Aqueous inkjet ink and printed article

Abstract

One embodiment of the present invention relates to an aqueous inkjet ink containing a colorant, a resin, a water-soluble organic solvent, and a surfactant, wherein the Tg of the resin is 50°C-130°C, the water-soluble organic solvent contains a (di)propylene glycol monoalkyl ether-based solvent (S1) having 2-4 carbon atoms at the molecular terminal thereof, and the surfactant contains an acetylenediol-based surfactant with an HLB value of 10 or less and a siloxane-based surfactant and / or a (poly)ethylene glycol monoalkyl ether-based surfactant.

Description

Water-based inkjet inks and printed materials

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

[0002] Unlike plate-based printing methods such as offset printing and gravure printing, digital printing does not require plate-making film or printing plates, making it easier to reduce costs and handle small lots of a wide variety of products.

[0003] Inkjet printing, a type of digital printing method, ejects droplets of inkjet ink directly from extremely fine nozzles onto a printing substrate, causing them to adhere to the substrate, thereby producing characters and images (hereinafter collectively referred to as "printed matter"; the term "image" includes solid images (images with a 100% coverage rate) and seamless images such as checkerboard patterns). Inkjet printing has advantages such as low noise from the equipment used, good operability, and ease of colorization, and is therefore widely used as an output device in offices and homes. Furthermore, with the advancement of inkjet technology, inkjet printing is now also being used in industrial applications.

[0004] Traditionally, solvent inks and UV-curable inks have been used in industrial inkjet printing, but in recent years, there has been a growing demand for water-based inks due to concerns about safety, health, and the environment.

[0005] Water-based inks used in inkjet printing (hereinafter simply referred to as "inkjet inks") have traditionally been intended for use on plain paper and the like. Specifically, they contain water as the main component, and a water-soluble organic solvent such as glycerin is added to control the wetting, spreading, and drying properties of the printing substrate. When a pattern of characters or images is printed on a printing substrate using an inkjet water-based ink (hereinafter simply referred to as "aqueous inkjet ink" or "ink") made of these liquid components, the liquid components penetrate into the printing substrate and dry, thereby fixing the pattern.

[0006] On the other hand, inkjet printing substrates include not only highly permeable substrates such as plain paper, high-quality paper, and recycled paper, but also low-permeable substrates such as coated art paper and lightly coated paper, and non-permeable substrates such as film substrates. Until now, aqueous inkjet inks have been used to produce prints with practical print quality on highly permeable and low-permeable printing substrates. In contrast, when printing on film substrates, the aqueous inkjet ink droplets do not penetrate into the printing substrate at all after landing, preventing drying due to penetration. As a result, the droplets coalesce, resulting in color bleeding, or solid images not being completely filled, resulting in whiteouts (a phenomenon in which areas of the printing substrate are not covered with the aqueous inkjet ink), resulting in deterioration of print quality. In particular, among the aforementioned industrial applications, there is a growing demand for expanded use in packaging applications such as label applications and flexible packaging applications. Therefore, the ability to produce prints with excellent print quality on film substrates, which are commonly used in these applications, is extremely important for the development of aqueous inkjet inks for these applications.

[0007] Furthermore, aqueous inkjet inks do not penetrate at all into non-permeable printing substrates, making it difficult to achieve sufficient adhesion. Insufficient adhesion to non-permeable substrates can result in problems such as the printed matter peeling off due to rubbing or the like, or, when the printed matter is stored in a rolled or stacked state, pressure is applied to the printed surface (the surface to which the aqueous inkjet ink is applied), causing blocking (a phenomenon in which, when peeling off a printing substrate or the like stuck to the printed surface, part of the dried aqueous inkjet ink film (ink film) is taken up by the printing substrate). Various methods have been investigated to address these problems (Patent Documents 1 to 3).

[0008] JP 2022-85548 A JP 2020-100851 A JP 2022-102163 A

[0009] Among these, a commonly known method for improving adhesion to a printing substrate is to add a resin with binder function to an aqueous inkjet ink. This effect is due to chemical bonding forces, such as hydrogen bonding and / or intermolecular interactions, between anionic groups in the resin and functional groups present on the surface of the printing substrate. In particular, by incorporating a certain amount or more of a resin with binder function and using such a resin with a high glass transition temperature (Tg), the ink film becomes stronger, making it possible to obtain printed matter with excellent adhesion, abrasion resistance, blocking resistance, etc.

[0010] For example, Patent Document 1 discloses a white ink composition using an acrylic resin having an acid value of 50.0 to 100.0 mgKOH / g and a glass transition temperature of 20.0 to 50.0°C as a fixing resin. It also states that the use of this white ink composition enables the production of printed matter with excellent blocking resistance. However, Patent Document 1 does not evaluate the ejection stability of the white ink composition, and follow-up tests by the present inventors have found that stable ejection is difficult depending on the ejection conditions. Furthermore, in terms of imparting particularly excellent blocking resistance to printed matter, the above-mentioned white ink composition, in which the acrylic resin contained therein has a glass transition temperature of at most 50.0°C, is not necessarily sufficient.

[0011] On the other hand, a method for improving solid filling is known in which a surfactant is blended into the aqueous inkjet ink. In this case, after droplets of the aqueous inkjet ink land on a printing substrate, the surfactant quickly orients itself on the surface of the droplets, reducing the surface tension of the ink and promoting wetting of the ink onto the printing substrate, thereby improving solid filling.

[0012] However, if the surfactant remains and localizes on the surface of the ink film, there is a risk that it will peel off from that area, causing blocking.

[0013] Patent Document 2 discloses an inkjet water-based magenta ink that uses a water-soluble organic solvent having a low surface tension and a hydroxyl group, an HLB value of 2.0 to 8.0, and a surfactant having an HLB value of 1.5 to 8.0, in combination with an azo pigment. More specifically, in the examples of Patent Document 2, an aqueous magenta ink is disclosed that contains a water-soluble resin with a glass transition temperature of 107°C, 1,2-hexanediol, an acetylene diol surfactant, a polyether-modified siloxane surfactant, and the like, and is said to produce printed matter that is free of whiteout and color bleeding. However, when the present inventors conducted an evaluation, they found that the water-based magenta ink disclosed in Patent Document 2 exhibited improvements in solid filling, etc., but had poor blocking resistance.

[0014] Furthermore, Patent Document 3 discloses a water-based ink for inkjet printing that contains polyethylene wax, 1,2-propanediol, a specific glycol monoether, and water, and specifies the weighted average boiling point and blending amount of the organic solvent. In the examples of Patent Document 3, it is stated that an acetylene diol surfactant (Surfynol 104) is further blended, and that this ink has excellent ejection stability and image fastness. However, Patent Document 3 does not take into consideration solid filling, and it can be said that the investigation is insufficient.

[0015] As described above, there has not been a water-based inkjet ink that achieves both ejection stability and solid coverage in printed matter, and that can produce printed matter that also has excellent blocking resistance.

[0016] Therefore, an object of one embodiment of the present invention is to provide an aqueous inkjet ink that is excellent in ejection stability and that can produce printed matter that is excellent in solid filling and blocking resistance.Another embodiment of the present invention is to provide a printed matter that is excellent in solid filling and blocking resistance.

[0017] As a result of extensive research, the present inventors have found that the aqueous inkjet ink described below can simultaneously solve all of the above-mentioned problems to a high degree.

[0018] That is, one embodiment of the present invention relates to an aqueous inkjet ink containing a colorant, a resin, a water-soluble organic solvent, and a surfactant, wherein the resin has a Tg of 50 to 130°C, the water-soluble organic solvent contains a (di)propylene glycol monoalkyl ether-based solvent (S1) represented by the following general formula 1, and the surfactant contains an acetylene diol-based surfactant having an HLB value of 10 or less, and a siloxane-based surfactant and / or a (poly)ethylene glycol monoalkyl ether-based surfactant. １ -(O-CH(CH ３ )-CH ２ ) ｎ -OH (in general formula 1, R １ represents an alkyl group having 2 to 4 carbon atoms, and n is 1 or 2. Another embodiment of the present invention relates to a printed matter obtained by printing the above-mentioned aqueous inkjet ink on a printing substrate.

[0019] The aqueous inkjet ink according to one embodiment of the present invention has the effect of providing a printed matter having excellent ejection stability, solid filling, and blocking resistance. In another embodiment of the present invention, the aqueous inkjet ink according to the present invention has the effect of providing a printed matter having excellent solid filling and blocking resistance.

[0020]

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

[0021] <Aqueous Inkjet Ink> The aqueous inkjet ink of this embodiment can produce printed matter with excellent ejection stability, solid ink coverage, and blocking resistance. While the reasons for this are unclear, the inventors speculate as follows. However, the present invention is not limited by this speculation. As described above, adding a resin with binder function to an aqueous inkjet ink generally improves adhesion to a printing substrate. Furthermore, by incorporating a certain amount or more of a resin with binder function into the aqueous inkjet ink and using the resin with a high glass transition temperature (Tg), the ink film becomes stronger, making it possible to produce printed matter with excellent adhesion, abrasion resistance, blocking resistance, and the like. Furthermore, the more the resin forms a film, the more the adhesion, abrasion resistance, and blocking resistance are improved. Therefore, the aqueous inkjet ink of this embodiment uses a resin with a glass transition temperature of 50 to 130°C. By using a resin with a glass transition temperature within the above range, the ink film is less likely to deform and blocking can be prevented, even when, for example, the printed matter is stored in a rolled state and high pressure is applied to the printed surface for a long period of time.

[0022] However, resins with high glass transition temperatures also have high minimum film-forming temperatures (the minimum temperature at which a uniform and continuous film is formed when a solution containing the resin is applied to a substrate and then dried). As a result, aqueous inkjet inks containing such resins have the problem of poor film-forming properties after landing on a printing substrate. An ink film formed without sufficient film formation cannot exhibit sufficient film strength and also has reduced blocking resistance, etc.

[0023] In such cases, a coalescence aid is generally used as a means of improving film-forming properties. For example, dipropylene glycol monomethyl ether is a material that is often used in aqueous inkjet inks because it has high water solubility, a low boiling point (190°C at 1 atmospheric pressure), and a strong function as a coalescence aid. However, high water solubility means poor affinity for resins, and therefore dipropylene glycol monomethyl ether has the problem of poor compatibility with some resins used. This poor compatibility is thought to be due in part to the fact that the terminal structure of dipropylene glycol monomethyl ether is a methyl group, which has little effect as a hydrophobic group.

[0024] As a result of intensive research, the present inventors have found (di)propylene glycol monoalkyl ether solvents (S1) having an alkyl group having 2 to 4 carbon atoms, which are represented by general formula 1. Compared with dipropylene glycol monomethyl ether and the like, these compounds have high compatibility with resins and also have moderately high water solubility, so when used in aqueous inkjet inks, they function favorably as film-forming aids and can improve the film-forming properties of resins.

[0025] On the other hand, if the film-forming properties are enhanced, the aqueous inkjet ink may dry and form a film near the nozzles of the inkjet head, even at room temperature, which may cause ejection defects.

[0026] In contrast, in an embodiment of the present invention, the above problem is solved by further using an acetylenic diol surfactant having an HLB value of 10 or less in combination. While the detailed mechanism is unknown, it is believed that the acetylenic diol surfactant has a high affinity for the solvent (S1), and therefore the acetylenic diol surfactant suppresses the function of the solvent (S1) within the inkjet head. On the other hand, after droplets of the aqueous inkjet ink land on a printing substrate, as described below, the acetylenic diol surfactant having an HLB value of 10 or less quickly orients to the droplet surface (air-liquid interface), thereby reducing components that inhibit the function of the solvent (S1), and the solvent (S1) effectively functions as a film-forming aid. In this way, by using a (di)propylene glycol monoalkyl ether solvent (S1) in combination with an acetylenic diol surfactant having an HLB value of 10 or less, it is possible to achieve both film-forming properties and ejection stability, even when a resin with a high glass transition temperature is used.

[0027] On the other hand, to obtain a printed material with good solid coverage, the aqueous inkjet ink must quickly wet and spread on the printing substrate. To achieve this, as described above, a common method is to incorporate a surfactant into the aqueous inkjet ink to reduce the surface tension of the ink. The acetylene diol surfactants used in embodiments of the present invention generally have a small molecular weight and are effective in significantly reducing surface tension. In particular, acetylene diol surfactants with an HLB value of 10 or less are effective in wetting and spreading the aqueous inkjet ink because they orient extremely quickly on the droplet surface. However, the acetylene diol surfactants with an HLB value of 10 or less have a low HLB value and low solubility in water. Therefore, acetylene diol surfactants with an HLB value of 10 or less may localize at the nozzle end surface of the inkjet head, destabilizing the gas-liquid interface and potentially resulting in ejection defects.

[0028] Therefore, the aqueous inkjet ink of this embodiment further contains a siloxane-based surfactant and / or a (poly)ethylene glycol monoalkyl ether-based surfactant in addition to the acetylenic diol-based surfactant having an HLB value of 10 or less. It is believed that the combined use of an acetylenic diol-based surfactant having an HLB value of 10 or less and a siloxane-based surfactant and / or a (poly)ethylene glycol monoalkyl ether-based surfactant makes the two surfactants compatible with each other, allowing both to exist stably in the aqueous inkjet ink. As a result, the surfactants are prevented from localizing at the gas-liquid interface at the nozzle end surface, improving ejection stability. Furthermore, after the aqueous inkjet ink lands on a printing substrate, the siloxane-based surfactant and / or the (poly)ethylene glycol monoalkyl ether-based surfactant also contribute to the orientation of the droplets on the surface and a reduction in the ink's surface tension, further promoting wetting and spreading on the printing substrate and resulting in a printed product with good solid coverage.

[0029] On the other hand, these surfactants remain on the surface of the ink film after drying. In particular, if localized areas of the surfactant are formed on the surface of the ink film, there are problems such as low cohesive strength and the localized areas of the surfactant peeling off from the printing substrate when the rolled-up printed matter is unfolded for post-processing, resulting in blocking.

[0030] In contrast, in an embodiment of the present invention, the presence of the (di)propylene glycol monoalkyl ether solvent (S1) represented by general formula 1, which has properties of both hydrophilic and hydrophobic groups, makes it easier for surfactants, such as acetylene diol surfactants having an HLB value of 10 or less, to be compatible with other materials such as water. That is, in the aqueous inkjet ink of this embodiment, the solvent (S1) is thought to function to improve the film-forming properties of the resin as described above, as well as to make the surfactant compatible. As a result, the surfactant is no longer excessively localized on the surface of the ink film, making it possible to improve blocking resistance.

[0031] As described above, the aqueous inkjet ink according to one embodiment of the present invention has excellent ejection stability and can produce printed matter with good solid coverage. Furthermore, it is possible to suppress blocking due to localized surfactants and insufficient film formation of resins with glass transition temperatures of 50 to 130°C.

[0032] Next, each component contained in the aqueous inkjet ink of this embodiment will be described in detail below.

[0033] <Colorant> The aqueous inkjet ink of this embodiment contains a colorant. In addition, it is preferable that the colorant contains a pigment, as this will result in a printed matter with high density or hiding power and excellent light resistance, water resistance, etc.

[0034] <<Pigment>> As the pigment, any conventionally known organic or inorganic pigment can be used, and for example, pigments represented by the following color index names can be used. That is, as red pigments, C.I. Pigment Red 52, 5, 7, 9, 12, 17, 22, 23, 31, 48:1, 48:2, 48:3, 48:4, 49:1, 49:2, 57:1, 57:2, 112, 122, 123, 146, 147, 149, 150, 166, 168, 170, 171, 175, 176, 177, 178, 184, 185, 188, 202, 207, 209, 254, 255, 260, 264, 266, 269, 282; as violet pigments, C.I. As orange pigments, C.I. Pigment Violet 19, 23, 29, 32, 36, 37, 42, 50; as orange pigments, C.I. Pigment Orange 1, 2, 3, 5, 7, 13, 14, 15, 16, 22, 34, 36, 38, 40, 43, 47, 48, 49, 51, 52, 53, 60, 61, 62, 64, 65, 66, 69, 71, 73; as blue pigments, C.I. Pigment Blue 15, 15:3, 15:4, 15:6, 16, 60, 64, 79; as green pigments, C.I. Pigment Green 7, 10, 36, 48; as yellow pigments, C.I. C.I. Pigment Yellow 1, 2, 3, 5, 12, 13, 14, 16, 17, 24, 73, 74, 83, 87, 93, 94, 95, 97, 98, 109, 110, 111, 112, 120, 126, 127, 128, 129, 137, 138, 139, 147, 150, 151, 154, 155, 166, 167, 168, 170, 180, 185, 213; black pigments include C.I. Pigment Black 1, 7, 11; and white pigments include C.I. Pigment White 4, 5, 6, 21, etc. These pigments may be used alone or in combination of two or more. A solid solution of two or more of the pigments listed above may also be used as a pigment.

[0035] In one embodiment, the aqueous inkjet ink preferably contains as a colorant a white pigment (preferably C.I. Pigment White 6). Although the detailed reason is unknown, when a white aqueous inkjet ink (aqueous white ink) containing a white pigment (preferably C.I. Pigment White 6) is the aqueous inkjet ink of this embodiment described above, the ejection stability and blocking resistance of the printed matter become particularly excellent.

[0036] The content of the pigment contained in the aqueous inkjet ink of this embodiment is adjusted depending on the intended use of the printed matter produced using the aqueous inkjet ink, but is preferably 0.5 to 30 mass% of the total amount of the aqueous inkjet ink. In the case of an aqueous white ink, the content of the pigment is more preferably 1 to 15 mass%, and particularly preferably 1.5 to 10 mass%, in order to obtain a printed matter with high density without deteriorating the jetting stability of the aqueous inkjet ink. In the case of an aqueous white ink, the content of the pigment is more preferably 5 to 25 mass%, and particularly preferably 10 to 20 mass%, in order to obtain a printed matter with high hiding power without deteriorating the jetting stability of the aqueous white ink.

[0037] Resin The aqueous inkjet ink of this embodiment contains a resin.

[0038] Generally, water-soluble resins and resin microparticles are known as the forms of resins used in aqueous inkjet inks. In the aqueous inkjet ink of this embodiment, the resin contained in the aqueous inkjet ink of this embodiment may be a water-soluble resin or resin microparticles. Furthermore, a combination of a water-soluble resin and resin microparticles may be used.

[0039] In an embodiment of the present invention, a resin having a solubility of 1 g or more in 100 g of water at 25° C. is referred to as a "water-soluble resin," and a resin having a solubility of less than 1 g is referred to as a "water-insoluble resin." Furthermore, among the water-insoluble resins, a resin that is dispersed in water in the form of particles and has a volume-based median diameter (also referred to as "D50" in an embodiment of the present invention) of 10 to 1,000 nm is referred to as a "resin particle."

[0040] In the embodiment of the present invention, D50 is a value measured using a dynamic light scattering particle size distribution analyzer in an environment of 25° C. An example of the apparatus is the Nanotrac UPA-EX150 manufactured by Microtrac Bell.

[0041] Examples of resins that can be used in the aqueous inkjet ink of this embodiment include acrylic resins, styrene resins, styrene-maleic acid (anhydride) resins, olefin-maleic acid (anhydride) resins, urethane resins, polyester resins, vinyl chloride resins, vinyl chloride-vinyl acetate resins, polyolefin resins, vinyl alcohol resins, etc. These resins may be used alone or in combination of two or more.

[0042] In the embodiments of the present invention, the term "acrylic resin" refers to a resin using one or more polymerizable monomers selected from the group consisting of acrylic acid, methacrylic acid, acrylic acid esters, and methacrylic acid esters (a styrene-based monomer may also be used). Furthermore, the term "maleic acid (anhydride)" refers to at least one polymerizable monomer selected from "maleic acid" and "maleic anhydride."

[0043] The resin is used for any purpose, such as a binder or a pigment dispersion. The resin may be used for a single purpose or for multiple purposes. In the aqueous inkjet ink of this embodiment, the resin is preferably used as a binder, from the viewpoint of imparting strength and blocking resistance to printed matter. Furthermore, in order to improve ejection stability, when the aqueous inkjet ink of this embodiment contains a pigment as a colorant, it is preferable that the ink contains a resin used as a pigment dispersion in addition to the resin used as the binder, and / or that the resin used as the binder is also a resin used as a pigment dispersion (in other words, the binder resin described below also serves as a pigment dispersion resin).

[0044] In an embodiment of the present invention, "use as a binder" refers to use in an application that imparts strength (fastness) and / or adhesion to a printing substrate to an ink film. An ink film that has strength also has excellent abrasion resistance. Examples of resins used in the above binder application include resins that are the main component of ink films. The form of the resin may be a water-soluble resin or resin fine particles, but resin fine particles are preferred. Examples of resins used in pigment dispersion applications include resin particles that encapsulate a pigment and resins (which may be water-soluble resins or resin particles) that have an adsorption rate for the pigment of 35% by mass or more. As an example of a method for measuring the adsorption rate for a pigment, a pigment dispersion (or an ink containing no solids other than the resin to be evaluated) diluted with water as necessary is centrifuged until the supernatant becomes transparent (for example, a 5 mL sample is centrifuged at 80,000 rpm for 4 hours), and the amount of resin contained in the recovered supernatant is then measured (for example, the supernatant is left to stand in a 100°C environment to completely remove the liquid components, and the mass of the evaporation residue is measured and used as the resin amount).The adsorption rate can then be calculated by subtracting the amount of resin contained in the supernatant from the amount of resin (WR0 [g]) contained in the centrifuged pigment dispersion (or ink), and dividing the resulting value by WR0.

[0045]

[0033] As described above, in one embodiment, the aqueous inkjet ink preferably contains a resin used as a binder (also referred to as a "binder resin" in the embodiment of the present invention) in order to improve the strength and blocking resistance of the printed matter. When the aqueous inkjet ink of this embodiment contains a binder resin, the binder resin is preferably one or more resins selected from the group consisting of acrylic resins, urethane resins, and polyester resins, among those listed above.

[0046] The glass transition temperature (Tg) of the resin is preferably 50 to 130°C, more preferably 80 to 130°C, and particularly preferably 90 to 130°C. By using a resin having the above glass transition temperature, the strength and blocking resistance of the printed matter are improved, as described above. In an embodiment of the present invention, the glass transition temperature (Tg) may be 50.0 to 130.0°C, 80.0 to 130.0°C, or 90.0 to 130.0°C.

[0047] The glass transition temperature of a resin can be measured by a method conforming to JIS K 7121:2012. Specifically, approximately 10 mg of the target resin sample is placed in an aluminum sample pan whose mass has been measured in advance, and after the mass is measured again, the pan is sealed with a lid. Next, this sample container and a sample pan prepared without the resin are placed in a holder in a Shimadzu DSC-60 (differential scanning calorimeter), and measurements are performed at a temperature increase rate of 10°C / min to obtain a DSC chart. The intersection of the low-temperature baseline and the tangent to the inflection point of the DSC curve is then determined, and the temperature of this intersection is taken as the glass transition temperature. Indium is used for temperature calibration.

[0048] On the other hand, for acrylic resins, the value calculated by the following formula 2 can be used as the glass transition temperature.

[0049] Equation 2: 1 / Tg = Σ(Wn / Tgn)

[0050] In the above formula 2, Tg represents the glass transition temperature (K) of the resin, Wn represents the mass fraction of the structural unit formed from polymerizable monomer n contained in the resin, and Tgn represents the glass transition temperature (K) of the homopolymer of each structural unit. For the Tgn, for example, values ​​described in "Polymer Handbook (4th Edition)" (Wiley, 1998) can be used.

[0051] The acid value of the binder resin is preferably 0 to 100 mgKOH / g, more preferably 0 to 80 mgKOH / g, and particularly preferably 10 to 60 mgKOH / g. By setting the acid value within the above range, even if a portion of the aqueous inkjet ink dries in the vicinity of the nozzle of the inkjet head, a significant increase in viscosity of the aqueous inkjet ink can be suppressed, thereby making it possible to improve the ejection stability.

[0052] In an embodiment of the present invention, the "acid value of a resin" refers to the number of milligrams of potassium hydroxide (KOH) required to neutralize the acid groups contained in 1 g of the resin. In an embodiment of the present invention, the acid value is calculated by the following method. For example, if a resin has na acid groups with a value of va per molecule and contains Wa mass % of polymerizable monomers with a molecular weight of Ma among all the polymerizable monomers forming the resin, the acid value (mg KOH / g) can be calculated by the following formula 3:

[0053] Equation 3: (Acid value) = {(va × na × Wa) ÷ (100 × Ma)} × 56.11 × 1000

[0054] In the above formula 3, the number "56.11" is the molecular weight of potassium hydroxide.

[0055] From the viewpoint of obtaining an aqueous inkjet ink that is excellent in all of ejection stability, solid coverage of printed matter, and blocking resistance, the content of the binder resin contained in the aqueous inkjet ink of this embodiment is preferably 0.3 to 15 mass %, more preferably 1.0 to 14 mass %, and particularly preferably 2.0 to 13 mass %, calculated as solid content, of the total amount of the aqueous inkjet ink.

[0056] The content of the binder resin is preferably 50% by mass or more, more preferably 60% by mass or more, of the total amount of resin, from the viewpoint of imparting adhesion to the substrate and improving blocking resistance and the like.

[0057] <Pigment Dispersion Resin> When the aqueous inkjet ink of this embodiment contains a pigment as a colorant, a resin used for pigment dispersion (also referred to as a "pigment dispersion resin" in the embodiment of the present invention) can also be used. In this case, the pigment dispersion resin is preferably at least one selected from the group consisting of acrylic resins, styrene-maleic anhydride resins, and olefin-maleic anhydride resins, among those listed above.

[0058] The acid value of the pigment dispersion resin is preferably 100 to 450 mgKOH / g, more preferably 120 to 400 mgKOH / g, and particularly preferably 150 to 350 mgKOH / g. By setting the acid value within the above range, it is possible to maintain the dispersion stability of the pigment, and stable ejection from the inkjet head is possible regardless of the use conditions. Furthermore, this is also preferable in that the solubility of the pigment dispersion resin in water can be ensured and the interaction between the pigment dispersion resins can be favorable, thereby reducing the viscosity of the pigment dispersion and further improving the ejection stability from the inkjet head.

[0059] From the viewpoint of pigment dispersion stability and ejection stability, the content of the pigment dispersing resin contained in the aqueous inkjet ink of this embodiment is preferably 1 to 40 mass % and more preferably 2 to 30 mass % in terms of solid content relative to the pigment content.

[0060] <Water-soluble organic solvent> The aqueous inkjet ink of this embodiment contains a water-soluble organic solvent. As described above, the water-soluble organic solvent contains the (di)propylene glycol monoalkyl ether solvent (S1) represented by the above general formula 1. In this embodiment of the present invention, the term "water-soluble organic solvent" refers to a solvent that has a solubility of 1% by mass or more in water at 25°C and is a liquid at 25°C.

[0061] <(Di)propylene glycol monoalkyl ether solvent (S1)> The (di)propylene glycol monoalkyl ether solvent (S1) represented by the above general formula 1 has high compatibility with resins and moderate water solubility. Therefore, when used in aqueous inkjet inks, it functions favorably as a film-forming aid and can improve the film-forming properties of the resin. Furthermore, by using it in combination with an acetylenic diol surfactant having an HLB value of 10 or less, the function of the solvent (S1) is suppressed in the inkjet head, making it possible to prevent drying and film formation of the aqueous inkjet ink, as well as ejection defects. Furthermore, the presence of the solvent (S1) makes surfactants, including acetylenic diol surfactants having an HLB value of 10 or less, more compatible with other materials in the aqueous inkjet ink. As a result, the surfactant is prevented from excessively localizing on the surface of the ink film, improving blocking resistance.

[0062] Propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, and dipropylene glycol monobutyl ether can be used as the (di)propylene glycol monoalkyl ether solvent (S1) represented by the above general formula 1. These compounds may be used alone or in combination of two or more.

[0063] Here, from the viewpoint of achieving both water solubility and compatibility with resins, and ensuring affinity with an acetylene diol surfactant having an HLB value of 10 or less, the alkyl group (R １ ) preferably has 2 or 3 carbon atoms, and particularly preferably has 3 carbon atoms.

[0064] Furthermore, as the (di)propylene glycol monoalkyl ether-based solvent (S1), dipropylene glycol monoalkyl ether, i.e., a compound in which n is 2 in the above general formula 1, can be suitably used. Although the detailed reason is unknown, dipropylene glycol monoalkyl ether functions excellently as a film-forming aid, and even adding a small amount can improve the film-forming properties of the resin. Furthermore, because it has a large number of hydrophobic propylene oxide structures, it also has excellent affinity with acetylene diol-based surfactants with an HLB value of 10 or less, which results in the prevention of ejection defects and the improvement of blocking resistance of printed matter.

[0065] From the above viewpoints, it is particularly preferable that the aqueous inkjet ink of this embodiment contains dipropylene glycol monopropyl ether as the (di)propylene glycol monoalkyl ether solvent (S1). Dipropylene glycol monopropyl ether has a propyl group at the molecular end, which ensures high compatibility with resins while also ensuring the water solubility of the dipropylene glycol monopropyl ether itself. Therefore, it functions favorably as a film-forming aid, significantly improving the film-forming properties of resins. Furthermore, it can favorably assist in the compatibility of surfactants, including acetylenic diol surfactants with an HLB value of 10 or less, with other materials, thereby improving the ejection stability and blocking resistance of printed matter.

[0066] The content of the (di)propylene glycol monoalkyl ether solvent (S1) contained in the aqueous inkjet ink of this embodiment is preferably from 0.3 to 8 mass %, more preferably from 0.5 to 7 mass %, and even more preferably from 1 to 6 mass %, of the total amount of the aqueous inkjet ink.

[0067] On the other hand, as described above, the (di)propylene glycol monoalkyl ether solvent (S1) functions as a film-forming aid for resins having a glass transition temperature of 50 to 130°C, and therefore the content of the (di)propylene glycol monoalkyl ether solvent (S1) is preferably determined based on the content of the resin having a glass transition temperature of 50 to 130°C. In one embodiment, when the content by mass of the (di)propylene glycol monoalkyl ether solvent (S1) contained in the aqueous inkjet ink of this embodiment is taken as 1, the content by mass of the resin having a glass transition temperature of 50 to 130°C is preferably 0.5 to 12.5, and particularly preferably 0.7 to 5.0. By setting the content of the resin having a glass transition temperature of 50 to 130°C within the above range, the (di)propylene glycol monoalkyl ether solvent (S1) functions favorably as a film-forming aid, improving the blocking resistance and abrasion resistance of the printed matter.

[0068] <<SP value is 12 to 14 (cal / cm ３ ) １／２ The aqueous inkjet ink of this embodiment contains, in addition to the (di)propylene glycol monoalkyl ether solvent (S1), a water-soluble organic solvent (S2) having an SP value of 12 to 14 (cal / cm ３ ) １／２ In particular, the water-soluble organic solvent (S2) has an SP value of 12 to 14 (cal / cm ３ ) １／２ The water-soluble organic solvent (S2) preferably contains an alkanediol having 3 to 5 carbon atoms. Since the alkanediol having 3 to 5 carbon atoms has both hydrophilic properties due to the hydroxyl group and hydrophobic properties due to the alkylene group, it is possible to make surfactants, such as acetylene diol surfactants, having an HLB value of 10 or less, and the resins described above compatible in the aqueous inkjet ink, and it is thought that together with the (di)propylene glycol monoalkyl ether solvent (S1), it contributes to improving the ejection stability and blocking resistance.

[0069] In the embodiments of the present invention, the "SP value" is an abbreviation for "Solubility Parameter." Known methods for determining the SP value include a method of calculating it from the physical properties of a compound, a method of calculating it from the molecular structure, and a method of actually measuring it experimentally. In the embodiments of the present invention, the SP value is a value calculated by Fedor's estimation method, which is represented by the following formula 4:

[0070] Equation 4: (SP value) = (ΣEcoh / ΣV) １／２

[0071] In the above formula 4, Ecoh represents the cohesive energy determined for each functional group, and V represents the molar volume determined for each functional group. The Ecoh and V are described in R. F. Fedors, "Polymer Engineering & Science" (Vol. 14, No. 2, 1974, pp. 147-154).

[0072] SP value is 12 to 14 (cal / cm ３ ) １／２ Examples of alkanediols having 3 to 5 carbon atoms that can be suitably used as the water-soluble organic solvent (S2) include 1,2-propanediol (13.5), 1,3-propanediol (13.7), 1,2-butanediol (12.8), 1,3-butanediol (12.8), 1,4-butanediol (12.9), 2,3-butanediol (12.5), 1,2-pentanediol (12.2), 1,3-pentanediol (12.2), 1,4-pentanediol (12.2), 1,5-pentanediol (12.4), 2-methyl-1,3-propanediol (12.8), and 3-methyl-1,3-butanediol (12.6). These compounds may be used alone or in combination of two or more. The numerical values ​​in the parentheses above are the SP values ​​of each compound (unit: (cal / cm ３ ) １／２ In an embodiment of the present invention, the SP value is 12.0 to 14.0 (cal / cm ３ ) １／２ It may be.

[0073] Among these, the water-soluble organic solvent (S2) preferably contains 1,2-propanediol and / or 1,2-butanediol, and more preferably 1,2-propanediol. These water-soluble organic solvents are highly hydrophilic while not being excessively compatible with the acetylene diol surfactant, the siloxane surfactant, and / or the (poly)ethylene glycol monoalkyl ether surfactant. This prevents the surfactant from being hindered from being oriented at the gas-liquid interface, maximizing its effects and making it possible to obtain a printed matter with good solid coverage. Furthermore, since these water-soluble organic solvents volatilize quickly after landing on the printing substrate, the printed matter also has excellent blocking resistance.

[0074] In addition to alkanediols having 3 to 5 carbon atoms, there are also alkanediols having an SP value of 12 to 14 (cal / cm ３ ) １／２ Examples of the water-soluble organic solvent (S2) that can be used include diethylene glycol (13.0), triethylene glycol (12.1), and ethanol (12.6). The values ​​in the parentheses above are the SP values ​​of each compound (unit: (cal / cm ３ ) １／２ )

[0075] The SP value of the aqueous inkjet ink of this embodiment is 12 to 14 (cal / cm ３ ) １／２ The content of the water-soluble organic solvent (S2) is preferably 5 to 35% by mass, more preferably 10 to 30% by mass, and even more preferably 10 to 25% by mass, based on the total amount of the aqueous inkjet ink. ３ ) １／２ When the water-soluble organic solvent (S2) contains 1,2-propanediol, it is highly preferable that the content of 1,2-propanediol is 10 to 15 mass % of the total amount of the aqueous inkjet ink.

[0076] In addition, the SP value is 12 to 14 (cal / cm ３ ) １／２When the water-soluble organic solvent (S2) contains an alkanediol having 3 to 5 carbon atoms, the compatibility with surfactants and resins can be improved, and from the viewpoint of improving the ejection stability and blocking resistance, when the mass of the (di)propylene glycol monoalkyl ether solvent (S1) contained in the aqueous inkjet ink is taken as 1.0, the mass of the alkanediol having 3 to 5 carbon atoms contained in the aqueous inkjet ink is preferably 0.5 to 8.0, more preferably 1.0 to 7.0, and particularly preferably 2.0 to 6.0.

[0077]

[0033] In one embodiment, the aqueous inkjet ink of this embodiment preferably contains at least one solvent selected from the (di)propylene glycol monoalkyl ether-based solvents (S1) represented by the above general formula 1, and further contains at least one solvent selected from the group consisting of the (di)propylene glycol monoalkyl ether-based solvents (S1) represented by the above general formula 1 and other water-soluble organic solvents described below. For example, the aqueous inkjet ink of this embodiment preferably contains dipropylene glycol monopropyl ether as the (di)propylene glycol monoalkyl ether-based solvent (S1) represented by the above general formula 1, and further contains one or more compounds selected from the group consisting of propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, and propylene glycol monobutyl ether. Note that propylene glycol monoethyl ether, propylene glycol monopropyl ether, and propylene glycol monobutyl ether are also the (di)propylene glycol monoalkyl ether-based solvents (S1) represented by the above general formula 1. As described above, dipropylene glycol monopropyl ether has excellent film-forming properties for resins and excellent affinity with acetylene diol surfactants having an HLB value of 10 or less. On the other hand, the dipropylene glycol monopropyl ether has slightly lower hydrophilicity than other (di)propylene glycol monoalkyl ether solvents (S1). Therefore, by using the compound having a smaller molecular weight than the dipropylene glycol monopropyl ether and excellent affinity with the dipropylene glycol monopropyl ether, the ejection stability and blocking resistance of printed matter become particularly excellent.

[0078] When the aqueous inkjet ink of this embodiment contains dipropylene glycol monopropyl ether and one or more compounds selected from the group consisting of propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, and propylene glycol monobutyl ether, the mass content of the dipropylene glycol monopropyl ether is preferably 0.2 to 5.0, more preferably 0.3 to 4.0, even more preferably 0.4 to 3.0, and particularly preferably 0.5 to 2.0, relative to the total mass content of the propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, and propylene glycol monobutyl ether, which is taken as 1.0.

[0079] Other Water-Soluble Organic Solvents The aqueous inkjet ink of this embodiment contains the above-mentioned (di)propylene glycol monoalkyl ether solvent (S1) and a water-soluble organic solvent having an SP value of 12 to 14 (cal / cm ３ ) １／２ In the embodiment of the present invention, the water-soluble organic solvent (S2) may contain a water-soluble organic solvent other than the water-soluble organic solvent (S2).

[0080] In the aqueous inkjet ink of this embodiment, the other water-soluble organic solvents may include alkanediols having 6 carbon atoms; alkanetriols (provided that the number of carbon atoms is 3 to 6); polyalkylene glycols (provided that the alkylene glycol group is an ethylene glycol group (ethylene oxide group) or a propylene glycol group (propylene oxide group), and the number of oxyalkylene groups is 2 to 4); (poly)ethylene glycol monoalkyl ethers (provided that the number of ethylene glycol groups is 1 to 4, and the number of carbon atoms in the terminal alkyl group is 1 to 4), (di)propylene glycol monomethyl ether, tripropylene glycol monoalkyl ethers (provided that the terminal wherein the alkyl group has 1 to 4 carbon atoms); alkylene glycol dialkyl ethers (wherein the alkylene glycol group is an ethylene glycol group or a propylene glycol group, the alkylene glycol group has 1 to 4 carbon atoms, and the terminal alkyl groups each have 1 to 4 carbon atoms); lactams (wherein the lactam ring has 5 to 7 atoms, and an alkyl group having 1 to 2 carbon atoms, a hydroxyalkyl group having 1 to 2 carbon atoms, or a vinyl group may be bonded to a nitrogen atom and / or a carbon atom forming the lactam ring); alkanolamines (wherein the number of amino groups is 1, the number of hydroxyl groups is 1 to 3, and the number of carbon atoms is 3 to 9); and the like can be used. These other water-soluble organic solvents may be used alone or in combination of two or more.

[0081] In the embodiments of the present invention, the term "(poly)ethylene glycol" refers to ethylene glycol and polyethylene glycol.

[0082] The total content of water-soluble organic solvents contained in the aqueous inkjet ink of this embodiment is preferably 5 to 50 mass %, more preferably 9 to 40 mass %, even more preferably 12 to 35 mass %, and particularly preferably 15 to 30 mass %, of the total amount of the aqueous inkjet ink.

[0083] <Surfactant> <Acetylene diol surfactant having an HLB value of 10 or less> The aqueous inkjet ink of this embodiment contains an acetylene diol surfactant having an HLB value of 10 or less as a surfactant. From the viewpoint of the orientation speed to the droplet surface as described above, and from the viewpoint of suppressing ejection defects that may occur in the vicinity of the nozzles of an inkjet head due to drying of the aqueous inkjet ink when used in combination with the (di)propylene glycol monoalkyl ether solvent (S1), and from the viewpoint of further improving blocking resistance, the HLB value is preferably 3 to 9, and more preferably 4 to 8. In an embodiment of the present invention, the HLB value may be 10.0 or less, 3.0 to 9.0, 4.0 to 8.4, or 4.0 to 8.0. In particular, an HLB value of 10 or less (preferably 9 or less, more preferably 8 or less) allows the acetylene diol surfactant to quickly orient to the droplet surface, and therefore, after orientation, there are no components that inhibit the function of the solvent (S1), and it is believed that the solvent (S1) can fully function as a film-forming aid. As a result, even when a resin with a high glass transition temperature is used, it becomes easy to obtain a water-based inkjet ink with excellent film-forming properties.

[0084] The HLB (Hydrophile-Lipophile Balance) value in the embodiment of the present invention is one of the parameters that represent the hydrophilicity / hydrophobicity of a material. There are various methods for calculating the HLB value, such as the Griffin method, the Davis method, and the Kawakami method. In the embodiment of the present invention, the value calculated using the Griffin method is used as the HLB value of the acetylene diol surfactant.

[0085] The Griffin method uses the molecular weight of the target compound to determine the HLB value according to the following formula 5. The smaller the HLB value, the more hydrophobic the target compound is, and the larger the HLB value, the more hydrophilic the target compound is.

[0086] Equation 5: HLB value = 20 x (sum of molecular weights of hydrophilic moieties) ÷ (molecular weight of material)

[0087] Examples of the acetylene diol surfactants having an HLB value of 10 or less include 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol, hexadec-8-yne-7,10-diol, 4,7-dipropyl-dec-5-yne-4,7-diol, 6,9-dimethyl-tetradec-7-yne-6,9-diol, and 3,6-diisopropyl-2,7-dimethyloct-4-yne-3,6-diol. , octadec-9-yne-8,11-diol, 7,10-dimethylhexadec-8-yne-7,10-diol, 5,8-dibutyldodec-6-yne-5,8-diol, 4,7-diisobutyl-2,9-dimethyl-dec-5-yne-4,7-diol, 5,14-diethyl-8,11-dimethyloctadec-9-yne-8,11-diol, and ethylene oxide and / or propylene oxide modified products of the above-listed compounds. However, the above-listed compounds may be used alone or in combination of two or more. Furthermore, these compounds may be synthesized by conventionally known synthesis methods or may be commercially available products. Examples of commercially available products include Surfynol 61, 104E, 104H, 104A, 104BC, 104DPM, 104PA, 104PG-50, 420, 440, 2502, SE, SE-F, Dynol 604, 607 (manufactured by Evonik Chemical Industry Co., Ltd.), Olfine E1004, PD-001, PD-002W, PD-004 (manufactured by Nissin Chemical Industry Co., Ltd.), and the like.

[0088] Among these, it is preferable to select one or more selected from the group consisting of Surfynol 440, Surfynol 2502, Surfynol SE-F, Dynol 607, and Olfine E 1004 as the acetylenic diol surfactant having an HLB value of 10 or less, because the above-mentioned mechanism functions effectively and is effective in wetting and spreading the ink, and further because the affinity between the acetylenic diol surfactant and the water-soluble organic solvent is improved and they are compatibilized, thereby enabling the production of printed matter with good solid coverage. Furthermore, because of their high affinity with the solvent (S1) and the ability to achieve both high levels of film-forming ability and discharge stability, it is more preferable for the acetylenic diol surfactant to include Surfynol 440 and / or 2502, and it is particularly preferable for it to include Surfynol 2502. Surfynol 440 is an ethylene oxide modified product of 2,4,7,9-tetramethyl-5-decyne-4,7-diol (number of moles of ethylene oxide added: 3.5), and Surfynol 2502 is an ethylene oxide and propylene oxide modified product of 2,4,7,9-tetramethyl-5-decyne-4,7-diol (number of moles of ethylene oxide added: 5, number of moles of propylene oxide added: 2).

[0089] The content of the acetylenic diol surfactant having an HLB value of 10 or less contained in the aqueous inkjet ink of this embodiment is preferably 0.2 to 3.0 mass%, more preferably 0.3 to 2.5 mass%, and particularly preferably 0.5 to 1.5 mass%, of the total amount of the aqueous inkjet ink. Use within the above ranges makes it possible to achieve high levels of ejection stability, solid filling, and blocking resistance. In particular, when the aqueous inkjet ink of this embodiment is an aqueous white ink, the content of the acetylenic diol surfactant having an HLB value of 10 or less is preferably 0.2 to 1.5 mass%, more preferably 0.3 to 1.0 mass%, of the total amount of the aqueous white ink.

[0090] <Siloxane-Based Surfactant and / or (Poly)ethylene Glycol Monoalkyl Ether-Based Surfactant> The aqueous inkjet ink of this embodiment contains a siloxane-based surfactant and / or a (poly)ethylene glycol monoalkyl ether-based surfactant, in addition to the acetylene diol-based surfactant having an HLB value of 10 or less.

[0091] The total content of the siloxane-based surfactant and / or (poly)ethylene glycol monoalkyl ether-based surfactant contained in the aqueous inkjet ink of this embodiment is preferably 0.2 to 2.5 mass% of the total amount of the aqueous inkjet ink, more preferably 0.3 to 2.0 mass%, even more preferably 0.6 to 2.0 mass%, and particularly preferably 0.6 to 1.8 mass%, from the viewpoint of compatibility with the acetylenic diol-based surfactant having an HLB value of 10 or less. The total content may be 0.6 to 2.5 mass%, or 1.0 to 2.5 mass%. Use within the above ranges makes it possible to achieve high levels of ejection stability, solid filling, and blocking resistance. The total content of the siloxane-based surfactant and / or (poly)ethylene glycol monoalkyl ether-based surfactant refers to the total content of both surfactants when the aqueous inkjet ink contains both surfactants. When the aqueous inkjet ink contains one surfactant but not the other, it refers to the content of that one surfactant.

[0092] Furthermore, from the viewpoint of improving the ejection stability of the aqueous inkjet ink and the solid coverage of the printed area by improving the compatibility between the surfactants as described above, it is preferable to control the mass content of the siloxane-based surfactant and / or (poly)ethylene glycol monoalkyl ether-based surfactant contained in the aqueous inkjet ink, assuming that the mass content of the acetylene diol-based surfactant having an HLB value of 10 or less contained in the aqueous inkjet ink is 1. In this case, it is preferable to change this value depending on the color of the ink. Specifically, in the case of white ink, this value is preferably 1.0 to 6.0, more preferably 1.5 to 5.0, and particularly preferably 1.5 to 4.0. In the case of colored inks other than white ink, it is preferably 0.2 to 5.0, more preferably 0.3 to 4.5, and particularly preferably 0.4 to 4.0.

[0093] Examples of commercially available siloxane surfactants include BY16-201, FZ-77, FZ-2104, FZ-2110, FZ-2162, F-2123, L-7001, L-7002, SF8427, SF8428, SH3749, SH8400, 8032 ADDITIVE, SH3773M (manufactured by Dow Corning Toray Co., Ltd.), TEGO Glide 100, TEGO Glide 410, TEGO Glide 432, TEGO Glide 435, TEGO Glide 440, TEGO Glide 450, TEGO Twin 4000, TEGO Twin4100, TEGO Wet250, TEGO Wet260, TEGO Wet270, TEGO Wet280 (manufactured by Evonik), SAG-002, SAG-503A (manufactured by Nissin Chemical Industry Co., Ltd.), BYK-331, BYK-333, BYK-345, BYK-346, BYK-347, BYK-348, BYK-349, BYK-3420, BYK-UV3500, BYK-UV3510 (manufactured by BYK-Chemie), KF-3 Examples of suitable surfactants include KF-51A, KF-352A, KF-353, KF-354L, KF-355A, KF-6004, KF-6011, KF-6012, KF-6013, KF-6015, KF-6016, KF-6017, KF-6043, KF-615A, KF-640, KF-642, and KF-643 (manufactured by Shin-Etsu Chemical Co., Ltd.). These products may be used alone or in combination of two or more. Furthermore, siloxane-based surfactants synthesized by conventionally known synthesis methods may also be used.

[0094] When the aqueous inkjet ink of this embodiment contains a siloxane surfactant, it is preferable to use a side-chain polyether-modified siloxane having 4 to 12 silicon atoms and at least an ethylene oxide group as the siloxane surfactant, from the viewpoint of excellent compatibility with the acetylene diol surfactant having an HLB value of 10 or less and the solvent (S1), and improving ejection stability and blocking resistance. In general, there is a positive correlation between the molecular weight and viscosity of a siloxane surfactant. For example, a side-chain polyether-modified siloxane that can be suitably used in the aqueous inkjet ink of this embodiment has a kinematic viscosity at 25°C of 20 to 75 mm２ The kinematic viscosity can be measured, for example, by an Ubbelohde viscometer.

[0095] In addition, examples of commercially available (poly)ethylene glycol monoalkyl ether surfactants include the Emulgen series (manufactured by Kao Corporation), such as Emulgen 104P, 105, 106, 108, 109P, 120, 123P, 150, 210, 220, 306P, 320P, and 350; Brownon series (manufactured by Aoki Oil & Fat Industries Co., Ltd.) such as EL-1502, 1503P, 1505P, 1507, 1509P, 1512P, 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, etc. Examples of such nonion series (manufactured by NOF Corporation) include K-204, 220, 230, 2100W, P-208, 210, 213, E-202, 205, 212, 215, 230, S-202, 207, 215, 220, EH-204, 208, ID-203, 206, and 209; Lutensol series (manufactured by BASF) such as Lutensol XL40, 50, 60, 70, 80, 90, and XP30, 40, 50, 60, 70, 80, 90, and 140; and Newcol series (manufactured by Nippon Nyukazai Co., Ltd.) such as Newcol 2302, 2303, 2305, 2308, 2310, 2320, and 2360. The above-listed products may be used alone or in combination of two or more. The (poly)ethylene glycol monoalkyl ether surfactant may be synthesized by a conventionally known synthesis method.

[0096] In the embodiment of the present invention, the "(poly)ethylene glycol monoalkyl ether surfactant" refers to a compound in which the alkyl group at the molecular terminal has 6 or more carbon atoms.

[0097] In one embodiment, when the aqueous inkjet ink of this embodiment contains a (poly)ethylene glycol monoalkyl ether surfactant, it is preferable to use a compound having an alkyl group (which may be branched) having 8 to 13 carbon atoms at the molecular end. Although the detailed reason is unknown, (poly)ethylene glycol monoalkyl ether surfactants having an alkyl group (which may be branched) having 8 to 13 carbon atoms at the molecular end have high affinity with the acetylene diol surfactants having an HLB value of 10 or less, thereby improving the ejection stability of the aqueous inkjet ink and the solidity of the printed area. From the same perspective, it is more preferable that the alkyl group (which may be branched) at the molecular end of the (poly)ethylene glycol monoalkyl ether surfactant has 8 to 12 carbon atoms, and particularly preferably 10 to 12 carbon atoms.

[0098] Furthermore, from the viewpoint that the aqueous inkjet ink of this embodiment can be stably present in the aqueous inkjet ink, thereby improving the ejection stability, solid coverage and blocking resistance of printed matter, when the aqueous inkjet ink of this embodiment contains a (poly)ethylene glycol monoalkyl ether surfactant, the number of ethylene glycol groups (ethylene oxide groups) is preferably an integer between CE×0.8 and CE×3.5 (however, when CE×0.8 and CE×3.5 are integers, these integers are also included), more preferably an integer between CE×1.2 and CE×3.2 (however, when CE×1.2 and CE×3.2 are integers, these integers are also included), and particularly preferably an integer between CE×1.5 and CE×2.7 (however, when CE×1.5 and CE×2.7 are integers, these integers are also included).

[0099] Other Surfactants The aqueous inkjet ink of this embodiment may contain surfactants other than the surfactants described above (referred to as "other surfactants" in this embodiment of the present invention). Any conventionally known surfactant can be used as the other surfactant. Among these, nonionic surfactants are preferably used. Nonionic surfactants have good affinity with acetylene diol surfactants having an HLB value of 10 or less, as well as siloxane surfactants and / or (poly)ethylene glycol monoalkyl ether surfactants, and do not impede the improvement in ejection stability described above. Furthermore, nonionic surfactants are preferably used because they allow printed matter with excellent solid coverage and blocking resistance to be easily obtained.

[0100] As the nonionic surfactant, for example, an acetylenic diol surfactant, an acetylene monool surfactant, a fluorine-based surfactant, or the like, each having an HLB value of greater than 10, can be used. Among these, it is preferable to use an acetylenic diol surfactant having an HLB value of 10 or less, and an acetylenic diol surfactant having an HLB value of greater than 10, because these surfactants have excellent affinity with the (di)propylene glycol monoalkyl ether solvent (S1) and can provide an aqueous inkjet ink that has excellent discharge stability, solid filling of printed matter, and blocking resistance.

[0101] When an acetylene diol surfactant having an HLB value of more than 10 is used, one synthesized by a conventionally known synthesis method may be used, or a commercially available product may be used. Examples of such commercially available products include Surfynol 465 and 485 (manufactured by Evonik Corporation), Olfine E1010, E1020, EXP. 4200, and EXP. 4123 (manufactured by Nissin Chemical Industry Co., Ltd.). The compounds listed above may be used alone or in combination of two or more.

[0102] The total content of surfactants contained in the aqueous inkjet ink of this embodiment is preferably 0.4 to 5 mass %, more preferably 0.5 to 4 mass %, and particularly preferably 0.6 to 3 mass %, of the total amount of the aqueous inkjet ink. By ensuring that the total content of surfactants is within the above range, the ejection stability of the aqueous inkjet ink, as well as the blocking resistance and abrasion resistance of the printed matter, are improved.

[0103] Other Components In addition to the components described above, the aqueous inkjet ink of this embodiment may contain a pH adjuster, a preservative, a crosslinking agent, an ultraviolet absorber, an infrared absorber, etc. As each of these components, one or more conventionally known compounds may be used.

[0104] <Method for Producing Aqueous Inkjet Ink> The aqueous inkjet ink of this embodiment can be produced by a conventionally known method. For example, when a pigment is used as the colorant, the pigment is dispersed in a medium containing at least water (aqueous medium) using a pigment dispersing resin to produce a pigment dispersion. Then, water, a binder resin, a (di)propylene glycol monoalkyl ether-based solvent (S1) represented by General Formula 1, an acetylene diol-based surfactant having an HLB value of 10 or less, and a siloxane-based surfactant and / or a (poly)ethylene glycol monoalkyl ether-based surfactant are added to the pigment dispersion, followed by thorough stirring and mixing, followed by removal of coarse particles by techniques such as filtration and centrifugation. However, the method for producing the aqueous inkjet ink of this embodiment is not limited to the above-described method.

[0105] <Characteristics of Aqueous Inkjet Ink> The aqueous inkjet ink of this embodiment preferably has a viscosity at 25°C of 3 to 15 mPa·s. This viscosity range allows droplets of the aqueous inkjet ink to be stably ejected not only from inkjet heads with ejection frequencies of approximately 4 to 10 kHz, but also from inkjet heads with high ejection frequencies of approximately 20 to 70 kHz. In particular, when the viscosity of the aqueous inkjet ink of this embodiment at 25°C is 4 to 10 mPa·s, the aqueous inkjet ink can be stably ejected even when an inkjet head with a design resolution of 600 dpi or higher is used. In this embodiment of the present invention, the viscosity is measured at 25°C using a cone-plate rotational viscometer (E-type viscometer, cone angle 1°34') such as the TVE25L viscometer manufactured by Toki Sangyo Co., Ltd.

[0106] Furthermore, in order to obtain an aqueous inkjet ink that is excellent in ejection stability and solid coverage of printed matter, the aqueous inkjet ink of this embodiment preferably has a static surface tension of 18 to 35 mN / m, and particularly preferably 21 to 32 mN / m, at 25° C. In this embodiment of the present invention, the static surface tension is a value measured in an environment of 25° C. using the Wilhelmy method (plate method) with an automatic surface tensiometer such as the CBVP-Z manufactured by Kyowa Interface Science Co., Ltd.

[0107] Furthermore, when the aqueous inkjet ink of this embodiment contains a pigment as a colorant, in order to achieve both high levels of ejection stability and high levels of density or hiding power of the printed matter, the volume-based median diameter (D50) of the pigment is preferably 30 to 450 nm, more preferably 50 to 400 nm, and particularly preferably 70 to 350 nm.

[0108] <Aqueous Inkjet Ink Set> Although only one aqueous inkjet ink of this embodiment may be used alone, two or more aqueous inkjet inks may also be combined to form an aqueous inkjet ink set. Examples of such aqueous inkjet ink sets include a four-color aqueous inkjet ink set (process color ink set) consisting of a cyan aqueous inkjet ink (aqueous cyan ink), a magenta aqueous inkjet ink (aqueous magenta ink), a yellow aqueous inkjet ink (aqueous yellow ink), and a black aqueous inkjet ink (aqueous black ink); and a five-color aqueous inkjet ink set in which an aqueous white ink is added to the process color ink set. The aqueous white ink in particular exhibits significant effects on ejection stability, solid fill, and blocking resistance, and is therefore preferably used in an ink set that includes an aqueous white ink that satisfies the requirements of the embodiment of the present invention described above. Furthermore, it is more preferable that all of the aqueous inkjet inks included in the aqueous inkjet ink set satisfy the requirements of the embodiment of the present invention described above.

[0109] <Ink-Pretreatment Liquid Set> The aqueous inkjet ink of this embodiment and the aqueous inkjet ink set described above can also be used in a form combined with a pretreatment liquid containing an aggregating agent (in the form of an ink-pretreatment liquid set). By applying a pretreatment liquid containing an aggregating agent to a printing substrate before printing with the aqueous inkjet ink, it is possible to form a layer (ink aggregation layer) that intentionally aggregates the solid components contained in the aqueous inkjet ink. Then, by landing the aqueous inkjet ink on this ink aggregation layer, it is possible to prevent coalescence and color mixing of droplets of the aqueous inkjet ink and to suppress excessive wetting and spreading, thereby significantly improving the print quality of printed matter, including solid areas.

[0110] As the flocculant, for example, a water-soluble inorganic or organic salt containing a polyvalent metal ion, and a resin having a cationic group in which the cationic group equivalent is greater than the anionic group equivalent can be used.

[0111] <Inkjet Recording Method> The aqueous inkjet ink of this embodiment is used in an inkjet printing method. That is, the aqueous inkjet ink of this embodiment is ejected onto a printing substrate from an inkjet head having fine nozzles (ejecting step). In addition, the aqueous inkjet ink ejected onto the printing substrate is preferably dried by a drying mechanism (drying step).

[0112] <<Ejection Process>> In the ejection process, the inkjet head can be operated in two ways: a shuttle (scan) method in which the inkjet head is scanned back and forth in a direction perpendicular to the transport direction of the printing substrate while ejecting and recording the aqueous inkjet ink; and a single-pass method in which the inkjet ink is ejected and recording is performed as the printing substrate passes below a fixedly disposed inkjet head. The inkjet head equipped with the aqueous inkjet ink of this embodiment may be either a shuttle method or a single-pass method. Of these, the single-pass method is preferably selected because it is less likely to cause deviation in the landing position of droplets of the aqueous inkjet ink, thereby improving the print quality of the printed matter.

[0113] The method of ejection from the inkjet head can also be selected from any known methods, such as a piezoelectric method that utilizes the volume change of a piezoelectric element, a thermal method that ejects aqueous inkjet ink by bubbles generated by heating a heater, and a valve method that ejects pressurized aqueous inkjet ink by opening and closing a nozzle cover (valve) with a solenoid.

[0114] The volume of droplets of the aqueous inkjet ink ejected from the inkjet head is preferably 0.5 to 20 picoliters, and particularly preferably 0.5 to 15 picoliters, from the viewpoints of reducing drying load and improving print quality, including solid coverage. Furthermore, from the viewpoint of improving print quality, it is preferable to adjust the printing conditions (specifically, the drive frequency and number of inkjet heads installed, and the printing speed) so that the recording resolution of the printed matter is 600 dpi or higher, and it is particularly preferable to adjust the printing conditions so that the resolution is 1200 dpi or higher.

[0115] <Drying Step> Examples of drying methods employed in the drying mechanism used in the drying step include heat drying, hot air drying, infrared drying (e.g., infrared with a wavelength of 700 to 2500 nm), microwave drying, and drum drying. One or more of these methods can be selected and used as desired in the drying step. Furthermore, when two or more of the above drying methods are used, they may be used separately (e.g., consecutively) or simultaneously. For example, by using heat drying and hot air drying in combination, the ink can be dried more quickly than when each method is used alone.

[0116] In particular, from the viewpoint of preventing bumping of the liquid components in the aqueous inkjet ink and obtaining printed matter with excellent print quality, when a heat drying method is employed, it is preferable that the drying temperature be 35 to 100° C., and when a hot air drying method is employed, it is preferable that the hot air temperature be 50 to 250° C. From the same viewpoint, when an infrared drying method is employed, it is preferable that 50% or more of the integrated value of the total output of the irradiated infrared rays be in the wavelength region of 700 to 1500 nm.

[0117] <Printing Substrate> The printing substrate on which the aqueous inkjet ink of this embodiment is printed is not particularly limited, and any known substrate such as a permeable substrate, a low-permeable substrate, or a non-permeable substrate can be used.

[0118] In an embodiment of the present invention, the permeability of a printing substrate is determined by the amount of water absorption measured by a dynamic scanning absorptivity meter. Specifically, the amount of pure water absorption measured by the following method for a contact time of 100 msec is 1 g / m ２ A printing substrate with a density of less than 1 g / m is called an "impermeable substrate." ２ 6g / m or more ２ A printing substrate with a permeability of less than 6 g / m is called a "low permeability substrate." ２ A printing substrate that satisfies the above criteria is referred to as a "permeable substrate." The water absorption of a printing substrate can be measured using a dynamic scanning absorptivity meter (for example, the "KM500win" manufactured by Kumagai Riki Kogyo Co., Ltd.) set under the following conditions, using a printing substrate approximately 15 to 20 cm square as a sample, in an environment of 23°C and 50% RH. Measurement method: Spiral scanning Measurement start radius: 20 mm Measurement end radius: 60 mm Contact time: 10 to 1,000 msec Number of sampling points: 19 (measured at approximately equal intervals relative to the square root of the contact time) Scanning interval: 7 mm Rotating table speed switching angle: 86.3 degrees Headbox conditions: width 5 mm, slit width 1 mm

[0119] Examples of permeable substrates include uncoated paper such as sawdust paper, medium-grade paper, fine paper, recycled paper, and plain paper; fabrics such as cotton, synthetic fiber fabrics, silk, hemp, and nonwoven fabrics; leather; etc. Among these, uncoated paper such as sawdust paper, medium-grade paper, fine paper, and recycled paper is preferably used because it allows prints with excellent print quality to be obtained.

[0120] Examples of non-permeable substrates or low-permeable substrates include plastic substrates such as polyvinyl chloride, polyethylene terephthalate (PET), polypropylene, polyethylene, nylon, polystyrene, and polyvinyl alcohol; coated paper such as coated paper, art paper, lightly coated paper, and cast paper; metals such as aluminum, iron, stainless steel, and titanium; and glass.

[0121] The printing substrates listed above may have a smooth or uneven surface. The printing substrates may be transparent, translucent, or opaque. Furthermore, the printing substrates may be in the form of rolls or sheets. Additionally, two or more of the printing substrates listed above may be bonded together and used as the printing substrate. A release adhesive layer or the like may be provided on the side opposite the printed surface, or an adhesive layer or the like may be provided on the printed surface after printing.

[0122] It is also preferable to subject the printing surface of the printing substrates listed above to surface modification such as corona treatment or plasma treatment, since this improves the wetting and spreading properties of the aqueous inkjet ink of this embodiment, and results in a printed product with excellent print quality and drying properties, and with a uniform printed surface, which also has good abrasion resistance and adhesion to the substrate.

[0123] <Printed Matter> The printed matter of this embodiment is obtained by printing the aqueous inkjet ink of this embodiment onto a printing substrate. The printed matter of this embodiment may have a printing substrate and a printed layer formed by printing the aqueous inkjet ink, and may further have an ink aggregation layer. For example, the printed matter of this embodiment has a printing substrate and a printed layer formed on the printing substrate. Alternatively, the printed matter of this embodiment has a printing substrate, an ink aggregation layer formed on the printing substrate, and a printed layer formed on the ink aggregation layer.

[0124] <Examples of Embodiments> Embodiments of the present invention relate to, for example, aqueous inkjet inks as shown in [1] to

[11] below, and a method for producing a printed matter using the aqueous inkjet ink as shown in

[12] below. [1] An aqueous inkjet ink containing a colorant, a resin, a water-soluble organic solvent, and a surfactant, wherein the resin has a Tg of 50 to 130°C, the water-soluble organic solvent contains a (di)propylene glycol monoalkyl ether-based solvent (S1) represented by the following general formula 1, and the surfactant contains an acetylene diol-based surfactant having an HLB value of 10 or less, and a siloxane-based surfactant and / or a (poly)ethylene glycol monoalkyl ether-based surfactant. General formula 1: R １-(O-CH(CH ３ )-CH ２ ) ｎ -OH (in general formula 1, R １ is an alkyl group having 2 to 4 carbon atoms, and n is 1 or 2. [2] Furthermore, the SP value is 12 to 14 (cal / cm ３ ) １／２ [3] The aqueous inkjet ink according to [1], which contains a water-soluble organic solvent (S2) having an SP value of 12 to 14 (cal / cm ３ ) １／２The aqueous inkjet ink according to [2], wherein the water-soluble organic solvent (S2) represented by the formula (I) contains an alkanediol having 3 to 5 carbon atoms. [4] The aqueous inkjet ink according to any one of [1] to [3], wherein the (di)propylene glycol monoalkyl ether solvent (S1) contains dipropylene glycol monopropyl ether. [5] The aqueous inkjet ink according to any one of [1] to [4], wherein the content of the acetylene diol surfactant having an HLB value of 10 or less is 0.5 to 1.5% by mass in the aqueous inkjet ink. [6] The aqueous inkjet ink according to any one of [1] to [5], wherein the total content of the siloxane surfactant and / or (poly)ethylene glycol monoalkyl ether surfactant in the aqueous inkjet ink is 0.6 to 2.5% by mass. [7] The aqueous inkjet ink according to any one of [1] to [5], wherein the total content of the siloxane surfactant and / or (poly)ethylene glycol monoalkyl ether surfactant in the aqueous inkjet ink is 0.6 to 2.0% by mass. [8] The aqueous inkjet ink according to any one of [1] to [5], wherein the total content of the siloxane-based surfactant and / or (poly)ethylene glycol monoalkyl ether-based surfactant in the aqueous inkjet ink is 0.6 to 1.8% by mass. [9] The aqueous inkjet ink according to any one of [1] to [4], wherein the content of the acetylene diol-based surfactant having an HLB value of 10 or less in the aqueous inkjet ink is 0.5 to 1.5% by mass, and the total content of the siloxane-based surfactant and (poly)ethylene glycol monoalkyl ether-based surfactant in the aqueous inkjet ink is 1.0 to 2.5% by mass.

[10] The aqueous inkjet ink according to any one of [1] to [9], wherein the water-soluble organic solvent contains dipropylene glycol monopropyl ether and further contains one or more compounds selected from the group consisting of propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, and propylene glycol monobutyl ether.

[11] The aqueous inkjet ink according to any one of [1] to

[10] , wherein the ratio of the mass content of the resin having a glass transition temperature of 50 to 130°C to the mass content of the (di)propylene glycol monoalkyl ether solvent (S1) is 0.5 to 12.5.

[12] A printed matter obtained by printing the aqueous inkjet ink according to any one of [1] to

[11] on a printing substrate.

[0125] The aqueous inkjet ink according to one embodiment of the present invention can provide a printed product that has excellent discharge stability, solid filling, and blocking resistance. Furthermore, according to one embodiment of the present invention, a printed product that also has excellent abrasion resistance in addition to the above-mentioned properties can be provided. Furthermore, according to another embodiment of the present invention, a printed product that has excellent solid filling and blocking resistance can be provided.

[0126] The present invention is related to the subject matter described in Japanese Patent Application No. 2023-166390, filed on September 27, 2023, the disclosure of which is incorporated herein by reference.

[0127] The aqueous inkjet ink of this embodiment will be described in more detail below with reference to examples and comparative examples. In the following description, "parts" and "%" mean "parts by mass" and "% by mass", respectively, unless otherwise specified.

[0128] <Production Example of Resin 1> A reaction vessel equipped with a gas inlet tube, thermometer, condenser, and stirrer was charged with 72.4 parts of 2-butanone and purged with nitrogen gas. The reaction vessel was heated to 80°C, and a mixture of 10 parts of styrene, 10 parts of methacrylic acid, 25 parts of butyl acrylate, 40 parts of methyl methacrylate, and 15 parts of stearyl methacrylate as polymerizable monomers, and 4 parts of V-601 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a polymerization initiator, was added dropwise over 2 hours. After completion of the dropwise addition, the mixture was allowed to react at 80°C for 3 hours, after which 0.6 parts of V-601 was added, and the reaction was continued for another 2 hours at 80°C to obtain a solution of Resin 1. The above Resin 1 solution was cooled to 50°C, and 10.3 parts of dimethylaminoethanol was added to neutralize the carboxyl groups, followed by the addition of 140 parts of water. The mixture was then heated to 78°C or higher and azeotropically distilled with water to remove 2-butanone, and the solids content was adjusted to 30%, yielding an aqueous solution of resin 1 (solids content 30%). The mass average molecular weight of resin 1 was measured using a GPC (HLC-8120GPC, manufactured by Tosoh Corporation) equipped with a TSKgel column (manufactured by Tosoh Corporation) and an RI detector, using THF as a developing solvent, and was found to be approximately 14,000. The acid value of resin 1, calculated from the above formula 3, was 65.2 (mg KOH / g). The glass transition temperature (Tg) of resin 1, calculated from the above formula 2, was 39.7°C.

[0129] In the embodiment of the present invention, the term "aqueous solution" refers to a solution containing an aqueous medium and components dispersed and / or dissolved in the aqueous medium.

[0130] <Production Example of Resins 2 to 4> Aqueous solutions of Resins 2 to 4 (each with a solid content of 30%) were produced in the same manner as in the case of Resin 1 described above, except that the polymerizable monomers used were changed as shown in Table 1 below.

[0131]

[0132] The meanings of the abbreviations used in Table 1 above are as follows: MAA: methacrylic acid BA: butyl acrylate MMA: methyl methacrylate STMA: stearyl methacrylate St: styrene

[0133] <Production Example of Resin 5 (A-B Block Polymer)> A reaction vessel equipped with a gas inlet tube, a thermometer, a condenser, and a stirrer was charged with 20 parts of 2-butanone, 10.0 parts of methacrylic acid as an ethylenically unsaturated monomer having an acid group, and 10.0 parts of methyl methacrylate as other ethylenically unsaturated monomers as polymerizable monomers, and 0.9 parts of 2,2'-azobisisobutyronitrile and 3.6 parts of 2-(dodecylthiocarbonothioylthio)-isobutyric acid as polymerization initiators. After the atmosphere inside the reaction vessel was purged with nitrogen gas, the temperature was raised to 75°C, and a polymerization reaction was carried out for 3 hours to obtain a copolymer (A block) composed of methacrylic acid and methyl methacrylate.

[0134] After completion of the polymerization reaction, the reaction system was cooled to room temperature, and then 60 parts of 2-butanone, 55 parts of methyl methacrylate as polymerizable monomers, and 25 parts of styrene were charged into the reaction vessel. After the atmosphere inside the reaction vessel was purged with nitrogen gas, the temperature was raised to 75°C, and the polymerization reaction was carried out for 3 hours, thereby obtaining Resin 5, which has an A-B block structure in which a copolymer (block B) composed of methyl methacrylate and styrene was added to the A block.

[0135] The reaction system was then cooled to room temperature, and 10.3 parts of dimethylaminoethanol was added to the reaction vessel to neutralize the mixture. Then, 200 parts of water was added. The resulting solution was then heated, and 2-butanone was azeotroped with water to remove the 2-butanone. The solids content was then adjusted to 30% with water, yielding an aqueous solution of Resin 5. The mass average molecular weight of Resin 5, measured in the same manner as Resin 1, was approximately 15,000. The acid value of Resin 5, calculated from Equation 3 above, was 65.2 (mg KOH / g). The glass transition temperature (Tg) of Resin 5, calculated from Equation 2 above, was 106.1°C.

[0136] <Synthesis of acetylenic diol compounds 1 and 2> Acetylene diol surfactants 1 and 2 were synthesized by using the method described in Example 6 of JP 2001-215690 A and further adjusting the amounts of ethylene oxide and propylene oxide used. The structures and HLB values ​​of acetylenic diol surfactants 1 and 2 are as shown in Table 2 below. Acetylene diol surfactant 1 is a compound represented by the general formula 6 shown below, where R ２ is a methyl group, R ３ is an isobutyl group, x1+y1 is 6, x2+y2 is 1, and it is a compound in which ethylene oxide groups and propylene oxide groups are added in a random manner.

[0137] General formula 6:

[0138]

[0139] <Production Example of White Pigment Dispersion> 3,000 g of titanium oxide ("Tipake CR-60" manufactured by Ishihara Sangyo Kaisha), 300 g of Resin 6 (a random polymer of styrene / acrylic acid / behenyl methacrylate = 45 / 30 / 25 (mass ratio), in which all acid groups had been neutralized with dimethylaminoethanol, acid value 233.6 mg KOH / g, weight average molecular weight 18,000), and 2,700 g of water were charged into a mixing vessel (volume 10 L) equipped with a stirrer, and stirring (premixing) was carried out for 1 hour. Next, circulatory dispersion of the mixture was initiated using a "Dyno Mill" (volume 0.6 L) manufactured by Shinmaru Enterprises, Inc., filled with 1,800 g of zirconia beads with a diameter of 0.5 mm. Then, the D50 of the mixture was measured using the above-mentioned device at regular intervals (for example, every hour), and the circulatory dispersion was terminated when the D50 reached 240 nm or less, thereby producing a white pigment dispersion.

[0140] <Production Example of Black Pigment Dispersion> 450 g of carbon black ("PrinteX85" manufactured by Orion Engineered Carbons), 90 g of Resin 7 (a random polymer of styrene / acrylic acid / behenyl methacrylate = 45 / 25 / 30 (mass ratio), in which all acid groups had been neutralized with dimethylaminoethanol, acid value 194.6 mg KOH / g, mass average molecular weight 20,000), and 2,460 g of water were placed in a mixing vessel (volume 10 L) equipped with a stirrer and premixed for 1 hour. Next, circulatory dispersion of the mixture was initiated using a "Dyno Mill" (volume 0.6 L) manufactured by Shinmaru Enterprises, Inc., filled with 1,800 g of zirconia beads with a diameter of 0.5 mm. The D50 of the mixture was measured using the above-mentioned device at regular intervals (e.g., every hour), and the circulatory dispersion was terminated when the D50 reached 120 nm or less, thereby producing a black pigment dispersion.

[0141] <Production of Water-Based Inkjet Inks 1 to 162> Using the pigment dispersions produced by the method described above, each raw material was charged into a mixing vessel equipped with a stirrer so as to obtain the formulation shown in each column of Table 3 below. After charging, the mixture was heated to 50°C and mixed for a further hour, and then filtered through a membrane filter with a pore size of 0.8 μm to produce water-based inkjet inks 1 to 162.

[0142] When producing the aqueous inkjet ink, each raw material was added while stirring the mixture in the mixing vessel. The raw materials were added in the order listed in each column of Table 3, starting with the component listed in the top row. However, when producing an aqueous inkjet ink that did not contain one or more of these components, that component was not added, and the next component was added in the order listed. For components containing two or more raw materials, the order of addition of the raw materials within that component was arbitrary.

[0143]

[0144]

[0145]

[0146]

[0147]

[0148]

[0149]

[0150]

[0151]

[0152]

[0153]

[0154] The meanings of the abbreviations and details of the product names listed in Table 3 above are as follows: In Table 3, "SP" stands for SP value (unit: (cal / cm ３ ) １／２), "HLB" represents the HLB value, and "Tg" represents the glass transition temperature.・PnP: Propylene glycol monopropyl ether ・DPnP: Dipropylene glycol monopropyl ether ・PnB: Propylene glycol monobutyl ether ・DPnB: Dipropylene glycol monobutyl ether ・1,5-PentD: 1,5-pentanediol (SP value: 12.4) ・1,2-BD: 1,2-butanediol (SP value: 12.8) ・1,3-BD: 1,3-butanediol (SP value: 12.8) ・1,2-PD: 1,2-propanediol (SP value: 13.5) ・1,3-PD: 1,3-propanediol (SP value: 13.7) ・DEG: Diethylene glycol (SP value: 13.0) ・EtOH: Ethanol (SP value: 12.6) ・EG: Ethylene glycol (SP value: 14.8) 1,2-HexD: 1,2-hexanediol (SP value: 11.8) BDG: diethylene glycol monobutyl ether (SP value: 10.5) PGM: propylene glycol monomethyl ether (SP value: 11.3) DPM: dipropylene glycol monomethyl ether (SP value: 10.4) SF104: Surfynol 104 (acetylene diol manufactured by Evonik Japan, HLB value: 3) SF420: Surfynol 420 (acetylene diol manufactured by Evonik Japan, HLB value: 4) SF2502: Surfynol 2502 (acetylene diol manufactured by Evonik Japan, HLB value: 8) SF440: Surfynol 440 (acetylene diol manufactured by Evonik Japan, HLB value: 8.1) TW280: TEGO Wet 280 (manufactured by Evonik Japan Co., Ltd., a side-chain polyether-modified siloxane having 4 to 12 silicon atoms and at least an ethylene oxide group, kinematic viscosity at 25°C: 30 mm ２ / s) TW270: TEGO Wet 270 (manufactured by Evonik Japan Co., Ltd., a side-chain polyether-modified siloxane having 4 to 12 silicon atoms and at least an ethylene oxide group, kinematic viscosity at 25°C: 25 mm ２ / s) KF642: KF-642 (manufactured by Shin-Etsu Chemical Co., Ltd., a side-chain polyether-modified siloxane having 4 to 12 silicon atoms and at least an ethylene oxide group, kinematic viscosity at 25°C: 50 mm ２ / s) KF351A: KF-351A (manufactured by Shin-Etsu Chemical Co., Ltd., a side-chain polyether-modified siloxane having 4 to 12 silicon atoms and at least an ethylene oxide group, kinematic viscosity at 25°C: 75 mm ２ / s) BYK-3420: BYK Japan siloxane surfactant (having 4 to 12 silicon atoms and at least an ethylene oxide group, not a side chain polyether-modified siloxane, kinematic viscosity at 25°C: 125 mm ２ / s) Nonion EH-208: polyethylene glycol mono-2-ethylhexyl ether manufactured by NOF Corporation (number of carbon atoms in the alkyl group at the molecular terminal: 8, number of ethylene oxide groups: 8) Lutensol XP40: polyethylene glycol monodecyl ether manufactured by BASF Japan Ltd. (number of carbon atoms in the alkyl group at the molecular terminal: 10, number of ethylene oxide groups: 4) Lutensol XP80: polyethylene glycol monodecyl ether manufactured by BASF Japan Ltd. (number of carbon atoms in the alkyl group at the molecular terminal: 10, number of ethylene oxide groups: 8) Lutensol XP140: polyethylene glycol monodecyl ether manufactured by BASF Japan Ltd. (number of carbon atoms in the alkyl group at the molecular terminal: 10, number of ethylene oxide groups: 14) Braunon EL-1509P: polyethylene glycol monolauryl ether manufactured by Aoki Oil & Fat Industries Co., Ltd. (number of carbon atoms in the alkyl group at the molecular terminal: 12, number of ethylene oxide groups: 9) Braunon EL-1512P: polyethylene glycol monolauryl ether manufactured by Aoki Oil & Fat Co., Ltd. (number of carbon atoms in the alkyl group at the molecular terminal: 12, number of ethylene oxide groups: 12) Braunon EL-1515: polyethylene glycol monolauryl ether manufactured by Aoki Oil & Fat Co., Ltd. (number of carbon atoms in the alkyl group at the molecular terminal: 12, number of ethylene oxide groups: 15) Braunon EL-1521: polyethylene glycol monolauryl ether manufactured by Aoki Oil & Fat Co., Ltd. (number of carbon atoms in the alkyl group at the molecular terminal: 12, number of ethylene oxide groups: 21) Braunon EL-1530: polyethylene glycol monolauryl ether manufactured by Aoki Oil & Fat Co., Ltd. (number of carbon atoms in the alkyl group at the molecular terminal: 12, number of ethylene oxide groups: 30) Braunon EL-1540P: polyethylene glycol monolauryl ether manufactured by Aoki Oil & Fat Co., Ltd. (number of carbon atoms in the alkyl group at the molecular terminal: 12, number of ethylene oxide groups: 40) Newcol 2303: Polyethylene glycol monoalkyl ether surfactant manufactured by Nippon Nyukazai Co., Ltd. (number of carbon atoms in the alkyl group at the molecular terminal: 12-13, number of ethylene oxide groups: 3) Newcol 2320: Polyethylene glycol monoalkyl ether surfactant manufactured by Nippon Nyukazai Co., Ltd. (number of carbon atoms in the alkyl group at the molecular terminal: 12-13, number of ethylene oxide groups: 20)・Brawnon SR-720: Polyethylene glycol monostearyl ether manufactured by Aoki Oil Industries Co., Ltd. (number of carbon atoms in the alkyl group at the molecular terminal: 18, number of ethylene oxide groups: 20) ・Brawnon SR-730: Polyethylene glycol monostearyl ether manufactured by Aoki Oil Industries Co., Ltd. (number of carbon atoms in the alkyl group at the molecular terminal: 18, number of ethylene oxide groups: 30) ・Brawnon SR-750F: Polyethylene glycol monostearyl ether manufactured by Aoki Oil Industries Co., Ltd. (number of carbon atoms in the alkyl group at the molecular terminal: 18, number of ethylene oxide groups: 50) ・Proxel GXL: 1,2-benzisothiazol-3-one dipropylene glycol-water solution (1,2-benzisothiazol-3-one:dipropylene glycol:water = 2:6:2, preservative manufactured by Arch Chemicals)

[0155] Examples 1 to 155, Comparative Examples 1 to 7 The aqueous inkjet inks 1 to 162 were used to carry out the following evaluations 1 to 3. The evaluation results are shown in Table 4.

[0156] <Evaluation 1: Evaluation of Discharge Stability> An inkjet printing apparatus was prepared, with a Kyocera Corporation inkjet head "KJ4B-1200" (design resolution 1200 dpi, nozzle diameter 20 μm) installed above a conveyor. The inkjet head was filled with each of the above aqueous inkjet inks, and a nozzle check pattern was printed to confirm the absence of nozzle clogs (a phenomenon in which aqueous inkjet ink is not discharged from the nozzles). Next, a Futamura Chemical Co., Ltd. OPP film (FOR-AQ, thickness 20 μm) pre-cut to A4 size (width 21 cm x length 30 cm) was fixed on the conveyor as a printing substrate. The conveyor was then driven at a constant speed, and as the printing substrate passed below the installation section of the inkjet head, the aqueous inkjet ink was discharged at a drop volume of 2 pL to print a solid image. After printing the following number of solid images using the above-described method, a nozzle check pattern was printed again, and the number of nozzle clogs was visually counted to evaluate discharge stability. The evaluation criteria were as follows, with A, B, and C being deemed usable. The number of solid images printed was also evaluated in two ways: "1 sheet" and "5 sheets." However, if the ejection stability evaluation after printing one solid image was rated "D," evaluation after printing five solid images was not performed. A: No missing nozzles occurred. B: 1 to 4 missing nozzles occurred. C: 5 to 9 missing nozzles occurred. D: 10 or more missing nozzles occurred.

[0157] <Preparation of Printed Material> An inkjet printing apparatus was prepared in which a Kyocera Corporation inkjet head "KJ4B-1200" (design resolution 1200 dpi, nozzle diameter 20 μm) was installed above a conveyor, and each of the above aqueous inkjet inks was filled into the inkjet head. In addition, the same OPP film as in Evaluation 1 was fixed onto the conveyor. Thereafter, the conveyor was driven at a speed of 50 m / min, and as the above printing substrate passed below the installation section of the inkjet head, the above aqueous inkjet ink was ejected at a drop volume of 2 pL to print an image. Thereafter, the printed printing substrate was immediately placed in a constant temperature incubator with a blower set at 70°C and dried for 1 minute to produce a printed material.

[0158] The following two types of prints were produced using the above method. For each aqueous inkjet ink, the following two types of prints were produced: Solid print: a print with a coverage of 100% (width 15 cm x length 30 cm) Gradient print: a print in which a gradation image with a coverage of 5-80% was printed in an area of ​​10 cm width x 30 cm length.

[0159] <Evaluation 2: Evaluation of solid filling> For the solid prints produced by the above method, the non-printed side of the print was attached to a backing (black backing if printed with water-based white ink, white backing if printed with water-based black ink), and then the number of streaks (white streaks 1 cm or longer) was visually observed to evaluate solid filling. The evaluation criteria were as follows, with A, B, and C being usable. A: No streaks were observed B: 1 to 4 streaks were observed C: 5 to 9 streaks were observed D: 10 or more streaks were observed

[0160] <Evaluation 3: Evaluation of Blocking Resistance> The solid print produced by the method described above was cut into a 4 cm x 4 cm square, and the printed surface was then superimposed on the non-printed surface of the same printing substrate as that used for printing. This superimposed piece was then used as a test piece, and a blocking test was carried out using a constant load permanent deformation tester ("CO-201" manufactured by Tester Sangyo Co., Ltd.). The conditions for the blocking test were a load of 10 kg / cm ２ The test conditions were an ambient temperature of 40°C, an ambient humidity of 80% RH, and the standing time as shown below. After the standing time had elapsed, the test piece was removed from the constant-load permanent deformation tester, and the overlapping printing substrate was instantaneously peeled off while maintaining a 90-degree angle. Blocking resistance was evaluated based on the feel upon peeling (peel resistance) and the appearance of the printed surface after peeling (visual inspection). The evaluation criteria were as follows, with A, B, and C being deemed usable. Evaluation was also performed using two standing times during the blocking test: "24 hours" and "48 hours." However, if the blocking resistance after a 24-hour standing time was rated "D," evaluation after a 48-hour standing time was not performed. A: There was no resistance to peeling, and no part of the aqueous inkjet ink layer adhered to the non-printed surface of the printing substrate. B: There was slight resistance when peeling, but no part of the aqueous inkjet ink layer adhered to the non-printed surface of the printing substrate. C: Part of the aqueous inkjet ink layer adhered to the non-printed surface of the printing substrate, and the extent of this was 30% or less of the area of ​​the overlapping parts. D: Part of the aqueous inkjet ink layer adhered to the non-printed surface of the printing substrate, and the extent of this was more than 30% of the area of ​​the overlapping parts.

[0161]

[0162]

[0163] From Table 4, it was confirmed that the aqueous inkjet ink of this embodiment is excellent in all of ejection stability, solid filling of printed matter, and blocking resistance.

[0164] [Examples 156 to 168] Furthermore, solid prints prepared by the above-described method using the aqueous inkjet inks 6, 11, 14, 16, 18, 20, 22, 23, 25, 27, 29, 31, and 33 were subjected to Evaluation 4 shown below. The evaluation results are shown in Table 5. The contents of the resins having a glass transition temperature of 50 to 130°C and the ratios of the mass of the (di)propylene glycol monoalkyl ether solvent (S1) to the mass of the resins having a glass transition temperature of 50 to 130°C shown in Table 3 are also shown in Table 5.

[0165] <Evaluation 4: Evaluation of Abrasion Resistance> The solid prints produced by the method described above were cut into pieces measuring 30 mm wide x 220 mm long and placed in a Gakushin-type abrasion fastness tester ("AB-301" manufactured by Tester Sangyo Co., Ltd.). A test cotton cloth (black cotton cloth was used for prints produced using aqueous inkjet inks 6, 14, 16, 18, 20, 22, 23, 25, 27, and 29, and white cotton cloth was used for prints produced using aqueous inkjet inks 11, 31, and 33) was attached to a friction element (weight: 200 g). After shaking the print a predetermined number of times, the condition of the surface of the print and the degree of coloring of the cotton cloth were visually observed to evaluate abrasion resistance. The evaluation criteria were as follows, with A, B, and C being considered usable. A: Even after shaking 10 times, there were no abrasion marks on the printed surface and no discoloration on the cotton cloth. B: After shaking 6 times, there were no abrasion marks on the printed surface and no discoloration on the cotton cloth, but after shaking 10 times, there were abrasion marks on the printed surface and / or discoloration on the cotton cloth. C: After shaking 3 times, there were no abrasion marks on the printed surface and no discoloration on the cotton cloth, but after shaking 6 times, there were abrasion marks on the printed surface and / or discoloration on the cotton cloth. D: After shaking 3 times, there were abrasion marks on the printed surface and / or discoloration on the cotton cloth.

[0166]

[0167] As a result of the above evaluation 4 and evaluation 3, it was confirmed that the examples using aqueous inkjet inks in which the content of the resin having a glass transition temperature of 50 to 130°C relative to the total amount of the aqueous inkjet ink was 2.0 to 13 mass % and the ratio of the mass of the (di)propylene glycol monoalkyl ether solvent (S1) to the mass of the resin having a glass transition temperature of 50 to 130°C was 0.7 to 5.0 had good quality, with both blocking resistance and abrasion resistance being at level A.

Claims

1. An aqueous inkjet ink containing a colorant, a resin, a water-soluble organic solvent, and a surfactant, wherein the resin has a Tg of 50 to 130°C, the water-soluble organic solvent contains a (di)propylene glycol monoalkyl ether-based solvent (S1) represented by the following general formula 1, and the surfactant contains an acetylene diol-based surfactant having an HLB value of 10 or less, and a siloxane-based surfactant and / or a (poly)ethylene glycol monoalkyl ether-based surfactant. General formula 1: R １ -(O-CH(CH ３ )-CH ２ ) ｎ -OH (in general formula 1, R １ is an alkyl group having 2 to 4 carbon atoms, and n is 1 or 2.

2. Furthermore, the SP value is 12 to 14 (cal / cm ３ ) １／２ 2. The aqueous inkjet ink of claim 1, further comprising a water-soluble organic solvent (S2) which is 3. The SP value is 12 to 14 (cal / cm ３ ) １／２ The aqueous inkjet ink according to claim 2, wherein the water-soluble organic solvent (S2) is an alkanediol having 3 to 5 carbon atoms.

4. The aqueous inkjet ink according to any one of claims 1 to 3, wherein the (di)propylene glycol monoalkyl ether solvent (S1) contains dipropylene glycol monopropyl ether.

5. The aqueous inkjet ink according to any one of claims 1 to 4, wherein the content of the acetylene diol surfactant having an HLB value of 10 or less is 0.5 to 1.5 mass % in the aqueous inkjet ink.

6. The aqueous inkjet ink according to any one of claims 1 to 5, wherein the total content of the siloxane-based surfactant and / or (poly)ethylene glycol monoalkyl ether-based surfactant in the aqueous inkjet ink is 0.6 to 2.5 mass %.

7. The aqueous inkjet ink according to any one of claims 1 to 5, wherein the total content of the siloxane-based surfactant and / or (poly)ethylene glycol monoalkyl ether-based surfactant in the aqueous inkjet ink is 0.6 to 2.0% by mass.

8. The aqueous inkjet ink according to any one of claims 1 to 5, wherein the total content of the siloxane-based surfactant and / or (poly)ethylene glycol monoalkyl ether-based surfactant in the aqueous inkjet ink is 0.6 to 1.8% by mass.

9. The aqueous inkjet ink according to any one of claims 1 to 8, wherein the water-soluble organic solvent contains dipropylene glycol monopropyl ether, and further contains one or more compounds selected from the group consisting of propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, and propylene glycol monobutyl ether.

10. The aqueous inkjet ink according to any one of claims 1 to 9, wherein the ratio of the mass of the resin having a glass transition temperature of 50 to 130°C to the mass of the (di)propylene glycol monoalkyl ether solvent (S1) is 0.5 to 12.

5.

11. A printed matter comprising a printing substrate on which the aqueous inkjet ink according to any one of claims 1 to 10 is printed.

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