JPWO2016080140A1 - Water-based ink composition for inkjet - Google Patents

Abstract

Disclosed is an aqueous ink composition for inkjet that has excellent fixing properties such as scratch resistance, tape peeling, and scratch resistance. The aqueous inkjet ink composition of the present invention is an inkjet aqueous ink composition comprising a self-dispersing pigment and a wax, wherein the pigment is a polymer bonded to the surface of pigment particles. The wax is a polyethylene wax having a melting point of 120 ° C. to 140 ° C. and does not contain a binder.

Description

  The present invention relates to an aqueous inkjet ink composition, and more particularly to an aqueous inkjet ink composition excellent in fixing properties such as scratch resistance, tape peeling, and scratch resistance.

  The ink jet recording method is a method in which ink containing a color material or a functional material is separated into droplets, and the droplets are ejected toward a recording medium such as paper in accordance with an image signal, and are printed. Due to recent advances in inkjet recording technology, inkjet recording methods have been used in the field of high-definition printing that has been realized by offset printing. Accordingly, an aqueous ink composition for ink jet (hereinafter referred to as “aqueous ink composition”) that can be used for a recording medium such as print-coated paper used in the field of offset printing has been developed. However, the conventionally proposed water-based ink composition cannot be said to have excellent scratch resistance of an image printed on a recording medium, and has a problem that the degree of color transfer is larger than that of an offset printed material.

  In this regard, for example, Patent Document 1 below provides a water-based ink composition for ink jet recording that has good dispersibility and dischargeability, excellent scratch resistance, scratch resistance, and high color developability and gloss. As a subject, a polyolefin wax and a water-dispersible urethane resin are disclosed. According to Patent Document 1, it has good scratch resistance and scratch resistance, and can achieve excellent color development and high gloss (for example, paragraph [0004]).

  Patent Document 2 listed below is coated with a water-insoluble resin for the purpose of providing an ink composition that is excellent in ink stability and maintainability and in which occurrence of press blocking of the obtained image is suppressed. An ink composition containing a pigment, water-insoluble polymer particles having a glass transition temperature of 100 ° C. or higher, a solid wetting agent, a water-soluble organic solvent, wax particles having a melting point of 40 ° C. or higher and lower than 100 ° C., and water is disclosed (for example, , Claim 1 etc.).

WO2011 / 093486 JP 2011-162692 A

  However, there is a problem that even if high-definition printing is performed by the ink jet recording method using the aqueous ink composition described in each of the above patent documents, the scratch resistance of the printed image is not sufficient.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a water-based ink composition for inkjet excellent in fixing properties such as scratch resistance, tape peeling, and scratch resistance.

  The inventors of the present application have studied the water-based ink composition for inkjet in order to solve the above-mentioned problems, and as a result, found that the above-mentioned problems can be solved by adopting the following configuration, and completed the present invention. It was.

  That is, an aqueous inkjet ink composition according to the present invention is an inkjet aqueous ink composition comprising a self-dispersing pigment and a wax in order to solve the above-described problems, and the pigment is a pigment. A polymer is bonded to the surface of the particles, and the wax is a polyethylene wax having a melting point of 120 ° C. to 140 ° C. and does not contain a binder.

  The aqueous inkjet ink composition of the present invention (hereinafter referred to as “aqueous ink composition”) includes a pigment having a polymer bonded to the surface of the pigment particle. Even when the aqueous ink composition is attached to the recording medium and printed, the fixing property is excellent, and the scratch resistance and tape peelability can be improved. In addition, since the polyethylene wax is contained in the above-described configuration, slip properties can be imparted to the coating film surface (of the ink), and scratch resistance, tape peeling, and scratch resistance can be improved. Furthermore, since polyethylene wax having a melting point in the range of 120 ° C. to 140 ° C. is used, it is possible to suppress thermal deformation or melting of the polyethylene wax due to frictional heat due to rubbing of the surface of the printed coating film, A decrease in scratch resistance can be prevented. That is, with the above-described configuration, it is possible to provide a water-based ink composition having excellent fixability to the recording medium even if the binder for fixing the pigment to the surface of the recording medium is omitted.

  In the said structure, it is preferable that the mass ratio of the pigment particle and polymer in the said pigment exists in the range of 14: 3-14: 6. By setting the ratio of the polymer in the numerical range to 3 or more in the mass ratio of the pigment particles to the polymer, it is possible to suppress a decrease in fixability of the aqueous ink composition to the recording medium. On the other hand, by setting the ratio of the polymer to 6 or less, it is possible to prevent the flying property from being lowered due to excessive increase in the viscosity of the aqueous ink composition.

  Further, in the above configuration, the polymer is an alkyl compound or an aromatic compound, and is bonded to the pigment particle through an NH bond or an N—C═N bond, or an anion group of the pigment particle. The anion group is at least one selected from the group consisting of a carboxyl group, a sulfone group, a phenyl group and a phosphate group, and the end of the polymer has the pigment It is preferable that a hydrophilic group imparting self-dispersibility to the particles is bonded.

  Furthermore, in the said structure, it is preferable that the mass mean molecular weight of the said polymer exists in the range of 300-20000. By setting the mass average molecular weight of the polymer to 300 or more, it is possible to suppress a decrease in fixability of the water-based ink composition to the recording medium. On the other hand, the dispersibility of the pigment can be prevented from being lowered by setting the mass average molecular weight of the polymer to 20000 or less. Further, it is possible to prevent the coating film from becoming too hard when the aqueous ink composition adheres to the recording medium.

  Furthermore, in the said structure, it is preferable that content of the said polyethylene-type wax exists in the range of 0.5 mass%-5 mass% in conversion of solid content with respect to the total mass of an aqueous ink composition. By setting the content of the polyethylene wax to 0.5% by mass or more, the slip property and the friction resistance on the surface of the printed coating film can be further improved. On the other hand, the occurrence of beading can be suppressed by setting the content of the polyethylene wax to 5% by mass or less.

The present invention has the following effects by the means described above.
That is, according to the water-based ink composition for inkjet of the present invention, the fixing property of the water-based ink composition to the recording medium is improved by including a self-dispersing pigment in which a polymer is bonded to the surface of the pigment particle. be able to. Further, since it contains a polyethylene wax, it is possible to impart slip properties to the coating surface (of the ink), and to improve scratch resistance, tape peeling, and scratch resistance. Furthermore, since polyethylene wax having a melting point in the range of 120 ° C. to 140 ° C. is used, it is possible to suppress thermal deformation or melting of the polyethylene wax due to frictional heat due to rubbing of the surface of the printed coating film, A decrease in scratch resistance can be prevented. That is, according to the present invention, it is possible to provide an ink-jet aqueous ink composition having excellent fixing properties such as scratch resistance, tape peeling, and scratch resistance.

(Water-based ink composition for inkjet)
The water-based ink composition of the present embodiment is a water-based ink that contains a self-dispersing pigment and a polyethylene wax, and the main solvent is water. However, the inclusion of an emulsion such as acrylic-styrene, urethane, polyester, and a water-soluble resin that functions as a binder can be omitted. Moreover, the water-based ink composition of the present embodiment is suitably used for inkjet recording. Since the pigment is used as the coloring material, the aqueous ink composition of the present embodiment is inherently superior in terms of color developability, weather resistance, water resistance, and the like as compared with the ink composition using the dye. . In the present embodiment, “self-dispersing” means that even an aqueous ink composition in which no dispersant is present exhibits dispersibility as an aqueous dispersion.

  The pigment has a structure in which a polymer is bonded to the surface of pigment particles via a bonding group (details will be described later). Furthermore, it is preferable that a hydrophilic group (water-dispersible functional group) that imparts self-dispersibility to the pigment particles is bonded to the terminal of the polymer. Here, the hydrophilic group means an atomic group that forms a weak bond with a water molecule by electrostatic interaction or hydrogen bond, and has an affinity for water. In the present embodiment, In particular, it has a function as a functional group that imparts water dispersibility to the pigment.

  The pigment particles in the pigment of the present embodiment are not particularly limited, and any of organic pigment particles and inorganic pigment particles can be used. Examples of the organic pigment particles include azo pigments, phthalocyanine pigments, anthraquinone pigments, quinacridone pigments, thioindigo pigments, triphenylmethane lake pigments, and oxazine lake pigments. More specifically, examples of those having a yellow color tone include C.I. I. Pigment yellow 1, 2, 3, 4, 5, 6, 10, 12, 13, 14, 16, 17, 65, 74, 83, 97, 138, 150, 151, 155. Examples of those having a red color tone include C.I. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 21, 22, 23, 31, 32, 37, 38, 41, 48, 49, 50, 51, 52, 57, 58, 60, 64, 83, 88, 89, 90, 112, 114, 122, 123, 166, 188, 202, C.I. I. Pigment Violet 19, 23. Examples of those having a blue color tone include C.I. I. Pigment blue 1, 2, 15, 15: 3, 15: 4, 16, 25, 75. Examples of those having a green color tone include C.I. I. Pigment Green 7, 36. Examples of those having a black color tone include C.I. I. And CI pigment blacks 1 and 7. Commercially available colored pigments include, for example, Pigment Red 122, Pigment Violet 19 (Lansco Colors, Montvale, NJ, or BASF Color, Charlotte, NC, or Clariant Colors, Charlotte, NC, or Sun Chemical, Cincinn Pigment Blue 15: 1 (available from Fanwood Chemical, Fanwood, NJ), Pigment Blue 15: 3, Pigment 15: 4, Pigment Yellow 74, Pigment Yellow 97 (available from OH) BASF Color, Charlotte, NC, or Clariant Colors, Charlotte, NC, or Sun C and those sold by Chemical, Cincinnati, OH).

  Examples of the inorganic pigment particles include carbon black. The carbon black is not particularly limited, and examples thereof include acidic carbon black, neutral carbon black, and alkaline carbon black, and more specifically, channel black, gas black, lamp black, thermal black, acetylene black, and furnace black. It is done. Of these carbon blacks, channel black is preferred in the present embodiment. It should be noted that the quality of the carbon black may affect important properties of the dispersion such as average particle size, opacity, hue, and stability.

  Moreover, you may use a commercial item as said carbon black. Commercially available products include, for example, Elftex 8, Black Pearls (registered trademark, hereinafter the same) 490, Black Pearls 120, Monarch (registered trademark, the same applies hereinafter) 120, Monarch 700, Monarch 880, Monarch 1000, Monarch 1100. , Monarch 1300, Monarch 1400, Mogul (registered trademark) L, Regal (registered trademark, the same applies hereinafter) 99R, Regal 250R, Regal 300R, Regal 330R, Regal 400R, Regal 500R, Regal 660R (all manufactured by Cabot) Etc. Also, NIPex (registered trademark, hereinafter the same) 150IQ, NIPex 150, Printex (registered trademark, the same applies hereinafter) 55, Printex 80, Printex 90, Printex A, Printex G, Printex U, Printex V, Printex 140U, Printex 140U, Printex 140V, Purex (registered trademark) LS35, Colax (registered trademark) HP160, Thermal Black N990, NIPex (registered trademark) 160 IQ, NIPex (registered trademark) 90, Special black 4, Special black 4A, Special black 4A, Special black 4A, Special black 4A, Special black 4A, Special black 4A, Special black 4A, Special black 4A, Special black 4A, Special black 4A Special black 100, Special black 250, Color black k FW1, Color black FW2, Color black FW2V, Color black FW18, Color black FW200, Color black S150, Color black S160, or Color black S170 (all manufactured by Deguss, etc.) In addition, Raven (registered trademark, the same applies hereinafter) 780, Raven 5000UII, Raven 1255, Raven 2500U, Raven 3600U, Raven 3500, Raven 7000, Raven 1220, Raven 1220, and Raven 1225 (all manufactured by Columbia), etc. Also, MA8, MA11, MA77, MA100, MA220, MA230, MA600, MCF88, # 10B, # 20B, # 30, # 33, # 40, # 44, # 45, # 45L, # 50, # 55, # 95 , # 260, # 900, 970 #, # 1000, # 2200B, # 2300, # 2350, # 2400B, # 2650, # 2700, # 4000B, or CF9 (all manufactured by Mitsubishi Chemical Corporation).

  The average particle diameter (volume average particle diameter) of the pigment particles is not particularly limited, and can be set as necessary. Usually, the thing within the range of 10 nm-1000 nm is preferable, and the thing within the range of 50 nm-200 nm is more preferable. The average particle diameter is a value measured by a dynamic light scattering method using Microtrac UPA-EX150 (trade name, manufactured by Nikkiso Co., Ltd.).

  The polymer is not particularly limited, and examples thereof include alkyl compounds and aromatic compounds having an alkyl chain in the main chain. More specifically, polystyrene-co-maleic anhydride resin (SMA), poly (styrene-co-maleic anhydride) cumene-terminated resin (molecular weight 1700-1900, manufactured by Aldrich), pentaethylenehexamine (PEHA, Akzo Nobel). Styrene-acrylic (SA), linear alkyl, branched ethoxy or propoxy chain polymers having a known molecular weight range of 300-3000 MW (Surfonamine® B30, L100, L300, B60, L207 (manufactured by Huntsman) )), Linear polyethoxy polymer amine, linear propoxy polymer amine, styrene acrylic copolymer (trade name: Joncryl HPD 96, HPD 296, HPD 196 (manufactured by BASF)), polyethyleneimine ( Trade name; Epomin SP-012, Nippon Shokubai Co., Ltd.) and the like.

  The mass average molecular weight of the polymer is preferably in the range of 300-20000. By setting the mass average molecular weight of the polymer to 300 or more, it is possible to suppress a decrease in fixability of the water-based ink composition to the recording medium. On the other hand, by setting the mass average molecular weight of the polymer to 20000 or less, it is possible to prevent a decrease in pigment dispersibility. Moreover, it is possible to prevent the coating film from becoming too hard when the aqueous ink composition adheres to the recording medium. In addition, in the mass average molecular weight of a polymer, the mass average molecular weight of the hydrophilic group couple | bonded with the terminal of the said polymer is remove | excluded.

  Moreover, as a pigment of this Embodiment, the commercial item can be used besides the thing by the arbitrary combinations of the said pigment particle and a polymer. Such commercial products include, for example, Sensijet (registered trademark), Ultra Magenta PR122, Sensijet Cyan PB15: 3, Sensijet Ultra Cyan PB15: 4, Sensijet Blue PB 60, Sensijet 7 PR Sensijet Red PR 254, Sensijet Orange PY 83, Sensijet Yellow PY 120, Sensijet Magenta PV19, Sensijet Cyan PB15: 3, Sensijet Yellow PY155, SenSjet Yellow PY155, SenSjet Yellow PY155 100, 1000 and 2000) (all trade names, include the Sensient Co., Ltd.), and the like.

  The polymer has a structure bonded to the surface of the pigment particle via an NH bond or an N—C═N bond bonding group, or the polymer is bonded to an anion group of the pigment particle with an NH bond. It has a structure linked through a group. It does not specifically limit as said anionic group, For example, a carboxyl group, a sulfone group, a phenyl group, a phosphoric acid group etc. are mentioned.

  Moreover, it is preferable that the hydrophilic group is couple | bonded with the terminal on the opposite side to the side couple | bonded with the pigment of the said polymer. Thereby, dispersibility can be imparted to the pigment, and the pigment can be self-dispersed even if the dispersant is not contained in the aqueous ink composition. Although it does not specifically limit as said hydrophilic group, For example, hydrogen, a carbonyl group, a carboxyl group, a sulfone group, a phenyl group, a phosphoric acid group, an ammonium group, a trimethylammonium group etc. are mentioned.

  The mass ratio of the pigment particles to the polymer is preferably in the range of 14: 3 to 14: 6. By setting the ratio of the polymer in the numerical range to 3 or more in the mass ratio of the pigment particles to the polymer, it is possible to suppress a decrease in fixability of the aqueous ink composition to the recording medium. On the other hand, by setting the ratio of the polymer to 6 or less, it is possible to prevent the flying property from being lowered due to excessive increase in the viscosity of the aqueous ink composition.

  The content of the pigment in the aqueous ink composition directly affects the image density, and also affects the storage stability, viscosity, pH, and the like of the aqueous ink composition. Therefore, the content of the pigment may be appropriately set in consideration of these points. Usually, the range of 1% by mass to 20% by mass in terms of solid content is preferable with respect to the total mass of the water-based ink composition, and the range of 5% by mass to 15% by mass is more preferable. By setting the pigment content to 1% by mass or more, a decrease in image density can be suppressed. On the other hand, by setting the pigment content to 20% by mass or less, it is possible to prevent a decrease in gloss, nozzle clogging, and a decrease in ejection stability.

  The polyethylene wax is preferably contained in a fine particle state (that is, an emulsion state or a suspension state) in the aqueous ink composition. By containing the polyethylene wax in a fine particle state, the viscosity of the aqueous ink composition can be easily adjusted to an appropriate range in the ink jet recording system. In addition, good storage stability and ejection stability can be maintained. As the polyethylene wax, one emulsified in water by a conventional method is used.

  Examples of the polyethylene wax include polyethylene wax, copolymer wax composed of a monomer having ethylene and a carboxylic acid group such as methacrylic acid or acrylic acid, and oxidized polyethylene wax. Moreover, as a commercial item, for example, JONCRYL (registered trademark) WAX 26J (manufactured by BASF Japan Co., Ltd.), AQUACER (registered trademark) 513 (manufactured by Big Chemie Japan Co., Ltd.), Chemipearl (registered trademark) W900, Chemipearl WF4KX12 (All manufactured by Mitsui Chemicals, Inc.), HYTEC E-6500, HYTEC E-9015, HYTEC E-1000, HYTEC E-4A (all manufactured by Toho Chemical Co., Ltd.) and the like. These can be used alone or in admixture of two or more.

  In the present embodiment, mixing other waxes such as natural waxes (for example, petroleum waxes, plant waxes, animal and plant waxes, etc.) into the water-based ink composition may be beading or the like. It may not be preferable from the viewpoint of occurrence.

  The melting point of the polyethylene wax is in the range of 120 ° C to 140 ° C, and preferably in the range of 130 ° C to 140 ° C. By using a polyethylene wax having a melting point of 120 ° C. or higher, it is possible to prevent the polyethylene wax from being thermally deformed or melted due to frictional heat generated by rubbing the surface of the printed coating film, thereby reducing the abrasion resistance. it can.

  It does not specifically limit as an average particle diameter (D50) of the said polyethylene-type wax, It can set suitably as needed.

  The content of the polyethylene wax is preferably in the range of 0.5% by mass to 5% by mass in terms of solid content with respect to the total mass of the water-based ink composition, and in the range of 0.5% by mass to 1.5% by mass. Is more preferable. By setting the content of the polyethylene wax to 0.5% by mass or more, it is possible to improve the slip property on the surface of the printed coating film and further improve the friction resistance. On the other hand, the occurrence of beading can be suppressed by setting the content of the polyethylene wax to 5% by mass or less.

  The water-based ink composition of the present embodiment contains a water-soluble organic solvent as a wetting agent (anti-drying agent) from the viewpoint of promoting drying, improving the ejection stability of the inkjet head, imparting moisture retention, and the like. It is preferable. As the water-soluble organic solvent, for example, a C2-C10 alkane or alkene diol, or a triol can be used. Of these water-soluble organic solvents, propylene glycol and 1,3-butanediol are preferable from the viewpoint of achieving both dryness and wettability. Moreover, these water-soluble organic solvents can be used individually or in mixture of 2 or more types.

  However, it is preferable that the water-based ink composition of the present embodiment does not substantially contain glycerin. Thereby, it can prevent that the drying property of printed matter falls. As a result, it is possible to suppress a decrease in image fixability on various recording media, particularly ink non-absorbing or low-absorbing recording media.

  It does not specifically limit as content of the said water-soluble organic solvent, It can set suitably as needed. Usually, the range of 6% by mass to 40% by mass is preferable with respect to the total mass of the aqueous ink composition, more preferably within the range of 8% by mass to 35% by mass, and particularly preferably within the range of 10% by mass to 35% by mass. preferable.

  The aqueous ink composition of the present embodiment may contain glycol ethers. Thereby, the solubility with respect to the water-based ink composition of another component can be improved. In addition, the permeability to the recording medium can be improved without causing an excessive decrease in surface tension as compared with a surfactant described later. Thereby, it is possible to record a high-definition image with little shading unevenness even on a non-absorbing or low-absorbing recording medium.

  Specific examples of the glycol ethers include, for example, ethylene glycol monoisobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monoisohexyl ether, diethylene glycol monohexyl ether, triethylene glycol monohexyl ether, diethylene glycol monoisohexyl ether, triethylene glycol Ethylene glycol monoisohexyl ether, ethylene glycol monoisoheptyl ether, diethylene glycol monoisoheptyl ether, triethylene glycol monoisoheptyl ether, ethylene glycol monooctyl ether, ethylene glycol monoisooctyl ether, diethylene glycol monoisooctyl ether, triethylene glycol Monoisooctyl A Ethylene glycol mono-2-ethylhexyl ether, diethylene glycol mono-2-ethylhexyl ether, triethylene glycol mono-2-ethylhexyl ether, diethylene glycol mono-2-ethylpentyl ether, ethylene glycol mono-2-ethylpentyl ether, ethylene glycol Mono-2-methylpentyl ether, diethylene glycol mono-2-methylpentyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monobutyl ether, propylene glycol monopropyl ether, dipropylene glycol monopropyl ether, tripropylene glycol A monomethyl ether etc. are mentioned. These can be used alone or in admixture of two or more.

  The content of the glycol ethers is such that the solubility of other components in the aqueous ink composition, the wettability with respect to the recording medium, the effect of improving the penetrability to reduce density unevenness, the storage stability of the aqueous ink composition and the ejection. It can be appropriately set from the viewpoint of ensuring stability. Usually, it is preferably in the range of 0.1% by mass to 40% by mass with respect to the total mass of the water-based ink composition. By setting the content to 0.1% by mass or more, it is possible to prevent the wettability, the permeability, and the drying property of the aqueous ink composition from being lowered, and a high-definition printed image can be obtained. In addition, the printing density (coloring property) can be ensured. On the other hand, by setting it to 40% by mass or less, the viscosity of the water-based ink composition can be prevented from becoming too high, and the occurrence of clogging of the head nozzle can be suppressed. Moreover, the solubility in a water-based ink composition can be prevented from decreasing, and storage stability can be ensured.

  Further, the water-based ink composition of the present embodiment may contain a surfactant. The image quality of the printed image and the ink drying time depend on the wettability and penetrability of the ink on the surface of the recording medium. By adding a surfactant to the aqueous ink composition, the interfacial tension at the interface between the droplet of the aqueous ink composition and the recording medium is reduced, so that the wettability and permeability of the droplet can be improved. . As a result, a high-definition image with little shading unevenness can be printed. The surfactant is not particularly limited, and examples thereof include acetylene glycol surfactants and silicone surfactants.

  The acetylene glycol-based surfactant has, for example, a property that it has excellent ability to keep the surface tension and the interfacial tension properly, and has almost no foaming property, as compared with, for example, a nonionic surfactant. Therefore, by blending the acetylene glycol surfactant into the aqueous ink composition, the surface tension and the interfacial tension with the printer member in contact with the ink such as the head nozzle surface can be properly maintained. As a result, it is possible to improve the ejection stability of droplets at the head nozzle. In addition, since the acetylene glycol surfactant exhibits good wettability with respect to the recording medium and also acts as a penetrating agent, it is possible to obtain a high-definition printed image by reducing the occurrence of uneven density and bleeding. Can do.

  The acetylene glycol surfactant is not particularly limited. For example, Surfynol (registered trademark) 104, 104E, 104H, 104A, 104BC, 104DPM, 104PA, 104PG-50, 104S, 420, 440, 465, 485, SE, SE-F, 504, 61, DF37, CT111, CT121, CT131, CT136, TG, GA, DF110D (trade names, all manufactured by Air Products and Chemicals, Inc.) and the like. These can be used alone or in admixture of two or more.

  The content of the acetylene glycol surfactant is preferably in the range of 0.2% by mass to 3% by mass, and 0.5% by mass to 2% by mass with respect to the total mass of the aqueous ink composition. It is more preferable to be within the range.

  Moreover, as said silicone type surfactant, a polysiloxane type compound etc. are used preferably, and polyether modified organosiloxane etc. are mentioned. More specifically, examples include BYK-306, 307, 333, 341, 345, 346, 348 (trade names, all manufactured by Big Chemie Japan Co., Ltd.). These can be used alone or in admixture of two or more.

  The content of the silicone surfactant is preferably in the range of 0.2% by mass to 3% by mass with respect to the total mass of the aqueous ink composition, and is 0.5% by mass to 2% by mass. More preferably within the range.

  The water-based ink composition according to this embodiment contains water (water as a main solvent). As the water, it is preferable to use water from which ionic impurities such as ion-exchanged water, ultrafiltered water, reverse osmosis water, distilled water, or ultrapure water have been removed. In particular, water sterilized by ultraviolet irradiation or addition of hydrogen peroxide or the like is preferable because generation of mold and bacteria can be prevented over a long period of time. Moreover, it does not specifically limit as content of water, It can set suitably as needed.

  The water-based ink composition according to the present embodiment can omit the inclusion of a binder resin (for example, a water-dispersed urethane resin) for fixing the pigment to the surface of the recording medium. Even if it does not contain a binder resin, the water-based ink composition of this embodiment is excellent in fixing properties such as scratch resistance, tape peeling, and scratch resistance to a recording medium. As a result, the addition of an organic solvent for dissolving the binder resin in the aqueous ink composition can be omitted.

  Furthermore, the water-based ink composition of the present embodiment may further contain a pH adjuster, antiseptic / fungal agent, chelating agent, and the like as other additives. The content of these additives can be appropriately set as necessary.

  The pH adjuster is not particularly limited. For example, potassium dihydrogen phosphate, disodium hydrogen phosphate, sodium hydroxide, lithium hydroxide, potassium hydroxide, ammonia, diethanolamine, triethanolamine, triisopropanolamine, carbonic acid Potassium, sodium carbonate, sodium hydrogen carbonate, etc. are mentioned.

  The antiseptic and antifungal agent is not particularly limited, and examples thereof include sodium benzoate, sodium pentachlorophenol, sodium 2-pyridinethiol-1-oxide, sodium sorbate, sodium dehydroacetate, 1,2-dibenzisothiazoline- 3-one etc. are mentioned. By adding an antiseptic and fungicidal agent, generation of microorganisms can be suppressed and nozzle clogging can be prevented.

  The chelating agent is not particularly limited, and examples thereof include ethylenediaminetetraacetic acid and salts thereof (e.g., ethylenediaminetetraacetic acid dihydrogen disodium salt). Generation | occurrence | production of nozzle clogging etc. can be prevented by addition of a chelating agent.

(Method for producing inkjet water-based ink composition)
The water-based ink composition of the present embodiment can be produced by dispersing and mixing the above-described components by an appropriate method. That is, for example, a separately prepared polyethylene wax is added to a uniform pigment dispersion and further diluted with water, a water-soluble organic solvent, or the like. Thereafter, the mixture is sufficiently stirred, and if necessary, filtration is performed to remove coarse particles and foreign matters that cause clogging. Thereby, the water-based ink composition which concerns on this Embodiment can be obtained.

  The mixing method of each material is not particularly limited. For example, the materials are sequentially added to a container equipped with a stirring device such as a mechanical stirrer or a magnetic stirrer, and stirring and mixing are performed. Moreover, it does not specifically limit as a filtration method, For example, centrifugal filtration, filter filtration, etc. are employable.

(Inkjet recording method)
Next, the ink jet recording method of the present embodiment will be described.
The ink jet recording method of the present embodiment can be performed by discharging the aqueous ink composition as droplets onto an arbitrary recording medium from fine nozzles and attaching the droplets to the recording medium. The discharge method is not particularly limited, and for example, a known method such as continuous injection type (charge control type, spray type, etc.), on-demand type (piezo type, thermal type, electrostatic suction type, etc.) can be adopted. it can.

  The recording medium is not particularly limited, and a conventionally known recording medium can be used. The water-based ink composition of this embodiment is excellent in fixing properties such as scratch resistance, tape peeling, and scratch resistance, even on non-absorbing or low-absorbing recording media, and prints high-definition images. Because it is possible. Specific examples include general printing paper, coated paper, art paper, paper container paper, and the like.

  After the droplets of the water-based inkjet ink composition are ejected and adhered to the recording medium, the deposited droplets are heated at a temperature lower than the melting point of the polyethylene wax contained in the water-based ink composition for inkjet. It is preferable to dry. Thereby, it can be made to exist in a printing coating film in the state which maintained the shape of particle | grains, without heat-melting or melt | dissolving a polyethylene-type wax. As a result, it is possible to print on the recording medium a print image having excellent scratch resistance, tape peeling, and scratch resistance. The heating temperature at this time means the temperature of the surface of the recording medium. The lower limit of the heating temperature can be appropriately set according to the solvent in the water-based ink composition, the type of the recording medium, the drying time, and the like. The drying time is not particularly limited, and can be appropriately set according to the solvent in the aqueous ink composition, the type of the recording medium, the printing speed, and the like.

  The method of heat drying is not particularly limited as long as it promotes evaporation of the solvent in the aqueous ink composition. For example, a method of spraying hot air on a recording medium to which droplets of the aqueous ink composition are attached, a method of bringing the recording medium into contact with a heating drum set to an appropriate temperature, and the like, are exemplified. Specifically, hot air treatment such as forced air heating, radiant heating, conduction heating, high-frequency drying, microwave drying, or heating by a heater is possible.

(Other matters)
The numerical ranges set forth herein are meant to include all numerical values from the lower limit to the upper limit. For example, when the mass average molecular weight of the polymer is 300 to 20000, it means that all combinable numerical ranges such as 500 to 10,000, 400 to 1000, 301 to 311 are included.

  Hereinafter, preferred embodiments of the present invention will be described in detail by way of example. However, materials, contents, and the like described in the following examples are not intended to limit the scope of the present invention only to those unless otherwise specified.

(Examples 1-4)
Water-based ink compositions of Examples 1 to 4 were prepared with the composition shown in Table 1 below. However, each Example 1-4 differs in the point which used the pigment and wax of the kind shown in following Table 2, respectively.

  The water-based ink composition of each example was prepared by the following operation. That is, each material shown in Table 1 was put in a container and mixed, and stirred with a magnetic stirrer at room temperature for 1 hour. Thereafter, the mixture was filtered to remove coarse particles and foreign matters. A membrane filter having a filtration accuracy of 1 μm was used as a filter for filtration. Thereby, the water-based ink compositions of Examples 1 to 4 were obtained. The numerical values in Table 1 are all expressed in mass%. Water was added so that the total amount of the water-based ink composition was 100% by mass.

(Examples 5-7, Comparative Example 1)
Water-based ink compositions of Examples 5 to 7 and Comparative Example 1 were prepared with the blending compositions shown in Tables 3 and 4 below. As a magenta pigment, Sensijet Ultra Magenta PR122 (manufactured by SENCENT) was used. Moreover, HYTEC E-1000 (trade name, manufactured by Toho Chemical Co., Ltd.) was used as the polyethylene wax.

  The aqueous ink compositions of the examples and comparative examples were prepared by the same method as in Example 1 and the like. The numerical values in Tables 3 and 4 are all expressed in mass%. Water was added so that the total amount of the water-based ink composition was 100% by mass.

(Abrasion resistance)
Measurement and evaluation regarding scratch resistance were performed according to JIS-K5701-1. That is, printing was performed on a coated paper (trade name: OK ball, manufactured by Oji Paper Co., Ltd.) as a recording medium using the water-based ink composition prepared in each example or comparative example. Printing was performed using an inkjet printer (trade name: PX-105, manufactured by Seiko Epson Corporation). After printing, the coated paper was heat-dried for 2 minutes so that the surface temperature of the coated paper was 120 ° C.

  Subsequently, using a Gakushin-type friction fastness tester (manufactured by Yasuda Seiki Co., Ltd.), the friction paper (trade name: OK Top Coat, manufactured by Oji Paper Co., Ltd.) is placed on the printed surface of the coated paper, and the load is 500 g. The printed surface was rubbed 10 times. Thereafter, in order to evaluate the degree of color transfer on the friction paper, the friction surface was captured as an image with a scanner (EPSON GT-X820, manufactured by Seiko Epson Corporation). The scan conditions were 48-bit color, resolution 600 dpi, and no image correction. Furthermore, the image was averaged using Photoshop (registered trademark). The averaging range was 15 mm × 15 mm. Thereafter, in order to digitize the degree of color transfer to the friction paper, the R, G, and B values of each color of cyan, magenta, and yellow on the friction paper were measured. In addition, the R, G, and B values of each color of cyan, magenta, and yellow were measured for friction paper that did not rub against the printed surface of the coated paper.

The method for calculating the degree of color transfer of a printed material using an aqueous ink composition containing a cyan pigment was as follows. That is, cyan can be represented by (R, G, B) = (0, 255, 255), and it can be considered that the cyan color transfer to the friction paper becomes darker as the R value approaches zero. For this reason, the degree of cyan color transfer was calculated by the following equation and digitized.
(Cyan color migration degree) = Ref. _R -C _R

Similarly, regarding the degree of color transfer of a printed material using an aqueous ink composition containing a magenta pigment, magenta can be represented by (R, G, B) = (255, 0, 255), and the G value is 0. Since it is considered that the color transfer of magenta to the friction paper becomes deeper as it gets closer, it was calculated by the following formula.
(Magenta color transfer degree) = Ref. _G -M _G

Further, regarding the degree of color transfer of a printed material using a water-based ink composition containing a yellow pigment, yellow can be represented by (R, G, B) = (255, 255, 0), and the B value approaches 0. Since the yellow color transfer to the friction paper is considered to be deeper, it was calculated by the following formula.
(Yellow color transfer degree) = Ref. _B- Y _B

Based on the obtained value of the color transfer degree, the scratch resistance was evaluated according to the following evaluation criteria. The results are shown in Tables 2 and 4. Note that the following evaluation criteria are the same as those in the case of performing offset printing. In addition, since the sensitivity of the scratch resistance varies depending on the color of the pigment, the evaluation criteria were changed as follows.
○: The value of the color transfer degree is 30 or less when a magenta pigment is used, 40 or less when a cyan pigment is used, and 30 or less when a yellow pigment is used Δ: The value of the color transfer degree is magenta In the case of more than 30 to 50 or less, in the case of using a cyan pigment, more than 40 to 55 or less, in the case of using a yellow pigment, more than 30 to 50 or less X: When the value of the color transfer degree is a magenta pigment Is greater than 50, with cyan pigments greater than 55 and with yellow pigments greater than 50

(Tape peelability)
For tape peelability, solid printing was performed on coated paper (OK ball, manufactured by Oji Paper Co., Ltd.) under the same conditions as in the evaluation of scratch resistance. Next, stick the adhesive tape (trade name: Cellotape (registered trademark) No. 405, Nichiban Co., Ltd.) on the printing surface, and then check the peeling of the printing surface and the transfer state to the tape when the adhesive tape is peeled off As a result, the tape peelability was evaluated. The evaluation criteria were as follows. The results are shown in Tables 2 and 4.

○: No peeling of the recording surface / adhesion to the adhesive tape Δ: No peeling of the recording surface, but slight adhesion to the adhesive tape was observed ×: Separation occurred on the recording surface

(Scratch resistance)
For scratch resistance, solid printing was performed on coated paper (OK ball, manufactured by Oji Paper Co., Ltd.) under the same conditions as in the evaluation of scratch resistance. Next, the printed surface of the coated paper was rubbed with a nail and it was confirmed whether or not the printed surface was scratched. The evaluation criteria were as follows. The results are shown in Tables 2 and 4.
○: No color material peeling ×: Color material peeling

(result)
As can be seen from Tables 2 and 4, the water-based ink compositions of Examples 1 to 7 each have a small color transfer degree value and excellent scratch resistance even if they do not contain a binder. It was shown that. Moreover, peeling of the printing surface by the adhesive tape was not confirmed, and the fixability was also good. Furthermore, the scratch resistance was also good.

Claims (5)

An aqueous inkjet ink composition comprising a pigment having self-dispersibility and a wax,
The pigment is one in which a polymer is bonded to the surface of pigment particles,
The wax is a polyethylene wax having a melting point of 120 ° C to 140 ° C;
And the aqueous ink composition for inkjets which does not contain a binder.   The aqueous ink composition for inkjet according to claim 1, wherein the mass ratio of the pigment particles to the polymer in the pigment is within a range of 14: 3 to 14: 6. The polymer is an alkyl compound or an aromatic compound, and is bonded to the pigment particle through an NH bond or N—C═N bond, or is bonded to the anion group of the pigment particle through an NH bond. ,
The anionic group is at least one selected from the group consisting of a carboxyl group, a sulfone group, a phenyl group, and a phosphoric acid group,
Furthermore, the water-based ink composition for inkjets of Claim 1 or 2 to which the hydrophilic group which provides the self-dispersibility to the said pigment particle is couple | bonded with the terminal of the said polymer.   The water-based ink composition for inkjet according to any one of claims 1 to 3, wherein the polymer has a mass average molecular weight in the range of 300 to 20,000. The inkjet according to any one of claims 1 to 4, wherein the content of the polyethylene wax is in the range of 0.5% by mass to 5% by mass in terms of solid content with respect to the total mass of the aqueous ink composition. Water-based ink composition.