Aqueous inkjet ink and printed matter

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, the resin having a Tg of 50-130 DEG C, the water-soluble organic solvent containing a (di) propylene glycol monoalkyl ether-based solvent having 2-4 carbon atoms at a molecular terminal (S1), and the surfactant containing a (S2) propylene glycol monoalkyl ether-based solvent having 2-4 carbon atoms at a molecular terminal (S3). The surfactant contains an acetylene glycol-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.

Description

Technical Field

[0001] Embodiments of the present invention relate to water-based inkjet inks and printed matter made using the water-based inkjet inks. Background Technology

[0002] Digital printing differs from traditional printing methods such as offset and gravure printing. It does not require printing plates or printing films, thus making it easier to reduce costs and handle small-batch, multi-variety production.

[0003] Inkjet printing, a type of digital printing, involves ejecting droplets of ink directly from very fine nozzles onto a printing substrate, allowing them to adhere and form text and images (hereinafter collectively referred to as "printed material"). It should be noted that the term "image" includes full-page images (100% print coverage) and seamless images such as gridded images. Inkjet printing offers advantages such as low noise, ease of operation, and ease of colorization, making it widely used as a printing press in offices and homes. Furthermore, advancements in inkjet technology have led to its application in industrial settings as well.

[0004] Previously, solvent-based inks and UV-curable inks were used in industrial applications for inkjet printing. However, in recent years, the demand for water-based inks has increased due to considerations of safety, health, and the environment.

[0005] Water-based inks used in inkjet printing (hereinafter also referred to as "inkjet inks") were traditionally designed for ordinary paper. These inks are primarily water-based, with water-soluble organic solvents such as glycerin added to control the wetting and drying properties of the printing substrate. When water-based inks (hereinafter also referred to as "water-based inkjet inks," or simply "inks") composed of these liquid components are used to print text and images onto a printing substrate, the liquid components penetrate the substrate and dry, thus fixing the image.

[0006] On the other hand, inkjet printing substrates include not only highly permeable substrates such as ordinary paper, premium paper, and recycled paper, but also low-permeability substrates such as coated paper and micro-coated paper, and non-permeable substrates such as film substrates. To date, water-based inkjet inks have been used to produce prints with usable image quality on both highly permeable and low-permeability substrates. In contrast, in printing on film substrates, the water-based ink droplets do not penetrate the substrate after adhering, thus preventing drying due to penetration. As a result, issues such as droplets merging and causing color bleeding, or incomplete filling of the image resulting in white gaps (areas where the water-based inkjet ink has not adhered to the substrate) occur, leading to a deterioration in image quality. In particular, with increasing demand for expanded applications in packaging such as labeling and flexible packaging, the ability to produce prints with excellent image quality on film substrates frequently used in these applications is crucial for the expansion of water-based inkjet inks into these applications.

[0007] Furthermore, in non-permeable printing substrates, water-based inkjet inks are completely impermeable, making it difficult to achieve sufficient adhesion. Insufficient adhesion relative to the non-permeable substrate leads to problems such as: the printed material peeling off due to friction; or, when storing the printed material in a rolled or stacked state, pressure is applied to the printed surface (the surface coated with water-based inkjet ink), causing adhesion (the phenomenon where, when peeling off the printing substrate or other material adhered to the printed surface, a portion of the dried water-based inkjet ink film (ink coating) is removed from the printing substrate). Various methods have been investigated to improve these problems (Patent Documents 1-3).

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Application Publication No. 2022-85548

[0011] Patent Document 2: Japanese Patent Application Publication No. 2020-100851

[0012] Patent Document 3: Japanese Patent Application Publication No. 2022-102163 Summary of the Invention

[0013] The problem that the invention aims to solve

[0014] One known method to improve adhesion to printing substrates is to add a resin with adhesive properties to water-based inkjet inks. This effect stems from chemical bonding forces, such as hydrogen bonds and / or intermolecular interactions, between the anionic groups in the resin and functional groups present on the surface of the printing substrate. In particular, by incorporating a sufficient amount of an adhesive resin and using such a resin with a high glass transition temperature (Tg), the ink coating becomes stronger, resulting in printed materials with excellent adhesion, scratch resistance, and anti-blocking properties.

[0015] For example, Patent Document 1 discloses a white ink composition that uses an acrylic resin with an acid value of 50.0~100.0 mgKOH / g and a glass transition temperature of 20.0~50.0°C or less as the fixing resin. It also describes how this white ink composition can produce printed materials with excellent anti-blocking properties. However, Patent Document 1 does not evaluate the ejection stability of the white ink composition, and in additional tests conducted by the inventors, it became difficult to eject stably depending on the ejection conditions. Furthermore, from the perspective of imparting particularly excellent anti-blocking properties to printed materials, the aforementioned white ink composition, with a maximum glass transition temperature of 50.0°C for the contained acrylic resin, may not be considered sufficient.

[0016] On the other hand, as a method to improve full-page filling performance, it is known to incorporate surfactants into water-based inkjet inks. In this case, after the droplets of water-based inkjet ink land on the printing substrate, the surfactant rapidly orients on the surface of the droplets, thereby reducing the surface tension of the ink, promoting wetting of the printing substrate, and improving full-page filling performance.

[0017] However, if surfactant residue remains on the surface of the ink coating and becomes locally present, it is possible to peel off from that part and cause adhesion.

[0018] Patent Document 2 discloses an inkjet water-based magenta ink that combines a water-soluble organic solvent with an HLB value of 2.0 to 8.0, low surface tension, and hydroxyl groups, and a surfactant with an HLB value of 1.5 to 8.0 with an azo pigment. More specifically, in the embodiments of Patent Document 2, an water-based magenta ink containing a water-soluble resin with a glass transition temperature of 107°C, 1,2-hexanediol, ethynylene glycol-based surfactants, and polyether-modified siloxane-based surfactants is disclosed, which can produce printed materials without white gaps and color bleeding. However, the inventors evaluated the ink and determined that, although improvements in full-page filling properties were observed with the water-based magenta ink disclosed in Patent Document 2, its anti-blocking properties were poor.

[0019] Furthermore, Patent Document 3 discloses a water-based inkjet recording ink containing polyethylene wax, 1,2-propanediol, a specific diol monoether, and water, specifying the weighted average boiling point and proportion of the organic solvents. In the embodiments of Patent Document 3, it is described that a acetylene glycol-based surfactant (Surfynol 104) is further incorporated, resulting in excellent inkjet stability and image durability. However, Patent Document 3 does not consider full-page embedding properties, indicating insufficient research.

[0020] As mentioned above, water-based inkjet inks that balance ejection stability and full-page filling properties in the printed material, thereby achieving excellent anti-blocking properties, are a situation that has not existed until now.

[0021] Therefore, one embodiment of the present invention aims to provide a water-based inkjet ink with excellent ejection stability, enabling the production of printed materials with excellent full-page filling and anti-blocking properties. Another embodiment of the present invention aims to provide printed materials with excellent full-page filling and anti-blocking properties.

[0022] Methods for solving problems

[0023] The inventors conducted in-depth research and found that the water-based inkjet ink described below can solve all the above-mentioned problems simultaneously and to a high degree.

[0024] 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 comprises a (di)propylene glycol monoalkyl ether solvent (S1) as shown in general formula 1, and the surfactant comprises an acetylene glycol surfactant with an HLB value of less than 10, as well as a siloxane surfactant and / or a (poly)ethylene glycol monoalkyl ether surfactant.

[0025] General Formula 1:

[0026] R 1 -(O-CH(CH3)-CH2) n -OH

[0027] (In general formula 1, R) 1 (It is an alkyl group with 2 to 4 carbon atoms, where n is 1 or 2.)

[0028] Another embodiment of the present invention relates to a printed matter formed by printing the above-mentioned water-based inkjet ink onto a printing substrate.

[0029] Invention Effects

[0030] As one embodiment of the present invention, the water-based inkjet ink exhibits the following effects: excellent ejection stability, resulting in printed materials with excellent full-page coverage and anti-blocking properties. Furthermore, in another embodiment of the present invention, it also exhibits the effect of obtaining printed materials with excellent full-page coverage and anti-blocking properties. Detailed Implementation

[0031] Hereinafter, a water-based inkjet ink (hereinafter referred to as "water-based inkjet ink of this embodiment" or "water-based inkjet ink") and a printed matter (hereinafter referred to as "printed matter of this embodiment") as one embodiment of the present invention will be described. It should be noted that the present invention is not limited to the embodiments described below, and includes variations that can be implemented without changing the essential parts of the present invention.

[0032] Water-based inkjet inks

[0033] The water-based inkjet ink according to this embodiment exhibits excellent ejection stability, resulting in printed materials with excellent full-page filling and anti-blocking properties. While the reason for this is not clearly defined, the inventors speculate as follows. However, the present invention is not limited to the following speculation.

[0034] As described above, adhesion to the printing substrate is typically improved by adding a resin with adhesive properties to water-based inkjet inks. Furthermore, by incorporating a resin with adhesive properties in a sufficient amount into the water-based inkjet ink, and using a resin with a high glass transition temperature (Tg), the ink film becomes more robust, resulting in printed materials with excellent adhesion, scratch resistance, and anti-blocking properties. Moreover, the more fully the resin forms a film, the better the adhesion, scratch resistance, and anti-blocking properties are further improved. Therefore, in the water-based inkjet ink of this embodiment, a resin with a glass transition temperature of 50 to 130°C is used. By using a resin with a glass transition temperature within this range, for example, even when the printed material is stored in a wound state and high pressure is applied to the printed surface for a long time, the ink film is less prone to deformation, preventing adhesion.

[0035] 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 resin-containing solution is applied to a substrate and allowed to dry). As a result, water-based inkjet inks containing this resin exhibit poor film-forming properties after being applied to the printing substrate. Ink films formed due to insufficient film formation cannot exhibit adequate film strength, and their resistance to tack is also reduced.

[0036] In such cases, film-forming aids are typically used to improve film-forming properties. For example, dipropylene glycol monomethyl ether (DMGE) is frequently used in water-based inkjet inks due to its high water solubility, low boiling point (190°C at 1 atmosphere), and strong film-forming ability. However, high water solubility implies poor resin affinity, resulting in inconsistent compatibility depending on the resin used. This poor compatibility is attributed to the fact that the terminal methyl group of DMGE has a relatively small effect as a hydrophobic group.

[0037] Therefore, the inventors conducted in-depth research and discovered (S1) dipropylene glycol monoalkyl ether solvents having 2 to 4 carbon atoms, as shown in Formula 1. Compared with dipropylene glycol monomethyl ether, these compounds have high compatibility with resins and moderately high water solubility. Therefore, when used in water-based inkjet inks, they can function appropriately as film-forming aids and improve the film-forming properties of the resin.

[0038] On the other hand, if film-forming properties are improved, for example, water-based inkjet inks will dry and form a film near the nozzle of the printhead even at room temperature, which may cause poor ejection.

[0039] In this embodiment of the invention, the aforementioned problem is solved by further using an acetylenediol-based surfactant with an HLB value of 10 or less. The detailed mechanism is not yet clear, but it is believed that due to the high affinity of the acetylenediol-based surfactant for the solvent (S1), the functional performance of the solvent (S1) is suppressed within the inkjet head by this acetylenediol-based surfactant. On the other hand, it is believed that after the droplets of water-based inkjet ink land on the printing substrate, as described later, the acetylenediol-based surfactant with an HLB value of 10 or less rapidly orients on the droplet surface (gas-liquid interface), thus reducing the components that hinder the functional performance of the solvent (S1), and the solvent (S1) effectively functions as a film-forming aid. Thus, by using a (di)propylene glycol monoalkyl ether solvent (S1) and an acetylenediol-based surfactant with an HLB value of 10 or less, film-forming properties and ejection stability can be balanced even when using resins with high glass transition temperatures.

[0040] On the other hand, to obtain prints with good full-page coverage, water-based inkjet inks need to rapidly wet and spread on the printing substrate. Therefore, as mentioned above, a common method is to incorporate surfactants into the water-based inkjet ink to reduce its surface tension. The acetylenic glycol-based surfactants used in the embodiments of the present invention typically have small molecular weights and a significant effect in reducing surface tension. In particular, acetylenic glycol-based surfactants with an HLB value of 10 or less exhibit extremely rapid orientation on the droplet surface, thus being effective for the wetting and spreading of water-based inkjet inks. However, these acetylenic glycol-based surfactants with an HLB value of 10 or less have low HLB values ​​and low solubility in water. Therefore, at the nozzle end face of the inkjet head, these acetylenic glycol-based surfactants with an HLB value of 10 or less are locally present, destabilizing the gas-liquid interface, and thus, poor ejection may still occur.

[0041] Therefore, the water-based inkjet ink of this embodiment further includes, in addition to the acetylene glycol-based surfactant with an HLB value of 10 or less, a siloxane-based surfactant and / or a (poly) glycol monoalkyl ether-based surfactant. It is believed that by using both the acetylene glycol-based surfactant with an HLB value of 10 or less and the siloxane-based surfactant and / or the (poly) glycol monoalkyl ether-based surfactant, the two surfactants are compatible with each other and can both exist stably in the water-based inkjet ink. As a result, the surfactants do not exist locally at the gas-liquid interface of the nozzle end face, thus improving ejection stability. Furthermore, after the water-based inkjet ink settles on the printing substrate, the siloxane-based surfactant and / or the (poly) glycol monoalkyl ether-based surfactant also contribute to the orientation of the droplets on the surface and reduce the surface tension of the ink, thereby further promoting wetting and spreading on the printing substrate, resulting in printed materials with good full-page filling properties.

[0042] On the other hand, these surfactants also remain on the surface of the dried ink coating. In particular, if areas with localized surfactant presence are formed on the ink coating surface, for example, when the printed material is unwound from its rolled state for post-processing, there is a problem of low cohesion, peeling of the surfactant-containing areas from the printing substrate, and adhesion.

[0043] In this regard, in the embodiments of the present invention, due to the presence of the (di)propylene glycol monoalkyl ether solvent (S1) of general formula 1, which has both hydrophilic and hydrophobic properties, surfactants, represented by acetylene glycol surfactants with an HLB value of 10 or less, are readily compatible with water and other materials. That is, in the water-based inkjet ink of this embodiment, the solvent (S1) is considered to not only improve the film-forming properties of the resin as described above, but also to facilitate surfactant compatibility. As a result, the surfactant does not excessively and locally exist on the surface of the ink coating, thus improving adhesion resistance.

[0044] As described above, the water-based inkjet ink, as one embodiment of the present invention, exhibits excellent ejection stability and can also produce printed materials with good full-page filling properties. Furthermore, it can suppress adhesion caused by insufficient film formation due to locally present surfactants and resins with a glass transition temperature of 50-130°C.

[0045] Next, the components contained in the water-based inkjet ink of this embodiment will be described in detail below.

[0046] <Coloring agent>

[0047] The water-based inkjet ink of this embodiment contains a colorant. Furthermore, from the viewpoint of obtaining printed materials with high concentration or opacity, excellent lightfastness, and water resistance, it is preferable to include a pigment as the colorant.

[0048] "pigment"

[0049] As the aforementioned pigments, any known organic and inorganic pigments may be used, such as the pigments indicated by the color index names below.

[0050] That is, as red pigments, there are CI Pigment Reds 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;

[0051] As a purple pigment, there are CI pigments purple 19, 23, 29, 32, 36, 37, 42, and 50;

[0052] As an orange pigment, there are CI Pigment Orange 1, 2, 3, 5, 7, 13, 14, 15, 16, 22, 34, 36, 38, 40, 43, 47, 48, 49, 51, 52, 53, 60, 61, 62, 64, 65, 66, 69, 71, 73;

[0053] As a blue pigment, there are CI Pigment Blue 15, 15:3, 15:4, 15:6, 16, 60, 64, and 79;

[0054] As green pigments, there are CI pigments Green 7, 10, 36, and 48;

[0055] As yellow pigments, there are CI Pigment Yellow 1, 2, 3, 5, 12, 13, 14, 16, 17, 24, 73, 74, 83, 87, 93, 94, 95, 97, 98, 109, 110, 111, 112, 120, 126, 127, 128, 129, 137, 138, 139, 147, 150, 151, 154, 155, 166, 167, 168, 170, 180, 185, 213;

[0056] As black pigments, there are CI Pigment Black 1, 7, and 11; and

[0057] As white pigments, there are CI pigments white 4, 5, 6, 21, etc.

[0058] These pigments can be used alone or in combination with two or more. Alternatively, a solid solution consisting of two or more of the pigments listed above can also be used as a pigment.

[0059] In one embodiment, the water-based inkjet ink preferably contains a white pigment (preferably CI Pigment White 6) as a colorant. The detailed reasons are not yet clear, but by making the white water-based inkjet ink (water-based white ink) containing a white pigment (preferably CI Pigment White 6) the water-based inkjet ink of this embodiment described above, the ejection stability and the resistance to tackiness of the printed material become particularly excellent.

[0060] The pigment content in the water-based inkjet ink of this embodiment is adjusted according to the intended use of the printed matter produced using the water-based inkjet ink. For example, it is preferably 0.5 to 30% by mass in the total amount of water-based inkjet ink. Furthermore, except for water-based white inks, from the viewpoint of obtaining printed matter with high concentration without deteriorating the ejection stability of the water-based inkjet ink, the pigment content is more preferably 1 to 15% by mass, and particularly preferably 1.5 to 10% by mass. On the other hand, in the case of water-based white inks, from the viewpoint of obtaining printed matter with high concealment without deteriorating the ejection stability of the water-based white ink, the pigment content is more preferably 5 to 25% by mass, and particularly preferably 10 to 20% by mass.

[0061] <Resin>

[0062] The water-based inkjet ink of this embodiment contains a resin.

[0063] Typically, water-soluble resins and resin microparticles are known forms of resins used in water-based inkjet inks. In the water-based inkjet ink of this embodiment, the resin contained in the water-based inkjet ink of this embodiment can be either a water-soluble resin or resin microparticles. Alternatively, water-soluble resins and resin microparticles can be used in combination.

[0064] In embodiments of the present invention, resins with a solubility of 1g or more in 100g of water at 25°C are referred to as "water-soluble resins," and resins with a solubility of less than 1g are referred to as "non-water-soluble resins." Furthermore, among the aforementioned non-water-soluble resins, resins dispersed in water in a particulate form and having a median particle size (also referred to as "D50" in embodiments of the present invention) of 10 to 1,000 nm based on volume are referred to as "resin microparticles."

[0065] It should be noted that the D50 in the embodiments of the present invention is a value measured using a dynamic light scattering particle size distribution measuring device at an environment of 25°C. Examples of such devices include the "Nanotrac UPA-EX150" manufactured by MicrotracBEL.

[0066] Examples of resins that can be used in the water-based inkjet inks of this embodiment include acrylic resins, styrene resins, styrene-maleic anhydride resins, olefin-maleic anhydride resins, polyurethane resins, polyester resins, vinyl chloride resins, vinyl chloride-vinyl acetate resins, polyolefin resins, and vinyl alcohol resins. These resins may be used individually or in combination of two or more.

[0067] It should be noted that, in the embodiments of the present invention, "acrylic resin" refers to a resin that uses one or more monomers selected from the group consisting of acrylic acid, methacrylic acid, acrylates and methacrylates as polymerizable monomers (styrene monomers may also be used). Additionally, "maleic acid (anhydride)" refers to at least one monomer selected from "maleic acid" and "maleic anhydride".

[0068] Resins can be used for any purpose, such as adhesives, pigment dispersions, etc. Furthermore, resins can be used for one application or multiple applications.

[0069] In the water-based inkjet ink of this embodiment, from the viewpoint of imparting firmness and anti-blocking properties to the printed matter, the aforementioned resin is preferably used for adhesive applications. Furthermore, from the viewpoint of improving ejection stability, when the water-based inkjet ink of this embodiment contains pigment as a colorant, it is preferable to contain a resin used for pigment dispersion and / or a resin used for pigment dispersion that is also used in the pigment dispersion application, separate from the resin used in the adhesive application (in other words, the adhesive resin described later also serves as a pigment dispersion resin).

[0070] In embodiments of the present invention, "use in adhesive applications" refers to use in applications that impart adhesion (firmness) and / or bonding to printing substrates to ink coatings. It should be noted that ink coatings with firmness also exhibit excellent scratch resistance. Resins used in the aforementioned adhesive applications include, for example, resins that are the main component of ink coatings. Furthermore, they can be in the form of water-soluble resins or resin microparticles, preferably resin microparticles.

[0071] In addition, resins used for pigment dispersion include, for example, resin particles containing pigments, and resins with an adsorption rate of 35% by mass or more for pigments (which may be water-soluble resins or resin particles).

[0072] It should be noted that, as an example of a method for determining the adsorption rate of pigments, a pigment dispersion (or ink containing no solid components other than the resin being evaluated), diluted with water as needed, is centrifuged until the supernatant becomes clear (e.g., for a 5 mL sample, at 80,000 rpm for 4 hours). The amount of resin contained in the recovered supernatant is then measured (e.g., after allowing the supernatant to stand at 100°C to completely remove the liquid components, the mass of the evaporated residue is measured as the amount of resin). Then, the amount of resin contained in the supernatant is subtracted from the amount of resin contained in the centrifuged pigment dispersion (or ink) (denoted as WR0[g]), and the subtracted value is divided by WR0 to calculate the adsorption rate.

[0073] Adhesive Resins

[0074] As described above, in one embodiment, from the perspective of improving the adhesion and anti-blocking properties of printed materials, the water-based inkjet ink preferably contains a resin used in adhesive applications (also referred to as "adhesive resin" in embodiments of the present invention). In the case where the water-based inkjet ink of this embodiment contains an adhesive resin, the adhesive resin is preferably one or more selected from the group consisting of acrylic resins, polyurethane resins, and polyester resins listed above.

[0075] The glass transition temperature (Tg) of the resin is preferably 50-130°C, more preferably 80-130°C, and particularly preferably 90-130°C. By using a resin having the above-mentioned glass transition temperature, as described above, the adhesion and anti-blocking properties of the printed material are improved. In embodiments of the present invention, the glass transition temperature (Tg) may be 50.0-130.0°C, 80.0-130.0°C, or 90.0-130.0°C.

[0076] The glass transition temperature of the resin can be determined according to JIS K 7121:2012. Specifically, approximately 10 mg of the resin sample to be tested is added to an aluminum sample dish whose mass has been pre-measured, and the mass is measured again before sealing the dish. Next, the sample container and a sample dish without resin are placed in a support within a Shimadzu DSC-60 (Differential Scanning Calorimeter), and the measurement is performed at a heating rate of 10 °C / min to obtain a DSC curve. Then, the intersection of the baseline on the low-temperature side and the tangent at the inflection point of the DSC curve is determined, and the temperature of this intersection point is taken as the glass transition temperature. It should be noted that indium is used in the temperature correction.

[0077] On the other hand, for acrylic resins, the glass transition temperature can be used as a value that can be calculated by the following formula 2.

[0078] Formula 2:

[0079] 1 / Tg=Σ(Wn / Tgn)

[0080] In Equation 2 above, Tg represents the glass transition temperature (K) of the resin, Wn represents the mass fraction of the structural unit formed by the polymerizable monomer n contained in the resin, and Tgn represents the glass transition temperature (K) of the homopolymer of each structural unit. The value of Tgn can be, for example, found in the "Polymer Handbook (Fourth Edition)" (Wiley, 1998).

[0081] The acid value of the binder resin is preferably 0 to 100 mg KOH / g, more preferably 0 to 80 mg KOH / g. Particularly preferably 10 to 60 mg KOH / g. By keeping the acid value within the above range, even if a portion of the water-based inkjet ink dries near the nozzle of the inkjet head, significant thickening of the water-based inkjet ink can be suppressed, thereby improving ejection stability.

[0082] In embodiments of the present invention, the "acid value of the resin" refers to the number of mg of potassium hydroxide (KOH) required to neutralize the acid groups contained in 1 g of the resin. In embodiments of the present invention, the acid value is a value calculated by the following method. For example, when the total polymerizable monomers forming the resin contain a polymerizable monomer with a mass percentage of Wa, one molecule having na va valence acid groups and a molecular weight of Ma, the acid value (mgKOH / g) of the resin is determined by the following formula 3.

[0083] Formula 3:

[0084] (Acid value) = {(va × na × Wa) ÷ (100 × Ma)} × 56.11 × 1000

[0085] In Equation 3 above, the value "56.11" represents the molecular weight of potassium hydroxide.

[0086] Regarding the content of binder resin contained in the water-based inkjet ink of this embodiment, from the viewpoint of water-based inkjet ink that has excellent spraying stability, as well as the ability to obtain full-page filling and anti-blocking properties of the printed matter, the content of the water-based inkjet ink in terms of solid content is preferably 0.3 to 15% by mass, more preferably 1.0 to 14% by mass, and particularly preferably 2.0 to 13% by mass.

[0087] Furthermore, from the viewpoint of imparting adhesion to the substrate and improving anti-blocking properties, the content of adhesive resin in the total resin is preferably 50% by mass or more, and more preferably 60% by mass or more.

[0088] Pigment Dispersion Resin

[0089] When the water-based inkjet ink of this embodiment contains pigment as a colorant, a resin used for pigment dispersion (also referred to as "pigment dispersion resin" in the embodiments of the present invention) may also be used. In this case, the pigment dispersion resin is preferably one or more selected from the group consisting of acrylic resin, styrene-maleic acid (anhydride) resin and olefin-maleic acid (anhydride) resin listed above.

[0090] The acid value of the pigment dispersion resin is preferably 100-450 mg KOH / g, more preferably 120-400 mg KOH / g, and particularly preferably 150-350 mg KOH / g. By setting the acid value within the above range, the dispersion stability of the pigment can be maintained, and it can be stably ejected from the inkjet head regardless of the operating conditions. In addition, by ensuring the water solubility of the pigment dispersion resin while making the interaction between the pigment dispersion resins suitable, the viscosity of the pigment dispersion can be suppressed, and the ejection stability from the inkjet head can be further improved. From this point of view, it is also suitable.

[0091] From the viewpoint of pigment dispersion stability and ejection stability, the content of pigment dispersion resin contained in the water-based inkjet ink of this embodiment is preferably 1 to 40% by mass relative to the pigment content, and more preferably 2 to 30% by mass.

[0092] Water-soluble organic solvents

[0093] The water-based inkjet ink of this embodiment contains a water-soluble organic solvent. Additionally, as described above, it contains a (ii) propylene glycol monoalkyl ether solvent (S1) as shown in General Formula 1. It should be noted that, in embodiments of the present invention, "water-soluble organic solvent" refers to a solvent with a solubility of 1% by mass or more in water at 25°C and which is a liquid at 25°C.

[0094] (II) Propylene Glycol Monoalkyl Ether Solvents (S1)

[0095] The (ii) propylene glycol monoalkyl ether solvent (S1) shown in General Formula 1 above exhibits high compatibility with the resin and moderately high water solubility. Therefore, when used in water-based inkjet inks, it functions appropriately as a film-forming aid, improving the film-forming properties of the resin. Furthermore, by using it in combination with an acetylene glycol surfactant with an HLB value of 10 or less, the functional performance of the solvent (S1) within the inkjet head is suppressed, preventing poor drying, film formation, and ejection of the water-based inkjet ink. Moreover, due to the presence of solvent (S1), surfactants, represented by acetylene glycol surfactants with an HLB value of 10 or less, are readily compatible with other materials in water-based inkjet inks. As a result, the surfactant does not excessively and locally exist on the surface of the ink coating, improving adhesion resistance.

[0096] As the (ii) propylene glycol monoalkyl ether solvent (S1) shown in general formula 1 above, 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. These compounds can be used alone or in combination of two or more.

[0097] Here, from the viewpoint of balancing water solubility and resin compatibility, and ensuring affinity with acetylene glycol-based surfactants with an HLB value of 10 or less, the alkyl group (R in the above general formula 1) present at the molecular end of the (di)propylene glycol monoalkyl ether solvent (S1) is considered. 1 The number of carbon atoms in the ) is preferably 2 or 3, and particularly preferably 3.

[0098] Furthermore, as a (di)propylene glycol monoalkyl ether solvent (S1), dipropylene glycol monoalkyl ethers, i.e., compounds with n=2 in the above general formula 1, can be suitable for use. While the detailed reasons are not clear, dipropylene glycol monoalkyl ethers function excellently as film-forming aids, improving the film-forming properties of resins even with small additions. Additionally, due to the large number of hydrophobic propylene oxide structures, they exhibit excellent affinity for acetylene glycol surfactants with HLB values ​​below 10, resulting in the prevention of poor spraying and improved resistance to sticking of printed materials.

[0099] Based on the above viewpoints, particularly in the water-based inkjet ink of this embodiment, dipropylene glycol monopropyl ether is preferably included as the (di)propylene glycol monoalkyl ether solvent (S1). Since dipropylene glycol monopropyl ether has a propyl group at its molecular end, it exhibits high compatibility with resins, while also ensuring its own water solubility. Therefore, it functions appropriately as a film-forming aid, particularly improving the film-forming properties of the resin. Furthermore, it can appropriately assist in the compatibility of surfactants, such as acetylene glycol-based surfactants with an HLB value of 10 or less, with other materials, improving inkjet stability and the resistance to sticking of printed materials.

[0100] The content of (ii)propylene glycol monoalkyl ether solvent (S1) in the water-based inkjet ink of this embodiment is preferably 0.3 to 8% by mass in the total amount of the water-based inkjet ink, more preferably 0.5 to 7% by mass, and even more preferably 1 to 6% by mass.

[0101] On the other hand, as described above, the (di)propylene glycol monoalkyl ether solvent (S1) functions as a film-forming aid for resins with a glass transition temperature of 50 to 130°C. Therefore, it is preferable to determine the content of the (di)propylene glycol monoalkyl ether solvent (S1) based on the content of the resin with a glass transition temperature of 50 to 130°C. In one embodiment, when the mass content of the above-mentioned (di)propylene glycol monoalkyl ether solvent (S1) contained in the water-based inkjet ink of this embodiment is set to 1, the mass content of the resin with 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 with a glass transition temperature of 50 to 130°C within the above range, the (di)propylene glycol monoalkyl ether solvent (S1) functions appropriately as a film-forming aid, and the anti-blocking and anti-scratch properties of the printed material are optimized.

[0102] SP value is 12~14 (cal / cm³) 3 ) 1 / 2 Water-soluble organic solvents (S2)

[0103] The water-based inkjet ink of this embodiment preferably contains, in addition to the propylene glycol monoalkyl ether solvent (S1) described above (II), an SP value of 12-14 (cal / cm). 3 ) 1 / 2 Water-soluble organic solvent (S2). In particular, the SP value is 12~14 (cal / cm³). 3 ) 1 / 2The water-soluble organic solvent (S2) is preferably an alkyl diol containing 3 to 5 carbon atoms. Alkane diols with 3 to 5 carbon atoms have both hydrophilicity based on hydroxyl groups and hydrophobicity based on alkylene groups. Therefore, it is believed that surfactants, such as acetylene glycol surfactants with an HLB value of less than 10, and the above-mentioned resins are compatible in water-based inkjet inks, and together with (di)propylene glycol monoalkyl ether solvents (S1), they help to improve ejection stability and anti-blocking properties.

[0104] In the embodiments of this invention, "SP value" is an abbreviation for "Solubility Parameter". Known methods for determining the SP value include methods calculated from the physical properties of the compound, methods calculated from the molecular structure, and methods measured experimentally. In the embodiments of this invention, the SP value is the one calculated using Fedor's derivation method, as expressed in Equation 4 below.

[0105] Formula 4:

[0106] (SP value) = (ΣEcoh / ΣV) 1 / 2

[0107] In Equation 4 above, Ecoh represents the cohesive energy determined for each functional group, and V represents the molar molecular volume determined for each functional group. Ecoh and V are described above in RFFedors, "Polymer Engineering & Science" (Vol. 14, No. 2, 1974, pp. 147-154).

[0108] As suitable for use with an SP value of 12~14 (cal / cm) 3 ) 1 / 2 Water-soluble organic solvents (S2) consisting of 3-5 carbon alkyl diols 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 can be used alone or in combination with two or more. It should be noted that the values ​​in parentheses above are the SP values ​​(unit: (cal / cm²)) of each compound. 3 ) 1 / 2 In embodiments of the present invention, the SP value can be 12.0~14.0 (cal / cm). 3 ) 1 / 2 .

[0109] The water-soluble organic solvent (S2) preferably comprises 1,2-propanediol and / or 1,2-butanediol, more preferably 1,2-propanediol. These water-soluble organic solvents are considered to have high hydrophilicity, and on the other hand, they do not exhibit excessive affinity for acetylene glycol-based surfactants, siloxane-based surfactants, and / or (poly)ethylene glycol monoalkyl ether-based surfactants. Therefore, they do not hinder the orientation of the surfactant on the gas-liquid surface, maximizing its effect and resulting in prints with excellent full-page filling properties. Furthermore, after adhering to the printing substrate, these water-soluble organic solvents evaporate rapidly, thus producing prints with excellent anti-blocking properties.

[0110] In addition, besides alkanediols with 3 to 5 carbon atoms, there are also those with an SP value of 12 to 14 (cal / cm). 3 ) 1 / 2 Water-soluble organic solvents (S2) can be used, such as diethylene glycol (13.0), triethylene glycol (12.1), and ethanol (12.6). It should be noted that the values ​​in parentheses above are the SP values ​​of each compound (unit: (cal / cm²)). 3 ) 1 / 2 ).

[0111] The SP value of the water-based inkjet ink in this embodiment is 12~14 (cal / cm³). 3 ) 1 / 2 The content of the water-soluble organic solvent (S2) in the total amount of the water-based inkjet ink is preferably 5-35% by mass, more preferably 10-30% by mass, and even more preferably 10-25% by mass. Particularly, the SP value is 12-14 (cal / cm³). 3 ) 1 / 2 When the water-soluble organic solvent (S2) contains 1,2-propanediol, the content of 1,2-propanediol in the total amount of water-based inkjet ink is preferably 10 to 15% by mass.

[0112] Additionally, alkanediols containing 3 to 5 carbon atoms have an SP value of 12 to 14 (cal / cm). 3 ) 1 / 2 When using a water-soluble organic solvent (S2), from the viewpoint of improving the compatibility of surfactants and resins, and improving ejection stability and anti-blocking properties, if the mass content of the (di)propylene glycol monoalkyl ether solvent (S1) in the water-based inkjet ink is set to 1.0, the mass content of alkanediols with 3 to 5 carbon atoms in the water-based inkjet ink is preferably 0.5 to 8.0, more preferably 1.0 to 7.0, and particularly preferably 2.0 to 6.0.

[0113] In one embodiment, the water-based inkjet ink of this embodiment preferably contains at least one solvent selected from the (di)propylene glycol monoalkyl ether solvent (S1) of the above-described general formula 1, and further contains at least one solvent selected from the group consisting of the (di)propylene glycol monoalkyl ether solvent (S1) of the above-described general formula 1 and other water-soluble organic solvents described later. For example, in the water-based inkjet ink of this embodiment, the (di)propylene glycol monoalkyl ether solvent (S1) of the above-described general formula 1 preferably 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. It should be noted that propylene glycol monoethyl ether, propylene glycol monopropyl ether, and propylene glycol monobutyl ether are also the (di)propylene glycol monoalkyl ether solvent (S1) of the above-described general formula 1. As described above, dipropylene glycol monopropyl ether has excellent resin film-forming properties and affinity for acetylene glycol surfactants with an HLB value of 10 or less. On the other hand, the aforementioned dipropylene glycol monopropyl ether has slightly lower hydrophilicity compared to other (di)propylene glycol monoalkyl ether solvents (S1). Therefore, by using the aforementioned compound, which has a smaller molecular weight than the aforementioned dipropylene glycol monopropyl ether and excellent affinity for it, the spraying stability and the anti-blocking properties of the printed material become particularly excellent.

[0114] When the water-based 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, and the total mass of the propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether and propylene glycol monobutyl ether is set to 1.0, the mass of the dipropylene glycol monopropyl ether is preferably 0.2 to 5.0, more preferably 0.3 to 4.0, further preferably 0.4 to 3.0, and particularly preferably 0.5 to 2.0.

[0115] Other water-soluble organic solvents

[0116] The water-based inkjet ink of this embodiment may contain the above-mentioned (ii) propylene glycol monoalkyl ether solvent (S1) and an SP value of 12-14 (cal / cm). 3 ) 1 / 2 Other water-soluble organic solvents besides water-soluble organic solvents (S2) (referred to as "other water-soluble organic solvents" in embodiments of the present invention).

[0117] In the water-based inkjet ink of this embodiment, as other water-soluble organic solvents mentioned above, alkanediols with 6 carbon atoms; alkanetriols (wherein, the number of carbon atoms is 3 to 6); polyalkylene glycols (wherein, the alkylene glycol groups are ethylene glycol (epoxyethylene) or propylene glycol (epoxypropylene), and the number of epoxy alkyl groups is 2 to 4); (poly)ethylene glycol monoalkyl ethers (wherein, 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 (wherein, ...)propylene glycol monoalkyl ethers (wherein, the number of carbon atoms in the terminal alkyl group is 1 to 4), (di)propylene glycol monomethyl ether, tri)propylene glycol monoalkyl ethers (wherein, the number of carbon atoms in the terminal alkyl group is 1 The following are examples of water-soluble organic solvents: alkylene glycol dialkyl ethers (wherein the alkylene glycol group is ethylene glycol or propylene glycol, the number of such alkylene glycol groups is 1 to 4, and the terminal alkyl group has 1 to 4 carbon atoms); lactams (wherein the number of atoms forming the lactam ring is 5 to 7, and in addition, the nitrogen atom and / or carbon atom forming the lactam ring may be bonded with an alkyl group having 1 to 2 carbon atoms, a hydroxyalkyl group having 1 to 2 carbon atoms, or a vinyl group having 1 to 2 carbon atoms); alkanolamines (wherein there is 1 amino group, 1 to 3 hydroxyl groups, and 3 to 9 carbon atoms); etc. These other water-soluble organic solvents can be used alone or in combination of two or more.

[0118] It should be noted that in the embodiments of the present invention, "(poly)ethylene glycol" refers to ethylene glycol and polyethylene glycol.

[0119] The total amount of water-soluble organic solvent contained in the water-based inkjet ink of this embodiment is preferably 5 to 50% by mass of the total amount of the water-based inkjet ink, more preferably 9 to 40% by mass, further preferably 12 to 35% by mass, and particularly preferably 15 to 30% by mass.

[0120] <surfactants>

[0121] Ethynylene glycol surfactants with an HLB value below 10

[0122] The aqueous inkjet ink of this embodiment contains an acetylene glycol-based surfactant with an HLB value of 10 or less as a surfactant. From the viewpoint of the orientation velocity on the droplet surface, and from the viewpoint of suppressing ejection defects that may occur near the nozzle of the inkjet head due to drying of the aqueous inkjet ink by using it in conjunction with a (di)propylene glycol monoalkyl ether solvent (S1), and from the viewpoint of further improving anti-blocking properties, the aforementioned HLB value is preferably 3 to 9, more preferably 4 to 8. In embodiments 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.

[0123] In particular, it is believed that by setting the HLB value to 10 or less (preferably 9 or less, more preferably 8 or less), the acetylene glycol-based surfactant rapidly oriented on the droplet surface. Therefore, after this orientation, the component that hinders the functional performance of the solvent (S1) disappears, allowing the solvent (S1) to fully function as a film-forming aid. As a result, even when using resins with high glass transition temperatures, it is easy to obtain water-based inkjet inks with excellent film-forming properties.

[0124] In the embodiments of the present invention, the HLB (Hydrophile-Lipophile Balance) value is one of the parameters representing the hydrophilicity / hydrophobicity of a material. Various methods exist for calculating the HLB value, such as the Griffin method, the Davis method, and the Kawakami method. In the embodiments of the present invention, the HLB value calculated using the Griffin method is used as the HLB value for the acetylene glycol-based surfactant.

[0125] The Griffin method uses the molecular weight of the target compound, as shown in Equation 5 below. It should be noted that the smaller the HLB value, the higher the hydrophobicity of the target compound; the larger the HLB value, the higher the hydrophilicity.

[0126] Formula 5:

[0127] HLB value = 20 × (total molecular weight of hydrophilic portions) ÷ (molecular weight of the material)

[0128] Examples of acetylene glycol surfactants with HLB values ​​below 10 include: 2,4,7,9-tetramethyl-5-decyn-4,7-diol, 2,5,8,11-tetramethyl-6-dodecyn-5,8-diol, hexadecane-8-yn-7,10-diol, 4,7-dipropyl-decane-5-yn-4,7-diol, 6,9-dimethyl-tetradecane-7-yn-6,9-diol, and 3,6-diisopropyl-2,7-dimethyloctane-4- The compounds include 3,6-ynediol, octadecane-9-yne-8,11-diol, 7,10-dimethylhexadecane-8-yne-7,10-diol, 5,8-dibutyldodecane-6-yne-5,8-diol, 4,7-diisobutyl-2,9-dimethyl-decane-5-yne-4,7-diol, 5,14-diethyl-8,11-dimethyloctadecane-9-yne-8,11-diol, and ethylene oxide and / or propylene oxide modified forms of the listed compounds. Only one of the listed compounds may be used, or two or more may be used in combination. Furthermore, these compounds may be those synthesized using conventionally known synthetic methods, or commercially available products. Examples of products sold in the city include Surfynol 61, 104E, 104H, 104A, 104BC, 104DPM, 104PA, 104PG-50, 420, 440, 2502, SE, SE-F, Dynol 604, 607 (manufactured by Evonik), OLFINE E1004, PD-001, PD-002W, and PD-004 (manufactured by Nissin Chemical Industry Co., Ltd.).

[0129] Specifically, considering the effective functioning of the aforementioned mechanism, the effective wetting and spreading of ink, and the improved affinity and compatibility of the acetylene glycol surfactant with water-soluble organic solvents, thereby achieving good full-page filling properties, the acetylene glycol surfactant with an HLB value of 10 or less is preferably selected from the group consisting of Surfynol 440, Surfynol 2502, Surfynol SE-F, Dynol 607, and OLFINE E1004. Furthermore, considering the high affinity with the solvent (S1) and the ability to balance film formation and ejection stability at a high level, the acetylene glycol surfactant further preferably includes Surfynol 440 and / or 2502, and particularly preferably includes Surfynol 2502.

[0130] It should be noted that Surfynol 440 is an ethylene oxide modified product of 2,4,7,9-tetramethyl-5-decyn-4,7-diol (ethylene oxide addition molar number 3.5), and Surfynol 2502 is an ethylene oxide and propylene oxide modified product of 2,4,7,9-tetramethyl-5-decyn-4,7-diol (ethylene oxide addition molar number 5, propylene oxide addition molar number 2).

[0131] The content of acetylene glycol-based surfactants with an HLB value of 10 or less in the water-based inkjet ink of this embodiment is preferably 0.2 to 3.0% by mass, more preferably 0.3 to 2.5% by mass, and particularly preferably 0.5 to 1.5% by mass. By using it within the above range, it is possible to achieve a high level of balance between print stability, full-page filling, and anti-blocking properties.

[0132] Especially when the water-based inkjet ink of this embodiment is a water-based white ink, the content of acetylene glycol-based surfactants with an HLB value of 10 or less is preferably 0.2 to 1.5% by mass in the total amount of water-based white ink, more preferably 0.3 to 1.0% by mass.

[0133] Siloxane-based surfactants and / or (poly) glycol monoalkyl ether-based surfactants

[0134] In addition to the acetylene glycol surfactants with an HLB value of 10 or less mentioned above, the water-based inkjet ink of this embodiment also contains siloxane surfactants and / or (poly) glycol monoalkyl ether surfactants.

[0135] From the viewpoint of compatibility with acetylene glycol-based surfactants with an HLB value of 10 or less, the total content of siloxane-based surfactants and / or (poly) glycol monoalkyl ether surfactants contained in the water-based inkjet ink of this embodiment is preferably 0.2 to 2.5% by mass, more preferably 0.3 to 2.0% by mass, even more preferably 0.6 to 2.0% by mass, and particularly preferably 0.6 to 1.8% by mass. The total content can be 0.6 to 2.5% by mass or 1.0 to 2.5% by mass. By using it within the above range, it is possible to achieve a high level of balance between print stability, full-page filling, and anti-blocking properties. Regarding the total content of siloxane-based surfactants and / or (poly) glycol monoalkyl ether surfactants, when the water-based inkjet ink contains two surfactants, it is the total content of the two surfactants; when it contains one surfactant but not the other, it is the content of that one surfactant.

[0136] Furthermore, from the viewpoint of improving the ejection stability and full-page filling of the printed area of ​​water-based inkjet ink by enhancing the compatibility of surfactants, it is preferable to control the content of siloxane surfactants and / or (poly) glycol monoalkyl ether surfactants in the water-based inkjet ink, when the mass of acetylene glycol surfactants with an HLB value of 10 or less in the water-based inkjet ink is set to 1. In this case, it is preferable to change the above values ​​according to the color of the ink. Specifically, in the case of white ink, the above values ​​are preferably 1.0 to 6.0, more preferably 1.5 to 5.0, and particularly preferably 1.5 to 4.0. In addition, for colored inks other than white ink, the values ​​are preferably 0.2 to 5.0, more preferably 0.3 to 4.5, and particularly preferably 0.4 to 4.0.

[0137] 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, 8032ADDITIVE, SH3773M (manufactured by Toray D. Corning), TEGO Glide 100, TEGO Glide 410, TEGO Glide 432, TEGO Glide 435, TEGO Glide 440, TEGO Glide 450, TEGO Twin 4000, TEGOTwin4100, TEGO Wet250, TEGO Wet260, TEGO Wet270, and TEGO Glide 450. 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), K F-351A, 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, KF-643 (manufactured by Shin-Etsu Chemical Industry Co., Ltd.), etc. It should be noted that only one of the products listed above may be used, or two or more may be used in combination. Furthermore, siloxane surfactants may also be substances synthesized using previously known synthetic methods.

[0138] When the water-based inkjet ink of this embodiment contains a siloxane-based surfactant, from the viewpoint of excellent compatibility with ethynyl glycol-based surfactants and solvents (S1) with an HLB value of 10 or less, and improved ejection stability and anti-blocking properties, it is preferable to use a polyether-modified siloxane with 4 to 12 silicon atoms and at least an ethylene oxide side chain as the siloxane-based surfactant.

[0139] It should be noted that, generally speaking, the molecular weight and viscosity of siloxane-based surfactants are positively correlated. For example, the side-chain polyether-modified siloxanes suitable for use in the water-based inkjet inks of this embodiment have a kinematic viscosity of 20 mmHg to 75 mmHg at 25°C. 2 The compound has a kinematic viscosity of / s. The kinematic viscosity described above can be measured, for example, using an Ubbelohde viscometer.

[0140] In addition, the following are examples of commercially available (poly)ethylene glycol monoalkyl ether surfactants: EMULGEN series (manufactured by Kao Corporation), including EMULGEN 104P, 105, 106, 108, 109P, 120, 123P, 150, 210, 220, 306P, 320P, 350; BLAUNON 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., BLAUNON series (manufactured by Aoki Oils & Fats Co., Ltd.); NONION The following are NONION series products (manufactured by Nippon Oil Company): K-204, 220, 230, 2100W, P-208, 210, 213, E-202, 205, 212, 215, 230, S-202, 207, 215, 220, EH-204, 208, ID-203, 206, 209, etc.; Lutensol series products (manufactured by BASF): Lutensol XL40, 50, 60, 70, 80, 90, XP30, 40, 50, 60, 70, 80, 90, 140, etc.; Newcol series products (manufactured by Nippon Emulsifier Co., Ltd.): Newcol 2302, 2303, 2305, 2308, 2310, 2320, 2360, etc. Only one of the listed products may be used, or two or more may be used in combination. In addition, (poly)ethylene glycol monoalkyl ether surfactants can also be substances synthesized by previously known synthetic methods.

[0141] It should be noted that compounds with alkyl groups at the molecule terminal having 6 or more carbon atoms are equivalent to "(poly)ethylene glycol monoalkyl ether surfactants" in the embodiments of the present invention.

[0142] 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) with 8 to 13 carbon atoms at the molecule's end. While the detailed rationale is not clear, since the (poly)ethylene glycol monoalkyl ether surfactant with an alkyl group (which may be branched) with 8 to 13 carbon atoms at the molecule's end has a high affinity for the aforementioned acetylene glycol surfactant with an HLB value of 10 or less, the ejection stability of the aqueous inkjet ink and the full-page filling performance of the printed area are improved. From the same viewpoint, it is more preferable that the (poly)ethylene glycol monoalkyl ether surfactant has an alkyl group (which may be branched) with 8 to 12 carbon atoms at the molecule's end, and particularly preferably 10 to 12.

[0143] Furthermore, since it can exist stably in water-based inkjet inks, from the viewpoint of improving ejection stability, as well as the full-page filling and anti-blocking properties of printed materials, when the water-based inkjet ink of this embodiment contains a (poly) glycol monoalkyl ether surfactant, when the number of carbon atoms of the alkyl group at the molecule end of the (poly) glycol monoalkyl ether surfactant is set as CE, the amount of glycol groups (ethylene oxide) is preferably an integer between CE×0.8 and CE×3.5 (wherein, 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 (wherein, 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 (wherein, when CE×1.5 and CE×2.7 are integers, these integers are also included).

[0144] Other Surfactants

[0145] The water-based inkjet ink of this embodiment may contain surfactants other than the surfactants mentioned above (referred to as "other surfactants" in embodiments of the present invention).

[0146] As other surfactants mentioned above, any conventionally known surfactants may be used. Among them, nonionic surfactants are preferred. Nonionic surfactants have good affinity with acetylene glycol surfactants with an HLB value of 10 or less, as well as siloxane surfactants and / or (poly) glycol monoalkyl ether surfactants, and will not hinder the improvement of the above-mentioned ejection stability. Furthermore, from the perspective of easily obtaining printed materials with excellent full-page filling and anti-blocking properties, nonionic surfactants are also preferred.

[0147] As the aforementioned nonionic surfactants, examples include acetylenic glycol surfactants, acetylenic monohydric alcohol surfactants, and fluorinated surfactants with an HLB value greater than 10. Among these, acetylenic glycol surfactants with an HLB value of less than 10 are preferred for their excellent affinity with acetylenic glycol surfactants and (di)propylene glycol monoalkyl ether solvents (S1), resulting in water-based inkjet inks with excellent ejection stability, full-page filling properties, and anti-blocking properties.

[0148] When using acetylene glycol-based surfactants with an HLB value greater than 10, substances synthesized using conventionally known synthetic methods or commercially available products can be used. Examples of such commercially available products include Surfynol 465 and 485 (manufactured by Evonik), OLFINE E1010, E1020, EXP.4200, and EXP.4123 (manufactured by Nissin Chemical Industry Co., Ltd.). Only one of the compounds listed above may be used, or two or more may be used in combination.

[0149] The total amount of surfactant contained in the water-based inkjet ink of this embodiment is preferably 0.4 to 5% by mass, more preferably 0.5 to 4% by mass, and particularly preferably 0.6 to 3% by mass. By setting the total amount of surfactant within the above range, the ejection stability of the water-based inkjet ink, as well as the tack resistance and scratch resistance of the printed material, are improved.

[0150] <Other Ingredients>

[0151] In addition to the components described above, the water-based inkjet ink of this embodiment may also contain pH adjusters, preservatives, crosslinking agents, ultraviolet absorbers, and infrared absorbers. These components may each be one or more previously known compounds.

[0152] <Manufacturing Method of Water-Based Inkjet Ink>

[0153] The water-based inkjet ink of this embodiment can be manufactured using conventionally known methods. For example, one method is as follows: when using a pigment as a colorant, a pigment dispersion is prepared in advance by dispersing the pigment in a medium (aqueous medium) containing at least water using a pigment dispersion resin. Then, water, a binder resin, a (di)propylene glycol monoalkyl ether solvent (S1) as shown in general formula 1, an acetylene glycol surfactant with an HLB value of 10 or less, and a siloxane surfactant and / or a (poly)ethylene glycol monoalkyl ether surfactant are added to the pigment dispersion. After thorough stirring and mixing, coarse particles are removed by filtration, centrifugation, or other methods. However, the manufacturing method of the water-based inkjet ink of this embodiment is not limited to the above method.

[0154] Characteristics of Water-Based Inkjet Inks

[0155] The water-based inkjet ink of this embodiment preferably has a viscosity of 3 to 15 mPa·s at 25°C. Within this viscosity range, water-based inkjet ink droplets can be stably ejected not only from inkjet heads with an ejection frequency of approximately 4 to 10 kHz, but also from inkjet heads with a high ejection frequency of approximately 20 to 70 kHz. In particular, when the viscosity of the water-based inkjet ink of this embodiment is 4 to 10 mPa·s at 25°C, water-based inkjet ink can be stably ejected even when using inkjet heads with a design resolution of 600 dpi or higher. It should be noted that in this embodiment of the invention, the viscosity is measured at 25°C using a cone-plate type rotational viscometer (E-type viscometer, cone angle 1°34') such as the "TVE25L type viscometer" manufactured by Toki Sangyo Co., Ltd.

[0156] Furthermore, from the viewpoint of obtaining water-based inkjet inks with excellent ejection stability and full-page filling properties of printed materials, the static surface tension of the water-based inkjet ink in this embodiment at 25°C is preferably 18~35 mN / m, and particularly preferably 21~32 mN / m. It should be noted that, in this embodiment of the invention, the static surface tension is the value measured at 25°C using the Wilhelmy method (plate method) with an "Automatic Surface Tensiometer CBVP-Z" manufactured by Kyowa Interface Science Co., Ltd.

[0157] Furthermore, in the case where the water-based inkjet ink of this embodiment contains pigment as a colorant, from the perspective of balancing high-level ejection stability and the concentration or concealment of the printed matter, the median particle size (D50) of the pigment based on volume is preferably 30 to 450 nm, more preferably 50 to 400 nm, and particularly preferably 70 to 350 nm.

[0158] <Water-based inkjet ink set>

[0159] The water-based inkjet ink of this embodiment can be used alone or as a group of water-based inkjet inks combining two or more water-based inkjet inks. Examples of such a group of water-based inkjet inks include: a four-color group (process color ink group) containing cyan water-based inkjet ink (water-based cyan ink), magenta water-based inkjet ink (water-based magenta ink), yellow water-based inkjet ink (water-based yellow ink), and black water-based inkjet ink (water-based black ink); a five-color group of water-based inkjet ink obtained by further adding water-based white ink to the process color ink group; and so on. In particular, in order to significantly improve print stability, full-page filling performance, and anti-blocking properties, it is preferable to use an ink group containing water-based white ink that satisfies the requirements of the embodiments of the present invention described above. Furthermore, it is more preferable that all water-based inkjet inks contained in the water-based inkjet ink group satisfy the requirements of the embodiments of the present invention described above.

[0160] <Ink Pretreatment Solution Group>

[0161] Furthermore, the water-based inkjet ink and the aforementioned water-based inkjet ink group of this embodiment can also be used in combination with a pretreatment liquid containing a coagulant (ink-pretreatment liquid group form). By applying the pretreatment liquid containing a coagulant to the printing substrate before printing with the water-based inkjet ink, a layer (ink coagulation layer) can be formed in which the solid components contained in the water-based inkjet ink are intentionally coagulated. Moreover, by allowing the water-based inkjet ink to settle on the ink coagulation layer, the merging and mixing of the water-based ink droplets are prevented, and excessive wetting and spreading are suppressed, thereby significantly improving the print quality of printed materials including full-page embedding.

[0162] It should be noted that, for example, water-soluble inorganic or organic salts containing polyvalent metal ions, and resins having cationic groups in an equivalent amount greater than that of anionic groups can be used as coagulants.

[0163] <Inkjet Recording Methods>

[0164] The water-based inkjet ink of this embodiment is used in an inkjet printing process. That is, the water-based inkjet ink of this embodiment is ejected from an inkjet head with micro-nozzles onto a printing substrate (ejection process). In addition, the water-based inkjet ink ejected onto the printing substrate is preferably dried by a drying unit (drying process).

[0165] Ejection Process

[0166] As for the operation mode of the inkjet head in the printing process, there are two types: a shuttle (scanning) mode in which the inkjet head reciprocates and scans in a direction orthogonal to the transport direction of the printing substrate while ejecting and recording water-based inkjet ink, and a single-pass mode in which the water-based inkjet ink is ejected and recorded as the printing substrate passes under the fixedly positioned inkjet head. The inkjet head equipped with the water-based inkjet ink of this embodiment can adopt either the shuttle mode or the single-pass mode. Among these, the single-pass mode is preferred from the perspective of minimizing the deviation of the droplet landing position of the water-based inkjet ink and improving the print quality of the printed material.

[0167] Regarding the ejection method from the inkjet head, any known method can be selected. Examples of such ejection methods include piezoelectric methods that utilize the volume change of a piezoelectric element, thermal methods that eject water-based inkjet ink by generating bubbles through heating by a heater, and valve methods that eject pressurized water-based inkjet ink while opening and closing the nozzle cap (valve) using a solenoid.

[0168] From the perspective of reducing drying load and improving print quality, including full-page filling, the droplet volume of water-based inkjet ink ejected from the inkjet head is preferably 0.5 to 20 picoliters, and particularly preferably 0.5 to 15 picoliters. Furthermore, from the viewpoint of improving print quality, it is preferable to adjust printing conditions (specifically, the drive frequency and number of inkjet heads, and the printing speed) to achieve a recording resolution of 600 dpi or higher for the printed material, and particularly preferably to adjust printing conditions to achieve a recording resolution of 1200 dpi or higher for the printed material.

[0169] Drying Process

[0170] Drying methods used in drying processes include heating drying, hot air drying, infrared (e.g., infrared radiation with wavelengths of 700-2500 nm) drying, microwave drying, and drum drying.

[0171] In the above drying process, one or more of these methods can be selected and used arbitrarily. Furthermore, when using two or more of the above drying methods, each method can be used separately (e.g., consecutively) or simultaneously. For example, by using heating drying and hot air drying together, the ink can be dried more quickly compared to using them separately.

[0172] In particular, from the viewpoint of preventing sudden boiling of the liquid components in water-based inkjet inks and obtaining printed materials with excellent image quality, when using a heat drying method, it is preferable to set the drying temperature to 35~100°C; and when using a hot air drying method, it is preferable to set the hot air temperature to 50~250°C. Furthermore, from the same viewpoint, when using an infrared drying method, it is preferable that at least 50% of the cumulative total output of the irradiated infrared radiation exists in the wavelength region of 700~1500 nm.

[0173] <Printing Substrate>

[0174] The printing substrate for printing the water-based inkjet ink of this embodiment is not particularly limited, and any known substrates such as permeable substrates, low-permeability substrates, and non-permeable substrates can be used.

[0175] In embodiments of the present invention, the permeability of the printing substrate is determined by the amount of water absorbed by a dynamic scanning absorbance meter. Specifically, the amount of pure water absorbed at a contact time of 100 msec, as measured by the following method, is less than 1 g / m. 2 The printing substrate is set as a "non-permeable substrate", and 1g / m 2 Above and less than 6g / m 2 The printing substrate is set as a "low-permeability substrate", with 6g / m 2 The above printing substrates are designated as "permeable substrates".

[0176] It should be noted that the water absorption of the printing substrate can be measured using a dynamic scanning absorber (e.g., the "KM 500win" manufactured by Kumagai Riki Kogyo Co., Ltd.) with the conditions set as shown below. A printing substrate of about 15 to 20 cm square is used as a sample and measured at 23°C and 50% RH.

[0177] • Measurement method: Spiral method

[0178] • Measurement starting radius: 20mm

[0179] • Measurement end radius: 60mm

[0180] • Contact time: 10~1,000 msec

[0181] • Number of sampling points: 19 (measured at approximately equal intervals relative to the square root of the contact time)

[0182] • Scanning interval: 7mm

[0183] • Rotary platform speed switching angle: 86.3 degrees

[0184] • Headbox specifications: 5mm width, 1mm slit width

[0185] Examples of permeable substrates include: uncoated papers such as straw paper, medium-quality paper, high-quality paper, recycled paper, and ordinary paper; fabrics such as cotton, synthetic fibers, silk, hemp, and non-woven fabrics; and leather. Among these, from the viewpoint of obtaining printed materials with excellent print quality, uncoated papers such as straw paper, medium-quality paper, high-quality paper, and recycled paper can be preferred.

[0186] In addition, examples of non-permeable or low-permeability substrates include plastic substrates such as polyvinyl chloride, polyethylene terephthalate (PET), polypropylene, polyethylene, nylon, polystyrene, and polyvinyl alcohol; coated papers such as coated paper, art paper, micro-coated paper, and cast coated paper; metals such as aluminum, iron, stainless steel, and titanium; and glass.

[0187] The surface of the printing substrates listed above can be smooth or textured. Furthermore, the printing substrates can be transparent, translucent, or opaque. Moreover, the printing substrates can be in roll or sheet form. Additionally, a substrate formed by bonding two or more of the printing substrates listed above together can be used as the printing substrate. Furthermore, a release liner or similar material can be provided on the opposite side of the printing surface, or an adhesive layer can be provided on the printed surface after printing.

[0188] From the perspective of improving the wetting and spreading properties of the water-based inkjet ink in this embodiment, obtaining prints with excellent image quality and drying properties, and good scratch resistance and substrate adhesion due to the homogenization of the printed surface, it is also preferable to perform surface modification such as corona treatment and plasma treatment on the printing surface of the printing substrate listed above.

[0189] <Printed Materials>

[0190] The printed material of this embodiment is formed by printing the water-based inkjet ink of this embodiment onto a printing substrate. The printed material of this embodiment may have a printing substrate and a printing layer formed by printing water-based inkjet ink, or it may have an ink coagulation layer. For example, the printed material of this embodiment has a printing substrate and a printing layer formed on the printing substrate. Alternatively, the printed material of this embodiment has a printing substrate, an ink coagulation layer formed on the printing substrate, and a printing layer formed on the ink coagulation layer.

[0191] <Examples of Implementation>

[0192] Embodiments of the present invention relate to, for example, water-based inkjet inks as shown below [1] to

[11] , and a method for manufacturing printed matter using the above-described water-based inkjet inks as shown below

[12] .

[0193] [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 includes a (di)propylene glycol monoalkyl ether solvent (S1) as shown in general formula 1, and the surfactant includes an acetylene glycol surfactant with an HLB value of less than 10, a siloxane surfactant and / or a (poly)ethylene glycol monoalkyl ether surfactant.

[0194] General Formula 1:

[0195] R 1 -(O-CH(CH3)-CH2) n -OH

[0196] (In general formula 1, R) 1 (It is an alkyl group with 2 to 4 carbon atoms, where n is 1 or 2.)

[0197] [2] The water-based inkjet ink according to [1] further comprises an SP value of 12~14 (cal / cm). 3 ) 1 / 2 Water-soluble organic solvent (S2).

[0198] [3] According to the water-based inkjet ink described in [2], wherein the SP value is 12~14 (cal / cm²). 3 ) 1 / 2 Water-soluble organic solvents (S2) include alkanediols with 3 to 5 carbon atoms.

[0199] [4] The water-based inkjet ink according to any one of [1] to [3], wherein the above-mentioned (ii) propylene glycol monoalkyl ether solvent (S1) comprises dipropylene glycol monopropyl ether.

[0200] [5] The water-based inkjet ink according to any one of [1] to [4], wherein the content of the acetylene glycol surfactant with an HLB value of 10 or less is 0.5 to 1.5 by mass in the water-based inkjet ink.

[0201] [6] The water-based inkjet ink according to any one of [1] to [5], wherein the total content of the above-mentioned siloxane surfactant and / or (poly) glycol monoalkyl ether surfactant in the above-mentioned water-based inkjet ink is 0.6 to 2.5 by mass.

[0202] [7] The water-based inkjet ink according to any one of [1] to [5], wherein the total content of the above-mentioned siloxane surfactant and / or (poly) glycol monoalkyl ether surfactant in the above-mentioned water-based inkjet ink is 0.6 to 2.0 by mass.

[0203] [8] The water-based inkjet ink according to any one of [1] to [5], wherein the total content of the above-mentioned siloxane surfactant and / or (poly) glycol monoalkyl ether surfactant is 0.6 to 1.8 by mass in the above-mentioned water-based inkjet ink.

[0204] [9] The water-based inkjet ink according to any one of [1] to [4], wherein the content of the acetylene glycol surfactant with an HLB value of 10 or less is 0.5 to 1.5% by mass in the water-based inkjet ink, and the total content of the siloxane surfactant and the (poly) glycol monoalkyl ether surfactant is 1.0 to 2.5% by mass in the water-based inkjet ink.

[0205]

[10] The water-based 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.

[0206]

[11] The water-based inkjet ink according to any one of [1] to

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

[0207]

[12] A printed matter which is formed by printing water-based inkjet ink as described in any one of [1] to

[11] onto a printing substrate.

[0208] In one embodiment of the present invention, the water-based inkjet ink exhibits excellent ejection stability, resulting in printed materials with excellent full-page coverage and anti-blocking properties. Furthermore, in another embodiment of the present invention, in addition to the aforementioned characteristics, printed materials with excellent scratch resistance are also obtained. Moreover, in yet another embodiment of the present invention, printed materials with excellent full-page coverage and anti-blocking properties are obtained.

[0209] This 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.

[0210] Example

[0211] The following examples and comparative examples further illustrate the water-based inkjet ink of this embodiment. It should be noted that, unless otherwise specified, "parts" and "%" in the following description refer to "parts by mass" and "% by mass," respectively.

[0212] <Example of Resin 1 Manufacturing>

[0213] 72.4 parts of 2-butanone were added to a reaction vessel equipped with a gas inlet tube, thermometer, condenser, and stirrer, and the mixture was purged with nitrogen. 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 and Koichi Chemical Co., Ltd.) as a polymerization initiator was added dropwise over 2 hours. After the dropwise addition was completed, the reaction was carried out at 80°C for 3 hours, and then 0.6 parts of V-601 were added, and the reaction was continued at 80°C for another 2 hours to obtain a solution of resin 1.

[0214] After cooling the solution of resin 1 to 50°C, 10.3 parts of dimethylaminoethanol were added to neutralize the carboxyl groups, followed by 140 parts of water. Then, the solution was heated to above 78°C, azeotropically mixed with water, and 2-butanone was removed by distillation. The solid content was then adjusted to 30%, thus obtaining an aqueous solution of resin 1 (30% solid content).

[0215] Using a GPC (Tosoh HLC-8120GPC) equipped with a TSKgel column (manufactured by Tosoh Corporation) and an RI detector, and with THF as the developing solvent, the mass-average molecular weight of the resin 1 was determined to be approximately 14,000. Furthermore, the acid value of resin 1 calculated using Equation 3 above is 65.2 (mgKOH / g). Additionally, the glass transition temperature (Tg) of resin 1 calculated using Equation 2 above is 39.7°C.

[0216] It should be noted that, in the embodiments of the present invention, "aqueous solution" refers to a solution containing an aqueous medium and components dispersed and / or dissolved in the aqueous medium.

[0217] <Examples of Resin 2-4 Manufacturing>

[0218] The polymerizable monomers used are changed as shown in Table 1 below. Otherwise, aqueous solutions of resins 2 to 4 (30% solids each) are prepared in the same manner as resin 1 described above.

[0219] [Table 1]

[0220]

[0221] The meanings of the abbreviations used in Table 1 above are as follows.

[0222] MAA: Methacrylic acid

[0223] ·BA: Butyl acrylate

[0224] MMA: Methyl methacrylate

[0225] STMA: Stearyl methacrylate

[0226] St: Styrene

[0227] <Example of manufacturing resin 5 (AB block polymer)>

[0228] In a reaction vessel equipped with a gas inlet pipe, thermometer, condenser, and stirrer, 20 parts of 2-butanone, 10.0 parts of methacrylic acid (an olefinically unsaturated monomer with an acidic group) and 10.0 parts of methyl methacrylate (another olefinically unsaturated monomer) were added, along with 0.9 parts of 2,2'-azobisisobutyronitrile (2,2'-azobisisobutyronitrile) and 3.6 parts of 2-(dodecylthiothiocarbonylthio)-isobutyric acid (2,2'-azobisisobutyronitrile) as polymerization initiators. After purging the reaction vessel with nitrogen, the temperature was raised to 75°C, and the polymerization reaction was carried out for 3 hours, thereby obtaining a copolymer (A block) containing methacrylic acid and methyl methacrylate.

[0229] After the polymerization reaction was completed, the reaction system was cooled to room temperature, and then 60 parts of 2-butanone, 55 parts of methyl methacrylate (as a polymerizable monomer), and 25 parts of styrene were added to the reaction vessel. After purging the reaction vessel with nitrogen, the temperature was raised to 75°C, and the polymerization reaction was carried out for 3 hours, thereby obtaining resin 5 with an AB block structure in which a copolymer (block B) containing methyl methacrylate and styrene was added to the A block.

[0230] Then, after cooling the reaction system to room temperature, 10.3 parts of dimethylaminoethanol were added to the reaction vessel for neutralization, followed by 200 parts of water. Next, the resulting solution was heated to azeotropically react 2-butanone with water. After removing the 2-butanone by distillation, the solution was adjusted with water to achieve a solid content of 30%, thus obtaining an aqueous solution of resin 5.

[0231] Similar to resin 1, the mass-average molecular weight of resin 5 was measured to be approximately 15,000. Furthermore, the acid value of resin 5, calculated using formula 3, was 65.2 (mg KOH / g). Additionally, the glass transition temperature (Tg) of resin 5, calculated using formula 2, was 106.1°C.

[0232] <Synthesis of acetylene diol compounds 1 and 2>

[0233] Using the method described in Example 6 of Japanese Patent Application Publication No. 2001-215690, the amounts of ethylene oxide and propylene oxide used were further adjusted to synthesize acetylenide glycol-based surfactants 1 and 2. The structures and HLB values ​​of acetylenide glycol-based surfactants 1-2 are shown in Table 2 below. It should be noted that acetylenide glycol-based surfactant 1 is defined as R in the following general formula 6. 2 Methyl, R 3It is a compound formed by the random addition of isobutyl, x1+y1 = 6, x2+y2 = 1, ethylene oxide and propylene oxide.

[0234] Formula 6:

[0235] [Chemistry 1]

[0236]

[0237] [Table 2]

[0238]

[0239] <Example of manufacturing white pigment dispersion>

[0240] 3,000 g of titanium dioxide (TIPAQUE CR-60, manufactured by Ishihara Sangyo Co., Ltd.), 300 g of resin 6 (a random polymer of styrene / acrylic acid / benzyl methacrylate neutralized with dimethylaminoethanol in a mass ratio of 45 / 30 / 25, with an acid value of 233.6 mg KOH / g and a weight-average molecular weight of 18,000), and 2,700 g of water were added to a mixing container (10 L volume) equipped with a stirrer and stirred for 1 hour (premixing). Next, a 0.6 L volume of DYNO-MILL (manufactured by Shinmaru Enterprises) filled with 1,800 g of zirconia beads with a diameter of 0.5 mm was used to begin circulating dispersion of the mixture. Then, the D50 of the mixture was measured using the aforementioned apparatus at regular intervals (e.g., 1 hour). Circulating dispersion was stopped when the D50 reached below 240 nm, thereby producing a white pigment dispersion.

[0241] <Example of manufacturing black pigment dispersion>

[0242] 450g of carbon black (PrinteX85, manufactured by Orion Engineered Carbons), 90g of resin 7 (a random polymer of styrene / acrylic acid / benzyl methacrylate neutralized with dimethylaminoethanol in a mass ratio of 45 / 25 / 30, acid value 194.6 mg KOH / g, mass average molecular weight 20,000), and 2,460g of water were added to a 10L mixing container equipped with a stirrer and premixed for 1 hour. Next, a 0.6L Shinmaru Enterprises "DYNO-MILL" container filled with 1,800g of 0.5mm diameter zirconia beads was used to begin circulating dispersion of the mixture. Then, the D50 of the mixture was measured using the aforementioned apparatus at regular intervals (e.g., 1 hour). Circulating dispersion was stopped when the D50 reached below 120nm, thereby producing a black pigment dispersion.

[0243] <Manufacturing of Water-Based Inkjet Inks 1-162>

[0244] Using the pigment dispersion prepared by the above method, each raw material is added to a mixing container equipped with a stirrer according to the formulations listed in each column of Table 3 below. After addition, the mixture is heated to 50°C and mixed for 1 hour, then filtered through a membrane filter with a pore size of 0.8 μm to produce water-based inkjet inks 1-162.

[0245] When manufacturing water-based inkjet inks, each raw material is added while stirring the mixture in the mixing container. Furthermore, in each column of Table 3, the ingredients are added sequentially, starting with the ingredients listed in the top row. However, when manufacturing water-based inkjet inks that do not contain one or more of these ingredients, that ingredient is omitted, and the next ingredient is added in sequence. Additionally, for ingredients containing two or more raw materials, the order in which they are added is arbitrary.

[0246] [Table 3]

[0247]

[0248] [Table 3]

[0249]

[0250] [Table 3]

[0251]

[0252] [Table 3]

[0253]

[0254] [Table 3]

[0255]

[0256] [Table 3]

[0257]

[0258] [Table 3]

[0259]

[0260] [Table 3]

[0261]

[0262] [Table 3]

[0263]

[0264] [Table 3]

[0265]

[0266] [Table 3]

[0267]

[0268] Here, the meanings of the abbreviations and detailed information on the product names recorded in Table 3 above are shown below. Additionally, in Table 3, "SP" represents the SP value (unit: (cal / cm³)). 3 ) 1 / 2 "HLB" indicates the HLB value, and "Tg" indicates the glass transition temperature.

[0269] •PnP: Propylene glycol monopropyl ether

[0270] •DPnP: Dipropylene glycol monopropyl ether

[0271] •PnB: Propylene Glycol Monobutyl Ether

[0272] ·DPnB: Dipropylene glycol monobutyl ether

[0273] ·1,5-PentD: 1,5-Pentanediol (SP value: 12.4)

[0274] ·1,2-BD: 1,2-Butanediol (SP value: 12.8)

[0275] ·1,3-BD: 1,3-Butanediol (SP value: 12.8)

[0276] ·1,2-PD: 1,2-Propanediol (SP value: 13.5)

[0277] ·1,3-PD: 1,3-propanediol (SP value: 13.7)

[0278] • DEG: Diethylene glycol (SP value: 13.0)

[0279] • EtOH: Ethanol (SP value: 12.6)

[0280] • EG: Ethylene glycol (SP value: 14.8)

[0281] ·1,2-HexD: 1,2-Hexanediol (SP value: 11.8)

[0282] • BDG: Diethylene glycol monobutyl ether (SP value: 10.5)

[0283] •PGM: Propylene glycol monomethyl ether (SP value: 11.3)

[0284] • DPM: Dipropylene glycol monomethyl ether (SP value: 10.4)

[0285] • SF104: Surfynol 104 (acetylene glycol manufactured by Evonik Japan, HLB value: 3)

[0286] • SF420: Surfynol 420 (acetylene glycol manufactured by Evonik Japan, HLB value: 4)

[0287] • SF2502: Surfynol 2502 (acetylene glycol manufactured by Evonik Japan, HLB value: 8)

[0288] • SF440: Surfynol 440 (acetylene glycol manufactured by Evonik Japan, HLB value: 8.1)

[0289] • TW 280: TEGO Wet 280 (manufactured by Evonik Japan, a polyether-modified siloxane with 4-12 silicon atoms and at least ethylene oxide side chains, kinematic viscosity at 25°C: 30 mmHg) 2 / s)

[0290] • TW 270: TEGO Wet 270 (manufactured by Evonik Japan, a polyether-modified siloxane with 4-12 silicon atoms and at least ethylene oxide side chains, kinematic viscosity at 25°C: 25 mm). 2 / s)

[0291] • KF642: KF-642 (manufactured by Shin-Etsu Chemical Industry Co., Ltd., a polyether-modified siloxane with 4-12 silicon atoms and at least ethylene oxide side chains, kinematic viscosity at 25°C: 50 mm). 2 / s)

[0292] • KF351A: KF-351A (manufactured by Shin-Etsu Chemical Industry Co., Ltd., a polyether-modified siloxane with 4-12 silicon atoms and at least an ethylene oxide side chain, kinematic viscosity at 25°C: 75 mm). 2 / s)

[0293] • BYK-3420: A siloxane surfactant manufactured by BYK Chemicals Japan Co., Ltd. (not a polyether-modified siloxane with 4-12 silicon atoms and at least an ethylene oxide side chain; kinematic viscosity at 25°C: 125 mm). 2 / s)

[0294] • NONION EH-208: Polyethylene glycol mono-2-ethylhexyl ether manufactured by Nippon Oil Company (number of carbon atoms in the terminal alkyl group: 8, number of ethylene oxide alkyl groups: 8)

[0295] • Lutensol XP40: Polyethylene glycol monodecyl ether manufactured by BASF Japan (10 carbon atoms in the terminal alkyl group, 4 ethylene oxide groups)

[0296] • Lutensol XP80: Polyethylene glycol monodecyl ether manufactured by BASF Japan (10 carbon atoms in the terminal alkyl group, 8 ethylene oxide groups)

[0297] • Lutensol XP140: Polyethylene glycol monodecyl ether manufactured by BASF Japan (number of carbon atoms in the terminal alkyl group: 10, number of ethylene oxide alkyl groups: 14)

[0298] • BLAUNON EL-1509P: Polyethylene glycol monolauryl ether manufactured by Aoki Oils & Fats Industries (number of carbon atoms in the terminal alkyl group: 12, number of ethylene oxide groups: 9)

[0299] • BLAUNON EL-1512P: Polyethylene glycol monolauryl ether manufactured by Aoki Oils & Fats Industries (number of carbon atoms in the terminal alkyl group: 12, number of ethylene oxide groups: 12)

[0300] • BLAUNON EL-1515: Polyethylene glycol monolauryl ether manufactured by Aoki Oils & Fats Industries (number of carbon atoms in the terminal alkyl group: 12, number of ethylene oxide groups: 15).

[0301] • BLAUNON EL-1521: Polyethylene glycol monolauryl ether manufactured by Aoki Oils & Fats Industries (number of carbon atoms in the terminal alkyl group: 12, number of ethylene oxide groups: 21)

[0302] • BLAUNON EL-1530: Polyethylene glycol monolauryl ether manufactured by Aoki Oils & Fats Industries (number of carbon atoms in the terminal alkyl group: 12, number of ethylene oxide groups: 30)

[0303] • BLAUNON EL-1540P: Polyethylene glycol monolauryl ether manufactured by Aoki Oils & Fats Industries (number of carbon atoms in the terminal alkyl group: 12, number of ethylene oxide groups: 40)

[0304] Newcol 2303: A polyethylene glycol monoalkyl ether surfactant manufactured by a Japanese emulsifier company (12-13 carbon atoms in the terminal alkyl group, 3 ethylene oxide groups).

[0305] Newcol 2320: A polyethylene glycol monoalkyl ether surfactant manufactured by a Japanese emulsifier company (12-13 carbon atoms in the terminal alkyl group, 20 ethylene oxide alkyl groups).

[0306] • BLAUNON SR-720: Polyethylene glycol monostearin ether manufactured by Aoki Oils & Fats Industries (number of carbon atoms in the terminal alkyl group: 18, number of ethylene oxide groups: 20)

[0307] • BLAUNON SR-730: Polyethylene glycol monostearin ether manufactured by Aoki Oils & Fats Industries (number of carbon atoms in the terminal alkyl group: 18, number of ethylene oxide groups: 30)

[0308] • BLAUNON SR-750F: Polyethylene glycol monostearin ether manufactured by Aoki Oils & Fats Industries (number of carbon atoms in the terminal alkyl group: 18, number of ethylene oxide groups: 50)

[0309] • Proxel GXL: Dipropylene glycol-water solution of 1,2-benzisothiazol-3-one (1,2-benzisothiazol-3-one:dipropylene glycol:water = 2:6:2, Arch Chemicals preservative)

[0310] [Examples 1-155, Comparative Examples 1-7]

[0311] Using the above-mentioned water-based inkjet inks 1 to 162, evaluations 1 to 3 as shown below were performed. The evaluation results are shown in Table 4.

[0312] <Evaluation 1: Evaluation of Ejection Stability>

[0313] An inkjet printing device is prepared to be installed above the conveyor belt, equipped with a Kyocera-manufactured inkjet head "KJ4B-1200" (design resolution 1200 dpi, nozzle diameter 20 μm). Furthermore, after filling the inkjet head with the aforementioned water-based inkjet ink, the pattern is printed and inspected at the nozzles to confirm that there are no nozzle leaks (the phenomenon of water-based inkjet ink not being ejected from the nozzles).

[0314] Next, an OPP film (FOR-AQ, 20μm thick) manufactured by Futamura Chemical Co., Ltd., pre-cut to A4 size (21cm wide x 30cm long) as a printing substrate is fixed on a conveyor belt. Then, the conveyor belt is driven at a certain speed, and as the printing substrate passes below the inkjet head setting section, the water-based inkjet ink is ejected with a droplet volume of 2pL to print a full-page image.

[0315] After printing the full-page image of the number shown below using the above method, the nozzle inspection pattern is printed again, and the number of missed nozzle prints is visually counted to evaluate the printout stability. The evaluation criteria are as follows, with A, B, and C considered as practically usable. Furthermore, the number of full-page images printed is evaluated using two methods: "1 sheet" and "5 sheets". When the printout stability is evaluated as "D" for printing 1 full-page image, the evaluation of printing 5 full-page images is not performed.

[0316] A: There was absolutely no nozzle leakage.

[0317] B: 1-4 nozzles experienced leakage.

[0318] C: 5-9 nozzles experienced leakage.

[0319] D: More than 10 nozzles experienced leakage.

[0320] <The Production of Printed Materials>

[0321] An inkjet printing apparatus was prepared, in which a Kyocera-manufactured inkjet head "KJ4B-1200" (design resolution 1200 dpi, nozzle diameter 20 μm) was mounted above a conveyor belt, and the aforementioned water-based inkjet inks were filled into the inkjet head. Additionally, the same OPP film as in Evaluation 1 was fixed onto the conveyor belt. Then, the conveyor belt was driven at a speed of 50 m / min, and as the printing substrate passed below the inkjet head mounting section, the aforementioned water-based inkjet inks were ejected at a droplet volume of 2 pL to print an image. The printed substrate was then immediately immersed in a constant-temperature, air-blown thermostat set to 70°C and dried for 1 minute, thereby producing a printed product.

[0322] It should be noted that the printed materials produced by the above method are of the following two types. Additionally, for each water-based inkjet ink, the following two types of printed materials are produced.

[0323] • Full-page print: Printed material with 100% print coverage (15cm wide x 30cm long)

[0324] • Gradient Printing: Printed materials containing a gradient image that continuously varies between 5% and 80% of the print rate within a width of 10cm and a length of 30cm.

[0325] <Evaluation 2: A full-page landfill-like evaluation>

[0326] For full-page printed materials produced using the above method, after attaching the non-printing side of the material to the backing paper (black backing paper for water-based white ink, and white backing paper for water-based black ink), the number of striped gaps (white striped gaps longer than 1 cm) is visually observed to evaluate the full-page filling performance. The evaluation criteria are as follows, with A, B, and C considered as practically usable.

[0327] A: Not a single stripe gap was observed.

[0328] B: Observed gaps in 1-4 stripes

[0329] C: Observed 5-9 stripe gaps

[0330] D: More than 10 stripe gaps were observed.

[0331] <Evaluation 3: Evaluation of Anti-adhesion>

[0332] The full-page print prepared using the above method was cut into 4cm x 4cm squares, and then the printed side was overlapped with the non-printed side of a printing substrate identical to the printing substrate used for printing. Next, this overlap was used as a test piece, and an adhesion test was conducted using a constant load permanent strain testing machine (Tester Industrial Co., Ltd. "CO-201"). The adhesion test conditions were set to a load of 10 kg / cm². 2 The ambient temperature was 40°C and the ambient humidity was 80%RH. The settling time was as follows. After this settling time, the test piece was removed from the constant load permanent strain tester, and the overlapping printed substrate was instantly peeled off while maintaining a 90-degree angle. Then, the adhesion resistance was evaluated based on the tactile feel during peeling (peeling resistance) and the condition of the printed surface after peeling (visual confirmation). The evaluation criteria are as follows, with A, B, and C considered practically usable. Furthermore, the settling time for the adhesion test was evaluated using two options: "24 hours" and "48 hours". When the adhesion resistance was evaluated as "D" with a settling time of 24 hours, the evaluation with a settling time of 48 hours was not performed.

[0333] A: There is no peeling resistance, and part of the water-based inkjet ink layer will not adhere to the non-printing surface of the printed substrate.

[0334] B: Although there is slight resistance during peeling, a portion of the water-based inkjet ink layer will not adhere to the non-printing surface of the printed substrate.

[0335] C: A portion of the water-based inkjet ink layer adheres to the non-printing surface of the printed substrate, to a degree that is less than 30% of the area of ​​the overlapping portion.

[0336] D: A portion of the water-based inkjet ink layer adheres to the non-printing surface of the printed substrate, exceeding 30% of the area of ​​the overlapping portion.

[0337] [Table 4]

[0338]

[0339] [Table 4]

[0340]

[0341] As confirmed by Table 4, the water-based inkjet ink of this embodiment exhibits excellent ejection stability, as well as excellent full-page filling and anti-blocking properties of the printed material.

[0342] [Examples 156-168]

[0343] In addition, using the aforementioned water-based inkjet inks 6, 11, 14, 16, 18, 20, 22, 23, 25, 27, 29, 31, and 33, and using full-page printed materials produced by the above method, the following evaluation 4 was conducted. The evaluation results are shown in Table 5.

[0344] It should be noted that Table 5 again shows the content of the resin with a glass transition temperature of 50~130℃ as shown in Table 3, and the ratio of the mass of (ii) propylene glycol monoalkyl ether solvent (S1) to the mass of the resin with a glass transition temperature of 50~130℃.

[0345] <Evaluation 4: Scratch Resistance Evaluation>

[0346] The full-page print prepared using the above method was cut into pieces 30mm wide and 220mm long, and placed in a vibration-type friction fastness tester (Tester Industrial Co., Ltd. "AB-301"). Then, test cotton cloth (black cotton cloth for prints made with water-based inkjet inks 6, 14, 16, 18, 20, 22, 23, 25, 27, and 29; white cotton cloth for prints made with water-based inkjet inks 11, 31, and 33) was mounted on the friction element (weighing 200g). After a predetermined number of vibrations, the surface condition of the print and the degree of coloration of the cotton cloth were visually inspected to evaluate scratch resistance. The evaluation criteria are as follows, with A, B, and C considered practically usable.

[0347] A: Even after 10 cycles of vibration, there were no scratches on the printed surface, and no color change was observed on the cotton fabric.

[0348] B: After 6 vibrations, there were no scratches on the printed surface and no staining of the cotton fabric was observed. However, after 10 vibrations, scratches on the printed surface and / or staining of the cotton fabric were observed.

[0349] C: After three cycles of vibration, no scratches were observed on the printed surface, and no coloring of the cotton fabric was observed. However, after six cycles of vibration, scratches on the printed surface and / or coloring of the cotton fabric were observed.

[0350] D: After three cycles of vibration, scratches were observed on the printed surface and / or staining of the cotton fabric.

[0351] [Table 5]

[0352]

[0353] The results of Evaluation 4 and Evaluation 3 above confirm that in the examples of water-based inkjet inks using resins with a glass transition temperature of 50 to 130°C at a content of 2.0 to 13% by mass relative to the total amount of water-based inkjet ink, and where the mass ratio of the (di) propylene glycol monoalkyl ether solvent (S1) to the mass ratio of the resin with a glass transition temperature of 50 to 130°C is 0.7 to 5.0, both the adhesion resistance and scratch resistance are at level A, indicating good quality.

Claims

1. A water-based inkjet ink, comprising a colorant, a resin, a water-soluble organic solvent, and a surfactant. The resin has a Tg of 50~130℃. The water-soluble organic solvent comprises a (di) propylene glycol monoalkyl ether solvent (S1) represented by general formula 1 below. The surfactants include acetylene glycol surfactants with an HLB value of less than 10, as well as siloxane surfactants and / or (poly) glycol monoalkyl ether surfactants. General Formula 1: R 1 -(O-CH(CH3)-CH2) n -OH In general formula 1, R 1 It is an alkyl group with 2 to 4 carbon atoms, where n is 1 or 2.

2. The water-based inkjet ink according to claim 1, further comprising an SP value of 12-14 (cal / cm³). 3 ) 1 / 2 Water-soluble organic solvent (S2).

3. The water-based inkjet ink according to claim 2, wherein, The SP value is 12~14 (cal / cm³). 3 ) 1 / 2 Water-soluble organic solvents (S2) include alkanediols with 3 to 5 carbon atoms.

4. The water-based inkjet ink according to any one of claims 1 to 3, wherein, The (ii) propylene glycol monoalkyl ether solvent (S1) contains dipropylene glycol monopropyl ether.

5. The water-based inkjet ink according to any one of claims 1 to 4, wherein, The content of the acetylene glycol-based surfactant with an HLB value of less than 10 in the water-based inkjet ink is 0.5 to 1.5% by mass.

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

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

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

9. The water-based 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 water-based inkjet ink according to any one of claims 1 to 9, wherein, The mass ratio of the resin with a glass transition temperature of 50~130℃ to the mass ratio of the (ii) propylene glycol monoalkyl ether solvent (S1) is 0.5~12.

5.

11. A printed matter formed by printing the water-based inkjet ink of any one of claims 1 to 10 onto a printing substrate.

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