JP7147821B2 - Inkjet recording method and inkjet printer - Google Patents

Description

TECHNICAL FIELD The present invention relates to an ink set, an inkjet recording method, and a recorded matter, and more particularly to an ink set, an inkjet recording method, and a recorded matter capable of forming a coating film having metallic luster.

Conventionally, in order to form a coating film with a metallic luster on a printed material, printing inks using gold or silver powder made from fine brass or aluminum particles as pigments, foil stamping using metal foil, and metal foil have been used. A thermal transfer method or the like is used.

However, in a coating film made of printing ink using gold powder or silver powder, the average particle size of the metal powder used is as large as 10 μm to 30 μm, and although matte metallic luster can be obtained, it is difficult to obtain specular gloss. there were. Also, in foil stamping or thermal transfer using a metal foil, an adhesive is applied to the printing medium, a smooth metal foil is pressed thereon, the recording medium and the metal foil are brought into close contact with each other, and the metal foil and the recording medium are heat-fused. Take the method of wearing it. Therefore, although a relatively good gloss can be obtained, the number of manufacturing processes is increased and pressure and heat are applied during the manufacturing process, so there is a limitation that the recording medium is limited to a recording medium that is resistant to heat and deformation.

In recent years, there have been many applications of inkjet in printing, one of which is metallic printing. For example, Japanese Patent Application Laid-Open No. 2002-179960 discloses a technique of forming a metal film on the surface of plastic spherical particles and printing an ink composition containing the pigment by inkjet printing (Patent Document 1). ). However, in order to obtain a high metallic luster, it is necessary to deform and flatten the spheres to smooth the surface, and this technology requires simultaneous pressing with rollers and heat treatment. Therefore, in this respect, the apparatus and manufacturing process are inevitably complicated, and the recording medium is also restricted.

Further, Japanese Patent Laid-Open No. 2003-292836 discloses a technique using an ink composition in which a precious metal colloid such as gold or silver is dispersed (Patent Documents 2 and 3). However, when the noble metal colloid gives priority to dispersion stability and has a particle size as small as several nanometers to several tens of nanometers, color development derived from plasmon absorption occurs, and metallic luster cannot be obtained as an ink composition. In this case, after the coating film is dried, it is heat-treated at 150° C. or higher to fuse the colloidal particles, thereby obtaining a metallic luster. Further, when the particle size is increased in favor of metallic luster, the dispersion stability is lowered, the problem of aggregation and sedimentation cannot be avoided, and the storage life of the ink composition is significantly reduced. In addition, as is obvious, the use of noble metals as a material greatly increases the cost of the ink composition, so that it can be used only for applications with high added value, which is disadvantageous in terms of cost.

In conventional metallic ink compositions, a method of mixing a metallic pigment and a coloring material and using it as one ink composition has been seen, but in this method, the metallic pigment and the coloring material are separated when printed. There is a problem that only the metal pigment settles and aggregates during storage, and only the coloring material is absorbed into the recording medium, leaving only the metal pigment on the surface. This caused printing errors.

Japanese Patent Application Laid-Open No. 2002-179960 JP-A-2003-292836 Japanese Patent Application Laid-Open No. 2003-306625

The present invention focuses on aluminum as a relatively inexpensive metal material, and forms an ink set containing an ink composition with high metallic specular gloss to form a coating film with metallic gloss in any color tone on a printed matter. An object of the present invention is to provide an ink set capable of

In order to solve the above problems, the present inventors conducted extensive studies and found that a metal pigment dispersion using a specific metal pigment, an ink composition, an ink jet recording method, and a recorded matter, which were conventionally impossible. The inventors have found that a printed matter having a high specular gloss can be obtained. The present invention has been made based on such findings, and provides the following inventions.

[1] At least one selected from the group consisting of an oil-based ink composition containing a metal pigment, a chromatic ink composition containing a chromatic pigment, a black ink composition containing a black pigment, and a white ink composition containing a white pigment and at least one oil-based ink composition.

Preferred aspects of the above invention are as follows. [2] When the metal pigment is a tabular grain, and the major axis on the plane of the tabular grain is X, the minor axis is Y, and the thickness is Z, the area of the XY plane of the tabular grain The ink set according to [1], wherein the metal pigment has a 50% average particle diameter R50 of the obtained equivalent circle diameter of 0.5 to 3 μm and satisfies the condition of R50/Z>5. [3] The ink set according to [1] or [2], wherein the metal pigment is aluminum or an aluminum alloy; [4] The metal pigment is produced by crushing a deposited metal film. [1] The ink set according to any one of [1] to [3]; [5] The oil-based ink composition containing the metal pigment contains the metal pigment, an organic solvent, and a resin, [1] The ink set according to any one of [4]; [6] Any one of [1] to [5], wherein the oil-based ink composition has a pigment concentration of 0.1 to 10.0% by weight. [7] The ink set according to [5] or [6], wherein the organic solvent contains one or more alkylene glycol ethers that are liquid at normal temperature and normal pressure; [8] The organic solvent is , alkylene glycol diether, alkylene glycol monoether and lactone; [9] the resin is polyvinyl butyral, cellulose acetate butyrate, polyacryl polyol, polyurethane , a vinyl chloride-vinyl acetate copolymer and/or a resin emulsion thereof; the ink set according to any one of [5] to [8]; The ink set according to any one of [5] to [9], wherein the oil-based ink composition contains at least one or more acetylene glycol-based and/or silicone-based surfactants; [11] the chromatic pigment; is an organic pigment, the black pigment is carbon black, and the white pigment is titanium dioxide and/or a hollow resin emulsion; [12] In an inkjet recording method in which droplets of an ink composition are ejected and adhered to a recording medium for recording, an image is formed using the ink set according to any one of [1] to [11]. [13] an oil-based ink composition containing the metal pigment, and at least one selected from the group consisting of the chromatic ink composition, the black ink composition, and the white ink composition; , are simultaneously ejected to form an image; [14] After forming an image using the oil-based ink composition containing the metal pigment, the chromatic ink composition is used to form an image. The inkjet recording method according to [12], wherein an image of any color tone is formed by After forming an image using the oil-based ink composition containing The inkjet recording method according to [12]; [16] The inkjet recording method according to any one of [12] to [15], wherein the method for ejecting the ink composition is a non-heating method; 17] The inkjet recording method according to any one of [12] to [16], wherein printing is performed by heating the recording medium; Inkjet recording method; [19] The inkjet recording method according to [18], wherein the heating is performed before and/or simultaneously with and/or after printing; [20] Any of [12] to [19] A recorded matter recorded by the inkjet recording method according to item (1).

According to the ink set, inkjet recording method, and recorded matter of the present invention, the use of an ink composition containing a metallic pigment makes it possible to form an image having a high metallic gloss (so-called metallic gloss) on a recording medium. Furthermore, by forming an ink set by combining a chromatic ink composition, a black ink composition, and a white ink composition, an image that could not be realized with a conventional ink set, i.e., an image having metallic luster of any color tone. can be formed.

[Ink set] As described above, the ink set of the present embodiment includes an oil-based ink composition containing a metal pigment, a chromatic ink composition containing a chromatic pigment, a black ink composition containing a black pigment, and a white pigment. and at least one or more oil-based ink compositions selected from the group consisting of white ink compositions containing. As a result, it is possible to form an image in which metallic luster is added to the color tones of the chromatic pigment, black pigment, and white pigment.

The metal pigment (also referred to as metallic pigment) is a tabular particle. The 50% average particle diameter R50 of the circle equivalent diameter obtained from the area of is preferably 0.5 to 3 μm, and the metal pigment satisfies the condition of R50/Z>5.

The term "tabular grain" refers to a grain having a substantially flat surface (XY plane) and a substantially uniform thickness (Z). Since the tabular particles are produced by crushing the vapor-deposited metal film, metal particles having substantially flat surfaces and substantially uniform thickness can be obtained. Therefore, it is possible to define X as the major axis of the tabular grain, Y as the minor axis, and Z as the thickness.

The "equivalent circle diameter" is the diameter of a circle, assuming that the substantially flat surface (XY plane) of a metallic pigment tabular particle is a circle having the same projected area as that of the metallic pigment particle. is. For example, when the substantially flat surface (XY plane) of a tabular particle of a metallic pigment is a polygon, the diameter of the circle obtained by converting the projection plane of the polygon into a circle is the diameter of the metallic pigment. It is called equivalent circle diameter of tabular grains.

The 50% average particle diameter R50 of the equivalent circle diameter obtained from the area of the XY plane of the tabular particles is more preferably 0.5 to 3 μm, more preferably 0.75 to 0.75, from the viewpoint of metallic luster and printing stability. More preferably, it is 2 μm.

From the viewpoint of ensuring high metallic luster, the relationship between the 50% average particle diameter R50 of the equivalent circle diameter and the thickness Z is preferably R50/Z>5.

The metallic pigment is preferably aluminum or an aluminum alloy from the viewpoint of cost and the viewpoint of ensuring metallic luster. When an aluminum alloy is used, another metallic or non-metallic element that can be added to aluminum is not particularly limited as long as it has metallic luster, but silver, gold, platinum, nickel, chromium, tin , zinc, indium, titanium, copper, etc., and at least one of these elements, alloys thereof, and mixtures thereof is preferably used.

The method for producing the metallic pigment includes, for example, the metal or alloy layer and the release resin of the composite pigment raw material, which has a structure in which a release resin layer and a metal or alloy layer are sequentially laminated on the surface of a sheet-like substrate. The particles are separated from the sheet-like substrate with the interface of the layer as a boundary, pulverized, and finely divided to obtain tabular grains. Then, where X is the major axis on the plane of the obtained tabular grain, Y is the minor axis, and Z is the thickness, the 50% average grain of the equivalent circle diameter obtained from the area of the XY plane of the tabular grain. Those having a diameter R50 of 0.5 to 3 μm and satisfying the condition of R50/Z>5 are fractionated.

The major axis X, minor axis Y and circle equivalent diameter on the plane of the metallic pigment (flat-plate-like particles) can be measured using a particle image analyzer. As the particle image analyzer, for example, flow type particle image analyzers FPIA-2100, FPIA-3000 and FPIA-3000S manufactured by Sysmex Corporation can be used.

The metal or alloy layer is preferably formed by vacuum deposition, ion plating or sputtering.

The metal or alloy layer has a thickness of 20 nm or more and 100 nm or less. As a result, a pigment having an average thickness of 20 nm or more and 100 nm or less can be obtained. When the thickness is 20 nm or more, the reflectivity and luster are excellent, and the performance as a metallic pigment is improved. .

The release resin layer in the composite pigment raw material is an undercoat layer of the metal or alloy layer, and is a release layer for improving the release property from the surface of the sheet-like substrate. As the resin used for this peeling resin layer, for example, polyvinyl alcohol, polyvinyl butyral, polyethylene glycol, polyacrylic acid, polyacrylamide, cellulose derivatives, polyvinyl butyral, acrylic acid polymer, or modified nylon resin is preferable.

A layer is formed by coating a recording medium with a solution of one or a mixture of two or more of the above, followed by drying and the like. Additives such as a viscosity modifier can be incorporated after coating.

The peeling resin layer is applied by commonly used methods such as gravure coating, roll coating, blade coating, extrusion coating, dip coating and spin coating. After coating and drying, if necessary, the surface is smoothed by calendering.

The thickness of the peeling resin layer is not particularly limited, but is preferably 0.5 to 50 μm, more preferably 1 to 10 μm. If it is less than 0.5 µm, the amount of the dispersing resin is insufficient, and if it exceeds 50 µm, when it is rolled, it tends to separate from the pigment layer at the interface.

Examples of the sheet-like substrate include, but are not limited to, polyester films such as polytetrafluoroethylene, polyethylene, polypropylene, and polyethylene terephthalate; polyamide films such as nylon 66 and nylon 6; polycarbonate films, triacetate films, and polyimide films. A type film is mentioned. A preferred sheet-like substrate is polyethylene terephthalate or a copolymer thereof.

Although the thickness of these sheet-like substrates is not particularly limited, it is preferably 10 to 150 μm.
If the thickness is 10 μm or more, there is no problem in handleability in the process or the like, and if it is 150 μm or less, there is no problem in rolling, peeling, etc., because the flexibility is high.

Further, 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 silicon oxide layer and a protective resin layer.

The silicon oxide layer is not particularly limited as long as it contains silicon oxide, but is preferably formed from a silicon alkoxide such as tetraalkoxysilane or a polymer thereof by a sol-gel method.

A coating film of a silicon oxide layer is formed by applying an alcohol solution in which the above silicon alkoxide or a polymer thereof is dissolved, followed by heating and baking.

The protective resin layer is not particularly limited as long as it is a resin that does not dissolve in a dispersion medium. Examples thereof include polyvinyl alcohol, polyethylene glycol, polyacrylic acid, polyacrylamide, and cellulose derivatives. Alternatively, it is preferably formed from a cellulose derivative.

A layer is formed by applying an aqueous solution of one or a mixture of two or more of the above resins, followed by drying or the like. The coating liquid may contain additives such as a viscosity modifier.

The application of the silicon oxide and the resin is performed by the same method as the application of the release resin layer.

Although the thickness of the protective layer is not particularly limited, it is preferably in the range of 50 to 150 nm. If it is less than 50 nm, the mechanical strength is insufficient, and if it exceeds 150 nm, the strength becomes too high, making it difficult to pulverize and disperse, and sometimes exfoliate at the interface with the metal or alloy layer.

Further, a coloring material layer may be provided between the "protective layer" and the "metal or alloy layer".

The coloring material layer is introduced to obtain an arbitrary colored composite pigment, and in addition to the metallic luster and luster of the metallic pigment used in the present invention, it can contain a coloring material capable of imparting an arbitrary color tone and hue. It is not particularly limited as long as it is. As the colorant used in this colorant layer, either a dye or a pigment may be used. Also, known dyes and pigments can be appropriately used.

In this case, the "pigment" used in the colorant layer means natural pigments, synthetic organic pigments, synthetic inorganic pigments and the like defined in the general field of pigment chemistry, and the "composite pigment" and the like of the present invention. , which is processed into a laminated structure.

Although the method for forming the coloring material layer is not particularly limited, it is preferably formed by coating.

In addition, when the colorant used in the colorant layer is a pigment, it is preferable to further contain a colorant-dispersing resin. It is preferable to form a resin thin film by dispersing or dissolving the additive in a solvent, forming a uniform liquid film by coating as a solution, and then drying it.

In the production of the composite pigment raw material, it is preferable from the standpoint of work efficiency that both the coloring material layer and the protective layer are formed by coating.

The composite pigment raw material may have a layer structure having a plurality of sequentially laminated structures of the release resin layer and the metal or alloy layer. At that time, the total thickness of the laminated structure consisting of a plurality of metal or alloy layers, that is, the metal or alloy layer excluding the sheet-like substrate and the release resin layer immediately above it - the release resin layer - the metal or alloy layer , or the thickness of the peeling resin layer-metal or alloy layer is preferably 5000 nm or less. If it is 5000 nm or less, even when the composite pigment base is rolled into a roll, cracking and peeling are unlikely to occur, and storage stability is excellent. Moreover, even when it is made into a pigment, it is excellent in brilliance and is therefore preferable.

Moreover, a structure in which a release resin layer and a metal or alloy layer are sequentially laminated on both sides of the sheet-like base material can also be mentioned, but it is not limited to this.

The method of peeling from the sheet-like substrate is not particularly limited, but a method of immersing the composite pigment raw material in a liquid, or immersing it in a liquid and performing ultrasonic treatment at the same time to peel it off. A method of pulverizing the treated and exfoliated composite pigment is preferred.

In the pigment obtained as described above, the release resin layer functions as a protective colloid, and a stable dispersion can be obtained simply by performing a dispersion treatment in a solvent. Further, in the ink composition using the pigment, the resin derived from the release resin layer also has a function of imparting adhesiveness to a recording medium such as paper.

The oil-based ink composition used in the ink set of this embodiment contains the above-described metallic pigment, organic solvent, and resin.

The concentration of the metallic pigment in the ink composition is preferably 0.1 to 10.0% by weight.

When the concentration of the metallic pigment in the ink composition is 0.1% by weight or more and less than 1.5% by weight, by ejecting an amount of ink that cannot sufficiently cover the printing surface, a half-mirror-like glossy surface, that is, Although it has a glossy feel, it is possible to print a texture that allows the background to be seen through, and by ejecting a sufficient amount of ink to cover the printed surface, it is possible to form a highly glossy metallic surface. Therefore, for example, it is suitable for forming a half-mirror image on a transparent recording medium or expressing a highly glossy metallic surface. In addition, when the concentration of the metallic pigment in the ink composition is 1.5% by weight or more and 3.0% by weight or less, the metallic pigment is randomly arranged on the printing surface, so high gloss cannot be obtained, and matte tone is obtained. A metallic luster surface can be formed. Therefore, for example, it is suitable for forming a shielding layer in a transparent recording medium.

The organic solvent is preferably a polar organic solvent such as alcohols (e.g., methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, isopropyl alcohol, or fluorinated alcohol), ketones (e.g., acetone, methyl ethyl ketone, or cyclohexanone, etc.), carboxylic acid esters (e.g., methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, ethyl propionate, etc.), or ethers (e.g., diethyl ether, dipropyl ether, tetrahydrofuran, or dioxane, etc.) can be used.

In particular, the organic solvent preferably contains one or more alkylene glycol ethers that are liquid at normal temperature and normal pressure.

Alkylene glycol ethers are ethylene glycols based on aliphatic, double-bonded allyl and phenyl groups of methyl, n-propyl, i-propyl, n-butyl, i-butyl, hexyl and 2-ethylhexyl. They are colorless and have little odor, and have ether groups and hydroxyl groups in their molecules, so they have the properties of both alcohols and ethers, and are liquid at room temperature. . In addition, there are a monoether type in which only one hydroxyl group is substituted and a diether type in which both hydroxyl groups are substituted, and a plurality of these types can be used in combination.

In particular, the organic solvent is preferably a mixture of alkylene glycol diether, alkylene glycol monoether and lactone.

Alkylene glycol monoethers include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monophenyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, Diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene Glycol monoethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether and the like can be mentioned.

Alkylene glycol diethers include ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol dibutyl ether, tetra Ethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol dibutyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether and the like.

Lactones include γ-butyrolactone, δ-valerolactone, ε-caprolactone and the like.

By adopting such a suitable configuration, the object of the present invention can be further achieved.

Examples of resins used in the oil-based ink composition include acrylic resins, styrene-acrylic resins, rosin-modified resins, terpene-based resins, polyester resins, polyamide resins, epoxy resins, vinyl chloride resins, and vinyl chloride-vinyl acetate copolymers. Coalescence, cellulose resins (eg, cellulose acetate butyrate, hydroxypropyl cellulose), polyvinyl butyral, polyacrylic polyol, polyvinyl alcohol, polyurethane and the like.

Non-aqueous emulsion type polymer particles (NAD=Non Aqueous Dispersion) can also be used as the resin. This is a dispersion liquid in which fine particles of polyurethane resin, acrylic resin, acrylic polyol resin, etc. are stably dispersed in an organic solvent. For example, polyurethane resins include "Samprene IB-501" and "Samprene IB-F370" manufactured by Sanyo Chemical Industries, Ltd., and acrylic polyol resins include "N-2043-60MEX" and "N-2043-60MEX" manufactured by Harima Chemicals. -2043-AF-1” and the like.

The resin emulsion is preferably added in an amount of 0.1% by weight or more and 10% by weight or less in the ink composition in order to further improve the fixability of the pigment to the recording medium. If the amount added is excessive, printing stability cannot be obtained, and if the amount added is too small, fixability will be insufficient.

The ink composition preferably contains at least one type of glycerin, polyalkylene glycol, or saccharides. The total amount of one or more types of glycerin, polyalkylene glycol, or saccharide is preferably 0.1% by weight or more and 10% by weight or less in the ink composition.

By adopting such a preferable configuration, it is possible to suppress the drying of the ink, prevent clogging, stabilize the ejection of the ink, and improve the image quality of the recorded matter.

Polyalkylene glycol is a linear polymer compound having a repeating structure of ether bonds in the main chain, and is produced, for example, by ring-opening polymerization of cyclic ether.

Specific examples of polyalkylene glycol include polymers such as polyethylene glycol and polypropylene glycol, ethylene oxide-propylene oxide copolymers and derivatives thereof. Any copolymer such as a random copolymer, a block copolymer, a graft copolymer and an alternating copolymer can be used as the copolymer.

Preferred specific examples of polyalkylene glycol include those represented by the following formula.

HO-( _CnH2nO )m-H
(In the above formula, n represents an integer of 1 to 5 and m represents an integer of 1 to 100)

In the above formula, ( _CnH2nO )m may be a constant or a combination of two or more numbers within the range of the integer value n. For example, when n is 3, it is (C ₃ H ₆ O)m, and when n is a combination of 1 and 4, it is (CH ₂ O--C ₄ H ₈ O)m. Also, the integer value m may be a constant or a combination of two or more numbers within its range. For example, in the above example, (CH ₂ O) ₂₀ —(C ₂ H ₄ O) ₄₀ when m is 20 and 40, and (CH ₂ O ) ₁₀ -(C ₄ H ₈ O) ₃₀ .
Further, the integer values n and m may be combined arbitrarily within the above ranges.

Examples of sugars include monosaccharides such as pentose, hectose, heptose, and octose, polysaccharides such as disaccharides, trisaccharides, and tetrasaccharides, and their derivatives such as sugar alcohols and reduced derivatives such as deoxy acids, and aldonic acids and uronic acids. Examples thereof include oxidized derivatives, dehydrated derivatives such as glycosene, amino acids, thiosugars, and the like. Polysaccharides refer to sugars in a broad sense, and include substances that exist widely in nature, such as alginic acid, dextrin, and cellulose.

The oil-based ink composition preferably contains at least one or more acetylene glycol-based surfactants and/or silicone-based surfactants. The surfactant is preferably added in an amount of 0.01% by weight or more and 10% by weight or less based on the pigment content in the ink composition.

With such a suitable configuration, the wettability of the oil-based ink composition to the recording medium is improved, and fast fixability can be obtained.

Examples of acetylene glycol-based surfactants include Surfynol 465 (trademark), Surfynol 104 (trademark) (trade names, manufactured by Air Products and Chemicals, Inc.), Olfine STG (trademark), Olfine E1010 (trademark) ( The above trade names, manufactured by Nissin Kagaku Co., Ltd.) and the like are preferably mentioned.

As the silicone-based surfactant, it is preferable to use polyester-modified silicone or polyether-modified silicone. Specific examples include BYK-347, BYK-348, BYK-UV3500, BYK-UV3510, BYK-UV3530, and BYK-UV3570 (BYK-Chemie Japan).

The oil-based ink composition can be prepared by a known conventional method. For example, after first mixing the metallic pigment, the dispersant, and the liquid medium described above, a pigment dispersion is prepared using a ball mill, bead mill, ultrasonic waves, jet mill, or the like, and adjusted to have the desired ink properties. do. Subsequently, the binder resin, the liquid medium, and other additives (for example, a dispersing aid and a viscosity modifier) can be added with stirring to obtain a pigment ink composition.

In addition, the composite pigment stock may be once ultrasonically treated in a liquid medium to form a composite pigment dispersion, and then mixed with the necessary ink liquid medium. An ink composition can be obtained as it is by ultrasonically treating it in an ink liquid medium.

Although physical properties of the oil-based ink composition are not particularly limited, for example, the surface tension is preferably 20 to 50 mN/m. When the surface tension is less than 20 mN/m, the ink composition wets and spreads on the surface of the inkjet recording printer head or oozes out, making it difficult to eject ink droplets. , it may not spread well on the surface of the recording medium, and good printing may not be possible.

Next, the chromatic ink composition, black ink composition, and white ink composition used in the ink set of the present embodiment will be described.

A chromatic ink composition is an ink composition containing a chromatic pigment. "Chromatic colors" refer to all colors other than those in the series from white through gray to black (achromatic colors). As the chromatic pigment, an organic pigment is preferable from the viewpoint of storage stability such as light resistance, weather resistance and gas resistance.

Specifically, azo pigments such as insoluble azo pigments, condensed azo pigments, azo lakes, chelate azo pigments, phthalocyanine pigments, perylene and perinone pigments, anthraquinone pigments, quinacridone pigments, dioxane pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, etc. polycyclic pigments, dye chelates (e.g. basic dye chelates, acid dye chelates, etc.), dye lakes (basic dye lakes, acid dye lakes), nitro pigments, nitroso pigments, aniline black, daylight Fluorescent pigments and the like are included. The above pigments may be used singly or in combination of two or more. More specifically, for example, C.I. 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. I. Pigment Red 1, 2, 3, 5, 7, 17, 22 (Brilliant First 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 (red red), 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. I. Pigment Violet 19, C.I. 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. I. Pigment Green 1, 4, 7, 8, 10, 17, 18, 36, etc. can be used.

Any pigment not listed in the Color Index can be used as long as it is insoluble in water.

A black ink composition is an ink composition containing a black pigment. Black pigments include carbon black (C.I. Pigment Black 7) such as furnace black, lamp black, acetylene black, and channel black, or copper oxide, iron oxide (C.I. Pigment Black 11), and the like. Organic pigments such as metals and aniline black (C.I. Pigment Black 1) can be used, but carbon black, which has a relatively low specific gravity and does not readily settle in water, is preferred for inkjet use. You may use these as 1 type or 2 types of mixtures.

A white ink composition is an ink composition containing a white pigment. White pigments include Group IV element oxides such as titanium dioxide and zirconia dioxide. Other examples include calcium carbonate, calcium sulfate, zinc oxide, barium sulfate, barium carbonate, silica, alumina, kaolin, clay, talc, clay, aluminum hydroxide, magnesium carbonate, white hollow resin emulsion, etc., and these are preferred. It is one or a mixture of two or more selected from the group consisting of

A hollow resin emulsion is an oily dispersion containing hollow polymer fine particles, wherein the hollow polymer fine particles are composed of a plurality of fine particle subgroups, and each fine particle subgroup is adjacent to each other in terms of average particle size. Refers to an oily dispersion in which the average particle size difference is less than 100 nm.

From the viewpoint of whiteness, the primary particle size of the white pigment is preferably 1.1.

Here, the term "primary particle size" refers to the size of a single crystal or a particle formed by an aggregation of crystallites close to it. The primary particle size of the pigment is measured by electron microscopy. This method measures the size of pigment particles from an electron micrograph.It is more reliable by dispersing the pigment in an organic solvent, fixing it on a support film, and processing the image from the transmission electron micrograph. value can be obtained. Specifically, the short axis diameter and long axis diameter of each primary particle diameter are measured, the diameter of a circle equal to the area is calculated arithmetically, and this is used as the primary particle diameter. Particles are randomly selected and averaged. If the same reliability can be obtained by other measurement methods, there is no problem, but if there is a substantial difference in the numerical values, the value obtained by the above method is adopted.

The chromatic ink composition and the black ink composition may be determined as appropriate, but the content of the ink composition is 0.1 to 30% by weight, preferably 0.5 to 12% by weight. From the viewpoint of whiteness, the content of the pigment in the white ink composition is preferably 1.0% by weight or more, more preferably 5.0% by weight or more, and still more preferably 10% by weight or more and 20% by weight or less. .

The ink composition used in the ink set of the present embodiment preferably contains a pigment as a colorant and a dispersant for dispersing the pigment. Any dispersant that can be used in this type of pigment ink can be used without particular limitation, and examples thereof include cationic dispersants, anionic dispersants, nonionic dispersants, and surfactants.

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-alkyl acrylate copolymer, styrene-methacrylic acid-alkyl acrylate copolymer, styrene-α-methylstyrene-acrylic acid copolymer , styrene-α-methylstyrene-acrylic acid-alkyl acrylate copolymer, styrene-maleic acid copolymer, vinyl naphthalene-maleic acid copolymer, vinyl acetate-ethylene copolymer, vinyl acetate-fatty acid vinyl ethylene copolymers, vinyl acetate-maleic acid ester copolymers, vinyl acetate-crotonic acid copolymers, vinyl acetate-acrylic acid copolymers, and the like.

Nonionic dispersants include polyvinylpyrrolidone, polypropylene glycol, vinylpyrrolidone-vinyl acetate copolymer and the like.

Surfactants as dispersants include anionic surfactants such as sodium dodecylbenzenesulfonate, sodium laurate, ammonium salts of polyoxyethylene alkyl ether sulfates, polyoxyethylene alkyl ethers, polyoxyethylene alkyl esters, poly nonionic surfactants such as oxyethylene sorbitan fatty acid esters, polyoxyethylene alkylphenyl ethers, polyoxyethylene alkylamines and polyoxyethylene alkylamides; In particular, it is preferable to use a styrene-(meth)acrylic acid copolymer from the viewpoint of enhancing the dispersion stability of the pigment.

The oil-based ink composition used in this embodiment can further contain other additives contained in ordinary oil-based ink compositions. Examples of such additives include stabilizers (eg, antioxidants or UV absorbers).

As an antioxidant, for example, BHA (2,3-butyl-4-oxyanisole) or BHT (2,6-di-t-butyl-p-cresol) can be used, and as an ultraviolet absorber, For example, benzophenone-based compounds or benzotriazole-based compounds can be used.

The above oil-based ink composition can be prepared by a known conventional method. For example, when a pigment is used as the colorant, first, the pigment, the dispersant, and the mixture (part) of the diethylene glycol compound and the dipropylene glycol compound are mixed, and then ball mill, bead mill, ultrasonic wave, or jet mill etc. to prepare a pigment dispersion and adjust it so as to have desired ink properties. Subsequently, the binder resin, the mixture of the diethylene glycol compound and the dipropylene glycol compound (remaining amount), and other additives (eg, dispersing aid and viscosity modifier) are added with stirring to prepare an oil-based pigment ink composition. can be obtained. Alternatively, an oil-based ink composition can be obtained by using both a pigment and a dye as colorants and by the same method as the method for preparing the oil-based pigment ink composition.

[Inkjet recording method]
The inkjet recording method of the present embodiment is an inkjet recording method in which droplets of an ink composition are ejected by driving an inkjet head, and the droplets are adhered to a recording medium for recording, and the ink set described above is used. It forms an image.

When used alone, the oil-based ink composition containing the above-described metal pigment has values of 200, 200, and 100 or more for the 20-degree, 60-degree, and 85-degree specular glosses defined in JIS Z8741, respectively. It is possible to form an image having a metallic luster exhibiting By using this oil-based ink composition, it is possible to form an image having a desired metallic luster, ranging from a matte image to a gloss image.

Specifically, when an image is formed in which the measured values of 20 degrees, 60 degrees, and 85 degrees specified by JIS Z8741 are 200 or more and less than 400, 200 or more and less than 400, or 100 or more. , an image having a matte metallic luster.

In addition, images showing values of 400 or more and less than 600, 400 or more and less than 600, and 100 or more for the 20 degree, 60 degree, and 85 degree specular glossiness values specified in JIS Z8741 are reflected in the formed image. A glossy metallic luster can be obtained, which makes it possible to discriminate a little object.

Furthermore, images having metallic gloss exhibiting numerical values of 600 or more, 600 or more, and 100 or more at the 20-degree, 60-degree, and 85-degree specular gloss values defined in JIS Z8741 have sharpness. , a metallic luster having a so-called "specular luster", which is so-called "specular luster", can be used so that an object reflected in the formed image can be clearly identified.

The oil-based ink composition containing the metal pigment, and the oil-based ink composition comprising the chromatic ink composition, the black ink composition, and the white ink composition can be ejected simultaneously to form an image. Thereby, a metallic color tone can be imparted to the color tone of the chromatic pigment, the black pigment and the white pigment.

When the oil-based ink composition containing the metal pigment and the oil-based ink composition such as the chromatic ink composition, the black ink composition, and the white ink composition are ejected separately, for example, the metal pigment is It is preferable to form an image using the chromatic ink composition after forming an image having metallic luster using the oil-based ink composition. Regardless of whether the recording medium has an ink-receiving layer, the metallic pigment hardly penetrates into the ink-receiving layer and adheres to the recording medium. On the other hand, when the pigment contained in the chromatic ink composition is ejected onto a recording medium having an ink-receiving layer, it easily permeates into the ink-receiving layer. Therefore, when an oil-based ink composition containing a metallic pigment is first ejected to form an adhesion layer of the metallic pigment on a recording medium, and a chromatic ink pigment is adhered thereon, the pigment of the chromatic ink composition is deposited. It is possible to develop colors more vividly.

Alternatively, after forming an image having metallic luster using the oil-based ink composition containing the metallic pigment, an image having metallic luster of any color tone is formed using the chromatic ink composition, and then the black ink is formed. Images can also be formed using the composition and/or the white ink pigment.

Methods for ejecting the ink composition include the methods described below.

The first method is the electrostatic attraction method, in which a strong electric field is applied between a nozzle and an acceleration electrode placed in front of the nozzle, and ink droplets are continuously ejected from the nozzle. There is a method in which a print information signal is applied to the deflection electrodes while the ink droplets are flying between the deflection electrodes for recording, or a method in which the ink droplets are ejected in accordance with the print information signal without being deflected.

The second method is a method of forcibly ejecting ink droplets by applying pressure to the ink liquid with a small pump and mechanically vibrating the nozzle with a crystal oscillator or the like. The ejected ink droplets are charged at the same time as they are ejected, and while the ink droplets are flying between the deflection electrodes, a print information signal is applied to the deflection electrodes for recording.

The third method is a method using a piezoelectric element (piezo element), in which pressure and a print information signal are simultaneously applied to the ink liquid by the piezoelectric element to eject and record ink droplets.

The fourth method is a method in which the volume of the ink liquid is rapidly expanded by the action of thermal energy, in which the ink liquid is heated and foamed by microelectrodes in accordance with a print information signal, and ink droplets are ejected and recorded.

Any of the above methods can be used in the inkjet recording method of the present embodiment, but from the viewpoint of high-speed printing, the method of ejecting the ink composition is preferably a non-heating method. That is, it is preferable to adopt the first method, the second method, or the third method.

The recording medium is not particularly limited, and examples include plain paper, inkjet paper (matte paper, glossy paper), glass, plastic films such as vinyl chloride, films coated with plastics or receiving layers on substrates, metals, and printed wiring. Various recording media such as substrates can be used.

When the recording medium has an ink-receiving layer, it is preferable to print on the recording medium without heating from the viewpoint of avoiding heat damage.

On the other hand, when the recording medium does not have an ink-receiving layer, it is preferable to print by heating the recording medium from the viewpoint of increasing the drying speed and obtaining high glossiness.

Heating is performed by bringing a heat source into contact with the recording medium, irradiating the recording medium with infrared rays or microwaves (electromagnetic waves having a maximum wavelength of about 2,450 MHz), or by blowing hot air without contacting the recording medium. methods and the like.

The heating is preferably performed before printing and/or simultaneously with printing and/or after printing. In other words, the recording medium may be heated before, at the same time as, or after printing, or may be heated during printing. Although the heating temperature depends on the type of recording medium, it is preferably 30 to 80.degree. C., more preferably 40 to 60.degree.

[Recordings]
The recorded matter of the present embodiment is obtained by recording by the ink jet recording method using the ink set described above. Since this recorded matter is obtained by the ink jet recording method using the ink set described above, it is possible to obtain a recorded matter having a metallic image with an arbitrary color tone.

〔Example〕
1. Metallic ink composition (1) Preparation of metallic pigment dispersion Liquid cellulose acetate butyrate (35 to 39% butylation rate, manufactured by Kanto Kagaku Co., Ltd.) 3.0% by weight and diethylene glycol diethyl are coated on a 100-thickness high-definition PET film. A resin layer coating solution containing 97% by weight of ether (manufactured by Nippon Nyukazai Co., Ltd.) was uniformly applied by a bar coating method and dried at 60° C. for 10 minutes to form a resin layer thin film on the PET film.

Next, an aluminum vapor deposition layer having an average thickness of 20 nm was formed on the resin layer using a vacuum vapor deposition apparatus (VE-1010 vacuum vapor deposition apparatus manufactured by Vacuum Device Co., Ltd.).

Next, the laminate formed by the above method is simultaneously subjected to peeling, miniaturization, and dispersion treatment using a VS-150 ultrasonic dispersion machine (manufactured by AS ONE) in diethylene glycol diethyl ether, and integrated ultrasonic dispersion treatment. A metallic pigment dispersion was made with a time of 12 hours.

The obtained metallic pigment dispersion was filtered through a SUS mesh filter with an opening of 5 μm to remove coarse particles. The filtrate was then placed in a round bottom flask and diethylene glycol diethyl ether was distilled off using a rotary evaporator. Thus, the metallic pigment dispersion was concentrated, and then the concentration of the metallic pigment dispersion was adjusted to obtain a metallic pigment dispersion 1 having a concentration of 5% by weight.

In addition, metallic pigment dispersions 2 and 3 were obtained, each having metallic pigments with varying vapor deposition conditions and/or ultrasonic dispersion times.

Then, using a particle size / particle size distribution measuring device (FPIA-3000S manufactured by Sysmex Corporation), the 50% average particle size R50 of the circle equivalent diameter of the major axis (X direction) - minor axis (Y direction) plane of each metallic pigment, The average film thickness Z was measured, and R50/Z was calculated based on the measured values of R50 and Z obtained. Table 1 shows the results.

(2) Preparation of Metallic Ink Composition Using the metallic pigment dispersion liquid prepared by the above method, metallic pigment ink compositions having the compositions shown in Tables 2 and 3 were prepared. After mixing and dissolving the solvent and additives to form an ink solvent, the metallic pigment dispersion is added to the ink solvent, and further mixed and stirred with a magnetic stirrer for 30 minutes at normal temperature and normal pressure to obtain a metallic pigment ink. Compositions (S1 to S7) were obtained.

In Tables 2 and 3, diethylene glycol diethyl ether (DEGDE) and tetraethylene glycol dimethyl ether (TEGDM) manufactured by Nippon Nyukazai Co., Ltd. were used. In addition, butyrolactone manufactured by Kanto Kagaku Co., Ltd. was used. In addition, N-2043-AF-1 and N-2043-60MEX (polyacrylic polyol resin emulsion) are manufactured by Harima Chemicals, and IB-F370 (polyurethane resin) is BYK-3500 (manufactured by Sanyo Chemical Industries, Ltd.). Surfactant) used was manufactured by BYK-Chemie Japan. The unit is % by weight.

2. Color Ink Compositions (1) Compositions of Color Ink Compositions With the compositions shown in Tables 4 and 5, a yellow ink composition, a magenta ink composition, a light magenta ink composition, a cyan ink composition, a light cyan ink composition, and a black ink composition. An ink composition and a white ink composition were prepared. The "dispersant" is a polyester polymer compound, "N-2043-AF-1" and "N-2043-60MEX" are the polyacrylic polyol resin emulsions, and the "mixed organic solvent" is , diethylene glycol diethyl ether (70% by weight), γ-butyrolactone (15% by weight) and tetraethylene glycol dimethyl ether (15% by weight). Further, the numerical values in Tables 4 and 5 mean % by weight.

(2) Preparation method of each ink composition Among the ingredients, the pigment, dispersant, and mixed organic solvent (partial) were stirred with a dissolver at 3000 rpm for 1 hour, and then a bead mill filled with zirconia beads (2 mm). pre-dispersed with . The average particle size of the pigment particles obtained by this preliminary dispersion was 5 μm or less.
Furthermore, main dispersion was carried out using a nanomill filled with zirconia beads (0.3 mm) to obtain a pigment dispersion. The average particle diameter of the pigment particles obtained by this main dispersion is 50 nm to 200 nm, although there are differences depending on the pigment species.

While stirring the obtained pigment dispersion at 4000 rpm, N-2043-AF-1, usual additives, polyoxyethylene derivative, hollow resin emulsion and mixed organic solvent (remainder) are mixed, and the pigment weight parts are as described above. The desired color ink compositions (Y1 to W8) were obtained by adjusting the weight percentages shown in the composition.
Desired color ink compositions (Y9 to W13) were obtained in the same manner.

The hollow resin emulsion was produced as follows.
(a) polymer particles 1
In a 2 L reaction vessel, 80 parts of styrene, 5 parts of methacrylic acid, 15 parts of methyl methacrylate, 1 part of α-methylstyrene dimer, 14 parts of t-dodecyl mercaptan, 0.8 parts of sodium dodecylbenzenesulfonate, 1 part of potassium persulfate 0 part and 200 parts of water were added, stirred in nitrogen gas, heated to 80° C., and emulsion polymerization was carried out for 6 hours. Polymer particles 1 thus obtained had an average particle size of 150 nm (0.15 μm).

(b) Hollow polymer fine particle emulsion 1
10 parts (solid content conversion) of the polymer particles 1 obtained in the preceding section (a), 0.3 parts of sodium lauryl sulfate, 0.5 parts of potassium persulfate, and 400 parts of water were placed in a reaction vessel, A crosslinkable monomer composition comprising a mixture of 11.6 parts of divinylbenzene (purity of 55% by weight; balance being monofunctional vinyl monomer), 8.4 parts of ethylvinylbenzene, 5 parts of acrylic acid, and 75 parts of methyl methacrylate. was added, stirred at 30° C. for 1 hour, and further stirred at 70° C. for 5 hours for emulsion polymerization treatment to obtain an aqueous dispersion. The particles obtained were measured with a particle size analyzer (Microtrac UPA: Nikkiso Co., Ltd.) to find a particle size of 320 nm, and separately observed with a transmission electron microscope to find hollow polymer fine particles.

3. Ink Set Using the ink compositions obtained in 1 and 2 above, an ink set was constructed with the combinations shown in Tables 6 and 7.

4. Printing evaluation test (1) Printing evaluation test 1
Using the ink set shown in 3 above, Roland D.I. G. Two inkjet printers SJ-540 manufactured by Co., Ltd. are used, and the first inkjet printer is loaded with ink compositions corresponding to the corresponding color series, that is, a black ink composition, a yellow ink composition, and a magenta ink. The composition, the cyan ink composition, the light magenta ink composition, and the light cyan ink composition are filled in the black row, yellow row, magenta row, cyan row, light magenta row, and light cyan row, respectively. The ink composition was filled in the black row, and the white ink composition was filled in the yellow row. Both ink jet printers printed under the condition of a heating temperature of 50° C. as shown in the following printing pattern. The recording medium is a vinyl chloride sheet cut to A4 size (Viewcal 2000 (white): manufactured by Sakurai Co., Ltd.), PET film (PG-50L: manufactured by Lamy Corporation), polycarbonate film (Iupilon FE-2000: Mitsubishi Engineering Plastics Co., Ltd.) was used. Then, sensory evaluation of the printed matter was performed based on the following evaluation criteria. Table 8 shows the results.
AAA: Arbitrary metallic gloss ranging from high metallic gloss to matte tone was obtained.
AA: A metallic luster was obtained to the extent that the reflected object could be clearly distinguished.
A: A metallic luster was obtained to the extent that the object reflected in the image was slightly recognizable.
B: A matte metallic luster was obtained.
C: No metallic gloss was obtained.

A print pattern using the above ink set is as follows.
a. Print pattern 1
Printing was carried out by ejecting each ink composition at the same time.
b. Print pattern 2
After performing printing by ejecting the metallic ink composition, printing was performed by ejecting the chromatic ink composition and the black ink composition. In this case, gloss can be masked by printing a black ink composition on the metallic print.
c. Print pattern 3
After printing by ejecting the metallic ink composition, printing was performed by ejecting the chromatic ink composition, and then printing was performed by ejecting the white ink composition and the black ink composition. In this case, by printing a white ink composition on glossy metallic printing, it is possible to change to a matte tone.

(2) Printing evaluation test 2
The metallic ink composition S1 and the above oil-based ink composition are combined to form an ink set, and two inkjet printers PM-4000PX (manufactured by Seiko Epson) are used. A yellow ink composition, a magenta ink composition, a cyan ink composition, a light magenta ink composition, and a light cyan ink composition were filled in corresponding color rows. Then, in the second inkjet printer, the metallic ink composition S1 was filled in the black row. The white ink composition was filled in the yellow row.

Then, printing was performed at room temperature on photo paper <Glossy> (manufactured by Seiko Epson, model number: KA450PSK) having an ink-receiving layer, manufactured by Seiko Epson, in the manner shown in the above printing pattern. Similarly, the same printing was performed using the metallic ink composition S2 instead of the metallic ink composition S1. Furthermore, based on the evaluation criteria described above, a sensory evaluation of the printed matter was performed. Table 9 shows the results.

As shown in Table 9, by the ink jet recording method using the ink set described above, a recorded material having a metallic image with an arbitrary color tone could be obtained.

(3) Printing evaluation test 3
A printed matter was formed in the same manner as in the printing evaluation test 1 of 4(1) above, and sensory evaluation of the same printed matter was performed based on the same evaluation criteria. Table 10 shows the results.

(4) Printing evaluation test 4
A printed matter was formed in the same manner as in the printing evaluation test 2 of 4(2) above, and sensory evaluation of the printed matter was performed based on the same evaluation criteria. Table 11 shows the results.

As shown in Table 11, by the ink jet recording method using the ink set described above, a recorded matter having a metallic image with an arbitrary color tone could be obtained.

Claims (9)

An inkjet recording method in which droplets of a metallic ink composition containing a metal pigment and an organic solvent and a chromatic ink composition containing a chromatic pigment are ejected and the droplets are adhered to a recording medium for recording. There is
the deposition is performed on the heated recording medium;
The metal pigment is aluminum or an aluminum alloy and is tabular particles,
The inkjet recording method, wherein the recording medium is a PET film or a polycarbonate film. The inkjet recording method according to claim 1, wherein the heating temperature of the recording medium is 30 to 80°C. The inkjet recording method according to claim 1 or 2, wherein the metallic ink composition further contains a silicone-based surfactant. 4. The set of at least one of a cyan ink composition and a light cyan ink composition and a magenta ink composition and a light magenta ink composition is used as the chromatic ink composition. The inkjet recording method described in . The inkjet recording method according to any one of claims 1 to 4, further comprising ejecting droplets of a black ink composition containing a black pigment and depositing the droplets on the recording medium. 6. The inkjet recording method according to claim 5, wherein the content of said black pigment in said black ink composition is 0.5 to 12% by weight. The inkjet recording method according to any one of claims 1 to 6, wherein droplets of a white ink composition containing a white pigment are further ejected to adhere the droplets to the recording medium. 7. The content of the white pigment in the white ink composition is 1 to 20% by weight.
The inkjet recording method described in . An inkjet printer that performs recording by the inkjet recording method according to any one of claims 1 to 8.