solvent and has a boiling point of 250°C or higher under 1 atm is preferably 1% by mass or less (it may be 0% by mass) in the total amount of the aqueous inkjet ink.

[0063] Furthermore, when the aqueous inkjet ink of the present embodiment contains a water-soluble organic solvent, the water-soluble organic solvent preferably has a boiling point (weighted average value) of 120 to 215°C under 1 atm, and particularly preferably 150 to 200°C under 1 atm. By setting the boiling point (weighted average value) within the above range, both the ejection stability and the abrasion resistance and water resistance of the printed matter can be achieved.

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

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

[0066] <Binder resin> The aqueous inkjet ink of the present embodiment contains a binder resin in that it can impart water resistance and rub resistance to the printed matter, and further, the above-described aqueous inkjet ink printed on a hardly permeable substrate or a non-permeable substrate increases in viscosity at a speed on the order of microseconds as it dries, so that bleeding (a phenomenon in which aqueous inkjet inks having different colors mix with each other) and beading (a phenomenon in which droplets of the aqueous inkjet ink attract and combine with each other) are suppressed, and a printed matter with excellent print quality can be obtained.

[0067] In the present disclosure, the "binder resin" is a resin used to bind the ink film to the printing substrate. For example, in the total resin amount contained in the aqueous inkjet ink of the present embodiment, it is preferable that 50% by mass of the resin contained is the binder resin in the present disclosure. Further, the "resin" refers to a compound formed by polymerization of a plurality of polymerizable monomers and having a mass average molecular weight of 1,000 or more.

[0068] In the present disclosure, as the mass average molecular weight of the compound, a polystyrene equivalent value measured by a method conforming to JIS K 7252 is used. Examples of specific measurement conditions are shown below. · Apparatus used: "HLC-8320GPC" manufactured by Tosoh Corporation · Columns used: TSKgel (registered trademark) SuperMultipore HZ-M (3 columns) · Column temperature: 40°C · Developing solvent: Tetrahydrofuran · Flow rate: 0.6 mL / min · Concentration of sample solution: 0.1 mass% · Injection volume of sample solution: 10 μL

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

[0070] In the present 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". Among the above water-insoluble resins, a resin that is dispersed in a particulate form in water and has a median diameter (also described as "D50" in the present disclosure) based on volume of 10 to 1,000 nm is referred to as "resin fine particles".

[0071] D50 in the present disclosure is a value measured using a dynamic light scattering particle size distribution measuring device such as "NanoTrac UPA-EX150" manufactured by Microtrac Bel Co., Ltd., with water as the dispersion medium and in an environment at 25°C.

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

[0073] Among these, since prints excellent in water resistance and rubbing resistance can be obtained, it is preferable to use one or more resins selected from the group consisting of acrylic resins (excluding acrylic-silicone copolymers described later), urethane resins (excluding urethane-silicone copolymers described later), and polyester resins, and it is more preferable to use at least acrylic resins (excluding acrylic-silicone copolymers described later).

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

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

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

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

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

[0079] On the other hand, when the wax that can be used in the aqueous inkjet ink of this embodiment is classified by chemical structure, hydrocarbon wax, ester wax (for example, fatty acid ester), silicone wax (for example, an acrylic resin having a silicone chain (siloxane chain) structure (acrylic-silicone copolymer), a urethane resin having a silicone chain structure (urethane-silicone copolymer), and a fatty acid ester having a silicone chain structure), polyalkylene glycol wax (for example, polyethylene glycol having a mass average molecular weight of 600 or more, polypropylene glycol having a mass average molecular weight of 10,000 or more, and a polyethylene glycol-polypropylene glycol copolymer having a mass average molecular weight of 6,000 or more), etc. can be mentioned. Among acrylic resins having a silicone chain structure, those having a glass transition temperature of 50°C or higher generally have a high possibility of not satisfying the above melting point conditions, and thus do not correspond to the wax in this embodiment.

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

[0081] Among them, hydrocarbon waxes and / or silicone waxes can be preferably used, and hydrocarbon waxes can be more preferably used, in that printed matter having excellent abrasion resistance and print image quality can be obtained with respect to various printing substrates. Further, examples of the hydrocarbon waxes include natural waxes such as paraffin wax and microcrystalline wax, and synthetic waxes such as polyolefin waxes and Fischer-Tropsch waxes. Among them, polyolefin waxes can be more preferably used as the hydrocarbon waxes. By including polyolefin waxes, the binder resin and the polyolefin wax form microscopic clusters respectively, and when the aqueous inkjet ink dries, the bias of the components contained in the aqueous inkjet ink is suppressed and beading is improved. Further, the clusters function to prevent local drying and viscosity increase in the vicinity of the inkjet nozzle, thereby improving the ejection stability.

[0082] Examples of the polyolefin waxes include polyethylene waxes and polypropylene waxes. Among them, from the viewpoints of improving the ejection stability and the abrasion resistance of the printed matter, it is preferable to use polyethylene waxes. The polyolefin waxes may be used alone or in combination of two or more.

[0083] Further, the polyolefin waxes are preferably soft polyolefins having a mass average molecular weight of 500 to 10,000. The mass average molecular weight is particularly preferably 600 to 8,000.

[0084] When using resin fine particles as the wax, its D50 is preferably 5 to 300 nm, more preferably 30 to 250 nm, and particularly preferably 40 to 200 nm. If the D50 of the wax is 5 nm or more, the abrasion resistance of the printed matter is improved. If it is 300 nm or less, not only the ejection stability is improved, but also a printed matter having excellent print quality regardless of the printing substrate can be obtained. The D50 of the wax can be measured by the same method as the D50 of the resin fine particles described above.

[0085] The wax having the form of resin fine particles can be produced, for example, by mixing a resin that is a normal-temperature solid heated and melted, hot water, and an emulsifier. Also, commercially available products can be used as the wax. For example, AQUACER-507, 513, 515, 526, 531, 533, 535, 537, 539, 552, 840, 593, 1547, HORDAMER PE 02, PE 03 manufactured by BYK Chemie; Nopcoat PEM-17 manufactured by San Nopco; JONCRYLWAX4, WAX26, WAX28, WAX120, etc. manufactured by BASF; High-Tech E series and High-Tech P series manufactured by Toho Chemical Industry Co., Ltd.; Charine FE230N, FE502, etc. manufactured by Shin-Etsu Chemical Co., Ltd.

[0086] It is possible to achieve both ejection stability and scratch resistance of the printed matter, and furthermore, in terms of obtaining a high-concentration 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 in the total mass of the aqueous inkjet ink. For the same reason, when the wax content in the total mass of the aqueous inkjet ink is W (% by mass) and the binder resin content is R (% by mass), the value represented by R / W is preferably 1 to 15, and particularly preferably 3 to 13. When R / W is 22 or less, preferably 15 or less, the scratch resistance of the printed matter can be further improved. When R / W is 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, still more preferably 2 to 14, and even more preferably 5 to 13. Within these ranges, the scratch resistance, water resistance, and ejection stability of the printed matter can be further improved.

[0087] As described above, in the present disclosure, the wax and the binder resin can be distinguished by their melting points. That is, the wax in the present disclosure is a compound that is solid at normal temperature (25°C) and has a melting point of 40 to 200°C. The melting point of the wax is preferably 100 to 170°C, and particularly preferably 110°C to 150°C. On the other hand, the binder resin in the present disclosure is, for example, a compound that is solid at normal temperature (25°C) and has a melting point higher than 200°C, or a compound that is solid at normal 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, the destabilization of the wax is suppressed, and it becomes easier to achieve both ejection stability and scratch 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 conversion.

[0089] <Colorant> The aqueous inkjet ink of the present embodiment may contain a colorant. As the colorant, conventionally known dyes and pigments can be used. Among them, pigments are preferably used because prints with high concentration or hiding power, excellent light resistance, water resistance, etc. can be obtained, and after landing on the printing substrate, they moderately dry and thicken, suppressing color mixing between aqueous inkjet inks and improving the printing image quality.

[0090] As the above pigments, conventionally known organic and inorganic pigments can be arbitrarily used. For example, pigments represented by the following Color Index names can be used. That is, as red pigments, 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, 282; As violet 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. 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 two or more of them may be used in combination. Also, a solid solution composed of two or more of the above-listed pigments can be used as a pigment.

[0091] The content of the pigment contained in the aqueous inkjet ink of this embodiment is adjusted according to the use purpose of the printed matter produced using the aqueous inkjet ink. For example, it is preferably 0.5 to 30% by mass in the total amount of the aqueous inkjet ink. Also, except in the case of white aqueous inkjet ink (aqueous white ink), from the point that a printed matter with a high density can be obtained without deteriorating the ejection stability of the aqueous inkjet ink, the content of the above pigment is more preferably 1 to 15% by mass, and particularly preferably 1.5 to 10% by mass. On the other hand, in the case of aqueous white ink, from the point that a printed matter with high hiding power can be obtained without deteriorating the ejection stability of the aqueous white ink, the content of the above pigment is more preferably 5 to 25% by mass, and particularly preferably 10 to 20% by mass.

[0092] <Pigment dispersion resin> When the aqueous inkjet ink of the present embodiment contains a pigment, a resin used for pigment dispersion (pigment dispersion resin) can be used. By selecting and examining the composition and mass average molecular weight of the polymerizable monomers constituting the pigment dispersion resin, the coating ability and charge of the pigment dispersion resin with respect to the pigment can be easily adjusted. Therefore, it is possible to impart dispersion stability even to fine pigments, and furthermore, it is possible to obtain a printed matter excellent in ejection stability, color development property, and color reproducibility.

[0093] The type of the pigment dispersion resin is not particularly limited, and resins such as acrylic resins (however, excluding the above-described acrylic-silicone copolymers), styrene resins, styrene-(anhydrous) maleic acid resins, olefin-(anhydrous) maleic acid resins, urethane resins (however, excluding the above-described urethane-silicone copolymers), polyester resins, vinyl chloride resins, vinyl chloride-vinyl acetate resins, polyolefin resins, and polyvinyl alcohol resins can be used. Among them, it is preferable to use one or more selected from the group consisting of acrylic resins, urethane resins, polyester-based resins, and polyolefin-based resins in terms of ejection stability, the magnitude of material selectivity, ease of synthesis, and the like.

[0094] The pigment dispersion resin may be synthesized by a known method or may be a commercially available product. There is also no particular limitation on its structure, and resins having, for example, a random structure, a block structure, a comb structure, a star structure, etc. can be used. Further, as the pigment dispersion resin, a water-soluble resin may be selected or a water-insoluble resin may be selected. Note that examples of the case where the pigment dispersion resin is a water-insoluble resin include resin fine particles containing a pigment. Further, when the aqueous inkjet ink contains a water-soluble resin, whether or not the water-soluble resin is a pigment dispersion resin can be confirmed by a method based on JIS K 5101-1-4.

[0095] Specifically, the primary particle diameter is 15 to 25 nm, the nitrogen adsorption specific surface area is 120 to 260 m 2 / g, and the DBP absorption amount (granular) is 40 to 80 cm 3600 g of carbon black, which is 100 g / 100 g, 300 g of the target water-soluble resin, and 2,100 g of water are thoroughly mixed (premixed). After that, using a bead mill with a volume of 0.6 L (for example, "Dyno Mill" manufactured by Simar Enterprises Co., Ltd.) filled with 1,800 parts of grinding beads (for example, zirconia beads with a diameter of 0.5 mm), dispersion is carried out for 4 hours. After dispersion, the viscosity of the obtained carbon black dispersion at 25°C is measured using an E-type viscometer (for example, "TVE25L-type viscometer" manufactured by Toki Sangyo Co., Ltd.). Then, the carbon black dispersion is stored in a forced-air constant-temperature thermostat set at 70°C for one week, and the viscosity is measured again. At this time, 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, it is determined that the above water-soluble resin is a pigment dispersion resin.

[0096] Furthermore, regardless of whether it is a water-soluble resin or a water-insoluble resin, the pigment dispersion resin may also have the function of 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 regardless of the use conditions, it can be stably discharged from the inkjet head. In addition, the solubility of the pigment dispersion resin in water can be ensured, and the interaction between the pigment dispersion resins becomes suitable, so that the viscosity of the pigment dispersion can be suppressed, which is also preferable from the point of expressing good dischargeability from the inkjet head.

[0098] On the other hand, when a water-insoluble resin is used as the pigment dispersion 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. If the acid value is within the above range, a printed matter with excellent drying properties and good printing quality can be obtained.

[0099] The acid value of the resin can be measured by a known apparatus. The acid value of the resin in the present disclosure is a value measured by the potentiometric titration method in accordance with JIS K 2501. As an example of a specific measurement method, after dissolving the resin in a toluene-ethanol mixed solvent using an AT-610 manufactured by Kyoto Electronics Industry Co., Ltd., it is titrated with a potassium hydroxide solution, and the acid value is calculated from the titration amount up to the end point.

[0100] In the aqueous inkjet ink of the present embodiment, from the viewpoint of improving the adsorption ability to the pigment and ensuring the dispersion stability and ejection stability, it is preferable to introduce an aromatic group into the pigment dispersion 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 them, a phenyl group, a naphthyl group, and a tolyl group are preferable from the viewpoint of sufficiently ensuring the dispersion stability.

[0101] From the viewpoints of improving the dispersion stability and ejection stability of the pigment, as well as the printing image quality and drying property of the printed matter, the introduction amount of the monomer containing an aromatic ring is preferably 5 to 75% by mass, more preferably 5 to 65% by mass, and even more preferably 10 to 50% by mass based on the total amount of the monomers constituting the pigment dispersion resin.

[0102] <Surfactant> The aqueous inkjet ink of the present embodiment may contain a surfactant. As the surfactant, an acetylene diol-based surfactant, an acetylene monoalcohol-based surfactant, a siloxane-based surfactant (however, excluding the above-described acrylic-silicone copolymer (having a glass transition temperature of less than 50°C), urethane-silicone copolymer, and fatty acid ester having a silicone chain structure), a fluorine-based surfactant, a polyoxyalkylene monoalkyl ether-based surfactant (however, excluding those having a terminal alkyl group with 1 to 4 carbon atoms); etc. can be used. These surfactants may be used alone or in combination of two or more.

[0103] Among them, the surface tension of the aqueous inkjet ink of the present embodiment can be significantly reduced in a very short time, and the printing image quality of the printed matter is improved. Also, for a printing substrate with a relatively large interfacial free energy, since the wettability is good, as the above surfactant, it is preferable to use one or more surfactants selected from the group consisting of acetylene diol-based surfactants and siloxane-based surfactants.

[0104] Examples of commercially available products of acetylene diol preferably 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 Co., Ltd.), Orfin (registered trademark) E1004, PD-001, PD-002W, PD-004 (manufactured by Nissin Chemical Industry Co., Ltd.), etc. Among them, from the viewpoint of excellent ejection stability, it is preferable to use Surfynol 440 and / or Surfynol 2502.

[0105] Examples of commercially available products of siloxane-based surfactants preferably 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, TEGO Glide 450 manufactured by Evonik Japan Co., Ltd.; Silface SAG series of Nissin Chemical Industry Co., Ltd., etc. Among them, 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. As the water contained in the ink, it is preferable to use ion-exchanged water (deionized water) rather than general water containing various ions. Further, the water content is preferably 45 to 75% by mass, and particularly preferably 50 to 70% by mass with respect to the total amount of the aqueous inkjet ink. Since water has a low boiling point, for example, it preferentially volatilizes at the nozzle end face of the inkjet head, and the solid content concentration at the gas-liquid interface tends to increase. As a result, film formation of the binder resin, non-uniformity of the surfactant, thickening of the aqueous inkjet ink, etc. may occur, leading to a possible deterioration in ejection stability. On the other hand, by setting the water content within the above range, for example, even after a long-term pause, the ejection stability becomes good.

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

[0108] <Method for producing aqueous inkjet ink> The aqueous inkjet ink of this embodiment can be manufactured by a conventionally known method. For example, when using a water-insoluble material (water-insoluble colorant) as the colorant, a water-insoluble colorant dispersion in which the water-insoluble colorant is dispersed in a medium containing at least water (aqueous medium) is manufactured in advance. On the other hand, when using a water-soluble material (water-soluble colorant) as the colorant, a water-soluble colorant aqueous solution in which the water-soluble colorant is dissolved in an aqueous medium is manufactured in advance. Then, water, diols (A), diols (B), a binder resin, wax, and, if necessary, a water-soluble organic solvent other than the above diols (A) and diols (B), a surfactant, etc. are added to the water-insoluble colorant dispersion and / or the water-soluble colorant aqueous solution, and after sufficiently stirring and mixing, a method of removing coarse particles by means such as filtration and centrifugation can be mentioned. However, the manufacturing method of the aqueous inkjet ink of this embodiment is not limited to the method described above.

[0109] <Properties of Aqueous Inkjet Ink> The aqueous inkjet ink of this embodiment preferably has a viscosity at 25°C of 3 to 15 mPa·s. In this viscosity range, droplets of the aqueous inkjet ink can be stably ejected not only from an inkjet head with a discharge frequency of about 4 to 10 KHz, but also from an inkjet head with a high discharge frequency of about 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 using an inkjet head having a design resolution of 600 dpi or more. In this disclosure, as the viscosity, a value measured in a 25°C environment using a cone-plate type rotational viscometer (E-type viscometer, cone angle 1°34’) such as the “TVE25L type viscometer” manufactured by Toki Sangyo Co., Ltd. is used.

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

[0111] Further, when the aqueous inkjet ink of the present embodiment contains a water-insoluble colorant, from the viewpoint of achieving high levels of both ejection stability and the density or hiding power of printed matter, the median diameter (D50) of the water-insoluble colorant on a volume basis 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 the D50 of the resin fine particles described above.

[0112] <Set of aqueous inkjet inks> The aqueous inkjet ink of the present embodiment may be used alone as only one type, or may be used as a set of two or more types of aqueous inkjet inks combined. Examples of the set of aqueous inkjet inks include a set of four-color aqueous inkjet inks (process color ink set) composed of a cyan-colored aqueous inkjet ink (aqueous cyan ink), a magenta-colored aqueous inkjet ink (aqueous magenta ink), a yellow-colored aqueous inkjet ink (aqueous yellow ink), and a black-colored aqueous inkjet ink (aqueous black ink); a set of five-color aqueous inkjet inks obtained by further adding an aqueous white ink to the process color ink set; and the like. It is preferable that all the aqueous inkjet inks constituting the set of aqueous inkjet inks satisfy the requirements of the present embodiment described above.

[0113] <Ink - pretreatment liquid set> In addition, the aqueous inkjet ink of the present embodiment and the set of the aqueous inkjet ink can also be used in a form combined with a pretreatment liquid containing a flocculant (in the form of an ink-pretreatment liquid set). By applying the pretreatment liquid containing a flocculant onto the printing substrate before printing with the aqueous inkjet ink, a layer (ink flocculation layer) for intentionally aggregating the solid components contained in the aqueous inkjet ink can be formed. Then, by landing the aqueous inkjet ink on the ink flocculation layer, the coalescence and color mixing of the droplets of the aqueous inkjet ink can be prevented, and the printing image quality of the printed matter can be significantly improved.

[0114] Note that as the above flocculant, for example, a water-soluble inorganic salt or organic salt containing polyvalent metal ions, and a resin having a cationic group and a cationic group equivalent larger than the anionic group equivalent can be used.

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

[0116] ≪Ejection step≫ In the ejection process, as the operation method of the inkjet head, there are a shuttle (scan) method in which the inkjet head is reciprocally scanned in a direction perpendicular to the conveyance direction of the printing substrate while ejecting and recording aqueous inkjet ink, and a single-pass method in which the aqueous inkjet ink is ejected and recorded when the printing substrate passes under a fixedly arranged inkjet head. The inkjet head equipped with the aqueous inkjet ink of this embodiment may adopt either the shuttle method or the single-pass method. Among them, the single-pass method is preferably selected because the landing position of the droplets of the aqueous inkjet ink is less likely to shift, the printing quality of the printed matter is improved, and furthermore, high-speed printing is possible and high productivity as an alternative to plate printing can be exhibited.

[0117] Regarding the ejection method from the inkjet head as well, known methods can be arbitrarily selected. Examples of the ejection method include a piezo method that utilizes the volume change of a piezoelectric element (piezo element), a thermal method that ejects aqueous inkjet ink by bubbles generated by heating a heater, a valve method that ejects pressurized aqueous inkjet ink while opening and closing the lid (valve) of the nozzle with a solenoid, and the like.

[0118] The droplet volume of the aqueous inkjet ink ejected from the inkjet head is preferably 0.5 to 20 picoliters, particularly preferably 0.5 to 15 picoliters, from the viewpoints of reducing the drying load and improving the printing quality. Also, from the viewpoint of improving the printing quality, it is preferable to adjust the printing conditions (specifically, the drive frequency and the number of installations of the inkjet head, as well as the printing speed) so that the recording resolution of the printed matter is 600 dpi or more, and it is particularly preferable to adjust the printing conditions so that it is 1200 dpi or more.

[0119] ≪Drying process≫ Examples of the drying method employed in the drying mechanism used in the drying process include a heat drying method, a hot air drying method, an infrared ray (for example, infrared ray with a wavelength of 700 to 2500 nm) drying method, a microwave drying method, a drum drying method, and the like. In the above drying process, one or more of these methods can be arbitrarily selected and used. Also, when two or more of the above drying methods are employed, each drying method may be used separately (e.g., successively) or simultaneously in combination. For example, by combining the heat drying method and the hot air drying method, the ink can be dried faster than when each is used alone.

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

[0121] <Printing substrate> The printing substrate on which the aqueous inkjet ink of the present embodiment is printed is not particularly limited. On the other hand, even for substrates with poor permeability or non-permeable substrates, which are generally prone to bleeding and beading, and even for high-speed printing, by using the aqueous inkjet ink of the present embodiment, a printed matter having the same print quality as that produced by the relief printing method can be obtained.

[0122] In the present disclosure, the permeability of the printing substrate is judged by the water absorption measured by a dynamic scanning liquid absorber. Specifically, the water absorption of pure water at a contact time of 100 msec, measured by the following method, is less than 1 g / m 2 is defined as a "non-permeable substrate", and a printing substrate with a water absorption of 1 g / m 2 or more and less than 6 g / m 2 is defined as a "poorly permeable substrate", and a printing substrate with a water absorption of 6 g / m 2 or more is defined as a "permeable substrate". The water absorption of the printing substrate can be measured under the environment of 23°C and 50% RH, using a dynamic scanning liquid absorber (for example, "KM500win" manufactured by Kumagai Riki Kogyo Co., Ltd.) set under the conditions shown below, with a printing substrate sized to about 15 to 20 cm square as the sample. · Measurement method: Spiral Method · Measurement start radius: 20 mm · Measurement end radius: 60 mm · Contact time: 10 to 1,000 msec · Number of sampling points: 19 (measured to be approximately equally spaced with respect to the square root of the contact time) · Scanning interval: 7 mm · Speed switching angle of the rotary table: 86.3 degrees · Head box conditions: width 5 mm, slit width 1 mm

[0123] Examples of non-permeable substrates and difficult-to-permeate 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, polyvinyl alcohol films, etc.; coated papers such as coated paper, art paper, cast paper, etc.; metals such as aluminum, iron, stainless steel, titanium, etc.; glass; and the like.

[0124] The above-listed printing substrates may have a smooth surface or a surface with irregularities. Also, the above printing substrates may be transparent, translucent, or opaque. Furthermore, the above printing substrates may be in roll form or in sheet form. In addition, a combination of two or more of the above-listed printing substrates bonded to each other may be used as the printing substrate. Also, a release adhesive layer or the like may be provided on the side opposite to the printing surface, or an adhesive layer or the like may be provided on the printing surface after printing.

[0125] From the viewpoint of improving the wettability of the aqueous inkjet ink of the present embodiment, being excellent in printing image quality and drying property, and obtaining a printed matter having good rubbing resistance and substrate adhesion along with the homogenization of the surface of the printed matter, it is also preferable to perform surface modification such as corona treatment and plasma treatment on the printing surface of the above-listed printing substrates.

[0126] Since the aqueous inkjet ink of the present embodiment is excellent in water resistance and rubbing resistance without lamination processing, it can be used for commercial printed matters, packaging printed matters, etc. For example, it can be used for labels, packages, etc. 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 a binder resin, it can be printed on a polyethylene sheet, a polypropylene sheet, etc.

[0127] <Printed matter> According to some embodiments, it is possible to provide a printed matter obtained by printing the aqueous inkjet ink of the present embodiment described above on a printing substrate. This printed matter includes a printing substrate and an ink film formed by applying the aqueous inkjet ink of the present embodiment to the printing substrate. Since this printed matter has an ink film formed by a binder resin and slip property is imparted to the ink film by wax, it can have good rubbing resistance and water resistance. Preferably, wax is oriented on the surface of the ink film, thereby imparting slip property and further enhancing the rubbing resistance.

Example

[0128] Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. In the following description, "parts" and "%" are based on mass unless otherwise specified.

[0129] <Production of binder resin> An aqueous solution (solid content: 30%) of an acrylic resin was produced by the same raw materials and method as the binder resin 28 produced in the examples of JP-A-2020-180178 and used as the 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] <Manufacture of Pigment Dispersion Liquid> (Manufacture of Black Pigment Dispersion Liquid) 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 are neutralized with dimethylaminoethanol, acid value 230 mgKOH / g, mass average molecular weight 20,000), and 82 parts of water were put into a mixing container equipped with a stirrer and premixed for 1 hour. Then, using a "Dyno-Mill" (volume 0.6 L) manufactured by Shinmaru Enterprises Co., Ltd. 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 became about 100 nm to produce a black pigment dispersion liquid. Here, the 50% diameter is the particle diameter at which the integrated value becomes 50% in the volume-based particle size distribution by the dynamic light scattering method. The same applies hereinafter.

[0132] (Manufacture of Cyan Pigment Dispersion Liquid, Magenta Pigment Dispersion Liquid, Yellow Pigment Dispersion Liquid) As the pigments, the following pigments were used, and cyan pigment dispersion liquid, magenta pigment dispersion liquid, and yellow pigment dispersion liquid were produced by the same raw materials and method as the above black pigment dispersion liquid except that circulation dispersion was carried out until the following 50% diameters were reached. · Cyan pigment dispersion liquid: LIONOL BLUE 7358G manufactured by Toyo Color Co., Ltd. (C.I. Pigment Blue 15:3), 50% diameter = 150 nm · Magenta pigment dispersion liquid: Toshiki Red 150TR manufactured by Tokyo Ink Co., Ltd. (C.I. Pigment Red 150), 50% diameter = 200 nm · Yellow pigment dispersion liquid: LIONOL YELLOW TT1405G manufactured by Toyo Color Co., Ltd. (C.I. Pigment Yellow 14), 50% diameter = 150 nm

[0133] <Manufacture of a Set of Aqueous Inkjet Inks> Using the pigment dispersions produced by the method described above, each raw material was introduced into a mixing vessel equipped with a stirrer so as to obtain the formulation described in each column of Table 1. After the introduction, the mixture was heated until it reached approximately 50°C and then mixed for an additional hour. Thereafter, the mixture was cooled to room temperature (approximately 25°C) and then filtered through a membrane filter with a pore size of 1.2 μm to produce aqueous inkjet inks 1 to 108. In the production of the aqueous inkjet inks, each of the above-described black pigment dispersion, cyan pigment dispersion, magenta pigment dispersion, and yellow pigment dispersion was used as the pigment dispersion, and aqueous inkjet inks were produced with the same composition except for the type of the pigment dispersion. Thus, a set of aqueous inkjet inks consisting of black (aqueous black ink), cyan (aqueous cyan ink), magenta (aqueous magenta ink), and yellow (aqueous yellow ink) was produced, respectively.

[0134] In the production of the aqueous inkjet inks, each raw material was introduced while stirring the mixture in the mixing vessel. Further, in each column of Table 1, the raw materials were introduced in order from those described in the upper row. However, when these components were not included, the corresponding component was skipped and the next component was added. For components containing two or more raw materials, the order of introduction within the component was arbitrary.

[0135]

Table 1

[0136]

Table 1

[0137]

Table 1

[0138]

Table 1

[0139]

Table 1

[0140]

Table 1

[0141]

Table 1

[0142]

Table 1

[0143]

Table 1

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

[0145] <Preparation of printed matter> An inkjet ejection device equipped with four inkjet heads KJ4B-1200 (designed resolution 1200 dpi, nozzle diameter 20 μm) manufactured by Kyocera Corporation arranged in the conveyance direction of the printing substrate was installed in an environment at 25°C. An aqueous black ink, an aqueous cyan ink, an aqueous magenta ink, and an aqueous yellow ink were filled in this order from the upstream inkjet head. Also, a biaxially stretched polypropylene film "OPU-1" (thickness 20 μm) manufactured by Mitsui Chemicals Toatsu Chemicals, Inc. was fixed on the conveyor. Then, the conveyor was driven at a speed of 50 m / min. When the film substrate passed under the installation part of the inkjet head, the aqueous inkjet inks were ejected under the condition of a drop volume of 2 pL each to print an image. And immediately, the printed substrate after printing was put into a 70°C air oven and dried for 3 minutes to produce a printed matter.

[0146] Also, as a printed image, water-based cyan ink, water-based magenta ink, water-based yellow ink, and water-based black ink were each solid-printed at a printing rate of 100% so as not to overlap with each other (width of 5 cm and length of 30 cm for each color), and an image (colored solid image) in which the solid image portions were arranged adjacent to each other in the order of cyan, magenta, yellow, and black was used.

[0147] [Examples 1 to 91, Comparative Examples 1 to 17] After printing a colored solid image on a polypropylene film by the method described above, the following evaluations were performed using these printed materials. The evaluation results were as shown in Table 1.

[0148] <Evaluation 1: Evaluation of Rub Resistance> From the printed materials of the colored solid images produced by the above method, each of the cyan ink printed portion, magenta ink printed portion, yellow ink printed portion, and black ink printed portion was cut out and set as a test piece in an AB-301 academic vibration type friction fastness tester manufactured by Tester Sangyo Co., Ltd. Next, a test attached white cotton cloth (Kanakin No. 3) was attached to the friction element (self-weight 200 g), and the load applied to the friction element was changed and shaken a predetermined number of times. Then, after the shaking, the state of the printed material surface and the degree of coloring of the cotton cloth were visually confirmed to evaluate the rub resistance. The evaluation criteria were as follows, and ◎, ○, and △ were considered usable in actual use. In Table 1, the results of the color with the worst evaluation among the four colors evaluated were described. ◎: Even after placing a 300 g weight on the friction element (total 500 g) and shaking it 50 times, there were no rubbing marks on the printed surface and no coloring on the cotton cloth. ○: Even after placing a 300 g weight on the friction element (total 500 g) and shaking it 25 times, there were no rubbing marks on the printed surface and no coloring on the cotton cloth, but after shaking it 50 times under the same load condition, rubbing marks on the printed surface and / or coloring on the cotton cloth were observed. △: After shaking 25 times without placing a weight on the friction element (load: 200 g), there were no rubbing marks on the printed surface and no coloring on the cotton cloth. However, after placing a 300 g weight on the friction element (total 500 g) and shaking 25 times, rubbing marks on the printed surface and / or coloring on the cotton cloth were observed. ×: After shaking 25 times without placing a weight on the friction element (load: 200 g), rubbing marks on the printed surface and / or coloring on the cotton cloth were observed.

[0149] <Evaluation 2: Evaluation of water resistance> Similar to Evaluation 1, test pieces were cut out for each color from the printed matter with solid-color images, and set in an AB-301 shaking-type friction fastness tester manufactured by Tester Sangyo Co., Ltd. Then, a test attached white cotton cloth (Kanakin No. 3) sufficiently moistened with ion-exchanged water was attached to the friction element (self-weight 200 g). By changing the load applied to the friction element and shaking a predetermined number of times, and then visually checking the state of the printed matter surface and the degree of coloring of the cotton cloth, the rubbing resistance was evaluated. The evaluation criteria were as follows, and ◎, ◎-, ○, and △ were considered suitable for actual use. Table 1 shows the evaluation results of the color with the lowest evaluation among the four colors. ◎: Even after placing a 300 g weight on the friction element (total 500 g) and shaking 20 times, there were no rubbing marks on the printed surface and no coloring on the cotton cloth. ◎-: Even after placing a 300 g weight on the friction element (total 500 g) and shaking 10 times, there were no rubbing marks on the printed surface and no coloring on the cotton cloth. However, after shaking 20 times under the same load condition, rubbing marks on the printed surface and / or coloring on the cotton cloth were observed. ○: Even after placing a 300 g weight on the friction element (total 500 g) and shaking 5 times, there were no rubbing marks on the printed surface and no coloring on the cotton cloth. However, after shaking 10 times under the same load condition, rubbing marks on the printed surface and / or coloring on the cotton cloth were observed. △: After shaking 5 times without placing a weight on the friction element (load: 200 g), there were no rubbing marks on the printed surface and no coloring on the cotton cloth. However, after placing a 300 g weight on the friction element (total 500 g) and shaking 5 times, rubbing marks on the printed surface and / or coloring on the cotton cloth were observed. ×: After performing 5 learning oscillations without placing a weight on the friction element (load: 200 g), scratches on the printed surface and / or coloring on the cotton cloth were observed.

[0150] <Evaluation 3: Evaluation of ejection stability> The inkjet printing devices used for producing the printed matter were each filled with the water-based inkjet inks described in Table 1. Next, a nozzle check pattern was printed, and after confirming that there was no nozzle clogging, it was left standing for 10 minutes in a 25°C environment. Then, the nozzle check pattern was printed again, and the ejection stability was evaluated by visually counting the number of clogged nozzles. The evaluation criteria were as follows, and ◎ and ○ were considered suitable for actual use. The above evaluation was performed for each of the water-based inkjet inks constituting the set of water-based inkjet inks. Also, Table 1 shows the evaluation results of the color with the lowest evaluation among the four colors. ◎: There was no nozzle clogging at all. ○: The number of clogged nozzles was 1 to 9. △: The number of clogged nozzles was 10 to 49. ×: The number of clogged nozzles was 50 or more.

[0151] As is clear from Table 1, an aqueous inkjet ink containing diols (A) with an SP value of 10.0 or more and less than 12.0 and containing a branched alkylene group, diols (B) with an SP value of 12.0 or more and 15.0 or less, a binder resin, and a wax, and having a difference in boiling point between the diols (A) and the diols (B) of 30°C or less can produce a printed matter excellent in water resistance and abrasion resistance, and at the same time has high ejection stability. In particular, by setting the difference in boiling point between the diols (A) and the diols (B) to 30°C or less, both the diols (A) and the diols (B) can remain in the aqueous inkjet ink droplets on the printing substrate, preventing the aggregation of the wax and promoting the softening and reorientation of the binder resin, making it possible to obtain a printed matter excellent in abrasion resistance and water resistance. Further, when a plurality of types of diols (A) and / or a plurality of types of diols (B) are used, the weighted average value of the boiling points is calculated for the plurality of types of diols (A) and / or the plurality of types of diols (B), and it has become clear that the same effect can be obtained by making the difference in the boiling point (weighted average value) 30°C or less.

[0152] Although the present invention has been described with reference to some of the above embodiments, the present invention is not limited by the above embodiments. Various changes can be made to the configuration and details of the present invention within the scope of the present invention.

[0153] The disclosure of the present application is related to the subject matter described in Japanese Patent Application No. 2023-198147 filed on November 22, 2023, and all the disclosure contents thereof are incorporated herein by reference.

Claims

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

2. The aqueous inkjet ink according to claim 1 , wherein the wax comprises a polyolefin wax having a melting point of 100° C. or more and 170° C. or less at 1 atmospheric pressure.

3. 3. The aqueous inkjet ink according to claim 2, wherein, when 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), a value expressed by R / W is 15 or less.

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

5. Further, it contains glycol monoethers (C) whose terminal alkyl group has 2 to 4 carbon atoms, 3. The aqueous inkjet ink according to claim 2, wherein, when 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), a value expressed by R / W is 15 or less.

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

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