JP2025024331A - Water-based ink-jet ink composition and recording method - Google Patents

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

The present invention relates to a water-based inkjet ink composition and a recording method.

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.

On the other hand, in the past, when using plain paper or the like as a recording medium, water-based inkjet inks could cause curling after printing.

In particular, when glycerin, which has moisturizing properties, is blended into the aqueous ink-jet ink composition in order to prevent solids from being precipitated in the aqueous ink-jet ink composition in the ink-jet head and the resulting ejection defects of the aqueous ink-jet ink composition, the above-mentioned problems are particularly noticeable.

In order to prevent such problems, there have been attempts to include silica and amino acids in the ink (see, for example, Patent Document 1).

JP 2020-7444 A

However, it was still insufficient in terms of suppressing curling, providing excellent discharge stability, and recovering from clogging.

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

The aqueous inkjet ink composition according to the application example of the present invention contains a sugar alcohol having 4 or more carbon atoms, glycerin, lactams having a 6- to 8-membered ring, and an acetylene glycol surfactant.

The recording method according to the application example of the present invention involves ejecting the water-based inkjet ink composition according to the application example of the present invention from an inkjet head to record.

FIG. 1 is a table showing all the conditions for the aqueous ink-jet ink compositions prepared in each of the Examples and Comparative Examples. FIG. 2 is a table showing the evaluation results for each of the examples and comparative examples.

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

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

This configuration makes the storage stability and ejection stability of the water-based inkjet ink composition sufficiently excellent, and allows the inkjet head nozzles to be easily restored even if they become clogged. It also effectively prevents the recording medium from curling when the water-based inkjet ink composition is applied to the recording medium for recording.

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 provide the aqueous ink-jet ink composition with sufficiently excellent moisturizing properties, 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 provide the aqueous ink-jet ink composition with sufficiently excellent moisturizing properties, 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.

Furthermore, if the aqueous ink-jet ink composition does not contain glycerin, the moisture retention of the aqueous ink-jet ink composition will be significantly reduced, and the ejection stability of the aqueous ink-jet ink composition when used in an ink-jet method will be significantly inferior.

Furthermore, if the aqueous ink-jet ink composition does not contain lactams having 6 to 8 membered rings, phase separation is likely to occur in the aqueous ink-jet ink composition, and the aqueous ink-jet ink composition will have 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, similar problems will occur if the lactams are those having 5 or less membered rings or those having 9 or more membered rings.

Furthermore, if the aqueous inkjet 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 result in bleeding on the printed matter or the ink will be difficult to penetrate into the printed matter. Furthermore, if the aqueous inkjet ink composition contains a surfactant other than an acetylene glycol surfactant, it will be difficult to ensure proper wetting, and ejection stability will be unstable.

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

Because it is ejected 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. Furthermore, the recording part can be suitably formed on curved surfaces, etc. Furthermore, it has excellent on-demand properties and can suitably form recording parts of various patterns. Furthermore, it is possible to eliminate ink waste, which is also preferable from the viewpoint of resource conservation, etc.

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

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

By containing a sugar alcohol having 4 or more carbon atoms, the ejection stability, etc. of the aqueous ink-jet ink composition can be sufficiently excellent even if the glycerin content is relatively small. In addition, because the glycerin content 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.

As sugar alcohols having 4 or more carbon atoms, for example, monosaccharide alcohols, oligosaccharide alcohols, etc. can be used, but monosaccharide alcohols are preferred in terms of reducing curling, etc.

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.

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.

This makes it possible to more effectively prevent curling of the recording medium when the aqueous inkjet ink composition is applied to the recording medium for recording.

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.

This makes it possible to improve the ejection stability of the aqueous inkjet ink composition, reduce the glycerin content, and more effectively suppress curling of the recording medium when the aqueous inkjet ink composition is applied to a recording medium for recording.

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

By including glycerin, the moisture retention of the water-based inkjet ink composition can be improved, and the ejection stability, etc. of the water-based inkjet ink composition can be made sufficiently excellent.

The content of glycerin in the aqueous inkjet ink composition is preferably 3.0% by mass or more and 9.0% by mass or less, more preferably 4.5% by mass or more and 8.0% by mass or less, and even more preferably 5.0% by mass or more and 7.0% by mass or less.

This allows the ejection stability of the aqueous inkjet ink composition to be sufficiently excellent, while more effectively suppressing curling of the recording medium when the aqueous inkjet ink composition is applied to a recording medium for recording.

In the aqueous inkjet ink composition of the present invention, the ratio of the content of glycerin to the content of sugar alcohols having 4 or more carbon atoms, in mass ratio, 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.

This improves the ejection stability of the aqueous inkjet ink composition, while more effectively suppressing curling of the recording medium when the aqueous inkjet ink composition is applied to a recording medium for recording.

[1-4] Lactams having 6 to 8 membered rings The water-based ink-jet ink composition of the present invention contains a lactam having 6 to 8 membered rings.

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 phase separation as described above can be effectively prevented even in an aqueous inkjet ink composition containing a sugar alcohol having 4 or more carbon atoms and an acetylene glycol surfactant.

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.

In particular, the water-based inkjet ink composition of the present invention preferably contains lactams with 7 members as lactams with 6 to 8 ring members, and more preferably contains ε-caprolactam.

This allows the water-based inkjet ink composition to have better storage stability, ejection stability, etc.

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.

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

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

By including an acetylene glycol surfactant, compatibility with the organic solvent used in the present invention is increased, resulting in recordings with excellent storage stability and ejection stability, as well as prevention of bleeding and good color development.

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, and one or more selected from these can be used in combination.

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

In the aqueous inkjet ink composition of the present invention, the ratio of the content of lactams having 6 to 8 membered rings to the content of acetylene glycol surfactants is preferably 1.0:0.2 or more and 1.0:1.2 or less, more preferably 1.0:0.3 or more and 1.0:1.0 or less, and even more preferably 1.0:0.4 or more and 1.0:0.8 or less, by mass.

This improves the compatibility of the surfactant while maintaining the surface tension, making it difficult for phase separation to occur in the aqueous inkjet ink composition.

[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.

The water content in the aqueous inkjet ink composition is preferably 60.0% by mass or less, more preferably 50.0% by mass or more and 60.0% by mass or less, and even more preferably 52.0% by mass or more and 60.0% by mass or less.

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 problem of reduced storage stability and ejection stability of the aqueous ink-jet ink composition occurs more significantly. In contrast, the present invention can suitably prevent the occurrence of such problems even when the water content is relatively low as described above. In other words, 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.

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

This allows for better adhesion of the recording area formed by the aqueous ink-jet ink composition to the recording medium to which the aqueous ink-jet ink composition is applied.

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

Examples of the resin component include urethane resins, acrylic resins (including styrene-acrylic resins), fluorene resins, polyolefin resins, rosin-modified resins, terpene resins, polyester resins, polyamide resins, epoxy resins, vinyl chloride resins, vinyl chloride-vinyl acetate copolymers, ethylene-vinyl acetate resins, etc., and one or more of these may be used in combination.

In particular, by including a styrene-acrylic copolymer, the storage stability, ejection stability, etc. of the water-based inkjet ink composition can be improved, and the adhesion of the recording portion of the water-based inkjet ink composition to the recording medium to which the water-based inkjet ink composition is applied can be improved.

The content of the resin component in the aqueous inkjet ink composition is preferably 0.2% by mass or more and 2.5% by mass or less, more preferably 0.3% by mass or more and 2.0% by mass or less, and even more preferably 0.5% by mass or more and 1.5% by mass or less.

This makes it possible to further improve the storage stability, ejection stability, etc., of the aqueous ink-jet ink composition, and also to further improve the adhesion of the recording portion of the aqueous ink-jet ink composition to the recording medium to which the aqueous ink-jet ink composition is applied.

[1-8] Coloring Material 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.

Coloring materials include, for example, various pigments such as organic pigments and inorganic pigments, various dyes, etc., and one or more selected from these can be used in combination.

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.

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

As the pigment, a self-dispersing surface-treated pigment in which hydrophilic groups are introduced onto the pigment particle surface by chemical reaction, that is, a so-called self-dispersing pigment, may be used.

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

Examples of disperse dyes and sublimation dyes include C.I. 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, 1 83, 184, 186, 192, 198, 199, 201, 202, 204, 210, 211, 215, 216, 218, 224, 227, 231, 232; C. I. C.I. 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; 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, 2 C. I. C.I. 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; C.I. Disperse Green 9; C.I. Disperse Brown 1, 2, 4, 9, 13, 19; C.I. 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; C.I. Disperse Black 1, 3, 10, 24, etc.

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

Fluorescent dyes include, for example, C.I. Disperse Red 362, 364; C.I. Vat Red 41; C.I. Disperse Yellow 43, 82, 184, 232, etc.

Examples of reactive dyes include yellow dyes such as C.I. Reactive Yellow 2, 3, 18, 81, 84, 85, 95, 99, and 102, orange dyes such as C.I. Reactive Orange 5, 9, 12, 13, 35, 45, and 99, brown dyes such as C.I. Reactive Brown 2, 8, 9, 17, and 33, red dyes such as C.I. Reactive Red 1, 3, 4, 13, 15, 24, 29, 31, 33, 120, 125, 151, 206, 218, 226, and 245, violet dyes such as C.I. Reactive Violet 24, and C.I. Examples of the dyes include blue dyes such as C.I. Reactive Blue 2, 4, 5, 10, 13, 14, 15, 15:1, 19, 21, 49, 63, 71, 72, 75, 162, 176, and 198, green dyes such as C.I. Reactive Green 5, 8, and 19, and black dyes such as C.I. Reactive Black 1, 8, 23, and 39.

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.

In particular, when the colorant is a self-dispersing pigment, the pigment has excellent dispersion stability. In addition, since there is no need to use a dispersant to disperse the pigment, the viscosity of the aqueous inkjet ink composition can be reduced.

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

By including a relatively high content of colorant in this manner, the color development of the recorded portion formed using the aqueous ink-jet ink composition can be improved. In addition, the occurrence of undesired color unevenness in the recorded matter produced using the aqueous ink-jet ink composition can be more effectively prevented.

[1-9] Penetrating Agent The water-based ink-jet ink composition of the present invention may further contain a penetrating agent.
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.

Examples of penetrating agents 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, and one or more selected from these may be used in combination.

The content of the penetrant in the aqueous inkjet ink composition is preferably 4.0% by mass or more and 12.0% by mass or less, more preferably 4.5% by mass or more and 10.0% by mass or less, and even more preferably 5.0% by mass or more and 8.5% by mass or less.

[1-10] Moisturizing agents other than glycerin The water-based ink-jet ink composition of the present invention may further contain a moisturizing agent other than glycerin.

This can more suitably enhance the moisturizing properties of the aqueous inkjet ink composition, and can improve the ejection stability, etc., of the aqueous inkjet ink composition.

Examples of humectants other than glycerin include betaine and trimethylolpropane, but there are no particular limitations as long as they are generally used in inkjet inks.

The content of humectants other than glycerin in the aqueous inkjet ink composition is preferably 1.0% by mass or more and 10.0% by mass or less, more preferably 3.0% by mass or more and 9.0% by mass or less, and even more preferably 4.0% by mass or more and 8.0% by mass or less.

[1-11] Other Components The water-based 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".

Other components include, for example, 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.

The content of other components in the aqueous inkjet 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.

[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.

The viscosity can be measured at 25° C. using a viscoelasticity tester (for example, VISCO 6800, manufactured by Atago Co., Ltd.) by reading the viscosity at a shear rate of 10 [s ⁻¹ ].

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

The ink composition set according to the present invention comprises a plurality of ink compositions. At least one of the ink compositions constituting the ink composition set is the water-based inkjet ink composition according to the present invention described above.

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 also include an ink composition that is not the aqueous ink-jet ink composition of the present invention described above. Hereinafter, such an ink composition may also 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.

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

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 subdivided according to their color densities. For example, in addition to cyan, magenta, and yellow, the ink composition set may include light cyan, light magenta, and light yellow.

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

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

The recording method of the present invention is a method of recording by ejecting the above-mentioned water-based inkjet ink composition of the present invention from an inkjet head.

This effectively prevents curling of the recording medium to which the aqueous inkjet ink composition is applied.

[3-1] Recording Medium 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.

Such recording media are advantageous in that they are relatively inexpensive, easily available, and can provide favorable ink permeability, etc., but on the other hand, they have the problem that they are prone to curling when a water-based inkjet ink composition is applied to them. In contrast, the present invention can sufficiently suppress curling even when using such recording media.

[3-2] Water-Based Ink-Jet Ink Composition Applying Step In the water-based ink-jet ink composition applying step, the water-based ink-jet ink composition of the present invention is ejected by an ink-jet method and adhered to a recording medium.

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

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

[3-3] Other Steps The recording method of the present invention may further include other steps in addition to the steps described above.

For example, the recording method of the present invention may further include a step of depositing an ink composition other than the aqueous inkjet ink composition of the present invention onto a recording medium.

When such a step is performed, the step may be performed, for example, before the step of applying the water-based inkjet ink composition, or after the step of applying the water-based inkjet ink composition.

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

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

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

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), a self-dispersing pigment, is called "carbon black", the solid content of X-436 (manufactured by Seiko PMC Corporation), an emulsion of styrene-acrylic copolymer, is called "X-436", triethylene glycol is called "TEG", triethylene glycol monobutyl ether is called "TEGMBE", 1,2-hexanediol is called "1,2HD", ε-caprolactam is called "εCL", the solid content of Surfynol 465 (manufactured by Nissin Chemical Industry Co., Ltd.), an acetylene glycol surfactant, is called "S465", the solid content of Olfin E1010 (manufactured by Nissin Chemical Industry Co., Ltd.), an acetylene glycol surfactant, is called "E1010", triethanolamine is called "TEA", ethylenediaminetetraacetic acid is called "EDTA", and benzotriazole is called "BTA".

The unit of the content of each component in Figure 1 is parts by mass. The viscosity at 25°C of the aqueous inkjet ink compositions of each of the examples and comparative examples was in the range of 2 mPa·s to 10 mPa·s.

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

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

Next, a black solid pattern was printed at room temperature at a resolution of 600×600 dpi on P paper (basis weight 64 g/m ² , paper thickness 88 μm) manufactured by Fuji Xerox Co., Ltd. as a recording medium.

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.

A: The maximum curl angle is less than 90°.
B: The maximum curl angle is 90° or more and less than 100°.
C: The maximum curl angle is 100° or more.

[6-2] Discharge Stability Using a modified inkjet recording apparatus: LX-6050MF (manufactured by Seiko Epson Corporation), the following evaluations were carried out.

That is, the water-based inkjet ink compositions of each of the examples and comparative examples were each injected into a dedicated ink cartridge for the LX-6050MF, and then these ink cartridges were installed in a modified LX-6050MF machine.

In an environment of 40° C. and 20% humidity, 30 sheets of a black solid pattern were printed at a resolution of 600×600 dpi on P paper (basis weight 64 g/ ^m2 , paper thickness 88 μm) manufactured by Fuji Xerox Co., Ltd. as a recording medium, 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.

A: There are 0 non-ejecting nozzles.
B: The number of non-ejecting nozzles is 1 to 9.
C: 10 or more non-ejecting nozzles.

[6-3] Clogging Recovery Property First, the water-based inkjet ink compositions of the respective Examples and Comparative Examples were poured into dedicated ink cartridges of an inkjet recording apparatus: LX-6050MF (manufactured by Seiko Epson Corporation), and then these ink cartridges were mounted on a modified LX-6050MF.

The inkjet head was then left uncapped in a 40°C environment for 7 days.

After leaving it for a while, a cleaning operation was performed and the number of cleanings until all nozzles were restored was counted and evaluated according to the following criteria. The fewer the number of cleanings, the better the ability to restore clogging.

A: The number of cleaning cycles required to restore all nozzles was three or less.
B: The number of cleaning operations required to restore all the nozzles is between 4 and 6.
C: The number of cleanings required to recover all the nozzles was 7 or more.

[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 to stand for 7 days in an environment of 60° C. From the viscosity measurement results of each aqueous ink-jet ink composition before and after standing, the viscosity change rate of each aqueous ink-jet ink composition before and after standing 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 an aqueous ink-jet ink composition is superior to that of a composition in which aggregates are not formed, compared to a composition in which aggregates are formed.

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

[6-5] Difficulty in Transfer Using a modified inkjet recording apparatus: LX-6050MF (manufactured by Seiko Epson Corporation), the following evaluations were carried out.

That is, the water-based inkjet ink compositions of each of the examples and comparative examples were each injected into a dedicated ink cartridge for the LX-6050MF, and then these ink cartridges were installed in a modified LX-6050MF machine.

At room temperature, 100 continuous black solid patterns were printed at a resolution of 600 x 600 dpi on both sides of a recording medium, P paper (basis weight 64 g/ ^m2 , paper thickness 88 μm) manufactured by Fuji Xerox Co., Ltd. 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.

A: No ink transfer traces were observed.
B: Ink transfer marks are observed.
These results are summarized in FIG.

As is clear from Figure 2, excellent results were obtained with the present invention. In contrast, the comparative example did not produce satisfactory results.

Claims (8)

An aqueous inkjet ink composition containing a sugar alcohol having 4 or more carbon atoms, glycerin, lactams having 6 to 8 membered rings, and an acetylene glycol surfactant. The aqueous ink-jet ink composition according to claim 1, wherein the ratio of the content of the glycerin to the content of the sugar alcohol having 4 or more carbon atoms in the aqueous ink-jet ink composition is 1.0:1.0 or more and 1.0:4.0 or less in mass ratio. The aqueous inkjet ink composition according to claim 1 or 2, wherein the sugar alcohol having 4 or more carbon atoms includes a sugar alcohol having 4 to 6 carbon atoms. The aqueous inkjet ink composition according to claim 1 or 2, wherein the lactams having 6 to 8 ring members include lactams having 7 ring members. The aqueous inkjet ink composition according to claim 1 or 2, wherein the water content in the aqueous inkjet ink composition is 60.0% by mass or less. The aqueous inkjet ink composition according to claim 1 or 2, further comprising a resin component. 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. A recording method in which the aqueous inkjet ink composition according to claim 1 or 2 is ejected from an inkjet head to perform recording.

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