Water-based ink for inkjet recording, inkjet recording method, inkjet recording apparatus, and ink container

Abstract

To provide a water-based ink for inkjet recording, containing lignosulfonic acid or a salt thereof and having preservative properties.SOLUTION: A water-based ink for inkjet recording according to the present invention contains water, a water-soluble organic solvent, and a colorant, and furthermore contains lignosulfonic acid or a salt thereof. The colorant contains at least one of a self-dispersing pigment, a resin-dispersed pigment, and a water-soluble dye.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to an aqueous ink for inkjet recording, an inkjet recording method, an inkjet recording apparatus, and an ink storage container. [Background technology]

[0002] Examples of water-based inkjet recording inks include the ink described in Patent Document 1. The ink described in Patent Document 1 uses a chemically synthesized product as a preservative. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2008-239733 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] In recent years, with the growing concern for environmental issues, the adoption of environmentally friendly products has progressed, and there is a demand for reduced environmental impact in water-based inkjet inks. Therefore, there is a need for water-based inkjet inks to use components derived from natural materials, which have a low environmental impact.

[0005] Therefore, the present invention aims to provide an inkjet recording ink containing components made from natural materials, which can contribute to reducing environmental impact. [Means for solving the problem]

[0006] To achieve the above objective, the water-soluble inkjet recording ink of the present invention comprises water, a water-soluble organic solvent, and a colorant, and further comprises lignin sulfonic acid or a salt thereof, wherein the colorant is at least one of a self-dispersing pigment, a resin-dispersing pigment, and a water-soluble dye. [Effects of the Invention]

[0007] The inventors, after investigating preservatives derived from natural materials, inferred that ligninsulfonic acid or its salts possess preservative properties based on their chemical structure. Based on this inference, they conceived the idea of ​​incorporating ligninsulfonic acid or its salts into inkjet inks. Accordingly, when ligninsulfonic acid or its salts were used as a preservative in inkjet inks, it was found to have a preservative effect on the ink. Thus, the inventors are the first to discover that ligninsulfonic acid or its salts can be used as a preservative in inkjet inks. In this way, the aqueous inkjet recording ink of the present invention contains ligninsulfonic acid or its salts derived from natural materials, thus possessing preservative properties and contributing to the reduction of environmental impact. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic perspective view showing an example configuration of the inkjet recording apparatus of the present invention. [Modes for carrying out the invention]

[0009] In this invention, the term "mass" may be interpreted as "weight" unless otherwise specified. For example, "mass ratio" may be interpreted as "weight ratio" unless otherwise specified, and "mass%" may be interpreted as "weight%" unless otherwise specified.

[0010] The water-based ink for inkjet recording of the present invention (hereinafter sometimes referred to as "water-based ink" or "ink") will be described. The water-based ink of the present invention contains water, a water-soluble organic solvent, and a colorant, and further contains lignin sulfonic acid or a salt thereof. The colorant is at least one of a self-dispersing pigment, a resin-dispersed pigment, and a water-soluble dye. In the ink of the present invention, since the colorant is at least one of a self-dispersing pigment, a resin-dispersed pigment, and a water-soluble dye, lignin sulfonic acid or a salt thereof does not function as a dispersant for the colorant. Further, lignin sulfonic acid or a salt thereof may have not only an antiseptic effect but also, for example, an aggregating effect (OD value improving effect) of a colorant.

[0011] The aforementioned water-soluble organic solvent can be one of the conventionally known types. The aforementioned water-soluble organic solvent is not particularly limited and includes, for example, polyhydric alcohols, polyhydric alcohol derivatives, alcohols, amides, ketones, keto alcohols, ethers, nitrogen-containing solvents, sulfur-containing solvents, propylene carbonate, ethylene carbonate, 1,3-dimethyl-2-imidazolidinone, and the like. Examples of the aforementioned polyhydric alcohols include glycerin, ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, hexylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, trimethylolpropane, 1,5-pentanediol, 1,2,6-hexanetriol, and the like. Examples of the polyhydric alcohol derivatives include ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol-n-propyl ether, ethylene glycol-n-butyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol-n-propyl ether, diethylene glycol-n-butyl ether, diethylene glycol-n-hexyl ether, triethylene glycol methyl ether, triethylene glycol ethyl ether, triethylene glycol-n-propyl ether, triethylene glycol-n-butyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol-n-propyl ether, propylene glycol-n-butyl ether, dipropylene glycol methyl ether, dipropylene glycol ethyl ether, dipropylene glycol-n-propyl ether, dipropylene glycol-n-butyl ether, tripropylene glycol methyl ether, tripropylene glycol ethyl ether, tripropylene glycol-n-propyl ether, and tripropylene glycol-n-butyl ether.Examples of the alcohol include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, and benzyl alcohol. Examples of the amide include dimethylformamide and dimethylacetamide. Examples of the ketone include acetone. Examples of the keto alcohol include diacetone alcohol. Examples of the ether include tetrahydrofuran and dioxane. Examples of the nitrogen-containing solvent include pyrrolidone, 2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexylpyrrolidone, and triethanolamine. Examples of the sulfur-containing solvent include thiodiethanol, thiodiglycol, thiodiglycerol, sulfolane, and dimethyl sulfoxide. The amount of the water-soluble organic solvent in relation to the total amount of the treatment agent is not particularly limited. The water-soluble organic solvent may be used alone or in combination of two or more types.

[0012] The self-dispersing pigment is, for example, a pigment particle to which at least one of a hydrophilic functional group such as a carbonyl group, hydroxyl group, carboxylic acid group, sulfonic acid group, or phosphate group, and salts thereof, is introduced directly or via other groups by chemical bonding, thereby being dispersible in water without the use of a dispersant. The self-dispersing pigment can be, for example, one in which the pigment has been treated by the method described in Japanese Patent Publication No. 8-3498, Japanese Patent Publication No. 2000-513396, Japanese Patent Publication No. 2008-524400, Japanese Patent Publication No. 2009-515007, Japanese Patent Publication No. 2011-515535, etc. The raw material for the self-dispersing pigment can be either an inorganic pigment or an organic pigment. Examples of pigments suitable for the above treatment include carbon black such as "MA8" and "MA100" manufactured by Mitsubishi Chemical Corporation. The self-dispersing pigment can also be, for example, a commercially available product. Examples of the aforementioned commercially available products include "CAB-O-JET(registered trademark) 200", "CAB-O-JET(registered trademark) 250C", "CAB-O-JET(registered trademark) 260M", "CAB-O-JET(registered trademark) 270Y", "CAB-O-JET(registered trademark) 300", "CAB-O-JET(registered trademark) 400", "CAB-O-JET(registered trademark) 450C", "CAB-O-JET(registered trademark) 465M", and "CAB-O-JET(registered trademark) 470Y" manufactured by Cabot Corporation; "BONJET(registered trademark) BLACK CW-2" and "BONJET(registered trademark) BLACK CW-3" manufactured by Orient Chemical Industry Co., Ltd.; and "LIOJET(registered trademark) WD BLACK 002C" manufactured by Toyo Ink Manufacturing Co., Ltd.

[0013] In the present invention, unless otherwise specified, the "resin-dispersed pigment" refers to a pigment to which a resin dispersant is adsorbed on the pigment surface to impart dispersion stability in a solvent or the like. As the resin dispersant, for example, a general polymer dispersant (also referred to as a resin for pigment dispersion or a resin dispersant) or the like may be used, or it may be prepared by oneself. Further, in the aqueous ink of the present invention, the pigment may be encapsulated with a polymer. As the resin dispersant, for example, those containing at least one of methacrylic acid and acrylic acid as a monomer can be used, and for example, commercially available products may be used. The resin dispersant may be, for example, a hydrophobic monomer such as styrene, a styrene derivative, vinyl naphthalene, a vinyl naphthalene derivative, an aliphatic alcohol ester of α,β-ethylenically unsaturated carboxylic acid, or a block copolymer, a graft copolymer, or a random copolymer composed of two or more monomers selected from the group consisting of acrylic acid, an acrylic acid derivative, maleic acid, a maleic acid derivative, itaconic acid, an itaconic acid derivative, fumaric acid, and a fumaric acid derivative, or a salt thereof. Examples of the commercially available products include "Joncryl (registered trademark) 611", "Joncryl (registered trademark) 60", "Joncryl (registered trademark) 586", "Joncryl (registered trademark) 687", "Joncryl (registered trademark) 63", and "Joncryl (registered trademark) HPD296" manufactured by Johnson Polymer Co., Ltd.; "Disperbyk190" and "Disperbyk191" manufactured by BYK Chemie GmbH; "Solsperse 20000" and "Solsperse 27000" manufactured by Zeneca Ltd.; and the like.

[0014] Examples of the method for dispersing the pigment using the resin for pigment dispersion include dispersing the pigment using a dispersing device. The dispersing device used for dispersing the pigment is not particularly limited as long as it is a general dispersing machine, and examples thereof include a ball mill, a roll mill, a sand mill (for example, a high-speed type), and the like.

[0015] The water-soluble dye is not particularly limited and includes, for example, direct dyes, acid dyes, basic dyes, and reactive dyes. Specific examples of the water-soluble dye include, for example, CI Direct Black, CI Direct Blue, CI Direct Red, CI Direct Yellow, CI Direct Orange, CI Direct Violet, CI Direct Brown, CI Direct Green, CI Acid Black, CI Acid Blue, CI Acid Red, CI Acid Yellow, CI Acid Orange, CI Acid Violet, CI Basic Black, CI Basic Blue, CI Basic Red, CI Basic Violet, and CI Food Black. Examples of CI Direct Black include CI Direct Black 17, 19, 32, 51, 71, 108, 146, 154, and 168. Examples of CI Direct Blue include CI Direct Blue 6, 22, 25, 71, 86, 90, 106, and 199. Examples of CI Direct Red include CI Direct Red 1, 4, 17, 28, 83, and 227. Examples of CI Direct Yellow include CI Direct Yellow 12, 24, 26, 86, 98, 132, 142, and 173. Examples of CI Direct Orange include CI Direct Orange 34, 39, 44, 46, and 60. Examples of CI Direct Violet include CI Direct Violet 47 and 48. Examples of CI Direct Brown include CI Direct Brown 109. Examples of CI Direct Green include CI Direct Green 59. Examples of CI Acid Black include CI Acid Black 2, 7, 24, 26, 31, 52, 63, 112, and 118. Examples of the aforementioned CI Acid Blue include CI Acid Blue 9, 22, 40, 59, 90, 93, 102, 104, 117, 120, 167, 229, and 234.Examples of the aforementioned CI Acid Red include CI Acid Red 1, 6, 32, 37, 51, 52, 80, 85, 87, 92, 94, 115, 180, 256, 289, 315, and 317. Examples of the aforementioned CI Acid Yellow include CI Acid Yellow 11, 17, 23, 25, 29, 42, 61, and 71. Examples of the aforementioned CI Acid Orange include CI Acid Orange 7 and 19. Examples of the aforementioned CI Acid Violet include CI Acid Violet 49. Examples of the aforementioned CI Basic Black include CI Basic Black 2. Examples of the aforementioned CI Basic Blue include CI Basic Blue 1, 3, 5, 7, 9, 24, 25, 26, 28, and 29. Examples of the aforementioned CI Basic Red include CI Basic Red 1, 2, 9, 12, 13, 14, and 37. Examples of the aforementioned CI Basic Violet include CI Basic Violet 7, 14, and 27. Examples of the aforementioned CI Hood Black include CI Hood Black 1 and 2.

[0016] The water-soluble dyes described above excel in properties such as clarity and stability. One type of water-soluble dye may be used alone, or two or more types may be used in combination.

[0017] The ligninsulfonate of the ligninsulfonic acid or its salt (hereinafter sometimes referred to as "ligninsulfonate, etc.") is not particularly limited, and examples include sodium ligninsulfonate, calcium ligninsulfonate, magnesium ligninsulfonate, and ammonium ligninsulfonate.

[0018] The aqueous ink of the present invention may contain, for example, components other than the lignin sulfonates as preservative components. Examples of components other than the lignin sulfonates include naturally derived components other than the lignin sulfonates, or chemically synthesized components. These components may be used individually or in combination of two or more. From an environmental perspective, it is preferable to contain more naturally derived components than chemically synthesized components, and it is even more preferable to contain only naturally derived components.

[0019] The amount of lignin sulfonate, etc., blended with the total amount of the aqueous ink is not particularly limited, and may be, for example, 0.1% by mass or more, 0.2% by mass or more, 0.4% by mass or more, 0.5% by mass or more, 1.2% by mass or more, or 2.0% by mass or more, and may also be 5.0% by mass or less, 4.5% by mass or less, 4.0% by mass or less, or 2.0% by mass or less, for example, 0.1% by mass to 5.0% by mass, preferably 0.2% by mass to 5.0% by mass, and more preferably 0.2% by mass to 4.5% by mass.

[0020] When the coloring agent includes the pigment, the amount of the lignin sulfonate, etc., relative to the total amount of the aqueous ink is, for example, 0.5% to 4.5% by mass, preferably 1.2% to 4.0% by mass, and more preferably 1.2% to 2.0% by mass.

[0021] When the coloring agent includes the dye, the amount of the lignin sulfonate, etc., relative to the total amount of the aqueous ink is, for example, 1.0% to 5.0% by mass, preferably 1.0% to 4.0% by mass, and more preferably 2.0% to 4.0% by mass.

[0022] The mass ratio (A / C) of the pigment content (A) to the lignin sulfonic acid or its salt content (C) in the total amount of the aforementioned water-based inkjet recording ink is not particularly limited, but is, for example, 1 to 9.5, preferably 2 to 9.5, and more preferably 2 to 5.

[0023] The mass ratio (B / C) of the content of the dye (B) and the content of the lignin sulfonic acid or its salt (C) in the total amount of the aforementioned water-based inkjet recording ink is not particularly limited, but is, for example, 1 to 10, preferably 1 to 5, and more preferably 1 to 2.

[0024] The water may be deionized water, pure water, etc. The amount of water (water ratio) to the total amount of the aqueous ink is appropriately determined according to the desired ink characteristics, etc. The water ratio may be, for example, the remainder of the other components. The amount of water is, for example, 50% to 95% by mass, preferably 55% to 90% by mass, and more preferably 60% to 80% by mass.

[0025] The aqueous ink may further contain conventionally known additives as needed. Examples of such additives include pH adjusters, viscosity modifiers, surface tension modifiers, and antifungal agents. Examples of viscosity modifiers include polyvinyl alcohol, cellulose, and water-soluble resins.

[0026] Next, the ink storage container of the present invention is an ink storage container containing an aqueous ink for inkjet recording, characterized in that the aqueous ink is the aqueous ink for inkjet recording of the present invention. For example, conventionally known ink storage containers can be used. Examples of such ink storage containers include ink cartridges, tanks, pouches, and the like.

[0027] Next, the inkjet recording apparatus and inkjet recording method of the present invention will be described.

[0028] The present invention relates to an inkjet recording apparatus that includes an ink storage section and an ink ejection section, wherein the ink stored in the ink storage section is ejected by the ink ejection section, and the ink storage section is characterized in that the aqueous inkjet recording ink of the present invention is stored in the ink storage section.

[0029] Figure 1 shows the configuration of an example of the inkjet recording apparatus of the present invention. As shown in the figure, this inkjet recording apparatus 1 mainly includes four ink storage units (ink cartridges 2), an ink ejection unit (inkjet head) 3, a head unit 4, a carriage 5, a drive unit 6, a platen roller 7, and a purge device 8.

[0030] The four ink cartridges 2 each contain one of four water-based inks: yellow, magenta, cyan, and black. For example, at least one of the four water-based inks is the water-based ink of the present invention. In this example, a set of four ink cartridges 2 is shown, but instead, an integrated ink cartridge may be used, whose interior is partitioned to form a water-based yellow ink storage section, a water-based magenta ink storage section, a water-based cyan ink storage section, and a water-based black ink storage section. For the body of the ink cartridge, for example, a conventionally known one can be used.

[0031] The inkjet head 3, installed in the head unit 4, records on the recording medium (e.g., recording paper) P. The carriage 5 is equipped with four ink cartridges 2 and the head unit 4. The drive unit 6 moves the carriage 5 back and forth in a linear direction. For example, a conventionally known drive unit 6 can be used (see, for example, Japanese Patent Application Publication No. 2008-246821). The platen roller 7 extends in the reciprocating direction of the carriage 5 and is positioned opposite the inkjet head 3.

[0032] The inkjet head 3 is constructed, for example, by stacking multiple layers of thin metal plates. Each plate has a through-hole formed in it. Multiple layers of plates with through-holes are stacked to form a channel for the water-based ink to pass through. The plates are bonded together, for example, with an adhesive.

[0033] The purging device 8 sucks up defective ink containing air bubbles and other debris that accumulates inside the inkjet head 3. For example, a conventionally known device can be used as the purging device 8 (see, for example, Japanese Patent Application Publication No. 2008-246821).

[0034] A wiper member 20 is positioned adjacent to the purge device 8 on the platen roller 7 side. The wiper member 20 is shaped like a spatula and wipes the nozzle forming surface of the inkjet head 3 as the carriage 5 moves. In Figure 1, the cap 18 covers the multiple nozzles of the inkjet head 3, which are returned to the reset position when recording is finished, in order to prevent the water-based ink from drying out.

[0035] In the inkjet recording device 1 of this example, the four ink cartridges 2 are mounted on a single carriage 5 together with the head unit 4. However, the present invention is not limited to this. In the inkjet recording device 1, each of the four ink cartridges 2 may be mounted on a carriage separate from the head unit 4. Alternatively, each of the four ink cartridges 2 may not be mounted on the carriage 5, but rather arranged and fixed within the inkjet recording device 1. In these embodiments, for example, each of the four ink cartridges 2 and the head unit 4 mounted on the carriage 5 are connected by a tube or the like, and the aqueous ink is supplied from each of the four ink cartridges 2 to the head unit 4. In these embodiments, instead of the four ink cartridges 2, four bottle-shaped ink bottles may be used. In this case, it is preferable that the ink bottles are provided with an inlet for injecting ink from the outside into the inside.

[0036] Inkjet recording using this inkjet recording device 1 is performed, for example, as follows. First, recording paper P is fed from a paper feed cassette (not shown) located to the side or below the inkjet recording device 1. The recording paper P is introduced between the inkjet head 3 and the platen roller 7. A predetermined record is made on the introduced recording paper P by aqueous ink ejected from the inkjet head 3. This ejection may be performed, for example, with a first ejection amount as described above, or with a second ejection amount when certain conditions are met. After recording, the recording paper P is ejected from the inkjet recording device 1. In Figure 1, the paper feeding mechanism and paper ejection mechanism for the recording paper P are not shown.

[0037] The apparatus shown in Figure 1 employs a serial inkjet head, but the present invention is not limited thereto. The inkjet recording apparatus may also employ a line inkjet head or a roll-to-roll system.

[0038] Next, the inkjet recording method of the present invention is an inkjet recording method that includes a recording step of ejecting aqueous ink onto a recording medium by an inkjet method, characterized in that, in the recording step, the aqueous inkjet recording aqueous ink of the present invention is used as the aqueous ink. The inkjet recording method of the present invention can be carried out, for example, using the inkjet recording apparatus of the present invention. The recording includes printing, image printing, and the like. [Examples]

[0039] Next, embodiments of the present invention will be described together with comparative examples. However, the present invention is not limited to or restricted by the following embodiments and comparative examples.

[0040] (Preparation of Pigment Dispersion A) A mixture was obtained by adding pure water to 20% by mass of pigment (carbon black) and 7% by mass of sodium hydroxide neutralized styrene-acrylic acid copolymer (acid value 175 mg KOH / g, molecular weight 10000) to make a total of 100% by mass and stirring. This mixture was placed in a wet sand mill packed with 0.3 mm diameter zirconia beads and dispersed for 6 hours. After that, the zirconia beads were removed with a separator and the mixture was filtered through a 3.0 μm pore size cellulose acetate filter to obtain pigment dispersion A. Styrene-acrylic acid copolymer is a water-soluble polymer commonly used as a dispersant for pigments. In pigment dispersion A, the amount of pigment solids (A) was 15% by mass of the total amount of pigment dispersion A. In pigment dispersion A, carbon black as the pigment is dispersed by styrene-acrylic acid copolymer as a resin dispersant.

[0041] (Examples 1-14, Comparative Examples 1-3) The components of the aqueous ink composition (Tables 1-2), excluding the colorant, were uniformly mixed to obtain an ink solvent. Next, the colorant was added to the ink solvent and uniformly mixed. Subsequently, the resulting mixture was filtered through a cellulose acetate type membrane filter (pore size 3.00 μm) manufactured by Toyo Roshi Co., Ltd. to obtain the aqueous inkjet recording inks of Examples 1-14 and Comparative Examples 1-3 shown in Tables 1-2.

[0042] For the aqueous inks of Examples 1-9 and Comparative Examples 1-2, (a) preservative properties, (b) optical density (OD value), (c) storage stability, and (d) dispensing stability were evaluated by the following methods.

[0043] For the aqueous inks of Examples 10-14 and Comparative Example 3, (a) preservative properties, (d) ejection stability, and (e) print quality were evaluated by the following methods.

[0044] The lignin sulfonates used in the aqueous inks of the present invention are typically brownish in color. Therefore, for the aqueous inks of Examples 1-9 and Comparative Examples 1-2, which use black pigment as an example of achromatic colorants, the optical density (OD value) was evaluated because there was no change in the color difference ΔE when mixed with the lignin sulfonates. On the other hand, for the aqueous inks of Examples 10-14 and Comparative Example 3, which use color dyes as an example of chromatic colorants, the color difference ΔE (print quality) was evaluated as described below to confirm the change in color due to mixing with the lignin sulfonates.

[0045] (a) Preservative property The aqueous inks of Examples 1-14 and Comparative Examples 1-3 were applied to standard food stamp agar (manufactured by Nissui Pharmaceutical Co., Ltd.) and stored at a temperature of 35°C. Afterward, the presence of mold colonies on the standard agar was visually inspected, and the preservative properties were evaluated according to the following evaluation criteria.

[0046] Criteria for evaluating preservative properties A: No mold has grown even after 5 days. B: Mold grows after 3 days. C: Mold will grow after 2 days.

[0047] (b) Optical density (OD value) Using a Brother Industries, Ltd. DCP-J987N inkjet recorder, images were recorded on recording paper (ASKUL Multi Paper Super White+ copy paper) using the water-based inks of Examples 1-9 and Comparative Examples 1-2 to prepare evaluation samples. The optical density (OD value) at three locations in the evaluation samples was measured using an X-Rite SpectroEye spectrophotometer (light source: D 50 The field of view was measured at 2° (ANSI-T), and the average value was calculated.

[0048] Optical Density (OD value) Evaluation Criteria A: The OD value increases by 0.05 or more compared to the additive-free product. B: The OD value increases by 0.01 or more compared to the additive-free product.

[0049] (c) Storage stability The aqueous inks of the examples and comparative examples, prepared immediately afterward, were placed in sealed containers and stored at 60°C for 3 days. The stored inks were observed under an optical microscope to check for the presence or absence of aggregates.

[0050] Storage stability evaluation criteria A: No agglomeration occurred after being left at 60 degrees Celsius for 3 days. B: Aggregation occurred after being left at 60°C for 3 days.

[0051] (d) Discharge stability Using a Brother Industries, Ltd. DCP-J987N inkjet recorder, evaluation samples were prepared by recording solid images on recording paper (ASKUL's "ASKUL Multi Paper Super White+" copy paper) using the water-based inks of Examples 1-9 and Comparative Examples 1-2. Leading edge defects were evaluated according to the evaluation criteria below. "Leading edge defects" refer to the failure of the initial printout during solid color printing, resulting in the leading portion remaining blank.

[0052] Discharge Stability Evaluation Criteria A: No leading edge missing during solid printing. B: Leading edge missing during solid printing.

[0053] (e) Print quality Using the DCP-J987N inkjet recording device manufactured by Brother Industries, Ltd., solid images were recorded on recording paper (ASKUL Multi Paper Super White+ copy paper manufactured by ASKUL Corporation) using the water-based inks of Examples 10-14 and Comparative Example 3 to create evaluation samples. Three color locations (L) in the evaluation samples were evaluated. * a * and b * ) is used with the X-Rite SpectroEye spectrophotometer (light source: D 50 The field of view was measured at 2° (ANSI-T), and the average value was calculated. * a * and b *It is based on the L * a * b * color space (CIE1976 (L * a * b * )) color space standardized by the International Commission on Illumination (CIE) in 1976 (see JIS Z 8729). The color difference (ΔE1) between the color of the evaluation sample of the recording paper and the color of the evaluation sample of the cotton was calculated by the following formula and evaluated according to the following evaluation criteria. ΔE = {(L * 1 - L * 2) 2 + (a * 1 - a * 2) 2 + (b * 1 - b * 2) 2} 1 / 2 Here, L * 1、 a * 1、 b * 1 is the measurement result of each example, and L * 2、 a * 2、 b * 2 is the measurement result of Comparative Example 3.

[0054] Print quality evaluation criteria A: ΔE is 3.0 or less B: ΔE is greater than 3.0

[0055] The aqueous ink compositions and evaluation results of the aqueous inks of Examples 1 to 14 and Comparative Examples 1 to 3 are shown in Tables 1 to 2.

[0056]

Table 1

[0057]

Table 2

[0058] As shown in Table 1, Examples 1 to 14 all received a preservative evaluation result of "B" or higher. Furthermore, as shown in Examples 1, 2, 9, and 10, the preservative evaluation was good regardless of the differences in lignin sulfonates, etc. Moreover, as shown in Examples 1 to 14, the preservative evaluation results were good in all cases, regardless of whether the colorant contained in the aqueous ink was a pigment or a dye.

[0059] Examples 1-5, 7-8, and 10-12, in which the amount of lignin sulfonate, etc., added to the total amount of the aqueous ink was 0.2% by mass or more and 4.5% by mass or less, showed better preservative properties and discharge stability than the other examples.

[0060] When the coloring agent was a pigment, Examples 1 to 5, in which the amount of lignin sulfonate or the like added to the aqueous ink was 0.5% by mass or more and 4.5% by mass or less, exhibited excellent preservative properties while also having superior OD values ​​and discharge stability compared to the other examples.

[0061] Furthermore, when the coloring agent was a pigment, Examples 1 to 4, in which the amount of lignin sulfonate or the like added to the aqueous ink was 1.2% by mass or more and 4.0% by mass or less, showed excellent preservative properties, OD value, discharge stability, and storage stability.

[0062] Furthermore, when the coloring agent was a pigment, Examples 1 to 4, in which the mass ratio (A / C) of the pigment content (A) to the content of the lignin sulfonate, etc. (C) in the total amount of the aqueous ink was 1 or more and 9.5 or less, showed superior preservative properties, OD value, discharge stability, and storage stability.

[0063] When the coloring agent was a dye, Examples 10 to 13, in which the amount of lignin sulfonate or the like added to the aqueous ink was 1.0% by mass or more and 5.0% by mass or less, showed superior preservative properties compared to the other examples.

[0064] Furthermore, when the coloring agent was a water-soluble dye, Examples 10 to 12, in which the mass ratio (B / C) of the content of the water-soluble dye (B) to the content of the lignin sulfonate, etc. (C) in the total amount of the aqueous ink was 1 or more and 10 or less, showed superior preservative properties, ejection stability, and print quality compared to the other examples.

[0065] On the other hand, Comparative Examples 1 to 3, which did not use the lignin sulfonate, all received a "C" rating for preservative performance, indicating poor results.

[0066] The above embodiments and some or all of the examples may also be described as follows, but are not limited to these. (Note 1) Containing water, a water-soluble organic solvent, and a coloring agent, Furthermore, it contains ligninsulfonic acid or a salt thereof. An aqueous inkjet recording ink characterized in that the coloring agent is at least one of a self-dispersing pigment, a resin-dispersing pigment, and a water-soluble dye. (Note 2) The water-based inkjet recording ink according to Appendix 1, wherein the amount of lignin sulfonic acid or its salt added to the total amount of the water-based inkjet recording ink is 0.2% by mass or more and 4.5% by mass or less. (Note 3) The aqueous inkjet recording ink according to Appendix 1 or 2, characterized in that the colorant comprises the self-dispersing pigment or the resin-dispersing pigment. (Note 4) The water-based inkjet recording ink according to Appendix 3, wherein the amount of lignin sulfonic acid or its salt added to the total amount of the water-based inkjet recording ink is 0.5% by mass or more and 4.5% by mass or less. (Note 5) The water-based inkjet recording ink according to Appendix 3 or 4, characterized in that the mass ratio (A / C) of the content (A) of the self-dispersing pigment or the resin-dispersed pigment to the content (C) of the lignin sulfonic acid or its salt in the total amount of the water-based inkjet recording ink is 1 or more and 9.5 or less. (Note 6) The inkjet recording aqueous ink according to Appendix 3, wherein the amount of lignin sulfonic acid or its salt added to the total amount of the inkjet recording aqueous ink is 1.2% by mass or more and 4.0% by mass or less. (Note 7) The colorant is an aqueous ink for inkjet recording as described in Appendix 1 or 2, comprising the water-soluble dye. (Note 8) The water-based inkjet recording ink according to Appendix 7, wherein the amount of the dye added to the total amount of the water-based inkjet recording ink is 1.0% by mass or more and 5.0% by mass or less. (Note 9) The water-soluble inkjet recording ink according to Appendix 7 or 8, characterized in that the mass ratio (B / C) of the content of the water-soluble dye (B) to the content of the lignin sulfonic acid or its salt (C) in the total amount of the water-soluble inkjet recording ink is 1 or more and 10 or less. (Note 10) The recording process includes ejecting water-based inkjet recording ink onto a recording medium using an inkjet method. An inkjet recording method characterized in that, in the recording step, the water-soluble inkjet recording ink described in any one of the appendices 1 to 9 is used as the water-soluble inkjet recording ink. (Note 11) Including an ink storage section and an ink ejection means, An inkjet recording apparatus that ejects ink contained in the ink storage section by the ink ejection means, An inkjet recording apparatus characterized in that the ink storage section contains an aqueous inkjet recording ink described in any one of the appendices 1 to 9. (Note 12) An ink container containing an inkjet water-based ink, characterized in that the inkjet water-based ink is an inkjet water-based ink described in any one of the appendices 1 to 9. [Industrial applicability]

[0067] As described above, the aqueous ink of the present invention has preservative properties due to the inclusion of ligninsulfonic acid or a salt thereof. The aqueous ink of the present invention can be widely applied to inkjet recording on various recording media. [Explanation of Symbols]

[0068] 1. Inkjet recording device 2 ink cartridges 3. Ink ejection unit (inkjet head) 4 Head Units 5 carriages 6 Drive Unit 7 Platen roller 8. Purge device

Claims

1. Containing water, a water-soluble organic solvent, and a coloring agent, Furthermore, it contains ligninsulfonic acid or a salt thereof. The colorant is at least one of a self-dispersing pigment and a resin-dispersing pigment. An inkjet water-based inkjet recording ink characterized in that the amount of lignin sulfonic acid or its salt added to the total amount of the inkjet water-based inkjet recording ink is 1.2% by mass or more and 2.0% by mass or less.

2. The aqueous inkjet recording ink according to claim 1, characterized in that the colorant comprises the self-dispersing pigment or the resin-dispersing pigment.

3. The water-based inkjet recording ink according to claim 2, characterized in that the mass ratio (A / C) of the content (A) of the self-dispersing pigment or the resin-dispersing pigment to the content (C) of the lignin sulfonic acid or its salt in the total amount of the water-based inkjet recording ink is 1 or more and 9.5 or less.

4. Containing water, a water-soluble organic solvent, and a coloring agent, Furthermore, it contains ligninsulfonic acid or a salt thereof. The aforementioned coloring agent is a water-soluble dye. The amount of the water-soluble dye blended with respect to the total amount of the water-soluble ink for inkjet recording is 1.0% by mass or more and 4.0% by mass or less. An inkjet water-based inkjet recording ink characterized in that the amount of lignin sulfonic acid or its salt blended with the total amount of the inkjet water-based inkjet recording ink is 2.0% by mass or more and 4.0% by mass or less.

5. The water-soluble inkjet recording ink according to claim 4, characterized in that the mass ratio (B / C) of the content of the water-soluble dye (B) to the content of the lignin sulfonic acid or its salt (C) in the total amount of the water-soluble inkjet recording ink is 1 or more and 10 or less.

6. The recording process includes ejecting water-based inkjet recording ink onto a recording medium using an inkjet method. An inkjet recording method characterized in that, in the recording step, the water-based inkjet recording ink described in claim 1 or 4 is used as the water-based inkjet recording ink.

7. Including an ink storage section and an ink ejection means, An inkjet recording apparatus that ejects ink contained in the ink storage section by the ink ejection means, An inkjet recording apparatus characterized in that the ink storage section contains the aqueous ink for inkjet recording described in claim 1 or 4.

8. An ink container containing an inkjet water-based ink, characterized in that the inkjet water-based ink is the inkjet water-based ink described in claim 1 or 4.

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