Active-ray curable ink, method for forming cured product, cured product, and phosphorescent plate

Abstract

To provide: an active energy ray-curable ink which can increase luminance of a cured material formed; a cured material; and a luminous plate.SOLUTION: An active ray-curable ink comprises: an active ray-curable compound: a luminous pigment; and a photoinitiator. The photoinitiator is such that transmittance of light having a peak wavelength of an excitation spectrum of the luminous pigment in a cured material having 40 μm thickness is 40 percent or more, obtained by repetitively forming a cured material on a cured material having 10 μm thickness formed by curing by irradiating a dipropylene glycol diacrylate solution (3 mass% concentration) of the photoinitiator with ultraviolet light of 365 nm wavelength in a nitrogen gas atmosphere so that the light volume becomes 2000 mJ / cm2.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an active-ray curable ink, a method for forming a cured product, a cured product, and a phosphorescent plate. [Background technology]

[0002] In the field of printing, active-ray curable inks containing active-ray polymerizable compounds are known as inks used in the printing industry. When irradiated with active rays, active-ray curable inks harden through polymerization of the active-ray polymerizable compounds, forming a cured film and thus enabling the formation of printed materials. Printed materials formed with active-ray curable inks have excellent durability and can therefore be used for outdoor signs and other applications.

[0003] However, when printed materials formed with the above ink were used for outdoor signs and the like, the printed areas were difficult to see in the dark at night. To address this, one could irradiate light from the back of the printed material's substrate to make the printed areas visible in the dark, but this requires driving a light source device, which poses an energy-saving problem.

[0004] Therefore, there is a growing expectation for improving the visibility of printed areas even in dark places without using the light source devices described above, and the development of inks that can achieve this is underway.

[0005] One such ink is an active-ray curing ink containing phosphorescent pigments (for example, Patent Documents 1-5). The phosphorescent pigment can absorb light of a predetermined wavelength and store the light energy. The light energy stored in the phosphorescent pigment is then emitted for a long time as light of a different wavelength than the absorbed light, even after light absorption has stopped. As a result, for example, when printed materials formed using ink containing phosphorescent pigments are used outdoors, the phosphorescent pigments can absorb light such as sunlight, store the light energy, and emit light even at night. Therefore, the printed portion can be seen even in dark places. [Prior art documents]

Patent Document

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0007] As in Patent Documents 1 to 5, active energy ray-curable inks containing a phosphorescent pigment are known. Regarding these inks, there is a desire to increase the luminance of the cured product formed in order to enhance the visibility in the dark of the printed portion.

[0008] The present invention has been made in view of the above circumstances, and an object thereof is to provide an active energy ray-curable ink containing a phosphorescent pigment, which can increase the luminance of the cured product formed, a method for forming a cured product using the same, a cured product, and a phosphorescent plate.

Means for Solving the Problems

[0009] One aspect of the present invention for solving the above problems relates to the active energy ray-curable inks of the following [1] to

[12] . [1] An active energy ray-polymerizable compound, a phosphorescent pigment, and a photoinitiator, wherein the photoinitiator is irradiated with ultraviolet light having a wavelength of 365 nm with a light amount of 2000 mJ / cm in a nitrogen gas atmosphere with respect to a dipropylene glycol diacrylate solution (concentration: 3% by mass) of the photoinitiator 2An actinic ray-curable ink, wherein on a cured product having a thickness of 10 μm formed by irradiating and curing so as to obtain a cured product, the transmittance of light having a peak wavelength of the excitation spectrum of the phosphorescent pigment in a cured product having a thickness of 40 μm obtained by repeatedly forming the cured product is 40% or more. [2] The actinic ray-curable ink according to [1], wherein the photopolymerization initiator includes a hydrogen abstraction type initiator. [3] The actinic ray-curable ink according to [1] or [2], wherein the photopolymerization initiator includes an intramolecular hydrogen abstraction type initiator. [4] The actinic ray-curable ink according to any one of [1] to [3], further including a photopolymerization initiator having a transmittance of less than 40% and being 3% by mass or more and 17% by mass or less with respect to the total mass of the photopolymerization initiator. [5] The actinic ray-curable ink according to any one of [1] to [4], further including an acylphosphine oxide-based photopolymerization initiator. [6] The actinic ray-curable ink according to any one of [1] to [5], wherein the photopolymerizable compound includes a compound having an aromatic ring. [7] The actinic ray-curable ink according to any one of [1] to [6], wherein the photopolymerizable compound includes a monofunctional compound. [8] The actinic ray-curable ink according to [1] to [7], wherein the photopolymerizable compound includes a compound having an alkylene glycol structure. [9] The actinic ray-curable ink according to [8], wherein the number of carbon atoms constituting the alkylene glycol structure is 3 or more.

[10] The actinic ray-curable ink according to any one of [1] to [9], wherein the content of the phosphorescent pigment is 10% by mass or more and 50% by mass or less with respect to the total mass of the actinic ray-curable ink.

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

[10] , wherein the peak wavelength of the excitation spectrum of the phosphorescent pigment is 300 nm or more and 400 nm or less.

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

[11] , which is an inkjet ink. [[]END]]

[0010] [[]END]] [[]END]]Also, one aspect of the present invention for solving the above problems relates to a method for forming a cured product described in

[13] below. [[]END]]A method for forming a cured product, comprising the steps of: applying an active-ray curable ink described in any of

[13] [1] to

[12] to a recording medium; and irradiating the applied active-ray curable ink with an active ray.

[0011] Furthermore, one aspect of the present invention for solving the above problems relates to the cured product forming method described in

[14] below. A cured product obtained by curing an active-wire-curable ink as described in any of

[14] [1] to

[12] .

[0012] Furthermore, one aspect of the present invention for solving the above problems relates to the phosphorescent plate described in

[15] below. A phosphorescent plate having the cured material described in

[15]

[14] . [Effects of the Invention]

[0013] The present invention provides an active-ray curable ink containing a phosphorescent pigment that can further enhance the brightness of the resulting cured product, a method for forming a cured product using the same, a cured product, and a phosphorescent plate. [Modes for carrying out the invention]

[0014] The embodiments of the present invention will be described in detail below. However, the present invention is not limited to the following embodiments.

[0015] 1. Active-ray curing ink The active-ray curable ink (hereinafter also simply referred to as "ink") according to this embodiment comprises an active-ray polymerizable compound, a phosphorescent pigment, and a photopolymerization initiator. The ink is preferably an inkjet ink.

[0016] As mentioned above, there is a demand for increased brightness of the cured product formed by active-ray curing inks containing phosphorescent pigments.

[0017] The cured product contains residue of the photopolymerization initiator used to cure the ink. According to the inventors' findings, this residue readily absorbs light of a wavelength that excites the phosphorescent pigment (excitation light) from the light incident on the cured product. Furthermore, according to the inventors, this residue can cause yellowing of the cured product. The yellowed areas in the cured product readily absorb the excitation light. For these reasons, the phosphorescent pigment in the cured product, especially the phosphorescent pigment near the substrate, did not receive sufficient excitation light, resulting in insufficient luminescence. In contrast, by selecting a photopolymerization initiator according to the phosphorescent pigment to reduce the absorption of the wavelength of excitation light due to the residue and yellowing after curing, it is possible to allow sufficient excitation light to reach the phosphorescent pigment in the cured product, and furthermore, to allow sufficient excitation light to reach the phosphorescent pigment near the substrate. As a result, it is believed that the phosphorescent pigment in the cured product can emit sufficient light.

[0018] Therefore, the inventors considered that when the transmittance of excitation light from the phosphorescent pigment to the cured product containing the photopolymerization initiator is high, the absorption of the excitation light due to the above-mentioned residue and yellowing is reduced, and selected a photopolymerization initiator that increases the above transmittance.

[0019] Specifically, a dipropylene glycol diacrylate solution (3% by mass) used as a photopolymerization initiator was exposed to ultraviolet light at a wavelength of 365 nm and an intensity of 2000 mJ / cm² under a nitrogen gas atmosphere. 2 The phosphorescent pigment and photopolymerization initiator are selected such that the transmittance of light at the peak wavelength of the excitation spectrum of the phosphorescent pigment in a 40 μm thick cured product, obtained by repeatedly forming the 10 μm thick cured product on top of the cured product, is 40% or more. This reduces the absorption of excitation light by the residue of the photopolymerization initiator contained in the cured product, allowing sufficient excitation light to reach the phosphorescent pigment in the cured product, causing the entire phosphorescent pigment to emit light sufficiently and further increasing the brightness of the cured product.

[0020] Since the transmittance of the photopolymerization initiator to the excitation light is different from that of the residue of the photopolymerization initiator used to cure the ink, measuring the transmittance using the method described above allows us to confirm that the absorption of the excitation light by the residue has been reduced. Furthermore, by measuring the transmittance using the method described above, we can confirm how easily the excitation light reaches the phosphorescent pigment, including the effect of yellowing that occurs during ink curing.

[0021] 1-1.Active radiation polymerizable compounds The activated-ray polymerizable compound contained in the ink according to this embodiment is a compound that polymerizes and crosslinks upon irradiation with activated rays.

[0022] Examples of active rays include electron beams, ultraviolet rays, alpha rays, gamma rays, and X-rays. Of these, ultraviolet rays and electron beams are preferred, with ultraviolet rays being more preferred.

[0023] Examples of active ray polymerizable compounds include radical polymerizable compounds and cationic polymerizable compounds. Of these, the active ray polymerizable compound is preferably a radical polymerizable compound. The active ray polymerizable compound may be a monomer, a polymerizable oligomer, or a mixture thereof. The active ray polymerizable compound may be present as a single compound or as a combination of two or more compounds in the ink.

[0024] Furthermore, the activated ray polymerizable compound may be monofunctional or polyfunctional. From the viewpoint of suppressing the decrease in the adhesion of the cured product to the substrate due to curing shrinkage, it is preferable that the activated ray polymerizable compound includes a monofunctional compound.

[0025] Radical polymerizable compounds are monofunctional or polyfunctional compounds that have ethylenically unsaturated bonds that can be radically polymerized within their molecules. Examples of compounds having ethylenically unsaturated bonds that can be radically polymerized 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.

[0026] The radical polymerizable compound is preferably an unsaturated carboxylic acid ester and a (meth)acrylate, and more preferably a (meth)acrylate.

[0027] Examples of monofunctional (meth)acrylates include isoamyl (meth)acrylate, stearyl (meth)acrylate, isobonyl (meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, isomirsutyl (meth)acrylate, isostearyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, 2-ethylhexyl-diglycol (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-(meth)acryloyloxyethylhexahydrophthalic acid, butoxyethyl (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, methoxydiethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, methoxypropylene glycol (meth)acrylate, and o-phenyl This includes phenoxyethyl (meth)acrylate, m-phenoxybenzyl (meth)acrylate, cyclic trimethylolpropaneformal (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 succinic acid, 2-(meth)acryloyloxyethyl phthalic acid, 2-(meth)acryloyloxyethyl-2-hydroxyethyl phthalic acid, and t-butylcyclohexyl (meth)acrylate, among others.

[0028] 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, tricyclodecanedimethanol diacrylate, dimethylol-tricyclodecane di(meth)acrylate, bisphenol A type di(meth)acrylate, and hydroxypivalate neopentyl glycol di(meth)acrylate. This includes difunctional (meth)acrylates comprising polytetramethylene glycol di(meth)acrylate, polyethylene glycol diacrylate, dipropylene glycol diacrylate, and tripropylene glycol diacrylate, as well as trifunctional or more (meth)acrylates comprising 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 ethoxytetra(meth)acrylate, and oligomers having a (meth)acryloyl group, including polyester acrylate oligomers.

[0029] Examples of cationic polymerizable compounds include epoxy compounds, vinyl ether compounds, and oxetane compounds.

[0030] Examples of the epoxy compounds mentioned above include 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-methyloxyranyl)-7-oxabicyclo[4,1,0]heptane, 2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexanone-meth-dioxane and bis(2,3-epoxycyclopentyl) ethers, alicyclic epoxy resins, diglycidyl ether of 1,4-butanediol, diglycidyl ether of 1,6-hexanediol, and triglycerin. This includes aliphatic epoxy compounds such as polyglycidyl 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 ricidyl ethers, triglycidyl ethers of trimethylolpropane, diglycidyl ethers of polyethylene glycol, diglycidyl ethers of propylene glycol, ethylene glycol, propylene glycol, and glycerin; and aromatic epoxy compounds such 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.

[0031] Examples of the vinyl ether compounds mentioned above 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, as well as 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.

[0032] Examples of the above 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, and 3-hydroxyethyl This includes -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, among others.

[0033] The activated linear polymerizable compound preferably contains a compound having an aromatic ring. Including a compound having an aromatic ring in the activated linear polymerizable compound can increase the refractive index of the ink and the resulting cured product.

[0034] The refractive index of phosphorescent pigments is high, and the refractive index difference between the phosphorescent pigment and the surrounding cured material is considered to be large. Therefore, even when attempting to expose the phosphorescent pigment to light, reflection of the incident light is likely to occur at the interface between the phosphorescent pigment and the cured material. In contrast, it is thought that increasing the refractive index of the cured material with a compound containing an aromatic ring can reduce the refractive index difference between the phosphorescent pigment and the surrounding cured material. This reduces the reflection of light occurring at the interface between the phosphorescent pigment and the cured material, allowing more light to be incident on the phosphorescent pigment. As a result, the phosphorescent pigment can emit more light, and thus the brightness of the cured material can be further improved.

[0035] Furthermore, when the ink is cured, the phosphorescent pigment absorbs a portion of the active rays irradiated onto the ink, resulting in a slight emission of light from the phosphorescent pigment. This slight emission is absorbed by the photopolymerization initiator, allowing the polymerization of the active-ray polymerizable compound to proceed. At this time, the presence of the compound having the aromatic ring in the ink can increase the refractive index of the ink. This reduces the difference in refractive index between the phosphorescent pigment and the ink surrounding it, reducing the reflection of active rays at the interface between the phosphorescent pigment and the ink, and allowing more active rays to be incident on the phosphorescent pigment. As a result, the emission generated by the phosphorescent pigment can be increased, and the polymerization of the active-ray polymerizable compound can be further advanced, thus improving the curability of the cured product.

[0036] Examples of compounds having the above 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, and 2-hydroxy-o-phenylphenolpropyl (meth)acrylate. In particular, 2-phenoxyethyl (meth)acrylate, o-phenylphenoxyethyl (meth)acrylate, m-phenoxybenzyl (meth)acrylate, and ethoxylated phenoxy(meth)acrylate are more preferred in terms of inkjet ejectability and brightness.

[0037] When the active-ray polymerizable compound contains a compound having an aromatic ring, the content of the compound having an aromatic ring is preferably 20% to 70% by mass, and more preferably 30% to 60% by mass, relative to the total mass of the ink. When the above content is 20% by mass or more, the difference in refractive index between the phosphorescent pigment and the cured material surrounding the phosphorescent pigment can be made smaller, so that more light is incident on the phosphorescent pigment and the phosphorescent pigment emits more light. This can further improve the brightness of the cured material. Also, when the above content is 20% by mass or more, the difference in refractive index between the phosphorescent pigment and the ink surrounding the phosphorescent pigment can be made smaller, so that more active rays are incident on the phosphorescent pigment and the phosphorescent pigment emits more light. This can further promote the polymerization of the active-ray polymerizable compound and further improve the curability of the cured material. When the above content is 70% by mass or less, it can further suppress the refractive index of the ink and cured material from becoming too high. This can appropriately adjust 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.

[0038] The activated linear polymerizable compound preferably contains a compound having an alkylene glycol structure. According to the inventors' findings, compounds having an alkylene glycol structure are considered to have a high affinity for the phosphorescent pigments described later. Therefore, the inclusion of the above compound in the ink allows the phosphorescent pigment to exist in a more dispersed state in the cured product. This is thought to further suppress the aggregation of the phosphorescent pigment in the cured product, thereby improving the adhesion of the cured product to 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, and polypropylene glycol di(meth)acrylate. In particular, polyethylene glycol di(meth)acrylate, dipropylene glycol diacrylate, tripropylene glycol di(meth)acrylate, and ethoxylated phenoxy(meth)acrylate are even more preferred from the viewpoint of adhesion.

[0039] Of these, it is preferable that the number of carbon atoms constituting the alkylene glycol structure is between 3 and 4. Including a compound having an alkylene glycol structure with 3 or more carbon atoms in the ink suppresses excessive hydrophilicity of the cured product, making it less susceptible to water absorption, and thus further enhances the weather resistance of the cured product formed by the ink. Furthermore, having 4 or fewer carbon atoms suppresses a decrease in affinity between the cured product and the phosphorescent pigment, further suppressing a decrease in the adhesion of the cured product to the substrate.

[0040] In the molecular structure of a compound having an alkylene glycol structure, it is preferable that the alkylene glycol structure is present in two to four units. The presence of two or more alkylene glycol structures can further enhance the adhesion of the cured product to the substrate. Having four or fewer alkylene glycol structures can further suppress the decrease in curability of the cured product. Since the alkylene glycol structure is considered a flexible structure that can enhance molecular mobility, it is thought that limiting the number of alkylene glycol structures to four or fewer can further suppress the decrease in curability due to excessive flexibility of the cured product.

[0041] The content of the compound having an alkylene glycol structure is preferably 5% by mass or more and 40% by mass or less, and more preferably 10% by mass or more and 35% by mass or less, based on the total mass of the ink. A content of 5% by mass or more can further improve the adhesion of the cured product to the substrate, while a content of 40% by mass or less can further suppress the decrease in the curability of the cured product.

[0042] The content of the active linearly polymerizable compound can be, for example, 1% to 95% by mass, preferably 30% to 95% by mass, and more preferably 50% to 95% by mass, based on the total mass of the ink.

[0043] 1-2. Luminous pigments In this embodiment, the ink contains a phosphorescent pigment.

[0044] Luminous pigments can absorb light of a specific wavelength and store its energy. Even after absorbing light, they can release the stored energy as light of a different wavelength than the absorbed light for a long period of time. In other words, luminous pigments can emit phosphorescence.

[0045] The type of phosphorescent pigment is not particularly limited as long as it has the above-mentioned characteristics. Examples of phosphorescent pigments include those in which the host crystal, which is a metal compound, has been activated.

[0046] Examples of the parent crystals mentioned above 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, alumina, and cerium oxide; and aluminates such as calcium aluminate, strontium aluminate, and barium aluminate. Of these, strontium aluminate is preferred.

[0047] Examples of activators used to activate the above-mentioned parent crystals include europium, terbium, yttrium, zirconium, dysprosium, and barium. Of these, europium and dysprosium are preferred.

[0048] The phosphorescent pigment may be included in the ink as a single type, or as a combination of two or more types.

[0049] The peak wavelength of the excitation spectrum of the phosphorescent pigment is preferably between 300 nm and 400 nm. Having the peak wavelength of the excitation spectrum of the phosphorescent pigment within this range allows for greater excitation of the phosphorescent pigment when sunlight strikes it. Therefore, for example, the cured product can be adapted for outdoor use. Furthermore, having the peak wavelength within this range makes it easier for the peak wavelength of the emission spectrum of the phosphorescent pigment to fall within the preferred range described later, thus improving the visibility (visibility) of the cured product (printed portion).

[0050] 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 product (printed portion), it is preferable that it be 450 nm to 600 nm.

[0051] The particle size at which the cumulative value in the volume-based particle size distribution of phosphorescent pigments reaches 50% (d 50The particle size is not particularly limited, but is preferably 10 μm or less, and more preferably 8 μm or less. When the ink according to this embodiment is used as an inkjet ink, a particle size of 10 μm or less can suppress a decrease in ejection stability. The lower limit of the particle size is not particularly limited, but is preferably 0.5 μm or more, and more preferably 1 μm or more. The particle size of the phosphorescent pigment can be measured using a particle size distribution analyzer that utilizes the Stokes sedimentation method (for example, LUMiSizer, manufactured by LUM Japan Co., Ltd.).

[0052] The phosphorescent pigment content is preferably 10% to 50% by mass, and more preferably 15% to 35% by mass, relative to the total mass of the ink. A content of 10% or more by mass can further improve the brightness of the cured product. A content of 50% or less by mass increases the proportion of activated linear polymerizable compounds in the ink, further improving the curability and adhesion of the cured product to the substrate. Furthermore, a content of 50% or less by mass can suppress a decrease in ejection stability when the ink is used as an inkjet ink.

[0053] 1-3. Photopolymerization Initiators The ink according to this embodiment contains a photopolymerization initiator.

[0054] The above photopolymerization initiator was prepared by irradiating a dipropylene glycol diacrylate solution (concentration 3% by mass) with ultraviolet light at a wavelength of 365 nm and an intensity of 2000 mJ / cm² under a nitrogen gas atmosphere. 2 The transmittance (hereinafter also referred to simply as transmittance) of light at the peak wavelength of the excitation spectrum of the phosphorescent pigment of a 40 μm thick cured product obtained by repeatedly forming the 10 μm thick cured product on a 10 μm thick cured product formed by irradiating and curing in such a manner is 40% or more.

[0055] Furthermore, because the thickness of the cured material formed in the above measurement is 10 μm, differences in the degree of curing of the cured material due to differences in the maximum absorption wavelength of the photopolymerization initiator are unlikely to occur. Therefore, differences in the curability of the 40 μm thick cured material obtained by laminating this material, depending on the type of photopolymerization initiator, are also unlikely to occur.

[0056] As described above, the inclusion of the above-mentioned photopolymerization initiator in the ink can enhance the brightness of the cured product.

[0057] The above transmittance can be measured, for example, using a spectrophotometer (V-650, manufactured by JASCO Corporation) to determine the transmittance 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 in the spectrophotometer to 90° and the incident angle of the sample stage to 0°.

[0058] The photopolymerization initiator can be a radical initiator when the ink contains a radical polymerizable compound, and a cationic initiator (photoacid generator) when the ink contains a cationic polymerizable compound.

[0059] Examples of radical polymerization initiators include intramolecular cleavage type photopolymerization initiators and hydrogen abstraction type polymerization initiators. The above photopolymerization initiators may be present in the ink as a single type or in combination of two or more types.

[0060] Examples of intramolecular cleavage-type photopolymerization initiators include acetophenone-based initiators such as 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethyl 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] Examples of commercially available intramolecular cleavage-type photopolymerization initiators include Omnirad127, Omnirad184, Omnirad651, Omnirad2959, Omnirad819, and Esacure One (manufactured by IGM Resins).

[0062] Among these intramolecular cleavage-type photopolymerization initiators, acylphosphine oxide-based initiators are preferred. Acylphosphine oxide-based initiators have photobleaching properties, which can further suppress yellowing. Photobleaching properties refer to the property of the absorption spectrum of a photopolymerization initiator to shift when irradiated with active rays. This further suppresses the shielding of the luminescence of the phosphorescent pigment in the yellow portion of the cured product, thereby further suppressing the decrease in brightness of the cured product.

[0063] Hydrogen abstraction type photopolymerization initiators include intermolecular hydrogen abstraction type photopolymerization initiators and intramolecular hydrogen abstraction type photopolymerization initiators.

[0064] In this specification, "intermolecular hydrogen abstraction type 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 radicals.

[0065] Examples of intermolecular hydrogen abstraction type photopolymerization initiators include benzophenone-based initiators such as benzophenone, o-benzoylmethyl benzoate, 4-phenylbenzophenone, 4,4'-dichlorobenzophenone, hydroxybenzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide, acrylic 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.

[0066] Examples of commercially available intermolecular hydrogen abstraction type photopolymerization initiators include Irgacure500 (BASF) and SpeedcureITX (Lambson).

[0067] Furthermore, in this specification, "intramolecular hydrogen abstraction type photopolymerization initiator" refers to a compound that is excited by irradiation with active light and undergoes an intramolecular hydrogen abstraction reaction to generate radicals.

[0068] Examples of intramolecular hydrogen abstraction type photopolymerization initiators include methyl benzoylformate-based photopolymerization initiators such as methyl phenylglyoxylate, and oxyphenyl-based photopolymerization initiators such as mixtures of oxyphenylacetic acid-2-[2-oxo-2-phenylacetoxy-ethoxy]ethyl ester and oxyphenylacetic acid-2-[2-hydroxy-ethoxy]ethyl ester.

[0069] Examples of commercially available intramolecular hydrogen abstraction type photopolymerization initiators include Omnirad MBF (manufactured by IGM Resins) and Irgacure 754 (manufactured by BASF).

[0070] The photopolymerization initiator preferably includes a hydrogen abstraction type photopolymerization initiator, and more preferably includes an intramolecular hydrogen abstraction type photopolymerization initiator.

[0071] By using a hydrogen abstraction type photopolymerization initiator, the curing of the ink by irradiation with active rays can be further accelerated, thereby improving the curability and water resistance of the resulting cured product.

[0072] Oxygen inhibition refers to the inhibition of the polymerization reaction when radicals generated during polymerization react with oxygen to produce peroxides. Hydrogen abstraction type photopolymerization initiators can abstract hydrogen atoms from these peroxides, thereby regenerating radicals. This can further accelerate the polymerization reaction and suppress oxygen inhibition. As a result, it is believed that the curability and water resistance of the cured product can be improved.

[0073] Furthermore, intramolecular hydrogen abstraction type photopolymerization initiators induce hydrogen abstraction reactions within the molecule, generating radicals. Therefore, it is thought that they can further suppress the generation of radicals caused by the abstraction of hydrogen from the molecular chains of the active linearly polymerizable compound during polymerization. This further suppresses the crosslinking reactions between the molecular chains, allowing the molecular chains to be extended. As a result, the hydrophobicity of the resulting cured product can be increased, thereby improving the water resistance and weather resistance of the cured product.

[0074] Intramolecular hydrogen abstraction type photopolymerization initiators are preferably compounds having a glycooxyacid structure. Compounds having a glycooxyacid structure are more likely to induce intramolecular hydrogen abstraction reactions, and therefore are thought to be able to further improve the water resistance and weather resistance of the resulting cured product.

[0075] The molecular weight of the photoinitiator is preferably 150 or more and 500 or less, more preferably 150 or more and 190 or less. When the molecular weight is 150 or more, the ejection stability can be improved when the ink is used as an inkjet ink. When it is 500 or less, the mobility of the photoinitiator molecules in the ink is increased, making it easier to initiate the polymerization of the actinic ray-polymerizable compound near the substrate, and thus the curability of the cured product can be further enhanced.

[0076] Examples of cationic photoinitiators include photoacid generators. Examples of photoacid generators include B(C6F5)4 of aromatic onium compounds such as diazonium, ammonium, iodonium, sulfonium, and phosphonium. - , PF6 - , AsF6 - , SbF6 - , CF3SO3 - Salts, sulfonides that generate sulfonic acid, halides that generate hydrogen halide by light, and iron arene complexes are included.

[0077] Among these, in this embodiment, the photoinitiator used is one 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 photoinitiator with a transmittance of 40% or more for light with a wavelength of 324 nm is used. Examples of the photoinitiator used at this time include Omnirad127 (transmittance 71%), Omnirad184 (transmittance 73%), Omnirad651 (transmittance 55%), Omnirad2959 (transmittance 63%), Irgacure500 (transmittance 62%), Omnirad754 (transmittance 46%) (all manufactured by BASF), Esacure One (transmittance 71%) (manufactured by IGM Resins), Omnirad MBF (transmittance 45%) (manufactured by IGM Resins), etc.

[0078] 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%. When the transmittance is 80% or less, the light that excites the phosphorescent pigment reaches the substrate, which can further suppress the deterioration of the substrate. For example, by suppressing the transmission of sunlight to the substrate, the deterioration of the substrate can be further suppressed, thereby improving the suitability of the cured product for outdoor use. Furthermore, when the transmittance is 70% or less, the excessive transmission of light at the peak wavelength of the excitation spectrum of the phosphorescent pigment can be further suppressed, thereby further suppressing the deterioration of the cured product and improving the weather resistance of the cured product.

[0079] The content of the photopolymerization initiator having a transmittance of 40% or more is preferably 3% to 15% by mass, more preferably 3% to 10% by mass, and even more preferably 5% to 10% by mass, based on the total mass of the ink. A content of 3% by mass or more can further enhance the brightness of the cured product. A content of 15% by mass or less can further enhance the adhesion of the cured product.

[0080] The ink according to this embodiment may further contain a photopolymerization initiator having a transmittance of less than 40%, within the range that achieves the effects of the present invention.

[0081] Preferably, the transmittance of the photopolymerization initiator with a transmittance of less than 40% is 20% or more and less than 40%. When the transmittance of the photopolymerization initiator with a transmittance of less than 40% is 20% or more, for example, when the peak wavelength of the excitation spectrum of the phosphorescent pigment is in the ultraviolet region, the residue of the photopolymerization initiator can further reduce the absorption of light of that wavelength. As a result, the yellowing of the cured product, which is the complementary color of that wavelength, can be further suppressed, and the brightness of the cured product due to yellowing can be further suppressed.

[0082] The photopolymerization initiator having a transmittance of less than 40% preferably contains an acylphosphine oxide-based initiator. Acylphosphine oxide-based initiators have photobleaching properties, which can further suppress yellowing. This further suppresses the shielding of the phosphorescent pigment's light emission in the yellow portion of the cured product, thereby further suppressing the decrease in the brightness of the cured product.

[0083] The content of the photopolymerization initiator having a transmittance of less than 40% is preferably 3% to 30% by mass, and more preferably 5% to 20% by mass, relative to the total mass of the photopolymerization initiator. The photopolymerization initiator having a transmittance of less than 40% is considered to readily absorb active rays. Therefore, a content of 3% by mass or more can further promote the polymerization reaction of the active ray polymerizable compound, thereby improving the curability of the resulting cured product. A content of 30% by mass or less allows sufficient light to excite the phosphorescent pigment to reach the phosphorescent pigment, thereby further increasing the brightness of the cured product.

[0084] The above-mentioned photopolymerization initiator, whose transmittance is less than 40%, preferably has a transmittance of 20% or more and less than 40%, and more preferably 30% or more and less than 40%. A transmittance of 20% or more allows sufficient light to reach the phosphorescent pigment to excite it, thereby further increasing the brightness of the cured product.

[0085] 1-4. Others The ink according to this embodiment may further contain other components such as non-phosphorescent pigments, pigment dispersants, surfactants, fluorescent whitening agents, and polymerization inhibitors, to the extent that it achieves the effects of the present invention.

[0086] Examples of non-phosphorescent pigments include red, yellow, blue, and white pigments, which can be used in image-forming inks. Known pigments can be used for these purposes.

[0087] Examples of pigment dispersants include hydroxyl group-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, naphthalene sulfonic acid formalin condensate salts, aromatic sulfonic acid formalin condensate salts, polyoxyethylene alkyl phosphate esters, polyoxyethylene nonylphenyl ether, and stearylamine acetate. Examples of commercially available pigment dispersants include the Solsperse® series (manufactured by Avecia), the PB series (manufactured by Ajinomoto Fine Techno), and the EFKA series (manufactured by BASF).

[0088] The pigment dispersant content is preferably 0.5% by mass or more and 20% by mass or less, relative to the total mass of the phosphorescent pigment.

[0089] Examples of surfactants include anionic surfactants such as dialkyl sulfosuccinates, alkylnaphthalene sulfonates, and fatty acid salts; nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, and polyoxyethylene-polyoxypropylene block copolymers; cationic surfactants such as alkylamine salts and quaternary ammonium salts; and silicone-based and fluorine-based surfactants.

[0090] The amount of surfactant relative to the total mass of the ink is not particularly limited within the range that achieves the effects of the present invention, but for example, it can be 0.001% by mass or more and less than 1.0% by mass.

[0091] Examples of polymerization inhibitors include N-oxyl polymerization inhibitors, phenol polymerization inhibitors, quinone polymerization inhibitors, amine polymerization inhibitors, and copper dithiocarbamate polymerization inhibitors. The ink may contain only one polymerization inhibitor, or a combination of two or more.

[0092] Examples of N-oxyl polymerization inhibitors include 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO), 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, 4-oxo-2,2,6,6-tetramethylpiperidine-N-oxyl, 4-methoxy-2,2,6,6-tetramethylpiperidine-N-oxyl, and 4-acetoxy-2,2,6,6-tetramethylpiperidine-N-oxyl. An example of a commercially available N-oxyl polymerization inhibitor is Irgastab UV10 (manufactured by BASF, "Irgastab" is a registered trademark of the company).

[0093] 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-t-butyl-p-cresol (butylated hydroxytoluene: BHT), 4-methoxyphenol, and 2-methoxy-4-methylphenol.

[0094] Examples of quinone polymerization inhibitors include hydroquinone, methoxyhydroquinone, benzoquinone, 1,4-naphthoquinone, and p-tert-butylcatechol.

[0095] Examples of amine polymerization inhibitors include alkylated diphenylamines, N,N′-diphenyl-p-phenylenediamine, and phenothiazines.

[0096] Examples of copper dithiocarbamate polymerization inhibitors include copper dimethyldithiocarbamate, copper diethyldithiocarbamate, and copper dibutyldithiocarbamate.

[0097] The content of the polymerization inhibitor is not particularly limited within the range that achieves the effects of the present invention, but for example, it can be 0.001% by mass or more and 0.5% by mass or less, preferably 0.1% by mass or less, and more preferably less than 0.01% by mass.

[0098] 1-5. Physical Properties The viscosity of the ink according to this embodiment is preferably 5 mPa·s or more and 50 mPa·s or less at 25°C. Having the viscosity within this range improves the ejection stability when the ink is used as an inkjet ink.

[0099] The viscosity of ink at 25°C can be determined using a rheometer under conditions of a shear rate of 1000 / sec. Specifically, it can be determined by heating the ink to 25°C and measuring it under conditions of a shear rate of 1000 / sec.

[0100] A rheometer from Anton Paar's PhysicaMCR series of stress-controlled rheometers can be used. The cone plate diameter can be set to 75 mm and the cone angle to 1.0°.

[0101] 1-6. Method for preparing activated radiation-curable inks The ink according to this embodiment can be prepared by mixing the components described above. In this case, it is preferable to mix the components other than the phosphorescent pigment first, and then add the phosphorescent pigment to the resulting mixture.

[0102] When the ink contains a pigment dispersant, a pigment dispersion containing a phosphorescent pigment and a pigment dispersant may be prepared in advance, and the remaining components may be added and mixed thereto. In this case, it is preferable to prepare the pigment dispersion by heating the pigment and dispersant while mixing them in order to increase the solubility of the pigment dispersant and other components.

[0103] 2. Cured product formation method The cured product formation method according to this embodiment comprises the steps of applying an active-ray curable ink to a substrate and irradiating the applied active-ray curable ink with an active ray.

[0104] 2-1. Ink application process In this process, the above-mentioned active-ray curing ink is applied to the substrate.

[0105] Examples of methods for applying ink to a substrate include methods using a roll coater or spin coater, methods using screen printing, and methods using inkjet technology. Of these, the inkjet method is preferred from the viewpoint of forming a cured product more precisely at a desired position on the substrate.

[0106] When ink is applied to a substrate by the inkjet method, the ejection method from the inkjet head may be either on-demand or continuous. The inkjet head for the on-demand method may be any of the following: electromechanical conversion methods such as single-cavity type, double-cavity type, bender type, piston type, shear-mode type and shared-wall type, as well as electrothermal conversion methods such as thermal inkjet type and bubble jet ("bubble jet" is a registered trademark of Canon Inc.).

[0107] The type of base material is not particularly limited, but examples include ABS resin sheets, acrylic resin sheets, aluminum sheets, glass sheets, polycarbonate sheets, and cloth.

[0108] 2-2. Process of irradiating with active light In this process, the ink applied to the substrate is cured by irradiating it with an active ray. The wavelength of the active ray used for irradiation may be appropriately set to match the maximum absorption wavelength of the photopolymerization initiator.

[0109] The active ray can be selected from, for example, electron beams, ultraviolet rays, alpha rays, gamma rays, and X-rays, but ultraviolet rays or electron beams are preferred. The ultraviolet ray is preferably light having a peak wavelength of 360 nm to 410 nm. Furthermore, the ultraviolet ray is preferably irradiated from an LED light source. Compared to conventional light sources (such as metal halide lamps), LEDs emit less radiant heat, so using LEDs makes it less likely for the ink to melt when irradiated with an active ray, thus reducing the occurrence of uneven gloss.

[0110] When using ultraviolet light as the active ray, the light intensity per irradiation is 500 mJ / cm². 2 More than 4000mJ / cm 2 Preferably, the following: 500 mJ / cm² 2 The above conditions can further improve the curability of the resulting cured product. 4000 mJ / cm 2 The following conditions can suppress discoloration of the hardened material.

[0111] 2-3. Further ink application process The cured product formation method according to this embodiment may include a step of applying further ink to the ink that has been irradiated with the active ray.

[0112] This process allows for a greater thickness of the resulting cured material. A thicker cured material allows for the inclusion of more phosphorescent pigment, thereby improving the overall brightness of the cured material.

[0113] The method for further applying the ink may be the same as the method used in the step of applying the ink to the substrate, or it may be a different method.

[0114] 2-4. The process of irradiating the ink, which has been further applied to the ink, with an active ray. The cured product formation method according to this embodiment may further include a step of irradiating the applied ink with an active ray.

[0115] In this process, the above ink is further applied, and the further applied ink is irradiated with an active ray to cure the ink.

[0116] The type of active ray and the amount of light used when ultraviolet light is used can be the same as in step S20 above.

[0117] In the cured product formation method according to this embodiment, the thickness of the formed cured product can be increased by repeatedly performing steps S30 and S40.

[0118] 3.Cured product The cured product according to this embodiment is obtained by curing the above-mentioned active-ray curable ink.

[0119] The above-mentioned cured product can be formed by the cured product formation method described above.

[0120] The thickness of the cured product is preferably between 300 μm and 2000 μm. A thickness of 300 μm or more allows for the inclusion of more phosphorescent pigment in the cured product, further improving the overall brightness of the cured product. A thickness of 2000 μm or less allows for post-processing such as lamination of the cured product.

[0121] 4. Luminous plate The phosphorescent plate according to this embodiment comprises a base material and the cured material formed on the base material.

[0122] Examples of the above-mentioned substrates include ABS resin sheets, acrylic resin sheets, aluminum sheets, and polycarbonate sheets, but ABS resin sheets, acrylic resin sheets, and polycarbonate sheets are preferred.

[0123] In this embodiment, the phosphorescent plate is preferably overcoated with, for example, a varnish, a laminate film, or an ink. Examples of varnishes include Overlay C (manufactured by Shinloihi Co., Ltd.) and SP-3100AU Clear (manufactured by Teikoku Ink Manufacturing Co., Ltd.). Examples of laminate films include SS50TO(V) (manufactured by Riken Technos Co., Ltd.). [Examples]

[0124] The present invention will be described in detail below with reference to examples, but the scope of the present invention is not limited to the examples.

[0125] 1. Preparation of inks 1-29 (Preparation of pigment dispersions) An ink solvent was prepared by mixing 99.9 parts by mass of photopolymerizable compound A-1 (1,6-hexanediol diacrylate, molecular weight: 242) and 0.01 parts by mass of polymerization inhibitor (Irgastab UV-10, manufactured by BASF), and stirring the mixture while heating at 70°C for 1 hour.

[0126] 49 parts by mass of the prepared ink solvent, 50 parts by mass of phosphorescent pigment (G-300FF, manufactured by Nemoto Special Chemicals Co., Ltd., peak wavelength of excitation spectrum: 324 nm), and 1 part by mass of pigment dispersant (EFKA PX 4701, manufactured by BASF) were placed in a polypropylene container together with 50 parts by mass of zirconia beads with an average particle size of 0.3 mm. Dispersion treatment was carried out using a paint shaker for 30 minutes, and the zirconia beads were removed to prepare a pigment dispersion.

[0127] The prepared pigment dispersion was diluted with dipropylene glycol diacrylate, and the particle size distribution of the pigment was analyzed using a particle size distribution analyzer (LUMiSizer, manufactured by LUM Japan Co., Ltd.). 50 The particle size of the measured pigment was d 50 It was 3.8 μm. 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 mixing machine. 40 parts by mass of phosphorescent pigment dispersion was added to the resulting mixture and mixed further to obtain an ink composition. The obtained ink composition was filtered through a 30 μm polypropylene pleated filter (manufactured by Rokitechno Co., Ltd.) to obtain ink 1.

[0128] Inks 2 to 25 were obtained in the same manner as ink 1, except that the type and amount of photopolymerizable compound used, the type and amount of photopolymerization initiator, and the amount of phosphorescent pigment were changed as shown in Tables 1 to 5. Note that the numerical values ​​for the ink composition in Tables 1 to 5 represent parts by mass.

[0129] Tables 1-5 show the types of photopolymerizable compounds and photopolymerization initiators used, as follows. The transmittance values ​​listed for the photopolymerization initiators were measured using the method described below. The measured transmittances are shown in parentheses next to each photopolymerization initiator in Tables 1-5. (Photopolymerizable compound) A-1: 1,6-Hexanediol diacrylate A-2: Tricyclodecanedimethanol diacrylate A-3: Bisphenol A type 4EO-modified diacrylate A-4: 2-Phenoxyethyl acrylate A-5: Polyethylene glycol (200) diacrylate A-6: Dipropylene glycol diacrylate (Photopolymerization initiator) B-1: Omnirad2959 (manufactured by IGM Resins, intramolecular cleavage type, transmittance: 63%, molecular weight: 224.3) B-2: Omnirad651 (manufactured by IGM Resins, intramolecular cleavage type, transmittance: 55%, molecular weight: 256.3) B-3: Esacure One (manufactured by IGM Resins, intramolecular cleavage type, transmittance: 71%, molecular weight: 256.3) B-4: Omnirad127 (manufactured by IGM Resins, intramolecular cleavage type, transmittance: 71%, molecular weight: 340.7) B-5: Omnirad184 (manufactured by IGM Resins, intramolecular cleavage type, transmittance: 73%, molecular weight: 204.7) B-6: Irgacure500 (BASF, intermolecular hydrogen abstraction type, transmittance: 62%, molecular weight: mixture of 204.3 and 182.2) B-7: Omnirad MBF (manufactured by IGM Resins, intramolecular hydrogen abstraction type, transmittance: 45%, molecular weight: 161.4) B-8: Omnirad754 (manufactured by IGM Resins, intramolecular hydrogen abstraction type, transmittance: 46%, molecular weight: 370.36) B-9: Omnirad819 (manufactured by IGM Resins, intramolecular cleavage type, transmittance: 36%, molecular weight: 418.5) B-10: Omnirad907 (manufactured by IGM Resins, intramolecular cleavage type, transmittance: 0%, molecular weight: 279.4) B-11: Omnirad369 (manufactured by IGM Resins, BASF, intramolecular cleavage type, transmittance: 1%, molecular weight: 366.51) B-12: Omnirad ITX (manufactured by IGM Resins, hydrogen abstraction type, transmittance: 12%, molecular weight: 254.35)

[0130] (Measurement of transmittance) Ink α was prepared by dissolving photopolymerization initiator B-1 in dipropylene glycol diacrylate to a content of 3% by mass. This ink was then applied to a polyimide film to a thickness of 10 μm using a wire bar. The applied ink was then subjected to UV light (FireJet FJ100, Phoseon) at a wavelength of 365 nm and an irradiance of 2.0 W / cm². 2 , light intensity 2000mJ / cm 2Ink α was cured by irradiation with ultraviolet light. Next, more ink α was applied to the cured ink α using a wire bar, and the newly applied ink α was irradiated with the same ultraviolet light using the UV light source. These steps were repeated to produce a cured material with a film thickness of 40 μm. After that, the prepared cured material was peeled off the polyimide film. The transmittance of this peeled cured material at the peak wavelength of the excitation spectrum of the phosphorescent pigment, 324 nm, was measured using a spectrophotometer (V-650, manufactured by JASCO Corporation). Specifically, the incident angle of the detector stage in the spectrophotometer was set to 90°, and the incident angle of the sample stage was set to 0° for the measurement. The transmittance of photopolymerization initiators B-2 to B-12 was measured in the same manner.

[0131] 2. Formation of cured material by ink Two independent drive heads of a piezo-type inkjet head (KM1024iLHE-30, manufactured by Konica Minolta, Inc., 360 dpi) were arranged with their nozzles staggered to create an inkjet recording head with a nozzle row of 720 dpi. Ink 1 was supplied to this head module from an ink tank containing ink 1, via an ink channel.

[0132] Next, a voltage was applied to the inkjet recording head so that the droplet ejection volume was 30 pL, and a solid pattern was printed on a 150 mm x 150 mm area of ​​the acrylic resin plate. Then, a Phoseon FireJet FJ100 was used with a wavelength of 365 nm and a light intensity of 2000 mJ / cm². 2 The ink was cured by irradiating it with ultraviolet light.

[0133] After curing the ink, another layer of ink was applied under the same conditions, and the applied ink was cured by irradiating it with ultraviolet light under the same conditions. This process was repeated to form a cured material with a thickness of 1000 μm.

[0134] The same procedure was performed for inks 2 through 25.

[0135] 3. Evaluation (brightness) The luminance of each cured material was measured according to phosphorescence luminance measurement in accordance with JIS Z9107A:2008. Specifically, printed materials containing cured materials formed using inks 1 to 25 were stored in a dark room for 48 hours or more, and then subjected to a normal light source fluorescent lamp D 65 The cured material was irradiated with light at an illuminance of 200 lx for 20 minutes. The afterglow luminance 20 minutes after stopping the light irradiation was measured using a luminance meter (LS110, Konica Minolta, Inc.). Based on the measured luminance values, a luminance evaluation was performed according to the following criteria. ◎: 150 mcd / m 2 That's all. ○: 100 mcd / m 2 More than 150mcd / m 2 less than △: 50 mcd / m 2 More than 100mcd / m 2 less than ×: 50 mcd / m 2 less than

[0136] (curable) The resulting cured material was rubbed with a JK wiper, and its curability was evaluated based on the residue left behind and its feel to the touch. ◎: Leaves no residue and no stickiness on the surface. ○: There is a slight residue, but the surface is not sticky. △: There are slight traces remaining, and the surface is slightly sticky. ×: Leaves residue and the surface is very sticky.

[0137] (water resistance) The resulting cured material was immersed in 25°C water for 24 hours, and then its brightness was measured. The brightness measurement was performed using the same method as described above. ◎: 100 mcd / m 2 More than 150mcd / m 2 less than ○: 50mcd / m 2 More than 100mcd / m 2 less than △: 50 mcd / m 2 less than ×: 50 mcd / m 2 Less than and peeling is observed.

[0138] (weather resistance) The resulting cured material was subjected to weathering tests in accordance with JIS B 7753:2007. Specifically, a sunshine carbon arc lamp accelerated weathering tester (Sunshine Weather Meter S80, manufactured by Suga Test Instruments Co., Ltd.) was used to measure the irradiance at 255 W / m² in the wavelength range of 300 nm to 700 nm. 2 The cured material was irradiated with light for 102 minutes, followed by 18 minutes of water spraying and then irradiation with the same light. This process was repeated for 78 hours. After that, the brightness of the cured material was measured. The brightness measurement was performed using the same method as described above. ◎◎: 125 mcd / m 2 More than 150mcd / m 2 less than ◎: 100 mcd / m 2 More than 125mcd / m 2 less than ○: 50mcd / m 2 More than 100mcd / m 2 less than △: 50 mcd / m 2 less than ×: 50 mcd / m 2 Less than and peeling is observed.

[0139] (Adhesion) The obtained cured material was cut in a grid pattern according to the JIS K5600 cross-cut method, adhesive tape was applied, and the tape was peeled off. The peeling state of the cured material was observed, the adhesion residue rate was determined, and it was evaluated according to the following criteria. Here, the adhesion residue rate is calculated as the ratio of the number of squares remaining after tape removal to the number of squares created by the cuts. ◎◎: 100% adhesion and residue rate ◎: Adhesion retention rate 95% or more but less than 100% ○: Adhesion residue rate 90% or more but less than 95% △: Adhesion / residue rate 70% or more but less than 90% ×: Adhesion residue rate less than 70%

[0140] (yellowing) The resulting cured material was subjected to a fluorescence spectrometer (FD-7, manufactured by Konica Minolta, Inc.) under the conditions of observation light source D50 and observation field of view 2°. * The value of b was measured. * The yellowing was evaluated for the value according to the following criteria. ○:b * is less than 5 △:b * 5 or more but less than 10 ×:b * 10 or more

[0141] The evaluation results are summarized in Tables 1-5.

[0142] [Table 1]

[0143] [Table 2]

[0144] [Table 3]

[0145] [Table 4]

[0146] [Table 5]

[0147] In inks 1-18, the brightness of the cured product was higher than that of inks 19-25. This is thought to be because the inks contained a photopolymerization initiator with a transmittance of 40% or more at the peak wavelength of the excitation spectrum of the phosphorescent pigment, making it easier for light of that wavelength to reach the phosphorescent pigment.

[0148] In inks 6-8, the use of hydrogen abstraction type photopolymerization initiators resulted in improved curability and water resistance of the cured products. This is thought to be because the use of hydrogen abstraction type photopolymerization initiators made the products less susceptible to oxygen inhibition. In particular, inks 7 and 8, which use intramolecular hydrogen abstraction type photopolymerization initiators, showed further improvements in water resistance and weather resistance.

[0149] In inks 9-12, the curing properties are thought to have been further improved by including a photopolymerization initiator with a transmittance of less than 40%. In particular, in ink 9, since the photopolymerization initiator with a transmittance of less than 40% is an acylphosphine oxide-based photopolymerization initiator, it is thought that yellowing was suppressed more effectively than in inks 10-12.

[0150] In inks 13-18, the inclusion of an acrylate with an aromatic ring in the active-ray polymerizable compound resulted in higher brightness of the cured product. This is thought to be because the inclusion of an acrylate with an aromatic ring allowed more light incident on the cured product to reach the phosphorescent pigment.

[0151] In ink 16, the inclusion of a monofunctional active-ray polymerizable compound is thought to have suppressed curing shrinkage and improved adhesion. In addition, in inks 17 and 18, the use of an active-ray polymerizable compound having an alkylene glycol structure improved adhesion, and in particular, ink 18, which used a compound having a propylene glycol structure, is thought to have improved weather resistance.

Claims

1. Actively polymerizable compounds, Luminous pigments, A hydrogen abstraction type photopolymerization initiator is included, The photopolymerization initiator is prepared by heating a dipropylene glycol diacrylate solution of the photopolymerization initiator (concentration 3% by mass) with ultraviolet light at a wavelength of 365 nm at a light intensity of 2000 mJ / cm² under a nitrogen gas atmosphere. ２ A 10 μm thick cured material is formed by irradiating and curing in such a manner, and the resulting 40 μm thick cured material is obtained by repeatedly forming the cured material on top of it, wherein the transmittance of light at the peak wavelength of the excitation spectrum of the phosphorescent pigment is 40% or more. Active-ray curing ink.

2. The aforementioned photopolymerization initiator includes an intramolecular hydrogen abstraction type photopolymerization initiator. The activated-ray curing ink according to claim 1.

3. The photopolymerization initiator further comprises 3% by mass or more and 30% by mass or less of the total mass of the photopolymerization initiator, wherein the transmittance is less than 40%. The activated-ray curing ink according to claim 1.

4. The photopolymerization initiator further comprises an acylphosphine oxide-based photopolymerization initiator. The activated-ray curing ink according to claim 1.

5. The aforementioned activated linear polymerizable compound includes a compound having an aromatic ring. The activated-ray curing ink according to claim 1.

6. The aforementioned activated linear polymerizable compound includes a monofunctional compound. The activated-ray curing ink according to claim 1.

7. The aforementioned activated linear polymerizable compound includes a compound having an alkylene glycol structure. The activated-ray curing ink according to claim 1.

8. The aforementioned alkylene glycol structure has an alkylene glycol structure with 3 or more carbon atoms. The activated-ray curing ink according to claim 7.

9. The content of the phosphorescent pigment is 10% by mass or more and 50% by mass or less, relative to the total mass of the active-ray curable ink. The activated-ray curing ink according to claim 1.

10. The peak wavelength of the excitation spectrum of the phosphorescent pigment is between 300 nm and 400 nm. The activated-ray curing ink according to claim 1.

11. It is inkjet ink. Active-ray curable ink according to claim 1

12. A step of applying the active-ray curable ink described in claim 1 to a substrate, The process involves irradiating the applied active-ray-curable ink with an active ray, Having, Method for forming cured product.

13. A cured product obtained by curing the active-ray curable ink described in claim 1.

14. A phosphorescent plate having a base material and a cured product according to claim 13 formed on the base material.

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