Inkjet ink, methods for producing pigment dispersion and inkjet ink, method for forming cured product, and cured product

Abstract

To provide an inkjet ink comprising a phosphorescent pigment, wherein the inkjet ink allows formation of a cured body with sufficiently high brightness and suppresses occurrence of nozzle failure.SOLUTION: An inkjet ink includes a polymerizable compound and a phosphorescent pigment, and further contains a dispersant having an acidic functional group, the inkjet ink being cured by irradiation of active energy rays. A pigment dispersion for an inkjet ink may be produced by kneading, in a grinder, a composition containing a polymerizable compound, a phosphorescent pigment, and a dispersant.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an inkjet ink, a method for producing a pigment dispersion, a method for producing an inkjet ink, a method for forming a cured product, and the cured product. [Background technology]

[0002] There are known phosphorescent pigments that absorb light of a specific wavelength, store the energy of the light, and emit light of a different wavelength for a long period of time even after the absorption of light has stopped (see, for example, Patent Document 1). There is also known a method of applying an inkjet head containing this phosphorescent pigment to a substrate to produce a phosphorescent cured product (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-210337 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-28484 Summary of the Invention [Problem to be solved by the invention]

[0004] It is expected that the use of inkjet inks containing luminous pigments will enable the production of highly precise patterned cured products. Incidentally, luminous cured products need to be thick to sufficiently increase their brightness. However, according to the findings of the present inventors, the brightness of luminous cured products saturates and does not increase any further once the film thickness reaches a certain level. Therefore, there is a need to develop a method for improving the brightness of luminous cured products.

[0005] Furthermore, ink containing a phosphorescent pigment is prone to clogging nozzles when ejected from an inkjet head, resulting in nozzle failure.

[0006] The present invention relates to an inkjet ink containing a phosphorescent pigment. The present invention provides an inkjet ink that can produce a cured product with sufficiently high brightness and is less likely to cause nozzle shortages. Another object of the present invention is to provide a method for producing a pigment dispersion and a method for producing the inkjet ink. Another object of the present invention is to provide a method for forming a cured product using the inkjet ink, and a cured product formed by this method. [Means for solving the problem]

[0007] One aspect of the present invention for solving the above problems relates to the following inkjet inks [1] to [9]. [1] A composition comprising a polymerizable compound, a phosphorescent pigment, and a dispersant having an acidic functional group, Inkjet ink that hardens when exposed to actinic radiation. [2] The phosphorescent pigment is an aluminate phosphor. [1] The inkjet ink according to [1]. [3] The phosphorescent pigment is at least one aluminate phosphor selected from the group consisting of calcium aluminate, strontium aluminate, and barium aluminate; [1] or [2]. The inkjet ink according to [1] or [2]. [4] The phosphorescent pigment is SrAl2O4 containing europium (Eu) and dysprosium (Dy) as activators, or Sr4Al containing europium (Eu) and dysprosium (Dy) as activators. 14 O 25 That is, The inkjet ink according to any one of [1] to [3]. [5] The concentration of the phosphorescent pigment is 5% by mass or more and 40% by mass or less. The inkjet ink according to any one of [1] to [4]. [6] The phosphorescent pigment is a particle having a median diameter of 2.0 μm or more and 5.0 μm or less. The inkjet ink according to any one of [1] to [5]. [7] The dispersant has an acid value of 30 mg KOH / g or more and 200 mg KOH / g or less. The inkjet ink according to any one of [1] to [6]. [8] The dispersant is a dispersant having a phosphate group or a carboxyl group. The inkjet ink according to any one of [1] to [7]. [9] The dispersant is a dispersant having a carboxyl group. The inkjet ink according to any one of [1] to [8].

[0008] Another aspect of the present invention for solving the above problems relates to the following methods for producing a pigment dispersion

[10] to

[11] .

[10] A composition containing a polymerizable compound, a phosphorescent pigment, and a dispersant is kneaded using a grinder. A method for producing a pigment dispersion for an inkjet ink.

[11] A step of dry-pulverizing the phosphorescent pigment, In the kneading step, a composition containing a polymerizable compound, the dry-ground phosphorescent pigment, and a dispersant is kneaded.

[10] A method for producing the pigment dispersion according to

[10] .

[0009] Another aspect of the present invention for solving the above problems relates to the following method for producing an inkjet ink

[12] .

[12] A step of preparing a pigment dispersion produced by the method for producing a pigment dispersion according to

[10] or

[11] ; and mixing the prepared pigment dispersion with a polymerizable compound. A method for manufacturing inkjet ink.

[0010] Another aspect of the present invention for solving the above problems relates to the following method for forming a cured product

[13] .

[13] A step of ejecting the inkjet ink according to any one of [1] to [9] from an inkjet head and applying it to a substrate; and curing the inkjet ink applied to the substrate by irradiating it with actinic rays. Method for forming a cured product.

[0011] Another aspect of the present invention for solving the above problems relates to the cured products of the following items

[14] and

[15] .

[14] A cured product formed by curing the inkjet ink according to any one of [1] to [9].

[15] The thickness is 0.3 mm or more and 1.5 mm or less.

[14] The cured product according to

[14] . [Effects of the Invention]

[0012] According to the present invention, there is provided an inkjet ink containing a phosphorescent pigment. According to the present invention, there is provided an inkjet ink that can produce a cured product with sufficiently high brightness and is less likely to cause nozzle shortage. According to the present invention, there are provided a method for producing a pigment dispersion and a method for producing the inkjet ink. According to the present invention, there are provided a method for forming a cured product using the inkjet ink, and a cured product formed by the method. DETAILED DESCRIPTION OF THE INVENTION

[0013] 1. Inkjet ink One embodiment of the present invention relates to an inkjet ink (hereinafter simply referred to as "ink") containing a polymerizable compound, a phosphorescent pigment, and a dispersant. The ink is an actinic ray-curable ink that cures upon exposure to actinic rays. Each component will be described below.

[0014] 1-1. Phosphorescent pigments A phosphorescent pigment absorbs light of a specific wavelength and stores the light energy. Even after the absorption of light is stopped, the stored light energy is emitted for a long time as light of a different wavelength from the absorbed light. In other words, a phosphorescent pigment is a pigment that emits phosphorescence. The ink may contain only one type of phosphorescent pigment, or two or more types of phosphorescent pigments.

[0015] There are no particular limitations on the phosphorescent pigment as long as it has the above characteristics. Examples of phosphorescent pigments include those in which the host crystal of a metal compound has been activated.

[0016] Examples of the host crystal include metal sulfides such as zinc sulfide, calcium sulfide, germanium sulfide, strontium sulfide, and yttrium sulfide. Examples of the host crystal further include metal oxides such as calcium oxide, strontium oxide, barium oxide, alumina, and cerium oxide. Examples of the host crystal include aluminates such as calcium aluminate, strontium aluminate, and barium aluminate.

[0017] Examples of the activator used to activate the mother crystal include europium, terbium, yttrium, zirconium, dysprosium, and barium, among which europium and dysprosium are preferred.

[0018] Of these, from the viewpoint of improving dispersibility with an acidic dispersant described later, it is preferable that the phosphorescent pigment is a phosphor containing an aluminate. Furthermore, from the viewpoint of improving dispersibility with an acidic dispersant described later, it is preferable that the phosphorescent pigment is a phosphor containing calcium aluminate, strontium aluminate, or barium aluminate. Furthermore, from the viewpoint of improving dispersibility with an acidic dispersant described later, it is preferable that the phosphorescent pigment is a phosphor containing SrAl2O4 or Sr4Al containing europium (Eu) and dysprosium (Dy) as an activator. 14 O 25 It is preferable that:

[0019] The peak wavelength of the excitation spectrum of the phosphorescent pigment is preferably 300 nm or more and 400 nm or less. When the peak wavelength of the excitation spectrum of the phosphorescent pigment is in this range, the phosphorescent pigment can be sufficiently excited by sunlight, making the cured product more suitable for outdoor use.

[0020] The peak wavelength of the emission spectrum of the phosphorescent pigment can be, for example, from 400 nm to 700 nm, and from the viewpoint of further enhancing the visibility of the cured product, it is preferably from 450 nm to 600 nm.

[0021] The median diameter of the phosphorescent pigment in the ink is not particularly limited and can be 0.2 μm or more and 20.0 μm or less. The median diameter of the phosphorescent pigment is preferably 1.0 μm or more and 10.0 μm or less, more preferably 1.0 μm or more and 5.0 μm or less, and even more preferably 1.5 μm or more and 3 μm or less. The larger the median diameter, the easier it is to increase the brightness of the cured product. The smaller the median diameter, the easier it is to disperse the phosphorescent pigment and improve the ejection properties from an inkjet head.

[0022] The median diameter of a phosphorescent pigment is the particle size at which the cumulative value in the volume-based particle size distribution reaches 50% (D 50 ) can be used.

[0023] The particle size (D 90 ) can be 1.0 μm or more and 20 μm or less, preferably 1.5 μm or more and 10 μm or less, and more preferably 2.0 μm or more and 8 μm or less. 90 The smaller the value, the easier it is for the phosphorescent pigment to disperse, and the easier it is to eject from an inkjet head.

[0024] In addition, phosphorescent pigments are 50 / D 90 is preferably 0.2 or more and 0.8 or less, and more preferably 0.3 or more and 0.6 or less. 50 / D 90 The smaller the particle size distribution, the more densely packed the luminescent pigments can be in a cured product, and the more improved the weather resistance of the cured product can be.

[0025] In addition, the phosphorescent pigment D 50 and D 90can be a value measured using a particle size measuring device, for example, LUMiSizer, manufactured by LUM Japan Co., Ltd.

[0026] The content of the phosphorescent pigment may be set depending on the application of the phosphorescent pigment. For example, the content of the phosphorescent pigment may be 5% by mass or more and 70% by mass or less, preferably 5% by mass or more and 40% by mass or less, and more preferably 10% by mass or more and 30% by mass or less, relative to the total mass of the ink. The higher the content of the phosphorescent pigment, the higher the brightness of the cured product. The lower the content of the phosphorescent pigment, the better the ink ejection properties.

[0027] 1-2. Dispersants The dispersant is a dispersant for dispersing the phosphorescent pigment. The ink may contain only one type of dispersant, or may contain two or more types of dispersants. The dispersant may be a polymer dispersant or a low molecular weight dispersant, but a polymer dispersant is preferred.

[0028] The dispersant contains an acidic dispersant having an acidic functional group as a functional group that adsorbs to the phosphorescent pigment. The ink may contain only one type of acidic dispersant, or two or more types of acidic dispersants. The acidic dispersant may be a polymeric dispersant or a low-molecular-weight dispersant, but is preferably a polymeric dispersant.

[0029] Actinic ray-curable inks that are cured by exposure to actinic rays can form cured products with high robustness, allowing for the production of cured products with high durability. Furthermore, phosphorescent pigments are susceptible to degradation by water. Therefore, actinic ray-curable inks that do not require water are less susceptible to degradation of phosphorescent pigments during storage than water-based inks, and the brightness of the cured product is less likely to decrease even after long-term storage.

[0030] On the other hand, the cured product formed by curing the actinic ray-curable ink functions as both a light-emitting layer that holds the luminescent pigment and a light-blocking layer. In other words, the luminescent pigment particles in the cured product may block light emitted from other luminescent pigments. Furthermore, the thicker the cured product, the more likely it is that light emitted from a luminescent pigment will be blocked by other luminescent pigments before it is released outside the cured product. In this way, it is thought that when the film thickness of the cured product is increased to a certain extent, the brightness saturates, and it becomes difficult to increase the brightness even if the film thickness is increased.

[0031] The phosphorescent pigment is formed from a basic compound such as a metal sulfide, metal oxide, or aluminate. Therefore, in this embodiment, an acidic dispersant is used as the dispersant for dispersing the phosphorescent pigment. Acidic dispersants have good adsorption properties to the phosphorescent pigment, which is thought to enhance the dispersibility of the phosphorescent pigment. As a result of the enhanced dispersibility of the phosphorescent pigment, the phosphorescent pigment is dispersed sparsely in the cured product, reducing the likelihood of light being blocked by other phosphorescent pigments. Furthermore, the enhanced dispersibility of the phosphorescent pigment reduces the likelihood of clogging the nozzles of the inkjet head, improving the ink's ejection performance. Furthermore, the enhanced dispersibility of the phosphorescent pigment reduces the likelihood of sedimentation of the phosphorescent pigment in the ink, improving the ink's fluidity and circulation within the inkjet head.

[0032] From the viewpoint of improving the dispersibility of the phosphorescent pigment and more effectively improving the brightness of the cured product and the ejection properties of the ink, the acidic dispersant preferably has an acid value of 30 mgKOH / g or more and 300 mgKOH / g or less, more preferably 30 mgKOH / g or more and 200 mgKOH / g or less, and even more preferably 50 mgKOH / g or more and 150 mgKOH / g or less.

[0033] The acid value of an acidic dispersant can be measured using an automatic titrator (Hiranuma Sangyo COM-555). 80 mL of acetone and 10 mL of water are added to 0.5 to 1 g of sample solution and stirred to dissolve uniformly. This sample solution is titrated with a 0.1 mol / L KOH aqueous solution to measure the acid value (mgKOH / g) of the sample solution. The acid value per solid of the sample is then calculated from the acid value of the sample solution and its solid concentration.

[0034] The acidic functional group possessed by the acidic dispersant is not particularly limited. Examples of the acidic functional group include a phosphate group, a carboxyl group, and a sulfonic acid group. Of these, from the viewpoint of improving the dispersibility of the phosphorescent pigment and more effectively improving the brightness of the cured product and the jetting properties of the ink, the phosphate group and the carboxyl group are preferred, and the carboxyl group is more preferred.

[0035] The type of functional group contained in the acidic dispersant can be measured by a conventional method.

[0036] Examples of acidic dispersants include Marialim SC0505K, SC1015F, and AKM-0531 manufactured by NOF Corporation ("Marialim" is a registered trademark of the company). Other examples of acidic dispersants include Efka FA4620 manufactured by BASF ("Efka" is a registered trademark of the company). Other examples of acidic dispersants include Solsperse S41000 and S79000 manufactured by Lubrizol ("Solsperse" is a registered trademark of the company).

[0037] The content of the acidic dispersant is preferably 0.01% by mass or more and 20% by mass or less, more preferably 1% by mass or more and 10% by mass or less, and even more preferably 1% by mass or more and 5% by mass or less, relative to the total mass of the phosphorescent pigment.

[0038] 1-3. Polymerizable compounds and photopolymerization initiators 1-3-1. Polymerizable compound The polymerizable compound may be a radically polymerizable compound or a cationically polymerizable compound, or a combination of a radically polymerizable compound and a cationically polymerizable compound may be used.

[0039] The radically polymerizable compound is a compound (monomer, oligomer, polymer, or a mixture thereof) having a radically polymerizable ethylenically unsaturated bond.

[0040] Examples of the compound having a radically polymerizable ethylenically unsaturated bond include unsaturated carboxylic acids and their salts, unsaturated carboxylic acid ester compounds, unsaturated carboxylic acid urethane compounds, unsaturated carboxylic acid amide compounds and their anhydrides, acrylonitrile, styrene, unsaturated polyesters, unsaturated polyethers, unsaturated polyamides, and unsaturated urethanes. Examples of unsaturated carboxylic acids include (meth)acrylic acid, itaconic acid, crotonic acid, isocrotonic acid, and maleic acid.

[0041] Among these, the radical polymerizable compound is preferably an unsaturated carboxylic acid ester compound, more preferably a (meth)acrylate. The (meth)acrylate may be not only a monomer described below, but also an oligomer, a mixture of a monomer and an oligomer, a modified product, an oligomer having a polymerizable functional group, or the like.

[0042] Examples of monofunctional (meth)acrylates include isoamyl (meth)acrylate, stearyl (meth)acrylate, isobornyl (meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, isomylstyryl (meth)acrylate, isostearyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, 2-ethylhexyl-diglycol (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-(meth)acryloyloxyethyl hexahydrophthalate, butoxyethyl (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, methoxydiethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, methoxypropylene glycol (meth)acrylate, o-phenylenediamine (meth)acrylate, methyl ... phenoxyethyl (meth)acrylate, m-phenoxybenzyl (meth)acrylate, cyclic trimethylolpropane formal (meth)acrylate, ethoxylated phenoxy (meth)acrylate, alkoxylated phenol (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, isobornyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-hydroxy-o-phenylphenolpropyl (meth)acrylate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxyethyl-2-hydroxyethyl-phthalate, and t-butylcyclohexyl (meth)acrylate.

[0043] Examples of polyfunctional (meth)acrylates include triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, tricyclodecane dimethanol diacrylate, dimethylol-tricyclodecane di(meth)acrylate, bisphenol A di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, bisphenol fluorene diacrylate (A-BPEF), bisphenol A di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, bisphenol fluorene diacrylate (A-BPEF), bisphenol B di(meth)acrylate, bisphenol C di(meth)acrylate, bisphenol B ... Examples of the acrylates include bifunctional (meth)acrylates such as phenol A type 10EO-modified diacrylate, bisphenol A type diacrylate, bisphenol A type PO-modified diacrylate, bisphenol A type EO-modified diacrylate, polytetramethylene glycol di(meth)acrylate, polyethylene glycol diacrylate, dipropylene glycol diacrylate, and tripropylene glycol diacrylate, as well as trifunctional or higher functional (meth)acrylates such as trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, glycerin propoxy tri(meth)acrylate, and pentaerythritol ethoxy tetra(meth)acrylate.

[0044] The (meth)acrylate may be a modified product. Examples of modified (meth)acrylates include ethylene oxide-modified (meth)acrylates such as ethylene oxide-modified trimethylolpropane tri(meth)acrylate and ethylene oxide-modified pentaerythritol tetraacrylate, caprolactone-modified (meth)acrylates such as caprolactone-modified trimethylolpropane tri(meth)acrylate, and caprolactam-modified (meth)acrylates such as caprolactam-modified dipentaerythritol hexa(meth)acrylate.

[0045] The (meth)acrylate may be a polymerizable oligomer. Examples of the (meth)acrylate that is a polymerizable oligomer include an epoxy (meth)acrylate oligomer, an aliphatic urethane (meth)acrylate oligomer, an aromatic urethane (meth)acrylate oligomer, a polyester (meth)acrylate oligomer, and a linear (meth)acrylic oligomer.

[0046] Examples of the cationically polymerizable compound include an epoxy compound, a vinyl ether compound, and an oxetane compound.

[0047] Examples of the epoxy compound include alicyclic epoxy resins such as 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate, bis(3,4-epoxycyclohexylmethyl)adipate, vinylcyclohexene monoepoxide, ε-caprolactone-modified 3,4-epoxycyclohexylmethyl 3',4'-epoxycyclohexanecarboxylate, 1-methyl-4-(2-methyloxiranyl)-7-oxabicyclo[4,1,0]heptane, 2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexanone-meta-dioxane and bis(2,3-epoxycyclopentyl)ether, diglycidyl ether of 1,4-butanediol, diglycidyl ether of 1,6-hexanediol, triglyceride of glycerin, and the like. Examples of epoxy compounds include aliphatic epoxy compounds including glycidyl ethers of polyether polyols obtained by adding one or more alkylene oxides (such as ethylene oxide and propylene oxide) to aliphatic polyhydric alcohols such as ethylene glycol, propylene glycol, and glycerin, as well as di- or polyglycidyl ethers of bisphenol A or its alkylene oxide adducts, di- or polyglycidyl ethers of hydrogenated bisphenol A or its alkylene oxide adducts, and novolac-type epoxy resins.

[0048] Examples of the vinyl ether compound include monovinyl ether compounds such as ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, octadecyl vinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexanedimethanol monovinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, isopropenyl ether-o-propylene carbonate, dodecyl vinyl ether, diethylene glycol monovinyl ether, and octadecyl vinyl ether; and di- or trivinyl ether compounds such as ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, cyclohexanedimethanol divinyl ether, and trimethylolpropane trivinyl ether.

[0049] Examples of the oxetane compound include 3-hydroxymethyl-3-methyloxetane, 3-hydroxymethyl-3-ethyloxetane, 3-hydroxymethyl-3-propyloxetane, 3-hydroxymethyl-3-n-butyloxetane, 3-hydroxymethyl-3-phenyloxetane, 3-hydroxymethyl-3-benzyloxetane, 3-hydroxyethyl-3-methyloxetane, 3-hydroxyethyl-3-ethyloxetane, 3-hydroxyethyl-3-propyloxetane, 3-hydroxyethyl 3-phenyloxetane, 3-hydroxypropyl-3-methyloxetane, 3-hydroxypropyl-3-ethyloxetane, 3-hydroxypropyl-3-propyloxetane, 3-hydroxypropyl-3-phenyloxetane, 3-hydroxybutyl-3-methyloxetane, 1,4 bis{[(3-ethyl-3-oxetanyl)methoxy]methyl}benzene, 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane, and di[1-ethyl(3-oxetanyl)]methyl ether.

[0050] The polymerizable compound preferably contains a monofunctional compound having an aromatic ring in the molecule. A polymerizable compound having an aromatic ring in the molecule can improve the storage stability of the ink and reduce nozzle clogging. Furthermore, a polymerizable compound having an aromatic ring in the molecule can improve the dispersibility of the phosphorescent pigment in the ink and increase the brightness of the cured product. Furthermore, a monofunctional compound is less likely to increase the viscosity of the ink.

[0051] The content of the monofunctional polymerizable compound having an aromatic ring is preferably 20% by mass or more and 80% by mass or less, and more preferably 25% by mass or more and 60% by mass or less, based on the total mass of the ink.

[0052] Examples of the monofunctional polymerizable compound having an aromatic ring include phenol 4EO-modified acrylate, 2-phenoxyethyl acrylate, m-phenoxybenzyl acrylate, EO-modified o-phenylphenol acrylate, benzyl acrylate, cumylphenoxyethyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate, and 2-hydroxy-o-phenylphenolpropyl acrylate.

[0053] The content of the polymerizable compound is preferably 50% by mass or more and 97% by mass or less, and more preferably 60% by mass or more and 95% by mass or less, based on the total mass of the polymerizable ink.

[0054] 1-3-2. Photopolymerization initiator The photopolymerization initiator can be a radical initiator when the polymerizable ink contains a radically polymerizable compound, or a cationic initiator (photoacid generator) when the polymerizable ink contains a cationic polymerizable compound. Note that when polymerization is initiated by irradiation with an electron beam, the polymerizable ink does not need to contain a photopolymerization initiator.

[0055] Examples of radical polymerization initiators include hydrogen abstraction type photopolymerization initiators, intramolecular cleavage type photopolymerization initiators, etc. Hydrogen abstraction type photopolymerization initiators include intramolecular hydrogen abstraction type photopolymerization initiators, intermolecular hydrogen abstraction type photopolymerization initiators, etc.

[0056] An intramolecular hydrogen abstraction photopolymerization initiator is a photopolymerization initiator that is excited by irradiation with active energy rays and undergoes an intramolecular hydrogen abstraction reaction to generate radicals. Examples of intramolecular hydrogen abstraction photopolymerization initiators include methyl benzoylformate-based photopolymerization initiators such as methyl phenylglyoxylate, and oxyphenyl-based photopolymerization initiators such as a mixture of oxyphenylacetic acid-2-[2-oxo-2-phenylacetoxy-ethoxy]ethyl ester and oxyphenylacetic acid 2-[2-hydroxy-ethoxy]ethyl ester. Among these, compounds having a glyoxylic acid structure such as methyl benzoylformate-based photopolymerization initiators are preferred because they are less likely to abstract hydrogen from the molecular chain of the polymerizable compound during polymerization.

[0057] Examples of commercially available intramolecular hydrogen abstraction photopolymerization initiators include Omnirad MBF and Omnirad 754 (both manufactured by IGM Resins, and "Omnirad" is a registered trademark of the company).

[0058] Intermolecular hydrogen abstraction photopolymerization initiators are photopolymerization initiators that are excited by irradiation with active energy rays such as ultraviolet rays and abstract hydrogen from other molecules to generate radicals. Examples of intermolecular hydrogen abstraction photopolymerization initiators include benzophenone-based initiators such as benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4,4'-dichlorobenzophenone, hydroxybenzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide, acrylated benzophenone, 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone, and 3,3'-dimethyl-4-methoxybenzophenone, as well as thioxanthone-based initiators such as 2-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, and 2,4-dichlorothioxanthone.

[0059] Commercially available examples of intermolecular hydrogen abstraction photopolymerization initiators include Omnirad 500 (manufactured by IGM Resins) and Speedcure ITX (manufactured by Sartomer, "Speedcure" is a registered trademark of Arkema France).

[0060] Examples of the intramolecular cleavage type photopolymerization initiator include acetophenone-based initiators such as 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzil dimethyl ketal, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone, 1-hydroxycyclohexyl-phenyl ketone, 2-methyl-2-morpholino(4-methylthiophenyl)propan-1-one, and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone; benzoin-based initiators such as benzoin, benzoin methyl ether, and benzoin isopropyl ether; and acylphosphine oxide-based initiators such as 2,4,6-trimethylbenzoin diphenylphosphine oxide and bis(2,4,6-trimethylbenzoin)phenylphosphine oxide.

[0061] Commercially available examples of intramolecular cleavage type photoinitiators include Omnirad 127, Omnirad 184, Omnirad 651, Omnirad 2959, Omnirad 819, and Esacure One.

[0062] The content of the photopolymerization initiator is preferably 3% by mass or more and 20% by mass or less, based on the total mass of the polymerizable compound. The content of the photopolymerization initiator is more preferably 3% by mass or more and 15% by mass or less, even more preferably 3% by mass or more and 10% by mass or less, and particularly preferably 5% by mass or more and 10% by mass or less, based on the total mass of the polymerizable compound. By making the content 3% by mass or more, the curability and adhesion of the polymerizable ink can be further improved.

[0063] 1-4.Other ingredients The ink may further contain other ingredients such as organic pigments, dyes, surfactants, optical brighteners, gelling agents, and polymerization inhibitors.

[0064] Examples of organic pigments include red pigments, yellow pigments, blue pigments, white pigments, etc., which are used in inks for forming images. Known pigments can be used for these pigments. Examples of dyes include red dyes, yellow dyes, blue dyes, etc., which are used in inks for forming images. Known dyes can be used for these dyes.

[0065] Examples of surfactants include anionic surfactants such as dialkyl sulfosuccinates, alkyl naphthalene sulfonates, and fatty acid salts. Examples of surfactants further include nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, and polyoxyethylene-polyoxypropylene block copolymers. Examples of surfactants further include cationic surfactants such as alkylamine salts and quaternary ammonium salts, as well as silicone-based and fluorine-based surfactants.

[0066] The content of the surfactant is not particularly limited, but can be, for example, 0.001% by mass or more and less than 1.0% by mass relative to the total mass of the ink.

[0067] A gelling agent is a compound that causes ink to gel at room temperature (25°C) and to sol when heated (e.g., 80°C). For example, the gelling agent is preferably a compound that dissolves in the liquid components (such as polymerizable compounds and organic solvents) contained in the ink at a temperature higher than the gelation temperature of the ink and crystallizes at a temperature lower than the gelation temperature of the ink. The gelation temperature refers to the temperature at which the ink undergoes a phase transition from sol to gel and the viscosity of the ink suddenly changes when the ink, which has been solated or liquefied by heating, is cooled. Specifically, the temperature at which the viscosity suddenly increases when the ink is cooled while measuring the viscosity with a rheometer (e.g., MCR300 manufactured by Anton Paar), can be determined as the gelation temperature of the ink.

[0068] Examples of gelling agents include ketone waxes, ester waxes, petroleum waxes, vegetable waxes, animal waxes, mineral waxes, hydrogenated castor oil, modified waxes, higher fatty acids, higher alcohols, hydroxystearic acid, fatty acid amides including N-substituted fatty acid amides and special fatty acid amides, higher amines, esters of sucrose fatty acids, synthetic waxes, dibenzylidene sorbitol, dimer acid and dimer diol.

[0069] The content of the gelling agent is preferably 1.0% by mass or more and 10.0% by mass or less, more preferably 2.0% by mass or more and 7.5% by mass or less, and even more preferably 2.0% by mass or more and 3.5% by mass or less, relative to the total mass of the ink.

[0070] Examples of the polymerization inhibitor include N-oxyl-based polymerization inhibitors, phenol-based polymerization inhibitors, quinone-based polymerization inhibitors, amine-based polymerization inhibitors, copper dithiocarbamate-based polymerization inhibitors, etc. The ink may contain only one type of polymerization inhibitor, or two or more types of polymerization inhibitors in combination.

[0071] Examples of N-oxyl polymerization inhibitors include 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO), 4-hydroxy-2,2,6,6-tetramethyl-piperidine-N-oxyl, 4-oxo-2,2,6,6-tetramethyl-piperidine-N-oxyl, 4-methoxy-2,2,6,6-tetramethyl-piperidine-N-oxyl, 4-acetoxy-2,2,6,6-tetramethyl-piperidine-N-oxyl, etc. An example of a commercially available N-oxyl polymerization inhibitor is Irgastab UV10 (manufactured by BASF ("Irgastab" is a registered trademark of the company)).

[0072] Examples of the phenolic polymerization inhibitor include 2,6-di-tert-butylphenol, 2,4-di-tert-butylphenol, 2-tert-butyl-4,6-dimethylphenol, 2,6-di-tert-butyl-4-methylphenol, 2,4,6-tri-tert-butylphenol, 2,6-di-t-butyl-p-cresol (butylated hydroxytoluene: BHT), 4-methoxyphenol, and 2-methoxy-4-methylphenol.

[0073] Examples of the quinone polymerization inhibitor include hydroquinone, methoxyhydroquinone, benzoquinone, 1,4-naphthoquinone, p-tert-butylcatechol, and the like.

[0074] Examples of the amine polymerization inhibitor include alkylated diphenylamine, N,N'-diphenyl-p-phenylenediamine, phenothiazine, and the like.

[0075] Examples of copper dithiocarbamate polymerization inhibitors include copper dimethyldithiocarbamate, copper diethyldithiocarbamate, copper dibutyldithiocarbamate, and the like.

[0076] The content of the polymerization inhibitor is not particularly limited, but can be, for example, 0.01% by mass or more and 0.5% by mass or less relative to the total mass of the ink.

[0077] 1-5. Ink properties The ink has a volume resistivity of 10 11 It is preferable that the cured film can be formed to a resistivity of Ω·m or more. The surface resistivity of the cured film can be measured using a Hiresta UX (MCP-HT800, manufactured by Nitto Seiko Analytech Co., Ltd.).

[0078] 1-6. Ink preparation method The ink can be prepared by mixing the above-mentioned components. In this case, the phosphorescent pigment, acidic dispersant, and a small amount of polymerizable compound may be kneaded together to prepare a pigment dispersion first, and the remaining polymerizable compound and other components may then be added to the resulting pigment dispersion. In this case, in order to increase the solubility of the dispersant and other components, it is preferable to prepare the dispersion by mixing the phosphorescent pigment and acidic dispersant while heating them.

[0079] The pigment dispersion can be prepared using a homogenizer, a grinder, a wet atomizer, a bead mill, or the like.

[0080] Of these, a grinder is preferred. A grinder can disperse the phosphorescent pigment while reducing its particle size. This reduces the proportion of coarse particles in the pigment dispersion and ink, and allows the acidic dispersant to be effectively adsorbed onto the phosphorescent pigment, significantly improving the brightness of the cured product and the jettability of the ink. Furthermore, unlike a bead mill or the like, a grinder is less likely to cause damage to the equipment when dispersing a hard phosphorescent pigment. Furthermore, unlike a jet mill or the like, a grinder can disperse the phosphorescent pigment together with the polymerizable compound.

[0081] The preparation of the pigment dispersion using a grinder may be carried out in a single step or in multiple steps. When carried out in multiple steps, the phosphorescent pigment, acidic dispersant, and a small amount of polymerizable compound may be subjected to a first-step dispersion treatment, after which the polymerizable compound is added and a second-step dispersion treatment is carried out. Alternatively, to make it easier to disperse the phosphorescent pigment, the first-step dispersion treatment (dry grinding) may be carried out on the phosphorescent pigment alone, after which the acidic dispersant and polymerizable compound are added and a second-step dispersion treatment may be carried out once or multiple times.

[0082] For preparing the ink by mixing with other components, a homogenizer, a ceramic grinder, a wet atomizer, or the like can be used.

[0083] 2. Method for forming the cured product The ink described above can be applied to a substrate by an ink jet method and cured to form a cured product.

[0084] The application of the ink to the substrate can be carried out by ejecting the ink from an inkjet head and causing it to land on the substrate.

[0085] The ejection method from the inkjet head may be either an on-demand method or a continuous method. On-demand inkjet heads may be electro-mechanical conversion types such as single-cavity, double-cavity, bender, piston, shear mode, and shared wall types. On-demand inkjet heads may also be electro-thermal conversion types such as thermal inkjet and bubble jet ("Bubble Jet" is a registered trademark of Canon Inc.).

[0086] These inkjet heads or image forming apparatuses having inkjet heads may be configured to circulate ink inside or outside the inkjet head.

[0087] Furthermore, the printer for forming the cured product may have a mechanism for stirring the ink inside the inkjet head or in the flow path between the main tank and the inkjet head in order to redisperse the phosphorescent pigment.

[0088] The type of substrate is not particularly limited, and may be, for example, paper, resin film, ABS resin plate, acrylic resin plate, aluminum plate, glass plate, polycarbonate plate, cloth, etc. The shape of the substrate is not particularly limited, and may be a plate, film, sheet, or various three-dimensional shapes. In addition, the composition may be applied to a space formed inside the substrate by various methods.

[0089] The ink can be cured by irradiating it with active energy rays, which polymerize and crosslink the polymerizable compound. Examples of active energy rays include electron beams, ultraviolet rays, α rays, γ rays, and X-rays. Of these, ultraviolet rays and electron beams are preferred. The ultraviolet rays are preferably light having a peak wavelength of 360 nm or more and 410 nm or less. The ultraviolet rays are preferably emitted from an LED light source. LEDs emit less radiant heat than conventional light sources (e.g., metal halide lamps). Therefore, when LEDs are used, the ink is less likely to melt when irradiated with active energy rays, making it less likely to produce uneven gloss.

[0090] When ultraviolet rays are used as active energy rays, the light intensity per irradiation is 500 mJ / cm 2 More than 4000mJ / cm 2 It is preferable that the dose is 500 mJ / cm or less. 2 When the intensity is 4000 mJ / cm or more, the curability of the polymerizable compound can be improved. 2 If the content is less than this, discoloration of the cured product can be suppressed.

[0091] When forming a thick cured product, the application and curing of the ink may be repeated.

[0092] After the cured product is produced in this manner, a protective film may be formed to cover the cured product using a varnish, a laminate film, an ink, or the like, or the product may be post-processed into a desired shape.

[0093] The thickness of the cured product thus formed is preferably 0.3 mm or more and 1.5 mm or less. Increasing the thickness of the cured product can increase the brightness of the cured product. In this embodiment, since an acidic dispersant is used, brightness is less likely to saturate even when the thickness is increased, and it is possible to form a cured product with a larger thickness and further increase brightness. [Example]

[0094] The present invention will be specifically described below with reference to examples, but the scope of the present invention is not limited to the descriptions in the examples.

[0095] 1. Prepare ingredients Inkjet inks were prepared using the following materials:

[0096] 1-1. Polymerizable compounds Monomer 1: Dipropylene glycol diacrylate Monomer 2: Phenol 4EO modified acrylate

[0097] 1-2. Photopolymerization initiator Initiator 1: Omnirad MBF, manufactured by IGM RESINS BV Initiator 2: Omnirad 819 (intramolecular cleavage type), manufactured by IGM Resins BV

[0098] 1-3. Phosphorescent pigments Glow-in-the-dark pigment 1: Luminova G-300FF manufactured by Nemoto Specialty Chemical Co., Ltd. ("Luminova" is a registered trademark of the company) Glow-in-the-dark pigment 2: Luminova BGL-300FF, manufactured by Nemoto Specialty Chemical Co., Ltd. Glow-in-the-dark pigment 3: Luminova G-300F, manufactured by Nemoto Specialty Chemical Co., Ltd.

[0099] 1-4. Dispersants Dispersant 1: Marialim SC0505K, manufactured by NOF Corporation ("Marialim" is a registered trademark of the company) Dispersant 2: Efka FA4620 manufactured by BASF ("Efka" is a registered trademark of the company) Dispersant 3: Solsperse S41000 manufactured by Lubrizol ("Solsperse" is a registered trademark of the company) Dispersant 4: Lubrizol Solsperse S79000 Dispersant 5: Marialim SC1015F, manufactured by NOF Corporation Dispersant 6: Marialim AKM-0531, manufactured by NOF Corporation Dispersant 7: BASF Efka PX4701 Dispersant 8: BASF Efka PX4703

[0100] 1-5.Other ingredients Polymerization inhibitor: BASF Irgastab UV-10 (Irgastab is a registered trademark of the company)

[0101] 2. Ink Preparation 2-1. Preparation of Ink 1 to Ink 12, Ink 18 and Ink 19 2-1-1. Preparation of pigment dispersion 50 parts by mass of phosphorescent pigment 1, 2.5 parts by mass of dispersant 1, and 47.5 parts by mass of monomer 1 were placed in a polypropylene container along with 50 parts by mass of zirconia beads with an average particle size of 0.3 mm. The mixture was then dispersed for 30 minutes using a paint shaker, and the zirconia beads were removed to prepare a pigment dispersion.

[0102] 2-1-2. Ink preparation 50.9 parts by mass of Monomer 1, 9 parts by mass of Initiator 1, and 0.1 parts by mass of a polymerization inhibitor were thoroughly mixed using a triple roll mill. 40 parts by mass of the pigment dispersion liquid was added to the resulting mixture, and further mixed using a triple roll mill. The mixture was then filtered through a 30 μm polypropylene pleated filter (manufactured by ROKI TECHNO Co., Ltd.) to obtain Ink 1.

[0103] Inks 2 to 12, Ink 18 and Ink 19 were obtained in the same manner except that the types and amounts (proportions) of each component were changed so that the ink compositions would be as shown in Tables 1 and 2.

[0104] 2-2. Preparation of Ink 13 to Ink 16 2-2-1. Preparation of pigment dispersion 50 parts by mass of phosphorescent pigment 1, 2.5 parts by mass of dispersant, and 11.5 parts by mass of monomer 1 were placed in a tabletop crusher (D18S, manufactured by Ishikawa Plant Co., Ltd.) and crushed for 30 minutes. After that, 36 parts by mass of monomer 1 was added, and the mixture was crushed for 5 minutes to prepare a pigment dispersion.

[0105] 2-2-2. Preparation of ink Inks 13 to 16 were obtained in the same manner as in the preparation of Ink 1, except that the pigment dispersion obtained above was used.

[0106] 2-3. Preparation of Ink 17 2-3-1. Preparation of pigment dispersion 50 parts by mass of phosphorescent pigment 1 was placed in a tabletop grinder (D18S, manufactured by Ishikawa Factory Co., Ltd.) and ground for 30 minutes. 2.5 parts by mass of dispersant and 11.5 parts by mass of Monomer 1 were then added and ground for another 30 minutes. 36 parts by mass of Monomer 1 was then added and ground for 5 minutes to prepare a pigment dispersion.

[0107] 2-3-2. Ink preparation Ink 17 was obtained in the same manner as Ink 1, except that the pigment dispersion obtained above was used.

[0108] The compositions of Inks 1 to 19 and the methods for preparing the pigment dispersions are shown in Tables 1 to 3. The units for the compositions are % by mass, and the units for the acid value and amine value are mgKOH / g. The types of functional groups possessed by the dispersants (P: phosphate group, C: carboxyl group, B: basic group), as well as the acid value and amine value, are catalog values.

[0109] [Table 1]

[0110] [Table 2]

[0111] [Table 3]

[0112] 4. Evaluation Brightness A head module with a resolution of 720 dpi was fabricated using a circulation type inkjet head (KM1024aLHG-RC, manufactured by Konica Minolta, Inc.) and was filled with each of the inks.

[0113] Next, voltage was applied to the inkjet head so that the droplet ejection volume was 140 pL (20 pL ejection volume per ejection, 7 ejections). This caused the ink to be ejected so that a 150 mm x 150 mm solid pattern was printed, and the ink was applied to a 2 mm thick acrylic resin plate as a substrate. After that, a UV LED curing lamp (FireJet FJ100 manufactured by Phoseon) was used to cure the ink with a wavelength of 365 nm and an illuminance of 2 W / cm. 2 , light intensity 2000mJ / cm 2 The ink applied to the substrate was then irradiated with ultraviolet light of 1000 kJ / cm. Thereby, the ink applied to the substrate was cured.

[0114] Further ink was applied onto the cured ink under the same conditions, and then cured by irradiating with ultraviolet light under the same conditions. This procedure was repeated to form a cured product with a thickness of 1000 μm.

[0115] The luminance of each cured product was measured by phosphorescence luminance measurement in accordance with JIS Z9107A:2008. Specifically, the substrate (luminous molded article) having each cured product was stored in a dark room for at least 48 hours, and then the cured product was irradiated with light for 15 minutes at an illuminance of 4500 lx using a D65 fluorescent lamp (commercial light source). The afterglow luminance of the cured product 2 seconds after the light irradiation was stopped was measured using a luminance meter (LS150, manufactured by Konica Minolta, Inc.). Based on the measured luminance, the luminance of the cured product obtained from each ink was evaluated according to the following criteria. A: Brightness is 15cd / m 2 That was all B: Brightness is 10 cd / m 2 More than 15cd / m 2 was less than C: Brightness is 5cd / m 2 More than 10cd / m 2 was less than D: Brightness is 5cd / m 2 was less than

[0116] 4-2.Dischargeability A nozzle check pattern was printed under the same conditions as when evaluating brightness, and head defects were confirmed and the ejection performance was evaluated. The ejection performance of each ink was evaluated based on the ratio of nozzles with missing nozzles to the total number of nozzles, according to the following criteria. A: Missing nozzles were between 0% and 1%. B: Missing nozzles were between 1% and 5%. C: Missing nozzles were between 5% and 10%. D: Nozzle defects were 10% or more.

[0117] 4-3. Pigment particle size The volume average particle diameters D50 and D90 of the phosphorescent pigment in the ink were measured by dynamic light scattering using a particle size measuring device (LUMiSizer, manufactured by LUM Japan Co., Ltd.) and the data analysis software installed in the particle size measuring device.

[0118] The evaluation results are shown in Tables 4 to 6. The units for D50 and D90 are μm.

[0119] [Table 4]

[0120] [Table 5]

[0121] [Table 6]

[0122] As shown in Tables 1 to 6, by dispersing the phosphorescent pigment with an acidic dispersant, it was possible to improve the ejection properties of the ink containing the polymerizable compound and the brightness of the cured product formed therefrom. [Industrial Applicability]

[0123] According to the present invention, it is possible to make it easier to use inkjet inks containing phosphorescent pigments. Therefore, the present invention is expected to further expand the applications to which inkjet inks containing phosphorescent pigments can be applied, and contribute to further developments in this field.

Claims

1. The composition includes a polymerizable compound, a phosphorescent pigment, and a dispersant having an acidic functional group, Inkjet ink that hardens when exposed to actinic radiation.

2. The phosphorescent pigment is a phosphor containing an aluminate. The ink-jet ink of claim 1.

3. The phosphorescent pigment is a phosphor containing at least one aluminate selected from the group consisting of calcium aluminate, strontium aluminate, and barium aluminate. The ink-jet ink of claim 1.

4. The phosphorescent pigment is SrAl containing europium (Eu) and dysprosium (Dy) as activators. ２ O ４ or Sr containing europium (Eu) and dysprosium (Dy) as activators ４ Al １４ O ２５ That is, The ink-jet ink of claim 1.

5. The content of the phosphorescent pigment is 5% by mass or more and 40% by mass or less. The ink-jet ink of claim 1.

6. The phosphorescent pigment is a particle having a median diameter of 2.0 μm or more and 5.0 μm or less. The ink-jet ink of claim 1.

7. The dispersant has an acid value of 30 mgKOH / g or more and 200 mgKOH / g or less. The ink-jet ink of claim 1.

8. The dispersant is a dispersant having a phosphate group or a carboxyl group. The ink-jet ink of claim 1.

9. The dispersant is a dispersant having a carboxyl group. The ink-jet ink of claim 1.

10. A composition containing a polymerizable compound, a phosphorescent pigment, and a dispersant is kneaded using a pounder. A method for producing a pigment dispersion for an inkjet ink.

11. dry-pulverizing the phosphorescent pigment; In the kneading step, a composition containing a polymerizable compound, the dry-ground phosphorescent pigment, and a dispersant is kneaded. The method for producing the pigment dispersion according to claim 10.

12. A step of preparing a pigment dispersion produced by the method for producing a pigment dispersion according to claim 10 or 11; and mixing the prepared pigment dispersion with a polymerizable compound. A method for manufacturing inkjet ink.

13. a step of ejecting the inkjet ink according to any one of claims 1 to 9 from an inkjet head and applying it to a substrate; and curing the inkjet ink applied to the substrate by irradiating it with actinic rays. Method for forming a cured product.

14. A cured product formed by curing the inkjet ink according to any one of claims 1 to 9.

15. The thickness is 0.3 mm or more and 1.5 mm or less. The cured product according to claim 14.

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