Water-based inkjet ink composition and recording method

Abstract

To provide a water-based inkjet ink composition which has excellent storage stability and discharge stability, can suitably recover from clogging in an inkjet nozzle even when the clogging occurs and can effectively suppress curling of a recording medium when recording is performed by applying to the recording medium and further to provide a recording method capable of effectively suppressing the curling of the recording medium to which the water-based inkjet ink composition is applied.SOLUTION: There is provided a water-based inkjet ink composition which comprises a sugar alcohol having 4 or more carbon atoms, glycerin, lactams having 6 or more membered rings and 8 or less membered rings and an acetylene glycol-based surfactant. The ratio between the content of glycerin and the content of the sugar alcohol having 4 or more carbon atoms in the water-based inkjet ink composition is preferably 1.0:1.0 or more and 1.0:4.0 or less in terms of mass ratio.SELECTED DRAWING: None

Description

[Technical field]

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

[0002] Conventionally, water-based ink-jet inks containing water as a dispersion medium or solvent have been used. Water-based inkjet inks are preferable in terms of their environmental impact and safety to the human body, as compared with solvent-based inkjet inks that contain organic solvents instead of water.

[0003] On the other hand, when plain paper or the like is used as a recording medium, conventionally, water-based inkjet inks sometimes caused curling after recording.

[0004] In particular, when glycerin, which has moisturizing properties, is blended into the aqueous ink-jet ink composition for the purpose of suppressing precipitation of solids in the aqueous ink-jet ink composition in an ink-jet head and resulting ejection defects of the aqueous ink-jet ink composition, the above-mentioned problems have been prominent.

[0005] In order to prevent such problems, there have been attempts to incorporate silica and amino acids into the ink (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2020-7444 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, the ink is still insufficient in terms of suppressing curling, achieving excellent ejection stability, and recovering from clogging. [Means for solving the problem]

[0008] The present invention has been made to solve the above-mentioned problems, and can be realized as the following application examples.

[0009] The water-based inkjet ink composition according to an embodiment of the present invention contains a sugar alcohol having 4 or more carbon atoms, glycerin, a lactam having a 6- to 8-membered ring, and an acetylene glycol surfactant.

[0010] In the recording method according to the application example of the present invention, the water-based ink-jet ink composition according to the application example of the present invention is ejected from an ink-jet head to record. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a table summarizing the conditions for the water-based ink-jet ink compositions prepared in each of the Examples and Comparative Examples. [Diagram 2] FIG. 2 is a table showing the evaluation results for each of the examples and comparative examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Preferred embodiments of the present invention will now be described in detail. [1] Water-based inkjet ink composition First, the water-based ink-jet ink composition of the present invention will be described.

[0013] The water-based inkjet ink composition of the present invention contains a sugar alcohol having 4 or more carbon atoms, glycerin, a lactam having a 6- to 8-membered ring, and an acetylene glycol surfactant.

[0014] With this configuration, the storage stability and ejection stability of the water-based inkjet ink composition are sufficiently excellent, and even if clogging occurs in the nozzles of the inkjet head, the nozzles can be suitably restored. Furthermore, when the water-based inkjet ink composition is applied to a recording medium for recording, curling of the recording medium can be effectively suppressed.

[0015] On the other hand, if the above conditions are not met, satisfactory results will not be obtained. For example, if the aqueous ink-jet ink composition does not contain a sugar alcohol having 4 or more carbon atoms, it becomes difficult to make the moisturizing property of the aqueous ink-jet ink composition sufficiently excellent, and the ejection stability of the aqueous ink-jet ink composition by the ink-jet method is reduced. In particular, when the content of glycerin is relatively low as described below, such a problem occurs more significantly. Furthermore, when the content of glycerin is increased instead of using a sugar alcohol having 4 or more carbon atoms in order to make the moisturizing property of the aqueous ink-jet ink composition sufficiently excellent, curling of the recording medium, particularly a recording medium containing cellulose fibers such as plain paper, cannot be sufficiently suppressed when the aqueous ink-jet ink composition is applied to a recording medium for recording.

[0016] Furthermore, if the water-based ink-jet ink composition does not contain glycerin, the moisture retention of the water-based ink-jet ink composition is significantly reduced, and the ejection stability of the water-based ink-jet ink composition when used in an ink-jet method is significantly deteriorated.

[0017] Furthermore, if the aqueous ink-jet ink composition does not contain lactams having 6 to 8 ring members, phase separation is likely to occur in the aqueous ink-jet ink composition, and the aqueous ink-jet ink composition has poor ejection stability when subjected to the ink-jet method. In particular, when the content of sugar alcohols having 4 or more carbon atoms is relatively high as described below, such problems occur more significantly. Furthermore, even if the aqueous ink-jet ink composition contains lactams, the same problems occur when the lactams are 5 or less ring members or 9 or more ring members.

[0018] Furthermore, if the aqueous ink-jet ink composition does not contain an acetylene glycol surfactant, the surface tension will be high, and the contact angle will also be high, which may cause bleeding on the recorded material or make it difficult for the ink to penetrate into the recorded material. Furthermore, if the aqueous ink-jet ink composition contains a surfactant other than the acetylene glycol surfactant, it will be difficult to ensure appropriate wettability, and the ejection stability will be unstable.

[0019] [1-1] About inkjet The water-based ink-jet ink composition of the present invention is ejected by an ink-jet method.

[0020] Since the ink is discharged by the inkjet method, for example, the recording part to be formed using the aqueous inkjet ink composition can be suitably formed even if it is a fine pattern. In addition, the recording part can be suitably formed on a curved surface or the like. In addition, the ink is excellent in on-demand property, and recording parts of various patterns can be suitably formed. In addition, the ink can be prevented from being wasted, which is preferable from the viewpoint of resource saving, etc.

[0021] Examples of the inkjet method include on-demand methods such as a charge deflection method, a continuous method, a piezoelectric method, and a bubble jet (registered trademark) method.

[0022] [1-2] Sugar alcohols with 4 or more carbon atoms The water-based ink-jet ink composition of the present invention contains a sugar alcohol having 4 or more carbon atoms.

[0023] By containing a sugar alcohol having 4 or more carbon atoms, the aqueous ink-jet ink composition can have sufficiently excellent ejection stability and the like even if the content of glycerin is relatively small. In addition, since the content of glycerin can be relatively small, curling of the recording medium can be effectively suppressed when the aqueous ink-jet ink composition is applied to a recording medium for recording.

[0024] As the sugar alcohol having 4 or more carbon atoms, for example, monosaccharide alcohols, oligosaccharide alcohols, etc. can be used, with the monosaccharide alcohols being preferred from the viewpoint of reducing curling, etc.

[0025] More specifically, sugar alcohols having 4 or more carbon atoms include threitol, erythritol, threitol, pentaerythritol, arabitol, ribitol, xylitol, sorbitol, mannitol, talitol, galactitol, allitol, altritol, iditol, inositol, dipentaerythritol, maltitol, isomaltitol, lactitol, tripentaerythritol, etc., and one or more selected from these can be used in combination.

[0026] In particular, the aqueous inkjet ink composition of the present invention preferably contains a sugar alcohol having 4 to 6 carbon atoms as the sugar alcohol having 4 or more carbon atoms, more preferably a sugar alcohol having 5 carbon atoms, and even more preferably xylitol.

[0027] This makes it possible to more effectively suppress curling of a recording medium when the water-based inkjet ink composition is applied to the recording medium for recording.

[0028] The content of sugar alcohols having 4 or more carbon atoms in the aqueous inkjet ink composition is preferably 5.0% by mass or more and 20.0% by mass or less, more preferably 7.0% by mass or more and 18.0% by mass or less, and even more preferably 7.5% by mass or more and 10.0% by mass or less.

[0029] This makes it possible to improve the ejection stability and the like of the aqueous ink-jet ink composition, while also reducing the glycerin content, and when the aqueous ink-jet ink composition is applied to a recording medium for recording, curling of the recording medium can be more effectively suppressed.

[0030] [1-3] Glycerin The water-based ink-jet ink composition of the present invention contains glycerin.

[0031] By including glycerin, the moisture retention of the water-based ink-jet ink composition can be improved, and the ejection stability and the like of the water-based ink-jet ink composition can be made sufficiently excellent.

[0032] The content of glycerin in the aqueous inkjet ink composition is preferably from 3.0% to 9.0% by mass, more preferably from 4.5% to 8.0% by mass, and even more preferably from 5.0% to 7.0% by mass.

[0033] This makes it possible to ensure that the ejection stability and the like of the aqueous ink-jet ink composition are sufficiently excellent, while at the same time making it possible to more effectively suppress curling of the recording medium when the aqueous ink-jet ink composition is applied to a recording medium for recording.

[0034] In the aqueous ink-jet ink composition of the present invention, the ratio by mass of the glycerin content to the sugar alcohol content having 4 or more carbon atoms is preferably 1.0:1.0 or more and 1.0:4.0 or less, more preferably 1.0:1.1 or more and 1.0:2.8 or less, and even more preferably 1.0:1.2 or more and 1.0:1.8 or less.

[0035] This makes it possible to improve the ejection stability and the like of the aqueous ink-jet ink composition, while more effectively suppressing curling of the recording medium when the aqueous ink-jet ink composition is applied to a recording medium for recording.

[0036] [1-4] Lactams with 6 to 8 ring members The water-based ink-jet ink composition of the present invention contains lactams having a 6- to 8-membered ring.

[0037] The present inventors have found that when a sugar alcohol having 4 or more carbon atoms and an acetylene glycol surfactant are contained, the acetylene glycol surfactant becomes less soluble in water and is more likely to cause phase separation. In contrast, by containing lactams having 6 to 8 membered rings, the occurrence of such phase separation can be effectively prevented even in a water-based inkjet ink composition containing a sugar alcohol having 4 or more carbon atoms and an acetylene glycol surfactant.

[0038] Examples of lactams having 6 to 8 membered rings include ε-caprolactam, 2-piperidone, N-acetylcaprolactam, N-methylcaprolactam, and 2,5-diketopiperazine, and one or more selected from these can be used in combination.

[0039] In particular, the water-based inkjet ink composition of the present invention preferably contains a 7-membered ring lactam as the 6- to 8-membered ring lactam, and more preferably contains ε-caprolactam.

[0040] This makes it possible to provide the water-based ink-jet ink composition with improved storage stability, ejection stability, and the like.

[0041] The content of lactams having 6 to 8 membered rings in the aqueous inkjet ink composition is preferably 1.0 to 4.0% by mass, more preferably 1.5 to 3.5% by mass, and even more preferably 2.0 to 3.0% by mass.

[0042] This makes it possible to further improve the storage stability, ejection stability, etc. of the water-based ink-jet ink composition.

[0043] [1-5] Acetylene glycol surfactants The water-based ink-jet ink composition of the present invention contains an acetylene glycol surfactant.

[0044] By including an acetylene glycol surfactant, compatibility with the organic solvent used in the present invention is increased, and recorded matter having excellent storage stability and ejection stability, as well as prevention of bleeding and good color development can be obtained.

[0045] Examples of acetylene glycol surfactants include 2,4,7,9-tetramethyl-5-decyne-4,7-diol and alkylene oxide adducts of 2,4,7,9-tetramethyl-5-decyne-4,7-diol, and 2,4-dimethyl-5-decyne-4-ol and alkylene oxide adducts of 2,4-dimethyl-5-decyne-4-ol. One or a combination of two or more selected from these can be used.

[0046] The content of the acetylene glycol surfactant in the aqueous inkjet ink composition is preferably from 0.3% to 3.5% by mass, more preferably from 0.5% to 3.0% by mass, and even more preferably from 0.8% to 2.5% by mass. This provides better permeability into the recording medium.

[0047] In the aqueous ink-jet ink composition of the present invention, the ratio of the content of the lactam having from 6 to 8 membered ring to the content of the acetylene glycol surfactant, in mass ratio, is preferably from 1.0:0.2 to 1.0:1.2, more preferably from 1.0:0.3 to 1.0:1.0, and even more preferably from 1.0:0.4 to 1.0:0.8.

[0048] This makes it possible to improve the compatibility of the surfactant while ensuring the surface tension, and to make phase separation less likely to occur in the aqueous ink-jet ink composition.

[0049] [1-6]Water The water-based ink-jet ink composition of the present invention contains water. In the aqueous ink-jet ink composition, water functions as a solvent for dissolving other components and as a dispersion medium for dispersing other components.

[0050] The water content in the aqueous ink-jet ink composition is preferably 60.0% by mass or less, more preferably from 50.0% to 60.0% by mass, and even more preferably from 52.0% to 60.0% by mass.

[0051] This makes it possible to more effectively suppress curling of the recording medium when the aqueous ink-jet ink composition is applied to the recording medium for recording. The present inventors have found that in aqueous ink-jet ink compositions containing a sugar alcohol having 4 or more carbon atoms, particularly aqueous ink-jet ink compositions containing a sugar alcohol having 4 or more carbon atoms together with an acetylene glycol surfactant, when the water content is relatively low as described above, the aqueous ink-jet ink composition is more likely to suffer from problems such as reduced storage stability and ejection stability. In contrast, the present invention can suitably prevent the occurrence of such problems even when the water content is relatively low as described above. That is, when the water content in the aqueous ink-jet ink composition is within the above range, the effects of the present invention are more significantly exhibited.

[0052] [1-7] Resin components The water-based ink-jet ink composition of the present invention may further contain a resin component.

[0053] This makes it possible to improve the adhesion of the recorded portion of the aqueous ink-jet ink composition to the recording medium to which the aqueous ink-jet ink composition is applied.

[0054] When the aqueous ink-jet ink composition of the present invention contains a resin component, the resin component may be, for example, contained in the aqueous ink-jet ink composition in a dissolved state or in a dispersed state.

[0055] Examples of the resin component include 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, and the like. One or a combination of two or more selected from these can be used.

[0056] In particular, by including a styrene-acrylic copolymer, the storage stability, ejection stability, etc. of the aqueous ink-jet ink composition can be improved, and the adhesion of the recorded portion of the aqueous ink-jet ink composition to the recording medium to which the aqueous ink-jet ink composition is applied can be improved.

[0057] The content of the resin component in the aqueous inkjet ink composition is preferably from 0.2 to 2.5% by mass, more preferably from 0.3 to 2.0% by mass, and even more preferably from 0.5 to 1.5% by mass.

[0058] This can further improve the storage stability, ejection stability, etc., of the aqueous ink-jet ink composition, and can also further improve the adhesion of the recorded portion of the aqueous ink-jet ink composition to the recording medium to which the aqueous ink-jet ink composition is applied.

[0059] [1-8] Coloring materials The water-based ink-jet ink composition of the present invention may further contain a coloring material. This allows the recorded portion formed using the aqueous ink-jet ink composition to be visually confirmed in a favorable manner. Furthermore, in the past, when the aqueous ink-jet ink composition contained a coloring material, it was particularly difficult to achieve both the ejection stability of the aqueous ink-jet ink composition and the suppression of curling of the recording medium when the aqueous ink-jet ink composition was applied to a recording medium for recording, but in the present invention, these can be achieved at the same time even when the aqueous ink-jet ink composition contains a coloring material. In other words, when the aqueous ink-jet ink composition contains a coloring material, the effects of the present invention are more significantly exhibited.

[0060] Examples of the coloring material include various pigments such as organic pigments and inorganic pigments, and various dyes. One or a combination of two or more selected from these may be used.

[0061] Examples of organic pigments include azo pigments such as azo lakes, insoluble azo pigments, condensed azo pigments, and chelate azo pigments; polycyclic pigments such as phthalocyanine pigments, perylene and perylene pigments, anthraquinone pigments, quinacridone pigments, dioxandinone pigments, thioindigo pigments, isoindolinone pigments, and quinophthaloni pigments; dye lakes such as basic dye lakes and acid dye lakes; nitro pigments, nitroso pigments, aniline black, and daylight fluorescent pigments.

[0062] Examples of inorganic pigments include titanium oxide, iron oxide, carbon black, etc. Carbon black that can be used includes those produced by known methods such as the contact method, furnace method, and thermal method.

[0063] As the pigment, a self-dispersing surface-treated pigment in which a hydrophilic group is introduced onto the surface of the pigment particle by utilizing a chemical reaction, that is, a so-called self-dispersing pigment, may be used.

[0064] Examples of dyes include sublimation dyes, oil dyes, disperse dyes, fluorescent dyes, reactive dyes, acid dyes, sulfur dyes, vat dyes, and cationic dyes.

[0065] Examples of disperse dyes and sublimation dyes include CI Disperse Yellow 1, 3, 4, 5, 7, 9, 13, 23, 24, 30, 33, 34, 42, 44, 49, 50, 51, 54, 56, 58, 60, 61, 63, 64, 66, 68, 71, 74, 76, 79, 82, 83, 85, 86, 88, 90, 91, 93, 98, 99, 100, 104, 108, 114, 116, 118, 119, 122, 124, 126, 135, 140, 141, 149, 154, 160, 162, 163, 164, 165, 179, 180, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 19 ... 6, 192, 198, 199, 201, 202, 204, 210, 211, 215, 216, 218, 224, 227, 231, 232;CI Disperse Orange 1, 3, 5, 7, 11, 13, 17, 20, 21, 25, 29, 30, 31, 32, 33, 37, 38, 42, 43, 44, 45, 46, 47, 48, 49, 50, 53, 54, 55, 56, 57, 58, 59, 60, 61, 66, 71, 73, 76, 78, 80, 89, 90, 91, 93, 96, 97, 119, 127, 130, 139, 142;CI Disperse Red 1, 4, 5, 7, 11, 12, 13, 15, 17, 27, 43, 44, 50, 52, 53, 54, 55, 56, 58, 59, 60, 65, 72, 73, 74, 75, 76, 78, 81, 82, 86, 88, 90, 91, 92, 93, 96, 103, 105, 106, 107, 108, 110, 111, 113, 117, 118, 121, 122, 126, 127, 128, 131, 132, 134, 135, 137, 143, 145, 146, 151, 152, 153, 154, 157, 159, 164, 167, 169, 177, 179, 181, 183, 184, 185, 188, 189, 190, 191, 192, 200, 201, 202, 203, 205, 206, 207, 210, 221, 224, 225, 227, 229, 239, 240, 257, 258, 277, 278, 279, 281, 288, 298, 302, 303, 310, 311, 312, 320, 324, 328, 364;CI Disperse Violet 1, 4, 8, 23, 26, 27, 28, 31, 33, 35, 36, 38, 40, 43, 46, 48, 50, 51, 52, 56, 57, 59, 61, 63, 69, 77;CIDisperse Green 9;CI Disperse Brown 1, 2, 4, 9, 13, 19;CI Disperse Blue 3, 7, 9, 14, 16, 19, 20, 24, 26, 27, 35, 43, 44, 54, 55, 56, 58, 60, 62, 64, 71, 72, 73, 75, 79, 81, 82, 83, 87, 91, 92, 93, 94, 95, 96, 102, 106, 108, 112, 113, 115, 118, 120, 122, 125, 128, 130, 139, 141, 142, 143, 146, 148, 149, 153, 154, 158, 165, 167, 171, 173, 174, 176, 181, 183, 185, 186, 187, 189, 197, 198, 200, 201, 205, 207, 211, 214, 224, 225, 257, 259, 267, 268, 270, 284, 285, 287, 288, 291, 293, 295, 297, 301, 315, 330, 333, 359, 360; CI Disperse Black 1, 3, 10, 24, etc.

[0066] Examples of oil-based dyes include CI Solvent Black 3, 7, 27, 29, 34; CI Solvent Yellow 14, 16, 19, 29, 56, 82; CI Solvent Red 1, 3, 8, 18, 24, 27, 43, 51, 72, 73, 132, 218; CI Solvent Violet 3; CI Solvent Blue 2, 5, 11, 70; CI Solvent Green 3, 7; and CI Solvent Orange 2.

[0067] Fluorescent dyes include, for example, CI Disperse Red 362, 364; CI Bat Red 41; CI Disperse Yellow 43, 82, 184, 232, and the like.

[0068] Examples of reactive dyes include yellow dyes such as CI Reactive Yellow 2, 3, 18, 81, 84, 85, 95, 99, and 102; orange dyes such as CI Reactive Orange 5, 9, 12, 13, 35, 45, and 99; brown dyes such as CI Reactive Brown 2, 8, 9, 17, and 33; and CI Reactive Red 1, 3, 4, 13, 15, 24, 29, 31, 33, 120, 125, 151, 206, 207, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 254, 255, 256, 257, 258, 259, 260, 261, 262, 263, 264, 265, 266, 267, 268, 269, 270, 271, 272, 273, 274, red dyes such as CI Reactive Violet 24; blue dyes such as CI Reactive Blue 2, 4, 5, 10, 13, 14, 15, 15:1, 19, 21, 49, 63, 71, 72, 75, 162, 176, 198; green dyes such as CI Reactive Green 5, 8, 19; and black dyes such as CI Reactive Black 1, 8, 23, 39.

[0069] Among these, pigments are preferred as coloring materials. This makes it possible to improve the color development of the recorded portion formed using the aqueous ink-jet ink composition. Furthermore, in the past, when the aqueous ink-jet ink composition contained a pigment, it was particularly difficult to simultaneously achieve the ejection stability and the like of the aqueous ink-jet ink composition and the suppression of curling of the recording medium when the aqueous ink-jet ink composition is applied to a recording medium for recording, but in the present invention, these can be simultaneously achieved even when the aqueous ink-jet ink composition contains a pigment. In other words, when the aqueous ink-jet ink composition contains a pigment, the effects of the present invention are even more remarkable.

[0070] In particular, when the coloring material is a self-dispersing pigment, the dispersion stability of the pigment is excellent, and since there is no need to use a dispersant for dispersing the pigment, the viscosity of the aqueous ink-jet ink composition can be reduced.

[0071] When the aqueous ink-jet ink composition contains a colorant, the content of the colorant in the aqueous ink-jet ink composition is preferably from 3.0% to 15.0% by mass, more preferably from 4.0% to 13.0% by mass, and even more preferably from 4.5% to 10.0% by mass.

[0072] By containing a coloring material at such a relatively high content, the color development of the recorded portion formed using the aqueous ink-jet ink composition can be improved, and the occurrence of undesired color unevenness in the recorded matter produced using the aqueous ink-jet ink composition can be more effectively prevented.

[0073] [1-9] Penetrating agent The water-based ink-jet ink composition of the present invention may further contain a penetrant. This makes it possible to suitably improve the permeability of the aqueous ink-jet ink composition into a recording medium, and to improve the abrasion resistance and other properties of recorded matter produced using the aqueous ink-jet ink composition.

[0074] Examples of the penetrating agent include triethylene glycol monomethyl ether, triethylene glycol monobutyl ether, diethylene glycol monomethyl ether, 1,2-hexanediol, 1,2-pentanediol, 1,2-butanediol, and 3-methyl-1,5-pentanediol. One or a combination of two or more selected from these can be used.

[0075] The content of the penetrant in the aqueous inkjet ink composition is preferably from 4.0% to 12.0% by mass, more preferably from 4.5% to 10.0% by mass, and even more preferably from 5.0% to 8.5% by mass.

[0076] [1-10] Moisturizers other than glycerin The water-based ink-jet ink composition of the present invention may further contain a humectant other than glycerin.

[0077] This makes it possible to more suitably enhance the moisture retention of the water-based ink-jet ink composition, and to improve the ejection stability and the like of the water-based ink-jet ink composition.

[0078] Examples of moisturizing agents other than glycerin include betaine and trimethylolpropane, but any agent generally used in ink-jet inks can be used without any particular limitation.

[0079] The content of the humectant other than glycerin in the aqueous inkjet ink composition is preferably from 1.0% to 10.0% by mass, more preferably from 3.0% to 9.0% by mass, and even more preferably from 4.0% to 8.0% by mass.

[0080] [1-11] Other ingredients The aqueous ink-jet ink composition of the present invention may contain components other than those described above. Hereinafter, in this section, such components are also referred to as "other components".

[0081] Examples of other components include dispersants, pH adjusters, surfactants other than acetylene glycol-based surfactants, chelating agents, preservatives / fungal inhibitors, rust inhibitors, antioxidants, ultraviolet absorbers, oxygen absorbers, etc., and one or more selected from these may be used in combination.

[0082] The content of other components in the aqueous ink-jet ink composition is preferably 10.0% by mass or less, more preferably 7.0% by mass or less, and even more preferably 5.0% by mass or less.

[0083] [1-12]Other conditions The viscosity of the aqueous ink-jet ink composition of the present invention at 25° C. is preferably from 2 mPa·s to 10 mPa·s, more preferably from 3 mPa·s to 8 mPa·s, and even more preferably from 4 mPa·s to 6 mPa·s. This provides the water-based ink-jet ink composition with better ejection stability when subjected to an ink-jet method.

[0084] The viscosity was measured at 25°C using a viscoelasticity tester (e.g., Atago Co., Ltd., VISCO 6800) at a shear rate of 10 [s -1 The viscosity can be measured by reading the viscosity at

[0085] [2] Ink composition set Next, the ink composition set according to the present invention will be described.

[0086] The ink composition set according to the present invention includes a plurality of ink compositions, at least one of which is the above-mentioned water-based inkjet ink composition according to the present invention.

[0087] At least one of the ink compositions constituting the ink composition set according to the present invention may be the aqueous ink-jet ink composition of the present invention described above, and the ink composition set according to the present invention may include an ink composition other than the aqueous ink-jet ink composition of the present invention described above. Hereinafter, such an ink composition may be referred to as "other ink composition". Examples of other ink compositions include non-aqueous ink compositions and ink compositions that are applied to a recording medium by a method other than the ink-jet method.

[0088] In particular, the ink composition set according to the present invention preferably comprises a plurality of types of water-based ink-jet ink compositions according to the present invention, and it is more preferable that all of the ink compositions constituting the ink composition set are water-based ink-jet ink compositions according to the present invention.

[0089] The ink composition set according to the present invention preferably includes three water-based inkjet ink compositions corresponding to the three primary colors, i.e., cyan, magenta, and yellow. The three primary colors may be further divided according to their color densities. For example, the ink composition set may include light cyan, light magenta, and light yellow in addition to cyan, magenta, and yellow.

[0090] The ink composition set according to the present invention may also include an achromatic ink, more specifically, a black ink.

[0091] [3] Recording method Next, the recording method of the present invention will be described.

[0092] The recording method of the present invention is a method in which recording is performed by ejecting the above-mentioned water-based ink-jet ink composition of the present invention from an ink-jet head.

[0093] This makes it possible to effectively prevent curling of the recording medium to which the aqueous ink-jet ink composition has been applied.

[0094] [3-1] Recording media In the recording method of the present invention, a recording medium containing cellulose fibers, such as plain paper, can be suitably used as the recording medium.

[0095]

[0023] Such recording media are advantageous in that they are relatively inexpensive, easily available, and can provide suitable ink permeability, etc., but on the other hand, they have a problem in that they are prone to curling when an aqueous ink-jet ink composition is applied to them. In contrast, in the present invention, even when such a recording medium is used, the occurrence of curling can be sufficiently suppressed.

[0096] [3-2] Water-based inkjet ink composition application process In the water-based ink-jet ink composition application step, the water-based ink-jet ink composition of the present invention is ejected by an ink-jet method and applied to a recording medium.

[0097] In this step, for example, solid printing may be performed so that the amount of the aqueous ink-jet ink composition applied to each portion of the recording medium is uniform, or the amount applied may vary from portion to portion of the recording medium. Also, there may be portions on the recording medium to which the aqueous ink-jet ink composition is not applied.

[0098] As the inkjet method, the method described above in [1-1] can be used. In this step, multiple types of water-based ink-jet ink compositions may be used.

[0099] [3-3] Other processes The recording method of the present invention may further include other steps in addition to the steps described above, for example.

[0100] For example, the recording method of the present invention may further include a step of depositing an ink composition other than the water-based ink-jet ink composition of the present invention onto a recording medium.

[0101] When such a step is carried out, the step may be carried out, for example, before the step of applying the water-based ink-jet ink composition, or may be carried out after the step of applying the water-based ink-jet ink composition.

[0102] [4] Recorded material A recorded matter can be obtained by the above-described recording method of the present invention. In the recorded matter according to the present invention, the occurrence of curling is suitably suppressed.

[0103] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these. EXAMPLES

[0104] Next, specific examples of the present invention will be described. [5] Preparation of Water-Based Inkjet Ink Composition (Examples 1 to 7, Comparative Examples 1 to 5) By mixing the components in the prescribed ratios, water-based inkjet ink compositions having the compositions shown in FIG. 1 were prepared.

[0105] The conditions for the aqueous inkjet ink compositions prepared in the above examples and comparative examples are summarized in Figure 1. The items shown in Figure 1 are as follows: the solid content of CAB-O-JET300 (manufactured by Cabot Corporation), which is a self-dispersing pigment, is referred to as "carbon black", the solid content of X-436 (manufactured by Seiko PMC Corporation), which is an emulsion of a styrene-acrylic copolymer, is referred to as "X-436", triethylene glycol is referred to as "TEG", triethylene glycol monobutyl ether is referred to as "TEGMBE", 1,2-hexanediol is referred to as "1,2HD", ε-caprolactam is referred to as "εCL", the solid content of Surfynol 465 (manufactured by Nissin Chemical Industry Co., Ltd.), which is an acetylene glycol surfactant, is referred to as "S465", the solid content of Olfine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.), which is an acetylene glycol surfactant, is referred to as "E1010", triethanolamine is referred to as "TEA", ethylenediaminetetraacetic acid is referred to as "EDTA", and benzotriazole is referred to as "BTA".

[0106] The unit of the content of each component in Figure 1 is parts by mass. The viscosity at 25°C of the water-based inkjet ink compositions of each of the Examples and Comparative Examples was in the range of 2 mPa s to 10 mPa s.

[0107] [6] Evaluation The water-based ink-jet ink compositions of the Examples and Comparative Examples were evaluated as follows.

[0108] [6-1] Curl suppression First, the water-based inkjet ink compositions of each of the Examples and Comparative Examples were each injected into a dedicated ink cartridge for an inkjet recording device: LX-6050MF (manufactured by Seiko Epson Corporation), and then these ink cartridges were mounted on a modified LX-6050MF.

[0109] Next, at room temperature, a recording medium was printed on P paper (64 g / m2) manufactured by Fuji Xerox. 2 A solid black pattern was printed on a paper (88 μm thick) at a resolution of 600 × 600 dpi.

[0110] After printing, the paper was placed face down on the floor, and the angle between the edge of the paper and the point where the paper touched the floor was measured as the curl angle, and was evaluated according to the following criteria: The smaller this angle, the better the curl of the recording medium was suppressed.

[0111] A: The maximum curl angle is less than 90°. B: The maximum curl angle is greater than or equal to 90° and less than 100°. C: Maximum curl angle is 100° or more.

[0112] [6-2] Discharge stability The following evaluations were carried out using a modified inkjet recording device, LX-6050MF (manufactured by Seiko Epson Corporation).

[0113] That is, the water-based inkjet ink compositions of the respective Examples and Comparative Examples were each poured into a dedicated ink cartridge for the LX-6050MF, and then these ink cartridges were mounted on a modified LX-6050MF.

[0114] In an environment of 40°C and 20% humidity, Fuji Xerox P paper (grammage 64 g / m) was used as a recording medium. 2 A black solid pattern was printed on 30 sheets of paper (88 μm thick) at a resolution of 600 × 600 dpi, and the number of non-ejecting nozzles was counted and evaluated according to the following criteria. The lower this number, the better the ejection stability of the aqueous inkjet ink composition.

[0115] A: There were zero non-ejecting nozzles. B: The number of non-ejecting nozzles is 1 to 9. C: There are 10 or more non-ejecting nozzles.

[0116] [6-3] Clogging recovery First, the water-based inkjet ink compositions of each of the Examples and Comparative Examples were each injected into a dedicated ink cartridge for an inkjet recording device: LX-6050MF (manufactured by Seiko Epson Corporation), and then these ink cartridges were mounted on a modified LX-6050MF.

[0117] Next, the inkjet head was left uncapped in an environment of 40° C. for 7 days.

[0118] After leaving it as it was, a cleaning operation was performed, and the number of cleaning operations until all nozzles were restored was counted and evaluated according to the following criteria. The fewer the number of cleaning operations, the better the restoration of clogging.

[0119] A: The nozzles need to be cleaned three or fewer times to recover completely. B: The number of cleanings required to recover all nozzles is between 4 and 6 times. C: The nozzles are completely restored after seven or more cleanings.

[0120] [6-4] Storage stability The aqueous ink-jet ink compositions of the Examples and Comparative Examples were filled into a predetermined sealable storage bottle, and these storage bottles were left for 7 days in an environment of 60°C. From the viscosity measurement results of each aqueous ink-jet ink composition before and after being left, the viscosity change rate of each aqueous ink-jet ink composition before and after being left was obtained, and the presence or absence of formation of aggregates was visually confirmed and evaluated according to the following criteria. It can be said that the smaller the viscosity change rate value, the better the storage stability of the aqueous ink-jet ink composition. It can also be said that the storage stability of the aqueous ink-jet ink composition is superior to that of the aqueous ink-jet ink composition in which aggregates are not formed, compared to the aqueous ink-jet ink composition in which aggregates are formed.

[0121] A: The rate of change from the initial viscosity is less than ±1%, and no agglomerates are formed. B: The rate of change from the initial viscosity is ±1% or more, and no agglomerates are formed. C: The rate of change from the initial viscosity is ±1% or more, and aggregates are generated.

[0122] [6-5] Difficulty in transfer The following evaluations were carried out using a modified inkjet recording device, LX-6050MF (manufactured by Seiko Epson Corporation).

[0123] That is, the water-based inkjet ink compositions of the respective Examples and Comparative Examples were each poured into a dedicated ink cartridge for the LX-6050MF, and then these ink cartridges were mounted on a modified LX-6050MF.

[0124] At room temperature, the recording medium was P paper manufactured by Fuji Xerox (basis weight 64 g / m 2 A continuous black solid pattern was printed on both sides of a sheet of paper (paper thickness 88 μm) at a resolution of 600 × 600 dpi for 100 sheets. Thereafter, the presence or absence of transfer marks of the aqueous inkjet ink composition on the sides of the printed recording medium was visually confirmed, and evaluated according to the following criteria.

[0125] A: No traces of ink transfer are observed. B: Ink transfer marks are visible. These results are summarized in FIG.

[0126] As is clear from Fig. 2, excellent results were obtained in the present invention. In contrast, satisfactory results were not obtained in the comparative example.

Claims

1. An aqueous ink-jet ink composition comprising a sugar alcohol having 4 or more carbon atoms, glycerin, a lactam having a 6- to 8-membered ring, and an acetylene glycol surfactant.

2. 2. The water-based ink-jet ink composition according to claim 1, wherein a ratio, in mass ratio, of the content of the glycerin to the content of the sugar alcohol having 4 or more carbon atoms in the water-based ink-jet ink composition is 1.0:1.0 or more and 1.0:4.0 or less.

3. The water-based ink-jet ink composition according to claim 1 or 2, wherein the sugar alcohol having 4 or more carbon atoms comprises a sugar alcohol having 4 to 6 carbon atoms.

4. The aqueous ink-jet ink composition according to claim 1 or 2, wherein the lactams having 6 to 8 members are 7-membered lactams.

5. The water-based ink-jet ink composition according to claim 1 or 2, wherein the water content in the water-based ink-jet ink composition is 60.0% by mass or less.

6. The water-based ink-jet ink composition according to claim 1 or 2, further comprising a resin component.

7. The aqueous ink-jet ink composition further contains a colorant, The water-based ink-jet ink composition according to claim 1 or 2, wherein the coloring material is a pigment.

8. A recording method comprising discharging the water-based ink-jet ink composition according to claim 1 or 2 from an ink-jet head to perform recording.

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