JP7750855B2 - curable composition - Google Patents

Description

The present invention relates to a curable composition and a cured film.

Organic electroluminescent devices are used in display devices, lighting devices, and other applications, and research is underway to control the refractive index to increase the light extraction efficiency from the light-emitting layer. The curable composition disclosed in Patent Document 1 aims to produce a cured film with a high refractive index, and contains, for example, 45% by weight of zirconia nanoparticles, 25% by weight of tricyclodecane dimethanol dimethacrylate as a ring-structure polyfunctional compound, 14% by weight of 1,9-nonanediol dimethacrylate as a non-ring-structure polyfunctional compound, and 10% by weight of isobutyl methacrylate as a monofunctional compound, along with a polymerization initiator and a surfactant.

Japanese Patent Application Laid-Open No. 2017-61606

However, when a polyfunctional compound with a ring structure and a polyfunctional compound with a non-ring structure are combined, the curable composition may not be cured sufficiently.
An object of the present invention is to provide a curable composition that has excellent curability.

The present invention, which has solved the above problems, has the following configuration.
[1] A composition comprising inorganic fine particles (A), a polymerizable compound (B), and a polymerization initiator (C),
The polymerizable compound (B) contains a compound represented by formula (B1),
(In the formula, ^R1 and ^R2 each independently represent a hydrogen atom or an alkyl group having 1 to 20 carbon atoms which may have a substituent. ^R3 represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or a (meth)acrylic group, and the alkyl group having 1 to 20 carbon atoms, alkenyl group having 2 to 20 carbon atoms, aryl group having 6 to 20 carbon atoms, and (meth)acrylic group may have a substituent.)
A curable composition having an average transmittance of 90% or more per 1.0 μm film thickness at wavelengths of 400 to 700 nm when formed into a film under the following conditions:
[Film formation conditions]
The curable composition is applied to a glass substrate so that the average thickness of the cured film falls within the range of 1.0±0.2 μm, and the substrate is irradiated with UV light having a wavelength of 385 nm at an integrated light intensity of 2000 J/m ² using an LED lamp.
[2] The curable composition according to [1], wherein the content of the inorganic fine particles (A) in the curable composition is 10 mass % or more.
[3] A cured film formed from the curable composition according to [1] or [2].

The present invention makes it possible to improve the curability of the curable composition.

The present invention is a curable composition containing inorganic fine particles (A), a polymerizable compound (B), and a polymerization initiator (C), and is characterized in that the polymerizable compound (B) contains specific monomers.

<Inorganic fine particles (A)>
The inorganic fine particles (A) are preferably particles that do not have the ability to convert wavelengths into the visible light region, and are preferably particles having a refractive index of 1.6 or more. The higher the refractive index of the inorganic fine particles (A), the higher the refractive index of the film obtained from the curable composition, and the light extraction efficiency from the light-emitting layer is improved. The refractive index is preferably 1.8 or more, more preferably 2.0 or more. The refractive index may be, for example, 3.5 or less, or 3.0 or less. The refractive index is a value at the D line of sodium.

The inorganic fine particles (A) include oxides, nitrides, etc., and specific examples thereof include TiO ₂ (titanium oxide; refractive index 2.3 to 2.7), Nb ₂ O ₅ (niobium oxide; refractive index 2.3), Ta ₂ O ₅ (tantalum oxide; refractive index 2.3), BN (boron nitride; refractive index 2.2), ZrO ₂ (zirconium oxide; refractive index 2.1), SnO ₂ (tin oxide; refractive index 2.0), ITO (tin-doped indium oxide; refractive index 2.0), Si ₃ N ₄ (silicon nitride; refractive index 2.0), CeO ₂ (cerium oxide; refractive index 1.9 to 2.0), ZnO (zinc oxide; refractive index 1.9), Y ₂ O ₃ (yttrium oxide; refractive index 1.9), ATO (antimony-doped tin oxide; refractive index 1.7 to 1.9), SbO ₅ (antimony oxide; refractive index 1.8), and Al ₂ O 3 . Examples of inorganic fine particles (A) include O ₃ (aluminum oxide; refractive index 1.8) and TiN (titanium nitride; refractive index 1.6), and are preferably oxides of elements in Groups 3 to 5 or 12 to 15 of the periodic table, or nitrides of elements in Group 4 of the periodic table, more preferably titanium oxide, zirconium oxide, aluminum oxide, niobium oxide, and silicon nitride, and even more preferably titanium oxide and zirconium oxide. These inorganic fine particles (A) may be of one type or a combination of two or more types.

The volume average particle diameter of the inorganic fine particles (A) is, for example, 100 nm or less, preferably 50 nm or less, and more preferably 30 nm or less. The smaller the particle diameter, the higher the visible light transmittance of the resulting film. There is no particular lower limit for the volume average particle diameter of the inorganic fine particles (A), but it is, for example, 0.1 nm or more, preferably 0.5 nm or more, and more preferably 1.0 nm or more.

The content of the inorganic fine particles (A) in the curable composition is, for example, 10% by mass or more, preferably 15% by mass or more, more preferably 20% by mass or more, and particularly preferably 30% by mass or more. The higher the content of the inorganic fine particles (A), the higher the refractive index of the film obtained from the curable composition, and the more improved the light extraction efficiency from the light-emitting layer. The content of the inorganic fine particles (A) is, for example, 80% by mass or less, preferably 70% by mass or less, more preferably 60% by mass or less, and even more preferably 50% by mass or less.

The inorganic fine particles (A) may be surface-treated with a coupling agent. Examples of coupling agents include silane-based coupling agents, zirconium-based coupling agents, titanate-based coupling agents, and aluminate-based coupling agents. These may be used alone or in combination of two or more.

Examples of silane coupling agents include γ-(meth)acryloyloxypropyldimethylmethoxysilane, γ-(meth)acryloyloxypropylmethyldimethoxysilane, γ-(meth)acryloyloxypropyltrimethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, phenyldimethylmethoxysilane, phenylmethyldimethoxysilane, phenyldiethylmethoxysilane, phenylethyldimethoxysilane, phenyltrimethoxysilane, and diphenyldimethoxysilane.

Examples of zirconium-based coupling agents include tetrapropyl zirconate, tetrabutyl zirconate, tetra(triethanolamine) zirconate, tetraisopropyl zirconate, zirconium acetylacetonate, acetylacetone zirconium butyrate, zirconium stearate, zirconium stearate butyrate, monoalkoxyzircoaluminate, trialkoxyzircoaluminate, and tetraalkoxyzircoaluminate.

Examples of titanate coupling agents include isopropyl triisostearoyl titanate, isopropyl tristearoyl titanate, isopropyl trioctanoyl titanate, isopropyl dimethacrylisostearoyl titanate, isopropyl tridodecylbenzenesulfonyl titanate, isopropyl isostearoyl diacryl titanate, isopropyl tri(dioctylphosphate) titanate, isopropyl titanium triisostearate, isopropyl tris(dioctylpyrophosphate) titanate, isopropyl tri(N-aminoethyl-aminoethyl) titanate, tetraoctylbis(ditridecylphosphite) titanate, tetra(2,2-diallyloxymethyl-1-butyl)bis(ditridecyl)phosphite titanate, bis(dioctylpyrophosphate)oxyacetate titanate, and bis(dioctylpyrophosphate)ethylene titanate.

Examples of aluminate coupling agents include diisobutyl (oleyl) acetoacetylaluminate and acetoalkoxyaluminum diisopropionate.

The inorganic fine particles (A) may be contained in the curable composition together with a dispersant. As the dispersant, any type of dispersant such as nonionic, anionic, or cationic can be used, and anionic dispersants are preferred. As the anionic dispersant, phosphate ester dispersants can be preferably used.
As the dispersant, commercially available products can also be used, such as DISPERBYK-101, DISPERBYK-130, DISPERBYK-140, DISPERBYK-160, DISPERBYK-161, DISPERBYK-162, DISPERBYK-163, DISPERBYK-164, DISPERBYK-165, DISPERBYK-166, DISPERBYK-170, DISPERBYK-171, DISPERBYK-182, DISPERBYK-2000, DISPERBYK-2001 (BYK Chemie, GMBH), Solsperse 32000, Solsperse Solsperse 36000, Solsperse 28000, Solsperse 20000, Solsperse 41000, and Solsperse 45000 (Lubrizol, Wickliffe, OH, USA).

The amount of dispersant is, for example, 1 part by mass or more, preferably 5 parts by mass or more, and more preferably 10 parts by mass or more, per 100 parts by mass of inorganic fine particles (A). The greater the amount of dispersant, the more improved the dispersibility of the inorganic fine particles (A). The amount of dispersant is, for example, 100 parts by mass or less, preferably 60 parts by mass or less, and more preferably 40 parts by mass or less, per 100 parts by mass of inorganic fine particles (A). The smaller the amount of dispersant, the more likely it is that the refractive index of the curable composition will be increased.

<Polymerizable compound (B)>
The polymerizable compound (B) contains a compound represented by formula (B1) (hereinafter, may be referred to as compound (B1)). A curable composition containing compound (B1) in the polymerizable compound (B) provides a cured film with excellent visible light transmittance and also excellent curability.

(In the formula, ^R1 and ^R2 each independently represent a hydrogen atom or an alkyl group having 1 to 20 carbon atoms which may have a substituent. ^R3 represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or a (meth)acrylic group, and the alkyl group having 1 to 20 carbon atoms, alkenyl group having 2 to 20 carbon atoms, aryl group having 6 to 20 carbon atoms, and (meth)acrylic group may have a substituent.)

The alkyl group having 1 to 20 carbon atoms may be either linear or branched. Specific examples of linear or branched alkyl groups include methyl, ethyl, propyl, isobutyl, butyl, tert-butyl, hexyl, heptyl, octyl, nonyl, decyl, heptadecyl, and undecyl groups. The alkyl group preferably has 1 to 12 carbon atoms, more preferably 1 to 8, and even more preferably 1 to 4 carbon atoms.

The alkenyl group having 2 to 20 carbon atoms may be either linear or branched. Specific examples of linear or branched alkenyl groups include vinyl, allyl, methallyl, propenyl, butenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, heptadecenyl, and undecenyl groups. The alkenyl group preferably has 2 to 12 carbon atoms, more preferably 2 to 8, and even more preferably 2 to 4 carbon atoms.

Examples of aryl groups having 6 to 20 carbon atoms include phenyl, tolyl, xylyl, trimethylphenyl, and naphthyl groups. The number of carbon atoms in the aryl group is preferably 6 to 15, more preferably 6 to 12, and even more preferably 6 to 9.

Examples of the substituent include halogen atoms such as fluorine, chlorine, bromine, and iodine atoms; hydroxy groups; —NR ^a R ^b (R ^a and R ^b each independently represent a hydrogen atom or an alkyl group having 1 to 20 carbon atoms); nitro groups; alkoxy groups having 1 to 10 carbon atoms such as methoxy and ethoxy groups; and alkoxycarbonyl groups having 2 to 10 carbon atoms such as methoxycarbonyl and ethoxycarbonyl groups.

R ¹ and R ² are preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
^R3 is preferably a hydrogen atom or a (meth)acrylic group.
As the compound (B1), the following compounds are preferred.

The polymerizable compound (B) may contain a compound having an ethylenic double bond other than the compound (B1) (hereinafter, sometimes referred to as "other polymerizable compound"). The proportion of the compound (B1) in the polymerizable compound (B) is, for example, 30% by mass or more, preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and may even be 100% by mass.

Other polymerizable compounds include polyfunctional compounds (B2) with a non-cyclic structure, polyfunctional compounds (B3) with a cyclic structure, and monofunctional compounds (B4). These other polymerizable compounds may be used alone or in combination of two or more.

Examples of polyfunctional compounds (B2) having a non-cyclic structure include compounds in which the polymerizable groups are two or more identical (meth)acryloyl groups. Examples of bifunctional compounds having a non-cyclic structure include di(meth)acrylates of alkanediols having 1 to 40 carbon atoms in which the methylene group may be replaced with -O-, such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,8-octanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, and neopentyl glycol di(meth)acrylate.

Examples of tri- or higher functional compounds with a non-cyclic structure include esters of diols having 4 to 40 carbon atoms, which have three or more hydroxyl groups and may have an ether bond, with 3 to 6 (meth)acrylic acids, such as trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, and dipentaerythritol hexa(meth)acrylate.

Examples of the polyfunctional compound (B3) having a ring structure include compounds in which the polymerizable group is two or more (meth)acryloyl groups. Examples of bifunctional compounds having a ring structure include di(meth)acrylates of cycloalkanediols having about 4 to 8 carbon atoms, such as tricyclodecane dimethanol di(meth)acrylate, cyclohexane dimethanol di(meth)acrylate, and cyclopentane dimethanol di(meth)acrylate; di(meth)acrylates of diols obtained by hydroxyalkylene etherification of OH groups of bisphenols, such as propoxylated bisphenol A di(meth)acrylate and ethoxylated bisphenol A di(meth)acrylate; and 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene.
Examples of tri- or higher functional compounds having a ring structure include ethoxylated isocyanuric acid tri(meth)acrylate and ε-caprolactone-modified tris-(2-acryloyloxyethyl)isocyanurate.

Examples of monofunctional compounds (B4) include (meth)acrylates of alkanols having 1 to 12 carbon atoms, such as ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and lauryl (meth)acrylate; (meth)acrylates of alkylene glycol monoethers, such as ethyl diethylene glycol (meth)acrylate; monofunctional compounds having a ring structure, such as dicyclopentadiene (meth)acrylate, isobornyloxyethyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and tetrahydrofurfuryl (meth)acrylate; and monofunctional compounds having a nitrogen atom, such as (meth)acryloylmorpholine and 7-amino-3,7-dimethyloctyl (meth)acrylate.

The polymerizable compound (B) is present in the curable composition in an amount of, for example, 80% by mass or less, preferably 70% by mass or less, and more preferably 60% by mass or less. The lower the content of polymerizable compound (B), the higher the refractive index of the film obtained from the curable composition, and the more improved the light extraction efficiency from the light-emitting layer. The content of polymerizable compound (B) is, for example, 20% by mass or more, preferably 30% by mass or more, and more preferably 40% by mass or more.

<Polymerization initiator (C)>
The polymerization initiator (C) is not particularly limited as long as it is a compound that can generate active radicals, acids, etc. and initiate polymerization by the action of light or heat, and known polymerization initiators can be used, with photopolymerization initiators being preferred. Examples of polymerization initiators that generate active radicals include O-acyloxime compounds, alkylphenone compounds, triazine compounds, acylphosphine oxide compounds, phosphinic acid ester compounds, and biimidazole compounds. These polymerization initiators may be used alone or in combination of two or more.

The O-acyloxime compound is a compound having a partial structure represented by formula (c1). Hereinafter, * represents a bond.

Examples of the O-acyloxime compound include N-benzoyloxy-1-(4-phenylsulfanylphenyl)butan-1-one-2-imine, N-benzoyloxy-1-(4-phenylsulfanylphenyl)octan-1-one-2-imine, N-benzoyloxy-1-(4-phenylsulfanylphenyl)-3-cyclopentylpropan-1-one-2-imine, N-acetoxy-1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]ethan-1-imine, and N-acetoxy Examples of suitable benzoyloxy compounds include benzoyl-1-[9-ethyl-6-{2-methyl-4-(3,3-dimethyl-2,4-dioxacyclopentanylmethyloxy)benzoyl}-9H-carbazol-3-yl]ethane-1-imine, N-acetoxy-1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-3-cyclopentylpropan-1-imine, and N-benzoyloxy-1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-3-cyclopentylpropan-1-one-2-imine. Commercially available products such as Irgacure OXE01 and OXE02 (both manufactured by BASF) and N-1919 (manufactured by ADEKA) may also be used.

The alkylphenone compound is a compound having a partial structure represented by formula (c2) or (c3): In these partial structures, the benzene ring may have a substituent.

Examples of compounds having a partial structure represented by formula (c2) include 2-methyl-2-morpholino-1-(4-methylsulfanylphenyl)propan-1-one, 2-dimethylamino-1-(4-morpholinophenyl)-2-benzylbutan-1-one, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]butan-1-one, etc. Commercially available products such as Irgacure 369, 907, and 379 (all manufactured by BASF) may also be used.
Examples of compounds having a partial structure represented by formula (c3) include 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]propan-1-one, 1-hydroxycyclohexyl phenyl ketone, oligomers of 2-hydroxy-2-methyl-1-(4-isopropenylphenyl)propan-1-one, α,α-diethoxyacetophenone, and benzyl dimethyl ketal.

Examples of the triazine compounds include 2,4-bis(trichloromethyl)-6-(4-methoxyphenyl)-1,3,5-triazine, 2,4-bis(trichloromethyl)-6-(4-methoxynaphthyl)-1,3,5-triazine, 2,4-bis(trichloromethyl)-6-piperonyl-1,3,5-triazine, 2,4-bis(trichloromethyl)-6-(4-methoxystyryl)-1,3,5-triazine, and 2,4-bis(trichloromethyl)-6-[ 2-(5-methylfuran-2-yl)ethenyl]-1,3,5-triazine, 2,4-bis(trichloromethyl)-6-[2-(furan-2-yl)ethenyl]-1,3,5-triazine, 2,4-bis(trichloromethyl)-6-[2-(4-diethylamino-2-methylphenyl)ethenyl]-1,3,5-triazine, 2,4-bis(trichloromethyl)-6-[2-(3,4-dimethoxyphenyl)ethenyl]-1,3,5-triazine, and the like.

Examples of the acylphosphine oxide compound include 2,4,6-trimethylbenzoyldiphenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide. Commercially available products such as Irgacure (registered trademark) 819 (manufactured by BASF) may also be used.

Examples of the phosphinic acid ester compound include ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate. Commercially available products such as Omnirad TPO-L (manufactured by IGM Resins B.V.) may also be used.

Examples of the biimidazole compound include 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetraphenylbiimidazole, 2,2'-bis(2,3-dichlorophenyl)-4,4',5,5'-tetraphenylbiimidazole, 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetraphenylbiimidazole, and 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetra(alkoxy). 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetra(dialkoxyphenyl)biimidazole, 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetra(trialkoxyphenyl)biimidazole, and biimidazole compounds in which the phenyl groups at the 4,4',5,5'-positions are substituted with carboalkoxy groups (see, for example, JP-A-7-10913).

Further examples of polymerization initiator (C) include benzoin compounds such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether; benzophenone compounds such as benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4'-methyldiphenyl sulfide, 3,3',4,4'-tetra(tert-butylperoxycarbonyl)benzophenone, and 2,4,6-trimethylbenzophenone; quinone compounds such as 9,10-phenanthrenequinone, 2-ethylanthraquinone, and camphorquinone; 10-butyl-2-chloroacridone, benzyl, methyl phenylglyoxylate, and titanocene compounds. These are preferably used in combination with the polymerization initiator aid (C1) described below (especially amines).

The polymerization initiator (C) also includes an acid generator. Examples of acid generators include onium salts such as 4-hydroxyphenyldimethylsulfonium p-toluenesulfonate, 4-hydroxyphenyldimethylsulfonium hexafluoroantimonate, 4-acetoxyphenyldimethylsulfonium p-toluenesulfonate, 4-acetoxyphenylmethylbenzylsulfonium hexafluoroantimonate, triphenylsulfonium p-toluenesulfonate, triphenylsulfonium hexafluoroantimonate, diphenyliodonium p-toluenesulfonate, and diphenyliodonium hexafluoroantimonate, as well as nitrobenzyl tosylates and benzoin tosylates.

The polymerization initiator (C) is preferably a polymerization initiator containing at least one selected from the group consisting of O-acyloxime compounds, alkylphenone compounds, triazine compounds, acylphosphine oxide compounds, phosphinic acid ester compounds, and biimidazole compounds, and more preferably a polymerization initiator containing at least one selected from the group consisting of acylphosphine oxide compounds and phosphinic acid ester compounds.
When the polymerization initiator (C) contains at least one selected from the group consisting of an acylphosphine oxide compound and a phosphinic acid ester compound, the total content of the acylphosphine oxide compound and the phosphinic acid ester compound in the polymerization initiator (C) is, for example, 50 mass% or more, preferably 70 mass% or more, more preferably 90 mass% or more, and may be 100 mass%.

The content of the polymerization initiator (C) is, for example, 0.1% by mass or more, preferably 1% by mass or more, and more preferably 10% by mass or more, per 100 parts by mass of the polymerizable compound (B), and is, for example, 40% by mass or less, preferably 30% by mass or less, and more preferably 25% by mass or less.

<Polymerization initiation aid (C1)>
The polymerization initiation aid (C1) is a compound used to promote the polymerization of a polymerizable compound whose polymerization has been initiated by a polymerization initiator, or a sensitizer. When the polymerization initiation aid (C1) is contained, it is usually used in combination with the polymerization initiator (C).
Examples of the polymerization initiation aid (C1) include amine compounds, alkoxyanthracene compounds, thioxanthone compounds, and carboxylic acid compounds.

Examples of the amine compound include triethanolamine, methyldiethanolamine, triisopropanolamine, methyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, 2-dimethylaminoethyl benzoate, 2-ethylhexyl 4-dimethylaminobenzoate, N,N-dimethyl-p-toluidine, 4,4'-bis(dimethylamino)benzophenone (commonly known as Michler's ketone), 4,4'-bis(diethylamino)benzophenone, and 4,4'-bis(ethylmethylamino)benzophenone. Commercially available products such as EAB-F (manufactured by Hodogaya Chemical Co., Ltd.) may also be used.

Examples of the alkoxyanthracene compounds include 9,10-dimethoxyanthracene, 2-ethyl-9,10-dimethoxyanthracene, 9,10-diethoxyanthracene, 2-ethyl-9,10-diethoxyanthracene, 9,10-dibutoxyanthracene, and 2-ethyl-9,10-dibutoxyanthracene.

Examples of the thioxanthone compounds include 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, and 1-chloro-4-propoxythioxanthone.

Examples of the carboxylic acid compound include phenylsulfanylacetic acid, methylphenylsulfanylacetic acid, ethylphenylsulfanylacetic acid, methylethylphenylsulfanylacetic acid, dimethylphenylsulfanylacetic acid, methoxyphenylsulfanylacetic acid, dimethoxyphenylsulfanylacetic acid, chlorophenylsulfanylacetic acid, dichlorophenylsulfanylacetic acid, N-phenylglycine, phenoxyacetic acid, naphthylthioacetic acid, N-naphthylglycine, and naphthoxyacetic acid.
When the polymerization initiation aid (C1) is used, the content thereof is, for example, 0.1% by mass or more, preferably 1% by mass or more, and more preferably 10% by mass or more, relative to 100 parts by mass of the polymerizable compound (B), and for example, 40% by mass or less, preferably 30% by mass or less, and more preferably 25% by mass or less.

The curable composition may contain a resin (D), a solvent (E), and the like, as required.
<Resin (D)>
The resin (D) is not particularly limited, but is preferably an alkali-soluble resin. Examples of the resin (D) include the following resins [K1] to [K6].
Resin [K1]: a copolymer having structural units derived from at least one member (a) (hereinafter sometimes referred to as "(a)") selected from the group consisting of unsaturated carboxylic acids and unsaturated carboxylic acid anhydrides, and structural units derived from a monomer (b) (hereinafter sometimes referred to as "(b)") having a cyclic ether structure having 2 to 4 carbon atoms and an ethylenically unsaturated bond;
Resin [K2]: a copolymer having structural units derived from (a), structural units derived from (b), and structural units derived from a monomer (c) copolymerizable with (a) (however, different from (a) and (b)) (hereinafter, may be referred to as "(c)");
Resin [K3]: a copolymer having structural units derived from (a) and structural units derived from (c);
Resin [K4]: a copolymer having a structural unit derived from (a) to which (b) has been added, and a structural unit derived from (c);
Resin [K5]: a copolymer having a structural unit derived from (c) and a structural unit derived from (b) to which (a) has been added;
Resin [K6]: A copolymer having a structural unit derived from (c) and a structural unit obtained by adding (a) to a structural unit derived from (b) and further adding a carboxylic acid anhydride.

Specific examples of (a) include unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, o-, m-, and p-vinylbenzoic acid;
Unsaturated dicarboxylic acids such as maleic acid, fumaric acid, citraconic acid, mesaconic acid, itaconic acid, 3-vinylphthalic acid, 4-vinylphthalic acid, 3,4,5,6-tetrahydrophthalic acid, 1,2,3,6-tetrahydrophthalic acid, dimethyltetrahydrophthalic acid, and 1,4-cyclohexenedicarboxylic acid;
bicyclounsaturated compounds containing a carboxy group, such as methyl-5-norbornene-2,3-dicarboxylic acid, 5-carboxybicyclo[2.2.1]hept-2-ene, 5,6-dicarboxybicyclo[2.2.1]hept-2-ene, 5-carboxy-5-methylbicyclo[2.2.1]hept-2-ene, 5-carboxy-5-ethylbicyclo[2.2.1]hept-2-ene, 5-carboxy-6-methylbicyclo[2.2.1]hept-2-ene, and 5-carboxy-6-ethylbicyclo[2.2.1]hept-2-ene;
unsaturated dicarboxylic acid anhydrides such as maleic anhydride, citraconic anhydride, itaconic anhydride, 3-vinylphthalic anhydride, 4-vinylphthalic anhydride, 3,4,5,6-tetrahydrophthalic anhydride, 1,2,3,6-tetrahydrophthalic anhydride, dimethyltetrahydrophthalic anhydride, and 5,6-dicarboxybicyclo[2.2.1]hept-2-ene anhydride;
Unsaturated mono[(meth)acryloyloxyalkyl] esters of divalent or higher polyvalent carboxylic acids, such as mono[2-(meth)acryloyloxyethyl] succinate and mono[2-(meth)acryloyloxyethyl] phthalate;
Examples include unsaturated acrylates containing a hydroxy group and a carboxy group in the same molecule, such as α-(hydroxymethyl)acrylic acid.
Among these, acrylic acid, methacrylic acid, maleic anhydride, etc. are preferred from the viewpoint of copolymerization reactivity and solubility of the resulting resin in an alkaline aqueous solution.

(b) refers to, for example, a polymerizable compound having a cyclic ether structure having 2 to 4 carbon atoms (for example, at least one selected from the group consisting of an oxirane ring, an oxetane ring, and a tetrahydrofuran ring) and an ethylenically unsaturated bond. (b) is preferably a monomer having a cyclic ether having 2 to 4 carbon atoms and a (meth)acryloyloxy group.
In this specification, the term "(meth)acrylic acid" refers to at least one selected from the group consisting of acrylic acid and methacrylic acid. The terms "(meth)acryloyl" and "(meth)acrylate" also have the same meaning.

Examples of (b) include a monomer (b1) (hereinafter sometimes referred to as "(b1)") having an oxiranyl group and an ethylenically unsaturated bond, a monomer (b2) (hereinafter sometimes referred to as "(b2)") having an oxetanyl group and an ethylenically unsaturated bond, and a monomer (b3) (hereinafter sometimes referred to as "(b3)") having a tetrahydrofuryl group and an ethylenically unsaturated bond.

Examples of (b1) include a monomer (b1-1) (hereinafter sometimes referred to as "(b1-1)") having a structure in which a linear or branched aliphatic unsaturated hydrocarbon has been epoxidized, and a monomer (b1-2) (hereinafter sometimes referred to as "(b1-2)") having a structure in which an alicyclic unsaturated hydrocarbon has been epoxidized.

(b1-1) includes glycidyl (meth)acrylate, β-methyl glycidyl (meth)acrylate, β-ethyl glycidyl (meth)acrylate, glycidyl vinyl ether, o-vinylbenzyl glycidyl ether, m-vinylbenzyl glycidyl ether, p-vinylbenzyl glycidyl ether, α-methyl-o-vinylbenzyl glycidyl ether, α-methyl-m-vinylbenzyl glycidyl ether, α-methyl-p-vinylbenzyl glycidyl ether, 2,3-bis(glycidyl Examples of such styrene include 2,4-bis(glycidyloxymethyl)styrene, 2,5-bis(glycidyloxymethyl)styrene, 2,6-bis(glycidyloxymethyl)styrene, 2,3,4-tris(glycidyloxymethyl)styrene, 2,3,5-tris(glycidyloxymethyl)styrene, 2,3,6-tris(glycidyloxymethyl)styrene, 3,4,5-tris(glycidyloxymethyl)styrene, and 2,4,6-tris(glycidyloxymethyl)styrene.

Examples of (b1-2) include vinylcyclohexene monoxide, 1,2-epoxy-4-vinylcyclohexane (e.g., Celloxide 2000; manufactured by Daicel Corporation), 3,4-epoxycyclohexylmethyl (meth)acrylate (e.g., Cyclomer A400; manufactured by Daicel Corporation), 3,4-epoxycyclohexylmethyl (meth)acrylate (e.g., Cyclomer M100; manufactured by Daicel Corporation), compounds represented by formula (I), and compounds represented by formula (II).

In formula (I) and formula (II), R ^a and R ^b represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and the hydrogen atom contained in the alkyl group may be substituted with a hydroxy group.
^Xa and ^Xb each represent a single bond, *-R ^c -, *-R ^c -O-, *-R ^c -S- or *-R ^c -NH-.
^Rc represents an alkanediyl group having 1 to 6 carbon atoms.
* represents a bond to O.]

Examples of the alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, and a tert-butyl group.
Examples of alkyl groups in which a hydrogen atom is substituted with a hydroxy group include a hydroxymethyl group, a 1-hydroxyethyl group, a 2-hydroxyethyl group, a 1-hydroxypropyl group, a 2-hydroxypropyl group, a 3-hydroxypropyl group, a 1-hydroxy-1-methylethyl group, a 2-hydroxy-1-methylethyl group, a 1-hydroxybutyl group, a 2-hydroxybutyl group, a 3-hydroxybutyl group, and a 4-hydroxybutyl group.
R ^{1 a} and R 1 ^b are preferably a hydrogen atom, a methyl group, a hydroxymethyl group, a 1-hydroxyethyl group, or a 2-hydroxyethyl group, and more preferably a hydrogen atom or a methyl group.

Examples of the alkanediyl group include a methylene group, an ethylene group, a propane-1,2-diyl group, a propane-1,3-diyl group, a butane-1,4-diyl group, a pentane-1,5-diyl group, and a hexane-1,6-diyl group.
^Xa and ^Xb are preferably a single bond, a methylene group, an ethylene group, *-CH ₂ -O-, and *-CH ₂ CH ₂ -O-, more preferably a single bond or *-CH ₂ CH ₂ -O- (* represents a bond to O).

Examples of compounds represented by formula (I) include compounds represented by any of formulas (I-1) to (I-15). Among these, compounds represented by formula (I-1), (I-3), (I-5), (I-7), (I-9), or (I-11) to (I-15) are preferred, and compounds represented by formula (I-1), (I-7), (I-9), or (I-15) are more preferred.

Examples of compounds represented by formula (II) include compounds represented by any of formulas (II-1) to (II-15). Among these, compounds represented by formula (II-1), (II-3), (II-5), (II-7), (II-9), or (II-11) to (II-15) are preferred, and compounds represented by formula (II-1), (II-7), (II-9), or (II-15) are more preferred.

The compound represented by formula (I) and the compound represented by formula (II) may be used alone or in combination of two or more. When the compound represented by formula (I) and the compound represented by formula (II) are used in combination, the content ratio thereof [compound represented by formula (I):compound represented by formula (II)] is preferably 5:95 to 95:5, more preferably 20:80 to 80:20, on a molar basis.

More preferably, (b2) is a monomer having an oxetanyl group and a (meth)acryloyloxy group. Examples of (b2) include 3-methyl-3-methacryloyloxymethyloxetane, 3-methyl-3-acryloyloxymethyloxetane, 3-ethyl-3-methacryloyloxymethyloxetane, 3-ethyl-3-acryloyloxymethyloxetane, 3-methyl-3-methacryloyloxyethyloxetane, 3-methyl-3-acryloyloxyethyloxetane, 3-ethyl-3-methacryloyloxyethyloxetane, and 3-ethyl-3-acryloyloxyethyloxetane.

More preferably, (b3) is a monomer having a tetrahydrofuryl group and a (meth)acryloyloxy group. Specific examples of (b3) include tetrahydrofurfuryl acrylate (e.g., Viscoat V#150, manufactured by Osaka Organic Chemical Industry Ltd.) and tetrahydrofurfuryl methacrylate.

(b) is preferably (b1) in that it can further increase the reliability of the heat resistance, chemical resistance, etc. of the resulting cured film. Furthermore, (b1-2) is more preferred in that it provides excellent storage stability to the curable composition.

Examples of (c) include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, dodecyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-methylcyclohexyl (meth)acrylate, tricyclo[5.2.1.0 ^2,6 ]decan-8-yl (meth)acrylate (commonly known in the art as "dicyclopentanyl (meth)acrylate" and sometimes referred to as "tricyclodecyl (meth)acrylate"), tricyclo[5.2.1.0 ^2,6 (meth)acrylic acid esters such as decene-8-yl (meth)acrylate (commonly known as "dicyclopentenyl (meth)acrylate" in the technical field), dicyclopentanyloxyethyl (meth)acrylate, isobornyl (meth)acrylate, adamantyl (meth)acrylate, allyl (meth)acrylate, propargyl (meth)acrylate, phenyl (meth)acrylate, naphthyl (meth)acrylate, and benzyl (meth)acrylate;
hydroxy group-containing (meth)acrylic acid esters such as 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate;
dicarboxylic acid diesters such as diethyl maleate, diethyl fumarate, and diethyl itaconate;
Bicyclo[2.2.1]hept-2-ene, 5-methylbicyclo[2.2.1]hept-2-ene, 5-ethylbicyclo[2.2.1]hept-2-ene, 5-hydroxybicyclo[2.2.1]hept-2-ene, 5-hydroxymethylbicyclo[2.2.1]hept-2-ene, 5-(2'-hydroxyethyl)bicyclo[2.2.1]hept-2-ene, 5-methoxybicyclo[2.2.1]hept-2-ene chloro[2.2.1]hept-2-ene, 5-ethoxybicyclo[2.2.1]hept-2-ene, 5,6-dihydroxybicyclo[2.2.1]hept-2-ene, 5,6-di(hydroxymethyl)bicyclo[2.2.1]hept-2-ene, 5,6-di(2'-hydroxyethyl)bicyclo[2.2.1]hept-2-ene, 5,6-dimethoxybicyclo[2.2.1]hept -2-ene, 5,6-diethoxybicyclo[2.2.1]hept-2-ene, 5-hydroxy-5-methylbicyclo[2.2.1]hept-2-ene, 5-hydroxy-5-ethylbicyclo[2.2.1]hept-2-ene, 5-hydroxymethyl-5-methylbicyclo[2.2.1]hept-2-ene, 5-tert-butoxycarbonylbicyclo[2.2.1]hept-2-ene bicyclounsaturated compounds such as ene, 5-cyclohexyloxycarbonylbicyclo[2.2.1]hept-2-ene, 5-phenoxycarbonylbicyclo[2.2.1]hept-2-ene, 5,6-bis(tert-butoxycarbonyl)bicyclo[2.2.1]hept-2-ene, and 5,6-bis(cyclohexyloxycarbonyl)bicyclo[2.2.1]hept-2-ene;
dicarbonyl imide derivatives such as N-phenylmaleimide, N-cyclohexylmaleimide, N-benzylmaleimide, N-succinimidyl-3-maleimidobenzoate, N-succinimidyl-4-maleimidobutyrate, N-succinimidyl-6-maleimidocaproate, N-succinimidyl-3-maleimidopropionate, and N-(9-acridinyl)maleimide;
Examples include styrene, α-methylstyrene, m-methylstyrene, p-methylstyrene, vinyltoluene, p-methoxystyrene, acrylonitrile, methacrylonitrile, vinyl chloride, vinylidene chloride, acrylamide, methacrylamide, vinyl acetate, 1,3-butadiene, isoprene, and 2,3-dimethyl-1,3-butadiene.
Among these, styrene, vinyltoluene, N-phenylmaleimide, N-cyclohexylmaleimide, N-benzylmaleimide, bicyclo[2.2.1]hept-2-ene, etc. are preferred from the viewpoints of copolymerization reactivity and heat resistance.

In the resin [K1], the ratio of the structural units derived from each of these to all the structural units constituting the resin [K1] is as follows:
Structural units derived from (a): 2 to 60 mol %
Structural units derived from (b): 40 to 98 mol%
Preferably,
Structural units derived from (a): 10 to 50 mol %
Structural units derived from (b): 50 to 90 mol %
It is more preferable that:
When the ratio of the structural units of the resin [K1] is within the above range, the storage stability of the curable composition, the developability when forming a pattern, and the solvent resistance of the resulting developed product tend to be excellent.

Resin [K1] can be produced, for example, by referring to the method described in the literature "Experimental Methods for Polymer Synthesis" (written by Takayuki Otsu, published by Kagaku Dojin Co., Ltd., 1st edition, 1st printing, published March 1, 1972) and the references cited therein.

Specifically, a method includes placing predetermined amounts of (a) and (b), a polymerization initiator, a solvent, etc. in a reaction vessel, creating a deoxygenated atmosphere by, for example, replacing oxygen with nitrogen, and then heating and maintaining the temperature while stirring. The polymerization initiators and solvents used here are not particularly limited, and those commonly used in the relevant field can be used. For example, polymerization initiators include azo compounds (2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), etc.) and organic peroxides (benzoyl peroxide, etc.). Solvents may be any that dissolve each monomer, such as those described below as solvent (E) for the curable composition.

The resulting copolymer may be used as a solution after the reaction as is, or as a concentrated or diluted solution, or as a solid (powder) obtained by reprecipitation or other methods. In particular, by using solvent (E) contained in the curable composition as the solvent during the polymerization, the solution after the reaction can be used as is to prepare the curable composition, thereby simplifying the manufacturing process of the curable composition.

In the resin [K2], the ratio of the structural units derived from each of these to all the structural units constituting the resin [K2] is as follows:
Structural units derived from (a): 2 to 45 mol %
Structural units derived from (b): 2 to 95 mol %
Structural units derived from (c): 1 to 65 mol%
Preferably,
Structural units derived from (a): 5 to 40 mol %
Structural units derived from (b): 5 to 80 mol %
Structural units derived from (c): 5 to 60 mol %
It is more preferable that:
When the ratio of the structural units of the resin [K2] is within the above range, the storage stability of the curable composition, the developability when forming a pattern, and the solvent resistance, heat resistance, and mechanical strength of the resulting developed product tend to be excellent.

Resin [K2] can be produced, for example, in the same manner as described above for producing resin [K1].

In the resin [K3], the ratio of the structural units derived from each of these to all the structural units constituting the resin [K3] is as follows:
Structural units derived from (a): 2 to 60 mol %
Structural units derived from (c): 40 to 98 mol%
Preferably,
Structural units derived from (a): 10 to 50 mol %
Structural units derived from (c): 50 to 90 mol %
It is more preferable that:
Resin [K3] can be produced, for example, in the same manner as described above for producing resin [K1].

Resin [K4] can be produced by obtaining a copolymer of (a) and (c), and then adding the cyclic ether having 2 to 4 carbon atoms contained in (b) to the carboxylic acid and/or carboxylic acid anhydride contained in (a).
First, a copolymer of (a) and (c) is produced in the same manner as described for the production of resin [K1]. In this case, the ratio of the structural units derived from each of the components is preferably the same as that described for resin [K3].

Next, a part of the carboxylic acid and/or carboxylic acid anhydride derived from (a) in the copolymer is reacted with a cyclic ether having 2 to 4 carbon atoms contained in (b).
Following the production of the copolymer of (a) and (c), the atmosphere in the flask is replaced with air from nitrogen, and (b) a catalyst for the reaction of a carboxylic acid or a carboxylic acid anhydride with a cyclic ether (e.g., tris(dimethylaminomethyl)phenol, etc.), a polymerization inhibitor (e.g., hydroquinone, etc.), etc. are placed in the flask, and the mixture is reacted, for example, at 60 to 130°C for 1 to 10 hours, thereby producing resin [K4].

The amount of (b) used is preferably 5 to 80 moles, more preferably 10 to 75 moles, per 100 moles of (a). This range tends to improve the storage stability of the curable composition, the developability when forming a pattern, and the balance of the solvent resistance, heat resistance, mechanical strength, and sensitivity of the resulting developed product. Because the reactivity of cyclic ethers is high and unreacted (b) is unlikely to remain, (b1) is preferred as the (b) used in resin [K4], and (b1-1) is even more preferred.

The amount of the reaction catalyst used is preferably 0.001 to 5 parts by mass per 100 parts by mass of the total of (a), (b), and (c), and the amount of the polymerization inhibitor used is preferably 0.001 to 5 parts by mass per 100 parts by mass of the total of (a), (b), and (c).
The reaction conditions such as the charging method, reaction temperature and time can be appropriately adjusted in consideration of the production equipment, the amount of heat generated by the polymerization, etc. As with the polymerization conditions, the charging method and reaction temperature can be appropriately adjusted in consideration of the production equipment, the amount of heat generated by the polymerization, etc.

Resin [K5] is obtained in the first step by the same method as in the production of Resin [K1] described above, to obtain a copolymer of (b) and (c). As in the above, the obtained copolymer may be used as a solution after the reaction as is, a concentrated or diluted solution, or a solid (powder) obtained by a method such as reprecipitation.
The ratios of the structural units derived from (b) and (c) to the total number of moles of all structural units constituting the copolymer are as follows:
Structural units derived from (b): 5 to 95 mol %
Structural units derived from (c): 5 to 95 mol%
Preferably,
Structural units derived from (b): 10 to 90 mol %
Structural units derived from (c): 10 to 90 mol%
It is more preferable that:

Furthermore, under the same conditions as in the production method of resin [K4], resin [K5] can be obtained by reacting a cyclic ether derived from (b) contained in a copolymer of (b) and (c) with a carboxylic acid or carboxylic anhydride contained in (a).
The amount of (a) used to react with the copolymer is preferably 5 to 80 moles per 100 moles of (b). Because the reactivity of cyclic ethers is high and unreacted (b) is unlikely to remain, (b1) is preferred as (b) used in resin [K5], and (b1-1) is more preferred.

Resin [K6] is a resin obtained by further reacting resin [K5] with a carboxylic acid anhydride. The hydroxyl group generated by the reaction of a cyclic ether with a carboxylic acid or a carboxylic acid anhydride is reacted with the carboxylic acid anhydride.
Examples of the carboxylic acid anhydride include maleic anhydride, citraconic anhydride, itaconic anhydride, 3-vinylphthalic anhydride, 4-vinylphthalic anhydride, 3,4,5,6-tetrahydrophthalic anhydride, 1,2,3,6-tetrahydrophthalic anhydride, dimethyltetrahydrophthalic anhydride, 5,6-dicarboxybicyclo[2.2.1]hept-2-ene anhydride, etc. The amount of the carboxylic acid anhydride used is preferably 0.5 to 1 mole per mole of the amount of (a) used.

Specific examples of the resin (D) include resins [K1] such as 3,4-epoxycyclohexylmethyl (meth)acrylate/(meth)acrylic acid copolymer, 3,4-epoxytricyclo[5.2.1.0 ^2,6 ]decyl acrylate/(meth)acrylic acid copolymer, glycidyl (meth)acrylate/benzyl (meth)acrylate/(meth)acrylic acid copolymer, glycidyl (meth)acrylate/styrene/(meth)acrylic acid copolymer, 3,4-epoxytricyclo[5.2.1.0 ^2,6 ]decyl acrylate/(meth)acrylic acid copolymer, ]decyl acrylate/(meth)acrylic acid/N-cyclohexylmaleimide copolymer, 3-methyl-3-(meth)acryloyloxymethyloxetane/(meth)acrylic acid/styrene copolymer, and other resins [K2]; benzyl (meth)acrylate/(meth)acrylic acid copolymer, styrene/(meth)acrylic acid copolymer, and other resins [K3]; resins obtained by adding glycidyl (meth)acrylate to benzyl (meth)acrylate/(meth)acrylic acid copolymer, resins obtained by adding glycidyl (meth)acrylate to tricyclodecyl (meth)acrylate/styrene/(meth)acrylic acid copolymer, tricyclodecyl (meth)acrylate/ Resins [K4] such as a resin obtained by adding glycidyl (meth)acrylate to a benzyl (meth)acrylate/(meth)acrylic acid copolymer; resins [K5] such as a resin obtained by reacting a tricyclodecyl (meth)acrylate/glycidyl (meth)acrylate copolymer with (meth)acrylic acid, or a resin obtained by reacting a tricyclodecyl (meth)acrylate/styrene/glycidyl (meth)acrylate copolymer with (meth)acrylic acid; and resins [K6] such as a resin obtained by reacting a tricyclodecyl (meth)acrylate/glycidyl (meth)acrylate copolymer with (meth)acrylic acid and further reacting the resulting resin with tetrahydrophthalic anhydride.
Among these, resin (D) is preferably resin [K1] or resin [K2], and particularly preferably resin [K2].

The polystyrene-equivalent weight average molecular weight of resin (D) is preferably 3,000 to 100,000, more preferably 5,000 to 50,000, and even more preferably 5,000 to 30,000. When the molecular weight is within this range, the hardness of the cured film tends to be improved.

The dispersity of resin (D) [weight average molecular weight (Mw)/number average molecular weight (Mn)] is preferably 1.1 to 6, more preferably 1.2 to 4.

The acid value of resin (D), calculated on a solids basis, is preferably 50 to 170 mg-KOH/g, more preferably 60 to 150 mg-KOH/g, and even more preferably 70 to 135 mg-KOH/g. The acid value is measured as the amount (mg) of potassium hydroxide required to neutralize 1 g of resin (D), and can be determined, for example, by titration using an aqueous potassium hydroxide solution.

The solid content of resin (D) in the curable composition is, for example, 500 parts by mass or less, preferably 200 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 30 parts by mass or less, particularly preferably 10 parts by mass or less, and may even be 0 parts by mass, per 100 parts by mass of polymerizable compound (B).

<Solvent (E)>
The solvent (E) is not particularly limited, and a solvent commonly used in the relevant field can be used. Examples thereof include ester solvents (solvents containing —COO— but not —O— in the molecule), ether solvents (solvents containing —O— but not —COO— in the molecule), ether ester solvents (solvents containing —COO— and —O— in the molecule), ketone solvents (solvents containing —CO— but not —COO— in the molecule), alcohol solvents (solvents containing OH in the molecule but not —O—, —CO—, or —COO—), alcohol ketone solvents (solvents containing OH and —CO— in the molecule), aromatic hydrocarbon solvents, amide solvents, and dimethyl sulfoxide.

Ester solvents include methyl lactate, ethyl lactate, butyl lactate, methyl 2-hydroxyisobutanoate, ethyl acetate, n-butyl acetate, isobutyl acetate, pentyl formate, isopentyl acetate, butyl propionate, isopropyl butyrate, ethyl butyrate, butyl butyrate, methyl pyruvate, ethyl pyruvate, propyl pyruvate, methyl acetoacetate, ethyl acetoacetate, cyclohexanol acetate, and gamma-butyrolactone.

Examples of ether solvents include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, 3-methoxy-1-butanol, 3-methoxy-3-methylbutanol, tetrahydrofuran, tetrahydropyran, 1,4-dioxane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol dipropyl ether, diethylene glycol dibutyl ether, anisole, phenetole, and methylanisole.

Ether ester solvents include methyl methoxyacetate, ethyl methoxyacetate, butyl methoxyacetate, methyl ethoxyacetate, ethyl ethoxyacetate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, methyl 3-ethoxypropionate, ethyl 3-ethoxypropionate, methyl 2-methoxypropionate, ethyl 2-methoxypropionate, propyl 2-methoxypropionate, methyl 2-ethoxypropionate, ethyl 2-ethoxypropionate, methyl 2-methoxy-2-methylpropionate, methyl 2-ethoxypropionate, Examples of the alkyl ether acetate include ethyl 2-methoxypropionate, 3-methoxybutyl acetate, 3-methyl-3-methoxybutyl acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monopropyl ether acetate, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, diethylene glycol monoethyl ether acetate, and diethylene glycol monobutyl ether acetate.

Ketone solvents include 4-hydroxy-4-methyl-2-pentanone, acetone, methyl ethyl ketone, 2-heptanone, 3-heptanone, 4-heptanone, 4-methyl-2-pentanone, cyclopentanone, cyclohexanone, and isophorone.

Alcohol solvents include methanol, ethanol, propanol, butanol, hexanol, cyclohexanol, ethylene glycol, propylene glycol, and glycerin.

Examples of alcohol ketone solvents include dimers of ketones selected from the above-mentioned ketone solvents, such as diacetone alcohol.

Aromatic hydrocarbon solvents include benzene, toluene, xylene, and mesitylene.
Amide solvents include N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

Of the above solvents, organic solvents with a boiling point of 120°C or higher and 180°C or lower at 1 atm are preferred in terms of workability and drying properties. Preferred solvents include propylene glycol monomethyl ether acetate, ethyl lactate, propylene glycol monomethyl ether, ethyl 3-ethoxypropionate, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, 4-hydroxy-4-methyl-2-pentanone, methyl ethyl ketone, butyl acetate, 2-heptanone, diacetone alcohol, and N,N-dimethylformamide, with propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, ethyl lactate, methyl ethyl ketone, and ethyl 3-ethoxypropionate being more preferred.

When the curable composition contains a solvent (E), the content of solvent (E) in the curable composition is, for example, 40% by mass or less, preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 15% by mass or less, particularly preferably 10% by mass or less, and most preferably 5% by mass or less, and may even be 0% by mass. The curable composition of the present invention has high fluidity and excellent workability even without containing a solvent.

<Surfactant (F)>
The curable composition may contain a surfactant (F). The surfactant (F) can be used as a leveling agent, and examples thereof include silicone surfactants, fluorine surfactants, and silicone surfactants containing fluorine atoms. These surfactants may have a polymerizable group in a side chain.

Examples of silicone surfactants include surfactants that have a siloxane bond in the molecule. An example of a surfactant that has a siloxane bond in the molecule is octamethylcyclotetrasiloxane. The silicone surfactant may be Toray Silicone DC3PA, SH7PA, DC11PA, SH21PA, SH28PA, SH29PA, SH30PA, or SH8400 (trade name: manufactured by Dow Corning Toray Co., Ltd.), KF994, KP321, KP322, KP323, KP324, KP326, KP340, or KP341 (manufactured by Shin-Etsu Chemical Co., Ltd.), or TSF400, TSF401, TSF410, TSF4300, TSF4440, TSF4445, TSF4446, TSF4452, or TSF4460 (manufactured by Momentive Performance Materials Japan LLC).

Examples of the fluorine-based surfactant include surfactants having a fluorocarbon chain in the molecule. Specific examples include Fluorad (registered trademark) FC430 and FC431 (manufactured by Sumitomo 3M Limited), Megafac (registered trademark) F142D, F171, F172, F173, F177, F183, F554, R30, and RS-718-K (manufactured by DIC Corporation), F-Top (registered trademark) EF301, EF303, EF351, and EF352 (manufactured by Mitsubishi Materials Electronic Chemicals Co., Ltd.), Surflon (registered trademark) S381, S382, SC101, and SC105 (manufactured by Asahi Glass Co., Ltd.), and E5844 (manufactured by Daikin Fine Chemicals Research Institute, Ltd.).

Examples of the silicone surfactants containing fluorine atoms include surfactants containing siloxane bonds and fluorocarbon chains in the molecule. Specific examples include Megafac (registered trademark) R08, BL20, F475, F477, and F443 (manufactured by DIC Corporation).

When surfactant (F) is contained, its content may be, for example, from 0.001% to 2% by mass, or from 0.001% to 1.5% by mass, relative to the total amount of the curable composition. This content is preferably from 0.001% to 0.2% by mass, more preferably from 0.002% to 0.1% by mass, and even more preferably from 0.005% to 0.07% by mass.

<Other ingredients>
The curable composition of the present invention may optionally contain additives known in the art, such as fillers, adhesion promoters, antioxidants, light stabilizers, chain transfer agents, and the like.

<Curable composition characteristics>
The viscosity of the curable composition of the present invention at a temperature of 23°C is, for example, 300 mPa·s or less, preferably 260 mPa·s or less, and more preferably 210 mPa·s or less. Furthermore, the viscosity is, for example, 1 mPa·s or more. When the viscosity is within this range, clogging and deflection of the ink are less likely to occur when the composition is applied using an inkjet method. The viscosity can be measured, for example, using an E-type viscometer and optimizing the rotor rotation speed (preferably 1 rpm).

The curable composition of the present invention has excellent transmittance for visible light. Specifically, the average transmittance for wavelengths of 400 to 700 nm of the cured film obtained by the following film-forming method 1 is 90% or more, preferably 93% or more, and more preferably 95% or more per 1.0 μm of film thickness. Furthermore, the transmittance for all wavelengths of 400 to 700 nm of the cured film obtained by the following film-forming method 1 is preferably 90% or more, more preferably 93% or more, and even more preferably 95% or more per 1.0 μm of film thickness.
[Film forming method 1]
The curable composition is applied to a glass substrate so that the average thickness of the cured film falls within the range of 1.0±0.2 μm, and the substrate is irradiated with UV light having a wavelength of 385 nm at an integrated light intensity of 2000 J/m ² using an LED lamp.
When the average thickness of the obtained cured film is 1.0 μm, the transmittance T (at a film thickness of 1.0 μm) is taken as the transmittance per 1.0 μm film thickness. When the average thickness of the obtained cured film is x μm (x is a value in the range of 1.0±0.2 and not 1.0), the transmittance T' (at a film thickness of x μm) is converted to absorbance A' (at a film thickness of x μm) based on A' = -log ₁₀ T', and this absorbance A' (at a film thickness of x μm) is multiplied by the reciprocal of film thickness x (μm) to determine absorbance A (at a film thickness of 1.0 μm). Next, the transmittance T (at a film thickness of 1.0 μm) is calculated based on A = -log ₁₀ T to determine the transmittance T per 1.0 μm film thickness. Then, an average value of the transmittance per 1.0 μm film thickness at wavelengths of 400 to 700 nm is calculated.

The cured film obtained from the curable composition of the present invention has a high refractive index. Specifically, the refractive index at a wavelength of 550 nm of the cured film obtained by the following Film Forming Method 2, as measured using a spectroscopic ellipsometer, is for example 1.5 or more, preferably 1.6 or more, more preferably 1.65 or more, and for example 3.0 or less, preferably 2.5 or less, more preferably 2.0 or less.
[Film forming method 2]
The obtained curable composition is applied to a 4-inch Si wafer substrate using a spin coater so that the average thickness of the cured film is 0.5 μm. Using an LED lamp, UV light with a wavelength of 385 nm is irradiated at an integrated light intensity of 2000 J/ ^m2 .

<Cured film>
A cured film can be produced by applying the curable composition onto a substrate by spin coating, casting, microgravure coating, gravure coating, bar coating, roll coating, wire bar coating, dip coating, spray coating, screen printing, flexographic printing, offset printing, inkjet printing, capillary coating, nozzle coating, or the like, and then irradiating the composition with radiation such as UV. Alternatively, a patterned cured film (i.e., a cured film formed only on a portion of a substrate) may be produced using photolithography, inkjet printing, or the like.
The thickness of the cured film is usually about 1 nm to 50 μm, preferably 1 μm to 50 μm.
The cured film can be used as a microlens, a sealant, etc., and is particularly preferably used as a microlens, a sealant, etc. for a light-emitting element.

The present invention will be explained in more detail below using examples, but the present invention is not limited to the examples below, and it is of course possible to make appropriate modifications within the scope of the above and below-described intent, and all such modifications are within the technical scope of the present invention.

Example 1
[Production of inorganic fine particle dispersion]
Glycerin triacrylate (MT3547, manufactured by Toagosei Co., Ltd.) was added as a polymerizable compound to a zirconium oxide dispersion (zirconium oxide/dispersant/methyl ethyl ketone = 55/15/30, mass ratio, volume average particle size of zirconium oxide: 10 nm), and the methyl ethyl ketone was removed by distillation under reduced pressure to obtain a glycerin triacrylate dispersion of zirconium oxide particles (hereinafter referred to as an inorganic fine particle dispersion). The amount of remaining methyl ethyl ketone was confirmed by gas chromatography (GC) analysis.
[Preparation of Curable Composition]
The component ratios of the inorganic fine particle dispersion were adjusted so that the zirconium oxide particles were 37 parts by mass, the dispersant was 9 parts by mass, and the glycerin triacrylate was 46 parts by mass. Further, 8 parts by mass of ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate (Omnirad TPO-L, manufactured by IGM Resins B.V., hereinafter referred to as TPO-L) was blended and dissolved as a polymerization initiator, and the mixture was filtered through a polytetrafluoroethylene (PTFE) membrane filter, thereby obtaining curable composition 1.

Example 2
An inorganic fine particle dispersion was prepared in the same manner as in Example 1.
The component ratio of the inorganic fine particle dispersion was adjusted to 37 parts by mass of zirconium oxide particles, 9 parts by mass of dispersant, and 45 parts by mass of glycerin triacrylate, and further 8 parts by mass of bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (IRGACURE (registered trademark) 819, manufactured by BASF, hereinafter referred to as IRG819) as a polymerization initiator and 1 part by mass of octamethylcyclotetrasiloxane (manufactured by Tokyo Chemical Industry Co., Ltd.) as a surfactant were blended and dissolved, and then filtered through a polytetrafluoroethylene (PTFE) membrane filter, to obtain curable composition 2.

Example 3
An inorganic fine particle dispersion was prepared in the same manner as in Example 1.
The component ratio of the inorganic fine particle dispersion was adjusted to 33 parts by mass of zirconium oxide particles, 8 parts by mass of dispersant, 41 parts by mass of glycerin triacrylate, and 10 parts by mass of tricylctodecanedimethanol diacrylate (A-DCP, manufactured by Shin-Nakamura Chemical Co., Ltd., hereinafter sometimes referred to as A-DCP), and 8 parts by mass of IRG819 was further blended and dissolved as a polymerization initiator, followed by filtration through a polytetrafluoroethylene (PTFE) membrane filter to obtain curable composition 3.

Comparative Example 1
Comparative curable composition 1 was obtained in the same manner as in Example 1, except that a mixture of tricylctodecanedimethanol diacrylate (A-DCP, manufactured by Shin-Nakamura Chemical Co., Ltd.), 1,10-decanediol diacrylate (A-DOD-N, manufactured by Shin-Nakamura Chemical Co., Ltd., hereinafter referred to as A-DOD-N), and isobutyl methacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) was used as the polymerizable compound instead of glycerin triacrylate, that octamethylcyclotetrasiloxane (manufactured by Tokyo Chemical Industry Co., Ltd.) was further used as the surfactant, and that 5 parts by mass of IRG819 was used as the polymerization initiator instead of 8 parts by mass of TPO-L.
Comparative curable composition 1 contained 37 parts by mass of zirconium oxide particles, 9 parts by mass of a dispersant, 24 parts by mass of A-DCP, 14 parts by mass of A-DOD-N, 10 parts by mass of isobutyl methacrylate, 5 parts by mass of IRG819, and 1 part by mass of octamethylcyclotetrasiloxane.

[Evaluation of Curable Composition]
The viscosity of the resulting curable composition at a temperature of 23° C. was measured using an E-type viscometer with a rotor rotation speed of 1 rpm.

[Production of cured films and their evaluation 1, 2]
The obtained curable composition was applied to a 2-inch square glass substrate (Eagle XG; manufactured by Corning Inc.) using a spin coater so that the average thickness of the cured film was 10 μm. Next, using an LED lamp, UV irradiation was performed at a wavelength of 385 nm and an integrated light dose of 2000 J/ ^m2 to obtain a cured film.
The obtained cured films and curable compositions were evaluated as follows. The results of the evaluations are shown in Table 1.
1. Hardening property (tackiness)
The surface of the cured film was lightly touched with embossed vinyl gloves. When the glove left no mark on the cured film, the result was marked as ◯, and when the glove left a mark on the cured film, the result was marked as ×.
2. Coatability The thickness of the cured film was measured at two points, and when the difference between the two film thicknesses was within 5% of the average value of the two film thicknesses, it was marked as O, and when it was more than 5%, it was marked as ×.
[Production of cured film and its evaluation 3]
3. Transmittance The obtained curable composition was applied to a 2-inch square glass substrate using a spin coater so that the average thickness of the cured film was 1.0 μm. Next, using an LED lamp, UV irradiation was performed at a wavelength of 385 nm and an integrated light intensity of 2000 J/ ^m2 to obtain a cured film. The transmittance of the cured film from 400 nm to 700 nm was measured using a microspectrophotometer, and the average transmittance was taken as the transmittance of the cured film.

[Production of cured film and its evaluation 4]
4. Refractive Index The curable composition was applied to a 4-inch Si wafer substrate using a spin coater so that the average thickness of the cured film was 0.5 μm. Next, using an LED lamp, UV light with a wavelength of 385 nm was irradiated at an integrated light intensity of 2000 J/ ^m2 . Using a spectroscopic ellipsometer, the cured product was irradiated with light with a wavelength in the range of 400 nm to 1600 nm at angles of 60°, 70°, and 75° to determine the refractive index at a wavelength of 550 nm, which was used as the refractive index of the cured film.

The results are shown in Table 1.
a-1: Zirconia nanoparticles b-1: Glycerin triacrylate b-2: A-DCP
b-3: A-DOD-N
b-4: Isobutyl methacrylate c-1: TPO-L
c-2: IRG819
e-1: Methyl ethyl ketone f-1: Octamethylcyclotetrasiloxane

Claims (3)

The composition contains inorganic fine particles (A), a polymerizable compound (B), and a polymerization initiator (C),
the inorganic fine particles (A) are at least one selected from the group consisting of titanium oxide, zirconium oxide, aluminum oxide, niobium oxide, and silicon nitride,
The polymerizable compound (B) contains a compound represented by formula (B1),

(In the formula, ^R1 and ^R2 each independently represent a hydrogen atom or an alkyl group having 1 to 20 carbon atoms which may have a substituent; ^R3 represents a ( meth)acrylic group.)
A curable composition having an average transmittance of 90% or more per 1.0 μm film thickness at wavelengths of 400 to 700 nm when formed into a film under the following conditions:
[Film formation conditions]
The curable composition is applied to a glass substrate so that the average thickness of the cured film falls within the range of 1.0±0.2 μm, and the substrate is irradiated with UV light having a wavelength of 385 nm at an integrated light intensity of 2000 J/m ² using an LED lamp. The curable composition according to claim 1, wherein the content of the inorganic fine particles (A) in the curable composition is 10 mass% or more. A cured film formed from the curable composition according to claim 1 or 2.