Aqueous inkjet ink and printed matter

Abstract

An embodiment of the present invention relates to an aqueous inkjet ink comprising a pigment, a binder resin, a water-soluble organic solvent, an unmodified acetylenediol-based surfactant (A1), and an alkylene oxide-modified acetylenediol-based surfactant (A2) having an HLB value of 4-10, wherein the contents of the unmodified acetylenediol-based surfactant (A1) and the alkylene oxide-modified acetylenediol-based surfactant (A2) are prescribed and the ratio between the content of the unmodified acetylenediol-based surfactant (A1) and the content of the alkylene oxide-modified acetylenediol-based surfactant (A2) is 10-5,000.

Description

Water-based inkjet inks and printed materials

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

[0002] Digital printing is rapidly becoming more popular as printing runs become smaller and market needs become more diverse. Because digital printing does not require plates, it is possible to handle small-lot printing, reduce printing costs, and make it possible to downsize printing equipment.

[0003] Inkjet printing, a type of digital printing method, involves ejecting and landing tiny ink droplets from an inkjet head onto a printing substrate (also referred to simply as "substrate" in this specification) to print an image and / or characters (hereinafter collectively referred to as "printed matter"; the above "image" also includes solid images and seamless images such as checkered patterns) on the printing substrate. Compared to other digital printing methods, inkjet printing is superior in terms of the size and cost of the printing device, ease of full colorization, etc., and has recently been increasingly used in industrial printing applications.

[0004] Inks used in inkjet printing methods range widely, including oil-based, solvent-based, actinic energy ray-curable, and water-based inks. Until now, solvent-based or actinic energy ray-curable inks have been used for industrial printing applications. However, in recent years, there has been an increasing demand for water-based inks due to concerns about and responses to the impact on the environment and people (see, for example, Patent Documents 1 to 4).

[0005] JP 2022-151398 A JP 2021-147400 A JP 2018-70730 A JP 2014-139004 A

[0006] In recent years, there has been an increasing demand for the packaging market as a market for water-based inks used in inkjet printing methods (referred to herein as "aqueous inkjet inks"; hereinafter, simply referred to as "inks"). In the packaging market, printing is performed on printing substrates such as paper containers, labels, and packaging films. These printing substrates are made of a variety of materials, including low-absorbency substrates such as coated paper and art paper, as well as non-absorbency substrates such as polypropylene film, polyethylene terephthalate film, and nylon film. Therefore, in order to promote the development of aqueous inkjet inks in the packaging market, it is necessary to be able to produce printed materials that have excellent color reproducibility and print image quality, and that have properties that can withstand practical use, even on low-absorbency and non-absorbency substrates.

[0007] In contrast, most of the aqueous inkjet inks available to date have been designed for printing on highly absorbent substrates such as plain paper and specialty paper. When such aqueous inkjet inks are used, particularly on non-absorbent substrates, the aqueous inkjet ink does not penetrate and is absorbed into the substrate, resulting in insufficient drying of the aqueous inkjet ink droplets that land on the substrate, and the droplets attract each other and coalesce (beading). When beading occurs, solid filling deteriorates (the occurrence of areas where the ink is not applied in a printed item with a 100% coverage), uneven density occurs, color bleeding occurs, and the like, resulting in a significant degradation of print quality.

[0008] A known method for suppressing beading is to reduce the surface tension of the aqueous inkjet ink. Surfactants are often used as a material for reducing the surface tension. In particular, to sufficiently reduce the surface tension of the aqueous inkjet ink immediately after it lands on the printing substrate, it is preferable to select a compound with a low molecular weight and a high orientation rate toward the droplet surface (air-liquid interface) as the surfactant. However, such surfactants are generally poorly miscible with water. For example, in aqueous inkjet ink present near the nozzle of an inkjet head, the surfactant may be concentrated and oriented at the air-liquid interface. This may result in a localized decrease in the surface tension of the aqueous inkjet ink present near the nozzle, causing the aqueous inkjet ink to overflow from the nozzle. In particular, if this overflowing of ink from the nozzle occurs and progresses during continuous ejection, it can lead to ejection defects (deterioration of continuous ejection performance) such as nozzle clogging or deflected ink flight.

[0009] Furthermore, surfactants with low molecular weights and high orientation rates are present in large amounts on the droplet surfaces, i.e., on the surface of the layer (ink layer) formed when the printed ink dries. Therefore, for example, when a printed matter is rolled up and stored, there is a risk of blocking (a phenomenon in which part of the ink layer is taken up by the printing substrate when the printing substrate stuck to the ink layer is peeled off) occurring.

[0010] Furthermore, when a laminate containing an ink layer inside is manufactured and used as a package such as a pouch (bag), a surfactant with a low molecular weight and a high orientation rate that is present on the surface of the ink layer and / or that has bled onto the surface of the ink layer (a phenomenon in which a certain component seeps out onto the layer surface over time) may pass through each layer constituting the laminate and reach the surface of the laminate (migration). In particular, if the surfactant migrates to the surface that comes into contact with the contents, it may adversely affect the safety of the contents, which may be a problem when the laminate is used for, for example, food packaging or cosmetic packaging.

[0011] As described above, it has conventionally been extremely difficult to simultaneously achieve improved print quality, continuous dischargeability, blocking resistance, and migration resistance.

[0012] As examples of suppressing beading when printing on low-absorbency or non-absorbency substrates by controlling the type and / or amount of surfactant, Patent Document 1 discloses an ink composition (set) that uses a silicone surfactant having a specific structure in combination with a nonionic surfactant having an HLB value of 6.0 or more but less than 12.0 (e.g., polyoxyalkylene alkyl ether surfactants such as "Lutensol XL40" manufactured by BASF and "GENAPOL EP2564" manufactured by Clariant); Patent Document 2 discloses an ink containing a polyoxyalkylene alkyl ether surfactant having a specific structure and having an HLB value measured to be 5.0 to 13.0; and Patent Document 3 discloses an ink that uses a silicone surfactant and a fluorine-based surfactant in combination with a glycol ether organic solvent. Meanwhile, Patent Documents 1 to 3 specifically use low-absorbency substrates such as coated paper to evaluate beading. As described above, when an aqueous inkjet ink is printed on a non-absorbent substrate such as a resin film, the aqueous inkjet ink does not penetrate into the substrate at all, and therefore beading is more likely to occur than when the ink is printed on a low-absorbent substrate. The aqueous inkjet inks specifically disclosed in the above Patent Documents 1 to 3 were also not sufficient in terms of improving beading when printed on a non-absorbent substrate.

[0013] Furthermore, Patent Document 4 discloses an inkjet recording method using an aqueous ink containing a specific acetylene glycol (acetylene diol surfactant) and a nonionic surfactant, with the blending amounts and blending ratios of each component specified. Furthermore, the main example of the aqueous ink specifically disclosed in Patent Document 4 uses 2,4,7,9-tetramethyl-5-decyne-4,7-diol as the acetylene glycol and a polyoxyalkylene alkyl ether surfactant such as polyoxyethylene lauryl ether (with 12 moles of ethylene oxide groups added) as the nonionic surfactant. Here, the 2,4,7,9-tetramethyl-5-decyne-4,7-diol corresponds to the aforementioned "compound having a small molecular weight and a high rate of orientation to the droplet surface (air-liquid interface)," and therefore, the aqueous ink is considered to be effective in suppressing beading. On the other hand, it cannot be said that Patent Document 4 has fully investigated blocking resistance and migration resistance in particular, and in fact, the blocking resistance and migration resistance of the above-mentioned water-based ink cannot be said to be good.

[0014] One embodiment of the present invention has been made to solve the above-mentioned problems, and its object is to provide an aqueous inkjet ink that is free from beading, can stably produce printed matter that is excellent in blocking resistance and migration resistance, even when printed on a low-absorbency printing substrate, and has good continuous ejection properties. Another embodiment of the present invention is to provide a printed matter that is free from beading, and has excellent in blocking resistance and migration resistance, even when printed on a low-absorbency printing substrate.

[0015] 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.

[0016] That is, one embodiment of the present invention relates to an aqueous inkjet ink containing a pigment, a binder resin, a water-soluble organic solvent, and an acetylenic diol-based surfactant (A), wherein the acetylenic diol-based surfactant (A) comprises an unmodified acetylenic diol-based surfactant (A1) and an alkylene oxide-modified acetylenic diol-based surfactant (A2) having an HLB value of 4 to 10, the content of the unmodified acetylenic diol-based surfactant (A1) is 5 to 2,000 ppm relative to the total amount of the aqueous inkjet ink, the content of the alkylene oxide-modified acetylenic diol-based surfactant (A2) is 0.2 to 5 mass% relative to the total amount of the aqueous inkjet ink, and the ratio of the content of the unmodified acetylenic diol-based surfactant (A1) to the content of the alkylene oxide-modified acetylenic diol-based surfactant (A2) [surfactant (A2) / surfactant (A1)] is in the range of 10 to 5,000. Another embodiment of the present invention relates to a printed matter obtained by printing an aqueous inkjet ink onto a printing substrate.

[0017] According to one embodiment of the present invention, it has become possible to provide an aqueous inkjet ink that can stably produce printed matter that is free of beading and has excellent blocking resistance and migration resistance, even when printed on a low-absorbency printing substrate, and that also has good continuous ejection properties. According to another embodiment of the present invention, it has become possible to provide printed matter that is free of beading and has excellent blocking resistance and migration resistance, even when printed on a low-absorbency printing substrate.

[0018]

[0033] The following describes an embodiment of the aqueous inkjet ink of the present invention (hereinafter also referred to simply as "the ink of the present invention") and a printed matter obtained by printing the aqueous inkjet ink. Note that the present invention is not limited to the following description, and includes various modifications that are implemented within the scope of the gist of the invention.

[0019] In general, water, the main solvent of aqueous inkjet inks, has a high surface tension and tends not to wet and spread easily on a printing substrate. Furthermore, when a droplet of aqueous inkjet ink that has landed on a printing substrate comes into contact with an adjacent wet droplet due to its high surface tension and while still wet, a force acts on each droplet in a direction that reduces the surface area, causing the droplets to attract each other and resulting in beading. As described above, beading can also lead to poor solid coverage, uneven density, color bleeding, and other problems, resulting in a significant degradation of print quality.

[0020] In addition, a suitable method for suppressing beading is to use a surfactant that has a small molecular weight and a high orientation rate to the droplet surface (air-liquid interface). However, such surfactants are poorly compatible with water, and therefore, for example, in aqueous inkjet inks present near the nozzles of an inkjet head, the surfactant may be concentrated at the air-liquid interface and oriented, causing the ink to overflow from the nozzles. This phenomenon can cause a deterioration in continuous ejection.

[0021] Furthermore, surfactants with low molecular weights and high orientation rates are present in large amounts on the surface of the ink layer. This can lead to blocking due to the movement of surfactant molecules caused by heat or humidity. In addition, these surfactants can bleed onto the surface of the laminate containing the ink layer, causing migration.

[0022] On the other hand, if the amount of surfactant with a low molecular weight and a high orientation rate is reduced in order to suppress deterioration of continuous ejection properties and the occurrence of blocking and migration, then the occurrence of the above-mentioned beading cannot be suppressed, and it becomes difficult to obtain printed matter with good print quality.

[0023] As described above, surfactants with low molecular weights and high orientation speeds are effective in improving print quality, but they come with a trade-off with properties such as continuous dischargeability, blocking resistance, and migration resistance.

[0024]

[0013] Therefore, in order to solve the above-mentioned trade-off, the present inventors have continued their intensive research and have found that it is possible to use an unmodified acetylenic diol surfactant (A1) and an alkylene oxide-modified acetylenic diol surfactant (A2) having a specific HLB value in combination in a specific ratio, and to specify the blending amounts of each, thereby arriving at the present invention. Although the details of the mechanism by which the aqueous inkjet ink having the above-mentioned configuration can suitably solve the above-mentioned problems are unknown, the present inventors speculate as follows.

[0025] First, the ink of the present invention contains an acetylene diol surfactant. Generally, the acetylene group contained in an acetylene diol surfactant does not undergo bond rotation, and therefore the molecular structure is less likely to deform than surfactants consisting of only single bonds, such as polyoxyethylene alkyl ether surfactants, and even when added in small amounts, the expected effects are achieved.

[0026] The ink of the present invention also contains, as acetylenic diol surfactants, an unmodified acetylenic diol surfactant (A1) and an alkylene oxide-modified acetylenic diol surfactant (A2) having an HLB value of 4 to 10. Of these, the unmodified acetylenic diol surfactant (A1) corresponds to the aforementioned "surfactant with a low molecular weight and a high orientation rate," and in the case of the ink of the present invention, it is an essential material from the viewpoint of suppressing beading. Furthermore, from the viewpoint of not only suppressing beading but also achieving good continuous dischargeability, blocking resistance, and migration resistance of printed matter when used in combination with other materials described below, the content of the unmodified acetylenic diol surfactant (A1) in the ink of the present invention is set to a range of 5 to 2,000 ppm based on the total amount of ink.

[0027] Furthermore, the ink of the present invention contains an alkylene oxide-modified acetylenic diol surfactant (A2) having an HLB value of 4 to 10 in an amount of 0.2 to 5 mass % in the ink, and in an amount 10 to 5,000 times the amount of the unmodified acetylenic diol surfactant (A1). Although the detailed mechanism is unclear, when the alkylene oxide-modified acetylenic diol surfactant (A2) is used in the above-mentioned amount and ratio, the alkylene oxide-modified acetylenic diol surfactant (A2) forms an emulsified state with the unmodified acetylenic diol surfactant (A1), which has a similar structure, and excessive orientation of the unmodified acetylenic diol surfactant (A1) is suppressed. Furthermore, because the amount of the unmodified acetylenic diol surfactant (A1), a low-molecular-weight surfactant, is small, the ink of the present invention can prevent deterioration of continuous dischargeability and produce printed materials and laminates that are less prone to blocking and migration.

[0028] Furthermore, a portion of the unmodified acetylenic diol surfactant (A1) is present at the gas-liquid interface together with the emulsified alkylene oxide-modified acetylenic diol surfactant (A2) and is oriented thereto. As a result, the ink of the present invention exhibits an effect greater than that achieved by the amount of unmodified acetylenic diol surfactant (A1) added to the ink, thereby enabling further suppression of beading.

[0029] As described above, in order to simultaneously solve the above-mentioned problems at a high level, an ink having the configuration of the present invention is indispensable.

[0030] In addition to the acetylenic diol surfactant described above, the ink of the present invention can further contain a nonionic surfactant (B) other than the acetylenic diol surfactant. The nonionic surfactant (B) is expected to have the effect of significantly reducing static surface tension. Therefore, the nonionic surfactant (B) is thought to function effectively in a time range later than "up to several tens of milliseconds after the ink droplets land on the printing substrate," the time range in which the unmodified acetylenic diol surfactant (A1) primarily functions. Since behavior in this time range primarily affects wetting and spreading and image density, the use of the nonionic surfactant (B) in combination can significantly improve the final print image quality. Furthermore, although the detailed mechanism is unknown, it is thought that the combined use of the nonionic surfactant (B) and the acetylenic diol surfactant allows them to interact with each other, allowing them to behave like a single surfactant. As a result, it is thought that during continuous ejection, the nonionic surfactant (B), like the alkylene oxide-modified acetylenic diol surfactant (A2), prevents the unmodified acetylenic diol surfactant (A1) from orienting at the gas-liquid interface, thereby suppressing ink overflow from the nozzles and enabling further improvement in continuous ejection properties.

[0031] Furthermore, the nonionic surfactant (B) present on the surface of the ink layer can reduce the surface energy of the ink layer surface, so that even if another printing substrate or the like sticks to the surface, the adhesion of the printing substrate can be reduced, improving blocking resistance. In addition, as mentioned above, in the ink of the present invention, it is thought that the surfactant is present as a single mass, so that the surfactant is less likely to bleed onto the ink layer surface and migration can also be prevented.

[0032] The aqueous inkjet inks specifically disclosed in the above Patent Documents 1 to 3 differ from the ink of the present invention in that they contain absolutely no acetylenic diol surfactant. Also, the aqueous inkjet ink specifically disclosed in the above Patent Document 4 differs from the ink of the present invention in that the content of the unmodified acetylenic diol surfactant (A1) ("Component (A)" in the examples of Patent Document 4) is significantly more than 2,000 ppm, or in that it does not contain any unmodified acetylenic diol surfactant (A1).

[0033] Next, the main components constituting the ink of the present invention will be described below.

[0034] <Unmodified acetylenic diol surfactant (A1)> As described above, the unmodified acetylenic diol surfactant (A1) has a low molecular weight, low hydrophilicity, and a high orientation rate at the gas-liquid interface. In addition, it can reduce the surface tension of the ink immediately after it lands on the printing substrate, thereby suppressing beading.

[0035] In an embodiment of the present invention, the unmodified acetylenic diol surfactant (A1) is contained in an amount of 5 to 2,000 ppm based on the total amount of the ink. The content of the unmodified acetylenic diol surfactant (A1) is preferably 10 to 2,000 ppm, more preferably 50 to 1,000 ppm, and particularly preferably 50 to 300 ppm. By using the unmodified acetylenic diol surfactant (A1) in the above range and further using it in combination with a surfactant described below, beading is suppressed and solid filling is improved, resulting in prints with good print quality. Furthermore, since the amount added is small to begin with, deterioration of continuous dischargeability is unlikely to occur, and blocking and migration in prints can also be prevented.

[0036] Specific examples of the unmodified acetylene diol surfactant (A1) that can be used in the embodiment of the present invention include 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol, hexadec-8-yne-7,10-diol, 4,7-dipropyl-dec-5-yne-4,7-diol, 6,9-dimethyl-tetradec-7-yne-6,9-diol, 3,6-diisopropyl- Examples of suitable diluents include 2,4,7,9-tetramethyl-5-decyne-4,7-diol and / or 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol. These compounds may be used singly or in combination. The above compounds may be synthesized by a conventional method or may be commercially available products, such as Surfynol 104, Surfynol DF110D, and Surfynol 82 manufactured by Evonik Corporation, and Acetylenol E00 manufactured by Kawaken Fine Chemicals Co., Ltd.

[0037] <Alkylene Oxide-Modified Acetylene Diol Surfactant (A2)> The ink of the present invention uses an alkylene oxide-modified acetylenic diol surfactant (A2) together with the unmodified acetylenic diol surfactant (A1). As described above, the alkylene oxide-modified acetylenic diol surfactant (A2) emulsifies the unmodified acetylenic diol surfactant (A1) and also exhibits its own surfactant activity, thereby enabling the production of printed matter that is free of beading and has excellent blocking resistance and migration resistance, and further enabling the production of an ink that also has excellent continuous dischargeability. From this perspective, the HLB value of the alkylene oxide-modified acetylenic diol surfactant (A2) is 4 to 10, preferably 7 to 9. Having an HLB value within the above range particularly enables the suppression of beading in printed matter and the improvement of continuous dischargeability. The HLB value of the alkylene oxide-modified acetylenic diol surfactant (A2) may be 3.5 to 10.4, 4.0 to 10.0, 4.4 to 9.5, 6.5 to 9.4, 6.5 to 9.0, or 7.0 to 9.0.

[0038] The HLB (Hydrophile-Lipophile Balance) value is one of the parameters that represent the hydrophilicity / hydrophobicity of a material. The smaller the HLB value, the more hydrophobic the material, and the larger the HLB value, the more hydrophilic the material. Known methods for determining the HLB value include experimental measurement and calculation from molecular structure, and methods for calculating from molecular structure include the Griffin method, Davis method, and Kawakami method. In the embodiments of the present invention, the value calculated using the Griffin method is used as the HLB value, except in the case of silicone-based surfactants, which will be described later.

[0039] The Griffin method is a method generally used for non-ionic materials, and is calculated using the molecular weight of the target material according to the following formula (2).

[0040] Formula (2): HLB value = 20 × (sum of molecular weights of hydrophilic portions) ÷ (molecular weight of material)

[0041] On the other hand, in the case of silicone surfactants, which will be described later, they are generally mixtures containing many compounds, and therefore the HLB value used is the value actually measured by the method described on page 324 of "Handbook of Surfactants" (edited by Nishi Ichiro et al., Sangyo Tosho Co., Ltd., 1960).

[0042] To explain the specific measurement method, 0.5 g of the target material is dissolved in 5 mL of ethanol, and then the solution is stirred and titrated with a 2% by mass aqueous phenol solution at 25° C. The point at which the solution becomes turbid is set as the endpoint, and the amount of phenol solution (referred to as A (mL)) added up to the endpoint is used to calculate the HLB value according to the following formula (3):

[0043] Formula (3): HLB value = 0.89 × A + 1.11

[0044] The amount of alkylene oxide-modified acetylenic diol surfactant (A2) having an HLB value of 4 to 10 added is 0.2 to 5 mass% based on the total amount of ink. From the viewpoints of improving continuous dischargeability and suppressing beading and blocking in printed matter, the amount added is preferably 0.5 to 3 mass%, more preferably 0.8 to 2.5 mass%. Furthermore, from the viewpoints of forming a suitable emulsified state with the unmodified acetylenic diol surfactant (A1) and supporting the function of the unmodified acetylenic diol surfactant (A1), improving continuous dischargeability and preventing beading, blocking, and migration in printed matter, the ratio of the content of alkylene oxide-modified acetylenic diol surfactant (A2) to the content of unmodified acetylenic diol surfactant (A1) is 10 to 5,000, preferably 30 to 500, and more preferably 50 to 300.

[0045] Specific examples of the alkylene oxide-modified acetylenic diol surfactant (A2) include compounds represented by the following general formula (4).

[0046] General formula (4):

[0047] In general formula (4), R １ and R２ each represents an alkyl group having 1 to 5 carbon atoms, which may be branched, EO represents an ethylene oxide group, and PO represents a propylene oxide group. Furthermore, m1, m2, n1, and n2 each represent an integer of 0 to 30, and m1+n1+m2+n2 is an integer of 1 to 120. However, the addition pattern of the ethylene oxide groups and propylene oxide groups in [ ] may be block or random.

[0048] The molecular weight of the alkylene oxide-modified acetylenic diol surfactant (A2) having a structure represented by the above general formula (4) is preferably 300 to 1,200, more preferably 350 to 900, and even more preferably 400 to 700. The acetylenic diol surfactant (A2) having a molecular weight within the above range has a high orientation rate to the gas-liquid interface, similar to the unmodified acetylenic diol surfactant (A1), making it easy to suppress beading and also preventing blocking and the like. The molecular weight of the alkylene oxide-modified acetylenic diol surfactant (A2) refers to the formula weight, which can be determined by calculation.

[0049] The alkylene oxide-modified acetylene diol surfactant represented by the general formula (4) may be synthesized by a conventionally known method, or a commercially available product may be used. Examples of commercially available products of the compound represented by the general formula (4) include Surfynol 420, Surfynol 440, Surfynol 465, Surfynol 485, Surfynol 2502, and Dynol 604 and 607 manufactured by Evonik Corporation; the Olfine series manufactured by Nissin Chemical Industry Co., Ltd.; and Acetylenol E13T, E40, E60, E100, and E200 manufactured by Kawaken Fine Chemicals Co., Ltd.

[0050] <Nonionic Surfactant (B)> As described above, in an embodiment of the present invention, in addition to the acetylenic diol-based surfactant (A), a nonionic surfactant (B) other than an acetylenic diol-based surfactant can be used in combination. By using the nonionic surfactant (B), an interaction occurs between the nonionic surfactant (B) and the acetylenic diol-based surfactant (A), and the nonionic surfactant (B) behaves like a single surfactant, thereby further improving continuous dischargeability and preventing blocking and migration in printed matter. Furthermore, compared to the acetylenic diol-based surfactant (A), the nonionic surfactant (B) gradually moves to the gas-liquid interface and is oriented. This can promote the wetting and spreading of ink droplets more than several tens of milliseconds after the ink droplets land on the printing substrate, and also enables the ink droplets to be uniformly wetting and spreading, thereby improving the print quality of printed matter.

[0051] The HLB value of the nonionic surfactant (B) is preferably 6 to 14, more preferably 8 to 11. When the HLB value is within the above range, it is believed that a strong interaction with the alkylene oxide-modified acetylene diol surfactant (A2) occurs, forming a favorable emulsified state, improving continuous dischargeability and producing printed matter that is free of blocking and migration. The HLB value of the nonionic surfactant (B) may be 5.5 to 14.4, 6.0 to 14.0, 6.4 to 13.5, 7.5 to 11.4, or 8.0 to 11.0.

[0052] Furthermore, from the viewpoint of improving continuous dischargeability and blocking resistance because the interaction between the acetylene diol surfactant (A) and the nonionic surfactant (B) can be strengthened and a suitable emulsified state can be created, the mass factor-added HLB value calculated by the following formula (1) is preferably 0.3 to 2.0, more preferably 0.5 to 1.5, and even more preferably 0.8 to 1.3. The HLB value is a value determined by the structure of the surfactant molecule, etc., and in order to evaluate the influence of the entire surfactant present in the ink, in the following formula (1), the HLB value is multiplied by the amount of surfactant blended, i.e., the amount of the surfactant molecule, and the sum is then taken for comparison.

[0053] Formula (1): (In formula (1), i represents the type of surfactant used as the unmodified acetylenic diol surfactant (A1), l represents the number of types of surfactants used as the unmodified acetylenic diol surfactant (A1), j represents the type of surfactant used as the alkylene oxide-modified acetylenic diol surfactant (A2), m represents the number of types of surfactants used as the alkylene oxide-modified acetylenic diol surfactant (A2), k represents the type of surfactant used as the nonionic surfactant (B), n represents the number of types of surfactants used as the nonionic surfactant (B). In addition, HLB ｉ represents the HLB value of surfactant i, and WT ｉ represents the content (mass%) of the surfactant i relative to the total mass of the aqueous inkjet ink, and HLB ｊ represents the HLB value of surfactant j, and WT ｊ represents the content (mass%) of the surfactant j relative to the total mass of the aqueous inkjet ink, and HLB ｋ represents the HLB value of surfactant k, and WT ｋ represents the content (mass%) of the surfactant k relative to the total mass of the aqueous inkjet ink.

[0054] In an embodiment of the present invention, the content of the nonionic surfactant (B) is preferably 0.3 to 3 mass% of the total amount of the ink, and more preferably 0.5 to 2 mass%. Furthermore, the ratio of the content of the nonionic surfactant (B) to the total content of the unmodified acetylenic diol surfactant (A1) and the alkylene oxide-modified acetylenic diol surfactant (A2) (value expressed as "content of nonionic surfactant (B) / {content of acetylenic diol surfactant (A1) + content of acetylenic diol surfactant (A2)}") is preferably 0.3 to 2.0, and more preferably 0.5 to 1.5. When the content of the nonionic surfactant (B) and the ratio of the content are within the above ranges, the surfactants are easily emulsified and function as a single surfactant, resulting in good continuous dischargeability and a printed matter that is free from blocking and migration.

[0055] The nonionic surfactant (B) in the embodiment of the present invention may be synthesized by a conventionally known method, or may be commercially available.In addition, the type of nonionic surfactant (B) may be, for example, acetylene monool surfactant, silicon surfactant, fluorine surfactant, polyoxyalkylene alkyl ether surfactant, polyoxyalkylene aryl ether surfactant, polyalkylene glycol alkylate surfactant, etc.These compounds may be used alone or in combination of two or more.

[0056] In particular, in an embodiment of the present invention, it is particularly preferable that the nonionic surfactant (B) contains a silicon-based surfactant, since this easily interacts with the acetylene diol-based surfactant (A) and the surface energy of the ink layer is reduced, making it easy to reduce blocking.

[0057] The silicone surfactant preferably used in the embodiment of the present invention is a compound represented by the following general formula (5).

[0058] General formula (5):

[0059] In general formula (5), p is an integer of 0 or more, and q is an integer of 1 or more. ３ is a methyl group or a structure represented by the following general formula (6), and R ４ is an alkyl group having 1 to 6 carbon atoms, or a structure represented by the following general formula (6): ３ When is a methyl group, p is 0.

[0060] General formula (6):

[0061] In general formula (6), r is an integer of 1 to 6, s is an integer of 0 to 50, and t is an integer of 0 to 50, provided that s+t is 1 or more. ５ is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a (meth)acrylic group. The addition of the ethylene oxide groups and propylene oxide groups in the brackets [ ] may be block or random.

[0062] The silicone surfactant used in the embodiment of the present invention may be one synthesized by a conventionally known method, or a commercially available product. Examples of commercially available products include SF8428, FZ-2162, 8032 ADDITIVE, SH3749, FZ-77, L-7001, L-7002, FZ-2104, FZ-2110, F-2123, SH8400, and SH3773M manufactured by Dow Corning Toray Co., Ltd.; BYK-345, BYK-346, BYK-347, BYK-348, BYK-349, and BYK-3420 manufactured by BYK-Chemie; and TEGO Wet250, TEGO Wet260, TEGO Wet270, TEGO Wet280, TEGO Glide100, TEGO Glide410, and TEGO Examples include Glide 432, TEGO Glide 435, TEGO Glide 440, TEGO Glide 450, TEGO Twin 4000, TEGO Twin 4100, and TEGO Twin 4200 manufactured by Shin-Etsu Chemical Co., Ltd.; KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-640, KF-642, and KF-643 manufactured by Shin-Etsu Chemical Co., Ltd.; and the Silface SAG series manufactured by Nissin Chemical Industry Co., Ltd. These commercially available products may be used alone or in combination of two or more.

[0063] In order for the nonionic surfactant (B) to behave like a single surfactant, it is preferable for an interaction to occur between the nonionic surfactant (B) and the acetylenic diol surfactant (A). On the other hand, from the viewpoints of further improving continuous dischargeability and improving solid coverage in printed matter, it is preferable for the nonionic surfactant (B) to be compatible with the acetylenic diol surfactant (A) to a certain extent. From these viewpoints, it is preferable to use two or more types of silicone surfactants in combination as the nonionic surfactant (B). Furthermore, it is particularly preferable to use a combination of two or more types of silicone surfactants whose HLB values, measured by the above-mentioned method, differ by two or more.

[0064] In an embodiment of the present invention, a polyoxyalkylene alkyl ether surfactant can also be used as the nonionic surfactant (B). Polyoxyalkylene alkyl ether surfactants have good compatibility with water and acetylene diol surfactants and can improve print quality, such as by suppressing beading, without affecting these materials.

[0065] Examples of polyoxyalkylene alkyl ether surfactants that can be used include compounds in which the number of moles of ethylene oxide groups and / or propylene oxide groups added is 5 to 100 moles and the carbon number of the terminal hydrocarbon group is 6 to 22. The terminal hydrocarbon group may be, for example, a chain alkyl group (which may have a branched structure), a chain alkenyl group (which may have a branched structure), an alicyclic alkyl group (to which one or more alkyl groups may be added), or an aromatic group (to which one or more alkyl groups may be added). Examples of commercially available polyoxyalkylene alkyl ether surfactants include the Emulgen series (manufactured by Kao Corporation), such as Emulgen 104P, 105, 106, 108, 109P, 120, 123P, 150, 210, 220, 306P, 320P, and 350; Brownon Brownon series (manufactured by Aoki Oil & Fat Industries Co., Ltd.) such as EL-1502.2, 1505, 1507, 1509, 1515, 1521, 1530, 1540P, CH-302L, 305, 310L, 315L, 320L, 325L, 330L, 340, SR-702L, 705, 707, 711, 715, 720, 730, 750F, BE-5, 10, 20, 30, and BN-3, and non-ionic surfactants Examples of such nonionic series (manufactured by NOF Corporation) include K-204, 220, 230, 2100W, P-208, 210, 213, E-202, 205, 212, 215, 230, S-202, 207, 215, 220, EH-204, 208, ID-203, 206, and 209; Lutensol series (manufactured by BASF) such as Lutensol XL40, 50, 60, 70, 80, 90, and XP30, 40, 50, 60, 70, 80, 90, and 100; and Newcol series (manufactured by Nippon Nyukazai Co., Ltd.) such as Newcol 2302, 2303, 2305, 2308, 2310, 2320, and 2360. The above-listed products may be used alone or in combination of two or more. Furthermore, the polyoxyalkylene alkyl ether surfactant may be synthesized by a conventionally known synthesis method.

[0066] <Water-soluble organic solvent> In an embodiment of the present invention, a water-soluble organic solvent is used to improve continuous ejection by ensuring moisture retention on the inkjet head, and to prevent beading by improving the compatibility of the surfactant described above. In this specification, the term "water-soluble organic solvent" refers to a solvent that has a solubility of 1% by mass or more in water at 25°C and is liquid at 25°C.

[0067] Examples of the water-soluble organic solvent in an embodiment of the present invention include: monohydric alcohols having 1 to 6 carbon atoms, such as ethanol, propanol, isopropanol, butanol, isobutanol, tert-butanol, isopentanol, and dimethylbutanol; alkanediols having 3 to 6 carbon atoms, such as 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,2-pentanediol, 1,5-pentanediol, and 1,2-hexanediol; polyalkylene glycols, such as diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol; alkylene glycol ethers represented by the following general formula (7); methoxybutanols, such as 3-methoxy-1-butanol and 3-methoxy-3-methylbutanol; Nitrogen-containing solvents such as 2-pyrrolidone, N-methylpyrrolidone, 3-methoxy-N,N-dimethylpropanamide, and 3-butoxy-N,N-dimethylpropanamide; lactone-based solvents such as γ-butyrolactone and ε-caprolactone; etc. The above water-soluble organic solvents may be used alone or in combination of two or more.

[0068] General formula (7): R ６ -O-(AO) ｕ -H

[0069] In the above general formula (7), R ６ represents an alkyl group having 1 to 4 carbon atoms, which may be branched; AO represents an ethylene oxide group and / or a propylene oxide group; and u represents an integer of 1 to 3.

[0070] <1,2-Propanediol> In an embodiment of the present invention, among the water-soluble organic solvents listed above, 1,2-propanediol is preferably used. Because 1,2-propanediol has a high proportion of hydroxyl groups relative to its molecular weight, it is particularly hydrophilic and can be uniformly distributed throughout the aqueous inkjet ink. On the other hand, 1,2-propanediol is not excessively compatible with the acetylene diol surfactant (A) and the nonionic surfactant (B), and therefore does not inhibit the orientation of these surfactants, thereby suppressing beading. Furthermore, because its boiling point is moderately low at 188°C, it not only suppresses ink drying on the nozzle and improves continuous dischargeability, but also volatilizes quickly after printing, resulting in an ink with excellent drying properties and blocking resistance. Additionally, 1,2-propanediol has the property of being less likely to disrupt the pigment dispersion state described below, preventing deterioration of the ink's storage stability and, as a result, further improving continuous dischargeability, making it suitable for use.

[0071] When 1,2-propanediol is used as the water-soluble organic solvent, its content is preferably 5 to 30% by mass, more preferably 10 to 25% by mass, of the total amount of ink. By making the 1,2-propanediol content 5% by mass or more, the effect of the surfactant can be fully exploited, making it easier to suppress beading. In addition, drying properties on non-absorbent substrates are favorable, allowing for the production of printed matter with excellent blocking resistance. On the other hand, by making the content 30% by mass or less, continuous discharge properties are improved. 1,2-propanediol may be used together with the water-soluble organic solvents other than 1,2-propanediol listed above.

[0072] <<Specific alkylene glycol ethers>> In an embodiment of the present invention, from the viewpoint of obtaining an ink with exceptionally excellent drying properties and of obtaining printed matter with excellent blocking resistance by functioning as a film-forming aid for the surfactant, it is also preferable to use one or more alkylene glycol ethers (also referred to in this specification as “specific alkylene glycol ethers”) selected from the group consisting of ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, and dipropylene glycol monopropyl ether, among the compounds represented by general formula (7) above.

[0073] When the above-mentioned specific alkylene glycol ethers are used, from the viewpoint of achieving both improved drying properties on non-absorbent substrates and improved continuous ejection properties by suppressing adhesion of the ink at the nozzle interface, the content thereof is preferably 1 to 15% by mass, and more preferably 3 to 10% by mass, of the total amount of the inkjet ink. The above-mentioned propylene glycol ethers may be used alone or in combination of two or more types. Furthermore, they may be used together with 1,2-propanediol and / or the above-listed water-soluble organic solvents other than 1,2-propanediol and the specific alkylene glycol ethers.

[0074] In an embodiment of the present invention, the amount of the water-soluble organic solvent having a boiling point of 235°C or higher contained in the ink is preferably 0 to 5% by mass, and more preferably 0 to 2% by mass, in order to obtain a printed matter that has excellent drying properties even on a non-absorbent substrate and is free from beading and blocking, and further to obtain an ink that has excellent continuous discharge properties.

[0075] In this specification, the "boiling point" is a value at 1 atmosphere and can be measured using, for example, a thermal analyzer. Furthermore, the description "the content (blending amount) is 0 mass %" means that the target compound is not contained.

[0076] The total content of water-soluble organic solvents contained in the ink of the present invention is preferably 5 to 40% by mass of the total amount of the ink, and more preferably 10 to 35% by mass in order to ensure sufficient drying properties even on a non-absorbent substrate.

[0077] <Binder Resin> In the embodiment of the present invention, a binder resin is used because it can significantly improve the scratch resistance, blocking resistance, migration resistance, and the like of the printed matter.

[0078] Generally, water-soluble resins and hydrosols and emulsions, which are types of water-insoluble resins, are known as binder resins used in aqueous inkjet inks. Here, "water-soluble resin" refers to a pigment dispersion resin whose 1% by mass aqueous mixture is transparent to the naked eye at 25°C. Furthermore, "hydrosol" refers to a "water-insoluble resin" (a resin that is not water-soluble) that contains acidic and / or basic functional groups in its structure and is dispersed in a dispersion medium without the use of an emulsifier such as a surfactant or polymer. Meanwhile, "emulsion" refers to a form in which the emulsifier is adsorbed and / or bonded to the resin surface, forcibly dispersing the resin in a dispersion medium. In this specification, the hydrosols and emulsions are collectively referred to as "resin microparticles."

[0079] <Water-Soluble Resin> In one embodiment of the present invention, it is preferable to use a water-soluble resin and / or a hydrosol as the binder resin. These resins have affinity with aqueous media (mediums consisting of liquids containing at least water) without the use of an emulsifier, and at least a portion of the resin swells and / or dissolves in the aqueous medium. Therefore, clogging due to precipitation of the resin near the nozzles of the inkjet head is unlikely to occur, and continuous discharge is excellent. Furthermore, these resins can function as compatibilizers for the unmodified acetylenic diol surfactant (A1), so that the unmodified acetylenic diol surfactant (A1) is uniformly oriented at the gas-liquid interface, and the occurrence of beading in printed matter can be suppressed.

[0080] Examples of resins that can be used as the water-soluble resin and hydrosol include acrylic resins, urethane resins, and polyester resins. Among these, acrylic resins are preferred in consideration of the storage stability and continuous dischargeability of the ink, as well as the abrasion resistance of the printed matter.

[0081] In this specification, 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 (a styrene-based monomer may also be used).

[0082] In the embodiment of the present invention, the water-soluble resin may be a resin synthesized by a conventionally known method or a commercially available product. There are no particular limitations on the structure of the resin, and any resin having, for example, a random structure, a block structure, a comb structure, a star structure, or the like may be used.

[0083] When a water-soluble resin is used as the binder resin, the weight-average molecular weight is preferably in the range of 5,000 to 50,000, and more preferably in the range of 10,000 to 40,000. By setting the weight-average molecular weight to 5,000 or more, the scratch resistance of the printed matter is improved and beading is easily suppressed. Furthermore, by setting the weight-average molecular weight to 50,000 or less, continuous ejection from an inkjet head is improved.

[0084] The weight-average molecular weight of the resin can be measured by a conventional method. In an embodiment of the present invention, the weight-average molecular weight is a weight-average molecular weight calculated in terms of standard polystyrene by gel permeation chromatography (GPC). For example, it is a value measured as a weight-average molecular weight calculated in terms of polystyrene using a TSKgel column (manufactured by Tosoh Corporation) and a GPC (manufactured by Tosoh Corporation, HLC-8120GPC) equipped with an RI detector, using THF as a developing solvent.

[0085] The acid value is also important when selecting a water-soluble resin. When a water-soluble resin is used as a binder resin, its acid value is preferably 5 to 80 mgKOH / g, and more preferably 15 to 50 mgKOH / g. By setting the acid value to 5 mgKOH / g or more, even if the resin solidifies near the nozzle of the inkjet head, it can be re-dissolved in the ink, which makes it easier to suppress clogging of the nozzle and improves continuous discharge. Furthermore, if the acid value is 80 mgKOH / g or less, printed matter with excellent water resistance and abrasion resistance can be obtained, and the resin can easily function as a compatibilizer for the unmodified acetylenic diol surfactant (A1), making it easier to obtain printed matter without beading.

[0086] 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 specification, the acid value is calculated using the following method. For example, if a resin has na acid groups with a value of va per molecule and contains Wa mass % of a polymerizable monomer having a molecular weight of Ma among the polymerizable monomers constituting the resin, the acid value (mg KOH / g) can be calculated using the following formula (8):

[0087] Equation (8): (Acid value) = {(va × na × Wa) ÷ (100 × Ma)} × 56.11 × 1000

[0088] In the above formula (8), the number "56.11" is the molecular weight of potassium hydroxide.

[0089] The content of the water-soluble resin is preferably 0.5 to 10% by mass, more preferably 1 to 8% by mass, and even more preferably 2 to 6% by mass, based on the total amount of the ink. If the content of the water-soluble resin is 0.5% by mass or more, the unmodified acetylene diol surfactant (A1) can be sufficiently compatible, the storage stability of the ink can be improved, and beading in printed matter can be suppressed. If the content is 10% by mass or less, the viscosity of the ink can be kept within a suitable range and the ink can have excellent continuous discharge properties.

[0090] <<Resin Particles>> Generally, resin particles such as hydrosols or emulsions have a higher molecular weight than water-soluble resins. Furthermore, when the same amount of resin is blended, resin particles can lower the viscosity of the ink compared to water-soluble resins. Therefore, by using resin particles, a larger amount of resin can be contained in the ink, which makes it easier to improve the abrasion resistance, blocking resistance, and migration resistance of printed matter.

[0091] Among the resins used as resin microparticles, types of resins that can be used as emulsions include acrylic resins, urethane resins, polyester resins, styrene-butadiene resins, acrylonitrile-butadiene resins, vinyl chloride resins, polyolefin resins, and the like. Among these, considering the maintenance of ink storage stability and the ease of improving the abrasion resistance and blocking resistance of printed matter, emulsions of one or more resins selected from the group consisting of acrylic, urethane, polyester, and polyolefin resins are preferably used. Furthermore, even when using a hydrosol as resin microparticles, it is preferable to use one or more resins selected from the group consisting of acrylic, urethane, and polyester resins from the viewpoint of improving the abrasion resistance and blocking resistance of printed matter. Furthermore, taking into further consideration the viewpoint of improving the continuous dischargeability described above, it is particularly preferable to use an acrylic resin.

[0092] However, when the binder resin in the ink is resin microparticles, especially when an emulsion is used, the minimum film-forming temperature (MFT) of the resin microparticles must be taken into consideration. When resin microparticles with a low MFT are used, the MFT of the resin microparticles may be further reduced depending on the water-soluble organic solvent added to the ink, causing the resin microparticles to adhere near the nozzles of the inkjet head, even at room temperature, resulting in clogging. In particular, in the case of emulsions, once a film is formed, it is difficult to redissolve the emulsion in the ink, and the adhered emulsion may impair continuous dischargeability. To avoid this problem, it is preferable to adjust the type and amount of polymerizable monomers constituting the emulsion to achieve an MFT of 60°C or higher. Furthermore, when a hydrosol is used as the resin microparticles, the possibility of continuous dischargeability being impaired is not as high as in the case of an emulsion. On the other hand, using a hydrosol with an MFT of 60°C or higher can reduce factors that can impair continuous dischargeability, so an MFT of 60°C or higher is preferred even in the case of hydrosols.

[0093] The MFT can be measured, for example, by an MFT tester manufactured by Tester Sangyo Co., Ltd.

[0094] When an emulsion is used, its content is preferably 2 to 15% by mass, more preferably 4 to 8% by mass, based on the total amount of the ink. If the emulsion content is 2% by mass or more, the abrasion resistance and blocking resistance are improved, and if it is 15% by mass or less, the viscosity of the ink can be kept within a suitable range and the ink will have excellent continuous discharge properties.

[0095] <Pigment> The ink of the present invention contains a pigment. As the pigment, inorganic pigments and / or organic pigments can be used as desired. These pigments may be used alone or in combination of two or more. The content of the pigment is preferably 0.1 to 20% by mass, more preferably 1 to 10% by mass, and even more preferably 2 to 7% by mass, based on the total mass of the ink.

[0096] When an inorganic pigment is used as the pigment, specific examples thereof include titanium oxide, zinc white, zinc sulfide, white lead, calcium carbonate, precipitated barium sulfate, white carbon, alumina white, kaolin clay, talc, bentonite, carbon black, black iron oxide, cadmium red, red iron oxide, molybdenum red, molybdate orange, chrome vermilion, yellow lead, cadmium yellow, yellow iron oxide, titanium yellow, chromium oxide, viridian, titanium cobalt green, cobalt green, cobalt chrome green, Victoria green, ultramarine, Prussian blue, cobalt blue, cerulean blue, cobalt silica blue, cobalt zinc silica blue, manganese violet, and cobalt violet.

[0097] Among the carbon blacks listed above, those produced by the furnace method or the channel method can be used. Among them, carbon black produced by the furnace method or the channel method, which has a primary particle diameter of 11 to 40 nm and a specific surface area measured by the BET method of 50 to 400 m, is particularly preferred. ２ / g, a volatile content of 0.5 to 10%, a pH of 2 to 10, etc. are suitable. Examples of commercially available products with such specifications include No. Examples of suitable carbon blacks include 33, 40, 45, 52, 900, 2200B, 2300, MA7, MA8, MCF88 (manufactured by Mitsubishi Chemical Corporation), RAVEN1255 (manufactured by Birla Carbon Corporation), REGAL330R, 400R, 660R, MOGUL L, ELFTEX415 (manufactured by Cabot Corporation), NIPex90, NIPex150T, NIPex160IQ, NIPex170IQ, NIPex75, PrinteX35, PrinteX85, PrinteX90, PrinteX95, and PrinteXU (manufactured by Orion Engineered Carbons), all of which can be preferably used.

[0098] On the other hand, examples of organic pigments include azo pigments, phthalocyanine pigments, anthraquinone pigments, quinacridone pigments, isoindolinone pigments, quinophthalone pigments, dye lake pigments, fluorescent pigments, and the like.

[0099] Specific examples of cyan pigments in terms of color index include C.I. Pigment Blue 1, 2, 3, 15:1, 15:3, 15:4, 15:6, 16, 21, 22, 60, 64, and the like.

[0100] Examples of magenta pigments include C.I. Pigment Red 5, 7, 9, 12, 31, 48, 49, 52, 53, 57, 97, 112, 120, 122, 146, 147, 149, 150, 168, 170, 176, 177, 178, 179, 184, 185, 188, 202, 206, 207, 209, 238, 242, 254, 255, 264, 269, 282, C.I. Pigment Violet 19, 23, 29, 30, 32, 36, 37, 38, 40, and 50.

[0101] Examples of yellow pigments include C.I. Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 20, 24, 74, 83, 86, 93, 94, 95, 109, 110, 117, 120, 125, 128, 129, 137, 138, 139, 147, 148, 150, 151, 154, 155, 166, 168, 180, 185, and 213.

[0102] Examples of black pigments include aniline black (C.I. Pigment Black 1), perylene black (C.I. Pigment Black 31, 32), azomethine azo black, etc. A black pigment can also be prepared by mixing a plurality of chromatic pigments such as the above-mentioned cyan pigments, magenta pigments, and yellow pigments, and the following brown pigments and orange pigments.

[0103] In addition to the above pigments, C.I. Pigment Green 7, 10, 36, C.I. Pigment Brown 3, 5, 25, 26, C.I. Pigment Orange 2, 5, 7, 13, 14, 15, 16, 24, 34, 36, 38, 40, 43, 62, 63, 64, 71, and the like can be mentioned.

[0104] <Pigment Dispersion Resin> In order to maintain the storage stability and continuous dischargeability of the ink for a long period of time, the pigment is preferably used in a dispersed state in the ink. Methods for stably dispersing and maintaining the pigment in the ink include (1) a method in which at least a portion of the pigment surface is covered with a pigment dispersing resin, (2) a method in which a water-soluble and / or water-dispersible surfactant is adsorbed onto the pigment surface, and (3) a method in which a hydrophilic functional group is chemically and / or physically introduced onto the pigment surface, and the pigment is dispersed in the ink without either a pigment dispersing resin or a surfactant (self-dispersing pigment).

[0105] For the ink of the present invention, method (1) above, i.e., the method using a pigment dispersion resin, is preferably selected because the pigment covering ability and charge of the pigment dispersion resin can be easily adjusted by selecting and considering the composition, weight average molecular weight, etc. of the polymerizable monomers that make up the resin, making it possible to impart stable storage stability even to fine pigments, and furthermore, to obtain printed matter that is excellent in continuous dischargeability, color development, and color reproducibility.

[0106] Examples of the pigment dispersing resin include acrylic resins, styrene-maleic acid (anhydride) resins, α-olefin-maleic acid (anhydride) resins, urethane resins, and polyester resins. Among these, from the viewpoint of strengthening adsorption to the pigment and improving storage stability and continuous ejection properties, it is preferable to use one or more resins selected from acrylic resins, styrene-maleic acid (anhydride) resins, and α-olefin-maleic acid (anhydride) resins. In this specification, "maleic acid (anhydride)" refers to maleic acid and / or maleic anhydride.

[0107] When a water-soluble resin is used as the pigment dispersion resin, its acid value is preferably 60 to 400 mgKOH / g. By setting the acid value within this range, the pigment dispersion stability, as well as the ink storage stability and continuous dischargeability, can be optimized. The acid value is more preferably 100 to 350 mgKOH / g, and even more preferably 120 to 300 mgKOH / g. On the other hand, when a water-insoluble resin is used as the pigment dispersion resin, its acid value is preferably 0 to 100 mgKOH / g, more preferably 5 to 90 mgKOH / g, and even more preferably 10 to 80 mgKOH / g. An acid value within the above range not only enables printed matter to be obtained with excellent drying properties and blocking resistance, but also improves the pigment dispersion stability and ink continuous dischargeability. The acid value of the pigment dispersion resin can be measured in the same manner as for the binder resin described above.

[0108] The weight-average molecular weight of the pigment dispersion resin is preferably 5,000 to 100,000. By setting the weight-average molecular weight to 5,000 or more, the dispersion stability of the pigment and the storage stability of the ink can be made favorable. Furthermore, by setting the weight-average molecular weight to 100,000 or less, the continuous ejection properties can be made favorable. The weight-average molecular weight is more preferably in the range of 10,000 to 50,000, and even more preferably in the range of 15,000 to 30,000. The weight-average molecular weight of the pigment dispersion resin can be measured in the same manner as in the case of the binder resin described above.

[0109] The amount of pigment dispersing resin relative to the amount of pigment is preferably 1 to 120% by mass. By making the ratio of pigment dispersing resin 1% by mass or more relative to the amount of pigment, the viscosity of the ink can be kept within a range suitable for use in inkjet printing applications, improving continuous dischargeability. Furthermore, by making the ratio 120% by mass or less, the dispersion stability of the pigment and the storage stability of the ink can be improved. The amount of pigment dispersing resin relative to the amount of pigment is more preferably 2 to 100% by mass, and even more preferably 5 to 50% by mass.

[0110] <Water> The water contained in the ink of the present invention is preferably ion-exchanged water (deionized water) rather than ordinary water containing various ions.

[0111] The amount of water contained in the ink of the present invention is preferably in the range of 20 to 90% by mass based on the total amount of the ink.

[0112] <Other Components> In addition to the above components, the ink of the present invention may contain additives such as a pH adjuster, an ultraviolet absorber, a preservative, etc., in order to impart desired physical properties as needed. The amount of these additives added is preferably 0.01% by mass or more and 10% by mass or less, based on the total mass of the ink.

[0113] <Ink Manufacturing Method> Examples of methods for manufacturing the ink of the present invention containing the above-mentioned components include the following methods, although the ink manufacturing method of the present invention is not limited to the following methods.

[0114] First, a pigment dispersion resin and water are mixed to prepare a water-based pigment dispersion resin solution. Next, a pigment and, if necessary, a water-soluble organic solvent are added to the water-based pigment dispersion resin solution, followed by mixing and stirring (premixing). After that, a dispersion treatment is carried out using a dispersing means described below, and, if necessary, a centrifugal separation or other treatment is carried out to remove coarse particles, thereby obtaining a pigment dispersion. Next, an unmodified acetylenic diol surfactant (A1), an alkylene oxide-modified acetylenic diol surfactant (A2), a binder resin, a water-soluble organic solvent, water, and, if necessary, a nonionic surfactant (B), and other components are added to the pigment dispersion, followed by thorough mixing and stirring. The resulting mixture is then filtered to remove coarse particles, thereby producing the ink of the present invention.

[0115] In this specification, the term "aqueous solution" refers to a solution containing an aqueous solvent and components dispersed and / or dissolved in the aqueous solvent.

[0116] As described above in the ink manufacturing method, it is effective to perform a premixing treatment before performing a dispersion treatment, as the premixing treatment improves the wetting and spreading properties of the pigment surface and promotes the adsorption of the pigment dispersing resin to the pigment surface, and is therefore preferably carried out.

[0117] The dispersing machine that can be used for dispersing the pigment may be any commonly used dispersing machine, such as a ball mill, a roll mill, a sand mill, a bead mill, or a Nanomizer, among which a bead mill is preferably used. Examples of bead mills include a Super Mill, a sand grinder, an agitator mill, a grain mill, a Dyno Mill, a Pearl Mill, and a Cobol Mill (all trade names).

[0118] Since the ink of the present invention is for inkjet printing, it is preferable to use a pigment having an optimal particle size distribution from the viewpoint of preventing nozzle clogging, etc. Methods for obtaining a pigment having a desired particle size distribution include reducing the size of the grinding media in the disperser mentioned above, increasing the packing rate of the grinding media, extending the dispersion treatment time, classifying the ink after dispersion treatment using a filter or centrifuge, or a combination of these methods. The particle size distribution of the ink can be measured using, for example, a Nanotrac UPA-EX150 manufactured by Microtrac-Bell.

[0119] <Ink Set> The ink of the present invention may be used in a single color, or may be used as an ink set combining multiple colors depending on the application. While the combination is not particularly limited, a full-color image can be obtained by using three colors: cyan, yellow, and magenta. The addition of black ink can improve the sense of black and increase the visibility of characters, etc. Color reproducibility can also be improved by adding colors such as orange and green. When printing on a printing substrate other than white, a clear image can be obtained by using a white ink in combination. The ink set may also include, as a component, an ink that substantially does not contain a colorant component (clear ink), which is obtained by excluding the pigment from the ink of the present invention.

[0120] <Ink-Pretreatment Liquid Set> The aqueous inkjet ink of the present invention can also be used in the form of an ink-pretreatment liquid set in combination with a pretreatment liquid containing an aggregating agent. By applying a pretreatment liquid containing an aggregating agent to a printing substrate, a layer (ink aggregation layer) can be formed that intentionally aggregates the solid components contained in the ink. Then, by landing the ink of the present invention on this ink aggregation layer, bleeding between ink droplets and uneven density can be prevented, significantly improving the print quality of the printed matter. Furthermore, depending on the material used in the pretreatment liquid, the adhesion and blocking resistance of the printed matter can also be improved.

[0121] In this specification, the term "flocculant" refers to a component contained in an aqueous inkjet ink that can disrupt the dispersion state of the pigment and cause it to flocculate, and / or insolubilize the resin contained in the aqueous inkjet ink, thereby thickening the aqueous inkjet ink. The flocculant used in the pretreatment liquid to be combined with the ink of the present invention preferably contains one or more selected from metal salts and cationic polymer compounds, from the viewpoint of significantly improving print image quality. Among these, from the viewpoint of obtaining excellent print image quality, it is preferable to use a metal salt as the flocculant, and Ca ２＋ , Mg ２＋ , Zn ２＋ , and Al ３＋ It is particularly preferred that the pretreatment liquid contains one or more salts of polyvalent metal ions selected from the group consisting of: When a metal salt is used as the flocculant, the content thereof is preferably 2 to 30 mass %, and particularly preferably 3 to 25 mass %, based on the total mass of the pretreatment liquid.

[0122] Other additives that can be added to the pretreatment liquid include water-soluble organic solvents, surfactants, pH adjusters, antifoaming agents, thickeners, preservatives, etc. The water-soluble organic solvents and surfactants that can be used in the pretreatment liquid are the same as those for the inks described above. When the pretreatment liquid contains a surfactant, from the viewpoint of obtaining printed matter with excellent blocking resistance and migration resistance, it is preferable that the pretreatment liquid contain an unmodified acetylenic diol surfactant (A1) and an alkylene oxide-modified acetylenic diol surfactant (A2) having an HLB value of 4 to 10.

[0123] <Printing Substrate> As described above, the ink of the present invention is particularly suitable for use on non-absorbent substrates such as films. Specifically, polyolefin resins such as polyethylene, biaxially oriented polypropylene (OPP), and nonaxially oriented polypropylene (CPP); polyester resins such as polyethylene terephthalate (PET), polycarbonate, and polylactic acid; polystyrene resins such as polystyrene, AS resin, and ABS resin; polyamide resins such as nylon; chlorine-containing resins such as polyvinyl chloride and polyvinylidene chloride; cellophane; or film or sheet-like substrates made of composite materials thereof can be used. These printing substrates may be subjected to surface treatments such as corona treatment or plasma treatment. Furthermore, they may be subjected to pre-coating treatment with a pre-coating composition (different from the pre-treatment liquid described above) containing one or more resins selected from the group consisting of urethane resins, acrylic resins, and olefin resins.

[0124] <Method for Producing Printed Material> The ink of the present invention is used in a printing method in which the ink is ejected from the nozzles of an inkjet head and droplets of the ink are deposited on a substrate.

[0125] Furthermore, after applying the ink of the present invention to a substrate, it is preferable to dry the ink on the substrate using a drying mechanism. Drying methods used in the drying mechanism include heat drying, hot air drying, infrared drying (e.g., infrared with a wavelength of 700 to 2500 nm), microwave drying, and drum drying. The above drying methods may be used alone, or multiple methods may be used in succession, or they may be used simultaneously in combination. For example, by using heat drying and hot air drying in combination, the ink can be dried more quickly than when each method is used alone. In an embodiment of the present invention, the printed matter has a substrate and a printed layer formed by printing the ink of the present invention on the substrate. The printed layer may contain images and / or characters.

[0126] <Post-coating treatment> If necessary, the printed surface of a printed material produced using the ink of the present invention can be subjected to a post-coating treatment. Specific examples of post-coating treatments include coating or printing with a post-coating composition, and lamination using a dry lamination method, a solventless lamination method, an extrusion lamination method, etc. Any of these methods may be selected, or a combination of two or more may be used.

[0127]

[0033] When a post-coating treatment is performed on a printed material by coating and printing the post-coating composition, the coating and printing method may be either a method of printing without contact with the printing substrate, such as inkjet printing, or a method of printing by bringing the post-coating composition into contact with the printing substrate. Furthermore, when the method of printing without contact with the printing substrate is selected, it is preferable to use, as the post-coating composition, an ink (clear ink) that is obtained by excluding the pigment from the ink of the present invention and that does not substantially contain a colorant component.

[0128] When a printed material is laminated, the adhesive used to laminate the sealant substrate is preferably composed of a mixture of a polyol component and a polyisocyanate component.

[0129] The polyol component is a resin component having multiple hydroxyl groups, and polyurethane resins or polyester resins are preferably used in view of coatability, wettability and permeability to the interface of printed matter, and laminate strength developed after aging. Among these, it is preferred that the polyol component contains a polyester polyol, as this provides good wettability and spreadability to the interface of printed matter obtained with the ink of the present invention, for example, to the printed layer (printed area) and the pretreatment liquid layer (non-printed area), and also provides excellent laminate strength to the laminated printed matter (laminate). The polyol component may be a single component, or multiple components may be used in combination.

[0130] Furthermore, the polyisocyanate component reacts with the polyol component to form a urethane bond, thereby increasing the molecular weight of the adhesive layer and improving the laminate strength. In particular, from the viewpoints of compatibility with the polyol component, wetting and spreading properties at the interface of printed materials obtained with the ink of the present invention, and the laminate strength of laminated printed materials (laminates), it is preferable that the polyisocyanate component contains a polyether-based urethane resin terminated with an isocyanate group. From the same viewpoints as above, the blending amount of the polyisocyanate component is preferably 50 to 80% by mass relative to the polyol component. The polyisocyanate component may be a single component, or multiple components may be used in combination.

[0131] Examples of the sealant substrate used in the lamination process include polypropylene films and polyethylene films such as CPP film and linear short-chain branched polyethylene (LLDPE) film. Also, a film having a vapor-deposited metal (oxide) layer such as aluminum oxide may be used.

[0132] <Examples of Embodiments> The embodiments of the present invention include the aqueous inkjet inks shown in [1] to [5] below, and the printed matter produced using the aqueous inkjet inks shown in [6] below. [1] An aqueous inkjet ink containing a pigment, a binder resin, a water-soluble organic solvent, and an acetylenic diol surfactant (A), wherein the acetylenic diol surfactant (A) comprises an unmodified acetylenic diol surfactant (A1) and an alkylene oxide-modified acetylenic diol surfactant (A2) having an HLB value of 4 to 10, the content of the unmodified acetylenic diol surfactant (A1) is 5 to 2,000 ppm relative to the total amount of the aqueous inkjet ink, the content of the alkylene oxide-modified acetylenic diol surfactant (A2) is 0.2 to 5 mass% relative to the total amount of the aqueous inkjet ink, and the ratio of the content of the unmodified acetylenic diol surfactant (A1) to the content of the alkylene oxide-modified acetylenic diol surfactant (A2) [surfactant (A2) / surfactant (A1)] is in the range of 10 to 5,000. [2] The aqueous inkjet ink according to [1], further comprising a nonionic surfactant (B) other than an acetylene diol surfactant. [3] The aqueous inkjet ink according to [2], having a mass factor-added HLB value of 0.3 to 2.0, calculated by the following formula (1): Formula (1): (In formula (1), i represents the type of surfactant used as the unmodified acetylenic diol surfactant (A1), l represents the number of types of surfactants used as the unmodified acetylenic diol surfactant (A1), j represents the type of surfactant used as the alkylene oxide-modified acetylenic diol surfactant (A2), m represents the number of types of surfactants used as the alkylene oxide-modified acetylenic diol surfactant (A2), k represents the type of surfactant used as the nonionic surfactant (B), n represents the number of types of surfactants used as the nonionic surfactant (B). In addition, HLB ｉrepresents the HLB value of surfactant i, and WT ｉ represents the content (mass%) of the surfactant i relative to the total mass of the aqueous inkjet ink, and HLB ｊ represents the HLB value of surfactant j, and WT ｊ represents the content (mass%) of the surfactant j relative to the total mass of the aqueous inkjet ink, and HLB ｋ represents the HLB value of surfactant k, and WT ｋ represents the content (% by mass) of the surfactant k relative to the total mass of the aqueous inkjet ink.) [4] The aqueous inkjet ink according to [2] or [3], wherein the nonionic surfactant (B) includes a silicone surfactant. [5] The aqueous inkjet ink according to any one of [1] to [4], wherein the water-soluble organic solvent includes 1,2-propanediol, and the content of the 1,2-propanediol is 5 to 30% by mass relative to the total amount of the aqueous inkjet ink. [6] A printed matter obtained by printing the aqueous inkjet ink according to any one of [1] to [5] on a printing substrate.

[0133] The disclosure of this application is related to the subject matter described in Japanese Patent Application No. 2023-198145, filed on November 22, 2023, the entire disclosure of which is incorporated herein by reference.

[0134] The present invention will be described in more detail below with reference to examples and comparative examples. In the following description, "parts" and "%" are by mass unless otherwise specified.

[0135] <Production Example of Pigment Dispersion Resin Water-Based Solution 1> 90 parts of butanol was charged into a reaction vessel equipped with a gas inlet tube, thermometer, condenser, and stirrer, and the atmosphere inside the reaction vessel was replaced with nitrogen gas. Next, the reaction vessel was heated to 110°C, and then a mixture of polymerizable monomers (30 parts of acrylic acid, 35 parts of behenyl acrylate, and 35 parts of styrene) and 4 parts of a polymerization initiator (V-601, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added dropwise to the reaction vessel over 2 hours. After completion of the addition, the polymerization reaction was continued for 3 hours while maintaining the internal temperature at 110°C. Thereafter, 0.4 parts of V-601 was added, and the polymerization reaction was continued for 1 hour while maintaining the internal temperature of the reaction vessel at 110°C, thereby obtaining a solution of pigment dispersion resin 1. Next, the contents of the reaction vessel were cooled to room temperature, and 38 parts of dimethylaminoethanol was added to neutralize the pigment dispersion resin 1, followed by the addition of 100 parts of ion-exchanged water. Thereafter, the contents were heated to 100°C or higher to form an azeotrope of butanol with the ion-exchanged water and distill off the butanol, and then ion-exchanged water was added to adjust the solids concentration to 50%, thereby obtaining an aqueous pigment dispersion resin solution 1 with a solids concentration of 50%. The molecular weight of the resulting pigment dispersion resin 1 was 16,000 and the acid value was 234 mgKOH / g.

[0136] <Production Example of Pigment Dispersion Resin Water-Soluble Solution 2> 56 parts of 2-butanone were charged into a reaction vessel equipped with a gas inlet tube, thermometer, condenser, and stirrer. Next, 56 parts of benzyl methacrylate as a polymerizable monomer, 0.3 parts of 2,2'-azobisisobutyronitrile as a polymerization initiator, and 2.2 parts of 2-(dodecylthiocarbonothioylthio)-isobutyric acid were charged. After the atmosphere inside the reaction vessel was purged with nitrogen gas, the contents inside the reaction vessel were heated to 75°C, and then a polymerization reaction was carried out for 3 hours while maintaining the internal temperature at 75°C, thereby obtaining a polymer (A block) composed of benzyl methacrylate. After completion of the polymerization reaction, 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 charged into the reaction vessel. The atmosphere inside the reaction vessel was again purged with nitrogen gas, and the contents of the reaction vessel were heated to 75°C. A polymerization reaction was then carried out for 3 hours while maintaining the internal temperature at 75°C, yielding a pigment dispersion resin 2 having an A-B 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 pigment dispersion resin 2. Then, 150 parts of ion-exchanged water was added. The contents were then heated to azeotrope 2-butanone with ion-exchanged water, and the 2-butanone was distilled off. Ion-exchanged water was then added to adjust the solids concentration to 50%, yielding a water-based pigment dispersion resin solution 2 with a solids concentration of 50%. The molecular weight of the resulting pigment dispersion resin was 23,000 and the acid value was 104 mgKOH / g.

[0137] <Production Example of Cyan Pigment Dispersion Liquid 1> 20 parts of LIONOGEN BLUE FG-7358G (C.I. Pigment Blue 15:3, manufactured by Toyocolor Co., Ltd.), 15 parts of Pigment Dispersion Resin Water-Based Solution 1, and 65 parts of ion-exchanged water were mixed and pre-dispersed using a Disper disperser. After that, main dispersion was carried out using a 0.6 L Dyno-Mill filled with 1,800 g of zirconia beads having a diameter of 0.5 mm, and cyan pigment dispersion liquid 1 was obtained.

[0138] <Production Example of Cyan Pigment Dispersion Liquid 2> Cyan pigment dispersion liquid 2 was produced using the same raw materials and method as for the above-mentioned Cyan Pigment Dispersion Liquid 1, except that the Pigment Dispersion Resin Water-Soluble Solution 2 was used instead of the Pigment Dispersion Resin Water-Soluble Solution 1.

[0139] <Production Example of Binder Resin 1> 72.4 parts of 2-butanone were charged into a reaction vessel equipped with a gas inlet tube, thermometer, condenser, and stirrer, and the atmosphere inside the reaction vessel was replaced with nitrogen gas. Next, the reaction vessel was heated to 80°C, and then a mixture of polymerizable monomers (15 parts of styrene, 4.5 parts of methacrylic acid, 5.0 parts of 2-hydroxyethyl methacrylate, 20 parts of stearyl methacrylate, 55.5 parts of methyl methacrylate), and 4 parts of a polymerization initiator (V-601, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added dropwise to the reaction vessel over 2 hours. After completion of the addition, the polymerization reaction was continued for 3 hours while maintaining the internal temperature at 80°C. Thereafter, 0.6 parts of V-601 was added, and the polymerization reaction was continued for 2 hours while maintaining the internal temperature at 80°C, to obtain a solution of binder resin 1. Next, the contents of the reaction vessel were cooled to 50°C, and 4.7 parts of dimethylaminoethanol were added to neutralize the binder resin 1. Then, 140 parts of water were added. The contents were then heated to 78°C or higher, and 2-butanone was azeotroped with water to distill off the 2-butanone. Water was then added to adjust the solids concentration to 30%, thereby obtaining an aqueous solution of binder resin 1 with a solids concentration of 30%. The weight-average molecular weight of the resulting binder resin 1 was 17,000.

[0140] <Synthesis of Unmodified Acetylenic Diol Surfactant (A1)> 2,4,7,9-tetramethyl-5-decyne-4,7-diol (unmodified acetylenic diol compound 1, HLB value = 3.0) was synthesized using the method described in Example 1 of JP 2002-356451 A and methyl isobutyl ketone as the raw material ketone. Similarly, 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol (unmodified acetylenic diol compound 2, HLB value = 2.7) was synthesized using methyl isoamyl ketone as the raw material ketone.

[0141] Synthesis of Alkylene Oxide-Modified Acetylene Diol Surfactant (A2) Using the method described in Example 1 of U.S. Pat. No. 3,268,593, alkylene oxide-modified acetylene diol surfactants (modified acetylene diol compounds 1 to 4 and 6 to 11) with different amounts of ethylene oxide modification were synthesized by adjusting the amount of ethylene oxide and synthesis conditions (pressure, temperature, and time) using the unmodified acetylene diol compound 1 (2,4,7,9-tetramethyl-5-decyne-4,7-diol) as a starting material. Furthermore, an ethylene oxide-modified acetylene diol surfactant (modified acetylene diol compound 5) with an HLB value of 8 was synthesized by adjusting the amount of ethylene oxide and synthesis conditions (pressure, temperature, and time) using the unmodified acetylene diol compound 2 (2,5,8,11-tetramethyl-6-dodecyne-5,8-diol) as a starting material. Furthermore, by utilizing the method described in Example 1 of JP-A No. 2001-215690, modified acetylenic diol compounds 7 and 9 were used as starting materials, and propylene oxide groups were added to the modified acetylenic diol compounds 7 and 9, thereby synthesizing ethylene oxide-propylene oxide modified acetylenic diol surfactants (modified acetylenic diol compounds 12 and 13).

[0142] The details of the modified acetylenic diol compounds 1 to 13 produced above (starting material, number of moles of ethylene oxide group (and propylene oxide group) added, and HLB value) are as shown in Table 1 below.

[0143]

[0144] <Production Example of Ink 1> 35.6 parts of ion-exchanged water, 20 parts of 1,2-propanediol, 1.5 parts of modified acetylenic diol compound 4, 1.0 part of BYK-349 (a silicone surfactant manufactured by BYK-Chemie, HLB value = 10.2), 0.2 parts of TEGO Glide 100 (a silicone surfactant manufactured by Evonik, HLB value = 6.8), 16.7 parts of aqueous binder resin 1 solution, and 25 parts of cyan pigment dispersion 1 were sequentially charged into a mixing vessel and stirred using a Disper disperser until the mixture was sufficiently uniform. The mixture was then filtered through a membrane filter with a pore size of 1 μm to remove coarse particles that may cause head clogging, thereby producing Ink 1.

[0145] <Production Examples of Inks 2 to 105> Inks 2 to 105 were produced in the same manner as in the production example of ink 1, except that the raw materials listed in Table 2 were used.

[0146]

[0147]

[0148]

[0149]

[0150]

[0151]

[0152] Details of the trade names and abbreviations listed in Table 2 above are as follows: In Table 2, "Nv" represents the solid content concentration, and "HLB" represents the HLB value. NeoCryl A-1127 (acrylic emulsion manufactured by DSM, solids concentration 44%, MFT 7°C) NeoRez R-600 (urethane emulsion manufactured by DSM, solids concentration 33%, MFT less than 0°C) BYK 349 (silicone surfactant manufactured by BYK, HLB value = 10.2) BYK 3420 (silicone surfactant manufactured by BYK, HLB value = 13.8) BYK 3451 (silicone surfactant manufactured by BYK, HLB value = 10.8) TEGO Glide 100 (silicone surfactant manufactured by Evonik, HLB value = 6.8) TEGO Glide 440 (silicone surfactant manufactured by Evonik, HLB value = 12.7) TEGO Twin 4200 (silicone surfactant manufactured by Evonik, HLB value = 8.2) Braunon EL-1502.2 (polyoxyethylene lauryl ether manufactured by Aoki Oil & Fat Co., Ltd., HLB value = 6.3) Braunon EL-1505 (polyoxyethylene lauryl ether manufactured by Aoki Oil & Fat Co., Ltd., HLB value = 10.5) Braunon EL-1515 (polyoxyethylene lauryl ether manufactured by Aoki Oil & Fat Co., Ltd., HLB value = 14.9) Braunon EL-1530 (polyoxyethylene lauryl ether manufactured by Aoki Oil & Fat Co., Ltd., HLB value = 17.4) Braunon BN-3 (polyoxyethylene beta naphthol ether manufactured by Aoki Oil & Fat Co., Ltd., HLB value = 9.6) Lutensol XP30 (nonionic surfactant manufactured by BASF, HLB value = 9.1) Lutensol XP50 (nonionic surfactant manufactured by BASF, HLB value = 11.6) Lutensol XP100 (nonionic surfactant manufactured by BASF, HLB value = 14.7) 1,2-PG (1,2-propanediol) PGM (propylene glycol monomethyl ether) BDG (diethylene glycol monobutyl ether) DPnP (dipropylene glycol monopropyl ether) 1,3-PG (1,3-propanediol) 1,2-BD (1,2-butanediol)

[0153] [Examples 1 to 93, Comparative Examples 1 to 12] The inks prepared above were evaluated as follows. The evaluation results are shown in Table 3.

[0154] <Evaluation 1: Beading (Solid Filling)> Each of the inks prepared above was filled into an inkjet ejection device equipped with a Kyocera Corporation head (KJ4B-1200) installed in a 25°C environment. A nozzle check pattern was printed, and after confirming that ink was being ejected normally from all nozzles, the device was left to stand for 1 minute. Subsequently, a solid print with a printing rate of 100% was performed on a PET film (FE2001, thickness 12 μm) manufactured by Futamura Chemical Co., Ltd. under printing conditions of a frequency of 40 kHz and 1200 × 1200 dpi, and then dried in an air oven at 85°C for 1 minute to obtain a solid print. Beading (solid filling) was then evaluated by visually checking the number of streaks (areas where the ink did not adhere to the printing substrate and appeared streaky). The evaluation criteria were as follows, with A, B, and C being considered to be within the practical range. A: Five or fewer streaks were visible to the naked eye. B: Six to ten or fewer streaks were visible to the naked eye. C: Eleven to twenty or fewer streaks were visible to the naked eye. D: 21 or more streaks were visible to the naked eye.

[0155] <Evaluation 2: Continuous Dischargeability> Each of the inks prepared above was filled into an inkjet discharge device equipped with a Kyocera head (KJ4B-1200). A nozzle check pattern was printed to confirm that ink was being discharged normally from all nozzles, and then ink was continuously discharged from all nozzles for one hour at a frequency of 40 kHz. A nozzle check pattern was then printed again to check the number of nozzles from which ink was not discharged (number of clogged nozzles), thereby evaluating continuous dischargeability. The evaluation criteria were as follows, with AA, A, B, and C being considered as practical ranges. AA: No clogged nozzles at all A: 1 to 2 clogged nozzles B: 3 to 6 clogged nozzles C: 7 to 10 clogged nozzles D: 11 clogged nozzles

[0156] <Evaluation 3: Blocking Resistance> A solid print with a printing rate of 100% was obtained using the same printing conditions and printing substrate as in Evaluation 1 above, and then cut into a 4 cm x 4 cm square. The PET film used as the printing substrate (but not used for printing) was also cut out in the same manner as the solid print. The cut-out solid print was then superimposed so that the ink layer faced the non-printed surface (rear surface) of the PET film to form a test piece, and a blocking test was carried out using a permanent deformation tester. The environmental conditions for the blocking test were a load of 10 kg / cm ２ The test was conducted at a temperature of 40°C, 80% RH, and for a test period of 24 hours, with a load applied using a constant-load permanent deformation tester manufactured by Tester Sangyo Co., Ltd. After 24 hours had passed, the PET film was pulled and peeled off instantaneously while maintaining a 90-degree angle, and blocking resistance was evaluated based on the degree of resistance felt upon peeling and the state of the ink layer after peeling (visual observation). The evaluation criteria were as follows, with AA, A, B, and C being considered to be in the practical range. AA: The ink layer was not taken up by the PET film, and there was no resistance when peeled off. A: The ink layer was not taken up by the PET film, but there was slight resistance when peeled off. B: The ink layer was observed to be taken up by the PET film over less than 5% of the total area of ​​the ink layer. C: The ink layer was observed to be taken up by the PET film over 5% to less than 10% of the total area of ​​the ink layer. D: The ink layer was observed to be taken up by the PET film over 10% or more of the total area of ​​the ink layer.

[0157] <Evaluation 4: Migration Resistance> A solid print with a printing rate of 100% was obtained using the same printing conditions and printing substrate as in Evaluation 1. Next, using a solventless test coater, a solventless laminating adhesive ("EA-N373A / B" manufactured by Toyo-Morton) was applied to the printed surface (ink layer side) of the prepared solid print at a temperature of 60°C, a coating speed of 50 m / min, and a coating amount of 2 g / m. ２The solvent-free laminating adhesive composition was applied under the following conditions. The coated surface of the solvent-free laminating adhesive was then placed face-to-face with the corona-treated surface of a CPP film (FHK2 unstretched polypropylene film (25 μm thick) manufactured by Futamura Chemical Co., Ltd.), and the resulting film was left standing (aged) for one day in an environment of 40°C and 80% RH to cure the solvent-free laminating adhesive composition and produce a laminated product. The resulting laminated product was placed in a migration cell (MigraCell (registered trademark) MC60 manufactured by Gassner Glastechnik) with the CPP film facing up, and 50 mL of a 95% ethanol solution was added. The contact area between the laminated product and the ethanol was 0.5 dm ２ The migration cell was then placed in a 40°C oven for 10 days, after which the 95% ethanol solution was removed and concentrated to 2 mL or less under conditions of 40°C and 50 mmHg. After that, when the amount of the concentrated ethanol solution was less than 2 mL, it was placed in a 2 mL volumetric flask and filled up with 95% ethanol. The ethanol solution after concentration and fill-up was used as a sample, and the amount (total amount) of acetylene diol surfactant (A) contained per mL of the ethanol solution after concentration and fill-up was quantified using a gas chromatograph mass spectrometer (Agilent 7890A / 5975C manufactured by Agilent Technologies), to evaluate migration resistance. The evaluation criteria were as follows, with A, B, and C ratings being considered as practical ranges. A: The amount of eluted acetylenic diol surfactant (A) was 0.1 μg / mL or less. B: The amount of eluted acetylenic diol surfactant (A) was more than 0.1 μg / mL and 1.0 μg / mL or less. C: The amount of eluted acetylenic diol surfactant (A) was more than 1.0 μg / mL and 3.0 μg / mL or less. D: The amount of eluted acetylenic diol surfactant (A) was more than 3.0 μg / mL.

[0158]

[0159]

[0160] As is clear from Examples 1 to 93, by using the ink of the present invention, which contains an unmodified acetylenic diol surfactant (A1) and an alkylene oxide-modified acetylenic diol surfactant (A2) having an HLB value of 4 to 10 in predetermined amounts and ratios, and further contains a binder resin, it was possible to obtain printed matter which was free of beading, had good solid coverage, and was also excellent in blocking resistance and migration resistance. Furthermore, the aqueous inkjet ink of the present invention also had good continuous dischargeability.

Claims

1. An aqueous inkjet ink containing a pigment, a binder resin, a water-soluble organic solvent, and an acetylenic diol-based surfactant (A), wherein the acetylenic diol-based surfactant (A) comprises an unmodified acetylenic diol-based surfactant (A1) and an alkylene oxide-modified acetylenic diol-based surfactant (A2) having an HLB value of 4 to 10, the content of the unmodified acetylenic diol-based surfactant (A1) is 5 to 2,000 ppm based on the total amount of the aqueous inkjet ink, the content of the alkylene oxide-modified acetylenic diol-based surfactant (A2) is 0.2 to 5 mass% based on the total amount of the aqueous inkjet ink, and the ratio of the content of the unmodified acetylenic diol-based surfactant (A1) to the content of the alkylene oxide-modified acetylenic diol-based surfactant (A2) [surfactant (A2) / surfactant (A1)] is in the range of 10 to 5,000.

2. The aqueous ink-jet ink according to claim 1, further comprising (B) a nonionic surfactant other than the acetylene diol surfactant.

3. The aqueous inkjet ink according to claim 2, wherein the mass factor added HLB value calculated by the following formula (1) is 0.3 to 2.

0. Formula (1): (In formula (1), i represents the type of surfactant used as the unmodified acetylenic diol surfactant (A1), l represents the number of types of surfactants used as the unmodified acetylenic diol surfactant (A1), j represents the type of surfactant used as the alkylene oxide-modified acetylenic diol surfactant (A2), m represents the number of types of surfactants used as the alkylene oxide-modified acetylenic diol surfactant (A2), k represents the type of surfactant used as the nonionic surfactant (B), n represents the number of types of surfactants used as the nonionic surfactant (B). In addition, the HLB ｉ represents the HLB value of surfactant i, and WT ｉ represents the content (mass%) of the surfactant i relative to the total mass of the aqueous inkjet ink, and HLB ｊ represents the HLB value of surfactant j, and WT ｊ represents the content (mass%) of the surfactant j relative to the total mass of the aqueous inkjet ink, and HLB ｋ represents the HLB value of surfactant k, and WT ｋ represents the content (mass%) of the surfactant k relative to the total mass of the aqueous inkjet ink.

4. The aqueous ink-jet ink according to claim 2 or 3, wherein the nonionic surfactant (B) comprises a silicone-based surfactant.

5. The aqueous inkjet ink according to any one of claims 1 to 4, wherein the water-soluble organic solvent contains 1,2-propanediol, and the content of the 1,2-propanediol is 5 to 30 mass % based on the total amount of the aqueous inkjet ink.

6. A printed matter obtained by printing the aqueous inkjet ink according to any one of claims 1 to 5 onto a printing substrate.

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