White ink, non-white ink, ink set, printing set, printing method, and printing device

Abstract

To provide an ink set that can prevent cissing and bleeding between different colors and can give a high image density.SOLUTION: Provided is an ink set including: a non-white ink, which contains water, a coloring material, an organic solvent, and an acetylene glycol compound; and a white ink, which contains water, a coloring material, an organic solvent, and a compound represented by General formula (1). In General formula (1), R represents a hydrogen atom or a methyl group, n1 and n2 each represent an integer of from 1 through 7, k represents an integer of from 0 through 5, and m represents an integer of from 1 through 20.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a white ink, a non-white ink, an ink set, a printing set, a printing method, and a printing device. [Background technology]

[0002] In recent years, even in the fields of commercial and industrial printing, where analog printing such as offset printing and flexography are mainstream, there has been a growing need for inkjet printers as a digital printing method that can print a wide variety of designs in small quantities without the need for plates.

[0003] In commercial printing, the main printing items include pamphlets, catalogs, posters, manuals, etc., while in industrial printing, the main printing items include labels, packages, textiles, cardboard, etc. In particular, in the field of industrial printing, designs that are produced in small quantities and in a wide variety of products are preferred and are used to promote product sales.

[0004] An example of such small-volume, high-mix printing is the packaging printing of food and daily necessities, which is printed on non-absorbent recording media such as plastic film. In packaging printing, the printed matter is often viewed at close range, so extremely high image quality is required.

[0005] In view of this, for example, an ink set has been proposed that has a first ink composition and a second ink composition, both of which contain a silicone surfactant, and in order to control bleeding of the two ink compositions into each other, the total concentrations of the silicone surfactant in both ink compositions are different (see, for example, Patent Document 1). Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide an ink set that can prevent repellency and bleeding between colors and obtain high image density. [Means for solving the problem]

[0007] The ink set of the present invention as a means for solving the above problems comprises a non-white ink containing water, a colorant, an organic solvent, and an acetylene glycol compound, and a white ink containing water, a colorant, an organic solvent, and a compound represented by the following general formula (1): [ka] In the general formula (1), R represents a hydrogen atom or a methyl group, n1 and n2 represent integers of 1 to 7, k represents an integer of 0 to 5, and m represents an integer of 1 to 20. Effect of the Invention

[0008] According to the present invention, it is possible to provide an ink set that can prevent repellency and bleeding between colors and obtain high image density. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view illustrating an example of a printing device. [Diagram 2] FIG. 2 is a perspective view illustrating an example of a main tank in a printing apparatus. [Diagram 3] FIG. 3 is a schematic diagram showing an example of the printing apparatus of the present invention used in the printing method of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] (Ink set) The ink set of the present invention has a non-white ink containing water, a colorant, an organic solvent, and an acetylene glycol compound, and a white ink containing water, a colorant, an organic solvent, and a compound represented by the following general formula (1):

[0011] [ka] In the general formula (1), R represents a hydrogen atom or a methyl group, n1 and n2 represent integers of 1 to 7, k represents an integer of 0 to 5, and m represents an integer of 1 to 20.

[0012] In the industrial printing field, such as food soft packaging, high productivity and machine miniaturization are required. From that perspective, it is necessary to print white ink on top of color ink after printing color ink. If the drying process in between can be omitted, it will contribute to productivity and machine miniaturization, but with conventional technology, there is an issue that bleeding between colors occurs during the printing process.

[0013] The ink set of the present invention allows the white ink to be printed on the non-white ink without repelling or bleeding, resulting in high-quality prints. This is because the acetylene glycol compound (acetylene glycol surfactant) contained in the non-white ink has good wettability with the compound represented by the above general formula (1) (silicone surfactant) contained in the white ink. In addition, the compound represented by the above general formula (1) exhibits high wettability to the printed material, thereby preventing the occurrence of pinholes, and as a result, even a solid image using only white ink can exhibit high white hiding power. Furthermore, the use of the compound represented by the above general formula (1) results in less nozzle leakage during ejection of the white ink after decapsulation. This is believed to be because the compound represented by the above general formula (1) stabilizes the dispersion of the pigment in the white ink even when the organic solvent volatilizes during decapsulation.

[0014] <White ink> The white ink contains water, a coloring material, an organic solvent, and a compound represented by the following general formula (1), and further contains other components as necessary.

[0015] [ka] In the general formula (1), R represents a hydrogen atom or a methyl group, n1 and n2 represent integers of 1 to 7, k represents an integer of 0 to 5, and m represents an integer of 1 to 20.

[0016] The compound represented by the above general formula (1) is preferably a compound represented by the following general formula (1-1).

[0017] [ka] In the general formula (1-1), k represents an integer of 0 to 5, and m represents an integer of 1 to 20.

[0018] As the compound represented by the above general formula (1), for example, a compound represented by the following general formula (1a) can be used. The compound represented by the above general formula (1) is not limited thereto.

[0019] [ka] In the general formula (1a), m represents an integer of 1 to 20.

[0020] The compound represented by the above general formula (1) is not particularly limited, and commercially available products can be used. Examples of the commercially available products include BYK-3450, BYK-348 (all manufactured by BYK), wet-240, wet-270, wet-280 (all manufactured by Evonik), SAG503A, and SAG002 (all manufactured by Nissin Chemical Industry Co., Ltd.).

[0021] The white ink may contain other surfactants in addition to the compound represented by the general formula (1) above. As the other surfactant, any of silicone surfactants, fluorine-based surfactants, amphoteric surfactants, nonionic surfactants, and anionic surfactants other than the compound represented by the above general formula (1) can be used. Silicone surfactants are not particularly limited as long as they are not compounds represented by the above general formula (1), and can be appropriately selected according to the purpose. Among them, those that do not decompose even at high pH are preferred, such as side chain modified polydimethylsiloxane, both end modified polydimethylsiloxane, one end modified polydimethylsiloxane, both end modified polydimethylsiloxane of side chain, etc., and those having polyoxyethylene group or polyoxyethylene polyoxypropylene group as a modified group are particularly preferred because they show good properties as an aqueous surfactant. In addition, polyether modified silicone surfactants can also be used as the silicone surfactant, such as a compound in which a polyalkylene oxide structure is introduced into the Si part side chain of dimethylsiloxane. As the fluorine-based surfactant, for example, perfluoroalkyl sulfonic acid compounds, perfluoroalkyl carboxylic acid compounds, perfluoroalkyl phosphate compounds, perfluoroalkyl ethylene oxide adducts, and polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups on the side chains are particularly preferred because of their low foaming properties. Examples of the perfluoroalkylsulfonic acid compound include perfluoroalkylsulfonic acid and perfluoroalkylsulfonate salts. Examples of the perfluoroalkyl carboxylic acid compound include perfluoroalkyl carboxylic acids and perfluoroalkyl carboxylates. Examples of the polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group on the side chain include sulfate ester salts of polyoxyalkylene ether polymers having a perfluoroalkyl ether group on the side chain, and salts of polyoxyalkylene ether polymers having a perfluoroalkyl ether group on the side chain. Counter ions of the salts in these fluorosurfactants include Li, Na, K, NH4, NH3CH2CH2OH, NH2(CH2CH2OH)2, NH(CH2CH2OH)3, and the like.

[0022] Examples of amphoteric surfactants include lauryl aminopropionate, lauryl dimethyl betaine, stearyl dimethyl betaine, and lauryl dihydroxyethyl betaine. Examples of nonionic surfactants include polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl esters, polyoxyethylene alkylamines, polyoxyethylene alkylamides, polyoxyethylene propylene block polymers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, and ethylene oxide adducts of acetylene alcohol. Examples of the anionic surfactant include polyoxyethylene alkyl ether acetates, dodecylbenzene sulfonates, laurates, and salts of polyoxyethylene alkyl ether sulfates. The other surfactants may be used alone or in combination of two or more kinds.

[0023] <<Organic solvents>> The organic solvent used in the present invention is not particularly limited, and any water-soluble organic solvent can be used. Examples of the water-soluble organic solvent include polyhydric alcohols, ethers such as polyhydric alcohol alkyl ethers and polyhydric alcohol aryl ethers, nitrogen-containing heterocyclic compounds, amides, amines, and sulfur-containing compounds. Examples of the water-soluble organic solvent include ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 3-methyl-1,3-butanediol, triethylene glycol, polyethylene glycol, polypropylene glycol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 2,4-pentanediol, 1,5-pentanediol, and the like. Diol, 1,2-hexanediol, 1,6-hexanediol, 1,3-hexanediol, 2,5-hexanediol, 1,5-hexanediol, glycerin, 1,2,6-hexanetriol, 2-ethyl-1,3-hexanediol, ethyl-1,2,4-butanetriol, 1,2,3-butanetriol, 2,2,4-trimethyl-1,3-pentanediol, polyhydric alcohols such as petriol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diene Examples of the alkyl ether include polyhydric alcohol alkyl ethers such as ethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, and propylene glycol monoethyl ether; polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether; nitrogen-containing heterocyclic compounds such as 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, ε-caprolactam, and γ-butyrolactone; amides such as formamide, N-methylformamide, N,N-dimethylformamide, 3-methoxy-N,N-dimethylpropionamide, and 3-butoxy-N,N-dimethylpropionamide; amines such as monoethanolamine, diethanolamine, and triethylamine; sulfur-containing compounds such as dimethyl sulfoxide, sulfolane, and thiodiethanol; propylene carbonate; and ethylene carbonate. It is preferable to use an organic solvent having a boiling point of 250° C. or less, since this not only functions as a wetting agent but also provides good drying properties.

[0024] The content of the organic solvent in the white ink is not particularly limited and can be selected appropriately depending on the purpose. From the viewpoints of the drying property and ejection reliability of the white ink, however, the content is preferably from 10% by mass to 60% by mass, and more preferably from 20% by mass to 60% by mass.

[0025] <<Wed>> The water is not particularly limited and can be appropriately selected depending on the purpose. Examples of the water include pure water such as ion-exchanged water, ultrafiltered water, reverse osmosis water, and distilled water, and ultrapure water. The water content in the white ink is not particularly limited and can be selected appropriately depending on the purpose. From the viewpoints of the drying property and ejection reliability of the white ink, however, it is preferably from 10% by mass to 90% by mass, and more preferably from 20% by mass to 60% by mass.

[0026] <<Coloring materials>> The coloring material is not particularly limited as long as it is white, and pigments and dyes can be used. Examples of white pigments include titanium oxide, iron oxide, calcium carbonate, barium sulfate, and aluminum hydroxide. In addition, resin hollow particles and inorganic hollow particles can also be used. The content of the coloring material in the white ink is preferably from 0.1% to 15% by mass, and more preferably from 1% to 10% by mass, from the viewpoints of improving image density, good fixing property, and ejection stability.

[0027] Methods for dispersing a pigment to obtain a white ink include a method in which a hydrophilic functional group is introduced into the pigment to make it a self-dispersing pigment, a method in which the surface of the pigment is coated with a resin and then dispersed, and a method in which a dispersant is used to disperse the pigment. An example of a method for introducing a hydrophilic functional group into a pigment to make it a self-dispersing pigment is a method in which a functional group such as a sulfone group or a carboxyl group is added to a pigment (e.g., carbon) to make it dispersible in water. As a method for dispersing a pigment by coating its surface with a resin, there is a method in which the pigment is encapsulated in a microcapsule to make it dispersible in water. This can be called a resin-coated pigment. In this case, it is not necessary for all of the pigments blended in the ink to be coated with a resin, and uncoated or partially coated pigments may be dispersed in the ink as long as the effect of the present invention is not impaired. Examples of the method for dispersing using a dispersant include a method for dispersing using a known low molecular weight dispersant or a known polymeric dispersant, such as a surfactant. As the dispersant, for example, anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, etc. can be used depending on the pigment. As the dispersant, RT-100 (nonionic surfactant) manufactured by Takemoto Oil Co., Ltd. and sodium naphthalenesulfonate formalin condensate can also be suitably used. The dispersants may be used alone or in combination of two or more.

[0028] -Pigment dispersion- White ink can be obtained by mixing the pigment with materials such as water and organic solvents. It is also possible to manufacture white ink by mixing the pigment with other materials such as water and dispersants to prepare a pigment dispersion, and then mixing the resulting mixture with materials such as water and organic solvents. The pigment dispersion is obtained by mixing and dispersing water, a pigment, a pigment dispersant, and other components as necessary, and adjusting the particle size. Dispersion is preferably performed using a dispersing machine. The particle size of the pigment in the pigment dispersion is not particularly limited, but the maximum frequency in terms of the maximum number is preferably 20 nm or more and 500 nm or less, and more preferably 20 nm or more and 150 nm or less, in order to improve the dispersion stability of the pigment and the image quality such as ejection stability and image density. The particle size of the pigment can be measured using a particle size analyzer (Nanotrac Wave-UT151, manufactured by Microtrac Bell Co., Ltd.). The pigment content in the pigment dispersion is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoints of obtaining good ejection stability and increasing image density, the pigment content is preferably from 0.1% by mass to 50% by mass, and more preferably from 0.1% by mass to 30% by mass. It is preferable to filter out coarse particles from the pigment dispersion using a filter or a centrifugal separator, and degas the pigment dispersion, if necessary.

[0029] <<Resin>> Examples of the resin include urethane resin, polyester resin, acrylic resin, vinyl acetate resin, styrene resin, butadiene resin, styrene-butadiene resin, vinyl chloride resin, acrylic-styrene resin, and acrylic-silicone resin. Resin particles made of these resins may be used. The resin particles may be dispersed in water as a dispersion medium to form a resin emulsion, and then mixed with materials such as coloring materials and organic solvents to obtain a white ink. The resin particles may be appropriately synthesized or may be commercially available. These may be used alone or in combination of two or more. The resin particles may be appropriately synthesized or may be commercially available. Examples of commercially available products include Microgel E-1002, E-5002 (styrene-acrylic resin particles, manufactured by Nippon Paint Co., Ltd.), Boncoat 4001 (acrylic resin particles, manufactured by DIC Corporation), Boncoat 5454 (styrene-acrylic resin particles, manufactured by DIC Corporation), SAE-1014 (styrene-acrylic resin particles, manufactured by Zeon Corporation), Cybinol SK-200 (acrylic resin particles, manufactured by Saiden Chemical Industry Co., Ltd.), Primal AC-22, AC-61 (acrylic resin particles, manufactured by Rohm and Haas), Nanocryl SBCX-2821, 3689 (acrylic-silicone resin particles, manufactured by Toyo Ink Co., Ltd.), #3070 (methyl methacrylate polymer resin particles, manufactured by Mikuni Color Co., Ltd.), etc.

[0030] The volume average particle size of the resin particles is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoint of obtaining good fixing property and high image hardness, however, it is preferably from 10 nm to 1,000 nm, more preferably from 10 nm to 200 nm, and particularly preferably from 10 nm to 100 nm. The volume average particle size can be measured, for example, using a particle size analyzer (Nanotrac Wave-UT151, manufactured by Microtrac-Bell Co., Ltd.).

[0031] The resin content is not particularly limited and can be selected appropriately depending on the purpose. From the viewpoints of fixation property and storage stability of the white ink, however, the resin content is preferably from 1% by mass to 30% by mass, and more preferably from 5% by mass to 20% by mass, of the total amount of the white ink.

[0032] <<Other ingredients>> Examples of other components include antifoaming agents, antiseptics, antifungals, and rust inhibitors.

[0033] - Defoaming agent - The defoaming agent is not particularly limited, and examples thereof include silicone-based defoaming agents, polyether-based defoaming agents, and fatty acid ester-based defoaming agents. These may be used alone or in combination of two or more. Among these, silicone-based defoaming agents are preferred because of their excellent foam breaking effect.

[0034] -Preservative and fungicidal agent- The antiseptic and antifungal agent is not particularly limited, and examples thereof include 1,2-benzisothiazolin-3-one.

[0035] -Rust inhibitor- The rust inhibitor is not particularly limited, and examples thereof include acid sulfite and sodium thiosulfate.

[0036] The white ink can be prepared by dispersing or dissolving the above-mentioned components in an aqueous medium, and further stirring and mixing as necessary. Stirring and mixing can be performed using a stirrer with a normal stirring blade, a magnetic stirrer, a high-speed disperser, or the like.

[0037] The physical properties of the white ink are not particularly limited and can be appropriately selected depending on the purpose. For example, it is preferable that the viscosity, surface tension, pH, etc. are within the following ranges. The viscosity of the white ink at 25°C is preferably from 5 mPa·s to 30 mPa·s, more preferably from 5 mPa·s to 25 mPa·s, in order to improve print density and character quality and to obtain good ejection properties. Here, the viscosity can be measured using, for example, a rotational viscometer (RE-80L, manufactured by Toki Sangyo Co., Ltd.). The measurement conditions are 25°C, a standard cone rotor (1°34' x R24), a sample liquid volume of 1.2 mL, a rotation speed of 50 rpm, and 3 minutes. The static surface tension of the white ink at 25° C. is preferably 30 mN / m or less, and more preferably 26 mN / m or more and 29 mN / m or less. The dynamic surface tension of the white ink at 25° C. with a surface life of 15 msec as measured by the maximum bubble pressure method is preferably 34 mN / m or less, and more preferably 32 mN / m or more and 33.5 mN / m or less. It is preferable that the static surface tension and 15 msec dynamic surface tension of the white ink satisfy the above numerical ranges, since this allows the ink to sufficiently wet and spread onto the printed material and non-white ink, thereby preventing the occurrence of pinholes and enabling the ink to exhibit high white hiding power. The pH of the white ink is preferably from 7 to 12, and more preferably from 8 to 11, from the viewpoint of preventing corrosion of metal members that come into contact with the ink. The white ink in the ink set of the present invention has excellent ejection reliability.

[0038] <Non-white ink> The non-white ink contains water, a coloring material, an organic solvent, and an acetylene glycol compound, and preferably contains a dialkylsulfosuccinic acid or a salt thereof, and further contains other components as necessary. The acetylene glycol compound and the dialkylsulfosuccinic acid or its salt have high wettability with the compound represented by the general formula (1) contained in the white ink, and therefore images with little repellency and bleeding can be obtained.

[0039] <<Acetylene glycol compounds>> The acetylene glycol compound preferably contains an acetylene glycol compound represented by the following general formula (2).

[0040] [ka] In the general formula (2), x and y each represent an integer of 0 or more, and x+y is an integer of 0 to 3.

[0041] As the acetylene glycol compound, a surfactant can be used, for example, Surfynol DF110D, Surfynol 104E, Surfynol 82 (all manufactured by Nissin Chemical Industry Co., Ltd.), and the like. Particularly, examples of the acetylene glycol compound represented by the above general formula (2) include Surfynol 420, Surfynol 440, Surfynol 465, Surfynol 485, Surfynol PSA-336, E1004, and EXP4200 (all manufactured by Nissin Chemical Industry Co., Ltd.).

[0042] <<Dialkylsulfosuccinic acid or its salt>> The alkyl group in the dialkylsulfosuccinic acid or a salt thereof is preferably a saturated alkyl group having 2 to 20 carbon atoms. Examples of the salt of dialkylsulfosuccinic acid include sodium salt and potassium salt. Examples of dialkyl sulfosuccinic acids or salts thereof include sodium bis(2-ethylhexyl) sulfosuccinate (manufactured by Tokyo Chemical Industry Co., Ltd.), Sanmorin OT (manufactured by Sanyo Chemical Industries, Ltd.), Carabon DA-72 (manufactured by Sanyo Chemical Industries, Ltd.), and Perex OT-P (manufactured by Kao Corporation).

[0043] The non-white ink may contain other surfactants in addition to the acetylene glycol compound represented by the above general formula (2) and the dialkylsulfosuccinic acid or a salt thereof. As the other surfactant, the same surfactant as that used in the non-white ink can be used.

[0044] -Coloring materials- The coloring material is not particularly limited, and pigments and dyes can be used. As the pigment, an inorganic pigment or an organic pigment can be used. These can be used alone or in combination of two or more. Also, mixed crystals can be used as the pigment. Examples of pigments that can be used include black pigments, yellow pigments, magenta pigments, cyan pigments, green pigments, orange pigments, glossy pigments such as gold and silver pigments, and metallic pigments. As inorganic pigments, in addition to barium yellow, cadmium red, and chrome yellow, carbon black produced by known methods such as the contact method, furnace method, and thermal method can be used. Examples of organic pigments that can be used include azo pigments, polycyclic pigments (e.g., phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, etc.), dye chelates (e.g., basic dye chelates, acid dye chelates, etc.), nitro pigments, nitroso pigments, aniline black, etc. Among these pigments, those having good affinity with the solvent are preferably used. Specific examples of pigments for black colors include carbon blacks (CI Pigment Black 7) such as furnace black, lamp black, acetylene black, and channel black; metals such as copper, iron (CI Pigment Black 11), and titanium oxide; and organic pigments such as aniline black (CI Pigment Black 1).

[0045] In addition, for color, CI Pigment Yellow 1, 3, 12, 13, 14, 17, 24, 34, 35, 37, 42 (yellow iron oxide), 53, 55, 74, 81, 83, 95, 97, 98, 100, 101, 104, 108, 109, 110, 117, 120, 138, 150, 153, 155, 180, 185, 213, CI Pigment Orange Range 5, 13, 16, 17, 36, 43, 51, CI Pigment Red 1, 2, 3, 5, 17, 22, 23, 31, 38, 48:2 (Permanent Red 2B (Ca)), 48:3, 48:4, 49:1, 52:2, 53:1, 57:1 (Brilliant Carmine 6B), 60:1, 63:1, 63:2, 64:1, 81, 83, 88, 101 ( Red iron oxide), 104, 105, 106, 108 (Cadmium Red), 112, 114, 122 (Quinacridone Magenta), 123, 146, 149, 166, 168, 170, 172, 177, 178, 179, 184, 185, 190, 193, 202, 207, 208, 209, 213, 219, 224, 254, 264, CI Pigment Examples of pigments include CI Pigment Green 1, 4, 7, 8, 10, 17, 18, and 36.

[0046] The dye is not particularly limited, and acid dyes, direct dyes, reactive dyes, and basic dyes can be used. One type of dye may be used alone, or two or more types may be used in combination. Dyes such as CI Acid Yellow 17, 23, 42, 44, 79, 142, CI Acid Red 52, 80, 82, 249, 254, 289, CI Acid Blue 9, 45, 249, CI Acid Black 1, 2, 24, 94, CI Food Black 1, 2, CI Direct Yellow 1, 12, 24, 33, 50, 55, 58, 86, 132, 142, 144, 1 73, CI Direct Red 1, 4, 9, 80, 81, 225, 227, CI Direct Blue 1, 2, 15, 71, 86, 87, 98, 165, 199, 202, CI Directed Black 19, 38, 51, 71, 154, 168, 171, 195, CI Reactive Red 14, 32, 55, 79, 249, CI Reactive Black 3, 4, 35, etc.

[0047] The content of the coloring material in the non-white ink is preferably from 0.1% to 15% by mass, and more preferably from 1% to 10% by mass, from the viewpoints of improving image density, good fixing property, and ejection stability.

[0048] The water, organic solvent, resin, and other components in the non-white ink may be the same as those in the white ink.

[0049] The physical properties of the non-white ink are not particularly limited and can be appropriately selected depending on the purpose. For example, it is preferable that the viscosity, surface tension, pH, etc. are within the following ranges. The viscosity of the non-white ink at 25°C is preferably from 5 mPa·s to 30 mPa·s, more preferably from 5 mPa·s to 25 mPa·s, in order to improve print density and character quality and to obtain good ejection properties. Here, the viscosity can be measured using, for example, a rotational viscometer (RE-80L, manufactured by Toki Sangyo Co., Ltd.). The measurement conditions are 25°C, a standard cone rotor (1°34' x R24), a sample liquid volume of 1.2 mL, a rotation speed of 50 rpm, and 3 minutes. The static surface tension of the non-white ink at 25° C. is preferably 20 mN / m or more and 40 mN / m or less. The dynamic surface tension of the non-white ink at a surface life of 15 msec according to the maximum bubble pressure method is preferably 28 mN / m or more and 43 mN / m or less at 25°C. The pH of the non-white ink is preferably from 7 to 12, and more preferably from 8 to 11, from the viewpoint of preventing corrosion of metal members that come into contact with the ink. The non-white inks in the ink set of the present invention have excellent ejection reliability.

[0050] (Print set) The printing set of the present invention comprises a non-white ink containing water, a colorant, an organic solvent, and an acetylene glycol compound, a white ink containing water, a colorant, an organic solvent, and a compound represented by the following general formula (1), and a treatment liquid containing water and a polyvalent metal salt.

[0051] [ka] In the general formula (1), R represents a hydrogen atom or a methyl group, n1 and n2 represent integers of 1 to 7, k represents an integer of 0 to 5, and m represents an integer of 1 to 20.

[0052] As the non-white ink and the white ink, the non-white ink and the white ink in the ink set of the present invention described above can be used.

[0053] <Processing solution> The treatment liquid contains water and a polyvalent metal salt, and may further contain other components as necessary. The treatment liquid may also be called a "pretreatment liquid," a "pre-coating liquid," or an "undercoat liquid."

[0054] <<Polyvalent metal salts>> The polyvalent metal salt quickly aggregates the pigments in the white ink and non-white ink after deposition, suppressing color bleeding and improving color development. The polyvalent metal salt is not particularly limited and can be appropriately selected depending on the purpose. Examples of the polyvalent metal salt include salts of titanium compounds, chromium compounds, copper compounds, cobalt compounds, strontium compounds, barium compounds, iron compounds, aluminum compounds, calcium compounds, and magnesium compounds. Among these, one or more salts selected from the group consisting of calcium compounds, magnesium compounds, nickel compounds, and aluminum compounds are preferred because they can effectively aggregate the pigment, and alkaline earth metals such as calcium and magnesium are more preferred.

[0055] Specific examples of polyvalent metal salts include calcium carbonate, calcium nitrate, calcium chloride, calcium acetate, calcium sulfate, magnesium chloride, magnesium acetate, magnesium sulfate, barium sulfate, zinc sulfide, zinc carbonate, aluminum silicate, calcium silicate, magnesium silicate, and aluminum hydroxide.

[0056] The medium of the treatment liquid is an aqueous medium, but if necessary, substances other than water may be added, such as water-soluble organic solvents, surfactants, other trace additives, etc. As the water-soluble organic solvents, surfactants, or other trace additives, the same substances as those in the white ink and non-white ink described above can be used.

[0057] <Print material> The printing substrate used in the present invention is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include plain paper, glossy paper, special paper, cloth, etc. Among these, soft packaging film is preferred. The flexible packaging film means polypropylene film, polyethylene terephthalate film, nylon film, and the like. Examples of the polypropylene film include P-2002, P-2102, P-2161, and P-4166 manufactured by Toyobo Co., Ltd., PA-20, PA-30, and PA-20W manufactured by Suntox Corporation, and FOA, FOS, and FOR manufactured by Futamura Chemical Co., Ltd. Examples of the polyethylene terephthalate film include E-5100 and E-5102 manufactured by Toyobo Co., Ltd., P60 and P375 manufactured by Toray Industries, Inc., and G2, G2P2, K and SL manufactured by Teijin DuPont Films Ltd. Examples of the nylon film include Harden Film N-1100, N-1102, and N-1200 manufactured by Toyobo Co., Ltd., and ON, NX, MS, and NK manufactured by Unitika Ltd.

[0058] (Printing device and printing method) The printing method of the present invention includes a non-white ink applying step of applying a non-white ink in the ink set of the present invention to a substrate to be printed, The method includes a white ink applying step of applying the white ink in the ink set of the present invention, and further includes other steps as necessary.

[0059] The printing device of the present invention includes a printing substrate which is a non-absorbent soft packaging film, and a non-white ink applying means for applying the non-white ink in the ink set of the present invention. The ink set of the present invention has a white ink applying means for applying the white ink, and further has other means as necessary.

[0060] The method of applying the ink is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include an inkjet method, a blade coating method, a gravure coating method, a gravure offset coating method, a bar coating method, a roll coating method, a knife coating method, an air knife coating method, a comma coating method, a U comma coating method, an AKKU coating method, a smoothing coating method, a microgravure coating method, a reverse roll coating method, a four-roll coating method, a five-roll coating method, a dip coating method, a curtain coating method, a slide coating method, a die coating method, etc. Among these, the inkjet method is preferred.

[0061] It is preferable to carry out the white ink applying step after carrying out the non-white ink applying step, in order to improve the image quality when viewed from the non-printed surface when printing on a transparent medium.

[0062] It is preferable not to include a drying step between the non-white ink applying step and the white ink applying step in terms of reducing the machine size by omitting a drying device and reducing power consumption used for drying. The drying method in the drying step includes, for example, heating, blowing air, etc., and does not include natural drying.

[0063] It is preferable to include a surface modification step of modifying the surface of the printing substrate. The surface modification step is preferably carried out before applying the inks in the ink set to the printing substrate. By subjecting the substrate to surface modification, the wettability of the ink to the substrate is improved, resulting in an image that is not repellent, which is preferable, and furthermore, when the surface modification step is a corona treatment, this is preferably because the wettability is further improved.

[0064] <Surface modification process> In the surface modification step, any treatment method that can eliminate unevenness when applying the ink in the ink set and improve adhesion may be used, and examples of such treatment methods include corona treatment, atmospheric pressure plasma treatment, frame treatment, and ultraviolet irradiation treatment. These processing methods can be carried out using known devices. Among the above-mentioned treatment methods, the surface modification of the recording surface is preferably performed by a corona treatment step in which a corona treatment is performed on the recording surface. Corona treatment is preferably used because it has superior corona discharge output stability and can perform a uniform surface treatment on the recording surface compared to atmospheric pressure plasma treatment, frame treatment, and ultraviolet irradiation treatment.

[0065] It is preferable to include a pretreatment step of applying a treatment liquid containing water and a polyvalent metal salt to a substrate to be printed. It is preferable to carry out a treatment liquid application step before applying the inks of the ink set to the substrate to be printed. By applying the treatment liquid to the substrate, when the ink hits the substrate, the ink thickens due to aggregation of the coloring material, which is more preferable since it is possible to obtain an image without bleeding.

[0066] The non-white ink of the present invention is used in the printing device of the present invention. The non-white ink of the present invention has excellent ejection reliability. The white ink of the present invention is used in the printing device of the present invention. The white ink of the present invention has excellent ejection reliability.

[0067] The ink set used in the present invention can be suitably used in various recording devices using an ink jet recording method, such as printers, facsimile machines, copying machines, printer / fax / copier combination machines, and three-dimensional modeling devices. In the present invention, the printing apparatus and printing method refer to an apparatus capable of ejecting ink, various treatment liquids, etc. onto a recording medium, and a method of recording using the apparatus. The recording medium refers to an object onto which ink or various treatment liquids can be attached even temporarily. This recording device can include not only a head portion that ejects ink, but also means related to feeding, transporting, and discharging the recording medium, as well as other devices called pre-processing devices and post-processing devices. The printing apparatus and printing method may have a heating means used in the heating step and a drying means used in the drying step. The heating means and drying means include, for example, a means for heating and drying the printed surface and back surface of the recording medium. The heating means and drying means are not particularly limited, but for example, a hot air heater or an infrared heater can be used. Heating and drying can be performed before, during, or after printing. The apparatus may not have a heating means for the heating step or a drying means for the drying step between the non-white ink application step and the white ink application step. By not having a heating means or a drying means, the apparatus can be made smaller. In addition, the printing device and printing method are not limited to those that visualize meaningful images such as characters and figures with ink. For example, they also include those that form patterns such as geometric designs and those that create three-dimensional images. Furthermore, unless otherwise specified, the printing device includes both a serial type device in which the ejection head moves and a line type device in which the ejection head does not move. Furthermore, this printing device includes not only desktop types, but also wide-width printing devices that can print on A0-sized recording media, and continuous-feed printers that can use continuous paper wound into a roll as a recording medium.

[0068] An example of a printing device will be described with reference to Figs. 1 and 2. Fig. 1 is a perspective view of the device. Fig. 2 is a perspective view of a main tank. An image forming device 400 as an example of a printing device is a serial type image forming device. A mechanism unit 420 is provided inside an exterior 401 of the image forming device 400. Each ink storage unit 411 of the main tanks 410 (410k, 410c, 410m, 410y) for each color of black (K), cyan (C), magenta (M), and yellow (Y) is formed of a packaging material such as an aluminum laminate film. The ink storage unit 411 is stored in a storage container case 414 made of plastic, for example. As a result, the main tanks 410 are used as ink cartridges of each color. On the other hand, a cartridge holder 404 is provided at the back side of the opening when the cover 401c of the apparatus body is opened. A main tank 410 is detachably attached to the cartridge holder 404. As a result, each ink outlet 413 of the main tank 410 communicates with an ejection head 434 for each color via a supply tube 436 for each color, and ink can be ejected from the ejection head 434 to a recording medium.

[0069] This printing device can include not only a portion that ejects ink, but also devices called pre-processing devices and post-processing devices. As an embodiment of the pre-treatment device and post-treatment device, a liquid storage section having a pre-treatment liquid and a liquid ejection head, similar to the case of inks such as black (K), cyan (C), magenta (M), and yellow (Y), and the like, are added, and the pre-treatment liquid and the post-treatment liquid are ejected by an inkjet recording method. As another embodiment of the pre-treatment device and the post-treatment device, there is an embodiment in which a pre-treatment device and a post-treatment device using a method other than the inkjet recording method, for example, a blade coating method, a roll coating method, or a spray coating method, are provided.

[0070] Here, Fig. 3 is a schematic diagram showing an example of a printing device used in the printing method of the present invention. The printing device 100 in Fig. 3 has a treatment liquid application device 2 that applies a treatment liquid, a white ink ejection head 3 that ejects white ink (W), non-white ink (color ink) ejection heads 4 that eject non-white inks, namely black ink (K), cyan ink (C), magenta ink (M) and yellow ink (Y), and a transport belt 5 that transports the printing substrate 1.

[0071] The ink can be used in a wide variety of ways, including, but not limited to, inkjet recording, blade coating, gravure coating, bar coating, roll coating, dip coating, curtain coating, slide coating, die coating, and spray coating.

[0072] In the present invention, the terms image formation, recording, printing, printing, etc. are all synonymous. Recording medium, media, and printed material are all synonymous. EXAMPLES

[0073] Examples of the present invention will be described below, but the present invention is not limited to these examples. Unless otherwise specified, the preparation and evaluation of the examples and comparative examples were carried out under conditions of 25°C and a relative humidity of 60%. In the following examples, a pretreatment liquid applied before printing is used as the treatment liquid.

[0074] (Pigment Dispersion Preparation Example 1) <Preparation of Black Pigment Dispersion> The following recipe was premixed and then dispersed in a disk-type bead mill (KDL model, manufactured by Shinmaru Enterprises, Inc., media: zirconia balls with a diameter of 0.3 mm) for 7 hours to obtain a black pigment dispersion (pigment concentration: 15% by mass). [Black pigment dispersion formulation] Carbon black (product name: Monarch 800, manufactured by Cabot Corporation): 15 parts by weight Acrylic polymer dispersant (product name: Disperbyk-2010, manufactured by BYK Japan): 5 parts by weight Ion-exchanged water: 80 parts by weight

[0075] (Pigment Dispersion Preparation Example 2) <Preparation of Cyan Pigment Dispersion> A cyan pigment dispersion (pigment solids concentration: 15% by mass) was obtained in the same manner as in Pigment Dispersion Preparation Example 1, except that the carbon black in Pigment Dispersion Preparation Example 1 was changed to Pigment Blue 15:3.

[0076] (Pigment Dispersion Preparation Example 3) <Preparation of Magenta Pigment Dispersion> A magenta pigment dispersion (pigment solids concentration: 15% by mass) was obtained in the same manner as in Pigment Dispersion Preparation Example 1, except that carbon black was changed to Pigment Red 269.

[0077] (Pigment Dispersion Preparation Example 4) <Preparation of Yellow Pigment Dispersion> A yellow pigment dispersion (pigment solids concentration: 15% by mass) was obtained in the same manner as in Pigment Dispersion Preparation Example 1, except that carbon black was changed to Pigment Yellow 74.

[0078] (Pigment Dispersion Preparation Example 5) <Preparation of White Pigment Dispersion> 25 parts by mass of titanium oxide (product name: STR-100W, manufactured by Sakai Chemical Industry Co., Ltd.), 5 parts by mass of a pigment dispersant (product name: TEGO Dispers 651, manufactured by Evonik), and 70 parts by mass of water were mixed, and dispersed with zirconia beads having a diameter of 0.3 mm at a filling rate of 60% and at 8 m / s for 5 minutes in a bead mill (product name: Research Lab, manufactured by Shinmaru Enterprises Co., Ltd.) to obtain a white pigment dispersion (pigment solids concentration: 25% by mass).

[0079] (Resin Particle Dispersion Production Example 1) <Production of acrylic resin particle dispersion 1> A mixture of 65 parts by mass of methyl methacrylate, 31 parts by mass of 2-ethylhexyl acrylate, 2 parts by mass of methacrylic acid, 2 parts by mass of Aqualon HS-10 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and 52 parts by mass of ion-exchanged water was emulsified using a homomixer to obtain a uniform milky white emulsion. In a 250 mL flask equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, and a reflux tube, 89 parts by mass of ion-exchanged water was charged, and the temperature was raised to 70°C while introducing nitrogen. Next, 0.8 parts by mass of a 10% by mass Aqualon HS-10 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) aqueous solution and 2.6 parts by mass of a 5% by mass ammonium persulfate aqueous solution were added, and then the emulsion prepared in advance was continuously added dropwise over 2.5 hours. In addition, 0.6 parts by mass of a 5% by mass ammonium persulfate aqueous solution was added every hour until 3 hours had elapsed from the start of the dropwise addition. After the dropwise addition, the mixture was aged at 70°C for 2 hours and then cooled, and the pH was adjusted to 7 to 8 with 28% by mass ammonia water, to obtain an acrylic resin particle dispersion 1. The glass transition temperature Tg of the obtained acrylic resin particles was 53° C. Tg was measured by DSC (Rigaku Corporation, Thermo plus EVO2 / DSC).

[0080] (Resin Particle Dispersion Production Example 2) <Preparation of acrylic resin particle dispersion 2> An acrylic resin particle dispersion 2 was obtained in the same manner as in Resin Particle Dispersion Production Example 1, except that 69 parts by mass of methyl methacrylate and 27 parts by mass of 2-ethylhexyl acrylate were used. The glass transition temperature Tg of the resulting acrylic resin particles was 62°C.

[0081] (Resin Particle Dispersion Production Example 3) <Production of Acrylic Resin Particle Dispersion 3> Acrylic resin particle dispersion 3 was obtained in the same manner as in Resin Particle Dispersion Production Example 1, except that 77 parts by mass of methyl methacrylate and 19 parts by mass of 2-ethylhexyl acrylate were used. The glass transition temperature Tg of the obtained acrylic resin particles was 85°C.

[0082] (Resin Particle Dispersion Production Example 4) <Preparation of urethane resin emulsion A> A reaction flask was charged with 1.4 moles of dicyclohexylmethane diisocyanate per mole of 1,6-hexanediol, 0.1 mole of a diisocyanate compound obtained by reacting 1 / 3 mole of polyethylene glycol monomethyl ether having a molecular weight of 1,000 with 1 mole of isocyanurate trimer of 1,6-hexamethylene diisocyanate, and 15 mass % of the total mass of N-methyl-2-pyrrolidone, and the mixture was reacted at 90° C. for 2 hours under a nitrogen stream to obtain a prepolymer. Next, 450 g of the prepolymer composition having a solid content of 85% by mass obtained above was added dropwise over a period of 15 minutes to 600 g of water in which 0.2 g of a silicone-based defoamer (SE-21, manufactured by Wacker Silicone) had been dissolved. After stirring for 10 minutes at 25°C, a compound represented by the following structural formula (2), ethylenediamine, and adipic acid hydrazide were added dropwise to obtain urethane resin emulsion A.

[0083] [ka]

[0084] (Non-white ink manufacturing example 1) <Preparation of non-white ink 1> The following formulation of non-white ink 1 was mixed and stirred, and filtered through a polypropylene filter with an average pore size of 0.8 μm to prepare non-white ink 1. [Non-white ink 1 formulation] Black pigment dispersion: 20 parts by weight Surfynol 420 (manufactured by Nissin Chemical Industry Co., Ltd.): 0.25 parts by mass Sodium bis(2-ethylhexyl) sulfosuccinate (Tokyo Chemical Industry Co., Ltd.): 0.25 parts by mass Proxel LV (Avecia, preservative): 0.1 parts by weight 1,2-propanediol: 19 parts by weight Ethylene glycol monobutyl ether: 10 parts by weight Ion-exchanged water: 50.4 parts by weight

[0085] (Non-white ink manufacturing examples 2 to 11) <Preparation of non-white inks 2 to 11> Non-white inks 2 to 11 were prepared in the same manner as in Non-white ink Production Example 1, except that the ink formulations in Non-white ink Production Example 1 were changed to those shown in Tables 1-1 and 1-2.

[0086] [Table 1-1]

[0087] [Table 1-2]

[0088] The details of each component in Tables 1-1 and 1-2 are as follows: <Surfactant> -Acetylene glycol compound represented by the above general formula (2)- Surfynol 420 (manufactured by Nissin Chemical Industry Co., Ltd.) Surfynol PSA-33 (manufactured by Nissin Chemical Industry Co., Ltd.) Surfynol 440 (manufactured by Nissin Chemical Industry Co., Ltd.) Surfynol 465 (manufactured by Nissin Chemical Industry Co., Ltd.) Surfynol 485 (manufactured by Nissin Chemical Industry Co., Ltd.)

[0089] -Acetylene glycol compound other than the above general formula (2)- Surfynol DF110D (manufactured by Nissin Chemical Industry Co., Ltd.) Surfynol 104E (manufactured by Nissin Chemical Industry Co., Ltd.) Surfynol 82 (manufactured by Nissin Chemical Industry Co., Ltd.)

[0090] -Dialkylsulfosuccinic acid or its salt- Sodium bis(2-ethylhexyl) sulfosuccinate (Tokyo Chemical Industry Co., Ltd.) Sanmorin OT (manufactured by Sanyo Chemical Industries, Ltd.) Pelex OT-P (Kao Corporation)

[0091] -Fluorosurfactants- FS-300 (DuPont)

[0092] (White ink manufacturing example 1) <Preparation of White Ink 1> The following formulation of white ink 1 was mixed and stirred, and filtered through a polypropylene filter with an average pore size of 0.8 μm to prepare white ink 1. [White ink 1 recipe] White pigment dispersion: 48 parts by weight BYK-3450 (BYK): 0.5 parts by weight Proxel LV (Avecia, preservative): 0.1 parts by weight 1,2-propanediol: 15 parts by weight Ethylene glycol monobutyl ether: 10 parts by weight Ion-exchanged water: 26.4 parts by weight

[0093] (White ink manufacturing examples 2 to 13) <Preparation of White Inks 2 to 13> In the white ink manufacturing example 1, the ink formulation was changed to that shown in Tables 2-1 and 2-2. Other than that, white inks 2 to 13 were prepared in the same manner as in white ink preparation example 1.

[0094] Next, the static surface tension and 15 msec dynamic surface tension of the resulting white ink were measured as follows, and the results are shown in Tables 2-1 and 2-2.

[0095] <Static surface tension measurement> The static surface tension of the white ink was measured at 25° C. using an automatic surface tensiometer (DY-300, manufactured by Kyowa Interface Science Co., Ltd.) More specifically, the white ink was poured into a petri dish having a diameter of 30 mm, left to stand for 5 minutes, and then measured by the Wilhelmy method using a platinum plate with the automatic surface tensiometer DY-300.

[0096] <15msec dynamic surface tension measurement> The dynamic surface tension of the white ink with a surface life of 15 msec by the maximum bubble pressure method was measured at 25° C. using a SITA DynoTester (manufactured by SITA). More specifically, 30 ml of the white ink was placed in a 30 ml beaker, and then placed in a water bath adjusted to 25° C. and left to stand for 10 minutes to adjust the temperature of the white ink to 25° C., and the dynamic surface tension for 15 msec was measured using the SITA DynoTester.

[0097] [Table 2-1]

[0098] [Table 2-2]

[0099] [Table 2-3] [ka]

[0100] The details of each component in Tables 2-1 to 2-3 are as follows. <Surfactant> -Compound represented by the above general formula (1)- BYK-348 (silicone surfactant, manufactured by BYK) BYK-3450 (silicone surfactant, manufactured by BYK) Wet-240 (silicone surfactant, manufactured by Evonik) Wet-270 (silicone surfactant, manufactured by Evonik) Wet-280 (silicone surfactant, manufactured by Evonik) SAG503A (silicone surfactant, manufactured by Nissin Chemical Industry Co., Ltd.) SAG002 (silicone surfactant, manufactured by Nissin Chemical Industry Co., Ltd.)

[0101] -Fluorosurfactants- FS-300 (DuPont)

[0102] (Pretreatment Liquid Manufacturing Example 1) <Preparation of pretreatment solution 1> The following recipe for pretreatment solution 1 was prepared, mixed and stirred, and then filtered through a filter with an average pore size of 5 μm (Minisart, manufactured by Sartorius). [Pretreatment solution 1 formulation] 1,2-propanediol: 15 parts by weight Ethylene glycol monobutyl ether: 13 parts by weight Emulgen LS-106 (Kao Corporation, surfactant): 0.5 parts by weight Magnesium sulfate: 3.0 parts by weight Proxel LV (Avecia, preservative): 0.1 parts by weight Ion-exchanged water: 68.4 parts by weight

[0103] (Pretreatment Solution Manufacturing Examples 2 to 9) <Preparation of pretreatment solutions 2 to 9> Pre-treatment liquids 2 to 9 were prepared in the same manner as in Pre-treatment liquid Production Example 1, except that the pre-treatment liquid formulation was changed to that shown in Tables 3-1 and 3-2.

[0104] [Table 3-1]

[0105] [Table 3-2]

[0106] The details of each component in Tables 3-1 and 3-2 are as follows: -Surfactants- Emulgen LS-106 (polyoxyalkyl ether surfactant, manufactured by Kao Corporation) BYK-333 (silicone surfactant, manufactured by BYK) BYK-3450 (silicone surfactant, manufactured by BYK) Wet-270 (silicone surfactant, manufactured by Evonik) Wet-280 (silicone surfactant, manufactured by Evonik) SAG503A (silicone surfactant, manufactured by Nissin Chemical Industry Co., Ltd.) · SAG016 (silicone surfactant, manufactured by Nissin Chemical Industry Co., Ltd.)

[0107] (Examples 1 to 13 and Comparative Examples 1 to 2) <Image formation> For the combinations of white ink, non-white ink, and pretreatment liquid shown in Tables 4-1 to 4-3, an image forming apparatus (IPSiO GXe-5500, manufactured by Ricoh Co., Ltd.) was used under environmental conditions adjusted to 23°C ± 0.5°C and 50 ± 5% RH. The driving voltage of the piezo element was varied so that the ejection amount of the white ink and non-white ink was uniform. The pretreatment liquid was applied in advance at 3 g / m using bar coater No. 1. 2 After coating, the white ink and the non-white ink were applied in equal amounts (5 g / m) to biaxially oriented polypropylene (OPP) (Toyobo Co., Ltd., Pylen P2102) as a flexible packaging film, which was then dried at 80°C for 2 minutes. 2 ) was applied to form a solid (uniform) image. The white ink and non-white ink were ejected by ejecting the non-white ink first, and then ejecting the white ink.

[0108] Next, various properties were evaluated as follows, and the results are shown in Tables 4-1 to 4-3.

[0109] <Evaluation of the bounce> A solid image of white ink was formed on the non-white ink as described above, and the solid image of non-white ink covered with white ink was observed and evaluated for repellency according to the following criteria. Note that a rating of B or higher is a practically usable level. [Evaluation Criteria] A: There is no exposure of the non-white ink solid image, and the white ink solid image is uniform. B: No exposure of non-white ink solid images, but slight unevenness in white ink solid images C: No exposure of non-white ink solid images, but large unevenness in white ink solid images D: A solid image of non-white ink is exposed

[0110] <White hiding property> The white ink was applied to the image forming apparatus (IPSiO GXe-5500, manufactured by Ricoh Co., Ltd.) under environmental conditions adjusted to 23°C ± 0.5°C and 50% ± 5% RH, with the white ink deposition amount of 5 g / m 2 The driving voltage of the piezoelectric element was changed so that the pretreatment liquid was applied at 3 g / m 2 After coating, the OPP (Pylen P2102, manufactured by Toyobo Co., Ltd.) was dried at 80° C. for 2 minutes, and a solid image was formed with the white ink. The formed image was placed on a hiding rate measuring paper (manufactured by TP Giken Co., Ltd.), and the black (Bk) density was measured using X-rite eXact (manufactured by X-rite Co., Ltd.) to evaluate the white hiding power according to the following criteria. Note that B or higher is a practically usable level. [Evaluation Criteria] A: Image density less than 0.30 B: Image density 0.30 or more and less than 0.40 C: Image density 0.40 or more and less than 0.50 D: Image density 0.50 or more

[0111] <Evaluation of ejection properties> The ink was filled into an inkjet printer (device name: modified IPSiO GXe5500, manufactured by Ricoh Co., Ltd.), and the ejection properties after decap were evaluated. First, in an environment of 25°C and 20% RH, head cleaning was performed using the maintenance command of the inkjet printer, and a test chart was printed to confirm that all nozzle channels were in an ejection state. Next, the head was left uncapped for 10 minutes, and then the test chart was printed again. The number of non-ejection channels was counted from the test chart before and after leaving it, and judged according to the following criteria. Note that for practical use, a number of non-ejection channels less than 10 is suitable. [Evaluation Criteria] A: The number of non-discharge channels is 1 or less B: The number of non-ejecting channels is 2 or more and less than 10 C: 10 or more non-ejecting channels

[0112] <Evaluation of bleeding> The white ink, non-white ink, and pretreatment liquid were applied to the image forming apparatus (IPSiO GXe-5500, Ricoh Co., Ltd.) under environmental conditions adjusted to 23°C ± 0.5°C and 50% ± 5% RH. The driving voltage of the piezoelectric element was varied so that the ejection amount of the white ink and non-white ink was uniform. The pretreatment liquid was applied in advance to the image forming apparatus using bar coater No. 1 at a rate of 3 g / m. 2 After coating, the white ink and the non-white ink were applied in equal amounts (5 g / m) to biaxially oriented polypropylene (OPP) (Toyobo Co., Ltd., Pylen P2102) as a flexible packaging film, which was then dried at 80°C for 2 minutes. 2 ) was set so that the ink would adhere to the paper, and a Gothic font white-spaced character chart was printed using non-white ink, after which a solid image was formed using white ink and dried at 80°C for 2 minutes. The readability of the characters in the resulting images was judged with the naked eye and visually rated according to the following criteria, with a grade of B or higher being considered to be at a practical level. [Evaluation Criteria] A: 3pt Gothic font is readable B: 3pt is unreadable, but 4pt is readable C: 4pt is unreadable, but 5pt is readable D:5pt is unreadable

[0113] [Table 4-1]

[0114] [Table 4-2]

[0115] [Table 4-3]

[0116] For example, aspects of the present invention are as follows. <1> a non-white ink including water, a coloring material, an organic solvent, and an acetylene glycol compound; a white ink containing water, a colorant, an organic solvent, and a compound represented by the following general formula (1); The ink set is characterized by having: [ka] In the general formula (1), R represents a hydrogen atom or a methyl group, n1 and n2 represent integers of 1 to 7, k represents an integer of 0 to 5, and m represents an integer of 1 to 20. <2> The acetylene glycol compound includes an acetylene glycol compound represented by the following general formula (2): <1> The ink set is as described above. [ka] In the general formula (2), x and y each represent an integer of 0 or more, and x+y is an integer of 0 to 3. <3> The non-white ink contains a dialkyl sulfosuccinic acid or a salt thereof. <1> from <2> 13. The ink set according to claim 12, <4> The compound represented by the general formula (1) includes a compound represented by the following general formula (1-1): <1> from <3> 13. The ink set according to claim 12, [ka] In the general formula (1-1), k represents an integer of 0 to 5, and m represents an integer of 1 to 20. <5> The white ink has a static surface tension of 30 mN / m or less, and a dynamic surface tension of the white ink at a surface life of 15 msec according to a maximum bubble pressure method of 34 mN / m or less. <1> from <4> 13. The ink set according to claim 12, <6> On the printing substrate, the above <1> from <5> a non-white ink applying step of applying a non-white ink in the ink set according to any one of the preceding claims; The above <1> from <5> a white ink applying step of applying a white ink in the ink set according to any one of the preceding claims; A printing method comprising the steps of: <7> The non-white ink applying step is followed by the white ink applying step. <6> 2 is a printing method according to the present invention. <8> A drying step is not included between the non-white ink application step and the white ink application step. <6> and <7> 13. The printing method according to claim 12, wherein <9> The method includes a surface modification step of modifying the surface of a printed material. <6> from <8> 13. The printing method according to claim 12, wherein <10> The method includes the step of applying a treatment liquid containing a polyvalent metal salt to a substrate. <6> from <9> 13. The printing method according to claim 12, wherein <11> The substrate is a non-absorbent flexible packaging film. <6> from <10> 13. The printing method according to claim 12, wherein <12> A substrate that is a non-absorbent flexible packaging film; The above <1> from <5> a non-white ink applying means for applying the non-white ink in the ink set according to any one of the preceding claims; The above <1> from <5> a white ink applying means for applying the white ink in the ink set according to any one of the preceding claims; The printing device is characterized by having: <13> a non-white ink including water, a coloring material, an organic solvent, and an acetylene glycol compound; a white ink containing water, a colorant, an organic solvent, and a compound represented by the following general formula (1); A treatment liquid containing water and a polyvalent metal salt; The printing set is characterized by having the following features. [ka] In the general formula (1), R represents a hydrogen atom or a methyl group, n1 and n2 represent integers of 1 to 7, k represents an integer of 0 to 5, and m represents an integer of 1 to 20. <14> The above <12> 2. A non-white ink characterized by being used in the printing device described in 1. <15> The above <12> 2. A white ink characterized by being used in the printing device described in 1.

[0117] The above <1> from <5> The ink set according to any one of the preceding claims. <6> from <11> The printing method according to any one of the preceding claims. <12> The printing device according to <13> The printing set according to <14> The non-white ink according to <15> According to the white ink described in the above, the conventional problems can be solved and the object of the present invention can be achieved. [Explanation of symbols]

[0118] 400 Image forming device 401 Exterior of image forming device 401c Device body cover 404 Cartridge Holder 410 Main Tank 410k, 410c, 410m, 410y Main tanks for black (K), cyan (C), magenta (M), and yellow (Y) 411 Ink storage unit 413 Ink outlet 414 Storage container case 420 Mechanism Department 434 Discharge Head 436 Supply Tube [Prior art documents] [Patent documents]

[0119]

Patent Document 1

Claims

1. a non-white ink including water, a coloring material, an organic solvent, and an acetylene glycol compound; a white ink containing water, a colorant, an organic solvent, and a compound represented by the following general formula (1); wherein the non-white ink contains sodium bis(2-ethylhexyl) sulfosuccinate. 【Chemistry 1】 In the general formula (1), R represents a hydrogen atom or a methyl group. １ , n ２ represents an integer of 1 to 7. k represents an integer of 0 to 5, and m represents an integer of 1 to 20.

2. The ink set according to claim 1 , wherein the acetylene glycol compound includes an acetylene glycol compound represented by the following general formula (2): 【Chemistry 2】 In the above general formula (2), x and y each represent an integer of 0 or more, and x+y is an integer of 0 to 3.

3. The ink set according to any one of claims 1 to 2, wherein the compound represented by general formula (1) includes a compound represented by the following general formula (1-1): 【Chemistry 3】 In the general formula (1-1), k represents an integer of 0 to 5, and m represents an integer of 1 to 20.

4. 4. The ink set according to claim 1, wherein the white ink has a static surface tension of 30 mN / m or less, and a dynamic surface tension of the white ink at a surface life of 15 msec according to a maximum bubble pressure method of 34 mN / m or less.

5. A non-white ink applying step of applying a non-white ink of the ink set according to any one of claims 1 to 4 to a substrate; a white ink applying step of applying the white ink in the ink set according to any one of claims 1 to 4; A printing method comprising:

6. The printing method according to claim 5 , wherein the white ink applying step is performed after the non-white ink applying step.

7. The printing method according to claim 5 , wherein a drying step is not included between the non-white ink applying step and the white ink applying step.

8. The printing method according to claim 5 , further comprising a surface modification step of modifying the surface of the printing substrate.

9. The printing method according to claim 5 , further comprising a treatment liquid applying step of applying a treatment liquid containing a polyvalent metal salt to a substrate.

10. 10. The printing method according to claim 5, wherein the substrate is a non-absorbent flexible packaging film.

11. A substrate that is a non-absorbent flexible packaging film; a non-white ink applying means for applying the non-white ink in the ink set according to any one of claims 1 to 4; a white ink applying unit that applies the white ink in the ink set according to any one of claims 1 to 4; A printing device comprising:

12. a non-white ink including water, a coloring material, an organic solvent, and an acetylene glycol compound; a white ink containing water, a colorant, an organic solvent, and a compound represented by the following general formula (1); A treatment liquid containing water and a polyvalent metal salt; wherein the non-white ink contains sodium bis(2-ethylhexyl) sulfosuccinate. 【Chemistry 4】 In the general formula (1), R represents a hydrogen atom or a methyl group. １ , n ２ represents an integer of 1 to 7. k represents an integer of 0 to 5, and m represents an integer of 1 to 20.

13. A non-white ink for use in the printing device according to claim 11.

14. A white ink for use in the printing device according to claim 11.

Images