Printing method and printed matter

Abstract

To provide a printing method that can prevent the bleeding of ink in a printing object that is porous one, and can achieve high image density.SOLUTION: A printing method includes a process liquid imparting step for imparting a process liquid containing silica and polyvalent metal salts to a printing object having a Cobb water absorbency of 20 g / m2 or more and 75 g / m2 or less after contact with water for 120 seconds, defined in JIS-P8140, and an ink application step for applying ink containing a colorant and water to the printing object.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a printing method, a printing device, and a printed matter. [Background technology]

[0002] In recent years, inkjet printers are not only used for home use, but the technology of forming images by inkjet printing on packaging materials for food, beverages, daily necessities, etc. Examples of printing substrates for packaging applications include cardboard.

[0003] Methods for printing on cardboard can be broadly divided into two types: pre-print method, in which an image is recorded on the base cardboard paper (surface liner paper) with printing ink, and then the core and back liner paper are attached using a corrugator machine to produce cardboard; and post-print method, in which an image is recorded on the surface liner paper of the already attached cardboard with printing ink.

[0004] Conventionally, printing on corrugated board has been done by offset printing, flexography, gravure printing, etc., but since all of these printing methods involve contacting a plate or blanket with the printing medium and applying printing pressure to transfer the ink, the post-print method is prone to uneven density due to the unevenness (flute marks) of the corrugated board surface, making post-print printing particularly difficult on thick corrugated board. On the other hand, the pre-print method solves printing problems, but the lamination process after printing takes time, and the box-making process cannot be started immediately after printing, which means that it is not possible to meet short delivery deadlines.

[0005] In contrast, inkjet printing is a non-contact method of recording an image onto a print medium, making it easy to post-print on thick corrugated board and enabling the box-making process to be started immediately after printing, enabling short delivery times. As a result, demand for inkjet printing in corrugated board printing is on the rise.

[0006] However, when it comes to printing on corrugated board, conventional water-based inkjet printing has quality issues such as low density and bleeding, and is unable to fully meet consumer demands for higher density and resolution.

[0007] Although base paper (liner paper) is attached to the printed surface of cardboard, general base paper does not have an ink-receiving layer or does not have a sufficient ink-receiving layer, and is characterized by being porous compared to coated paper for offset printing, etc. In particular, aqueous inkjet ink, which is a printing ink with low viscosity, tends to penetrate and diffuse into the inside of the base paper, making it difficult to achieve sufficient print density and prone to bleeding, which causes images to bleed.

[0008] In view of this, for example, liner paper provided with an ink receiving layer has been proposed (see, for example, Patent Document 1). Furthermore, a method of applying a treatment liquid containing a polyvalent metal salt has been proposed for the purpose of improving the image quality and durability of the ink-jet ink (see, for example, Patent Document 2). Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide a printing method capable of preventing ink bleeding on a porous printing substrate and realizing high image density. [Means for solving the problem]

[0010] The printing method of the present invention as a means for solving the above problems is a method for producing a printing sheet having a Cobb water absorbency of 20 g / m2 or less after a contact time of 120 seconds with water as specified in JIS-P8140. 2 More than 75g / m 2 The method includes a treatment liquid applying step of applying a treatment liquid containing silica and a polyvalent metal salt to a printing substrate, and an ink applying step of applying an ink containing a coloring material and water to the printing substrate. Effect of the Invention

[0011] According to the present invention, it is possible to provide a printing method capable of preventing ink bleeding on a porous printing substrate and realizing a high image density. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram showing an example of a method for printing on cardboard using the preprint method. [Diagram 2] FIG. 2 is a schematic diagram showing an example of a method for printing on cardboard using the post-printing method. [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

[0013] (Printing method and printing device) The printing method of the present invention is characterized in that the Cobb water absorbency after a contact time of 120 seconds with water as specified in JIS-P8140 is 20 g / m 2 More than 75g / m 2 The method includes a treatment liquid application step of applying a treatment liquid containing silica and a polyvalent metal salt to a printing substrate, which is described below, and an ink application step of applying an ink containing a coloring material and water, and preferably includes a drying step, and further includes other steps as necessary.

[0014] The printing device of the present invention has a Cobb water absorbency of 20 g / m2 after a contact time of 120 seconds with water as specified in JIS-P8140. 2 More than 75g / m 2 The printing apparatus has a treatment liquid applying means for applying a treatment liquid containing silica and a polyvalent metal salt to a printing substrate as described below, and an ink applying means for applying an ink containing a coloring material and water, and preferably has a drying means, and further has other means as necessary.

[0015] The printing method of the present invention can be suitably carried out by the printing apparatus of the present invention, and the treatment liquid application step can be carried out by a treatment liquid application means, the ink application step can be carried out by an ink application means, the drying step can be carried out by a drying means, and the other steps can be carried out by other means.

[0016] The conventional technology described in Patent Document 1 proposes a cardboard base paper (liner paper) with an ink-receiving layer, but it cannot be used with the wide variety of cardboard available on the market, and is not sufficiently versatile. Furthermore, the conventional technology described in Patent Document 2 proposes a method of applying a treatment liquid containing a polyvalent metal salt for the purpose of improving the image quality and resistance of the inkjet ink. However, when cardboard base paper (liner paper) is used as the printing substrate, there is a problem that the color density and bleeding resistance are not sufficient.

[0017] In the present invention, the Cobb water absorbency after a contact time of 120 seconds with water as specified in JIS-P8140 is 20 g / m 2 More than 75g / m 2 By applying a treatment liquid containing silica and a polyvalent metal salt to a substrate to be printed, as described below, the polyvalent metal salt acting as a flocculant remains on the surface due to the silica, preventing ink sedimentation and resulting in a printed material with excellent color density and bleed resistance. Furthermore, even when cardboard base paper (liner paper) is used as the printing substrate, it is possible to obtain a print with excellent color density and bleeding resistance.

[0018] <Treatment liquid application step and treatment liquid application means> The treatment liquid application step is carried out on a substrate that has a Cobb water absorption of 20 g / m2 or less after a contact time of 120 seconds with water as specified in JIS-P8140. 2 More than 75g / m 2 This is a process of applying a treatment liquid containing silica and a polyvalent metal salt to a substrate to be printed, which is described below, and is carried out by a treatment liquid applying means.

[0019] <<Processing liquid>> The treatment liquid is applied to the substrate before the ink is applied to the substrate, and may be referred to as a "pre-treatment liquid" or a "pre-coating liquid."

[0020] The treatment liquid contains silica and a polyvalent metal salt, and preferably contains a resin, and further contains other components as necessary.

[0021] The viscosity of the treatment liquid at 25°C may be adjusted in the range of 5 mPa·s to 1,000 mPa·s depending on the coating method, and such a viscosity can be measured using, for example, a rotational viscometer (RE-80L, manufactured by Toki Sangyo Co., Ltd.). 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. If the viscosity of the treatment liquid at 25°C is 5 mPa·s to 200 mPa·s, the coating on the printed material becomes more uniform, and as a result, the ink coating is more likely to result in a uniform and even image, which is preferable.

[0022] The coating method of the treatment liquid 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. The coating method can be appropriately selected depending on the material, thickness, etc. of the printed material.

[0023] The coating amount of the treatment liquid is 2 g / m2 in solids coating amount on the printed material. 2 More than 30g / m 2 Less than 5 g / m is preferable. 2 More than 20g / m 2 The following is more preferred:

[0024] -silica- As the silica, there can be used vapor phase silica, wet process silica synthesized by a precipitation method or a sol-gel method, colloidal silica, or the like.

[0025] In the present invention, by applying a treatment liquid containing silica to a substrate, the silica layer formed near the surface of the substrate suppresses the loss of density and bleeding caused by the penetration and absorption of ink, thereby producing a high-quality printed material.

[0026] The silica is in a particulate form, and the particle size of the silica is sufficient if it is possible to apply the treatment liquid to the substrate, and the number-average primary particle size is in the range of 5 nm to 40 nm, and the BET specific surface area is 30 m 2 / g or more 350m 2 / g or less, and a silica having a BET specific surface area of ​​35 m 2 / g or more 155m 2 The BET specific surface area of ​​the silica is preferably in the range of 30 m / g or less, because the transparency of the treatment solution can be increased and the appearance of the cardboard can be prevented from being changed. 2 / g or more is preferable, and a BET specific surface area of ​​350 m is preferable because it has excellent fixability to the surface layer of the corrugated board and provides a high ink concentration. 2 It is preferable that the molecular weight is not more than 1 / g. The BET specific surface area of ​​silica is a value measured by the Brunauer, Emmett, and Teller method (BET method), and can be measured by a general gas adsorption method. The number average primary particle size of silica can be measured, for example, by observation with a transmission electron microscope.

[0027] Specific examples of silica include gas phase silica such as AEROSIL50, 90G, 130, 200, 200V, 200CF, 200FAD, 300, 300CF, R972, R976, and W7520 (manufactured by Nippon Aerosil Co., Ltd.), wet process silica such as SYLOJET series (manufactured by Grace Davison Co., Ltd.), and colloidal silica such as Snowtex series (manufactured by Nissan Chemical Co., Ltd.). These may be used alone or in combination of two or more kinds.

[0028] As the silica, hydrophilic silica, with or without surface treatment, and hydrophobic silica treated with dimethylcyclosilane or the like can be used. However, when using hydrophobic silica, it is necessary to disperse it in an organic solvent such as 1,2-propanediol beforehand, which may result in restrictions on the formulation. Therefore, it is more preferable to use hydrophilic silica, which has excellent water dispersibility.

[0029] The amount of silica applied to the printed material is 0.02 g / m 2 More than 0.8g / m 2 Less than 0.04 g / m is preferred. 2 More than 0.6g / m 2 The silica deposition amount is preferably 0.02 g / m or less, because it provides high ink density and prevents bleeding. 2 The above is preferable, and 0.8 g / m is preferable because it can avoid changing the appearance of the cardboard, which is the substrate. 2 The following is preferred:

[0030] The content of silica in the treatment liquid is not particularly limited as long as the amount of silica attached on the substrate satisfies the above range and the treatment liquid can be suitably applied to the substrate surface, but the content of silica in the treatment liquid is preferably 0.3% by mass or more and 6% by mass or less, and more preferably 0.4% by mass or more and 5% by mass or less. From the viewpoint of obtaining high ink concentration and anti-bleeding effect, the silica concentration is preferably 0.3% by mass or more, and from the viewpoint of suppressing the increase in viscosity of the treatment liquid and enabling good coating, the silica concentration is preferably 6% by mass or less.

[0031] -Polyvalent metal salts- The polyvalent metal salt has the function of destabilizing the dispersion of the coloring material in the ink, and causes the pigment in the ink to quickly aggregate after deposition, thereby suppressing color bleeding and improving color development.

[0032] The cation in the polyvalent metal salt is not particularly limited and can be appropriately selected depending on the purpose. For example, aluminum (Al(III)), calcium (Ca(II)), magnesium (Mg(II)), copper (Cu(II)), iron (Fe(II) or Fe(III)), zinc (Zn(II)), tin (Sn(II) or Sn(IV)), strontium (Sr(II)), nickel (Ni(II)), cobalt (Co (II)), barium (Ba(II)), lead (Pb(II)), zirconium (Zr(IV)), titanium (Ti(IV)), antimony (Sb(III)), bismuth (Bi(III)), tantalum (Ta(V)), arsenic (As(III)), cerium (Ce(III)), lanthanum (La(III)), yttrium (Y(III)), mercury (Hg(II)), beryllium (Be(II)), and the like ions. These may be used alone or in combination of two or more. Among these, calcium (Ca(II)) and magnesium (Mg(II)) are preferred.

[0033] The anion in the polyvalent metal salt is not particularly limited and can be appropriately selected depending on the purpose. Examples of the anion include ions of halogen elements such as fluorine (F), chlorine (Cl), bromine (Br), and iodine (I); nitrate ion (NO3 - ), sulfate ion (SO4 2- ions of organic carboxylic acids such as formic acid, acetic acid, lactic acid, malonic acid, oxalic acid, maleic acid, and benzoic acid; ions of organic sulfonic acids such as benzenesulfonic acid, naphtholsulfonic acid, and alkylbenzenesulfonic acid; thiocyanate ion (SCN - , thiosulfate ion S2O3 2- ), phosphate ion (PO4 3- ), nitrite ion (NO 2-These may be used alone or in combination of two or more. Among these, chloride ions (Cl - ), sulfate ion (SO4 2- ), acetate ion, nitrate ion (NO3 - ) is preferred.

[0034] The polyvalent metal salt is not particularly limited and can be appropriately selected according to the purpose. For example, aluminum chloride, calcium chloride, nickel chloride, potassium acetate, sodium acetate, calcium acetate, magnesium acetate, aluminum nitrate, magnesium nitrate, magnesium chloride, calcium nitrate, magnesium hydroxide, aluminum sulfate, magnesium sulfate, ammonium alum, etc. are mentioned. More specifically, calcium acetate monohydrate, calcium nitrate tetrahydrate, calcium chloride hexahydrate, magnesium acetate tetrahydrate, magnesium sulfate (anhydrous), aluminum nitrate nonahydrate, nickel chloride hexahydrate, etc. are mentioned. These may be used alone or in combination of two or more. Among these, calcium acetate monohydrate, calcium nitrate tetrahydrate, calcium chloride hexahydrate, magnesium acetate tetrahydrate, magnesium sulfate (anhydrous) are preferred.

[0035] The content of the polyvalent metal salt is preferably 1% by mass or more and 25% by mass or less, more preferably 3% by mass or more and 20% by mass or less, and even more preferably 5% by mass or more and 12% by mass or less, based on the total amount of the treatment liquid. From the viewpoint of effectively suppressing color bleeding, 1% by mass or more is preferable, and from the viewpoint of high stability during storage and suppression of quality defects such as precipitation, 25% by mass or less is preferable.

[0036] -resin- The treatment liquid may contain a resin. The type of resin is not particularly limited, but at least one selected from acrylic resin, polyolefin resin, polyvinyl acetate resin, polyvinyl chloride resin, urethane resin, and copolymers thereof is preferred because it provides strong adhesion to various printing substrates. When the resin is added to the treatment liquid, it may be added as a liquid in which resin particles are dispersed in water, or a resin commercially available as a resin emulsion may be used. 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 dispersibility, fixing property, and high image hardness, the volume average particle size 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.).

[0037] Considering compatibility and stability when mixed with the polyvalent metal salt, the acid value of the resin is preferably 20 mgKOH / g or less.

[0038] The glass transition temperature (Tg) of the resin may be any temperature that maintains adhesion to the printed material and drying properties, and for example, a resin in the range of -25°C to 70°C can be suitably used. In order to prevent stickiness on the printed material surface and blocking when stacked, the Tg is preferably -25°C or higher, and in order to maintain adhesion and prevent cracking or peeling during folding in the box-making process, the Tg is preferably 70°C or lower. In particular, when cardboard is used as the printed material, a suitable effect can be obtained.

[0039] The resin content is preferably 30% by mass or less, more preferably 0.5% by mass or more and 20% by mass or less, based on the total amount of the treatment liquid. The content indicates the mass % of the resin solid content contained in the treatment liquid. If the content is 30% by mass or less, the thickness of the resin after coating with the treatment liquid is not too thick, which is preferable because it suppresses the occurrence of blocking and changes in the appearance of the corrugated paper, and also because the effect of the polyvalent metal salt is fully exerted.

[0040] -Other ingredients- Examples of other components include organic solvents, water, surfactants, antifoaming agents, antiseptic and antifungal agents, rust inhibitors, and pH adjusters.

[0041] --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 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, petriol and other polyhydric alcohols; ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diene Examples of the alkyl ethers include polyhydric alcohols such as ethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, and propylene glycol monoethyl ether; polyhydric alcohols 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.

[0042] The content of the organic solvent in the treatment liquid is not particularly limited and can be selected appropriately depending on the purpose. Taking into consideration the suitability for application to the substrate, uniform dispersibility, drying properties, etc., the content is preferably 5% by mass or more and 90% by mass or less, and more preferably 10% by mass or more and 70% by mass or less.

[0043] --water-- The water is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include pure water such as ion-exchanged water, ultrafiltered water, reverse osmosis water, distilled water, and ultrapure water. These may be used alone or in combination of two or more. There is no particular limit to the content of water in the treatment liquid, and it is sufficient that the treatment liquid contains a sufficient amount of water so that the polyvalent metal salt does not precipitate during storage at room temperature.

[0044] --Surfactant-- Surfactants have the effect of lowering the surface tension of the treatment liquid, improving its wettability onto various substrates, enabling it to be applied evenly, and of distributing the silica and polyvalent metal salts contained in the treatment liquid evenly onto the substrate.

[0045] As the surfactant, any of silicone-based surfactants, fluorine-based surfactants, amphoteric surfactants, nonionic surfactants, and anionic surfactants can be used. Silicone surfactants are not particularly limited and can be appropriately selected according to 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, side chain both end modified polydimethylsiloxane, etc., and those having polyoxyethylene group or polyoxyethylene polyoxypropylene group as modified group are particularly preferred because they show good properties as aqueous surfactants. 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 dimethylpolysiloxane.

[0046] As the fluorosurfactant, for example, perfluoroalkylsulfonic 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 chain are particularly preferred because they have low foaming properties. As the perfluoroalkylsulfonic acid compounds, for example, perfluoroalkylsulfonic acid, perfluoroalkyl sulfonate, etc. are included. As the perfluoroalkyl carboxylic acid compounds, for example, perfluoroalkyl carboxylic acid, perfluoroalkyl carboxylate, etc. are included. As the polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups on the side chain, for example, sulfate ester salts of polyoxyalkylene ether polymers having perfluoroalkyl ether groups on the side chains, salts of polyoxyalkylene ether polymers having perfluoroalkyl ether groups on the side chains, etc. are included. As counter ions of the salts in these fluorosurfactants, Li, Na, K, NH4, NH3CH2CH2OH, NH2(CH2CH2OH)2, NH(CH2CH2OH)3, etc. are included. 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 polyoxyethylene alkyl ether sulfates. These may be used alone or in combination of two or more.

[0047] The silicone surfactant is not particularly limited and can be appropriately selected depending on the purpose. Examples of the silicone surfactant include side-chain modified polydimethylsiloxane, both-end modified polydimethylsiloxane, one-end modified polydimethylsiloxane, and both-end side-chain modified polydimethylsiloxane. Among these, polyether-modified silicone surfactants having a polyoxyethylene group or a polyoxyethylene polyoxypropylene group as a modifying group are particularly preferred because they exhibit good properties as an aqueous surfactant. Such surfactants may be appropriately synthesized or commercially available products, such as those available from BYK-Chemie Co., Ltd., Shin-Etsu Chemical Co., Ltd., Dow Corning Toray Silicone Co., Ltd., Nippon Emulsion Co., Ltd., and Kyoeisha Chemical Co., Ltd.

[0048] The polyether-modified silicone surfactant is not particularly limited and can be appropriately selected depending on the purpose. For example, it can be one in which a polyalkylene oxide structure is introduced into the Si part side chain of dimethylpolysiloxane, as represented by the following general formula (S-1).

[0049] [ka] (In the general formula (S-1), m, n, a, and b each independently represent an integer, R represents an alkylene group, and R' represents an alkyl group.)

[0050] As the polyether-modified silicone surfactant, commercially available products can be used, and examples thereof include KF-618, KF-642, KF-643 (all manufactured by Shin-Etsu Chemical Co., Ltd.), EMALEX-SS-5602, SS-1906EX (all manufactured by Nippon Emulsion Co., Ltd.), FZ-2105, FZ-2118, FZ-2154, FZ-2161, FZ-2162, FZ-2163, FZ-2164 (all manufactured by Dow Corning Toray Silicone Co., Ltd.), BYK-33, BYK-387 (all manufactured by BYK-Chemie Co., Ltd.), TSF4440, TSF4452, TSF4453 (all manufactured by Toshiba Silicon Co., Ltd.), and the like.

[0051] The fluorine-based surfactant is preferably a compound having 2 to 16 fluorine-substituted carbon atoms, and more preferably a compound having 4 to 16 fluorine-substituted carbon atoms. Examples of the fluorine-based surfactant include perfluoroalkyl phosphate compounds, perfluoroalkyl ethylene oxide adducts, and polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups on the side chains. Among these, polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups in the side chains are preferred because they have low foaming properties, and fluorine-based surfactants represented by any of general formulas (F-1) and (F-2) are particularly preferred.

[0052] [ka] In the compound represented by the above general formula (F-1), m is preferably an integer of 0 to 10, and n is preferably an integer of 0 to 40 in order to impart water solubility.

[0053] [General formula (F-2)] C n F 2n+ -CH2CH(OH)CH2-O-(CH2CH2O) a -Y In the compound represented by the above general formula (F-2), Y is H or C m F2m+1 m is an integer from 1 to 6, or CH2CH(OH)CH2-C m F 2m+1 m is an integer between 4 and 6, or C p H 2P+1 where p is an integer from 1 to 19. n is an integer from 1 to 6. a is an integer from 4 to 14.

[0054] The fluorine-based surfactant may be a commercially available product, such as Surflon S-111, S-112, S-113, S-121, S-131, S-132, S-141, and S-145 (all manufactured by Asahi Glass Co., Ltd.); Fullard FC-93, FC-95, FC-98, FC-129, FC-135, FC-170C, FC-430, and FC-431 (all manufactured by Sumitomo 3M Limited); Megaf FAC F-470, F-1405, F-474 (all manufactured by DIC Corporation); Zonyl TBS, FSP, FSA, FSN-100, FSN, FSO-100, FSO, FS-300, UR, Capstone FS-30, FS-31, FS-3100, FS-34, FS-35 (all manufactured by Chemours); FT-110, FT-250 , FT-251, FT-400S, FT-150, FT-400SW (all manufactured by NEOS Corporation), Polyfox PF-136A, PF-156A, PF-151N, PF-154, PF-159 (manufactured by OMNOVA), Unidyne DSN-403N (manufactured by Daikin Industries, Ltd.), and the like. Among these, FS-3100, FS-34, FS-300 manufactured by Chemours; FT-110, FT-250, FT-251, FT-400S, FT-150, FT-400SW manufactured by NEOS Corporation; Polyfox PF-151N manufactured by OMNOVA, and Unidyne DSN-403N manufactured by Daikin Industries, Ltd. are particularly preferred from the viewpoint of achieving good printing quality, particularly improved color development, penetration into paper, wettability, and dye uniformity.

[0055] The content of the surfactant is not particularly limited and can be appropriately selected depending on the purpose. However, from the viewpoints of excellent wettability and ejection stability and improved image quality, the content is preferably 0.001% by mass or more and 5% by mass or less, and more preferably 0.05% by mass or more and 5% by mass or less.

[0056] --Antifoaming 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.

[0057] --Preservative and fungicidal agent-- The antiseptic and antifungal agent is not particularly limited, and examples thereof include 1,2-benzisothiazolin-3-one.

[0058] --Rust inhibitor-- The rust inhibitor is not particularly limited, and examples thereof include acid sulfite and sodium thiosulfate.

[0059] --pH adjuster-- The treatment liquid in the present invention may contain a pH adjuster. There are no particular limitations on the pH adjuster, and examples thereof include amines such as diethanolamine and triethanolamine. The pH of the treatment liquid is preferably 7 to 12, more preferably 8 to 11, from the viewpoint of preventing corrosion of metal members that come into contact with the liquid.

[0060] <<Print material>> By applying the treatment liquid of the present invention, the Cobb water absorbency after a contact time of 120 seconds with water as specified in JIS-P8140 is 20 g / m 2 More than 75g / m 2 It is possible to obtain an ink print having excellent density and excellent bleeding resistance on the following printed substrate. Even when cardboard (liner paper) is used as the printed substrate, it is possible to obtain an ink print having excellent density and excellent bleeding resistance.

[0061] Here, printing methods for cardboard can be broadly divided into a method (preprint method) in which an image 11 is recorded with printing ink on cardboard base paper (surface liner paper 10) as shown in Figure 1, and then a core 12 and a back liner paper 13 are laminated using a corrugator machine to produce cardboard, and a method (postprint method) in which an image 11 is recorded with printing ink on the surface liner paper 10 of the already laminated cardboard as shown in Figure 2, and the present invention can be suitably used for either method. The preprint method is preferably used because the surface liner paper can be wound into a roll, so that the substrate to be printed is a continuous paper, and printing can be performed using a printing machine for continuous paper. The postprint method is preferably used because the substrate to be printed is easy to store, and furthermore, it can be delivered directly to the customer after printing.

[0062] Corrugated cardboard is basically composed of three sheets of paper: a surface liner paper, a core, and a back liner paper. The strength can be adjusted by changing the materials of the surface liner paper, the core, and the back liner paper. The core comes in different wave heights, with the basic ones being 5mm and 3mm. There are also cardboards with multiple cores stacked together, for example a five-ply structure called "double-sided cardboard," which can be used as the printed material in the present invention. The present invention is suitable for printing on the front liner paper in both the preprinting method and the postprinting method. It is also possible to print on the back liner paper and print on double-sided printed corrugated board.

[0063] Examples of fiber materials used in the manufacture of liner paper include bleached hardwood or softwood kraft pulp, unbleached hardwood or softwood kraft pulp, sulfite hardwood or softwood pulp, etc. In addition, chemically treated pulp, pulp chemically treated using kenaf, hemp, reed, etc., virgin pulp such as ground pulp, chemi-ground pulp, semi-chemical pulp, and recycled paper such as cardboard, newspapers, magazines, and flyers can also be used.

[0064] The cardboard base paper (liner paper) has a Cobb water absorption of 20 g / m2 or more after 120 seconds of contact with water, as specified in JIS-P8140. 2 More than 75g / m 2 Less than 23 g / m 2 More than 69g / m 2 Less than 35 g / m is preferred. 2 More than 60g / m 2 More preferably, the Cobb water absorbency is 20 g / m or less. 2 If the ink is more than 75g / m2, the ink will spread appropriately and will not be repelled by the surface. 2 If the amount is less than this, the fixation of the ink is good and bleeding can be prevented. The Cobb water absorbency is the Cobb water absorbency at a contact time of 120 seconds as specified in JIS-P8140. For example, 2 The measurement can be made by placing a cylinder on the cardboard base paper (test piece) to be used, and pouring 100 mL of water into it while clamping the base paper and cylinder to prevent water leakage. After a contact time of 120 seconds, the water is discarded, and the excess water on the base paper is quickly removed with blotting paper, and the change in weight of the base paper is weighed.

[0065] The basis weight of cardboard base paper (liner paper) is 100g / m 2 More than 400g / m 2 From the viewpoint of lamination suitability by a corrugator machine, 150 g / m or less is preferable. 2 More than 300g / m 2 The following is more preferred:

[0066] <Ink application process and ink application means> The ink applying step is a step of applying ink containing a coloring material and water, and is carried out by an ink applying device.

[0067] The method of applying the ink is not particularly limited, 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 preferably used. In order to achieve excellent solid filling, suppress color bleeding, and form high-quality images, the amount of ink applied when creating a solid image is 4 g / m 2 More than 14g / m 2 Less than 7 g / m is preferable. 2 More than 14g / m 2 The following is more preferred: When printing small droplets of ink, it is preferable to apply a small amount of ink.

[0068] <<Ink>> The ink used in the present invention contains a coloring material and water, but may also contain organic solvents, resins, additives, and the like. The organic solvent, water, coloring material, resin, additives, etc. used in the ink will be described below.

[0069] -Organic solvents- The organic solvent is not particularly limited and can be appropriately selected depending on the purpose, and for example, the same organic solvent as that contained in the treatment liquid can be used. However, when any one of 1,2-propanediol, 1,2-butanediol, and 2,3-butanediol is contained, the film-forming property of the resin is improved and further the scratch resistance is improved, which is preferable. The content of the organic solvent in the ink is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoints of the drying property and ejection reliability of the 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.

[0070] -water- The water content in the ink is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoints of the drying property and ejection reliability of the ink, however, it is preferably from 10% by mass to 90% by mass, and more preferably from 20% by mass to 60% by mass.

[0071] -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, white pigments, green pigments, orange pigments, glossy pigments such as gold and silver pigments, and metallic pigments. As inorganic pigments, titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, chrome yellow, as well as carbon black produced by known methods such as the contact method, furnace method, and thermal method can be used. As organic pigments, 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. can be used. Among these pigments, those having good affinity with the solvent are preferably used. In addition, resin hollow particles and inorganic hollow particles can also be 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).

[0072] 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.

[0073] 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.

[0074] The content of the coloring material in the 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.

[0075] Methods for dispersing a pigment to obtain an 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 making a pigment self-dispersible by introducing a hydrophilic functional group into the pigment is a method in which a functional group such as a sulfone group or a carboxyl group is added to the 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 polymeric dispersant, typified by 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.

[0076] -Pigment dispersion- It is possible to obtain ink by mixing a pigment with materials such as water or an organic solvent, or it is also possible to manufacture ink by mixing a pigment with other materials such as water and a dispersant to prepare a pigment dispersion, and then mixing the resulting mixture with materials such as water or an organic solvent. 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. There are no particular restrictions on the particle size of the pigment in the pigment dispersion. However, in terms of the maximum number, the maximum frequency 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 average particle size of the pigment can be measured, for example, 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.

[0077] -resin- The type of resin contained in the ink is not particularly limited and can be appropriately selected depending on the purpose. 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 an 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 types of resin particles.

[0078] 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.).

[0079] The resin content is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoints of fixation property and storage stability of the 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 ink.

[0080] The particle size of the solid content in the ink is not particularly limited and can be appropriately selected depending on the purpose, but in terms of improving image quality such as ejection stability and image density, the maximum frequency in terms of maximum number is preferably 20 nm or more and 1,000 nm or less, more preferably 20 nm or more and 150 nm or less. The solid content includes resin particles, pigment particles, etc. The particle size can be measured using a particle size analyzer (Nanotrac Wave-UT151, manufactured by Microtrac Bell Co., Ltd.).

[0081] -Additives- If necessary, surfactants, antifoaming agents, antiseptic and antifungal agents, rust inhibitors, pH adjusters, etc. may be added to the ink.

[0082] --Surfactant-- The surfactant is not particularly limited and can be appropriately selected depending on the purpose. For example, the same surfactant as that contained in the treatment liquid can be used.

[0083] --Antifoaming agent-- The defoaming agent is not particularly limited and may be appropriately selected depending on the purpose. For example, the same defoaming agent as that contained in the treatment liquid may be used.

[0084] --Preservative and fungicidal agent-- The antiseptic and fungicide is not particularly limited and may be appropriately selected depending on the purpose. For example, the same antiseptic and fungicide as that contained in the treatment liquid may be used.

[0085] --Rust inhibitor-- The rust inhibitor is not particularly limited and can be appropriately selected depending on the purpose. For example, the same rust inhibitor as that contained in the treatment liquid can be used.

[0086] --pH adjuster-- There are no particular limitations on the pH adjuster, and it can be appropriately selected depending on the purpose. For example, the same pH adjuster as that contained in the treatment liquid can be used.

[0087] The ink can be prepared by dispersing or dissolving each of the components in, for example, water as a solvent, and further mixing the components by stirring as necessary. For the stirring and mixing, for example, a stirrer using a normal stirring blade, a magnetic stirrer, a high-speed disperser, or the like can be used.

[0088] The physical properties of the 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 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 surface tension of the ink is preferably 35 mN / m or less, and more preferably 32 mN / m or less at 25° C., in order to ensure good leveling of the ink on the substrate and shorten the drying time of the ink. The pH of the 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.

[0089] <Drying process and drying means> The drying step is a step of drying the printing substrate to which the treatment liquid and the ink have been applied, and is carried out by a drying means. In the present invention, the treatment liquid is applied to the substrate by the above-mentioned coating method, and then ink is applied to record an image. After the treatment liquid is applied to the substrate, printing with ink may be performed before the applied treatment liquid dries, or printing with ink may be performed after the applied treatment liquid dries.

[0090] Drying of the treatment liquid and ink is a process in which the printed material (cardboard base paper) is heated and dried by known methods such as a roll heater, drum heater, hot air dryer, infrared dryer, or ultraviolet dryer, and it is preferable to provide a state in which the surface temperature of the printed material is 60° C. or higher, and preferably 60° C. or higher and 100° C. or lower. The drying time is preferably 1 second or longer and shorter than 300 seconds.

[0091] (Printed material) The printed matter of the present invention has a Cobb water absorbency of 20 g / m2 after a contact time of 120 seconds with water as specified in JIS-P8140. 2 More than 75g / m 2 The printing method includes the following: a printing substrate, a treatment liquid layer containing silica and a polyvalent metal salt, and an ink layer containing a coloring material, which are provided on the printing substrate. As the printing substrate, cardboard base paper can be suitably used. The printed matter has an image formed on a substrate using the ink used in the present invention. A printed matter can be produced by printing using the printing device and printing method of the present invention. The printing device does not have to be a device dedicated to printing on cardboard; an inkjet printing device can be used.

[0092] <Printing device, printing method> Fig. 3 is a schematic diagram showing an example of a printing device and a printing method. The printing device in Fig. 3 has a treatment liquid application device 2 that applies a treatment liquid, an ink ejection head 3 that ejects black ink (K), cyan ink (C), magenta ink (M), and yellow ink (Y), a drying device 5, and a conveyor belt 6 that conveys the printing substrate 1. The recording apparatus and the recording method may have a heating means used in the heating step and a drying means used in the drying step. The heating means and the drying means include, for example, a means for heating and drying the printed surface or the back surface of the printed material. The heating means and the 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. In addition, the recording device and recording method are not limited to those that visualize meaningful images such as characters and figures with ink. For example, those that form patterns such as geometric designs and those that create three-dimensional images are also included. Furthermore, unless otherwise specified, the recording apparatus includes both a serial type apparatus in which the ejection head moves and a line type apparatus in which the ejection head does not move. Furthermore, this recording device includes not only desktop types, but also wide-width recording devices that can print on A0-sized substrates, and continuous-feed printers that can use continuous paper wound into a roll as the substrate.

[0093] 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

[0094] 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%.

[0095] (Pigment Dispersion Preparation Example 1) -Preparation of magenta pigment dispersion 1- The mixture of the following formulation was premixed and then circulated and dispersed for 7 hours in a disk-type bead mill (KDL model, manufactured by Shinmaru Enterprises, media: zirconia balls with a diameter of 0.3 mm) to obtain magenta pigment dispersion 1 (pigment concentration: 15% by mass). [Magenta pigment dispersion 1 formulation] CI Pigment Red 269 (Clariant): 15 parts by weight Acrylic polymer dispersant (Disperbyk-2010, manufactured by BYK Japan Co., Ltd.): 5 parts by weight Ion-exchanged water: 80 parts by weight

[0096] (Ink Production Example 1) - Preparation of magenta ink 1 - A mixture of the following formulation was premixed, stirred at 2,000 rpm for 10 minutes with a dissolver (DISPERMAT LC30, manufactured by Eiko Seiki Co., Ltd.), and then filtered through a polypropylene filter with an average pore size of 0.8 μm to obtain magenta ink 1. [Magenta ink 1 recipe] The magenta pigment dispersion 1:20 parts by weight TEGO (registered trademark) Wet 270 (silicone-based surfactant, manufactured by Evonik): 1 part by weight Proxel LV (antiseptic and antifungal agent, manufactured by Avecia): 0.1 parts by weight 1,2-propanediol: 25 parts by weight Propylene glycol monomethyl ether acetate: 5 parts by weight Ion-exchanged water: 48.9 parts by weight

[0097] (Silica Dispersion Preparation Example 1) -Preparation of Silica Dispersion 1- The mixture having the following recipe was premixed and then stirred at 10,000 rpm for 20 minutes with a homogenizer (T25 Digital ULTRA-TURRAX, manufactured by IKA Corporation) to obtain Silica Dispersion 1 (silica concentration: 10% by mass). [Formulation of Silica Dispersion 1] AEROSIL 50 (hydrophilic silica, specific surface area 50±15m 2 / g, manufactured by Nippon Aerosil Co., Ltd.): 10 parts by mass Ion-exchanged water: 90 parts by weight

[0098] (Silica Dispersion Preparation Examples 2 to 4) -Preparation of Silica Dispersions 2 to 4- Silica Dispersions 2 to 4 (silica concentration: 10 mass %) were prepared in the same manner as in Silica Dispersion Preparation Example 1, except that the formulation in Silica Dispersion Preparation Example 1 was changed to that shown in Table 1.

[0099] [Table 1]

[0100] Details of each component in Table 1 are as follows. AEROSIL 50 (hydrophilic silica, BET specific surface area 50m 2 / g, number average primary particle size: approx. 30 nm, manufactured by Nippon Aerosil Co., Ltd.) AEROSIL 130 (hydrophilic silica, BET specific surface area 130m 2 / g, number average primary particle size: approx. 16 nm, manufactured by Nippon Aerosil Co., Ltd.) AEROSIL 300 (hydrophilic silica, BET specific surface area 300m 2 / g, number average primary particle size: approx. 7 nm, manufactured by Nippon Aerosil Co., Ltd.) AEROSIL R972 (hydrophobic silica, BET specific surface area 110m 2 / g, number average primary particle size: approx. 16 nm, manufactured by Nippon Aerosil Co., Ltd.) The BET specific surface area of ​​silica can be measured by the Brunauer, Emmett, and Teller method (BET method), and is a value measured by a general gas adsorption method.

[0101] (Preparation Example 1 of Processing Solution) -Preparation of processing solution 1- The mixture having the following composition was premixed and then stirred at 2,000 rpm for 10 minutes with a dissolver (DISPERMAT LC30, manufactured by Eiko Seiki Co., Ltd.) to obtain treatment liquid 1. [Formulation for Processing Solution 1] 1,2-propanediol: 10.0 parts by weight 3-Methoxybutanol: 10.0 parts by weight TEGO (registered trademark) Wet 270 (silicone-based surfactant, manufactured by Evonik): 0.5 parts by weight Proxel LV (manufactured by Avecia, antiseptic and antifungal agent): 0.1 parts by weight The silica dispersion 1: 10.0 parts by weight Calcium acetate monohydrate: 6.0 parts by weight Ion-exchanged water: 63.4 parts by weight

[0102] (Processing solution preparation examples 2 to 16) - Preparation of treatment solutions 2 to 16 - Treatment liquids 2 to 16 were prepared in the same manner as in Treatment liquid Preparation Example 1, except that the formulations in Treatment liquid Preparation Example 1 were changed to those shown in Tables 2 to 4.

[0103] Next, the viscosity of each of the resulting treatment liquids was measured at 25° C. as follows. The results are shown in Tables 2 to 4.

[0104] <Viscosity measurement> The viscosity of each treatment liquid was measured at 25° C. using a standard cone rotor (1°34′×R24), a sample liquid volume of 1.2 mL, a rotation speed of 50 rpm, and for 3 minutes.

[0105] [Table 2]

[0106] [Table 3]

[0107] [Table 4]

[0108] Details of each component in Tables 2 to 4 are as follows. ·Hirosu-X·M-141 (acrylic resin emulsion, solid content 45% by mass, acid value 19 mgKOH / g, manufactured by Seiko PMC Corporation) TEGO® Wet 270 (silicone surfactant, manufactured by Evonik)

[0109] <Coating of treatment liquid> Each treatment liquid was applied to each of the substrates for printing in the combinations shown in Tables 5 to 8 using a bar coater. After application of the treatment liquid, the substrate was dried for 2 minutes in a dryer set at 80°C. Tables 5 to 8 show the coating amount (g / m 2 ), silica adhesion amount after drying (g / m 2 ) is shown.

[0110] Next, the change in appearance of each printed material after coating with the treatment liquid was evaluated as follows. The results are shown in Tables 5 to 8.

[0111] <Evaluation of changes in appearance of printed materials> The treatment liquid was applied, and after drying, the degree of change in appearance of each of the printed materials in the combinations shown in Tables 5 to 8 was visually observed and evaluated according to the following criteria, with △ or better being at a level that can be used practically. [Evaluation Criteria] ○: Almost no change in appearance compared to before coating △: Slight cloudiness and whitening observed compared to before coating ×: Significant cloudiness and whitening are observed compared to before coating

[0112] (Examples 1 to 16 and Comparative Examples 1 to 4) <Image recording process> Magenta ink 1 in the combinations shown in Tables 5 to 8 was filled into an inkjet printer (IPSiO GXe5500, manufactured by Ricoh Co., Ltd.), and a solid image was formed at 1,200 dpi on a printing substrate that had been coated with the treatment liquid.

[0113] <Print material> Details of the printed material are as follows: ·Printing substrate A: NPK liner TF (weight 170g / m 2 , cardboard base paper, Cobb water absorption 55g / m 2 (Manufactured by Nippon Paper Industries Co., Ltd.) ·Print substrate B: TPK-F (weight 170g / m 2 , cardboard base paper, Cobb water absorption 23g / m 2 (Manufactured by Shin Tokai Paper Co., Ltd.) ·Printing substrate C: NCNF liner (weight 160g / m 2 , cardboard base paper, Cobb water absorption 69g / m 2 (Manufactured by Nippon Paper Industries Co., Ltd.) The Cobb water absorbency is a value measured after a contact time with water of 120 seconds as specified in JIS-P8140.

[0114] Next, "optical density (magenta density)" and "bleeding (color bleeding)" were evaluated as follows. The results are shown in Tables 5 to 8.

[0115] <Evaluation of optical density (magenta density)> Ten sheets of Ricopy PPC paper type 6200 (manufactured by Ricoh Co., Ltd.) were placed under each of the printed materials in the combinations shown in Tables 5 to 8 as backing for color measurement, and a spectrophotometric densitometer (device name: X-Rite939, manufactured by X-Rite Co., Ltd.) was used to measure the optical density (magenta density) at any five points in the printed image, and the average value was evaluated according to the following criteria. Note that △ or higher is a level that can be used practically. [Evaluation Criteria] ◎: Optical density (magenta density) is 1.5 or more 〇: Optical density (magenta density) is 1.25 or more and less than 1.5 △: Optical density (magenta density) is 1.0 or more and less than 1.25 ×: Optical density (magenta density) less than 1.0

[0116] <Evaluation of color bleeding> The edges of the solid images formed were visually observed to measure the distance of the image portion that had seeped out into the non-printed portion of each printed substrate for the combinations shown in Tables 5 to 8, and evaluated according to the following criteria. Note that a grade of △ or better is considered to be usable. [Evaluation Criteria] ◎: Almost no bleeding is observed ○: Bleeding is observed with a distance of less than 1 mm △: Bleeding is observed with a distance of 1mm or more but less than 2mm. ×: Bleeding is observed with a distance of 2 mm or more.

[0117] [Table 5]

[0118] [Table 6]

[0119] [Table 7]

[0120] [Table 8]

[0121] The results in Tables 5 to 8 show that, compared with Comparative Examples 1 to 4, Examples 1 to 16 have higher optical density (magenta density) and can prevent bleeding (color bleeding). Moreover, in Comparative Example 4, it was found that if the treatment liquid was not applied, the decrease in magenta density and bleeding became significant.

[0122] For example, aspects of the present invention are as follows. <1> Cobb water absorption of 20g / m2 after 120 seconds of contact with water as specified in JIS-P8140 2 More than 75g / m 2 A treatment liquid application step of applying a treatment liquid containing silica and a polyvalent metal salt to a printing substrate, which is an ink applying step of applying an ink containing a coloring material and water; A printing method comprising the steps of: <2> The printing material is a cardboard base paper. <1> 2 is a printing method according to the present invention. <3> In the treatment liquid application step, the silica deposition amount was 0.02 g / m 2 More than 0.8g / m 2 The above-mentioned <1> from <2> 13. The printing method according to claim 12, wherein <4> The BET specific surface area of ​​the silica is 30m 2 / g or more 350m 2 / g or less. <1> from <3> 13. The printing method according to claim 12, wherein <5> The BET specific surface area of ​​the silica is 35m 2 / g or more 155m 2 / g or less. <4> 2 is a printing method according to the present invention. <6> The content of the polyvalent metal salt in the treatment liquid is 1% by mass or more and 25% by mass or less. <1> from <5> 13. The printing method according to claim 12, wherein <7> The content of the silica in the treatment liquid is 0.3% by mass or more and 6% by mass or less. <1> from <6> 13. The printing method according to claim 12, wherein <8> The silica is a hydrophilic silica. <1> from <7> 13. The printing method according to claim 12, wherein <9> The treatment liquid contains a resin having an acid value of 20 mgKOH / g or less, and the content of the resin is 0.5% by mass or more and 20% by mass or less. <1> from <8> 13. The printing method according to claim 12, wherein <10> a drying step of drying the printing substrate to which the treatment liquid and the ink have been applied, <1> from <9> 13. The printing method according to claim 12, wherein <11> In the ink applying step, the ink is applied by an inkjet method. <1> from <10> 13. The printing method according to claim 12, wherein <12> Cobb water absorption of 20g / m2 after 120 seconds of contact with water as specified in JIS-P8140 2 More than 75g / m 2 A treatment liquid applying means for applying a treatment liquid containing silica and a polyvalent metal salt to a printing substrate, which is an ink applying means for applying an ink containing a coloring material and water; The printing device is characterized by having: <13> a drying means for drying the printing substrate to which the treatment liquid and the ink have been applied, <12> The printing apparatus according to the present invention is <14> Cobb water absorption of 20g / m2 after 120 seconds of contact with water as specified in JIS-P8140 2 More than 75g / m 2 A printed material, which is a layer containing silica and a polyvalent metal salt; A layer containing a color material; The printed matter is characterized by having the following:

[0123] The above <1> from <11> The printing method according to any one of the preceding claims. <12> from <13> The printing apparatus according to any one of the preceding claims, <14> According to the printed matter described in the above, the conventional problems can be solved and the object of the present invention can be achieved. [Explanation of symbols]

[0124] 1 Printing material 2 Processing liquid application device 3. Ink ejection head 5 Drying equipment 6 Conveyor belt [Prior art documents] [Patent documents]

[0125] [Patent Document 1] JP 2006-150694 A [Patent Document 2] Special Publication No. 2013-538132

Claims

1. Cobb water absorbency of 20 g / m2 after 120 seconds of contact with water as specified in JIS-P8140 ２ 75g / m or more ２ A treatment liquid application step of applying a treatment liquid containing silica and a polyvalent metal salt to a printing substrate, which is an ink applying step of applying an ink containing a coloring material and water; Including, A printing method, characterized in that the number average primary particle diameter of the silica is 5 nm or more and 40 nm or less.

2. The printing method according to claim 1 , wherein the substrate is a corrugated cardboard sheet.

3. In the treatment liquid application step, the amount of silica attached was 0.02 g / m ２ 0.8g / m or more ２ 3. The printing method according to claim 1, wherein:

4. The BET specific surface area of ​​the silica is 30 m ２ / g or more 350m ２ The printing method according to claim 1 , wherein the viscosity is 0.1 to 0.5 μm.

5. The BET specific surface area of ​​the silica is 35 m ２ / g or more 155m ２ The printing method according to claim 4 , wherein the viscosity is 0.1 to 1.0 μm.

6. The printing method according to claim 1 , wherein the content of the polyvalent metal salt in the treatment liquid is 1% by mass or more and 25% by mass or less.

7. The printing method according to claim 1 , wherein the content of the silica in the treatment liquid is 0.3% by mass or more and 6% by mass or less.

8. A printing method according to any one of claims 1 to 7, wherein the silica is a hydrophilic silica.

9. 9. The printing method according to claim 1, wherein the treatment liquid contains a resin having an acid value of 20 mgKOH / g or less, and the content of the resin is 0.5% by mass or more and 20% by mass or less.

10. The printing method according to claim 1 , further comprising a drying step of drying the printing substrate to which the treatment liquid and the ink have been applied.

11. The printing method according to claim 1 , wherein in the ink applying step, the ink is applied by an inkjet method.

12. The treatment liquid contains an organic solvent, The printing method according to claim 1 , wherein a content of the organic solvent in the treatment liquid is 10% by mass or more and 70% by mass or less.

13. The printing method of claim 12, wherein the organic solvent comprises 1,2-propanediol.

14. Cobb water absorbency of 20 g / m2 after 120 seconds of contact with water as specified in JIS-P8140 ２ 75g / m or more ２ A printed material, which is a layer containing silica and a polyvalent metal salt; A layer containing a color material; having A printed matter, characterized in that the number average primary particle diameter of the silica is 5 nm or more and 40 nm or less.

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