Water-based inkjet inks and printed materials

Abstract

This invention provides a water-based inkjet ink that, even when printed on non-absorbent printing substrates, produces printed materials free of pinholes, with excellent blocking resistance, lamination properties, and low migration, and also exhibits good standby ejection performance. [Solution] An aqueous inkjet ink comprising a pigment, an acetylenediol-based surfactant (A), a plurality of water-soluble organic solvents (B), and water, wherein the acetylenediol-based surfactant (A) contains an unmodified acetylenediol-based surfactant (A1) and an alkylene oxide-modified acetylenediol-based surfactant (A2) having an HLB value of 6 to 12, in specific amounts and ratios, and the difference between the weighted average value of the HLB values ​​of the acetylenediol-based surfactant (A) and the weighted average value of the HLB values ​​of the water-soluble organic solvent (B), and the weighted average value of the boiling points of the water-soluble organic solvent (B) and the water are defined.

Description

[Technical Field]

[0001] This invention relates to an aqueous inkjet ink and printed materials produced using the aqueous inkjet ink. [Background technology]

[0002] The demand for smaller print runs and cost reductions, along with the diversification of market needs, has led to the rapid spread of digital printing methods. One type of digital printing method is inkjet printing. Inkjet printing is a method in which tiny droplets of ink are ejected and deposited onto a printing substrate from an inkjet head, thereby printing images and / or text onto the substrate. Compared to other digital printing methods, inkjet printing is superior in terms of the size and cost of the printing equipment and the ease of full-color printing. For this reason, the use of inkjet printing is also increasing in industrial printing applications.

[0003] In recent years, the packaging market has attracted considerable interest as a potential application for the industrial printing mentioned above. Furthermore, in response to the growing demand for consideration of environmental and human hazards, the deployment of water-based inks in the packaging market is being actively explored. In the packaging market, many of the printing substrates used are non-absorbent, such as polypropylene film, polyethylene terephthalate film, and nylon film. Therefore, in order to use water-based inks in the packaging market, it is necessary to be able to produce printed materials with excellent print quality and durability for actual use, even on non-absorbent printing substrates.

[0004] For example, blocking in printed materials stored by rolling or stacking them poses a significant problem in terms of storage. "Blocking" is a phenomenon in which rolled or stacked printed materials stick together, causing a portion of the ink layer (the layer formed when the printed ink dries) to adhere to the back surface of the printing substrate.

[0005] Furthermore, in the packaging market, in order to impart functionality to printed materials, these materials are sometimes laminated by bonding them to another film or other material via an adhesive (laminating adhesive). In such cases, if the lamination strength is insufficient, there is a risk of delamination occurring between the layers.

[0006] Furthermore, when a laminate containing an ink layer is manufactured and used as packaging such as a pouch, components present on the surface of the ink layer, and / or that have bled (a phenomenon in which a certain component seeps out onto the surface of the layer 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.

[0007] These practical defects, namely blocking in printed materials, reduced laminate strength in laminates containing such printed materials, and migration, can often be fatal problems in the packaging market. However, with conventional water-based inks used in inkjet printing, it has been extremely difficult to produce printed materials free from the aforementioned defects on non-absorbent printing substrates.

[0008] In this disclosure, water-based inks used in inkjet printing methods are referred to as "water-based inkjet inks."

[0009] Furthermore, as a water-based inkjet ink, it must also possess the quality generally required for use in inkjet printing systems. For example, water-based inkjet inks are required to be able to be ejected stably from the inkjet head. If ejection defects (deterioration of standby ejection performance) such as nozzle clogging or flight deflection occur when ejection is resumed after being stopped for a certain period of time, it could become a major problem. In addition, pinholes in the printed material (a phenomenon in which areas where ink did not adhere appear as dots of exposed printing substrate) negatively affect the print quality.

[0010] As described above, conventionally, it has been extremely difficult to obtain an aqueous inkjet ink that, even when printed on non-absorbent printing substrates, does not produce pinholes or blocking, does not cause a decrease in laminate strength or migration when formed into a laminate, and also exhibits good standby ejection performance.

[0011] To date, as an example of studies conducted to address some of the aforementioned issues, Patent Document 1 discloses an aqueous inkjet ink containing two types of acetylenediol-based surfactants with different structures, a butyl ether-based solvent, 2-pyrrolidone, etc. Patent Document 1 states that by using the aqueous inkjet ink having the above configuration, it is possible to obtain printed materials with excellent ejection stability, no bleeding (smudging that occurs at the boundary when two colors of aqueous inkjet ink are printed side by side), and excellent print quality, and that the aqueous inkjet ink can be suitably printed on plastic sheets such as polyethylene terephthalate, polycarbonate, and polypropylene. However, Patent Document 1 does not provide evaluations regarding blocking, lamination strength, migration, etc. When the present inventors actually reproduced and evaluated an aqueous inkjet ink having the configuration specifically disclosed in the example of Patent Document 1, it was confirmed that blocking may occur in printed materials, and that when laminated, it may cause a decrease in lamination strength and migration.

[0012] Patent Document 2 also discloses a white, aqueous inkjet ink for non-absorbent printing substrates, comprising an acetylenediol-based surfactant, a polyether-modified siloxane-based surfactant, a water-soluble organic solvent, etc., with a specified blending ratio of the acetylenediol-based surfactant and the polyether-modified siloxane-based surfactant. Patent Document 2 states that using an aqueous inkjet ink having the above configuration prevents migration and provides printed materials with excellent solid printing uniformity and whiteness. Patent Document 3 also discloses an aqueous inkjet ink using a specific acetylenediol-based surfactant in combination with a nonionic surfactant. Patent Document 3 states that an aqueous inkjet ink having the above configuration does not cause turbidity such as oil separation or clouding, and that using this aqueous inkjet ink allows for the production of printed materials without color unevenness on low-absorbency and non-water-absorbent printing substrates. On the other hand, aqueous inkjet inks having the configurations specifically disclosed in the examples of Patent Documents 2 and 3 may experience problems with standby ejection depending on the printing conditions. Furthermore, it has been found that laminates made using the above aqueous inkjet inks may experience a decrease in laminate strength.

[0013] Patent Document 4 discloses an aqueous inkjet ink that can produce printed materials with excellent print quality and fixation on a variety of printing substrates at high speed. Specifically, the aqueous inkjet ink is characterized by containing three or more acetylenediol-based surfactants. However, Patent Document 4 does not mention blocking, lamination strength, migration, etc. Furthermore, when the present inventors reproduced and evaluated an aqueous inkjet ink having the configuration specifically disclosed in the examples of Patent Document 4, it was confirmed that blocking may occur in printed materials, and a decrease in lamination strength may occur when the material is laminated. [Prior art documents] [Patent Documents]

[0014]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0015] The present invention has been made to solve the above-described problems. That is, an object of the present invention is to obtain a printed matter that has no pinholes, is excellent in blocking resistance, laminating property, and low migration property, and also has good standby ejection property even when printed on a non-absorbent printing substrate, and to provide an aqueous inkjet ink.

[0016] In the present disclosure, a printed matter with suppressed blocking is also described as a "printed matter excellent in blocking resistance". Further, a printed matter and a laminate having high lamination strength are also described as a "printed matter excellent in laminating property", and a printed matter and a laminate having low lamination strength are also described as a "printed matter with deteriorated laminating property". Furthermore, a printed matter and a laminate with suppressed migration are also described as a "printed matter excellent in low migration property".

Means for Solving the Problems

[0017] As a result of intensive studies by the present inventors, it has been found that all of the above-described problems can be solved simultaneously and at a high level by an aqueous inkjet ink having the following configuration.

[0018] That is, one embodiment of the present invention relates to an aqueous inkjet ink shown in [1] to [6] below, and a printed matter manufactured using the above aqueous inkjet ink shown in [7] below. [1] An aqueous inkjet ink containing a pigment, an acetylene diol-based surfactant (A), a water-soluble organic solvent (B), and water, where the acetylene diol-based surfactant (A) includes an unmodified acetylene diol-based surfactant (A1) and an alkylene oxide-modified acetylene diol-based surfactant (A2) having an HLB value of 6 to 12, the content of the unmodified acetylene diol-based surfactant (A1) is 2 to 600 ppm with respect to the total amount of the aqueous inkjet ink, the content of the alkylene oxide-modified acetylene diol-based surfactant (A2) is 0.1 to 5% by mass with respect to the total amount of the aqueous inkjet ink, the ratio [surfactant (A2) / surfactant (A1)] of the content of the unmodified acetylene diol-based surfactant (A1) to the content of the alkylene oxide-modified acetylene diol-based surfactant (A2) is in the range of 10 to 5000 on a mass basis, the water-soluble organic solvent (B) includes two or more water-soluble organic solvents, the absolute value of the difference between the weighted average value of the HLB value of the acetylene diol-based surfactant (A) and the weighted average value of the HLB value of the water-soluble organic solvent (B) is 0 to 3.5, and the weighted average value of the boiling points of the water-soluble organic solvent (B) and the water is 102 to 135°C, an aqueous inkjet ink. [2] The aqueous inkjet ink according to [1], wherein the water-soluble organic solvent (B) includes alkanediols having 2 to 6 carbon atoms and (poly)propylene glycol monoalkyl ethers. [3] The aqueous inkjet ink according to [1] or [2], further including a nonionic surfactant (C) other than the acetylene diol-based surfactant. [4] The aqueous inkjet ink according to [3], wherein the nonionic surfactant (C) comprises a siloxane-based surfactant and / or a polyoxyalkylene alkyl ether-based surfactant. [5] The aqueous inkjet ink according to [3] or [4], wherein the nonionic surfactant (C) comprises a nonionic surfactant having an HLB value of 6 to 15. [6] Furthermore, the pigment dispersion resin having a crosslinked structure The aforementioned crosslinked pigment dispersion resin is a reaction product of a pigment dispersion resin before crosslinking treatment and a compound that can react with functional groups present in the pigment dispersion resin before crosslinking treatment. An aqueous inkjet ink according to any one of [1] to [5], wherein the ratio of the molar amount of functional groups present in the compound that can react with the pigment dispersion resin before crosslinking treatment to the molar amount of functional groups present in the pigment dispersion resin before crosslinking treatment that can react with the compound [number of moles of functional groups in the compound / number of moles of functional groups in the pigment dispersion resin before crosslinking treatment] is 0.2 to 0.7. A printed material having been printed on a printing substrate using any of the water-based inkjet inks described in [7][1] to [6]. [Effects of the Invention]

[0019] The present invention makes it possible to provide an aqueous inkjet ink that, even when printed on a non-absorbent printing substrate, is free of pinholes and exhibits excellent blocking resistance, lamination properties, and low migration characteristics, as well as good standby ejection performance. [Modes for carrying out the invention]

[0020] The following describes the aqueous inkjet ink of the present invention (hereinafter also simply referred to as "the ink of the present invention") and printed materials obtained by printing with the aqueous inkjet ink. However, the present invention is not limited to the following description and includes various modifications that do not depart from the spirit of the invention.

[0021] Generally, surfactants are used to adjust the surface tension of water-based inkjet inks and to obtain printed materials with excellent print quality without white spots (a phenomenon where areas of ink do not adhere to the printed material). However, depending on the type and amount of surfactant selected, there is a risk of deterioration of standby discharge performance, blocking in the printed material, a decrease in laminate strength in the laminate containing the printed material, and migration. These problems tend to occur particularly significantly with surfactants that have low molecular weight and high orientation rates. Furthermore, when these low molecular weight and high orientation rate surfactants combine during the drying process of water-based inkjet ink on the printing substrate, there is a possibility of pinholes, a type of white spot, occurring. On the other hand, the presence of these low molecular weight and high orientation rate surfactants is essential for producing printed materials with excellent print quality without white spots on non-absorbent printing substrates.

[0022] Therefore, in order to resolve these problems, the inventors diligently continued their research and, as a result, discovered an aqueous inkjet ink having the above-described configuration, leading to the present invention. The details of the mechanism by which the above-described aqueous inkjet ink can suitably solve the above-described problems are unknown, but the inventors speculate as follows.

[0023] The ink of the present invention uses an acetylenediol-based surfactant (A). Generally, the acetylene group present in the molecular structure of an acetylenediol-based surfactant does not undergo bond rotation, so the molecular structure is not easily deformed. Therefore, it is believed that the above-mentioned acetylenediol-based surfactant will produce the intended effect even if only a small amount is added.

[0024] Furthermore, the ink of the present invention uses both an unmodified acetylenediol-based surfactant (A1) and an alkylene oxide-modified acetylenediol-based surfactant (A2) with an HLB value of 6 to 12 as the acetylenediol-based surfactant (A). Of these, the unmodified acetylenediol-based surfactant (A1) corresponds to the "surfactant with low molecular weight and high orientation rate" mentioned above. Since surfactants with low molecular weight and high orientation rate can cause deterioration of standby discharge performance, blocking, reduced lamination, migration, and pinholes, it is preferable to use a small amount. Therefore, in the ink of the present invention, the content of the unmodified acetylenediol-based surfactant (A1) is in the range of 2 to 600 ppm of the total amount of ink. However, if the unmodified acetylenediol-based surfactant (A1) is not used at all, it becomes extremely difficult to produce printed materials with suppressed blocking, no white spots, and excellent print quality on non-absorbent printing substrates. Furthermore, even if the content of unmodified acetylenediol surfactant (A1) is low, the risk of pinhole formation remains because association of these unmodified acetylenediol surfactants (A1) can occur during drying on the printing substrate. In addition, because unmodified acetylenediol surfactant (A1) has a high orientation rate, depending on the configuration of the inkjet head on which the water-based inkjet ink is mounted and the printing conditions, the surface tension of the gas-liquid interface formed at the discharge port (nozzle opening) may decrease excessively and locally, potentially worsening standby discharge performance.

[0025] Therefore, in the ink of the present invention, 0.1 to 5% by mass of alkylene oxide-modified acetylenediol-based surfactant (A2) having an HLB value of 6 to 12 is used together with the unmodified acetylenediol-based surfactant (A1). Furthermore, the content of the alkylene oxide-modified acetylenediol-based surfactant (A2) relative to the content of the unmodified acetylenediol-based surfactant (A1) is set to 10 to 5000 by mass. It is believed that the alkylene oxide-modified acetylenediol-based surfactant (A2) can emulsify and compatibilize the unmodified acetylenediol-based surfactant (A1). In addition, it is presumed that the unmodified acetylenediol-based surfactant (A1) is stabilized in the aqueous inkjet ink in the presence of the alkylene oxide-modified acetylenediol-based surfactant (A2). As a result, when the aqueous inkjet ink dries on the printing substrate, the alkylene oxide-modified acetylenediol-based surfactant (A2) suppresses the association of unmodified acetylenediol-based surfactants (A1), thereby suppressing pinhole formation. Furthermore, in the aqueous inkjet ink present near the ejection port of the inkjet head, the excessive and localized orientation of unmodified acetylenediol-based surfactants (A1) at the gas-liquid interface is suppressed, improving standby ejection performance.

[0026] Furthermore, in the ink of the present invention, the emulsification and compatibilization effects of the alkylene oxide-modified acetylenediol-based surfactant (A2) described above are optimized, and from the viewpoint of reducing pinholes in printed materials, suppressing blocking, improving lamination properties, and improving standby discharge properties, the ratio of the content of alkylene oxide-modified acetylenediol-based surfactant (A2) to the content of unmodified acetylenediol-based surfactant (A1) is specified as 10 to 5000 by mass.

[0027] In the present invention, the water-soluble organic solvent (B) contained in the ink is also specified, from the viewpoint of suitably resolving the above-mentioned problems. Specifically, the ink of the present invention contains two or more water-soluble organic solvents as the water-soluble organic solvent (B), and the absolute value of the difference between the weighted average value of the HLB of the acetylenediol-based surfactant (A) and the weighted average value of the HLB of the water-soluble organic solvent (B) is 3.5 or less, i.e., 0 to 3.5. The absolute value of the above difference is preferably 2.5 or less (0 to 2.5), and particularly preferably 1.5 or less (0 to 1.5).

[0028] As is clear from the mechanism described above, alkylene oxide-modified acetylenediol-based surfactant (A2) is thought to be more stable in water-based inkjet inks than unmodified acetylenediol-based surfactant (A1). On the other hand, the HLB value of alkylene oxide-modified acetylenediol-based surfactant (A2) is 6-12, and its affinity for water, the main component of water-based inkjet inks, is not sufficiently high. Therefore, in printed materials produced using the above water-based inkjet inks, alkylene oxide-modified acetylenediol-based surfactant (A2) and unmodified acetylenediol-based surfactant (A1) are thought to be present in large quantities at the interface, i.e., on the surface of the ink layer. Such surfactants present on the surface of the ink layer may cause blocking, reduced lamination, and migration.

[0029] In contrast, the ink of the present invention specifies that the absolute value of the difference between the weighted average HLB value of the acetylenediol-based surfactant (A) and the weighted average HLB value of the water-soluble organic solvent (B) is 3.5 or less. This specification allows the alkylene oxide-modified acetylenediol-based surfactant (A2) and the unmodified acetylenediol-based surfactant (A1) to be homogenized in the ink for a long period of time. As a result, excessive orientation of the alkylene oxide-modified acetylenediol-based surfactant (A2) and the unmodified acetylenediol-based surfactant (A1) on the ink layer surface can be prevented, which is thought to enable suppression of pinholes and further improvement of standby discharge performance. Furthermore, by preventing the above-mentioned excessive orientation, blocking, reduction of laminating properties, and migration can be further suppressed.

[0030] Furthermore, by using multiple types of water-soluble organic solvents as the above-mentioned water-soluble organic solvent (B), it becomes easier to adjust the weighted average value of the HLB values ​​mentioned above. In addition, by selecting and combining water-soluble organic solvents with appropriate boiling points and surface tensions, it becomes easier to suppress pinholes and improve standby discharge performance.

[0031] In particular, the present invention specifies that the weighted average of the boiling points of the water-soluble organic solvent (B) and water is 102 to 135°C. If the weighted average of the boiling points of the water-soluble organic solvent (B) and water is within the above range, the drying properties of the present invention are improved, and printed materials with good lamination properties and no blocking can be easily obtained. Furthermore, in the present invention, by specifying that the difference between the weighted average of the HLB values ​​of the acetylenediol surfactant (A) and the weighted average of the HLB values ​​of the water-soluble organic solvent (B) is within the above range, and then specifying the weighted average of the boiling points, it is considered that the alkylene oxide-modified acetylenediol surfactant (A2) and the unmodified acetylenediol surfactant (A1) are suitably stabilized in the ink until the ink dries on the printing substrate. As a result, further suppression of pinholes and migration and further improvement of waiting stability become easier.

[0032] As described above, in order to solve the aforementioned problems simultaneously and at a high level, an aqueous inkjet ink having the configuration of the present invention is absolutely essential.

[0033] Furthermore, the aqueous inkjet ink specifically disclosed in Patent Document 1 differs from the present invention in that the content of the unmodified acetylenediol surfactant (A1) ("compound (I)" in Patent Document 1) exceeds 600 ppm, the ratio of the alkylene oxide-modified acetylenediol surfactant (A2) to the content of the unmodified acetylenediol surfactant (A1) is less than 10, and the weighted average of the boiling points of the water-soluble organic solvent (B) and water exceeds 135°C. Furthermore, the aqueous inkjet ink specifically disclosed in Patent Document 2 differs from the present invention in terms of the content of the unmodified acetylenediol-based surfactant (A1). Conversely, the aqueous inkjet ink specifically disclosed in Patent Document 3 does not contain the alkylene oxide-modified acetylenediol-based surfactant (A2). On the other hand, among the aqueous inkjet inks specifically disclosed in Patent Document 4, the aqueous inkjet ink disclosed in Example 9 satisfies the requirements for surfactants of the ink of the present invention. However, in the aqueous inkjet ink of Example 9, the weighted average value of the boiling points of the water-soluble organic solvent (B) and water is significantly higher than 135°C, and in this respect it differs from the ink of the present invention.

[0034] Next, the main components constituting the ink of the present invention will be described in detail below.

[0035] <Acetylenediol-based surfactant (A)> The ink of the present invention contains, as an acetylenediol-based surfactant (A), an unmodified acetylenediol-based surfactant (A1) and an alkylene oxide-modified acetylenediol-based surfactant (A2) having an HLB value of 6 to 12. Furthermore, the content of the unmodified acetylenediol-based surfactant (A1) is 2 to 600 ppm relative to the total amount of ink, and the content of the alkylene oxide-modified acetylenediol-based surfactant (A2) is 0.1 to 5% by mass relative to the total amount of ink. Moreover, the ratio of the content of the alkylene oxide-modified acetylenediol-based surfactant (A2) to the content of the unmodified acetylenediol-based surfactant (A1) [surfactant (A2) / surfactant (A1)] is 10 to 5000 by mass.

[0036] The HLB (Hydrophile-Lipophile Balance) value is one of the parameters that represent the degree of hydrophilicity of a material. A smaller HLB value indicates higher hydrophobicity of the material, while a larger HLB value indicates higher hydrophilicity. Methods for determining the HLB value include experimental measurement and calculation from molecular structure. Methods for calculation from molecular structure include the Griffin method, Davis method, and Kawakami method. In the case of the ink of this invention, the HLB value used is the value calculated using the Griffin method.

[0037] The Griffin method is a method generally used for nonionic materials, and its molecular weight is determined using the following formula (1) with respect to the molecular weight of the material in question.

[0038] Formula (1): HLB value = 20 × (sum of molecular weights of hydrophilic parts) ÷ (molecular weight of material)

[0039] However, in the case of siloxane-based surfactants, which will be discussed later, since they are generally mixtures containing many compounds, the HLB value used is the value measured by the method described on page 324 of "Handbook of Surfactants" (edited by Ichiro Nishi et al., Sangyo Tosho Co., Ltd., 1960).

[0040] 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 titrated with a 2% by mass phenol aqueous solution while stirring, at a temperature of 25°C. The endpoint is defined as the point when the solution becomes turbid, and if the amount of phenol aqueous solution added up to that endpoint is A (mL), the HLB value can be calculated using the formula "0.89 × A + 1.11".

[0041] <<Unmodified Acetylenediol-based surfactant (A1)>> As described above, the unmodified acetylene glycol surfactant (A1) corresponds to a "surfactant with a low molecular weight and a high orientation rate." Furthermore, the above unmodified acetylene glycol surfactant (A1) is a necessary material for producing printed materials with no white spots and excellent print quality on non-absorbent printing substrates.

[0042] In the ink of the present invention, the unmodified acetylene glycol-based surfactant (A1) is contained in an amount of 2 to 600 ppm of the total amount of ink. The content of the unmodified acetylene glycol-based surfactant (A1) is preferably 4 to 400 ppm, and more preferably 6 to 250 ppm. By including the unmodified acetylene glycol-based surfactant (A1) in the range of 2 to 600 ppm, it becomes easy to obtain the printed material without pinholes while improving the blocking resistance and low migration properties of the printed material. Furthermore, the above-mentioned blending amount is preferable in that it also improves the standby discharge performance of the ink.

[0043] In one embodiment, by setting the content of the unmodified acetylene glycol-based surfactant (A1) to 6-45 ppm, blocking and migration are suppressed, and printed materials with good lamination properties can be produced particularly easily.

[0044] Specific examples of unmodified acetylenediol-based surfactants (A1) that can be used in the present invention include 3,6-dimethyl-4-octin-3,6-diol, 3,6-diisopropyl-2,7-dimethyl-4-octin-3,6-diol, 2,4,7,9-tetramethyl-5-decine-4,7-diol, 4,7-dipropyl-5-decine-4,7-diol, 4,7-diisobutyl-2,9-dimethyl-5-decine-4,7-diol, and 2,5,8,11-tetramethyl-5-decine-4,7-diol. Examples include methyl-6-dodecine-5,8-diol, 5,8-dibutyl-6-dodecine-5,8-diol, 7-tetradecine-6,9-diol, 6,9-dimethyl-7-tetradecine-6,9-diol, 8-hexadecin-7,10-diol, 7,10-dimethyl-8-hexadecin-7,10-diol, 9-octadecine-8,11-diol, 5,14-diethyl-8,11-dimethyl-9-octadecine-8,11-diol, and the like. Among these compounds, it is preferable to use one or more compounds selected from the group consisting of 3,6-dimethyl-4-octyne-3,6-diol, 2,4,7,9-tetramethyl-5-decine-4,7-diol, and 2,5,8,11-tetramethyl-6-dodecine-5,8-diol, as this allows for easy acquisition of printed materials with excellent blocking resistance, lamination properties, and low migration.

[0045] Furthermore, the unmodified acetylenediol-based surfactant (A1) may contain only one of the compounds listed above, or it may contain two or more of the compounds listed above. In addition, commercially available products may be used as the compounds listed above. Examples of such commercially available products include Surfinol 104, Surfinol DF-110D, and Surfinol 82 from Evonik, and Acetylenel E00 from Kawaken Fine Chemicals.

[0046] <Alkylene oxide-modified acetylenediol-based surfactant (A2)> In the ink of the present invention, an alkylene oxide-modified acetylenediol-based surfactant (A2) with an HLB value of 6 to 12 is used together with an unmodified acetylenediol-based surfactant (A1). As described above, the alkylene oxide-modified acetylenediol-based surfactant (A2) emulsifies and compatibilizes the unmodified acetylenediol-based surfactant (A1), which facilitates the reduction of pinholes in printed materials and the improvement of the standby ejection performance of the ink. From this viewpoint, that is, from the viewpoint of reducing pinholes and improving standby ejection performance, it is preferable that the HLB value of the alkylene oxide-modified acetylenediol-based surfactant (A2) is 7 to 11.

[0047] The amount of alkylene oxide-modified acetylenediol-based surfactant (A2) with an HLB value of 6 to 12 added is 0.1 to 5% by mass relative to the total amount of the ink of the present invention. If the amount of alkylene oxide-modified acetylenediol-based surfactant (A2) added is within the above range, it becomes easier to improve standby ejection performance, reduce pinholes in printed materials, improve lamination, and suppress blocking. Furthermore, from the viewpoint of more favorably exhibiting these effects, the amount added is preferably 0.3 to 3% by mass, and particularly preferably 0.45 to 2.5% by mass.

[0048] Furthermore, in the ink of the present invention, the ratio of the content of alkylene oxide-modified acetylene diol-based surfactant (A2) to the content of unmodified acetylene diol-based surfactant (A1) [surfactant (A2) / surfactant (A1)] is 10 to 5000 by mass. By setting the above ratio to 10 to 5000, the emulsification and compatibilization effects by the alkylene oxide-modified acetylene diol-based surfactant (A2) described above are optimized, making it easier to reduce pinholes in printed materials, suppress blocking, improve lamination, and improve standby discharge performance. From the viewpoint of more favorably exhibiting these effects, the above ratio is preferably 20 to 2000, more preferably 30 to 1000, and particularly preferably 50 to 450.

[0049] Furthermore, if the ink of the present invention contains two or more compounds as unmodified acetylenediol-based surfactants (A1), the "content of unmodified acetylenediol-based surfactants (A1)" used when calculating the above ratio value shall be the total amount of the two or more compounds. Similarly, if the ink contains two or more compounds as alkylene oxide-modified acetylenediol-based surfactants (A2), the "content of alkylene oxide-modified acetylenediol-based surfactants (A2)" used when calculating the above ratio value shall be the total amount of the two or more compounds.

[0050] Specific examples of alkylene oxide-modified acetylenediol-based surfactants (A2) that can be used in the ink of the present invention include compounds in which an ethylene oxide group and / or a propylene oxide group are added to the position of the hydroxyl group in each of the compounds described above that can be used as unmodified acetylenediol-based surfactants (A1).

[0051] In the case of the ink of the present invention, it is preferable that the alkylene oxide-modified acetylenediol-based surfactant (A2) has at least ethylene oxide groups. Furthermore, it is preferable that the number of moles of ethylene oxide groups added is 3 to 8 moles. The alkylene oxide-modified acetylenediol-based surfactant (A2) containing a predetermined amount of ethylene oxide groups has excellent affinity for both the unmodified acetylenediol-based surfactant (A1) and for water, which is the main component of aqueous inkjet ink. Therefore, it is easy to reduce pinholes in printed materials and improve the standby ejection performance of the ink.

[0052] The compounds used as alkylene oxide-modified acetylenediol-based surfactants (A2) may be synthesized by conventionally known methods or may be commercially available products. Examples of commercially available products that can be used as alkylene oxide-modified acetylenediol-based surfactants (A2) include Surfinol 440, Surfinol 2502, Dynol 604, and Dynol 607 from Evonik; Olfin E1004 from Nisshin Chemical Industry Co., Ltd.; and Acetylenel E40 and Acetylenel E60 from Kawaken Fine Chemical Co., Ltd.

[0053] <<Other Acetylenediol-based surfactants>> The ink of the present invention may include, as the acetylenediol-based surfactant (A), acetylenediol-based surfactants other than the unmodified acetylenediol-based surfactant (A1) and the alkylene oxide-modified acetylenediol-based surfactant (A2) (also referred to as "other acetylenediol-based surfactants" in this disclosure). Examples of other acetylenediol-based surfactants include alkylene oxide-modified acetylenediol-based surfactants with an HLB value of less than 6, and alkylene oxide-modified acetylenediol-based surfactants with an HLB value greater than 12.

[0054] The compounds used as other acetylenediol-based surfactants mentioned above may be synthesized by conventionally known methods or may be commercially available products. Examples of such commercially available products include Surfinol 420, Surfinol 465, and Surfinol 485 from Evonik; Olfin E1010 from Nisshin Chemical Industry; and Acetylenel E13T, Acetylenel E100, and Acetylenel E200 from Kawaken Fine Chemical Co., Ltd.

[0055] When the ink of the present invention contains other acetylenediol-based surfactants, it is preferable to use an alkylene oxide-modified acetylenediol-based surfactant having an HLB value of 14 or higher as the other acetylenediol-based surfactant. By using the alkylene oxide-modified acetylenediol-based surfactant having an HLB value of 14 or higher, the unmodified acetylenediol-based surfactant (A1) can be suitably emulsified and compatible in the ink, and the alkylene oxide-modified acetylenediol-based surfactant (A2) can be suitably homogenized in the ink. This not only facilitates the reduction of pinholes in printed materials and the improvement of the standby ejection performance of the ink, but also enables further suppression of blocking, reduced lamination, and migration.

[0056] In one embodiment, the ink of the present invention preferably has a weighted average HLB value of 6.0 to 12.0, more preferably 7.0 to 11.0, and particularly preferably 7.5 to 10.2. By using a combination of an unmodified acetylenediol surfactant (A1) and an alkylene oxide-modified acetylenediol surfactant (A2) (and other acetylenediol surfactants as needed) such that the weighted average HLB value falls within the above range, these acetylenediol surfactants are suitably emulsified and compatible, making it easier to suppress pinholes in printed materials and improve standby ejection performance. Furthermore, since the orientation rate of these acetylenediol surfactants at the interface is in a suitable state, the occurrence of blocking in printed materials and the decrease in lamination performance can also be suppressed. Furthermore, it is preferable that the weighted average HLB value of the acetylenediol-based surfactant (A) described above be adjusted so that the difference from the weighted average HLB value of the water-soluble organic solvent (B) is 3.5 or less, and then further adjusted so that it falls within the above range.

[0057] The weighted average of HLB values ​​is the average value of HLB values ​​calculated by weighting the content of each compound in question. For example, if an ink contains three compounds, and the HLB values ​​of these three compounds are A, B, and C, respectively, and the content of these three compounds in the total amount of ink is P (mass%), Q (mass%), and R (mass%), respectively, then the formula for calculating the weighted average of the HLB values ​​of the three compounds in the ink is "(A × P + B × Q + C × R) ÷ (P + Q + R)".

[0058] <Water-soluble organic solvent (B)> The ink of the present invention contains a water-soluble organic solvent (B). The water-soluble organic solvent (B) contains two or more water-soluble organic solvents. Furthermore, the difference between the weighted average HLB value of the acetylenediol-based surfactant (A) and the weighted average HLB value of the water-soluble organic solvent (B) is 3.5 or less, that is, the absolute value of the difference is 0 to 3.5. The absolute value of the difference is preferably 2.5 or less (0 to 2.5), and particularly preferably 1.5 or less (0 to 1.5). By setting the difference in the weighted average HLB values ​​to 3.5 or less, the alkylene oxide-modified acetylenediol-based surfactant (A2) and the unmodified acetylenediol-based surfactant (A1) can be homogenized in the ink for a long time, and rapid and excessive orientation at the interface can be prevented. As a result, pinhole suppression and further improvement of standby discharge performance can be achieved, and blocking, deterioration of laminating properties, and migration can be easily suppressed.

[0059] In this disclosure, "water-soluble organic solvent" refers to a substance that has a solubility of 1% by mass or more in water at 25°C and is a liquid at 25°C.

[0060] As the above water-soluble organic solvent (B), Alkane monools with 2 to 5 carbon atoms, such as ethanol, (n / iso)propanol, (n / iso / tert)butanol, and (n / iso)pentanol; Alkanediols with 2 to 6 carbon atoms, such as 1,2-ethanediol (ethylene glycol), 1,2-propanediol (propylene glycol), 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,2-pentanediol, 1,5-pentanediol, 2,4-pentanediol, 3-methyl-1,3-butanediol (isoprene glycol), 1,2-hexanediol, and 2-methyl-2,4-pentanediol (hexylene glycol); Polyalkylene glycols with 4 to 10 carbon atoms, such as diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, dipropylene glycol, and tripropylene glycol; (Poly)ethylene glycol monoalkyl ethers such as ethylene glycol monoethyl ether, ethylene glycol mono(n / iso)propyl ether, ethylene glycol mono(n / iso)butyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono(n / iso)propyl ether, diethylene glycol mono(n / iso / tert)butyl ether, diethylene glycol mono-n-hexyl ether, and triethylene glycol monomethyl ether (provided that the number of ethylene oxide groups is 1 to 3 and the number of carbon atoms in the alkyl group at the molecular terminus is 1 to 6); (Poly)propylene glycol monoalkyl ethers such as propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono(n / iso)propyl ether, propylene glycol mono(n / iso / tert)butyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono(n / iso)propyl ether, dipropylene glycol mono(n / iso / tert)butyl ether, tripropylene glycol monomethyl ether, and tripropylene glycol mono(n / iso / tert)butyl ether (provided that the number of propylene oxide groups is 1 to 3 and the number of carbon atoms in the alkyl group at the molecular terminus is 1 to 4); 3-methoxy-1-butanol, 3-methoxy-3-methylbutanol, and other 3-methoxybutanol compounds; Nitrogen-containing solvents such as 2-pyrrolidone, N-methylpyrrolidone, 3-methoxy-N,N-dimethylpropanamide, and 3-butoxy-N,N-dimethylpropanamide; Lactones such as γ-butyrolactone and ε-caprolactone can be used. The water-soluble organic solvents listed above may be used individually or in combination of two or more.

[0061] In addition, "(n / iso)" above refers to the normal and / or iso form, and "(n / iso / tert)" refers to one or more selected from the group consisting of the normal, iso, and tertiary forms.

[0062] Alkanediols with 2 to 6 carbon atoms In the ink of the present invention, it is preferable to use the above-mentioned C2-C6 alkanediols as the water-soluble organic solvent (B). C2-C6 alkanediols have particularly high affinity with alkylene oxide-modified acetylenediol-based surfactants (A2). Therefore, the alkylene oxide-modified acetylenediol-based surfactant (A2) is suitably emulsified and compatible with the unmodified acetylenediol-based surfactant (A1), making it easier to reduce pinholes in printed materials and improve the standby discharge performance of the ink.

[0063] In particular, from the viewpoint of exhibiting the above-mentioned effects especially well, and achieving further reduction of pinholes and further improvement of standby dispensing performance, it is especially preferable to use C3-C6 alkanediols having a 1-hydroxyethyl group (CH3-CH(OH)-). Examples of C3-C6 alkanediols having a 1-hydroxyethyl group include 1,2-propanediol, 1,3-butanediol, 2,3-butanediol, 2,4-pentanediol, and 2-methyl-2,4-pentanediol. Among these compounds, one or more compounds selected from the group consisting of 1,2-propanediol, 1,3-butanediol, and 2-methyl-2,4-pentanediol can be suitably used, and the use of 1,2-propanediol is particularly preferred. 1,2-Propanediol has a relatively high HLB value among alkanediols with 2 to 6 carbon atoms, and therefore does not readily agree with unmodified acetylenediol-based surfactants (A1). Furthermore, it is believed that the orientation rate of the unmodified acetylenediol-based surfactant (A1) at the interface is optimized in the presence of 1,2-propanediol and alkylene oxide-modified acetylenediol-based surfactant (A2). As a result, it is believed that pinhole suppression, improved standby discharge performance, and further suppression of blocking, lamination, and migration can be easily achieved.

[0064] When the ink of the present invention contains 1,2-propanediol as a water-soluble organic solvent (B), its content is preferably 5 to 30% by mass of the total amount of the ink, and more preferably 8 to 25% by mass. By keeping the content of 1,2-propanediol within the above range, the effects of the unmodified acetylenediol-based surfactant (A1) and the alkylene oxide-modified acetylenediol-based surfactant (A2) described above are suitably expressed, and further suppression of pinholes, blocking, reduced lamination, and migration, as well as further improvement of standby discharge performance, can be easily achieved.

[0065] Furthermore, the total amount of C2-C6 alkanediols contained in the ink of the present invention is preferably 5 to 35% by mass of the total amount of ink. In addition, from the viewpoint of obtaining printed materials with excellent print quality even on non-absorbent substrates, and furthermore, from the viewpoint of effectively suppressing pinholes, blocking, reduced lamination, and migration in the printed materials, the total amount of the above content is particularly preferably 8 to 30% by mass.

[0066] (Poly)propylene glycol monoalkyl ethers In the ink of the present invention, it is also preferable to use the above-mentioned (poly)propylene glycol monoalkyl ethers as the water-soluble organic solvent (B). Many of the (poly)propylene glycol monoalkyl ethers have low HLB values ​​and are therefore highly hydrophobic. For this reason, the (poly)propylene glycol monoalkyl ethers can emulsify and compatibilize the unmodified acetylenediol surfactant (A1) together with the alkylene oxide-modified acetylenediol surfactant (A2). As a result, during the drying process of the ink of the present invention on the printing substrate, the above-mentioned unmodified acetylenediol surfactants (A1) are less likely to associate with each other, making it easier to suppress pinholes in the printed material. Furthermore, excessive orientation of the above-mentioned unmodified acetylenediol surfactants (A1) on the surface of the ink layer can be prevented, making it easier to further suppress blocking, deterioration of laminating properties, and migration.

[0067] When the ink of the present invention contains (poly)propylene glycol monoalkyl ethers as the water-soluble organic solvent (B), it is preferable to use one or more compounds selected from the group consisting of propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monon-propyl ether, dipropylene glycol monomethyl ether, and dipropylene glycol monon-propyl ether. These compounds are considered to have a good balance between boiling point and hydrophobicity. Therefore, the unmodified acetylenediol-based surfactant (A1) is suitably emulsified and compatible, and further suppression of pinholes, blocking, reduced lamination, and migration can be particularly easily achieved. Furthermore, these compounds are suitably selected because they improve drying properties on non-absorbent substrates and improve the print quality of the resulting printed material.

[0068] When the ink of the present invention contains one or more compounds selected from the group consisting of propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monon-propyl ether, dipropylene glycol monomethyl ether, and dipropylene glycol monon-propyl ether as a water-soluble organic solvent (B), the total amount of these compounds is preferably 1.5 to 15% by mass of the total amount of the ink, and more preferably 2 to 10% by mass. By keeping the total amount of the above content within the above range, pinholes, blocking, reduced lamination, and migration can be suitably suppressed, and deterioration of standby discharge performance can also be suppressed.

[0069] Furthermore, the total amount of (poly)propylene glycol monoalkyl ethers contained in the ink of the present invention is preferably 1.5 to 20% by mass relative to the total amount of the ink. In addition, from the viewpoint of obtaining printed materials with excellent print quality even on non-absorbent substrates, and furthermore, from the viewpoint of suitably suppressing pinholes, blocking, reduced lamination, and migration in the printed materials, the total amount of the above content is particularly preferably 2 to 12% by mass.

[0070] Furthermore, when the ink of the present invention contains (poly)propylene glycol monoalkyl ethers as a water-soluble organic solvent (B), the ratio of the amount of (poly)propylene glycol monoalkyl ethers to the amount of unmodified acetylenediol-based surfactant (A1) is preferably 80 to 30,000 by mass, more preferably 120 to 15,000, and particularly preferably 200 to 5,000. By defining the mixing ratio of the two in this way, the unmodified acetylenediol-based surfactant (A1) is suitably emulsified and compatibilized, thereby suitably suppressing pinholes, blocking, reduced lamination, and migration, as well as suppressing deterioration of standby discharge performance.

[0071] ≪Combinations of water-soluble organic solvents≫ As described above, the ink of the present invention contains two or more water-soluble organic solvents as the water-soluble organic solvent (B). Furthermore, C2-C6 alkanediols and (poly)propylene glycol monoalkyl ethers can be suitably used as the water-soluble organic solvent (B). Therefore, in one embodiment, the ink of the present invention is particularly suitable to contain one or more C2-C6 alkanediols and one or more (poly)propylene glycol monoalkyl ethers as the water-soluble organic solvent (B). Moreover, the combination of C2-C6 alkanediols and (poly)propylene glycol monoalkyl ethers is also suitable because it makes it easier to keep the weighted average value of the HLB value of the water-soluble organic solvent (B) within a suitable range described later, further suppression of pinholes, blocking, and deterioration of lamination, and further improvement of standby discharge performance.

[0072] On the other hand, when the ink of the present invention contains (poly)ethylene glycol monoalkyl ethers as the water-soluble organic solvent (B), the total amount of these ethers is preferably 0.5 to 50% by mass, more preferably 1 to 25% by mass, and particularly preferably 1.5 to 10% by mass, relative to the total amount of the water-soluble organic solvent (B). By keeping the total amount of (poly)ethylene glycol monoalkyl ethers within the above range, it becomes easier to keep the weighted average value of the HLB value of the water-soluble organic solvent (B) within the preferred range described later, thereby enabling further suppression of pinholes, blocking, and deterioration of lamination, as well as further improvement of standby discharge performance.

[0073] In one embodiment, the ink of the present invention preferably has a weighted average HLB value of 6.0 to 12.0, more preferably 6.5 to 11.0, and particularly preferably 6.5 to 9.0. By adjusting the type and amount of water-soluble organic solvent used so that the weighted average HLB value of water-soluble organic solvent (B) falls within the above range, the unmodified acetylenediol-based surfactant (A1) and the alkylene oxide-modified acetylenediol-based surfactant (A2) can be homogenized in the ink for a long period of time. As a result, pinholes, blocking, and a decrease in lamination properties in printed materials are suppressed, and standby discharge performance is improved.

[0074] Furthermore, in the ink of the present invention, the weighted average value of the boiling point of the water-soluble organic solvent (B) is preferably 120 to 220°C, and particularly preferably 170 to 210°C. If the weighted average value of the boiling point of the water-soluble organic solvent (B) is within the above range, the ink will have excellent drying properties on non-absorbent substrates, resulting in printed materials that do not block and have good lamination properties. In addition, although the detailed mechanism is unknown, the ink will also have excellent standby discharge properties.

[0075] Furthermore, in the ink of the present invention, the weighted average value of the boiling points of the water-soluble organic solvent (B) and water is preferably 102 to 135°C, and particularly preferably 105 to 130°C. If the weighted average value of the boiling points of the water-soluble organic solvent (B) and water is within the above range, it is possible to suppress pinholes, blocking, deterioration of lamination, and migration while maintaining favorable standby discharge performance.

[0076] In this disclosure, "boiling point" refers to the value at 1 atmosphere and can be measured, for example, using a thermal analyzer. Furthermore, the method for calculating the weighted average of boiling points is the same as the method for calculating the weighted average of HLB values ​​described above, but with "HLB value" replaced by "boiling point".

[0077] The total amount of water-soluble organic solvent (B) contained in the ink of the present invention is preferably 5 to 40% by mass relative to the total amount of ink. Furthermore, from the viewpoint of obtaining printed materials with excellent print quality even on non-absorbent substrates, and furthermore, from the viewpoint of effectively suppressing pinholes, blocking, reduced lamination, and migration in the printed materials, the total amount of the above content is particularly preferably 8 to 35% by mass.

[0078] <Nonionic surfactant (C)> The ink of the present invention can be used in combination with an acetylenediol-based surfactant (A) and a nonionic surfactant (C) other than an acetylenediol-based surfactant. By using the nonionic surfactant (C), an interaction occurs between it and the acetylenediol-based surfactant (A), and it is believed that the nonionic surfactant (C) and the acetylenediol-based surfactant (A) behave as a single surfactant. As a result, further improvement in standby discharge performance and suppression of pinholes, reduced lamination, and migration in printed materials become easier. In addition, since the nonionic surfactant (C) gradually orients at the gas-liquid interface compared to the acetylenediol-based surfactant (A), it can promote the wetting and spreading of ink droplets on the printing substrate, making it possible to uniformly wet the ink droplets and easily obtain printed materials without pinholes.

[0079] The HLB value of the nonionic surfactant (C) is preferably 6 to 15, and more preferably 8 to 12. When the HLB value is within this range, a strong interaction occurs, particularly with the alkylene oxide-modified acetylenediol surfactant (A2), resulting in improved standby discharge performance, no pinholes or blocking, and a printed material with good lamination properties.

[0080] When the ink of the present invention contains a nonionic surfactant (C), the value obtained by dividing the weighted average HLB value of the acetylenediol-based surfactant (A) by the weighted average HLB value of the nonionic surfactant (C) is preferably 0.5 to 1.0, and more preferably 0.6 to 0.8. If the value obtained by dividing the weighted average HLB value of the acetylenediol-based surfactant (A) by the weighted average HLB value of the nonionic surfactant (C) is within the above range, pinholes, reduced lamination, and migration in printed materials can be suitably suppressed, and the standby ejection performance of the ink is also improved.

[0081] The above statement, "HLB value (weighted average) of nonionic surfactant (C)," means that if there is only one nonionic surfactant (C) contained in the ink of the present invention, the HLB value of that nonionic surfactant (C) is used, and if there are two or more nonionic surfactants (C) contained in the ink, the weighted average of the HLB values ​​of the nonionic surfactants (C) calculated by the method described above is used.

[0082] The content of the nonionic surfactant (C) in the present invention is preferably 0.1 to 5% by mass, more preferably 0.3 to 2.5% by mass, and even more preferably 0.5 to 2.0% by mass, of the total amount of the ink of the present invention. Furthermore, the ratio of the content of the nonionic surfactant (C) to the total amount of the unmodified acetylenediol surfactant (A1) and the alkylene oxide-modified acetylenediol surfactant (A2) (expressed as "content of nonionic surfactant (C) / {content of unmodified acetylenediol surfactant (A1) + content of alkylene oxide-modified acetylenediol surfactant (A2)}") is preferably 0.3 to 2.0, and more preferably 0.5 to 1.5. When the content of nonionic surfactant (C) and the ratio of the above content are within the above range, the surfactants are more likely to function as a single surfactant, resulting in good standby discharge performance and making it easier to obtain printed materials that do not produce pinholes, reduced lamination, or migration.

[0083] The nonionic surfactant (C) in this invention may be synthesized by conventionally known methods or may be a commercially available product. Examples of surfactants that can be used as the nonionic surfactant (C) include acetylene monool surfactants, siloxane surfactants, fluorine surfactants, polyoxyalkylene alkyl ether surfactants, polyoxyalkylene aryl ether surfactants, and polyalkylene glycol alkylate surfactants. These compounds may be used individually or in combination of two or more.

[0084] In particular, in the present invention, it is especially preferable to use a siloxane-based surfactant and / or a polyoxyalkylene alkyl ether-based surfactant as the nonionic surfactant (C) because it readily interacts with the acetylene glycol-based surfactant (A), thereby improving standby discharge performance, preventing pinholes, reduced lamination, and migration as described above, and further reducing blocking by lowering the surface energy of the ink layer.

[0085] The siloxane-based surfactant preferred in the present invention is a compound represented by the following general formula (1).

[0086] General formula (1): [ka]

[0087] In general formula (1), p is a non-negative integer and q is a non-negative integer. Also, R 1 R is an alkyl group having 1 to 6 carbon atoms, or a structure represented by the following general formula (2), 2 R is a methyl group, or a structure represented by the general formula (2) below. However, R 2 If it is a methyl group, then p is 0.

[0088] General formula (2): [ka]

[0089] In general formula (2), r is an integer from 1 to 6, s is an integer from 0 to 50, and t is an integer from 0 to 50. However, s+t is 1 or greater. Also, R 3 The group is a hydrogen atom, a C1-C6 alkyl group, a (meth)acryloyl group, or a 2-hydroxy-3-((meth)acryloyloxy)propyl group. The addition of the ethylene oxide group and propylene oxide group within the square brackets may be in a block or random manner.

[0090] The siloxane-based surfactant used in this invention may be one synthesized by a conventionally known method, or a commercially available product may be used. Examples of commercially available products include: SF8428, FZ-2162, 8032ADDITIVE, SH3749, FZ-77, L-7001, L-7002, FZ-2104, FZ-2110, F-2123, SH8400, SH3773M from Toray Dow Corning; BYK-345, BYK-346, BYK-347, BYK-348, BYK-349, BYK-3420 from Bic Chemie; and TEGO Wet250, TEGO Wet260, TEGO Wet270, TEGO Wet280, TEGO Glide100, TEGO Glide410, TEGO Glide432, TEGO Glide435, TEGO Glide440, TEGO Glide450, TEGO Rad2200, TEGO Examples include Rad2250, TEGO Rad2300, TEGO Twin 4000, TEGO Twin 4100, TEGO Twin 4200; KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-640, KF-642, KF-643, KF-644, KF-6004, KF-6011, KF-6012, KF-6043, KF-6123, KF-6204 from Shin-Etsu Chemical Co., Ltd.; and Silface SAG001, Silface SAG002, Silface SAG003, Silface SAG005, Silface SAG503A from Nisshin Chemical Co., Ltd. These commercially available products may be used individually or in combination of two or more.

[0091] For the nonionic surfactant (C) to behave as a single surfactant with the acetylenediol-based surfactant (A), it is preferable that an interaction occurs between the two. On the other hand, from the viewpoint of further improving standby discharge performance and suppressing pinholes and reduced lamination in printed materials, it is preferable that the acetylenediol-based surfactant (A) and the nonionic surfactant (C) are compatible to some extent. From the above viewpoints, that is, from the viewpoint of improving standby discharge performance and easily preventing pinholes, reduced lamination, and migration, it is preferable to use two or more siloxane-based surfactants in combination as the nonionic surfactant (C). Furthermore, it is particularly preferable to use the two or more siloxane-based surfactants in combination such that the difference in HLB values ​​between them is 2 or more.

[0092] On the other hand, in the ink of the present invention, it is also preferable to use a polyoxyalkylene alkyl ether surfactant as the nonionic surfactant (C). Polyoxyalkylene alkyl ether surfactants have good compatibility with water and acetylenediol surfactants (A), and can suppress pinholes and deterioration of lamination without affecting these materials.

[0093] As a polyoxyalkylene alkyl ether surfactant, for example, a compound represented by the following general formula (3) can be used.

[0094] General formula (3): R 4 -O-(C2H4O) v -H

[0095] In the above general formula (3), R 4v represents one selected from the group consisting of a chain alkyl group having 7 to 22 carbon atoms which may be branched, a chain alkenyl group which may have a branched structure, an alicyclic alkyl group which may have one or more alkyl groups attached, and an aromatic group which may have one or more alkyl groups attached, and v represents an integer from 2 to 100.

[0096] 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, and Brownon. 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, BN-3, etc. Brownon series (manufactured by Aoki Oil & Fat Industry Co., Ltd.), Nonion Nonionic series such as 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, 209 (manufactured by NOF Corporation), Lutensol series such as Lutensol XL40, 50, 60, 70, 80, 90, XP30, 40, 50, 60, 70, 80, 90, 100 (manufactured by BASF), Newcol series such as Newcol 2302, 2303, 2305, 2308, 2310, 2320, 2360 (manufactured by Nippon Emulsifier Co., Ltd.), Emulmin Examples include LS-80, LS-90, NL-70, NL-80, NL-90, NL-100, NL-110, Sannonic SS-30, SS-50, SS-70, SS-90, SS-120 (manufactured by Sanyo Chemical Industries), Adekatol LA-675B, LA-775, LA-875, LA-975, LA-1275, SO-80, SO-105, SO-120, SO-135, SO-145, SO-160 (manufactured by ADEKA), etc. In addition to the commercially available products mentioned above, diethylene glycol monohexyl ether, triethylene glycol monohexyl ether, tetraethylene glycol monohexyl ether, etc. may also be used. One of the listed products may be used alone, or two or more may be used in combination. Furthermore, polyoxyalkylene alkyl ether surfactants synthesized by conventionally known synthesis methods may also be used.

[0097] In the case of polyoxyalkylene alkyl ether surfactants, as with the siloxane surfactants described above, it is preferable to use two or more polyoxyalkylene alkyl ether surfactants in combination, and to use them in such a combination that the difference in HLB values ​​between the two or more polyoxyalkylene alkyl ether surfactants is 2 or more, because it is easier to improve standby discharge performance and suppress pinholes, reduced lamination, and migration.

[0098] Furthermore, for similar reasons, namely, improved standby discharge performance and easier suppression of pinholes, reduced lamination, and migration, it is also preferable that the ink of the present invention uses a combination of a siloxane-based surfactant and a polyoxyalkylene alkyl ether-based surfactant, and that the difference between the HLB value of the siloxane-based surfactant and the HLB value of the polyoxyalkylene alkyl ether-based surfactant is 2 or more.

[0099] <Other surfactants> The aqueous inkjet ink of the present invention may contain surfactants other than those described above, for example, ionic (anionic or cationic) surfactants, amphoteric surfactants, etc. can be used.

[0100] <Binder resin> In embodiments of the present invention, it is preferable to include a binder resin because it allows for easy acquisition of printed materials with excellent abrasion resistance, good lamination properties, and suppressed blocking and migration.

[0101] In this disclosure, "binder resin" refers to a resin (binding resin) that has the function of binding the ink layer to the printing substrate. Specifically, the binder resin in this disclosure is a resin that accounts for 50% by mass or more (preferably 60% by mass or more, particularly preferably 70% by mass or more) of the resin components contained in the ink layer. The above binder resin may also serve as the pigment dispersion resin described later.

[0102] Generally, water-soluble resins, dispersions, and emulsions are known as resins used in water-based inkjet inks. Of these, dispersions and emulsions are types of non-water-soluble resins (resins that are not water-soluble resins). The term "water-soluble resin" refers to a water mixture containing 1% by mass of the target resin that appears transparent to the naked eye at 25°C. "Emulsion" refers to a form of resin that is forcibly dispersed in a dispersion medium by adsorbing and / or bonding emulsifiers such as surfactants and resins (however, different from the resins that constitute the emulsion) to the resin surface. On the other hand, "dispersion" is a form of resin that has properties intermediate between water-soluble resins and emulsions. Specifically, dispersion refers to a form of resin that is dispersed in a dispersion medium without using the above emulsifiers by utilizing the hydrophilic structure present in the resin molecule (ionizing functional groups such as acidic groups and basic groups, hydrophilic groups such as ethylene oxide groups, etc.). In this disclosure, dispersions and emulsions are collectively referred to as "resin fine particles."

[0103] In the ink of the present invention, it is preferable to use a water-soluble resin and / or dispersion as the binder resin. These resins are compatible with aqueous media (at least liquid media containing water) without the use of emulsifiers. Furthermore, at least a portion of the above resin swells and / or dissolves in the above aqueous media. As a result, clogging due to resin precipitation and the like is less likely to occur near the nozzles of the inkjet head, resulting in an ink with excellent continuous ejection properties. These resins are also thought to be able to function as compatibilizers for unmodified acetylenediol-based surfactants (A1), and are considered effective in suppressing blocking and deterioration of lamination properties in printed materials.

[0104] Examples of resins that can be used as water-soluble resins and dispersions include acrylic resins, urethane resins, and polyester resins. Among these, acrylic resins are preferred when considering the storage stability and continuous discharge performance of the ink, as well as the abrasion resistance and blocking resistance of the printed material.

[0105] In this disclosure, "acrylic resin" refers to a resin using one or more polymerizable monomers selected from the group consisting of acrylic acid, methacrylic acid, acrylic acid esters, and methacrylic acid esters (styrene monomers may also be used). However, resins containing (anhydride) maleic acid (maleic acid and / or maleic anhydride) as the polymerizable monomer are not included in the definition of "acrylic resin" in this application.

[0106] Furthermore, as the water-soluble resin and dispersion mentioned above, resins synthesized by conventionally known methods may be used, or commercially available products may be used. There are no particular restrictions on their structure, and resins having, for example, random structures, block structures, comb-shaped structures, star-shaped structures, etc., can be used as desired.

[0107] When a water-soluble resin and dispersion are used as the binder resin, the acid value is preferably 5 to 80 mgKOH / g, more preferably 10 to 65 mgKOH / g, and particularly preferably 15 to 50 mgKOH / g. If the acid value of the water-soluble resin and dispersion is 5 mgKOH / g or higher, even if the water-soluble resin and dispersion solidify near the nozzle of an inkjet head filled with the ink of the present invention, it becomes easy to dissolve them in the ink, thereby improving the continuous ejection performance of the ink. Furthermore, if the acid value is 80 mgKOH / g or lower, printed materials with excellent water resistance and abrasion resistance can be obtained, and they also function more easily as a compatibilizer for the unmodified acetylenediol-based surfactant (A1), making it easier to obtain printed materials with suppressed blocking and lamination.

[0108] The "acid value of a resin" is the number of milligrams of potassium hydroxide (KOH) required to neutralize the acid groups contained in 1 gram of the resin. In this disclosure, the value calculated by the following method is used as the acid value. For example, if a resin contains Wa mass% of polymerizable monomers in the polymerizable monomers that make up the resin, each polymerizable monomer having na acid groups with a va value and a molecular weight of Ma, its acid value (mgKOH / g) can be determined by the following formula (4).

[0109] Formula (4): (Acid value) = {(va × na × Wa) ÷ (100 × Ma)} × 56.11 × 1000

[0110] In equation (4) above, the value "56.11" is the molecular weight of potassium hydroxide.

[0111] Furthermore, when a water-soluble resin is used as the binder resin, its weight-average molecular weight is preferably 3,000 to 50,000, and more preferably 5,000 to 40,000. A weight-average molecular weight of 3,000 or more improves the abrasion resistance of the printed material and suppresses the reduction of blocking and lamination properties in the printed material. In addition, a weight-average molecular weight of 50,000 or less ensures good continuous ejection from the inkjet head.

[0112] The weight-average molecular weight in this disclosure is the amount equivalent to standard polystyrene, measured by gel permeation chromatography (GPC). Specifically, for example, the weight-average molecular weight can be measured using a TSKgel column (manufactured by Tosoh Corporation) and a gel permeation chromatograph measuring device (Tosoh Corporation's "HLC-8120GPC") equipped with an RI detector, with THF as the developing solvent.

[0113] When a water-soluble resin is used as the binder resin, its content is preferably 0.5 to 10% by mass, more preferably 1 to 8% by mass, and particularly preferably 1.5 to 6% by mass, relative to the total amount of ink of the present invention. When a dispersion is used as the binder resin, its content is preferably 1 to 12% by mass, more preferably 1.5 to 10% by mass, and particularly preferably 2 to 8% by mass, relative to the total amount of ink of the present invention. By setting the content of the water-soluble resin and dispersion within the above ranges, the unmodified acetylenediol-based surfactant (A1) can be sufficiently miscible, making it easier to improve continuous discharge performance, suppress blockage and lamination in printed materials, and improve the abrasion resistance of the printed materials.

[0114] On the other hand, emulsions generally allow the use of resins with a larger weight-average molecular weight compared to water-soluble resins and dispersions. Furthermore, when the same amount of resin is blended, emulsions can lower the viscosity of the water-based inkjet ink compared to water-soluble resins and dispersions. Therefore, when using an emulsion as a binder resin, a larger amount can be blended into the water-based inkjet ink than with water-soluble resins and dispersions. As a result, it becomes easier to improve the abrasion resistance, blocking resistance, lamination properties, and low migration properties of printed materials while maintaining favorable standby ejection performance.

[0115] Examples of resins that can be used as the emulsion include acrylic resins, urethane resins, polyester resins, styrene-butadiene resins, acrylonitrile-butadiene resins, vinyl acetate resins, and ethylene-vinyl acetate resins. In particular, emulsions of one or more resins selected from the group consisting of acrylic resins, urethane resins, and polyester resins are preferably used because they can easily improve the abrasion resistance, blocking resistance, and lamination properties of printed materials while maintaining a suitable standby discharge state.

[0116] When the ink of the present invention contains an emulsion as a binder resin, the minimum film-forming temperature (MFT) of the emulsion is preferably 40°C or higher, and particularly preferably 60°C or higher. If the minimum film-forming temperature of the emulsion is 40°C or higher, it becomes easy to improve the rub resistance, blocking resistance, and laminating property of the printed matter while maintaining the standby ejection property in a suitable state.

[0117] The minimum film-forming temperature can be measured by, for example, an MFT tester manufactured by Tester Sangyo Co., Ltd. The minimum film-forming temperature can also be adjusted by the type and amount of the polymerizable monomer constituting the resin.

[0118] When using an emulsion as the binder resin, its content is preferably 2 to 20% by mass, more preferably 2.5 to 15% by mass, and particularly preferably 3 to 12% by mass based on the total amount of the ink of the present invention. By setting the content of the emulsion within the above range, the viscosity of the ink can be suppressed within a suitable range, and the standby ejection property can be maintained in a suitable state. Also, the rub resistance, blocking resistance, laminating property, and low migration property of the printed matter will be good.

[0119] <Pigment> The ink of the present invention contains a pigment. As the pigment, an inorganic pigment and / or an organic pigment can be arbitrarily used. These pigments may be used alone or in combination of two or more. The content volume of the pigment with respect to the total volume of the ink is preferably 0.3 to 10% by volume, more preferably 0.7 to 7.0% by volume. By setting the volume content of the pigment within the above range, the standby ejection property is improved, and it becomes easy to suppress the reduction of the laminating property and blocking in the printed matter.

[0120] Note that the content volume of the pigment with respect to the total volume of the ink of the present invention (unit: % by volume) is "[density of the ink (unit: g / cm 3 )] × [content of the pigment contained in 100 g of the ink (unit: g)] ÷ [density of the pigment (unit: g / cm 3This value can be calculated using the formula ). Furthermore, the density of ink and pigment can be measured using, for example, a pycnometer. Specifically, the density of ink can be measured by the method described in JIS K 0061:2001, and the density of pigment can be measured by the method specified in JIS K 5101-11-1:2004.

[0121] When using inorganic pigments as pigments, specific examples include titanium dioxide, zinc oxide, zinc sulfide, calcium carbonate, precipitated barium sulfate, white carbon, alumina white, aluminum phosphate, aluminum polyphosphate, carbon black, black iron oxide, cadmium red, red iron oxide, molybdenum red, molybdate orange, chrome vermilion, lead yellow, cadmium yellow, yellow iron oxide, titanium yellow, chromium oxide, viridian, titanium cobalt green, cobalt green, cobalt chrome green, Victoria green, ultramarine, dark blue, cobalt blue, cerulean blue, cobalt silica blue, cobalt zinc silica blue, manganese violet, and cobalt violet.

[0122] When using carbon black as a pigment, carbon black produced by the furnace process or channel process can be used. In particular, carbon black produced by the furnace process or channel process with a primary particle size of 10-40 nm and a specific surface area of ​​50-400 m² as measured by the BET method is suitable. 2 Particles with characteristics such as a density of / g and a pH of 2-10 are preferred. Furthermore, because the density of the resulting printed material increases and the print quality of the printed material can be improved, and although the detailed mechanism is unknown, the blocking resistance and lamination properties of the printed material are improved, a primary particle size of 10-20 nm and a specific surface area of ​​200-350 m² by the BET method are preferred. 2 Carbon black with a weight of 0.5-10% volatile content and a pH of 7-10 is particularly suitable for use.

[0123] Furthermore, when titanium dioxide is used as a pigment, it is preferable to use titanium dioxide with an oil absorption capacity of 14-20 g / 100 g, and particularly preferable to use titanium dioxide with an oil absorption capacity of 14-18 g / 100 g. Generally, the higher the oil absorption capacity of titanium dioxide, the higher the hydrophobicity of the surface of the titanium dioxide. Titanium dioxide with an oil absorption capacity within the above range has relatively high surface hydrophilicity, and is thought to capture a portion of the unmodified acetylenediol-based surfactant (A1), which is thought to facilitate the suppression of pinholes and the improvement of standby ejection performance. Moreover, the surface area of ​​the titanium dioxide is increased, making it easier to capture a portion of the unmodified acetylenediol-based surfactant (A1), thus suppressing pinholes and improving standby ejection performance. From the viewpoint of improving the storage stability of the water-based inkjet ink, the primary particle size of the titanium dioxide is preferably 200-260 nm, and particularly preferably 200-230 nm.

[0124] In this disclosure, the primary particle size of the pigment is the equivalent circular diameter of the pigment particles (average value of 100 pigment particles) observed using a transmission electron microscope (TEM). Furthermore, the oil absorption amount of titanium dioxide in this disclosure is the value measured in accordance with JIS K 5101-13-1:2004.

[0125] On the other hand, specific examples of organic pigments, as illustrated by the color index, include CIPigment Blue 1, 2, 3, 15:1, 15:3, 15:4, 15:6, 16, 21, 22, 60, and 64, among others, as examples of cyan pigments.

[0126] Examples of red and violet pigments include CIPigment 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, and CIPigment Violet 19, 23, 29, 30, 32, 36, 37, 38, 40, 50, etc.

[0127] Other examples of yellow pigments include CIPigment 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.

[0128] Other examples of black pigments include aniline black (CIPigment Black 1), perylene black (CIPigment Black 31, 32), and azomethine azoblack. Furthermore, a black pigment can be created by mixing multiple chromatic pigments, such as the cyan, red, violet, and yellow pigments mentioned above, as well as the brown and orange pigments listed below.

[0129] Other options include using CIPigment Green 7, 10, 36; CIPigment Brown 3, 5, 25, 26; CIPigment Orange 2, 5, 7, 13, 14, 15, 16, 24, 34, 36, 38, 40, 43, 62, 63, 64, 71, etc.

[0130] <Pigment-dispersed resin> In the ink of the present invention, the following methods can be exemplified as methods for stably dispersing the above-mentioned pigments and maintaining the storage stability and standby discharge performance of the ink in a good state for a long period of time: (1) a method of coating at least a portion of the pigment surface with a pigment dispersion resin; (2) a method of adsorbing a water-soluble and / or water-dispersible surfactant onto at least a portion of the pigment surface; and (3) a method of chemically and / or physically introducing hydrophilic functional groups onto the pigment surface and dispersing them in the ink without the above-mentioned pigment dispersion resin and superior surfactant. Furthermore, pigments dispersed by the method described in (3) above are generally referred to as "self-dispersing pigments." The method described in (1) above also includes a method of adsorbing a pigment dispersion resin onto at least a portion of the pigment surface.

[0131] In the ink of the present invention, the method described in (1) above, that is, the method using a pigment dispersion resin, is preferably selected. This is because, by selecting and adjusting the composition of the polymerizable monomers constituting the resin, the weight-average molecular weight, etc., the pigment coating ability and charge of the pigment dispersion resin can be easily adjusted. Therefore, even when using fine pigments, it is possible to stably impart storage stability, and furthermore, printed materials with excellent standby ejection, color development, and color reproducibility can be obtained.

[0132] Acrylic resin, maleic acid resin, urethane resin, polyester resin, etc., can be used as the pigment dispersion resin. Among these, it is preferable to use acrylic resin and / or maleic acid resin as the pigment dispersion resin because it provides strong adsorption to the pigment and improves storage stability and discharge performance.

[0133] In this disclosure, "maleic acid resin" refers to a resin using at least (anhydrous) maleic acid as a polymerizable monomer. Furthermore, the maleic acid resin may also use one or more selected from the group consisting of α-olefins, acrylic acid, methacrylic acid, acrylic acid esters, methacrylic acid esters, styrene, and styrene derivatives as a polymerizable monomer.

[0134] The pigment dispersion resin described above may be either a water-soluble resin or a non-water-soluble resin. When a water-soluble resin is used as the pigment dispersion resin, its acid value is preferably 60 to 400 mgKOH / g, more preferably 100 to 350 mgKOH / g, and even more preferably 120 to 300 mgKOH / g. By setting the acid value of the water-soluble pigment dispersion resin within the above range, the dispersion stability of the pigment, as well as the storage stability and standby discharge performance of the ink, are improved. On the other hand, when a non-water-soluble resin is used as the pigment dispersion resin, its acid value is preferably 0 to 100 mgKOH / g, more preferably 2 to 80 mgKOH / g, and even more preferably 5 to 60 mgKOH / g. If the acid value of the non-water-soluble pigment dispersion resin is within the above range, blocking in printed materials becomes easier to prevent, and the water resistance and abrasion resistance of the printed materials are also improved. The acid value of the pigment dispersion resin can be calculated in the same way as in the case of the binder resin described above.

[0135] The ratio of the "content of pigment-dispersing resin relative to the total amount of ink of the present invention" to the "volume of pigment content" [content of pigment-dispersing resin / volume of pigment content] is preferably 0.040 to 2.4, more preferably 0.060 to 1.8, and particularly preferably 0.080 to 1.2. By keeping the above ratio within the above range, the viscosity of the ink of the present invention tends to fall within a range suitable for ejection from an inkjet head, improving standby ejection performance, as well as improving the dispersion stability of the pigment and the storage stability of the ink.

[0136] In one embodiment, the pigment dispersion resin may have a crosslinked structure. Preferably, the crosslinked structure is formed by a crosslinking reaction after at least a portion of the pigment surface has been coated with the pigment dispersion resin. Furthermore, as the method for the crosslinking reaction, either of the following may be adopted: a method in which an intramolecularly reactive pigment dispersion resin is coated onto the pigment surface and then the pigment dispersion resin is reacted; or a method in which a compound (crosslinking agent) that can react with functional groups present in the pigment dispersion resin is added after the pigment dispersion resin has been coated onto the pigment surface, and the pigment dispersion resin is reacted with the compound. When the latter method is adopted, from the viewpoint of improving the standby discharge performance of the ink, suppression of pinholes, and the blocking resistance and lamination properties of the printed material, the ratio of the molar amount of functional groups present in the added crosslinking agent that can react with the pigment dispersion resin to the molar amount of functional groups present in the pigment dispersion resin that can react with the crosslinking agent [moles of functional groups in the crosslinking agent / moles of functional groups in the pigment dispersion resin] is preferably 0.2 to 0.7, and particularly preferably 0.3 to 0.6.

[0137] <Water> The water contained in the ink of the present invention is preferably ion-exchanged water (deionized water) and / or distilled water, rather than ordinary water containing various ions.

[0138] The amount of water contained in the ink of the present invention is preferably 40 to 90% by mass of the total amount of ink.

[0139] <Other ingredients> In addition to the above-mentioned components, the ink of the present invention may optionally contain additives such as pH adjusters, waxes, colloidal silica, ultraviolet absorbers, and preservatives to impart desired physical properties.

[0140] pH adjuster The ink may contain a pH adjuster because it can reduce damage to the components of the inkjet head and improve the storage stability of the ink by suppressing pH fluctuations over time.

[0141] There are no restrictions on the materials that can be used as pH adjusters, and one type may be used alone or two or more types may be used in combination. For example, when acidifying the ink of the present invention, inorganic acids such as hydrochloric acid, sulfuric acid, phosphoric acid, and boric acid can be used, as well as organic acids such as acetic acid, citric acid, maleic acid, maleic anhydride, succinic acid, tartaric acid, malic acid, fumaric acid, malonic acid, ascorbic acid, and glutamic acid can be used. Furthermore, when basicizing the ink, organic amine solvents such as monoethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, dimethylaminoethanol, diethylaminoethanol, and aminomethylpropanol can be used; ammonia water; alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; and alkali metal carbonates such as lithium carbonate, sodium carbonate, sodium bicarbonate, and potassium carbonate can be used.

[0142] In particular, when the ink of the present invention is made basic, from the viewpoint of improving storage stability and standby discharge performance, and from the viewpoint of obtaining printed materials that are less likely to remain in the printed material and have excellent lamination and low migration properties, one or more compounds selected from the group consisting of monoethanolamine, N-methyldiethanolamine, dimethylaminoethanol, diethylaminoethanol, aminomethylpropanol, and aqueous ammonia can be preferably used.

[0143] In order to improve storage stability and standby discharge performance, if the ink of the present invention contains a pH adjusting agent, the content thereof is preferably 0.05 to 2.5% by mass, and particularly preferably 0.1 to 1.5% by mass, of the total amount of the ink.

[0144] ≪Wax≫ The ink of the present invention may contain wax, as this can improve the abrasion resistance, substrate adhesion, blocking resistance, and lamination properties of printed materials. The "wax" refers to a resin that is solid at room temperature (25°C) but becomes liquid when heated and / or pressurized. For example, a resin with a melting point of 50 to 160°C that melts in a temperature environment above that melting point is considered a wax in this disclosure.

[0145] The resin used as the wax described above is preferably in the form of resin microparticles. Because the wax is in the form of resin microparticles, it is easier to ensure a large amount of it is present at the interface of the ink layer, which further improves the abrasion resistance, substrate adhesion, blocking resistance, and lamination properties of the printed material.

[0146] Furthermore, resins that can be used as the above-mentioned wax include polyethylene, polypropylene, oxidized polyethylene, oxidized polypropylene, polyethylene modified products, polypropylene modified products, solid normal paraffin, solid isoparaffin, etc. Specific examples of the above modifications include carboxylic acid modification, maleic acid modification, fatty acid modification, and polytetrafluoroethylene modification.

[0147] In order to further improve the abrasion resistance, substrate adhesion, blocking resistance, and lamination properties of printed materials, the amount of wax added is preferably 0.2 to 2.5% by mass in terms of solid content, more preferably 0.4 to 2% by mass, and particularly preferably 0.5 to 1.5% by mass, in terms of solid content, of the total amount of ink of the present invention.

[0148] Colloidal Silica From the viewpoint of easily suppressing pinholes and blocking in printed materials while maintaining standby ejection performance, the ink of the present invention may contain colloidal silica. "Colloidal silica" is a colloid consisting of fine particles of silica (silicon dioxide). The colloidal silica may contain alkali metal hydroxides, ammonia, quaternary ammonium salt compounds, etc., as stabilizers, and the surface of the colloidal silica may be treated with a silane coupling agent, etc. By adding these stabilizers and treating the surface, the dispersion state of the silica fine particles in the ink of the present invention is stabilized, and the above-mentioned effects, namely improved standby ejection performance and suppression of pinholes and blocking, can be suitably expressed.

[0149] When the ink of the present invention contains colloidal silica, the average particle size (volume-based median diameter (D50)) of the colloidal silica is preferably 3 to 100 nm, and particularly preferably 5 to 30 nm. Furthermore, the amount of colloidal silica added is preferably 0.01 to 0.8% by mass in terms of solid content, and particularly preferably 0.03 to 0.5% by mass in terms of solid content, of the total amount of ink of the present invention. When the average particle size of the colloidal silica is within the above range, or when the amount of colloidal silica added is within the above range, the above-mentioned effects, namely improved standby ejection performance and suppression of pinholes and blocking, are suitably achieved.

[0150] The average particle size in this disclosure is a value measured at 25°C using a dynamic light scattering particle size distribution analyzer such as the "NanoTrac UPA-EX150" manufactured by Microtrac-Bell.

[0151] Examples of commercially available colloidal silica products that can be used with the ink of the present invention include Nissan Chemical's Snowtex XS, Snowtex S, Snowtex 30, Snowtex 40, Snowtex 50T, Snowtex NXS, Snowtex NS, Snowtex N, Snowtex N-40, Snowtex CXS, Snowtex C, Snowtex CM, etc. Note that one of the listed products may be used alone, or two or more may be used in combination.

[0152] <Method for manufacturing the ink of the present invention> The following is an example of a method for producing the ink of the present invention, which contains the above-mentioned components. However, the method for producing the ink of the present invention is not limited to the following method.

[0153] First, a pigment dispersion resin and water are mixed to produce an aqueous solution of the pigment dispersion resin. Next, pigment, water, and, if necessary, an unmodified acetylenediol-based surfactant (A1), an alkylene oxide-modified acetylenediol-based surfactant (A2), a water-soluble organic solvent (B), and other components are added to the aqueous solution of the pigment dispersion resin. After thorough mixing and stirring (premixing), dispersion is performed using the dispersion method described later. Then, if necessary, coarse particles are removed from the mixture after dispersion by filtration, centrifugation, etc., to obtain a pigment dispersion. Subsequently, an unmodified acetylenediol-based surfactant (A1), an alkylene oxide-modified acetylenediol-based surfactant (A2), a water-soluble organic solvent (B), water, and, if necessary, a nonionic surfactant (C), a binder resin, and other components are added to the pigment dispersion and thoroughly mixed and stirred. Then, the resulting mixture is subjected to filtration, centrifugation, or other treatments to remove coarse particles, thereby obtaining the ink of the present invention.

[0154] In this disclosure, "aqueous solution" refers to a solution comprising an aqueous solvent and a component dispersed and / or dissolved in said aqueous solvent.

[0155] As mentioned above, premixing before the dispersion process is effective. Premixing ensures that the pigment surface is sufficiently wetted with the aqueous medium and promotes the adsorption of the pigment dispersion resin onto the pigment surface, thereby improving the storage stability and discharge performance of the final ink.

[0156] Any commonly used wet disperser can be used for the above dispersion process. Specifically, examples include media-agitated dispersers such as ball mills and bead mills, as well as media-less dispersers such as roll mills, high-pressure jet mills, and high-pressure homogenizers. Among these, it is preferable to use one or more dispersers selected from the group consisting of bead mills, high-pressure jet mills, and high-pressure homogenizers. Using these wet dispersers facilitates the fine dispersion of pigments, improving the storage stability and standby discharge performance of the final ink. Examples of commercially available bead mills include Alpha Mill, Glen Mill, Sand Grinder, Star Mill, Dyno Mill, Dual Apex Mill, and Pearl Mill (all trade names). Examples of commercially available high-pressure jet mills and high-pressure homogenizers include Starburst, Nanomizer, and Microfluidizer (all trade names).

[0157] Since the ink of the present invention is for inkjet printing, it is preferable that the particle size distribution of the pigment particles be sharply uniform, from the viewpoint of preventing clogging of the nozzles of the inkjet head and greatly improving standby ejection performance. Methods for obtaining a pigment having a desired particle size distribution include reducing the size of the pulverized media used in the media stirring type disperser mentioned above; increasing the packing rate of the pulverized media; increasing the dispersion processing time; using multiple types of wet dispersers in combination; performing filtration, centrifugation, etc. on the mixture after dispersion processing; and combinations of these methods. As an example of the method of using multiple types of wet dispersers in combination, a method is to crush coarse pigment particles by primary dispersion processing using a ball mill, bead mill, or roll mill, and then perform secondary dispersion processing using a bead mill, high-pressure jet mill, or high-pressure homogenizer.

[0158] <Ink Set> The ink of the present invention may be used as a single color, but it can also be used as an ink set combining multiple colors. The above combination is not particularly limited, but for example, a full-color image can be obtained by using three colors: cyan, yellow, and magenta. In addition, the blackness can be improved by adding black ink, and the visibility of text and other elements can be increased. Furthermore, it is possible to improve color reproduction by adding colors such as orange and green. When printing on printing substrates other than white, a clear image can be obtained by using white ink in combination. Alternatively, the ink set may include as a component an ink (clear ink) that is substantially free of colorant components, by removing the pigment from the ink of the present invention.

[0159] In particular, it is preferable that all of the inks constituting the above ink set contain a pigment dispersion resin having a cross-linked structure. As described above, using a pigment dispersion resin having a cross-linked structure improves the standby discharge performance of the ink, as well as the suppression of pinholes and the blocking resistance and lamination properties of the printed material.

[0160] <Ink Pretreatment Solution Set> The ink of the present invention can also be used in combination with a pretreatment solution containing a flocculant, in the form of an ink-pretreatment solution set. By applying the pretreatment solution containing the flocculant onto a printing substrate, a layer (ink flocculation layer) can be formed on the substrate in which the solid components (pigments, binder resins, etc.) contained in the ink are intentionally flocculated. Then, by depositing droplets of the ink of the present invention onto this ink flocculation layer, bleeding between the droplets and uneven density in the printed material can be prevented, and the print quality of the printed material can be significantly improved. Furthermore, depending on the material used in the pretreatment solution, the substrate adhesion, blocking resistance, and lamination properties of the printed material can also be improved.

[0161] In this disclosure, "coagulant" means a component contained in an aqueous inkjet ink that disrupts the dispersion state of pigments and causes aggregation, and / or insolubilizes the binder resin contained in the aqueous inkjet ink, thereby increasing the viscosity of the aqueous inkjet ink. From the viewpoint of significantly improving print quality while suppressing a decrease in blocking and lamination properties in printed materials, the coagulant contained in the pretreatment liquid combined with the ink of the present invention is preferably a metal salt and / or a cationic polymer compound. In particular, from the viewpoint of obtaining excellent print quality, it is preferable to use a metal salt as the coagulant, and it is especially preferable to contain a salt of one or more polyvalent metal ions selected from the group consisting of Ca2+, Mg2+, and Al3+. When a metal salt is used as the coagulant, its content is preferably 2 to 30% by mass, and particularly preferably 3 to 25% by mass, based on the total amount of the pretreatment liquid.

[0162] Furthermore, the above pretreatment solution may appropriately contain water-soluble organic solvents, surfactants, binder resins, pH adjusters, waxes, colloidal silica, preservatives, etc. Specific examples of each component are the same as those for the ink of the present invention described above. When the above pretreatment solution contains a surfactant, it is preferable that the surfactant includes an unmodified acetylenediol-based surfactant (A1) and an alkylene oxide-modified acetylenediol-based surfactant (A2) having an HLB value of 6 to 12, from the viewpoint of effectively suppressing blocking, reduced lamination, and migration in printed materials.

[0163] <Printed material> One embodiment of the present invention is a printed material comprising a printing substrate described later and an ink layer formed using the ink of the present invention. The ink layer is a layer formed by drying aqueous inkjet ink printed in the shape of an image and / or characters. The printed material produced using the ink of the present invention described above is free of pinholes and has excellent blocking resistance, lamination properties, and low migration properties. The method for manufacturing printed materials described later can be suitably used as a method for drying the aqueous inkjet ink after it has been printed in the shape of an image and / or characters to form an ink layer. The "image" also includes solid images (images printed at 100% print density so as to completely cover the surface of the printing substrate) and seamless images such as checkerboard patterns.

[0164] <Printing base material> The ink of the present invention can be used particularly suitably on non-absorbent printing substrates. Specific examples of non-absorbent printing substrates include polyolefin resins such as polyethylene, biaxially oriented polypropylene (OPP), and axially 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; and films and sheets manufactured from cellophane and the like. Furthermore, composite materials can be used, which are made by laminating multiple films and / or sheets of different materials. Examples of such composite materials include composite films made by laminating a polyolefin resin film and a polyethylene terephthalate film, composite films made by laminating a polystyrene resin film and a polyethylene terephthalate film, and composite films made by laminating a polyolefin resin film and a nylon film.

[0165] Furthermore, the printing substrate used for printing the ink of the present invention may be subjected to surface treatments such as corona treatment or plasma treatment.

[0166] <Manufacturing methods for printed materials> The ink of the present invention is used in a printing method in which droplets of the ink are dispensed from a nozzle of an inkjet head and applied to a printing substrate. Any known method can be arbitrarily selected for the water-based inkjet ink dispensing method from the inkjet head. Examples of such dispensing methods include a piezoelectric method that utilizes the volume change of a piezoelectric element, a thermal method that dispenses water-based inkjet ink using bubbles generated by heating with a heater, and a valve method that dispenses pressurized water-based inkjet ink while opening and closing the nozzle cover (valve) with a solenoid.

[0167] Furthermore, from the viewpoint of preventing the orientation of the acetylenediol-based surfactant (A), drying of the water-soluble organic solvent (B) and water, and film formation of the binder resin, thereby significantly improving standby discharge performance, and from the viewpoint of homogenizing the components within the ink of the present invention, thereby enabling further suppression of blocking, deterioration of lamination, and migration, the ink of the present invention is preferably used in a printing apparatus having an ink circulation mechanism configured to communicate with an inkjet head.

[0168] An example of an ink circulation mechanism configured to connect an inkjet head is a system comprising: an inkjet head having an ink supply port, nozzles, ink communication passages, and an ink discharge port; an ink supply channel connected to the ink supply port; an ink discharge channel connected to the ink discharge port; and a pump connected to the ink supply channel and / or the ink discharge channel. The ink supply channel and the ink discharge channel may be directly connected or connected via another configuration. An example of connection via another configuration is a configuration in which one end of the ink supply channel and one end of the ink discharge channel are both connected to the same ink tank.

[0169] Furthermore, in the above-described inkjet head, the ink supplied from the ink supply port passes through either the nozzle or the ink communication channel. The ink that flows into the nozzle is ejected from the inkjet head. On the other hand, the ink that flows into the ink communication channel is discharged from the ink discharge port and returns to the inkjet head via the ink discharge channel and the ink supply channel.

[0170] On the other hand, it is preferable to dry the ink on the printing substrate using a drying mechanism after applying the ink of the present invention to the printing substrate. Examples of drying methods used in the drying mechanism include heating drying, hot air drying, infrared (for example, infrared with a peak wavelength of 700 to 2500 nm) drying, microwave drying, and drum drying. These drying methods may be used individually, in succession, or simultaneously. For example, by using heating drying and hot air drying in combination, the ink can be dried more quickly than when each method is used individually.

[0171] <Post-coating treatment> Printed materials made using the ink of the present invention can be post-coated. Specific examples of this post-coating treatment include coating or printing of a post-coating composition; lamination by methods such as dry lamination, solvent-free lamination, or extrusion lamination. One of these methods may be selected, or a combination of multiple methods may be used.

[0172] When applying a post-coating treatment to a printed material by coating and printing with a post-coating composition, either a non-contact printing method, such as inkjet printing, or a method in which the post-coating composition is brought into contact with the printing substrate before printing may be used as the coating and printing method. When selecting a non-contact printing method for the post-coating composition to the printing substrate, it is preferable to use an ink (clear ink) that is substantially free of colorant components, obtained by removing the pigment from the ink of the present invention, as the post-coating composition.

[0173] On the other hand, when laminating printed materials, the adhesive used to laminate the sealant substrate is preferably composed of a mixture of a polyol component and a polyisocyanate component.

[0174] The polyol component mentioned above is a resin component having multiple hydroxyl groups. From the viewpoint of coating properties, wettability and penetration on the surface of printed materials, and laminate strength developed after aging, polyether polyols and polyester polyols are preferably used. In particular, it is preferable that the polyol component contains polyester polyol because it exhibits good wettability on the surface of printed materials obtained with the ink of the present invention, specifically on the surface of the ink layer and the ink aggregate layer (when a pretreatment liquid is used), and also exhibits excellent lamination properties of the laminated printed material (laminated body). The polyol component may be a single component or multiple components may be used in combination.

[0175] On the other hand, as the polyisocyanate component that reacts with the polyol component, it is preferable to use a polyether-based urethane resin having isocyanate groups at its ends, from the viewpoint of compatibility with the polyol component, wettability on the surface of the printed material, and lamination properties of the laminated printed material (laminated material). Also from the same viewpoint, it is preferable that the amount of the polyisocyanate component blended is 50 to 80% by mass relative to the total amount of the polyol component. The polyisocyanate component may be used as a single component or in combination of multiple components.

[0176] Examples of sealant substrates used in the above lamination process include polypropylene films and polyethylene films, such as CPP films and linear short-chain branched polyethylene (LLDPE) films. Furthermore, films having a metal (oxide) vapor-deposited layer, such as aluminum oxide, can also be used as the sealant substrate. [Examples]

[0177] The present invention will be described in more detail below with reference to examples and comparative examples. In the following description, "parts" and "%" refer to mass unless otherwise specified.

[0178] [Example A] First, we evaluated the impact on the quality of water-based inkjet inks when primarily adjusting the type and amount of acetylenediol-based surfactant (A) and water-soluble organic solvent (B).

[0179] <Preparation of aqueous solution of pigment-dispersed resin 1> 90 parts of butanol were charged into a reaction vessel equipped with a gas inlet tube, thermometer, condenser, and stirrer, and the inside of the reaction vessel was replaced with nitrogen gas. Next, the contents of the reaction vessel were heated until they reached 110°C, and then a mixture of 30 parts of polymerizable monomers, acrylic acid, 40 parts of benzyl methacrylate, and 30 parts of styrene, and 4 parts of the polymerization initiator V-601 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added dropwise to the reaction vessel over 2 hours. After the dropwise addition was complete, the polymerization reaction was continued for 3 hours while maintaining the internal temperature at 110°C. Subsequently, 0.4 parts of V-601 were added, and the polymerization reaction was continued for 1 hour while maintaining the internal temperature of the reaction vessel at 110°C to obtain a solution of pigment dispersion resin 1. Next, the contents of the reaction vessel were cooled to room temperature (25°C), and 40 parts of a 48% potassium hydroxide aqueous solution were added to neutralize the pigment dispersion resin 1. Then, 80 parts of deionized water were added. After that, the contents were heated to over 100°C, and the butanol was removed by azeotropic dissolution with the deionized water. Finally, deionized water was added to adjust the solid content concentration to 30%, thereby obtaining an aqueous solution of pigment dispersion resin 1. The weight-average molecular weight of the obtained pigment dispersion resin 1 was 16,000, and the acid value was 234 mgKOH / g.

[0180] <Preparation of aqueous solution of pigment-dispersed resin 2> Fifty-six parts of methyl ethyl ketone were charged into a reaction vessel equipped with a gas inlet tube, thermometer, condenser, and stirrer. Next, 16 parts of benzyl methacrylate, 40 parts of cyclohexyl methacrylate, 0.3 parts of 2,2'-azobisisobutyronitrile, and 2.2 parts of 2-(dodecylthiocarbonothio)-isobutyric acid were added, and the reaction vessel was then purged with nitrogen gas. After that, the contents of the reaction vessel were heated to 75°C, and the polymerization reaction was carried out for 3 hours while maintaining the internal temperature at 75°C to obtain a polymer (block A) consisting of benzyl methacrylate and cyclohexyl methacrylate. After the polymerization reaction described above was completed, the contents of the reaction vessel were cooled to room temperature. Then, 44 parts of methyl ethyl ketone, 28 parts of butyl methacrylate, and 16 parts of methacrylic acid were added to the reaction vessel, and the contents of the reaction vessel were again replaced with nitrogen gas. Subsequently, the contents of the reaction vessel were heated to 75°C, and the polymerization reaction was carried out for 3 hours while maintaining the internal temperature at 75°C. This yielded a solution of pigment dispersion resin 2 having an AB block structure, in which a copolymer (block B) consisting of butyl methacrylate and methacrylic acid was added to block A. Subsequently, after the contents of the reaction vessel were cooled to room temperature, 17 parts of dimethylaminoethanol were added to neutralize the pigment dispersion resin 2, and then 150 parts of deionized water were added. The contents were then heated, and the methyl ethyl ketone was removed by azeotrope with the deionized water. Deionized water was then added to adjust the solid content to 30%, thereby obtaining an aqueous solution of pigment dispersion resin 2. The weight-average molecular weight of the obtained pigment dispersion resin 2 was 19,000, and the acid value was 104 mgKOH / g.

[0181] <Manufacturing of Magenta Pigment Dispersion 1> 480g of FASTGEN SUPER MAGENTA RG (CIPigment Red 122, manufactured by DIC), 800g of an aqueous solution of pigment dispersion resin 1, 1,470g of deionized water, and 250g of methyl ethyl ketone were added to a mixing vessel equipped with a stirrer. After adding all the raw materials and stirring (premixing) for 1 hour, the mixture was circulated and dispersed using a 0.6L bead mill (DinoMill, manufactured by Shinmaru Enterprises) filled with 1,800g of 0.5mm diameter zirconia beads. The average particle size of the mixture was then measured at regular intervals (e.g., every hour) using the aforementioned device (NanoTrac UPA-EX150, manufactured by MicroTrac-Bell), and the circulating dispersion was terminated when the average particle size fell below 180nm. Next, 400g of deionized water was added to the dispersion mixture after the circulating dispersion was completed. Furthermore, while heating the mixture at 60°C, some of the deionized water and methyl ethyl ketone were removed by vacuum distillation. Then, using the deionized water, the pigment concentration was adjusted to 15%, and a magenta pigment dispersion precursor was produced. Subsequently, 966.7 g of the magenta pigment dispersion precursor obtained by the method described above, 22.3 g of Denacol EX-321 (an epoxy compound manufactured by Nagase ChemteX, epoxy equivalent: 140 g / eq.), and 11.0 g of deionized water were added to a reaction vessel equipped with a stirrer. Next, the contents of the reaction vessel were heated to 80°C while stirring, and after reaching 80°C, stirring was continued for 3 hours while maintaining the temperature to carry out the crosslinking reaction. After that, the internal temperature of the reaction vessel was cooled to room temperature, and then deionized water was added to adjust the pigment concentration to 14.5%. After adjusting the pigment concentration, the mixture was filtered through a 5 μm membrane filter to obtain magenta pigment dispersion 1 (pigment concentration 14.5%). In the magenta pigment dispersion 1 described above, the ratio of the molar amount of functional groups (epoxy groups) present in the crosslinking agent (Denacol EX-321) that can react with the pigment dispersion resin 1 to the molar amount of acid groups (functional groups that can react with the crosslinking agent) present in the pigment dispersion resin 1 [number of moles of functional groups in the crosslinking agent / number of moles of functional groups in the pigment dispersion resin] was 0.52.

[0182] <Manufacturing of White Pigment Dispersion 1> 2,500g of Typeque CR-60 (titanium dioxide surface-treated with alumina, oil absorption: 15g / 100g, manufactured by Ishihara Sangyo Co., Ltd.), 833g of an aqueous solution of pigment dispersion resin 2, and 1,667g of deionized water were added to a mixing container equipped with a stirrer. After adding all the raw materials and stirring (premixing) for 1 hour, the mixture was circulated and dispersed using a 0.6L bead mill (DinoMill, manufactured by Shinmaru Enterprises) filled with 1,800g of zirconia beads with a diameter of 0.5mm. The average particle size of the mixture was measured at regular intervals (e.g., every hour) using the aforementioned device (NanoTrac UPA-EX150, manufactured by Microtrac-Bell), and the circulating dispersion was terminated when the average particle size fell below 260nm. Finally, deionized water was added to adjust the pigment concentration to 48% to obtain white pigment dispersion 1 (pigment concentration 48%).

[0183] <Manufacturing of aqueous solutions for binder resins> 72 parts of methyl ethyl ketone were charged into a reaction vessel equipped with a gas inlet tube, thermometer, condenser, and stirrer, and the inside of the reaction vessel was replaced with nitrogen gas. Next, the reaction vessel was heated to 80°C, and then a mixture of polymerizable monomers, consisting of 4.5 parts methacrylic acid, 15 parts styrene, 5.5 parts 2-hydroxyethyl methacrylate, 20 parts stearyl methacrylate, and 55 parts methyl methacrylate, along with 4 parts of the polymerization initiator V-601 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), was added dropwise to the reaction vessel over 2 hours. After the dropwise addition was complete, the polymerization reaction was continued for 3 hours while maintaining the internal temperature at 80°C. Subsequently, 0.6 parts of V-601 were added, and the polymerization reaction was continued for 2 hours while maintaining the internal temperature at 80°C to obtain a binder resin solution. Next, the contents of the reaction vessel were cooled to 50°C, 4.7 parts of dimethylaminoethanol were added to neutralize the binder resin, and then 140 parts of deionized water were added. After that, the contents were heated to over 78°C, and the methyl ethyl ketone was azeotropically removed with the deionized water by distillation. Then, deionized water was added to adjust the solid content to 30%, thereby obtaining an aqueous solution of the binder resin. The weight-average molecular weight of the obtained binder resin was 17,500, and the acid value was 29 mgKOH / g.

[0184] <Synthesis and preparation of unmodified acetylenediol-based surfactants> Using the method described in Example 1 of Japanese Patent Publication No. 2002-356451, and employing methyl isobutyl ketone as the starting ketone, 2,4,7,9-tetramethyl-5-decine-4,7-diol (unmodified acetylenediol compound 1, HLB value = 3.0) was synthesized. Similarly, using methyl isoamyl ketone as the starting ketone, 2,5,8,11-tetramethyl-6-dodecine-5,8-diol (unmodified acetylenediol compound 2, HLB value = 2.7) was synthesized.

[0185] In addition, 3,6-dimethyl-4-octin-3,6-diol (manufactured by Tokyo Chemical Industry Co., Ltd.) was used as unmodified acetylenediol compound 3 (HLB value = 4.0).

[0186] <Synthesis of alkylene oxide-modified acetylenediol-based surfactants> Using the method described in Example 1 of U.S. Patent No. 3,268,593, alkylene oxide-modified acetylenediol surfactants (modified acetylenediol compounds 4-7) with different ethylene oxide modification levels were synthesized by adjusting the amount of ethylene oxide and the synthesis conditions (pressure, temperature, time) using the unmodified acetylenediol compound 1 (2,4,7,9-tetramethyl-5-decine-4,7-diol) as a starting material. Furthermore, ethylene oxide-modified acetylenediol surfactants (modified acetylenediol compounds 8-10) were synthesized by adjusting the amount of ethylene oxide and the synthesis conditions (pressure, temperature, time) using the unmodified acetylenediol compound 2 (2,5,8,11-tetramethyl-6-dodecine-5,8-diol) as a starting material. Furthermore, using the method described in Example 1 of Japanese Patent Publication No. 2001-215690, a modified acetylenediol compound 6 was used as a starting material to synthesize an ethylene oxide-propylene oxide modified acetylenediol surfactant (modified acetylenediol compound 11, HLB value = 8.0) in which a propylene oxide group was added to the modified acetylenediol compound 6.

[0187] The details of the modified acetylenediol compounds 1 to 11 synthesized and prepared as described above (abbreviations used in Table 3, starting materials used in synthesis, number of moles of ethylene oxide and propylene oxide groups added, and HLB values) are shown in Table 1.

[0188] [Table 1]

[0189] <Preparation of 1-3 diluted solutions of unmodified acetylenediol-based surfactants> One part of the above-mentioned unmodified acetylenediol compound 1 was thoroughly mixed with 99 parts of deionized water to prepare a diluted solution of unmodified acetylenediol compound 1. In addition, diluted solutions of unmodified acetylenediol compound 2 and unmodified acetylenediol compound 3 were prepared in the same manner as for the diluted solution of unmodified acetylenediol compound 1, except that unmodified acetylenediol compounds 2 and 3 were used instead of unmodified acetylenediol compound 1, respectively.

[0190] Note that the abbreviations "Ac1," "Ac2," and "Ac3" used in Table 3 represent the first dilution of unmodified acetylenediol compound, the second dilution of unmodified acetylenediol compound, and the third dilution of unmodified acetylenediol compound, respectively.

[0191] <Preparation of water-soluble organic solvent solutions S1-S30> Water-soluble organic solvents and deionized water were added to a mixing container equipped with a stirrer, according to the formulations described in each column of Tables 2-1 to 2-2. After adding all the materials, the contents of the mixing container were stirred and mixed until they were sufficiently uniform to produce water-soluble organic solvent solutions S1 to S30.

[0192] [Table 2-1]

[0193] [Table 2-2]

[0194] Note that the unit of the blending amount in Tables 2-1 to 2-2 is "parts by mass". Also, blank spaces in Tables 2-1 to 2-2 indicate that the material is not blended.

[0195] Further details regarding the abbreviations listed in Tables 2-1 to 2-2 are as follows. 1,2PD:1,2-Propanediol (Boiling point: 188°C, HLB value: 8.9) 1,3PD:1,3-Propanediol (Boiling point: 214°C, HLB value: 8.9) 1,2BD:1,2-Butanediol (Boiling point: 194°C, HLB value: 7.6) 2,3BD:2,3-butanediol (boiling point: 182°C, HLB value: 7.6) 1,3BD:1,3-butanediol (boiling point: 207°C, HLB value: 7.6) 1,2PeD:1,2-Pentanediol (Boiling point: 210°C, HLB value: 6.5) 1,5PeD:1,5-Pentanediol (Boiling point: 239°C, HLB value: 6.5) 1,2HeD:1,2-Hexanediol (Boiling point: 223°C, HLB value: 5.8) PM: Propylene glycol monomethyl ether (boiling point: 121°C, HLB value: 3.8) PnP: Propylene glycol monon-n-propyl ether (boiling point: 150°C, HLB value: 2.9) PnB: Propylene glycol monon-butyl ether (boiling point: 170°C, HLB value: 2.6) DPM: Dipropylene glycol monomethyl ether (boiling point: 189°C, HLB value: 2.3) DPnP: Dipropylene glycol monon-propyl ether (boiling point: 212°C, HLB value: 1.9) DPnB: Dipropylene glycol mono-n-butyl ether (boiling point: 229°C, HLB value: 1.8) iPDG: Diethylene glycol monoisopropyl ether (boiling point: 207°C, HLB value: 11.9) iBDG: Diethylene glycol monoisobutyl ether (boiling point: 220°C, HLB value: 10.9) nBDG: Diethylene glycol mono-n-butyl ether (boiling point: 231°C, HLB value: 10.9) HeDG: Diethylene glycol mono-n-hexyl ether (boiling point: 258°C, HLB value: 9.3)

[0196] <Manufacturing of ink sets 1-164> 10.7 g of deionized water, 30 g of water-soluble organic solvent solution S1, 0.1 g of modified acetylenediol compound 12, 0.2 g of TEGO Glide 450 (siloxane-based surfactant manufactured by Evonik), 26.7 g of aqueous binder resin solution, 31.3 g of magenta pigment dispersion 1, and 1 g of a 1% aqueous solution of 1,2-benzisothiazolin-3-one were sequentially added to a mixing container equipped with a stirrer in this order. Each material was added while stirring the contents of the mixing container. After all materials had been added, the contents of the mixing container were heated to 50°C while stirring, and then stirring and mixing were continued for 10 minutes while maintaining the temperature at 50°C. Afterward, the contents were cooled to room temperature (25°C), and then filtered using a disposable syringe filter (25 mm in diameter) equipped with a membrane filter with a pore size of 1 μm to remove coarse particles that could cause printhead clogging, thereby producing magenta ink 1. Furthermore, white ink 1 was manufactured using the same materials and methods as magenta ink 1, except that white pigment dispersion 1 was used instead of magenta pigment dispersion 1. The magenta ink 1 and white ink 1 were then combined to form ink set 1.

[0197] Furthermore, ink sets 2 to 164 were manufactured in the same manner as the manufacturing method for ink set 1, except that the materials listed in each column of Tables 3-1 to 3-9 were used in the proportions listed in each column of Tables 3-1 to 3-9. In the manufacturing of each ink set, the order of mixing the materials was as follows: ion-exchanged water, water-soluble organic solvent solution, alkylene oxide-modified acetylenediol-based surfactant (A2), diluted unmodified acetylenediol-based surfactant (A1), other surfactants, aqueous binder resin solution, pigment dispersion, and other components.

[0198] [Table 3-1]

[0199] [Table 3-2]

[0200] Table 3-3

[0201] Table 3-4

[0202] Table 3-5

[0203] Table 3-6

[0204] Table 3-7

[0205] Table 3-8

[0206] Table 3-9

[0207] Note that the unit of the blending amount in Tables 3-1 to 3-9 is "g". Also, blank spaces in Tables 3-1 to 3-9 indicate that the material is not blended. Furthermore, in Tables 3-1 to 3-9, there are cases where the value entered in the column for "Absolute value of the difference between the weighted average HLB value of acetylenediol-based surfactant (A) and the weighted average HLB value of water-soluble organic solvent (B)" differs from the value entered in the column for "Weighted average HLB value of acetylenediol-based surfactant (A)" and the value entered in the column for "Weighted average HLB value of water-soluble organic solvent (B)". This is because the values ​​entered in each of the above columns have been rounded to two decimal places.

[0208] Furthermore, the details of the abbreviations listed in Tables 3-1 to 3-9 are as follows. S465: Surfinol 465 (Acetylenediol-based surfactant manufactured by Evonik, HLB value: 13.2) TG450: TEGO Glide 450 (Siloxane-based surfactant manufactured by Evonik, HLB value: 11.2) B3420: BYK3420 (Siloxane-based surfactant manufactured by Bic Chemie, HLB value: 13.8) B3455: BYK3455 (Siloxane-based surfactant manufactured by Bic Chemie, HLB value: 7.4) B345: BYK345 (Siloxane-based surfactant manufactured by Bic Chemie, HLB value: 9.1) EL1505: Brownon EL-1505 (Polyoxyethylene lauryl ether manufactured by Aoki Oil Co., Ltd., HLB value: 10.5) EL1515: Brownon EL-1515 (Polyoxyethylene lauryl ether manufactured by Aoki Oil Co., Ltd., HLB value: 14.9) EL1530: Brownon EL-1530 (Polyoxyethylene lauryl ether manufactured by Aoki Oil Co., Ltd., HLB value: 17.4) XP100: Lutensol XP100 (BASF polyoxyethylene isodecyl ether, HLB value: 14.7) HE6400: Hi-Tec E-6400 (Polyethylene resin emulsion (wax) manufactured by Toho Chemical Co., Ltd., solid content concentration: 35%) ST-30: Snowtex 30 (Colloidal silica manufactured by Nissan Chemical Corporation, solid content concentration: 30%)

[0209] <Manufacturing of pretreatment solution> 67.7g of deionized water, 5.6g of calcium lactate pentahydrate, 16.7g of NeoCryl XK-190 (acrylic resin emulsion, manufactured by DSM Coating Resins, solid content 45%), 3g of Hi-Tec E-6400 (polyethylene resin emulsion, manufactured by Toho Chemical, solid content 35%), 5g of isopropanol, 1g of modified acetylenediol compound 5, and 1g of a 1% aqueous solution of 1,2-benzisothiazolin-3-one were sequentially added to a mixing container equipped with a stirrer in this order. Each material was added while stirring the contents of the mixing container. After all materials had been added, the contents of the mixing container were heated to 50°C while stirring, and then stirring and mixing were continued for 10 minutes while maintaining the temperature at 50°C. Afterward, the contents were cooled to room temperature (25°C), and then filtered through a stainless steel mesh with a mesh size of 200 mesh to produce a pre-treatment solution.

[0210] [Examples 1-153, Comparative Examples 1-11] The following evaluations were performed using the ink sets prepared as described above. The evaluation results are shown in Tables 3-1 to 3-9.

[0211] <Evaluation 1: Evaluation of standby dispensing performance> An inkjet printing apparatus was prepared, consisting of two Kyocera inkjet heads (KJ4B-1200, design resolution 1,200 dpi, nozzle diameter 20 μm) installed above the conveyor used to transport the printing substrate, and positioned side by side in the direction of transport of the printing substrate. After setting up the inkjet printing apparatus in an environment of 25°C and 50% RH, the inkjet head located upstream in the transport direction was filled with magenta ink from the water-based inkjet inks that make up each ink set. Next, a nozzle check pattern was printed to confirm that magenta ink was being ejected normally from all nozzles, and then the apparatus was left to stand for one hour. After a one-hour waiting period, A4-sized coated paper (OK Topcoat+, 101 μm thick) was fixed onto the conveyor as the printing substrate. The conveyor was then driven at a speed of 50 m / min, and as the printing substrate passed below the inkjet head mounting area, magenta ink was ejected at a drop volume of 2 pL each to print an image. The printed substrate was then quickly placed in a 70°C air oven and dried for 3 minutes to produce the printed material. The image used above is a solid color image (hereinafter referred to as "solid color image") printed with magenta ink at 100% print density, measuring 10 cm wide by 25 cm long. Subsequently, the resulting solid image printouts were examined with a magnifying glass to check for any defects at the start of printing, i.e., whether the magenta ink was properly printed at that starting point. The degree of defects was then compared relatively to evaluate the standby ejection performance. The evaluation criteria were as follows, with ◎, ○, ○△, and △ indicating usable condition.

[0212] ≪Evaluation Criteria for Standby Dispensing Performance≫ ◎: No chipping was observed at the start of printing in the solid image print, or the degree of chipping was better than in ink set 29 (Example 26). ○: The degree of chipping at the start of printing in solid image prints was similar to that in ink set 29 (Example 26). ○△: The degree of chipping at the start of printing in solid image prints was worse than that of ink set 29 (Example 26), but better than that of ink set 3 (Example 1). △: The degree of chipping at the start of printing in solid image prints was similar to that in ink set 3 (Example 1). ×: The degree of chipping at the start of printing in solid image printouts was worse than in ink set 3 (Example 1).

[0213] <Rating 2: Pinhole evaluation> Prior to printing with magenta ink, the above pretreatment solution was applied to an A4-sized Futamura Chemical PET film (FE2001, 12 μm thick) using an OSG System Products 250-OSP-02 non-wire bar coater to a wet film thickness of 2.0 ± 0.2 μm. Then, the printed substrate was quickly placed in a 70°C air oven and dried for 2 minutes to produce a PET film coated and dried with the pretreatment solution. Except for preparing 10 PET films coated with the above-mentioned pretreatment solution and dried, and using them as printing substrates, 10 solid image prints were produced in succession using the same method as the solid image prints produced in the evaluation of standby ejection performance described above. Then, the number of pinholes in the obtained solid image prints was visually checked, and the pinholes were evaluated by comparing the sum of the number of pinholes in the 10 prints. The evaluation criteria were as follows, with ◎, ○, ○△, and △ being considered usable for practical purposes.

[0214] ≪Pinhole Evaluation Criteria≫ ◎: No pinholes were observed in the 10 solid image prints, or the pinholes present were less severe than those in ink set 18 (Example 15). ○: The pinholes in the solid image prints were comparable to those in ink set 18 (Example 15). ○△: Pinholes in solid image prints were worse than those in ink set 18 (Example 15), but better than those in ink set 3 (Example 1). △: The pinholes in the solid image print were comparable to those in ink set 3 (Example 1). ×: Pinholes in solid image prints were worse than those in ink set 3 (Example 1).

[0215] <Evaluation 3: Evaluation of blocking resistance> The same inkjet printing apparatus used in the above-mentioned evaluation of standby ejection performance was set up in an environment of 25°C and 50% RH. Next, magenta ink and white ink, which constitute each ink set, were filled into the conveyor from the upstream side in the conveying direction. Furthermore, an A4-sized PET film (FE2001, 12 μm thick) manufactured by Futamura Chemical Co., Ltd. was fixed on the conveyor as a printing substrate. Subsequently, the conveyor was driven at a speed of 50 m / min, and as the printing substrate passed below the inkjet head mounting area, magenta ink and white ink were ejected at a drop volume of 2 pL each to print the image. The printed substrate was then quickly placed in a 70°C air oven and dried for 3 minutes to produce the printed material. The image used above is one in which magenta ink is printed at 100% opacity, measuring 10 cm wide x 25 cm long, and then white ink is printed at 100% opacity, overlapping the area printed with magenta ink (hereinafter referred to as the "solid overlay image").

[0216] Subsequently, the resulting solid overlay image printout was cut into 4cm x 4cm squares. Similarly, the PET film used as the printing substrate (but not the one used for printing) was cut out in the same manner as the solid overlay image printout. Then, the printed side of the cut solid overlay image printout was placed opposite the unprinted side (back side) of the PET film to form a test specimen, and a blocking test was performed using a permanent strain tester. The environmental conditions for the blocking test were a load of 10kg / cm². 2 The test was conducted at a temperature of 40°C, 80% RH, and for a period of 24 hours, using a constant-load permanent strain tester manufactured by Tester Sangyo Co., Ltd. After 24 hours, the PET film was instantaneously pulled off while maintaining a 90-degree angle, and the blocking resistance was evaluated based on the degree of resistance felt during peeling and the condition of the ink layer after peeling (visual observation). The evaluation criteria were as follows, with ◎, ○, ○△, and △ indicating that the product was usable in practice.

[0217] ≪Evaluation Criteria for Blocking Resistance≫ ◎: The ink layer was not adhered to the PET film and there was no resistance when peeled off. ○: The ink layer was not adhered to the PET film, but there was a slight resistance when peeled off. ○△: Less than 5% of the total area of the ink layer was observed to be adhered to the PET film. △: 5% or more and less than 10% of the total area of the ink layer was observed to be adhered to the PET film. ×: 10% or more of the total area of the ink layer was observed to be adhered to the PET film.

[0218] <Evaluation 4: Evaluation of low migration property> The printed matter of the solid-overprint image prepared in the above Evaluation 3 was set in a migration cell (「MigraCell (registered trademark) MC60」manufactured by Gassner Glastechnik) such that the non-printed surface (PET film surface) of the printed matter was on the upper side. Then, 50 mL of 95% ethanol was added to the grooved high lid of the above migration cell. The contact area between the non-printed surface of the printed matter and 95% ethanol was 0.5 dm 2 It was. Thereafter, the above migration cell was left standing in an oven at 40 °C for 10 days, then the 95% ethanol solution was taken out and concentrated to 2 mL or less under the conditions of 40 °C and 50 mmHg. Also, when the amount of the ethanol solution after concentration was less than 2 mL, it was put into a volumetric flask with a capacity of 2 mL and filled up with 95% ethanol. Then, using the ethanol solution after concentration and filling up as a sample, a gas chromatograph mass spectrometer (「Agilent 7890A / 5975C」manufactured by Agilet Technologies), the amount (total amount) of the acetylene diol-based surfactant (A) contained per 1 mL of the ethanol solution after concentration and filling up was quantified to evaluate the low migration property. The evaluation criteria are as follows, and ◎, ○, and △ were considered to be usable in actual use.

[0219] ≪Evaluation criteria for low migration property≫ ◎: The elution amount of the acetylene diol-based surfactant (A) was 0.15 μg / mL or less. ○: The elution amount of the acetylene diol-based surfactant (A) exceeded 0.15 μg / mL and was 1.5 μg / mL or less. △: The elution amount of the acetylene diol-based surfactant (A) exceeded 1.5 μg / mL and was 4.5 μg / mL or less. ×: The elution amount of the acetylene diol-based surfactant (A) exceeded 4.5 μg / mL.

[0220] <Evaluation 5: Evaluation of laminating property> [[ID=]12] Using a solventless test coater, a solventless laminating adhesive ("EA-N373A / B" manufactured by Toyo Morton Co., Ltd.) was applied to the printed surface of the solid-overprint image printed in the above Evaluation 3 under the conditions of a temperature of 60°C and a coating speed of 50 m / min (coating amount: 2 g / m 2 ). Then, the corona-treated surface of a CPP film (FHK2, thickness 25 μm) manufactured by Futamura Chemical Co., Ltd. was overlapped with the coated surface of the laminating adhesive, and after performing an aging treatment for 1 day in an environment of 40°C and 80% RH, a laminated product was produced. Thereafter, the above laminated product was cut into test pieces with a width of 15 mm and a length of​​​​​​​​​​​​​​​As is clear from Tables 3-1 to 3-9 above, in Examples 1 to 153, which used inks that satisfy the components of the present invention, it was possible to obtain printed materials on non-absorbent printing substrates that were free of pinholes and exhibited excellent blocking resistance, lamination properties, and low migration properties, as well as good standby ejection performance.

[0223] [Example B] Next, we evaluated the influence of the crosslinking conditions of the pigment dispersion resin and other components on the quality of the water-based inkjet ink.

[0224] <Manufacturing of magenta pigment dispersions 2-7> Magenta pigment dispersions 2 to 6 (each with a pigment concentration of 14.5%) were produced using the same method and materials as in the case of magenta pigment dispersion 1, except that the proportions of magenta pigment dispersion precursor, Denacol EX-321, and ion-exchanged water used in the crosslinking reaction were changed as shown in Table 4 below. Furthermore, in the production of the magenta pigment dispersion 1 described above, without performing a crosslinking reaction, the magenta pigment dispersion precursor was adjusted to a pigment concentration of 14.5% by adding deionized water, and then filtered through a 5 μm membrane filter to produce magenta pigment dispersion 7 (pigment concentration 14.5%).

[0225] [Table 4]

[0226] Table 4 also includes information on magenta pigment dispersion 1. Furthermore, Table 4 also includes the ratio of the molar amount of functional groups (epoxy groups) in the crosslinking agent (Denacol EX-321) that can react with the pigment dispersion resin 1 to the molar amount of acid groups present in the pigment dispersion resin 1 [moles of functional groups in the crosslinking agent / moles of functional groups in the pigment dispersion resin].

[0227] <Manufacturing of White Pigment Dispersion 2> 2,500g of Typeque CR-60 (titanium dioxide, manufactured by Ishihara Sangyo Co., Ltd.), 833g of an aqueous solution of pigment dispersion resin 2, and 1,667g of deionized water were added to a mixing vessel equipped with a stirrer. After adding all the raw materials and stirring (premixing) for 1 hour, the mixture was circulated and dispersed using a 0.6L bead mill (DinoMill, manufactured by Shinmaru Enterprises) filled with 1,800g of zirconia beads with a diameter of 0.5mm. The average particle size of the mixture was then measured at regular intervals (e.g., every hour) using the aforementioned device (NanoTrac UPA-EX150, manufactured by Microtrac-Bell), and the circulating dispersion was terminated when the average particle size fell below 260nm, thereby producing a white pigment dispersion precursor. Subsequently, 1634.0 g of the white pigment dispersion precursor obtained by the method described above, 11.0 g of Denacol EX-314 (an epoxy compound manufactured by Nagase ChemteX, epoxy equivalent: 144 g / eq.), and 15.0 g of deionized water were added to a reaction vessel equipped with a stirrer. Next, the contents of the reaction vessel were heated to 80°C while stirring, and after reaching 80°C, stirring was continued for 3 hours while maintaining the temperature to carry out the crosslinking reaction. After that, the internal temperature of the reaction vessel was cooled to room temperature, and then deionized water was added to adjust the pigment concentration to 48%. After adjusting the pigment concentration, the mixture was filtered through a 5 μm membrane filter to obtain white pigment dispersion 2 (pigment concentration 48%).

[0228] In the above white pigment dispersion 2, the ratio of the molar amount of functional groups (epoxy groups) present in the crosslinking agent (Denacol EX-314) that can react with the pigment dispersion resin 2 to the molar amount of acid groups (functional groups that can react with the crosslinking agent) present in the pigment dispersion resin 2 [moles of functional groups in the crosslinking agent / moles of functional groups in the pigment dispersion resin] was 0.50.

[0229] <Manufacturing of White Pigment Dispersion 3-7> In the production of the above-mentioned white pigment dispersion liquid 2, except that the blending amounts of the white pigment dispersion liquid precursor, Denacol EX-314, and ion-exchanged water during the cross-linking reaction were changed as shown in Table 5 below, the same methods and materials as in the case of the above-mentioned white pigment dispersion liquid 2 were used to produce white pigment dispersion liquids 3 to 7 (each with a pigment concentration of 48%).

[0230]

Table 5

[0231] In addition, the white pigment dispersion liquid 2 was also described in Table 5. Table 5 also described the value of the ratio [number of moles of functional groups in the cross-linking agent / number of moles of functional groups in the pigment dispersion resin] of the number of moles of functional groups (epoxy groups) present in the cross-linking agent (Denacol EX-314) that can react with the above-mentioned pigment dispersion resin 2 to the number of moles of acid groups present in the pigment dispersion resin 2.

[0232] <Production of White Pigment Dispersion Liquids 8 to 14> Except for using titanium oxide described in Table 6 below, the same methods and materials as in the case of the above-mentioned white pigment dispersion liquid 2 were used to produce white pigment dispersion liquids 8 to 14 (each with a pigment concentration of 48%).

[0233]

Table 6

[0234] Note that Table 6 also described the type CR-60 used in the white pigment dispersion liquid 2.

[0235] <Production of White Pigment Dispersion Liquids 15 to 18> Except for using titanium oxide described in Table 7 below, the same methods and materials as in the case of the above-mentioned white pigment dispersion liquid 1 were used to produce white pigment dispersion liquids 15 to 18 (each with a pigment concentration of 48%).

[0236]

Table 7

[0237] Table 7 also lists the Typake CR-60 used in White Pigment Dispersion 1.

[0238] <Manufacturing of ink sets 165-237> Ink sets 165 to 237 were manufactured in the same manner as the manufacturing method for ink set 1 described above, except that the materials listed in each column of Tables 8-1 to 8-4 were used in the proportions listed in each column of Tables 8-1 to 8-4. In the manufacturing of each ink set, the order of mixing the materials was as follows: ion-exchanged water, water-soluble organic solvent solution, alkylene oxide-modified acetylenediol-based surfactant (A2), diluted unmodified acetylenediol-based surfactant (A1), other surfactants, aqueous binder resin solution, pigment dispersion, and other components.

[0239] [Table 8-1]

[0240] [Table 8-2]

[0241] [Table 8-3]

[0242] [Table 8-4]

[0243] Note that the unit of the blending amount in Tables 8-1 to 8-4 is "g". Also, blank spaces in Tables 8-1 to 8-4 indicate that the material is not blended. Furthermore, in Tables 8-1 to 8-4, there are cases where the value entered in the column for "Absolute value of the difference between the weighted average HLB value of acetylenediol surfactant (A) and the weighted average HLB value of water-soluble organic solvent (B)" differs from the value entered in the column for "Weighted average HLB value of acetylenediol surfactant (A)" and the value entered in the column for "Weighted average HLB value of water-soluble organic solvent (B)". This is because the values ​​entered in each of the above columns have been rounded to two decimal places.

[0244] [Examples 154-226] The ink sets prepared as described above were used to perform evaluations 1 to 5 as described above. The evaluation results are shown in Tables 8-1 to 8-4.

[0245] As is clear from the comparisons between Example 157 and Examples 160-163, Example 177 and Examples 171-176, Example 203 and Examples 197-202, etc., using a pigment dispersion resin having a crosslinked structure improved all aspects, including standby discharge performance, pinhole suppression on non-absorbent printing substrates, blocking resistance, lamination properties, and low migration properties. In particular, it was confirmed that when the ratio of the molar amount of functional groups that can react with the pigment dispersion resin to the molar amount of functional groups that can react with the crosslinking agent is 0.2-0.7 (preferably 0.3-0.6), standby discharge performance, pinhole suppression on non-absorbent printing substrates, and blocking resistance are significantly improved.

[0246] Furthermore, comparisons between Example 178 and Examples 182-188, and between Example 197 and Examples 204-210, etc., confirmed that when titanium dioxide with an oil absorption capacity of 14-20 g / 100 g (preferably 14-18 g / 100 g) and a primary particle size of 200-260 nm (preferably 200-230 nm) was used, standby discharge performance and pinhole suppression performance were improved. A similar trend was also observed when using pigment dispersion resins without a crosslinking structure (comparison between Example 157 and Examples 167-170, comparison between Example 181 and Examples 189-192).

Claims

1. A water-based inkjet ink comprising a pigment, an acetylenediol-based surfactant (A), a water-soluble organic solvent (B), a pigment dispersion resin having a cross-linked structure, a nonionic surfactant other than the acetylenediol-based surfactant (C), and water, The acetylenediol-based surfactant (A) comprises an unmodified acetylenediol-based surfactant (A1) and an alkylene oxide-modified acetylenediol-based surfactant (A2) having an HLB value of 6 to 12. The content of the unmodified acetylenediol-based surfactant (A1) is 6 to 250 ppm relative to the total amount of the aqueous inkjet ink. The content of the alkylene oxide-modified acetylenediol-based surfactant (A2) is 0.45 to 2.5% by mass relative to the total amount of the aqueous inkjet ink. The ratio of the content of the unmodified acetylenediol-based surfactant (A1) to the content of the alkylene oxide-modified acetylenediol-based surfactant (A2) [surfactant (A2) / surfactant (A1)] is in the range of 20 to 2000 by mass. The water-soluble organic solvent (B) comprises two or more water-soluble organic solvents, The absolute difference between the weighted average HLB value of the acetylenediol-based surfactant (A) and the weighted average HLB value of the water-soluble organic solvent (B) is 0 to 1.5, the weighted average boiling point of the water-soluble organic solvent (B) and water is 102 to 135°C, and the weighted average boiling point of the water-soluble organic solvent (B) is 170 to 210°C. The aforementioned crosslinked pigment dispersion resin is a reaction product of a pigment dispersion resin before crosslinking treatment and a compound that can react with functional groups present in the pigment dispersion resin before crosslinking treatment. The ratio of the molar amount of functional groups present in the compound that can react with the pigment dispersion resin before crosslinking treatment to the molar amount of functional groups present in the pigment dispersion resin before crosslinking treatment that can react with the compound [moles of functional groups in the compound / moles of functional groups in the pigment dispersion resin before crosslinking treatment] is 0.2 to 0.

7. A water-based inkjet ink in which the weighted average value of the HLB value of the acetylenediol-based surfactant (A) is divided by the weighted average value of the HLB value of the nonionic surfactant (C) is 0.6 to 1.

0.

2. The aqueous inkjet ink according to claim 1, wherein the water-soluble organic solvent (B) comprises alkanediols having 2 to 6 carbon atoms and (poly)propylene glycol monoalkyl ethers.

3. The aqueous inkjet ink according to claim 1, wherein the nonionic surfactant (C) comprises a siloxane-based surfactant and / or a polyoxyalkylene alkyl ether-based surfactant.

4. The aqueous inkjet ink according to claim 1, wherein the nonionic surfactant (C) comprises a nonionic surfactant having an HLB value of 6 to 15.

5. A printed article comprising an aqueous inkjet ink according to claim 1 or 2 printed on a printing substrate.

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