WO2022172937A1

WO2022172937A1 - Inkjet ink, ink set, ink medium set, and printing medium

Info

Publication number: WO2022172937A1
Application number: PCT/JP2022/005008
Authority: WO
Inventors: 圭史朗吉田; 俊太三澤; 麻衣子岩見
Original assignee: 日本化薬株式会社
Priority date: 2021-02-15
Filing date: 2022-02-09
Publication date: 2022-08-18
Also published as: JPWO2022172937A1

Abstract

Provided is an inkjet ink that contains a water-insoluble colorant, a dispersant, a fixing resin, and water, in which the fixing resin is a resin obtained by polymerizing a monomer mixture including at least one monomer selected from among butyl acrylate, methyl methacrylate, and methyl acrylate in the presence of a reactive emulsifier, and the butyl acrylate content in the monomer mixture is 0.1 mass% or more and less than 31.5 mass%. The present invention also provides: an ink set comprising the inkjet ink; an ink medium set comprising the inkjet ink or the ink set and a printing medium; and a printing medium with the inkjet ink or each of the inkjet inks included in the ink set adhering thereto.

Description

Inkjet inks, ink sets, ink media sets, and printing media

The present invention relates to inkjet inks, ink sets, ink media sets, and printing media.

Among various color printing methods, a printing method using an inkjet printer (inkjet printing method) is one of the representative methods. In this method, droplets of ink are generated and deposited on a print medium such as paper for printing. In recent years, the inkjet printing method has been applied to industrial applications, and is required to be compatible with various printing media.

Among the printing media used for industrial purposes, there are non-ink-absorbing media represented by films. In order to print on such non-ink-absorbing media, solvent inks using organic solvents as main solvents, curable inks containing polymerizable monomers, and the like have been developed. However, these inks have many safety problems against the natural environment and living organisms, and their applications are limited.

Therefore, the development of water-based inks that make it possible to print images with high durability even on non-ink-absorbing media by adding fixing resins while using water as the main solvent has been actively developed ( For example, see Patent Documents 1 to 4).

Japanese Patent No. 5504890 Japanese Patent No. 6295825 JP 2012-72354 A Japanese Patent No. 3257391

However, even if water-based inks such as those disclosed in Patent Documents 1 to 4 are used, the water resistance of images printed on non-ink-absorbing media such as PET (polyethylene terephthalate) film and PP (polypropylene) film is insufficient. Improvement is required.

In order to improve the water resistance of the printed image, it is necessary to make the film formed by the ink strong. However, when such ink dries in the inkjet head and solid matter is produced, the ink cannot be stably ejected, resulting in a problem of deterioration in image quality of the printed image. For this reason, the ink is also required to have the ability to easily dissolve and remove solid matter, even if it occurs in the inkjet head. However, the improvement in water resistance due to the formation of a film conflicts with the ability to be easily dissolved and washed, and an ink that satisfies both of these effects has not yet been proposed.

The present invention provides an inkjet ink capable of obtaining a printed image with excellent water resistance even on non-ink-absorbing media and having excellent resolubility when dried, an ink set comprising the inkjet ink, An object of the present invention is to provide an ink media set including the inkjet ink or the ink set and a print medium, and a print medium to which the inkjet ink or each inkjet ink included in the ink set is adhered.

Specific means for solving the above problems include the following embodiments.
1)
containing a water-insoluble colorant, a dispersant, a fixing resin, and water;
The fixing resin is a resin obtained by polymerizing a monomer mixture containing butyl acrylate and at least one monomer selected from methyl methacrylate and methyl acrylate in the presence of a reactive emulsifier, An inkjet ink containing 0.1% by mass or more and less than 31.5% by mass of butyl acrylate in a monomer mixture.
2)
The inkjet ink according to 1), wherein the monomer mixture further comprises at least one monomer selected from the group consisting of allyl methacrylate, butyl methacrylate, and sodium styrenesulfonate.
3)
The inkjet ink according to 1), wherein the monomer mixture further comprises at least two monomers selected from the group consisting of allyl methacrylate, butyl methacrylate, and sodium styrenesulfonate.
4)
An ink set comprising the inkjet ink according to any one of 1) to 3) and another inkjet ink different from the inkjet ink.
5)
An ink media set comprising the inkjet ink according to any one of 1) to 3) or the ink set according to 4) and a print medium.
6)
A printing medium to which the inkjet ink according to any one of 1) to 3) or each inkjet ink included in the ink set according to 4) is adhered.

ADVANTAGE OF THE INVENTION According to the present invention, an inkjet ink that can obtain a printed image with excellent water resistance even on a non-ink-absorbing medium and has excellent resolubility when dried, and an ink comprising the inkjet ink. A set, an ink media set comprising the inkjet ink or ink set and print media, and a print media having the inkjet ink or each inkjet ink of the ink set deposited thereon can be provided.

Specific embodiments to which the present invention is applied will be described in detail below.
As used herein, "C.I." means "color index."
In addition, the terms "alkylene", "propylene" and "alkyl" are used herein to include both linear and branched structures unless otherwise specified.

<Inkjet ink>
The inkjet ink according to the present embodiment (hereinafter also simply referred to as "ink") contains a water-insoluble colorant, a dispersant, a fixing resin, and water, and the fixing resin contains butyl acrylate and methyl methacrylate. and at least one monomer selected from methyl acrylate, in the presence of a reactive emulsifier, by polymerizing a monomer mixture, wherein the content of butyl acrylate in the monomer mixture is 0.5. It is 1% by mass or more and less than 31.5% by mass.

The ink according to the present embodiment can obtain a printed image with excellent water resistance even on non-ink-absorbing media, and is also excellent in resolubility when dried. The reason is not necessarily clear, but is presumed as follows.

In order to achieve both water resistance and resolubility, it is considered important to balance the flexibility and hardness of the dried and coated ink. This is because if the film-formed ink is excessively flexible, water easily penetrates and the water resistance deteriorates. This is because sexuality deteriorates. In this regard, in the ink according to the present embodiment, by using a specific resin as the fixing resin, the balance between the flexibility and hardness of the dried and coated ink becomes appropriate, and the desired performance is exhibited. presumed to have been possible.

The components contained in the ink according to this embodiment will be described in detail below. In addition, each component demonstrated below may be used individually by 1 type of them, and may use 2 or more types together.

[Water-insoluble colorant]
The water-insoluble colorant means a colorant whose solubility in water at 25°C is usually 5 g/L or less, preferably 3 g/L or less, more preferably 1 g/L or less, and still more preferably 0.5 g/L or less. . Lower limits of solubility include 0 g/L.

As the water-insoluble colorant, known colorants such as pigments, disperse dyes and solvent dyes can be used. Among these, pigments are preferred.

Examples of pigments include inorganic pigments, organic pigments, extender pigments, and hollow particles.

Examples of inorganic pigments include carbon black, metal oxides, metal hydroxides, metal sulfides, metal ferrocyanides, and metal chlorides.

When the ink according to the present embodiment is a black ink and the water-insoluble colorant is an inorganic pigment, the inorganic pigments contained in the black ink include thermal black, acetylene black, oil furnace black, gas furnace black, Carbon blacks such as lamp black, gas black and channel black are preferred. Specific examples of carbon black include, for example, Raven series manufactured by Columbia Carbon; Monarch series, Regal series, and Mogul series manufactured by Cabot Corporation; ColorBlack series, Printex series, and SpecIalBlack series manufactured by Orion Engineered Carbons; and Nerox series; Mitsubishi Chemical Corporation MA series, MCF series, No. 25, No. 33, No. 40, No. 47, No. 52, No. 900, and No. 2300;

When the ink according to the present embodiment is a white ink and the water-insoluble colorant is an inorganic pigment, the inorganic pigment contained in the white ink includes metals such as zinc, silicon, aluminum, titanium, strontium, and zirconium. oxides, nitrides, or oxynitrides of; inorganic compounds such as glass and silica; and the like. Among these, titanium dioxide and zinc oxide are preferred.

Examples of organic pigments include various pigments such as azo, disazo, phthalocyanine, quinacridone, isoindolinone, dioxazine, perylene, perinone, thioindigo, anthraquinone, and quinophthalone. Among these, disazo pigments are preferred.

Specific examples of organic pigments include C.I. I. Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 24, 55, 73, 74, 75, 83, 93, 94, 95, 97, 98, 108, 114, 128, 129, 138, 139, 150, 151, 154, 155, 180, 185, 193, 199, 202, 213; I. Pigment Red 5, 7, 12, 48, 48: 1, 57, 88, 112, 122, 123, 146, 149, 150, 166, 168, 177, 178, 179, 184, 185, 202, 206, 207, 254, 255, 257, 260, 264, 269, 272; C.I. I. Pigment Blue 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 22, 25, 60, 66, 80, and other blue pigments; I. Pigment Violet 19, 23, 29, 37, 38, 50 and other violet pigments; C.I. I. Pigment Orange 13, 16, 43, 68, 69, 71, 73 and other orange pigments; C.I. I. Pigment Green 7, 36, 54 and other green pigments; C.I. I. Black pigments such as Pigment Black 1; Among these, C.I. I. Pigment Yellow 155 (a disazo pigment) is preferred.

Examples of extender pigments include silica, calcium carbonate, talc, clay, barium sulfate, and white carbon. These extender pigments are often used in combination with other colorants.

Hollow particles are described in, for example, US Pat. No. 4,880,465, US Pat. No. 3,562,754, US Pat. A known hollow particle can be used, and it is particularly preferable to use it as a white pigment.

Disperse dyes include, for example, C.I. I. Dyes selected from Dispers are preferred. Specific examples include, for example, C.I. I. Dispers Yellow 9, 23, 33, 42, 49, 54, 58, 60, 64, 66, 71, 76, 79, 83, 86, 90, 93, 99, 114, 116, 119, 122, 126, 149, yellow dyes such as C.I. I. Red dyes such as Dispers Red 60, 73, 88, 91, 92, 111, 127, 131, 143, 145, 146, 152, 153, 154, 167, 179, 191, 192, 206, 221, 258, 283; C. I. Orange dyes such as Dispers Orange 9, 25, 29, 30, 31, 32, 37, 38, 42, 44, 45, 53, 54, 55, 56, 61, 71, 73, 76, 80, 96, 97; C. I. Violet dyes such as Dispers Violet 25, 27, 28, 54, 57, 60, 73, 77, 79, 79:1; C.I. I. Dispers Blue 27, 56, 60, 79:1, 87, 143, 165, 165:1, 165:2, 181, 185, 197, 202, 225, 257, 266, 267, 281, 341, 353, 354, blue dyes such as 358, 364, 365, 368;

As a solvent dye, for example, C.I. I. Dyes selected from Solvent are preferred.

The average particle size of the water-insoluble colorant is preferably 30-300 nm, more preferably 50-250 nm. As used herein, the average particle size refers to the average particle size of particles measured using a laser light scattering method.

The content of the water-insoluble colorant is usually 1 to 30% by mass, preferably 1 to 10% by mass, more preferably 2 to 7% by mass, relative to the total mass of the ink according to this embodiment.

[Dispersant]
Dispersants include, for example, styrene and its derivatives; vinylnaphthalene and its derivatives; α,β-ethylenically unsaturated carboxylic acid aliphatic alcohol esters; (meth)acrylic acid and its derivatives; maleic acid and its derivatives; itaconic acid and its derivatives; faric acid and its derivatives; vinyl acetate, vinyl alcohol, vinylpyrrolidone, acrylamide, and derivatives thereof; and hydrophilic monomers). Hydrophilic monomers include monomers such as acrylic acid and methacrylic acid, in which a carboxyl group remains after polymerization.

Such copolymers include, for example, styrene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid-(meth)acrylic acid ester copolymer, (meth)acrylic acid ester-(meth) Examples include acrylic acid copolymers, polyethylene glycol (meth)acrylate-(meth)acrylic acid copolymers, styrene-maleic acid copolymers, and the like. Among these, styrene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid-(meth)acrylic acid ester copolymer, (meth)acrylic acid ester-(meth)acrylic acid copolymer, and Polyethylene glycol (meth) acrylate - (meth) acrylic acid copolymer is preferred, styrene - (meth) acrylic acid copolymer, styrene - (meth) acrylic acid - (meth) acrylic acid ester copolymer, and (meth) ) acrylic acid ester-(meth)acrylic acid copolymer is more preferred, (meth)acrylic acid ester-(meth)acrylic acid copolymer is more preferred, and methacrylic acid ester-(meth)acrylic acid copolymer is particularly preferred. Types of copolymers include, for example, block copolymers, random copolymers, and graft copolymers. These copolymers may be in the form of salts.

The term "(meth)acryl" used in this specification includes both "acryl" and "methacryl". The same applies to "(meth)acrylate" and the like.

Dispersants can be synthesized or obtained as commercial products.

Dispersants obtained by synthesis include, for example, AB block polymers disclosed in WO 2013/115071. Monomers constituting the A block of the AB block polymer disclosed in WO 2013/115071 are selected from (meth) acrylic acid and linear or branched C4 alkyl (meth) acrylates At least one type of monomer is preferably used, and at least one type of monomer selected from methacrylic acid and n-butyl methacrylate is preferred, and it is more preferred to use these two types of monomers together. Further, the monomer constituting the B block of the AB block polymer disclosed in WO 2013/115071 is at least one monomer selected from benzyl methacrylate and benzyl acrylate, preferably benzyl methacrylate. Specific examples of AB block polymers include block copolymers disclosed in Synthesis Examples 3-8 of WO 2013/115071.

Commercially available dispersants include, for example, Joncyl 62, 67, 68, 678, 687 (styrene-acrylic copolymer manufactured by BASF); acrylic acid);

The mass average molecular weight (MW) of the dispersant is, for example, 3000-50000, preferably 7000-25000. The mass average molecular weight of the dispersant can be measured by gel permeation chromatography (GPC method). Specifically, HLC-8320GPC (manufactured by Tosoh Corporation) is used as the GPC apparatus, and two columns of TSK gel Super Multipore HZ-H (manufactured by Tosoh Corporation, inner diameter 4.6 mm × 15 cm) are used for elution. It can be measured using tetrahydrofuran as a liquid and TSK Standard (manufactured by Tosoh Corporation) as a standard sample.

The acid value of the dispersant is, for example, 50-300 mgKOH/g, preferably 80-275 mgKOH/g, more preferably 80-250 mgKOH/g.

The dispersant can be used in a state of being mixed with the water-insoluble colorant. Also, the water-insoluble colorant may be used in a state in which part or all of the surface is coated with a dispersant. Alternatively, both of these states may be used together.

The ratio of the total mass of the dispersant to the total mass of the water-insoluble colorant (value represented by "total mass of dispersant/total mass of water-insoluble colorant") is usually 0.1 to 1.0, preferably 0.1 to 0.6, more preferably 0.2 to 0.5.

[Fixing resin]
As the fixing resin, a resin obtained by polymerizing a monomer mixture containing butyl acrylate and at least one monomer selected from methyl methacrylate and methyl acrylate in the presence of a reactive emulsifier is used. .

At least one monomer selected from methyl methacrylate and methyl acrylate may contain either one or both of them. From the viewpoint of improving resolubility, it preferably contains at least methyl methacrylate, and more preferably contains only methyl methacrylate.

The content of butyl acrylate is 0.1% by mass or more and less than 31.5% by mass, preferably 0.1 to 25% by mass, more preferably 1 to 25% by mass, based on the total mass of the monomer mixture. , more preferably 3 to 25% by mass, particularly preferably 4 to 22% by mass.

The total content of at least one monomer selected from methyl methacrylate and methyl acrylate is usually 0.1% by mass or more, preferably 10% by mass or more, and more, relative to the total mass of the monomer mixture. It is preferably 30 to 95% by mass, more preferably 50 to 90% by mass, particularly preferably 60 to 90% by mass, and most preferably 67 to 85% by mass.

In addition, the monomer mixture preferably further contains at least one monomer selected from the group consisting of allyl methacrylate, butyl methacrylate, and sodium styrenesulfonate, and more preferably contains at least two monomers. . Among these, a combination of allyl methacrylate, butyl methacrylate and sodium styrenesulfonate, and a combination of allyl methacrylate and sodium styrenesulfonate are preferred.

When the monomer mixture contains at least one monomer selected from the group consisting of allyl methacrylate, butyl methacrylate, and sodium styrenesulfonate, the total content thereof is usually 0 relative to the total mass of the monomer mixture. .1 to 20% by mass, preferably 0.1 to 15% by mass, more preferably 0.2 to 10% by mass, still more preferably 0.5 to 7% by mass, particularly preferably 1 to 5% by mass. be.

In addition, the monomer mixture may further contain other monomers than the above. Other monomers include, for example, methacrylic acid.

When the monomer mixture contains methacrylic acid, its content is usually 1 to 50% by mass, preferably 1 to 25% by mass, more preferably 1 to 15% by mass, based on the total mass of the monomer mixture. .

The fixing resin is obtained by polymerizing the above monomer mixture in the presence of a reactive emulsifier. Thus, by polymerizing the monomer mixture in the presence of a reactive emulsifier, an emulsion of the fixing resin can be obtained. When preparing the ink according to the present embodiment, it is preferable to use such an emulsion of the fixing resin.

A reactive emulsifier is an emulsifier that has a radically polymerizable double bond in its molecule. The number of radically polymerizable double bonds is usually one.

Specific examples of reactive emulsifiers include polyoxyalkylene alkenyl ether ammonium sulfate, ether sulfate type ammonium, phosphoric acid ester, bis(polyoxyethylene polycyclic phenyl ether) methacrylate sulfate, 2-sodium sulfoethyl methacrylate, and alkoxypolyethylene glycol. maleic acid esters, and salts thereof. Specific examples of reactive emulsifiers include sodium alkylallylsulfosuccinate (manufactured by Sanyo Chemical Industries, Ltd., Eleminol JS-20), dipotassium alkenylsuccinate (manufactured by Kao Corporation, Latemul ASK), polyoxyethylene alkylpropenylphenyl Ether sulfate (Daiichi Kogyo Seiyaku Co., Ltd., Aqualon HS-10), α-[1-[(allyloxy)methyl]-2-(nonylphenoxy)ethyl]-ω-polyoxyethylene sulfate ( ADEKA Co., Ltd., Adekaria Soap SE series such as Adekaria Soap SE-10N), polyoxyethylene-1-(allyloxymethyl) alkyl ether sulfate ester ammonium salt (Daiichi Kogyo Seiyaku Co., Ltd., Aqualon KH -1025, etc. Aqualon KH series), styrene sulfonate (manufactured by Tosoh Finechem Co., Ltd., Spinomer NaSS), α-[2-[(allyloxy)-1-(alkyloxymethyl)]ethyl]-ω-poly Oxyethylene sulfate (made by ADEKA Co., Ltd., Adekari Soap SR series such as Adekari Soap SR-1025), polyoxyethylene polyoxybutylene (3-methyl-3-butenyl) ether sulfate (Kao ( Co., Ltd., Latemul PD-104) and the like. Among these, the Adekari Soap SR series manufactured by ADEKA Corporation is preferable, and the Adekari Soap SR-1025 (that is, [({α-[2-(allyloxy)-1-({C10-C14 alkyloxy}methyl ) Reaction formation of {C10-C14 branched chain alkanols with 1-(allyloxy)-2,3-epoxypropane, based on ethyl]-ω-hydroxypoly(n=1-100)(oxyethylene)} oxirane polyadduct) of the compound)) is more preferred.

The amount of reactive emulsifier used when synthesizing the fixing resin is not particularly limited. As a standard of the amount to be used, it is usually 0.1 to 10% by mass, preferably 0.3 to 5% by mass, more preferably 0.5 to 3% by mass, more preferably 0.5 to 3% by mass, based on the total mass of the monomer mixture. It is 1 to 3% by mass. By using the reactive emulsifier within the above range, the fixing resin can be stably synthesized, and the viscosity of the fixing resin emulsion tends to be adjusted within a suitable range.

In addition, when synthesizing the fixing resin, an emulsifier other than the reactive emulsifier may be used. Other emulsifiers include, for example, alkyl sulfates, alkyl allyl sulfates, alkyl sulfonates, alkyl allyl sulfonates, dialkyl sulfosuccinates, sodium dodecylbenzene sulfonate, sodium polyoxyethylene alkyl ether sulfate, alkyl sulfonic acid anionic surfactants such as sodium; nonionic surfactants such as polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl ethers, polyoxyethylene carboxylic acid esters, polyoxyethylene glycol types, and polyoxyethylene propylene glycol types;4 secondary ammonium salts (alkyltrimethylammonium bromide, alkylpyridinium bromide, alkyltrimethylammonium chloride, alkylbenzylammonium chloride, imidazolinium laurate, etc.), pyridinium salts, imidazolinium salt-type cationic surfactants; . Among these, sodium dodecylbenzenesulfonate is preferred.

In addition, a polymerization initiator can be used when synthesizing the fixing resin. Examples of polymerization initiators include persulfates such as ammonium persulfate, potassium persulfate and sodium persulfate; 2,2′-azobis[N-(2-hydroxyethyl)-2-methyl-propionamidine] dihydrochloride , 2,2′-azobis(2-amidinopropane) dihydrochloride, 2,2′-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride, 2,2′-azobis[2- (2-imidazolin-2-yl)propane], water-soluble azo polymerization initiators such as 4,4′-azobis(4-cyanovaleric acid); Among these, persulfates are preferred, ammonium persulfate and potassium persulfate are more preferred, and potassium persulfate is even more preferred.

The glass transition point (Tg) of the fixing resin is, for example, 0 to 200.degree. C., preferably 80 to 150.degree. C., more preferably 90 to 145.degree.

The content of the fixing resin is usually 0.1 to 30% by mass, preferably 1 to 20% by mass, more preferably 2 to 15% by mass, and still more preferably 0.1 to 30% by mass, relative to the total mass of the ink according to the present embodiment. is 3 to 10% by weight, particularly preferably 7 to 9% by weight.

[water]
As the water, water having a low content of impurities such as metal ions, that is, ion-exchanged water, distilled water, or the like is preferable.

The water content is usually 30 to 80% by mass, preferably 35 to 80% by mass, more preferably 40 to 80% by mass, relative to the total mass of the ink according to this embodiment.

[Organic solvent]
The ink according to this embodiment may further contain an organic solvent. Examples of organic solvents include C1-C6 alkanols such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol and tert-butanol; carboxylic acids such as N,N-dimethylformamide and N,N-dimethylacetamide; acid amides; lactams such as 2-pyrrolidone, N-methyl-2-pyrrolidone and N-methylpyrrolidin-2-one; 1,3-dimethylimidazolidin-2-one or 1,3-dimethylhexahydropyrimid-2 - Cyclic ureas such as acetone, 2-methyl-2-hydroxypentan-4-one, ketones such as ethylene carbonate, ketoalcohols, or carbonates; Cyclic ethers such as tetrahydrofuran and dioxane; Ethylene glycol, diethylene glycol, 1 , 2-propylene glycol, 1,3-propylene glycol, 1,2-butylene glycol, 1,4-butylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, polyethylene glycol (preferably having a molecular weight of 400, 800, 1540 or higher), mono-, oligo- or polyalkylene glycols or thioglycols having C2-C6 alkylene units such as polypropylene glycol, thiodiglycol, dithiodiglycol; glycerin, diglycerin, hexane-1 , 2,6-triol, trimethylolpropane, etc.; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoallyl ether, ethylene glycol monoisopropyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether (butyl carbitol), triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monopropyl ether Glycol ethers such as propylene glycol monomethyl ether (preferably the group consisting of C4-C10 mono-, di- or triethylene glycol ethers and C4-C13 mono-, di- or tripropylene glycol ethers 1,2-pentanediol, 1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 2-methyl-2,4-pentanediol, 2-ethyl -C5-C9 alkanediol such as 1,3-hexanediol and 2,4-diethyl-1,5-pentanediol; γ-butyrolactone; dimethylsulfoxide;

The organic solvent content is usually 0 to 60% by mass, preferably 1 to 60% by mass, more preferably 2 to 50% by mass, still more preferably 3 to 45% by mass, relative to the total mass of the ink according to the present embodiment. % by weight, particularly preferably 5 to 40% by weight.

[Surfactant]
The ink according to this embodiment may further contain a surfactant. Surfactants include anionic, nonionic, silicone, and fluorine surfactants. Among these, surfactants selected from silicone-based surfactants and fluorine-based surfactants are preferred, and silicone-based surfactants are more preferred from the viewpoint of safety to the living body and the environment.

Examples of anionic surfactants include alkylsulfocarboxylates, α-olefin sulfonates, polyoxyethylene alkyl ether acetates, polyoxyethylene alkyl ether sulfates, N-acyl amino acids or salts thereof, N-acyl Methyl taurate, alkyl sulfate polyoxyalkyl ether sulfate, alkyl sulfate polyoxyethylene alkyl ether phosphate, rosin acid soap, castor oil sulfate, lauryl alcohol sulfate, alkylphenol type phosphate, alkyl type phosphate , alkylarylsulfonate, diethylsulfosuccinate, diethylhexylsulfosuccinate, dioctylsulfosuccinate, and the like.

Examples of nonionic surfactants include polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, polyoxyethylene alkyl ether, poly Ethers such as oxyethylene distyrenated phenyl ether (e.g. Emulgen A-60, A-90, A-500 manufactured by Kao Corporation); polyoxyethylene oleate, polyoxyethylene distearate, sorbitan lau sorbitan monostearate, sorbitan monooleate, sorbitan sesquioleate, polyoxyethylene monooleate, esters such as polyoxyethylene stearate; , 7-diol, 3,6-dimethyl-4-octyne-3,6-diol, 3,5-dimethyl-1-hexyn-3-ol and other acetylene glycol (or acetylene alcohol) systems (for example, Evonik Japan ( Surfynol 104, 104PG50, 82, 420, 440, 465, 485; Olfine STG; etc.); polyglycol ether;

Examples of silicone-based surfactants include polyether-modified siloxane and polyether-modified polydimethylsiloxane. Examples include Dynol 960 and 980 manufactured by Air Products; Silface SAG001, SAG002, SAG003, SAG005, SAG503A, SAG008, SAG009, and SAG010 manufactured by Nissin Chemical Industries; BYK-345 manufactured by BYK; 347, 348, 349, 3455, LP-X23288, LP-X23289, LP-X23347; Evonic Tego Chemie TEGO Twin 4000, TEGO Wet KL 245, 250, 260, 265, 270, 280;

Examples of fluorine-based surfactants include perfluoroalkylsulfonic acid compounds, perfluoroalkylcarboxylic acid compounds, perfluoroalkylphosphoric acid ester compounds, perfluoroalkylethylene oxide adducts, and perfluoroalkyl ether groups in side chains. polyoxyalkylene ether polymer compounds having Examples of commercially available products include Capstone FS-30 and FS-31 manufactured by Chemours.

[Other ingredients]
The ink according to the present embodiment may contain antifungal agents, preservatives, pH adjusters, chelating reagents, rust inhibitors, antifoaming agents, water-soluble ultraviolet absorbers, antioxidants, resin emulsions, waxes, etc., as necessary. of ink preparation agents. The content of each ink preparation agent can be arbitrarily set according to the use of the ink.

(antifungal agent)
Antifungal agents include, for example, sodium dehydroacetate, sodium benzoate, sodium pyridinethione-1-oxide, ethyl p-hydroxybenzoate, 1,2-benzisothiazolin-3-one and salts thereof.

(Preservative)
Examples of antiseptics include organic sulfur, organic nitrogen sulfur, organic halogen, haloarylsulfone, iodopropargyl, haloalkylthio, nitrile, pyridine, 8-oxyquinoline, benzothiazole, Isothiazolines, dithiols, pyridine oxides, nitropropanes, organic tins, phenols, quaternary ammonium salts, triazines, thiazines, anilides, adamantanes, dithiocarbamates, brominated indanones, benzyl bromide Acetate-based compounds, inorganic salt-based compounds, and the like can be mentioned. Specific examples of organic halogen compounds include sodium pentachlorophenol. Specific examples of pyridine oxide compounds include sodium 2-pyridinethiol-1-oxide. Specific examples of isothiazoline compounds include 1,2-benzisothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3- on, 5-chloro-2-methyl-4-isothiazolin-3-one magnesium chloride, 5-chloro-2-methyl-4-isothiazolin-3-one calcium chloride, 2-methyl-4-isothiazolin-3-one calcium chloride and the like. Specific examples of other antiseptic and antifungal agents include anhydrous sodium acetate, sodium sorbate, sodium benzoate, trade names Proxel GXL (S), Proxel LV, and Proxel XL-2 (S) manufactured by Arch Chemicals. are mentioned.

(pH adjuster)
Examples of pH adjusters include alkanolamines such as diethanolamine, triethanolamine and N-methyldiethanolamine; alkali metal hydroxides such as lithium hydroxide, sodium hydroxide and potassium hydroxide; ammonium hydroxide (ammonia water). alkali metal carbonates such as lithium carbonate, sodium carbonate, sodium hydrogencarbonate and potassium carbonate; alkali metal salts of organic acids such as sodium silicate and potassium acetate; inorganic bases such as disodium phosphate;

(chelating reagent)
Chelating agents include, for example, disodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, sodium uracil diacetate and the like.

(anti-rust)
Examples of rust preventives include acidic sulfites, sodium thiosulfate, ammonium thioglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite.

(Antifoaming agent)
Antifoaming agents include, for example, silicone-based, silica-mineral oil-based, olefin-based, and acetylene-based compounds. Commercially available antifoaming agents include, for example, Surfynol DF37, DF58, DF110D, DF220, MD-20, Olefin SK-14 and the like manufactured by Shin-Etsu Chemical Co., Ltd.

(Water-soluble UV absorber)
Examples of water-soluble ultraviolet absorbers include sulfonated benzophenone-based compounds, benzotriazole-based compounds, salicylic acid-based compounds, cinnamic acid-based compounds, and triazine-based compounds.

(Antioxidant)
Antioxidants include, for example, various organic and metal complex antifading agents. Examples of organic anti-fading agents include hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromans, alkoxyanilines, and heterocycles.

(resin emulsion)
When the ink according to the present embodiment contains a resin emulsion in addition to the fixing resin, the image fastness of the printed image, such as water resistance, scratch resistance, and alcohol resistance, tends to be improved. As the resin emulsion, at least one selected from polymer emulsions and wax emulsions is preferable.

Examples of polymer emulsions include emulsions containing urethane, polyester, acrylic, vinyl acetate, vinyl chloride, styrene-acrylic, acrylic-silicone, and styrene-butadiene polymers. Among these, emulsions of polymers selected from urethane, acrylic, and styrene-butadiene systems are preferred.

Commercially available polymer emulsions include, for example, Superflex 420, 470, 890 (the above are urethane-based resin emulsions manufactured by Daiichi Kogyo Seiyaku Co., Ltd.); Hydran HW-350, HW-178, HW-163, HW- 171, AP-20, AP-30, WLS-201, WLS-210 (the above are urethane resin emulsions manufactured by DIC Corporation); 0569, 0850Z, 2108 (the above are styrene-butadiene-based resin emulsion); AE980, AE981A, AE982, AE986B, AE104 (these are acrylic resin emulsions manufactured by ETEC Co., Ltd.);

As the wax emulsion, an emulsion in which natural wax or synthetic wax is dispersed in an aqueous medium can be used.

Natural wax emulsions include, for example, petroleum waxes such as paraffin wax and microcrystalline wax; lignite waxes such as montan wax; plant waxes such as carnauba wax and candelia wax; animal and plant waxes such as beeswax and lanolin; and emulsions of each wax.

Examples of synthetic wax emulsions include emulsions of polyalkylene wax (preferably poly-C2-C4 alkylene wax), polyalkylene oxide wax (preferably poly-C2-C4 alkylene oxide oxide), and paraffin wax. Among these, emulsions of waxes selected from polyethylene wax, polypropylene wax, oxidized polyethylene wax, oxidized polypropylene wax, and paraffin wax are preferred.

The average particle size of the wax is preferably 50 nm to 5 μm, more preferably 100 nm to 1 μm, in order to prevent clogging of the inkjet head.

Commercial wax emulsion products include, for example, CERAFLOUR 925, 929, 950, 991, AQUACER 498, 515, 526, 531, 537, 539, 552, 1547, AQUAMAT 208, 263, 272; Mitsui Hi-Wax NL100, NL200, NL500, 4202E, 1105A, 2203A, NP550, NP055, NP505 (manufactured by Mitsui Chemicals, Inc.); KUE-100, 11 (manufactured by Sanyo Chemical Industries, Ltd.) HYTEC E-6500, 9015, 6400 (manufactured by Toho Chemical Industry Co., Ltd.);

The total content of the solid content of the resin emulsion and the fixing resin is preferably 1 to 20% by mass, more preferably 3 to 10% by mass, with respect to the total mass of the ink according to the present embodiment. . By setting the total content of the solid content of the resin emulsion and the fixing resin to 1% by mass or more, there is a tendency to exhibit good fixability to the printing media. In addition, by setting the total content of the solid content of the resin emulsion and the fixing resin to 20% by mass or less, the ejection property and storage stability of the ink tend to be improved.

[Ink preparation method, etc.]
A method for preparing the ink according to the present embodiment is not particularly limited, and a known preparation method can be employed. For example, an aqueous dispersion containing a water-insoluble colorant and a dispersant is prepared, and an emulsion of a fixing resin, water, an organic solvent, and, if necessary, an ink preparation agent are added to the aqueous dispersion. a method of mixing with

Methods for preparing the aqueous dispersion include, for example, a phase inversion emulsification method, an acid precipitation method, an interfacial polymerization method, an in-situ polymerization method, an in-liquid curing coating method, a coacervation (phase separation) method, an in-liquid drying method, Examples include a melting dispersion cooling method, an air suspension coating method, a spray drying method, and the like. Among these, the phase inversion emulsification method, the acid precipitation method, and the interfacial polymerization method are preferable, and the phase inversion emulsification method is more preferable.

When preparing an aqueous dispersion by a phase inversion emulsification method, for example, a dispersant is dissolved in an organic solvent such as 2-butanone, and an aqueous solution of a neutralizer is added to prepare an emulsion. A water-insoluble colorant is added to the obtained emulsified liquid for dispersion treatment. The desired aqueous dispersion can be obtained by distilling off the organic solvent and part of the water from the thus obtained liquid under reduced pressure.

Dispersion treatment can be performed using a sand mill (bead mill), roll mill, ball mill, paint shaker, ultrasonic disperser, microfluidizer, or the like. For example, when a sand mill is used, beads having a particle size of about 0.01 to 1 mm can be used, and the filling rate of the beads can be appropriately set for dispersion treatment. The particle size of the particles contained in the aqueous dispersion can be uniformed by subjecting the aqueous dispersion obtained as described above to operations such as filtration and centrifugation. If foaming occurs during the preparation of the aqueous dispersion, a very small amount of known silicone-based or acetylene glycol-based antifoaming agents can be added.

The ink according to the present embodiment preferably has a low content of inorganic impurities such as metal cation chlorides (eg, sodium chloride) and metal cation sulfates (eg, sodium sulfate). Such inorganic impurities are often contained in commercially available water-insoluble colorants. A guideline for the content of inorganic impurities is approximately 1% by mass or less relative to the total amount of the water-insoluble colorant, and the lower limit is ideally below the detection limit of the analytical instrument, that is, 0% by mass. Methods for obtaining a water-insoluble colorant with less inorganic impurities include, for example, a method using a reverse osmosis membrane; A method of separating and drying the water-insoluble colorant by filtration; a method of exchanging and adsorbing inorganic impurities with an ion-exchange resin;

The ink according to the present embodiment is preferably fine filtered. Membrane filters, glass filter paper and the like can be used for precision filtration. The pore size of a filter or the like for microfiltration is usually 0.5 to 20 μm, preferably 0.5 to 10 μm.

The ink according to the present embodiment is also excellent in storage stability, redispersibility, various abrasion resistance, color developability, and chroma. In addition, printed images recorded using the ink according to the present embodiment are excellent in various fastnesses such as water resistance, light resistance, heat resistance, oxidation gas resistance (for example, ozone gas resistance). In addition, the ink according to the present embodiment has little coating unevenness during image formation, and is excellent in image formability.

<Ink set, ink media set>
The ink set according to this embodiment includes the ink according to this embodiment described above and another ink different from the ink. The other ink is not particularly limited as long as it has a different composition from the ink according to the present embodiment, but preferably has a different hue from the ink according to the present embodiment.

Further, the ink set according to this embodiment includes the ink or ink set according to this embodiment described above, and printing media.

The print media are not particularly limited, but preferably print media that hardly absorb ink, and more preferably print media that do not absorb ink. Examples of the ink-poor printing media include plain paper having no ink-receiving layer, media used for gravure printing and offset printing, art paper, coated paper, matte paper, cast paper, and the like. Examples of non-ink-absorbing printing media include PET (polyethylene terephthalate) film, PP (polypropylene) film, vinyl chloride sheet, glass, and rubber.

<Inkjet printing method>
In the inkjet printing method according to the present embodiment, the ink according to the present embodiment described above or droplets of each ink included in the ink set according to the present embodiment described above are ejected according to a print signal, and adhered to the print medium. In this method, printing is performed by There are no particular restrictions on the ink nozzles and the like of the inkjet printer for ejecting ink, and they can be appropriately selected according to the purpose.

The inkjet printing method according to the present embodiment includes a method of ejecting a large number of inks with a low content of water-insoluble colorant in the ink in a small volume to improve image quality; A method for improving image quality by using multiple inks with different colorant content; By using both a colorless and transparent ink and an ink containing a water-insoluble colorant, the fixability of the water-insoluble colorant to the printing medium and the like.

A known method can be adopted as the inkjet printing method. Examples thereof include a charge control method, a drop-on-demand method (also referred to as a pressure pulse method), an acoustic inkjet method, a thermal inkjet method, and the like. Moreover, the inkjet printing method may be either a multi-pass method or a single-pass method (one-pass printing method). In an industrial inkjet printer, single-pass printing using a line head type inkjet printer is also preferably performed for the purpose of increasing the printing speed. According to the ink according to the present embodiment, even under such printing conditions, it is possible to obtain a printed image with good coating properties and excellent abrasion resistance.

When printing on print media, for example, a container (ink tank) containing ink is loaded in a predetermined position of an inkjet printer, and the print media is printed by the above printing method. Full-color printing can also be achieved by loading containers containing inks of respective colors into predetermined positions of an inkjet printer and printing on printing media by the above-described printing method.

When using a printing medium that does not have an ink-receiving layer, it is preferable to subject the printing medium to surface modification treatment for the purpose of improving the fixability of the water-insoluble colorant. Examples of surface modification treatment include corona discharge treatment, plasma treatment, and flame treatment. It is generally known that the effect of surface modification treatment decreases over time. Therefore, it is preferable to perform the surface modification treatment step and the inkjet recording step continuously, and it is more preferable to perform the surface modification treatment step immediately before the inkjet recording step.

For all of the above items, a combination of preferable items is more preferable, and a combination of more preferable items is even more preferable. The same applies to combinations of preferable and more preferable items, combinations of more preferable and more preferable items, and the like.

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

In the examples, "parts" means parts by mass and "%" means % by mass, unless otherwise specified. Unless otherwise specified, all operations such as various syntheses in Examples were carried out under stirring. Further, when it was necessary to quantify the pigment solid content in the pigment dispersion, it was determined by the dry weight method using MS-70 manufactured by A&D Co., Ltd. The pigment solid content is a conversion value obtained by calculating only the pigment solid content from the total amount of solid content.

<Preparation Example 1: Preparation of Pigment Dispersion Liquid DP1>
A block copolymer (dispersant) was obtained by repeating Synthesis Example 3 of International Publication No. 2013/115071. The resulting block copolymer (6 parts) was dissolved in 2-butanone (30 parts) to form a homogeneous solution. A solution obtained by dissolving a 28% aqueous ammonia solution (0.68 parts) in ion-exchanged water (53 parts) was added to this solution, and the mixture was stirred for 1 hour to obtain an emulsified solution. C.I. I. Pigment Yellow 155 (manufactured by Clariant) (20 parts) was added and dispersed in a sand grinder at 1500 rpm for 15 hours to obtain a liquid. Ion-exchanged water (100 parts) was added dropwise to the obtained liquid, and after filtering to remove the dispersing beads, 2-butanone and part of the water were distilled off under reduced pressure using an evaporator to obtain a pigment solid content of 12.8%. was obtained. The obtained pigment dispersion is designated as "DP1".

<Preparation Example 2: Preparation of Fixing Resin Emulsions PEM-1 to PEM-9>
A glass reaction vessel (capacity 3 L) equipped with a stirrer was equipped with a condenser, a thermometer, and a dropping funnel, and ion-exchanged water (150 parts), sodium dodecylbenzenesulfonate (1.4 parts), and potassium persulfate (0.4 parts) were added. 3) was prepared. After the air inside the reaction vessel was replaced with nitrogen, the internal temperature was adjusted to 80° C. while stirring, and the raw material solution was continuously added dropwise over 3 hours. During dropping of the raw material liquid, the internal temperature was maintained at 80° C. while introducing nitrogen. The raw material solution is ion-exchanged water (50 parts), Adekaria Soap SR-1025 (that is, [({α-[2-(allyloxy)-1-({C10-C14 alkyloxy}methyl)ethyl]- Oxiranes of {reaction products of C10-C14 branched chain alkanols and 1-(allyloxy)-2,3-epoxypropane} based on ω-hydroxypoly(n=1-100) (oxyethylene)} Sulfuric acid ester of polyadduct)] ammonium salt mixture) (1 part), sodium dodecylbenzenesulfonate (1 part), and the monomer mixture shown in Table 1 (100 parts) were previously mixed and stirred in a separate container. It was prepared by After the dropwise addition of the raw material solution was completed, the mixture was further stirred at 85°C for 2 hours, and then cooled to 40°C. After cooling, triethanolamine (0.8 parts) was added to give a fixing resin emulsion which was a pale suspension. The resulting fixing resin emulsions are named "PEM-1" to "PEM-9".

Table 1 below shows the solid content (%) and the glass transition point (Tg) of the fixing resin emulsions PEM-1 to PEM-9. The glass transition point was measured with a differential scanning calorimeter DSC Q2000 (TA Instruments) at a heating rate of 10°C/min. value.

The abbreviations of the respective monomers in Table 1 below represent the following. In addition, the numerical value in the column of each monomer represents the amount (parts) of the component used, and "-" means that the monomer is not used.
MMA: Methyl methacrylate MA: Methyl acrylate MAA: Methacrylic acid BA: Butyl acrylate AMA: Allyl methacrylate BMA: Butyl methacrylate

<Examples 1 to 5, Comparative Examples 1 to 2: Preparation of ink>
After mixing each component shown in Table 2 below, the mixture was filtered through a membrane filter with a pore size of 3 μm to obtain inks of Examples 1 to 5 and Comparative Examples 1 and 2 for evaluation tests.

The abbreviations of the respective components in Table 2 below represent the following. In addition, the numerical value in the column of each component represents the amount (part) of the component used, and "-" means that the component is not used.
DP1: Pigment dispersion DPnP: Dipropylene glycol monopropyl ether BDG: Diethylene glycol monobutyl ether BYK349: Silicone surfactant (BYK-349 manufactured by BYK)

<Evaluation>
[Resolubility evaluation test]
20 μL of each of the inks of Examples 1 to 5 and Comparative Examples 1 and 2 was dropped onto a glass petri dish (flat petri dish, diameter 94 mm×height 22 mm, model number FS-90B manufactured by AS ONE Co., Ltd.) using a micropipette. After that, the ink was dried in a constant temperature bath at 60° C. for 1 hour to obtain a dried ink product. A cleaning solution described in Example 2 of International Publication No. 2020/175033 was prepared, and 10 g of the cleaning solution was poured into a petri dish and allowed to stand for 2 hours. After that, the petri dish was shaken horizontally at 10 times/5 seconds with an amplitude of 2 cm, and whether or not the dried ink was dissolved was visually evaluated. The evaluation criteria were the following five stages. The results are shown in Table 3 below.
-Resolubility Evaluation Criteria-
A: No solid matter was observed, and no deposit was found on the petri dish.
B: No solid matter was observed, but deposits remained on the petri dish.
C: Solids with a maximum diameter of less than 5 mm remain, and deposits remain on the petri dish.
D: Solids with a maximum diameter of 5 mm or more remained, and deposits remained on the petri dish.
E: The dried ink product does not dissolve at all and remains on the petri dish.

[Water resistance evaluation test]
The inks of Examples 1 to 5 and Comparative Examples 1 and 2 were coated using an automatic coater (PI-1210 manufactured by Tester Sangyo Co., Ltd.). 3 was used, and the entire surface was coated on a PET film (manufactured by Toyobo Co., Ltd., E5102). After that, the film was dried in a constant temperature bath at 70° C. for 2 minutes to obtain a test print. The obtained test print was cut into a rectangle of 15 cm long×5.0 cm wide to obtain a test piece. Then, the abrasion resistance of each of the obtained test pieces was evaluated using No. 1 manufactured by Yasuda Seiki Seisakusho. It was evaluated using a 428 Gakushingata Color Fastness to Rubbing Tester. That is, while a wiper impregnated with ion-exchanged water was applied, the inkjet-recorded portion was rubbed 10 times, and the degree of deterioration of the image was evaluated according to the following 5-grade evaluation criteria. The results are shown in Table 3 below.
- Water resistance evaluation criteria -
A: Rubbing of the image cannot be confirmed.
B: The area of the colorant rubbed off is less than 40% of the printed portion.
C: The area of the colorant rubbed off is 40% or more and less than 60% of the printed portion.
D: The area of the colorant rubbed off is 60% or more and less than 80% of the printed portion.
E: The area of the colorant rubbed off is 80% or more of the printed portion.

[Inkjet printing evaluation test]
Using an inkjet head KJ4B-1200 (manufactured by Kyocera Corporation), the inks of Examples 1 to 5 were printed on paper and PET film. As a result, all of them exhibited good ink ejection properties, and good image formation was carried out.

As shown in Table 3, the inks of Examples 1 to 5 were able to obtain printed images with excellent water resistance even on PET films, and were also excellent in resolubility when dried.

Claims

containing a water-insoluble colorant, a dispersant, a fixing resin, and water;
The fixing resin is a resin obtained by polymerizing a monomer mixture containing butyl acrylate and at least one monomer selected from methyl methacrylate and methyl acrylate in the presence of a reactive emulsifier, An inkjet ink containing 0.1% by mass or more and less than 31.5% by mass of butyl acrylate in a monomer mixture.
The inkjet ink according to claim 1, wherein the monomer mixture further comprises at least one monomer selected from the group consisting of allyl methacrylate, butyl methacrylate, and sodium styrenesulfonate.
The inkjet ink according to claim 1, wherein the monomer mixture further comprises at least two monomers selected from the group consisting of allyl methacrylate, butyl methacrylate, and sodium styrenesulfonate.
An ink set comprising the inkjet ink according to any one of claims 1 to 3 and another inkjet ink different from the inkjet ink.
An ink media set comprising the inkjet ink according to any one of claims 1 to 3 or the ink set according to claim 4, and printing media.
A printing medium to which the inkjet ink according to any one of claims 1 to 3 or each inkjet ink included in the ink set according to claim 4 is adhered.