Patent Application
20160376451
The invention relates to a photocurable inkjet ink suitably used for manufacturing a light guide as a member of a backlight unit built in an optical instrument such as an image display device, etc. More specifically, the invention relates to a photocurable inkjet ink, the photocurable inkjet ink being employed in a microlens that is employed in manufacturing a light guide and also being employed in a liquid-repellent cured film used for controlling a shape of the microlens.
Conventionally, a microlens formed on a light guide for an image display device has been formed by injection molding using a mold. However, when manufacturing various kinds of microlenses in small quantities using this method, it is necessary to remake the mold according to product designs, and an increase in manufacturing steps has become a problem.
In recent years, as a manufacturing method having high design freedom, a method has been proposed of using an inkjet method to directly form a microlens on a substrate surface (e.g., see Patent Documents 1 and 2).
In such a microlens manufacturing method using an inkjet method, a microlens pattern to be printed can be easily modified by means of a computer or the like. Therefore, even for production of various kinds in small quantities, the number of manufacturing steps does not change and manufacturing cost can be reduced. In view of this, the manufacturing method is expected.
As a substrate employed in the light guide, an acrylic resin-based substrate (hereinafter “PMMA substrate”) has conventionally been employed. However, from the viewpoint of weight reduction, moisture resistance and heat resistance of the substrate, recently, development has been underway of a light guide using a polycarbonate resin-based substrate (hereinafter “PC substrate”), a polystyrene resin-based substrate (hereinafter “PS substrate”) and an acryl-styrene copolymer polymer substrate (hereinafter “MS substrate”), etc., all having a higher refractive index than the PMMA substrate.
In the light guide, in order to well extract light, the refractive indexes of all the microlens, a liquid-repellent cured film that controls a shape of the microlens, and the substrate are expected to be substantially the same. The reason is that, if the refractive index of the liquid-repellent cured film is lower than the refractive index of the substrate, a refractive index difference occurs at an interface between the substrate and the liquid-repellent cured film, and light having a small incidence angle is more likely to be totally reflected, thus causing a problem that light extraction efficiency is reduced. The same holds true for the relationship between the refractive index of the liquid-repellent cured film and the refractive index of the microlens. Accordingly, to solve these problems, it is necessary to form a microlens and a liquid-repellent cured film that have substantially the same refractive index as the substrate.
Furthermore, for the microlens and the liquid-repellent cured film that controls the shape of the microlens, a cured product reduced in yellowness as much as possible and high in light transmittance is desired. The reason is that, when the cured product has high yellowness, there is a risk that the light guide may appear yellowish so that high image quality cannot be achieved any longer, and that high light transmittance is required for achieving higher light extraction efficiency.
When an inkjet ink that has been employed in the PMMA substrate is used in the PC substrate, the PS substrate and the MS substrate that have a high refractive index, the light extraction efficiency is reduced. Therefore, an inkjet ink that allows a cured product having a higher refractive index to be obtained is desired.
As a composition having a high refractive index, there are known a composition using a monomer that has a fluorene skeleton in a molecule (e.g., see Patent Documents 3 to 5), a composition using a monomer that has a phosphine oxide in a molecule (e.g., see Patent Document 6), and a composition using a monomer that has a bisphenol A skeleton in a molecule (e.g., see Patent Documents 7 to 8).
However, even though these compositions can be discharged by inkjet, they have a problem that the composition that forms a cured product having a high refractive index has strong yellowness, and the composition that forms a cured product having low yellowness has a low refractive index.
Under such conditions, an inkjet ink having excellent photocurability and a high refractive index as well as allowing a photocured product that has reduced yellowness to be obtained is desired.
As a result of earnest studies, the inventors were successful in developing an inkjet ink having excellent photocurability and a high refractive index as well as allowing a photocured product that has low yellowness to be obtained, by using an acrylate having a specific structure.
The invention includes the following items.
The inkjet ink of the invention has excellent discharge properties and photocurability, and a photocured product obtained therefrom has a high refractive index and low yellowness.
In addition, the photocured product is suitably used as the microlens and as the liquid-repellent cured film that controls the shape of the microlens.
In this specification, “(meth)acrylate” is used for indicating both or either of acrylate and methacrylate. “Refractive index” is a value with respect to light of a wavelength of 589 nm. In addition, an ink that forms a microlens is sometimes called a “lens ink,” and an ink that forms a liquid-repellent cured film capable of controlling a shape of a microlens is sometimes called a “surface treatment agent.”
The ink of the invention is preferably colorless from the viewpoint of light transmittance. However, it may also be colored as long as the effects of the invention are not impaired. In this case, since it is undesirable that an obtained cured film or the like be yellowish, the ink may be colored, e.g., blue. In addition, the ink of the invention may contain a colorant in order to make it easier to distinguish the cured film or the like from a substrate during inspection of a state of the cured film or the like.
In addition, in the skeleton structure, all bonds between the benzene rings are formed through one of the groups. In other words, all the bonds between each benzene ring and another benzene ring are formed through the group selected from the organic groups a. Accordingly, the skeleton structure does not include a biphenyl bond or the like that is formed by directly bonding benzene rings. In addition, each benzene ring is bonded to another benzene ring through only one of the groups, but not through two or more groups. The compound (A) has a structure obtained by replacing a hydrogen atom bonded to the benzene rings contained in the skeleton structure with the group selected from the organic groups b.
Among such compounds, a compound having a group (b-1) is preferred, and a compound in which the benzene rings are bonded to each other by a propane-2,2-diyl group or an ethane-1,1,1-triyl group is more preferred. Furthermore, the compound (A) is preferably a compound represented by any one of formulae (1) to (3), and is more preferably a compound represented by any one of formulae (4) to (6) since the ink having low viscosity and a cured film having a high refractive index are obtained.
Examples of the existing polyhydric phenol include TrisP-PA (trade name, made by Honshu Chemical Industry Co., Ltd.), TrisP-HAP (trade name, made by Honshu Chemical Industry Co., Ltd.), TrisP-TC (trade name, made by Honshu Chemical Industry Co., Ltd.), BIP-BZ (trade name, made by Asahi Organic Chemicals Industry Co., Ltd.), BIP-PHBZ (trade name, made by Asahi Organic Chemicals Industry Co., Ltd.), 3PC (trade name, made by Asahi Organic Chemicals Industry Co., Ltd.), TEP-TPA (trade name, made by Asahi Organic Chemicals Industry Co., Ltd.), and Bisphenol-M (trade name, made by Mitsui Fine Chemicals, Inc.).
A method of adding the acryloyl group is not particularly limited, and the acryloyl group can be synthesized by an existing method. Examples thereof include a dehydration esterification method using acrylic acid, a transesterification method of reacting an ester to obtain a new ester, a method using acrylic acid chloride, a method using acrylic acid anhydride and a method of adding an acrylate having an isocyanate group. Among them, the method using acrylic acid chloride that has high reactivity and can be synthesized at low cost is desired.
The compound (A) may be one kind of compound, or may be a mixture of two or more kinds of compounds.
In the inkjet ink of the invention, the content of the compound (A) is preferably 3 to 60 wt %, more preferably 5 to 40 wt %, of a total amount of the ink. When the content of the compound (A) is within the aforementioned range, a cured film having reduced yellowness and a high refractive index is more easily obtained.
The compound (B) may be one kind of compound, or may be a mixture of two or more kinds of compounds.
In the inkjet ink of the invention, the content of the compound (B) is preferably 1 to 60 wt %, more preferably 5 to 40 wt %, of the total amount of the ink. When the content of the compound (B) is within the aforementioned range, the ink has low viscosity, and it is easy to increase the refractive index of a cured film of the ink.
Specific examples of the photopolymerization initiator (C) include benzophenone, Michler's ketone, 4,4′-bis(diethylamino)benzophenone, xanthone, thioxanthone, isopropylxanthone, 2,4-diethylthioxanthone, 2-ethylanthraquinone, acetophenone, 2-hydroxy-2-methyl-4′-isopropylpropiophenone, isopropyl benzoin ether, isobutyl benzoin ether, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, camphorquinone, benzanthrone, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, 4,4′-di(t-butylperoxycarbonyl)benzophenone, 3,4,4′-tri(t-butylperoxycarbonyl)benzophenone, 3,3′,4,4′-tetra(t-butylperoxycarbonyl)benzophenone, 3,3′,4,4′-tetra(t-hexylperoxycarbonyl)benzophenone, 3,3′-di(methoxycarbonyl)-4,4′-di(t-butylperoxycarbonyl)benzophenone, 3,4′-di(methoxycarbonyl)-4,3′-di(t-butylperoxycarbonyl)benzophenone, 4,4′-di(methoxycarbonyl)-3,3′-di(t-butylperoxycarbonyl)benzophenone, 2-(4′-methoxystyryl)-4,6-bis(trichloromethyl)-s-triazine, 2-(3′,4′-dimethoxystyryl)-4,6-bis(trichloromethyl)-s-triazine, 2-(2′,4′-dimethoxystyryl)-4,6-bis(trichloromethyl)-s-triazine, 2-(2′-methoxystyryl)-4,6-bis(trichloromethyl)-s-triazine, 2-(4′-pentyloxystyryl)-4,6-bis(trichloromethyl)-s-triazine, 4-[p-N,N-di(ethoxycarbonylmethyl)]-2,6-di(trichloromethyl)-s-triazine, 1,3-bis(trichloromethyl)-5-(2′-chlorophenyl)-s-triazine, 1,3-bis(trichloromethyl)-5-(4′-methoxyphenyl)-s-triazine, 2-(p-dimethylaminostyryl)benzoxazole, 2-(p-dimethylaminostyryl)benzthiazole, 2-mercaptobenzothiazole, 3,3′-carbonylbis(7-diethylaminocoumarin), 2-(o-chlorophenyl)-4,4′,5,5′-tetraphenyl-1,2′-biimidazole, 2,2′-bis(2-chlorophenyl)-4,4′,5,5′-tetrakis(4-ethoxycarbonylphenyl)-1,2′-biimidazole, 2,2′-bis(2,4-dichlorophenyl)-4,4′,5,5 ′-tetraphenyl-1,2′-biimidazole, 2,2′-bis(2,4-dibromophenyl)-4,4′,5,5′-tetraphenyl-1,2′-biimidazole, 2,2′-bis(2,4,6-trichlorophenyl)-4,4′,5,5′-tetraphenyl-1,2′-biimidazole, 3-(2-methyl-2-dimethylaminopropionyl)carbazole, 3,6-bis(2-methyl-2-morpholinopropionyl)-9-n-dodecylcarbazole, bis(η5-2,4-cyclopentadiene-1-yl)-bis(2,6-difluoro-3-(1H-pyrrole-1-yl)-phenyl)titanium, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propanone, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-1-propan one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-1-propanone, 2-(dimethylamino)-1-(4-morpholinophenyl)-2-benzyl-1-butanone, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone, oxy-phenyl-acetic acid 2-[2-oxo-2-phenyl-acetoxy-ethoxy]-ethyl ester, oxy-phenyl-acetic acid 2-[2-hydroxy-ethoxy]-ethyl ester, methyl benzoylformate, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenyl phosphinate, 1-[4-(phenylthio)phenyl]-1,2-octanedione 2-(O-benzoyloxime)], and 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazole-3-yl]-ethanone-1-(O-acetyloxime).
Among them, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propanone, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-1-propan one, 2,2-dimethoxy-2-phenylacetophenone, oxy-phenyl-acetic acid 2-[2-oxo-2-phenyl-acetoxy-ethoxy]-ethyl ester, oxy-phenyl-acetic acid 2-[2-hydroxy-ethoxy]-ethyl ester, methyl benzoylformate, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, and 2,4,6-trimethylbenzoyldiphenyl phosphinate are preferred.
As a commercially available photopolymerization initiator (C), Irgacure 184, Irgacure 651, Irgacure 127, Irgacure 1173, Irgacure 500, Irgacure 2959, Irgacure 754, Irgacure MBF, and Irgacure TPO (trade names, made by BASF Japan Ltd.), etc. are preferred.
Among them, Irgacure 754, Irgacure MBF and Irgacure TPO are more preferred since the light transmittance of the obtained cured film or the like is the highest when they are used.
The photopolymerization initiator (C) used in the ink of the invention may be one kind of compound, or may be a mixture of two or more kinds of compounds.
In the inkjet ink of the invention, the content of the photopolymerization initiator (C) is preferably 1 to 15 wt % or more of the total amount of the ink, more preferably 1 to 10 wt % or more of the total amount of the ink in consideration of balance with other materials, and even more preferably 1 to 8 wt % of the total amount of the ink in view of more excellent photocurability with respect to ultraviolet light, and more easily obtaining a cured film having high light transmittance.
The solvent (D) is not particularly limited, and is preferably an organic solvent having a boiling point of 100° C. to 300° C.
Specific examples of the organic solvent having a boiling point of 100 to 300° C. include butyl acetate, isobutyl acetate, butyl propionate, methyl methoxyacetate, ethyl methoxyacetate, butyl methoxyacetate, methyl ethoxyacetate, ethyl ethoxyacetate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, methyl 3-ethoxypropionate, ethyl 3-ethoxypropionate, methyl pyruvate, ethyl pyruvate, propyl pyruvate, methyl acetoacetate, ethyl acetoacetate, methyl 2-hydroxyisobutyrate, i-propyl 2-hydroxyisobutyrate, methyl lactate, propyl lactate, dioxane, 3-methoxybutanol, 3-methoxybutyl acetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, propylene glycol monophenyl ether, ethylene glycol monobutyl ether, ethylene glycol monophenyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monophenyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, dipropylene glycol monophenyl ether, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, benzyl alcohol, cyclohexanol, 1,4-butanediol, triethylene glycol, tripropylene glycol, tripropylene glycol methyl ether, tripropylene glycol monobutyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monopropyl ether acetate, dipropylene glycol monomethyl ether acetate, dipropylene glycol monoethyl ether acetate, dipropylene glycol monobutyl ether acetate, ethylene glycol monomethyl ether acetate, ethylene glycol monobutyl ether acetate, cyclohexanone, cyclopentanone, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, dipropylene glycol dimethyl ether, toluene, xylene, anisole, γ-butyrolactone, N,N-dimethylacetamide, N-methyl-2-pyrrolidone and dimethyl imidazolidinone.
The solvent (D) used in the ink of the invention may be one kind of compound, or may be a mixture of two or more kinds of compounds.
In the ink of the invention, the content of the solvent (D) is preferably 30 to 85 wt %, more preferably 40 to 80 wt %, and even more preferably 50 to 75 wt %, relative to a total weight of the ink. When the content of the solvent (D) is within the aforementioned range, photocurability is improved.
1.5. (Meth)acrylate Monomer (E) Other than Compounds (A) and (B)
The (meth)acrylate monomer (E) is not particularly limited, and has viscosity of preferably 0.1 to 70 mPa·s, more preferably 0.1 to 50 mPa·s, at 25° C.
Specific examples of the (meth)acrylate monomer (E) include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 1,4-cyclohexanedimethanol mono(meth)acrylate, N-hydroxyethyl (meth)acrylamide, glycidyl (meth)acrylate, 3,4-epoxycyclohexyl (meth)acrylate, methylglycidyl (meth)acrylate, 3-methyl-3-(meth)acryloxymethyloxetane, 3-ethyl-3-(meth)acryloxymethyloxetane, 3-methyl-3-(meth)acryloxyethyloxetane, 3-ethyl-3-(meth)acryloxyethyloxetane, 2-phenyl-3-(meth)acryloxymethyloxetane, 2-trifluoromethyl-3-(meth)acryloxymethyloxetane, 4-trifluoromethyl-2-(meth)acryloxymethyloxetane, (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, iso-butyl (meth)acrylate, t-butyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, tricyclo[5.2.1.02,6]decanyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, isobornyl (meth)acrylate, phenyl (meth)acrylate, glycerol mono(meth)acrylate, tetrahydrofurfuryl (meth)acrylate, 5-tetrahydrofurfuryloxycarbonylpentyl (meth)acrylate, (meth)acrylate of ethylene-oxide adduct of lauryl alcohol, ω-carboxypolycaprolactone mono(meth)acrylate, mono[2-(meth)acryloyloxyethyl]succinate, mono[2-(meth)acryloyloxyethyl]maleate, mono[2-(meth)acryloyloxyethyl]cyclohexene-3,4-dicarboxylate, (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, N,N-dimethylaminopropyl (meth)acrylamide, N-isopropyl (meth)acrylamide, N-(meth)acryloyl morpholine, thioglycidyl (meth)acrylate, phenylthioethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, γ-butyrolactone (meth)acrylate, lauryl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, methoxybutyl (meth)acrylate, and phenoxyethyl (meth)acrylate.
When the (meth)acrylate monomer (E) is at least one compound selected from the group consisting of cyclohexyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, tricyclodecanedimethanol di(meth)acrylate, 1,4-cyclohexanedimethanol di(meth)acrylate, γ-butyrolactone (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, lauryl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, methoxybutyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, and (meth)acrylic acid, viscosity of an obtained composition can be adjusted to enable inkjet discharge, and a cured film or the like having a good balance between a high refractive index and high light transmittance can be fabricated, which is therefore preferred.
The (meth)acrylate monomer (E) may be one kind of compound, or may be a mixture of two or more kinds of compounds.
In the ink of the invention, the content of the (meth)acrylate monomer (E) is preferably 1 to 80 wt %, more preferably 1 to 70 wt %, and even more preferably 1 to 60 wt %, relative to the total weight of the ink. When the content of the (meth)acrylate monomer (E) is within the aforementioned range, the refractive index can be adjusted within a range not impairing the high light transmittance of the cured film obtained from the ink.
Specific examples of the surfactant (F) include Polyflow No. 45, Polyflow KL-245, Polyflow No. 75, Polyflow No. 90, Polyflow No. 95 (trade names, made by Kyoeisha Chemical Co., Ltd.), Disperbyk 161, Disperbyk 162, Disperbyk 163, Disperbyk 164, Disperbyk 166, Disperbyk 170, Disperbyk 180, Disperbyk 181, Disperbyk 182, BYK 300, BYK 306, BYK 310, BYK 320, BYK 330, BYK 342, BYK 344, BYK 346 (trade names, made by BYK Japan KK), KP-341, KP-358, KP-368, KF-96-50CS, KF-50-100CS (trade names, made by Shin-Etsu Chemical Co., Ltd.), Surflon SC-101, Surflon KH-40 (trade names, made by AGC Seimi Chemical Co., Ltd.), Ftergent 222F, Ftergent 251, FTX-218 (trade names, made by Neos Corporation), EFTOP EF-351, EFTOP EF-352, EFTOP EF-601, EFTOP EF-801, EFTOP EF-802 (trade names, made by Mitsubishi Materials Corporation), Megafac F-171, Megafac F-177, Megafac F-475, Megafac R-08, Megafac R-30 (trade names, made by DIC Corporation), fluoroalkyl benzene sulfonate, fluoroalkyl carboxylate, fluoroalkyl polyoxyethylene ether, fluoroalkylammonium iodide, fluoroalkyl betaine, fluoroalkyl sulfonate, diglycerin tetrakis(fluoroalkyl polyoxyethylene ether), fluoroalkyltrimethyl ammonium salt, fluoroalkyl amino sulfonate, polyoxyethylene nonylphenylether, polyoxyethylene octylphenylether, polyoxyethylene laurylether, polyoxyethylene oleylether, polyoxyethylene tridecylether, polyoxyethylene cetylether, polyoxyethylene stearylether, polyoxyethylene laurate, polyoxyethylene olerate, polyoxyethylene stearate, polyoxyethylene laurylamine, sorbitan laurate, sorbitan palmitate, sorbitan stearate, sorbitan oleate, a sorbitan fatty acid ester, polyoxyethylene sorbitan laurate, polyoxyethylene sorbitan palmitate, polyoxyethylene sorbitan stearate, polyoxyethylene sorbitan oleate, polyoxyethylene naphthylether, alkylbenzene sulfonate, and alkyldiphenylether disulfonate.
In addition, when the surfactant (F) is a surfactant having a reactive group, the surfactant hardly bleeds out from the formed cured film or the like, and unevenness in lens diameter of the microlens formed on the cured film is reduced, which is therefore more preferred.
It is preferred that the reactive group be at least one group selected from the group consisting of a (meth)acryloyl group, an oxirane group, and an oxetanyl group, in view of obtaining an ink having high curability.
Specific examples of the surfactant having a (meth)acryloyl group as the reactive group include RS-72K (trade name, made by DIC Corporation), BYK UV 3500, BYK UV 3570 (trade names, made by BYK Japan KK), and TEGO Rad 2200 N, TEGO Rad 2250, TEGO Rad 2300 and TEGO Rad 2500 (trade names, made by Evonik Degussa Japan Co., Ltd.).
In addition, examples of the surfactant having an oxirane group as the reactive group include RS-211K (trade name, made by DIC Corporation), etc.
The surfactant (F) used in the ink of the invention may be one kind of compound, or may be a mixture of two or more kinds of compounds.
In the ink of the invention, the content of the surfactant (F) is preferably 0.1 to 1 wt %, more preferably 0.1 to 0.9 wt %, and even more preferably 0.1 to 0.8 wt %, relative to the total weight of the ink. When the content of the surfactant (F) is within the aforementioned range, the photocurability of the ink and the surface liquid repellency of the obtained cured film are more excellent.
Specific examples of the ultraviolet absorbent include a benzotriazole compound, such as 2-(5-methyl-2-hydroxyphenyl)benzotriazole, 2-(3,5-di-t-butyl-2-hydroxyphenyl)benzotriazole, 2-(3,5-di-t-butyl-2-hydroxyphenyl)-5-chlorobenzotriazole, 2-(3,5-di-t-amyl-2-hydroxyphenyl)benzotriazole, etc.; a triazine compound, such as 2-[4,6-diphenyl-1,3,5-triazin-2-yl]-5-[(hexyl)oxy]phenol, etc.; a benzophenone compound, such as 2-hydroxy-4-n-octyloxybenzophenone, etc.; and an oxalic anilide compound, such as 2-ethoxy-2′-ethyloxalic acid bisanilide, etc.
The ultraviolet absorbent used in the ink of the invention may be one kind of compound, or may be a mixture of two or more kinds of compounds.
Specific examples of the antioxidant include a hindered phenolic compound, such as pentaerythritoltetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, triethylene glycol-bis-[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate], 1,6-hexanediol-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 3,5-di-t-butyl-4-hydroxybenzylphosphonate diethylester, etc.; and an amine compound, such as n-butylamine, triethylamine and diethylaminomethyl methacrylate, etc.
The antioxidant used in the ink of the invention may be one kind of compound, or may be a mixture of two or more kinds of compounds.
The polymerization inhibitor used in the ink of the invention may be one kind of compound, or may be a mixture of two or more kinds of compounds.
The thermosetting compound may be one kind of compound, or may be a mixture of two or more kinds of compounds.
In the ink of the invention, the content of the thermosetting compound is preferably 1 to 10 wt %, more preferably 1 to 8 wt %, and even more preferably 1 to 6 wt %, relative to the total weight of the ink. When the content of the thermosetting compound is within the aforementioned range, a cured film having higher strength is obtained.
(1) Epoxy Compound
The epoxy compound is not particularly limited as long as being a compound having at least one structure represented by the following formula (9-1) or (9-2) in one molecule.
The epoxy compound may be an epoxy resin produced by a well-known method, or may be commercially available.
Examples of the commercially available epoxy compound include: a bisphenol A-type epoxy resin, such as jER 828, jER 834, jER 1001, jER 1004 (all being trade names, made by Mitsubishi Chemical Corporation), Epiclon 840, Epiclon 850, Epiclon 1050, Epiclon 2055, (all being trade names, made by DIC Corporation), Epo Tohto YD-011, Epo Tohto YD-013, Epo Tohto YD-127, Epo Tohto YD-128 (all being trade names, made by Nippon Steel Chemical Co., Ltd.), D.E.R. 317, D.E.R. 331, D.E.R. 661, D.E.R. 664 (all being trade names, made by The DOW Chemical Company), Araldite 6071, Araldite 6084, Araldite GY250, Araldite GY260 (all being trade names, made by Huntsman Japan KK), Sumi-Epoxy ESA-011, Sumi-Epoxy ESA-014, Sumi-Epoxy ELA-115, Sumi-Epoxy ELA-128 (all being trade names, made by Sumitomo Chemical Co., Ltd.), A.E.R. 330, A.E.R. 331, A.E.R. 661 and A.E.R. 664 (all being trade names, made by Asahi Kasei E-materials Corporation), etc.;
Among them, when jER 828, jER 834, jER 1001, jER 1004 (all being trade names, made by Mitsubishi Chemical Corporation), Techmore VG3101L (trade name, made by Printec Co.), as well as EPPN-501 and EPPN-502 (both being trade names, made by Nippon Kayaku Co., Ltd.) are used, the cured film obtained from the ink has high strength, and these epoxy resins are therefore preferred.
The epoxy resin that can be used in the ink of the invention may be one kind, or may be a mixture of two or more kinds.
(2) Epoxy Curing Agent
Examples of the anhydride-based curing agent include maleic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, hexahydrotrimellitic anhydride, phthalic anhydride, trimellitic anhydride and a styrene-maleic anhydride copolymer, etc.
Examples of the polyamine-based curing agent include diethylenetriamine, triethylenetetraamine, tetraethylenepentamine, dicyandiamide, polyamide amine (polyamide resin), a ketimine compound, isophorondiamine, m-xylenediamine, m-phenylenediamine, 1,3-bis(aminomethyl)cyclohexane, N-aminoethylpiperazine, 4,4′-diaminodiphenylmethane, 4,4′-diamino-3,3′-diethyldiphenylmethane, and diaminodiphenyl sulfone, etc.
The epoxy curing agent that can be used in the ink of the invention may be one kind of compound, or may be a mixture of two or more kinds of compounds.
(3) Bismaleimide
[Chemical Formula 20]
—R28—R29— (11)
(4) Phenolic Resin, or Phenolic Hydroxyl Group-Containing Resin
Specific examples of the aromatic compound having a phenolic hydroxyl group include phenol, o-cresol, m-cresol, p-cresol, o-ethylphenol, m-ethylphenol, p-ethylphenol, o-butylphenol, m-butylphenol, p-butylphenol, o-xylenol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 3,4-xylenol, 3,5-xylenol, 2,3,5-trimethylphenol, 3,4,5-trimethylphenol, p-phenylphenol, resorcinol, hodroquinone, hydroquinone monomethyl ether, pyrogallol, bisphenol A, bisphenol F, terpene skeleton-containing diphenol, gallic acid, gallate, α-naphthol and β-naphthol.
Specific examples of the aldehydes include formaldehyde, paraformaldehyde, frafural, benzaldehyde, nitrobenzaldehyde and acetaldehyde.
Specific examples of the compound copolymerizable with vinylphenol include (meth)acrylic acid or a derivative thereof, styrene or a derivative thereof, maleic anhydride, vinyl acetate and acrylonitrile.
Specific examples of the phenolic resin include Resitop PSM-6200 (trade name, made by Gunei Chemical Industry Co., Ltd.), Shonol BRG-555 (trade name, made by Showa Denko K.K.); specific examples of the phenolic hydroxyl group-containing resin include Maruka Lyncur M S-2G, Maruka Lyncur CST70 and Maruka Lyncur PHM-C (all being trade names, made by Maruzen Petrochemical Co., Ltd.).
The phenolic resin or the phenolic hydroxyl group-containing resin used in the ink of the invention may be one kind of compound, or may be a mixture of two or more kinds of compounds.
(5) Melamine Resin
Specific examples of the melamine resin include Nikalac MW-30, MW-30HM, MW-390, MW-100LM and MX-750LM (trade names, made by Sanwa Chemical Co., Ltd.).
The melamine resin that can be used in the ink of the invention may be one kind of compound, or may be a mixture of two or more kinds of compounds.
(6) Silane Coupling Agent
The silane coupling agent that can be used in the ink of the invention may be one kind of compound, or may be a mixture of two or more kinds of compounds.
The thermopolymerization initiator that can be used in the ink of the invention may be one kind of compound, or may be a mixture of two or more kinds of compounds.
Particularly, the ink of the invention is preferably prepared by mixing the aforementioned component (A) with, if necessary, the component (B), the component (C), the component (D), the component (E), the component (F), the ultraviolet absorbent, the antioxidant, the polymerization inhibitor, the thermosetting compound and the thermopolymerization initiator, etc., and filtering an obtained solution using, e.g., a membrane filter made of ultra-high-molecular-weight polyethylene (UPE) to deaerate the solution. The thus prepared ink has excellent discharge properties when coated by an inkjet method.
Examples of the inkjet head include a head having a heating portion formed of a metal and/or a metal oxide, etc. Specific examples of the metal and/or the metal oxide include a metal such as Ta, Zr, Ti, Ni, Al, etc., and a metal oxide thereof.
Examples of a preferred coating device used in coating the ink of the invention include a device that applies energy corresponding to a coating signal to an ink in an inkjet head that has an ink containing portion in which the ink is contained, and that, while generating an ink drop by the energy, performs coating (drawing) corresponding to the coating signal.
The inkjet coating device is not limited to a device having the inkjet head and the ink containing portion separated, and a device having the inkjet head and the ink containing portion inseparably integrated with each other may also be used. In addition, the ink containing portion may be detachably or undetachably integrated with the inkjet head, and may be mounted to a carriage, or may be provided on a fixed part of the device. In the latter case, the ink containing portion may be in a form of supplying the ink to the inkjet head through an ink supply member, e.g., a tube.
The inkjet ink may be heated, and a heating temperature is preferably 80° C. or lower, more preferably 50° C. or lower. The viscosity of the ink of the invention at that heating temperature is preferably 1.0 to 30 mPa·s.
Specifically, the ink of the invention can be used as an ink for forming a liquid-repellent cured film and as an ink for forming a microlens.
When the ink of the invention is the ink for forming a liquid-repellent cured film, the ink preferably contains a compound (A1) represented by either of the following formulae (15) and (16) and the surfactant (F).
The content of the compound (A1) is preferably 3 to 60 wt %, more preferably 5 to 40 wt %, and even more preferably 5 to 30 wt %; the content of the surfactant (F) is preferably 0.1 to 1 wt %, more preferably 0.1 to 0.9 wt %, and even more preferably 0.1 to 0.8 wt %. When the contents of the compound (A1) and the surfactant (F) are within the aforementioned ranges, a liquid-repellent cured film having reduced yellowness, a high refractive index and excellent surface liquid repellency is easily obtained.
The compound (A1) is preferably a compound represented by either of the above formulae (5) and (6), more preferably a compound represented by formula (5).
In the case of the ink for forming a liquid-repellent cured film, from the viewpoint of curability, the ink preferably further contains, in addition to the compound (A1) and the surfactant (F), the photopolymerization initiator (C). The photopolymerization initiator (C) is as described above.
In the case of the ink for forming a liquid-repellent cured film, from the viewpoint of reduction in yellowness and inkjet discharge properties, the ink preferably further contains, in addition to the compound (A1) and the surfactant (F), the solvent (D), or a (meth)acrylate monomer (G) other than the compound (A1). The solvent (D) is as described above. Specific examples, content, etc. of the (meth)acrylate monomer (G) are the same as those of the (meth)acrylate monomer (E).
When the ink of the invention is the ink for forming a microlens, the ink preferably contains a compound (A2), and the compound (B) represented by the following formula (7) or (8), wherein the compound (A2) has a skeleton structure consisting of at least three benzene rings and at least one group selected from the following organic groups a, wherein all bonds between the benzene rings are formed through one of the groups, and has at least one group selected from the following organic groups d that are bonded to the benzene rings.
[Organic Groups a]
The content of the compound (A2) is preferably 3 to 60 wt %, more preferably 5 to 40 wt %; the content of the compound (B) is preferably 1 to 60 wt %, more preferably 5 to 40 wt %. When the contents of the compounds (A2) and (B) are within the aforementioned ranges, the ink has low viscosity, reduced yellowness and a high refractive index, and a microlens having a high refractive index is easily obtained.
The compound (A2) is preferably a compound represented by any one of the above formulae (1) to (3), more preferably a compound represented by any one of the above formulae (4) to (6), and even more preferably a compound represented by formula (5).
The compound (B) is preferably m-phenoxybenzyl (meth)acrylate, o-phenylphenol EO-modified (meth)acrylate or paracumylphenol EO-modified (meth)acrylate.
In the case of the ink for forming a microlens, from the viewpoint of curability, the ink preferably further contains, in addition to the compounds (A2) and (B), the photopolymerization initiator (C). The photopolymerization initiator (C) is as described above.
In the case of the ink for forming a microlens, from the viewpoint of reduction in yellowness and inkjet discharge properties, the ink preferably further contains, in addition to the compounds (A2) and (B), the solvent (D), or a (meth)acrylate monomer (H) other than the compounds (A2) and (B). The solvent (D) is as described above. Specific examples, content, etc. of the (meth)acrylate monomer (H) are the same as those of the (meth)acrylate monomer (E).
When the liquid-repellent cured film and the microlens obtained from the ink of the invention have a thickness of 0.5 μm, the light transmittance at a wavelength of 400 nm is preferably 95% or higher, more preferably 97% or higher.
The refractive index of the liquid-repellent cured film and the microlens obtained from the ink of the invention is preferably 1.55 or more, more preferably 1.55 to 1.65, and even more preferably 1.56 to 1.60.
Moreover, in the invention, the refractive index of the liquid-repellent cured film and the microlens is a value measured using a refractive index measuring device FE-3000 (trade name, made by Otsuka Electronics Co., Ltd.); the light transmittance of the cured film at a wavelength of 400 nm is a value measured using a transmittance measuring device V-670 (trade name, made by JASCO Corporation).
When the ink of the invention is irradiated with an ultraviolet ray or a visible ray, etc., an amount (exposure amount) of light irradiated depends on the composition of the ink of the invention, and is preferably 100 to 5,000 mJ/cm2, more preferably 300 to 4,000 mJ/cm2, and even more preferably 500 to 3,000 mJ/cm2, as measured using an accumulated light meter UIT-201 equipped with an optical receiver UVD-365PD made by Ushio Inc. In addition, a wavelength of the irradiated ultraviolet ray or visible ray, etc. is preferably 200 to 500 nm, more preferably 250 to 450 nm.
Moreover, the exposure amount hereinafter described is a value measured using the accumulated light meter UIT-201 equipped with the optical receiver UVD-365PD made by Ushio Inc.
Moreover, an exposure machine is not particularly limited as long as being a device that is equipped with an electrodeless lamp, a low-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a metal halide lamp, and a halogen lamp, etc. and that irradiates an ultraviolet ray or a visible ray, etc. within a range of 200 to 500 nm.
The lens diameter of the microlens is not particularly limited, and is generally preferably 10 to 100 μm, more preferably 20 to 60 μm. In addition, a lens height is not particularly limited, and is generally preferably 0.5 to 20 μm, more preferably 2 to 15 μm.
The substrate is not particularly limited, and examples thereof include a polyester-based resin substrate made of polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), etc., a polyolefin-based resin substrate made of polyethylene and polypropylene, etc., a polyvinyl chloride-based resin substrate, a fluorine-based resin substrate, a PMMA substrate, a PC substrate, a PS substrate, an MS substrate, an organic polymer film made of polyamide, polycarbonate and polyimide, etc., a substrate made of cellophane, and a glass substrate.
Among them, particularly the PC substrate, the PS substrate and the MS substrate and the like having a refractive index of 1.55 or more, preferably 1.55 to 1.65, are preferred since a refractive index difference at an interface between the substrate and the liquid-repellent cured film obtained from the ink of the invention is reduced.
The thickness of the substrate is not particularly limited and is generally 10 μm to 10 mm, and is suitably adjusted depending on purposes of use.
The invention is further explained below according to examples, but is not limited thereto.
A surface treatment agent 4 was prepared in the same manner as in Example 1 except that propylene glycol monomethyl ether (made by Tokyo Chemical Industry Co., Ltd., hereinafter abbreviated as “PGME”) was used in place of HBM as the organic solvent (D) and that the following composition ratios were adopted.
(Evaluation of Inkjet Ink and Photocured Product)
The evaluation methods are as follows. The evaluation results are shown in Table 1.
The following evaluation of lens and liquid-repellent cured film was carried out by evaluating those exposed with a lowest exposure amount for curing the film (where no finger marks remain on the pattern surface).
Moreover, the thickness was measured using a contact-type thickness meter (P-15 (trade name) of KLA-Tencor Japan).
The refractive index of the cured film pattern was measured using a refractive index measuring device FE-3000 (trade name, made by Otsuka Electronics Co., Ltd.). The light transmittance and the yellowness were measured using a transmittance measuring device V-670 (made by Japan Electronics Co., Ltd.).
The cured film having yellowness (b* value) of 0.30 or more was determined to have high yellowness.
As clear from Table 1 and the evaluation results of the microlens, the inks (the surface treatment agents 1 to 4) obtained in Examples 1 to 4 have excellent inkjet discharge properties and photocurability. In addition, the cured products thereof have a high refractive index, high transparency and reduced yellowness, and moreover enable a microlens having a good shape to be formed thereon. Therefore, the inks are suitably used as photocurable inkjet ink In contrast, the surface treatment agents 5 to 7 have high yellowness after photocuring, and are unsuitable as photocurable inkjet ink. In addition, the surface treatment agents 8 and 9 have low yellowness after photocuring but have a low refractive index, and are unsuitable as photocurable inkjet ink.
The surface treatment agents 1 to 4 obtained in Examples 1 to 4 according to the invention have the optimum characteristics as photocurable inkjet ink, and are therefore industrially effective.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013-246163 | Nov 2013 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2014/081212 | 11/26/2014 | WO | 00 |
