Aqueous inkjet ink and printed matter

Abstract

To provide a water-based inkjet ink which, even when used for printing on a non-permeable substrate, can give a printed matter that is free from voids and mixed color bleeding and is excellent in scratch resistance, and which is excellent in discharge stability immediately after the start of printing and after a long period of suspension of printing.SOLUTION: An aqueous inkjet ink comprising a pigment, an acetylenediol-based compound (A), polyethylene glycol, a binder resin, and an organic compound (B) (excluding the components described above and those that are resins), the acetylenediol-based compound (A) has an HLB value of 7.5 to 17.5, the organic compound (B) consists solely of carbon atoms, hydrogen atoms and oxygen atoms, has a plurality of hydroxyl groups, and has an HLB value of 2.5 to 5.2, and the binder resin contains a resin (C-1) having a glass transition temperature of - 60 to 50 °C. in an amount of at least 50% by mass relative to the total mass of resin in the aqueous inkjet ink.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to aqueous inkjet inks and printed materials. [Background technology]

[0002] With the increasing need for small-lot printing and reduced printing costs, digital printing methods that do not require plate making are rapidly becoming more popular.

[0003] Inkjet printing, which is one type of digital printing method, is a method of printing images and / or characters on a printing substrate (also simply referred to as "substrate" in this disclosure) by ejecting ink droplets from fine nozzles and applying them to the printing substrate. Inkjet printing has features such as easy operation of the printing device and low noise during printing, and therefore printing devices (inkjet printers) that employ this inkjet printing method are in high demand among digital printing methods.

[0004] The above "image" also includes seamless images such as solid images and checkered pattern images.

[0005] Inks used in inkjet printing methods (referred to as "inkjet inks" in this disclosure) are classified into solvent-based, water-based, ultraviolet-curable, and other types depending on their composition. Meanwhile, in recent years, there has been an accelerating movement to restrict the use of raw materials that are harmful to humans and the environment. Accordingly, there has been an increasing demand for water-based inkjet inks (also simply referred to as "water-based inkjet inks" in this disclosure) rather than solvent-based inkjet inks and ultraviolet-curable inkjet inks that use these raw materials.

[0006] Recently, with the improvement in inkjet head performance, the use of inkjet printing has expanded not only for consumer use but also for industrial printing. In particular, in the packaging (label and package) printing market, there is active consideration of replacing plate-based printing methods such as offset printing and gravure printing with inkjet printing.

[0007] However, in the past, solid prints (prints with a coverage of 100%) made using aqueous inkjet inks on non-permeable substrates such as plastic films and sheets have suffered from a phenomenon known as "whiteout," in which areas where the aqueous inkjet ink does not adhere to the printed substrate, and a phenomenon known as "color bleeding," in which aqueous inkjet inks of different colors mix together, making it difficult to obtain prints with the same print quality as those made using plate-based printing. This is because water, the main solvent for aqueous inkjet inks, has a particularly high surface tension, which results in poor wetting and spreading properties on the printed substrate, particularly on the order of microseconds.

[0008] In general, highly hydrophobic, non-polymeric organic compounds are often used to improve wetting and spreading properties on a printing substrate. These organic compounds orient at the interface with the printing substrate within microseconds, improving wetting and spreading properties on the printing substrate. However, high hydrophobicity also means poor solubility in water, and aqueous inkjet inks containing these organic compounds are prone to the formation of bubbles, which can contribute to nozzle clogging (a phenomenon in which aqueous inkjet ink is not ejected from a nozzle). Furthermore, the orientation of these organic compounds at the air-liquid interface formed on the nozzle end surface of an inkjet head can destabilize the meniscus of the aqueous inkjet ink. These problems are likely to lead to nozzle clogging immediately after the start of printing and when printing is resumed after a long pause, respectively. Furthermore, due to the structure of the inkjet head, the nozzle diameter is extremely small, at only a few tens of micrometers. In particular, when printing is suspended for an extended period of time, the liquid components (water, water-soluble organic solvents, etc.) in the aqueous inkjet ink may volatilize from the nozzle end face, while a sufficient amount of fresh aqueous inkjet ink may not be supplied to the inkjet head. This may result in an increase in the solid content concentration and / or an increase in the proportion of water-soluble organic solvents with high boiling points in the aqueous inkjet ink present near the nozzle end face, causing an increase in viscosity due to aggregation and insolubilization of solid components (pigments, resins, etc.), and nozzle clogging due to this increase in viscosity may occur.

[0009] In this disclosure, the ejection stability immediately after the start of printing is referred to as "initial ejection stability," and the ejection stability after a long period of printing pause is also referred to as "standby ejection stability."

[0010] On the other hand, particularly in the packaging printing market, it is necessary for the coating (ink film) of the aqueous inkjet ink after drying to not peel off even when the printed material is rubbed hard with a finger or the like. That is, the ink film is required to have a certain degree of abrasion resistance. One method for imparting abrasion resistance to the ink film of an aqueous inkjet ink is to add a binder resin to the aqueous inkjet ink to form a uniform, strong, continuous ink film. On the other hand, if a certain amount or more of binder resin is contained in the aqueous inkjet ink (liquid) before printing, problems such as a local increase in viscosity and non-uniform viscoelasticity may occur in the aqueous inkjet ink, resulting in a deterioration in ejection stability, and the binder resin may inhibit the orientation of the organic compound, thereby worsening the wetting and spreading properties of the aqueous inkjet ink.

[0011] Thus, in order to expand the use of aqueous inkjet inks in the packaging printing market, multiple issues, such as initial ejection stability, standby ejection performance, print image quality, and abrasion resistance of the ink film, must be simultaneously resolved. However, no aqueous inkjet ink that can simultaneously and suitably resolve all of these issues has been discovered to date.

[0012] In this disclosure, a printed matter that is free from white spots and color mixing is also referred to as a "printed matter with excellent print quality."

[0013] As an example of a study aimed at improving the print quality of printed matter on non-permeable substrates, Patent Document 1 discloses an ink suitable for use in inkjet printing, which contains water, an organic solvent, a polysiloxane surfactant with an HLB value of 8 or less, and acrylic silicone resin particles. Patent Document 1 also provides examples of inks that use 1,2-propanediol (propylene glycol), 1,3-propanediol, 3-methoxy-3-methylbutanol, 2-methyl-2,4-pentanediol, or the like as the organic solvent, and further contain urethane resin emulsion, polyester resin emulsion, acrylic-styrene resin emulsion, or the like as other resin particles. Patent Document 1 also describes that inks having the above-described configuration have good storage stability and can produce printed matter with excellent fixability (suppression of density unevenness) and adhesion to non-permeable substrates (see paragraphs 0006 and 0019 of Patent Document 1).

[0014] Patent Document 2 discloses an aqueous inkjet ink containing an organic solvent selected from ethylene glycol, propylene glycol, 3-methoxy-1-butanol, etc., and a polyoxyalkylene monoallyl ether compound having a specific structure. Patent Document 2 also discloses, in its examples, an example of an aqueous inkjet ink containing, in addition to the organic solvent, 2,2-dimethyl-1,3-propanediol, 1,4-butanediol, 2-methyl-2,4-pentanediol, etc., and further containing a water-insoluble resin such as a urethane resin emulsion or an acrylic resin emulsion, and a surfactant such as an acetylene glycol surfactant or a silicone surfactant. Patent Document 2 also discloses that the aqueous inkjet ink having the above-described composition has excellent ejection properties and can produce printed matter with no uneven density and good wetting and spreading properties even on non-water-absorbent recording media (see paragraphs 0014 and 0028 of Patent Document 2).

[0015] Meanwhile, as an example of a study aimed at improving the abrasion resistance of printed matter on an impermeable substrate, Patent Document 3 discloses an inkjet ink composition containing a water-soluble polymer having a number-average molecular weight of 1,000 or more, particles having polymerizable groups, a colorant, and water, with a specified ratio of the content of the water-soluble polymer to the content of the particles. Patent Document 3 also provides an example of an inkjet ink composition in its examples, which contains polyethylene glycol having a number-average molecular weight of 2,000 to 100,000, an ultraviolet-curable urethane acrylate resin emulsion, water, and Olfine E1010 (an acetylene diol surfactant). Patent Document 3 also describes that an inkjet ink composition having the above configuration has excellent ejection stability, and that specifying the above ratio enables the printed matter to achieve both abrasion resistance and flexibility (see paragraphs 0010, 0014, and 0017 of Patent Document 3).

[0016] Patent Document 4 discloses an ink containing water, a compound having a specific solubility parameter (e.g., 3-butoxy-N,N-dimethylpropionamide, diethylene glycol diethyl ether, or 2-pyrrolidone), an alkanediol compound having 3 to 4 carbon atoms, and 3-methoxy-3-methyl-1-butanol. Example 2 of Patent Document 4 describes an ink containing 3-butoxy-N,N-dimethylpropionamide, 1,2-propanediol, 1,3-propanediol, and 3-methoxy-3-methyl-1-butanol, as well as 2-methyl-2,4-pentanediol, a polyurethane resin emulsion having a minimum film-forming temperature of 43°C, and a fluorine-based surfactant. Patent Document 4 also describes that an ink having the above-described composition has excellent fixability to non-permeable substrates, ejection reliability (standby ejection), and abrasion resistance of printed matter (see paragraphs 0004, 0009, and 0016 of Patent Document 4). [Prior art documents] [Patent documents]

[0017] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-115127 [Patent Document 2] Patent Publication No. 2021-109904 [Patent Document 3] Japanese Patent Application Laid-Open No. 2015-48435 [Patent Document 4] Japanese Patent Publication No. 2020-73665 Summary of the Invention [Problem to be solved by the invention]

[0018] However, the ink specifically disclosed in Patent Document 1 does not contain the aforementioned non-polymeric hydrophobic organic compound other than the polysiloxane surfactant. The polysiloxane surfactant used in the ink is also known to have excellent interfacial orientation and is an effective material for improving print quality. However, its orientation speed is not particularly fast, and it is insufficient from the perspective of ensuring wetting and spreading properties on the order of microseconds. Furthermore, the polyoxyalkylene monoallyl ether compounds, acetylene glycol-based surfactants, and silicone-based surfactants specifically used in the examples of Patent Document 2 (see also paragraphs 0117-0118 of Patent Document 2) are all highly hydrophilic (i.e., have large HLB values, as described below) compounds, and, like Patent Document 1, do not contain non-polymeric hydrophobic organic compounds. To produce printed materials with excellent print quality regardless of printing conditions, such as inkjet printing on printing substrates with very low interfacial free energy or high-speed inkjet printing, further improvements, including the use of non-polymeric hydrophobic organic compounds, are necessary.

[0019] As with Patent Documents 1 and 2, Patent Document 3 does not use a hydrophobic organic compound in the inkjet ink composition specifically disclosed, and therefore, depending on the printing substrate, printing speed, etc., it may be necessary to improve the print quality. On the other hand, Patent Document 4 specifically discloses an ink in which a fluorosurfactant is used together with various water-soluble organic solvents. Generally, fluorosurfactants are highly hydrophobic, and as described above, the incorporation of such a fluorosurfactant is considered effective in improving print quality. However, simply incorporating the hydrophobic organic compound into an aqueous inkjet ink can cause bubbles and meniscus instability, which may result in a deterioration in initial ejection stability and standby ejection stability depending on the device configuration, printing conditions, etc.

[0020] As described above, the techniques described in Patent Documents 1 to 4 have not yet been able to solve all of the above-mentioned problems at a high level. Therefore, an object of one embodiment of the present disclosure is to provide an aqueous inkjet ink that can produce printed matter that is free from white voids and color bleeding, and has excellent abrasion resistance, even when printed on a non-permeable substrate, and that also has excellent ejection stability immediately after the start of printing and after a long period of printing pause. [Means for solving the problem]

[0021] As a result of extensive research, the present inventors have found that all of the above-mentioned problems can be solved simultaneously and to a high degree by using an aqueous inkjet ink having the following composition.

[0022] That is, one embodiment of the present disclosure relates to aqueous inkjet inks as described below in [1] to [3], and to printed matter produced using the aqueous inkjet inks as described below in [4]. [1] A water-based inkjet ink comprising a pigment, an acetylenic diol compound (A), polyethylene glycol, a binder resin, and an organic compound (B) (excluding the pigment, the acetylenic diol compound (A), the polyethylene glycol, and the resin), the acetylene diol compound (A) has an HLB value of 7.5 to 17.5; the organic compound (B) consists of only carbon atoms, hydrogen atoms, and oxygen atoms and has a plurality of hydroxyl groups; the organic compound (B) has an HLB value of 2.5 to 5.2; the binder resin contains a resin (C-1) having a glass transition temperature of −60 to 50° C., An aqueous inkjet ink, wherein the content of the resin (C-1) is 50 mass % or more of the total mass of the resins contained in the aqueous inkjet ink. [2] The aqueous inkjet ink according to [1], wherein the mass of the polyethylene glycol is 1.0 to 20, relative to the mass of the acetylene diol compound (A) taken as 1. [3] The aqueous inkjet ink according to [1] or [2], wherein the mass content of the organic compound (B) is 0.05 to 2.0 when the mass content of the acetylene diol compound (A) is taken as 1. [4] A printed matter obtained by printing the aqueous inkjet ink according to any one of [1] to [3] on a printing substrate. [Effects of the Invention]

[0023] The aqueous inkjet ink of one embodiment of the present disclosure has the effect of producing printed matter that is free from white voids and color bleeding and has excellent abrasion resistance, even when printed on a non-permeable substrate, and further has excellent ejection stability immediately after the start of printing and after a long period of printing pause. DETAILED DESCRIPTION OF THE INVENTION

[0024] An aqueous inkjet ink according to one embodiment of the present disclosure (hereinafter also simply referred to as "the aqueous inkjet ink of this embodiment") will be described below. Note that the present invention is not limited to the embodiment described below, and includes embodiments that can be modified without changing the essential parts of the present invention.

[0025] Generally, aqueous inkjet inks do not wet and spread on non-permeable substrates due to the extremely high surface tension of their main component, water, making it difficult to produce fine prints. In contrast, when organic compounds with low HLB values, such as surfactants, are used, the organic compounds orient at the interface with the printing substrate within microseconds. As a result, aqueous inkjet inks can wet and spread well even on non-permeable substrates, particularly those with very low interfacial free energy, such as polypropylene (PP) film, potentially improving print quality. However, these organic compounds have the drawbacks of easily forming bubbles, which can contribute to nozzle clogging, and of destabilizing the meniscus of the aqueous inkjet ink due to rapid orientation at the air-liquid interface formed at the nozzle end of the inkjet head. These drawbacks ultimately lead to poor initial and standby ejection stability.

[0026] Furthermore, to obtain a printed matter with excellent abrasion resistance, it is preferable that the binder resin form a uniform, continuous ink film constituting the printed matter. Generally, the lower the glass transition temperature of the binder resin, the easier it is to form a uniform, continuous film. Therefore, from the perspective of forming such a uniform, continuous film, it is effective to use a binder resin with a low glass transition temperature. On the other hand, binder resins with low glass transition temperatures easily form films, for example, on the nozzle end surfaces of inkjet heads, which may deteriorate the initial ejection stability. Furthermore, the binder resin contained in the aqueous inkjet ink before printing (liquid) may inhibit the orientation of the organic compound at the interface. If the orientation of the organic compound is inhibited, the above-mentioned effects cannot be achieved, and the print quality of the printed matter deteriorates. To fully achieve the above-mentioned effects, one method is to increase the amount of the organic compound added so that a sufficient amount is still oriented at the interface even when inhibited. However, an excessive amount of the organic compound also poses the problem of inhibiting the formation of a continuous binder resin film, resulting in a deterioration in the abrasion resistance of the printed matter.

[0027] In contrast, the aqueous inkjet ink of this embodiment contains an organic compound (B) which is composed only of carbon, hydrogen, and oxygen atoms and has multiple hydroxyl groups and has an HLB value of 2.5 to 5.2, and a resin (C-1) which has a glass transition temperature of -60 to 50°C, as well as an acetylene diol compound (A) which has an HLB value of 7.5 to 17.5 and polyethylene glycol.

[0028] Generally, acetylenic diol compounds are used as surfactants. Adding an acetylenic diol compound to an aqueous inkjet ink improves the ink's wetting and spreading properties on a printing substrate, resulting in improved print quality. The aqueous inkjet ink of this embodiment uses an acetylenic diol compound (A) with an HLB value of 7.5 to 17.5. The acetylenic diol compound (A) with a relatively large HLB value facilitates stabilization of the organic compound (B) in the aqueous inkjet ink. Furthermore, the presence of the acetylenic diol compound (A) suppresses rapid orientation of the organic compound (B) toward the interface. As a result, the aqueous inkjet ink in the inkjet head is prevented from generating bubbles and from destabilizing the meniscus, improving initial ejection stability and standby ejection performance.

[0029] Furthermore, the acetylenic diol compound (A) also has affinity with the resin (C-1). Therefore, for example, even after water evaporates from the aqueous inkjet ink applied to a printing substrate, the organic compound (B) and the resin (C-1) become compatible with each other via the acetylenic diol compound (A), allowing the resin (C-1) to diffuse uniformly together with the organic compound (B). As described above, the aqueous inkjet ink of this embodiment contains, as a binder resin, a resin (C-1) that has a low glass transition temperature, i.e., that easily forms a uniform continuous film, and the content of the resin (C-1) is 50% by mass or more of the total mass of the resins contained in the aqueous inkjet ink. As a result, it is believed that the aqueous inkjet ink of this embodiment promotes the formation of a continuous ink film, improving the abrasion resistance of printed materials.

[0030] On the other hand, as mentioned above, the acetylenic diol compound (A) also functions as a surfactant. Therefore, for example, in an aqueous inkjet ink that has been left in an inkjet head for a long time without being printed, the acetylenic diol compound (A) may be oriented at the gas-liquid interface, which may deteriorate the standby dischargeability. In particular, if the organic compound (B) is oriented at the gas-liquid interface due to the orientation of the acetylenic diol compound (A), the standby dischargeability may be significantly deteriorated.

[0031] Therefore, the aqueous inkjet ink of this embodiment further contains polyethylene glycol. Polyethylene glycol is a compound consisting only of a hydroxyl group and an ethylene oxide group, and therefore has extremely high affinity with water. It is also believed to have good affinity with the acetylenic diol-based compound (A). As a result, even when the aqueous inkjet ink is left in the inkjet head for a long period of time, orientation of the acetylenic diol-based compound (A) at the gas-liquid interface can be suppressed, thereby preventing deterioration of standby discharge performance. It is also believed that polyethylene glycol diffuses freely throughout the aqueous inkjet ink. As a result, the polyethylene glycol functions as a plasticizer and promotes film formation of the resin (C-1), resulting in a uniform and continuous ink film and improved abrasion resistance of the printed material.

[0032] As described above, in order to solve all of the above-mentioned problems at a high level, an aqueous inkjet ink having the above-mentioned configuration is essential. Note that the above-mentioned mechanism is a conjecture by the inventors, and the present invention is not limited by the above conjecture.

[0033] The aqueous inkjet inks specifically disclosed in Patent Documents 1-4 differ from the aqueous inkjet ink of the present embodiment in that they do not contain the organic compound (B) or polyethylene glycol. Furthermore, the aqueous inkjet ink specifically disclosed in paragraph 0104 of Patent Document 3 contains the acetylene diol compound (A) "Olfine E1010" and the polyethylene glycol "PEG8000," but, like Patent Documents 1-4, does not contain the organic compound (B). As described above, the aqueous inkjet ink of the present embodiment, which contains the organic compound (B), can produce printed materials free of whiteout and color bleeding on printing substrates with very low interfacial free energy. Furthermore, by using the organic compound (B) in combination with the acetylene diol compound (A) and polyethylene glycol, it is possible to improve the initial ejection stability and standby ejection performance that can occur when using the organic compound (B). Patent Documents 1-4 do not disclose or suggest such a method.

[0034] Next, each component constituting the aqueous inkjet ink according to one embodiment of the present disclosure will be described in detail below.

[0035] <Acetylene diol compound (A)> As described above, the aqueous inkjet ink of this embodiment contains an acetylenic diol-based compound (A) having an HLB value of 7.5 to 17.5. By including the acetylenic diol-based compound (A) in the aqueous inkjet ink, the organic compound (B) is stabilized in the aqueous inkjet ink, and rapid orientation of the organic compound (B) to the interface is suppressed, improving the initial ejection stability and standby ejection performance. Furthermore, by uniformly diffusing the resin (C-1) in the aqueous inkjet ink, the formation of a continuous ink film is promoted, improving the abrasion resistance of the printed matter.

[0036] From the viewpoint of suitably achieving the above-mentioned effects, the HLB value of the acetylenic diol compound (A) is preferably 7.5 to 17.5. Furthermore, from the viewpoint of obtaining the effect of improving print quality due to the function of the acetylenic diol compound (A) as a surfactant in addition to the above-mentioned effects, the HLB value of the acetylenic diol compound (A) is preferably 7.5 to 17.1, more preferably 7.5 to 16.0, particularly preferably 7.5 to 13.5, and may further be 7.9 to 13.2.

[0037] The HLB (Hydrophile-Lipophile Balance) value is one of the parameters that indicates the hydrophilicity and hydrophobicity of a material, and in the present disclosure, the HLB value is calculated using the Griffin method.

[0038] The Griffin method is a method for calculating the HLB value using the molecular weight of a material according to the following formula (1): The smaller the HLB value, the more hydrophobic the material, and the larger the HLB value, the more hydrophilic the material.

[0039] Formula (1): HLB value = 20 × (total molecular weight of hydrophilic parts) ÷ (molecular weight of material)

[0040] The acetylene diol compound (A) that can be preferably used in the aqueous inkjet ink of this embodiment is a compound represented by the following general formula (2), in which i1+i2 is an integer of 3-30.

[0041] General formula (2): [ka]

[0042] In general formula (2), a and b are each 1 or 2. Furthermore, i1 and i2 are each an integer of 0 to 30, and j1 and j2 are each an integer of 0 to 5. The addition of the ethylene oxide groups and propylene oxide groups in each square bracket may be either block addition or random addition.

[0043] The acetylene diol compound (A) represented by the general formula (2) above, in which i1 + i2 is an integer of 3 to 30, may be a compound synthesized by a conventionally known method, or may be a commercially available product. Examples of the commercially available product include Surfynol 440 (8.1), Surfynol 465 (13.2), Surfynol 485 (17.1), Surfynol 2502 (7.9), Dynol 604 (8.2), and Dynol 607 (11.0), all of which are sold by Evonik Japan K.K. and Nissin Chemical Industry Co., Ltd.; Olfine E1004 (8.8), all of which are sold by Nissin Chemical Industry Co., Ltd.; Examples include Olfine E1006 (10.8), Olfine E1010 (13.2), Olfine E1020 (15.9), Olfine E1030W (17.1), and Acetylenol E40 (8.8), Acetylenol E60 (10.8), Acetylenol E100 (13.2), and Acetylenol E200 (15.9) sold by Kawaken Fine Chemicals Co., Ltd. The numbers in parentheses are the HLB values ​​of each commercially available product.

[0044] Two or more types of acetylenic diol compounds (A) can also be used in combination.

[0045] The total amount of the acetylene diol compound (A) added is preferably 0.2 to 2.5 mass %, more preferably 0.3 to 2.0 mass %, and particularly preferably 0.5 to 1.5 mass %, of the total amount of the aqueous inkjet ink, from the viewpoints of improving the initial ejection stability and standby ejection property and also improving the abrasion resistance of the printed matter.

[0046] Furthermore, since the print quality of the printed matter, the initial ejection stability, and the standby ejection properties are all improved by suitably stabilizing the organic compound (B), the mass content of the organic compound (B) relative to the mass content of the acetylene diol compound (A) taken as 1 is preferably 0.04 to 2.8, more preferably 0.05 to 2.0, particularly preferably 0.1 to 1.5, and may further be 0.1 to 1.2, 0.2 to 1.0, or 0.1 to 0.5.

[0047] Furthermore, from the viewpoint of increasing affinity with polyethylene glycol and improving initial ejection stability, standby ejection property, and abrasion resistance of printed matter, the mass content of the polyethylene glycol is preferably 0.8 to 25, more preferably 1.0 to 20, and particularly preferably 1.4 to 15, relative to the mass content of the acetylene diol compound (A) taken as 1.

[0048] <Organic compounds (B)> The aqueous inkjet ink of this embodiment contains an organic compound (B) consisting solely of carbon, hydrogen, and oxygen atoms, and having multiple hydroxyl groups, the organic compound having an HLB value of 2.5 to 5.2. During printing, the organic compound (B) quickly orients at the interface with the printing substrate, resulting in a printed product free of white spots and color bleeding, even on non-permeable substrates. Furthermore, the combined use of the acetylene diol compound (A) and the organic compound (B) suppresses the generation of bubbles and meniscus instability in the aqueous inkjet ink present in the inkjet head, improving initial ejection stability and standby ejection performance. Furthermore, the combined use of these compounds prevents the formation of a continuous film by the resin (C-1), improving the abrasion resistance of the printed product.

[0049] It should be noted that pigments, acetylene diol compounds (A), and polyethylene glycol are not included in the organic compound (B). Also, resins including the resin (C-1) are not included in the organic compound (B).

[0050] In the present disclosure, a "resin" refers to a compound in which one or more types of polymerizable monomers are linked together by covalent bonds to form a main chain, and the compound has a weight average molecular weight of 1,000 or more, which can be measured by the method described below. However, polyethylene glycol, which will be described later, is not included in the "resin" in the present disclosure.

[0051] As described above, the HLB value of the organic compound (B) is 2.5 to 5.2. Furthermore, since the organic compound (B) has good affinity with other components, the HLB value of the organic compound (B) is preferably 2.7 to 5.2, more preferably 3.0 to 5.2, particularly preferably 3.8 to 5.2, and may be 4.0 to 5.2, from the viewpoint of improving the initial ejection stability and standby ejection performance while suppressing white spots and color bleeding in printed matter.

[0052] Examples of compounds that can be used as the organic compound (B) include: Acetylene diol compounds represented by the above general formula (2), in which i1 + i2 is 0 or 1 (e.g., 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol (2.7), 2,4,7,9-tetramethyl-5-decyne-4,7-diol (3.0), 5,8-dimethyl-6-dodecaine-5,8-diol (3.0), 3,6-dimethyl-4-octyne-3,6-diol (4.0)); Sorbitan fatty acid ester compounds such as sorbitan monostearate (4.7), sorbitan distearate (4.4), sorbitan monooleate (4.3), and their ethylene oxide and / or propylene oxide adducts; Glycerol fatty acid ester compounds such as glycerol monostearate (3.5), glycerol monobehenate (3.0), glycerol monooleate (2.8), and their ethylene oxide and / or propylene oxide adducts; Medium-chain (e.g., carbon number 7 to 12) alkanediol compounds such as 1,2-heptanediol (5.2), 1,7-heptanediol (5.2), 1,2-octanediol (4.7), 1,8-octanediol (4.7), 2-ethyl-1,3-hexanediol (4.7), 1,2-nonanediol (4.2), and 1,9-nonanediol (4.2); Cycloalkanediol compounds such as cyclohexanedimethanol (4.7) and cyclohexanediethanol (4.0); Examples include polypropylene glycol compounds such as dipropylene glycol (5.1) and tripropylene glycol (3.5). The numbers in parentheses are the HLB values ​​of each material.

[0053] Among these compounds, one or more compounds selected from the group consisting of acetylenic diol compounds represented by the above general formula (2) in which i1 + i2 is 0 or 1 and medium-chain alkanediol compounds are preferably used, from the viewpoints of having high affinity with the acetylenic diol compound (A), improving the initial ejection stability and standby ejection property, and also improving the abrasion resistance of the printed matter.

[0054] The organic compound (B) has an excellent orientation speed to the interface and good affinity with the acetylene diol compound (A). Therefore, while suppressing white spots and color bleeding in the printed matter, the initial ejection stability and standby ejection property are improved, and the abrasion resistance of the printed matter is also improved. From these viewpoints, the molecular weight of the organic compound (B) is preferably 100 to 750, particularly preferably 130 to 650.

[0055] The amount of organic compound (B) added is preferably 0.05 to 1.6% by mass, more preferably 0.05 to 1.5% by mass, and particularly preferably 0.1 to 1% by mass, of the total amount of the aqueous inkjet ink, from the viewpoints that a printed matter free from white voids and color bleeding and having excellent abrasion resistance can be obtained, and that the initial ejection stability and standby ejection properties are also improved.

[0056] Furthermore, from the viewpoint of improving the initial ejection stability and standby ejection property, as well as the print quality of the printed matter, the mass content of the organic compound (B) is preferably 0.03 to 0.40, and particularly preferably 0.05 to 0.30, when the mass content of polyethylene glycol described below is taken as 1.

[0057] <Other nonionic surfactants> The aqueous inkjet ink of the present embodiment may contain a nonionic surfactant other than the surfactant corresponding to the acetylene diol compound (A) and the organic compound (B) described above (also referred to as "other nonionic surfactants" in the present disclosure).

[0058] Specific examples of the other nonionic surfactants include acetylene monool surfactants and their ethylene oxide and / or propylene oxide adducts, sorbitan fatty acid ester surfactants and their ethylene oxide and / or propylene oxide adducts (with an HLB value of less than 2.5 or more than 5.2), glycerin fatty acid ester surfactants and their ethylene oxide and / or propylene oxide adducts (with an HLB value of less than 2.5 or more than 5.2), polyether-modified siloxane surfactants, fluorine-based surfactants, polyoxyalkylene alkyl ether surfactants, polyoxyalkylene alkylamine surfactants, etc.

[0059] Among these, it is preferable to use a polyether-modified siloxane surfactant as the other nonionic surfactant because it has a high ability to reduce the surface tension of the aqueous inkjet ink, enables the aqueous inkjet ink droplets to wet and spread uniformly, and can easily suppress whiteout and color bleeding in printed materials, and because it has affinity with the binder resin, it suppresses the formation of a binder resin film on the nozzle end face of the inkjet head, improving initial ejection stability.In another embodiment, it is preferable to use a polyoxyalkylene alkyl ether surfactant because it has a high affinity with the organic compound (B), the acetylene diol compound (A), and polyethylene glycol, improving initial ejection stability and standby ejection performance, and also improving the abrasion resistance of printed materials.

[0060] <Polyether-modified siloxane surfactant> When the aqueous inkjet ink of this embodiment contains a polyether-modified siloxane surfactant, a compound having a structure represented by the following general formula (3) can be preferably used as the polyether-modified siloxane surfactant.

[0061] General formula (3): [ka]

[0062] In the general formula (3), m is an integer of 0 to 99, and n is an integer of 1 to 100, provided that m+n is an integer of 1 to 100. 1 is a methyl group or a structure represented by the following general formula (4), and R 2 is an alkyl group having 1 to 6 carbon atoms (which may be branched), or a structure represented by the following general formula (4), where R 1 When R is a methyl group, m is 0. 1 and R 2 At least one of the groups has a structure represented by the following general formula (4) (R 1 and R 2However, both may have a structure represented by the following general formula (4):

[0063] General formula (4): [ka]

[0064] In the general formula (4), p is an integer of 1 to 6, q is an integer of 1 to 50, and r is an integer of 0 to 50, provided that q+r is an integer of 1 to 100. 3 is any one of a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an acryloyl group, a methacryloyl group, a 3-(acryloyloxy)-2-hydroxypropyl group, and a 3-(methacryloyloxy)-2-hydroxypropyl group. The addition of the ethylene oxide group and the propylene oxide group in the square brackets may be in the form of block addition or random addition.

[0065] In the above general formula (3), R 2 is a structure represented by the above general formula (4), and R 1

[0033] Polyether-modified siloxane surfactants (also referred to as "double-end polyether-modified siloxane surfactants" in the present disclosure) that do not have a structure represented by the above general formula (4) have high affinity with binder resins and are effective in improving the initial ejection stability and the scratch resistance of printed matter. Furthermore, double-end polyether-modified siloxane surfactants also have excellent uniform orientation at interfaces and can also reduce color bleeding, making them particularly suitable for use as polyether-modified siloxane surfactants in the aqueous inkjet ink of this embodiment. On the other hand, in the above general formula (3), R 1 is a structure represented by the above general formula (4), and R 2 Polyether-modified siloxane surfactants (also referred to as "side-chain polyether-modified siloxane surfactants" in the present disclosure) having a structure other than that represented by the above general formula (4) have a high ability to reduce surface tension and an excellent orientation speed to the interface, and are therefore effective in suppressing white voids in printed materials.

[0066] Examples of commercially available products of the above-mentioned siloxane surfactants modified at both ends with polyether include BYK-331, BYK-333, BYK-UV3500, and BYK-3420 manufactured by BYK Japan; TEGO Glide 410, TEGO Glide 432, TEGO Glide 435, TEGO Glide 440, and TEGO Glide 450 manufactured by Evonik Japan; Silface SWP001, Silface SAG003, and Silface SAG005 manufactured by Nissin Chemical Industry Co., Ltd.; X-22-4952, X-22-4272, and KF-6123 manufactured by Shin-Etsu Chemical Co., Ltd.; and SILWET L-8610 and SILWET L-8620 manufactured by Momentive Performance Materials.

[0067] Commercially available examples of the side chain polyether-modified siloxane surfactant include 8032ADDITIVE, FZ-77, L-7001, L-7002, FZ-2104, FZ-2110, SH 3746, and SH 8400 manufactured by Toray Dow Corning Co., Ltd.; BYK-345, BYK-346, BYK-347, BYK-348, BYK-349, BYK-379, BYK-3450, and BYK-3451 manufactured by BYK Japan; and TEGO Wet 240, TEGO Wet 250, TEGO Wet 260, TEGO Wet 270, and TEGO Wet 345 manufactured by Evonik Japan. 280, and Shin-Etsu Chemical Co., Ltd.'s KF-351A, KF-352A, KF-353, KF-354L, KF355A, KF-615A, KF-640, KF-642, KF-643, KF-644, KF-945, KF-6204, KF-6011, KF-6012, KF-6015, KF-6017, and KF-6020.

[0068] The amount of polyether-modified siloxane surfactant added is preferably 0.1 to 4 mass % of the total amount of the aqueous inkjet ink, more preferably 0.2 to 3 mass %, and particularly preferably 0.3 to 2 mass %. When the amount of polyether-modified siloxane surfactant added is within the above range, it becomes easy to improve the initial ejection stability and standby ejection performance, and to obtain printed matter that is free from white voids and color bleeding and has excellent abrasion resistance.

[0069] Furthermore, from the viewpoint of achieving favorable affinity with resin (C-1), improving initial ejection stability, and suppressing white spots and color bleeding in printed matter, the content of resin (C-1) is preferably 3.3 to 72, more preferably 3.5 to 50, and particularly preferably 5.0 to 35, relative to the content of the polyether-modified siloxane surfactant, which is taken as 1.

[0070] <Polyoxyalkylene alkyl ether surfactants> When the aqueous inkjet ink of this embodiment contains a polyoxyalkylene alkyl ether surfactant, a compound having a structure represented by the following general formula (5) can be preferably used as the polyoxyalkylene alkyl ether surfactant. By using a compound represented by the following general formula (5) as the polyoxyalkylene alkyl ether surfactant, the affinity with the organic compound (B), the acetylene diol compound (A), and polyethylene glycol is increased, and the initial ejection stability, standby ejection property, and abrasion resistance of the printed matter are improved.

[0071] General formula (5): [ka]

[0072] In the general formula (5), s is an integer of 10 to 100, and t is an integer of 0 to 50, provided that s>t. 4is an alkyl group or alkylene group (which may be branched) having 8 to 22 carbon atoms. The addition of the ethylene oxide group and propylene oxide group in the square brackets may be block addition or random addition.

[0073] In particular, from the viewpoint of improving all of the initial ejection stability, standby ejection property, and scratch resistance of the printed matter, s in the above general formula (5) is preferably 20 to 50, and t is preferably 0 to 10. From the same viewpoint, R 4 is preferably an alkyl group having 10 to 22 carbon atoms (which may be branched), and particularly preferably an alkyl group having 12 to 18 carbon atoms (which may be branched).

[0074] The total content of other nonionic surfactants in the aqueous inkjet ink is preferably 0.1 to 3% by mass, more preferably 0.2 to 2% by mass. A total content of 0.1% by mass or more ensures the above-mentioned effects, and also facilitates the suppression of white spots and color bleeding in printed matter, improving the abrasion resistance of printed matter. Furthermore, a total content of other nonionic surfactants of 3% by mass or less improves initial ejection stability and standby ejection performance.

[0075] <Polyethylene glycol> The aqueous inkjet ink of this embodiment contains polyethylene glycol. The polyethylene glycol has affinity with water, the main component of the aqueous inkjet ink, and the acetylenic diol compound (A), which has moderate hydrophilicity. This inhibits the orientation of the acetylenic diol compound (A) at the gas-liquid interface, improving standby ejection properties. Furthermore, a uniform and continuous ink film is more easily obtained, improving the abrasion resistance of the printed matter.

[0076] In the present disclosure, "polyethylene glycol" refers to a compound having 4 to 300 ethylene oxide groups.

[0077] From the viewpoint of improving the initial ejection stability in addition to standby ejection properties and abrasion resistance of printed matter, the number average molecular weight of the polyethylene glycol is preferably 200 to 10,000, more preferably 200 to 4,000, and particularly preferably 200 to 2,000.

[0078] In the aqueous inkjet ink of this embodiment, two or more types of polyethylene glycols having different number average molecular weights may be used in combination.

[0079] From the viewpoint of improving all of the initial ejection stability, standby ejection properties, and abrasion resistance of printed matter, the content of polyethylene glycol contained in the aqueous inkjet ink of this embodiment (when two or more types of polyethylene glycol are contained, the total content) is preferably 0.5 to 20 mass %, more preferably 1 to 15 mass %, particularly preferably 2 to 10 mass %, and may further be 2 to 8 mass %, or 2 to 5 mass %.

[0080] Furthermore, when the aqueous inkjet ink of this embodiment contains polyethylene glycol having a number average molecular weight of MP in an amount of WP [mass %] relative to the total amount of the aqueous inkjet ink, the value expressed as MP x WP is preferably 200 to 10,000, and particularly preferably 500 to 6,000. An aqueous inkjet ink having this value of 200 to 10,000 exhibits particularly excellent initial ejection stability and standby ejection properties. When the aqueous inkjet ink of this embodiment contains two or more types of polyethylene glycol, it is preferable that the sum of the MP×WP values ​​calculated for the respective polyethylene glycols falls within the above range.

[0081] Furthermore, from the viewpoint of improving both the print quality and abrasion resistance of the printed matter, when the mass content of polyethylene glycol is taken as 1, the mass content of resin (C-1) is preferably 0.2 to 7.5, more preferably 0.3 to 6.5, and particularly preferably 0.5 to 5.5.

[0082] <Water-soluble organic solvent> The aqueous inkjet ink of this embodiment may contain a water-soluble organic solvent, although the term "water-soluble organic solvent" in this disclosure does not include polyethylene glycol or compounds that fall under the category of the organic compound (B) described above.

[0083] Specific examples of the water-soluble organic solvent include alkane monools having 2 to 4 carbon atoms; alkane diols having 2 to 6 carbon atoms; alkane triols having 3 to 6 carbon atoms; polypropylene glycols (provided that the number of propylene oxide groups is 2 or 3); (poly)ethylene glycol monoalkyl ethers (provided that the alkyl group at the molecular terminal has 1 to 4 carbon atoms and the number of ethylene oxide groups is 1 to 3); (poly)propylene glycol monoalkyl ethers (provided that the alkyl group at the molecular terminal has 1 to 4 carbon atoms and the number of propylene oxide groups is 1 to 3); butylene glycol monoalkyl ethers (provided that the alkyl group at the molecular terminal has 1 to 4 carbon atoms). pentylene glycol monoalkyl ethers (wherein the alkyl group at the molecular terminal has 1 to 4 carbon atoms); (poly)ethylene glycol dialkyl ethers (wherein the alkyl groups at the molecular terminal each have 1 to 4 carbon atoms and the number of ethylene oxide groups is 1 to 4); lactams (wherein the lactam ring has 5 to 7 atoms, and an alkyl group having 1 to 2 carbon atoms, a hydroxyalkyl group having 1 to 2 carbon atoms, or a vinyl group may be bonded to the nitrogen atom and / or carbon atom that constitutes the lactam ring); alkanolamines (wherein the number of amino groups is 1, the number of hydroxyl groups is 1 to 3, and the number of carbon atoms is 3 to 9); and the like can be used. These other water-soluble organic solvents may be used alone or in combination of two or more. In the present disclosure, "(poly)ethylene glycol" and "(poly)propylene glycol" respectively refer to "ethylene glycol and / or polyethylene glycol" and "propylene glycol and / or polypropylene glycol."

[0084] When the aqueous inkjet ink of this embodiment contains the above-mentioned water-soluble organic solvents, the total content thereof is preferably 2 to 35 mass% of the total amount of the aqueous inkjet ink, more preferably 3 to 25 mass%, and particularly preferably 5 to 20 mass%. By keeping the total content of the water-soluble organic solvents within the above range, it is possible to maintain an appropriate viscosity for ejection from the inkjet head, and the initial ejection stability and standby ejection performance are improved. Furthermore, no water-soluble organic solvent remains in the printed matter, resulting in a printed matter with good abrasion resistance.

[0085] <Alkanediols with 2 to 6 carbon atoms> In one embodiment, the aqueous inkjet ink of this embodiment preferably contains an alkanediol having 2 to 6 carbon atoms as the water-soluble organic solvent. Because alkanediols having 2 to 6 carbon atoms have two hydroxyl groups, they have good affinity with the acetylenic diol compound (A) and polyethylene glycol, which also have hydroxyl groups. As a result, the organic compound (B) and resin (C-1) can be suitably stabilized, resulting in significantly improved initial ejection stability, standby ejection, and abrasion resistance of printed matter. This effect is particularly pronounced when the organic compound (B) is one or more compounds selected from the group consisting of acetylenic diol compounds represented by the above general formula (2) where i1 + i2 is 0 or 1, and medium-chain alkanediol compounds. Furthermore, alkanediols having 2 to 6 carbon atoms volatilize quickly on the printing substrate, making it easier to obtain printed matter that is free from color bleeding.

[0086] Examples of the alkanediols having 2 to 6 carbon atoms that can be used include ethylene glycol, propylene glycol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,2-pentanediol, 1,5-pentanediol, 1,2-hexanediol, 2-methyl-1,3-propanediol, 3-methyl-1,3-butanediol, 2-methyl-2,4-pentanediol, and 3-methyl-1,5-pentanediol. These compounds may be used alone or in combination of two or more.

[0087] Among these, it is preferable to use one or more selected from the group consisting of propylene glycol, 1,3-butanediol, 2,3-butanediol, 3-methyl-1,3-butanediol, and 2-methyl-2,4-pentanediol, because they have an easy balance of drying properties, excellent standby ejection properties, abrasion resistance of printed matter, and excellent suppression of mixed color bleeding. In particular, when using, as the organic compound (B), one or more compounds selected from the group consisting of acetylene diol compounds represented by the above general formula (2) where i1 + i2 is 0 or 1, and medium-chain alkanediol compounds, it is particularly preferable to use one or more compounds selected from the group consisting of propylene glycol, 1,3-butanediol, and 2-methyl-2,4-pentanediol, since all of the above-mentioned effects, i.e., standby ejection properties, abrasion resistance of printed matter, and suppression of color bleeding, are significantly improved.

[0088] The content of the alkanediols having 2 to 6 carbon atoms is preferably 1 to 25% by mass, more preferably 3 to 20% by mass, and particularly preferably 5 to 15% by mass, of the total amount of the aqueous inkjet ink, from the viewpoints of improving the initial ejection stability and standby ejection property, as well as obtaining printed matter that is free from color bleeding and has excellent abrasion resistance.

[0089] Furthermore, since the effects of the polyethylene glycol described above are preferably exhibited, the standby ejection properties of the aqueous inkjet ink are improved, and printed matter with excellent abrasion resistance can be obtained. Therefore, when the mass content of polyethylene glycol is taken as 1, the mass content of the alkanediol having 2 to 6 carbon atoms is preferably 0.2 to 12, and particularly preferably 0.6 to 8.0.

[0090] <Specific (poly)propylene glycol monoalkyl ethers> Meanwhile, the aqueous inkjet ink of this embodiment may contain, among (poly)propylene glycol monoalkyl ethers, compounds in which the alkyl group at the molecular terminal has 2 to 4 carbon atoms and the number of propylene oxide groups is 1 or 2 (referred to as "specific (poly)propylene glycol monoalkyl ethers" in this disclosure). Specific (poly)propylene glycol monoalkyl ethers have an appropriately low surface tension at 25°C, which makes it easy to improve initial ejection stability and prevent white voids in printed materials. Furthermore, since the specific (poly)propylene glycol monoalkyl ethers also function as a film-forming aid for the binder resin, a uniform and continuous ink film can be obtained, significantly improving the abrasion resistance of printed materials.

[0091] Examples of specific (poly)propylene glycol monoalkyl ethers that can be used include propylene glycol monoethyl ether, propylene glycol mono-n-propyl ether, propylene glycol monoisopropyl ether, propylene glycol mono-n-butyl ether, propylene glycol monoisobutyl ether, propylene glycol mono-tert-butyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol monoisopropyl ether, dipropylene glycol mono-n-butyl ether, dipropylene glycol monoisobutyl ether, and dipropylene glycol mono-tert-butyl ether. These compounds may be used alone or in combination of two or more.

[0092] Among these compounds, it is preferable to use a compound in which the alkyl group at the molecular terminal is an unbranched alkyl group having 2 or 3 carbon atoms, because these compounds have appropriate boiling points at 1 atmospheric pressure and surface tensions at 25°C, thereby improving ejection stability immediately after the start of printing, improving the abrasion resistance of printed matter, and preventing white spots and color bleeding. Of the compounds listed above, those that satisfy these requirements include propylene glycol monoethyl ether, propylene glycol mono-n-propyl ether, dipropylene glycol monoethyl ether, and dipropylene glycol mono-n-propyl ether. Furthermore, it is particularly preferred to use a compound in which the alkyl group at the molecular terminal is an n-propyl group, i.e., propylene glycol mono-n-propyl ether and / or dipropylene glycol mono-n-propyl ether, because improved affinity with the acetylene diol compound (A) improves standby jetting properties, promotes uniformity and continuous formation of the ink film, and improves the abrasion resistance of printed matter. In particular, it is particularly preferred to use dipropylene glycol mono-n-propyl ether as the specific (poly)oxypropylene monoalkyl ether, also taking into consideration the improvement in standby jetting properties.

[0093] In order to achieve all of the effects of improving the initial ejection stability, preventing white spots in printed matter, and improving abrasion resistance, the content of the specific (poly)propylene glycol monoalkyl ethers is preferably 0.2 to 10 mass%, and particularly preferably 0.5 to 8 mass%, of the total amount of the aqueous inkjet ink.

[0094] <Binder resin> ≪Resin (C-1)≫ The aqueous inkjet ink of this embodiment contains a binder resin. The binder resin includes a resin (C-1) having a glass transition temperature of −60 to 50° C., and the content of the resin (C-1) is 50 mass % or more of the total mass of the resins contained in the aqueous inkjet ink. As described above, by using a certain amount of the resin (C-1), which has a low glass transition temperature and easily forms a uniform continuous film, and by using it in combination with the acetylene diol compound (A) and polyethylene glycol, the abrasion resistance, initial ejection stability, and standby ejection performance of the printed matter are all excellent. Furthermore, when the aqueous inkjet ink containing the binder resin is printed on an impermeable substrate, the viscosity of the aqueous inkjet ink increases significantly as the liquid components volatilize, thereby suppressing color bleeding and improving print quality.

[0095] In this disclosure, the term "binder resin" refers to a resin that contributes to the formation of a continuous ink film. Specifically, a resin contained in an aqueous inkjet ink and whose content is 1.5% by mass or more of the total amount of the aqueous inkjet ink is defined as a "binder resin" in this disclosure. The content is preferably 2.0% by mass or more, and particularly preferably 2.4% by mass or more of the total amount of the aqueous inkjet ink.

[0096] As mentioned above, the glass transition temperature (Tg) of the resin (C-1) is −60 to 50° C. Furthermore, from the viewpoints of being able to form a uniform continuous film and improving the scratch resistance of the printed matter, as well as improving the standby discharge properties of the aqueous inkjet ink, the glass transition temperature of the resin (C-1) is preferably −47 to 49° C., more preferably −50 to 40° C., and particularly preferably −40 to 30° C., and may also be −31 to 25° C.

[0097] The glass transition temperature of binder resins, including resin (C-1), can be measured by a method conforming to JIS K 7121. Specifically, approximately 10 mg of the target resin sample is placed in an aluminum sample pan whose mass has been measured in advance, and the mass is measured again. The sample container and a sample pan prepared without the resin are then placed in a holder in a Shimadzu DSC-60 (differential scanning calorimeter) and measured at a temperature increase rate of 10°C / min to obtain a DSC chart. The intersection of the low-temperature baseline and the tangent to the inflection point of the DSC curve is then determined, and the temperature at this intersection is taken as the glass transition temperature. Indium is used for temperature calibration.

[0098] On the other hand, for acrylic resins, the value calculated by the following formula (6) can be used as the glass transition temperature.

[0099] Formula (6): 1 / Tg=Σ(Wn / Tgn)

[0100] In the above formula (6), Tg represents the glass transition temperature (K) of the resin, Wn represents the mass fraction of the structural unit consisting of polymerizable monomer n constituting the resin, and Tgn represents the glass transition temperature (K) of the homopolymer consisting of each polymerizable monomer n. For the Tgn, for example, values ​​described in "Polymer Handbook (4th Edition)" (Wiley, 1998) can be used.

[0101] The resin (C-1) may be a water-soluble resin or resin microparticles. A combination of a water-soluble resin and resin microparticles may also be used. From the viewpoints of improving initial ejection stability and standby ejection performance, as well as improving the abrasion resistance of printed matter, the resin (C-1) is preferably resin microparticles.

[0102] In this disclosure, a resin with 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 with a solubility of less than 1 g is referred to as a "water-insoluble resin." Furthermore, in this disclosure, among the above-mentioned water-insoluble resins, a resin dispersed in particulate form in water and having a volume-based median diameter (also referred to as "D50" in this disclosure) of 10 to 1,000 nm is referred to as a "resin microparticle." Note that D50 in this disclosure is a value measured at 25°C using a dynamic light scattering particle size distribution analyzer such as the Nanotrac UPA-EX150 manufactured by Microtrac-Bell.

[0103] The resin (C-1) may be any of acrylic resins, styrene resins, maleic anhydride resins, urethane resins, polyester resins, vinyl chloride resins, vinyl acetate resins, vinyl chloride-vinyl acetate copolymer resins, ethylene-vinyl acetate copolymer resins, etc. These resins may be used alone or in combination of two or more.

[0104] Among these, it is preferable to use one or more resins selected from the group consisting of acrylic resins, urethane resins, and polyester resins as resin (C-1).Furthermore, from the viewpoint of being able to produce printed matter with excellent adhesion and scratch resistance to non-absorbent substrates and also being able to improve standby dischargeability, it is preferable to use an acrylic resin and / or a urethane resin as resin (C-1).

[0105] In the present disclosure, the term "acrylic resin" refers to a resin using one or more polymerizable monomers selected from the group consisting of acrylic acid, methacrylic acid, acrylic acid esters, and methacrylic acid esters. In addition to the polymerizable monomers listed above, a styrene-based monomer may also be used as the polymerizable monomer constituting the acrylic resin. However, resins containing maleic acid (anhydride) (at least one selected from "maleic acid" and "maleic anhydride") as a polymerizable monomer are not included in the "acrylic resin" in the present disclosure. The term "maleic anhydride resin" refers to a resin containing at least maleic anhydride as a polymerizable monomer. The maleic anhydride resin may further contain, as a polymerizable monomer, an α-olefin, a styrene-based monomer, acrylic acid, methacrylic acid, an acrylic acid ester, a methacrylic acid ester, or the like.

[0106] The acid value of the resin (C-1) is preferably 0 to 100 mgKOH / g, more preferably 0.5 to 90 mgKOH / g. It is particularly preferably 1 to 80 mgKOH / g. By setting the acid value within the above range, even if a portion of the aqueous inkjet ink dries near the nozzle of the inkjet head, it is possible to suppress a significant increase in viscosity of the aqueous inkjet ink, thereby improving the ejection stability (particularly standby ejection performance). Furthermore, since the printed matter is less susceptible to the influence of the surrounding environment (humidity, etc.), the abrasion resistance of the printed matter is also improved.

[0107] In this disclosure, the "acid value of a resin" refers to the number of milligrams of potassium hydroxide (KOH) required to neutralize the acid groups contained in 1 g of the resin. In this disclosure, the acid value is calculated using the following method. For example, if a resin contains Wa mass% of polymerizable monomers having na acid groups with a valence of va per molecule and a molecular weight of Ma, the acid value (mg KOH / g) can be calculated using the following formula (7):

[0108] Formula (7): (Acid value) = {(va × na × Wa) ÷ (100 × Ma)} × 56.11 × 1000

[0109] In the above formula (7), the number "56.11" is the molecular weight of potassium hydroxide.

[0110] Furthermore, when a water-soluble resin is used as the resin (C-1), the mass average molecular weight of the resin (C-1) is preferably 1,000 to 25,000, and more preferably 5,000 to 20,000. By using a resin (C-1) having the above mass average molecular weight, a uniform continuous film can be formed even in a short drying time, and the scratch resistance of the printed matter is improved.

[0111] In the present disclosure, the mass average molecular weight of a compound is a polystyrene equivalent value that can be measured by a method in accordance with JIS K 7252. Examples of specific measurement conditions are shown below. Equipment used: Tosoh HLC-8320GPC Column used: TSKgel (registered trademark) SuperMultipore HZ-M (3 bottles) Column temperature: 40℃ Developing solvent: tetrahydrofuran ·Flow rate: 0.6mL / min Sample solution concentration: 0.1% by mass Sample solution injection volume: 10 μL

[0112] The preferred content of resin (C-1) contained in the aqueous inkjet ink of this embodiment is preferably 1.5 to 20 mass %, more preferably 2 to 18 mass %, and particularly preferably 5 to 15 mass %, of the total amount of the aqueous inkjet ink, from the viewpoints of improving initial ejection stability and standby ejection performance, and of obtaining printed matter that is free from color bleeding and has excellent abrasion resistance.

[0113] As described above, the content of resin (C-1) is 50% by mass or more of the total mass of resins contained in the aqueous inkjet ink. When at least half of the resins contained in the aqueous inkjet ink are resins (C-1) with a low glass transition temperature, the ink film becomes a uniform, continuous film, improving the abrasion resistance of the printed matter. Furthermore, when the aqueous inkjet ink is printed on an impermeable substrate, the viscosity of the aqueous inkjet ink increases significantly as the liquid components volatilize, thereby suppressing color bleeding and improving print quality. From the above perspectives, the content of resin (C-1) is preferably 50% by mass or more of the total mass of resins contained in the aqueous inkjet ink, more preferably 65% ​​by mass or more, and particularly preferably 75% by mass or more.

[0114] Other binder resins The aqueous inkjet ink of this embodiment may contain binder resins other than the resin (C-1) (also referred to as "other binder resins" in the present disclosure).

[0115] The other binder resin may be a water-soluble resin or resin particles. The types of resins that can be used as the other binder resin are the same as those for the resin (C-1). In one embodiment, it is preferable to use the same type of resin as the resin (C-1) from the viewpoint of improving the scratch resistance of the printed matter because it has good affinity with the resin (C-1).

[0116] Furthermore, from the viewpoint of improving the scratch resistance of the printed matter and also improving standby discharge properties, it is preferable to use a resin having a glass transition temperature of 55 to 130°C as the other binder resin, more preferably a resin having a glass transition temperature of 60 to 120°C, and particularly preferably a resin having a glass transition temperature of 65 to 110°C.

[0117] Furthermore, from the same viewpoint as that of the resin (C-1), that is, from the viewpoint of improving the ejection stability (particularly standby ejection property) and the scratch resistance of the printed matter, the acid value of the other binder resin is preferably 0 to 100 mgKOH / g, more preferably 0.5 to 90 mgKOH / g, and particularly preferably 1 to 80 mgKOH / g.

[0118] When the aqueous inkjet ink of this embodiment contains another binder resin, the suitable content of the other binder resin is preferably 1.5 to 12 mass %, more preferably 1.5 to 10 mass %, and particularly preferably 2 to 8 mass %, of the total amount of the aqueous inkjet ink, from the viewpoint of improving the initial ejection stability and standby ejection performance.

[0119] <Wax resin microparticles> The aqueous inkjet ink of this embodiment may contain wax resin microparticles. It is preferable to use polyolefin resin microparticles as the wax resin microparticles. Although the detailed reason is unclear, polyolefin resin microparticles can be stably dispersed in the aqueous inkjet ink even when used in combination with the resin (C-1) described above. Furthermore, polyolefin resin microparticles are preferably selected from the viewpoint of improving the abrasion resistance, adhesion, etc. of printed matter.

[0120] As the polyolefin, one or more selected from the group consisting of polyethylene, polypropylene, and polybutene can be suitably used, but polyethylene is particularly preferred because it can improve the scratch resistance of printed matter.

[0121] When wax resin microparticles are used, their D50 is preferably 10 to 200 nm, more preferably 20 to 180 nm. When the D50 is within the above range, it is possible to improve the abrasion resistance and adhesion of printed matter. Furthermore, since clogging of inkjet head nozzles is prevented, an aqueous inkjet ink with excellent initial ejection stability can be obtained.

[0122] When wax resin microparticles are used, the amount of the wax resin microparticles relative to the total amount of all resins contained in the aqueous inkjet ink (pigment dispersion resin, binder resin, wax resin microparticles, etc.) is preferably 2 to 25 mass %, and particularly preferably 4 to 20 mass %. By keeping the amount within this range, the scratch resistance and adhesion of the printed matter can be improved without deteriorating the initial ejection stability and standby ejection performance. Furthermore, even during high-speed printing, a printed matter having sufficient abrasion resistance can be obtained while maintaining favorable initial ejection stability and standby ejection properties. Therefore, the blending amount of wax resin microparticles relative to the total amount of the aqueous inkjet ink is preferably 0.2 to 2.5 mass%, and particularly preferably 0.5 to 2.0 mass%.

[0123] <Pigments> The aqueous inkjet ink of this embodiment contains a pigment. Any conventionally known organic or inorganic pigment can be used as the pigment, and for example, pigments represented by the following color index names can be used. Namely, as red pigments, CI 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; Violet pigments include CI Pigment Violet 19, 23, 29, 32, 36, 37, 42, and 50; As orange pigments, CI 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, CI Pigment Blue 15, 15:3, 15:4, 15:6, 16, 60, 64, 79; As green pigments, CI Pigment Green 7, 10, 36, 48; As yellow pigments, CI 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; Black pigments include CI Pigment Black 1, 7, and 11; White pigments include CI Pigment White 4, 5, 6, 21, and the like. These pigments may be used alone or in combination of two or more. Also, a solid solution of two or more of the pigments listed above may be used as a pigment.

[0124] The content of the pigment in the aqueous inkjet ink of this embodiment is adjusted depending on the intended use of the printed matter produced using the aqueous inkjet ink, but is preferably 0.5 to 30 mass% of the total amount of the aqueous inkjet ink. In addition, except for white aqueous inkjet inks (aqueous white inks), the content of the pigment is more preferably 0.5 to 12 mass%, and particularly preferably 1 to 8 mass%, in order to obtain printed matters with high density without deteriorating the jetting stability of the aqueous inkjet ink. On the other hand, in the case of aqueous white inks, the content of the pigment is more preferably 5 to 25 mass%, and particularly preferably 10 to 20 mass%, in order to obtain printed matters with high hiding power without deteriorating the jetting stability of the aqueous white ink.

[0125] <Pigment dispersing resin> The aqueous inkjet ink of this embodiment may contain a resin (pigment dispersing resin) used for pigment dispersion purposes. Compared to pigments dispersed without using a pigment dispersing resin (self-dispersing pigments, pigments dispersed with a surfactant, etc.), pigments dispersed using a pigment dispersing resin have superior dispersion stability, resulting in an aqueous inkjet ink with excellent initial ejection stability and standby ejection stability. Furthermore, selecting a pigment dispersing resin is preferable because it does not adversely affect the abrasion resistance of printed matter.

[0126] When a pigment dispersing resin is used, a resin having pigment dispersibility from among the binder resins described above may be used as the pigment dispersing resin. In this case, a resin having pigment dispersibility from among the resins (C-1) described above may be used as the pigment dispersing resin. The content of the resin (C-1) used as the pigment dispersing resin is included in the content of the resin (C-1) in the total mass of the resins described above. However, since the pigment dispersion resin is present near the surface of the pigment and can inhibit the formation of a continuous film, and from the viewpoint that the formation of a uniform continuous film improves the scratch resistance of the printed matter, it is preferable that the pigment dispersion resin is provided as a pigment dispersion liquid in which the pigment and the pigment dispersion resin are dispersed in advance, and then the binder resin is added to the pigment dispersion liquid and blended into the aqueous inkjet ink.

[0127] The type of pigment dispersion resin is not particularly limited, and any of acrylic resins, styrene resins, maleic acid (anhydride) resins, urethane resins, polyester resins, etc. can be used. These resins may be used alone or in combination of two or more. Among these, it is preferable to use one or more selected from the group consisting of acrylic resins, maleic acid (anhydride) resins, and urethane resins, because they can improve initial ejection stability and standby ejection performance, have wide material selectivity, and are easy to synthesize. Furthermore, it is particularly preferable to use the same type of resin as the resin (C-1) as the pigment dispersion resin, because this improves affinity with the resin (C-1), making it less likely for the pigment to become non-uniform within the aqueous inkjet ink and preventing the pigment from inhibiting the formation of a uniform and continuous ink film, thereby improving the abrasion resistance of printed matter.

[0128] The pigment dispersion resin may be a resin synthesized by a conventional method or a commercially available product. There are no particular limitations on its structure; for example, resins having a random structure, block structure, graft structure, hyperbranched structure, etc. can be used. In one embodiment, the pigment dispersion resin preferably has a block structure or a graft structure. Pigment dispersion resin free in the aqueous inkjet ink may adsorb to the acetylene diol compound (A), polyethylene glycol, organic compound (B), etc., potentially deteriorating the initial ejection stability, standby ejection stability, and print quality and abrasion resistance of the printed material. Therefore, in the aqueous inkjet ink of this embodiment, a pigment dispersion resin having a block structure or a graft structure, which is less likely to detach from the pigment, is preferably used. For the same reason, it is also preferable to crosslink the pigment dispersion resin adsorbed on the pigment surface with a crosslinking agent or the like (i.e., use a crosslinked pigment dispersion resin).

[0129] In the aqueous inkjet ink of this embodiment, a water-soluble resin may be selected as the pigment dispersing resin, or a water-insoluble resin may be selected, or a water-soluble resin and a water-insoluble resin may be used in combination.

[0130] When a water-soluble resin is used as the pigment dispersing resin, its acid value is preferably 60 to 400 mgKOH / g, more preferably 70 to 350 mgKOH / g, particularly preferably 80 to 300 mgKOH / g, and may be 90 to 300 mgKOH / g or 100 to 300 mgKOH / g. By setting the acid value within the above range, it becomes easy to maintain the dispersion stability of the pigment, and the initial ejection stability and standby ejection performance are improved.

[0131] On the other hand, when a water-insoluble resin is used as the pigment dispersing resin, its acid value is preferably 0 to 100 mgKOH / g, more preferably 5 to 90 mgKOH / g, and even more preferably 10 to 80 mgKOH / g. If the acid value is within the above range, it becomes easy to obtain a printed matter with excellent abrasion resistance.

[0132] In the aqueous inkjet ink of this embodiment, it is preferable to introduce an aromatic group into the pigment dispersion resin, because improved pigment adsorption not only improves the pigment dispersion stability but also suppresses liberation of the pigment dispersion resin, thereby preventing deterioration in initial jetting stability, standby jetting performance, and the print quality of the printed matter. Examples of aromatic groups include, but are not limited to, phenyl, naphthyl, anthryl, tolyl, xylyl, mesityl, and anisyl groups. Of these, one or more groups selected from the group consisting of phenyl, naphthyl, and tolyl are preferably selected from the viewpoint of improving the pigment dispersion stability, initial jetting stability, standby jetting performance, and the print quality of the printed matter.

[0133] From the viewpoint of improving the dispersion stability of the pigment, the initial ejection stability and standby ejection properties, and the print quality of the printed matter, the amount of the aromatic ring-containing polymerizable monomer introduced is preferably 5 to 75 mass %, more preferably 10 to 65 mass %, and particularly preferably 15 to 55 mass %, relative to the total amount of polymerizable monomers constituting the pigment dispersion resin.

[0134] When the pigment dispersing resin does not also serve as the resin (C-1), the blending amount of the pigment dispersing resin is preferably 3 to 80 mass %, more preferably 5 to 70 mass %, and particularly preferably 10 to 60 mass %, relative to the blending amount of the pigment. Furthermore, from the viewpoint of obtaining a printed matter with excellent abrasion resistance, the blending amount of the pigment dispersing resin is preferably 2 to 50 mass %, more preferably 3 to 45 mass %, and particularly preferably 4 to 40 mass %, relative to the blending amount of the resin (C-1).

[0135] <Water> The aqueous inkjet ink of this embodiment contains water. The water is preferably ion-exchanged water (deionized water) or distilled water. The water content is preferably 45 to 85% by mass, and particularly preferably 50 to 80% by mass, of the total amount of the aqueous inkjet ink. Water has a low boiling point, so it volatilizes preferentially from the aqueous inkjet ink. By setting the water content within the above range, after the water volatilizes preferentially on the printing substrate, the acetylene diol compound (A) and polyethylene glycol have favorable affinity with the organic compound (B) and resin (C-1), forming a continuous ink film, thereby improving the scratch resistance of the printed matter.

[0136] <Other ingredients> The aqueous inkjet ink of this embodiment may contain, in addition to the above-mentioned components, a pH adjuster and other additives. Examples of the other additives include preservatives, ultraviolet absorbers, and infrared absorbers. These components may each contain one or more conventionally known compounds.

[0137] <Method for manufacturing water-based inkjet ink> The aqueous inkjet ink of this embodiment can be produced by a conventionally known method. For example, a pigment dispersion is produced by dispersing a pigment in a medium containing at least water (aqueous medium). Then, water, the acetylene diol compound (A), polyethylene glycol, the organic compound (B), the resin (C-1), and the like are added to the pigment dispersion, followed by thorough stirring and mixing, and then removing coarse particles by filtration, centrifugation, or the like. However, the method for producing the aqueous inkjet ink of this embodiment is not limited to the above-described method.

[0138]

[0044] From the viewpoint that the organic compound (B) and the resin (C-1) are suitably stabilized in the aqueous inkjet ink, and that the initial ejection stability, standby ejection property, print quality, and scratch resistance of the printed matter are all excellent, it is preferable to produce the aqueous inkjet ink by a method in which a mixed solution containing a pigment dispersion, water, the acetylene diol compound (A), and polyethylene glycol is produced, and then the organic compound (B) and the resin (C-1) are added and mixed.

[0139] <Characteristics of water-based inkjet ink> The aqueous inkjet ink of this embodiment preferably has a viscosity of 3 to 15 mPa·s at 25°C. This viscosity range allows stable ejection of aqueous inkjet ink droplets not only from inkjet heads with ejection frequencies of approximately 4 to 10 kHz, but also from inkjet heads with high ejection frequencies of approximately 20 to 70 kHz. In particular, when the aqueous inkjet ink of this embodiment has a viscosity of 4 to 10 mPa·s at 25°C, the aqueous inkjet ink can be ejected stably even when an inkjet head with a design resolution of 600 dpi or higher is used. In this disclosure, the viscosity is measured at 25°C using a cone-plate rotational viscometer (E-type viscometer, cone angle 1°34') such as the TVE25L viscometer manufactured by Toki Sangyo Co., Ltd.

[0140] Furthermore, in order to obtain an aqueous inkjet ink that is excellent in initial ejection stability and print quality of printed matter, the static surface tension of the aqueous inkjet ink of this embodiment at 25°C is preferably 18 to 35 mN / m, and particularly preferably 21 to 32 mN / m. Note that in the present disclosure, the static surface tension is a value measured in an environment of 25°C using the Wilhelmy method (plate method) using an "Automatic Surface Tensiometer CBVP-Z" manufactured by Kyowa Interface Science Co., Ltd.

[0141] <Water-based inkjet ink set> The aqueous inkjet ink of this embodiment may be used alone, or two or more aqueous inkjet inks may be combined to form an aqueous inkjet ink set. Examples of aqueous inkjet ink sets include a four-color aqueous inkjet ink set (process color ink set) consisting of a cyan aqueous inkjet ink (aqueous cyan ink), a magenta aqueous inkjet ink (aqueous magenta ink), a yellow aqueous inkjet ink (aqueous yellow ink), and a black aqueous inkjet ink (aqueous black ink); a five-color aqueous inkjet ink set that further includes an aqueous white ink in addition to the process color ink set; and the like. It is preferable that all of the aqueous inkjet inks constituting the aqueous inkjet ink set satisfy the requirements of the embodiment of the present disclosure described above.

[0142] <Ink-pretreatment liquid set> The aqueous inkjet ink of this embodiment and the aqueous inkjet ink set described above can also be used in a form combined with a pretreatment liquid containing an aggregating agent (in the form of an ink-pretreatment liquid set). By applying a pretreatment liquid containing an aggregating agent to a printing substrate before printing with the aqueous inkjet ink, a layer (ink aggregation layer) can be formed that intentionally aggregates the solid components contained in the aqueous inkjet ink. By then landing the aqueous inkjet ink on the ink aggregation layer, coalescence of droplets of the aqueous inkjet ink and color bleeding can be prevented, significantly improving the print quality of the printed matter.

[0143] As the flocculant, for example, a water-soluble inorganic or organic salt containing a polyvalent metal ion, and a resin having a cationic group in which the cationic group equivalent is greater than the anionic group equivalent can be used.

[0144] In the case of a pretreatment liquid that is printed on a printing substrate by being ejected from an inkjet head, the pretreatment liquid preferably contains, in addition to the above-mentioned coagulant, an acetylene diol compound (A), polyethylene glycol, and an organic compound (B). The inclusion of these components in the pretreatment liquid improves the initial ejection stability, standby ejection performance, and wetting and spreading performance on the printing substrate, as in the case of the aqueous inkjet ink of this embodiment. Furthermore, uniform printing of the pretreatment liquid on the printing substrate significantly improves the print quality of the final print.

[0145] Furthermore, it is particularly preferable that the pretreatment liquid printed on the printing substrate by ejection from an inkjet head contains, in addition to the above-mentioned components, a resin (C-1). When the pretreatment liquid further contains a resin (C-1), it becomes easy to significantly improve the scratch resistance of the final printed matter while maintaining the initial ejection stability and standby ejection properties in a suitable state.

[0146] Below, examples of the composition of the pretreatment liquid that is preferably used in a method in which the liquid is printed onto a printing substrate by being ejected from an inkjet head are shown. Calcium lactate pentahydrate (flocculant) 5.0% by mass Surfynol 2502 (acetylene diol compound (A)) 1.0% by mass Polyethylene glycol (number average molecular weight 600) 10.0% by mass 1,2-octanediol (organic compound (B)) 0.5% by mass Superflex 650 (Resin (C-1)) 19.4% by mass Proxel GXL 0.1% by mass Ion-exchanged water 64.0% by mass

[0147] Of the above compositions, "Superflex 650" refers to urethane resin particles (solid content = 26% by mass, glass transition temperature = -17°C) manufactured by Daiichi Kogyo Seiyaku Co., Ltd. "Surfynol 2502" and "Proxel GXL" will be described later.

[0148] <Inkjet printing method> The aqueous inkjet ink of this embodiment is used in the inkjet printing method described above. That is, the inkjet printing method performed using the aqueous inkjet ink of this embodiment includes a step of ejecting the ink onto a printing substrate from an inkjet head having fine nozzles (ejecting step). In addition, the aqueous inkjet ink ejected onto the printing substrate is preferably dried by a drying mechanism (drying step).

[0149] ≪Discharge process≫ In the ejection process, the inkjet head can be operated in two ways: a shuttle (scan) method, in which the inkjet head is scanned back and forth in a direction perpendicular to the transport direction of the printing substrate while ejecting and recording the aqueous inkjet ink; and a single-pass method, in which the inkjet head is scanned back and forth in a direction perpendicular to the transport direction of the printing substrate while ejecting and recording the aqueous inkjet ink as the printing substrate passes below a fixedly disposed inkjet head. The inkjet head equipped with the aqueous inkjet ink of this embodiment may be either a shuttle method or a single-pass method. Of these, the single-pass method is preferably selected because it reduces deviation in the landing position of aqueous inkjet ink droplets, improving the print quality of printed matter, and further enables high-speed printing and high productivity as an alternative to plate-based printing.

[0150] The method of ejection from the inkjet head can also be selected from any known methods, such as a piezoelectric method that uses the volume change of a piezoelectric element, a thermal method that ejects aqueous inkjet ink by bubbles generated by heating a heater, and a valve method that ejects pressurized aqueous inkjet ink by opening and closing a nozzle cover (valve) with a solenoid.

[0151] The volume of droplets of the aqueous inkjet ink ejected from the inkjet head is preferably 0.5 to 20 picoliters, and particularly preferably 0.5 to 15 picoliters, from the viewpoints of reducing the drying load and improving print quality. Furthermore, from the viewpoint of improving print quality, it is preferable to adjust the printing conditions (specifically, the driving frequency and number of inkjet heads installed, and the printing speed) so that the recording resolution of the printed matter is 600 dpi or higher, and particularly preferably 1200 dpi or higher.

[0152] ≪Drying process≫ Examples of drying methods used in the drying mechanism used in the drying step include heat drying, hot air drying, infrared drying (e.g., infrared with a wavelength of 700 to 2500 nm), microwave drying, and drum drying. One or more of these methods can be selected and used as desired in the drying step. When two or more of the above drying methods are used, they may be used separately (e.g., consecutively) or simultaneously. For example, by using heat drying and hot air drying in combination, the aqueous inkjet ink can be dried more quickly than when each method is used alone.

[0153] In particular, from the viewpoint of preventing bumping of the liquid components in the aqueous inkjet ink and obtaining printed matter with excellent print quality, when a heat drying method is used, it is preferable that the drying temperature be 35 to 100° C., and when a hot air drying method is used, it is preferable that the hot air temperature be 50 to 250° C. From the same viewpoint, when an infrared drying method is used, it is preferable that 50% or more of the integrated value of the total output of the irradiated infrared rays is in the wavelength range of 700 to 2200 nm.

[0154] <Printing base material> The printing substrate onto which the aqueous inkjet ink of this embodiment is printed is not particularly limited. On the other hand, the aqueous inkjet ink of this embodiment can be suitably used on non-permeable substrates. Generally, when a non-permeable substrate is used as the printing substrate, the aqueous inkjet ink does not penetrate, and therefore the printed matter is likely to suffer from color bleeding and deterioration of abrasion resistance. In contrast, by using the aqueous inkjet ink of this embodiment, it is easy to obtain a printed matter that is free from color bleeding and has excellent water resistance, even on a non-permeable substrate.

[0155] Examples of impermeable substrates include plastic films and sheets such as polyethylene terephthalate (PET) film, polypropylene (PP) film, polyethylene film, nylon film, polystyrene film, and polystyrene sheet; metals such as aluminum, iron, stainless steel, and titanium; and glass.

[0156] The aqueous inkjet ink of this embodiment can also be used for printing on printing substrates other than the above-mentioned impermeable substrates. Examples of printing substrates other than impermeable substrates include paper such as high-quality paper, plain paper, recycled paper, liner paper, coated paper, art paper, and cast paper.

[0157] The printing substrates listed above may have a smooth or uneven surface. The printing substrates may be transparent, translucent, or opaque. The printing substrates may be in the form of rolls or sheets. Two or more of the printing substrates listed above may be bonded together to form the printing substrate. A release adhesive layer or the like may be provided on the side opposite the printed surface, or an adhesive layer or the like may be provided on the printed surface after printing.

[0158] The improved wetting and spreading properties of the aqueous inkjet ink of this embodiment improve the print quality and drying properties, and the uniformity of the printed surface results in a printed product with good abrasion resistance and water resistance. Therefore, it is also preferable to subject the printing surface of the printing substrates listed above to surface modification such as corona treatment and plasma treatment before printing.

[0159] For example, when corona treatment is performed on the above plastic films and sheets, the discharge amount of the corona treatment is 20 to 1,000 W·min / m 2 It is preferable to set the temperature to 30W to 800W·min / m 2 By setting the discharge amount in the corona treatment within the above range, damage to the printing substrate is suppressed, and the print quality and abrasion resistance of the printed matter are improved.

[0160] <Printed material> A printed matter produced using the aqueous inkjet ink of this embodiment has a printing substrate and a printed layer containing an image and / or characters formed on the printing substrate. The printed layer is a layer formed by drying the aqueous inkjet ink of this embodiment printed on the printing substrate, i.e., a layer consisting of an ink film. In one embodiment, the above-mentioned inkjet printing method can be used as a method for printing the aqueous inkjet ink of this embodiment to produce a printed matter. [Example]

[0161] The aqueous inkjet ink of this embodiment will be described in more detail below with reference to examples and comparative examples. In the following description, "parts" and "%" mean "parts by mass" and "% by mass", respectively, unless otherwise specified.

[0162] <Example of manufacturing a water-based solution of acrylic pigment dispersion resin> A reaction vessel equipped with a gas inlet tube, thermometer, condenser, and stirrer was charged with 56 parts of 2-butanone. Next, 56 parts of benzyl methacrylate (polymerizable monomer), 0.3 parts of 2,2'-azobisisobutyronitrile (polymerization initiator), and 2.2 parts of 2-(dodecylthiocarbonothioylthio)-isobutyric acid were added. After the atmosphere inside the reaction vessel was replaced with nitrogen gas, the contents inside the reaction vessel were heated to 75°C, and a polymerization reaction was carried out for 3 hours while maintaining the internal temperature at 75°C, yielding a polymer (A block) composed of benzyl methacrylate. After the polymerization reaction was completed, the contents were cooled to room temperature, and then 44 parts of 2-butanone, 28 parts of butyl methacrylate, and 16 parts of methacrylic acid were added to the reaction vessel. The atmosphere inside the reaction vessel was again purged with nitrogen gas, and the contents inside the reaction vessel were heated to 75°C. The polymerization reaction was carried out for 3 hours while maintaining the internal temperature at 75°C, thereby obtaining an acrylic pigment dispersion resin having an AB block structure in which a copolymer (block B) composed of butyl methacrylate and methacrylic acid was added to the A block. The contents of the reaction vessel were then cooled to room temperature, and 17 parts of dimethylaminoethanol was added to neutralize the acrylic pigment dispersion resin. 150 parts of ion-exchanged water was then added. The contents were then heated, and 2-butanone was distilled off by azeotropy with the ion-exchanged water. Ion-exchanged water was then added to adjust the solids concentration to 20%, yielding an aqueous solution of the acrylic pigment dispersion resin. The mass-average molecular weight of the acrylic pigment dispersion resin measured using the method described above was 23,000. The glass transition temperature of the acrylic pigment dispersion resin calculated using the above formula (6) was 53°C. The acid value of the acrylic pigment dispersion resin calculated using the above formula (7) was 104 mgKOH / g.

[0163] In the present disclosure, the term "aqueous solution" refers to a solution containing an aqueous medium and components dispersed and / or dissolved in the aqueous medium.

[0164] <Production example of magenta pigment dispersion> 450 g of CI Pigment Red 122 (DIC Corporation, "FASTOGEN SUPER MAGENTA RG"), 560 g of an aqueous solution of acrylic pigment dispersion resin, and 1,990 g of ion-exchanged water were added to a mixing vessel (10 L volume) equipped with a stirrer and stirred (premixed) for 1 hour. Next, the mixture was circulated and dispersed using a Shinmaru Enterprises "Dynomill" (0.6 L volume) filled with 1,800 g of 0.5 mm diameter zirconia beads. The D50 of the mixture was measured using the above-mentioned device at regular intervals (e.g., every hour), and the circulatory dispersion was terminated when the D50 reached 180 nm or less, producing a magenta pigment dispersion with a pigment concentration of 15%.

[0165] <Production example of yellow pigment dispersion> A yellow pigment dispersion with a pigment concentration of 15% was obtained using the same materials and method as for the magenta pigment dispersion, except that CI Pigment Yellow 74 (Heubach's "Inkjet Yellow 5GX-W") was used as the pigment.

[0166] <Production example of cyan pigment dispersion> A cyan pigment dispersion with a pigment concentration of 15% was obtained using the same materials and method as for the magenta pigment dispersion, except that CI Pigment Blue 15:3 (FASTOGEN BLUE LA5380 manufactured by DIC Corporation) was used as the pigment and circulatory dispersion was continued until the D50 reached 150 nm or less.

[0167] <Production example of acrylic binder resin 1> A reaction vessel equipped with a thermometer, a condenser, a stirrer, and a dropping funnel was charged with 40 parts of ion-exchanged water and 0.2 parts of an emulsifier, Aqualon KH-10 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) Separately, a separate mixing vessel equipped with a stirrer was charged with polymerizable monomers, namely, 52 parts of methyl methacrylate, 36 parts of butyl acrylate, 11 parts of methacrylic acid, and 1 part of sodium p-toluenesulfonate; 53 parts of ion-exchanged water; and 1.8 parts of an emulsifier, Aqualon KH-10 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), and the mixture was thoroughly stirred and mixed to prepare an emulsion. Five portions of the emulsion were taken and placed in the reaction vessel. The contents were then heated to 60°C. The atmosphere inside the reaction vessel was then purged with nitrogen gas. Then, 3 parts of a 5% aqueous solution of potassium persulfate and 4 parts of a 1% aqueous solution of anhydrous sodium bisulfite were added to initiate the polymerization reaction. After the polymerization reaction began, the temperature of the contents inside the reaction vessel was maintained at 60°C. The remaining emulsion, 2 parts of a 5% aqueous solution of potassium persulfate, and 6 parts of a 1% aqueous solution of anhydrous sodium bisulfite were added dropwise over 1.5 hours. After the addition was completed, stirring was continued for another 2 hours. The contents inside the reaction vessel were then cooled to room temperature, and diethylaminoethanol was added until the pH of the contents reached 8.5. Ion-exchanged water was then added to adjust the solids concentration to 30%, yielding an aqueous dispersion of acrylic binder resin 1, which is resin microparticles. The glass transition temperature of the acrylic binder resin 1 calculated using the above formula (6) was 28°C, and the acid value of the acrylic binder resin 1 calculated using the above formula (7) was 74 mgKOH / g.

[0168] <Production examples of acrylic binder resins 2 to 7> Aqueous dispersions of acrylic binder resins 2 to 7 (each with a solid content of 30%), which are resin particles, were obtained using the same materials and method as for the acrylic binder resin 1, except that the type and amount of polymerizable monomer used to prepare the emulsion were changed as shown in Table 1 below.

[0169] [Table 1]

[0170] Table 1 above also lists the type and amount of polymerizable monomer used in producing acrylic binder resin 1, as well as the glass transition temperatures (calculated using the above formula (6)) and acid values ​​(calculated using the above formula (7)) of acrylic binder resins 1 to 7.

[0171] <Production Examples of Acetylene Diol Compounds 1 and 2> Using the method described in Examples 6 to 9 of JP 2001-215690 A, 2,4,7,9-tetramethyl-5-decyne-4,7-diol ("Surfynol 104" manufactured by Evonik Japan Ltd.) was used as a diol starting material, and the amounts of ethylene oxide and propylene oxide and the synthesis conditions (pressure, temperature, time) were adjusted to synthesize compounds in which ethylene oxide groups and propylene oxide groups were added to the 2,4,7,9-tetramethyl-5-decyne-4,7-diol (acetylene diol compounds 1 and 2). Specifically, two types of compounds were produced: acetylenic diol compound 1 (HLB value 2.7) in which 3 moles of ethylene oxide groups and 11 moles of propylene oxide groups were added to 2,4,7,9-tetramethyl-5-decyne-4,7-diol; and acetylenic diol compound 2 (HLB value 5.0) in which 3.5 moles of ethylene oxide groups and 4 moles of propylene oxide groups were added to 2,4,7,9-tetramethyl-5-decyne-4,7-diol.

[0172] <Manufacturing of aqueous inkjet ink sets> Using the pigment dispersion liquid prepared by the above method, each raw material was added to a mixing vessel equipped with a stirrer so as to obtain the formulation shown in each column of Tables 2-1 to 2-6 below. After all raw materials were added, stirring and mixing was continued until the mixture became sufficiently uniform. The mixture was then filtered through a membrane filter with a pore size of 0.8 μm to produce an aqueous inkjet ink. Furthermore, aqueous inkjet ink sets consisting of an aqueous magenta ink, an aqueous yellow ink, and an aqueous cyan ink were produced by producing aqueous inkjet inks using the above magenta pigment dispersion liquid, yellow pigment dispersion, and cyan pigment dispersion liquid, respectively.

[0173] When producing aqueous inkjet inks, each raw material was added while stirring the mixture in the mixing vessel. In addition, in each column of Tables 2-1 to 2-6, the ingredients were added in the order listed, starting with the top row. However, when producing an aqueous inkjet ink that did not contain one or more of these ingredients, that ingredient was not added, and the next ingredient was added in the order listed. Furthermore, for ingredients containing two or more ingredients, the order of addition of the ingredients within that ingredient was arbitrary.

[0174] [Table 2-1]

[0175] [Table 2-2]

[0176] [Table 2-3]

[0177] [Table 2-4]

[0178] [Table 2-5]

[0179] [Table 2-6]

[0180] The meanings of the abbreviations and details of the product names listed in Tables 2-1 to 2-6 above are as follows. In Tables 2-1 to 2-6, "HLB" represents the HLB value, "Tg" represents the glass transition temperature, and "Nv" represents the solid content concentration. Furthermore, in Tables 2-1 to 2-6, "PEGn" represents polyethylene glycol with a number average molecular weight of n. Surfynol 485: A compound in which an average of 30 moles of ethylene oxide groups are added to 2,4,7,9-tetramethyl-5-decyne-4,7-diol (acetylene diol compound manufactured by Evonik Japan, HLB value = 17.1) Acetylenol E200: A compound in which an average of 20 moles of ethylene oxide groups are added to 2,4,7,9-tetramethyl-5-decyne-4,7-diol (Kawaken Fine Chemicals Co., Ltd., acetylene diol compound, HLB value = 15.9) Surfynol 465: A compound in which an average of 10 moles of ethylene oxide groups are added to 2,4,7,9-tetramethyl-5-decyne-4,7-diol (acetylene diol compound manufactured by Evonik Japan, HLB value = 13.2) Dynol 607: A compound in which an average of 7 moles of ethylene oxide groups are added to 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol (an acetylene diol compound manufactured by Evonik Japan, HLB value = 11.0) Acetylenol E60: A compound in which an average of 6 moles of ethylene oxide groups are added to 2,4,7,9-tetramethyl-5-decyne-4,7-diol (Kawaken Fine Chemicals Co., Ltd., acetylene diol compound, HLB value = 10.8) Surfynol 2502: A compound in which an average of 5 moles of ethylene oxide groups and 2 moles of propylene oxide groups are added to 2,4,7,9-tetramethyl-5-decyne-4,7-diol (acetylene diol compound manufactured by Evonik Japan, HLB value = 7.9) Surfynol DF110D: 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol (acetylene diol compound (surfactant), manufactured by Evonik Japan Co., Ltd., HLB value = 2.7) Surfynol 420: A compound in which an average of 1.3 moles of ethylene oxide groups are added to 2,4,7,9-tetramethyl-5-decyne-4,7-diol (acetylene diol compound (surfactant) manufactured by Evonik Japan, HLB value = 4.0) 1,7-HepD: 1,7-heptanediol (medium-chain alkanediol compound, HLB value = 5.2) 1,2-OctD: 1,2-octanediol (medium-chain alkanediol compound, HLB value = 4.7) 1,8-OctD: 1,8-octanediol (medium-chain alkanediol compound, HLB value = 4.7) 1,9-NonD: 1,9-nonanediol (medium-chain alkanediol compound, HLB value = 4.2) BYK-3420: Polyether-modified siloxane surfactant (manufactured by BYK Japan) BYK-333: Polyether-modified siloxane surfactant (manufactured by BYK Japan) BYK-348: Side-chain polyether-modified siloxane surfactant (manufactured by BYK Japan) KF-6015: Side-chain polyether-modified siloxane surfactant (Shin-Etsu Silicone Co., Ltd.) Nonion K-230: In general formula (5), R 4 is an alkyl group having 12 carbon atoms, s=30, t=0 (NOF Corporation, HLB value=17.5) Takelac W-6061: Polyurethane resin particles manufactured by Mitsui Chemicals (solid content = 30%, glass transition temperature = 25°C) Takelac W-6110: Urethane resin particles manufactured by Mitsui Chemicals (solid content = 32%, glass transition temperature = -20°C) SF470: Superflex 470 (Dai-ichi Kogyo Seiyaku urethane resin particles, solids concentration = 38%, glass transition temperature = -31°C) SF300: Superflex 300 (Dai-ichi Kogyo Seiyaku urethane resin particles, solids concentration = 30%, glass transition temperature = -42°C) Eliter KT-0507: Unitika polyester resin particles (solid content = 25%, glass transition temperature = -25°C) AQUACER515: Wax resin microparticles manufactured by BYK Japan (polyethylene oxide resin microparticles, solid content = 35%, D50 = 30 nm) Proxel GXL: 1,2-benzisothiazol-3-one in dipropylene glycol (1,2-benzisothiazol-3-one: dipropylene glycol: water = 2:6:2, preservative manufactured by Arch Chemicals)

[0181] [Examples 1 to 99, Comparative Examples 1 to 6] The aqueous inkjet ink sets produced by the above-described methods were used to carry out the following evaluations, and the evaluation results are shown in Tables 2-1 to 2-6 above.

[0182] <Evaluation 1: Evaluation of ejection stability (initial ejection)> An inkjet ejection device equipped with a Kyocera inkjet head "KJ4B-QA" (design resolution 600 dpi) was placed in an environment of 25°C, and the water-based cyan ink that makes up the above water-based inkjet ink set was filled in.A nozzle check pattern was then printed, and it was confirmed that the ink was being ejected normally from all nozzles. Next, under the printing conditions of a frequency of 30 kHz and 600 × 600 dpi, OK top coat + paper (Oji Paper Co., Ltd. coated paper, basis weight 104.7 g / m 2) was subjected to a solid print with a printing rate of 100%. The obtained solid print was then visually and with a magnifying glass to check whether the aqueous cyan ink had been applied to the area where it was supposed to be printed first, and the ejection stability (initial ejection) was evaluated. The evaluation criteria were as follows, with ◎, ○, and △ being considered usable. ◎: In the solid print, no chips were found in the area that was supposed to be printed first, or chips were found but were 3 mm or less in length ○: In solid prints, chips measuring more than 3 mm and less than 1 cm were found in the area that was supposed to be printed first. △: In solid prints, chipping of more than 1 cm and less than 2 cm was observed in the area that should have been printed first. ×: In a solid print, a chip of more than 2 cm was found in the area that was supposed to be printed first.

[0183] <Evaluation 2: Evaluation of standby discharge properties> An inkjet head "Samba G3L" (design resolution 1,200 dpi) manufactured by FUJIFILM Dimatix was installed in an inkjet ejection device placed in an environment of 25°C, and a pump, a tube, and an ink tank were also prepared, and the ink supply port of the Samba G3L was connected to the pump, the pump to the ink tank, and the ink tank to the ink outlet of the Samba G3L. Next, the ink tank was filled with the aqueous cyan ink constituting the aqueous inkjet ink set, and the pump was operated to fill the inkjet head and flow channels with the aqueous inkjet ink. A nozzle check pattern was printed to confirm that ink was being ejected normally from all nozzles, and then the inkjet ejection device was left on standby for one hour with the pump running. After one hour, a nozzle check pattern was printed again, and the number of missing nozzles was visually counted to evaluate standby ejection performance. The evaluation criteria were as follows, with ◎, ○, and △ indicating that the ink was usable. ◎: No nozzle missing at all ○: 1 to 4 nozzles missing △: 5 to 9 nozzles were missing ×: 10 or more nozzles were missing

[0184] <Creating printed materials> An inkjet ejection device was prepared, with three Kyocera KJ4B-1200 inkjet heads (design resolution 1200 dpi, nozzle diameter 20 μm) arranged along the transport direction of the printing substrate. Each set of aqueous inkjet inks was loaded in the following order from upstream to downstream in the transport direction: aqueous cyan ink, aqueous magenta ink, and aqueous yellow ink. Additionally, an A4-sized (21 cm wide x 30 cm long) OPP film (RM Tocello OPU-1, 20 μm thick) cut to serve as the printing substrate was fixed on the conveyor with the corona-treated side facing up. The conveyor was then driven at 50 m / min. As the printing substrate passed under the inkjet heads, the aqueous inkjet inks were ejected at a drop volume of 2.6 pL, printing a three-color gradation image or a three-color overprint image. Immediately after printing, the printed substrate was placed in a constant temperature incubator set at 70°C and dried for 3 minutes to produce a three-color gradation image print and a three-color overprinted image print. The "three-color gradation image" is an image in which a cyan gradation image 5 cm wide x 25 cm long printed using aqueous cyan ink (an image with a printing rate varied in 10% increments between 10 and 100%), a magenta gradation image 5 cm wide x 25 cm long printed using aqueous magenta ink, and a yellow gradation image 5 cm wide x 25 cm long printed using aqueous yellow ink are arranged side by side in the order of cyan, magenta, and yellow, with their long sides touching. Furthermore, the above-mentioned "three-color printed image" refers to an image in which a halftone image (10 cm wide x 20 cm long) with a printing rate of 60% using aqueous cyan ink, a halftone image (10 cm wide x 20 cm long) with a printing rate of 60% using aqueous magenta ink, and a halftone image (10 cm wide x 20 cm long) with a printing rate of 60% using aqueous yellow ink are all printed so that they overlap each other (total printing rate of 180%).

[0185] <Evaluation 3: Evaluation of print quality (white areas)> The three-color gradation image prints produced by the above method were visually observed. The print quality of the three-color gradation image prints was evaluated by checking for the presence or absence of blank spaces in the areas printed at 100% coverage. The evaluation criteria were as follows, with ◎, ○, and △ being considered usable. ⊚: No white spots were observed in any of the printed areas of the cyan gradation image, the magenta gradation image, and the yellow gradation image. ○: Slight white spots were observed in one or more of the printed areas of the cyan gradation image, the magenta gradation image, and the yellow gradation image. △: Obvious white spots were observed in only one of the printed areas of the cyan gradation image, the magenta gradation image, and the yellow gradation image. ×: Obvious white spots were observed in two or more of the printed areas of the cyan gradation image, the magenta gradation image, and the yellow gradation image.

[0186] <Evaluation 4: Evaluation of print quality (color bleeding)> The three-color gradation image prints produced by the above-described method were visually observed. The print quality (color bleeding) of the three-color gradation image prints was evaluated by checking the coverage rate at the boundary between the printed area of ​​the cyan gradation image and the printed area of ​​the magenta gradation image, and at the boundary between the printed area of ​​the magenta gradation image and the printed area of ​​the yellow gradation image, where color bleeding began to occur. The evaluation criteria were as follows, with ◎, ○, and △ indicating usable quality. Tables 2-1 to 2-6 list the results of the poorest evaluation results for the cyan-magenta boundary and the magenta-yellow boundary. ◎: No color bleeding was observed even at a printing rate of 80% ○: Color bleeding was observed at a print rate of 80%, but no color bleeding was observed at a print rate of 70% △: Color bleeding was observed at a print rate of 70%, but no color bleeding was observed at a print rate of 60%. ×: Mixed color bleeding was observed at a printing rate of 60%

[0187] <Evaluation 5: Evaluation of abrasion resistance> The three-color superimposed printed image produced by the above method was rubbed strongly with a finger a predetermined number of times. The state of the print after rubbing was then visually inspected to evaluate the rub resistance of the three-color superimposed printed image. The evaluation criteria were as follows, with ◎, ○, and △ being considered usable. ◎: The printed layer did not peel off and the printed substrate did not become exposed even after rubbing it hard with a finger 20 times. ○: The printed layer did not peel off and the printed substrate was not exposed even after rubbing strongly with a finger 15 times, but after rubbing 20 times, the printed matter peeled off and / or the printed substrate was exposed. △: The printed layer did not peel off and the printed substrate was not exposed even after rubbing strongly with a finger 10 times, but after rubbing 15 times, the printed matter peeled off and / or the printed substrate was exposed. ×: When rubbed strongly with a finger 10 times, the printed layer peeled off and / or the printed substrate was exposed.

[0188] As shown in Tables 2-1 to 2-6 above, the aqueous inkjet inks (sets) of Examples 1 to 99 were superior in ejection stability to the aqueous inkjet inks of Comparative Examples 1 to 6, and also had good solid coverage and little color mixing. Furthermore, the print layer also had good abrasion resistance. These results confirmed that the aqueous inkjet inks having the configurations of the present disclosure are excellent aqueous inkjet inks that combine ejection stability, print quality of printed matter, and abrasion resistance.

[0189] Although the present invention has been described with reference to the above-mentioned several embodiments, the present invention is not limited to these several embodiments. Various modifications can be made to the configuration and details of the present invention within the scope of the present invention.

[0190] This disclosure is related to the subject matter described in Japanese Patent Application No. 2024-127605, filed August 2, 2024, the entire disclosure of which is incorporated herein by reference.

Claims

1. An aqueous inkjet ink comprising a pigment, an acetylenic diol compound (A), polyethylene glycol, a binder resin, and an organic compound (B) (excluding the pigment, the acetylenic diol compound (A), the polyethylene glycol, and the resin), The HLB value of the acetylene diol compound (A) is 7.5 to 17.5, the organic compound (B) consists of only carbon atoms, hydrogen atoms, and oxygen atoms and has a plurality of hydroxyl groups; the HLB value of the organic compound (B) is 2.5 to 5.2; the binder resin contains a resin (C-1) having a glass transition temperature of −60 to 50° C., The content of the resin (C-1) is 50% by mass or more of the total mass of the resins contained in the aqueous inkjet ink.

2. 2. The aqueous inkjet ink according to claim 1, wherein the mass of the polyethylene glycol is 1.0 to 20, relative to the mass of the acetylene diol compound (A) taken as 1.

3. 3. The aqueous inkjet ink according to claim 1, wherein the mass of the organic compound (B) is 0.05 to 2.0 relative to the mass of the acetylene diol compound (A) taken as 1.

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

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