Water-based inkjet ink composition and inkjet recording method

Abstract

To provide an aqueous ink jet ink composition that can be stored in a condition with a good dispersion state while retaining good image quality.SOLUTION: An aqueous ink jet ink composition contains a color material, water, 1-(2-hydroxyethyl)-2-pyrrolidone, and a 1,2-alkanediol. The content ratio of the 1-(2-hydroxyethyl)-2-pyrrolidone content and the 1,2-alkanediol content is 1:10 to 10:1 in mass ratio.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a water-based inkjet ink composition and an inkjet recording method. [Background technology]

[0002]

[0003] The inkjet method is capable of forming high-quality images on a recording medium, and thus various technical developments have been made in the past. Not only have inkjet recording apparatuses been developed, but extensive research has also been carried out to improve the ink compositions used therein.

[0003] For example, Patent Document 1 discloses an aqueous inkjet ink containing a pigment, a polymer dispersant, a specific water-soluble acrylic resin, and at least one water-soluble organic solvent selected from glycol ethers and 1,2-alkanediols. The document states that this aqueous inkjet ink suppresses intermittent ejection failures, achieves a fast drying speed, and provides high-quality image quality without spots and abrasion resistance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-047660 Summary of the Invention [Problem to be solved by the invention]

[0005] As described in Patent Document 1, 1,2-alkanediols are expected to improve the permeability of ink compositions into recording media and the quality of the resulting images. However, 1,2-alkanediols may destabilize the dispersion state of dispersed components, such as colorants and resin particles, present in the ink composition. Therefore, there is a demand for aqueous inkjet compositions that can be stored in a well-dispersed state while maintaining good image quality. [Means for solving the problem]

[0006] One aspect of the water-based inkjet ink composition according to the present invention is Contains a colorant, water, 1-(2-hydroxyethyl)-2-pyrrolidone, and a 1,2-alkanediol, The ratio of the content of the 1-(2-hydroxyethyl)-2-pyrrolidone to the content of the 1,2-alkanediol is 1:10 to 10:1 in terms of mass ratio.

[0007] One aspect of the inkjet recording method according to the present invention comprises: The method includes ejecting the above-mentioned water-based ink-jet ink composition from a recording head and depositing it onto a recording medium. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a perspective view showing a schematic configuration of a first embodiment of a recording apparatus in a see-through state. [Figure 2] FIG. 2 is a perspective view showing an ink supply unit provided in the housing of the recording apparatus. [Figure 3] FIG. [Figure 4] FIG. 4 is a partially broken cross-sectional view taken along line 4-4 in FIG. 3. [Figure 5] FIG. 5 is a partially broken cross-sectional view taken along line 5-5 in FIG. 3. [Figure 6] FIG. 4 is a perspective view of the ink container with the cap removed. [Figure 7] FIG. [Figure 8] FIG. [Figure 9] FIG. [Figure 10] 10 is a cross-sectional view taken along line 10-10 in FIG. 9. [Figure 11] 11 is a cross-sectional view taken along line 11-11 in FIG. 9. [Figure 12] FIG. 10 is a partially cutaway front view showing a state immediately before ink is replenished to the ink accommodating body. [Figure 13] FIG. 10 is a partially cutaway side view showing a state immediately before ink is replenished to the ink accommodating body. [Figure 14] FIG. 10 is a partially cutaway front view showing a state in which ink is being refilled into the ink container. [Figure 15] FIG. 10 is a partially cutaway side view showing a state in which ink is being refilled into the ink container. [Figure 16] FIG. 10 is a partially cutaway front view showing a state in which the positioning portion of the ink accommodating body abuts against a receiving surface on the ink accommodating body side during ink replenishment. [Figure 17] FIG. 10 is a partially cutaway side view showing a state in which the positioning portion of the ink accommodating body abuts against a receiving surface on the ink accommodating body side during ink refilling. DETAILED DESCRIPTION OF THE INVENTION

[0009] The following describes embodiments of the present invention. The embodiments described below are examples of the present invention. The present invention is not limited to the following embodiments, and includes various modified forms that are implemented within the scope of the present invention. Note that not all of the configurations described below are necessarily essential configurations of the present invention.

[0010] In this specification, "(meth)acrylic" refers to acrylic or methacrylic, and "(meth)acrylate" refers to acrylate or methacrylate.

[0011] 1. Water-based inkjet ink composition The water-based inkjet ink composition according to this embodiment contains a colorant, water, 1-(2-hydroxyethyl)-2-pyrrolidone, and a 1,2-alkanediol.

[0012] 1.1. Colorants The water-based inkjet ink composition contains a colorant. Examples of the colorant include water-soluble dyes, disperse dyes, and pigments. Any of these may be used, or a mixture of these may be used. However, the water-based inkjet ink composition preferably contains a pigment, and more significant effects are achieved when the water-based inkjet ink composition contains only a pigment.

[0013] 1.1.1.Water-soluble dyes The aqueous inkjet ink composition of this embodiment may contain one or more water-soluble dyes selected from acid dyes, reactive dyes, and direct dyes. The hue of the water-soluble dye is not limited, and may be a process color such as cyan, magenta, yellow, or black, or a special color such as blue, red, orange, or fluorescent color. The water-soluble dye can dye recording media such as fabrics (fibers), but the dyeing mechanism is not particularly limited. These dyes may be used alone or in combination.

[0014] Specific examples of acid dyes include: CIAcid Red 1, 6, 8, 9, 13, 14, 18, 19, 24, 26, 27, 28, 32, 35, 37, 42, 51, 52, 57, 62, 75, 77, 80, 82, 83, 85, 87, 88, 89, 92, 94, 9 5, 97, 106, 111, 114, 115, 117, 118, 119, 127, 128, 129, 130, 131, 133, 134, 138, 143, 145, 149, 151, 154, 155, 1 58, 168, 180, 183, 184, 186, 194, 198, 199, 209, 211, 215, 216, 217, 219, 249, 252, 254, 256, 257, 260, 261, 262 , 263, 265, 266, 274, 276, 282, 283, 289, 299, 301, 303, 305, 315, 318, 320, 321, 322, 336, 337, 361, 396, 397, etc.; CIAcid Violet 5, 7, 11, 15, 31, 34, 35, 41, 43 , 47, 48, 49, 51, 54, 66, 68, 75, 78, 90, 97, 103, 106, 126, etc.; C.I. Acid Yellow 1, 3, 7, 11, 17, 19, 23, 25, 29, 36, 38, 39, 40, 42, 44, 49, 50, 59, 61, 64, 70, 72, 75, 76, 78, 79, 98, 99, 110, 111, 112, 114, 116, 118, 119, 127, 128, 131, 135, 141, 142, 143, 151, 159, 161, 162, 163, 164, 165, 169, 174, 184, 190, 195, 196, 197, 199, 207, 218, 219, 222, 227, 246, etc.; C.I. Acid Blue 1, 7, 9, 15, 22, 23, 25, 27, 29, 40, 41, 43, 45, 49, 54, 59, 60, 62, 72, 74, 76, 78, 80, 82, 83, 87, 90, 92, 93, 100, 102, 103, 104, 106, 112, 113, 114, 117, 120, 126, 127, 127:1, 128, 129, 130, 131, 133, 138, 140, 142, 143, 151, 154, 156, 158, 161, 166, 167, 168, 170, 171, 175, 181, 182, 183, 184, 185, 187, 192, 193, 201, 203, 204, 205, 207, 209, 220, 221, 224, 225, 229, 230, 232, 239, 247, 249, 258, 260, 264, 271, 277, 277:1, 278, 279, 280, 284, 288, 290, 296, 298, 300, 317, 324, 326, 333, 335, 338, 342, 350, etc.; C.I. Acid Black 1, 2, 7, 24, 26, 29, 31, 44, 48, 50, 51, 52, 52:1, 58, 60, 62, 63, 64, 67, 72, 76, 77, 94, 107, 108, 109, 110, 112, 115, 118, 119, 121, 122, 131, 132, 139, 140, 155, 156, 157, 158, 159, 172, 191, 194, 234, etc.; C.I. Acid Orange 1, 7, 8, 10, 19, 20, 24, 28, 33, 41, 43, 45, 51, 56, 63, 64, 65, 67, etc.; It should be noted that there are some incorrect or incomplete expressions in the original Chinese text you provided. I have translated it as accurately as possible according to the rules. If you can correct and clarify the original text, it will be more conducive to obtaining a more accurate translation result.CIAcid Green 3, 7, 9, 12, 16, 19, 20, 25, 27, 28, 35, 36, 40, 41, 43, 44, 48, 56, 57, 60, 61, 65, 73, 75, 76, 78, 79, etc.; CI Acid Brown 2, 4, 13, 14, 19, 20, 27, 28, 30, 31, 39, 44, 45, 46, 48, 53, 100, 101, 103, 104, 106, 160, 161, 165, 188, 224, 225, 226, 231, 232, 236, 247, 256, 257, 266, 268, 276, 277, 282, 289, 294, 295, 296, 297, 298, 299, 300, 301, 302, and the like.

[0015] Examples of direct dyes include: CI Direct Red 2, 4, 9, 23, 26, 31, 39, 62, 63, 72, 75, 76, 79, 80, 81, 83, 84, 89, 92, 95, 111, 173, 184, 20 7, 211, 212, 214, 218, 221, 223, 224, 225, 226, 227, 232, 233, 240, 241, 242, 243, 247, etc.; CIDirect Violet 7, 9, 47, 48, 51, 66, 90, 93, 94, 95, 98, 100, 101 etc; CIDirect Yellow 8, 9, 11, 12, 27, 28, 29, 33, 35, 39, 41, 44, 50, 53, 58, 59, 68, 86, 87, 93, 95, 96, 98, 100, 106, 108, 109, 110, 130, 132, 142, 144, 161, 163, etc.; CIDirect Blue 1, 10, 15, 22, 25, 41, 55, 67, 68, 71, 76, 77, 78, 80, 84, 86, 87, 90, 98, 106, 108, 109, 120, 151, 156, 158, 159, 160, 153, 168, 189, 192, 193, 194, 199, 200, 201, 202, 203, 207, 211, 213, 214, 218, 225, 226, 229, 236, 237, 244, 248, 249, 251, 252, 264, 270, 280, 288, 289, 291, etc.; CI Direct Black 9, 17, 19, 22, 32, 51, 56, 62, 69, 77, 80, 91, 94, 97, 108, 112, 113, 114, 117, 118, 121, 122, 125, 132, 146, 154, 166, 168, 173, 195, 199, etc.

[0016] Examples of reactive dyes include: CIReactive Yellow 1, 2, 3, 5, 11, 13, 14, 15, 17, 18, 20, 21, 22, 23, 24, 25, 26, 27, 29, 35, 37, 40, 41, 42, 47, 51, 55, 65, 67, 81, 95, 116, 142, 161, etc.; CIReactive Red 1, 3, 3:1, 4, 13, 14, 17, 19, 21, 22, 23, 24, 24:1, 25, 26, 29, 31, 32, 35, 37, 40, 41, 43, 44, 45, 46, 49, 55, 60, 66, 74, 79, 96, 97, 108, 141, 180, 218, 226, 245, etc.; CIReactive Violet 1, 3, 4, 5, 6, 7, 8, 9, 16, 17, 22, 23, 24, 26, 27, 33, 34 etc; CIReactive Blue 1, 2, 3, 5, 7, 8, 10, 13, 14, 15, 17, 18, 19, 21, 23, 25, 26, 27, 28, 29, 32, 35, 38, 41, 49, 63, 72, 75, 80, 95, 190, etc.; CIReactive Orange 1, 2, 4, 5, 7, 12, 13, 14, 16, 20, 29, 33, 35, 38, 64, 67, 71, 72, 72:1, 78, 82, 84, 86, 87, 91, 99, 99:1, 107, 113, 122, 124, 125, etc.; CI Reactive Black 1, 3, 4, 5, 7, 8, 11, 12, 14, 17, 21, 23, 26, 31, 32, 34, 39, etc.

[0017] When a water-soluble dye is used, its content relative to the total amount of the aqueous inkjet ink composition is not limited, but is generally from 0.1% to 30% by mass in total, preferably from 0.5% to 25% by mass, more preferably from 1% to 20% by mass, and even more preferably from 5% to 15% by mass.

[0018] 1.1.2.Dispersed colorant The aqueous inkjet ink composition may use a disperse colorant as the colorant. A disperse colorant is a colorant that is insoluble or poorly soluble in a solvent, such as a pigment or a disperse dye. Pigments and disperse dyes that are insoluble or poorly soluble in a solvent are not particularly limited, and examples thereof include inorganic pigments, organic pigments, oil-soluble dyes, and disperse dyes. The hue of the pigment or disperse dye is also not limited, and may be a so-called process color such as cyan, magenta, yellow, or black, or a so-called special color such as blue, red, orange, white, fluorescent color, or brilliant color.

[0019] Examples of inorganic pigments that can be used include carbon blacks such as furnace black, lamp black, acetylene black, and channel black (CI Pigment Black 7, etc.), iron oxide, titanium oxide, zinc oxide, and silica.

[0020] Examples of carbon black include No. 2300, 900, MCF88, No. 20B, No. 33, No. 40, No. 45, No. 52, MA7, MA8, MA100, and No. 2200B manufactured by Mitsubishi Chemical Corporation. Examples of carbon black include Color Black FW1, FW2, FW2V, FW18, FW200, S150, and S manufactured by Degussa. Examples of carbon black include Conductex SC, Raven 1255, 5750, 5250, 5000, 3500, 1255, and 700 manufactured by Columbia Carbon Corporation. Examples of carbon black include Regal 400R, 330R, and 660R, Mogul L, Monarch 700, 800, 880, 900, 1000, 1100, 1300, and 1400, and Elftex 12 manufactured by Cabot Corporation. Examples of carbon black include BONJET manufactured by Orient Chemical Industries Co., Ltd. Examples include BLACK CW-1, CW-1S, CW-2, CW-3, and M-800.

[0021] Examples of organic pigments include quinacridone pigments, quinacridonequinone pigments, dioxazine pigments, phthalocyanine pigments, anthrapyrimidine pigments, anthanthrone pigments, indanthrone pigments, flavanthrone pigments, perylene pigments, diketopyrrolopyrrole pigments, perinone pigments, quinophthalone pigments, anthraquinone pigments, thioindigo pigments, benzimidazolone pigments, isoindolinone pigments, azomethine pigments, and azo pigments.

[0022] Examples of cyan pigments include CI Pigment Blue 1, 2, 3, 15:3, 15:4, 15:34, 16, 22, 60, etc.; CI Vat Blue 4, 60, etc., and preferably, one or a mixture of two or more selected from the group consisting of CI Pigment Blue 15:3, 15:4, and 60 can be exemplified.

[0023] Examples of magenta pigments include CI Pigment Red 5, 7, 12, 48(Ca), 48(Mn), 57(Ca), 57:1, 112, 122, 123, 168, 184, 202, and CI Pigment Violet 19, and preferably, one or a mixture of two or more selected from the group consisting of CI Pigment Red 122, 202, and 209, and CI Pigment Violet 19.

[0024] Examples of yellow pigments include CI Pigment Yellow 1, 2, 3, 12, 13, 14C, 16, 17, 73, 74, 75, 83, 93, 95, 97, 98, 119, 110, 114, 128, 129, 138, 150, 151, 154, 155, 180, and 185, and preferably, one or a mixture of two or more selected from the group consisting of CI Pigment Yellow 74, 109, 110, 128, and 138 can be mentioned.

[0025] Examples of orange pigments include CI Pigment Orange 36 or 43, or a mixture thereof. Examples of pigments used in water-based inks for green inkjet printing include CI Pigment Green 7 or 36, or a mixture thereof.

[0026] The luster pigment is not particularly limited as long as it can exhibit luster when attached to a medium, but examples include metal particles of one or more alloys (also called metal pigments) selected from the group consisting of aluminum, silver, gold, platinum, nickel, chromium, tin, zinc, indium, titanium, and copper, and pearl pigments with pearly luster. Representative examples of pearl pigments include pigments with pearly luster or interference luster, such as titanium dioxide-coated mica, fish scale foil, and bismuth oxychloride. The luster pigment may also be surface-treated to suppress reaction with water.

[0027] Examples of white pigments include metal oxides, barium sulfate, calcium carbonate, and other metal compounds. Examples of metal oxides include titanium dioxide, zinc oxide, silica, and alumina. , magnesium oxide, etc. Furthermore, particles having a hollow structure may be used as the white pigment.

[0028] The pigment may be used in a state in which it has been dispersed in advance using a dispersant. Examples of dispersants include (meth)acrylic resins and salts thereof, such as poly(meth)acrylic acid, (meth)acrylic acid-acrylonitrile copolymers, (meth)acrylic acid-(meth)acrylic acid ester copolymers, vinyl acetate-(meth)acrylic acid ester copolymers, vinyl acetate-(meth)acrylic acid copolymers, and vinylnaphthalene-(meth)acrylic acid copolymers; styrene resins and salts thereof, such as styrene-(meth)acrylic acid copolymers, styrene-(meth)acrylic acid-(meth)acrylic acid ester copolymers, styrene-α-methylstyrene-(meth)acrylic acid copolymers, styrene-α-methylstyrene-(meth)acrylic acid-(meth)acrylic acid ester copolymers, styrene-maleic acid copolymers, and styrene-maleic anhydride copolymers; and polymer compounds (resins) containing urethane bonds formed by the reaction of an isocyanate group with a hydroxyl group. These may be linear and / or branched, and examples of water-soluble resins include urethane resins and salts thereof, with or without crosslinking; polyvinyl alcohols; vinyl naphthalene-maleic acid copolymers and salts thereof; vinyl acetate-maleic acid ester copolymers and salts thereof; and vinyl acetate-crotonic acid copolymers and salts thereof.

[0029] Commercially available dispersants for styrene-acrylic resins include, for example, X-200, X-1, X-205, X-220, and X-228 (manufactured by Seiko PMC Co., Ltd.), Nopcosperse (registered trademark) 6100 and 6110 (manufactured by San Nopco Ltd.), Joncryl 67, 586, 611, 678, 680, 682, and 819 (manufactured by BASF), DISPERBYK-190 (manufactured by BYK Japan KK), N-EA137, N-EA157, N-EA167, N-EA177, N-EA197D, N-EA207D, and E-EN10 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.).

[0030] Commercially available acrylic resin dispersants include BYK-187, BYK-190, BYK-191, BYK-194N, and BYK-199 (manufactured by BYK-Chemie Co., Ltd.), Aron A-210, A6114, AS-1100, AS-1800, A-30SL, A-7250, and CL-2 (manufactured by Toagosei Co., Ltd.).

[0031] Commercially available urethane resin dispersants include BYK-182, BYK-183, BYK-184, and BYK-185 (manufactured by BYK-Chemie Co., Ltd.), TEGO Disperse 710 (manufactured by Evonic Tego Chemi), and Borchi (registered trademark) Gen 1350 (manufactured by OMG Borschers).

[0032] The dispersants may be used alone or in combination of two or more. The total content of the dispersants is preferably 0.1 to 30 parts by mass, more preferably 0.5 to 25 parts by mass, even more preferably 1 to 20 parts by mass, and even more preferably 1.5 to 15 parts by mass, per 50 parts by mass of the pigment. By using a dispersant content of 0.1 parts by mass or more per 50 parts by mass of the pigment, the dispersion stability of the pigment can be further improved. Furthermore, by using a dispersant content of 30 parts by mass or less per 50 parts by mass of the pigment, the viscosity of the resulting dispersion can be further reduced.

[0033] Any disperse dye or oil-soluble dye can be used as long as it is a coloring material that disperses in the ink vehicle without dissolving, and examples of such dyes include azo dyes, metal complex azo dyes, anthraquinone dyes, phthalocyanine dyes, and triarylmethane dyes.

[0034] Disperse dyes include CIDisperse Red 60, 82, 86, 86:1, 92, 152, 154, 167:1, 191, 279, and CIDisperse Ye Examples include CI Disperse Blue 64, 71, 86, 114, 153, 163, 233, 245, CI Disperse Blue 27, 60, 73, 77, 77:1, 87, 165, 165:1, 257, 367, CI Disperse Violet 26, 33, 36, 57, CI Disperse Orange 30, 41, 61, 80, etc.

[0035] The dispersible colorant is preferably one that can be stably dispersed in the ink. For example, the colorant surface may be oxidized or sulfonated with ozone, hypochlorous acid, fuming sulfuric acid, or the like to modify the surface of the colorant particles, and the colorant may be used as a self-dispersible colorant, or the colorant may be dispersed using the above-mentioned dispersant.

[0036] The pigments and disperse dyes exemplified above as disperse colorants are only examples, and these pigments and disperse dyes may be used alone or in combination of two or more. It is also possible to use a pigment and a disperse dye in combination, or a water-soluble dye and a disperse colorant in combination.

[0037] When a pigment is used in the aqueous inkjet ink composition, among the above coloring materials, the pigment can maintain good dispersibility despite its dispersion state being easily attacked by 1,2-hexanediol, and both dispersion stability and the image quality of the resulting image can be improved. In other words, the effect of stabilizing the dispersion state is more pronounced.

[0038] 1.2. Water The aqueous inkjet ink composition according to this embodiment contains water. Examples of water include pure water such as ion-exchanged water, ultrafiltered water, reverse osmosis water, and distilled water, as well as ultrapure water, which has reduced ionic impurities. Furthermore, using water that has been sterilized by ultraviolet irradiation or the addition of hydrogen peroxide can suppress the growth of bacteria and fungi when the aqueous inkjet ink composition is stored for a long period of time.

[0039] The water content of the aqueous inkjet ink composition is 30% by mass or more, preferably 40% by mass or more, more preferably 45% by mass or more, and even more preferably 50% by mass or more, based on the total amount of the aqueous inkjet ink composition. The water in the aqueous inkjet ink composition includes, for example, water contained in raw materials, as well as added water. A water content of 30% by mass or more allows the aqueous inkjet ink composition to have a relatively low viscosity. The upper limit of the water content is preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less, based on the total amount of the aqueous inkjet ink composition.

[0040] 1.3. 1-(2-hydroxyethyl)-2-pyrrolidone The aqueous inkjet ink composition according to this embodiment contains 1-(2-hydroxyethyl)-2-pyrrolidone, which is also known as N-hydroxyethylpyrrolidone or 1-(2-hydroxyethyl)pyrrolidin-2-one (sometimes abbreviated as "HEP" in this specification).

[0041] Although HEP has amphiphilic properties, it does not have a structure in which the hydrophilic and hydrophobic portions are clearly separated, as compared with surfactants. Therefore, it is less likely to destabilize the dispersion state of substances dispersed in the aqueous inkjet ink composition, such as pigments, dispersible colorants, and resin particles. Therefore, among surfactants and organic solvents that have amphiphilic properties, HEP has the property of being less likely to cause aggregation of substances dispersed in the aqueous inkjet ink composition.

[0042] Furthermore, the inclusion of HEP in the aqueous inkjet ink composition inhibits the dispersibility of dispersed substances by inhibiting the dispersibility of 1,2-alkanediols (described below). The inventors believe that this effect is due in part to the fact that HEP has properties that complement the hydrophobic-hydrophilic relationship between 1,2-alkanediols, which have relatively strong hydrophobicity, and water, polyhydric alcohols, organic solvents, and the like, which have relatively weak hydrophobicity or high hydrophilicity.

[0043] The content of HEP is preferably 0.5% by mass to 30.0% by mass, more preferably 1.0% by mass to 20.0% by mass, and even more preferably 2.0% by mass to 10.0% by mass, based on the total amount of the aqueous inkjet ink composition.

[0044] 1.4. 1,2-Alkanediols The aqueous inkjet ink composition of this embodiment contains a 1,2-alkanediol. 1,2-Alkanediol is a general term for compounds in which hydroxyl groups are substituted at the 1- and 2-positions of an alkane. Examples of 1,2-alkanediols include ethylene glycol, propane-1,2-diol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol, 1,2-octanediol, 1,2-nonanediol, 1,2-decanediol, 3-methyl-1,2-butanediol, 3-methyl-1,2-pentanediol, 4-methyl-1,2-pentanediol, 3,4-dimethyl-1,2-pentanediol, and 3-ethyl-1,2- Examples include pentanediol, 4-ethyl-1,2-pentanediol, 3-methyl-1,2-hexanediol, 4-methyl-1,2-hexanediol, 5-methyl-1,2-hexanediol, 3,4-dimethyl-1,2-hexanediol, 3,5-dimethyl-1,2-hexanediol, 4,5-dimethyl-1,2-hexanediol, 3-ethyl-1,2-hexanediol, 4-ethyl-1,2-hexanediol, and 3-ethyl-4-methyl-1,2-hexanediol.

[0045] Furthermore, the aqueous inkjet ink composition of this embodiment more preferably contains, among the 1,2-alkanediols, a 1,2-alkanediol having an alkyl group having from 2 to 8 carbon atoms. This can improve both dispersion stability and the quality of the resulting image. The alkyl group of the 1,2-alkanediol having from 2 to 8 carbon atoms may be linear or branched, and examples thereof include ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, linear or branched pentyl, linear or branched hexyl, linear or branched heptyl, and linear or branched octyl.

[0046] Specific examples of 1,2-alkanediols having an alkyl group having from 2 to 8 carbon atoms include 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol, 1,2-octanediol, 1,2-nonanediol, 1,2-decanediol, 3-methyl-1,2-butanediol, 3-methyl-1,2-pentanediol, 4-methyl-1,2-pentanediol, 3,4-dimethyl-1,2-pentanediol, 3-ethyl-1,2-pentanediol, and 4-ethyl-1,2-pentanediol.

[0047] Furthermore, it is more preferable that the aqueous inkjet ink composition of this embodiment contains, among these 1,2-alkanediols, 1,2-hexanediol, in particular, which can further improve both the dispersion stability and the image quality of the resulting image.

[0048] The aqueous inkjet ink composition of this embodiment may contain multiple types of 1,2-alkanediols. The total content of the 1,2-alkanediols in the aqueous inkjet ink composition is in the range according to the ratio with HEP described below, and is preferably 0.1% by mass to 20% by mass, and more preferably 0.2% by mass to 15% by mass, based on the total amount of the aqueous inkjet ink composition. % by mass or less, more preferably 0.5% by mass or more and 10% by mass or less, and even more preferably 1% by mass or more and 10% by mass or less.

[0049] The inclusion of a 1,2-alkanediol in the aqueous inkjet ink composition of this embodiment improves the permeability into recording media, enabling the formation of images with better image quality. Furthermore, the interaction with HEP described above suppresses the 1,2-alkanediol from damaging the dispersibility of dispersible components.

[0050] 1.5. Other substances In addition to the components described above, the water-based inkjet ink composition of this embodiment may also contain the following components.

[0051] 1.5.1. Other organic solvents The aqueous inkjet ink composition of this embodiment may contain an organic solvent other than the above-mentioned HEP and 1,2-alkanediol. Examples of the organic solvent include alkyl polyols other than 1,2-alkanediols, glycol ethers, and cyclic amides.

[0052] 1.5.1.1. Alkyl polyols The aqueous inkjet ink composition of this embodiment may contain an alkyl polyol. While alkyl polyols conceptually include polyhydric alcohols and 1,2-alkanediols, the alkyl polyols described in this section are compounds other than 1,2-alkanediols. When an alkyl polyol is contained, the moisture retention of the aqueous inkjet ink composition is further enhanced, and the ejection stability when using an inkjet method is excellent, while effectively suppressing water evaporation from the recording head when left unused for a long period of time. Furthermore, this allows the ink composition to maintain good recovery after being left unused and continuous ejection stability even when using a colorant that is prone to nozzle clogging.

[0053] Specific examples of alkyl polyols include 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2-ethyl-2-methyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 3-methyl-1,3-butanediol, 2-ethyl-1,3-hexanediol, 3-methyl-1,5-pentanediol, 2-methylpentane-2,4-diol, diethylene glycol, propylene glycol, dipropylene glycol, glycerin, triethylene glycol, tetraethylene glycol, etc. These alkyl polyols may be used alone or in combination of two or more.

[0054] The aqueous inkjet ink composition more preferably contains an alkyl polyol containing an alkanediol having from 3 to 6 carbon atoms. Examples of alkanediols having from 3 to 6 carbon atoms include 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2-ethyl-2-methyl-1,3-propanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 3-methyl-1,3-butanediol, 3-methyl-1,5-pentanediol, and 2-methylpentane-2,4-diol.

[0055] When the aqueous inkjet ink composition contains an alkanediol having from 3 to 6 carbon atoms, the viscosity is further suppressed and better ejection stability (reliability of continuous ejection) can be obtained. In addition, the solubility and dispersibility of the colorant are easily improved, and good clogging recovery properties can be obtained.

[0056] 1.5.1.2. Glycol ethers The aqueous inkjet ink composition of this embodiment may contain a glycol ether. Examples of glycol ethers include monoalkyl ethers or dialkyl ethers of glycols selected from ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, and polyoxyethylene polyoxypropylene glycol. More specific examples include methyl triglycol (triethylene glycol monomethyl ether), butyl triglycol (triethylene glycol monobutyl ether), butyl diglycol (diethylene glycol monobutyl ether), and dipropylene glycol monopropyl ether, with diethylene glycol monobutyl ether being a typical example.

[0057] The water-based inkjet ink composition may contain one or more glycol ethers selected from glycol ethers represented by the following formula (1). R 1 -O-(CH2-CH2-O) n -R 2 ···(1) (In formula (1), R 1 represents H or an alkyl group having 1 to 4 carbon atoms, and R 2 represents an alkyl group having 1 to 4 carbon atoms, and n represents an integer of 2 to 3.

[0058] Examples of glycol ethers represented by formula (1) include methyl triglycol (triethylene glycol monomethyl ether), butyl triglycol (triethylene glycol monobutyl ether), butyl diglycol (diethylene glycol monobutyl ether), triethylene glycol dimethyl ether, triethylene glycol dibutyl ether, and diethylene glycol dibutyl ether.

[0059] A mixture of two or more glycol ethers may be used. When glycol ethers are used, the total amount of glycol ethers added is from 0.5% to 30% by mass, preferably from 1.0% to 20% by mass, and more preferably from 3.0% to 10.0% by mass, based on the total amount of the aqueous inkjet ink composition, from the viewpoints of adjusting the viscosity of the aqueous inkjet ink composition and suppressing clogging due to the moisturizing effect.

[0060] 1.5.1.3. Cyclic amides The water-based inkjet ink composition of this embodiment may contain a cyclic amide. Examples of cyclic amides include compounds having a ring structure containing an amide group. Examples of such compounds include γ-lactams such as 2-pyrrolidone, 1-methyl-2-pyrrolidone (N-methyl-2-pyrrolidone), 1-ethyl-2-pyrrolidone (N-ethyl-2-pyrrolidone), 1-propyl-2-pyrrolidone, 1-butyl-2-pyrrolidone, and N-vinyl-2-pyrrolidone (NVP), β-lactams, δ-lactams, and ε-lactams such as ε-caprolactam. These cyclic amides may be used alone or in combination of two or more.

[0061] 1.5.1.4. Other organic solvents The water-based inkjet ink composition of this embodiment may contain other organic solvents, such as lactones such as γ-butyrolactone, and betaine compounds.

[0062] 1.5.2.Resin particles The aqueous inkjet ink composition may contain resin particles. The resin particles can further improve the adhesion of an image formed by the aqueous inkjet ink composition adhered to a recording medium. When the aqueous inkjet ink composition further contains resin particles, Although the dispersion state is easily attacked by 1,2-hexanediol, the dispersion stability and the image quality of the resulting image are both improved, and the abrasion resistance of the resulting image can be improved. In other words, the effect of stabilizing the dispersion state in the aqueous inkjet ink composition of this embodiment is more pronounced, and the abrasion resistance of the image can also be improved.

[0063] Examples of resin particles include resin particles made of urethane-based resins, acrylic-based resins (including styrene-acrylic-based resins), fluorene-based resins, polyolefin-based resins, rosin-modified resins, terpene-based resins, polyester-based resins, polyamide-based resins, epoxy-based resins, vinyl chloride-based resins, vinyl chloride-vinyl acetate copolymers, ethylene-vinyl acetate-based resins, etc. Among these, urethane-based resins, acrylic-based resins, polyolefin-based resins, and polyester-based resins are preferred. These resin particles are often handled in the form of an emulsion, but may also be in the form of a powder. Furthermore, the resin particles can be used alone or in combination of two or more types.

[0064] When the aqueous inkjet ink composition contains resin particles, the resulting image can have better abrasion resistance. In addition, the dispersibility of the resin particles is less likely to become unstable, making it easier to achieve both abrasion resistance and storage stability.

[0065] Urethane resin is a general term for resins having urethane bonds. In addition to urethane bonds, the urethane resin may be a polyether urethane resin containing ether bonds in the main chain, a polyester urethane resin containing ester bonds in the main chain, or a polycarbonate urethane resin containing carbonate bonds in the main chain. Furthermore, commercially available products may be used as the urethane resin, and examples thereof include Superflex 460, 460s, 840, and E-4000 (trade names, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), Rezamin D-1060, D-2020, D-4080, D-4200, D-6300, and D-6455 (trade names, manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.), Takelac WS-5100, WS-6021, and W-512-A-6 (trade names, manufactured by Mitsui Chemicals Polyurethanes Inc.), Sancure 2710 (trade name, manufactured by Lubrizol), and Permarin UA-150 (trade name, manufactured by Sanyo Chemical Industries, Ltd.).

[0066] Acrylic resin is a general term for polymers obtained by polymerizing at least an acrylic monomer such as (meth)acrylic acid or a (meth)acrylic acid ester as one component. Examples include resins obtained from acrylic monomers and copolymers of acrylic monomers with other monomers. Examples include acrylic-vinyl resins, which are copolymers of acrylic monomers and vinyl monomers. Another example of a vinyl monomer is styrene.

[0067] Examples of acrylic monomers that can be used include acrylamide and acrylonitrile. Commercially available products may be used for the resin emulsion made from an acrylic resin, such as FK-854 (trade name, manufactured by Chuo Rika Kogyo Co., Ltd.), Movinyl 952B and 718A (trade names, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), and Nipol LX852 and LX874 (trade names, manufactured by Nippon Zeon Co., Ltd.).

[0068] In this specification, the acrylic resin may be a styrene-acrylic resin, which will be described later. In addition, in this specification, the term "(meth)acrylic" means at least one of acrylic and methacrylic.

[0069] Styrene-acrylic resins are copolymers obtained from styrene monomers and (meth)acrylic monomers, and include styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid ester copolymer, styrene-α-methylstyrene-acrylic acid copolymer, and styrene-α-methylstyrene-acrylic acid-acrylic acid ester copolymer. The styrene-acrylic resin may be a commercially available product, such as JONCRYL 62J, 7100, 390, 711, 511, 7001, 632, 741, 450, 840, 74J, HRC-1645J, 734, 852, 7600, 775, 537J, 1535, PDX-7630A, 352J, 352D, PDX-7145, 538J, 7640, 7641, 631, 790, 780, or 7610 (trade names, manufactured by BASF), Mowinyl 966A or 975N (trade names, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), or Vinyblan 2586 (manufactured by Nissin Chemical Industry Co., Ltd.).

[0070] The polyolefin resin has an olefin such as ethylene, propylene, or butylene in its structural skeleton, and known polyolefin resins can be appropriately selected and used. As the olefin resin, commercially available products can be used, such as Arrowbase CB-1200 and CD-1200 (trade names, manufactured by Unitika Ltd.).

[0071] The resin particles may also be supplied in the form of an emulsion. Examples of commercially available resin emulsions include Microgel E-1002 and E-5002 (trade names of Nippon Paint Co., Ltd., styrene-acrylic resin emulsions), Boncoat 4001 (trade name of DIC Corporation, acrylic resin emulsion), Boncoat 5454 (trade name of DIC Corporation, styrene-acrylic resin emulsion), Polysol AM-710, AM-920, AM-2300, AP-4735, AT-860, PSASE-4210E ( ... Polysol AP-7020 (styrene-acrylic resin emulsion), Polysol SH-502 (vinyl acetate resin emulsion), Polysol AD-13, AD-2, AD-10, AD-96, AD-17, AD-70 (ethylene-vinyl acetate resin emulsion), Polysol PSASE-6010 (ethylene-vinyl acetate resin emulsion) (product name, manufactured by Showa Denko K.K.), Polysol SAE1014 (product name, styrene-acrylic resin emulsion, manufactured by Nippon Zeon Co., Ltd.), Saivinol SK-200 (product name, acrylic resin emulsion, manufactured by Saiden Chemical Co., Ltd.) , AE-120A (trade name, acrylic resin emulsion, manufactured by JSR Corporation), AE373D (trade name, carboxy-modified styrene-acrylic resin emulsion, manufactured by E-Tech Co., Ltd.), Seikadyne 1900W (trade name, ethylene-vinyl acetate resin emulsion, manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.), Vinyblan 2682 (acrylic resin emulsion), Vinyblan 2886 (vinyl acetate-acrylic resin emulsion), Vinyblan 5202 (acetic acid acrylic resin emulsion) (trade name, manufactured by Nissin Chemical Industry Co., Ltd.), Elitel KA-5071S, KT-8803, KT-9204, KT-870 1, KT-8904, KT-0507 (trade names of Unitika Ltd., polyester resin emulsion), Hi-Tec SN-2002 (trade name of Toho Chemical Co., Ltd., polyester resin emulsion), Takelac W-6020, W-635, W-6061, W-605, W-635, W-6021 (trade names of Mitsui Chemicals Polyurethanes, urethane resin emulsion), Superflex 870, 800, 150, 420, 460, 470, 610, 700 (trade names of Daiichi Kogyo Seiyaku Co., Ltd., urethane resin emulsion), Parmarin UA-150 (trade name of Sanyo Chemical Industries, Ltd.,Urethane resin emulsion), Sancure 2710 (manufactured by Lubrizol Japan, urethane resin emulsion), NeoRez R-9660, R-9637, R-940 (manufactured by Kusumoto Chemicals Co., Ltd., urethane resin emulsion), Adeka Bontitor HUX-380, 290K (manufactured by ADEKA Corporation, urethane resin emulsion), Mowinyl 966A, Mowinyl 7320 (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), Joncryl 7100, 390, 711, 511, 7001, 632, 741, 450, 840, 74J, HRC-1645J, 734, 852, 7600, 775, 537J, 1535, P Examples of binders include DX-7630A, 352J, 352D, PDX-7145, 538J, 7640, 7641, 631, 790, 780, and 7610 (all manufactured by BASF), NK Binder R-5HN (manufactured by Shin-Nakamura Chemical Co., Ltd.), Hydran WLS-210 (non-crosslinked polyurethane: manufactured by DIC Corporation), and Joncryl 7610 (manufactured by BASF).

[0072] When resin particles are contained in the aqueous inkjet ink composition, the content thereof is, in terms of solid content, from 0.1% to 20% by mass, preferably from 1% to 15% by mass, and more preferably from 2% to 10% by mass, relative to the total mass of the aqueous inkjet ink composition.

[0073] Surfactants The aqueous inkjet ink composition according to this embodiment may contain a surfactant. The surfactant can be used to reduce the surface tension of the aqueous inkjet ink composition and adjust or improve its wettability with a recording medium, for example, its penetrability into fabrics. As the surfactant, any of nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants can be used, and these surfactants may also be used in combination. Furthermore, among the surfactants, acetylene glycol surfactants, silicone surfactants, and fluorine-based surfactants are more preferably used.

[0074] The acetylene glycol surfactant is not particularly limited, but examples thereof include Surfynol 104, 104E, 104H, 104A, 104BC, 104DPM, 104PA, 104PG-50, 104S, 420, 440, 465, 485, SE, SE-F, 504, 61, DF37, CT111, CT121, CT131, CT136, TG, GA, and DF110D (trade names, Air Products and Chemicals). Examples of suitable acrylic acid esters include Olfine B, Y, P, A, STG, SPC, E1004, E1010, PD-001, PD-002W, PD-003, PD-004, PD-005, EXP.4001, EXP.4036, EXP.4051, EXP.4123, EXP.4200, EXP.4300, AF-103, AF-104, AK-02, SK-14, and AE-3 (trade names, manufactured by Nissin Chemical Industry Co., Ltd.), and Acetylenol E00, E00P, E40, and E100 (trade names, manufactured by Kawaken Fine Chemicals Co., Ltd.).

[0075] The silicone surfactant is not particularly limited, but a polysiloxane compound is preferred. The polysiloxane compound is not particularly limited, but for example, a polyether-modified organosiloxane is exemplified. Commercially available polyether-modified organosiloxanes include, for example, BYK-306, BYK-307, BYK-333, BYK-341, BYK-345, BYK-346, and BYK-348 (trade names, manufactured by BYK), KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-945, KF-640, KF-642, KF-643, KF-6020, X-22-4515, KF-6011, KF-6012, KF-6015, and KF-6017 (trade names, manufactured by Shin-Etsu Chemical Co., Ltd.).

[0076] As the fluorine-based surfactant, it is preferable to use a fluorine-modified polymer, and a specific example thereof is BYK-340 (trade name, manufactured by BYK Japan KK).

[0077] When a surfactant is added to the aqueous inkjet ink composition, the total amount of the surfactant is preferably 0.01% by mass or more and 3% by mass or less, more preferably 0.05% by mass or more and 2% by mass or less, even more preferably 0.1% by mass or more and 1.5% by mass or less, and particularly preferably 0.2% by mass or more and 1% by mass or less, based on the total amount of the aqueous inkjet ink composition.

[0078] Furthermore, by including a surfactant in the water-based inkjet ink composition, the stability of the ink when ejected from the head tends to increase.

[0079] 1.5.4. Chelating Agents The water-based ink-jet ink composition of this embodiment may contain a chelating agent. The chelating agent can remove certain ions from the water-based ink-jet ink composition. do.

[0080] Examples of chelating agents include ethylenediaminetetraacetic acid and its salts such as EDTA, EDTA-2Na (ethylenediaminetetraacetic acid dihydrogen disodium salt), EDTA-3Na (ethylenediaminetetraacetic acid monohydrogen trisodium salt), EDTA-4Na (ethylenediaminetetraacetic acid tetrasodium salt), and EDTA-3K (ethylenediaminetetraacetic acid monohydrogen tripotassium salt); diethylenetriaminepentaacetic acid such as DTPA, DTPA-2Na (diethylenetriaminepentaacetic acid disodium salt), and DTPA-5Na (diethylenetriaminepentaacetic acid pentasodium salt); Examples of suitable nitrilotriacetic acids include acetic acid and its salts, nitrilotriacetic acid and its salts such as NTA, NTA-2Na (nitrilotriacetic acid disodium salt), and NTA-3Na (nitrilotriacetic acid trisodium salt), ethylenediamine-N,N'-disuccinic acid and its salts, 3-hydroxy-2,2'-iminodisuccinic acid and its salts, L-aspartic acid-N,N'-diacetic acid and its salts, L-glutamic acid diacetic acid and its salts, N-(1-carboxylatomethyl)iminodiacetic acid and its salts, and N-(2-hydroxyethyl)iminodiacetic acid and its salts.

[0081] Examples of chelating agents other than acetic acid analogs include ethylenediaminetetramethylenephosphonic acid and its salts, ethylenediaminetetrametaphosphoric acid and its salts, ethylenediaminepyrophosphoric acid and its salts, and ethylenediaminemetaphosphoric acid and its salts.

[0082] When a chelating agent is contained in the water-based inkjet ink composition of this embodiment, one or more types selected from the above examples can be used.

[0083] pH adjusters A pH adjuster may be added to the aqueous inkjet ink composition of this embodiment. The pH adjuster is not particularly limited, but may be a suitable combination of an acid, a base, a weak acid, or a weak base. Examples of acids and bases used in such combinations include inorganic acids such as sulfuric acid, hydrochloric acid, and nitric acid; inorganic bases such as lithium hydroxide, sodium hydroxide, potassium hydroxide, potassium dihydrogen phosphate, disodium hydrogen phosphate, potassium carbonate, sodium carbonate, sodium bicarbonate, and ammonia; organic bases such as triethanolamine, tripropanolamine, diethanolamine, monoethanolamine, triisopropanolamine, diisopropanolamine, and trishydroxymethylaminomethane (THAM); and organic acids such as adipic acid, citric acid, succinic acid, lactic acid, and N,N-bis(2-hydroxyethyl)-2-amine. Other buffers that may be used include Good's buffers such as iminoethanesulfonic acid (BES), 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES), morpholinoethanesulfonic acid (MES), morpholinopropanesulfonic acid (MOPS), carbamoylmethyliminobisacetic acid (ADA), piperazine-1,4-bis(2-ethanesulfonic acid) (PIPES), N-(2-acetamido)-2-aminoethanesulfonic acid (ACES), cholamine hydrochloride, N-tris(hydroxymethyl)methyl-2-aminoethanesulfonic acid (TES), acetamidoglycine, tricine, glycinamide, and bicine, as well as phosphate buffer, citrate buffer, and Tris buffer. Furthermore, among these, it is preferable that the pH adjuster contains, as part or all of a tertiary amine such as triethanolamine or triisopropanolamine, or a carboxyl group-containing organic acid such as adipic acid, citric acid, succinic acid or lactic acid, since this makes it possible to obtain a more stable pH buffering effect.

[0084] 1.5.6.Ureas Ureas may be used as a moisturizing agent for the aqueous ink-jet ink composition or as a dyeing aid that improves the dyeing property of the dye. Specific examples of ureas include urea, ethylene Examples of urea include urea, tetramethylurea, thiourea, 1,3-dimethyl-2-imidazolidinone, etc. When ureas are contained, the content thereof can be 1% by mass or more and 10% by mass or less relative to the total mass of the aqueous inkjet ink composition.

[0085] 1.5.7. Antiseptics, mildew inhibitors, and rust inhibitors The aqueous inkjet ink composition may contain an antiseptic or an antifungal agent. Examples of the antiseptic or antifungal agent include sodium benzoate, sodium pentachlorophenol, sodium 2-pyridinethiol-1-oxide, sodium sorbate, sodium dehydroacetate, 1,2-dibenzisothiazolin-3-one (Proxel CRL, Proxel BDN, Proxel GXL, Proxel XL-2, Proxel TN, Proxel LV, manufactured by Zeneca), and 4-chloro-3-methylphenol (Preventol CMK, manufactured by Bayer). Examples of the rust inhibitor include benzotriazole.

[0086] Sugars The aqueous inkjet ink composition may contain sugars. Specific examples of sugars include glucose, mannose, fructose, ribose, xylose, arabinose, galactose, aldonic acid, glucitol (sorbitol), maltose, cellobiose, lactose, sucrose, trehalose, and maltotriose.

[0087] Other In addition to the above components, the ink composition may contain additives that can be commonly used in aqueous ink-jet ink compositions, such as antioxidants, ultraviolet absorbers, oxygen absorbers, and solubilizing agents.

[0088] 1.6. Content ratio In the water-based inkjet ink composition according to this embodiment, 1-(2-hydroxyethyl)-2-pyrrolidone (HEP) is contained (C HEP ) and the content of 1,2-alkanediol (C 12AD) is 1:10 to 10:1 (1 / 10 to 10 / 1) by mass ratio. In other words, the content of 1-(2-hydroxyethyl)-2-pyrrolidone (HEP) (C HEP ) of 1,2-alkanediol content (C 12AD ) to the ratio (C HEP :C 12AD )(C HEP / C 12AD ) is a mass ratio of 1:10 to 10:1 (1 / 10 to 10 / 1).

[0089] When a 1,2-alkanediol is used in an aqueous inkjet ink composition, it is necessary to consider at least the amount thereof and the combination with other solvents. The inventors have found that in such a case, by selecting HEP as a combination and appropriately selecting the ratio of the amounts of the two, it is possible to suppress the decrease in dispersibility caused by the 1,2-alkanediol while fully exhibiting the performance of the 1,2-alkanediol.

[0090] Ratio(C HEP :C 12AD ) is preferably in a mass ratio of 2:8 to 8:2, more preferably in a mass ratio of 3:7 to 7:3, and even more preferably in a mass ratio of 4:6 to 6:4.

[0091] 1.7. Preparation and Properties of Water-Based Inkjet Ink Composition The aqueous inkjet ink composition can be obtained by mixing the above-mentioned components in any order, and removing impurities by filtration, etc., as needed. A suitable mixing method is to add the materials sequentially to a container equipped with a stirring device such as a mechanical stirrer or a magnetic stirrer, and then stir and mix them. As a filtration method, for example, centrifugal filtration or filter filtration can be used as needed.

[0092] From the viewpoint of reliability as an inkjet ink, the water-based inkjet ink composition From this perspective, the surface tension at 20°C is preferably 20 mN / m or more and 40 mN / m or less, and more preferably 22 mN / m or more and 35 mN / m or less. From the same perspective, the viscosity of the ink at 20°C is preferably 1.5 mPa·s or more and 10 mPa·s or less, and more preferably 2 mPa·s or more and 8 mPa·s or less. One method for keeping the surface tension and viscosity within the above ranges is to adjust the types of organic solvents and surfactants mentioned above, and the amounts of these and water added.

[0093] 1.8. Effects The aqueous inkjet ink composition of this embodiment has good storage stability due to the good dispersibility of the colorant, and good permeability into recording media, resulting in good image quality. That is, 1-(2-hydroxyethyl)-2-pyrrolidone (HEP) reduces the effect of 1,2-alkanediol on the dispersion state of the colorant, thereby maintaining a good dispersion state of the colorant.

[0094] 2. Inkjet recording method The inkjet recording method of this embodiment includes ejecting the above-described water-based inkjet ink composition from a recording head and depositing it onto a recording medium.

[0095] According to the inkjet recording method of this embodiment, the water-based inkjet ink composition contains 1-(2-hydroxyethyl)-2-pyrrolidone (HEP) and a 1,2-alkanediol, and therefore the water-based inkjet ink composition has good storage stability and can form images with good image quality.

[0096] The inkjet recording method of this embodiment can be carried out, for example, by filling an inkjet recording apparatus equipped with an ink container with the water-based inkjet ink composition. An example of an inkjet recording apparatus to which the water-based inkjet ink composition is applied will be described below.

[0097] The inkjet recording apparatus includes the above-described water-based inkjet ink composition, an ink container that contains the water-based inkjet ink composition, and a recording head that ejects the water-based inkjet ink composition. In the inkjet recording apparatus described below, the ink container has an ink inlet that can be opened and closed for filling with the water-based inkjet ink composition, but the present invention is not limited to this, and any inkjet recording apparatus may be used. In other words, the inkjet recording apparatus described below is an example of an apparatus that can be used to carry out the inkjet recording method of this embodiment.

[0098] The inkjet recording device will be described with reference to the drawings. The ink container serves as an ink tank for an inkjet printer (inkjet recording device) that records (prints) images or the like on a medium by ejecting ink onto the medium. In the following description, the inkjet recording device may be simply referred to as the recording device, and the aqueous inkjet ink composition may be simply referred to as the ink.

[0099] As shown in FIG. 1, the recording device 21 has a housing 22 in the shape of a rectangular parallelepiped with its longitudinal direction in the left-right direction. Note that FIG. 1 shows a simplified perspective view of the inside of the housing 22 of the recording device 21. A support base 23 with its longitudinal direction in the left-right direction is provided in the lower rear portion of the housing 22, with its upper surface aligned approximately horizontally. Paper P, an example of a medium, is supported on the upper surface of the support base 23 and transported forward in the transport direction. Furthermore, a guide shaft 24 extending in the left-right direction is installed above the support base 23 in the housing 22, and a carriage 26 having a recording head 25 on its underside that ejects ink is supported on the guide shaft 24. In other words, the carriage 26 is configured to move in the left-right direction. With the guide shaft 24 inserted through the support hole 27, the support member 26 is supported so as to be movable back and forth in the left and right direction relative to the guide shaft 24.

[0100] A drive pulley 28 and a driven pulley 29 are rotatably supported in positions near both ends of the guide shaft 24 within the housing 22. An output shaft of a carriage motor 30 is connected to the drive pulley 28, and an endless timing belt 31, a portion of which is connected to the carriage 26, is wound between the drive pulley 28 and the driven pulley 29. When the carriage 26 is driven by the carriage motor 30 and guided by the guide shaft 24 via the timing belt 31 to move back and forth along the left-right direction, which is the scanning direction for the paper P, ink is ejected from the recording head 25 on the underside of the carriage 26 onto the paper P, which is transported forward on the support base 23.

[0101] 1, a rectangular discharge opening 32 is opened at a position on the front side of the housing 22 in front of the support base 23, through which paper P, on which recording has been performed by ejecting ink from the recording head 25 as the paper is transported on the support base 23 within the housing 22, is discharged forward. A rectangular plate-shaped discharge tray 33 capable of supporting paper P discharged from the housing 22 is provided at the discharge opening 32 so as to be movable forward in the discharge direction. A paper feed cassette 34 capable of accommodating a plurality of sheets of paper P to be used for recording in a stacked state is attached below the discharge tray 33 within the discharge opening 32 so as to be removable in the front-to-rear direction.

[0102] 1, on the front side of the housing 22, at a position closer to the left-right end than the outlet 32 ​​(the right end in FIG. 1), there is provided an opening / closing door 35 whose front and top are rectangular and whose right side is shaped like a right triangle, so that it can be opened and closed in the front-rear direction around a rotation shaft 36 provided at the bottom of the opening / closing door 35 and extending in the left-right direction. A window 37 made of a rectangular transparent member is formed on the front side of the opening / closing door 35, so that the user can see inside the housing 22 (particularly, the back side of the front side of the opening / closing door 35) when the opening / closing door 35 is closed.

[0103] An ink supply unit 40 that supplies ink to the recording head 25 is housed inside the housing 22 of the recording device 21 at a position behind the opening / closing door 35, that is, at a position closer to the front and closer to the end (closer to the right end in this case). The ink supply unit 40 is a structure that includes a plurality of (five in this embodiment) ink containers 41-45 and can be handled as a unit, and as will be described later, each of the ink containers 41-45 can be replenished with ink.

[0104] 2 and 3, the ink supply unit 40 includes five ink containers 41 to 45 each having a rectangular box shape that is elongated in the front-to-rear direction, five ink supply tubes 46 extending from the rear side of each ink container 41 to 45, and a rectangular parallelepiped ink supply adapter 47 to which the ink containers 41 to 45 are attached together. The ink supply adapter 47 is attached to stepped portions 48 cut out and formed in the upper front half portions of all the ink containers 41 to 45 when all the ink containers 41 to 45 are arranged side by side with their thicknesses aligned left to right, thereby integrating the ink containers 41 to 45. As shown in FIG. 1, the ink supply tubes 46 extending from the ink containers 41 to 45 are connected to ink flow paths (not shown) formed in the carriage 26 and are connected to the recording head 25 via the ink flow paths. The ink supply adapter 47 may be a part of the housing 22 that covers the ink containers 41-45, or may be formed integrally with the ink containers 41-45.

[0105] As shown in Figures 4 and 5, the ink containers 41 to 45 each have an ink storage chamber 49 therein capable of storing the ink composition IK. In the present embodiment, the ink storage chamber 49 of the ink container 41 located at the right end in the lateral arrangement direction stores black ink. The ink storage chambers 49 of the other ink storage bodies 42 to 45 arranged to the left of the right-end ink storage body 41 in the horizontal arrangement direction store ink of colors other than black (cyan, magenta, yellow, etc.). Furthermore, the front wall of each of the ink storage bodies 41 to 45, which is visible through the window 37 on the front surface of the housing 22, is provided with a visibility portion 50 made of a transparent resin that allows the liquid level of the ink composition IK in the ink storage chamber 49 to be visible. The visibility portion 50 is marked with an upper limit mark 51 that indicates an upper limit of the liquid level of the ink composition IK stored in the ink storage chamber 49 (an example of an indication of the amount of ink that can be poured without the ink overflowing from the ink inlet 53) and a lower limit mark 52 that indicates a lower limit (for example, an indication to encourage ink replenishment).

[0106] As shown in FIG. 4, an ink inlet 53 (ink injection port) that can be opened and closed is provided above the horizontal portion of the stepped portion 48 in each of the ink containers 41-45, allowing ink to flow from the outside into the ink storage chamber 49. The ink inlet 53 includes a needle 56 that extends vertically upward and has flow paths 54, 55 that connect the inside of the ink storage chamber 49 to the outside. The flow paths 54, 55 of the needle 56 are composed of two flow paths 54, 55 arranged side by side in a radial direction with their tip openings centered on the needle 56. One of the two flow paths 54, 55 (the flow path 54 on the right side in FIG. 4) has a lower tip opening and a larger cross-sectional area than the other flow path 55 (the flow path 55 on the left side in FIG. 4). A remaining amount sensor 57 is provided at a lower rear portion of the ink storage chamber 49 to detect the remaining amount of ink composition IK in the ink storage chamber 49. The remaining amount sensor 57 is not required.

[0107] 2 to 5, ink supply adapter 47 has an upper surface 58 that is a horizontal surface extending in a direction perpendicular to (intersecting with) the direction in which needle 56 extends, and a through-hole 60 that serves as an ink inlet formation portion is formed in upper surface 58 and extends vertically to lower surface 59. This through-hole 60 is made up of a circular ink inlet 53 with needle 56 located in the center, and a pair of rectangular holes connected to the front and rear of ink inlet 53, and the lower opening is closed by the horizontal portion of step 48 that protrudes needle 56 upward in ink containers 41 to 45.

[0108] Therefore, in the through-hole 60, a pair of front and rear rectangular hole portions with their lower openings blocked form a pair of front and rear recesses 61 that open upward, in the direction in which the needle 56 extends, recessed in the depth direction vertically downward and symmetrically about the ink inlet 53. That is, in the ink refill adapter 47 integrated with the ink accommodating bodies 41 to 45, a plurality of recesses 61 (two pairs of front and rear recesses in this case) are formed that are point-symmetrical about the ink inlet 53 in the area outside the ink inlet 53 including the needle 56. In this case, the tip of the needle 56, which is located at the center of the circular ink inlet 53, is located closer to the ink storage chamber 49 than the top surface 58 of the ink refill adapter 47, which forms the opening edge of the through-hole 60 that includes the ink inlet 53 and the recesses 61. That is, the upper surface 58 of the ink supply adapter 47 extends in a direction intersecting the extension direction of the needle 56 at a position outside the tip of the needle 56 in the extension direction of the needle 56. On the other hand, the lower surface 59 of the ink supply adapter 47 functions as a tank engaging portion that collectively engages from above with the multiple ink containers 41 to 45 that are arranged side by side in the left-right direction.

[0109] Furthermore, the upper surface 58 of the ink supply adapter 47, the peripheral portion of the opening edge on the upper side of each through-hole 60, is colored a specific color. That is, it is colored the same color as the color of the ink stored in the ink storage chamber 49 of the ink accommodating body 41-45 into which the ink flows through the ink inlet 53 of the through-hole 60. In this respect, the peripheral portion of the opening edge on the upper side of each through-hole 60 in the ink supply adapter 47 functions as a first portion that externally indicates information related to the ink stored inside the ink accommodating body 41-45, whose ink inlet 53 of the through-hole 60 communicates with the ink storage chamber 49. There are no particular restrictions on the ink, but if the ink container supplied from the ink container containing the ink composition of this embodiment is the ink container 41, it will store black or gray ink, so the surrounding area of ​​the upper opening of the through hole 60, where the ink inlet 53 communicating with the ink storage chamber 49 of the ink container 41 is located, is colored black or gray.

[0110] Furthermore, on the inner surface of the recess 61 (specifically, the inner surface along the vertical direction), a first uneven portion (first key structure portion) 62 having a characteristic uneven shape in the horizontal direction is provided at a position closer to the bottom surface than the upper opening edge of the recess 61 (i.e., closer to the horizontal portion of the stepped portion 48), so as to extend along the depth direction of the recess 61 (in other words, the direction of the central axis of the ink inlet 53). As shown in FIGS. 2 and 3 , the first uneven portion 62 is provided for each of the ink inlets 53 of the multiple (five in this embodiment) ink containers 41 to 45. Therefore, in the ink refill adapter 47, the rectangular recess 61 in each through hole 60 formed at a position corresponding to each of the ink containers 41 to 45 in the vertical direction has a first uneven portion 62 formed therein that is different from the first uneven portions 62 provided on the inner surface of the recess 61 of each of the other through holes 60. That is, these first uneven portions 62 function as identification portions that enable identification of ink bottles 63 (see FIG. 6, etc.) that have ink outlets 65 (see FIG. 6, etc.) that are connected to ink inlets 53 in through-holes 60 in which the first uneven portions 62 are formed. Note that "a position that is closer to the bottom than the upper opening edge of recess 61" means that it is sufficient that the position is set back slightly toward the bottom from the opening edge.

[0111] Next, the ink bottle 63 will be described as an ink supply container that constitutes an ink supply system together with the ink containers 41 to 45 and supplies ink to the ink containers 41 to 45 when the remaining ink level is low. The ink bottle 63 contains the above-mentioned water-based inkjet ink composition.

[0112] 6 to 8, the ink bottle 63 comprises a cylindrical container body 64 that forms the main body of the ink bottle 63; an ink outlet forming portion 66 that is provided at the tip of the container body 64 and has an ink outlet 65 formed at its tip to allow ink to flow out of the ink bottle 63; and a container attachment portion 67 that is attached to the ink outlet forming portion 66 so as to surround the ink outlet 65. The ink outlet 65 of the ink outlet forming portion 66, together with the surrounding container attachment portion 67, is covered by a cylindrical cap 68 with a bottom, so that it is concealed from the outside when the ink bottle 63 is stored. That is, a male thread portion 69 is formed on the outer peripheral surface of the cylindrical lower end of the container attachment portion 67, while a female thread portion (not shown) is formed on the inner peripheral surface of the cap 68. By screwing the female thread portion of the cap 68 onto the male thread portion 69 of the container attachment portion 67, the cap 68 is attached to the tip of the ink bottle 63 so as to cover the ink outlet 65.

[0113] The entire outer surface of the container additional portion 67 is colored a specific color. That is, it is colored the same color as the ink contained in the container main body 64 to which the container additional portion 67 is attached. Incidentally, the outer surface of the container additional portion 67 of an ink bottle 63 containing black or gray ink is colored black or gray. Furthermore, multiple (four in this embodiment) protrusions 70 are formed at equal angular intervals (for example, 90-degree intervals) on the outer periphery of each base end of the container main body 64 and the cap 68. Incidentally, these protrusions 70 are formed to prevent the cylindrical ink bottle 63 from rolling. Furthermore, for example, the container main body 64 of an ink bottle 63 containing black ink may be formed thicker than the container main body 64 of an ink bottle 63 containing other colors of ink. In this case, the ink outlet forming portion 66 for black ink and the other colors of ink may have the same thickness and shape.

[0114] 6 to 8, in the upper part of the cylindrical lower end portion where the male screw portion 69 is formed on the outer peripheral surface of the container additional portion 67, in the area that is outside the ink outlet 65 in the radial direction from the ink outlet 65 as the center, there is provided a portion that is closer to the container body than the ink outlet 65 in the direction of the central axis of the ink outlet 65. A protrusion 71 is formed that protrudes upward in the opposite direction from the body 64. This protrusion 71 functions as a second fitting portion that can fit into the recess 61 on the top surface 58 of the ink refill adapter 47 as a first fitting portion when the tip of the needle 56 on the ink inlet 53 side is inserted into the ink outlet 65, and is provided to form a pair on both sides of the ink outlet 65, similar to the pair of recesses 61 that sandwich the ink inlet 53 from the front and back. Note that, as shown in Figures 6 and 7, the protrusions 71 are formed inward from the outer circumferential surface of the container body 64 in the ink bottle 63 in the radial direction centered on the ink outlet 65.

[0115] 6 and 9, the outer surface of each convex portion 71 (both left and right side surfaces in FIGS. 6 and 9) is formed with a second concave-convex portion (second key structure portion) 72 that can engage with a first concave-convex portion (first key structure portion) 62 formed on the inner surface of the concave portion 61 of the ink refill adapter 47. This second concave-convex portion 72 is provided to extend along the protruding direction of the convex portion 71 (in other words, the direction of the central axis of the ink outlet 65), and when the convex portion 71 is fitted into the concave portion 61 and the second concave-convex portion 72 is engaged with the first concave-convex portion 62, the ink outlet 65 of the ink bottle 63 is connected to the ink inlet 53 on the ink accommodating body 41-45 side.

[0116] Furthermore, a planar positioning portion 73 that is perpendicular to (intersects with) the central axis of the ink outlet 65 is provided between the cylindrical lower end of the container additional portion 67, where the male thread portion 69 is formed, and the convex portion 71, where the second uneven portion 72 is formed, so as to be located radially outward from the ink outlet 65 when the ink outlet 65 is viewed in the direction of its central axis. In other words, this positioning portion 73 constitutes part of the outer surface of the container additional portion 67, which is part of the outer surface of the ink bottle 63, and is provided at a position closer to the container main body 64 than the tip of the convex portion 71 in the direction of the central axis of the ink outlet 65. And because this positioning portion 73 is provided on the container additional portion 67 that is added to the ink outlet forming portion 66 of the ink bottle 63, it can be said that it is a separate member from the ink outlet forming portion 66 and is provided outside the ink outlet forming portion 66.

[0117] 9, a valve 74 made of an elastic material such as a silicone membrane is provided in the ink outlet 65 formed in the ink outlet forming portion 66, sealing the ink outlet 65 so that it can be opened and closed. The valve 74 is provided at a position where the positioning portion 73 is closer to the container main body 64 in the direction of the central axis of the ink outlet 65 (see, for example, FIG. 14). The valve 74 is provided with a plurality of slits 75 (three in this embodiment) that intersect at equal angular intervals (for example, 120-degree intervals) with the center of the valve 74 as the intersection point, and is configured to open when the slits 75 are pushed inward from the outside of the ink outlet 65. In other words, when the tip of the needle 56 on the ink inlet 53 side is inserted into the ink outlet 65, the normally closed valve 74 is pushed inward by the tip of the needle 56 and opens.

[0118] At this time, the positioning portion 73 comes into contact with the upper surface 58 of the ink refill adapter 47, in which the through-hole 60 including the ink inlet 53 and the recess 61 is formed, on the radial outside of the ink outlet 65, and positions the valve 74 with respect to the ink accommodating bodies 41 to 45 in the direction of the central axis of the ink outlet 65. In this regard, the upper surface 58 of the ink refill adapter 47 is part of the ink accommodating bodies 41 to 45 against which the positioning portion 73 of the ink bottle 63 comes into contact when the valve 74 of the ink outlet 65 of the ink bottle 63 is opened to replenish the ink accommodating bodies 41 to 45 with ink, and functions as a receiving surface that receives the planar positioning portion 73.

[0119] 10 and 11, the container body 64 of the ink bottle 63 is a bottle-shaped member having an ink storage chamber 76 therein capable of storing an ink composition IK, and a male thread portion 78 is formed on the outer peripheral surface of a neck portion 77 at the upper end of the container body 64. Meanwhile, the ink outlet forming portion 66 provided at the upper end of the container body 64 has a large diameter portion 79 located on the outer peripheral side of the neck portion 77 of the container body 64, a small diameter portion 80 that forms the ink outlet 65 at a position farthest from the container body 64, and an intermediate portion 81 that connects the large diameter portion 79 and the small diameter portion 80. The ink outlet forming portion 66 is attached to the upper end of the container body 64 by threading the female thread portion 82 formed on the inner peripheral surface of the large diameter portion 79 into the male thread portion 78 formed on the outer peripheral surface of the neck portion 77 of the container body 64.

[0120] Furthermore, the container attachment portion 67, which is attached to the ink outlet forming portion 66 of the ink bottle 63 so as to surround the ink outlet 65, has a cylindrical lower end portion with a male thread portion 69 formed on its outer circumferential surface, which forms a joining portion 83 whose lower end surface is joined to the upper end surface of the large diameter portion 79 of the ink outlet forming portion 66. This joining portion 83 is joined to the large diameter portion 79 of the ink outlet forming portion 66 such that opposing surface areas in the front-to-rear direction of its inner circumferential surface are in surface contact with the front outer surface and the rear outer surface of the intermediate portion 81 of the ink outlet forming portion 66.

[0121] Next, the operation of the ink supply system configured as above will be described below, focusing on the operation when ink is supplied to the ink containers 41 to 45 of the ink supply unit 40 using the ink bottle 63.

[0122] 2, the ink level in the ink container 41 for black ink, which is located at the far right of the multiple ink containers 41-45 arranged side by side, has dropped to the height of the lower limit mark 52 marked below the visible portion 50. Therefore, the following description will be given assuming that ink is replenished to this ink container 41. It is also assumed that the ink bottle 63 used for ink replenishment contains a sufficient amount of black ink, and that the cap 68 has been removed from the ink bottle 63 in advance. Furthermore, it is assumed that the shape of the second uneven portion 72 formed on the outer surface of the protruding portion 71 of the ink bottle 63 matches the shape of the first uneven portion 62 formed on the inner surface of the recessed portion 61 located before and after the ink inlet 53 to the ink container 41, and that the protruding portion 71 can be engaged with the recessed portion 61 when inserted.

[0123] When refilling the ink container 41 with ink, the user first rotates the open / close door 35 of the housing 22 from the closed state shown in Fig. 1 forward around the rotation shaft 36 to open it. Then, in the ink supply unit 40, the top surface 58 of the ink refill adapter 47, on which the ink inlet 53 leading to the ink containers 41 to 45 is formed, is exposed to the outside of the housing 22, and the user can connect the ink outlet 65 of the ink bottle 63 to the desired ink inlet 53 from above.

[0124] 12 and 13, the user turns the ink bottle 63 containing the ink composition to be used for ink refill upside down and holds it so that the ink outlet 65 is positioned above the rightmost through-hole 60 of the ink refill adapter 47. That is, the user aligns the central axis of the ink outlet 65 of the ink bottle 63 with the central axis of the ink inlet 53 of the ink container 41 to be refilled. At this time, the user compares the color (second portion) of the container attachment portion 67 of the ink bottle 63 being held with the color (first portion) of the periphery of the upper opening edge of the through-hole 60 where the ink inlet 53 of the ink container 41 to be refilled is provided. If the colors are the same (in this case, both are black), the user confirms that the ink bottle 63 being held is suitable for this ink refill and proceeds to the subsequent ink refill operation.

[0125] 12 and 13, the ink bottle 63 is lowered and the protrusion 71 of the ink bottle 63 is inserted into the recess 61 of the ink supply adapter 47 that is integral with the ink container 41. Then, by realizing the insertion state of the protrusion 71 into the recess 61, the central axis of the ink outlet 65 is ensured to coincide with the central axis of the ink inlet 53. In this case, since the recess 61 is positioned point-symmetrically with respect to the needle 56, which is the center of the ink inlet 53, the protrusion 71 can be inserted into either recess 61. The user can easily insert the convex portion 71 into the concave portion 61 without having to repeatedly rotate the ink bottle 63 around the central axis of the ink outlet 65 to check the correct positional relationship between the concave portion 61 and the convex portion 71.

[0126] However, at this point, the protrusion 71 is only slightly inserted into the recess 61, and the tip of the needle 56 located at the center of the ink inlet 53 is inserted into the opening of the ink outlet 65, which protrudes slightly beyond the tip of the protrusion 71, but has not yet reached the valve 74 located deep inside the ink outlet 65. The reason for this is that, as shown in Figure 13, the distance L2 between the tip of the protrusion 71 and the valve 74 inside the ink outlet 65 is longer than the distance L1 between the top surface 58 of the ink refill adapter 47, where the edge of the opening of the recess 61 is located, and the upper end of the first uneven portion 62 inside the recess 61. Therefore, if the protrusion 71 is further inserted downward in the depth direction of the recess 61 from this state, the second uneven portion 72 on the outer surface of the protrusion 71 will engage with the first uneven portion 62 on the inner surface of the recess 61. Then, while maintaining this engagement, if the convex portion 71 is further inserted in the depth direction of the concave portion 61 toward the bottom side, the tip of the needle 56 of the ink inlet 53 will reach the position of the valve 74 of the ink outlet 65, opening the valve 74.

[0127] 14 and 15 , the tip of the needle 56 pushes the slit 75 from below toward above (i.e., from the outside toward the inside of the ink outlet 65) relative to the valve 74, thereby opening the valve 74. As a result, the ink outlet 65 of the ink bottle 63 is connected to the needle 56 of the ink inlet 53 of the ink container 41, and the ink composition is replenished from the ink bottle 63 to the ink container 41. At this time, of the two flow paths 54, 55 of the needle 56 of the ink inlet 53, the one whose tip opening first touches the ink flowing out of the ink outlet 65 by opening the valve 74 functions as an ink flow path through which the ink flows, and the other flow path functions as an air flow path through which air flows. For example, if a user attempts to connect the ink outlet 65 to the ink inlet 53 while tilting the ink bottle 63, the direction of tilt will determine which of the two flow paths 54, 55 will serve as the ink flow path.

[0128] If the second uneven portion 72 does not engage with the first uneven portion 62 after inserting the protrusion 71 into the recess 61, the user will recognize at that point that they are inserting an ink bottle 63 of a color other than black. In this case, if the upper end of the first uneven portion 62 were positioned at the same height as the opening edge of the recess 61, not only would the second uneven portion 72 not be able to engage with the first uneven portion 62, but insertion of the protrusion 71 into the recess 61 would also be rejected. This could lead to the user repeatedly trying to insert the protrusion 71 into the recess 61, wasting time. In this regard, in the present embodiment, the height of the first uneven portion 62 is lower than the opening edge of the recess 61, so when the protrusion 71 is inserted into the recess 61, it is more likely to be guided toward the bottom in the depth direction of the recess 61, preventing the protrusion 71 from being unnecessarily long.

[0129] 14, 16, and 17, when the needle 56 of the ink inlet 53 on the ink accommodating body 41 side opens the valve 74 in the ink outlet 65 of the ink bottle 63, the positioning portion 73 of the ink bottle 63 abuts against the upper surface 58 of the ink refill adapter 47, which is part of the ink accommodating body 41 side. In other words, due to the abutment of this positioning portion 73 with the upper surface 58 of the ink refill adapter 47, the ink bottle 63 is opened with the valve 74 positioned relative to the needle 56 on the ink accommodating body 41 side in the direction of the central axis of the ink outlet 65.

[0130] 14 and 15, when the positioning portion 73 of the ink bottle 63 abuts against the upper surface 58 of the ink supply adapter 47, the ink bottle 63 is stably maintained in a position where the ink outlet 65 is connected to the ink inlet 53. Therefore, although ink tends to accumulate on the bottom surface where the base end of the needle 56 of the ink inlet 53 is located, this prevents the accumulated ink from adhering to the tip of the ink outlet 65 and soiling the ink bottle 63.

[0131] 14 and 16, when the ink replenishment from the ink bottle 63 to the ink container 41 is completed, if the ink level in the ink container 41 is still lower than the upper limit mark 51 of the visible portion 50, the same black ink bottle 63 may be used to further replenish the ink up to the upper limit mark 51. Note that the ink replenishment operation as described above is also performed in the same way for the ink containers 42 to 45 of other colors other than the ink container 41 containing the ink composition (black or gray ink composition).

[0132] The inkjet recording method of this embodiment can be easily carried out by ejecting the above-described water-based inkjet ink composition from the recording head of the above-described inkjet recording apparatus and depositing it onto a recording medium.

[0133] According to this inkjet recording method, the aqueous inkjet ink composition contains 1-(2-hydroxyethyl)-2-pyrrolidone and a 1,2-alkanediol, and therefore it is possible to form images of good quality while maintaining good storage stability of the aqueous inkjet ink composition.

[0134] The recording medium is not particularly limited, and may be one having a recording surface that absorbs liquid, or one that does not have a recording surface that absorbs liquid. Therefore, the recording medium is not particularly limited, and for example, paper, film, cloth, metal, glass, polymer, etc. can be used. Transfer paper for performing sublimation transfer onto the recording medium can also be a recording medium.

[0135] The step of depositing the aqueous inkjet ink composition on a recording medium can be carried out using the inkjet recording apparatus described above. That is, the aqueous inkjet ink composition is filled into a recording head so that it can be ejected from predetermined nozzles, and then ejected onto a recording medium at predetermined timing in this state, thereby depositing the aqueous inkjet ink composition on a recording medium.

[0136] The recording method of this embodiment may also include a step of heating the recording medium as appropriate. For example, when an inkjet recording apparatus is used, the step of heating the recording medium can be performed using the drying means described above. Furthermore, the step is not limited to an inkjet recording apparatus, and can be performed using any appropriate drying means. This dries the resulting image, thereby preventing image bleeding and allowing for more efficient fixation.

[0137] The recording method of this embodiment can further include other steps as appropriate, such as a step of applying another composition, a washing step, etc. The recording method of this embodiment uses the above-mentioned water-based inkjet ink composition, so that foaming of the water-based inkjet ink composition and aggregation of the coloring material can be suppressed, and images with good color development can be formed.

[0138] 3. Working Example The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "%" below is based on mass.

[0139] 3.1. Preparation of Water-Based Inkjet Ink Composition Each component was placed in a container to obtain the composition shown in Table 1, and mixed and stirred for 2 hours using a magnetic stirrer. The mixture was then filtered through a membrane filter with a pore size of 5 μm. A water-based inkjet ink composition according to the example was obtained.

[0140] [Table 1]

[0141] The ingredients listed in the table by abbreviation and trade name are as follows: Chromofine Blue CI Pigment Blue 15:3: Pigment (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.) Bayscript Cyan BA: dye (manufactured by Lanxess) TEGmBE: Triethylene glycol monobutyl ether HEP: 1-(2-hydroxyethyl)-2-pyrrolidone Olfine E1010: Acetylene glycol surfactant (manufactured by Nissin Chemical Industry Co., Ltd.) Resin: Takelac W6061: Urethane resin emulsion (Mitsui Chemicals)

[0142] 3.2.Evaluation Method

[0143] 3.2.1. Storage stability The viscosity of the ink composition immediately after preparation and after standing at 70°C for 6 days was measured using a viscoelasticity tester MCR-300 (trade name, manufactured by Pysica), and the rate of change was calculated. Evaluation was performed according to the following criteria, and the results are shown in Table 1. A: Viscosity change rate is less than 5%. B: Viscosity change rate is 5% or more but less than 10% C: Viscosity change rate is 10% or more

[0144] 3.2.2.Image Quality (Graininess) For the inks of the examples and comparative examples, printing was carried out using an inkjet printer EP-803A (manufactured by Seiko Epson Corporation) on an inkjet-specific recording medium (photo paper <gloss>: model number KA450PSK (manufactured by Seiko Epson Corporation), 60° glossiness = 41) at a duty of 30% or 50%, and the prints were evaluated according to the following criteria. (Evaluation criteria) A: There is no graininess in the image even at a duty of 30%. B: At a duty of 30%, image graininess is noticeable, but at a duty of 50%, there is no image graininess. C: Image roughness is observed even at a duty of 50%

[0145] 3.2.3.Abrasion resistance The inkjet printer was used to print on the media at a duty of 100%, the printed surface was rubbed strongly with a finger, and the condition of the printed surface was visually observed. The evaluation criteria were as follows: A: Some ink comes off, but your fingers won't get dirty. B: The ink comes off and your fingers get dirty.

[0146] 3.3.Evaluation Results It was found that the aqueous inkjet ink compositions of the examples, which contained a colorant, water, 1-(2-hydroxyethyl)-2-pyrrolidone, and a 1,2-alkanediol, had good storage stability and produced images with good quality (graininess).

[0147] The above-described embodiment and modifications are merely examples, and the present invention is not limited to these. For example, the embodiments and modifications can be combined as appropriate.

[0148] The present invention includes configurations that are substantially the same as the configurations described in the embodiments, for example, configurations with the same functions, methods, and results, or configurations with the same purpose and effects. The present invention also includes configurations that replace non-essential parts of the configurations described in the embodiments. The present invention also includes configurations that achieve the same effects as the configurations described in the embodiments, or configurations that can achieve the same purpose. The present invention also includes configurations that add publicly known technology to the configurations described in the embodiments. Includes:

[0149] The following can be derived from the above-described embodiment and modifications.

[0150] The aqueous inkjet ink composition comprises Contains a colorant, water, 1-(2-hydroxyethyl)-2-pyrrolidone, and a 1,2-alkanediol, The ratio of the content of the 1-(2-hydroxyethyl)-2-pyrrolidone to the content of the 1,2-alkanediol is 1:10 to 10:1 in terms of mass ratio.

[0151] This aqueous inkjet ink composition has good storage stability due to the good dispersibility of the colorant, and good permeability into recording media, resulting in good image quality. That is, 1-(2-hydroxyethyl)-2-pyrrolidone (HEP) reduces the effect of 1,2-alkanediol on the dispersion state of the colorant, thereby maintaining a good dispersion state of the colorant.

[0152] In the above aqueous inkjet ink composition, The 1,2-alkanediol may have an alkyl group having 2 or more and 8 or less carbon atoms.

[0153] This water-based inkjet ink composition can improve both dispersion stability and the quality of the resulting images.

[0154] In the above aqueous inkjet ink composition, The 1,2-alkanediol may be 1,2-hexanediol.

[0155] This water-based ink-jet ink composition can further improve both the dispersion stability and the quality of the resulting images.

[0156] In the above aqueous inkjet ink composition, The colorant may be a pigment.

[0157] This aqueous inkjet ink composition can improve both dispersion stability and the image quality of the resulting image, even for pigments whose dispersion state is easily attacked by 1,2-hexanediol. In other words, the effect of stabilizing the dispersion state is more pronounced.

[0158] In the above aqueous inkjet ink composition, Resin particles may also be contained.

[0159] This aqueous inkjet ink composition can improve both dispersion stability and the image quality of the resulting image, even when it contains resin particles whose dispersion state is easily attacked by 1,2-hexanediol. That is, the dispersion state stabilization effect is more pronounced. Furthermore, the inclusion of resin particles can further improve the abrasion resistance of the resulting image.

[0160] The inkjet recording method is The method includes ejecting the above-mentioned water-based ink-jet ink composition from a recording head and depositing it onto a recording medium.

[0161] According to the inkjet recording method, the water-based inkjet ink composition contains 1-(2-hydroxyethyl)-2-pyrrolidone (HEP) and a 1,2-alkanediol, so that the water-based inkjet ink composition has good storage stability and can produce images with good image quality. can be formed. [Explanation of symbols]

[0162] 21...recording device, 22...casing, 23...support stand, 24...guide shaft, 25...recording head, 26...carriage, 27...support hole, 28...drive pulley, 29...driven pulley, 30...carriage motor, 31...timing belt, 32...discharge outlet, 33...discharge tray, 34...paper feed cassette, 35...opening / closing door, 36...rotating shaft, 37...window portion, 40...ink supply unit, 41-45...ink container, 46...ink supply tube, 47...ink refill adapter, 48...step portion, 49...ink storage chamber, 50...visible portion, 51...upper limit mark, 52...lower limit mark, 53...ink inlet, 54, 55...flow path, 56...needle (ink inlet / flow path portion) ), 57... remaining amount sensor, 58... upper surface (receiving surface), 59... lower surface (tank engagement portion), 60... through hole, 61... recess (first fitting portion), 62... first uneven portion (identification portion), 63... ink bottle, 64... container main body portion, 65... ink outlet, 66... ​​ink outlet forming portion, 67... container additional portion, 68... cap, 69... male thread portion, 70... protrusion, 71... convex portion (second fitting portion), 72... second uneven portion, 73... positioning portion, 74... valve, 75... slit, 76... ink storage chamber, 77... neck portion, 78... male thread portion, 79... large diameter portion, 80... small diameter portion, 81... middle portion, 82... female thread portion, 83... joint portion, L1... distance, L2... distance, P... paper, IK... ink composition

Claims

1. Contains a colorant, water, 1-(2-hydroxyethyl)-2-pyrrolidone, a 1,2-alkanediol, and triethylene glycol monobutyl ether; the content of the triethylene glycol monobutyl ether is 3.0% by mass or more and 10.0% by mass or less, based on the total amount of the composition; The water-based inkjet ink composition has a mass ratio of the content of the 1-(2-hydroxyethyl)-2-pyrrolidone to the content of the 1,2-alkanediol of 4:6 to 6:

4.

2. In claim 1, The 1,2-alkanediol has an alkyl group having from 2 to 8 carbon atoms.

3. In claim 1 or claim 2, The water-based ink-jet ink composition, wherein the 1,2-alkanediol is 1,2-hexanediol.

4. In any one of claims 1 to 3, The water-based inkjet ink composition, wherein the coloring material is a pigment.

5. In any one of claims 1 to 4, The water-based inkjet ink composition further contains resin particles.

6. An inkjet recording method, comprising ejecting the water-based inkjet ink composition according to claim 1 from a recording head and depositing the ink onto a recording medium.

Images