JP7592929B1 - Method for manufacturing inkjet printed matter - Google Patents

Abstract

The present invention provides an inkjet printed material having improved coating resistance of a layer printed with a water-based inkjet ink.
[Solution] A method for producing an inkjet printed product includes, in order: a primer coating step in which an aqueous primer composition containing a binder resin and a water-soluble polyvalent metal salt is coated on a substrate and dried to produce a primer coated product; an inkjet printing step in which an aqueous ink composition containing an aqueous resin emulsion and a pigment and having a glass transition temperature (Tg) of -20 to 50°C is printed on the primer coated product using an inkjet device, and then dried to produce an inkjet printed product; and a heat treatment step in which the inkjet printed product is subjected to a heat treatment while being exposed to moisture.
[Selected Figure] Figure 1

Description

The present invention relates to a method for producing inkjet printed matter using aqueous inkjet ink.

Inkjet inks are used to form print layers by spraying small ink droplets onto various recording media and depositing them on the recording media. They are broadly classified into water-based inks, solvent-based inks, and curable inks. Water-based inkjet inks are primarily made of water and have the advantage of being environmentally friendly.

On the other hand, aqueous inkjet inks may not have sufficient coating resistance, such as hardness and strength, such as resistance to dry friction, and moisture and water resistance, such as resistance to wet friction and retort. For this reason, printed matter printed with aqueous inkjet inks is often used with the printed surface protected from exposure by, for example, laminating a laminate film on the printed surface. For example, when an inkjet printed matter printed with aqueous inkjet ink is used as a packaging container, it is common to use the aqueous inkjet ink for so-called reverse printing, and the printed surface is often not exposed to the outside when used as a packaging container.

In addition, an inkjet printing method has been proposed in which a pretreatment liquid (primer) is applied to a recording medium before applying an aqueous inkjet ink (see Patent Documents 1 and 2). Patent Document 1 proposes that a reaction liquid containing a reactant that enhances the aggregation effect is applied to a recording medium, and then a colored ink and a clear ink are applied to increase the aggregation of the applied colored ink and clear ink, thereby improving the quality of the printed image. Patent Document 2 discloses an ink set of an aqueous primer composition and an aqueous inkjet ink composition; it proposes applying the aqueous primer composition and the aqueous inkjet ink composition to a resin film, which is a recording medium, and further laminating a laminate film on the printed surface to obtain a laminate film with high laminate strength.

JP 2016-196177 A JP 2018-203905 A

As mentioned above, the printing layer of an inkjet print printed with an aqueous inkjet ink has low coating resistance and is easily worn away by friction, or the coating can peel off when exposed to humidity or moisture. For this reason, there have been attempts to improve the physical properties of inkjet prints by applying a primer before printing with aqueous inkjet ink, but this has not been able to sufficiently improve the coating physical properties of the printing layer itself of the print. Therefore, the object of the present invention is to improve the coating resistance of the printing layer of a print made with an aqueous inkjet ink.

That is, a first aspect of the present invention relates to a method for producing an inkjet printed matter, which will be described below.
[1] A method for producing an inkjet printed product, the method comprising the steps of: a primer coating step of coating a substrate with an aqueous primer composition containing a binder resin and a water-soluble polyvalent metal salt, and drying the coating to produce a primer coated product; an inkjet printing step of printing an aqueous inkjet ink composition containing an aqueous resin emulsion and a pigment having a glass transition temperature (Tg) of -20 to 50°C onto the primer coated product using an inkjet printing device, and drying the coating to produce an inkjet printed product; and a heat treatment step of subjecting the inkjet printed product to a heat treatment while exposing it to moisture.

The present invention preferably relates to a method for producing an inkjet printed matter as described below.
[2] The method for producing an inkjet printed matter described in [1] above, wherein the heat treatment is a steam treatment or a hot water immersion treatment.
[3] The method for producing an inkjet printed matter described in [1] or [2] above, wherein the binder resin contained in the aqueous primer composition contains an acrylic resin and/or a vinyl acetate resin.
[4] The method for producing an inkjet printed matter according to any one of [1] to [3] above, wherein the water-soluble polyvalent metal salt contained in the aqueous primer composition contains a calcium salt.
[5] The method for producing an inkjet printed matter according to any one of [1] to [4] above, wherein the aqueous resin emulsion contained in the aqueous inkjet ink composition contains a styrene-acrylic resin.
[6] The method for producing an inkjet printed matter according to any one of [1] to [5] above, wherein the water-based resin emulsion contained in the water-based inkjet ink composition has a glass transition temperature (Tg) of 9 to 50° C.
[7] The method for producing an inkjet printed matter according to any one of [1] to [6] above, wherein the substrate is a resin film, metal, or cardboard.
[8] The method for producing an inkjet printed matter described in any one of [1] to [7] above, wherein the inkjet printed matter is a surface-printed printed matter.

A second aspect of the present invention relates to an inkjet printing apparatus described below.
[9] An inkjet printing device including a primer applying means, an inkjet printing means, and a heat treatment means, comprising:
An inkjet printing apparatus in which the primer application means applies an aqueous primer composition containing a binder resin and a water-soluble polyvalent metal salt to a substrate and dries the applied material to provide a primer-coated product; the inkjet printing means prints an aqueous inkjet ink composition containing an aqueous resin emulsion and a pigment having a glass transition temperature (Tg) of -20 to 50°C onto the primer-coated product and dries the resulting product to provide an inkjet printed product; and the heat treatment means heat-treats the inkjet printed product while exposing it to moisture.

According to the present invention, it is possible to improve the various coating film resistances of the ink-printed layer in an inkjet print made with an aqueous inkjet ink. Therefore, according to the present invention, an inkjet print made with an aqueous inkjet ink can be used as a surface-printed print, etc., in a state where the printed surface can come into contact with the outside.

FIG. 1 is a diagram illustrating an outline of an inkjet printing apparatus according to the present invention.

1. Regarding the Method for Producing an Inkjet Printed Material The method for producing an inkjet printed material of the present invention includes, in this order, 1) a primer application step, 2) an inkjet printing step, and 3) a heat treatment step.

1-1. Primer Coating Step The primer coating step in the method for producing an inkjet printed matter of the present invention is a step including coating an aqueous primer composition on a substrate to be printed and drying it.

1-1-1. Printing substrate Examples of the printing substrate in the method for producing an inkjet printed matter of the present invention include, but are not limited to, plastic substrates such as polyethylene terephthalate (PET) film, polypropylene film, and polyvinyl chloride sheet; metal substrates such as aluminum; corrugated paper; coated paper such as art paper, inkjet paper, and inkjet glossy paper; uncoated paper such as plain paper and offset paper; and fabrics such as cotton. It is sometimes preferable that the printing substrate is a substrate for a packaging container; examples of the printing substrate include plastic films, metals, and corrugated paper.

1-1-2. Aqueous primer composition The aqueous primer composition used in the primer application step contains a binder resin, a water-soluble polyvalent metal salt, and water, and may contain other optional components (hydrazine derivatives, chlorinated polyolefins, etc.). The main component of the aqueous primer composition is water, and the content of water in the aqueous primer composition is usually 80% by mass or more, preferably 85% by mass or more, and more preferably 90% by mass or more.

1-1-2A. Binder Resin The binder resin is present as an emulsion or dissolved in the aqueous primer composition. Examples of the binder resin include acrylic resin, vinyl acetate resin, polyester resin, polyurethane resin, polyvinyl chloride resin, polybutadiene resin, polyolefin resin, etc.; however, acrylic resin and/or vinyl acetate resin are preferred.

The content of the binder resin in the aqueous primer composition is preferably 0.5% by mass or more, more preferably 1% by mass or more; on the other hand, it is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less. By including the binder resin, the adhesion of the aqueous primer composition to the substrate to be printed is increased, but if the content of the binder resin is excessively high, the storage stability of the aqueous primer composition may decrease.

Acrylic resins are made of monomers such as unsaturated carboxylic acids, such as (meth)acrylic acid and (anhydrous) maleic acid; (meth)acrylic acid esters having aliphatic hydrocarbon groups, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, myristyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, oleyl (meth)acrylate, and eicosyl (meth)acrylate; 2-hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, and (meth)acrylic acid. It is a resin obtained by polymerizing (meth)acrylic acid ester compounds having hydroxyalkyl groups such as 2-hydroxypropyl acrylate and 3-hydroxypropyl (meth)acrylate; (meth)acrylamide, acrylonitrile, olefin-based compounds, etc.; styrene-based monomers such as styrene, α-methylstyrene, vinyltoluene, dimethylstyrene, ethylstyrene, isopropylstyrene, t-butylstyrene, chlorostyrene, dichlorostyrene, bromostyrene, fluorostyrene, and styrene; benzyl (meth)acrylate-based monomers such as benzyl (meth)acrylate; and phenyl (meth)acrylate-based monomers such as phenyl (meth)acrylate. These acrylic resins may be used alone or in combination of two or more.

The glass transition temperature (Tg) of the acrylic resin is preferably -30 to 120°C, the weight average molecular weight is preferably 3,000 to 50,000, and the acid value is preferably 30 to 500 mgKOH/g.

The vinyl acetate resin is a resin containing 50 mol% or more of vinyl acetate monomer. The vinyl acetate resin may be a vinyl acetate homopolymer or a copolymer of vinyl acetate and other monomers. The vinyl acetate resin may be partially saponified or 100% saponified as necessary. Examples of other monomers include ethylene, propylene; vinyl halides such as vinyl chloride, vinylidene chloride, and vinyl fluoride; (meth)acrylic acid alkyl esters such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate; carboxyl group-containing monomers such as (meth)acrylic acid, maleic acid, fumaric acid, and crotonic acid, and their anhydrides.

The weight average molecular weight of the vinyl acetate resin is preferably 3,000 to 50,000.

The binder resin in the aqueous primer composition may contain chlorinated polyolefin. Chlorinated polyolefin is a resin obtained by chlorinating polyolefin resin, and may be an emulsion of the resin. Examples of polyolefin resins to be chlorinated include polypropylene resin, polyethylene resin, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, ethylene-propylene-α-olefin copolymer, propylene-α-olefin copolymer, ethylene-vinyl acetate copolymer, etc. In addition, the chlorinated polyolefin may be acid-modified with maleic acid (anhydride) or the like to improve the storage stability as an aqueous resin emulsion, and in that case, a basic compound is further added to the system before use. Two or more types of chlorinated polyolefin emulsions may be used in combination.

The degree of chlorination (chlorine content) of the chlorinated polyolefin is preferably 1 to 40% by mass, and more preferably 10 to 30% by mass, based on the total resin. If the degree of chlorination of the chlorinated polyolefin is too high, the polarity of the resin itself becomes excessively high, and when the resin is contained in a primer composition, the adhesion to the substrate to be printed may decrease.

The content of chlorinated polyolefin in the aqueous primer composition is not particularly limited, but from the viewpoint of the adhesion of the aqueous primer composition to the substrate to be printed and the storage stability of the primer composition itself, the content in the primer composition is preferably 0.2 mass% or more, more preferably 0.3 mass% or more, even more preferably 1 mass% or more, and may be 1.5 mass% or more, calculated as solid content; on the other hand, the content is preferably 20 mass% or less, more preferably 15 mass% or less, even more preferably 10 mass% or less, and may be 5 mass%.

1-1-2B. Water-soluble polyvalent metal salt The water-soluble polyvalent metal salt contained in the aqueous primer composition may be a polyvalent metal salt of an organic acid and/or an inorganic acid, but is preferably a polyvalent metal salt of an organic acid. Examples of polyvalent metals include calcium, magnesium, iron, aluminum, zinc, strontium, copper, nickel, etc., but are preferably calcium and magnesium, and more preferably calcium.

The polyvalent metal salt of an organic acid is, for example, a polyvalent metal salt of a fatty acid. Fatty acids preferably include those in which the carbon number of R in the fatty acid anion ^RCOO- is 1 or more and 30 or less. Specific examples of fatty acids include acetic acid, propionic acid, octylic acid, lauric acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, 12-hydroxystearic acid, ricinoleic acid, oleic acid, vaccenic acid, linoleic acid, linolenic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, montanic acid, melissic acid, and the like. Among these, those in which the carbon number of R in the fatty acid anion ^RCOO- is 1 or more and 10 or less is more preferable, and those in which the carbon number is 1 or more and 5 or less are even more preferable. Examples of such fatty acids include acetic acid, etc.

The polyvalent metal salt of an inorganic acid may be, for example, a polyvalent metal salt of hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, or the like, and may preferably be a polyvalent metal salt of hydrochloric acid or nitric acid. Specific examples of preferred polyvalent metal salts of an inorganic acid include calcium salts such as calcium nitrate, calcium chloride, and calcium hydroxide; and magnesium salts such as magnesium chloride, magnesium hydroxide, and magnesium sulfate.

The content of the water-soluble polyvalent metal salt in the primer composition is preferably 0.3% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more; on the other hand, it is preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less. By adjusting the content of the water-soluble polyvalent metal salt, the primer layer and the printed layer of the aqueous inkjet ink composition formed thereon can be laminated more closely.

The method for producing an inkjet print of the present invention includes a heat treatment step (steam treatment or hot water immersion treatment), and the heat treatment step may cause the water-soluble polyvalent metal salt contained in the primer layer to change in quality (for example, by reacting with the aqueous resin emulsion in the aqueous inkjet ink composition) and become an insoluble substance.

1-1-2C. Hydrazine Derivative The aqueous primer composition may contain a hydrazine derivative. The hydrazine derivative has at least two hydrazine residues; for example, a compound represented by the following general formula A, a compound represented by the following general formula B, maleic acid dihydrazide, fumaric acid dihydrazide, itaconic acid dihydrazide, etc. may be mentioned, and two or more kinds may be used in combination. Among these, adipic acid dihydrazide, sebacic acid dihydrazide, and isophthalic acid dihydrazide are more preferable.
(Chemical formula 1)
General formula A
(In the general formula A, n is 1 to 10.)

General formula B
(In the general formula B, m is 1 to 4.)

The content of the hydrazine derivative in the aqueous primer composition is not particularly limited, but is preferably 0.5% by mass or more, and more preferably 1% by mass or more; on the other hand, it is preferably 10% by mass or less, and more preferably 5% by mass or less. The hydrazine derivative can increase adhesion to the substrate to be printed, but if the amount is excessive, the storage stability of the primer composition may decrease.

1-1-3. Application and Drying of Aqueous Primer Composition The aqueous primer composition is applied to a substrate (substrate to be printed) and dried to form a primer layer, thereby forming a primer coating.

The means for applying the aqueous primer composition is not particularly limited. Examples of application means include application using various coating devices such as a bar coater, blade coater, air knife coater, roll coater, gravure coater, rod blade coater, lip coater, curtain coater, and die coater. The aqueous primer composition may also be applied using an inkjet printing device.

The amount of the aqueous primer composition applied can be adjusted so that the thickness of the dried primer layer is 0.01 to 1 μm, preferably 0.05 to 0.8 μm. If the dried primer layer thickness is less than 0.01 μm, it is difficult to form a uniform, defect-free primer layer on the substrate. On the other hand, if the dried primer layer thickness exceeds 1 μm, it may take a long time to dry the primer layer, which may reduce workability and may be economically inefficient.

The applied primer composition is dried to form a primer layer. There are no particular limitations on the drying method, but drying by heating is preferred. The heating temperature is about 30 to 80°C, and in some cases, a temperature of about 40 to 70°C is preferred. The drying time varies depending on the heating temperature, but is about 1 second to 1 minute, and may be 10 seconds or less.

1-2. Inkjet Printing Step An aqueous ink composition for inkjet printing is printed on the primer-coated product obtained in the above primer coating step, and then dried to produce an inkjet print.

1-2-1. Aqueous Inkjet Ink Composition The aqueous inkjet ink composition contains an aqueous resin emulsion, a pigment, and water, and may contain other components such as wax, a surfactant, a water-soluble organic solvent, a pigment dispersant, etc. The water content in the aqueous inkjet ink composition is preferably 10% by mass or more, and more preferably 20% by mass or more; on the other hand, it is preferably 60% by mass or less, and more preferably 50% by mass or less.

1-2-1A. Aqueous Resin Emulsion Examples of the aqueous resin emulsion contained in the aqueous inkjet ink composition include acrylic resin emulsion, acrylic-styrene resin emulsion, acrylic-vinyl acetate resin emulsion, polyester resin emulsion, polyurethane resin emulsion, polyvinyl acetate resin emulsion, polyvinyl chloride resin emulsion, polybutadiene resin emulsion, polyethylene resin emulsion, etc. More preferred examples of the aqueous resin emulsion include acrylic resin emulsion and acrylic-styrene resin emulsion, and among these, acrylic-styrene resin emulsion is even more preferred. Depending on the composition of the aqueous resin emulsion, the physical properties (such as abrasion resistance and moisture resistance) of the inkjet printing layer of the obtained inkjet printed matter can be improved.

The aqueous resin emulsion may preferably be a styrene-acrylic resin; the styrene-acrylic resin may be a copolymer of styrene, (meth)acrylic acid, and an alkyl (meth)acrylic ester. Acrylamide, acrylonitrile, or other monomers may be copolymerized as comonomers within the scope of the effect of the styrene-acrylic resin emulsion. Specific examples of commercially available styrene-acrylic resins include Yodosol AD199, Neocryl A-1092, and Neocryl A-655.

The glass transition temperature (Tg) of the aqueous resin emulsion is -20°C or higher, preferably -10°C or higher, more preferably 0°C or higher, and even more preferably 9°C or higher; on the other hand, it is 50°C or lower, and preferably 40°C or lower. If the glass transition temperature (Tg) of the aqueous resin emulsion is 50°C or lower, it is easy to improve the film-forming properties of the ink composition on the primer-coated material; on the other hand, if it is -20°C or higher, it is easy to improve the ejection stability of the ink composition, and the physical properties (abrasion resistance, moisture resistance, etc.) of the inkjet printing layer of the inkjet printed material obtained after the heat treatment process can be improved.

The glass transition temperature (Tg) of the aqueous resin emulsion may be a theoretical glass transition temperature or an actually measured glass transition temperature. For example, when the aqueous resin emulsion is an acrylic resin or a styrene-acrylic resin, the theoretical glass transition temperature Tg is calculated by the following Wood's formula.
Wood's formula: 1/Tg=W ₁ /Tg ₁ +W ₂ /Tg ₂ +W ₃ /Tg ₃ +...+W _x / _Tg
[In the formula, Tg ₁ to Tg _X are the glass transition temperatures of the homopolymers of the monomers 1, 2, 3, . . . x constituting the anionic group-containing resin, W ₁ to W _X are the polymerization fractions of the monomers 1, 2, 3, . . . x, and Tg is the theoretical glass transition temperature. The glass transition temperature in Wood's formula is an absolute temperature.]

The actual glass transition temperature can be measured by thermal analysis. The thermal analysis method is in accordance with JIS K7121 (Method for measuring the transition temperature of plastics). For example, the glass transition temperature can be measured using a PerkinElmer Pyris1 DSC under conditions of a temperature rise rate of 20°C/min and a nitrogen gas flow rate of 20 milliliters/min.

From the viewpoint of improving the ejection stability of the ink composition, the average particle diameter of the aqueous resin emulsion is preferably 500 nm or less, and more preferably 300 nm or less. As an example, the average particle diameter of the emulsion can be determined by measuring the D50 value using a Nikkiso Microtrac particle size distribution analyzer "UPA-150" for a measurement time of 60 seconds, with water as the dilution solvent.

The content of the aqueous resin emulsion in the aqueous inkjet ink composition is preferably 1% by mass or more, more preferably 2% by mass or more, in terms of resin solids; on the other hand, it is preferably 10% by mass or less, more preferably 8% by mass or less. If the content of the aqueous resin emulsion is 1% by mass or more, in terms of resin solids, the appearance and various resistances of the resulting printed matter can be improved; on the other hand, if it is 10% by mass or less, the inkjet ejection of the ink composition can be stabilized.

1-2-1B. Pigment The pigment contained in the aqueous inkjet ink composition may be any known inorganic pigment or organic pigment that has been conventionally used.

Examples of inorganic pigments include carbon black, titanium oxide, zinc oxide, lithopone, iron oxide, aluminum oxide, silicon dioxide, kaolinite, montmorillonite, talc, barium sulfate, calcium carbonate, silica, alumina, cadmium red, red iron oxide, molybdenum red, chrome vermilion, molybdate orange, yellow lead, chrome yellow, cadmium yellow, yellow iron oxide, titanium yellow, chromium oxide, viridian, cobalt green, titanium cobalt green, cobalt chrome green, ultramarine blue, Prussian blue, cobalt blue, cerulean blue, manganese violet, cobalt violet, mica, and the like.

Examples of organic pigments include azo, azomethine, polyazo, phthalocyanine, quinacridone, anthraquinone, indigo, thioindigo, quinophthalone, benzimidazolone, isoindoline, and isoindolinone organic pigments.

Specific examples of organic pigments are shown in the color index: Pigment Black 7; Pigment Blue 15, 15:1, 15:3, 15:4, 15:6, 60; Pigment Green 7, 36; Pigment Red 9, 48, 49, 52, 53, 57, 97, 122, 149, 168, 177, 178, 179, 206, 207, 209, 242, 254, 255; Pigment Violet 19, 23, 2 9, 30, 37, 40, 50; Pigment Yellow 12, 13, 14, 17, 20, 24, 74, 83, 86, 93, 94, 95, 109, 110, 117, 120, 125, 128, 137, 138, 139, 147, 148, 150, 151, 154, 155, 166, 168, 180, 185; Pigment Orange 36, 43, 51, 55, 59, 61, 71, 74; etc. These pigments can be used alone or in combination of two or more.

The pigment content of the entire aqueous inkjet ink composition other than the white ink is preferably 1% by mass or more, and more preferably 2% by mass or more; on the other hand, it is preferably 10% by mass or less, and more preferably 7% by mass or less. The pigment content of the white ink is preferably 5 to 15% by mass of the entire aqueous inkjet ink composition. By making the pigment content a certain amount or more, it is easy to obtain sufficient coloring power, while by making it a certain amount or less, it is easy to suppress an increase in the viscosity of the ink composition and ensure the fluidity of the ink.

1-2-1C. Wax The aqueous inkjet ink composition may contain a wax. The wax is preferably a hydrocarbon wax; preferred examples of the hydrocarbon wax include polyethylene wax, polypropylene wax, Fischer-Tropsch wax, carnauba wax, paraffin wax, microstearate wax, etc., which may be used alone or in combination of two or more. As the wax, polyethylene wax and/or Fischer-Tropsch wax are more preferred, and polyethylene wax is even more preferred.

Specific examples of polyethylene waxes include AQUACER 507, AQUACER 515, AQUACER 531, AQUACER 539 (all manufactured by BYK Japan), Hitec E-6314 (solid content 35%, nonionic emulsified polyethylene wax, manufactured by Toho Chemical Industry Co., Ltd.), Hitec E-1000 (solid content 35%, nonionic emulsified polyethylene wax, manufactured by Toho Chemical Industry Co., Ltd.), etc. These may be used alone or in combination of two or more kinds.

The wax content in the aqueous inkjet ink composition is preferably 0.5% by mass or more, more preferably 1% by mass or more; on the other hand, it is preferably 7% by mass or less, more preferably 5% by mass or less. Wax can improve the blocking resistance and abrasion resistance (especially dry abrasion resistance) of the printed matter.

1-2-1D. Surfactant The aqueous inkjet ink composition may contain a surfactant. Examples of the surfactant include acetylene diol surfactants, silicon surfactants, fluorine surfactants, alcohol ethoxylate surfactants, alcohol alkoxylate surfactants, etc.; however, acetylene diol surfactants may be preferred. The acetylene diol surfactant may improve the solid filling of the printed (recorded) image of the aqueous inkjet ink composition.

Specific examples of acetylene diol surfactants include Surfynol 104E, Surfynol 104H, Surfynol 104A, Surfynol 104BC, Surfynol 104DPM, Surfynol 104PA, Surfynol 104PG-50, Surfynol 420, and Surfynol 440 manufactured by Evonik Corporation; and Olfin E1004, Olfin E1010, Olfin E1020, Olfin PD-001, Olfin PD-002W, Olfin PD-004, Olfin PD-005, Olfin EXP. 4001, Olfin EXP. 4200, Olfin EXP. 4123, and Olfin EXP. 4300 manufactured by Nissin Chemical Industry Co., Ltd. These may be used alone or in combination of two or more kinds.

The surfactant content in the aqueous inkjet ink composition is preferably 0.1% by mass or more, more preferably 0.5% by mass or more; and is preferably 3% by mass or less, more preferably 2.5% by mass or less, and even more preferably 2% by mass or less.

In the method for producing an inkjet printed matter of the present invention, the white aqueous inkjet ink composition may be used as whiteout printing. Whiteout printing refers to concealing the color of the base (substrate) by printing with white ink before printing an aqueous inkjet ink composition other than the white ink. In this case, the surface tension of the white aqueous inkjet ink composition and the surface tension of the aqueous inkjet ink composition other than the white ink can be adjusted with a surfactant to make it easier to overcoat printed layers of the aqueous inkjet ink composition other than the white ink.

1-2-1E. Water-soluble organic solvent The aqueous inkjet ink composition may contain a water-soluble organic solvent. Examples of the water-soluble organic solvent include monoalcohols such as methanol, ethanol, n-propanol, n-butanol, n-pentanol, n-hexanol, n-heptanol, n-octanol, n-nonyl alcohol, n-decanol, cyclopentanol, and cyclohexanol; diols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, butanediol, 1,5-pentanediol, 1,2-pentanediol, 1,6-hexanediol, heptanediol, 1,2-cyclohexanediol, octanediol, 1,9-nonanediol, and 1,10-decanediol; tetraethylene glycol, polyethylene glycol, tetrapropylene glycol, thiamine diol, tetramethylphenyl ether ... Examples of the water-soluble organic solvent include glycerin, monoalkyl esters, monoalkyl ethers or dialkyl ethers of these alcohols, acetone, methyl ethyl ketone, methyl butyl ketone, methyl isobutyl ketone, diisopropyl ketone, cyclopentanone, cyclohexanone, and other ketones, isopropyl ether, n-butyl ether, tetrahydrofuran, tetrahydropyran, 1,4-dioxane, and other ethers, propylene carbonate, methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, amyl acetate, ethyl lactate, ethyl butyrate, dibutyl phthalate, dioctyl phthalate, and other esters, cyclic esters, ε-caprolactone, ε-caprolactam, and other cyclic amides, such as N-methyl-2-pyrrolidone. The water-soluble organic solvent contained in the aqueous inkjet ink composition may be one or more types alone, or two or more types may be combined.

The content of the water-soluble organic solvent in the aqueous inkjet ink composition is preferably 20% by mass or more; on the other hand, it is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less. Furthermore, the total content of the water-soluble organic solvent and water in the aqueous inkjet ink composition is preferably 40% by mass or more, more preferably 50% by mass or more; on the other hand, it is preferably 80% by mass or less, and more preferably 70% by mass or less.

1-2-1F. Pigment dispersant The aqueous inkjet ink composition may contain a pigment dispersant. The pigment dispersant is preferably a resin-type pigment dispersant (pigment dispersing resin). A pigment dispersing resin has a hydrophobic group (for example, styrene or a long-chain alkyl group) in the molecule, and the hydrophobic group imparts affinity to the pigment. Examples of pigment dispersing resins include acrylic resins, styrene-acrylic resins, maleic acid resins, styrene-maleic acid resins, α-olefin-maleic acid resins, urethane resins, ester resins, and the like. From the viewpoint of stabilizing the pigment dispersion, it is preferable to use acrylic resins, and styrene-acrylic resins such as styrene-lauroyl acrylate-acrylic acid copolymers.

From the viewpoints of pigment dispersibility and dispersion stability, the acid value of the pigment dispersion resin is preferably 40 to 300 mgKOH/g, and more preferably 70 to 250 mgKOH/g. From the viewpoints of pigment dispersibility and dispersion stability, and of imparting an appropriate viscosity to the ink composition, the weight average molecular weight of the pigment dispersion resin is preferably 3,000 to 200,000, and more preferably 10,000 to 50,000.

The content of the pigment dispersion resin in the aqueous inkjet ink composition is preferably 10 parts by mass or more per 100 parts by mass of the pigment, and more preferably 200 parts by mass or less.

1-2-2. Printing and drying of aqueous inkjet ink composition The aqueous inkjet ink composition is printed on the primer-coated material using an inkjet printing device and dried to form a printed layer, thereby providing an inkjet print. In the inkjet printing process, only a single-color aqueous inkjet ink composition may be printed, or multiple colors of aqueous inkjet ink compositions may be printed (color printing). In addition, in the inkjet printing process, a white aqueous inkjet ink composition may be printed (referred to as white printing), and then aqueous inkjet ink compositions of other colors may be overcoated and printed.

The type of inkjet printing device that can be used is not particularly limited, and may be a line head type (single pass type) or a serial head type (multi-pass type). A continuous type inkjet printing device may also be used, in which case a conductivity imparting agent can be further added to adjust the electrical conductivity of the ink composition.

The aqueous inkjet ink composition is supplied to the printer head of an inkjet printing device, and droplets of the ink composition are ejected from the printer head onto the substrate to be printed. The ink composition is ejected from the printer head onto the substrate (printing of an image) so that the film thickness on the substrate after drying is, for example, 1 to 60 μm.

When droplets of the aqueous inkjet ink composition of the present invention land on a substrate, the water-soluble polyvalent metal salt contained in the primer layer interacts with the binder resin contained in the aqueous inkjet ink composition (e.g., by forming an ionic bond), which can prevent the droplets of the aqueous inkjet ink composition from excessively wetting and spreading on the substrate.

The aqueous inkjet ink composition printed on the substrate is dried to form a printed layer. The drying method is not particularly limited, but can be heat drying. The drying temperature can be about 60°C to 130°C, and in some cases it may be preferable to set it in the range of 80°C to 120°C. The drying time depends on the drying temperature, but can be about 1 to 10 minutes, and can also be 5 minutes or less.

The inkjet print obtained in the inkjet printing process is subjected to a heat treatment, specifically, a heat treatment while being exposed to moisture. Specific examples of the heat treatment include, but are not limited to, a steam treatment and a hot water immersion treatment.

1-3-1. Steam Treatment Steam treatment refers to bringing water vapor into contact with the printed surface of an inkjet printed matter. The temperature of the water vapor brought into contact with the printed matter (the temperature of the water vapor when it comes into contact with the printed matter) is preferably 70°C or higher, more preferably 80°C or higher, even more preferably 90°C or higher, and may be 100°C. The steam treatment may be a pressurized water vapor treatment, and the steam temperature may exceed 100°C. The treatment time of the steam treatment may be 0.1 seconds or more and 10 seconds or less.

The method of contacting the inkjet print with steam is not particularly limited, but examples include filling a box with steam generated by a water boiling method and passing the inkjet print through the box, or spraying steam from a steam nozzle of a steam cleaner or the like directly onto the inkjet print. The temperature of the steam that comes into contact with the print can be adjusted by adjusting the distance between the printed surface of the inkjet print and the steam nozzle.

1-3-2. Hot water immersion treatment Hot water immersion treatment refers to immersing an inkjet printed matter in hot water. The temperature of the hot water used for immersion is preferably 60°C or higher, more preferably 70°C or higher, and even more preferably 80°C or higher, and may be 90°C or higher (for example, 100°C). The immersion time may be 0.1 seconds to 10 seconds or less.

By subjecting inkjet prints to heat treatment using methods such as steam treatment or hot water immersion treatment, the coating film properties of the printed layer in the inkjet prints are improved. The coating film properties that are improved include abrasion resistance in a dry state (dry abrasion resistance), abrasion resistance in a moist state (wet abrasion resistance), and abrasion resistance when exposed to hot air of 100°C or higher, such as in a retort test (retort resistance).

The reason why the coating properties of the printed layer in the inkjet print are improved by heat treatment while exposing it to moisture is not particularly limited, but it is thought that the water-soluble metal salt contained in the primer layer and the aqueous pigment dispersion resin and aqueous resin emulsion contained in the printed layer of the aqueous inkjet ink composition are crosslinked and hardened by the heat treatment, and become more insoluble in water. However, the reason is not limited to this.

It was difficult to obtain sufficient coating film properties from the printed layer obtained by printing a conventional aqueous inkjet ink composition. The present invention can dramatically improve the coating film properties by treating the printed substrate with a specific primer composition and subjecting the printed layer of the aqueous inkjet ink composition to a specific heat treatment.

2. Uses of the Inkjet Printed Material The inkjet printed material of the present invention may be a surface-printed printed material. In other words, the printed layer of the inkjet ink may be disposed on the outer surface. The inkjet printed material of the present invention is unlikely to deteriorate even if it is disposed on the outer surface because the printed layer (the coating film of the primer composition and the printed layer of the inkjet ink) has high physical resistance (abrasion resistance, etc.).

The inkjet printed matter of the present invention may be a surface-printed packaging container; for example, it may be a plastic film container, a cardboard container, an aluminum pouch container, an aluminum can, etc. Plastic film containers and aluminum pouch containers may be used as retort packaging containers. The printed layer of the inkjet printed matter of the present invention can maintain its abrasion resistance even after retort treatment (exposure to 100°C or higher), so it can also be preferably used as a retort packaging container.

The inkjet printed matter of the present invention may have an overcoat varnish that covers the printed layer of the inkjet ink, or may be a laminate in which a laminate film is laminated on the printed surface of the inkjet ink.

3. Inkjet Printing Apparatus The inkjet printing apparatus of the present invention is an apparatus capable of carrying out the above-mentioned method for producing an inkjet printed matter. Preferably, the inkjet printing apparatus can carry out the above-mentioned process for producing an inkjet printed matter in-line, but is not limited thereto. In other words, the primer application step, the inkjet printing step, and the heat treatment step may be carried out in one apparatus, or each may be carried out in a different apparatus.

The inkjet printing device 100 of the present invention comprises a primer application means 20, an inkjet printing means 30, and a heat treatment means 40; and preferably further comprises a transport means 10 for transporting the printing substrate 1 (see FIG. 1).

The primer application means 20 may be any means for applying the aqueous primer composition to the substrate 1; it is preferable that the primer application means 20 is equipped with a coating device 21 such as a bar coater, blade coater, air knife coater, roll coater, gravure coater, rod blade coater, lip coater, curtain coater, or die coater. The primer application means 20 also preferably is equipped with a drying means 22 for drying the primer composition applied to the substrate 1. The drying means 22 may be, for example, a heating oven, a hot air dryer, or a heated fixing roller.

The inkjet printing means 30 is a means for printing the above-mentioned aqueous inkjet ink composition on the printing substrate 1, and includes at least an inkjet recording head 31. The inkjet printing means 30 may include one inkjet recording head 31, in which case only a single color (e.g., black) ink composition can be printed; or it may include multiple (e.g., five) inkjet recording heads (31A-31E), in which case multiple colors (e.g., white, black, yellow, magenta, cyan) of ink compositions can be printed (color printing). Note that white-out printing can also be performed using a white aqueous inkjet ink composition.

The type of inkjet recording head 31 is not particularly limited and may be a piezoelectric type, a bubble jet type, or the like. In addition, the nozzle of the inkjet recording head may be a single nozzle, but is preferably a multi-nozzle head.

The inkjet printing means 30 preferably includes a drying means 32 for drying the printed inkjet ink. The drying means 32 may be arranged corresponding to each inkjet recording head 31, or may be a drying means for drying inkjet ink printed by a plurality of inkjet recording heads 31 (A to E) collectively as shown in FIG. 1. The drying means 32 may be, for example, a heating oven, a hot air dryer, a heated fixing roller, etc.

The heat treatment means 40 is a means for heat treating the printing substrate 1 on which the inkjet ink has been printed, preferably while exposing it to moisture, and more specifically, a means for steam treatment or hot water immersion treatment. The heat treatment means 40 can be, for example, a device for spraying water vapor (such as a steam cleaner), a box filled with water vapor, a bath containing hot water, etc.

The transport means 10 may be any means that transports the printing substrate 1 to the primer application means 20, the inkjet printing means 30, and the heat treatment means 40 in that order. For example, as shown in FIG. 1, it may be composed of a roller 11. The inkjet printing device 100 may also have a winding device (not shown) for winding up the inkjet printed material.

The present invention will be described in more detail below with reference to examples, but the scope of the present invention should not be interpreted as being limited by these examples. Unless otherwise specified, "%" means "% by mass" and "parts" means "parts by mass."

A. Preparation of primer compositions Primer compositions P1 and P2 were prepared with the compositions shown in Table 1. Specifically, calcium acetate, an aqueous resin emulsion, a chlorinated polyolefin, and a surfactant were dissolved in water. The units of values in Table 1 are parts by mass.
Acrylic emulsion: Vinyblan 2687 (acrylic type, manufactured by Nissin Chemical Industry Co., Ltd.)
Vinyl acetate emulsion: Vinyblan 1002 (vinyl acetate type, manufactured by Nissin Chemical Industry Co., Ltd.)
Chlorinated polyolefin (chlorination degree 21%): Superchlorine E-604 (chlorination degree 21%, manufactured by Nippon Paper Industries Co., Ltd.)
Surfactant: Olfin E1010 (acetylene diol type, manufactured by Nissin Chemical Industry Co., Ltd.)

B. Preparation of Aqueous Inkjet Ink Composition B-1. Preparation of Aqueous Resin Varnish 20 parts by mass of an acrylic acid/n-butyl acrylate/benzyl methacrylate/styrene copolymer having a glass transition temperature of 40° C., a weight average molecular weight of 30,000, and an acid value of 185 mgKOH/g was dissolved in a mixed solution of 2.5 parts by mass of potassium hydroxide and 77.5 parts by mass of water to obtain an aqueous resin varnish with a solid content of 20%.

B-2. Preparation of ink base B-2-Bk. Preparation of water-based black ink base 23.7 parts by mass of the above water-based resin varnish was mixed with 64.3 parts by mass of water to prepare a resin varnish for dispersing pigments. 12 parts by mass of carbon black (product name Printex 90, manufactured by Degussa) was further added to this varnish, stirred and mixed, and then milled in a wet circulation mill to prepare a water-based black ink base.

B-2-Y. Preparation of aqueous yellow ink base 23.7 parts by mass of the above aqueous resin varnish was mixed with 64.3 parts by mass of water to prepare a resin varnish for dispersing pigments. 12 parts by mass of a yellow pigment (product name Novapalm Yellow 4G01, manufactured by Clariant) was further added to this varnish, stirred and mixed, and then milled in a wet circulation mill to prepare an aqueous yellow ink base.

B-2-M. Preparation of Water-Based Magenta Ink Base 23.7 parts by mass of the above water-based resin varnish was mixed with 64.3 parts by mass of water to prepare a resin varnish for dispersing pigments. 12 parts by mass of magenta pigment (product name Inkjet Magenta E5B02, manufactured by Clariant) was further added to this varnish, stirred and mixed, and then milled in a wet circulation mill to prepare a water-based magenta ink base.

B-2-C. Preparation of aqueous cyan ink base 23.7 parts by mass of the above aqueous resin varnish was mixed with 64.3 parts by mass of water to prepare a resin varnish for dispersing pigments. 12 parts by mass of a cyan pigment (product name Heliogen Blue L7101F, manufactured by BASF) was further added to this varnish, stirred and mixed, and then milled in a wet circulation mill to prepare an aqueous cyan ink base.

B-2-W. Preparation of Water-Based White Ink Base 20.0 parts by mass of water was added to 40.0 parts by mass of the above water-based resin varnish and mixed to prepare a resin varnish for dispersing pigments. 40 parts by mass of titanium oxide (product name R-960, manufactured by DuPont) was further added to this varnish, stirred and mixed, and then milled in a wet circulation mill to prepare a water-based white ink base.

B-3. Preparation of Water-Based Inkjet Inks Water-based inkjet inks were prepared according to the compositions of Examples 1 to 12 shown in Table 2. The materials used in the preparation are shown below.
<Water-based resin emulsion>
Acrylic-styrene (Tg-14°C): Yodosol AD199, acrylic-styrene emulsion, manufactured by Henkel
Acrylic-styrene (Tg 9°C): Neocryl A-1092, acrylic-styrene emulsion, manufactured by DSM Neoresins. Acrylic-styrene (Tg 33°C): Neocryl A-655, acrylic-styrene emulsion, manufactured by DSM Neoresins. Acrylic-styrene (Tg -32°C): Movinyl 966A, acrylic-styrene emulsion, manufactured by Nippon Synthetic Chemical Industry Co., Ltd. Acrylic-vinyl acetate (Tg -13°C): Vinyblan 1245L, acrylic-vinyl acetate emulsion, manufactured by Nissin Chemical Industry Co., Ltd. Acrylic-vinyl chloride (Tg 33°C): Vinyblan 278L, acrylic-vinyl chloride emulsion, manufactured by Nissin Chemical Industry Co., Ltd. Vinyl acetate (Tg 30°C): Vinyblan GV6181, vinyl acetate emulsion, manufactured by Nissin Chemical Industry Co., Ltd. <Wax emulsion>
AQUACER 539 (35% solids, manufactured by BYK)
<Surfactant>
Olfin E1010 (100% solids, HLB 13-14, manufactured by Nissin Chemical Co., Ltd.)
Olfin E1004 (100% solids, HLB 7-9, manufactured by Nissin Chemical Co., Ltd.)

Aqueous inkjet ink compositions of Examples 1 to 12 were prepared with the compositions shown in Table 2. Specifically, an aqueous resin emulsion, a wax emulsion, a surfactant, a water-soluble organic solvent, and water were added to the ink base, and mixed using a mixer.

C. Production of Inkjet Printed Matter The following steps (C-1 to C-3) were carried out under the conditions shown in Tables 3 to 5 to produce inkjet printed matters of the examples and comparative examples.

C-1. Primer Coating Step The primer composition (P1 or P2) was applied to a PET film (E5100, 12 μm, Toyobo), an aluminum plate (0.3 mm thick), a coated board (OK board, 230 g/m2, Oji Materia), or a cardboard base paper (K liner, 170 g/m2, Oji Materia) using a bar coater with a wire diameter of 0.1 mm, and then dried by heating in an oven at 50° C. for 5 seconds to form a primer coating film. However, in Comparative Example 1 (Table 5), the primer coating film was not dried.

C-2. Inkjet printing process The aqueous inkjet ink compositions (Examples 1 to 12) were filled into the cartridges of an Epson printer PX105, and printing was carried out on the primer coating film formed in C-1 above, followed by heating and drying for 3 minutes in an oven at 70° C. or 100° C. to form an ink coating film. However, in Comparative Examples 1 and 2 (Table 5), the ink coating film was not dried.

C-3. Heat Treatment Step <Steam Treatment> Steam treatment was performed by spraying steam onto the ink coating film formed in C-2 above using a steam cleaner so that the temperature of the water vapor contacting the ink coating film was 70° C., 100° C., or 120° C. (specifically, the distance between the coating film surface and the steam spray nozzle was adjusted). The steam treatment time was set to 1 second, 5 seconds, or 10 seconds.
<Hot Water Immersion Treatment> The ink coating film formed in C-2 above was treated by immersing it in boiled water (100° C.) or water at 80° C. for 1 or 2 seconds.
<Oven Treatment> The ink coating film formed in C-2 above was treated by storing it in an oven at 100° C. for 10 seconds or 30 seconds.

D. Evaluation of Inkjet Prints The inkjet prints obtained in each of the Examples and Comparative Examples were evaluated for the following D-1 to D-3. The results are shown in Tables 3 to 5.

D-1. Dry Rub Resistance The printed surface of the prints obtained in each of the Examples and Comparative Examples was rubbed with a dry cotton swab, and the dry rub resistance was evaluated according to the following evaluation criteria.
◎: The coating surface was not scratched at all even after rubbing with a cotton swab 200 times. ○: The coating surface was not scratched at all even after rubbing with a cotton swab 100 times. △: After rubbing the coating surface with a cotton swab 100 times, the color transferred to the cotton swab and the rubbed area was slightly scratched. ×: After rubbing the coating surface with a cotton swab 100 times, most of the rubbed area peeled off.

D-2. Wet Rub Resistance The printed surface of the prints obtained in each of the Examples and Comparative Examples was rubbed with a cotton swab moistened with water, and the wet rub resistance was evaluated according to the following evaluation criteria.
◎: The coating surface was not scratched at all even after rubbing 100 times with a cotton swab. ○: The coating surface was not scratched at all even after rubbing 50 times with a cotton swab. △: After rubbing the coating surface 50 times with a cotton swab, the color transferred to the cotton swab and the rubbed area was slightly scratched. ×: After rubbing the coating surface 50 times with a cotton swab, most of the rubbed area peeled off.

D-3. Retort Resistance The printed matter obtained in each of the Examples and Comparative Examples was treated in a retort tester at 120° C./30 min, and then the printed surface was rubbed with a dry cotton swab to evaluate the retort resistance according to the following evaluation criteria.
◎: The coating surface was not scratched at all even after rubbing 100 times with a cotton swab. ○: The coating surface was not scratched at all even after rubbing 50 times with a cotton swab. △: After rubbing the coating surface 50 times with a cotton swab, the color transferred to the cotton swab and the rubbed area was slightly scratched. ×: After rubbing the coating surface 50 times with a cotton swab, most of the rubbed area peeled off.

As shown in Comparative Example 1 in Table 5, when a PET film was used as a printing substrate and the applied primer composition was not dried, the image quality deteriorated even when the inkjet ink composition was printed on it. Also, as shown in Comparative Example 2 in Table 5, when the coating of the inkjet ink composition was not dried, various coating resistances were poor even after subsequent heat treatment by steam treatment.

As shown in Comparative Example 3 in Table 5, when a PET film was used as a printing substrate, the applied primer composition was dried, and the coating of the inkjet ink composition was dried, a certain degree of dry friction resistance was obtained without heat treatment (evaluation △), but the wet friction resistance and retort resistance were insufficient (evaluation ×). Furthermore, as shown in Comparative Examples 4 and 5 in Table 5, when the applied primer composition was dried, the coating of the inkjet ink composition was dried, and then heat treatment was performed by oven treatment, a certain degree of dry friction resistance was obtained, as in Comparative Example 3 (evaluation △), but the wet friction resistance and retort resistance were insufficient (evaluation ×).

In contrast, as shown in Examples 1 to 6 in Table 3, when a PET film was used as the printing substrate, the applied primer composition was dried, the coating of the inkjet ink composition was dried, and steam treatment was then performed, various coating performances were significantly improved (all evaluations except for the evaluation of wet friction resistance in Example 2 were ◯). As shown in Example 2, when the drying temperature for drying the coating of the inkjet ink composition was slightly low (70°C), the evaluation of wet friction resistance was slightly lower, suggesting that it is preferable to thoroughly dry the coating of the inkjet ink composition. It was also suggested that steam treatment by contacting the coating with water vapor at 70°C or higher for about 1 second was sufficient.

As shown in Examples 7 and 8 in Table 3, when a PET film was used as the printing substrate, the applied primer composition was dried, the coating of the inkjet ink composition was dried, and then the coating was immersed in hot water, various coating performances were also significantly improved. As shown in Example 8, when the temperature of the water used in the hot water immersion treatment was slightly low (80°C), the wet abrasion resistance of the coating was slightly decreased, suggesting that a higher hot water temperature is preferable.

As shown in Examples 9 to 11 in Table 3, when the printing substrate was an aluminum plate, coated cardboard, or corrugated board, various coating film performances were significantly improved by producing inkjet prints under the same conditions as in Example 1. That is, in the case of aluminum plate, dry rub resistance, wet rub resistance, and retort resistance were all rated as ◯. In the case of coated cardboard, since the substrate is paper, retort resistance is not obtained, but both dry rub resistance and wet rub resistance were rated as ◯. In the case of corrugated board, dry rub resistance was rated as ◯ and wet rub resistance was rated as △.

As shown in Example 12 of Table 4, even when the binder resin of the primer composition was changed (changing from acrylic resin emulsion to vinyl acetate emulsion), various coating film performances were significantly improved, as in Example 1. As shown in Examples 13 to 16 of Table 4, even when the pigment of the inkjet ink composition was changed, various coating film performances were significantly improved, as in Example 1. As shown in Example 17 of Table 4, when no wax was blended into the inkjet ink composition, various coating film performances were significantly improved, but on the other hand, the dry rub resistance rating was slightly lower (rating △).

Furthermore, as shown in Examples 18 to 22 in Table 4, even when the aqueous resin emulsion of the inkjet ink composition was changed, various coating film performances were significantly improved, as in Example 1. In particular, when an acrylic-styrene resin emulsion was used, as in Examples 18 and 19, all coating film performances were evaluated as ⊚. On the other hand, when an emulsion of acrylic-vinyl acetate resin, acrylic-vinyl chloride resin, or vinyl acetate resin was used (Examples 20 to 22), various coating film performances were slightly decreased (evaluated as △). Furthermore, as shown in Comparative Example 6 in Table 5, when an acrylic-vinyl acetate resin emulsion with a glass transition temperature (Tg) of -32°C was used, wet friction resistance and retort resistance were insufficient (evaluated as ×).

According to the method for producing an inkjet printed matter of the present invention, the coating resistance of the printed layer of the aqueous inkjet ink composition can be significantly improved compared to conventional methods, and peeling and discoloration of the printed layer can be suppressed. Therefore, the applications of the aqueous inkjet ink composition can be significantly expanded, and the method for producing an inkjet printed matter of the present invention can be applied to, for example, the production of packaging containers with surface printing.

Claims (9)

a primer coating step of coating an aqueous primer composition containing a binder resin and a water-soluble polyvalent metal salt on a substrate and drying the composition to form a primer coating;
an inkjet printing step of printing an aqueous ink composition for inkjet printing, the aqueous ink composition containing an aqueous resin emulsion having a glass transition temperature (Tg) of −20 to 50° C. and a pigment, on the primer-coated product using an inkjet printing device, and drying the ink to produce an inkjet printed product;
a heat treatment step of subjecting the inkjet printed matter to a heat treatment while exposing it to moisture;
A method for producing an inkjet printed matter comprising the steps of: The method for producing an inkjet printed matter according to claim 1, wherein the heat treatment is a steam treatment or a hot water immersion treatment. The method for producing an inkjet printed matter according to claim 1 or 2, wherein the binder resin contained in the aqueous primer composition contains an acrylic resin and/or a vinyl acetate resin. The method for producing an inkjet printed matter according to claim 1 or 2, wherein the water-soluble polyvalent metal salt contained in the aqueous primer composition contains a calcium salt. The method for producing an inkjet printed matter according to claim 1 or 2, wherein the aqueous resin emulsion contained in the aqueous inkjet ink composition contains a styrene-acrylic resin. The method for producing an inkjet printed matter according to claim 1 or 2, wherein the glass transition temperature (Tg) of the aqueous resin emulsion contained in the aqueous inkjet ink composition is 9 to 50°C. The method for producing an inkjet printed matter according to claim 1 or 2, wherein the substrate is a resin film, metal, or cardboard. The method for producing an inkjet printed matter according to claim 1 or 2, wherein the inkjet printed matter is a surface-printed printed matter. An inkjet printing apparatus including a primer applying means, an inkjet printing means, and a heat treating means:
The primer applying means applies an aqueous primer composition containing a binder resin and a water-soluble polyvalent metal salt to a substrate, and dries the composition to provide a primer coating;
the inkjet printing means prints an aqueous inkjet ink composition containing an aqueous resin emulsion having a glass transition temperature (Tg) of −20 to 50° C. and a pigment on the primer-coated product, and dries the inkjet printed product;
The heat treatment means performs a heat treatment on the inkjet printed matter while exposing it to moisture.