Water-based ink and ink cartridge for ink-jet recording

Abstract

To provide a water-based ink for ink-jet recording which, without the need for increasing the colorant concentration, can improve the optical density (OD value) of prints formed with the water-based ink.SOLUTION: This water-based ink for ink-jet recording comprises a dye; water; an acidic antiseptic; and at least one of a surfactant and a penetrant. The acidic antiseptic includes, for example, at least one of polyvalent unsaturated fatty acids, salts of polyvalent unsaturated fatty acids, dehydroacetic acid, and salts of dehydroacetic acid.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a water-based ink for ink-jet recording and an ink cartridge. [Background technology]

[0002] A known method for improving the optical density (OD value) of a printed matter using aqueous ink is to increase the colorant concentration (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-231711 Summary of the Invention [Problem to be solved by the invention]

[0004] However, increasing the colorant concentration increases the cost and reduces the stability of the aqueous ink.

[0005] Therefore, an object of the present invention is to provide a water-based ink for ink-jet recording that can improve the optical density (OD value) of a recorded product using the water-based ink without increasing the colorant concentration. [Means for solving the problem]

[0006] In order to achieve the above object, the water-based ink for ink-jet recording of the present invention comprises: The composition is characterized by containing a dye, water, an acidic preservative, and at least one of a surfactant and a penetrant. [Effects of the Invention]

[0007] The aqueous ink for inkjet recording of the present invention can improve the optical density (OD value) of the recorded matter using the aqueous ink without increasing the colorant concentration by blending the acidic preservative, and can also impart preservative properties. Furthermore, the aqueous ink for inkjet recording of the present invention can improve saturation by blending the acidic preservative. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic perspective view showing the configuration of an example of an inkjet recording apparatus of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] In the present invention, chroma (C * ) is, for example, the L standardized by the International Commission on Illumination (CIE) in 1976. * a * b * Color system (CIE1976(L) * a * b * ) color system) based on a * and b * It is calculated from the following formula (see JIS Z 8729): C * ={(a *2 )+(b *2 )} 1 / 2

[0010] The aqueous ink for inkjet recording (hereinafter, sometimes referred to as "aqueous ink" or "ink") of the present invention will be described. The aqueous ink of the present invention contains a dye, water, an acidic preservative, and at least one of a surfactant and a penetrant.

[0011] The dye is not particularly limited, and examples thereof include direct dyes, acid dyes, basic dyes, and reactive dyes. Specific examples of the dyes include 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 the CI Direct Black include CI Direct Black 17, 19, 32, 51, 71, 108, 146, 154, and 168. Examples of the CI Direct Blue include CI Direct Blue 6, 22, 25, 71, 86, 90, 106, and 199. Examples of the CI Direct Red include CI Direct Red 1, 4, 17, 28, 83, and 227. Examples of the CI Direct Yellow include CI Direct Yellow 12, 24, 26, 86, 98, 132, 142, and 173. Examples of the CI Direct Orange include CI Direct Orange 34, 39, 44, 46, and 60. Examples of the CI Direct Violet include CI Direct Violet 47 and 48. Examples of the CI Direct Brown include CI Direct Brown 109. Examples of the CI Direct Green include CI Direct Green 59. Examples of the CI Acid Black include CI Acid Black 2, 7, 24, 26, 31, 52, 63, 112, and 118. Examples of the CI Acid Blue include CI Acid Blue 9, 22, 40, 59, 90, 93, 102, 104, 117, 120, 167, 229, and 234.Examples of the 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 CI Acid Yellow include CI Acid Yellow 11, 17, 23, 25, 29, 42, 61, and 71. Examples of the CI Acid Orange include CI Acid Orange 7 and 19. Examples of the CI Acid Violet include CI Acid Violet 49. Examples of the CI Basic Black include CI Basic Black 2. Examples of the CI Basic Blue include CI Basic Blue 1, 3, 5, 7, 9, 24, 25, 26, 28, and 29. Examples of the CI Basic Red include CI Basic Red 1, 2, 9, 12, 13, 14, and 37. Examples of the CI Basic Violet include CI Basic Violet 7, 14, and 27. Examples of the CI Food Black include CI Food Black 1 and 2.

[0012] The amount of the dye to be blended relative to the total amount of the aqueous ink is not particularly limited, and is, for example, 0.1% by weight to 20% by weight, and preferably 0.3% by weight to 10% by weight.

[0013] The dyes may be used alone or in combination of two or more.

[0014] The water is preferably ion-exchanged water or pure water. The amount of water to be added to the total amount of the aqueous ink (water ratio) is determined appropriately depending on the desired ink properties, etc. The water ratio may be, for example, the remainder of the other components.

[0015] As mentioned above, the aqueous ink of the present invention further comprises an acidic preservative.

[0016] The acidic preservative preferably contains at least one of a polyunsaturated fatty acid, a polyunsaturated fatty acid salt, dehydroacetic acid, and a dehydroacetate salt. The polyunsaturated fatty acid is preferably sorbic acid, and the polyunsaturated fatty acid salt is preferably a sorbate salt. The sorbate salt preferably contains at least one of potassium sorbate and sodium sorbate. The dehydroacetate salt is preferably sodium dehydroacetate.

[0017] The acidic preservative may contain other preservatives (hereinafter referred to as "other preservatives") in addition to or instead of at least one of the polyunsaturated fatty acids, polyunsaturated fatty acid salts, dehydroacetic acid, and dehydroacetic acid salts. Examples of the other preservatives include salicylic acid, benzoic acid, and benzoates.

[0018] The acidic preservatives may be used alone or in combination of two or more.

[0019] The amount of the acidic preservative relative to the total amount of the aqueous ink is not particularly limited and is, for example, 0.1 to 10% by weight, preferably 0.1 to 6% by weight, and more preferably 0.3 to 6.0% by weight. When the acidic preservative is at least one of dehydroacetic acid and a dehydroacetate salt, the amount of the acidic preservative relative to the total amount of the aqueous ink is, for example, 0.1 to 10% by weight, preferably 0.3 to 6% by weight, and more preferably 1.0 to 5.0% by weight.

[0020] As described above, the incorporation of the acidic preservative into the aqueous ink of the present invention can improve the optical density (OD value) and saturation of the aqueous ink recording without increasing the colorant concentration, and can also impart antiseptic properties. The mechanism by which the incorporation of the acidic preservative improves the optical density (OD value) is presumed to be as follows: When the acidic preservative is a polyunsaturated fatty acid and / or its salt, the polyunsaturated fatty acid and / or its salt has a smaller molecular weight than the dye, and is therefore thought to penetrate into the fibers of the recording medium before the dye. Furthermore, because the polyunsaturated fatty acid and / or its salt has many carbon (C) double bonds (unsaturated bonds), it bonds with components contained in the recording medium, preventing the dye from penetrating deep into the fibers of the recording medium and making it easier for the dye to remain on the surface of the recording medium. This is presumed to result in improved optical density (OD value) and saturation. Furthermore, it is presumed that the surfactant promotes the dye to spread along the fibers of the recording medium, thereby filling in the gaps between dots and improving the optical density (OD value) and saturation. On the other hand, when the acidic preservative is dehydroacetic acid and / or its salt, the dehydroacetic acid and / or its salt and the dye are compatible with water. However, on the surface of the recording medium, the solvent and the like penetrate and evaporate, reducing the amount of water. As a result, it is presumed that the dye aggregates, improving the optical density (OD value) and saturation. However, the above mechanism is merely presumed, and the present invention is not limited thereto.

[0021] The aqueous ink of the present invention can be provided with antiseptic properties without using industrial acidic preservatives, and therefore can be used safely without adversely affecting the environment or human health, for example.

[0022] The water-based ink further contains a surfactant, such as an acetylene-based surfactant.

[0023] The acetylene surfactant may be, for example, a commercially available product. Examples of the commercially available product include "Olfine (registered trademark) E1004," "Olfine (registered trademark) E1008," and "Olfine (registered trademark) E1010" manufactured by Nissin Chemical Industry Co., Ltd.; "Surfynol (registered trademark) 440," "Surfynol (registered trademark) 465," and "Surfynol (registered trademark) 485" manufactured by Air Products and Chemicals, Inc.; and "Acetylenol (registered trademark) E40" and "Acetylenol (registered trademark) E100" manufactured by Kawaken Fine Chemicals Co., Ltd.

[0024] The aqueous ink may contain other surfactants in addition to or in place of the acetylenic surfactant. Examples of the other surfactants include nonionic surfactants manufactured by Kao Corporation such as the "EMULGEN (registered trademark)" series, "RHEODOL (registered trademark)" series, "EMASOL (registered trademark)" series, "EXCEL (registered trademark)" series, "EMANON (registered trademark)" series, "AMIET (registered trademark)" series, and "AMINON (registered trademark)" series; nonionic surfactants manufactured by Toho Chemical Industry Co., Ltd. such as the "SORBON (registered trademark)" series; nonionic surfactants manufactured by Lion Corporation such as the "DOBANOX (registered trademark)" series, "LEOCOL (registered trademark)" series, "LEOX (registered trademark)" series, "LAOL,LEOCOL (registered trademark)" series, "LIONOL (registered trademark)" series, "CADENAX (registered trademark)" series, "LIONON (registered trademark)" series, and "LEOFAT (registered trademark)" series; and anionic surfactants manufactured by Kao Corporation such as the "EMAL (registered trademark)" series, "LATEMUL (registered trademark)" series, "VENOL (registered trademark)" series, and "NEOPELEX (registered trademark)" series, NS SOAP, KS SOAP, OS Examples include SOAP and the "PELEX (registered trademark)" series; anionic surfactants manufactured by Lion Corporation, such as the "LIPOLAN (registered trademark)" series, "LIPON (registered trademark)" series, "SUNNOL (registered trademark)" series, "LIPOTAC (registered trademark) TE, ENAGICOL" series, "LIPAL (registered trademark)" series, and "LOTAT (registered trademark)" series; and cationic surfactants manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., such as "Catiogen (registered trademark) ES-OW" and "Catiogen (registered trademark) ES-L." The surfactants may be used alone or in combination of two or more.

[0025] The blending amount of the surfactant is, for example, 0.01% to 5% by weight, preferably 0.05% to 5% by weight, and more preferably 0.05% to 3.0% by weight. In particular, the blending amount of the acetylene surfactant relative to the total amount of the aqueous ink is, for example, 0.01% to 5% by weight, and preferably 0.05% to 3% by weight.

[0026] The blending amounts of the acidic preservative and the surfactant relative to the total amount of the aqueous ink preferably satisfy the following condition (X1), for example, when the acidic preservative is at least one of a polyunsaturated fatty acid and a polyunsaturated fatty acid salt. From the viewpoint of improving the OD value and saturation, the lower limit of the following condition (X1) is preferably 1 or more. Furthermore, from the viewpoint of ink ejection stability, the following condition (X1) is preferably 55 or less. Condition (X1): 1≦A1 / B≦55 A1: Amount of the acidic preservative (wt%) B: Amount of the surfactant (wt%)

[0027] On the other hand, when the acidic preservative is at least one of dehydroacetic acid and dehydroacetate salt, the blending amounts of the acidic preservative and the surfactant relative to the total amount of the aqueous ink preferably satisfy the following condition (X2): From the viewpoint of improving the OD value and saturation, the lower limit of the following condition (X2) is preferably 1 or more. Furthermore, from the viewpoint of ink ejection stability, the following condition (X2) is preferably 60 or less. Condition (X2): 1≦A2 / B≦60 A2: Amount of the acidic preservative (wt%) B: Amount of the surfactant (wt%)

[0028] The water-based ink further contains a penetrant that adjusts the drying speed on the recording medium.

[0029] The penetrating agent includes at least one of an alkylene diol and a glycol ether compound. Examples of the alkylene diol include 1,2-hexanediol, 1,2-heptanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 3-methyl-1,3-butanediol, 1,3-propanediol, 1,2-butanediol, 1,2-pentanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2-methyl-2,4-pentanediol, and 3-methyl-1,5-pentanediol. Examples of the glycol ether compounds include ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol-n-propyl 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, tripropylene glycol-n-butyl ether, etc. One type of penetrating agent may be used alone, or two or more types may be used in combination.

[0030] The amount of the penetrant relative to the total amount of the aqueous ink is, for example, 1% by weight to 20% by weight, preferably 1% by weight to 15% by weight, and more preferably 1% by weight to 10% by weight. In particular, the amount of at least one of the alkylene diol and the glycol ether compound relative to the total amount of the aqueous ink is, for example, 1% by weight to 20% by weight, preferably 1% by weight to 15% by weight, and more preferably 1% by weight to 10% by weight.

[0031] The blending amounts of the acidic preservative and the penetrant relative to the total amount of the aqueous ink preferably satisfy the following condition (Y1), for example, when the acidic preservative is at least one of a polyunsaturated fatty acid and a polyunsaturated fatty acid salt. From the viewpoint of improving the OD value and saturation, the lower limit of the following condition (Y1) is preferably 0.1 or more. Furthermore, from the viewpoint of ink ejection stability, the following condition (Y1) is preferably 10 or less. Condition (Y1): 0.1≦A1 / C≦10 A1: Amount of the acidic preservative (wt%) C: Amount of the penetrating agent (wt%)

[0032] On the other hand, when the acidic preservative is at least one of dehydroacetic acid and dehydroacetate salt, the blending amounts of the acidic preservative and the penetrant relative to the total amount of the aqueous ink preferably satisfy the following condition (Y2): From the viewpoint of improving the OD value and saturation, the lower limit of the following condition (Y2) is preferably 0.02 or more. Furthermore, from the viewpoint of ink ejection stability, the following condition (Y2) is preferably 6 or less. Condition (Y2): 0.02≦A2 / C≦6 A2: Amount of the acidic preservative (wt%) C: Amount of the penetrating agent (wt%)

[0033] The water-based ink may further contain a humectant that prevents the water-based ink from drying at the nozzle tip of the ink-jet head.

[0034] The wetting agent is not particularly limited, and examples thereof include lower alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, and tert-butyl alcohol; amides such as dimethylformamide and dimethylacetamide; ketones such as acetone; ketoalcohols such as diacetone alcohol; ethers such as tetrahydrofuran and dioxane; polyethers such as polyalkylene glycols; polyhydric alcohols such as alkylene glycol, glycerin, trimethylolpropane, and trimethylolethane; 2-pyrrolidone; N-methyl-2-pyrrolidone; and 1,3-dimethyl-2-imidazolidinone. Examples of the polyalkylene glycol include polyethylene glycol and polypropylene glycol. Examples of the alkylene glycol include ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, thiodiglycol, and hexylene glycol. These wetting agents may be used alone or in combination. Among these, polyhydric alcohols such as alkylene glycols and glycerin are preferred.

[0035] The amount of the humectant blended relative to the total amount of the aqueous ink is, for example, 0% by weight to 95% by weight, preferably 5% by weight to 80% by weight, and more preferably 5% by weight to 50% by weight.

[0036] The aqueous ink may further contain conventionally known additives as needed. Examples of the additives include a pH adjuster, a viscosity adjuster, a surface tension adjuster, and an antifungal agent. Examples of the viscosity adjuster include polyvinyl alcohol, cellulose, and a water-soluble resin.

[0037] The ink cartridge of the present invention is an ink cartridge containing a water-based ink for ink-jet recording, characterized in that the water-based ink is the water-based ink for ink-jet recording of the present invention. As the main body of the ink cartridge, for example, a conventionally known ink cartridge can be used.

[0038] Next, the ink jet recording apparatus and ink jet recording method of the present invention will be described.

[0039] The inkjet recording apparatus of the present invention includes an ink storage unit and an ink ejection means, and ejects ink stored in the ink storage unit by the ink ejection means, and is characterized in that the ink storage unit stores the water-based ink for inkjet recording of the present invention.

[0040] The inkjet recording method of the present invention is an inkjet recording method in which a water-based ink is ejected onto a recording medium by an inkjet system to record, and is characterized in that the water-based ink for inkjet recording of the present invention is used as the water-based ink.

[0041] The inkjet recording method of the present invention can be carried out, for example, by using the inkjet recording apparatus of the present invention. The recording includes printing, photographic printing, printing, and the like.

[0042] The configuration of an example of an inkjet recording apparatus of the present invention is shown in Figure 1. As shown in the figure, this inkjet recording apparatus 1 includes, as its main components, four ink cartridges 2, an ink ejection means (inkjet head) 3, a head unit 4, a carriage 5, a drive unit 6, a platen roller 7, and a purge device 8.

[0043] The four ink cartridges 2 contain one each of four water-based inks: yellow, magenta, cyan, and black. At least one of the four water-based inks is the water-based ink for inkjet recording of the present invention. An inkjet head 3 installed in a head unit 4 performs recording on a recording medium (e.g., recording paper) P. A carriage 5 is equipped with the four ink cartridges 2 and the head unit 4. A drive unit 6 moves the carriage 5 back and forth in a linear direction. A conventionally known drive unit can be used as the drive unit 6 (see, for example, Japanese Patent Application Laid-Open No. 2008-246821). A platen roller 7 extends in the direction of reciprocation of the carriage 5 and is disposed opposite the inkjet head 3.

[0044] The purging device 8 sucks out defective ink containing air bubbles and the like that accumulates inside the inkjet head 3. As the purging device 8, for example, a conventionally known device can be used (for example, see Japanese Patent Application Laid-Open No. 2008-246821).

[0045] A wiper member 20 is disposed adjacent to the purging device 8 on the platen roller 7 side of the purging device 8. The wiper member 20 is formed in a spatula shape and wipes the nozzle formation surface of the inkjet head 3 as the carriage 5 moves. In Figure 1, a cap 18 covers the multiple nozzles of the inkjet head 3, which are returned to the reset position when recording is completed, to prevent the water-based ink from drying.

[0046] In the inkjet recording apparatus 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 apparatus 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 may be disposed and fixed within the inkjet recording apparatus 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 water-based ink is supplied from each of the four ink cartridges 2 to the head unit 4.

[0047] Inkjet recording using this inkjet recording apparatus 1 is carried out, for example, as follows. First, recording paper P is fed from a paper feed cassette (not shown) provided to the side or below the inkjet recording apparatus 1. The recording paper P is introduced between the inkjet head 3 and the platen roller 7. A predetermined image is recorded on the introduced recording paper P using aqueous ink ejected from the inkjet head 3. After recording, the recording paper P is ejected from the inkjet recording apparatus 1. Recorded matter recorded with the aqueous ink of the present invention has a high optical density (OD value). In FIG. 1, the paper feed mechanism and paper ejection mechanism for the recording paper P are not shown.

[0048] 1 employs a serial inkjet head, but the present invention is not limited to this. The inkjet recording apparatus may employ a line inkjet head. [Example]

[0049] Next, examples of the present invention will be described together with comparative examples. However, the present invention is not limited or restricted by the following examples and comparative examples.

[0050] [Examples 1-1 to 1-10 and Comparative Examples 1-1 to 1-5] The components in the aqueous ink compositions (Tables 1 and 2) were mixed uniformly. The resulting mixture was then filtered using a hydrophilic polytetrafluoroethylene (PTFE) type membrane filter (pore size: 0.20 μm) manufactured by Toyo Roshi Kaisha, Ltd., to obtain aqueous inks for inkjet recording of Examples 1-1 to 1-10 and Comparative Examples 1-1 to 1-5. As shown in Table 1, in Examples 1-1 to 1-10, either potassium sorbate or sodium sorbate was used as the acidic preservative.

[0051] The aqueous inks of Examples 1-1 to 1-10 and Comparative Examples 1-1 to 1-5 were evaluated for (a) recording density, (b) saturation, and (c) antiseptic properties by the following methods.

[0052] (a) Recording density evaluation The aqueous inks of Examples 1-1 to 1-10 and Comparative Examples 1-1 to 1-5 were applied in an amount of about 0.90 mg / cm 2 per unit area. 2 The ink was applied to a recording medium (Askul Corporation's "Multi-Paper Super White+") so that the ink was 100% white, and an evaluation sample was prepared. The optical density (OD value) of five points in the evaluation sample was measured using a SpectroEye spectrophotometer (X-Rite Corporation) (light source: D50, viewing angle: 2°, ANSI-T), and the average value was calculated. Next, the optical density (OD value) difference (ΔOD) was calculated by subtracting the optical density (OD value) of Comparative Example 1-1, in which the evaluation sample was prepared using only aqueous cyan ink (CI Direct Blue 199) without any acidic preservative, from the optical densities (OD values) of Examples 1-1 to 1-9 and Comparative Examples 1-2 to 1-4. Similarly, the optical density (OD value) difference (ΔOD) was calculated by subtracting the optical density (OD value) of Comparative Example 1-5, in which the evaluation sample was prepared using only aqueous magenta ink (CI Acid Red 289) without using any acidic preservative, from the optical density (OD value) of Example 1-10. The recording density was then evaluated according to the following evaluation criteria.

[0053] Recording density evaluation criteria A: The improvement (ΔOD) in optical density (OD value) was 0.03 or more. B: The improvement (ΔOD) in optical density (OD value) was 0.01 or more and 0.02 or less. C: The improvement (ΔOD) in optical density (OD value) was 0 or less.

[0054] (b) Saturation evaluation The saturation (C * ) was measured using the above-mentioned spectrocolorimeter SpectroEye, the average value was calculated, and the cyan chroma and magenta chroma were evaluated according to the following evaluation criteria.

[0055] Cyan saturation evaluation criteria A: Saturation (C * ) was 51 or more. B: Saturation (C * ) was between 50 and 51. C: Saturation (C * ) was 49 or less.

[0056] Magenta saturation evaluation criteria A: Saturation (C * ) was 72 or more. B: Saturation (C * ) was between 71 and 72. C: Saturation (C * ) was below 70.

[0057] (c) Antiseptic evaluation The aqueous inks of Examples 1-1 to 1-10 and Comparative Examples 1-1 to 1-5 were applied to standard agar media and stored for 3 days in an environment at a temperature of 35° C. Thereafter, the standard agar was visually inspected for the presence of mold colonies, and the antiseptic properties were evaluated according to the following evaluation criteria.

[0058] Antiseptic evaluation Evaluation criteria A: No colony formation C: Colony outbreak occurred.

[0059] Tables 1 and 2 show the compositions and evaluation results of the aqueous inks of Examples 1-1 to 1-10 and Comparative Examples 1-1 to 1-5.

[0060] [Table 1]

[0061] [Table 2]

[0062] As shown in Table 1, in Examples 1-1 to 1-10, the results of the recording density evaluation, saturation evaluation, and antiseptic evaluation were all good.

[0063] On the other hand, as shown in Table 2, Comparative Examples 1-1 and 1-5, which did not use the acidic preservative, had poor results in the saturation evaluation and antiseptic evaluation. Comparative Example 1-2, which did not use either the surfactant or the penetrant, also had poor saturation evaluation. Comparative Example 1-3, which used 1,2-dibenzinethiazolin-3-one (LONZA Corporation's trade name: PROXEL GXL) instead of the acidic preservative, also had poor results in the recording density evaluation. Comparative Example 1-4, which used sodium ascorbate instead of the acidic preservative, also had poor results in the saturation evaluation and antiseptic evaluation.

[0064] [Examples 2-1 to 2-14 and Comparative Examples 2-1 to 2-6] The components in the aqueous ink compositions (Tables 3 and 4) were mixed uniformly. The resulting mixture was then filtered using a hydrophilic polytetrafluoroethylene (PTFE) membrane filter (pore size: 0.20 μm) manufactured by Toyo Roshi Kaisha, Ltd., to obtain aqueous inks for inkjet recording of Examples 2-1 to 2-14 and Comparative Examples 2-1 to 2-6. As shown in Table 3, in Examples 2-1 to 2-14, sodium dehydroacetate was used as the acidic preservative.

[0065] For the aqueous inks of Examples 2-1 to 2-14 and Comparative Examples 2-1 to 2-6, (b) saturation evaluation and (c) antiseptic evaluation were carried out in the same manner as in Examples 1-1 to 1-10 and Comparative Examples 1-1 to 1-5, except that (a) recording density evaluation was carried out as follows.

[0066] (a) Recording density evaluation The aqueous inks of Examples 2-1 to 2-14 and Comparative Examples 2-1 to 2-6 were applied in an amount of about 0.90 mg / cm 2 per unit area. 2 The ink was applied to a recording medium (Askul Corporation's "Multi-Paper Super White+") so that the ink was 100% white, and an evaluation sample was prepared. The optical density (OD value) of five points in the evaluation sample was measured using a SpectroEye spectrophotometer (X-Rite Corporation) (light source: D50, viewing angle: 2°, ANSI-T), and the average value was calculated. Next, the optical density (OD value) difference (ΔOD) was calculated by subtracting the optical density (OD value) of Comparative Example 2-1, in which the evaluation sample was prepared using only aqueous cyan ink (CI Direct Blue 199) without any acidic preservative, from the optical densities (OD values) of Examples 2-1 to 2-13 and Comparative Examples 2-2 to 2-5. Similarly, the optical density (OD value) difference (ΔOD) was calculated by subtracting the optical density (OD value) of Comparative Example 2-6, in which the evaluation sample was prepared using only aqueous magenta ink (CI Acid Red 289) without using any acidic preservative, from the optical density (OD value) of Example 2-14. The recording density was then evaluated according to the following evaluation criteria.

[0067] Recording density evaluation criteria A: The improvement (ΔOD) in optical density (OD value) was 0.03 or more. B: The improvement (ΔOD) in optical density (OD value) was 0.01 or more and 0.02 or less. C: The improvement (ΔOD) in optical density (OD value) was 0 or less.

[0068] Tables 3 and 4 show the ink compositions and evaluation results of the water-based inks of Examples 2-1 to 2-14 and Comparative Examples 2-1 to 2-6.

[0069] [Table 3]

[0070] [Table 4]

[0071] As shown in Table 3, in Examples 2-1 to 2-14, the results of the recording density evaluation and the antiseptic property evaluation were all good.

[0072] On the other hand, as shown in Table 4, Comparative Examples 2-1 and 2-6, which did not use the acidic preservative, showed poor results in the saturation and antiseptic properties evaluations. Comparative Example 2-2, which did not use either the surfactant or the penetrant, also showed poor saturation. Comparative Example 2-3, which used 1,2-dibenzinethiazolin-3-one (LONZA's trade name: PROXEL GXL) instead of the acidic preservative, also showed poor results in the recording density evaluation. Comparative Example 2-4, which used sodium ascorbate instead of the acidic preservative, also showed poor results in the saturation and antiseptic properties evaluations. Comparative Example 2-5, which used kojic acid instead of the acidic preservative, also showed poor results in the recording density evaluation, saturation evaluation, and antiseptic properties evaluations. [Industrial Applicability]

[0073] As described above, the aqueous ink of the present invention can improve the optical density (OD value) and saturation of recorded matter without increasing the colorant concentration, and furthermore, the aqueous ink of the present invention is endowed with antiseptic properties. The uses of the aqueous ink of the present invention are not particularly limited, and the ink can be widely applied to various types of inkjet recording. [Explanation of symbols]

[0074] 1. Inkjet recording device 2 ink cartridges 3. Ink ejection means (inkjet head) 4 Head Unit 5 Carriage 6 Drive Unit 7 Platen roller 8 Purging device

Claims

1. A dye, water, an acidic preservative, and at least one of a surfactant and a penetrant; the acidic preservative is at least one of a polyunsaturated fatty acid, a polyunsaturated fatty acid salt, dehydroacetic acid, and a dehydroacetate salt; the surfactant is an acetylene-based surfactant, The penetrating agent includes at least one of an alkylene diol and a glycol ether compound, The content of the acidic preservative is 0.5% by mass or more and 6.0% by mass or less, When the penetrating agent is included, The aqueous ink for ink-jet recording, wherein the amounts of the acidic preservative and the penetrant added satisfy the following condition (Y): Condition (Y): 0.2≦A / C≦10 A: Amount of the acidic preservative (wt%) C: Amount of the penetrant (wt%)

2. The surfactant is an acetylene glycol surfactant. The water-based ink for ink-jet recording according to claim 1.

3. The content of the acidic preservative is 1.0% by mass or more and 5.0% by mass or less, When the penetrating agent is included, The water-based ink for ink-jet recording according to claim 1 , wherein the amounts of the acidic preservative and the penetrant added satisfy the following condition (Y): Condition (Y): 0.9≦A / C≦5.0 A: Amount of the acidic preservative (wt%) C: Amount of the penetrant (wt%)

4. the polyunsaturated fatty acid is sorbic acid; The water-based ink for ink-jet recording according to any one of claims 1 to 3, wherein the polyunsaturated fatty acid salt is a sorbate salt.

5. The water-based ink for ink-jet recording according to claim 4, wherein the sorbate comprises at least one of potassium sorbate and sodium sorbate.

6. The water-based ink for ink-jet recording according to any one of claims 1 to 5, wherein the dehydroacetate is sodium dehydroacetate.

7. the acidic preservative is at least one of dehydroacetic acid and a salt of dehydroacetate; The water-based ink for ink-jet recording according to any one of claims 1 to 6, wherein the content of at least one of the dehydroacetic acid and the dehydroacetate salt is 1.0% by mass or more and 5.0% by mass or less.

8. When the surfactant is contained, The water-based ink for ink-jet recording according to any one of claims 1 to 7, wherein the content of the surfactant is 0.05% by mass or more and 3.0% by mass or less.

9. When the penetrating agent is contained, The water-based ink for ink-jet recording according to any one of claims 1 to 8, wherein the blending amount of the penetrant is 1.0% by mass or more and 10.0% by mass or less.

10. The water-based ink for ink-jet recording according to any one of claims 1 to 9, wherein at least one of the alkylene diol and the glycol ether compound is at least one selected from the group consisting of 1,2-hexanediol, 3-methyl-1,5-pentanediol, and triethylene glycol-n-butyl ether (BTG).

11. When the acidic preservative is at least one of a polyunsaturated fatty acid and a polyunsaturated fatty acid salt, and the surfactant is included, The blending amounts of the acidic preservative and the surfactant satisfy the following condition (X1), When the acidic preservative is at least one of dehydroacetic acid and a salt of dehydroacetate, The aqueous ink for ink-jet recording according to any one of claims 1 to 10, wherein the blending amounts of the acidic preservative and the surfactant satisfy the following condition (X2): Condition (X1): 1≦A1 / B≦55 A1: Amount of the acidic preservative (wt%) B: Amount of the surfactant (wt%) Condition (X2): 1≦A2 / B≦60 A2: Amount of the acidic preservative (wt%) B: Amount of the surfactant (wt%)

12. The content of the acidic preservative is 1.0% by mass or more and 5.0% by mass or less, When the surfactant is contained, The water-based ink for ink-jet recording according to claim 1 , wherein the blending amounts of the acidic preservative and the surfactant satisfy the following condition (X): Condition (X): 5.0≦A / B≦25.0 A: Amount of the acidic preservative (wt%) B: Amount of the surfactant (wt%)

Images