JP6689655B2 - Inkjet ink, inkjet recording method, and inkjet recording apparatus - Google Patents

Description

  The present invention relates to inkjet inks. The present invention also relates to an inkjet recording method using the inkjet ink. The present invention also relates to an inkjet recording device including the inkjet ink.

  Inkjet printers that employ the inkjet printing method are widely used as output devices for digital printing. Conventionally, when printing on a recording medium (hard-to-absorbent recording medium) that hardly absorbs ink such as polyvinyl chloride or polyethylene terephthalate (PET) using an inkjet printer, while melting the surface of the recording medium, A so-called solvent ink that fixes the coloring material and the binder resin, and a UV curable ink that cures the ink that has landed on the recording medium by UV light and makes it adhere to the recording medium are used.

  However, from the viewpoint of safety of ink and reduction of environmental load, the development of water-based inkjet ink suitable for printing on absorptive recording medium is being advanced. In printing on a non-absorbent recording medium using an aqueous inkjet ink, image quality, drying property, image strength and the like equivalent to those of solvent ink and UV curable ink are required. In order to meet such a demand, an aqueous inkjet ink containing water, a resin component (particularly resin fine particles), and a coloring material has been developed.

  It is known to add a thickening agent in order to improve the properties of such an aqueous inkjet ink. For example, Patent Document 1 discloses an aqueous inkjet ink containing water, a coloring material, a water-soluble thickener, and resin particles. Such an aqueous inkjet ink prevents curling of a recording medium. It is described that it can be suppressed, the storage stability of the ink is good, the ejection stability of the ink is good, and the occurrence of image deformation can be suppressed.

JP, 2010-65205, A

  As a result of diligent studies by the present inventors, when a water-soluble thickener is used in an aqueous inkjet ink as described in Patent Document 1, when a water-soluble thickening agent is ejected from an inkjet head onto a non-absorbent recording medium, the recording medium is It was found that the ink excessively wets and spreads on the surface, resulting in image bleeding. It was also found that the drying property and the image characteristics may be insufficient as compared with the water-based inkjet ink in which the thickener is not added.

  Therefore, the present invention provides a water-based inkjet ink in which excessive wetting and spreading when discharged from an inkjet head to a hardly-absorbent recording medium is suppressed, image bleeding is suppressed, and drying characteristics and image characteristics are good. The purpose is to

  The inkjet ink of the present invention is an inkjet ink containing at least water, a resin component, a coloring material, and an associative thickener, and the associative thickener is a urethane-modified polyether polymer.

For the ink-jet ink of the present invention, it is preferable that the following formula is established when the viscosity at 25 ° C. is V1, the viscosity at 40 ° C. is V2, and the viscosity at 40 ° C. when 10% by weight drying loss is V3.
5.0 mPa · s ≦ V1 ≦ 20.0 mPa · s
V1 / V2 ≧ 1.6
V3 / V2 ≧ 1.3

  In the inkjet ink of the present invention, the resin component is preferably resin fine particles.

  In the inkjet ink of the invention, it is preferable that the coloring material is a pigment.

  The inkjet ink of the present invention preferably further contains an organic solvent.

  The inkjet ink of the present invention preferably further contains a surfactant.

  In the inkjet ink of the present invention, the solid content concentration is preferably 20.0% by weight or less.

  The present invention is also an inkjet recording method including a step of heating a hardly-absorbent recording medium, and a step of ejecting an inkjet ink onto the heated hardly-absorbent recording medium, wherein the inkjet ink is The inkjet recording method is an inkjet ink of

  The present invention also includes a transport unit that transports the hardly-absorbent recording medium, a heating unit that heats the transported hardly-absorbent recording medium, and an ejection unit that ejects an inkjet ink onto the heated hardly-absorbent recording medium. An ink jet recording apparatus, comprising: an ink accommodating portion that accommodates the ink jet ink and supplies the ink jet ink to the ejection portion, wherein the ink jet ink is the above ink jet ink.

  According to the present invention, there is provided an aqueous inkjet ink in which excessive wetting and spreading when discharged from an inkjet head to a hardly-absorbent recording medium is suppressed, image bleeding is suppressed, and drying characteristics and image characteristics are good. To be done.

1 is a conceptual diagram of an embodiment of an inkjet recording apparatus of the present invention.

  The inkjet ink of the present invention is an inkjet ink containing at least water, a resin component, a coloring material, and an associative thickener, and the associative thickener is a urethane-modified polyether polymer. The inkjet ink of the present invention may further contain an organic solvent, a surfactant and the like. Hereinafter, each component of the inkjet ink of the present invention will be described.

(water)
<Kind>
The inkjet ink of the present invention contains water as an essential component. The water is preferably ion-exchanged water, ultrafiltered water, reverse osmosis water, distilled water, or ultrapure water, and more preferably ion-exchanged water, from the viewpoint of preventing impurities from entering.

<Addition amount>
The content of water in the ink is preferably 30% by weight or more, more preferably 50% by weight or more. On the other hand, it is preferably 95% by weight or less, more preferably 90% by weight or less.

(Resin component)
<Kind>
The inkjet ink of the present invention contains a resin component as an essential component. The resin component is a binder component that enhances the fixability on the recording medium and the coating film resistance. The resin component may be a water-soluble resin or a hydrophobic resin. Therefore, it may be dissolved in the ink, or may be dispersed without being dissolved. The resin component may be used alone or in combination of two or more at any ratio.

  The resin component is preferably in the form of resin fine particles in the ink. When resin fine particles are used as the resin component, a relatively high molecular weight hydrophobic resin can be used, so that the scratch resistance and water resistance of the image can be improved.

  Examples of the resin forming the resin fine particles include urethane resin, polyester resin, acrylic resin, vinyl acetate resin, polyethylene resin, polypropylene resin, fluoroolefin resin, butadiene resin, styrene resin, styrene-butadiene resin, styrene-acrylic resin, Examples thereof include vinyl chloride resin, acrylic-silicone resin, and fluororesin.

  The resin fine particles do not have to be composed of one kind of resin, and may be composed of two or more kinds of resins. For example, emulsifying a different type of monomer with respect to core-shell type resin fine particles in which the resin composition is different between the core portion and the shell portion, or acrylic fine particles (seed particles) prepared in advance to control the particle diameter. Fine particles obtained by polymerization can be used. Furthermore, hybrid type resin fine particles in which resin fine particles made of different resins are chemically bonded, such as fine particles made of acrylic resin and fine particles made of urethane resin, can be used.

<Particle size>
The particle size of the resin fine particles is, for example, 30 nm or more and 200 nm or less, preferably 40 nm or more and 150 nm or less, and more preferably 50 nm or more and 100 nm or less. If it is less than 30 nm, there is a possibility that problems such as deterioration in storage stability of the ink may occur. If it exceeds 200 nm, the coalescence of the resin fine particles due to heating becomes non-uniform, which may cause a problem such as a decrease in image transparency.

<Glass transition temperature>
The glass transition temperature of the resin component is preferably at least not higher than the heating temperature after the recording medium is attached, and particularly preferably sufficiently lower than the heating temperature. For example, when the heating temperature is 60 ° C., the glass transition temperature of the resin component is preferably −20 ° C. to 50 ° C., more preferably 0 ° C. to 40 ° C. The lower the glass transition temperature is, the more excellent the film-forming property is. However, if the glass transition temperature is too low, not only sufficient image strength cannot be obtained, but also image offset due to winding of the recording medium is likely to occur, which is not preferable.

<Addition amount>
The addition amount of the resin component (the total amount when there are plural kinds of resins) is preferably 1.0% by weight or more and 20.0% by weight or less as a solid content, and 2.5% by weight or more and 17.5% by weight or less. Is preferable, and 5.0% by weight or more and 15.0% by weight is more preferable. If it is less than 1.0% by weight, the effect as a binder cannot be obtained, and there is a possibility that problems such as a decrease in scratchability may occur. If it exceeds 20.0% by weight, the increase in the viscosity of the ink with respect to the loss on drying becomes too large, which may cause a problem such as deterioration in ejection stability. In addition, storage stability may decrease.

(Coloring material)
<Kind>
The inkjet ink of the present invention contains a coloring material as an essential component. Examples of the coloring material include dyes and pigments. The colorants may be used alone or in combination of two or more at any ratio.

  As the dye, for example, various dyes known to be usable in an aqueous inkjet ink can be used, and examples thereof include a direct dye, an acid dye, an edible dye, a basic dye, and a reactive dye. , Disperse dyes, vat dyes and the like.

  More specifically, examples of cyan dyes include C.I. I. Acid Blue 1,7,9,15,22,23,25,27,29,40,41,43,45,54,59,60,62,72,74,78,80,82,83,90, 92, 93, 100, 102, 103, 104, 112, 113, 117, 120, 126, 127, 129, 130, 131, 138, 140, 142, 143, 151, 154, 158, 161, 166, 167, 168, 170, 171, 182, 183, 184, 187, 192, 199, 203, 204, 205, 229, 234, 236, 249, C.I. I. Direct Blue 1,2,6,15,22,25,41,71,76,77,78,80,86,87,90,98,106,108,120,123,158,160,163,165,165 168, 192, 193, 194, 195, 196, 199, 200, 201, 202, 203, 207, 225, 226, 236, 237, 246, 248, 249, C.I. I. Reactive Blue 1,2,3,4,5,7,8,9,13,14,15,17,18,19,20,21,25,26,27,28,29,31,32,33, 34, 37, 38, 39, 40, 41, 43, 44, 46, C.I. I. Food Blue 1, 2, C.I. I. Basic Blue 9, 25, 28, 29, 44 and the like can be mentioned.

  Examples of magenta dyes include C.I. I. Acid Red 1,6,8,9,13,14,18,26,27,32,35,37,42,51,52,57,75,77,80,82,85,87,88,89, 92, 94, 97, 106, 111, 114, 115, 117, 118, 119, 129, 130, 131, 133, 134, 138, 143, 145, 154, 155, 158, 168, 180, 183, 184. 186, 194, 198, 209, 211, 215, 219, 249, 252, 254, 262, 265, 274, 282, 289, 303, 317, 320, 321, 322, C.I. I. Direct Red 1,2,4,9,11,13,17,20,23,24,28,31,33,37,39,44,46,62,63,75,79,80,81,83, 84, 89, 95, 99, 113, 197, 201, 218, 220, 224, 225, 226, 227, 228, 229, 230, 231, C.I. I. Reactive Red 1,2,3,4,5,6,7,8,11,12,13,15,16,17,19,20,21,22,23,24,28,29,31,32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 45, 46, 49, 50, 58, 59, 63, 64, C.I. I. Food Red 7,9,14 etc. are mentioned.

  Examples of yellow dyes include C.I. I. Acid Yellow 1,3,11,17,19,23,25,29,36,38,40,42,44,49,59,61,70,72,75,76,78,79,98,99, 110, 111, 127, 131, 135, 142, 162, 164, 165, C.I. I. Direct Yellow 1,8,11,12,24,26,27,33,39,44,50,58,85,86,87,88,89,98,110,132,142,144, Reactive Yellow 1, 2, 3, 4, 6, 7, 11, 12, 13, 14, 15, 16, 17, 18, 22, 23, 24, 25, 26, 27, 37, 42, C.I. I. Food Yellow 3,4 etc. are mentioned.

  Examples of black dyes include C.I. I. Direct Black 1,7,19,32,51,71,108,146,154,166 etc. are mentioned.

  Examples of dyes other than cyan, magenta, yellow, and black include C.I. I. Acid Green 7, 12, 25, 27, 35, 36, 40, 43, 44, 65, 79, C.I. I. Direct Green 1, 6, 8, 26, 28, 30, 31, 37, 59, 63, 64, C.I. I. Reactive Green 6,7, C.I. I. Direct Violet 2, 48, 63, 90, C.I. I. Reactive Violet 1, 5, 9, 10 etc. are mentioned.

  As the pigment, both an inorganic pigment and an organic pigment can be used. Examples of the inorganic pigment include titanium oxide, zinc white, zinc sulfide, lead white, calcium carbonate, precipitated barium sulfate, white carbon, alumina white, kaolin clay, talc, bentonite, black iron oxide, cadmium red, red iron oxide, molybdenum. Red, molybdate orange, chrome vermillion, yellow lead, cadmium yellow, yellow iron oxide, titanium yellow, chromium oxide, viridian, titanium cobalt green, cobalt green, cobalt chrome green, Victoria green, ultramarine blue, navy blue, cobalt blue, cerulean. Blue, cobalt silica blue, cobalt zinc silica blue, manganese violet, cobalt violet and the like can be mentioned.

  Examples of organic pigments include azo pigments, phthalocyanine pigments, anthraquinone pigments, quinacridone pigments, isoindolinone pigments, quinophthalone pigments, dye lake pigments, and fluorescent pigments.

  More specifically, examples of cyan pigments include C.I. I. Pigment Blue 1, 2, 3, 15: 1, 15: 3, 15: 4, 15: 6, 16, 21, 22, 60, 64 and the like.

  Examples of magenta pigments include C.I. I. Pigment Red 5,7,9,12,31,48,49,52,53,57,97,112,120,122,146,147,149,150,168,170,177,178,179,184. 188, 202, 206, 207, 209, 238, 242, 254, 255, 264, 269, 282, C.I. I. Pigment Violet 19, 23, 29, 30, 32, 36, 37, 38, 40, 50 and the like.

  Examples of the yellow pigment include C.I. I. Pigment Yellow 1,2,3,12,13,14,16,17,20,24,74,83,86,93,94,95,109,110,117,120,125,128,129,137, 138, 139, 147, 148, 150, 151, 154, 155, 166, 168, 180, 185, 213 and the like.

Examples of the black pigment include carbon black manufactured by the furnace method and the channel method. In particular, these carbon blacks have characteristics such as a primary particle diameter of 11 to 40 nm, a specific surface area by BET method of 50 to 400 m ² / g, a volatile content of 0.5 to 10%, and a pH value of 2 to 10. Those having a are preferred. Examples of commercially available products having such characteristics include No. 33, 40, 45, 52, 900, 2200B, 2300, MA7, MA8, MCF88 (manufactured by Mitsubishi Chemical Co., Ltd.), RAVEN1255 (manufactured by Colombian Carbon Co.), REGA330R, 400R, 660R, MOGUL L, ELFTEX415 (manufactured by, Cabot), Nipex90, Nipex150T, Nipex160IQ, Nipex170IQ, Nipex75, Printex85, Printex95, Printex90, Printex35, PrintexU (above, manufactured by Evonik Degussa).

  Examples of pigments other than cyan, magenta, yellow, and black include C.I. I. Pigment Green 7, 10, 36, C.I. I. Pigment Brown 3, 5, 25, 26, C.I. I. Pigment Orange 2, 5, 7, 13, 14, 15, 16, 24, 34, 36, 38, 40, 43, 62, 63, 64, 71 and the like.

  When these pigments are used, it is preferable to uniformly disperse them in the ink in order to maintain the ink stability for a long time. As a method for dispersing the pigment, there are a method in which the surface of the pigment is modified by oxidation treatment or the like and the pigment is self-dispersed without a dispersant, and a method in which a surfactant or a resin is used as a dispersant to disperse the pigment. In order to obtain a more stable inkjet ink, it is preferable to self-disperse the pigment or disperse the pigment using a resin as a dispersant.

  The inkjet ink of the present invention may be used in a single color, but may also be used as an ink set in which a plurality of colors are combined according to the application. The combination is not particularly limited, but a full-color image can be obtained by using three colors of cyan, magenta, and yellow. Further, by adding the black ink, it is possible to improve the black feeling and improve the visibility of characters and the like. Further, it is possible to improve color reproducibility by adding colors such as orange and green. When printing on a printing medium other than white, a clear image can be obtained by using white ink together.

  When a combination of cyan, magenta and yellow pigments is used as the coloring material in the inkjet ink of the present invention, C.I. I. Pigment Blue 15: 3, 15: 4, and C.I. I. Pigment Red 122, 202, 209, 269, C.I. I. Pigment Violet 19, a yellow pigment such as C.I. I. Pigment Yellow 74, 120, 150, 155, 185 can be used in combination to obtain high color reproducibility.

  As the coloring material, a pigment is preferable from the viewpoint of light resistance and weather resistance of the image.

<Addition amount>
The addition amount of the coloring material (when there are plural kinds of coloring materials, the total amount) is, for example, 0.1% by weight or more and 20.0% by weight or less as a solid content, and 1.0% by weight or more and 15.% by weight or more. 0 wt% or less is preferable, and 2.0 wt% or more and 10.0 wt% or less is more preferable.

(Associative thickener)
<Kind>
The inkjet ink of the present invention contains an associative thickener as an essential component. A urethane-modified polyether-based polymer is used as the associative thickener (hereinafter, the urethane-modified polyether-based polymer used as the associative thickener is referred to as "urethane-modified polyether-based associative thickener"). Also called). The associative thickener is a thickener that has a hydrophobic site and a hydrophilic site, and causes molecules to associate with each other by hydrophobic interaction in an aqueous medium to increase the viscosity of the system. The urethane-modified polyether-based associative thickener can be used alone or in combination of two or more at an arbitrary ratio. Examples of the urethane-modified polyether-based associative thickener include compounds represented by the following general formula (1).

In formula (1), R ¹ and R ² each represent an aliphatic hydrocarbon group or an aromatic hydrocarbon group, and m1 and n1 each represent an integer of 1 or more.

  Such a urethane-modified polyether-based associative thickener can be produced according to a known method, and is also available as a commercial product. Examples of commercially available products include SN thickeners 603, 607, 612, 612NC, 625N, A803, A804, A812, A814 (above, manufactured by San Nopco), Adekanol UH series (manufactured by Asahi Denka Kogyo Co., Ltd.) and the like.

<Addition amount>
The amount of the urethane-modified polyether-based associative thickener added (the total amount when there are a plurality of urethane-modified polyether-based associative thickeners) is, for example, 0.01% by weight or more 2 It is 0.000% by weight or less, preferably 0.05% by weight or more and 1.00% by weight or less, and more preferably 0.10% by weight or more and 0.50% by weight or less. If it is less than 0.01% by weight, the effect of adjusting the viscosity of the ink may not be sufficiently obtained. On the other hand, if it exceeds 2.00% by weight, not only the viscosity becomes too high, but also the temperature dependency of the viscosity, the increase in viscosity when the weight is reduced by drying, etc. may become too great. In addition, problems such as a decrease in image transparency and a decrease in ink storage stability may occur.

(Organic solvent)
The inkjet ink of the present invention may contain an organic solvent as an optional component. When the inkjet ink of the present invention appropriately contains an organic solvent, it is possible to improve the drying property, the moisturizing property, the substrate adhesion property and the like. The organic solvent may be used alone or in combination of two or more at an arbitrary ratio.

<Boiling point>
The boiling point of the organic solvent used is preferably 100 ° C. or higher and 290 ° C. or lower from the viewpoint of stably forming an image. When the boiling point of the organic solvent is less than 100 ° C., for example, the solvent of the inkjet ink may be vaporized from the inkjet nozzle even in a normal temperature environment, resulting in unstable ejection or non-ejection. is there. On the other hand, if the boiling point of the organic solvent exceeds 290 ° C., the ink deposited on the recording medium may not be completely dried, resulting in a decrease in image strength and a problem such as offset during winding.

<Kind>
Of the organic solvents, a diol compound (that is, a compound having two OH groups in the chemical structural formula) has a higher moisturizing property than a compound containing no OH group or only one OH group, and is therefore preferably used. . Examples of the diol compound include ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, 1,2-butanediol, 2,3-butanediol, 2-methyl-2,4-pentanediol, 1, 3-propanediol, 1,2-butanediol, 1,3-butanediol, 3-methyl-1,3-butanediol, 2,2-dimethyl-1,3-propanediol, 2-methyl-1,3 -Propanediol, 1,2-pentanediol, 2,4-pentanediol, 1,5-pentanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,5-pentanediol, 1,6 -Hexanediol, 2-ethyl-1,3-hexanediol, 1,2-hexanediol, , 5-hexanediol, and the like.

  Among the organic solvents, the glycol ether compound is preferably used because it has high penetrability into the hardly-absorbent recording medium and improves the drying property and the adhesiveness. Examples of the glycol ether compound include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monopentyl ether, diethylene glycol monohexyl ether, triethylene glycol. Monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monobutyl ether, propylene glycol monomethyl ether, pro Ren glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol dimethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol Monobutyl ether, 3-methoxy-1-butanol, 3-methoxy-3-methylbutanol, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol diethyl ether, tetraethylene glycol die Ether, diethylene glycol methyl ethyl ether, triethylene glycol methyl ethyl ether, tetraethylene glycol methyl ethyl ether, diethylene glycol butyl methyl ether, triethylene glycol butyl methyl ether, tetraethylene glycol butyl methyl ether, propylene glycol dimethyl ether, tripropylene glycol dimethyl ether, etc. Can be mentioned.

  A water-soluble nitrogen-containing solvent may be used as the organic solvent. Examples of the nitrogen-containing solvent include 2-pyrrolidone, N-methylpyrrolidone, N-ethylpyrrolidone, 3-methyl-2-oxazolidinone, 3-ethyl-2-oxazolidinone, N, N-dimethyl-β-methoxypropionamide. , N, N-dimethyl-β-ethoxypropionamide, N, N-dimethyl-β-butoxypropionamide, N, N-dimethyl-β-pentoxypropionamide, N, N-dimethyl-β-hexoxypropionamide , N, N-dimethyl-β-heptoxypropionamide, N, N-dimethyl-β-2-ethylhexoxypropionamide, N, N-dimethyl-β-octoxypropionamide, N, N-diethyl-β -Butoxypropionamide, N, N-diethyl-β-pentoxypropionamide, N, N-die Le -β- hexoxyphenyl propionamide, N, N-diethyl -β- heptene Toki Cipro propionamide, N, N-diethyl -β- octoxynol propionamide, and the like.

<Addition amount>
The amount of the organic solvent added (the total amount when there are a plurality of organic solvents) is, for example, 10% by weight or more and 40% by weight or less, preferably 12% by weight or more and 35% by weight or less, and 15% by weight or more 30%. It is more preferably less than or equal to wt%. If the addition amount is less than 10% by weight, problems such as non-ejection due to drying of ink in the nozzles of the inkjet head and deterioration of image quality due to low wettability with respect to the hardly-absorbent recording medium may occur. On the other hand, if the addition amount exceeds 40% by weight, problems such as deterioration in storage stability of the ink may occur.

(Surfactant)
The inkjet ink of the present invention may contain a surfactant as an optional component. The surfactant contributes to adjusting the surface tension of the ink and improving the wettability with respect to the recording medium. From the viewpoint of the storage stability of the ink, the surfactant is preferably a nonionic surfactant.

<Kind>
Examples of the nonionic surfactant include acetylene glycol-based surfactants, silicone-based surfactants, and fluorine-based surfactants. The surfactants may be used alone or in combination of two or more at any ratio.

  The acetylene glycol-based surfactant does not need an antifoaming agent because it has less foaming, and can improve wettability to a hard-to-absorbent recording medium, and is therefore preferably used. Examples of the acetylene glycol-based surfactant include Olfine E1004 and E1010 (manufactured by Nisshin Chemical Industry Co., Ltd.). Silicone-based surfactants are known to have a high surface tension lowering ability and can impart slip properties, and thus are preferably used. Examples of the silicone-based surfactants include Silface 503A and Silface 014 (manufactured by Nisshin Chemical Industry Co., Ltd.). Fluorine-based surfactants are suitable for use because they have a high ability to reduce surface tension. Examples of the fluorine-based surfactant include Futegent 250, 212M, 215M, 251 (manufactured by Neos) and the like.

<Addition amount>
The amount of the surfactant added (the total amount of the surfactants when there are plural kinds) is, for example, 0.1% by weight or more and 5.0% by weight or less, and 0.5% by weight or more and 4.0% by weight. It is preferably not more than 1.0% by weight, more preferably not less than 1.0% by weight and not more than 3.0% by weight. If the amount added is less than 0.1% by weight, the effect of improving the wettability with respect to the hard-to-absorbent recording medium may not be sufficiently obtained, and the density uniformity of the solid image and the drying property may decrease. There may be a problem. On the other hand, if the addition amount exceeds 5.0% by weight, problems such as deterioration in storage stability of the ink may occur. In addition, the adhesion to the substrate may be impaired.

(Other additives)
The inkjet ink of the present invention may contain additives such as an antifoaming agent, a thickener, a pH adjuster, and an antiseptic agent, in addition to the above components, in order to obtain an ink having desired characteristics, if necessary. Good. The additive amount of these additives is, for example, 0.01 wt% or more and 10.0 wt% or less, preferably 0.05 wt% or more and 5.0 wt% or less, and 0.1 wt% or more and 3. It is more preferably 0% by weight or less.

(Solid content concentration)
The solid content concentration (solid content ratio) of the inkjet ink of the present invention is preferably 20.0% by weight or less, more preferably 16.0% by weight or less, still more preferably 12.0% by weight or less. If the solid content concentration exceeds 20.0% by weight, problems such as deterioration in storage stability of the ink may occur.

  The solid content concentration of the inkjet ink of the present invention can be measured, for example, by the following method. As the measuring device, a heat-drying moisture meter (eg, heat-drying moisture meter MS-70 (manufactured by A & D Company)) is used. 0.5 g of the ink is dropped within 10 seconds so as to be contained in the glass fiber sheet placed on the aluminum dish, and the temperature is set to 180 ° C. for 1 hour to evaporate the solvent. The solid concentration of ink is calculated from the mass of the dropped ink before evaporation and the mass of solid ink after evaporation.

  When image recording is performed by the inkjet method using the inkjet ink of the present invention, it is possible to suppress excessive wetting and spreading when ejected from the inkjet head onto the hardly absorptive recording medium, thereby suppressing image bleeding. be able to. Moreover, color mixing can be suppressed. Also, good drying properties and image characteristics can be obtained.

  In the inkjet ink of the present invention, a urethane-modified polyether-based associative thickener is used, but the urethane-modified polyether-based associative thickener has a hydrophobic site and a hydrophilic site. For example, when the resin component is resin fine particles, the hydrophobic site of the urethane-modified polyether-based associative thickener is adsorbed on the surface of the resin fine particles by hydrophobic interaction. On the other hand, hydrophilic sites associate with each other by intermolecular force or hydrogen bond. As a result, the resin fine particles and the urethane-modified polyether-based associative thickener form a three-dimensional network structure and exhibit a high viscosity. With such a three-dimensional network structure, elasticity is imparted to the inkjet ink, the generation of minute droplets during ejection can be significantly suppressed, and ejection stability is improved.

  In the ink jet recording system, it is first important how to wet and spread the ink on the hard-to-absorb recording medium. The ink droplets that have landed on the recording medium that has been heated in advance during image formation (printing) are instantaneously heated and have a reduced viscosity and spread wet. At this time, heating causes vaporization of the solvent contained in the inkjet ink. From the viewpoint of high drying property, it is preferable that this wetting and spreading occur in a very short time. Therefore, it is preferable that the viscosity decrease largely when the temperature rises. On the other hand, in order to prevent the ink from spreading excessively, it is preferable that the ink viscosity be reasonably large at the time when a certain amount of the solvent is vaporized. On the other hand, the urethane-modified polyether-based associative thickener increases the viscosity by adsorbing the hydrophobic site to the resin fine particles and associating the hydrophilic site, but when the temperature rises, the hydrophobic site becomes Inkjet inks containing a urethane-modified polyether-based associative thickener have a large temperature dependence of viscosity (that is, the temperature becomes high) because they are desorbed from the resin fine particles and the association of hydrophilic sites is released. The degree of decrease in viscosity is great). Further, the urethane-modified polyether-based associative thickener has a large viscosity increase when a certain amount of solvent is dried (vaporized). Therefore, when the inkjet ink of the present invention containing the urethane-modified polyether-based associative thickener is discharged onto a preheated hardly-absorbent recording medium, the ink droplets have a large decrease in viscosity due to heating. As the solvent wets and spreads and vaporizes, the viscosity increases greatly and the spreading and wetting stops. Therefore, when image recording is performed by the inkjet method using the inkjet ink of the present invention, it is possible to suppress excessive wetting and spreading when ejected from the inkjet head onto the hardly-absorbent recording medium, It is considered that bleeding can be suppressed. Further, it is considered that good drying properties and image characteristics can be obtained.

(viscosity)
In order to greatly enjoy the effect of the addition of the urethane-modified polyether-based associative thickener as described above, the ink-jet ink of the present invention has a viscosity at 25 ° C. of V1, a viscosity at 40 ° C. of V2, and 10% by weight loss on drying. When the viscosity at 40 ° C. in this case is V3, it is preferable that the following formula is satisfied.
5.0 mPa · s ≦ V1 ≦ 20.0 mPa · s
V1 / V2 ≧ 1.6
V3 / V2 ≧ 1.3

<V1>
The viscosity V1 of the inkjet ink of the present invention at 25 ° C. is preferably 5.0 mPa · s or more and 20.0 mPa · s or less, more preferably 6.0 mPa · s or more and 15.0 mPa · s or less, and 7.0 mPa · s or more. It is more preferably 10.0 mPa · s or less. If the viscosity V1 is less than 5.0 mPa · s, the ejection stability may be too low. On the other hand, if the viscosity V1 is higher than 20.0 mPa · s, ejection failure may occur or image quality may deteriorate.

<V1 / V2>
The ratio (V1 / V2) of the viscosity V1 at 25 ° C. to the viscosity V2 at 40 ° C. of the inkjet ink of the present invention is preferably 1.6 or more. If the ratio V1 / V2 is less than 1.6, the viscosity of the ink when it is deposited on a heated recording medium is high, the wetting and spreading tend to be insufficient, the drying is insufficient, and the solid image is unsatisfactory. It may become uniform.

<V3 / V2>
The ratio (V3 / V2) of the viscosity V3 at 40 ° C. when the inkjet ink of the present invention is reduced by 10% by weight to the viscosity V2 at 40 ° C. of the inkjet ink of the present invention is preferably 1.3 or more. . If the ratio V3 / V2 is less than 1.3, the ink having a low viscosity on the recording medium may spread more than necessary, which causes a problem such as color mixing with an adjacent ink of another color or blurring of fine lines. May occur.

  By optimizing the type and amount of the urethane-modified polyether-based associative thickener contained in the inkjet ink, it is easy to satisfy the preferable ranges of V1, the ratio V1 / V2, and the ratio V3 / V2. be able to. In addition, each viscosity can be measured by the following method.

<Measurement method>
As a measuring device, a viscometer (eg, viscometer TVE-25L (manufactured by Toki Sangyo Co., Ltd.)) is used. As the corn rotor, R01 is used, the measurement is started at 40.0 rpm, and the value when stable is adopted. A measured value at 25 ° C. is adopted as the viscosity V1, and a measured value at 40 ° C. is adopted as the viscosity V2. The viscosity V3 at 40 ° C. when the ink-jet ink is dried and reduced by 10% by weight is 10.0 g of the ink put in an aluminum dish, and a heat-drying moisture meter (eg, heat-drying moisture meter MS-70 (A & D) is used. Manufactured by K.K.), heated to 60 ° C., when the loss on drying reaches 10% by weight, the ink is sampled, and the viscosity of the ink at 40 ° C. after standing for 24 hours is measured to obtain the value.

(Inkjet recording method)
Another aspect of the present invention is an inkjet recording including a step of heating a hardly-absorbent recording medium (heating step) and a step of ejecting an inkjet ink onto the heated hardly-absorbent recording medium (ejection step). The method is an inkjet recording method, wherein the inkjet ink is the inkjet ink described above (the inkjet ink of the present invention).

<Heating process>
In the heating step, the hardly-absorbent recording medium is heated. In the present specification, the “non-absorbent recording medium” refers to a recording medium having a water absorption amount of 10 mL / m ² or less from the start of contact to 30 msec ^1/2 in the Bristow method. The water absorption amount is, specifically, the standard No. of “JAPAN TAPPI paper pulp test method 2000 version”. 51 "Paper and paperboard-Liquid absorption test method-Bristow method". Examples of the non-absorptive recording medium include art paper, coated paper, matte paper, plastic film, a medium in which a plastic layer is formed on a paper base material, and the like. Examples of plastics include PET (polyethylene terephthalate), polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), polystyrene, polycarbonate, polyurethane and the like.

  The heating method is not particularly limited and can be performed according to a known method, for example, a method of heating a recording medium by directly contacting a heat source, a method of irradiating the recording medium with infrared rays or microwaves, and a method of heating the recording medium. A method of blowing wind can be adopted. If the temperature of the recording medium is too low, the ink may not be sufficiently fixed on the recording medium. Therefore, the heating is performed such that the temperature of the recording medium is, for example, 30 ° C. or higher, preferably 40 ° C. or higher. On the other hand, if the temperature of the recording medium is too high, the recording medium may be deformed. Therefore, the heating is performed so that the temperature of the recording medium is usually lower than the softening point of the recording medium, preferably 80 ° C. or lower, more preferably 60 ° C. or lower.

<Discharging process>
The inkjet ink is ejected onto the heat-absorptive recording medium. The inkjet ink used in this step is the inkjet ink described above (the inkjet ink of the present invention). The inkjet ink can be discharged by, for example, a discharge method adopted in a known inkjet recording method. Specifically, for example, the vibration of the piezoelectric element can be used to eject droplets of inkjet ink from the nozzles of the inkjet head. By ejecting the inkjet ink toward the recording medium, the inkjet ink adheres to the recording medium, and the inkjet ink adhered to the recording medium dries, whereby an image can be recorded on the recording medium.

  In the inkjet recording method of the present invention, when the inkjet ink is ejected onto the hardly-absorbent recording medium, it is possible to suppress excessive wetting and spreading of the ink on the surface of the hardly-absorbent recording medium, thereby suppressing image bleeding. can do. Moreover, color mixing can be suppressed. Also, good ink drying properties and image characteristics can be obtained.

(Image forming device)
From another aspect, the present invention provides a transport unit that transports the hardly-absorbent recording medium, a heating unit that heats the transported hardly-absorbent recording medium, and an inkjet ink on the heated hardly-absorbent recording medium. An inkjet recording apparatus comprising: an ejecting unit for ejecting; and an ink containing unit that contains the inkjet ink and supplies the inkjet ink to the ejecting unit, wherein the inkjet ink is the above-described inkjet ink (inkjet of the present invention. (Ink), which is an inkjet recording device.

  Hereinafter, the inkjet recording apparatus of the present invention will be described with reference to FIG. 1 by taking an embodiment as an example, but the inkjet recording apparatus of the present invention is not limited to the embodiment.

  FIG. 1 is a conceptual diagram of an inkjet recording apparatus 100 according to an embodiment of the present invention. The inkjet recording apparatus 100 includes a supply roller 21, a take-up roller 22, and a conveyance roller 23 as a conveyance unit 20 that conveys the recording medium 10. The recording medium 10 is unwound from the supply roller 21, passes over the platen 30, is conveyed by the conveying roller 23, and is wound by the winding roller 22. Therefore, in the present embodiment, the recording medium 10 is conveyed in the direction from the supply roller 21 to the take-up roller 22. The recording medium 10 is illustrated for convenience of description, and is not a constituent element of the inkjet recording apparatus 100. As the recording medium 10, a non-absorbent recording medium is usually used.

  The inkjet recording device 100 includes a heating unit 40. The heating unit 40 serves as a preheater that heats the recording medium 10. The heating unit 40 includes, for example, a contact heating type sheet heater, a radiant heater that radiates infrared rays and microwaves, a warm air heater, and the like. The heating unit 40 may be installed on either the upper part or the lower part of the recording medium 10, or may be installed on both the upper part and the lower part. The heating unit 40 sets heating conditions such that the temperature of the recording medium 10 is, for example, 30 ° C. or higher and lower than the softening point of the recording medium (preferably 30 to 80 ° C., more preferably 40 to 60 ° C.). Has been done.

  The inkjet recording apparatus 100 includes an ejection unit 50 that ejects the inkjet ink 11 onto the recording medium 10. The ejection unit 50 is provided downstream of the heating unit 40 in the transport direction of the recording medium 10. The ejection unit 50 has, for example, an inkjet head that ejects the inkjet ink 11 in the form of droplets from a fine nozzle by utilizing vibration of a piezoelectric element. The inkjet recording device 100 has an ink containing section 60, and the ink containing section 60 is connected to the ejection section 50. The ink container 60 has, for example, an ink cartridge. The inkjet ink 11 before ejection is accommodated in the ink accommodating portion 60, and the accommodated inkjet ink 11 is appropriately supplied to the ejection portion 50. Here, the inkjet ink 11 is the above-mentioned aqueous inkjet ink (the inkjet ink of the present invention).

  The inkjet recording apparatus 100 includes a drying unit 70 that dries the ejected inkjet ink 11. The drying unit 70 is provided on the downstream side of the ejection unit 50 in the transport direction of the recording medium 10, and is incorporated in the carriage 71. The drying unit 70 has, for example, a radiant heater that radiates infrared rays or microwaves, a heater such as a warm air heater, or an air blow dryer. The drying unit 70 is set to a drying condition that allows image recording by drying the inkjet ink 11 attached on the recording medium 10. This drying condition is appropriately selected according to the type and amount of the solvent contained in the inkjet ink 11.

  In the inkjet recording apparatus of the present invention, when the inkjet ink is ejected onto the hardly-absorbent recording medium, it is possible to suppress excessive wetting and spreading of the ink on the surface of the hardly-absorbent recording medium, thereby suppressing image bleeding. can do. Moreover, color mixing can be suppressed. Also, good ink drying properties and image characteristics can be obtained.

  Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. In the following description, "part" means "part by weight".

(Example 1)
Water 35.0 parts, propylene glycol 10.0 parts, 2-methyl-1,3-propanediol 5.0 parts, Olfine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) 1.0 part, Futgent 251 (manufactured by Neos) ) 0.1 part, resin fine particles J-140A (manufactured by Starlight PMC, solid content 41.0% by weight) 19.5 parts, pigment dispersion CAB-O-JET 250C (manufactured by Cabot Specialty Chemicals, Inc., Solid content 10.0 wt%) 26.1 parts and urethane modified polyether-based associative thickener SN Thickener 625N (manufactured by San Nopco Ltd., solid content 15.0 wt%) 3.3 parts under 25 ° C. environment. After mixing and stirring, an ink 1 was obtained by filtering with a 3 μm cellulose acetate filter.

(Example 2)
Water 36.6 parts, propylene glycol 10.0 parts, 2-methyl-1,3-propanediol 5.0 parts, Olfine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) 1.0 part, Futagent 251 (manufactured by Neos) ) 0.1 part, resin fine particles J-140A (manufactured by Starlight PMC, solid content 41.0% by weight) 19.5 parts, pigment dispersion CAB-O-JET 250C (manufactured by Cabot Specialty Chemicals, Inc., Solid content 10.0 wt%) 26.1 parts and urethane modified polyether-based associative thickener SN thickener 625N (manufactured by San Nopco, solid content 15.0 wt%) 1.7 parts under a 25 ° C. environment. After mixing and stirring, an ink 2 was obtained by filtering with a 3 μm cellulose acetate filter.

(Example 3)
Water 33.3 parts, propylene glycol 10.0 parts, 2-methyl-1,3-propanediol 5.0 parts, Olfine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) 1.0 part, Futgent 251 (manufactured by Neos) ) 0.1 part, resin fine particles J-140A (manufactured by Starlight PMC, solid content 41.0% by weight) 19.5 parts, pigment dispersion CAB-O-JET 250C (manufactured by Cabot Specialty Chemicals, Inc., Solid content 10.0 wt%) 26.1 parts and urethane modified polyether-based associative thickener SN Thickener 625N (manufactured by San Nopco Ltd., solid content 15.0 wt%) 5.0 parts under 25 ° C. environment. After mixing and stirring, an ink 3 was obtained by filtering with a 3 μm cellulose acetate filter.

(Example 4)
Water 41.1 parts, propylene glycol 10.0 parts, 2-methyl-1,3-propanediol 5.0 parts, Olfine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) 1.0 part, Futgent 251 (manufactured by Neos) 0.1 parts, resin fine particles J-140A (manufactured by Starlight PMC, solid content 41.0% by weight) 19.5 parts, Dye dispersion Duasyncet M250 (Clariant, solid content 10.0% by weight) 20. 0 parts and 3.3 parts of urethane modified polyether-based associative thickener SN thickener 625N (manufactured by San Nopco Ltd., solid content 15.0% by weight) were mixed and stirred in an environment of 25 ° C., and then a 3 μm cellulose acetate filter was used. Ink 4 was obtained by filtration.

(Example 5)
Water 38.4 parts, propylene glycol 10.0 parts, 2-methyl-1,3-propanediol 5.0 parts, Olfine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) 1.0 part, Futgent 251 (manufactured by Neos) ) 0.1 part, water-soluble resin X-01 (manufactured by Seikou PMC, solid content 24.8% by weight) 16.1 parts, pigment dispersion CAB-O-JET 250C (manufactured by Cabot Specialty Chemicals, Inc.) , Solid content 10.0% by weight) 26.1 parts, and urethane modified polyether-based associative thickener SN thickener 625N (manufactured by San Nopco, solid content 15.0% by weight) 3.3 parts under 25 ° C. environment. Ink 5 was obtained by mixing and stirring with, and filtering with a 3 μm cellulose acetate filter.

(Comparative Example 1)
Water 38.3 parts, propylene glycol 10.0 parts, 2-methyl-1,3-propanediol 5.0 parts, Olfine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) 1.0 part, Futagen 251 (manufactured by Neos). 0.1 part, resin fine particles J-140A (manufactured by Starlight PMC, solid content 41.0% by weight) 19.5 parts, and pigment dispersion CAB-O-JET 250C (manufactured by Cabot Specialty Chemicals, Inc., 26.1 parts (solid content 10.0% by weight) were mixed and stirred in an environment of 25 ° C., and then filtered through a 3 μm cellulose acetate filter to obtain ink 6.

(Comparative example 2)
190.0 parts of water and 10.0 g of carboxymethyl cellulose (CEKOL100000, manufactured by Sansho Co., Ltd.) were stirred while heating to 45 ° C. to obtain a thickener aqueous solution A having a solid content of 5.0% by weight. Water 18.3 parts, propylene glycol 10.0 parts, 2-methyl-1,3-propanediol 5.0 parts, Olfine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) 1.0 part, Futgent 251 (manufactured by Neos) ) 0.1 part, resin fine particles J-140A (manufactured by Starlight PMC, solid content 41.0% by weight) 19.5 parts, pigment dispersion CAB-O-JET 250C (manufactured by Cabot Specialty Chemicals, Inc., 26.1 parts of solid content 10.0% by weight and 20.0 parts of thickener aqueous solution A were mixed and stirred in an environment of 25 ° C., and then filtered through a 3 μm cellulose acetate filter to obtain ink 7.

(Comparative example 3)
198.0 parts of water and 2.0 g of xanthan gum (KELZAN S, manufactured by Sansho Co., Ltd.) were stirred while being heated to 45 ° C. to obtain a thickener aqueous solution B having a solid content of 1.0% by weight. Water 33.3 parts, propylene glycol 10.0 parts, 2-methyl-1,3-propanediol 5.0 parts, Olfine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) 1.0 part, Futgent 251 (manufactured by Neos) ) 0.1 part, resin fine particles J-140A (manufactured by Starlight PMC, solid content 41.0% by weight) 19.5 parts, pigment dispersion CAB-O-JET 250C (manufactured by Cabot Specialty Chemicals, Inc., 26.1 parts (solid content 10.0% by weight) and 5.0 parts thickener aqueous solution B were mixed and stirred in an environment of 25 ° C., and then filtered through a 3 μm cellulose acetate filter to obtain ink 8.

(Comparative example 4)
140.0 parts of water and 60.0 g of polyethylene glycol (PEG-20000, manufactured by Sanyo Kasei Co., Ltd.) were stirred while being heated to 45 ° C to obtain a thickener aqueous solution C having a solid content of 30.0% by weight. Water 25.0 parts, propylene glycol 10.0 parts, 2-methyl-1,3-propanediol 5.0 parts, Olfine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) 1.0 part, Futgent 251 (manufactured by Neos) ) 0.1 part, resin fine particles J-140A (manufactured by Starlight PMC, solid content 41.0% by weight) 19.5 parts, pigment dispersion CAB-O-JET 250C (manufactured by Cabot Specialty Chemicals, Inc., 26.1 parts (solid content 10.0% by weight) and 13.3 parts of thickener aqueous solution C were mixed and stirred in an environment of 25 ° C., and then filtered through a 3 μm cellulose acetate filter to obtain ink 9.

(Comparative example 5)
170.0 parts of water and 30.0 g of polyaminoplastol ether-based associative thickener TVS-VF (manufactured by Big Chemie Japan, solid content 40.0% by weight) are stirred while heating at 45 ° C. to obtain solid content. A 6.0 wt% thickener aqueous solution D was obtained. Water 12.3 parts, propylene glycol 10.0 parts, 2-methyl-1,3-propanediol 5.0 parts, Olfine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) 1.0 part, Futgent 251 (manufactured by Neos) ) 0.1 part, resin fine particles J-140A (manufactured by Starlight PMC, solid content 41.0% by weight) 19.5 parts, pigment dispersion CAB-O-JET 250C (manufactured by Cabot Specialty Chemicals, Inc., 26.1 parts of solid content 10.0% by weight and 12.3 parts of thickener aqueous solution D were mixed and stirred in an environment of 25 ° C., and then filtered through a 3 μm cellulose acetate filter to obtain ink 10.

(Evaluation methods)
The ink characteristics of the examples and comparative examples obtained above were evaluated by the following methods and criteria.

<Image blur>
The platen heater of the inkjet printer VG-640 (manufactured by Roland DG) is set to 60 ° C., and a predetermined evaluation image including characters and fine lines is printed on the PET film in the standard mode. After being left in an environment of 23 ° C. and 50% RH for 24 hours, the image quality of characters and fine lines is visually evaluated in four levels.
◎: good image without bleeding ○: bleeding with image, but image quality is within acceptable range △: bleeding with image is seen and affects image quality × ・..Blurring of images is seen, which greatly affects image quality

<Drying property>
The platen heater of the inkjet printer VG-640 (manufactured by Roland DG) is set to 60 ° C., and a solid image is printed on the PET film in the standard mode. After 5 minutes, the same PET film and a weight of 300 g are placed on the image surface and left in an environment of 23 ° C. and 50% RH for 24 hours. After that, both are peeled off, and the peeled state of the image is visually evaluated in four levels.
◎ ・ ・ ・ Peeling is not observed ○ ・ ・ ・ Peeling is observed in an area of less than 1% △ ・ ・ ・ Peeling is observed in an area of 1% or more and less than 10% × ・ ・ ・ In an area of 10% or more Peeling is seen

<Substrate adhesion>
The platen heater of the inkjet printer VG-640 (manufactured by Roland DG) is set to 60 ° C., and a solid image is printed on the PET film in the standard mode. After standing for 24 hours in an environment of 23 ° C. and 50% RH, six cuts are made at 1 mm intervals using spacers at equal intervals on the image surface, and the spacers are rotated by 90 ° to make further cuts. This makes a cut of 25 squares. A tape with a width of 30 mm is attached from above so that at least 25 squares with cuts are included, and pressed with a finger to make proper contact. After that, the tape was peeled off within an interval of 1.0 second at an angle of 60 °, and the peeled state of the image in the cut portion was visually evaluated in four levels.
◎ ・ ・ ・ Peeling is not seen ○ ・ ・ ・ Cuts are seen linearly △ ・ ・ ・ Peeling is seen at the intersection × ・ ・ ・ Peeling is seen on the entire surface of the image

<Transparency>
The platen heater of the inkjet printer VG-640 (manufactured by Roland DG) is set to 60 ° C., and a solid image is printed on the PET film in the standard mode. After standing for 24 hours in an environment of 23 ° C. and 50% RH, the haze value is obtained with a spectroscopic haze meter SH7000 (manufactured by Nippon Denshoku Industries Co., Ltd.).
◎ ・ ・ ・ less than 20% ○ ・ ・ ・ 20% or more and less than 50% △ ・ ・ ・ 50% or more and less than 70% × ・ ・ ・ 70% or more

<Scratchability>
The platen heater of the inkjet printer VG-640 (manufactured by Roland DG) is set to 60 ° C., and a solid image is printed on the PET film in the standard mode. After leaving it in an environment of 23 ° C. and 50% RH for 24 hours, attach a white cotton cloth (gold width 3) to Gakushin-type friction fastness tester AB-301 (manufactured by Tester Sangyo Co., Ltd.) and load it on the image surface. A load of 500 g and a repetition rate of 30 reciprocations per minute are repeated 100 times. The peeling state of the image of the tested portion is visually evaluated in four levels.
∘: No peeling was observed ○: Peeling was observed in an area of less than 10% Δ: Peeling was observed in an area of 10% or more and less than 25% ×: In an area of 25% or more Peeling is seen

<Water resistance>
The platen heater of the inkjet printer VG-640 (manufactured by Roland DG) is set to 60 ° C., and a solid image is printed on the PET film in the standard mode. After leaving it in an environment of 23 ° C. and 50% RH for 24 hours, a white cotton cloth (Gold Width No. 3) in which water was added to Gakushin-type friction fastness tester AB-301 (manufactured by Tester Sangyo Co., Ltd.) for the image surface. ) Is attached, and the load is 200 g, and the reciprocating speed is 30 reciprocations per minute for 100 reciprocations. The peeling state of the image of the tested portion is visually evaluated in four levels.
∘: No peeling was observed ○: Peeling was observed in an area of less than 10% Δ: Peeling was observed in an area of 10% or more and less than 25% ×: In an area of 25% or more Peeling is seen

  The compositions of the inkjet inks of Examples 1 to 5 and Comparative Examples 1 to 5 are shown in Table 1, and the evaluation results are shown in Table 2.

  Comparative Example 1 is an example in which no thickening agent was added. From a comparison between Examples 1 to 5 and Comparative Example 1, it can be seen that image bleeding is suppressed by using the urethane-modified polyether-based associative thickener. Further, the evaluation results of the drying properties and the image characteristics of Examples 1 to 5 are also equal to or close to those of Comparative Example 1, and it is understood that the drying properties and the image characteristics are good. Comparative Examples 2 to 4 are systems to which a water-soluble thickener is added. From the comparison between Examples 1 to 5 and Comparative Examples 2 to 4, it can be seen that image bleeding is suppressed by using the urethane-modified polyether-based associative thickener. Further, it is understood that Examples 1 to 5 have higher drying properties and image characteristics than Comparative Examples 2 to 4. Comparative Example 5 is a system to which a polyaminoplastol ether associative thickener is added. The ink produced in Comparative Example 5 exhibited irreversible deterioration at the time of loss on drying. From the comparison between Examples 1 to 5 and Comparative Example 5, in order to obtain the effects of suppressing image bleeding and good drying properties and image characteristics, among the associative thickeners, urethane-modified polyether-based association It turns out that a sex thickener should be used. Further, in Examples 1 to 4, hydrophobic resin fine particles were used as the resin component, and in Example 5, the water-soluble resin was used as the resin component. However, the resin component is either hydrophobic resin fine particles or water-soluble resin. It can be seen that even in this case, good results are obtained.

  The inkjet ink of the present invention can be suitably used for image recording (printing) on a hardly-absorbent recording medium.

10 Recording Medium 11 Ink 20 Conveying Section 21 Supply Roller 22 Winding Roller 23 Conveying Roller 30 Platen 40 Heating Section 50 Ejection Section 60 Ink Storage Section 70 Drying Section 71 Carriage 100 Inkjet Recording Device

Claims (8)

At least water, a resin component, an inkjet ink containing a coloring material, and associative thickeners, the associative thickener is Ri urethane-modified polyether polymer der,
An inkjet ink having the following formula, where V1 is the viscosity at 25 ° C., V2 is the viscosity at 40 ° C., and V3 is the viscosity at 40 ° C. when 10% by weight dry reduction is used .
5.0 mPa · s ≦ V1 ≦ 20.0 mPa · s
V1 / V2 ≧ 1.6
V3 / V2 ≧ 1.3 The inkjet ink according to claim 1, wherein the resin component is resin fine particles. The coloring material is a pigment, the inkjet ink according to claim 1 or 2. Further contains an organic solvent, the ink-jet ink according to any one of claims 1-3. Further contains a surfactant, the ink-jet ink according to any one of claims 1-4. Solid concentration is 20.0 wt% or less, the ink-jet ink according to any one of claims 1-5. A step of heating the non-absorbent recording medium,
A step of ejecting an inkjet ink onto the heated non-absorbent recording medium;
An inkjet recording method including:
The inkjet ink, an inkjet ink according to any one of claims 1 to 6 an ink jet recording method. A transport unit for transporting the non-absorbent recording medium,
A heating unit for heating the conveyed hardly-absorbent recording medium,
An ejecting unit that ejects an inkjet ink onto the heated non-absorbent recording medium,
An ink storage unit that stores the inkjet ink and supplies the discharge unit with the inkjet ink;
An inkjet recording apparatus comprising:
An inkjet recording apparatus, wherein the inkjet ink is the inkjet ink according to any one of claims 1 to 7 .

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