WO2023276974A1

WO2023276974A1 - Overcoat ink and ink set including same

Info

Publication number: WO2023276974A1
Application number: PCT/JP2022/025621
Authority: WO
Inventors: 俊也両角; 祐二牧本
Original assignee: 株式会社Ｄｎｐファインケミカル
Priority date: 2021-06-30
Filing date: 2022-06-27
Publication date: 2023-01-05
Also published as: JPWO2023276974A1

Abstract

Provided is an overcoat ink capable of forming an overcoat layer reduced in slipperiness on the surface of printed matter.　The overcoat ink, which is for forming an overcoat layer on the surface of printed matter, comprises a resin, an organic solvent, and water, wherein the resin includes one having a glass transition temperature of 10°C or lower.

Description

Overcoat ink and ink set containing the same

The present invention relates to an overcoat ink and an ink set containing the same.

The inkjet recording method is a recording method in which droplets of an ink composition are directly ejected from very fine nozzles onto a base material such as paper and applied to obtain letters and images. This recording method is easy to reduce size, increase speed, reduce noise, save power, and colorize. , the range of application has expanded to include commercial printing applications.

As ink compositions used in inkjet recording systems, aqueous inks in which various coloring materials are dissolved in water or a mixture of water and a water-soluble organic solvent are widely used. Such water-based inks, which contain water as a main component, have little impact on the environment and are not flammable, so they are highly safe for workers.

Here, an overcoat ink for forming an overcoat layer on the surface of a printed matter is known. For example, Patent Literature 1 describes an overcoat ink containing a predetermined resin, a neutralizer, and a solvent.

Patent Document 1 describes that this overcoat ink has excellent ejection stability and excellent abrasion resistance and abrasion resistance to an image printed on a recording medium.

JP 2020-070416 A

Now, there are cases where a plurality of recorded materials with an overcoat layer formed on the surface are stacked and transported by transport or stored in a warehouse or the like.

However, if the slipperiness of the overcoat layer of the recorded matter is high, multiple stacked recorded matter may collapse due to vibration during transportation or storage.

An object of the present invention is to provide an overcoat ink capable of forming an overcoat layer with low lubricity on the surface of a recorded matter.

As a result of intensive studies to solve the above problems, the present inventors found that an overcoat ink containing a resin having a predetermined glass transition temperature can solve the above problems, and completed the present invention. reached. Specifically, the present invention provides the following.

(1) An overcoat ink for forming an overcoat layer on the surface of a printed matter, comprising at least a resin, an organic solvent, and water, wherein the resin has a glass transition temperature of 10° C. or less. An overcoat ink containing

(2) The overcoat ink according to (1), wherein the resin is an acrylic and/or urethane resin.

(3) The overcoat ink according to (1) or (2), wherein the content of the resin is in the range of 5% by mass or more and 30% by mass or less based on the total amount of the overcoat ink.

(4) The overcoat ink according to any one of (1) to (3), which is ejected onto the surface of a recorded matter by an inkjet method.

(5) The overcoat ink according to any one of (1) to (4), which further contains a surfactant, and the surfactant contains a silicone-based surfactant and/or an acetylene glycol-based surfactant. .

(6) The overcoat ink according to any one of (1) to (5), further containing wax.

(7) the overcoat ink according to any one of (1) to (6);
An ink set including a water-based ink.

(8) The ink set according to (7), wherein the static surface tension of each ink contained in the ink set satisfies the following relationship.
Static surface tension of overcoat ink S _O < Static surface tension of water-based ink S _C

(9) The ink set according to (7) or (8), which further contains a pretreatment ink.

(10) The ink set according to (9), wherein the static surface tension of each ink contained in the ink set satisfies the following relationship.
Static surface tension S _O of overcoat ink ≤ Static surface tension S _P of pretreatment ink < Static surface tension S _C of water-based ink

(11) An inkjet recording method using the ink set according to any one of (7) to (10), wherein each ink contained in the ink set is inkjet-discharged onto a substrate.

(12) The recording method according to (11), wherein after each ink contained in the ink set is discharged, the ink is dried.

(13) A method for producing a recorded matter using the ink set according to any one of (7) to (10), comprising inkjet-ejecting each ink contained in the ink set onto a substrate. manufacturing method.

(14) An apparatus for inkjet-ejecting the ink set according to any one of (7) to (10).

(15) The apparatus according to (14), comprising a drying mechanism for drying each ink contained in the ink set after each ink is discharged.

(16) A recording medium, an aqueous ink layer formed from an aqueous ink, and an overcoat layer formed from the overcoat ink according to any one of (1) to (6) on the aqueous ink layer. and a recording comprising:

The overcoat ink of the present invention can form an overcoat layer with low slip on the surface of a printed matter.

A device for ejecting an ink set that can be suitably used for the ink set of one embodiment of the present invention.

Hereinafter, specific embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments at all, and can be implemented with appropriate modifications within the scope of the purpose of the present invention. can do.

≪Overcoat ink≫
The overcoat ink according to this embodiment is an overcoat ink for forming an overcoat layer on the surface of a printed matter. This overcoat ink is a water-based overcoat ink containing at least a resin, an organic solvent, and water. Since it is a water-based overcoat ink, it has little impact on the environment and is highly safe for workers because it is non-flammable.

The term "overcoat ink for forming an overcoat layer on the surface of a printed matter" refers to a colored ink containing a coloring material (including colored coloring materials and black and white coloring materials) (e.g., water-based It may be an overcoat ink for forming an overcoat layer directly on the surface of the liquid while the ink has fluidity and exists as a liquid, such as a colored ink (e.g., water-based ink ) or the like to form an overcoat layer directly on the surface of the ink layer.

In addition, "overcoat ink for forming an overcoat layer on the surface of a recorded matter" is not limited to colored ink or overcoat ink for forming an overcoat layer directly on a layer of colored ink. Even if it is an ink containing a glitter pigment (scale-like metal particles) to make the (object) metallic, or an overcoat ink for forming an overcoat layer directly on that layer, clear ink that does not contain a coloring material is used. It may be an overcoat ink for forming an overcoat layer directly on the ink or its layer. In the case of a clear ink that does not contain a coloring material, inks for forming a layer having a desired function can be used. Such inks include, for example, matte ink compositions that eliminate the matte of recorded matter (substrate), inks and primer inks containing ultraviolet absorbers and light stabilizers for forming weather resistant layers, and the like. be done.

The resin contained in the overcoat ink according to the present embodiment contains a resin having a glass transition temperature of 10°C or less.

Research by the present inventors has revealed that an overcoat ink containing a resin with a predetermined glass transition temperature can form an overcoat layer with low slip on the surface of a printed matter. The reason for this is not necessarily clear, but the low glass transition temperature of the resin that makes up the overcoat layer reduces the hardness of the overcoat layer and increases the static frictional force of the coating film (overcoat layer). It is believed that this is because the coefficient of friction with the back surface of the recorded matter increases.

The overcoat ink according to the present embodiment and the water-based ink and pretreatment ink contained in the ink set described later may be used, for example, in a gravure method, a flexo method, a spray method, a screen method, a coater method, or the like. good. Among them, the ink jet method is particularly preferable because it is excellent in forming a small lot of recorded matter.

In particular, an ink set containing the overcoat ink according to the present embodiment and a water-based ink described later, or an ink set containing a receiving solution, wherein the ink contained in these ink sets is ejected by an inkjet method, It is possible to form a water-based ink layer and an overcoat layer on the surface at once, and it is possible to produce a recorded matter having these layers at a high speed, so that a recorded matter having an overcoat layer with low slippage can be produced. can be manufactured with high productivity.

Next, each component contained in the overcoat ink according to this embodiment will be described.

(resin)
The resin contained in the overcoat ink according to this embodiment imparts abrasion resistance to the overcoat layer.

And this resin contains a resin with a glass transition temperature of 10°C or less. As a result, it is possible to reduce the slipperiness of the overcoat layer and prevent collapse of a stack of recorded materials due to vibration during transportation or storage.

Resins having a glass transition temperature of 10° C. or less are not particularly limited, and acrylic resins, polyurethane resins, polyester resins, vinyl chloride resins, vinyl acetate resins, polyether resins, vinyl chloride vinyl acetate copolymer resins, One or more resins or copolymer resins selected from the group consisting of polyethylene resins, silicone (silicon) resins, acrylamide resins, epoxy resins, polycarbonate resins and polystyrene resins, or mixtures thereof can be done. Among these, it is particularly preferable to use those containing an acrylic resin having an acrylic skeleton in at least one of the constituent monomers and/or a polyurethane resin having a urethane skeleton in at least one of the constituent monomers.

Further, it is preferable that at least part of the resin contained in the overcoat ink according to the present embodiment, such as a resin having a glass transition temperature of 10°C or less, contains a resin emulsion. Since the overcoat ink according to the present embodiment contains water, by forming a resin emulsion, the resin can be dispersed as fine resin particles in the water-containing overcoat ink by electrostatic repulsion or steric repulsion. can be done. Therefore, in particular, when the overcoat ink is ejected onto the surface of a recording material by an inkjet method, the ejection stability can be enhanced by using at least a portion of the resin containing a resin emulsion.

Commercially available resin emulsions include, for example, NeoCryl XK-190 (acrylic resin Tg: 0°C), Bonlon PS-001 (acrylic resin Tg: 3°C), Neocryl A1125 (acrylic resin Tg: 13°C), Takelac W-6110 (urethane-based resin Tg: -12°C), Elitel KZT-9204 (polyester-based resin Tg: 19°C), Joncryl ECO 2124 (acrylic-styrene resin: Tg: -35°C), NE2260 (acrylic-styrene-based resin : Tg: -10°C), Acryt UW-550CS (acrylic styrene resin: Tg: 4°C), and J-140A (acrylic styrene resin: Tg: 5°C), but are not limited to these. not something.

The average particle size of the resin emulsion is preferably 30 nm or more, more preferably 40 nm or more, and even more preferably 50 nm. The average particle size of the resin emulsion is preferably 300 nm or less, more preferably 270 nm or less, and even more preferably 250 nm, from the viewpoints of dispersion stability in the ink composition and inkjet ejection properties. This further improves the dispersion stability of the resin emulsion in the overcoat ink. In particular, when the overcoat ink is ejected onto the surface of a recorded material by an inkjet method, the ejection stability can be further improved by using a resin that contains at least a part of a resin emulsion. In the present embodiment, the average particle size of the resin emulsion can be measured using a concentrated particle size analyzer (manufactured by Otsuka Electronics Co., Ltd., model: FPAR-1000) at a measurement temperature of 25°C.

From the viewpoint of the water resistance of the overcoat layer, the weight average molecular weight of the resin emulsion is preferably 10,000 or more, more preferably 50,000 or more, and even more preferably 100,000 or more. From the viewpoint of the stability of the ink composition, the weight average molecular weight of the resin emulsion is preferably 1,000,000 or less, more preferably 700,000 or less, and even more preferably 500,000 or less. In the present embodiment, the molecular weight of the resin indicates the mass average molecular weight Mw, which is a value measured by GPC (gel permeation chromatography), using "HLC-8120GPC" manufactured by Tosoh Corporation. , can be measured using a polystyrene standard for a calibration curve as a standard.

The content of the resin having a glass transition temperature of 10° C. or less is preferably 50% by mass or more, more preferably 70% by mass or more, of the total amount of the resin contained in the overcoat ink according to the present embodiment. It is more preferably 90% by mass or more, and even more preferably 99% by mass or more.

The content of the resin contained in the overcoat ink according to the present embodiment is not particularly limited. It is more preferable that the content is 10% by mass or more. As a result, it becomes possible to impart further abrasion resistance to the overcoat layer and to further reduce the slipperiness, so that the overcoat ink further exerts the effects of the present invention. The upper limit of the resin content is preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less, based on the total amount of the overcoat ink. This further improves the dispersion stability of the resin. In particular, when the overcoat ink is ejected onto the surface of a recorded material by an inkjet method, the ejection stability can be further improved by setting the resin content to 30% by mass or less.

[water]
The overcoat ink contains water as a main component. As water, it is preferable to use deionized water rather than containing various ions. The water content is not particularly limited as long as it can disperse or dissolve each component, but the lower limit of the water content is in the range of 30% by mass or more based on the total amount of the overcoat ink. is preferably 40% by mass or more, more preferably 45% by mass or more, even more preferably 50% by mass or more. The upper limit of the water content is preferably 85% by mass or less, more preferably 82% by mass or less, and 80% by mass or less based on the total amount of the overcoat ink. is more preferred.

[Organic solvent]
The overcoat ink according to this embodiment contains an organic solvent. The organic solvent is capable of dispersing or dissolving the resin and the like.

Since the overcoat ink according to the present embodiment contains water, the organic solvent preferably contains a water-soluble solvent. In this specification, the water-soluble solvent is 5 parts by mass or more, preferably 20 parts by mass or more, more preferably 50 parts by mass or more, and still more preferably 70 parts by mass in 100 parts by mass of water at 25°C under 1 atmosphere. Above, most preferably, it refers to a substance that can dissolve 90 parts by mass or more.

Examples of organic solvents include alkyl alcohols having 1 to 5 carbon atoms such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, isobutyl alcohol and n-pentanol. alcohol; formamide, acetamide, propanamide, butanamide, isobutyramide, pentanamide, N-methylformamide, N-methylacetamide, N-methylpropanamide, N-methylbutanamide, N-methylisobutyramide, N-methyl Pentanamide, N-ethylformamide, N-ethylacetamide, N-ethylpropanamide, N-ethylbutanamide, N-ethylisobutyramide, N-ethylpentanamide, N-propylformamide, N-propylacetamide, N-propyl Propanamide, N-propylbutanamide, N-propylisobutyramide, N-propylpentanamide, N-isopropylformamide, N-isopropylacetamide, N-isopropylpropanamide, N-isopropylbutanamide, N-isopropylisobutyramide, N - isopropylpentanamide, N-butylformamide, N-butylacetamide, N-butylpropanamide, N-butylbutanamide, N-butylisobutylamide, N-butylpentanamide, N,N-dimethylformamide, N,N- Dimethylacetamide, N,N-dimethylpropanamide, N,N-dimethylbutanamide, N,N-dimethylisobutyramide, N,N-dimethylpentanamide, N,N-diethylformamide, N,N-diethylacetamide, N , N-diethylpropanamide, N,N-diethylbutanamide, N,N-diethylisobutyramide, N,N-diethylpentanamide, N,N-dipropylformamide, N,N-dipropylacetamide, N,N -dipropylpropanamide, N,N-dipropylbutanamide, N,N-dipropylisobutyramide, N,N-dipropylpentanamide, N,N-diisopropylformamide, N,N-diisopropylacetamide, N,N -diisopropylpropanamide, N,N-diisopropylbutanamide, N,N-diisopropylisobutyramide, N,N-diisopropylpentanamide, N,N-dibutylformamide, N,N-di Butylacetamide, N,N-dibutylpropanamide, N,N-dibutylbutanamide, N,N-dibutylisobutylamide, N,N-dibutylpentanamide, N-ethyl-N-methylformamide, N-ethyl-N- Methylacetamide, N-ethyl-N-methylpropanamide, N-ethyl-N-methylbutanamide, N-ethyl-N-methylisobutyramide, N-ethyl-N-methylpentanamide, N-methyl-N-propyl formamide, N-methyl-N-propylacetamide, N-methyl-N-propylpropanamide, N-methyl-N-propylbutanamide, N-methyl-N-propylisobutyramide, N-methyl-N-propylpentanamide , N-ethyl-N-propylformamide, N-ethyl-N-propylacetamide, N-ethyl-N-propylpropanamide, N-ethyl-N-propylbutanamide, N-ethyl-N-propylisobutyramide, N - amides such as ethyl-N-propylpentanamide; ketones or ketoalcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; oxyethylene or oxypropylene copolymers such as polyethylene glycol and polypropylene glycol; Ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, 1,3-propanediol, isobutylene glycol, triethylene glycol, tripropylene glycol, tetraethylene glycol, 1,3-propanediol, 2-methyl-1,2-propane Diol, 2-methyl-1,2-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,3-pentanediol, 1, 2-hexanediol, 1,5-pentanediol, 1,6-hexanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,3-butanediol, 3-methyl-1,5-pentane diols such as diols and 2-methyl-2,4-pentanediol; triols such as glycerin, trimethylolethane, trimethylolpropane and 1,2,6-hexanetriol; tetrahydric alcohols such as mesoerythritol and pentaerythritol , ethylene glycol monomethyl (or ethyl, isopropyl, n-butyl, isobutyl, n-hexyl 2-ethylhexyl) ether, diethylene glycol monomethyl (or ethyl, isopropyl, n-butyl, isobutyl, n-hexyl, 2-ethylhexyl) ether, triethylene glycol monomethyl (or ethyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl, pentyl, n-hexyl, 2-ethylhexyl) ether, propylene glycol monomethyl (or ethyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl, pentyl, n-hexyl, 2-ethylhexyl) ether, di Propylene glycol monomethyl (or ethyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl, pentyl, n-hexyl, 2-ethylhexyl) ether, tripropylene glycol monomethyl (or ethyl, propyl, isopropyl, n-butyl, isobutyl , t-butyl, pentyl, n-hexyl, 2-ethylhexyl) ethers; diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol ethyl methyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol ethyl Methyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol ethyl methyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol ethyl methyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, dipropylene glycol Dialkyl ethers of polyhydric alcohols such as ethyl methyl ether, tripropylene glycol dimethyl ether, tripropylene glycol diethyl ether, tripropylene glycol ethyl methyl ether Ethylene glycol monomethyl (or ethyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl , pentyl, n-hexyl, 2-ethylhexyl) ether acetate, diethylene glycol monomethyl (or ethyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl, pentyl, n-hexyl, 2-ethylhexyl) ether acetate, triethylene glycol monomethyl (or ethyl, propyl, Sopropyl, n-butyl, isobutyl, t-butyl, pentyl, n-hexyl, 2-ethylhexyl) ether acetate, propylene glycol monomethyl (or ethyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl, pentyl, n- hexyl, 2-ethylhexyl) ether acetate, dipropylene glycol monomethyl (or ethyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl, pentyl, n-hexyl, 2-ethylhexyl) ether acetate, tripropylene glycol monomethyl (or ethyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl, pentyl, n-hexyl, 2-ethylhexyl) ether acetate, ethylene glycol diacetate, diethylene glycol diacetate, propylene glycol diacetate, dipropylene glycol diacetate, etc. Acetates; γ-butyrolactone, α-methylene-γ-butyrolactone, ε-caprolactone, γ-valerolactone, γ-hexanolactone, γ-heptanolactone, δ-valerolactone, δ-hexanolactone, δ-hepta Lactone, δ-octalactone, δ-nonalactone, δ-decalactone, δ-undecalactone, γ,γ-dimethyl-γ-butyrolactone, α-methyl-γ-butyrolactone, γ-crotolactone, α-methylene-γ- Lactones such as butyrolactone, β-methyl-γ-butyrolactone, 6-methylvalerolactone, carbonate esters such as 2,3-butylene carbonate, ethylene carbonate, propylene carbonate, 3-methyl-2-oxazolidinone, 3-ethyl- Oxazolidinone solvents such as 2-oxazolidinone and N-vinylmethyloxazolidinone, methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, isobutyl alcohol, n-pen Alkyl alcohols having 1 to 5 carbon atoms such as tanol, 3-methoxy-3-methyl-1-butanol, 3-methoxy-1-propanol, 1-methoxy-2-propanol, 3-methoxy-n-butanol monohydric alcohols, ketones or ketoalcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; Oxyethylene or oxypropylene copolymer such as propylene glycol; ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, 1,3-propanediol, isobutylene glycol, triethylene glycol, tripropylene glycol, tetraethylene glycol, 1, 3-propanediol, 2-methyl-1,2-propanediol, 2-methyl-1,2-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1, 2-pentanediol, 1,2-hexanediol, 1,5-pentanediol, 1,6-hexanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,3-butanediol, 3- diols such as methyl-1,5-pentanediol and 2-methyl-2,4-pentanediol; triols such as glycerin, trimethylolethane, trimethylolpropane, and 1,2,6-hexanetriol: mesoerythritol, Tetrahydric alcohols such as pentaerythritol; monoethanolamine, diethanolamine, triethanolamine, N-methylethanolamine, N-ethylethanolamine, N-butylethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, N-butyl alkanolamines such as diethanolamine; nitrogen-containing heterocyclic compounds such as N-methyl-2-pyrrolidone, 2-pyrrolidone and 1,3-dimethyl-2-imidazolidinone; cyclic compounds such as γ-butyrolactone and sulfolane; Examples include morpholines such as methylmorpholine, N-ethylmorpholine and N-formylmorpholine, and terpene solvents. Among these, it is preferable to select a water-soluble solvent so that the overcoat ink has a desired static surface tension such that the static surface tension relationship described later is obtained. It is preferred to use

The content of the organic solvent is not particularly limited as long as it is capable of dispersing or dissolving each component. is preferably 10% by mass or more, more preferably 12% by mass or more. The upper limit of the content of the water-soluble solvent is preferably 50% by mass or less, more preferably 45% by mass or less, and 40% by mass or less in the total amount of the overcoat ink. It is even more preferable to have

[wax]
The overcoat ink may contain wax. Wax is an organic substance or silicone compound that is solid at room temperature or below and liquefies when heated. By containing wax together with a resin having a predetermined glass transition temperature range, the abrasion resistance of the overcoat layer can be further improved.

Specific examples of waxes include low-molecular-weight polyolefin waxes such as polyethylene, polypropylene, polybutene, polyethylene mixed wax, polypropylene wax, and polypropylene mixed wax, silicones (silicon) having a softening point, and silicone (silicon)-acrylic. Waxes, fatty acid amides such as oleic acid amide, erucic acid amide, ricinoleic acid amide, and stearic acid amide, ester wax, carnauba wax, rice wax, candelilla wax, tree wax, jojoba oil, and other vegetable waxes, beeswax , lanolin, whale wax, and other animal waxes; montan wax, ozokerite, ceresin, Fischer-Tropsch wax, and other mineral waxes; paraffin wax, microcrystalline wax, petrolatum, paraffin mixed wax, and other petroleum waxes; Modified products of These waxes are readily available as commercial products. These waxes also include what are called lubricants and slip agents. Among these, it is preferable to use polyethylene and silicone-based surfactants as the wax. Examples of such polyethylene and silicone-based surfactants include AQUACER 515 and 531 (polyethylene wax emulsion manufactured by BIK-Chemie), Nopcoat PEM-17 (polyethylene wax emulsion manufactured by San Nopco Co., Ltd.), TEGO Glide 410, 440, 450, 482, 485, 496 (silicone surfactant manufactured by Evonik), Silface SAG005, and Silface SAG008 (silicone surfactant manufactured by Nissin Kagaku Kogyo Co., Ltd.). In the overcoat ink according to the present embodiment, waxes may be used singly or in combination of two or more.

When wax is contained in the overcoat ink, the lower limit of the wax content is preferably 0.05% by mass or more, more preferably 0.10% by mass or more, based on the total amount of the overcoat ink. It is more preferably 15% by mass or more. The upper limit of the wax content is preferably 5.0% by mass or less, more preferably 3.0% by mass or less, and even more preferably 2.0% by mass or less in the total amount of the overcoat ink. . This makes it possible to improve the dispersibility of the wax in the overcoat ink, and in particular, in the case of an overcoat ink that is discharged onto the surface of a recorded matter by an inkjet method, it is possible to improve the discharge stability. becomes possible.

[Surfactant]
The overcoat ink according to this embodiment may contain a surfactant. By containing a surfactant, the surface tension of the overcoat ink can be controlled within an appropriate range. The surfactant is not particularly limited, but anionic surfactants, nonionic surfactants, silicone (silicon) surfactants, and fluorine-based surfactants are preferred because of their excellent ability to adjust surface tension. Active agents, acetylene glycol-based surfactants, and the like are preferably used. Among these, those containing a silicone (silicon)-based surfactant or an acetylene glycol-based surfactant are particularly preferred. As a result, it is possible to control the surface tension of the overcoat ink within an appropriate range. It is possible to control within a range. Furthermore, when the water-containing overcoat ink according to the present embodiment is used in an inkjet method, the ejection stability is maintained by containing a silicone (silicon)-based surfactant or an acetylene glycol-based surfactant. becomes possible. The reason for this is not necessarily clear, but when an overcoat containing water is used in an inkjet method, the water may evaporate during the inkjet ejection, and the component ratio changes, resulting in dispersibility of the resin contained in the overcoat ink. may decrease, and ejection stability may decrease. In the overcoat ink containing a resin having a predetermined glass transition temperature range according to the present embodiment, by containing a silicone (silicon)-based surfactant or an acetylene glycol-based surfactant, the water volatilizes to the resin. This is considered to be because the decrease in dispersibility can be suppressed.

Specific examples of surfactants include Emal, Latemul, Pelex, Neoperex, Demol (all of which are anionic surfactants; manufactured by Kao Corporation), Sunol, Liporan, Lipon, and Lipal (all of which are anionic surfactants). Agent; Lion Co., Ltd.), Noigen, Epan, Sorgen (all nonionic surfactants; Daiichi Kogyo Seiyaku Co., Ltd.) Emulgen, Amit, Emazol (all nonionic surfactants; Kao Corporation ), Naloacty, Emalmin, Sannonic (all nonionic surfactants; manufactured by Sanyo Chemical Industries, Ltd.), Surfynol 104, 82, 420, 440, 465, 485, TG, 2502, SE-F, 107L, Dynol 360, Dynol 604, Dynol 607 (all are acetylene glycol-based surfactants; manufactured by Evonik), Inol 960 (mixture of acetylene glycol-based and silicon-based surfactants; manufactured by Evonik), Surfynol AD01 (alkane Glycol-based surfactant; manufactured by Evonik), Olfine E1004, E1010, PD004, EXP4300 (all of which are acetylene glycol-based surfactants; manufactured by Nissin Chemical Industry Co., Ltd.), Megafac (fluorine-based surfactant; DIC stock company), Surflon (fluorosurfactant; manufactured by AGC Seimi Chemical Co., Ltd.), BYK302, 306, 307, 331, 333, 345, 346, 347, 348, 349, 3420, 3450, 3451, 3455, 3456 (any Silicone (silicon)-based surfactants; manufactured by BYK Chemie), KP-110, 112, 323, 341, 6004 (all silicone (silicon)-based surfactants; manufactured by Shin-Etsu Chemical Co., Ltd.) Silface SAG002, Silface SAG005, Silface SAG008, Silface SAG014, Silface SAG503A, Silface SJG002, Silface SJM-002, Silface SJM-003 (all are silicone (silicon) surfactants; manufactured by Nissin Chemical Industry Co., Ltd. ), TEGO Flow 425, TEGO Glide 100, 110, 130, 410, 432, 440, 450, 482, 490, 492, 494, 496, ZG400, TEGO Twin 4000, TEGO Twin 4100, TEGO Twin 4200, TEGO Wet 240 KL245, 2 50, 260, 265, 270, 280, (all silicone surfactants; manufactured by Evonik), TEGO Wet 500, 505, 510, 520 (all nonionic surfactants; manufactured by Evonik), etc. are mentioned.

The content of the surfactant is not particularly limited, but the lower limit of the content of the surfactant is preferably in the range of 0.5% by mass or more in the total amount of the overcoat ink, and 0.8% by mass or more. It is more preferably within the range, and further preferably within the range of 1.0% by mass or more. The upper limit of the surfactant content is preferably 5.0% by mass or less, more preferably 4.5% by mass or less, and 4.0% by mass of the total amount of the overcoat ink. % or less is more preferable. When the content of the surfactant is within such a range, it becomes possible to improve the dispersibility of the resin or wax in the overcoat ink. In the case of ink, it is possible to improve ejection stability.

[Antibacterial agent]
The overcoat ink according to this embodiment may contain an antibacterial agent. Examples of antibacterial agents include inorganic antibacterial agents and water-soluble organic antibacterial agents. Antibacterial agents are those that exert a bactericidal effect against bacteria such as Staphylococcus aureus and Escherichia coli, fungi such as mold and yeast, and viruses that exist around us. Used.

Organic antibacterial agents include phenol ether derivatives, imidazole derivatives, sulfone derivatives, N-haloalkylthio compounds, anilides derivatives, pyrrole derivatives, quaternary ammonium salts, pyridines, triazines, benzoisothiazolines, isothiazolines, and the like. mentioned.

For example, 1,2-benzisothiazolin-3-one, N-fluorodichloromethylthio-phthalimide, 2,3,5,6-tetrachloroisophthalonitrile, 2,4,5,6-tetrachloroisophthalonitrile <hereinafter , also referred to as "TPN". >, N-trichloromethylthio-4-cyclohexene-1,2-dicarboximide, copper 8-quinolinate, bis(tributyltin) oxide, 2-(4-thiazolyl)benzimidazole <hereinafter also referred to as “TBZ”. >, 2-benzimidazole methyl carbamate <hereinafter also referred to as “BCM”. >, 10,10′-oxybisphenoxyarsine <hereinafter also referred to as “OBPA”. >, 2,3,5,6-tetrachloro-4-(methylsulfone)pyridine, bis(2-pyridylthio-1-oxide)zinc <hereinafter also referred to as “ZPT”. >, N,N-dimethyl-N'-(fluorodichloromethylthio)-N'-phenylsulfamide <dichlorofluanid>, poly-(hexamethylenebiguanide) hydrochloride, dithio-2-2'-bis( benzmethylamide), 2-methyl-4,5-trimethylene-4-isothiazolin-3-one, 2-bromo-2-nitro-1,3-propanediol, hexahydro-1,3-tris-(2-hydroxy ethyl)-S-triazine, p-chloro-m-xylenol, 1,2-benzisothiazolin-3-one and the like, but are not limited thereto.

Inorganic antibacterial agents include mercury, silver, copper, zinc, iron, lead, bismuth, etc., in descending order of bactericidal activity. Examples thereof include metals such as silver, copper, zinc and nickel, and metal ions supported on silicate-based carriers, phosphate-based carriers, oxides, glass, potassium titanate, amino acids, and the like. For example, zeolite antibacterial agent, calcium silicate antibacterial agent, zirconium phosphate antibacterial agent, calcium phosphate antibacterial agent, zinc oxide antibacterial agent, soluble glass antibacterial agent, silica gel antibacterial agent, activated carbon antibacterial agent, titanium oxide antibacterial agent Antibacterial agents, titania antibacterial agents, organometallic antibacterial agents, ion exchange ceramic antibacterial agents, layered phosphate-quaternary ammonium salt antibacterial agents, antibacterial stainless steel, etc., but are not limited to these. No.

[Infrared absorber]
The overcoat ink according to this embodiment may contain an infrared absorber. The infrared absorbing agent is not particularly limited as long as it has a property of effectively absorbing infrared rays, particularly light in the near-infrared region, and both inorganic and organic agents can be used.

Examples of inorganic infrared absorbers include at least one selected from titanium oxide, zinc oxide, indium oxide, tin-doped indium oxide (ITO), tin oxide, antimony-doped tin oxide (ATO), and zinc sulfide. can be done.

Examples of organic infrared absorbers include cyanine compounds, squarylium compounds, thiolnickel complex compounds, naphthalocyanine compounds, phthalocyanine compounds, triallylmethane compounds, naphthoquinone compounds, anthraquinone compounds, and N, N,N',N'-tetrakis(p-di-n-butylaminophenyl)-p-phenylenediaminium perchlorate, phenylenediaminium chloride, phenylenediaminium hexafluoroantimonate, phenylene Amino compounds such as diaminium fluoroborate, phenylenediaminium fluoride, and phenylenediaminium perchlorate, copper compounds and bisthiourea compounds, phosphorus compounds and copper compounds, phosphate ester compounds and copper compounds Phosphate ester copper compound obtained by the reaction of.

[Ultraviolet absorber]
The overcoat ink according to this embodiment may contain an ultraviolet absorber. Thereby, the light resistance of the overcoat layer can be improved. Examples of the ultraviolet absorber include known ultraviolet absorbers such as benzotriazole-based compounds, benzophenone-based compounds, triazine-based compounds, and benzoxazole-based compounds.

[Light stabilizer]
The overcoat ink according to this embodiment may contain a light stabilizer. Thereby, the light resistance of the overcoat layer can be improved. Examples of light stabilizers include conventionally known hindered amine light stabilizers (HALS).

[Antioxidant]
The overcoat ink according to this embodiment may contain an antioxidant. Thereby, the light resistance of the overcoat layer can be improved. Examples of antioxidants include conventionally known antioxidants, such as phenolic antioxidants such as hindered phenol, chroman-based antioxidants, chroman-based antioxidants, hydroquinone derivatives, benzotriazole-based antioxidants (having no ultraviolet absorption ability), spiroindane-based antioxidants, and the like. . Epoxy-based compounds and polyvalent carboxylic acid compounds may also be used.

[Other ingredients]
The overcoat ink may further contain conventionally known additives as needed. Examples of additives include coloring materials, viscosity modifiers, pH modifiers, preservatives, antifungal agents, and the like.

Although the overcoat ink according to the present embodiment may contain a coloring material, it preferably contains little coloring material. This makes it possible to improve the visibility of the recording surface of the recorded matter. Specifically, the content of the coloring material is preferably 3.0% by mass or less, more preferably 1.0% by mass or less, and 0.5% by mass or less in the total amount of the overcoat ink. is more preferable, more preferably 0.1% by mass or less, and most preferably no coloring material is contained.

In addition, when the overcoat layer is a white layer, it may contain a white pigment. Furthermore, when the overcoat layer is a metallic layer, it may contain a luster pigment. In these cases, the lower limit of the pigment content is preferably in the range of 0.05 mass % or more, more preferably 0.08 mass % or more, and 0.1 in the total amount of the overcoat ink. More preferably, it is in the range of mass % or more. The upper limit of the pigment content is preferably within the range of 20% by mass or less, more preferably within the range of 15% by mass or less, and preferably within the range of 10% by mass or less based on the total amount of the aqueous ink. More preferred. Inorganic pigments such as white pigment barium sulfate, barium carbonate, barium sulfate, silica, clay, talc, titanium oxide, calcium carbonate, synthetic mica, and alumina can be used. Luster pigments include mica, titanium dioxide-coated mica, fish scale foil, bismuth oxide, silicon dioxide, metal oxides, pearl pigments with pearl luster and interference luster such as laminates thereof, aluminum, silver, gold, and nickel. , chromium, tin, zinc, indium, titanium, copper and the like; metal compounds; alloys and mixtures thereof.

The method of preparing the overcoat ink is not particularly limited. For example, a method of adding a resin, a surfactant and, if necessary, other components to a water-soluble solvent.

The surface tension of the overcoat ink is not particularly limited, but the upper limit of the surface tension is preferably 30.0 mN/m or less, more preferably 29.0 mN/m or less, and even more preferably 28.0 mN/m or less. The lower limit of the surface tension is preferably 19.0 mN/m or more, more preferably 20.0 mN/m or more, and even more preferably 21.0 mN/m or more. Incidentally, the static surface tension is a value measured at a measurement temperature of 25° C. by the Wilhelmy method (manufactured by Kyowa Interface Science, model: DY-300).

The overcoat ink has a surface tension within a predetermined range by adjusting the type and content of the organic solvent and surfactant contained in the overcoat ink.

<<Ink set of the first embodiment>>
The ink set according to the present embodiment is an ink set containing the above-described overcoat ink and water-based ink.

Below, the water-based ink included in the ink set according to the present embodiment will be described.

[Water-based ink]
The water-based ink is an ink that contains water as a main component and may contain a coloring material, and is applied in advance onto a base material when applying the above-described overcoat ink. Aqueous inks containing water as a main component have little impact on the environment and are highly safe for workers because they do not catch fire.

[water]
Aqueous ink contains water as a main component. As water, it is preferable to use deionized water rather than containing various ions. The content of water is not particularly limited as long as it can disperse or dissolve each component, but the lower limit of the content of water should be in the range of 30% by mass or more based on the total amount of water-based ink. is preferred, more preferably 45% by mass or more, and even more preferably 50% by mass or more. The upper limit of the water content is preferably within the range of 85% by mass or less, more preferably within the range of 80% by mass or less, and preferably within the range of 75% by mass or less based on the total amount of the aqueous ink. More preferred.

[Organic solvent]
The water-based ink according to this embodiment contains an organic solvent. The organic solvent is capable of dispersing or dissolving the coloring material and the like. Since the water-based ink according to this embodiment contains water, the organic solvent preferably contains a water-soluble solvent.

Examples of organic solvents include alkyl alcohols having 1 to 5 carbon atoms such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, isobutyl alcohol and n-pentanol. Alcohols; formamide, acetamide, propanamide, butanamide, isobutyramide, pentanamide, N-methylformamide, N-methylacetamide, N-methylpropanamide, N-methylbutanamide, N-methylisobutyramide, N-methylpentane Amide, N-ethylformamide, N-ethylacetamide, N-ethylpropanamide, N-ethylbutanamide, N-ethylisobutyramide, N-ethylpentanamide, N-propylformamide, N-propylacetamide, N-propylpropane Amide, N-propylbutanamide, N-propylisobutyramide, N-propylpentanamide, N-isopropylformamide, N-isopropylacetamide, N-isopropylpropanamide, N-isopropylbutanamide, N-isopropylisobutyramide, N- Isopropylpentanamide, N-butylformamide, N-butylacetamide, N-butylpropanamide, N-butylbutanamide, N-butylisobutylamide, N-butylpentanamide, N,N-dimethylformamide, N,N-dimethyl Acetamide, N,N-dimethylpropanamide, N,N-dimethylbutanamide, N,N-dimethylisobutyramide, N,N-dimethylpentanamide, N,N-diethylformamide, N,N-diethylacetamide, N, N-diethylpropanamide, N,N-diethylbutanamide, N,N-diethylisobutyramide, N,N-diethylpentanamide, N,N-dipropylformamide, N,N-dipropylacetamide, N,N- Dipropylpropanamide, N,N-dipropylbutanamide, N,N-dipropylisobutyramide, N,N-dipropylpentanamide, N,N-diisopropylformamide, N,N-diisopropylacetamide, N,N- Diisopropylpropanamide, N,N-diisopropylbutanamide, N,N-diisopropylisobutyramide, N,N-diisopropylpentanamide, N,N-dibutylformamide, N,N-dibu Thilacetamide, N,N-dibutylpropanamide, N,N-dibutylbutanamide, N,N-dibutylisobutyramide, N,N-dibutylpentanamide, N-ethyl-N-methylformamide, N-ethyl-N- Methylacetamide, N-ethyl-N-methylpropanamide, N-ethyl-N-methylbutanamide, N-ethyl-N-methylisobutyramide, N-ethyl-N-methylpentanamide, N-methyl-N-propyl formamide, N-methyl-N-propylacetamide, N-methyl-N-propylpropanamide, N-methyl-N-propylbutanamide, N-methyl-N-propylisobutyramide, N-methyl-N-propylpentanamide , N-ethyl-N-propylformamide, N-ethyl-N-propylacetamide, N-ethyl-N-propylpropanamide, N-ethyl-N-propylbutanamide, N-ethyl-N-propylisobutyramide, N - amides such as ethyl-N-propylpentanamide; ketones or ketoalcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; oxyethylene or oxypropylene copolymers such as polyethylene glycol and polypropylene glycol; Ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, 1,3-propanediol, isobutylene glycol, triethylene glycol, tripropylene glycol, tetraethylene glycol, 1,3-propanediol, 2-methyl-1,2-propane Diol, 2-methyl-1,2-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,3-pentanediol, 1, 2-hexanediol, 1,5-pentanediol, 1,6-hexanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,3-butanediol, 3-methyl-1,5-pentane diols such as diols and 2-methyl-2,4-pentanediol; triols such as glycerin, trimethylolethane, trimethylolpropane and 1,2,6-hexanetriol; tetrahydric alcohols such as mesoerythritol and pentaerythritol , ethylene glycol monomethyl (or ethyl, isopropyl, n-butyl, isobutyl, n-hexyl , 2-ethylhexyl) ether, diethylene glycol monomethyl (or ethyl, isopropyl, n-butyl, isobutyl, n-hexyl, 2-ethylhexyl) ether, triethylene glycol monomethyl (or ethyl, propyl, isopropyl, n-butyl, isobutyl, t -butyl, pentyl, n-hexyl, 2-ethylhexyl) ether, propylene glycol monomethyl (or ethyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl, pentyl, n-hexyl, 2-ethylhexyl) ether, dipropylene glycol monomethyl (or ethyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl, pentyl, n-hexyl, 2-ethylhexyl) ether, tripropylene glycol monomethyl (or ethyl, propyl, isopropyl, n-butyl, isobutyl, monoalkyl ethers such as t-butyl, pentyl, n-hexyl, 2-ethylhexyl) ether; diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol ethyl methyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol ethyl methyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol ethyl methyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol ethyl methyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, dipropylene glycol ethyl Dialkyl ethers of polyhydric alcohols such as methyl ether, tripropylene glycol dimethyl ether, tripropylene glycol diethyl ether, tripropylene glycol ethyl methyl ether; ethylene glycol monomethyl (or ethyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl , pentyl, n-hexyl, 2-ethylhexyl) ether acetate, diethylene glycol monomethyl (or ethyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl, pentyl, n-hexyl, 2-ethylhexyl) ether acetate, triethylene glycol monomethyl (or ethyl, propyl, Sopropyl, n-butyl, isobutyl, t-butyl, pentyl, n-hexyl, 2-ethylhexyl) ether acetate, propylene glycol monomethyl (or ethyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl, pentyl, n- hexyl, 2-ethylhexyl) ether acetate, dipropylene glycol monomethyl (or ethyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl, pentyl, n-hexyl, 2-ethylhexyl) ether acetate, tripropylene glycol monomethyl (or ethyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl, pentyl, n-hexyl, 2-ethylhexyl) ether acetate, ethylene glycol diacetate, diethylene glycol diacetate, propylene glycol diacetate, dipropylene glycol diacetate, etc. Acetates; γ-butyrolactone, α-methylene-γ-butyrolactone, ε-caprolactone, γ-valerolactone, γ-hexanolactone, γ-heptanolactone, δ-valerolactone, δ-hexanolactone, δ-hepta Lactone, δ-octalactone, δ-nonalactone, δ-decalactone, δ-undecalactone, γ,γ-dimethyl-γ-butyrolactone, α-methyl-γ-butyrolactone, γ-crotolactone, α-methylene-γ- Lactones such as butyrolactone, β-methyl-γ-butyrolactone, 6-methylvalerolactone, carbonate esters such as 2,3-butylene carbonate, ethylene carbonate, propylene carbonate, 3-methyl-2-oxazolidinone, 3-ethyl- Oxazolidinone solvents such as 2-oxazolidinone and N-vinylmethyloxazolidinone, methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, isobutyl alcohol, n-pen Alkyl alcohols having 1 to 5 carbon atoms such as tanol, 3-methoxy-3-methyl-1-butanol, 3-methoxy-1-propanol, 1-methoxy-2-propanol, 3-methoxy-n-butanol monohydric alcohols, ketones or ketoalcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; Oxyethylene or oxypropylene copolymer such as propylene glycol; ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, 1,3-propanediol, isobutylene glycol, triethylene glycol, tripropylene glycol, tetraethylene glycol, 1, 3-propanediol, 2-methyl-1,2-propanediol, 2-methyl-1,2-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1, 2-pentanediol, 1,2-hexanediol, 1,5-pentanediol, 1,6-hexanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,3-butanediol, 3- diols such as methyl-1,5-pentanediol and 2-methyl-2,4-pentanediol; triols such as glycerin, trimethylolethane, trimethylolpropane, and 1,2,6-hexanetriol: mesoerythritol, Tetrahydric alcohols such as pentaerythritol; monoethanolamine, diethanolamine, triethanolamine, N-methylethanolamine, N-ethylethanolamine, N-butylethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, N-butyl alkanolamines such as diethanolamine; nitrogen-containing heterocyclic compounds such as N-methyl-2-pyrrolidone, 2-pyrrolidone and 1,3-dimethyl-2-imidazolidinone; cyclic compounds such as γ-butyrolactone and sulfolane; Examples include morpholines such as methylmorpholine, N-ethylmorpholine and N-formylmorpholine, and terpene solvents.

Among these, it is preferable to contain an organic solvent having a water-octanol partition coefficient of -0.3 or less. The water-octanol partition coefficient is the common logarithm of the concentration ratio of the organic solvent in the two solvent phases, water and 1-octanol, when a chemical substance is added to the two solvent phases and the equilibrium state is reached. .

If the water-based ink has a high permeability to the base material (recording medium), the amount of the water-based ink remaining on the base material surface will decrease, and as a result, the water-based ink will wet and spread on the base material (spread in the direction of the base material surface). It may drop and cause a filling failure. The research of the present invention has revealed that penetration into the substrate (recording medium) can be suppressed by containing an organic solvent having a water-octanol partition coefficient of −0.3 or less together with water. By suppressing the permeation of the water-based ink into the base material (recording medium), it becomes possible to effectively suppress the filling failure due to the deterioration of the wetting and spreading properties, thereby obtaining an image with high reproducibility.

An organic solvent with a water-octanol partition coefficient of -0.3 or less has a high affinity with water, and when it is contained together with water, the contact angle with respect to the substrate is reduced (that is, the wettability is increased). This is because it becomes easier to wet and spread than permeate into the substrate (recording medium).

Furthermore, by applying an overing containing a resin having a glass transition temperature within the above-described predetermined range on a water-based ink containing an organic solvent having a water-octanol partition coefficient of −0.3 or less, poor filling is suppressed and reproducibility is improved. It is possible to form a low slip overcoat layer on a high image. As a result, it is possible to protect the highly reproducible image with the overcoat layer, and prevent collapse of a stack of recorded materials due to vibration during transportation or storage, for example. Further, abrasion resistance and glossiness can be imparted to a recording layer obtained by using an aqueous ink containing an organic solvent having a water-octanol distribution coefficient of −0.3 or less.

Such an organic solvent having a water-octanol partition coefficient of −0.3 or less is preferably an alkanediol organic solvent having a water-octanol partition coefficient of −0.3 or less. butanediol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,3-butanediol and the like.

The content of the organic solvent is not particularly limited as long as it can disperse or dissolve each component. It is preferably in the range of 10% by mass or more, more preferably in the range of 12% by mass or more. The upper limit of the content of the organic solvent is preferably 50% by mass or less, more preferably 45% by mass or less, and 40% by mass or less based on the total amount of the aqueous ink. is more preferred.

In addition, the content of the organic solvent having a water-octanol partition coefficient of -0.3 or less (for example, an alkanediol organic solvent having a water-octanol partition coefficient of -0.3 or less) is not particularly limited. However, the lower limit of the content is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more in the total amount of the aqueous ink. The lower limit of the content of the organic solvent having a water-octanol partition coefficient of −0.4 or less is preferably 50% by mass or less, more preferably 30% by mass or less, more preferably 23% by mass, based on the total amount of the aqueous ink. % or less.

[resin]
The water-based ink according to this embodiment may contain a resin. By containing the resin, it is possible to suppress the penetration of the pigment into the substrate (recording medium) and promote the fixation of the coloring material. As the resin, a resin emulsion is preferable from the viewpoint of excellent fixability and excellent water resistance of the aqueous ink layer. Further, by forming a resin emulsion, the resin can be dispersed as fine resin particles in the water-based ink by electrostatic repulsion or steric repulsion, and dispersion stability can be improved.

Specifically, acrylic resin, styrene-acrylic resin, polystyrene resin, polyester resin, vinyl chloride resin, vinyl acetate resin, vinyl chloride vinyl acetate copolymer resin, polyethylene resin, urethane resin, silicone One or more resins or copolymer resins selected from the group consisting of (silicon)-based resins, acrylamide-based resins, epoxy-based resins, polycarbonate-based resins, and polystyrene-based resins, or mixtures thereof can be used. These are preferable because they can improve not only water resistance but also solvent resistance. Among them, it is preferable that at least one of the constituent monomers contains an acrylic resin having an acrylic skeleton, since it can be excellent in ejection stability, water resistance, and solvent resistance.

Commercially available resin emulsions include, for example, Acryt WEM-031U, WEM-200U, WEM-321, WEM-3000, WEM-202U, WEM-3008 (manufactured by Taisei Fine Chemical Co., Ltd., acrylic-urethane resin emulsion). , Acryt UW-550CS, UW-223SX, AKW107, RKW-500 (manufactured by Taisei Fine Chemical Co., Ltd., acrylic resin emulsion), LUBRIJET N240 (manufactured by Lubrizol, acrylic resin emulsion), Superflex 150, 210, 470, 500M, 620, 650, E2000, E4800, R5002 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., urethane resin emulsion), Vinyblan 701FE35, 701FE50, 701FE65, 700, 701, 711, 737, 747 (manufactured by Nisshin Chemical Co., Ltd., chloride vinyl-acrylic resin emulsion), Vinyblan 2706, 2685 (manufactured by Nisshin Chemical Co., Ltd., acrylic resin emulsion), Movinyl 743N, 6520, 6600, 6820, 7470, 7720, (manufactured by Japan Coating Resin Co., Ltd., acrylic resin emulsion), PRIMAL AC-261P, AC-818 (Dow Chemical Company acrylic resin particle emulsion), NeoCryl A2091, A2092, A639, A655, A662 (DSM Coating Resin styrene-acrylic resin particle emulsion), QE-1042, KE- 1062 (Styrene-acrylic resin particle emulsion manufactured by Seiko PMC), JE-1056 (Acrylic resin particle emulsion manufactured by Seiko PMC), JONCRYL7199, PDX-7630A (Styrene-acrylic resin emulsion manufactured by BASF Japan), Charine R170BX (Nissin) Kagaku Kogyo, silicone-acrylic resin emulsion), Takelac W-6010 (Mitsui Chemicals, urethane resin emulsion), Elitel KA-5071S (Unitika, polyester resin emulsion), Polysol AP-1350 (Showa Denko, acrylic resin emulsion) ), etc., but are not limited to these.

The content of the resin (resin emulsion) contained in the water-based ink is not particularly limited, but the lower limit of the content of the resin is preferably 0.05% by mass or more based on the total amount of the water-based ink. It is preferably 1% by mass or more, more preferably 0.5% by mass or more, and more preferably 1% by mass or more. This makes it possible to suppress the water-based ink from penetrating into the base material (recording medium), effectively suppressing ink filling defects due to partial reduction in print density, and achieving highly reproducible images. will be obtained. The upper limit of the resin content is preferably 15% by mass or less, more preferably 12% by mass or less, and even more preferably 10% by mass or less, based on the total amount of the aqueous ink. This further improves the dispersion stability of the resin. In particular, when the water-based ink is ejected onto the surface of the base material by an inkjet method, the ejection stability can be further improved by setting the resin content to 15% by mass or less.

Among these, in the ink set according to the present embodiment (ink set of the first embodiment) and the ink set described later (ink set of the second embodiment), the content of the resin (resin emulsion) contained in the water-based ink is excessive. It is preferably less than the content of the resin (resin emulsion) contained in the coating ink. In particular, when the overcoat ink is applied directly onto the surface of the liquid while the water-based ink has fluidity and exists as a liquid, these inks mix at the interface between the water-based ink and the overcoat ink. . If the content of the resin contained in the water-based ink is greater than the content of the resin contained in the overcoat ink, part of the resin contained in the water-based ink will be contained in the overcoat ink. Then, the slipperiness of the overcoat layer may relatively increase under the influence of the resin contained in the water-based ink. Since the content of the resin (resin emulsion) contained in the water-based ink is less than the content of the resin (resin emulsion) contained in the overcoat ink, the resin contained in the water-based ink causes the overcoat layer to slip. Since it is possible to suppress the increase in the properties, the ink set further exhibits the effects of the present invention.

The average particle size of the resin emulsion is preferably 30 nm or more, more preferably 40 nm or more, and even more preferably 50 nm or more. The average particle size of the resin emulsion is preferably 300 nm or less, more preferably 270 nm or less, and even more preferably 250 nm or less. This further improves the dispersion stability of the resin emulsion in the water-based ink. In particular, when water-based ink is ejected onto the surface of a recorded material by an inkjet method, the ejection stability can be further enhanced by using a resin that contains a resin emulsion at least in part. In the present embodiment, the average particle size of the resin emulsion can be measured using a concentrated particle size analyzer (manufactured by Otsuka Electronics Co., Ltd., model: FPAR-1000) at a measurement temperature of 25°C.

The weight average molecular weight of the resin emulsion is preferably 10,000 or more, more preferably 50,000 or more, and even more preferably 100,000 or more, from the viewpoint of water resistance of the aqueous ink layer. From the viewpoint of the stability of the ink composition, the weight average molecular weight of the resin emulsion is preferably 1,000,000 or less, more preferably 700,000 or less, and even more preferably 500,000 or less. In the present embodiment, the molecular weight of the resin indicates the mass average molecular weight Mw, which is a value measured by GPC (gel permeation chromatography), using "HLC-8120GPC" manufactured by Tosoh Corporation. , can be measured using a polystyrene standard for a calibration curve as a standard.

[Color material]
The water-based ink according to this embodiment may contain a coloring material. By containing a coloring material, it becomes possible to print on the surface of the substrate, and a recording layer forming a desired image pattern can be formed. The colorant may be either a dye or a pigment, but is preferably a pigment.

Pigments conventionally used in inkjet inks include inorganic pigments such as barium sulfate, iron oxide, zinc oxide, barium carbonate, barium sulfate, silica, clay, talc, titanium oxide, calcium carbonate, synthetic mica, and alumina. A pigment, an organic pigment, or the like can be used. These may be used individually by 1 type, or may be used in combination of 2 or more type. Specific organic pigments include, for example, insoluble azo pigments, soluble azo pigments, derivatives from dyes, phthalocyanine-based organic pigments, quinacridone-based organic pigments, perylene-based organic pigments, perinone-based organic pigments, azomethine-based organic pigments, and anthraquinone-based pigments. Organic pigments (anthrone-based organic pigments), xanthene-based organic pigments, diketopyrrolopyrrole-based organic pigments, dioxazine-based organic pigments, nickel azo-based pigments, isoindolinone-based organic pigments, pyranthrone-based organic pigments, thioindigo-based organic pigments, condensed azo organic solid solution pigments such as organic pigments, benzimidazolone organic pigments, quinophthalone organic pigments, isoindoline organic pigments, quinacridone solid solution pigments, perylene solid solution pigments, and other pigments such as carbon black.

When organic pigments are exemplified by color index (C.I.) numbers, C.I. I.

Pigment Yellow

1, 2, 3, 12, 13, 14, 16, 17, 20, 24, 73, 74, 75, 83, 93, 95, 97, 98, 109, 110, 114, 117, 120, 125, 128, 129, 130, 137, 138, 139, 147, 148, 150, 151, 153, 154, 155, 166, 168, 180, 185, 213, 214; I. Pigment Red 5, 7, 9, 12, 48, 48:2, 48:3, 49, 52, 53, 57, 57:1, 97, 112, 122, 123, 146, 149, 150, 168, 176, 177, 180, 184, 185, 192, 202, 206, 208, 209, 213, 215, 216, 217, 220, 223, 224, 226, 227, 228, 238, 240, 254, 269, 291; I. Pigment Orange 16, 36, 43, 51, 55, 59, 61, 64, 71, 73; C.I. I. Pigment Violet 19, 23, 29, 30, 37, 40, 50; C.I. I. Pigment Blue 15, 15:1, 15:3, 15:4, 15:6, 16, 22, 60, 64; C.I. I. Pigment Green 7, 36, 58, 59, 62, 63; C.I. I. Pigment Brown 23, 25, 26; C.I. I. Pigment Black 7 and the like.

Specific examples of dyes that can be used in the water-based ink according to the present embodiment include azo dyes, benzoquinone dyes, naphthoquinone dyes, anthraquinone dyes, cyanine dyes, squarylium dyes, croconium dyes, and merocyanine dyes. dyes, stilbene dyes, diarylmethane dyes, triarylmethane dyes, fluorane dyes, spiropyran dyes, phthalocyanine dyes, indigo dyes such as indigoids, fulgide dyes, nickel complex dyes, and azulene dyes is mentioned.

Specific examples of the inorganic pigments include titanium oxide, barium sulfate, calcium carbonate, zinc white, lead sulfate, yellow lead, zinc yellow, red iron oxide (III), cadmium red, ultramarine blue, Prussian blue, oxide Chromium green, cobalt green, amber, titanium black, synthetic iron black, inorganic solid solution pigments and the like can be mentioned.

The average dispersed particle size of the pigment is not particularly limited as long as the desired color development is possible. Although it varies depending on the type of pigment, the lower limit of the average dispersed particle diameter of the pigment is preferably in the range of 10 nm or more, preferably 20 nm or more, from the viewpoint of obtaining sufficient coloring power with good dispersion stability of the pigment. It is more preferably within the range, and even more preferably within the range of 30 nm or more. The upper limit of the average dispersed particle size of the pigment is preferably 300 nm or less, more preferably 250 nm or less, and even more preferably 200 nm or less. When the average dispersed particle diameter is 300 nm or less, nozzle clogging of an inkjet head is less likely to occur, and a uniform image with high reproducibility can be obtained. When the average dispersed particle diameter is 10 nm or more, the light resistance of the resulting printed matter can be improved. In the present embodiment, the average dispersed particle diameter of the pigment is the average particle diameter ( D50).

The content of the pigment is not particularly limited as long as the desired image can be formed, and is adjusted as appropriate. Specifically, although it varies depending on the type of pigment, the lower limit of the content of the pigment is preferably in the range of 0.05% by mass or more in the total amount of the aqueous ink, and is in the range of 0.08% by mass or more. It is more preferable that the content is in the range of 0.1% by mass or more. The upper limit of the pigment content is preferably within the range of 20% by mass or less, more preferably within the range of 15% by mass or less, and preferably within the range of 10% by mass or less based on the total amount of the aqueous ink. More preferred. When the content of the pigment is in the range of 0.05% by mass or more and 20% by mass or less, the balance between the dispersion stability and the coloring power of the pigment can be excellent.

[Pigment Dispersant]
The water-based ink according to this embodiment may contain a pigment dispersant. Here, the pigment dispersant means a resin or surfactant that has a function of improving the dispersibility of the pigment in the ink by adhering to a part of the pigment surface.

The pigment dispersant that can be used in the water-based ink according to this embodiment is not particularly limited. For example, cationic, anionic, nonionic, amphoteric, silicone (silicon), and fluorine surfactants can be used. Among surfactants, polymer surfactants (polymer dispersants) such as those exemplified below are preferred.

A water-soluble polymer dispersant can be preferably used as a pigment dispersant that can be used in the water-based ink according to the present embodiment. Examples of water-soluble polymer dispersants include polyester-, polyacrylic-, polyurethane-, polyamine-, and polycaptolactone-based main chains, and side chains containing amino, carboxy, sulfo, and hydroxy groups. Dispersing agents having polar groups such as For example, (co)polymers of unsaturated carboxylic acid esters such as polyacrylic acid esters; copolymers of aromatic vinyl compounds such as styrene and α-methylstyrene and unsaturated carboxylic acid esters such as acrylic acid esters; (partial) amine salts, (partial) ammonium salts and (partial) alkylamine salts of (co)polymers of unsaturated carboxylic acids such as polyacrylic acid; hydroxyl group-containing unsaturated carboxylic acid esters such as hydroxyl group-containing polyacrylic acid esters Polyurethanes; Unsaturated polyamides; Polysiloxanes; Long-chain polyaminoamide phosphates; Polyethyleneimine derivatives (poly (lower alkylene imine) and free carboxyl group-containing polyester amides obtained by reaction and their bases); polyallylamine derivatives (polyallylamine and polyester having a free carboxyl group, polyamide or co-condensation product of ester and amide (polyesteramide)) reaction products obtained by reacting with one or more compounds) and the like. Among them, a water-soluble polymer dispersant containing a (meth)acrylic resin is preferable from the viewpoint of ink dispersion stability and image clarity of printed matter.

水溶性高分子分散剤の具体例としては、Ｃｒａｙ　Ｖａｌｌｅｙ製ＳＭＡ１４４０、ＳＭＡ２６２５、ＳＭＡ１７３５２、ＳＭＡ３８４０、ＳＭＡ１０００、ＳＭＡ２０００、ＳＭＡ３０００、ＢＡＳＦジャパン社製ＪＯＮＣＲＹＬ６７、ＪＯＮＣＲＹＬ６７８、ＪＯＮＣＲＹＬ５８６、ＪＯＮＣＲＹＬ６１１、ＪＯＮＣＲＹＬ６８０、ＪＯＮＣＲＹＬ６８２、ＪＯＮＣＲＹＬ６９０、ＪＯＮＣＲＹＬ８１９、ＪＯＮＣＲＹＬ－ＪＤＸ５０５０、ＥＦＫＡ４５５０、ＥＦＫＡ４５６０、ＥＦＫＡ４５８５、ＥＦＫＡ５２２０、ＥＦＫＡ６２３０、Ｄｉｓｐｅｘ　Ｕｌｔｒａ　ＰＸ４５７５、ルーブリゾール社製ＳＯＬＳＰＥＲＳＥ２００００、ＳＯＬＳＰＥＲＳＥ２７０００、ＳＯＬＳＰＥＲＳＥ４００００、ＳＯＬＳＰＥＲＳＥ４１０００、ＳＯＬＳＰＥＲＳＥ４１０９０、ＳＯＬＳＰＥＲＳＥ４３０００、ＳＯＬＳＰＥＲＳＥ４４０００、ＳＯＬＳＰＥＲＳＥ４５０００、ＳＯＬＳＰＥＲＳＥ４６０００、ＳＯＬＳＰＥＲＳＥ４７０００、ＳＯＬＳＰＥＲＳＥ５３０９５、ＳＯＬＳＰＥＲＳＥ５４０００、ＳＯＬＳＰＥＲＳＥ６４０００、ＳＯＬＳＰＥＲＳＥ６５０００、ＳＯＬＳＰＥＲＳＥ６６０００、ＳＯＬＳＰＥＲＳＥ　Ｊ４００、ＳＯＬＳＰＥＲＳＥ　Ｗ１００、ＳＯＬＳＰＥＲＳＥ　Ｗ２００、ＳＯＬＳＰＥＲＳＥ　Ｗ３２０、ＳＯＬＳＰＥＲＳＥ　ＷＶ４００、ビックケミー社製ＡＮＴＩ－ＴＥＲＲＡ－２５０、ＢＹＫＪＥＴ－９１５０、ＢＹＫＪＥＴ－９１５１、ＢＹＫＪＥＴ－９１５２、ＢＹＫＪＥＴ－９１７０、ＤＩＳＰＥＲＢＹＫ－１０２、ＤＩＳＰＥＲＢＹＫ－１６８、ＤＩＳＰＥＲＢＹＫ -180, DISPERBYK-184, DISPERBYK-185, DISPERBYK-187, DISPERBYK-190, DISPERBYK-191, DISPERBYK-193, DISPERBYK-194N, DISPERBYK-198, DISPERBYK-199, DISPERBYK-2010, DISPERBYK-198, DISPERBYK-199, DISPERBYK-2010, DISPERBYK-20DISPERBYK-20DISPERBYK-20B1BYK-20 , DISPERBYK-2014, DISPERBYK-2015, DISPERBYK-2018, DISPERBYK-2019, DISPERBYK-2055, DISPERBYK-2060, DISPERBYK-2061, DISPERBYK-2081, DISPERBYK-2096, Ebonyク社製ＴＥＧＯ　ＤＩＳＰＥＲＳ６５０、ＴＥＧＯ　ＤＩＳＰＥＲＳ６５１、ＴＥＧＯ　ＤＩＳＰＥＲＳ６５２、ＴＥＧＯ　ＤＩＳＰＥＲＳ６５５、ＴＥＧＯ　ＤＩＳＰＥＲＳ６６０Ｃ、ＴＥＧＯ　ＤＩＳＰＥＲＳ６７０、ＴＥＧＯ　ＤＩＳＰＥＲＳ７１５Ｗ、ＴＥＧＯ　ＤＩＳＰＥＲＳ７４０Ｗ、ＴＥＧＯ　ＤＩＳＰＥＲＳ７４１Ｗ、ＴＥＧＯ　ＤＩＳＰＥＲＳ７５０Ｗ、ＴＥＧＯ　ＤＩＳＰＥＲＳ７５２Ｗ、ＴＥＧＯ　ＤＩＳＰＥＲＳ７５５Ｗ、ＴＥＧＯ　ＤＩＳＰＥＲＳ７５７Ｗ、ＴＥＧＯ　ＤＩＳＰＥＲＳ７６０Ｗ、ＴＥＧＯ　ＤＩＳＰＥＲＳ７６１Ｗ、ＴＥＧＯ　ＤＩＳＰＥＲＳ７６５Ｗ、ＺＥＴＡＳＰＥＲＳＥ１７０、ＺＥＴＡＳＰＥＲＳＥ１７９、ＺＥＴＡＳＰＥＲＳＥ１８２、ＺＥＴＡＳＰＥＲＳＥ３１００、ＺＥＴＡＳＰＥＲＳＥ３４００、ＺＥＴＡＳＰＥＲＳＥ３７００、ＺＥＴＡＳＰＥＲＳＥ３８００、サンノプコ社製ＳＮディスパーサント２０１０、ＳＮディスパーサント２０６０、ＳＮディスパーサント４２１５、ＳＮディスパーサント５０２７、ＳＮディスパーサント５０２９、ＳＮディスパーサント５０３４、ＳＮディスパーSanto 5468, Nopcol 5200, Nopcosant K, Nopcosant R, Nopcos Perth 44-C, Nopcos Perth 6100, Nopcos Perth 6150 and the like. These pigment dispersants can be suitably used in the water-based ink according to this embodiment.

In the water-based ink according to the present embodiment, the pigment that can be used is a pigment dispersion in which a pigment is dispersed in a water-soluble solvent using a pigment dispersant. It may also be a pigment dispersion in the form of a modified self-dispersing pigment. In the present embodiment, the pigment that can be used in the ink for inkjet recording may be a combination of a plurality of the above-described organic pigments and inorganic pigments, and a pigment dispersion dispersed in a water-soluble solvent with the above-described pigment dispersant. and a self-dispersing pigment may be used in combination. Among them, it is preferable to use a pigment that does not contain a self-dispersing pigment in the ink set according to the present embodiment. Thereby, repelling of water-based ink can be effectively suppressed. Although the reason for this is not necessarily clear, it is presumed that the water-based ink spreads appropriately and embeds well in the substrate, effectively suppressing repelling of the water-based ink.

[Surfactant]
The water-based ink according to this embodiment may contain a surfactant. The surfactant is not particularly limited, but anionic surfactants, nonionic surfactants, silicone (silicon) surfactants, and fluorine-based surfactants are preferred because of their excellent ability to adjust surface tension. Active agents, acetylene glycol-based surfactants, and the like are preferably used.

Specific examples include Emal, Latemul, Pelex, Neoperex, Demol (all of which are anionic surfactants; manufactured by Kao Corporation), Sunol, Liporan, Lipon, and Ripal (all of which are anionic surfactants; Lion Co., Ltd. company), Noigen, Epan, Solgen (all nonionic surfactants; Daiichi Kogyo Seiyaku Co., Ltd.) Emulgen, Amit, Emsol (all nonionic surfactants; Kao Corporation), Naloacty , Emalmin, Sannonic (both nonionic surfactants; manufactured by Sanyo Chemical Industries, Ltd.), Surfynol 104, 82, 420, 440, 465, 485, TG, 2502, SE-F, 107L, Dynol 360, Dynol 604, Dynol 607 (both are acetylene glycol-based surfactants; manufactured by Evonik), Dynol 960 (mixture of acetylene glycol-based and silicon-based surfactants; manufactured by Evonik), Surfynol AD01 (alkane glycol-based surfactant agent; manufactured by Evonik), Olfine E1004, E1010, PD004, EXP4300 (all of which are acetylene glycol-based surfactants; manufactured by Nissin Chemical Industry Co., Ltd.), Megafac (fluorine-based surfactant; manufactured by DIC Corporation), Surflon (fluorosurfactant; manufactured by AGC Seimi Chemical Co., Ltd.), BYK302, 306, 307, 331, 333, 345, 346, 347, 348, 349, 3420, 3450, 3451, 3455, 3456 (all silicone )-based surfactant; manufactured by BYK Chemie), KP-110, 112, 323, 341, 6004 (all silicone (silicon)-based surfactants; manufactured by Shin-Etsu Chemical Co., Ltd.), Silface SAG002, Silface SAG005, Sil Face SAG008, Silface SAG014, Silface SAG503A, Silface SJM-002, Silface SJM-003 (all silicone (silicon) surfactants; manufactured by Nissin Chemical Industry Co., Ltd.), TEGO FLOW 425, TEGO Glide 100, 110, 130, 410, 432, 440, 450, 482, 490, 492, 494, 496, ZG400, TEGO Twin 4000, TEGO Twin 4100, TEGO Twin 4200, TEGO Wet 240, TEGO Wet 250, TEGO Wet 240 , KL245, 250, 260, 265, 270, 280, (all silicone (silicon) surfactants; manufactured by Evonik), TEGO Wet 500, 505, 510, 520 (all nonionic surfactants; Evonik made), etc.

The content of the surfactant is not particularly limited as long as the static surface tension of each ink is within a predetermined range, but the lower limit of the content of the surfactant is in the range of 0.30% by mass or more based on the total amount of the aqueous ink. It is preferably within the range of 0.40% by mass or more, more preferably 0.50% by mass or more. The upper limit of the surfactant content is preferably 5.0% by mass or less, more preferably 4.0% by mass or less, and 3.0% by mass, based on the total amount of the aqueous ink. More preferably, it falls within the following range.

[Other ingredients]
The water-based ink may further contain conventionally known additives as needed. Examples of additives include waxes, viscosity modifiers, pH modifiers, antioxidants, preservatives, antifungal agents, and the like.

The method for preparing the water-based ink is not particularly limited. After dispersing by adding a dispersant, a resin, a surfactant and, if necessary, other ingredients are added to prepare it. A method of preparing by dispersing the pigment after adding the pigment may be mentioned.

The surface tension of the aqueous ink is not particularly limited, but the upper limit of the surface tension is preferably 35.0 mN/m or less, more preferably 32.0 mN/m or less, and even more preferably 30.0 mN/m or less. The lower limit of the surface tension is preferably 21.5 mN/m or more, more preferably 22.5 mN/m or more, and even more preferably 23.5 mN/m or more.

By adjusting the type and content of the water-soluble solvent and surfactant contained in the water-based ink, the water-based ink has a surface tension within a predetermined range. The surface tension (static surface tension) of the water-based ink is determined so that the static surface tension So of the overcoat ink contained in the ink set and the static surface tension Sc of the water-based ink satisfy the following relationship. It is preferable to adjust the target surface tension.

　Static surface tension So of overcoat ink < Static surface tension Sc of water-based ink

Due to this static surface tension relationship, it is possible to effectively suppress bleeding of water-based ink. Although the reason for this is not clear, at the interface between the overcoat ink and the water-based ink, the overcoat ink flows in the expanding direction (outward direction), and the water-based ink flows in the shrinking direction (inward direction). It is presumed that the wetting and spreading of the water-based ink can be controlled and the bleeding of the water-based ink can be effectively suppressed.

The overcoat ink may land on a layer of water-based ink formed by solidifying or drying the water-based ink, but while the water-based ink lands on the substrate and exists as a liquid ( It is preferable that the ink be ejected in a fluid state) and land on the substrate. Even if the overcoat ink lands on the water-based ink on the substrate in a state where the fluidity of the water-based ink on the substrate is high, spreading of the water-based ink can be suppressed. Moreover, when the water-based ink on the substrate has high fluidity, the overcoat ink lands on the water-based ink on the substrate, making it possible to print at a higher speed and improve the production speed of printed matter. It is possible to

The lower limit of the difference (S _c −S _O ) between the static surface tension So of the overcoat ink and the static surface tension Sc of the water-based ink is preferably 0.6 mN/m or more, and 0.8 mN/m It is more preferably 0.9 mN/m or more, and more preferably 0.9 mN/m or more. When the difference between S 2 _O and S _c ₍ S _c −S 0 ) is 0.6 mN/m or more, bleeding of water-based ink can be suppressed more effectively. Although the reason for this is not necessarily clear, when the difference between S 2 _O and S _c (S _c −S 2 _O ) is 0.6 mN/m or more, the mixture (pretreatment ink and water-based ink It is presumed that this is because the mixture of ) flows in the shrinking direction (inward direction) and can suppress bleeding of the water-based ink.

The upper limit of the difference between S _O and S _c (S _c -S _O ) is not particularly limited, but is preferably 7.5 mN/m or less, more preferably 6.0 mN/m or less. It is more preferably 4.5 mN/m or less. In particular, when the difference (S _c −S ₀ ) between S 2 _O and S _c is 7.5 mN/m or less, bleeding of water-based ink can be more effectively suppressed. The reason for this is not necessarily clear, but if the difference between S _O and S _c (S _c −S _O ) is too large, the overcoat ink will wet and spread too much, and the water-based ink will physically follow and wet and spread. There is a tendency for water-based ink to bleed relatively poorly. This is because when the difference between S ₀ and S _c (S _c _−S 0 ) is 7.5 mN/m or less, it is possible to more effectively suppress the bleeding of the water-based ink due to the large wetting and spreading of the overcoat ink. It is estimated to be.

<<Ink set of the second embodiment>>
The ink set according to the present embodiment is an ink set containing the overcoat ink, the water-based ink, and the pretreatment ink.

The pretreatment ink included in the ink set according to the present embodiment will be described below.

[Pretreatment ink]
The pretreatment ink is a water-based ink containing water as a main component and a cationic compound as a reaction liquid before the water-based ink is ejected onto the substrate. The pretreatment ink is not particularly limited as long as it contains a cationic compound as a reaction liquid.

(Reaction solution)
The reaction liquid contains a cationic compound, aggregates the colorant contained in the water-based ink, and suppresses bleeding caused by spreading around the landing position. Cationic compounds include cationic resins having cationic groups and metal salts composed of metal ions (cationic compounds) and anions. Among these, it is preferable to use a cationic resin having a cationic group. This makes it possible to more effectively suppress bleeding of the water-based ink. The reason for this is not necessarily clear, but cationic resins have many reaction points in their molecular chains, and the entanglement of the molecular chains that make up the resin is also added, improving cohesion with the coloring material contained in the water-based ink. . Also, the permeability of the pretreatment ink can be improved. From these, it is presumed that the bleeding of the water-based ink can be suppressed more effectively.

Examples of cationic resins include resins having cationic groups such as amino groups, ammonium groups, amide groups, and _--NHCONH2 groups. A cationic resin can be synthesized by a known method, or a commercially available product can be used.

　The cationic resin can be synthesized by a known method, or a commercially available product can be used. Examples of commercially available products are as follows: APC-810, 815; D-6010, 6020, 6030, 6040, 6050, 6060, 6080, 6310; FQP-1264; RSL-18-22, 4071H, 4400, 8391, 8391H, HD70C, HF70D; WS-72 (manufactured by SNF), Arafix 100, 251S, 255, 255LOX (manufactured by Arakawa Chemical), DK-6810, 6853, 6885 WS-4010, 4011, 4020, 4024, 4027, 4030 (manufactured by Seiko PMC), Senka F-300; Papiogen P-105, P-113, P-271, P-316; Pitchnol QG5A; Myriogen P- ２０；ユニセンスＦＰＡ１００Ｌ、ＦＰＡ１０１Ｌ、ＦＰＡ１０２Ｌ、ＦＰＡ１０００Ｌ、ＦＰＡ１００１Ｌ、ＦＰＡ１００ＬＵ、ＦＰＡ１０２ＬＵ、ＦＰＡ１０００ＬＵ；ユニセンスＦＣＡ１０００Ｌ、ＦＣＡ１００１Ｌ、ＦＣＡ１００２Ｌ、ＦＣＡ１００３Ｌ、ＦＣＡ５０００Ｌ；ユニセンスＫＣＡ１００Ｌ、ＫＣＡ１００ＬＵ、ＫＣＡ１０００ＬＵ、ＫＣＡ１００１ＬＵ；ユニセンスＫＨＥ１００Ｌ、ＫＨＥ１０１Ｌ、ＫＨＥ１０２Ｌ、Ｅ１０４Ｌ、ＫＨＥ１０５Ｌ、ＫＨＥ１０７Ｌ、ＫＨＥ１０００Ｌ、ＫＨＥ１００１Ｌ；ユニセンスＫＨＰ１０Ｐ、ＫＨＰ１１Ｌ、ＫＨＰ１０ＬＵ、ＫＨＰ１１ＬＵ、ＫＨＰ１２ＬＵ、ＫＨＰ２０ＬＵ：ユニセンスＫＨＦ１０Ｌ、ＫＨＦ１１Ｌ；ユニセンスＦＰＶ１０００Ｌ、ＦＰＶ１０００ＬＵ；ユニセンスＦＣＶ１０００Ｌ；ユニセンスＺＣＡ１０００Ｌ、ＺＣＡ１００１Ｌ、ＺＣＡ１００２Ｌ、ＺＣＡ５０００Ｌ；ユニセンスＫＰＶ１００ＬＵ、ＫＰＶ１０００ＬＵ（センカ社製） , Paralock 410K101, 410K111, 420K308, 420K300, 460K313, 460K318, 470K308, 480K300, 490K300, 490K309, 500K30E, 500K40E, 59D, 920AP500, 975AP500, PD710L, PD710L, Asada Kagaku, PD710L, PD71400 ), Sumireze Resin 650 (30), 675A, 6615, SLX-1 (manufactured by Taoka Chemical Co., Ltd.), EP-1137; MZ-477, 480; D11-HCL, D19-HCL, D41-HCL, D19A; PAA-HCL-03, 05, 3L, 10L; PAA-1112CL, 21CL, AC5050A, N5050CL, SA; PAS-A-1, 5; PAS-H- PAS-J-81, 81L; PAS-M-1, 1A, 1L; PAS-21, 21CL, 22SA-40, 24, 92, 92A, 880, 2201CL, 2401 (manufactured by Nittobo Medical ), PP-17 (manufactured by Meisei Chemical Co., Ltd.); Catiomaster PD-1, 7, 30, A, PDT-2, PE-10, PE-30, DT-EH, EPA-SK01, TMHMDA-E (Yokkaichi Gosei company), Jetfix 36N, 38A, 5052 (manufactured by Satoda Kako Co., Ltd.).

The cationic resin may exist in the pretreatment ink in a dissolved state or in a dispersed state as fine resin particles.

Examples of metal salts include polyvalent metal salts containing ions of polyvalent metals having a valence of at least two and anions. Examples of polyvalent metal ions include calcium ions, magnesium ions, aluminum ions, titanium ions, iron (II) ions, iron (III) ions, cobalt ions, nickel ions, copper ions, zinc ions, barium ions, strontium ions, and the like. is mentioned. Among them, one selected from calcium ions, magnesium ions, nickel ions, zinc ions, and aluminum ions, because it has a large interaction with the colorant in the ink composition and has a high effect of suppressing bleeding and unevenness. It is preferable to contain the above.

The anion may be an anion of an inorganic substance or an anion of an organic substance. Specific examples of organic anions include acetic acid, benzoic acid, salicylic acid, 2,4-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, dimethylolpropionic acid, pantothenic acid, succinic acid, maleic acid, glutaric acid, Mention may be made of the anions of suberic acid, trimellitic acid, methylmalonic acid. Specific examples of inorganic anions include chloride ions, bromide ions, nitrate ions, sulfate ions, and the like.

The content of the cationic compound is not particularly limited, but the lower limit of the content of the cationic compound is preferably in the range of 0.5% by mass or more based on the total amount of the pretreatment ink. It is more preferably in the range of 0.8% by mass or more, and even more preferably in the range of 1.0% by mass or more. When the content of the cationic compound is within the range of 0.5% by mass or more based on the total amount of the pretreatment ink, it becomes possible to fix the coloring material more effectively and effectively suppress the bleeding of the water-based ink. can do. The upper limit of the content of the cationic compound is preferably 9% by mass or less, more preferably 8% by mass or less, and 7% by mass or less in the total amount of the pretreatment ink. is more preferable. When the content of the cationic compound is within the range of 9% by mass or less based on the total amount of the pretreatment ink, the storage stability of the pretreatment ink is improved. In particular, when the pretreatment ink is ejected onto the surface of the base material by an inkjet method, the content of the cationic compound is within the range of 9% by mass or less, so that the ejection stability can be further improved. .

[resin]
At least part of the resin contained in the pretreatment ink may be contained as a resin emulsion. A resin emulsion means an aqueous dispersion in which the secondary phase is a water-soluble solvent and the dispersed particles are resin microparticles. By forming a resin emulsion, the resin can be dispersed in the receiving solution as fine resin particles by steric repulsion or electrostatic repulsion.

The resin contained in the pretreatment ink is not particularly limited, and examples include acrylic resins, styrene-acrylic resins, polyurethane resins, polyester resins, vinyl chloride resins, vinyl acetate resins, polyether one or more resins or copolymer resins selected from the group consisting of vinyl chloride vinyl acetate copolymer resins, polyethylene resins, acrylamide resins, epoxy resins, polycarbonate resins, silicone resins, and polystyrene resins or mixtures thereof can be used.

The content of the resin contained in the pretreatment ink is not particularly limited, but the lower limit of the content of the resin is preferably in the range of 0.5% by mass or more based on the total amount of the pretreatment ink. It is more preferably in the range of 0.8% by mass or more, and even more preferably in the range of 1.0% by mass or more. The upper limit of the resin content is preferably 20.0% by mass or less, more preferably 15.0% by mass or less, and 10.0% by mass or less based on the total amount of the pretreatment ink. is more preferably within the range of

[water]
The pretreatment ink may contain water. As water, it is preferable to use deionized water rather than containing various ions. The water content is not particularly limited as long as it can disperse or dissolve each component, but the lower limit of the water content is in the range of 30% by mass or more based on the total amount of the pretreatment ink. preferably 50% by mass or more, more preferably 55% by mass or more, and even more preferably 60% by mass or more of the total amount of the pretreatment ink. preferable. The upper limit of the water content is preferably 85% by mass or less, more preferably 82% by mass or less, and 80% by mass or less in the total amount of the pretreatment ink. is more preferred.

[Organic solvent]
The pretreatment ink may contain an organic solvent. The organic solvent is capable of dispersing or dissolving the resin and the like. Since the pretreatment ink according to this embodiment contains water, the organic solvent preferably contains a water-soluble solvent.

Examples of the organic solvent include those having 1 to 5 carbon atoms such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, isobutyl alcohol, and n-pentanol. Alkyl alcohols; formamide, acetamide, propanamide, butanamide, isobutyramide, pentanamide, N-methylformamide, N-methylacetamide, N-methylpropanamide, N-methylbutanamide, N-methylisobutyramide, N- methylpentanamide, N-ethylformamide, N-ethylacetamide, N-ethylpropanamide, N-ethylbutanamide, N-ethylisobutyramide, N-ethylpentanamide, N-propylformamide, N-propylacetamide, N- Propylpropanamide, N-propylbutanamide, N-propylisobutyramide, N-propylpentanamide, N-isopropylformamide, N-isopropylacetamide, N-isopropylpropanamide, N-isopropylbutanamide, N-isopropylisobutyramide, N-isopropylpentanamide, N-butylformamide, N-butylacetamide, N-butylpropanamide, N-butylbutanamide, N-butylisobutylamide, N-butylpentanamide, N,N-dimethylformamide, N,N -dimethylacetamide, N,N-dimethylpropanamide, N,N-dimethylbutanamide, N,N-dimethylisobutyramide, N,N-dimethylpentanamide, N,N-diethylformamide, N,N-diethylacetamide, N,N-diethylpropanamide, N,N-diethylbutanamide, N,N-diethylisobutyramide, N,N-diethylpentanamide, N,N-dipropylformamide, N,N-dipropylacetamide, N, N-dipropylpropanamide, N,N-dipropylbutanamide, N,N-dipropylisobutyramide, N,N-dipropylpentanamide, N,N-diisopropylformamide, N,N-diisopropylacetamide, N, N-diisopropylpropanamide, N,N-diisopropylbutanamide, N,N-diisopropylisobutyramide, N,N-diisopropylpentanamide, N,N-dibutylformamide, N, N-dibutylacetamide, N,N-dibutylpropanamide, N,N-dibutylbutanamide, N,N-dibutylisobutyramide, N,N-dibutylpentanamide, N-ethyl-N-methylformamide, N-ethyl- N-methylacetamide, N-ethyl-N-methylpropanamide, N-ethyl-N-methylbutanamide, N-ethyl-N-methylisobutyramide, N-ethyl-N-methylpentanamide, N-methyl-N -propylformamide, N-methyl-N-propylacetamide, N-methyl-N-propylpropanamide, N-methyl-N-propylbutanamide, N-methyl-N-propylisobutyramide, N-methyl-N-propyl Pentanamide, N-ethyl-N-propylformamide, N-ethyl-N-propylacetamide, N-ethyl-N-propylpropanamide, N-ethyl-N-propylbutanamide, N-ethyl-N-propylisobutyramide , N-ethyl-N-propylpentanamide and other amides; acetone, diacetone alcohol and other ketones or ketoalcohols; tetrahydrofuran, dioxane and other ethers; polyethylene glycol, polypropylene glycol and other oxyethylene or oxypropylene copolymers Combined; ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, 1,3-propanediol, isobutylene glycol, triethylene glycol, tripropylene glycol, tetraethylene glycol, 1,3-propanediol, 2-methyl-1,2 -propanediol, 2-methyl-1,2-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,5-pentanediol, 1,6-hexanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,3-butanediol, 3-methyl-1,5-pentanediol, 2-methyl -Diols such as 2,4-pentanediol; Triols such as glycerin, trimethylolethane, trimethylolpropane, and 1,2,6-hexanetriol; Tetrahydric alcohols such as mesoerythritol and pentaerythritol; Ethylene glycol monomethyl (or ethyl, isopropyl, n-butyl, isobutyl, n-hexyl, 2-ethylhexyl n) ether, diethylene glycol monomethyl (or ethyl, isopropyl, n-butyl, isobutyl, n-hexyl, 2-ethylhexyl) ether, triethylene glycol monomethyl (or ethyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl, pentyl, n-hexyl, 2-ethylhexyl) ether, propylene glycol monomethyl (or ethyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl, pentyl, n-hexyl, 2-ethylhexyl) ether, dipropylene glycol monomethyl ( or ethyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl, pentyl, n-hexyl, 2-ethylhexyl) ether, tripropylene glycol monomethyl (or ethyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl , pentyl, n-hexyl, 2-ethylhexyl) ether; diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol ethyl methyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol ethyl methyl ether, tetra ethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol ethyl methyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol ethyl methyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, dipropylene glycol ethyl methyl ether, Dialkyl ethers of polyhydric alcohols such as tripropylene glycol dimethyl ether, tripropylene glycol diethyl ether, tripropylene glycol ethyl methyl ether; ethylene glycol monomethyl (or ethyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl, pentyl, n-hexyl, 2-ethylhexyl) ether acetate, diethylene glycol monomethyl (or ethyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl, pentyl, n-hexyl, 2-ethylhexyl) ether acetate, triethylene glycol monomethyl (or ethyl, propyl, isopropyl, n-but ethyl, isobutyl, t-butyl, pentyl, n-hexyl, 2-ethylhexyl) ether acetate, propylene glycol monomethyl (or ethyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl, pentyl, n-hexyl, 2- ethylhexyl) ether acetate, dipropylene glycol monomethyl (or ethyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl, pentyl, n-hexyl, 2-ethylhexyl) ether acetate, tripropylene glycol monomethyl (or ethyl, propyl, Acetates such as isopropyl, n-butyl, isobutyl, t-butyl, pentyl, n-hexyl, 2-ethylhexyl) ether acetate, ethylene glycol diacetate, diethylene glycol diacetate, propylene glycol diacetate, dipropylene glycol diacetate; γ -butyrolactone, α-methylene-γ-butyrolactone, ε-caprolactone, γ-valerolactone, γ-hexanolactone, γ-heptanolactone, δ-valerolactone, δ-hexanolactone, δ-heptalactone, δ- Octalactone, δ-nonalactone, δ-decalactone, δ-undecalactone, γ,γ-dimethyl-γ-butyrolactone, α-methyl-γ-butyrolactone, γ-clotolactone, α-methylene-γ-butyrolactone, β- Lactones such as methyl-γ-butyrolactone and 6-methylvalerolactone, carbonate esters such as 2,3-butylene carbonate, ethylene carbonate and propylene carbonate, 3-methyl-2-oxazolidinone, 3-ethyl-2-oxazolidinone, Oxazolidinone solvents such as N-vinylmethyloxazolidinone, carbon such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, isobutyl alcohol, n-pentanol Monohydric alcohols such as alkyl alcohols of number 1 to 5, 3-methoxy-3-methyl-1-butanol, 3-methoxy-1-propanol, 1-methoxy-2-propanol, 3-methoxy-n-butanol ketones or ketoalcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; polyethylene glycol and polypropylene glycol ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, 1,3-propanediol, isobutylene glycol, triethylene glycol, tripropylene glycol, tetraethylene glycol, 1,3 -propanediol, 2-methyl-1,2-propanediol, 2-methyl-1,2-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2 -pentanediol, 1,2-hexanediol, 1,5-pentanediol, 1,6-hexanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,3-butanediol, 3-methyl -Diols such as 1,5-pentanediol and 2-methyl-2,4-pentanediol; Triols such as glycerin, trimethylolethane, trimethylolpropane, and 1,2,6-hexanetriol: mesoerythritol, penta Tetrahydric alcohols such as erythritol; monoethanolamine, diethanolamine, triethanolamine, N-methylethanolamine, N-ethylethanolamine, N-butylethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, N-butyldiethanolamine alkanolamines such as; N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone and other nitrogen-containing heterocyclic compounds; γ-butyrolactone, sulfolane and other cyclic compounds, N-methyl morpholines such as morpholine, N-ethylmorpholine and N-formylmorpholine; and terpene-based solvents.

Among these, it is preferable to contain an organic solvent selected from the group consisting of alkanediols and monools. This makes it possible to reduce the static surface tension SP of the pretreatment ink, improve the permeability of the pretreatment ink, and allow the water _- based ink applied on the pretreatment ink to spread appropriately. It becomes possible to effectively suppress poor filling, and an image with high reproducibility can be obtained.

An alkanediol is a polyhydric alcohol having two hydroxyl groups (OH groups), and a monool is a monovalent alcohol having one hydroxyl group (OH group). The alkanediol is preferably 1,2-alkanediol. 1,2-alkanediol includes 1,2-propanediol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 4-methyl-1,2-pentanediol, 3, 3-dimethyl-1,2-butanediol and the like can be mentioned. Examples of monools include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, isobutyl alcohol, n-pentanol, 3-methoxy-3-methyl- 1-butanol, 3-methoxy-1-propanol, 1-methoxy-2-propanol, 3-methoxy-n-butanol and the like can be mentioned.

The content of the organic solvent is not particularly limited as long as it can disperse or dissolve each component. is preferably 10% by mass or more, more preferably 12% by mass or more. The upper limit of the content of the organic solvent is preferably 50% by mass or less, more preferably 45% by mass or less, and 40% by mass or less based on the total amount of the pretreatment ink. is more preferred.

[Surfactant]
The pretreatment ink may contain a surfactant. Surfactants are not particularly limited, but nonionic surfactants, fluorine-based surfactants, acetylene glycol-based surfactants, silicone (silicon)-based surfactants, and the like are preferably used.

Nonionic surfactants include Noigen, Epan, Solgen (all manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), Emulgen, Amit, Emsol (all manufactured by Kao Corporation), Naroacty, Emalmin, and Sannonic (all manufactured by Sanyo). manufactured by Kasei Kogyo Co., Ltd.) and the like.

Fluorinated surfactants include Megafac F-114, F-410, F-440, F-447, F-553, F-556 (manufactured by DIC), Surflon S-211, S-221, S- 231, S-233, S-241, S-242, S-243, S-420, S-661, S-651, S-386 (manufactured by AGC Seimi Chemical Co., Ltd.), and the like.

Examples of acetylene glycol-based surfactants include Surfynol 104, 82, 420, 440, 465, 485, TG, 2502, Dynol 604, Dynol 607, and Dynol 960 (all of which are acetylene glycol-based surfactants; ), Olfine E1004, E1010, PD004, EXP4300 (all are acetylene glycol-based surfactants; manufactured by Nissin Chemical Industry Co., Ltd.), acetylenol EH, E40, E60, E81, E100, E200 (all are acetylene glycol-based surfactants Activator; manufactured by Kawaken Fine Chemicals Co., Ltd.) and the like.

Examples of silicone (silicon) surfactants include FZ-2122, FZ-2110, FZ-7006, FZ-2166, FZ-2164, FZ-7001, FZ-2120, SH 8400, FZ-7002, FZ- 2104, 8029 ADDITIVE, 8032 ADDITIVE, 57 ADDITIVE, 67 ADDITIVE, 8616 ADDITIVE (all manufactured by Dow Toray), KF-6012, KF-6015, KF-6004, KF-6013, KF-6011, KF-6043 , KP-104, 110, 112, 323, 341, 6004 (all manufactured by Shin-Etsu Chemical Co., Ltd.), BYK-300, BYK-302, BYK-306, BYK-307, BYK-320, BYK-325, BYK- 330, BYK-331, BYK-333, BYK-337, BYK-341, BYK-344, BYK-345, BYK-346, BYK-347, BYK-348, BYK-349, BYK-3420, BYK-3450, BYK-3451, BYK-3456, BYK-375, BYK-377, BYK-378, BYK-UV3500, BYK-UV3510, BYK-310, BYK-315, BYK-370, BYK-UV3570, BYK-322, BYK- 323, BYK-350, BYK-352, BYK-354, BYK-355, BYK-358N, BYK-361N, BYK-380N, BYK-381, BYK-392, BYK-340, BYK-Silclean3700, BYK-Dynwet800 ( Both are manufactured by BYK Chemie), Silface SAG002, Silface SAG005, Silface SAG008, Silface SAG014, Silface SAG503A, Silface SJM-002, Silface SJM-003 (all manufactured by Nissin Chemical Industry Co., Ltd.) TEGO Flow 425, TEGO Glide 100, 110, 130, 410, 432, 440, 450, 482, 490, 492, 494, 496, ZG400, TEGO Twin 4000, TEGO Twin 4100, TEGO Wet 240, TEGO Wet 250 , TEGO Wet 240, KL245, 250, 260, 265, 270, 280 (all manufactured by Evonik).

An anionic surfactant may be used, but since the pretreatment ink contains a cationic compound, if an anionic surfactant is used, make sure that it can be mixed with the pretreatment ink. It is preferable to keep

When using an anionic surfactant, anionic surfactants include Emal, Latemul, Pelex, Neoperex, Demol (all manufactured by Kao Corporation), Sunol, Liporan, Lipon, Lipal (all of which are Lion Co., Ltd.), etc., which can be mixed with the pretreatment ink can be used.

These surfactants may be used alone or in combination of two or more. The content of the surfactant is appropriately adjusted according to ink miscibility, washability, wettability to the inner wall of the flow path, and inkjet ejection properties.

The content of the surfactant is not particularly limited, but the lower limit of the content of the surfactant is preferably in the range of 0.50% by mass or more in the total amount of the pretreatment ink, and 0.60% by mass or more. It is more preferably within the range, and further preferably within the range of 0.70% by mass or more. The upper limit of the surfactant content is preferably 5.0% by mass or less, more preferably 4.0% by mass or less, and 3.0% by mass, based on the total amount of the pretreatment ink. % or less is more preferable.

[Other ingredients]
The pretreatment ink may further contain conventionally known additives as needed. Examples of additives include viscosity modifiers, pH modifiers, antioxidants, preservatives, antifungal agents, and the like.

The method of preparing the pretreatment ink is not particularly limited. For example, a method of adding a resin, a surfactant and, if necessary, other components to a water-soluble solvent.

The surface tension of the pretreatment ink is not particularly limited, but the upper limit of the surface tension is preferably 30.0 mN/m or less, more preferably 29.0 mN/m or less, and even more preferably 28.0 mN/m or less. The lower limit of the surface tension is preferably 20.0 mN/m or more, more preferably 21.0 mN/m or more, and even more preferably 22.0 mN/m or more. The surface tension is a value measured by the Wilhelmy method (manufactured by Kyowa Interface Science, model: DY-300) at a measurement temperature of 25°C.

The pretreatment ink has a surface tension within a predetermined range by adjusting the type and content of the water-soluble solvent and surfactant contained in the pretreatment ink. It is preferable that the static surface tension So of the overcoat ink, the static surface tension Sc of the water _- based ink, and the static surface tension SP of the pretreatment ink, which are contained in the ink set, satisfy the following relationship.

Static surface tension So of overcoat ink ≤ Static surface tension S _P of pretreatment ink < Static surface tension S _C of water-based ink

Due to this static surface tension relationship, it is possible to effectively suppress bleeding of water-based ink. Although the reason for this is not clear, after the water-based ink lands on the surface of the pretreatment ink, the water-based ink flows in the shrinking direction (inward direction), thereby wetting the water-based ink that lands on the surface of the pretreatment ink. It is presumed that the spreading can be controlled and the bleeding of water-based ink can be effectively suppressed. Furthermore, at the interface between the overcoat ink and the mixture (mixture of pretreatment ink and water-based ink), the overcoat ink flows in the spreading direction (outward direction), and the mixture (mixture of pretreatment ink and water-based ink) It is presumed that by flowing in the shrinking direction (inward direction), the wetting and spreading of the water-based ink can be controlled, and the bleeding of the water-based ink can be effectively suppressed.

The overcoat ink may land on a layer formed by solidifying or drying the water-based ink, but the mixture of the water-based ink and the pretreatment ink may land on the substrate and exist as a liquid. It is preferable that the ink be ejected while the ink is in the air (in a fluid state) and land on the substrate. Even if the overcoat ink lands on the mixture of water-based ink and pre-treatment ink on the substrate in a state where the fluidity of the mixture of water-based ink and pre-treatment ink on the substrate is high, the spread of the water-based ink is suppressed. be able to. Moreover, the overcoat ink lands on the mixture of the water-based ink and the pretreatment ink on the base material in a state where the fluidity of the mixture of the water-based ink and the pretreatment ink on the base material is high, so that printing can be performed at a higher speed. becomes possible, and the production speed of printed matter can be improved.

In addition, in the static surface tension of each ink, the lower limit of the difference between S _P and S _c (S _c −S _P ) is not particularly limited, but it is preferably 0.5 mN/m or more, and 0.7 mN /m or more, and more preferably 0.9 mN/m or more. When the difference between S _P and S _c (S _c −S _P ) is 0.5 mN/m or more, bleeding of water-based ink can be suppressed more effectively. The reason for this is not necessarily clear, but after the water-based ink lands on the surface of the pretreatment ink, the water-based ink flows in the shrinking direction (inward direction), thereby more effectively suppressing the bleeding of the water-based ink. presumed to be possible.

The upper limit of the difference between S _P and S _c (S _c −S _P ) is not particularly limited, but is preferably 7.0 mN/m or less, more preferably 5.5 mN/m or less. It is more preferably 3.0 mN/m or less. When the difference between S _P and S _c (S _c −S _P ) is 7.0 mN/m or less, repelling of water-based ink can be effectively suppressed. Although the reason for this is not necessarily clear, when the difference between S _P and S _c (S _c −S _P ) is 7.0 mN/m or less, the water-based ink spreads appropriately and fills the substrate well. It is presumed that this is because

The lower limit of the difference between S 2 _O and S 2 _P ₍ S _P −S 0 ) is not particularly limited, but it is preferably 0 mN/m or more, more preferably 0.2 mN/m or more, and 0.2 mN/m or more. More preferably, it is 4 mN/m or more. When the difference between S 2 _O and S 2 _P ₍ S _P −S 0 ) is 0 mN/m or more, bleeding of water-based ink can be suppressed. Although the reason is not necessarily clear, the difference between S 2 _O and S 2 _P (S _P −S 2 _O ) is 0 mN/m or more. ) is presumed to flow in the shrinking direction (inward direction) and suppress bleeding of the water-based ink.

The upper limit of the difference between S _O and S _P (S _P −S _O ) is not particularly limited, but is preferably 3.5 mN/m or less, more preferably 3.0 mN/m or less. It is more preferably 2.7 mN/m or less. When the difference between S 2 _O and S 2 _P ₍ S _P −S 0 ) is 3.5 mN/m or less, bleeding of water-based ink can be suppressed more effectively. Although the reason for this is not necessarily clear, if the difference between S _O and S _P (S _P −S _O ) is too large, the overcoat ink will wet and spread too much, resulting in a mixture (mixture of pretreatment ink and water-based ink). is physically followed and wetted and spread, and the bleeding of water-based ink tends to be relatively worse. This is because when the difference between S _O and S _P (S _P −S _O ) is 3.5 mN/m or less, it is possible to more effectively suppress the bleeding of the water-based ink due to the large wetting and spreading of the overcoat ink. It is estimated to be.

The lower limit of the difference between S _O and S _c (S _c -S _O ) is not particularly limited, but is preferably 0.6 mN/m or more, more preferably 0.8 mN/m or more. More preferably, it is 0.9 mN/m or more. When the difference between S 2 _O and S _c ₍ S _c −S 0 ) is 0.6 mN/m or more, bleeding of water-based ink can be suppressed more effectively. Although the reason for this is not necessarily clear, when the difference between S 2 _O and S _c (S _c −S 2 _O ) is 0.6 mN/m or more, the mixture (pretreatment ink and water-based ink It is presumed that this is because the mixture of ) flows in the shrinking direction (inward direction) and can suppress bleeding of the water-based ink.

The upper limit of the difference between S _O and S _c (S _c -S _O ) is not particularly limited, but is preferably 7.5 mN/m or less, more preferably 6.0 mN/m or less. It is more preferably 4.5 mN/m or less. In particular, when the difference (S _c −S ₀ ) between S 2 _O and S _c is 7.5 mN/m or less, bleeding of water-based ink can be more effectively suppressed. Although the reason for this is not necessarily clear, if the difference between S _O and S _c (S _c −S _O ) is too large, the overcoat ink will be too wet and spread, resulting in a mixture (mixture of pretreatment ink and water-based ink). is physically followed and wetted and spread, and the bleeding of water-based ink tends to be relatively worse. This is because when the difference between S ₀ and S _c (S _c _−S 0 ) is 7.5 mN/m or less, it is possible to more effectively suppress the bleeding of the water-based ink due to the large wetting and spreading of the overcoat ink. It is estimated to be.

≪Recording method≫
The recording method according to the present embodiment is an inkjet recording method using an ink set containing the above-described pretreatment ink, water-based ink, and overcoat ink. This is a recording method in which ink is ejected onto a material.

The resin contained in the above overcoat ink contains a resin with a glass transition temperature of 10°C or less. Therefore, even in the recording method according to the present embodiment, it is possible to form an overcoat layer with low lubricity on the surface of the recorded matter.

The recording method according to the present embodiment uses an inkjet head that moves in a direction perpendicular to the transport direction, and is a scanning method that prints on the entire base material (recording medium) by matching the reciprocation of the head and the base material (recording medium). It may be an inkjet recording method or a one-pass method in which an image is formed by passing the substrate through an inkjet head once. Among them, when the static surface tension of each ink contained in the ink set is controlled within the range of, for example, So≦ _S _P <SC, the recording method is preferably one-pass ink jet ejection. . A recording method that uses inkjet ejection in a single pass allows for faster printing, so the time it takes for each ink to land on the substrate is shorter, and the water-based ink spreads and bleeds around the landing position. can occur more prominently. When the static surface tension of each ink contained in the ink set is controlled within the range of, for example, _So≤S _P <SC, it can be used in a recording method in which ink is ejected by a one-pass method such as a line head method. Therefore, it is possible to enjoy the advantage of being able to print at a higher speed without causing problems that may occur in a recording method in which ink is ejected in a one-pass method.

FIG. 1 shows an apparatus 1 for ejecting an ink set onto a base material in which the recording method according to the present embodiment can be preferably used. This device 1 comprises a pretreatment ink ejection section 21 for ejecting the pretreatment ink 11, an aqueous ink ejection section 22 for ejecting the aqueous ink 12, and an overcoat ink ejection section 23 for ejecting the overcoat ink 13. They are arranged in order along the conveying direction of the base material (recording medium). A drying mechanism is not provided between the pretreatment ink ejection section 21 and the water-based ink ejection section 22 and between the water-based ink ejection section 22 and the overcoat ink ejection section 23 .

When the static surface tension of each ink is controlled within a predetermined range as in the above-described ink set having the relationship of "S _O ≤ S _P < S _C ", a drying mechanism is provided between each ejection section. Using the device 1 as shown in FIG. Even in such a case, bleeding of the water-based ink can be effectively suppressed.

In the recording method according to the present embodiment, the inkjet recording method using the ink set of the second embodiment including the pretreatment ink, the water-based ink, and the overcoat ink has been described. In the ink set of the first embodiment including the overcoat ink as well, if the ink set has a relationship of “ _S _O <SC ”, bleeding of the water-based ink can be similarly effectively suppressed.

Also, printing may be performed using a device having a drying mechanism between the ejection portions, but using a device that does not have a drying mechanism between the ejection portions prevents water-based ink from bleeding. While effectively suppressing this, the size of the apparatus can be reduced, and the length of the entire conveying section can be shortened, thereby improving the manufacturing speed of printed matter.

The recording speed (conveyance speed of the base material) in the recording method according to the present embodiment is such that the static surface tension of each ink is predetermined as in the above-described ink set relationship of "S _O ≤ S _P < S _C ". is preferably 30 m/min or more, more preferably 40 m/min or more, and even more preferably 50 m/min or more. Even if the base material (recording medium) is transported at such a high speed and each ink contained in the ink set is jetted onto the base material, bleeding of the water-based ink can be effectively suppressed.

Furthermore, it is preferable to dry each ink after ejection of each ink included in the ink set. As a result, it is possible to effectively remove the volatile components contained in each ink, and it is possible to more effectively suppress bleeding of the water-based ink.

As a method for drying each ink, there are methods such as drying with a heater from the back side of the base material (the side opposite to the ink ejection surface side), and blowing warm air to the recorded matter. It should be noted that it is not necessary to consciously dry each ink after the ejection of such ink, and so-called natural drying may be performed.

≪Manufacturing Method of Recorded Matter≫
A method for producing a printed matter according to the present embodiment is a method for producing a printed matter using an ink set that includes the above-described pretreatment ink, water-based ink, and overcoat ink, and is included in the ink set. This is a method for producing a recorded matter in which each ink is jetted onto a base material.

The resin contained in the above overcoat ink contains a resin with a glass transition temperature of 10°C or less. Therefore, it is possible to form an overcoat layer with low slip on the surface of the recorded matter also in the method of manufacturing the recorded matter according to the present embodiment.

Furthermore, when the static surface tension of each ink is controlled within a predetermined range as in the above-described ink set having the relationship of "S _O ≤ S _P < S _C ," Even when printing is performed at high speed by a 1-pass method using the device 1 shown in FIG. is obtained.

Furthermore, it is preferable to dry each ink after ejection of each ink included in the ink set. As a result, the volatile components contained in each ink can be effectively removed, and bleeding of the water-based ink can be suppressed more effectively. As a method for drying each ink, the method described in the above recording method can be used.

≪Records≫
Each layer constituting the recorded matter manufactured by the method for manufacturing the recorded matter of the above-described embodiment will be described.

[Medium (recording medium)]
The base material (recording medium) that can be used in the recording method according to the present embodiment is not particularly limited. Various substrates can be used, such as an absorbent substrate such as a woven fabric, or a surface-coated substrate such as a substrate having a receiving layer. The same applies to the base material that can be used in the method of manufacturing a recorded matter according to an embodiment described later.

Examples of non-absorbent substrates include resin substrates such as polyester-based resins, polypropylene-based synthetic papers, vinyl chloride resins, and polyimide resins, metals, metal foil-coated paper, glass, synthetic rubber, natural rubber, and the like. .

Examples of absorbent substrates include dry paper, medium-quality paper, fine paper, cotton, synthetic fiber fabric, silk, hemp, fabric, non-woven fabric, and leather.

Examples of surface-coated substrates include coated paper, art paper, cast paper, lightweight coated paper, and lightly coated paper.

Among these substrates, in the case of an ink set containing water-based ink, an absorbent substrate is preferable. In particular, when the water-based ink contains an alkanediol organic solvent having a water-octanol partition coefficient of −0.3 or less, the water-based ink should be prevented from penetrating into the substrate (recording medium). is possible, and the printing density is partially lowered, and it is possible to effectively suppress the filling failure.

[Aqueous ink layer]
The water-based ink layer is a layer formed by volatilization of the solvent contained in the above-described water-based ink. For example, when a coloring material is contained in water-based ink, it becomes a decorative layer or a recording layer that forms a desired image.

[Overcoat layer]
The overcoat layer is a layer formed by volatilization of the solvent contained in the overcoat ink described above, and is a layer capable of imparting a desired function by containing a specific component. Moreover, this overcoat layer is mainly arranged on the upper layer of the water-based ink layer. The overcoat layer is a layer that mainly imparts abrasion resistance to recorded matter.

The resin contained in the above overcoat ink contains a resin having a glass transition temperature of 10°C or less. Therefore, it is possible to form an overcoat layer with low lubricity on the surface of the recorded matter.

At this time, the slip angle of the overcoat layer surface is preferably 27.0° or more, more preferably 27.5° or more, and even more preferably 28.0° or more. If the overcoat layer has such a slip angle, the slipperiness is low, and it is possible to prevent a stack of recorded materials from collapsing due to vibration during transportation or storage, for example.

≪Equipment≫
The apparatus according to this embodiment is an apparatus that ejects an ink set that can be used for an ink set that includes a pretreatment ink, a water-based ink, and an overcoat ink. Specifically, at least a pretreatment ink ejection section for ejecting pretreatment ink, an aqueous ink ejection section for ejecting aqueous ink, and an overcoat ink ejection section are provided in this order along the conveying direction of the base material. ing.

The resin contained in the above overcoat ink contains a resin with a glass transition temperature of 10°C or less. Therefore, it is possible to form an overcoat layer with low slip property on a water-based ink layer formed from water-based ink.

When the static surface tension of each ink is controlled within a predetermined range, as in the above-mentioned ink set having the relationship of "S _O ≤ S _P < S _C ", when printing is performed by an inkjet recording method, Even if it is, the bleeding of water-based ink can be effectively suppressed.

In addition, the device may be provided with a drying mechanism between the water-based ink discharge section and the overcoat ink discharge section, and a drying mechanism between the pretreatment ink discharge section and the water-based ink discharge section. . Further, in an apparatus comprising a pretreatment ink ejection section, an aqueous ink ejection section, and an overcoat ink ejection section, a drying mechanism is not provided between the aqueous ink ejection section and the overcoat ink ejection section, The apparatus may include a drying mechanism between the pretreatment ink ejection section and the water-based ink ejection section. Furthermore, even if the apparatus does not have a drying mechanism between the pretreatment ink ejection section and the water-based ink ejection section, but has a drying mechanism between the water-based ink ejection section and the overcoat ink ejection section, good. Unlike the apparatus shown in FIG. 1, a drying mechanism is not provided between the water-based ink discharge section and the overcoat ink discharge section, but a drying mechanism is provided between the pretreatment ink discharge section and the water-based ink discharge section. In the case of an apparatus without such an apparatus, the size of the apparatus can be reduced, and the entire conveying section can be shortened, thereby improving the manufacturing speed of printed matter.

In addition, it is preferable that this device include a drying mechanism that dries each ink contained in the ink set after the ink is ejected. As a result, it is possible to effectively remove the volatile components contained in each ink, and it is possible to more effectively suppress bleeding of the water-based ink.

The drying mechanism for drying the ink after ejection is not particularly limited, and may be a heater or the like, or a mechanism for blowing hot air or room temperature air.

Also, the ejection method in each ejection part may be any method such as a piezo method, a thermal method, or an electrostatic method. Either method can effectively suppress bleeding of the water-based ink.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these descriptions.

1. Preparation of Overcoat Ink Each component shown in Tables 1 and 2 was mixed and stirred at room temperature (20 to 25° C.) for 1 hour. After that, it was confirmed that there was no undissolved residue. Thereafter, filtration was performed using a membrane filter to prepare overcoat inks of Examples and Comparative Examples.

2. Evaluation of Overcoat Inks Each evaluation was performed on the overcoat inks of Examples and Comparative Examples.

(sliding angle)
An overcoat layer was formed using the overcoat inks of Examples and Comparative Examples, and the slip angle of the surface of the overcoat layer was determined. Specifically, the overcoat ink was applied to MF paper (coated cardboard manufactured by Oji Materia) using a bar coater #4 and dried to form an overcoat layer. Then, the sliding angle of the overcoat layer surface was measured with a friction measuring machine AN-S2 manufactured by Toyo Seiki.

(Discharge stability evaluation)
An inkjet head (KJ4B-QA manufactured by Kyocera Corporation) was used to eject the overcoat inks of Examples and Comparative Examples from all nozzles at a frequency of 12 kHz, and left for 10 minutes. Thereafter, ejection was performed again under the same ejection conditions from all the nozzles, and the presence or absence of non-ejection nozzles was visually observed.
Evaluation criteria ○: No ejection failure nozzles △: There are ejection failure nozzles, but all nozzles eject immediately after cleaning ×: There are ejection failure nozzles, and it is difficult to recover even after cleaning Ejection stability evaluation is 〇, △ If so, it is within the practical range.

(Scratch resistance evaluation)
The scratch resistance of the recorded matter was evaluated. Specifically, recorded matter in which an overcoat layer was formed with the overcoat inks of Examples and Comparative Examples was produced, and the results were measured using a Gakushin type rubbing fastness tester (AB-301 manufactured by Tester Sangyo Co., Ltd.). A sample was reciprocated 500 times with a 500 g load applied by contacting the recording surface of the recorded matter on which the overcoat layer was formed and Kanawa No. 3 (cotton), and evaluated according to the following evaluation criteria.
Evaluation Criteria A: No peeling of the coating film (overcoat layer) B: The peeling area of the coating film (overcoat layer) is less than 10% of the entire test area C: Peeling of the coating film (overcoat layer) The area is 10% or more and less than 20% of the entire test area D: The peeling area of the coating (overcoat layer) is 20% or more and less than 50% of the entire test area E: Coating (overcoat layer) The peeled area is 50% or more of the entire test area. If the scratch resistance evaluation is AC evaluation, it is within the practical range.

In the table, "AQUACER531" is a polyethylene wax emulsion manufactured by BYK-Chemie.
"BYK345" in the table is a silicone surfactant manufactured by BYK-Chemie.
In the table, "Dynol 604" is 2,5,8,11-tetramethyl-6-dodecine-5,8-diol, ethoxylate manufactured by Evonik.

As can be seen from Table 1, the overcoat inks of Examples containing a resin having a glass transition temperature of 10° C. or less have a slip angle of more than 25, and compared with the overcoat inks of Comparative Examples, It can be seen that an overcoat layer with low lubricity can be formed on the surface of the recorded matter.

2. Preparation of Aqueous Ink and Pretreatment Ink Each material was mixed in proportions (unit: % by mass) shown in the table below, and stirred at room temperature (20 to 25° C.) for 1 hour. After that, it was confirmed that there was no undissolved residue. After that, filtration was performed using a membrane filter to prepare each pretreatment ink and water-based ink, and the static surface tension was measured.

The static surface tension was measured by the Wilhelmy method (model: DY-300 manufactured by Kyowa Interface Science) at a measurement temperature of 25°C.

"Olfine E1010" in the table is an acetylene glycol-based surfactant manufactured by Nissin Chemical Industry Co., Ltd.

"BYK345" in the table is a silicone surfactant manufactured by BYK-Chemie.

"Hydran CP-7050" in the table is a cationic urethane resin emulsion manufactured by DIC.

"Unisense KHE100L" in the table is a water-soluble quaternary ammonium salt type resin manufactured by Senka.

In Table 4, "cyan pigment" means C.I. I. Pigment Blue 15:3 (PB 15:3).

In the table, "BYK345" is a silicone surfactant manufactured by BYK-Chemie.

In the table, "Dynol604" is 2,5,8,11-tetramethyl-6-dodecine-5,8-diol, ethoxylate manufactured by Evonik.

In the table, "Movinyl 6820" is an anionic acrylic resin emulsion manufactured by Japan Coating Resin.

In the table, "AQUACER531" is a polyethylene wax emulsion manufactured by BIK-Chemie.

　In the table, "DISPERBYK-190" is a water-soluble polymer dispersant manufactured by BYK-Chemie.

In the above cyan water-based ink, C.I. I. Pigment Blue 15:3, carbon black (C.I. Pigment Black 7), C.I. I. Pigment Red 122 (PR122), C.I. I. A black water-based ink, a magenta water-based ink, and a yellow water-based ink were obtained in the same manner, except that Pigment Yellow 74 (PY74) was used. Each water-based ink with a different colorant had the same value as the static surface tension of the cyan water-based ink.

3. Ink Set Evaluation An ink set containing a pretreatment ink, a water-based ink, and an overcoat ink was used to evaluate bleed. Specifically, using a line head type (one-pass type) inkjet printer having the configuration shown in FIG. A pretreatment ink, a water-based ink, and an overcoat ink were discharged in this order onto the surface of (coated cardboard manufactured by Oji Materia) to produce a printed matter having a predetermined print pattern.

(Bleeding evaluation)
Bleeding of the recorded matter was visually confirmed based on the following evaluation criteria.
Evaluation Criteria A: No bleeding was observed, and the image was clear.
B: The image was clear, although bleeding was observed very slightly.
C: Some bleeding was observed, but the image was within the practical range.
D: Bleeding was observed, and a clear image could not be obtained.
E: Significant bleeding was observed.

(repellent evaluation)
The repellence of the recorded matter was visually confirmed based on the following evaluation criteria.
Evaluation Criteria A: No repelling was observed, and it was judged that the printed surface was sufficiently filled with ink.
B: Repelling was observed very slightly, but the printed surface was buried.
C: Some repelling was observed, but the embedding was within the practical range.
D: Repelling was observed, and the printing surface was insufficiently filled.
E: Remarkable repelling was observed.

(Penetration evaluation)
After applying 5 g/m ² of the pretreatment liquid to the base material with a bar coater, the time required for the base material to be completely exposed without the liquid remaining on the base material surface was measured.
Evaluation criteria A: Less than 10 seconds B: 10 seconds or more and less than 15 seconds C: 15 seconds or more and less than 20 seconds D: 20 seconds or more and less than 25 seconds E: 25 seconds or more

(Scratch resistance evaluation)
The scratch resistance of the recorded matter was evaluated. Specifically, using a Gakushin-type rubbing fastness tester (AB-301 manufactured by Tester Sangyo Co., Ltd.), the recording surface of the recorded material and Kanawa No. 3 (cotton) are brought into contact with each other, and a load of 500 g is applied. The samples reciprocated were evaluated according to the following evaluation criteria.
Evaluation Criteria A: No peeling of the coating film (overcoat layer or water-based ink layer).
B: The peeling area of the coating film (overcoat layer or water-based ink layer) is less than 10% of the entire test area.
C: The peeling area of the coating film (overcoat layer or water-based ink layer) is 10% or more and less than 20% of the entire test area.
D: The peeling area of the coating film (overcoat layer or water-based ink layer) is 20% or more and less than 50% of the entire test area.
E: The peeling area of the coating film (overcoat layer or water-based ink layer) is 50% or more of the entire test area.

(gloss evaluation)
The 60° gloss was measured using a gloss meter (RHOPOINT IQs manufactured by Rhopoint Instruments) and evaluated according to the following criteria.
A: Gloss value 35 or more B: Gloss value 30 or more and less than 35 C: Gloss value 25 or more and less than 30 D: Gloss value 20 or more and less than 25 E: Gloss value less than 20

(sliding angle)
The sliding angle of the overcoat layer side surface of the recorded matter was measured using a Toyo Seiki friction measuring machine AN-S2.

As can be seen from Table 5, inks 2-1 to 2-11, which are overcoat inks containing a resin having a predetermined glass transition temperature range and in which the static surface tension of each ink is controlled within a predetermined range With a set, in addition to being able to form an overcoat layer with low slip on the surface of the printed material, it effectively prevents water-based ink from bleeding even when printing at a higher speed with an inkjet recording method. It turns out that it can be suppressed.

In particular, the ink set of Example 2-2, in which S _P -S _o is in the range of 0.2 or more, is more water-based than the ink sets of Examples 2-1, 2-7, 2-9, and 2-10. Ink bleeding could be suppressed more effectively. Further, the ink set of Example 2-2, in which S _P -S _o is in the range of 3.5 or less, can more effectively suppress bleeding of the water-based ink than the ink set of Example 2-6. did it.

Further, the ink set of Example 2-2, in which S _C -S _p is in the range of 3.0 or less, can more effectively suppress repelling of the water-based ink than the ink set of Example 2-3. did it.

In addition, the ink set of Example 2-2, in which S _C -S _o is in the range of 4.5 or less, is less susceptible to bleeding of the water-based ink than the ink sets of Examples 2-5, 2-6, and 2-8. could be effectively suppressed.

Further, the ink set of Example 2-2, in which the content of the resin contained in the water-based ink is less than the content of the resin contained in the overcoat ink, has a slip angle as compared with the ink set of Example 2-12. was declining. From this, it is possible to suppress a decrease in slipperiness of the overcoat layer due to the content of the resin contained in the water-based ink being smaller than the content of the resin contained in the overcoat ink. It can be seen that the ink set further exhibits the effects of the present invention.

REFERENCE SIGNS LIST 1 device 11 pretreatment ink 12 water-based ink 13 overcoat ink 21 pretreatment ink discharge section 22 water-based ink discharge section 23 overcoat ink discharge section 31 drying mechanism

Claims

An overcoat ink for forming an overcoat layer on the surface of a recorded matter,
including at least a resin, an organic solvent, and water,
The overcoat ink, wherein the resin contains a resin having a glass transition temperature of 10° C. or less.
The overcoat ink according to claim 1, wherein the resin is acrylic and/or urethane resin.
The overcoat ink according to claim 1 or 2, wherein the content of the resin is in the range of 5% by mass or more and 30% by mass or less based on the total amount of the overcoat ink.
The overcoat ink according to any one of Claims 1 to 3, which is ejected onto the surface of a recorded matter by an inkjet method.
Furthermore, it contains a surfactant,
The overcoat ink according to any one of claims 1 to 4, wherein the surfactant contains a silicone-based surfactant and/or an acetylene glycol-based surfactant.
The overcoat ink according to any one of claims 1 to 5, further comprising wax.
the overcoat ink according to any one of claims 1 to 6;
water-based ink and
Ink set containing .
The static surface tension of each ink contained in the ink set satisfies the following relationship:
The ink set according to claim 7.
Static surface tension of overcoat ink S O < Static surface tension of water-based ink S C
9. The ink set according to claim 7, further comprising a pretreatment ink.
The static surface tension of each ink contained in the ink set satisfies the following relationship:
The ink set according to claim 9.
Static surface tension S O of overcoat ink ≤ Static surface tension S P of pretreatment ink < Static surface tension S C of water-based ink
An inkjet recording method using the ink set according to any one of claims 7 to 10,
each ink contained in the ink set is inkjet-discharged onto a substrate;
Recording method.
12. The recording method according to claim 11, further comprising drying the ink after each ink contained in the ink set is ejected.
A method for producing a printed matter using the ink set according to any one of claims 7 to 10,
each ink contained in the ink set is inkjet-discharged onto a substrate;
A method for producing a recorded matter.
An apparatus for inkjet-ejecting the ink set according to any one of claims 7 to 10.
15. The apparatus according to claim 14, further comprising a drying mechanism for drying each ink contained in the ink set after ejection of the ink.
a recording medium;
a water-based ink layer formed by water-based ink;
an overcoat layer formed of the overcoat ink according to any one of claims 1 to 6 on the aqueous ink layer;
Recordings with