Recording method.

Abstract

To provide an ink set that can give an image having excellent metallic luster and excellent durability.SOLUTION: An ink set contains a metallic ink composition containing a metallic pigment, and a primer ink composition. The metallic ink composition has a surface tension lower than that of the primer ink composition. The metallic pigment is composed of surface-treated metal particles.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an ink set and a recording method.

Background Art

[0002] An inkjet recording method is known in which minute ink droplets are ejected from nozzles of an inkjet head of an inkjet recording apparatus to record an image on a recording medium. The development of inkjet recording methods is active, and attempts have been made to form a glossy image using an inkjet recording method.

[0003] For example, Patent Document 1 discloses an inkjet recording method using metallic ink and white ink, and studies have been made to obtain an image with improved aesthetics, such as forming a metallic gloss image.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] As one method for improving the image quality of a metallic gloss image, it is conceivable to form an underlayer on a recording medium with an underlayer ink composition and attach a metallic ink composition on the underlayer. As one method for improving the image quality of a metallic gloss image, when trying to improve the wet spreading of the metallic ink composition to promote the leafing of metallic pigments, although good metallic gloss can be obtained, there has been a problem that the metallic gloss cannot be maintained for a long period.

Means for Solving the Problems

[0006] One aspect of the ink set according to the present invention is An ink set including a metallic ink composition containing a metal pigment and an underlayer ink composition, wherein the surface tension of the metallic ink composition is lower than that of the underlayer ink composition, and the metal pigment is metal particles whose surfaces are treated.

[0007] One aspect of the recording method according to the present invention is a recording method using the above ink set, including a step of attaching the underlayer ink composition to a recording medium, and a step of attaching the metallic ink composition to the attached underlayer ink composition.

Brief Description of the Drawings

[0008]

Figure 1

Modes for Carrying Out the Invention

[0009] Some embodiments of the present invention will be described below. The embodiments described below illustrate an example of the present invention. The present invention is not limited to the following embodiments, and various modifications implemented without changing the gist of the present invention are also included. Note that not all of the configurations described below are essential configurations of the present invention.

[0010] 1. Ink Set The ink set of the present embodiment is an ink set including a metallic ink composition containing a metal pigment and an underlayer ink composition, wherein the surface tension of the metallic ink composition is lower than that of the underlayer ink composition, and the metal pigment is metal particles whose surfaces are treated.

[0011] 1.1. Metallic Ink Composition The metallic ink composition contains a metal pigment.

[0012] 1.1.1. Metal Pigment The metallic pigment is not limited as long as it can form an image having metallic luster. The shape of the particles of the metallic pigment is not particularly limited and can be, for example, plate-like, flaky, spherical, columnar, etc. Among them, from the viewpoint of more efficiently expressing metallic luster, the metallic pigment is more preferably plate-like particles or flaky particles.

[0013] Here, the "plate-like particles" or "flaky particles" refer to particles having a substantially flat surface (X-Y plane) and a substantially uniform thickness (Z). Since plate-like particles or flaky particles can be produced, for example, by crushing a metal vapor deposition film, they can be obtained as metal particles having a substantially flat surface and a substantially uniform thickness. Therefore, the major axis on the plane of the plate-like particles or flaky particles can be defined as X, the minor axis as Y, and the thickness as Z.

[0014] The material of the metallic pigment can be various metals such as aluminum, silver, gold, platinum, nickel, chromium, tin, zinc, indium, titanium, copper, and their alloys, etc. However, from the viewpoints of cost and ensuring excellent metallic luster, it is preferably aluminum or an aluminum alloy. When using an aluminum alloy, the metallic element or non-metallic element to form the alloy is not particularly limited, and examples thereof include silver, gold, platinum, nickel, chromium, tin, zinc, indium, titanium, copper, etc. At least one of these single substances, their alloys, and their mixtures is preferably used.

[0015] The thickness of the metal or alloy layer of the metal pigment particles is preferably, for example, 2.0 nm or more and 150.0 nm or less. More preferably, it is 5.0 nm or more and 120.0 nm or less, and even more preferably, it is 5.0 nm or more and 90.0 nm or less. By setting it within the above range, it has excellent reflectivity and brilliance, and the performance as a metal pigment is enhanced. Preferably, it is 100.0 nm or less, and more preferably 90.0 nm or less, which can suppress the increase in apparent specific gravity and improve the dispersion stability of the metal pigment. Also, the average thickness of the metal pigment may be within the above range. The average thickness is measured, for example, as follows. Dilute the ink containing the metal pigment, apply the diluted solution to a substrate and dry it, and measure the thickness of the dried metal pigment with AFM. The measurement is taken at 50 random points and the average value is obtained.

[0016] The volume average particle diameter D50 of the metal pigment particles is not particularly limited, but is preferably 0.05 μm or more and 3.00 μm or less, more preferably 0.10 μm or more and 1.50 μm or less, and even more preferably 0.20 μm or more and 1.00 μm or less. The volume average particle diameter D50 refers to the median diameter D50 of the volume distribution measured by the laser diffraction / scattering method for the particle dispersion liquid. When the volume average particle diameter is within the above range or more, the reflectivity and brilliance of the recorded matter are more excellent, and when it is within the above range or less, the dispersion stability and dischargeability are more excellent and preferable.

[0017] A method for producing a metal pigment includes, for example, a method of peeling from a sheet-like substrate with the interface between the metal or alloy layer and the peeling resin layer of a composite pigment precursor having a structure in which a peeling resin layer and a metal or alloy layer are sequentially laminated on the surface of a sheet-like substrate, pulverizing, and miniaturizing to obtain plate-like particles. The metal or alloy layer is preferably formed by vacuum deposition, ion plating, or sputtering method.

[0018] The resin layer for peeling in the composite pigment precursor is an undercoat layer of a metal or alloy layer, but it is a peelable layer for improving the peelability from the sheet-like substrate surface. Examples of the resin used for this resin layer for peeling include polyvinyl alcohol, polyvinyl butyral, polyethylene glycol, polyacrylic acid, polyacrylamide, cellulose derivatives, polyvinyl butyral, acrylic acid polymers, or modified nylon resins.

[0019] The application of the resin layer for peeling is formed by generally used methods such as gravure coating, roll coating, blade coating, extrusion coating, dip coating, spin coating method, etc. After coating and drying, if necessary, surface smoothing is performed by calendering.

[0020] The sheet-like substrate is not particularly limited, and examples include polyester films such as polytetrafluoroethylene, polyethylene, polypropylene, and polyethylene terephthalate, polyamide films such as 66 nylon and 6 nylon, polycarbonate films, triacetate films, and release films such as polyimide films. Preferred sheet-like substrates are polyethylene terephthalate or its copolymers.

[0021] The metal or alloy layer may be sandwiched between protective layers as exemplified in JP-A-2005-68250. Examples of the protective layer include a metal / alloy layer, a metal oxide layer, and an organic film layer. The metal / alloy layer is a layer of a metal (including semi-metals) or alloy made of a material different from the metal or alloy of the pigment precursor. The metal oxide layer is a layer of an oxide of a metal (including semi-metals), and it may be a film formed by natural oxidation of the metal or alloy of the pigment precursor. Examples include an alumina layer and a silicon oxide layer. A ceramic layer may also be used. The organic film layer includes, for example, a resin layer, which may be the resin layer remaining as the protective resin layer from the above-mentioned resin layer for peeling, or a resin layer different from the resin for peeling.

[0022] An example of the metal oxide layer, the silicon oxide layer, is not particularly limited as long as it is a layer containing silicon oxide, but it is preferably formed from a silicon alkoxide such as tetraalkoxysilane or a polymer thereof by the sol-gel method. The silicon oxide layer can be formed, for example, by applying an alcohol solution in which a silicon alkoxide or a polymer thereof is dissolved and then heating and baking it.

[0023] Furthermore, when forming the metal oxide film layer, for example, it can be formed by applying an alcohol solution in which a metal alkoxide or a polymer thereof is dissolved and then heating and baking it.

[0024] The method for peeling from the sheet-like substrate is not particularly limited, but a method in which the composite pigment precursor is immersed in a liquid, or a method in which ultrasonic treatment is performed simultaneously with immersion in the liquid, and the peeling treatment and the pulverization treatment of the peeled composite pigment are performed are preferred.

[0025] The flat metal pigment obtained as described above has a peeling resin layer that serves as a protective colloid, and it is possible to obtain a stable dispersion liquid only by performing a dispersion treatment in a solvent.

[0026] When the metallic ink composition is an aqueous composition, it is more preferable that the metal pigment is surface-treated so that the metal is less likely to react with moisture and oxygen. In addition, even when the metallic ink composition is a solvent-based composition, it is more preferable that the surface treatment is performed so that the metal is less likely to react with oxygen and moisture.

[0027] The ink is preferably a solvent ink containing a solvent component that dissolves or disperses the solid component contained in the ink.

[0028] Here, the "aqueous ink" refers to an ink among solvent inks that contains at least water as the main component of the solvent constituting the ink. Examples of the solvent include water and organic solvents. The aqueous ink contains 20% by mass or more of water based on the total mass of the ink. It is more preferable that 40% by mass or more of water, still more preferable that 50% by mass or more, and particularly preferable that 60% by mass or more.

[0029] Also, the "solvent-based ink" refers to an ink among solvent inks in which the main component of the solvent constituting the ink is an organic solvent. The solvent-based ink contains less than 20% by mass (not exceeding 20% by mass) of water based on the total mass of the ink. Further, 10% by mass or less is preferable, 1% by mass or less is preferable, and 0.1% by mass or less is preferable. Also, the content of the organic solvent is preferably 10% by mass or more, preferably 40% by mass or more, preferably 50% by mass or more, more preferably 60% by mass or more, and particularly preferably 80% by mass based on the total mass of the ink.

[0030] Note that the metallic ink composition may be a UV ink (an ink that is cured by irradiation with ultraviolet rays or the like and used for recording).

[0031] When surface treatment is performed on the metal pigment, it is more preferably surface-treated with a phosphorus-based compound or a silicon-based compound. By doing so, the metallic luster on the surface of the metal pigment particles is maintained better. For example, the storage stability of the metallic ink composition can be improved, or the luster can be maintained for a long time when the image is stored. Note that when surface treatment is performed, the above-described protective layer may or may not be present on the mother particles.

[0032] Specific methods of surface treatment include, for example, allowing at least one of a phosphorus-based compound, a silicon-based compound, and a fluorine-based compound to act on metal pigment particles (mother particles). Methods for allowing these to act include, for example, heating and stirring.

[0033] As phosphorus compounds, for example, phosphate derivatives, phosphonic acid derivatives, phosphinic acid derivatives, etc. can be used. Examples of derivatives include tautomers, esterified products, etherified products, those in which a hydrogen atom in the structural formula is replaced with an organic substituent, and the like. Further, the phosphorus compound preferably has a hydrophobic atom or atomic group such as an alkyl group or a fluoroalkyl group.

[0034] Examples of the hydrophobic atom or atomic group include a fluorine atom, an alkyl group having 3 or more carbon atoms, an alkyl group in which at least a part of hydrogen atoms is replaced with a fluorine atom, and the like. The carbon number of the alkyl group or the alkyl group in which at least a part of hydrogen atoms is replaced with a fluorine atom is preferably 3 or more, more preferably 5 or more, and still more preferably 8 or more. Further, the carbon number is not particularly limited, but is preferably 35 or less, more preferably 30 or less, and still more preferably 25 or less. The alkyl group or the alkyl group in which at least a part of hydrogen atoms is replaced with a fluorine atom is preferably one bonded to the phosphorus atom of the phosphorus compound or one in which the hydroxyl group bonded to the phosphorus atom of the phosphorus compound is etherified.

[0035] Among them, the phosphorus compound is more preferably a fluorine-based phosphorus compound which is a phosphorus compound having at least one fluorine atom in the molecule. Thereby, the hydrophobicity in the state of adhering to the particles of the metal pigment can be further enhanced, and the dispersion stability of the particles of the metal pigment in the metallic ink composition can be made more excellent. In particular, in a recording material manufactured by using an inkjet recording method, the particles of the metal pigment can be suitably arranged near the outer surface of the recording portion, and the characteristics such as the glossiness inherent to the metal material constituting the particles of the metal pigment can be more effectively exhibited.

[0036] When the phosphorus-based compound is a fluorine-based phosphorus-based compound, the fluorine-based phosphorus-based compound preferably has a perfluoroalkyl structure. The fluorine-based phosphorus-based compound is a compound having a phosphorus-containing group and a fluorine-containing group. Examples of the fluorine-containing group include a perfluoroalkyl structure. Examples of the phosphorus-containing group include a phosphoric acid group, a phosphorous acid group, a phosphonic acid group, and a phosphinic acid group.

[0037] More specifically, examples of the fluorine-based phosphorus-based compound include, for example, a compound represented by the general formula P(O)R n (OH) 3-n and the like. n is an integer from 1 to 3. R is a perfluoroalkyl group (perfluoroalkyl structure). Examples include 2-(perfluorohexyl)ethylphosphonic acid.

[0038] The metallic ink composition may contain a plurality of compounds as the phosphorus-based compound. In such a case, the surface treatment of the same metal particles may be performed with a plurality of phosphorus-based compounds. Also, the metallic ink composition may contain metal particles surface-treated with different phosphorus-based compounds.

[0039] In addition, the surface treatment of the metal pigment particles with the phosphorus-based compound may be performed, for example, by including the phosphorus-based compound in the liquid when forming the metal pigment particles by pulverizing a metal film formed by a vapor deposition method in the liquid.

[0040] When performing surface treatment of the same particles with a plurality of phosphorus-based compounds, the surface treatment may be performed in a plurality of steps corresponding to each phosphorus-based compound, or the surface treatment with a plurality of phosphorus-based compounds may be performed in the same step.

[0041] When using a phosphorus-based compound, the content is 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 0.2% by mass or more, still more preferably 0.25% by mass or more, based on 100% by mass of the metallic pigment. Further, the upper limit of the content when using a phosphorus-based compound is, for example, 50% by mass or less, preferably 40% by mass or less, more preferably 30% by mass or less, still more preferably 20% by mass or less, based on 100% by mass of the metallic pigment. When the content when using a phosphorus-based compound is within this range, it is possible to make the glossiness of the image formed by the metallic ink composition excellent and to make the gloss last longer.

[0042] Examples of the silicon-based compound include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, tetraphenoxysilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, trimethoxyphenylsilane, triethoxyphenylsilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, and the like.

[0043] In addition, a silicon-containing fluorine compound may be used as the silicon-based compound. The silicon-containing fluorine compound is a compound having a silicon-containing group and a fluorine-containing group. Examples of the fluorine-containing group include a perfluoroalkyl structure and the like. Examples of the silicon-containing group include an alkoxysilyl group and the like. When using a silicon-containing fluorine compound, it is easier to obtain a metallic pigment excellent in glossiness and dispersibility, and the weather resistance tends to be better when recording an image.

[0044] Examples of the silicon-containing fluorine compound, such as the fluorine-containing compound having a perfluoroalkyl structure, are not particularly limited. For example, CF3-CH2CH2-Si(OCH3)3, CF3(CF2)3-CH2CH2-Si(OCH3)3, CF3(CF2)5-CH2CH2-Si(OCH3)3, CF3(CF2)5-CH2CH2-Si(OC2H5)3, CF3(CF2)7-CH2CH2-Si(OCH3)3, CF3(CF2) 11 -CH2CH2-Si(OC2H5)3, CF3(CF2)3-CH2CH2-Si(CH3)(OCH3)2, CF3(CF2)7-CH2CH2-Si(CH3)(OCH3)2, CF3(CF2)8-CH2CH2-Si(CH3)(OC2H5)2, and CF3(CF2)8-CH2CH2-Si(C2H5)(OC2H5)2, and 1H,1H,2H,2H-perfluorodecyltriethoxysilane, etc.

[0045] In addition, as the above-mentioned perfluoroalkyl structure, a perfluoroalkyl ether structure (C n F 2n+1 O) can also be used. Therefore, a fluorine compound having a perfluoroalkyl ether structure can also be used. Examples of the fluorine-containing silicon compound having a perfluoroalkyl ether structure are not particularly limited. For example, CF3O(CF2O)6-CH2CH2-Si(OC2H5)3, CF3O(C3F6O)4-CH2CH2-Si(OCH3)3, CF3O(C3F6O)2(CF2O)3-CH2CH2-Si(OCH3)3, CF3O(C3F6O)8-CH2CH2-Si(OCH3)3, CF3O(C4F9O)5-CH2CH2-Si(OCH3)3, CF3O(C4F9O)5-CH2CH2-Si(CH3)(OC2H5)2, CF3O(C3F6O)4-CH2CH2-Si(C2H5)(OCH3)2, etc.

[0046] When surface-treating a metallic pigment, a fluorine compound may be used. As the fluorine compound, a fluorine-containing fatty acid may be used. For example, CF3-CH2CH2-COOH, CF3(CF2)3-CH2CH2-COOH, CF3(CF2)5-CH2CH2-COOH, CF3(CF2)6-CH2CH2-COOH, CF3(CF2)7-CH2CH2-COOH, and CF3(CF2)9-CH2CH2-COOH and their esters may be used.

[0047] Furthermore, as the fluorine compound, a fluorine-containing isocyanate compound may be used. As the fluorine-containing isocyanate compound, for example, those having a chemical structure represented by the following formula (1) can be used. R f NCO ···(1) Here, in formula (1), R f is CF3(CF2) m -, or CF3(CF2) m (CH2) l -, m is an integer of 2 or more and 18 or less, and l is an integer of 1 or more and 18 or less.

[0048] By surface-treating the mother particles with such phosphorus-based compounds or silicon-based compounds, a film can be formed, and furthermore, an image with good gloss can be formed. Note that surface treatment may be performed by selecting two or more from the above phosphorus-based compounds, silicon-based compounds, and fluorine-based compounds.

[0049] The concentration of the metallic pigment in the metallic ink composition is 0.1% by mass or more and 10.0% by mass or less, more preferably 0.5% by mass or more and 8.0% by mass or less, and still more preferably 1.0% by mass or more and 5.0% by mass or less.

[0050] 1.1.2. Other Components The metallic ink composition can contain the following components in addition to the metallic pigment.

[0051] (Water) The metallic ink composition may contain water, whether it is an aqueous ink or a solvent-based ink. As the water, it is preferable to use pure water or ultrapure water such as ion-exchanged water, ultrafiltration water, reverse osmosis permeated water, distilled water, etc. In particular, water sterilized by ultraviolet irradiation or hydrogen peroxide addition is preferable because it can suppress the generation of mold and bacteria over a long period of time.

[0052] (Organic solvent) The metallic ink composition may contain an organic solvent. When the metallic ink composition is a solvent-based ink, the water content is preferably 1.0% by mass or less, more preferably 0.5% by mass or less, still more preferably 0.1% by mass or less, and particularly preferably no water. The organic solvent is not particularly limited, and examples thereof include glycol ether solvents. Examples of the glycol ether solvent include compounds represented by the following general formula (2). R 1 O-(R 2 O) m -R 3 ···(2) (In formula (2), R 1 is a hydrogen atom or an alkyl group having 1 or more and 6 or less carbon atoms, R 2 is an alkylene group having 2 or more and 4 or less carbon atoms, and R 3 is a hydrogen atom, an acetyl group, or an alkyl group having 1 or more and 6 or less carbon atoms. However, at least one of R 1 and R 3 is an alkyl group having 1 or more and 6 or less carbon atoms. m is an integer of 1 or more and 7 or less.)

[0053] Specific examples of the compound represented by the general formula (2) include methyl glycol (ethylene glycol monomethyl ether: EGMME), methyl diglycol (diethylene glycol monomethyl ether: DEGMME), methyl triglycol (triethylene glycol monomethyl ether: TEGMME), isopropyl glycol (ethylene glycol monoisopropyl ether: EGMiPE), isopropyl diglycol (diethylene glycol monoisopropyl ether: DEGMiPE), butyl glycol (ethylene glycol monobutyl ether: EGMBE), butyl diglycol (diethylene glycol monobutyl ether: DEGMBE), butyl triglycol (triethylene glycol monobutyl ether: TEGMBE), isobutyl glycol (ethylene glycol monoisobutyl ether: EGMiBE), isobutyl diglycol (diethylene glycol monoisobutyl ether: DEGMiBE), hexyl glycol (ethylene glycol monohexyl ether: EGMHE), hexyl diglycol (diethylene glycol monohexyl ether: DEGMHE), methyl propylene glycol (propylene glycol monomethyl ether: PGMME), methyl propylene diglycol (dipropylene glycol monomethyl ether: DPGMME), methyl propylene triglycol (tripropylene glycol monomethyl ether: DPGMME), propyl propylene glycol (propylene glycol monopropyl ether: PGMPE), propyl propylene diglycol (dipropylene glycol monopropyl ether: DPGMPE), butyl propylene glycol (propylene glycol monobutyl ether: PGMBE), butyl propylene diglycol (dipropylene glycol monobutyl ether: DPGMBE), butyl propylene triglycol (tripropylene glycol monobutyl ether: TPGMBE) and other glycol monoethers, dimethyl glycol (ethylene glycol dimethyl ether: EGDME), dimethyl diglycol (diethylene glycol dimethyl ether: DEGDME), dimethyl triglycol (triethylene glycol dimethyl ether: TEGDME),Glycol diethers such as methylethyl diglycol (diethylene glycol ethyl methyl ether: DEGEME), diethyl diglycol (diethylene glycol diethyl ether: DEGDEE), dibutyl diglycol (diethylene glycol dibutyl ether: DEGDBE), dimethylpropylene diglycol (dipropylene glycol dimethyl ether: DPGDME) and the like can be mentioned.

[0054] Also, in the above formula (2), R 2 or R 3 , particularly R 3 which is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms is particularly preferable in that the printing unevenness, gloss, and dot size are further excellent. Further, from the viewpoints of the drying property and glossiness of the printed matter, R 1 and R 3 in the general formula (2) are both preferably alkyl groups, and are preferably glycol diethers. On the other hand, a glycol monoether in which one is hydrogen and the other is an alkyl group is preferable in terms of excellent wet spreading of the ink. Further, from the viewpoints of the drying property and printing stability of the printed matter, the carbon number of R 2 in the general formula (2) is preferably 2 or 3, and is preferably ethylene glycol (mono or di) ether having 2.

[0055] The metallic ink composition preferably contains alkylene glycol ether esters which are one kind of glycol ether solvents.

[0056] Examples of alkylene glycol ether esters include glycol monoacetates such as ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate, methoxybutyl acetate, etc.; glycol diesters such as ethylene glycol diacetate, diethylene glycol diacetate, propylene glycol diacetate, dipropylene glycol diacetate, ethylene glycol acetate propionate, ethylene glycol acetate butyrate, diethylene glycol acetate butyrate, diethylene glycol acetate propionate, diethylene glycol acetate butyrate, propylene glycol acetate propionate, propylene glycol acetate butyrate, dipropylene glycol acetate butyrate, dipropylene glycol acetate propionate, etc.

[0057] The metallic ink composition preferably contains a lactone. By containing a cyclic lactone, a part of a low-absorbency recording medium (for example, a vinyl chloride-based resin) can be dissolved to allow the ink composition to penetrate into the interior of the recording medium. By thus allowing the ink composition to penetrate into the interior of the recording medium, the rubbing resistance of the image recorded on the recording medium can be improved.

[0058] The term "lactone" generally refers to cyclic compounds having an ester group (-CO-O-) in the ring. The lactone is not particularly limited as long as it is included in the above definition, but it is preferably a lactone having 2 to 9 carbon atoms. Specific examples of such lactones include α-ethyl lactone, α-acetolactone, β-propiolactone, γ-butyrolactone, δ-valerolactone, ε-caprolactone, ζ-enantiolactone, η-caprylolactone, γ-valerolactone, γ-heptalactone, γ-nonalactone, β-methyl-δ-valerolactone, 2-butyl-2-ethyl propiolactone, α,α-diethyl propiolactone, etc. Among these, γ-butyrolactone is particularly preferred. The lactones exemplified above may be used alone or in combination of two or more.

[0059] The metallic ink composition may further contain solvents such as esters, ketones, alcohols, amides, alkanediols, pyrrolidones, etc., other than the compounds exemplified above, as other solvents.

[0060] When the total content of the organic solvent in the metallic ink composition is based on 100.0% by mass of the total mass of the composition, it is preferably 70.0% by mass or more, more preferably 80.0% by mass or more, still more preferably 90.0% by mass or more, particularly preferably 95.0% by mass or more, and the upper limit is preferably 99.5% by mass or less, more preferably 99.0% by mass or less.

[0061] (Surfactant) From the viewpoints of reducing the surface tension and improving the wettability with the recording medium, etc., the metallic ink composition may contain a silicone-based surfactant, a fluorine-based surfactant, or a polyoxyethylene derivative which is a nonionic surfactant.

[0062] As silicone surfactants, it is preferable to use polyester-modified silicone, polyether-modified silicone, or silicone-acrylic copolymer systems. Specific examples include BYK-315, 315N, 325, 333, 347, 348, BYK-UV3500, 3510, 3530, 3550, 3570 (all manufactured by BYK Chemie Japan).

[0063] As fluorine surfactants, it is preferable to use fluorine-modified oligomers. Specific examples include BYK-340 (manufactured by BYK Chemie Japan), Megafac F-251, 430, 477, 552, 553, 554, 556, 557, 559, 562, 563, 565, Megafac R-40 and other Megafac series (manufactured by DIC Corporation), Surflon S-242, 243, 386, 420, 431, 611, 647, 651, 656, 658, 693 and other Surflon series (manufactured by AGC Seimi Chemical Co., Ltd.), Ftergent 251, 208M, 212M, 215M, 250, 209F, 222F, 245F, 208G, 218GL, 240G, 212P, 220P, 228P, 710FL, FTX-218, DFX-18 and other Ftergent series (manufactured by Neos Co., Ltd.), etc.

[0064] Also, as polyoxyethylene derivatives, it is preferable to use acetylene glycol-based surfactants. Specific examples include Surfynol 82, 104, 465, 485, TG (all manufactured by Air Products Japan), Olfin STG, E1010 (both manufactured by Nissin Chemical Industry Co., Ltd.), Nissann Nonion A-10R, A-13R (both manufactured by NOF Corporation), Flowlen TG-740W, D-90 (manufactured by Kyoeisha Chemical Co., Ltd.), Neugen CX-100 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), etc.

[0065] As the surfactant, an acetylene glycol-based surfactant or a polysiloxane-based surfactant may be contained. The acetylene glycol-based surfactant and the polysiloxane-based surfactant can enhance the wettability to the recording surface such as a recording medium and improve the ink permeability. Examples of the acetylene glycol-based surfactant include 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, 3,5-dimethyl-1-hexyne-3-ol, 2,4-dimethyl-5-hexyne-3-ol and the like. Also, commercially available products of the acetylene glycol-based surfactant can be used, for example, Orfin E1010, STG, Y (manufactured by Nissin Chemical Industry Co., Ltd. above), Surfynol 104, 82, 465, 485, TG (manufactured by Air Products and Chemicals Inc. above). As the polysiloxane-based surfactant, commercially available products can be used, for example, BYK-347, BYK-348 (manufactured by BYK-Chemie Japan Co., Ltd. above) and the like. Further, the metallic ink composition may also contain other surfactants such as anionic surfactants, nonionic surfactants, amphoteric surfactants.

[0066] In addition, as the surfactant, it is preferable to contain an acetylene glycol-based surfactant or a polysiloxane-based surfactant. The acetylene glycol-based surfactant and the polysiloxane-based surfactant can enhance the wettability and penetrability to the coating target. Examples of the acetylene glycol-based surfactant include 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, 3,5-dimethyl-1-hexyne-3-ol, 2,4-dimethyl-5-hexyne-3-ol, etc. Also, commercially available products of the acetylene glycol-based surfactant can be used. For example, Olfine E1010, STG, Y (manufactured by Nissin Chemical Industry Co., Ltd.), Surfynol 104, 82, 465, 485, TG (manufactured by Air Products and Chemicals Inc.) can be mentioned. As the polysiloxane-based surfactant, commercially available products can be used. For example, BYK-347, BYK-348 (manufactured by BYK-Chemie Japan Co., Ltd.) etc. can be mentioned. Furthermore, other surfactants such as anionic surfactants, nonionic surfactants, and amphoteric surfactants can also be added. Examples of such surfactants include Disperbyk 102 (manufactured by BYK-Chemie), Disparon DA-325 (manufactured by Kusumoto Chemicals, Ltd.).

[0067] When a surfactant is used in the metallic ink composition, the content of the surfactant in the composition is preferably 0.05% by mass or more and 3% by mass or less, more preferably 0.5% by mass or more and 2% by mass or less.

[0068] (Resin) The metallic ink composition may contain a resin (hereinafter also referred to as "fixing resin") for fixing the above-mentioned metal pigment to the recording medium.

[0069] Examples of the fixing resin include acrylic resins, rosin-modified resins, phenolic resins, terpene resins, polyester resins, polyamide resins, epoxy resins, vinyl acetate resins, vinyl chloride resins, fibrous resins such as cellulose acetate butyrate, and vinyl toluene-α-methylstyrene copolymer resins. Among these, it is preferably at least one resin selected from the group consisting of acrylic resins and vinyl chloride resins. By containing these fixing resins, the fixability to the recording medium can be improved, and the abrasion resistance can also be improved.

[0070] The solid content of the fixing resin in the metallic ink composition is preferably 0.05% by mass or more and 15% by mass or less, more preferably 0.1% by mass or more and 10% by mass or less. When the content of the fixing resin is within the above range, excellent fixability can be obtained for low-absorbency recording media.

[0071] As the acrylic resin, a copolymer composed of conventionally known polymerizable monomers can be used. Examples of the polymerizable monomers include acrylic esters such as methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, and 2-ethylhexyl acrylate; methacrylic esters such as methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, and 2-ethylhexyl methacrylate; carboxy group-containing monomers such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, maleic acid mono n-butyl ester, fumaric acid mono n-butyl ester, and itaconic acid mono n-butyl ester, as well as hydroxyl group-containing (meth)acrylic esters, amide group-containing monomers, glycidyl group-containing monomers, cyano group-containing monomers, hydroxyl group-containing allyl compounds, tertiary amino group-containing monomers, alkoxysilyl group-containing monomers, etc. can be used alone or in combination of two or more. The acrylic resin may be a copolymer of an acrylic monomer and other monomers, for example, a styrene acrylic resin. Preferably, it is an acrylic resin using 90% by mass or more of the acrylic monomer as the monomer, more preferably 95% by mass or more, and still more preferably 99% by mass or more.

[0072] As the above acrylic resin, commercially available products may be used. For example, Acrypet MF (trade name, manufactured by Mitsubishi Rayon Co., Ltd., acrylic resin), Sumipex LG (trade name, manufactured by Sumitomo Chemical Co., Ltd., acrylic resin), Paraloid B series (trade name, manufactured by Rohm and Haas Co., acrylic resin), Parapet G-1000P (trade name, manufactured by Kuraray Co., Ltd., acrylic resin), UC-3000 (trade name, manufactured by Toagosei Co., Ltd., acrylic resin), etc. may be mentioned. The acrylic monomer includes (meth)acrylic monomers. For example, (meth)acrylic acid means one or both of acrylic acid and methacrylic acid, and (meth)acrylate means one or both of acrylate and methacrylate.

[0073] When the metallic ink composition contains an acrylic resin, an image with better fixing property can be formed.

[0074] Examples of the vinyl chloride resin include copolymers of vinyl chloride and other monomers such as vinyl acetate, vinylidene chloride, acrylic acid, maleic acid, and vinyl alcohol. Among these, a copolymer containing structural units derived from vinyl chloride and vinyl acetate (hereinafter also referred to as " vinyl chloride-vinyl acetate copolymer") is preferred, and a vinyl chloride-vinyl acetate copolymer having a glass transition temperature of 60 to 80°C is more preferred.

[0075] The vinyl chloride-vinyl acetate copolymer can be obtained by a conventional method, for example, by suspension polymerization. Specifically, water, a dispersant, and a polymerization initiator are charged into a polymerization vessel, and after degassing, vinyl chloride and vinyl acetate are press-fitted to carry out suspension polymerization, or a part of vinyl chloride and vinyl acetate are press-fitted to start the reaction, and the remaining vinyl chloride is press-fitted during the reaction to carry out suspension polymerization.

[0076] The vinyl chloride - vinyl acetate copolymer preferably contains 70 to 90% by mass of vinyl chloride units in its composition. If it is within the above range, it can be stably dissolved in the ink composition, so it has excellent long - term storage stability. Furthermore, it has excellent ejection stability and can obtain excellent fixing property with respect to the recording medium. It can be achieved.

[0077] In addition, the vinyl chloride - vinyl acetate copolymer may, as necessary, have other constituent units together with vinyl chloride units and vinyl acetate units. For example, carboxylic acid units, vinyl alcohol units, hydroxyalkyl acrylate units can be mentioned, and among them, vinyl alcohol units are preferably mentioned. It can be obtained by using monomers corresponding to the above - mentioned respective units. Specific examples of monomers that give carboxylic acid units include, for example, maleic acid, itaconic acid, maleic anhydride, itaconic anhydride, acrylic acid, and methacrylic acid. Specific examples of monomers that give hydroxyalkyl acrylate units include, for example, hydroxyethyl (meth) acrylate, hydroxyethyl vinyl ether, etc. The content of these monomers is not limited as long as the effects of the present invention are not impaired, but for example, they can be copolymerized in the range of 15% by mass or less of the total amount of monomers.

[0078] Also, commercially available vinyl chloride - vinyl acetate copolymers may be used. For example, Solvayne CN, Solvayne CNL, Solvayne C5R, Solvayne TA5R, Solvayne CL, Solvayne CLL (the above are manufactured by Nisshin Chemical Industry Co., Ltd.) and the like can be mentioned.

[0079] The average degree of polymerization of these resins is not particularly limited, but is preferably 150 to 1100, more preferably 200 to 750. When the average degree of polymerization of these resins is within the above range, they can be stably dissolved in the metallic ink composition, so they have excellent long - term storage stability. Furthermore, they have excellent ejection stability and can obtain excellent fixing property with respect to the recording medium. The average degree of polymerization of these resins is calculated by measuring the specific viscosity and can be determined according to the average degree of polymerization calculation method described in "JIS K6720 - 2".

[0080] Also, the number average molecular weight of these resins is not particularly limited, but is preferably 10,000 to 50,000, more preferably 12,000 to 42,000. The number average molecular weight can be measured by GPC and can be determined as a relative value in terms of polystyrene conversion.

[0081] (Other) In addition to the above components, the metallic ink composition may also contain substances for imparting predetermined performances, such as chelating agents, preservatives, viscosity modifiers, dissolution aids, antioxidants, and antifungal agents, as necessary.

[0082] The viscosity of the metallic ink composition at 20 °C is preferably 2 mPa·s or more and 15 mPa·s or less. When the viscosity of the metallic ink composition at 20 °C is within the above range, an appropriate amount of the metallic ink composition is discharged from the nozzle, and the flight curve and scattering of the metallic ink composition can be further reduced, so it can be suitably used in an inkjet recording apparatus.

[0083] The metallic ink composition can be obtained by mixing the above-described components in an appropriate order and, if necessary, performing filtration or the like to remove impurities. As a method for mixing each component, a method of adding materials to a container equipped with a stirring device such as a mechanical stirrer or a magnetic stirrer and stirring and mixing is preferably used.

[0084] 1.2. Ink composition for base The ink composition for base may be a clear ink composition that does not contain a coloring material or a colored ink composition that contains a coloring material. When the ink composition for base is a colored ink composition, it may be colored in a chromatic color or an achromatic color. Further, the ink composition for base may be an aqueous ink composition or a solvent-based ink composition, and can be appropriately designed according to the image to be formed and the metallic ink composition.

[0085] The ink composition for base may contain a coloring material, water, an organic solvent, a surfactant, a resin, and other components. (1) Colorant When a colorant is contained in the ink composition for the substrate, the image formed by the inkjet can be colored as a colored metallic image. Examples of the colorant include colored materials and colorants of colors in the series from white through gray to black (achromatic colors). In this specification, any colorant may be referred to as a "coloring colorant" in some cases.

[0086] As the coloring colorant, either a pigment or a dye can be used, but from the viewpoint of storage stability such as light resistance, weather resistance, and gas resistance, a pigment is preferable. Examples of the ink composition for the substrate include cyan ink, yellow ink, magenta ink, black ink called process color ink, white ink, orange ink, green ink, red ink, blue ink called special color ink, and further ink forms with a low colorant concentration called light ink. When the ink composition for the substrate does not contain a colorant, the ink composition for the substrate becomes a clear ink.

[0087] Examples of the coloring pigment include white pigments, insoluble azo pigments, condensed azo pigments, azo lakes, azo pigments such as chelate azo pigments, phthalocyanine pigments, perylene and perinone pigments, anthraquinone pigments, quinacridone pigments, dioxane pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments and other polycyclic pigments, dye chelates (for example, basic dye type chelates, acid dye type chelates, etc.), dyed lakes (basic dye type lakes, acid dye type lakes), nitro pigments, nitroso pigments, aniline black, daylight fluorescent pigments, and the like.

[0088] Examples of the white pigment include metal oxides, metal compounds such as barium sulfate, and calcium carbonate. Examples of the metal oxide include titanium dioxide, zinc oxide, silica, alumina, magnesium oxide, and the like.

[0089] Specific examples of coloring pigments include, for example, C.I. Pigment Yellow 1 (Fast Yellow G), 2, 3, 12 (Disazo Yellow AAA), 13, 14, 16, 17, 24, 34, 35, 37, 42 (Yellow Iron Oxide), 53, 55, 73, 74, 75, 81, 83 (Disazo Yellow HR), 93, 94, 95, 97, 98, 100, 101, 104, 108, 109, 110, 117, 120, 128, 129, 138, 139, 150, 153, 154, 155, 180, 185, 213, C.I. Pigment Red 1, 2, 3, 5, 7, 17, 22 (Brilliant Fast Scarlet), 23, 31, 38, 48:2 (Permanent Red 2B (Ba)), 48:2 (Permanent Red 2B (Ca)), 48:3 (Permanent Red 2B (Sr)), 48:4 (Permanent Red 2B (Mn)), 49:1, 52:2, 53:1, 57:1 (Brilliant Carmine 6B), 60:1, 63:1, 63:2, 64:1, 81 (Rhodamine 6G Lake), 83, 88, 101 (Vermilion), 104, 105, 106, 112, 114, 122 (Quinacridone Magenta), 123, 146, 149, 166, 168, 170, 172, 177, 178, 179, 184, 185, 190, 193, 202, 209, 219, C.I. Pigment Violet 19, C.I. Pigment Blue 1, 2, 15 (Phthalocyanine Blue R), 15:1, 15:2, 15:3 (Phthalocyanine Blue G), 15:4, 15:6 (Phthalocyanine Blue E), 16, 17:1, 22, 56, 60, 63, C.I. Pigment Green 1, 4, 7, 8, 10, 17, 18, 36, etc. can be used. Note that pigments not described in the Color Index can also be used. Also, the above pigments can be used alone or in combination of two or more.

[0090] In the base ink composition, when a pigment is used as a coloring material, it is preferable to contain a dispersant for dispersing the pigment. The dispersant can be used without particular limitation as long as it can be used in this type of pigment ink, and examples include cationic dispersants, anionic dispersants, nonionic dispersants, and surfactants.

[0091] Examples of anionic dispersants include polyacrylic acid, polymethacrylic acid, acrylic acid-acrylonitrile copolymer, vinyl acetate-acrylic acid ester copolymer, acrylic acid-acrylic acid alkyl ester copolymer, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-acrylic acid-acrylic acid alkyl ester copolymer, styrene-methacrylic acid-acrylic acid alkyl ester copolymer, styrene-α-methylstyrene-acrylic acid copolymer, styrene-α-methylstyrene-acrylic acid-acrylic acid alkyl ester copolymer, styrene-maleic acid copolymer, vinyl naphthalene-maleic acid copolymer, vinyl acetate-ethylene copolymer, vinyl acetate-fatty acid vinyl ethylene copolymer, vinyl acetate-maleic acid ester copolymer, vinyl acetate-crotonic acid copolymer, vinyl acetate-acrylic acid copolymer, and the like.

[0092] Examples of nonionic dispersants include polyvinylpyrrolidone, polypropylene glycol, vinyl pyrrolidone-vinyl acetate copolymer, and the like.

[0093] Examples of surfactants as dispersants include anionic surfactants such as sodium dodecylbenzenesulfonate, sodium laurate, ammonium salts of polyoxyethylene alkyl ether sulfate, and nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkylamine, polyoxyethylene alkylamide. In particular, from the viewpoint of enhancing the dispersion stability of the pigment, it is preferable to use a styrene-(meth)acrylic acid copolymer.

[0094] Dyes may be used as coloring materials, and examples of such dyes include acid dyes, direct dyes, reactive dyes, and basic dyes in the water-soluble system, and disperse dyes, oil-soluble dyes, sublimation dyes, etc. in the water-dispersion system.

[0095] The above-exemplified coloring materials are examples of suitable coloring materials, and the present invention is not limited thereto. One or more of these coloring materials may be used, or a pigment and a dye may be used in combination.

[0096] The undercoat ink composition is more preferably a white ink composition containing a white pigment or a clear ink composition containing no coloring material. When the undercoat ink composition is a white ink composition or a clear ink composition, a metallic gloss image with higher brightness may be obtained.

[0097] When a coloring material is used in the undercoat ink composition, the content of the coloring material can be adjusted as appropriate, but is preferably 0.10% by mass or more and 20.0% by mass or less, more preferably 0.20% by mass or more and 15.0% by mass or less, still more preferably 1.0% by mass or more and 10.0% by mass or less. Further, 1.5% by mass or more and 5.0% by mass or less is preferable.

[0098] (2) Water The undercoat ink composition may contain water whether it is an aqueous ink or a solvent-based ink. As the water, it is preferable to use pure water or ultrapure water such as ion-exchanged water, ultrafiltration water, reverse osmosis permeated water, and distilled water. In particular, water sterilized by ultraviolet irradiation or hydrogen peroxide addition of these waters is preferable because it can suppress the generation of mold and bacteria over a long period.

[0099] (3) Organic solvent The undercoat ink composition may contain an organic solvent. When the undercoat ink composition is a solvent-based ink composition, the water content is preferably 1.0% by mass or less, more preferably 0.5% by mass or less, still more preferably 0.1% by mass or less, and particularly preferably no water. The organic solvent that can be used in the undercoat ink composition is the same as that described in "(organic solvent)" in the section of the above metallic ink composition, and is explained by replacing "metallic ink composition" in the same section with "undercoat ink composition".

[0100] (4) Surfactant The underlayer ink composition may contain a surfactant. The surfactant that can be used in the underlayer ink composition is the same as that described in "(Surfactant)" in the section of the above metallic ink composition, and is described by replacing "metallic ink composition" in the same section with "underlayer ink composition".

[0101] (5) Resin The underlayer ink composition may contain a resin. The resin that can be used in the underlayer ink composition is the same as that described in "(Resin)" in the section of the above metallic ink composition, and is described by replacing "metallic ink composition" in the same section with "underlayer ink composition".

[0102] (6) Other Components The underlayer ink composition may contain the components exemplified in "(Other Components)" in the section of the above metallic ink composition. Since the components are the same as those described in "(Other Components)", they are described by replacing "metallic ink composition" in the same section with "underlayer ink composition".

[0103] The underlayer ink composition is obtained by mixing the above-described components in an appropriate order and, if necessary, performing filtration or the like to remove impurities. As a method for mixing the components, a method of adding materials to a container equipped with a stirring device such as a mechanical stirrer or a magnetic stirrer and stirring and mixing them is preferably used.

[0104] The viscosity of the underlayer ink composition at 20°C is preferably 2 mPa·s or more and 15 mPa·s or less. When the viscosity of the metallic ink composition at 20°C is within the above range, an appropriate amount of the metallic ink composition is discharged from the nozzle, and the flight deflection and scattering of the metallic ink composition can be further reduced, so it can be preferably used in an inkjet recording apparatus.

[0105] 1.3. Relationship of Surface Tension In the ink set of the present embodiment, the surface tension of the metallic ink composition is set lower than that of the base ink composition. Therefore, the metallic ink composition easily spreads on the base ink composition. As a result, leaching of the metal pigment contained in the metallic ink composition easily occurs, and the metallic luster surface of the metal pigment particles is likely to be fixed along the surface of the recording medium. As a result, an image excellent in metallic luster is formed.

[0106] In the ink set, in terms of further improving the spreading of the metallic ink composition on the base ink composition, it is more preferable that the surface tension of the metallic ink composition is 0.5 mN / m or more lower than that of the base ink composition, more preferably 1.0 mN / m or more lower, and even more preferably 2.0 mN / m or more lower. In terms of preventing the spreading of the metallic ink composition on the base ink composition from becoming excessive, the difference between the surface tension of the metallic ink composition and the surface tension of the base ink composition is preferably 15.0 mN / m or less, more preferably 10.0 mN / m or less, and even more preferably 5.0 mN / m or less.

[0107] The surface tensions of the metallic ink composition and the base ink composition can be adjusted by the types and contents of components such as surfactants and solvents. Note that the surface tensions of both the metallic ink composition and the base ink composition are preferably 15.0 mN / m or more and 35.0 mN / m or less, more preferably 20.0 mN / m or more and 30.0 mN / m or less, and even more preferably 22.0 mN / m or more and 28.0 mN / m or less.

[0108] 1.4. Other ink compositions The ink set of the present embodiment may contain other ink compositions as long as it contains the above-described metallic ink composition and base ink composition that satisfy the relationship of surface tension. The ink set may further contain, for example, the above-described base ink composition regardless of the surface tension.

[0109] 1.5. Uses of the ink set, etc. The ink set of the present embodiment may use a metallic ink composition and an undercoat ink composition as inkjet inks and may be used in an inkjet recording method. Thereby, a high-definition metallic gloss image can be obtained more simply.

[0110] Further, in the ink set of the present embodiment, both the metallic ink composition and the undercoat ink composition may be solvent-based inks. By doing so, the relationship between the surface tensions of the two

[0111] 1.6. Operational Effects In the ink set of the present embodiment, the surface tension of the metallic ink composition is set lower than the surface tension of the undercoat ink composition. Therefore, the metallic ink composition easily wets and spreads on the undercoat ink composition. As a result, leafing of the metal pigment contained in the metallic ink composition is likely to occur, and the metallic gloss surface of the metal pigment particles is likely to be fixed along the surface of the recording medium. As a result, an image excellent in metallic gloss is formed.

[0112] Generally, when the metallic ink composition wets and spreads, the contact area between the metallic gloss image and the air increases. Since the metal pigment contained in the metallic ink composition of the ink set of the present embodiment is surface-treated, the metallic gloss of the image is likely to be maintained well. Therefore, according to the ink set of the present embodiment, an image capable of maintaining good metallic gloss for a long period can be obtained.

[0113] 2. Recording Method The recording method according to the present embodiment is a recording method using the above-described ink set, and includes a step of attaching an undercoat ink composition to a recording medium and a step of attaching a metallic ink composition to the attached undercoat ink composition.

[0114] According to this recording method, the metallic ink composition easily spreads on the base ink composition, and leafing of the metal pigment contained in the metallic ink composition easily occurs. Moreover, since the surface of the metal pigment is treated, the metallic luster is easily maintained well. Thereby, an image capable of maintaining good luster for a long period can be obtained.

[0115] 2.1. Recording medium The recording medium used in the recording method of this embodiment is not particularly limited. For example, various recording media such as plain paper, inkjet special paper (mat paper, glossy paper), glass, plastic films such as vinyl chloride, films obtained by coating a substrate with plastic or a receiving layer, metal, and printed wiring boards can be used. When the recording medium has an ink receiving layer, from the viewpoint of being less likely to be damaged by heat, it is preferable to print the recording medium without heating. On the other hand, when the recording medium does not have an ink receiving layer, from the viewpoint of increasing the drying speed and obtaining high gloss, it is preferable to perform recording by heating the recording medium.

[0116] 2.2. Base ink adhesion step The base ink composition is adhered to the recording medium. As a method for adhering the base ink composition to the recording medium, a non-contact method, a contact method, or a combination thereof can be used, such as an inkjet method, a method by coating, a method of coating the recording medium using various sprays, a method of immersing the recording medium in the base ink composition for coating, and a method of coating the recording medium with the base ink composition using a brush or the like.

[0117] When the base ink composition is adhered to the recording medium by the inkjet method, it is easy to efficiently form a predetermined image on the recording medium. Also, in this way, it is possible to efficiently perform printing of a small amount of various types with a small device.

[0118] 2.3. Metallic ink adhesion step In the metallic ink application step, a metallic ink composition is applied to the undercoat ink composition applied to the recording medium. As a method for applying the metallic ink composition, a non-contact method, a contact method, or a combination of both can be used, such as an inkjet method, a method by coating, a method of applying to the recording medium using various sprays, a method of applying by immersing the recording medium in the metallic ink composition, or a method of applying the metallic ink composition to the recording medium with a brush or the like.

[0119] When the metallic ink composition is applied to the recording medium by the inkjet method, it is easy to efficiently form a predetermined image on the recording medium. Also, in this way, it is possible to efficiently perform printing of a small amount of multiple types with a small-sized device.

[0120] 2.4. Order of steps, etc. The undercoat ink application step is performed prior to the metallic ink application step. In the ink set of the present embodiment, as described above, the surface tension of the metallic ink composition is smaller than the surface tension of the undercoat ink composition. Therefore, when the metallic ink composition is applied to a specific region of the recording medium after the undercoat ink composition is applied to the specific region of the recording medium, the wet spreading of the metallic ink composition becomes good. As a result, an image excellent in metallic luster can be formed. Also, as described above, since the surface of the metal pigment is treated, the metallic luster is easily maintained well. As a result, an image capable of maintaining good luster for a long period of time can be obtained.

[0121] When each step is performed by the inkjet method, ink droplets of the ink composition are attached to the recording medium from the inkjet head of the printer. At this time, the ink droplets are intermittently discharged at a predetermined timing and with a predetermined mass, whereby the ink droplets are attached to the recording medium, and a design such as a desired image, character, pattern, or color is formed (recorded).

[0122] The adhesion of the ink composition by the inkjet method can be carried out by either a serial type recording apparatus equipped with a serial type inkjet head or a line type recording apparatus equipped with a line type inkjet head.

[0123] 2.5. Other Processes In addition to the above-described metallic ink adhesion step and colored ink adhesion step, the recording method of the present embodiment may include a primary drying step of adhering ink to a heated recording medium, a secondary drying step of heating the recording medium after the ink is adhered, a lamination step, etc., and these steps may be performed multiple times.

[0124] 2.6. Recording Apparatus FIG. 1 is a schematic cross-sectional view showing the configuration of an example of an inkjet recording apparatus that can be used in the recording method of the present invention. As shown in FIG. 1, the inkjet recording apparatus 1 includes an inkjet head 2, an IR heater 3, a platen and a platen heater 4, a heating heater 5, a cooling fan 6, a preheater 7, and a blower fan 8. The overall operation of the inkjet recording apparatus 1 is controlled by a control unit CONT (not shown). The example of the recording apparatus in FIG. 1 is an example of a line printer, and recording is performed by discharging ink from the inkjet head 2 while the recording medium 10 is conveyed in the conveyance direction X. Primary drying is performed by the platen heater 4, the preheater 7, the blower fan 8, the IR heater 3, etc., and secondary drying is performed by the heating heater 5.

[0125] 3. Examples and Comparative Examples Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples. Hereinafter, "parts" and "%" are based on mass unless otherwise specified. The evaluation was performed under an environment of a temperature of 25.0°C and a relative humidity of 40.0% unless otherwise specified.

[0126] 3.1. Manufacture of Undercoat Ink Composition The components were mixed so as to have the formulations described in Table 1, and the undercoat ink compositions used in each example were prepared.

[0127]

Table 1

[0128] 3.2. Preparation of Metal Pigment Suspension A resin solubilized in acetone was coated on a PET substrate with a thickness of 20 μm using a roll coater. After coating, it was conveyed to an aluminum vacuum evaporator at a speed of 5 m / s, and an aluminum layer with a thickness of 20 nm was formed on the resin / PET substrate under a pressure of 4×10 -3 kPa. The prepared aluminum / resin / PET substrate was immersed in an acetone bath and irradiated with ultrasonic waves at 40 kHz to peel the aluminum pigment from the PET substrate. Then, after removing acetone with a centrifuge, an appropriate amount of diethylene glycol diethyl ether (DEDG) was added and pulverization was carried out to obtain an aluminum pigment suspension with an aluminum pigment concentration of 5% by mass.

[0129] After the pulverization process, the phosphorus-based compound shown in Table 2 was added to the obtained aluminum pigment suspension at 6 parts per 100 parts of aluminum, and heat treatment was carried out at 55 °C for 3 hours under irradiation with 28 kHz ultrasonic waves to react the phosphorus-based compound on the pigment surface, thereby obtaining an aluminum pigment dispersion liquid with high leafing ability. The aluminum pigment had a volume average particle diameter D50 of 0.5 μm and a thickness of 19 nm as tabular particles.

[0130] 3.3. Manufacture of Metallic Ink Composition Each component was mixed so as to have the formulation described in Table 2, and a metallic ink composition used in each example was prepared.

[0131]

Table 2

[0132] The abbreviations in Table 1 and Table 2 are as follows. ·TiO2 = 50%: Suspension of titanium dioxide pigment (white pigment) with a solid content of 50% by mass · Paraloid B60: Manufactured by Rohm and Haas, acrylic resin · DEDG: Diethylene glycol diethyl ether · MEDG: Diethylene glycol ethyl methyl ether · γBL: γ-Butyrolactone · BYK-350: Manufactured by BYK-Chemie GmbH, silicone surfactant · Disparon UVX-35: Manufactured by Kusumoto Chemicals, Ltd., anionic surfactant (acrylic type) · BYK-315N: Manufactured by BYK-Chemie GmbH, silicone surfactant · BYK-325: Manufactured by BYK-Chemie GmbH, silicone surfactant · BYK-333: Manufactured by BYK-Chemie GmbH, silicone surfactant · Megafac R-40: Manufactured by DIC Corporation, fluorine-based surfactant · AL=5%: Aluminum pigment suspension adjusted to a solid content of 50% by mass · JP512: Manufactured by Johoku Chemical Industry Co., Ltd., alkyl (C12, C14, C16, C18) acid phosphate · JP518S: Manufactured by Johoku Chemical Industry Co., Ltd., stearyl phosphate · FHP: Manufactured by Unimatech Co., Ltd., 2-(perfluorohexyl)ethylphosphonic acid · BTGH: Triethylene glycol monobutyl ether · BYK-3550: Manufactured by BYK-Chemie GmbH, silicone surfactant

[0133] In addition, Table 1 and Table 2 list the surface tensions of the respective compositions.

[0134] 3.4. Evaluation Test Recording test: Recording tester: SC-S606850 (a modified printer manufactured by Seiko Epson Corporation. The nozzle density of the nozzle row was 360 dpi, with 360 nozzles.)

[0135] Ink adhesion amount: For the undercoat ink composition, the adhesion amount was 3.0 mg / inch 2and the recording resolution was set to 1440×1440 dpi. The metallic ink composition was also applied at an application amount of 3.0 mg / inch 2 and recorded by overlaying on the metallic ink layer.

[0136] During ink application, the surface temperature of the recording medium was set to 45°C by a platen heater, and during heating by an after-heater, the temperature of the recording medium was set to 50°C.

[0137] Recording medium: Vinyl chloride film was used. In addition, Table 3 describes the undercoat ink composition and metallic ink composition used in each example, and the surface tension and the difference thereof (surface tension difference) "undercoat ink composition - metallic ink composition" are described.

[0138] 3.5. Initial gloss Initial gloss: Image quality evaluation of the recorded matter (60° gloss) Measurement of gloss: Using a gloss meter (MINOLTA MULTI GLOSS 268), the gloss at a flaring angle of 60° was measured, and the measured values were evaluated according to the following criteria and the results were described in Table 3. A: Over 450 B: 430 or more and 450 or less C: 400 or more and 430 or less D: 350 or more and 400 or less E: Less than 350

[0139] 3.6. Gloss after durability test Gloss after durability test: The recorded matter for which the initial gloss was measured was subjected to a durability test. Durability test conditions: It was left in a high-temperature and high-humidity chamber at 50°C and 80% RH for one week, and then the gloss was measured in the same manner as the above measurement of gloss. The measured values were evaluated according to the following criteria based on the decrease in gloss from the initial state, and the results were described in Table 3. A: Decrease is 10 or less B: Decrease is more than 10 and 20 or less C: Decrease is more than 20 and 50 or less D: Decrease is more than 50 and 70 or less E: Decrease is more than 70

[0140]

Table 3

[0141] 3.7. Evaluation Results As is clear from Tables 1 to 3, in the recording using the ink sets of the examples in which the surface tension of the metallic ink composition is lower than that of the undercoat ink composition and the metal pigment is the metal particles whose surfaces are treated, good metallic luster and an image with good durability thereof were obtained.

[0142] The present invention includes a configuration substantially the same as the configuration described in the embodiments, for example, a configuration having the same functions, methods, and results, or a configuration having the same objectives and effects. Further, the present invention includes a configuration in which a non-essential part of the configuration described in the embodiments is replaced. Further, the present invention includes a configuration having the same operational effects as the configuration described in the embodiments or a configuration capable of achieving the same objective. Further, the present invention includes a configuration in which a known technique is added to the configuration described in the embodiments.

[0143] The following contents are derived from the above-described embodiments and modified examples.

[0144] An ink set is an ink set including a metallic ink composition containing a metal pigment and an undercoat ink composition, wherein the surface tension of the metallic ink composition is lower than that of the undercoat ink composition, and the metal pigment is metal particles whose surfaces are treated.

[0145] According to this ink set, the metallic ink composition easily spreads and wets on the undercoat ink composition, and leafing of the metal pigment contained in the metallic ink composition easily occurs. Moreover, since the surfaces of the metal pigments are treated, the metallic luster is easily maintained well. Thereby, an image capable of maintaining good luster for a long period can be obtained.

[0146] In the above ink set, The surface tension of the metallic ink composition may be 0.5 mN / m or more lower than the surface tension of the base ink composition.

[0147] According to this ink set, the metallic ink composition is more likely to spread wet on the base ink composition, and leafing of the metal pigment contained in the metallic ink composition is more likely to occur.

[0148] In the above ink set, The base ink composition may be a white ink composition or a clear ink composition.

[0149] In the above ink set, The surface of the particles of the metal pigment may be treated with a phosphorus compound or a silicon compound as a surface treatment agent.

[0150] According to this ink set, metallic luster can be maintained better.

[0151] In the above ink set, The particles of the metal pigment may be flaky.

[0152] According to this ink set, an image with stronger metallic luster can be formed.

[0153] In the above ink set, The average thickness of the particles of the metal pigment may be 5.0 nm or more and 90.0 nm or less.

[0154] In the above ink set, The particles of the metal pigment may be made of aluminum or an aluminum alloy.

[0155] According to this ink set, an image with excellent metallic feeling can be obtained.

[0156] In the above ink set, The volume average particle diameter D50 of the particles of the metallic pigment may be 0.2 μm or more and 1.0 μm or less.

[0157] According to this ink set, an image excellent in metallic feeling can be obtained.

[0158] In the above ink set, The metallic ink composition may be an inkjet ink.

[0159] According to this ink set, a high-definition metallic luster image can be obtained more simply.

[0160] In the above ink set, The metallic ink composition and the underlayer ink composition may each be a solvent-based ink.

[0161] The recording method is a recording method using any of the above ink sets, A step of attaching the underlayer ink composition to a recording medium, A step of attaching the metallic ink composition to the attached underlayer ink composition, and includes.

[0162] According to this recording method, the metallic ink composition easily wets and spreads on the underlayer ink composition, and leafing of the metallic pigment contained in the metallic ink composition easily occurs. Moreover, since the surface of the metallic pigment is treated, the metallic luster is easily maintained well. Thereby, an image capable of maintaining good luster for a long period can be obtained.

Explanation of Signs

[0163] 1... Inkjet recording apparatus, 2... Inkjet head, 3... IR heater, 4... Platen and platen heater, 5... Heating heater, 6... Cooling fan, 7... Preheater, 8... Blower fan, 10... Recording medium, X... Conveying direction

Claims

1. A recording method using an ink set including a metallic ink composition containing a metallic pigment and an undercoat ink composition, the method including: a step of attaching the undercoat ink composition to a recording medium by an inkjet method; a step of attaching the metallic ink composition to the attached undercoat ink composition by an inkjet method; wherein the recording medium is a plastic film which is a low-absorbency recording medium; the surface tension of the metallic ink composition is lower than the surface tension of the undercoat ink composition; the metallic pigment is metal particles whose surface is treated with a phosphorus-based compound having an alkyl group with 14 or more carbon atoms; the metal particles are flat plate-shaped, and the volume average particle diameter D50 is 0.05 μm or more and 0.5 μm or less; the undercoat ink composition is a solvent-based ink; the metallic ink composition is a solvent-based ink containing 70.0% by mass or more of an organic solvent with respect to the total mass of the metallic ink composition; the organic solvent includes one or more selected from glycol diethers and lactones, the recording method.

2. The recording method according to claim 1, wherein the surface tension of the metallic ink composition is 0.5 mN / m or more lower than the surface tension of the undercoat ink composition.

3. The recording method according to claim 1 or claim 2, wherein the undercoat ink composition is a white ink composition or a clear ink composition.

4. The recording method according to any one of claims 1 to 3, wherein the metal particles of the metallic pigment are surface-treated with a phosphorus-based compound having an alkyl group with 14 to 35 carbon atoms as a surface treatment agent.

5. The recording method according to any one of claims 1 to 4, including a primary drying step, wherein the primary drying step is to attach the metallic ink composition and the undercoat ink composition to the heated recording medium.

6. The recording method according to claim 5, wherein the average thickness of the metal particles of the metallic pigment is 5.0 nm or more and 90.0 nm or less.

7. The recording method according to any one of claims 1 to 6, wherein the metal particles of the metallic pigment are made of aluminum or an aluminum alloy.

8. The recording method according to any one of claims 1 to 7, wherein the volume average particle diameter D50 of the metal particles of the metallic pigment is 0.2 μm or more and 0.5 μm or less.

9. ​ ​ ​ ​ ​ ​ ​ ​ ​ In any one of claims 1 to 8, the metal particles of the metal pigment are surface-treated with a phosphorus-based compound having an alkyl group with 18 or more carbon atoms as a surface treatment agent Recording method.

10. In any one of claims 1 to 9, the recording medium is made of vinyl chloride, recording method.

11. In any one of claims 1 to 10, the metallic ink composition contains a fixing resin, recording method.

12. In any one of claims 1 to 11, the metallic ink composition contains a silicone-based surfactant, recording method.

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