Active ray-curable ink, cured product forming method, cured product, and light storage panel

Abstract

The present invention provides a kind of active ray curable ink that can improve the brightness of the formed solidification, a solidification forming method using the ink, a solidification and a light storage plate. The active ray curable ink comprises active ray polymerizable compound, light storage pigment and photopolymerization initiator. For the photopolymerization initiator, the transmittance of the light of the peak wavelength of the excitation spectrum of the light storage pigment is 40% or more for the solidification with a thickness of 40 μm repeatedly formed on the solidification with a thickness of 10 μm formed by curing the solution of dipropylene glycol diacrylate (concentration of 3 mass%) of the photopolymerization initiator under nitrogen atmosphere by irradiating ultraviolet light with a wavelength of 365 nm in a manner to reach the light quantity of 2000 mJ / cm 2 .

Description

Technical Field

[0001] This invention relates to active radiation-curable inks, methods for forming cured products, cured products, and photoluminescent plates. Background Technology

[0002] As inks usable in the printing field, there are known reactive ray-curing inks containing reactive ray polymerizable compounds. Reactive ray-curing inks can be cured by the polymerization of reactive ray polymerizable compounds when irradiated with reactive rays, forming a cured film and thus creating printed matter. Printed matter formed from reactive ray-curing inks has excellent durability and can therefore also be used for outdoor billboards, etc.

[0003] However, when the printed material formed from the above-mentioned ink is used for outdoor billboards, etc., the printed parts are difficult to see in the dark at night. In contrast, a method can be used to illuminate the printed parts from the back of the substrate to make them visible in the dark, but this is problematic from an energy-saving point of view because it requires a light source device to drive the light.

[0004] Therefore, there is a growing expectation for improving the visibility of printed parts in the dark without using the light source device described above, and inks that can achieve this expectation are being developed.

[0005] As such inks, there are known active ray-curable inks containing phosphorescent pigments (for example, Patent Documents 1-5). Phosphorescent pigments can absorb light of a specified wavelength and store light energy. Furthermore, the light energy stored by the phosphorescent pigments can be released for a long time after light absorption ceases, in the form of light with a wavelength different from the absorbed light. Therefore, for example, when printed materials made using inks containing phosphorescent pigments are used outdoors, the phosphorescent pigments can absorb sunlight and store light energy, and emit light even at night. Thus, the printed areas can be clearly seen in the dark.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2013-135192

[0009] Patent Document 2: Japanese Patent Application Publication No. 11-140368

[0010] Patent Document 3: Japanese Patent Application Publication No. 2014-028484

[0011] Patent Document 4: Japanese Patent Application Publication No. 2019-210337

[0012] Patent Document 5: International Publication No. 2013 / 099565 Summary of the Invention

[0013] According to patent documents 1-5, there are active ray-curable inks containing phosphorescent pigments. For these inks, there is a strong desire to further increase the brightness of the cured product in order to further improve the visibility of dark areas in the printed area.

[0014] The present invention was made in view of the above circumstances, and its object is to provide an active ray-curable ink containing phosphorescent pigments and capable of further improving the brightness of the formed cured product, a method for forming a cured product using the ink, a cured product, and a phosphorescent plate.

[0015] In order to solve the above-mentioned problems, one aspect of the present invention relates to the active ray curable inks described below [1] to

[12] .

[0016] [1] An active ray-curable ink comprises an active ray-polymerizable compound, a photoluminescent pigment, and a photopolymerization initiator. The photopolymerization initiator is used in a dipropylene glycol diacrylate solution (concentration 3% by mass) under a nitrogen atmosphere to achieve a light intensity of 2000 mJ / cm². 2 The transmittance of light with a peak wavelength of 40 μm obtained by repeatedly forming the above-mentioned cured material on a cured material with a thickness of 10 μm formed by irradiating it with ultraviolet light with a wavelength of 365 nm is 40% or more.

[0017] [2] The active ray curable ink according to [1], wherein the photopolymerization initiator includes a hydrogen abstraction initiator.

[0018] [3] The active ray curable ink according to [1] or [2], wherein the photopolymerization initiator comprises an intramolecular hydrogen abstraction initiator.

[0019] [4] The active ray curable ink according to any one of [1] to [3], wherein it further comprises a photopolymerization initiator having a transmittance of less than 40% in an amount of 3% to 17% by mass relative to the total mass of the photopolymerization initiator.

[0020] [5] The active ray-curable ink according to any one of [1] to [4], wherein the photopolymerization initiator further comprises an acylphosphine oxide-based photopolymerization initiator.

[0021] [6] The active ray curable ink according to any one of [1] to [5], wherein the photopolymerizable compound comprises a compound having an aromatic ring.

[0022] [7] The active ray curable ink according to any one of [1] to [6], wherein the photopolymerizable compound comprises a monofunctional compound.

[0023] [8] The active ray curable ink according to any one of [1] to [7], wherein the photopolymerizable compound comprises a compound having an alkylene glycol structure.

[0024] [9] According to the active ray curable ink of [8], the number of carbon atoms constituting the above-mentioned alkylene glycol structure is 3 or more.

[0025]

[10] The active ray curable ink according to any one of [1] to [9], wherein the content of the phosphorescent pigment is 10% to 50% by mass relative to the total mass of the active ray curable ink.

[0026]

[11] The active ray curable ink according to any one of [1] to

[10] , wherein the peak wavelength of the excitation spectrum of the above-mentioned phosphorescent pigment is 300 nm to 400 nm.

[0027]

[12] The active ray curable ink according to any one of [1] to

[11] , wherein the ink is an inkjet ink.

[0028] In addition, one aspect of the present invention for solving the above-mentioned problems relates to the following method for forming a cured product

[13] .

[0029]

[13] A method for forming a cured product includes: a step of applying an active ray curable ink as described in any one of [1] to

[12] to a recording medium, and a step of irradiating the applied active ray curable ink with active rays.

[0030] In addition, one aspect of the present invention for solving the above-mentioned problems relates to the cured product formation method described below

[14] .

[0031]

[14] A cured product is formed by curing any one of the active ray-curable inks described in [1] to

[12] .

[0032] In addition, one aspect of the present invention for solving the above-mentioned problems relates to a photoluminescent plate as described below

[15] .

[0033]

[15] A photoluminescent plate having the cured material described in

[14] .

[0034] According to the present invention, it is possible to provide an active ray-curable ink containing phosphorescent pigments and which can further improve the brightness of the formed cured product, a method for forming a cured product using the ink, a cured product, and a phosphorescent plate. Detailed Implementation

[0035] The embodiments of the present invention will now be described in detail. It should be noted that the present invention is not limited to the following embodiments.

[0036] 1. Active X-ray Curable Ink

[0037] The active ray-curable ink (hereinafter, also simply referred to as ink) of this embodiment contains an active ray-polymerizable compound, a photoluminescent pigment, and a photopolymerization initiator. The ink described above is preferably an inkjet ink.

[0038] As mentioned above, there is an urgent desire to further improve the brightness of the cured product formed from the ink for active ray-curable inks containing phosphorescent pigments.

[0039] The cured product contains residues of the photopolymerization initiator used in the curing of the ink. According to the inventors, these residues readily absorb light of the wavelength that excites the phosphorescent pigment (excitation light) incident on the cured product. Furthermore, the inventors' research indicates that the cured product can yellow due to these residues. The yellowed portions of the cured product readily absorb the excitation light. For these reasons, the excitation light cannot sufficiently reach the phosphorescent pigment in the cured product, particularly the phosphorescent pigment near the substrate, resulting in insufficient luminescence. To address this, by selecting a photopolymerization initiator based on the phosphorescent pigment to reduce the absorption of the excitation light wavelength caused by residues and yellowing after curing, the excitation light can sufficiently reach the phosphorescent pigment in the cured product, and further, the excitation light can also sufficiently reach the phosphorescent pigment near the substrate. It is believed that this enables the phosphorescent pigment in the cured product to emit sufficient luminescence.

[0040] Therefore, the inventors believe that when the transmittance of the excitation light of the phosphorescent pigment is higher than that of the cured product containing the photopolymerization initiator, the absorption of the excitation light caused by the aforementioned residues and yellowing can be reduced, and the photopolymerization initiator is selected in such a way as increasing the transmittance.

[0041] Specifically, the photoluminescent pigment and photopolymerization initiator are selected in the following manner: a dipropylene glycol diacrylate solution (concentration 3% by mass) of the photopolymerization initiator is prepared under a nitrogen atmosphere to achieve a light intensity of 2000 mJ / cm². 2 The transmittance of light with a peak wavelength of 40 μm obtained by repeatedly forming a 10 μm thick cured material on a 365 nm ultraviolet light irradiation method to cure the phosphorescent pigment is 40% or more. This reduces the absorption of excitation light caused by photopolymerization initiator residues in the cured material, allowing the excitation light to fully reach the phosphorescent pigment in the cured material, thus enabling the phosphorescent pigment to emit light fully and further improving the brightness of the cured material.

[0042] The transmittance of the photopolymerization initiator to the excitation light differs from the transmittance of the residue from the photopolymerization initiator used in the ink curing process. Therefore, by measuring the transmittance using the above method, it can be confirmed that the absorption of the excitation light caused by the residue is reduced. Furthermore, by measuring the transmittance using the above method, the effect of yellowing during ink curing can also be included, confirming the ease with which the excitation light reaches the phosphorescent pigment.

[0043] 1-1. Active X-ray polymerizable compounds

[0044] The active ray polymerizable compound contained in the ink of this embodiment is a compound that is polymerized and cross-linked by irradiation with active rays.

[0045] Examples of active rays include electron beams, ultraviolet rays, alpha rays, gamma rays, and X-rays. Among these, ultraviolet rays and electron beams are preferred, with ultraviolet rays being more preferred.

[0046] Examples of reactive ray polymerizable compounds include free radical polymerizable compounds and cationic polymerizable compounds. Among them, free radical polymerizable compounds are preferred. Reactive ray polymerizable compounds can be any of monomers, polymerizable oligomers, and mixtures thereof. It should be noted that the ink may contain only one type of reactive ray polymerizable compound, or it may contain two or more types in combination.

[0047] Furthermore, the active X-ray polymerizable compound can be monofunctional or polyfunctional. From the viewpoint of suppressing the decrease in adhesion between the cured product and the substrate caused by curing shrinkage, the active X-ray polymerizable compound preferably contains a monofunctional compound.

[0048] Free radical polymerizable compounds are monofunctional or polyfunctional compounds with intramolecularly formed olefinic unsaturated bonds capable of free radical polymerization. Examples of compounds with olefinic unsaturated bonds capable of free radical polymerization include unsaturated carboxylic acids and their salts, unsaturated carboxylic acid esters, unsaturated carboxylic acid carbamates, unsaturated carboxylic acid amides and their anhydrides, acrylonitrile, styrene, unsaturated polyesters, unsaturated polyethers, unsaturated polyamides, and unsaturated polyurethanes. Examples of unsaturated carboxylic acids include (meth)acrylic acid, itaconic acid, crotonic acid, isocrotonic acid, and maleic acid.

[0049] The free radical polymerizable compound is preferably an unsaturated carboxylic acid ester and a (meth)acrylate, more preferably a (meth)acrylate.

[0050] Examples of monofunctional (meth)acrylates include: isoamyl (meth)acrylate, stearyl (meth)acrylate, isobornyl (meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, isomyristyl (meth)acrylate, isostearyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, 2-ethylhexyl ether (meth)acrylate, diethylene glycol (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, and others. Phenylacetyl phenoxyethyl (meth)acrylate, m-phenoxybenzyl (meth)acrylate, cyclotrimethylolpropane methyl acetal (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-phenylphenol propyl (meth)acrylate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxyethyl-2-hydroxyethyl-phthalate, and tert-butylcyclohexyl (meth)acrylate, etc.

[0051] Examples of polyfunctional (meth)acrylates include: triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, dipropylene glycol dimethacrylate, tripropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, neopentyl glycol dimethacrylate, tricyclodecanediethanol dimethacrylate, tricyclodecanediethanol dimethacrylate, bisphenol A type dimethacrylate, hydroxypiperidine acid neopentyl glycol dimethacrylate. Difunctional (meth)acrylates, including acrylates, polytetramethylene glycol di(meth)acrylate, polyethylene glycol diacrylate, dipropylene glycol diacrylate, and tripropylene glycol diacrylate; and trifunctional (meth)acrylates, including trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, bis(trimethylolpropane tetra(meth)acrylate, glycerol propoxy tri(meth)acrylate, and pentaerythritol ethoxy tetra(meth)acrylate; and oligomers containing (meth)acryloyl groups, including polyester acrylate oligomers.

[0052] Examples of cationic polymerizable compounds include epoxides, vinyl ethers, and oxetanes.

[0053] Examples of the aforementioned epoxy compounds include: 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexane carboxylate, bis(3,4-epoxycyclohexylmethyl) adipic acid ester, vinylcyclohexene monoepoxide, ε-caprolactone-modified 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexane carboxylate, 1-methyl-4-(2-methyloxacyclopropane)-7-oxabicyclo[4,1,0]heptane, and 2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexanone-m-di Alicyclic epoxy compounds, including alicyclic epoxy resins such as alkyl groups and bis(2,3-epoxycyclopentyl) ethers, diglycidyl ethers of 1,4-butanediol, diglycidyl ethers of 1,6-hexanediol, triglycidyl ethers of glycerol, trimethylolpropane, diglycidyl ethers of polyethylene glycol, diglycidyl ethers of propylene glycol, polyethers of ethylene glycol, propylene glycol, and glycerol, which are obtained by adding one or more epoxides (such as ethylene oxide and propylene oxide) to aliphatic polyols, as well as polyglycidyl ethers of polyether polyols, including bisphenol A or its epoxide adducts, diglycidyl ethers of hydrogenated bisphenol A or its epoxide adducts, and phenolic varnish-type epoxy resins, etc.

[0054] Examples of the aforementioned vinyl ether compounds 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, cyclohexanediol monovinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, isopropylene 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, cyclohexanediol divinyl ether, and trimethylolpropane trivinyl ether.

[0055] Examples of the above-mentioned oxetane compounds 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-hydroxy Ethyl-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-oxetane)methoxy]methyl}benzene, 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane, and di[1-ethyl(3-oxetane)]methyl ether, etc.

[0056] The active X-ray polymerizable compound preferably contains a compound having an aromatic ring. By including a compound having an aromatic ring in the active X-ray polymerizable compound, the refractive index of the ink and the resulting cured product can be increased.

[0057] It is believed that due to the high refractive index of the phosphorescent pigment and the large difference in refractive index between it and the surrounding cured material, light reflection easily occurs at the interface between the pigment and the cured material, even when light is incident on the pigment. To address this, it is proposed that by using compounds with aromatic rings to increase the refractive index of the cured material, the difference in refractive index between the phosphorescent pigment and the surrounding cured material can be reduced. This reduces light reflection at the interface, allowing more light to enter the phosphorescent pigment. It is believed that this results in further luminescence from the phosphorescent pigment, thus further improving the brightness of the cured material.

[0058] Furthermore, during ink curing, the phosphorescent pigment absorbs a portion of the active rays irradiating the ink, resulting in a slight luminescence from the phosphorescent pigment itself. The photopolymerization initiator absorbs this slight luminescence, allowing the polymerization of the active ray polymerizable compound to proceed. At this time, by including the aforementioned compound with aromatic rings in the ink, the refractive index of the ink can be increased. This reduces the difference in refractive index between the phosphorescent pigment and the surrounding ink, decreasing the reflection of active rays at the interface between the phosphorescent pigment and the ink, and allowing more active rays to enter the phosphorescent pigment. As a result, the luminescence generated in the phosphorescent pigment can be further enhanced, allowing the polymerization of the active ray polymerizable compound to proceed further, thus further improving the curability of the cured product.

[0059] Examples of the aforementioned compounds having an aromatic ring include: 2-phenoxyethyl (meth)acrylate, bisphenol A type diacrylate, o-phenylphenoxyethyl (meth)acrylate, m-phenoxybenzyl (meth)acrylate, ethoxylated phenoxy (meth)acrylate, alkoxylated phenol (meth)acrylate, 2-hydroxy-o-phenylphenol propyl (meth)acrylate, etc. In particular, from the viewpoint of inkjet ejection properties and brightness, 2-phenoxyethyl (meth)acrylate, o-phenylphenoxyethyl (meth)acrylate, m-phenoxybenzyl (meth)acrylate, and ethoxylated phenoxy (meth)acrylate are more preferred.

[0060] When the active X-ray polymerizable compound contains a compound with an aromatic ring, the content of the compound with an aromatic ring relative to the total mass of the ink is preferably 20% to 70% by mass, more preferably 30% to 60% by mass. When the content is 20% by mass or more, the difference in refractive index between the phosphorescent pigment and the cured material surrounding the phosphorescent pigment becomes smaller, thus allowing light to be further incident on the phosphorescent pigment, causing the phosphorescent pigment to emit light further. This further improves the brightness of the cured material. Furthermore, when the content is 20% by mass or more, the difference in refractive index between the phosphorescent pigment and the ink surrounding the phosphorescent pigment becomes smaller, thus allowing active X-rays to be further incident on the phosphorescent pigment, causing the phosphorescent pigment to emit light further. This further promotes the polymerization of the active X-ray polymerizable compound, further improving the curability of the cured material. When the content is 70% by mass or less, excessively high refractive indices of the ink and the cured material can be further suppressed. This allows for appropriate adjustment of the difference in refractive index between the phosphorescent pigment and the cured material surrounding the phosphorescent pigment, and the difference in refractive index between the phosphorescent pigment and the ink surrounding the phosphorescent pigment.

[0061] The reactive ray polymerizable compound preferably contains a compound having an alkylene glycol structure. According to the inventors, compounds having an alkylene glycol structure are considered to have a high affinity for the phosphorescent pigments described later. Therefore, by including the above-mentioned compound in the ink, the phosphorescent pigment can be present in a state of further dispersion in the cured product. This is believed to further suppress phosphorescent pigment aggregation in the cured product and further improve the adhesion between the cured product and the substrate. Examples of compounds having an alkylene glycol structure include: polyethylene glycol diacrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, ethoxylated phenoxy(meth)acrylate, dipropylene glycol diacrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, etc. Particularly from the viewpoint of adhesion, polyethylene glycol di(meth)acrylate, dipropylene glycol diacrylate, tripropylene glycol di(meth)acrylate, and ethoxylated phenoxy(meth)acrylate are further preferred.

[0062] The number of carbon atoms constituting the alkylene glycol structure is preferably 3 to 4. By including a compound with an alkylene glycol structure having 3 or more carbon atoms in the ink, excessive hydrophilicity of the cured product is suppressed, making the cured product less hygroscopic and thus further improving the weather resistance of the cured product formed from the ink. In addition, by making the number of carbon atoms 4 or less, the decrease in affinity between the cured product and the phosphorescent pigment can be suppressed, further suppressing the decrease in adhesion between the cured product and the substrate.

[0063] In compounds having an alkylene glycol structure, the molecular structure preferably contains 2 to 4 alkylene glycol structures. By including 2 or more alkylene glycol structures, the adhesion between the cured product and the substrate can be further improved. By including 4 or fewer alkylene glycol structures, the reduction in curability of the cured product can be further suppressed. Since the alkylene glycol structure is considered a flexible structure that can improve molecular mobility, it is believed that by including 4 or fewer alkylene glycol structures, excessive flexibility of the cured product can be further prevented from reducing its curability.

[0064] The content of the compound having an alkylene glycol structure relative to the total mass of the ink is preferably 5% to 40% by mass, more preferably 10% to 35% by mass. By setting the above content to 5% by mass or more, the adhesion between the cured product and the substrate can be further improved, and by setting the above content to 40% by mass or less, the reduction in the curability of the cured product can be further suppressed.

[0065] The content of the active ray polymerizable compound relative to the total mass of the ink can be, for example, 1% to 95% by mass, preferably 30% to 95% by mass, and more preferably 50% to 95% by mass.

[0066] 1-2. Phosphorescent pigments

[0067] In this embodiment, the ink contains phosphorescent pigments.

[0068] Phosphorescent pigments can absorb light of a specified wavelength, store light energy, and release the stored light energy in the form of light with a different wavelength than the absorbed light for a long time after the absorption stops. That is, phosphorescent pigments can produce phosphorescence.

[0069] There are no particular limitations on the types of phosphorescent pigments as long as they possess the aforementioned characteristics. Examples of phosphorescent pigments include substances obtained by activating a parent crystal, which is a metal compound.

[0070] Examples of the aforementioned parent crystals include: sulfides such as zinc sulfide, calcium sulfide, germanium sulfide, strontium sulfide, and yttrium sulfide; metal oxides such as calcium oxide, strontium oxide, barium oxide, aluminum oxide, and cerium oxide; and aluminates such as calcium aluminate, strontium aluminate, and barium aluminate. Among these, strontium aluminate is preferred.

[0071] Examples of activators used for activating the aforementioned parent crystal include europium, terbium, yttrium, zirconium, dysprosium, and barium. Among these, europium and dysprosium are preferred.

[0072] The ink may contain only one type of phosphorescent pigment, or it may contain two or more types in combination.

[0073] The peak wavelength of the excitation spectrum of the phosphorescent pigment is preferably 300 nm to 400 nm. By ensuring that the peak wavelength of the excitation spectrum of the phosphorescent pigment is within this range, the phosphorescent pigment can be further excited when sunlight is incident on it. Therefore, for example, the cured product can be made more suitable for outdoor use. In addition, by ensuring that the peak wavelength is within the above range, it is easier to include the peak wavelength of the emission spectrum of the phosphorescent pigment within the preferred range described later, thereby further improving the visibility (visual sensitivity) of the cured product (printed portion).

[0074] The peak wavelength of the emission spectrum of the phosphorescent pigment can be, for example, 400 nm to 700 nm, but from the viewpoint of further improving the visibility of the cured material (printed part), it is preferably 450 nm to 600 nm.

[0075] The cumulative value in the volume-based particle size distribution of phosphorescent pigments reaches 50% of the particle size (d). 50 The particle size is not particularly limited, but preferably 10 μm or less, more preferably 8 μm or less. When the ink of this embodiment is used as an inkjet ink, the reduction in ejection stability can be suppressed by making the above-mentioned particle size 10 μm or less. The lower limit value of the above-mentioned particle size is not particularly limited, but preferably 0.5 μm or more. More preferably 1 μm or more. The above-mentioned particle size of the phosphorescent pigment can be determined by a particle size distribution analysis device using the Stokes sedimentation method (e.g., LUMiSizer, manufactured by LUM Japan Co., Ltd.).

[0076] The content of phosphorescent pigment relative to the total mass of the ink is preferably 10% to 50% by mass, more preferably 15% to 35% by mass. When the content is 10% by mass or more, the brightness of the cured product can be further improved. When it is 50% by mass or less, the proportion of active ray polymerizable compounds in the ink can be increased, further improving the curability of the cured product and its adhesion to the substrate. In addition, by being 50% by mass or less, the decrease in ejection stability can be suppressed when the ink is used as an inkjet ink.

[0077] 1-3. Photopolymerization initiators

[0078] The ink in this embodiment contains a photopolymerization initiator.

[0079] For the aforementioned photopolymerization initiator, a dipropylene glycol diacrylate solution (concentration 3% by mass) of the aforementioned photopolymerization initiator was subjected to a nitrogen atmosphere to achieve a light intensity of 2000 mJ / cm. 2 The transmittance (hereinafter also referred to as transmittance) of the light at the peak wavelength of the excitation spectrum of the above-mentioned phosphorescent pigment is 40% or more. This is obtained by repeatedly forming the above-mentioned cured material with a thickness of 10 μm on a cured material with a wavelength of 365 nm by irradiating it with ultraviolet light.

[0080] It should be noted that by making the thickness of the cured material formed in the above measurements 10 μm, the degree of curing of the cured material is less likely to vary due to differences in the maximum absorption wavelength of the photopolymerization initiator. Therefore, the curing properties of the 40 μm thick cured material obtained by stacking this cured material are also less likely to vary due to the type of photopolymerization initiator.

[0081] As described above, the gloss of the cured product can be improved by including the aforementioned photopolymerization initiator in the ink.

[0082] The aforementioned transmittance can be measured, for example, using a spectrophotometer (V-650, manufactured by Nippon Spectrophotometer Co., Ltd.) at the peak wavelength of the excitation spectrum of the phosphorescent pigment. For example, the transmittance is measured by setting the incident angle of the detector stage of the spectrophotometer to 90° and the incident angle of the sample stage to 0°.

[0083] Photopolymerization initiators can be free radical initiators when the ink contains free radical polymerizable compounds, or cationic initiators (photoacid generators) when the ink contains cationic polymerizable compounds.

[0084] Examples of free radical polymerization initiators include molecular cleavage-type photopolymerization initiators and hydrogen abstraction-type polymerization initiators. The ink may contain only one of these photopolymerization initiators, or it may contain a combination of two or more.

[0085] Examples of molecular cleavage-type photopolymerization initiators include: acetophenone-based initiators such as 2-hydroxy-2-methyl-1-phenylpropane-1-one, benzoyladium dimethyl ketal, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)one, 1-hydroxycyclohexyl-phenyl ketone, 2-methyl-2-morpholino(4-methylthiophenyl)propane-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.

[0086] Examples of commercially available molecular fracture photopolymerization initiators include Omnirad 127, Omnirad 184, Omnirad 651, Omnirad 2959, Omnirad 819, and Esacure One (manufactured by IGM Resins).

[0087] Among these molecularly fragmented photopolymerization initiators, acylphosphine oxide initiators are preferred. Acylphosphine oxide initiators possess photobleaching properties, thus further suppressing yellowing. Photobleaching property refers to the property of the absorption spectrum shift of the photopolymerization initiator when irradiated with active radiation. Therefore, it is possible to further suppress the obscuring of the luminescence of phosphorescent pigments by the yellow portion in the cured product, and to further suppress the reduction in brightness of the cured product.

[0088] Hydrogen-abstraction photopolymerization initiators include intermolecular hydrogen-abstraction photopolymerization initiators and intramolecular hydrogen-abstraction photopolymerization initiators.

[0089] In this specification, "intermolecular hydrogen abstraction photopolymerization initiator" refers to a compound that is excited by irradiation with active light such as ultraviolet light and abstracts hydrogen from other molecules to generate free radicals.

[0090] Examples of intermolecular hydrogen abstraction type photopolymerization initiators include: benzophenone-based initiators such as methyl benzoyl peroxide, 4-phenylbenzophenone, 4,4'-dichlorobenzophenone, hydroxybenzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide, acrylated benzophenone, 3,3',4,4'-tetra(tert-butylperoxycarbonyl)benzophenone and 3,3'-dimethyl-4-methoxybenzophenone, as well as thioxanone-based initiators such as 2-isopropylthioxanone, 2,4-dimethylthioxanone, 2,4-diethylthioxanone, and 2,4-dichlorothioxanone.

[0091] Commercially available examples of intermolecular hydrogen abstraction photopolymerization initiators include Irgacure 500 (manufactured by BASF) and Speedcure ITX (manufactured by Lambson).

[0092] In addition, in this specification, "intramolecular hydrogen abstraction photopolymerization initiator" refers to a compound that is excited by irradiation with active light and initiates an intramolecular hydrogen abstraction reaction to generate free radicals.

[0093] Examples of intramolecular hydrogen abstraction type photopolymerization initiators include: methyl benzoyl carboxylate and other methyl benzoate photopolymerization initiators, and hydroxyphenyl-based photopolymerization initiators such as mixtures of 2-[2-oxo-2-phenylacetoxy-ethoxy]ethyl hydroxyphenylacetate and 2-[2-hydroxy-ethoxy]ethyl hydroxyphenylacetate.

[0094] Commercially available examples of intramolecular hydrogen abstraction photopolymerization initiators include Omnirad MBF (manufactured by IGM Resins) and Irgacure 754 (manufactured by BASF).

[0095] The photopolymerization initiator preferably includes a hydrogen-abstracting photopolymerization initiator, and more preferably an intramolecular hydrogen-abstracting photopolymerization initiator.

[0096] By using hydrogen-abstracting photopolymerization initiators, the curing of ink caused by active ray irradiation can be further promoted, thereby further improving the curability and water resistance of the resulting cured product.

[0097] Oxygen inhibition refers to the suppression of polymerization by the reaction of free radicals generated during polymerization with oxygen to form peroxides. Hydrogen-abstracting photopolymerization initiators can abstract hydrogen atoms from these peroxides to generate free radicals again. This further promotes the polymerization reaction and thus inhibits oxygen inhibition. It is believed that this can further improve the curability and water resistance of the cured product.

[0098] Furthermore, it is believed that intramolecular hydrogen-abstraction photopolymerization initiators generate free radicals by initiating hydrogen-abstraction reactions within the molecule, thus further suppressing the generation of free radicals caused by the abstraction of hydrogen from the molecular chains of polymerizable compounds undergoing polymerization. This further inhibits the cross-linking reactions between the aforementioned molecular chains, leading to chain elongation. Consequently, the hydrophobicity of the resulting cured product is further improved, thereby enhancing its water resistance and weather resistance.

[0099] Intramolecular hydrogen abstraction photopolymerization initiators are preferably compounds with a glyoxylic acid structure. It is believed that compounds with a glyoxylic acid structure are more likely to initiate hydrogen abstraction reactions intramolecularly, thus further improving the water resistance and weather resistance of the resulting cured product.

[0100] The molecular weight of the photopolymerization initiator is preferably 150 to 500, more preferably 150 to 190. By setting the molecular weight to 150 or higher, the ejection stability can be improved when the ink is used as an inkjet ink. By setting it to 500 or lower, the mobility of the photopolymerization initiator molecules in the ink can be increased, making it easier to initiate the polymerization of active ray-polymerizable compounds near the substrate, thereby further improving the curability of the cured product.

[0101] Examples of cationic photopolymerization initiators include photoacid generators. Examples of photoacid generators include aromatic ononium compounds such as B(C6F5)4, including diazoonium, ammonium, iodonium, sulfonium, and phosphonium. － PF6 － AsF6 － SbF6 － CF3SO3－ Sulfonates that produce sulfonic acids from salts, halides that produce hydrogen halides through photoluminescence, and iron-containing aromatic complexes, etc.

[0102] In this embodiment, the photopolymerization initiator used is a photopolymerization initiator with a transmittance of 40% or more at the peak wavelength of the excitation spectrum of the phosphorescent pigment. For example, when the peak wavelength of the excitation spectrum of the phosphorescent pigment is 324 nm, a photopolymerization initiator with a transmittance of 40% or more for light at a wavelength of 324 nm is used. Examples of photopolymerization initiators used in this case include Omnirad 127 (71% transmittance), Omnirad 184 (73% transmittance), Omnirad 651 (55% transmittance), Omnirad 2959 (63% transmittance), Irgacure 500 (62% transmittance), Omnirad 754 (46% transmittance) (all manufactured by BASF), Esacure One (71% transmittance) (manufactured by IGM Resins), and Omnirad MBF (45% transmittance) (manufactured by IGM Resins), etc.

[0103] The transmittance of the photopolymerization initiator is 40% or more, preferably 45% to 80%, more preferably 40% to 70%, and even more preferably 40% to 65%. By making the transmittance 80% or less, it is possible to suppress the light that excites the phosphorescent pigment from reaching the substrate and causing substrate degradation. Therefore, for example, it is possible to suppress sunlight from passing through the substrate and further suppress substrate degradation, thereby further improving the adaptability of the cured product for outdoor use. In addition, when the transmittance is 70% or less, it is possible to further suppress excessive transmission of light at the peak wavelength of the excitation spectrum of the phosphorescent pigment, further suppress the degradation of the cured product, and further improve the durability of the cured product.

[0104] The content of the photopolymerization initiator with a transmittance of 40% or more relative to the total mass of the ink is preferably 3% to 15% by mass, more preferably 3% to 10% by mass, and even more preferably 5% to 10% by mass. By setting the content to 3% by mass or more, the gloss of the cured material can be further improved. By setting the content to 15% by mass or less, the adhesion of the cured material can be further improved.

[0105] The ink of this embodiment may further contain the aforementioned photopolymerization initiator with a transmittance of less than 40% within the scope of achieving the effects of the present invention.

[0106] The transmittance of the aforementioned photopolymerization initiator with a transmittance of less than 40% is preferably 20% or more and less than 40%. By ensuring that the transmittance of the aforementioned photopolymerization initiator with a transmittance of less than 40% is 20% or more, the absorption of light at the wavelength of light, such as that of a phosphorescent pigment, can be further reduced by the residue of the photopolymerization initiator when the peak wavelength of the excitation spectrum is in the ultraviolet region. As a result, the coloring of the cured product into yellow, which is the complementary color of the aforementioned wavelength, can be further suppressed, and the brightness of the cured product caused by yellowing can be further suppressed.

[0107] The aforementioned photopolymerization initiator with a transmittance of less than 40% preferably comprises an acylphosphine oxide-based initiator. Because acylphosphine oxide-based initiators possess photobleaching properties, they can further suppress yellowing. Therefore, the luminescence of the phosphorescent pigment can be further suppressed from being blocked by the yellow portion in the cured product, further suppressing the reduction in the brightness of the cured product.

[0108] The content of the photopolymerization initiator with a transmittance of less than 40% relative to the total mass of the photopolymerization initiator is preferably 3% to 30% by mass, more preferably 5% to 20% by mass. It is believed that the photopolymerization initiator with a transmittance of less than 40% readily absorbs active radiation. Therefore, by setting the content to 3% by mass or more, the polymerization reaction of the active radiation polymerizable compound can be further promoted, and the curability of the formed cured product can be further improved. By setting the content to 30% by mass or less, the light that excites the phosphorescent pigment can fully reach the phosphorescent pigment, and the brightness of the cured product can be further improved.

[0109] The transmittance of the aforementioned photopolymerization initiator with a transmittance of less than 40% is preferably 20% or more and less than 40%, more preferably 30% or more and less than 40%. By setting it to 20% or more, the light that excites the phosphorescent pigment can fully reach the phosphorescent pigment, further improving the brightness of the cured product.

[0110] 1-4. Others

[0111] The ink of this embodiment may further include other components such as non-photoluminescent pigments, pigment dispersants, surfactants, fluorescent whitening agents, and polymerization inhibitors within the scope of achieving the effects of this invention.

[0112] Examples of non-photoluminescent pigments include red, yellow, blue, and white pigments that can be used in image-forming inks. These pigments can be any known pigments.

[0113] Examples of pigment dispersants include: hydroxyl-containing carboxylic acid esters, salts of long-chain polyaminoamides and high molecular weight acid esters, salts of high molecular weight polycarboxylic acids, salts of long-chain polyaminoamides and polar acid esters, high molecular weight unsaturated acid esters, polymer copolymers, modified polyurethanes, modified polyacrylates, polyether ester-type anionic surfactants, formalin condensate salts of naphthalene sulfonate, formalin condensate salts of aromatic sulfonate, polyoxyethylene alkyl phosphates, polyoxyethylene nonylphenyl ether, and stearamine acetate, etc. Commercially available examples of pigment dispersants include: the Solsperse (registered trademark) series (manufactured by Avecia Corporation), the PB series (manufactured by Ajinomoto Fine Technology Co., Ltd.), and the EFKA series (manufactured by BASF Corporation), etc.

[0114] The content of pigment dispersant relative to the total mass of phosphorescent pigment is preferably 0.5% to 20% by mass.

[0115] Examples of surfactants include: anionic surfactants such as dialkyl sulfosuccinates, alkyl naphthalene sulfonates, and fatty acid salts; nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylacetonate diols, and polyoxyethylene / polyoxypropylene block copolymers; cationic surfactants such as alkylamine salts and quaternary ammonium salts; and silicone-based and fluorinated surfactants.

[0116] The content of surfactant relative to the total mass of ink is not particularly limited within the range that achieves the effect of the present invention; for example, it can be more than 0.001% by mass and less than 1.0% by mass.

[0117] Examples of polymerization inhibitors include: nitroxide radical inhibitors, phenolic inhibitors, quinone inhibitors, amine inhibitors, and copper dithiocarbamate inhibitors.

[0118] The ink may contain only one type of polymerization inhibitor, or it may contain two or more types in combination.

[0119] Examples of nitroxide radical-based polymerization inhibitors include 4-hydroxy-2,2,6,6-tetramethylpiperidine nitroxide radical (TEMPO), 4-hydroxy-2,2,6,6-tetramethyl-piperidine nitroxide radical, 4-oxo-2,2,6,6-tetramethyl-piperidine nitroxide radical, 4-methoxy-2,2,6,6-tetramethyl-piperidine nitroxide radical, and 4-acetoxy-2,2,6,6-tetramethyl-piperidine nitroxide radical. Commercially available examples of nitroxide radical-based polymerization inhibitors include Irgastab UV10 (manufactured by BASF, "Irgastab" is a registered trademark of the company).

[0120] Examples of phenolic polymerization inhibitors 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-tert-butyl-p-cresol (butylated hydroxytoluene: BHT), 4-methoxyphenol, 2-methoxy-4-methylphenol, etc.

[0121] Examples of quinone polymerization inhibitors include hydroquinone, methoxyhydroquinone, benzoquinone, 1,4-naphthoquinone, and p-tert-butylcatechol.

[0122] Examples of amine polymerization inhibitors include: alkylated diphenylamine, N,N'-diphenyl-p-phenylenediamine, phenothiazine, etc.

[0123] Examples of copper dithiocarbamate-based polymerization inhibitors include: copper dimethyl dithiocarbamate, copper diethyl dithiocarbamate, copper dibutyl dithiocarbamate, etc.

[0124] The content of the polymerization inhibitor is not particularly limited within the range that achieves the effect of the present invention. For example, it can be 0.001% to 0.5% by mass, preferably less than 0.1% by mass, and more preferably less than 0.01% by mass.

[0125] 1-5.Physical properties

[0126] The viscosity of the ink in this embodiment at 25°C is preferably 5 mPa·s to 50 mPa·s or less. By keeping the viscosity within this range, the ejection stability can be improved when the ink is used as an inkjet ink.

[0127] The viscosity of the ink at 25°C can be determined using a rheometer at a shear rate of 1000 / sec. Specifically, it can be determined by heating the ink to 25°C and measuring it at a shear rate of 1000 / sec.

[0128] The rheometer can be the PhysicaMCR series stress-controlled rheometer manufactured by Anton Paar. The diameter of the cone can be set to 75 mm, and the cone angle can be set to 1.0°.

[0129] 1-6. Preparation method of active ray-curable ink

[0130] The ink of this embodiment can be prepared by mixing the above-described components. In this case, it is preferable to first mix the components other than the phosphorescent pigment, and then add the phosphorescent pigment to the resulting mixture.

[0131] When the ink contains a pigment dispersant, a pigment dispersion containing a phosphorescent pigment and a pigment dispersant can be prepared in advance, and the remaining components can be added and mixed. In this case, in order to improve the solubility of the pigment dispersant, etc., it is preferable to prepare the pigment dispersion by heating and mixing the pigment and dispersant, etc.

[0132] 2. Methods for forming solidified products

[0133] The cured product formation method of this embodiment includes a step of applying an active ray curable ink to a substrate, and a step of irradiating the applied active ray curable ink with active rays.

[0134] 2-1. The process of applying ink

[0135] In this process, the above-mentioned active ray curable ink is applied to the substrate.

[0136] Examples of methods for applying ink to a substrate include: methods using roller coaters, spin coaters, etc.; methods using screen printing; and methods using inkjet printing. Among these, inkjet printing is preferred from the viewpoint of forming a cured product more precisely at the desired location on the substrate.

[0137] When applying ink to a substrate using inkjet printing, the ejection method from the printhead can be either on-demand or continuous. On-demand printheads can be any of the following: electromechanical conversion types such as single-cavity, dual-cavity, curved, piston, shared-mode, and shared-wall types; and thermoelectric conversion types such as thermal inkjet and bubble jet (“bubble jet” is a registered trademark of Canon).

[0138] There are no particular restrictions on the type of substrate, such as ABS resin board, acrylic resin board, aluminum board, glass board, polycarbonate board, cloth, etc.

[0139] 2-2. Procedure for irradiating with active rays

[0140] In this process, the ink applied to the substrate is irradiated with active rays to cure the ink. The wavelength of the irradiated active rays can be appropriately set according to the maximum absorption wavelength of the photopolymerization initiator.

[0141] The active radiation can be selected from electron beams, ultraviolet light, alpha rays, gamma rays, and X-rays, with ultraviolet light or electron beams being preferred. The ultraviolet light is preferably light with a peak wavelength in the range of 360 nm to 410 nm. Furthermore, the ultraviolet light is preferably irradiated by an LED light source. Since LEDs emit less heat compared to conventional light sources (such as metal halide lamps), the ink is less likely to melt during active radiation irradiation, thus reducing the likelihood of uneven gloss.

[0142] When using ultraviolet light as the active ray, the preferred light intensity for each irradiation is 500 mJ / cm. 2 ~4000mJ / cm 2 It is 500 mJ / cm. 2 At the above levels, the curing properties of the resulting cured product can be further improved. The value is 4000 mJ / cm². 2 The following methods can inhibit discoloration of the cured material.

[0143] 2-3. Further processes for applying ink

[0144] The curing method of this embodiment may include a step of further applying ink to the ink after it has been irradiated with the above-mentioned active rays.

[0145] This process can increase the thickness of the cured product. Increased thickness allows for the inclusion of more phosphorescent pigments, thereby further enhancing the overall brightness of the cured product.

[0146] The method for further applying ink can be the same as the method for applying ink to the substrate used in the above-described process of applying ink to the substrate, or it can be a different method.

[0147] 2-4. The process of irradiating the ink that is further coated onto the ink with active rays.

[0148] The curing method of this embodiment may include a step of irradiating the ink that has been further applied with active rays.

[0149] In this process, the ink that was further applied in the above-mentioned ink application process is irradiated with active rays to cure the ink.

[0150] The type of active ray and the amount of light used when using ultraviolet light can be the same as in step S20 described above.

[0151] In the cured material formation method of this embodiment, the thickness of the cured material can be increased by repeating steps S30 and S40.

[0152] 3. Cured product

[0153] The cured product in this embodiment is formed by curing the above-mentioned active ray curable ink.

[0154] The aforementioned cured material can be formed using the aforementioned cured material forming method.

[0155] The thickness of the cured material is preferably between 300 μm and 2000 μm. A thickness of 300 μm or more allows for the inclusion of more phosphorescent pigments, further enhancing the overall brightness of the cured material. A thickness of less than 2000 μm makes the cured material more suitable for post-processing such as lamination.

[0156] 4.Light storage panel

[0157] The photoluminescent plate of this embodiment has a substrate and the cured material formed on the substrate.

[0158] Examples of the aforementioned substrates include: ABS resin boards, acrylic resin boards, aluminum boards, polycarbonate boards, etc., with ABS resin boards, acrylic resin boards, and polycarbonate boards being preferred.

[0159] In this embodiment, the photoluminescent plate is preferably coated with, for example, a varnish, a laminating film, or an ink. Examples of the varnish include Overlay C (manufactured by SINLOIHI Corporation) and SP-3100AU Clear (manufactured by Teikoku Ink Manufacturing Co., Ltd.). Examples of the laminating film include SS50TO(V) (manufactured by Riken Technos Co., Ltd.).

[0160] Example

[0161] The present invention will now be described in detail with reference to the embodiments, but the scope of the present invention is not limited to the embodiments described herein.

[0162] 1. Production of inks 1-29

[0163] (Preparation of pigment dispersions)

[0164] The ink solvent was prepared by mixing 99.9 parts by weight of photopolymerizable compound A-1 (1,6-hexanediol diacrylate, molecular weight: 242) with 0.01 parts by weight of polymerization inhibitor (Irgastab UV-10, manufactured by BASF) and heating and stirring at 70°C for 1 hour.

[0165] 49 parts by mass of the ink solvent prepared above, 50 parts by mass of the phosphorescent pigment (G-300FF, manufactured by Nemoto Special Chemicals Co., Ltd., peak wavelength of excitation spectrum: 324nm) and 1 part by mass of the pigment dispersant (EFKA PX 4701, manufactured by BASF) and 50 parts by mass of zirconia beads with an average particle size of 0.3mm were placed together in a polypropylene container and dispersed using a Paintshaker for 30 minutes to remove the zirconia beads and prepare the pigment dispersion.

[0166] The prepared pigment dispersion was diluted with dipropylene glycol diacrylate, and the particle size d of the pigment was determined using a particle size distribution analyzer (LUMiSizer, manufactured by LUM Japan Co., Ltd.). 50 The measured particle size d of the pigment 50 It is 3.8μm.

[0167] 20 parts by mass of photopolymerizable compound A-1, 35 parts by mass of photopolymerizable compound A-2, and 5 parts by mass of photopolymerization initiator B-1 were thoroughly mixed using a three-roll mill. 40 parts by mass of phosphorescent pigment dispersion were added to the resulting mixture, and the mixture was further mixed to obtain an ink composition. The obtained ink composition was filtered through a 30 μm polypropylene pleated cartridge filter (manufactured by ROKI TECHNO Co., Ltd.) to obtain ink 1.

[0168] By varying the types and amounts of photopolymerizable compounds, the types and amounts of photopolymerization initiators, and the amount of phosphorescent pigments as shown in Tables 1-5, inks 2-25 were obtained in the same manner as ink 1. It should be noted that the numerical values ​​for the ink composition in Tables 1-5 represent parts by mass.

[0169] The types of photopolymerizable compounds and photopolymerization initiators used are shown in Tables 1-5 below. It should be noted that the transmittance values ​​recorded for the photopolymerization initiators are values ​​determined by the methods shown below. The measured transmittance is expressed in Tables 1-5 by the values ​​in parentheses for each photopolymerization initiator.

[0170] (Photopolymerizable compounds)

[0171] A-1: 1,6-Hexanediol diacrylate

[0172] A-2: Tricyclodecanediethanol diacrylate

[0173] A-3: Bisphenol A type 4EO modified diacrylate

[0174] A-4: 2-Phenoxyethyl acrylate

[0175] A-5: Polyethylene glycol (200) diacrylate

[0176] A-6: Dipropylene glycol diacrylate

[0177] (Photopolymerization initiator)

[0178] B-1: Omnirad 2959 (manufactured by IGM Resins, molecularly fractured type, transmittance: 63%, molecular weight: 224.3)

[0179] B-2: Omnirad 651 (manufactured by IGM Resins, molecularly fractured type, transmittance: 55%, molecular weight: 256.3)

[0180] B-3: Esacure One (manufactured by IGM Resins, molecularly fractured type, transmittance: 71%, molecular weight: 256.3)

[0181] B-4: Omnirad127 (manufactured by IGM Resins, molecularly fractured type, transmittance: 71%, molecular weight: 340.7)

[0182] B-5: Omnirad184 (manufactured by IGM Resins, molecularly fractured type, transmittance: 73%, molecular weight: 204.7)

[0183] B-6: Irgacure 500 (manufactured by BASF, intermolecular hydrogen abstraction type, transmittance: 62%, molecular weight: a mixture of 204.3 and 182.2)

[0184] B-7: Omnirad MBF (manufactured by IGM Resins, intramolecular hydrogen abstraction type, transmittance: 45%, molecular weight: 161.4)

[0185] B-8: Omnirad 754 (manufactured by IGM Resins, intramolecular hydrogen abstraction type, transmittance: 46%, molecular weight: 370.36)

[0186] B-9: Omnirad 819 (manufactured by IGM Resins, molecularly fractured type, transmittance: 36%, molecular weight: 418.5)

[0187] B-10: Omnirad 907 (manufactured by IGM Resins, molecularly fractured type, transmittance: 0%, molecular weight: 279.4)

[0188] B-11: Omnirad 369 (manufactured by IGM Resins and BASF, molecularly fractured type, transmittance: 1%, molecular weight: 366.51)

[0189] B-12: Omnirad ITX (manufactured by IGM Resins, hydrogen-abstracting type, transmittance: 12%, molecular weight: 254.35)

[0190] (Measurement of transmittance)

[0191] Ink α was prepared by dissolving photopolymerization initiator B-1 in dipropylene glycol diacrylate at a content of 3% by mass. This ink was then applied to a polyimide film using a wire rod to achieve a film thickness of 10 μm. The applied ink was then irradiated with a UV light source (FireJet FJ100, Phoseon) at a wavelength of 365 nm and an illuminance of 2.0 W / cm². 2 Light intensity 2000mJ / cm 2 Ultraviolet light was used to cure ink α. Next, ink α was further applied to the cured ink α using a wire rod, and the further applied ink α was irradiated with the same ultraviolet light source. These steps were repeated to produce a cured film with a thickness of 40 μm. Then, the cured film was peeled off from the polyimide film. The transmittance of the peeled cured film at the peak wavelength of the excitation spectrum of the phosphorescent pigment at 324 nm was measured using a spectrophotometer (V-650, manufactured by Nippon Spectrophotometer Co., Ltd.). Specifically, the incident angle of the detector stage of the spectrophotometer was set to 90°, and the incident angle of the sample stage was set to 0° for measurement. The transmittance of photopolymerization initiators B-2 to B-12 was also measured in the same manner.

[0192] 2. Formation of ink-based cured products

[0193] Two independently driven printheads of a piezoelectric printhead (KM1024iLHE-30, manufactured by Konica Minolta, 360 dpi) are arranged with their nozzles staggered to create an inkjet recording head with a nozzle array of 720 dpi. In this printhead module, ink 1 is filled from an ink tank containing ink 1 via an ink flow path.

[0194] Next, a voltage was applied to the inkjet printing head at a droplet ejection rate of 30 pL to print a solid pattern on a 150 mm × 150 mm area of ​​the acrylic resin plate. Then, the plate was irradiated with a FireJet FJ100 from Phoseon at a wavelength of 365 nm and a light intensity of 2000 mJ / cm². 2 The ultraviolet light causes the ink to cure.

[0195] The cured ink is then further coated with ink under the same conditions, and the coated ink is then irradiated with ultraviolet light under the same conditions to cure the ink. This process is repeated to form a cured product with a thickness of 1000 μm.

[0196] Perform the same operation on inks 2 to 25.

[0197] 3. Evaluation

[0198] (brightness)

[0199] The brightness of each cured product was measured according to the phosphorescence brightness measurement method in JIS Z9107A:2008. Specifically, after storing the printed product with cured products formed using inks 1 to 25 in a dark room for more than 48 hours, the brightness was measured using a common light source fluorescent lamp D. 65 The cured material was irradiated with light at an illuminance of 200 lx for 20 minutes. The residual luminance was measured 20 minutes after the light irradiation was stopped using a luminance meter (LS110, manufactured by Konica Minolta Co., Ltd.). Based on the measured luminance values, the luminance was evaluated according to the following criteria.

[0200] ◎:150mcd / m 2 above

[0201] ○: 100mcd / m 2 Above and below 150 mcd / m 2

[0202] △: 50mcd / m 2 Above and below 100 mcd / m 2

[0203] ×: Less than 50 mcd / m 2

[0204] (Curing properties)

[0205] The cured material was rubbed with a JK wiper, and the curing properties were evaluated by the presence of residue and finger touch.

[0206] ◎: No residue left, and no stickiness on the surface.

[0207] ○: Slight traces remain, but the surface is not sticky.

[0208] △: Slight traces remain, and the surface is slightly sticky.

[0209] ×: There are traces left, and the surface is quite sticky.

[0210] (Water resistance)

[0211] The cured material was immersed in water at 25°C for 24 hours, and then its brightness was measured. The brightness measurement was performed using the same method as described above.

[0212] ◎:100mcd / m 2 Above and below 150 mcd / m 2

[0213] ○: 50mcd / m 2 Above and below 100 mcd / m 2

[0214] △: Less than 50 mcd / m 2

[0215] ×: Less than 50 mcd / m 2 And see peeling

[0216] (Weather resistance)

[0217] The cured material was subjected to weathering resistance testing according to JIS B 7753:2007. Specifically, the cured material was irradiated with 255 W / m² of radiation in the wavelength range of 300 nm to 700 nm using a Sunshine weather meter S80 (manufactured by Suga Testing Equipment Co., Ltd.). 2 After 102 minutes of light exposure, the product was sprayed with water for 18 minutes and then irradiated with the same light. This process was repeated for 78 hours. The brightness of the cured product was then measured. The brightness measurement was performed using the same method as described above.

[0218] ◎◎:125mcd / m 2 Above and below 150 mcd / m 2

[0219] ◎:100mcd / m 2 Above and below 125 mcd / m 2

[0220] ○: 50mcd / m 2 Above and below 100 mcd / m 2

[0221] △: Less than 50 mcd / m 2

[0222] ×: Less than 50 mcd / m 2 And see peeling

[0223] (Seamless fit)

[0224] According to the cross-cutting method of JIS K5600, the cured material was cut into a checkerboard pattern, adhesive tape was applied, and then peeled off. The peeling state of the cured material was observed, and the adhesion residue rate was calculated and evaluated according to the following criteria. Here, the adhesion residue rate is calculated as the ratio of the number of squares remaining after tape peeling to the number of squares made by the cut.

[0225] ◎◎: 100% adhesion residue rate

[0226] ◎: Adhesion residue rate is above 95% and less than 100%.

[0227] ○: Adhesion residue rate is above 90% and less than 95%.

[0228] △: Adhesion residue rate is above 70% and less than 90%.

[0229] ×: Adhesion residue rate is less than 70%.

[0230] (Yellowish)

[0231] The obtained solidified material was analyzed using a fluorescence spectrophotometer (FD-7, Konica Minolta, Inc.) under conditions of an observation light source D50 and an observation field of view of 2°, with b being measured. * The value of b. ＊ The value is used to evaluate yellowing according to the following criteria.

[0232] ○:b ＊ Less than 5

[0233] △:b ＊ 5 or more and less than 10

[0234] ×:b ＊ 10 or above

[0235] The evaluation results are summarized in Tables 1 to 5.

[0236] [Table 1]

[0237]

[0238] [Table 2]

[0239]

[0240] [Table 3]

[0241]

[0242] [Table 4]

[0243]

[0244] [Table 5]

[0245]

[0246] Ink 1 to 18, the brightness of the cured product is higher than that of ink 19 to 25. This is believed to be because the ink contains a photopolymerization initiator with a transmittance of more than 40% for the peak wavelength of the excitation spectrum of the phosphorescent pigment, which makes it easier for light of that wavelength to reach the phosphorescent pigment.

[0247] In inks 6-8, the curing properties and water resistance of the cured products are higher because the photopolymerization initiator is a hydrogen-abstraction type photopolymerization initiator. This is believed to be due to the fact that the use of a hydrogen-abstraction type photopolymerization initiator makes the product less susceptible to oxygen inhibition. In particular, inks 7 and 8, which use an intramolecular hydrogen-abstraction type photopolymerization initiator, show further improvements in water resistance and weather resistance.

[0248] It is believed that the curability is further improved in inks 9-12 due to the inclusion of the aforementioned photopolymerization initiator with a transmittance of less than 40%. It is particularly believed that in ink 9, since the aforementioned photopolymerization initiator with a transmittance of less than 40% is an acylphosphine oxide-based photopolymerization initiator, yellowing can be suppressed compared to inks 10-12.

[0249] It is believed that the cured products of inks 13-18 have higher brightness because the active ray polymerizable compounds contain acrylates with aromatic rings. This is because the inclusion of acrylates with aromatic rings allows light incident on the cured product to further reach the phosphorescent pigment.

[0250] It is believed that the curing shrinkage of ink 16 is suppressed by including a monofunctional reactive ray-polymerizable compound, thereby improving adhesion. Furthermore, it is believed that the adhesion of inks 17 and 18 is improved by using reactive ray-polymerizable compounds with alkylene glycol structures, and weather resistance is particularly improved in ink 18 due to the use of a compound with a propylene glycol structure.

Claims

1. An active X-ray curable ink, comprising an active X-ray polymerizable compound, a phosphorescent pigment, and a photopolymerization initiator, For the aforementioned photopolymerization initiator, a 3% by mass solution of the photopolymerization initiator in dipropylene glycol diacrylate is used under a nitrogen atmosphere to achieve a light intensity of 2000 mJ / cm². 2 The transmittance of light with a peak wavelength of 40 μm obtained by repeatedly forming a 10 μm thick cured material on a 365 nm ultraviolet light irradiation method is 40% or more. The photopolymerization initiator is an intramolecular hydrogen abstraction type photopolymerization initiator.

2. The active radiation-curable ink according to claim 1, wherein, The active ray polymerizable compound includes compounds having aromatic rings.

3. The active radiation-curable ink according to claim 1, wherein, The active ray-polymerizable compound comprises a monofunctional compound.

4. The active radiation-curable ink according to claim 1, wherein, The active X-ray polymerizable compound includes compounds having an alkylene glycol structure.

5. The active radiation-curable ink according to claim 4, wherein, The compound having an alkylene glycol structure has an alkylene glycol structure having 3 or more carbon atoms.

6. The active radiation-curable ink according to claim 1, wherein, The content of the phosphorescent pigment is 10% to 50% by mass relative to the total mass of the active ray curable ink.

7. The active radiation-curable ink according to claim 1, wherein, The peak wavelength of the excitation spectrum of the phosphorescent pigment is 300 nm to 400 nm.

8. The active radiation-curable ink according to claim 1, wherein, The ink is inkjet ink.

9. A method for forming a solidified product, comprising: The process of applying the active radiation-curable ink of claim 1 to a substrate, and The process of irradiating the applied active-ray curable ink with active rays.

10. A cured product, formed by curing the active radiation-curable ink of claim 1.

11. A photoluminescent panel having a substrate and a cured product of claim 10 formed on said substrate.

Images