JP7647130B2 - Inkjet recording method, curable composition, ink, container, and two-dimensional or three-dimensional image forming apparatus - Google Patents

Description

The present invention relates to an inkjet recording method, a curable composition, an ink, a storage container, and a two-dimensional or three-dimensional image forming device.

Inkjet recording methods have become increasingly popular in recent years because they are capable of easily recording color images and have low running costs.
As inkjet recording inks, aqueous dye inks in which a dye is dissolved in an aqueous medium and solvent-based inks in which an oil-soluble dye is dissolved in an organic solvent are used. In general, from the viewpoint of environment and safety, inks in which a water-soluble dye is dissolved in water or in which water and a water-soluble organic solvent are used in offices and homes.
In addition, water-based pigment inks, in which pigments are dispersed in water in the form of fine particles, have been attracting attention. Inkjet recording inks using water-dispersible pigments are known to have excellent water resistance and light resistance.

In recent years, aqueous pigment inks have been proposed that contain water as a base agent and a radical-reactive polymerizable material with an acrylate structure as part of its structure, and that can form an ink film with abrasion resistance through a radical reaction (see, for example, Patent Document 1).

The present invention aims to provide an inkjet recording method that has excellent ejection properties, abrasion resistance, and beading suppression.

The above problem is solved by the following configuration 1).
1) a step of irradiating a curable composition containing, in order from the largest content (by mass) of components to the smallest content (by mass), water, a polymerizable compound, and a water-soluble polymerization initiator having a maximum absorption in a wavelength range of 300 nm or less with ultraviolet light from a light-emitting diode having a peak irradiance in a wavelength range of 265 to 300 nm, thereby curing the curable composition ;
The inkjet recording method according to claim 1, wherein the curable composition further contains a pigment .

The present invention provides an inkjet recording method that is excellent in ejection properties, abrasion resistance, and beading suppression.

FIG. 1 is a schematic diagram showing an example of an image forming apparatus according to the present invention. FIG. 2 is a schematic diagram showing another example of an image forming apparatus according to the present invention. FIG. 3 is a schematic diagram showing another example of an image forming apparatus according to the present invention.

Hereinafter, an embodiment of the present invention will be described.
The inkjet recording method of the present invention is characterized by comprising a step of irradiating a curable composition containing, in order from the largest content (by mass) of components, water, a polymerizable compound, and a water-soluble polymerization initiator having a maximum absorption in a wavelength region of 300 nm or less, with ultraviolet light from a light-emitting diode having a peak irradiance in a wavelength region of 265 to 300 nm, thereby curing the curable composition.

First, the curable composition will be described.
(Curable Composition)
The curable composition of the present invention contains, in order of the amount (by mass) of the components from the greatest to the least, water, a polymerizable compound, and a water-soluble polymerization initiator having a maximum absorption at a wavelength of 300 nm or less, and further contains other components as necessary.

The present inventors have investigated curable compositions that are excellent in terms of ejection properties, abrasion resistance, and beading suppression, and have obtained the following findings.
For example, inks containing conventional water-soluble polymerization initiators cannot be cured sufficiently with light-emitting diodes (LEDs), so high-pressure mercury lamps or metal halide lamps are used for curing. This makes the equipment larger, requires an exhaust system, and causes problems such as an increase in the temperature inside the machine due to heat generated by the lamps.
Therefore, the present inventors have found that the above-mentioned problems can be solved by adopting a process of using a water-soluble polymerization initiator having a maximum absorption in a wavelength region of 300 nm or less and curing the curable composition by irradiating it with ultraviolet light from a light-emitting diode having a peak irradiance in a wavelength region of 265 to 300 nm.

<Polymerizable Compound>
Examples of the polymerizable compound include polymerizable monomers and dimers having an acrylate group in the molecule, and polymer particles having a polymerizable group, and are compounds that can be polymerized in the presence of radicals.
Examples of the polymer particles having a polymerizable group include reactive polyurethane particles, etc. Examples of the reactive polyurethane particles include (meth)acrylated polyurethane particles, etc.
As the (meth)acrylated polyurethane particles, for example, commercially available products may be used. Examples of commercially available products include Ucecoat (registered trademark) 6558 (manufactured by Daicel-Allnex Corporation), Ucecoat (registered trademark) 6559 (manufactured by Daicel-Allnex Corporation), Ebecryl (registered trademark) 2002 (manufactured by Daicel-Allnex Corporation), Ebecryl (registered trademark) 2003 (manufactured by Daicel-Allnex Corporation), Ucecoat (registered trademark) 7710 (manufactured by Daicel-Allnex Corporation), and Ucecoat (registered trademark) 7720 (manufactured by Daicel-Allnex Corporation). (registered trademark) 7655 (manufactured by Daicel Allnex Corporation), NeoradR (registered trademark) 440 (manufactured by Avecia Corporation), NeoradR (registered trademark) 441 (manufactured by Avecia Corporation), NeoradR (registered trademark) 447 (manufactured by Avecia Corporation), NeoradR (registered trademark) 448 (manufactured by Avecia Corporation), Bayhydrol (registered trademark) UV2317 (manufactured by COVESTRO Corporation), Bayhydrol (registered trademark) UV Examples of the VP LS2348 (manufactured by COVESTRO), Lux (registered trademark) 430 (manufactured by ALBERDING BOLEY), Lux (registered trademark) 399 (manufactured by ALBERDING BOLEY), Lux (registered trademark) 484 (manufactured by ALBERDING BOLEY), Laromer (registered trademark) LR8949 (manufactured by BASF), Laromer (registered trademark) LR8983 (manufactured by BASF), Laromer (registered trademark) PE22WN (manufactured by BASF), Laromer (registered trademark) PE55WN (manufactured by BASF), Laromer (registered trademark) UA9060 (manufactured by BASF), and the like. Among these, Laromer (registered trademark) LR8949 (manufactured by BASF) and Laromer (registered trademark) LR8983 (manufactured by BASF) are preferred. Laromer (registered trademark) LR8949 (manufactured by BASF) and Laromer (registered trademark) LR8983 (manufactured by BASF) can improve abrasion resistance.
The polymer particles having a polymerizable group are preferably used in the form of a dispersion, and the polymer particles having a polymerizable group preferably account for 1 to 10% by mass of the polymerizable compound.

The polymerizable monomer is not particularly limited as long as it has a reactive substituent capable of undergoing a polymerization reaction, and can be appropriately selected depending on the purpose.
As the polymerizable monomer, for example, (meth)acrylate, (meth)acrylamide, vinyl ether, etc. can also be used in combination. More specifically, for example, ethylene glycol di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, γ-butyrolactone acrylate, isobornyl (meth)acrylate, formalized trimethylolpropane mono(meth)acrylate, polytetramethylene glycol di(meth)acrylate, trimethylolpropane (meth)acrylic acid benzoate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol diacrylate [CH ₂ ═CH—CO—(OC ₂ H ₄ )n-OCOCH═CH ₂ (n≈4)], polyethylene glycol diacrylate [CH _{2 ═CH} —CO—(OC ₂ H ₄ )n-OCOCH═CH ₂ (n≈9)], polyethylene glycol diacrylate [CH ₂ ═CH—CO—(OC ₂ H ₄ )n-OCOCH=CH ₂ (n≈14)], polyethylene glycol diacrylate [CH ₂ ≈CH-CO-(OC ₂ H ₄ )n-OCOCH=CH ₂ (n≈23)], dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol dimethacrylate [CH ₂ ≈C(CH ₃ )-CO-(OC ₃ H ₆ )n-OCOC(CH ₃ )=CH ₂ (n≒7)】, 1,3-butanediol di(meth)acrylate, 1,4-butanediol diacrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, neopentyl glycol diacrylate, tricyclodecane dimethanol diacrylate, propylene oxide modified bisphenol A di(meth)acrylate, polyethylene glycol di(meth)acrylate, dipentaerythritol hexa(meth)acrylate, (meth)acryloylmorpholine, propylene oxide modified tetramethylolmethane tetra(meth)acrylate, dipentaerythritol dipentaerythritol hydroxypenta(meth)acrylate, caprolactone modified dipentaerythritol hydroxypenta(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, trimethylolpropane triacrylate, ethylene oxide modified trimethylolpropane tri(meth)acrylate, propylene oxide modified trimethylolpropane tri(meth)acrylate, caprolactone modified trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, tris(2-hydroxyethyl)isocyanate anurate tri(meth)acrylate, neopentyl glycol diacrylate, ethoxylated neopentyl glycol di(meth)acrylate, propylene oxide modified neopentyl glycol di(meth)acrylate, propylene oxide modified glyceryl tri(meth)acrylate, polyester di(meth)acrylate, polyester tri(meth)acrylate, polyester tetra(meth)acrylate, polyester penta(meth)acrylate, polyester poly(meth)acrylate, polyurethane di(meth)acrylate, polyurethane tri(meth)acrylate, polyurethane tetra(meth)acrylate Examples of suitable acrylates include acrylate, polyurethane penta(meth)acrylate, polyurethane poly(meth)acrylate, 2-hydroxypropyl(meth)acrylamide, N-vinylcaprolactam, N-vinylpyrrolidone, N-vinylformamide, cyclohexane dimethanol monovinyl ether, cyclohexane dimethanol divinyl ether, hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, diethylene glycol divinyl ether, dicyclopentadiene vinyl ether, tricyclodecane vinyl ether, benzyl vinyl ether, and ethyloxetane methyl vinyl ether. Among these, the acrylate may be selected and added in consideration of the solubility in water as a dispersion medium, the viscosity of the composition, and the thickness of the cured film (coating film) on the substrate. In terms of solubility in water, acryloylmorpholine, dimethylaminopropylacrylamide, polyethylene glycol, or polypropylene glycol modified acrylate is preferred. These may be used alone or in combination of two or more.

<Water-soluble polymerization initiator>
The curable composition of the present invention contains a water-soluble polymerization initiator having a maximum absorption in a wavelength region of 300 nm or less. Here, the term "water-soluble" as used herein means that the solubility in 100 g of water at a temperature of 25° C. is 1 g or more. The water-soluble polymerization initiator is capable of generating active species such as radicals and cations by the energy of ultraviolet light and initiating the polymerization of a polymerizable compound (monomer or oligomer).
The water-soluble polymerization initiator is preferably a photopolymerization initiator having a hydroxyl group in the molecule, and among these, acetophenone-based, alkylphenone-based and monoacylphosphine oxide-based water-soluble polymerization initiators are preferred.
As the alkylphenone-based water-soluble polymerization initiator, from the viewpoint of improving the effects of the present invention, 2-hydroxy-2-methyl-1-phenylpropanone (Omnirad 1173 manufactured by IGM Resins BV, absorption wavelength peaks = 244 nm, 330 nm), 1-[4-(2-hydroxyethoxyl)-phenyl]-2-hydroxymethylpropanone (Omnirad 2959 manufactured by IGM Resins BV, absorption wavelength peaks = 274 nm, 330 nm), and the like are particularly preferred.

In the present invention, the maximum absorption of the water-soluble polymerization initiator can be measured using an ultraviolet-visible spectrophotometer.

In addition to the polymerization initiator, a polymerization accelerator (sensitizer) can also be used. The polymerization accelerator is not particularly limited, but is preferably, for example, an amine compound such as trimethylamine, methyldimethanolamine, triethanolamine, p-diethylaminoacetophenone, ethyl p-dimethylaminobenzoate, 2-ethylhexyl p-dimethylaminobenzoate, N,N-dimethylbenzylamine, or 4,4'-bis(diethylamino)benzophenone, and the content thereof may be appropriately set depending on the polymerization initiator used and its amount.

<Water>
The water content in the curable composition is not particularly limited and may be appropriately selected depending on the purpose. From the viewpoints of the drying property and discharge reliability of the curable composition, the water content is preferably from 10% by mass to 90% by mass, and more preferably from 20% by mass to 60% by mass.

The curable composition of the present invention contains the above-mentioned water, polymerizable compound, and water-soluble polymerization initiator in the order of the content (mass) of the component from the most to the least. From the viewpoint of improving the effects of the present invention, the content of the polymerizable compound in the curable composition of the present invention is preferably 10 mass% or more, and more preferably 10 to 40 mass%. From the viewpoint of improving the effects of the present invention, the content of the water-soluble polymerization initiator in the curable composition of the present invention is preferably 0.5 mass% or more, and more preferably 0.5 to 1.0 mass%.

In addition, if the ratio of the water-soluble polymerization initiator to the polymerizable compound is 1:8 to 1:40, preferably 1:10 to 1:30 by mass, the curability is improved, which is preferable.

In addition to the above components, the curable composition of the present invention may contain the following components as needed.

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

Polyol compounds having 8 or more carbon atoms and glycol ether compounds are also suitably used. Specific examples of polyol compounds having 8 or more carbon atoms include 2-ethyl-1,3-hexanediol and 2,2,4-trimethyl-1,3-pentanediol.
Specific examples of the glycol ether compound include polyhydric alcohol alkyl ethers such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, and propylene glycol monoethyl ether; and polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether.

Polyol compounds with 8 or more carbon atoms and glycol ether compounds can improve the permeability of ink when paper is used as the recording medium.

The content of the organic solvent in the curable composition is not particularly limited and can be appropriately selected depending on the purpose, but from the viewpoint of the drying property and discharge reliability of the curable composition, it is preferably 10% by mass or more and 60% by mass or less, and more preferably 20% by mass or more and 60% by mass or less.

<Coloring material>
The curable composition of the present invention may contain a coloring material. As the coloring material, various pigments and dyes that impart glossy colors such as black, white, magenta, cyan, yellow, green, orange, gold, and silver can be used depending on the purpose and required characteristics of the composition of the present invention. The content of the coloring material may be appropriately determined in consideration of the desired color concentration and dispersibility in the composition, and is not particularly limited, but is preferably 0.1 to 20% by mass with respect to the total mass (100% by mass) of the composition. The curable composition of the present invention may be colorless and transparent without containing a coloring material, and in that case, it is suitable as an overcoat layer for protecting an image, for example.
As the pigment, an inorganic pigment or an organic pigment can be used, and one type may be used alone, or two or more types may be used in combination.
Examples of inorganic pigments that can be used include carbon blacks (C.I. Pigment Black 7) such as furnace black, lamp black, acetylene black, and channel black, iron oxide, and titanium oxide.
Examples of organic pigments include azo pigments such as insoluble azo pigments, condensed azo pigments, azo lakes, and chelate azo pigments; polycyclic pigments such as phthalocyanine pigments, perylene and perinone pigments, anthraquinone pigments, quinacridone pigments, dioxane pigments, thioindigo pigments, isoindolinone pigments, and quinophthalone pigments; dye chelates (e.g., basic dye chelates, acid dye chelates, etc.); dye lakes (basic dye lakes, acid dye lakes), nitro pigments, nitroso pigments, aniline black, and daylight fluorescent pigments.
In order to improve the dispersibility of the pigment, a dispersant may be further included. The dispersant is not particularly limited, but examples thereof include dispersants commonly used in preparing pigment dispersions, such as polymer dispersants.
As the dye, for example, acid dyes, direct dyes, reactive dyes, and basic dyes can be used, and one type of dye may be used alone, or two or more types may be used in combination.

<Pigment Dispersion>
It is possible to obtain a curable composition by mixing a pigment with materials such as water or an organic solvent. It is also possible to manufacture a curable composition by mixing a pigment with other materials such as water or a dispersant to prepare a pigment dispersion, and then mixing the pigment with materials such as water or an organic solvent.
The pigment dispersion is obtained by dispersing water, a pigment, a pigment dispersant, and other components as required, and adjusting the particle size. Dispersion is preferably performed using a dispersing machine.
The particle size of the pigment in the pigment dispersion is not particularly limited, but in terms of improving the dispersion stability of the pigment and improving the image quality such as ejection stability and image density, the maximum frequency calculated as the maximum number is preferably 20 nm or more and 500 nm or less, and more preferably 20 nm or more and 150 nm or less. The particle size of the pigment can be measured using a particle size analyzer (Nanotrac Wave-UT151, manufactured by Microtrac Bell Co., Ltd.).
The content of the pigment in the pigment dispersion is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoints of obtaining good ejection stability and increasing image density, the content of the pigment is preferably from 0.1% by mass to 50% by mass, and more preferably from 0.1% by mass to 30% by mass.
It is preferable that the pigment dispersion is degassed, if necessary, by filtering coarse particles using a filter, a centrifugal separator, or the like.

<Resin>
The type of resin contained in the curable composition is not particularly limited and can be appropriately selected depending on the purpose. Examples of the resin include urethane resin, polyester resin, acrylic resin, vinyl acetate resin, styrene resin, butadiene resin, styrene-butadiene resin, vinyl chloride resin, acrylic styrene resin, and acrylic silicone resin.
Resin particles made of these resins may be used. The resin particles may be mixed with materials such as coloring materials and organic solvents in a resin emulsion state in which the resin particles are dispersed using water as a dispersion medium to obtain a curable composition. The resin particles may be appropriately synthesized or may be commercially available. These may be used alone or in combination of two or more types of resin particles.

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

There are no particular limitations on the resin content, and it can be selected appropriately depending on the purpose. From the viewpoint of fixation and storage stability of the curable composition, however, it is preferably from 1% by mass to 30% by mass, more preferably from 5% by mass to 20% by mass, based on the total amount of the curable composition.

There are no particular limitations on the particle size of the solid content in the curable composition and it can be appropriately selected depending on the purpose, but in terms of improving image quality such as ejection stability and image density, the maximum frequency in terms of maximum number is preferably 20 nm or more and 1000 nm or less, and more preferably 20 nm or more and 150 nm or less. The solid content includes resin particles, pigment particles, etc. The particle size can be measured using a particle size analyzer (Nanotrac Wave-UT151, manufactured by Microtrac Bell Co., Ltd.).

<Additives>
If necessary, surfactants, antifoaming agents, antiseptic and antifungal agents, rust inhibitors, pH adjusters, etc. may be added to the curable composition.

<Surfactant>
As the surfactant, any of silicone-based surfactants, fluorine-based surfactants, amphoteric surfactants, nonionic surfactants, and anionic surfactants can be used.
Silicone surfactants are not particularly limited and can be appropriately selected according to purpose. Among them, those that do not decompose even at high pH are preferred, such as side chain modified polydimethylsiloxane, both end modified polydimethylsiloxane, one end modified polydimethylsiloxane, side chain both end modified polydimethylsiloxane, etc., and those having polyoxyethylene group or polyoxyethylene polyoxypropylene group as modified group are particularly preferred because they show good properties as aqueous surfactants. In addition, polyether modified silicone surfactants can also be used as the silicone surfactant, such as a compound in which a polyalkylene oxide structure is introduced into the Si part side chain of dimethylsiloxane.
As the fluorine-based surfactant, for example, perfluoroalkyl sulfonic acid compound, perfluoroalkyl carboxylic acid compound, perfluoroalkyl phosphate compound, perfluoroalkyl ethylene oxide adduct, and polyoxyalkylene ether polymer compound having perfluoroalkyl ether group in the side chain are particularly preferred because they have low foaming properties.As the perfluoroalkyl sulfonic acid compound, for example, perfluoroalkyl sulfonic acid, perfluoroalkyl sulfonate, etc. can be mentioned.As the perfluoroalkyl carboxylic acid compound, for example, perfluoroalkyl carboxylic acid, perfluoroalkyl carboxylate, etc. can be mentioned.As the polyoxyalkylene ether polymer compound having perfluoroalkyl ether group in the side chain, for example, sulfate ester salt of polyoxyalkylene ether polymer having perfluoroalkyl ether group in the side chain, salt of polyoxyalkylene ether polymer having perfluoroalkyl ether group in the side chain, etc. can be mentioned. Examples of counter ions of the salts in these fluorosurfactants include _Li , Na, K, _NH4 , _NH3CH2CH2OH , _NH2 ( _{CH2CH2OH ) 2} , and _NH ( _CH2CH2OH ) _{3 .}
Examples of amphoteric surfactants include lauryl aminopropionate, lauryl dimethyl betaine, stearyl dimethyl betaine, and lauryl dihydroxyethyl betaine.
Examples of nonionic surfactants include polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl esters, polyoxyethylene alkylamines, polyoxyethylene alkylamides, polyoxyethylene propylene block polymers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, and ethylene oxide adducts of acetylene alcohol.
Examples of the anionic surfactant include polyoxyethylene alkyl ether acetates, dodecylbenzene sulfonates, laurates, and polyoxyethylene alkyl ether sulfates.
These may be used alone or in combination of two or more.

The silicone surfactant is not particularly limited and can be appropriately selected depending on the purpose. Examples of the silicone surfactant include side-chain modified polydimethylsiloxane, both-end modified polydimethylsiloxane, one-end modified polydimethylsiloxane, and both-end side-chain modified polydimethylsiloxane. Polyether-modified silicone surfactants having a polyoxyethylene group or a polyoxyethylene polyoxypropylene group as a modifying group are particularly preferred because they exhibit good properties as an aqueous surfactant.
Such surfactants may be synthesized appropriately or may be commercially available products, such as those available from BYK-Chemie Co., Ltd., Shin-Etsu Chemical Co., Ltd., Dow Corning Toray Silicone Co., Ltd., Nippon Emulsion Co., Ltd., and Kyoeisha Chemical Co., Ltd.
The polyether-modified silicone surfactant is not particularly limited and can be appropriately selected depending on the purpose. For example, it can be a surfactant represented by the general formula (S-1) in which a polyalkylene oxide structure is introduced into the Si part side chain of dimethylpolysiloxane.

(In the general formula (S-1), m, n, a, and b represent integers. R and R' represent alkyl and alkylene groups.)

As the polyether-modified silicone surfactant, commercially available products can be used, such as KF-618, KF-642, KF-643 (Shin-Etsu Chemical Co., Ltd.), EMALEX-SS-5602, SS-1906EX (Nihon Emulsion Co., Ltd.), FZ-2105, FZ-2118, FZ-2154, FZ-2161, FZ-2162, FZ-2163, FZ-2164 (Dow Corning Toray Silicone Co., Ltd.), BYK-33, BYK-387 (BYK-Chemie Co., Ltd.), TSF4440, TSF4452, TSF4453 (Toshiba Silicon Co., Ltd.), etc.

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

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

General formula (F-2)
C _n F _2n+1- CH ₂ CH(OH)CH ₂ -O-(CH ₂ CH ₂ O) _a -Y
In the compound represented by the above general formula (F-2), Y is H, or CnF _2n+1 where n is an integer from 1 to 6, or CH ₂ CH(OH)CH ₂ -CnF _2n+1 where n is an integer from 4 to 6, or CpH _2p+1 where p is an integer from 1 to 19. a is an integer from 4 to 14.

As the fluorine-based surfactant, commercially available products may be used. Examples of such commercially available products include Surflon S-111, S-112, S-113, S-121, S-131, S-132, S-141, and S-145 (all manufactured by Asahi Glass Co., Ltd.); Fullard FC-93, FC-95, FC-98, FC-129, FC-135, FC-170C, FC-430, and FC-431 (all manufactured by Sumitomo 3M Limited); Megafac F-470, F-1405, and F-474 (all manufactured by Dainippon Ink and Chemicals, Inc.); Zonyl TBS, FSP, FSA, FSN-100, and F SN, FSO-100, FSO, FS-300, UR (all manufactured by DuPont); FT-110, FT-250, FT-251, FT-400S, FT-150, FT-400SW (all manufactured by Neos Co., Ltd.), Polyfox PF-136A, PF-156A, PF-151N, PF-154, PF-159 (manufactured by Omnova), Unidyne DSN-403N (manufactured by Daikin Industries, Ltd.), and the like are preferred. Among these, DuPont is particularly preferred because of its excellent printing quality, particularly its color development, penetrability into paper, wettability, and uniform dyeing. Particularly preferred are FS-300 manufactured by Pont, FT-110, FT-250, FT-251, FT-400S, FT-150, and FT-400SW manufactured by Neos Co., Ltd., Polyfox PF-151N manufactured by Omnova, and Unidyne DSN-403N manufactured by Daikin Industries, Ltd.

The content of the surfactant in the curable composition is not particularly limited and can be appropriately selected depending on the purpose, but from the viewpoint of excellent wettability and ejection stability and improved image quality, it is preferably 0.001% by mass or more and 5% by mass or less, and more preferably 0.05% by mass or more and 5% by mass or less.

<Other ingredients>
The curable composition of the present invention may contain other known components as necessary. The other components are not particularly limited, but examples thereof include conventionally known polymerization inhibitors, leveling agents, defoamers, fluorescent brighteners, penetration promoters, wetting agents (moisturizing agents), fixing agents, viscosity stabilizers, antifungal agents, preservatives, antioxidants, ultraviolet absorbers, chelating agents, pH adjusters, and thickeners.

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

<Anti-septic and anti-fungal agents>
The antiseptic and antifungal agent is not particularly limited, and examples thereof include 1,2-benzisothiazolin-3-one.

<Rust inhibitor>
The rust inhibitor is not particularly limited, and examples thereof include acid sulfite and sodium thiosulfate.

<Curing means>
The curable composition of the present invention is cured by irradiation with ultraviolet light from a light-emitting diode having a peak irradiance in the wavelength range of 265 to 300 nm.
The maximum illuminance on the recording medium can be, for example, 100 to 1000 mJ/cm ² , and is preferably 100 to 500 mJ/cm ² .
From the viewpoint of beading, it is preferable to irradiate the curable composition with ultraviolet light for a period of 0.1 sec to 0.6 sec after the composition is discharged onto the recording medium.

<Preparation of Curable Composition>
The curable composition of the present invention can be prepared using the various components described above. The preparation means and conditions are not particularly limited. For example, the composition can be prepared by putting water, a polymerizable compound, a pigment, a dispersant, etc. into a dispersing machine such as a ball mill, a Kitty mill, a disk mill, a pin mill, or a Dyno mill, dispersing the ingredients to prepare a pigment dispersion, and further mixing a polymerizable compound, a water-soluble polymerization initiator, a polymerization inhibitor, a surfactant, etc. into the pigment dispersion.

<Viscosity>
The viscosity of the curable composition of the present invention may be adjusted appropriately depending on the application and application means, and is not particularly limited. For example, when a discharge means is used that discharges the composition from a nozzle, the viscosity in the range of 20°C to 65°C, desirably the viscosity at 25°C is preferably 3 to 40 mPa·s, more preferably 5 to 15 mPa·s, and particularly preferably 6 to 12 mPa·s. It is particularly preferable that the viscosity range is satisfied without containing the organic solvent. The viscosity can be measured by using a cone-plate type rotational viscometer VISCOMETER TVE-22L manufactured by Toki Sangyo Co., Ltd., using a cone rotor (1°34'×R24), at a rotation speed of 50 rpm, and by appropriately setting the temperature of the constant temperature circulating water in the range of 20°C to 65°C. A VISCOMATE VM-150III can be used to adjust the temperature of the circulating water.

<Applications>
The use of the curable composition of the present invention is not particularly limited as long as it is in a field in which ultraviolet ray curable materials are generally used, and can be appropriately selected depending on the purpose. Examples of the use include molding resins, paints, adhesives, insulating materials, release agents, coating materials, sealing materials, various resists, various optical materials, etc.
Furthermore, the curable composition of the present invention can be used as an ink to form two-dimensional characters and images, and design coatings on various substrates, and can also be used as a material for three-dimensional modeling to form a three-dimensional image (three-dimensional object). This material for three-dimensional modeling may be used, for example, as a binder between powder particles used in a powder lamination method in which a three-dimensional modeling is performed by repeatedly curing and laminating powder layers, or may be used as a three-dimensional construction material (model material) or a support member (support material) used in a layered modeling method (photo-modeling method) as shown in FIG. 2 or FIG. 3. FIG. 2 shows a method of discharging the curable composition of the present invention into a predetermined area, irradiating it with ultraviolet rays, and sequentially laminating the cured product to perform three-dimensional modeling (described in detail later), and FIG. 3 shows a method of irradiating ultraviolet rays 4 to a storage pool (container) 1 of the curable composition 5 of the present invention to form a cured layer 6 of a predetermined shape on a movable stage 3, and sequentially laminating the cured layer 6 to perform three-dimensional modeling.
As a three-dimensional modeling apparatus for forming a three-dimensional object using the curable composition of the present invention, a known one can be used, and is not particularly limited. For example, the three-dimensional modeling apparatus may be one equipped with a means for storing, supplying, and discharging the composition, and an ultraviolet ray irradiation means.
The present invention also includes a molded article obtained by processing a cured product obtained by curing the curable composition or a structure formed on a substrate with the cured product. The molded article is, for example, a cured product or structure formed in a sheet or film shape, which is molded by heat stretching, punching, or the like, and is suitable for use in applications requiring molding after surface decoration, such as meters and operation panels for automobiles, office automation equipment, electric and electronic devices, and cameras.
The substrate is not particularly limited and can be appropriately selected depending on the purpose. Examples of the substrate include paper, thread, fiber, cloth, leather, metal, plastic, glass, wood, ceramics, and composite materials thereof. From the viewpoint of processability, a plastic substrate is preferred.

<Recording media>
The recording medium used for recording is not particularly limited, but examples thereof include plain paper, glossy paper, special paper, cloth, film, OHP sheets, general-purpose printing paper, and the like.

<Containment container>
The container of the present invention means a container in which the curable composition is contained, and is suitable for the above-mentioned applications. For example, when the curable composition of the present invention is used for ink, the container containing the ink can be used as an ink cartridge or ink bottle, which eliminates the need to directly touch the ink during ink transport, ink replacement, and other operations, and can prevent the dirt on hands, fingers, and clothing. In addition, it is possible to prevent foreign matter such as dust from being mixed into the ink. In addition, the shape, size, material, and the like of the container itself may be suitable for the application and usage, and are not particularly limited, but it is preferable that the material is a light-shielding material that does not transmit light, or that the container is covered with a light-shielding sheet or the like.

<Image forming method and apparatus>
The image forming method of the present invention comprises an irradiation means for irradiating ultraviolet light, which is a light emitting diode (LED) having a peak illuminance in the wavelength range of 265 to 300 nm, and a storage section for storing the curable composition or ink of the present invention, and the storage section may store the container. The method may further comprise a discharge step and a discharge means for discharging the curable composition. The discharge method is not particularly limited, and examples thereof include a continuous jet type and an on-demand type. Examples of the on-demand type include a piezo type, a thermal type, and an electrostatic type.

FIG. 1 shows an example of an image forming apparatus equipped with an inkjet ejection means. The ink is ejected onto a recording medium 22 supplied from a supply roll 21 by color printing units 23a, 23b, 23c, and 23d equipped with ink cartridges and ejection heads for yellow, magenta, cyan, and black curable inks. After that, the ink is cured by irradiating it with ultraviolet rays from light sources 24a, 24b, 24c, and 24d for curing the ink, forming a color image. It is preferable to provide a distance between the ejection head and the light source to adjust the time until the ultraviolet rays are irradiated. The distance is preferably 10 cm to 200 cm, and more preferably 30 cm to 100 cm. By providing this distance, it is possible to control beading.
Thereafter, the recording medium 22 is transported to a processing unit 25 and a print take-up roll 26. Each of the printing units 23a, 23b, 23c, and 23d may be provided with a heating mechanism so that the ink is liquefied in the ink ejection section. If necessary, a mechanism for cooling the recording medium to about room temperature by contact or non-contact may be provided. In addition, as the inkjet recording method, either a serial method in which the head is moved to eject ink onto the recording medium, which moves intermittently according to the ejection head width, or a line method in which the recording medium is moved continuously and ink is ejected onto the recording medium from a head held at a fixed position, may be applied.

The recording medium 22 is not particularly limited, but may be paper, film, ceramics, glass, metal, composite materials thereof, etc., and may be in sheet form. It may also be configured to allow single-sided printing only, or double-sided printing. It is not limited to materials commonly used as recording media, and cardboard, building materials such as wallpaper and flooring, concrete, cloth for clothing such as T-shirts, textiles, leather, etc. may be used as appropriate.

Furthermore, the ultraviolet light irradiation from light sources 24a, 24b, and 24c may be weakened or omitted, and after printing multiple colors, ultraviolet light may be irradiated from light source 24d. This can save energy and reduce costs.

Recorded items recorded with the curable composition of the present invention include not only those printed on smooth surfaces such as ordinary paper or resin film, but also those printed on uneven printing surfaces and those printed on printing surfaces made of various materials such as metals and ceramics. In addition, by laminating two-dimensional images, it is also possible to form images with a partially three-dimensional effect (images that are two-dimensional and three-dimensional) or three-dimensional objects.

Figure 2 is a schematic diagram showing an example of another image forming apparatus (apparatus for forming a three-dimensional solid image) according to the present invention. The image forming apparatus 39 in Figure 2 uses a head unit (movable in the AB direction) in which inkjet heads are arranged, and ejects a first curable composition from the ejection head unit for a model 30, ejects a second curable composition having a different composition from the first curable composition from the ejection head units for a support 31, 32, and layers these compositions while curing them with the adjacent ultraviolet irradiation means 33, 34. More specifically, for example, the second curable composition is discharged from the support head units 31 and 32 onto the object support substrate 37, and solidified by irradiating ultraviolet rays to form a first support layer having a reservoir. The first curable composition is then discharged from the object discharge head unit 30 into the reservoir, and solidified by irradiating ultraviolet rays to form a first object layer. This process is repeated multiple times while lowering the vertically movable stage 38 according to the number of layers to be stacked, thereby stacking the support layer and the object layer to produce a three-dimensional object 35. Thereafter, the support layer 36 is removed as necessary. Note that in FIG. 2, only one object discharge head unit 30 is provided, but two or more can be provided.

(ink)
The ink of the present invention comprises the curable composition of the present invention.

(Cured product)
The cured product of the present invention is formed using at least one of the curable composition of the present invention and the ink of the present invention.

<Recordings>
The ink recorded matter of the present invention comprises an image formed on a recording medium using the ink of the present invention.
A recorded matter can be obtained by recording using an inkjet recording apparatus and an inkjet recording method.

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

The following describes examples of the present invention, but the present invention is not limited to these examples.

- Preparation example of cyan pigment dispersion -
After the inside of a 1 L flask equipped with a mechanical stirrer, a thermometer, a nitrogen gas inlet tube, a reflux condenser, and a dropping funnel was thoroughly replaced with nitrogen gas, 11.2 parts by mass of styrene, 2.8 parts by mass of acrylic acid, 12.0 parts by mass of lauryl methacrylate, 4.0 parts by mass of polyethylene glycol methacrylate, 4.0 parts by mass of styrene macromer, and 0.4 parts by mass of mercaptoethanol were mixed and heated to 65°C.
Next, a mixed solution of 100.8 parts by mass of styrene, 25.2 parts by mass of acrylic acid, 108.0 parts by mass of lauryl methacrylate, 36.0 parts by mass of polyethylene glycol methacrylate, 60.0 parts by mass of hydroxylethyl methacrylate, 36.0 parts by mass of styrene macromer, 3.6 parts by mass of mercaptoethanol, 2.4 parts by mass of azobismethylvaleronitrile, and 18 parts by mass of methyl ethyl ketone was dropped into the flask over 2.5 hours. After dropping, a mixed solution of 0.8 parts by mass of azobismethylvaleronitrile and 18 parts by mass of methyl ethyl ketone was dropped into the flask over 0.5 hours. After aging at 65 ° C. for 1 hour, 0.8 parts by mass of azobismethylvaleronitrile was added and further aged for 1 hour. After the reaction was completed, 364 parts by mass of methyl ethyl ketone was added to the flask to obtain 800 parts by mass of polymer solution A having a concentration of 50% by mass.
Next, 28 parts by mass of the obtained polymer solution A, 26 parts by mass of phthalocyanine pigment (Dainichiseika Chemicals Co., Ltd., Chromofine Blue A-220JC), 13.6 parts by mass of 1 mol/L potassium hydroxide aqueous solution, 20 parts by mass of methyl ethyl ketone, and 13.6 parts by mass of ion-exchanged water were thoroughly stirred, and then kneaded using a roll mill to obtain a paste. The obtained paste was put into 200 parts by mass of pure water, thoroughly stirred, and then methyl ethyl ketone and water were distilled off using an evaporator. Furthermore, in order to remove coarse particles, this dispersion was pressure-filtered through a polyvinylidene fluoride membrane filter with an average pore size of 5.0 μm to obtain a pigment-containing polymer fine particle dispersion containing 15% by mass of pigment and 20% by mass of solids. The average particle diameter (D ₅₀ ) of the polymer fine particles in the obtained pigment dispersion was measured. The average particle diameter (D ₅₀ ) measured with a particle size distribution measuring device (Nanotrac UPA-EX150, manufactured by Nikkiso Co., Ltd.) was 56.0 nm.

Example 1
- Preparation of Inkjet Ink 1 -
The water-soluble organic solvent (wetting agent) and water shown in Table 1 below were mixed and stirred for 1 hour to obtain a homogeneous mixture. A polymerizable compound was added thereto and stirred for 1 hour, and then a pigment dispersion, a water-soluble polymerization initiator, and a surfactant were added and stirred for 1 hour. This dispersion was pressure-filtered through a polyvinylidene fluoride membrane filter with an average pore size of 5.0 μm to remove coarse particles and dust, thereby preparing inkjet ink 1.

(Examples 2 to 6)
--Preparation of Inkjet Inks 2 to 6--
Ink-jet inks 2 to 6 were obtained in the same manner as in Example 1, except that the compositions in Example 1 were changed to those shown in Table 1.
Next, the obtained ink-jet inks 1 to 9 were measured and evaluated for "ejection property,""beading," and "abrasion resistance" as follows. The results are shown in Table 2.

<Printing device>
A single-pass printing device equipped with a Ricoh MH5220 head was prepared, and a solid image chart was printed. A UV-LED lamp with airtight SMDs with maximum wavelengths of 265 nm, 285 nm, and 325 nm was installed 50 cm from the head on the single-pass printing machine, and a hot air dryer was installed 150 cm from the head, allowing UV irradiation while printing. The printing conditions were head gap 2 mm, discharge amount per drop 16 pl, 600 dpi, and deposition amount 8.9 g/ ^m2 , and the image pattern was a 5 cm x 20 cm solid image.
Under environmental conditions adjusted to 23±0.5° C. and 50±5% RH, an inkjet recording device was used, and the driving voltage of the piezoelectric element was varied and set so that the same amount of ink was deposited on a commercially available PET film (film thickness 100 μm).
The UV integrated light amount can be adjusted as desired by changing the media transport speed. The illuminance was measured using a Heraeus UV PowerPack II. The time from ink droplet ejection to UV irradiation was set to 0.5 seconds. The distance between the inkjet ink ejection head and the irradiation unit that irradiates ultraviolet light from a light-emitting diode was set to 50 cm.

<Dischargeability>
The obtained inkjet inks were ejected continuously for 2 minutes using an inkjet ejection device equipped with an MH5220 head (manufactured by Ricoh Co., Ltd.). After confirming that all inks were ejected, the inks were left to stand for 5 minutes, and then the number of nozzles that had missed nozzles after 1000 ejections was counted and the "ejectability" was evaluated based on the following evaluation criteria. A and B were acceptable.
The ink jet ejection device was set to a driving frequency of 18 kHz, a heating temperature of 25° C., and an ink ejection amount of 15 pL per ejection.

[Evaluation Criteria]
A: 3 or less B: 4 to less than 20 C: 20 or more

<Beading evaluation>
A solid image of 5 cm x 20 cm was printed using a single pass printing apparatus equipped with the Ricoh head MH5220, and the presence or absence of color unevenness in the image was evaluated as beading. A and B are acceptable.

[Evaluation Criteria]
A: No beading is visible. B: Some beading is visible, but not a problem (not visible from 1m away).
C: Severe beading is visible (visible from 1m away)

<Abrasion resistance>
A 5 cm x 20 cm solid image was printed using a single-pass printing device equipped with the Ricoh head MH5220, and then dried with hot air for 30 seconds from a distance of 20 cm using a plastic jet manufactured by Ishizaki Electric Manufacturing Co., Ltd. Next, the prepared cured product and a test attachment white cloth (Canakin No. 3) conforming to JIS L 0803 were attached to a friction fastness tester RT-300 (manufactured by Daiei Scientific Instruments Co., Ltd.) (a device conforming to the friction tester type II (Gakushin type) specified in the dye fastness test method (JIS L-0849)), and a weight of 500 g was attached, and the cured product was rubbed back and forth 100 times. The density of the cotton cloth after the test was measured with an eXact Scan (manufactured by X-Rite), and the density difference with the cotton cloth that was not tested was evaluated. The measurement results were evaluated based on the following evaluation criteria. A and B ratings are pass.

[Evaluation Criteria]
A: 0.02 or less B: More than 0.02 and less than 0.2 C: More than 0.2

The results in Tables 1 and 2 show that the inks prepared in each Example were cured by irradiating each ink with ultraviolet light from a light-emitting diode with a peak irradiance in the wavelength range of 265 to 300 nm, and the inks were found to have excellent ejection properties, abrasion resistance, and beading suppression.

The details of each component shown in Table 1 are as follows.
2-hydroxy-2-methyl-1-phenylpropanone: Hydroxyacetophenone-based water-soluble polymerization initiator N,N'-Methylenebismethacrylamide: Water-soluble monomer Laromer LR 8983: Reactive urethane dispersion (manufactured by BASF) (The solid content is shown in Table 1)
Surfynol 440: surfactant (manufactured by Nissin Chemical Industry Co., Ltd.)

1. Storage pool (containment area)
3 Movable stage 4 Active energy rays 5 Active energy ray curable composition 6 Cured layer 21 Supply roll 22 Recording medium 23a, 23b, 23c, 23d Each color printing unit 24a, 24b, 24c, 24d Light source 25 Processing unit 26 Printed matter take-up roll 30 Discharge head unit for object 31, 32 Discharge head unit for support 33, 34 Ultraviolet ray irradiation means 35 Three-dimensional object 36 Support layer 37 Object support substrate 38 Stage 39 Image forming device

JP 2018-83352 A

Claims (8)

the method includes a step of irradiating a curable composition containing, in order from the largest content (mass) of components to the smallest content (mass) of components, water, a polymerizable compound, and a water-soluble polymerization initiator having a maximum absorption in a wavelength range of 300 nm or less, with ultraviolet light from a light-emitting diode having a peak irradiance in a wavelength range of 265 to 300 nm, thereby curing the curable composition;
The inkjet recording method according to claim 1, wherein the curable composition further contains a pigment. The inkjet recording method according to claim 1, characterized in that the curable composition contains 50% by mass or more of the water, 10% by mass or more of the polymerizable compound, and 0.5% by mass or more of the water-soluble polymerization initiator. The inkjet recording method according to claim 1 or 2, characterized in that the ratio of the water-soluble polymerization initiator to the polymerizable compound is 1:8 to 1:40 in terms of the mass ratio of the former:the latter. The inkjet recording method according to any one of claims 1 to 3, characterized in that the content of the polymerizable compound in the curable composition is 10% by mass or more and 20% by mass or less. The inkjet recording method according to any one of claims 1 to 4, characterized in that the curable composition further contains polymer particles having a polymerizable group. The inkjet recording method according to any one of claims 1 to 5, characterized in that after the curable composition is ejected onto the recording medium, the ultraviolet light is irradiated for an irradiation time of 0.1 sec to 0.6 sec. The inkjet recording method according to any one of claims 1 to 6, characterized in that a distance is provided between the ejection head of the curable composition and an irradiation unit that irradiates ultraviolet light from a light-emitting diode in order to adjust the time until the ultraviolet light is irradiated. The present invention has a storage section for storing a curable composition or an ink comprising the curable composition in a container, and an irradiation section for irradiating ultraviolet light from a light emitting diode having a peak irradiance in a wavelength range of 265 to 300 nm ,
The curable composition contains, in order from the most abundant component to the least abundant component, water, a polymerizable compound, and a water-soluble polymerization initiator having a maximum absorption at a wavelength of 300 nm or less, and further contains a pigment;
A two-dimensional or three-dimensional image forming apparatus for carrying out the ink jet recording method according to any one of claims 1 to 7.

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