Hardening composition

Abstract

The present invention provides a curable composition which can form cured objects having both a low degree of thermal expansion and a low modulus.　The present invention relates to a curable composition comprising (A) an epoxy compound having two or more alicyclic epoxy groups, (B) an inorganic filler, (C) hollow organic-polymer particles, and (D) a cationic-polymerization initiator.

Description

[Technical Field]

[0001] The present invention relates to a curable composition. [Background technology]

[0002] When fixing components in optical devices such as communication base stations, even slight misalignment of the components can result in a decrease in performance. Therefore, curable compositions used as adhesives to fix components are required to be able to form cured products with a low coefficient of thermal expansion to prevent minute misalignments. Furthermore, when used as adhesives in locations where the effects of vibration are a concern, curable compositions are required to be able to form cured products with a low modulus of elasticity to reduce the effects of vibration (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-177013 Summary of the Invention [Problem to be solved by the invention]

[0004] To achieve a low coefficient of thermal expansion of the cured product, inorganic particles such as silica can be added to the curable composition, but this significantly increases the modulus of elasticity of the cured product. On the other hand, to reduce the modulus of elasticity of the cured product, an organic filler can be added to the curable composition, but this increases the coefficient of thermal expansion of the cured product. Thus, it has been difficult to form a cured product that has both a low coefficient of thermal expansion and a low modulus of elasticity.

[0005] The present invention has been made in light of the above-mentioned circumstances, and an object of the present invention is to provide a curable composition that can form a cured product that has both a low coefficient of thermal expansion and a low modulus of elasticity. [Means for solving the problem]

[0006] As a result of intensive research to achieve the above object, the present inventors have found that a curable composition containing an epoxy compound having two or more alicyclic epoxy groups, an inorganic filler, hollow organic polymer particles, and a cationic polymerization initiator can form a cured product that has both a low coefficient of thermal expansion and a low modulus of elasticity, and have thus completed the present invention. The present invention based on this finding is as follows.

[0007] [1] The following components (A) to (D): (A) an epoxy compound having two or more alicyclic epoxy groups; (B) Inorganic filler, (C) hollow organic polymer particles, and (D) Cationic polymerization initiator 1. A curable composition comprising: [2] The curable composition according to [1] above, wherein the content of component (B) is 5 to 80 mass % based on the solid content of the curable composition. [3] The curable composition according to [1] or [2] above, wherein the content of component (C) is 3 to 70 mass % based on the solid content of the curable composition. [4] The curable composition according to any one of the above [1] to [3], wherein the mass ratio of component (B):component (C) is 1:10 to 20:1. [5] The curable composition according to any one of the above [1] to [4], wherein the porosity of component (C) is 20% by volume or more. [6] The curable composition according to any one of the above [1] to [4], wherein the porosity of component (C) is 40 to 85% by volume. [7] The curable composition according to any one of the above [1] to [6], wherein the component (D) is selected from a photoacid generator and a thermal acid generator. [8] The curable composition according to any one of the above [1] to [7], further comprising an oxetane compound having two or more oxetanyl groups. [9] The curable composition according to any one of the above [1] to [8], further comprising a polyester polyol.

[10] The curable composition according to any one of [1] to [9] above, which is used for bonding optical devices.

[11] An optical device having a cured layer formed from the curable composition according to any one of [1] to

[10] . [Effects of the Invention]

[0008] The curable composition of the present invention can form a cured product that has both a low coefficient of thermal expansion and a low modulus of elasticity, making the curable composition of the present invention extremely useful for bonding optical devices. DETAILED DESCRIPTION OF THE INVENTION

[0009] Each component contained in the curable composition of the present invention will be described below in order. Unless otherwise specified, each component may be used alone or in combination of two or more types.

[0010] <(A) Epoxy Compound Having Two or More Alicyclic Epoxy Groups> The curable composition of the present invention contains, as component (A), an epoxy compound having two or more alicyclic epoxy groups (sometimes referred to as an "alicyclic epoxy compound" in this specification). In curing by cationic polymerization, the alicyclic epoxy group has higher reactivity than a terminal epoxy group such as a glycidyl ether, and therefore the curable composition of the present invention has good curability. Furthermore, compared with (meth)acrylates and vinyl ethers that are generally used in curable compositions, epoxy compounds have a low cure shrinkage rate, and therefore the curable composition of the present invention has low cure shrinkage and is suitable as a precision fixing adhesive.

[0011] In this specification, the term "alicyclic epoxy group" refers to a fused ring group consisting of an alicyclic group and an oxirane ring, in which two adjacent carbon atoms constituting the alicyclic group form an oxirane ring (epoxy group) with an oxygen atom. Examples of the alicyclic epoxy group include an epoxycyclopentyl group and an epoxycyclohexyl group, and the epoxycyclohexyl group is preferred. The alicyclic epoxy compound may have an alicyclic fused alicyclic structure in which a plurality of alicyclic epoxy groups are condensed at an alicyclic moiety. The number of alicyclic epoxy groups in the alicyclic epoxy compound is preferably 2 to 4, and particularly preferably 2.

[0012] Examples of the alicyclic epoxy compound include those represented by the formulas (I) to (III):

[0013] [ka]

[0014] [In the formula, L 1 represents a single bond, a divalent hydrocarbon group, a carbonyl group, an ether bond, an ester bond, a carbonate bond, an amide bond, or a group in which a plurality of these are linked together, L 2 ~L 7 each independently represent a divalent hydrocarbon group, a carbonyl group, an ether bond, an ester bond, a carbonate bond, an amide bond, or a group in which a plurality of these are linked together. In this specification, "a compound represented by formula (I)" may be abbreviated as "compound (I)", and compounds represented by other formulas may also be abbreviated in the same manner.

[0015] In the above formula, the divalent hydrocarbon group is preferably an alkylene group having 1 to 18 carbon atoms or a divalent alicyclic hydrocarbon group having 5 to 7 carbon atoms. The alkylene group having 1 to 18 carbon atoms may be either linear or branched. Examples of the alkylene group having 1 to 18 carbon atoms include a methylene group, a methylmethylene group, a dimethylmethylene group, an ethylene group, a trimethylene group, and a propylene group. The divalent alicyclic hydrocarbon group having 5 to 7 carbon atoms is preferably a cycloalkylene group having 5 to 7 carbon atoms or a cycloalkylidene group having 5 to 7 carbon atoms. Examples of the cycloalkylene group having 5 to 7 carbon atoms include a 1,2-cyclopentylene group, a 1,3-cyclopentylene group, a 1,2-cyclohexylene group, a 1,3-cyclohexylene group, and a 1,4-cyclohexylene group. Examples of the cycloalkylidene group having 5 to 7 carbon atoms include a cyclopentylidene group and a cyclohexylidene group.

[0016] Preferred compounds (I) include, for example, compounds represented by formulae (I-1) to (I-8):

[0017] [ka]

[0018] [In the formula, n1 represents an integer from 1 to 30, n2 represents an integer from 6 to 30, and L 8 represents an alkylene group having 1 to 8 carbon atoms.] The compound (I-6) and the compound (I-8) may each be a mixture of compounds having different numbers of repeating units.

[0019] In formula (I-6), n1 is preferably an integer of 1 to 6. The alkylene group having 1 to 8 carbon atoms in formula (I-8) may be either linear or branched. Examples of the alkylene group having 1 to 8 carbon atoms include methylene, methylmethylene, dimethylmethylene, ethylene, trimethylene, propylene, tetramethylene, pentamethylene, hexamethylene, and octamethylene.

[0020] Preferred examples of the compound (II) include compounds represented by the formula (II-1):

[0021] [ka]

[0022] [In the formula, n3 and n4 each independently represent an integer of 2 to 30.] Compound (II-1) may be a mixture of compounds having different numbers of repeating units.

[0023] A preferred compound (III) is, for example, a compound represented by formula (III-1):

[0024] [ka]

[0025] [In the formula, n5 to n8 each independently represent an integer of 2 to 30.] Compound (III-1) may be a mixture of compounds having different numbers of repeating units.

[0026] The alicyclic epoxy compounds may be used alone or in combination of two or more. The alicyclic epoxy compound is preferably selected from compounds (I-1) to (I-8), compounds (II-1) and compounds (III-1). The alicyclic epoxy compound is more preferably selected from compounds (I-1) to (I-7). The alicyclic epoxy compound is further preferably selected from compounds (I-1) and (I-3).

[0027] Commercially available alicyclic epoxy compounds can be used, such as "Celloxide 2021P," "Celloxide 2081," and "Celloxide 8000" manufactured by Daicel Corporation; "Synasia S-21E," "Synasia S-28," and "Synasia S-60" manufactured by Synasia; and "TTA60," "TTA2081," and "TTA2083" manufactured by Tetrachem.

[0028] From the viewpoint of fluidity of the curable composition at room temperature, the molecular weight of the alicyclic epoxy compound is preferably less than 1,000, more preferably 900 or less, even more preferably 800 or less, even more preferably 700 or less, and particularly preferably 600 or less. There is no particular lower limit for the molecular weight of the alicyclic epoxy compound, but from the viewpoint of suppressing outgassing, the molecular weight is preferably 100 or more, more preferably 125 or more, and particularly preferably 150 or more. In addition, when the alicyclic epoxy compound is a compound having a repeating unit and is a mixture of multiple compounds having different numbers of repeating units, the molecular weight of the alicyclic epoxy compound means the weight average molecular weight (sometimes abbreviated as "Mw" in this specification). This Mw can be calculated, for example, by gel permeation chromatography (GPC) in terms of polystyrene.

[0029] The viscosity (25°C) of the alicyclic epoxy compound is preferably 10 to 3000 mPa·s, more preferably 25 to 2000 mPa·s, from the viewpoint of the fluidity of the curable composition at room temperature. In this specification, "viscosity (25°C)" means the viscosity at 25°C measured using a vibration viscometer.

[0030] From the viewpoint of reactivity, the epoxy equivalent of the alicyclic epoxy compound is preferably 50 to 500 g / eq, more preferably 75 to 450 g / eq, and particularly preferably 90 to 400 g / eq. In this specification, the "epoxy equivalent" of an epoxy compound refers to the number of grams of an epoxy compound containing 1 gram equivalent of epoxy groups. This epoxy equivalent value can be determined according to the method specified in JIS K 7236. Theoretically, the epoxy equivalent can be calculated by dividing the molecular weight of the epoxy compound by the number of epoxy groups contained in the epoxy compound.

[0031] From the viewpoints of good curability of the curable composition and a low coefficient of thermal expansion of the cured product, the content of component (A) is preferably 20.0 mass% or more, more preferably 30 mass% or more, and particularly preferably 40 mass% or more, based on the resin content of the curable composition, and is preferably 99.99 mass% or less, more preferably 99.9 mass% or less, and particularly preferably 99.8 mass% or less, based on the resin content of the curable composition. In this specification, the term "resin content of the curable composition" refers to the total amount of the "alicyclic epoxy compound" of component (A), which is an essential component, and the "oxetane compound having two or more oxetanyl groups" and "polyester polyol," which are optional components, as described below.

[0032] From the viewpoints of good curability of the curable composition and a low coefficient of thermal expansion of the cured product, the content of component (A) is preferably 3% by mass or more, more preferably 5% by mass or more, and particularly preferably 10% by mass or more, based on the solid content of the curable composition. From the viewpoint of the balance with the contents of the inorganic filler of component (B) and the hollow organic polymer particles of component (C), the content of component (A) is preferably 80% by mass or less, more preferably 70% by mass or less, and particularly preferably 60% by mass or less, based on the solid content of the curable composition.

[0033] <(B) Inorganic filler> The curable composition of the present invention contains an inorganic filler as component (B). In the present invention, the inorganic filler contributes to a low coefficient of thermal expansion of the cured product and improves the fillability of the hollow organic polymer particles (component (C)) described below in the curable composition. The use of an organic filler results in low fillability of the hollow organic polymer particles, and without the use of a filler, the hollow styrene particles cannot be sufficiently dispersed, resulting in a homogeneous composition. The incorporation of an inorganic filler in the curable composition of the present invention makes it possible to fill the curable composition with a sufficient amount of hollow organic polymer. Therefore, the curable composition of the present invention can form a cured product that has both a low coefficient of thermal expansion and a low modulus of elasticity due to the incorporation of the hollow organic polymer.

[0034] Examples of inorganic fillers include silica, alumina, glass, cordierite, silicon oxide, barium sulfate, barium carbonate, talc, clay, mica powder, zinc oxide, hydrotalcite, boehmite, aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, magnesium oxide, boron nitride, aluminum nitride, manganese nitride, aluminum borate, strontium carbonate, strontium titanate, calcium titanate, magnesium titanate, bismuth titanate, titanium oxide, zirconium oxide, barium titanate, barium titanate zirconate, barium zirconate, calcium zirconate, zirconium phosphate, and zirconium tungstate phosphate. The inorganic filler may be used alone or in combination of two or more kinds. The inorganic filler is preferably selected from silica and cordierite, more preferably silica. Examples of silica include amorphous silica, fused silica, crystalline silica, synthetic silica, and hollow silica. Spherical silica is preferred.

[0035] Commercially available inorganic fillers can be used, including, for example, "UFP-30" manufactured by Denka Chemical Industry Co., Ltd.; "SP60-05" and "SP507-05" manufactured by Nippon Steel & Sumikin Materials Co., Ltd.; "40SE-C3," "YC100C," "YA050C," "YA050C-MJE," "YA010C," "SC2500SQ," "SO-C4," "SO-C2," and "SO-C1" manufactured by Admatechs Co., Ltd.; "UFP-30," "DAW-03," and "FB-105FD" manufactured by Denka Company Limited; "Silfil NSS-3N," "Silfil NSS-4N," and "Silfil NSS-5N" manufactured by Tokuyama Corporation; and "SS-1000" manufactured by Marusu Glaze Co., Ltd.

[0036] The particle size of the inorganic filler is preferably 20 μm or less, more preferably 15 μm or less, and particularly preferably 10 μm or less, from the viewpoint of reducing the practical adhesive thickness and reducing misalignment due to thermal expansion, etc. The lower limit of the particle size of the inorganic filler is not particularly limited, but is preferably 0.01 μm or more, more preferably 0.05 μm or more, even more preferably 0.1 μm or more, and particularly preferably 0.2 μm or more. In this specification, the "particle size" of the inorganic filler refers to the median size that can be calculated by a laser diffraction / scattering method based on Mie scattering theory. Specifically, the particle size distribution of the inorganic filler can be prepared on a volume basis using a laser diffraction / scattering particle size distribution analyzer, and the median size can be calculated. More specifically, 100 mg of inorganic filler and 10 g of dispersion medium are weighed into a vial as a measurement sample and dispersed with sound waves for 10 minutes. A laser diffraction particle size distribution analyzer is used, with blue and red wavelengths as light sources, to measure the volumetric particle size distribution of the inorganic filler using a flow cell system, and the median diameter can be calculated from the particle size distribution obtained. Examples of laser diffraction particle size distribution analyzers include the LA-960 manufactured by Horiba, Ltd.

[0037] The specific surface area of ​​the inorganic filler is preferably 0.1 m from the viewpoint of improving the packing property of the hollow organic polymer particles. 2 / g or more, more preferably 0.5m 2 / g or more, particularly preferably 1m 2 The upper limit of the specific surface area of ​​the inorganic filler is not particularly limited, but is preferably 100 m 2 / g or less, more preferably 70m 2 / g or less, particularly preferably 50m 2 The specific surface area of ​​the inorganic filler can be measured by the BET method using a specific surface area measuring device (Macsorb HM-1210 manufactured by Mountech Co., Ltd.) to adsorb nitrogen gas onto the surface of a sample and then using the BET multipoint method.

[0038] The inorganic filler may be surface-treated with an appropriate surface treatment agent. The surface treatment can improve the moisture resistance and dispersibility of the inorganic filler. Examples of the surface treatment agent include vinyl-based silane coupling agents such as vinyltrimethoxysilane and vinyltriethoxysilane; epoxy-based silane coupling agents such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, and 8-glycidoxyoctyltrimethoxysilane; p-styryl Styryl-based silane coupling agents such as trimethoxysilane; methacrylic-based silane coupling agents such as 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropyltriethoxysilane; acrylic-based silane coupling agents such as 3-acryloxypropyltrimethoxysilane; N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)- Amino-based silane coupling agents such as )-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N-phenyl-8-aminooctyltrimethoxysilane, and N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane; isocyanurate-based silane coupling agents such as tris-(trimethoxysilylpropyl)isocyanurate; ureido-based silane coupling agents such as 3-ureidopropyltrialkoxysilane; mercapto-based silane coupling agents such as 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane; isocyanate-based silane coupling agents such as 3-isocyanatepropyltriethoxysilane; acid anhydride-based silane coupling agents such as 3-trimethoxysilylpropylsuccinic anhydride; and other silane coupling agents;Examples of suitable surface treatment agents include non-silane coupling alkoxysilane compounds such as methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, 1,6-bis(trimethoxysilyl)hexane, and trifluoropropyltrimethoxysilane. The surface treatment agents may be used alone or in combination of two or more in any ratio.

[0039] Commercially available surface treatment agents include, for example, "KBM-1003" and "KBE-1003" (vinyl silane coupling agents); "KBM-303", "KBM-402", "KBM-403", "KBM-4803", "KBE-402", and "KBE-403" (epoxy silane coupling agents); "KBM-1403" (styryl silane coupling agents); "KBM-502", "KBM-503", "KBE-502", and "KBE-503" (methacrylic silane coupling agents); "KBM-5103" (acrylic silane coupling agents); "KBM-602", "KBM-603", "KBM-903", "KBE-903", "KBE-9103P", "KBM-573", and "KBM-575" (amino silane coupling agents) manufactured by Shin-Etsu Chemical Co., Ltd. coupling agent); "KBM-9659" (isocyanurate-based silane coupling agent); "KBE-585" (ureido-based silane coupling agent); "KBM-802", "KBM-803" (mercapto-based silane coupling agent); "KBE-9007N" (isocyanate-based silane coupling agent); "X-12-967C" (acid anhydride-based silane coupling agent); "KBM-13", "KBM-22", "KBM-103", "KBE-13", "KBE-22", "KBE-103", "KBM-3033", "KBE-3033", "KBM-3063", "KBE-3063", "KBE-3083", "KBM-3103C", "KBM-3066", "KBM-7103" (non-silane coupling alkoxysilane compound), and the like.

[0040] The degree of surface treatment with the surface treatment agent is preferably within a predetermined range from the viewpoint of improving the dispersibility of the inorganic filler. Specifically, the inorganic filler is preferably surface-treated with 0.2 to 5 parts by mass of the surface treatment agent, more preferably 0.2 to 3 parts by mass, and even more preferably 0.3 to 2 parts by mass, per 100 parts by mass of the inorganic filler.

[0041] The degree of surface treatment with the surface treatment agent can be evaluated by the amount of carbon per unit surface area of ​​the inorganic filler. From the viewpoint of improving the dispersibility of the inorganic filler, the amount of carbon per unit surface area of ​​the inorganic filler is set to 0.02 mg / m 2 More than 0.1 mg / m is preferable. 2 More preferably, 0.2 mg / m or more 2 On the other hand, from the viewpoint of preventing an increase in the viscosity of the curable composition, it is more preferable that the amount is 1.0 mg / m 2 Preferably less than 0.8 mg / m 2 Less than 0.5 mg / m is more preferable. 2 The following is even more preferred:

[0042] The carbon amount per unit surface area of ​​the inorganic filler can be measured after the surface-treated inorganic filler is washed with a solvent (e.g., methyl ethyl ketone (MEK)). Specifically, a sufficient amount of MEK as a solvent is added to the inorganic filler that has been surface-treated with a surface treatment agent, and ultrasonic cleaning is performed at 25°C for 5 minutes. After removing the supernatant and drying the solid content, the carbon amount per unit surface area of ​​the inorganic filler can be measured using a carbon analyzer. The carbon analyzer that can be used is the "EMIA-320V" manufactured by Horiba, Ltd.

[0043] From the viewpoints of the filling ability of component (C) and a low coefficient of thermal expansion of the cured product, the content of component (B) is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, and particularly preferably 50 parts by mass or more, relative to 120 parts by mass of the resin content of the curable composition. Also, from the viewpoint of a low modulus of elasticity of the cured product, the content of component (B) is preferably 500 parts by mass or less, more preferably 400 parts by mass or less, and particularly preferably 300 parts by mass or less, relative to 120 parts by mass of the resin content of the curable composition.

[0044] From the viewpoints of the filling ability of component (C) and a low coefficient of thermal expansion of the cured product, the content of component (B) is preferably 5% by mass or more, more preferably 10% by mass or more, and particularly preferably 20% by mass or more, based on the solid content of the curable composition. From the viewpoint of a low modulus of elasticity of the cured product, the content of component (B) is preferably 80% by mass or less, more preferably 70% by mass or less, and particularly preferably 60% by mass or less, based on the solid content of the curable composition.

[0045] <(C) Hollow organic polymer particles> The curable composition of the present invention comprises hollow organic polymer particles as component (C). The hollow organic polymer particles are organic polymer-containing particles having voids inside the particles, and are present in the composition in the form of particles. The hollow organic polymer particles contribute to a low modulus of elasticity and a low coefficient of thermal expansion of the cured product, as well as to a low cure shrinkage of the curable composition. When typical non-hollow organic polymer particles are incorporated into a curable composition, the cure shrinkage rate of the curable composition and the modulus of elasticity of the cured product decrease, but the coefficient of thermal expansion of the cured product increases. It is presumed that by incorporating hollow organic polymer particles, the volume increase due to thermal expansion of the cured product is absorbed by the compression of the hollow portions of the hollow organic polymer particles, resulting in a reduced coefficient of thermal expansion of the cured product.

[0046] The form of the pores in the hollow organic polymer particles is not particularly limited, and may be in the form of monohollow particles having one pore inside the particle, or in the form of multihollow particles (including hollow porous particles having a porous interior) having multiple pores inside the particle, but is preferably in the form of monohollow particles. The hollow organic polymer particles may be spherical or non-spherical, but are preferably spherical. Furthermore, the hollow organic polymer particles preferably have a shell consisting of at least one layer. The shell may consist of one layer or two or more layers. The hollow organic polymer particles may have pores covered by a shell.

[0047] In one embodiment, the organic polymer contained in the hollow organic polymer particles is an organic polymer composed of a monomer containing an ethylenically unsaturated monomer. The ethylenically unsaturated monomer has at least one ethylenically unsaturated group. The ethylenically unsaturated group is not particularly limited as long as it is radically polymerizable, but may be an ethylenically unsaturated group having a terminal or internal carbon-carbon double bond. Specific examples include unsaturated aliphatic groups such as allyl and 3-cyclohexenyl; unsaturated aliphatic group-containing aromatic groups such as p-vinylphenyl, m-vinylphenyl, and styryl; and α,β-unsaturated carbonyl groups such as acryloyl, methacryloyl, maleoyl, and fumaroyl.

[0048] Examples of the ethylenically unsaturated monomer include monofunctional ethylenically unsaturated monomers, polyfunctional ethylenically unsaturated monomers, silyl group-containing ethylenically unsaturated monomers, and epoxy group-containing ethylenically unsaturated monomers.

[0049] The monofunctional ethylenically unsaturated monomer is a compound having one ethylenically unsaturated group. The monofunctional ethylenically unsaturated monomer is not particularly limited, but examples thereof include monofunctional aromatic vinyl compounds such as styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o-ethylstyrene, m-ethylstyrene, p-ethylstyrene, 1-vinylnaphthalene, 2-vinylnaphthalene, etc.; monofunctional aromatic allyl compounds such as allylbenzene, 1-allyl-4-methylbenzene, etc.; monofunctional aromatic olefin compounds such as vinyl acetate, vinyl propionate, allyl acetate, allyl propionate, etc. Monofunctional olefin ester compounds such as allyl, vinyl butyrate, and vinyl benzoate; monofunctional olefin ether compounds such as allyl ethyl ether; methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, aliphatic (meth)acrylate compounds such as methyl (meth)acrylate, norbornyl (meth)acrylate, isobornyl (meth)acrylate, adamantyl (meth)acrylate, lauryl (meth)acrylate, tetradecyl (meth)acrylate, stearyl (meth)acrylate, isobornyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate; aromatic (meth)acrylate compounds such as phenoxyethyl (meth)acrylate and phenoxydiethylene glycol (meth)acrylate; monofunctional ethylenically unsaturated carboxylic acid ester compounds such as hydroxyl group-containing (meth)acrylic acid ester compounds such as hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate, halogen-containing (meth)acrylic acid ester compounds such as 2,2,2-trifluoroethyl (meth)acrylate, and cyano group-containing (meth)acrylic acid ester compounds such as methyl cyano (meth)acrylate, ethyl cyano (meth)acrylate, propyl cyano (meth)acrylate and isopropyl cyano (meth)acrylate;Examples of the monofunctional ethylenically unsaturated carboxylic acid amide compounds include (meth)acrylamide, maleimide, N-methylmaleimide, and N-phenylmaleimide; monofunctional ethylenically unsaturated carboxylic acid compounds include (meth)acrylic acid, maleic acid, fumaric acid, and itaconic acid; and monofunctional ethylenically unsaturated nitrile compounds such as (meth)acrylonitrile. The term "(meth)acrylate" encompasses acrylate and methacrylate. The same applies to "(meth)acrylic acid," "(meth)acrylamide," and "(meth)acrylonitrile." The monofunctional ethylenically unsaturated monomers may be used alone or in combination of two or more.

[0050] The polyfunctional ethylenically unsaturated monomer is a compound having a plurality of ethylenically unsaturated groups. The polyfunctional ethylenically unsaturated monomer is not particularly limited, but examples thereof include conjugated diolefin compounds such as butadiene and isoprene; polyfunctional aromatic olefin compounds such as p-divinylbenzene and m-divinylbenzene; polyfunctional olefin ester compounds such as diallyl phthalate, triallyl isocyanurate, triallyl cyanurate, diallyl maleate, divinyl adipate, and divinyl glutarate; polyfunctional olefin ether compounds such as tetraallyloxyethane and diallyl ether; ethylene glycol di(meth)acrylate, diethylene glycol di ... Examples of the polyfunctional ethylenically unsaturated carboxylic acid ester compounds include glycerol di(meth)acrylate, triethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, and dipentaerythritol hexa(meth)acrylate; and polyfunctional ethylenically unsaturated carboxylic acid amide compounds such as N,N'-ethylenebis(meth)acrylamide. The polyfunctional ethylenically unsaturated monomers may be used alone or in combination of two or more.

[0051] The silyl group-containing ethylenically unsaturated monomer is a compound having at least one ethylenically unsaturated group and a silyl group such as a trialkoxysilyl group or an alkyldialkoxysilyl group. Examples of the silyl group-containing ethylenically unsaturated monomer include, but are not limited to, vinylsilane compounds such as vinyltrimethoxysilane and vinyltriethoxysilane; aromatic olefin silane compounds such as p-vinylphenyltrimethoxysilane; and ethylenically unsaturated carboxylic acid ester silane compounds such as 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 8-methacryloxyoctyltriethoxysilane, and 3-acryloxypropyltrimethoxysilane. The silyl group-containing ethylenically unsaturated monomer may be used alone or in combination of two or more.

[0052] The epoxy group-containing ethylenically unsaturated monomer is a compound having at least one ethylenically unsaturated group and an epoxy group. The epoxy group-containing ethylenically unsaturated monomer is not particularly limited, but examples thereof include epoxy group-containing aromatic olefin compounds such as styrene-4-glycidyl ether and 4-glycidylstyrene; epoxy group-containing olefin ether compounds such as allyl glycidyl ether; and epoxy group-containing ethylenically unsaturated carboxylic acid ester compounds such as glycidyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate glycidyl ether, and 3,4-epoxycyclohexylmethyl (meth)acrylate. The epoxy group-containing ethylenically unsaturated monomer may be used alone or in combination of two or more.

[0053] When the monomer constituting the organic polymer contained in the hollow organic polymer particles includes an epoxy group-containing ethylenically unsaturated monomer, it is preferable that the monomer further includes a crosslinkable monomer. Examples of the crosslinkable monomer include ethylenediamine, diethylenetriamine, dipropylenetriamine, triethylenetetramine, tetraethylenepentamine, hexamethylenediamine, N-(2-aminoethyl)piperazine, 1,4-bis(3-aminopropyl)piperazine, 2,4,4-trimethylhexamethylenediamine, 2,2,4-trimethylhexamethylenediamine, bis(hexamethylene)triamine, poly(propylene glycol)diamine, 4,4'-diamino-3,3'-dimethyldicyclohexylmethane, 3-amino Examples of the crosslinkable monomer include aliphatic polyamine compounds such as 1-(cyclohexylamino)propane, 4,4'-diaminodicyclohexylmethane, isophoronediamine, 1,3-bis(aminomethyl)cyclohexane, and bis(aminomethyl)norbornane; and aromatic amine compounds such as 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, m-phenylenediamine, p-phenylenediamine, 2,3-toluylenediamine, 2,4-toluylenediamine, and 2,5-toluylenediamine. The crosslinkable monomer may be used alone or in combination of two or more.

[0054] In one embodiment, the organic polymer contained in the hollow organic polymer particles is preferably an organic polymer composed of a monomer containing one or more monomers selected from aromatic olefin compounds (e.g., monofunctional aromatic olefin compounds, polyfunctional aromatic olefin compounds, aromatic olefin silane compounds, epoxy group-containing aromatic olefin compounds, etc.), ethylenically unsaturated carboxylic acid ester compounds (e.g., monofunctional ethylenically unsaturated carboxylic acid ester compounds, polyfunctional ethylenically unsaturated carboxylic acid ester compounds, ethylenically unsaturated carboxylic acid ester silane compounds, epoxy group-containing ethylenically unsaturated carboxylic acid ester compounds, etc.), and ethylenically unsaturated nitrile compounds. The organic polymer contained in the hollow organic polymer particles is more preferably an organic polymer composed of a monomer containing one or more monomers selected from aromatic olefin compounds, an organic polymer composed of a monomer containing one or more monomers selected from ethylenically unsaturated carboxylic acid ester compounds, or an organic polymer composed of a monomer containing one or more monomers selected from ethylenically unsaturated nitrile compounds. The organic polymer contained in the hollow organic polymer particles is more preferably an organic polymer composed of a monomer containing styrene, an organic polymer composed of a monomer containing a (meth)acrylic acid ester, or an organic polymer composed of a monomer containing a (meth)acrylamide.

[0055] In another embodiment, the organic polymer contained in the hollow organic polymer particles is a thermosetting polymer (cured product), and examples thereof include organic polymers composed of monomers including an isocyanate compound, a compound having an amino group, and a compound having a hydroxy group. Preferably, the organic polymer is an organic polymer having urea bonds and / or urethane bonds obtained by reacting an isocyanate compound having multiple isocyanate groups with an active hydrogen compound having multiple amino groups or hydroxy groups and / or water.

[0056] The hollow organic polymer particles may be treated with a surface treatment agent. Examples of the surface treatment agent for the hollow organic polymer particles include inorganic acids such as hydrochloric acid, nitric acid, and sulfuric acid; carboxylic acids such as acetic acid, propionic acid, butyric acid, and acrylic acid; sulfonic acids such as p-toluenesulfonic acid, ethylsulfonic acid, and dodecylbenzenesulfonic acid; phosphoric acids such as polyoxyethylene alkyl ether phosphoric acid; organic acids such as phosphonic acid and phosphinic acid; silane coupling agents such as tetraethoxysilane, methyltrimethoxysilane, phenyltrimethoxysilane, 3-(meth)acryloxypropyltrimethoxysilane, and 8-(meth)acryloxyoctyltrimethoxysilane; and isocyanate compounds such as ethyl isocyanate.

[0057] The porosity of the hollow organic polymer particles is preferably 20% by volume or more, more preferably 30% by volume or more, and particularly preferably 40% by volume or more, from the viewpoint of a low thermal expansion coefficient of the cured product. The upper limit of the porosity of the hollow organic polymer particles is preferably 95% by volume or less, more preferably 90% by volume or less, and particularly preferably 85% by volume or less, from the viewpoint of maintaining the shape of the particles. The porosity is the ratio (%) of the volume of pores inside the hollow organic polymer particles to the total volume of the hollow organic polymer particles.

[0058] The particle diameter of the hollow organic polymer particles is preferably 100 μm or less, more preferably 50 μm or less, and particularly preferably 30 μm or less, from the viewpoint of reducing the practical adhesive thickness and reducing misalignment due to thermal expansion, etc. The lower limit of the particle diameter of the hollow organic polymer particles is preferably 0.05 μm or more, more preferably 0.1 μm or more, and particularly preferably 0.3 μm or more, from the viewpoint of particle packing properties. In this specification, the "particle diameter" of the hollow organic polymer particles refers to the median diameter that can be calculated by a laser diffraction / scattering method based on Mie scattering theory, as in the case of the "particle diameter" of inorganic fillers. Specifically, the particle diameter distribution of the hollow organic polymer particles can be prepared on a volume basis using a laser diffraction / scattering particle size distribution analyzer, and the median diameter can be calculated.

[0059] The hollow organic polymer particles may be commercially available or may be produced by a known method. Examples of commercially available products include "XX-6214Z", "XX-6368Z", and "XX-5598Z" manufactured by Sekisui Plastics Co., Ltd.; "NC-751C" manufactured by Sansui Plastics Co., Ltd.; and "MFL-80GCA" manufactured by Matsumoto Fine Chemical Co., Ltd. Examples of known methods include those described in WO2018 / 051794, JP2017-119843A, JP2017-119843A, JP2016-119230A, JP-B-4-68324A, JP63-135409A, and JP2002-241448A.

[0060] From the viewpoint of a low elastic modulus of the cured product, the content of component (C) is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and particularly preferably 30 parts by mass or more, relative to 120 parts by mass of the resin content of the curable composition. Also, from the viewpoint of the viscosity of the curable composition (the viscosity sufficient for use as an adhesive), the content of component (C) is preferably 300 parts by mass or less, more preferably 250 parts by mass or less, and particularly preferably 200 parts by mass or less, relative to 120 parts by mass of the resin content of the curable composition.

[0061] From the viewpoint of a low elastic modulus of the cured product, the content of component (C) is preferably 3% by mass or more, more preferably 5% by mass or more, and particularly preferably 10% by mass or more, based on the solid content of the curable composition. From the viewpoint of the viscosity of the curable composition (the viscosity sufficient for use as an adhesive), the content of component (C) is preferably 70% by mass or less, more preferably 60% by mass or less, and particularly preferably 50% by mass or less, based on the solid content of the curable composition.

[0062] The mass ratio of component (B):component (C) is preferably 1:10 to 20:1, more preferably 1:5 to 15:1, and particularly preferably 1:3 to 10:1, from the viewpoints of the filling ability of component (C) and the low elastic modulus and low thermal expansion coefficient of the cured product.

[0063] <(D) Cationic polymerization initiator> The present invention includes a cationic polymerization initiator as component (D) to cure the curable composition. Curing by cationic polymerization results in a lower cure shrinkage of the curable composition and higher heat resistance of the resulting cured product compared to curing by photoradical polymerization or thermal anionic polymerization.

[0064] The cationic polymerization initiator of component (D) may be a photo-cationic polymerization initiator or a thermal-cationic polymerization initiator, as long as it can react with the alicyclic epoxy group in the alicyclic epoxy compound of component (A) and the oxetanyl group in the oxetane compound having two or more oxetanyl groups described below to initiate a cationic polymerization reaction.

[0065] The photocationic polymerization initiator is preferably a photoacid generator, which is an agent that generates protons or Lewis acids upon irradiation with light.

[0066] Representative photoacid generators include those described in WO2019 / 146736, such as triphenylsulfonium hexafluoroantimonate, triphenylsulfonium hexafluorophosphate, p-(phenylthio)phenyldiphenylsulfonium hexafluoroantimonate, p-(phenylthio)phenyldiphenylsulfonium hexafluorophosphate, 4-chlorophenyldiphenylsulfonium hexafluorophosphate, 4-chlorophenyldiphenylsulfonium hexafluoroantimonate, bis[4-(diphenylsulfonio)phenyl]sulfide bishexafluorophosphate, bis[4-(diphenylsulfonio)phenyl]sulfide bishexafluoroantimonate, (2,4-cyclopentadien-1-yl)[(1-methylethyl)benzene]-Fe-hexafluorophosphate, and diaryliodonium hexafluoroantimonate. Further, examples of the photoacid generator include the photoacid generators described in WO2018 / 110297 and the photoacid generators described in WO2020 / 171186 (for example, p-(phenylthio)phenyldiphenylsulfonium tris(pentafluoroethyl)trifluorophosphate). Further, other known salts containing sulfonium cations and commercially available salts containing sulfonium cations can also be used as the photoacid generator. The photoacid generator may be used alone or in combination of two or more kinds.

[0067] Commercially available photoacid generators can be used. Examples of commercially available photoacid generators include "Irgacure 261", "Irgacure 290", and "CG-24-61" manufactured by BASF; "CPI-110P", "CPI-110A", "CPI-110B", "CPI-210S", "CPI-310B", "VC-1S", "CPI-410S", and "CPI-410B" manufactured by San-Apro; and "Cyracure UVI-6970", "Cyracure UVI-6974", "Cyracure UVI-6990", and "Cyracure UVI-6994" manufactured by Union Carbide Corporation, USA. Examples of such products include "UVI-950" manufactured by Daicel Corporation, "DAICAT II" manufactured by Daicel-Allnex Corporation, "UVAC1591" manufactured by Daicel-Allnex Corporation, "CI-2481", "CI-2734", "CI-2823", and "CI-2758" manufactured by Nippon Soda Co., Ltd., "FFC509" manufactured by 3M Corporation, and "BBI-102", "BBI-101", "BBI-103", "MPI-103", "TPS-103", "MDS-103", "DTS-103", "NAT-103", and "NDS-103" manufactured by Midori Chemical Industry Co., Ltd.

[0068] The thermal cationic polymerization initiator is preferably a thermal acid generator, which is an agent that generates protons or Lewis acids upon heating.

[0069] Representative examples of thermal acid generators include organic onium salt compounds, which are described in WO2019 / 146736 and have a cationic and anionic component pair. Examples of the cationic component include organic sulfonium, organic oxonium, organic ammonium, organic phosphonium, and organic iodonium. Examples of the anionic component include BF4 - , B(C6F5)4 - , SbF4 - , Sb(C6F5)4 - , AsF6 - , PF6 -, PF6 - , CF3SO3 - , C4F9SO3 - or (CF3SO2)3C - etc. Further, examples of the thermal acid generator include the thermal acid generators described in WO2018 / 110297. Further examples of the thermal acid generator include other known salts containing quaternary ammonium cations, or commercially available salts containing quaternary ammonium cations. The thermal acid generator may be used alone or in combination of two or more kinds.

[0070] Commercially available thermal acid generators can be used, such as "K-PURE TAG-2678", "K-PURE TAG-2681", "K-PURE TAG-2689", "K-PURE TAG-2690", "K-PURE TAG-2700", "K-PURE CXC-1612", "K-PURE CXC-1614", "K-PURE CXC-1615", "K-PURE CXC-1616", "K-PURE CXC-1733", "K-PURE CXC-1738", "K-PURE CXC-1742", "K-PURE CXC-1802", and "K-PURE CXC-1803", all manufactured by King Industries. CXC-1821; San-Apro's TA-60, TA-60B, TA-90, TA-100, TA-120, TA-160, IK-1, and IK-2; Sanshin Chemical Industry's San-Aid SI-45, San-Aid SI-47, San-Aid SI-45L, San-Aid SI-60, San-Aid SI-60L, San-Aid SI-80, San-Aid SI-80L, San-Aid SI-100, San-Aid SI-100L, San-Aid SI-110, San-Aid SI-110L, San-Aid SI-145, and San-Aid SI-15 0", "Sanaid SI-150L", "Sanaid SI-160", "Sanaid SI-180", "Sanaid SI-180L", "Sanaid SI-B2", "Sanaid SI-B2A", "Sanaid SI-B3", "Sanaid SI-B3A", "Sanaid SI-B4", "Sanaid SI-B5", "Sanaid SI-200", "Sanaid SI-210", "Sanaid SI-220", "Sanaid SI-300", "Sanaid SI-360"; "ADEKA Opton CP-66" and "ADEKA Opton CP-77" manufactured by ADEKA Corporation; and "FC-520" manufactured by 3M Corporation.

[0071] From the viewpoint of good curability of the curable composition, the content of component (D) is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and particularly preferably 0.2% by mass or more, based on the amount of the curable composition excluding components (B) and (C). Also, from the viewpoint of storage stability of the curable composition, the content of component (D) is preferably 15% by mass or less, more preferably 10% by mass or less, and particularly preferably 5% by mass or less, based on the amount of the curable composition excluding components (B) and (C).

[0072] From the viewpoint of obtaining a curable composition with good curability, the content of component (D) is preferably 0.005% by mass or more, more preferably 0.01% by mass or more, and particularly preferably 0.1% by mass or more, based on the solid content of the curable composition. From the viewpoint of the storage stability of the curable composition, the content of component (D) is preferably 15% by mass or less, more preferably 10% by mass or less, and particularly preferably 5% by mass or less, based on the solid content of the curable composition.

[0073] <Other ingredients> The curable composition of the present invention may further contain optional components other than components (A) to (D) (sometimes referred to as "other components" in this specification). The other components may be used singly or in combination of two or more. Examples of the other components include an oxetane compound having two or more oxetanyl groups, a polyester polyol, and a photosensitizer.

[0074] (Oxetane compounds having two or more oxetanyl groups) An oxetane compound having two or more oxetanyl groups (sometimes abbreviated as "oxetane compound" in this specification) contributes to low cure shrinkage of a curable composition. The number of oxetanyl groups in the oxetane compound is preferably 2 to 4, and particularly preferably 2.

[0075] Examples of the oxetane compound include those represented by formula (IV) or (V):

[0076] [ka]

[0077] [In the formula, R 1 ~R 4 each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, an aryl group having 6 to 10 carbon atoms which may be substituted with an alkyl group having 1 to 6 carbon atoms, an aralkyl group having 6 to 16 carbon atoms, an allyl group, a furyl group or a thienyl group; L 9 represents a polyoxyalkylene group, an alkylene group having 1 to 6 carbon atoms, a cycloalkylene group having 5 to 7 carbon atoms, an arylene group having 6 to 10 carbon atoms, a divalent group in which an alkylene group having 1 to 6 carbon atoms and an arylene group having 6 to 10 carbon atoms are linked together, or a group represented by the following formula (VI) or (VII):

[0078] [ka]

[0079] (In the formula, * indicates the bond position, -L 10 - represents -O-, -S-, -CH2-, -NH-, -SO-, -SO2-, -C(CF3)2- or -C(CH3)2-, and L 11 represents an alkylene group having 1 to 6 carbon atoms, a cycloalkylene group having 5 to 7 carbon atoms, or an arylene group having 6 to 10 carbon atoms. and m1 represents an integer of 1 to 3. Examples of the compound include compounds represented by any one of the following formulas: Compound (V) may be a mixture of compounds having different numbers of repeating units.

[0080] The alkyl group having 1 to 6 carbon atoms in formulas (IV) and (V) may be either linear or branched. Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group.

[0081] Examples of the cycloalkyl group having 5 to 7 carbon atoms in the formulae (IV) and (V) include a cyclopentyl group, a cyclohexyl group, and a cycloheptyl group.

[0082] In the formulae (IV) and (V), examples of the aryl group having 6 to 10 carbon atoms which may be substituted with an alkyl group having 1 to 6 carbon atoms include a phenyl group, a naphthyl group, a tolyl group, and a xylyl group.

[0083] Examples of the aralkyl group having 6 to 16 carbon atoms in the formulae (IV) and (V) include a benzyl group and a phenethyl group.

[0084] The number of carbon atoms in the alkylene group in the polyoxyalkylene group in formula (V) is preferably 1 to 4. The number of repetitions of the oxyalkylene group in the polyoxyalkylene group is preferably 2 to 30.

[0085] The alkylene group having 1 to 6 carbon atoms in formulas (VI) and (VII) may be either linear or branched. Examples of the alkylene group having 1 to 6 carbon atoms include methylene, ethylene, trimethylene, propylene, tetramethylene, pentamethylene, and hexamethylene.

[0086] Examples of the cycloalkylene group having 5 to 7 carbon atoms in formulas (VI) and (VII) include a 1,2-cyclopentylene group, a 1,3-cyclopentylene group, a 1,2-cyclohexylene group, a 1,3-cyclohexylene group, a 1,4-cyclohexylene group, a 1,2-cycloheptylene group, a 1,3-cycloheptylene group, and a 1,4-cycloheptylene group.

[0087] Examples of the arylene group having 6 to 10 carbon atoms in the formulae (VI) and (VII) include a benzenediyl group and a biphenyldiyl group.

[0088] In the divalent group in formulas (VI) and (VII) in which an alkylene group having 1 to 6 carbon atoms and an arylene group having 6 to 10 carbon atoms are linked together, the alkylene group having 1 to 6 carbon atoms and the arylene group having 6 to 10 carbon atoms may each be one or more, and examples thereof include a benzene-4,4-diylbismethylene group (-CH2-Ph-CH2-) and a biphenyl-4,4'-diylbismethylene (-CH2-Ph-Ph-CH2-) group.

[0089] The oxetane compound is preferably selected from a compound represented by the following formula (IV-1) and a compound represented by the following formula (V-1).

[0090] [ka]

[0091] [In the following formula (V-1), m2 represents an integer of 1 to 3.] The compound (V-1) may be a mixture of compounds having different numbers of repeating units.

[0092] The oxetane compounds may be used alone or in combination of two or more. Commercially available oxetane compounds can be used, such as "OXT-121" and "OXT-221" manufactured by Toagosei Co., Ltd., and "OXBP" and "OXIPA" manufactured by Ube Industries, Ltd.

[0093] The molecular weight of the oxetane compound is preferably 180 or more, more preferably 190 or more, and even more preferably 200 or more. The upper limit of the molecular weight of the oxetane compound is appropriately selected depending on the viscosity of the curable composition, but is preferably 400 or less. When the molecular weight of the oxetane compound is 180 or more, the oxetane compound is less likely to volatilize from the curable composition. As a result, when the composition is applied by an inkjet method, the composition is less likely to change, and the working environment is less likely to deteriorate. Note that when the oxetane compound is a compound having a repeating unit and is a mixture of multiple compounds with different numbers of repeating units, the molecular weight of the oxetane compound refers to the weight-average molecular weight (Mw). This Mw can be calculated, for example, using gel permeation chromatography (GPC) in terms of polystyrene.

[0094] The viscosity (25°C) of the oxetane compound is preferably 1 to 10,000 mPa·s, and more preferably 2 to 5,000 mPa·s, from the viewpoint of the fluidity of the curable composition at room temperature. In this specification, "viscosity (25°C)" means "the viscosity at 25°C measured using a vibration viscometer."

[0095] From the viewpoint of reactivity, the oxetanyl equivalent of an oxetane compound is preferably 30 to 5,000 g / eq, more preferably 50 to 2,000 g / eq, and particularly preferably 100 to 1,000 g / eq. In this specification, the "oxetanyl equivalent" of an oxetane compound refers to the number of grams of an oxetane compound containing 1 gram equivalent of oxetanyl groups. This oxetanyl equivalent value can be determined according to the method specified in JIS K 7236. Theoretically, the oxetanyl equivalent can be calculated by dividing the molecular weight of the oxetane compound by the number of oxetanyl groups contained in the oxetane compound.

[0096] From the viewpoint of low cure shrinkage of the curable composition, the content of the oxetane compound is preferably 1% by mass or more, more preferably 2% by mass or more, and particularly preferably 3% by mass or more, based on the resin content of the curable composition. Also, from the viewpoint of adhesiveness of the curable composition, the content of the oxetane is preferably 65% ​​by mass or less, more preferably 55% by mass or less, and particularly preferably 45% by mass or less, based on the resin content of the curable composition.

[0097] From the viewpoint of low cure shrinkage of the curable composition, the content of the oxetane compound is preferably 0.5% by mass or more, more preferably 1% by mass or more, and particularly preferably 2% by mass or more, based on the solid content of the curable composition. From the viewpoint of adhesiveness of the curable composition, the content of the oxetane compound is preferably 30% by mass or less, more preferably 25% by mass or less, and particularly preferably 20% by mass or less, based on the solid content of the curable composition.

[0098] (polyester polyol) By using polyester polyol, the wet heat resistant adhesive properties of the curable composition can be improved.

[0099] Examples of polyester polyols include polyester polyols obtained by condensation polymerization of dicarboxylic acids and diols. Examples of dicarboxylic acids include aliphatic carboxylic acids such as adipic acid, azelaic acid, sebacic acid, and dodecanedioic acid; and aromatic carboxylic acids such as terephthalic acid and isophthalic acid. Examples of diols include linear diols such as ethylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,9-nonanediol, and diethylene glycol; 1,2-propylene glycol, 1,3-butylene glycol, 2-methyl-1,3-propanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, and 2-methyl-1,8-octanediol. The polyester polyol may be used alone or in combination of two or more kinds.

[0100] From the viewpoint of obtaining good adhesion, the number average molecular weight of the polyester polyol is preferably from 500 to 20000, more preferably from 1000 to 15000. The number average molecular weight can be calculated in terms of polystyrene by gel permeation chromatography (GPC).

[0101] From the viewpoint of adhesion, the hydroxyl value of the polyester polyol is preferably 5 to 500 mgKOH / g, more preferably 10 to 400 mgKOH / g, and particularly preferably 20 to 300 mgKOH / g. In this specification, the "hydroxyl value" refers to the number of milligrams of potassium hydroxide corresponding to the hydroxyl groups in 1 g of sample. The hydroxyl value can be measured according to the method specified in JIS K 1557-1.

[0102] Commercially available polyester polyols can be used, including, for example, "OD-X-102," "OD-X-668," "OD-X-2068," and "OD-X-3100" manufactured by DIC Corporation; "P-1010," "P-2010," "P-3010," and "P-2050" manufactured by Kuraray Co., Ltd.; and "NS-2400," "YT-101," "F7-67," "#50," "F1212-29," "YG-108," "V14-90," and "Y65-55" manufactured by ADEKA Corporation.

[0103] From the viewpoint of the wet heat resistant adhesion of the curable composition, the content of polyester polyol is preferably 1% by mass or more, more preferably 2% by mass or more, and particularly preferably 3% by mass or more, based on the resin content of the curable composition. Also, from the viewpoint of obtaining a cured product with high Tg and high heat resistance stability, the content of polyester polyol is preferably 40% by mass or less, more preferably 30% by mass or less, and particularly preferably 20% by mass or less, based on the resin content of the curable composition.

[0104] From the viewpoint of the wet heat resistance of the curable composition, the content of the polyester polyol is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and particularly preferably 1% by mass or more, based on the solid content of the curable composition. From the viewpoint of obtaining a cured product with high Tg and high heat resistance stability, when a polyester polyol is used, the content is preferably 30% by mass or less, more preferably 20% by mass or less, and particularly preferably 10% by mass or less, based on the solid content of the curable composition.

[0105] (photosensitizer) When a cationic photopolymerization initiator (particularly a photoacid generator) is used as component (D), it is preferable to use a photosensitizer in order to increase the activity of the cationic photopolymerization initiator and thereby improve the curability of the curable composition. A sensitizer is a compound that has an absorption band in a longer wavelength region than the absorption band of a photocationic polymerization initiator, and after excitation by light absorption, electrons or energy are transferred, contributing to the decomposition of the photoacid generator and the generation of polymerization initiation species. Sensitizers can be blended appropriately depending on the wavelength of the light source used for photocuring.

[0106] Specific examples of the sensitizer include anthracene compounds such as dimethylanthracene, 9,10-diethoxyanthracene, and 9,10-dibutoxyanthracene; thioxanthone compounds such as 2-isopropylthioxanthone and diethylthioxanthone; quinone compounds such as 2-ethylanthraquinone and (±)-camphorquinone; naphthalene compounds such as dialkoxynaphthalene; and aromatic diketone compounds such as benzil and curcumin. The photosensitizer may be used alone or in combination of two or more kinds.

[0107] Furthermore, it is preferable to use a photosensitizer selected from the group consisting of anthracene compounds (e.g., 9,10-dibutoxyanthracene), thioxanthone compounds, and quinone compounds, which have an absorption band in a wavelength region longer than 350 nm and are likely to undergo electron transfer with aromatic sulfonium salt-based or aromatic iodonium salt-based photocationic polymerization initiators, because the absorbance in the long wavelength region is at a suitable level, poor dispersion in the composition is unlikely to occur, and the photosensitizer is preferable from the viewpoints of improving curability and increasing the curing speed during curing.

[0108] Commercially available photosensitizers can be used, including, for example, Anthracure UVS-1331, Anthracure UVS-1101, Anthracure UVS-581, and Anthracure UVS-2171 manufactured by Air Water Performance Chemicals, Inc., and 2-isopropylthioxanthone, 2,4-diethylthioxanthone, and 2-ethylanthraquinone manufactured by Tokyo Chemical Industry Co., Ltd.

[0109] From the viewpoint of good curability of the curable composition, the content of the photosensitizer is preferably 0.01% or more, more preferably 0.03% or more, and particularly preferably 0.05% or more, based on the resin content of the curable composition. From the viewpoint of deep curability, the content of the photosensitizer is preferably 5% or less, more preferably 4% or less, and particularly preferably 3% or less, based on the resin content of the curable composition.

[0110] <Method for producing curable composition> The curable composition of the present invention is prepared by mixing the essential components (components (A) to (D)) and optional components (e.g., an oxetane compound having two or more oxetanyl groups, a polyester polyol, a photosensitizer, etc.) using a known stirrer or disperser. Examples of stirrers and dispersers include a dissolver, a planetary mixer, a roll mill, a sand mill, a ball mill, a bead mill, a homogenizer, a high-pressure homogenizer, an azimuth homomixer, and a rotation-revolution mixer.

[0111] The curable composition of the present invention is liquid at 25°C and preferably has a viscosity (25°C) of less than 300,000 mPa·s, more preferably 250,000 mPa·s or less. There is no particular lower limit, but the viscosity is preferably 10 mPa·s or more, and more preferably 20 mPa·s or more.

[0112] <Application> The curable composition of the present invention can be used to form a cured product that exhibits both a low coefficient of thermal expansion and a low modulus of elasticity. In other words, an optical device can be obtained having a cured layer formed from the curable composition, which exhibits both a low coefficient of thermal expansion and a low modulus of elasticity. Therefore, the curable composition of the present invention can be suitably used for bonding optical devices (specifically, bonding components in optical devices). Specifically, it can be used, for example, as an adhesive for fiber arrays and ball lenses. Because the curable composition of the present invention has excellent fluidity at room temperature, it can be directly applied to the object to be sealed, easily forming a composition layer (coated layer) with uniform properties. Coating methods such as bar coating, comma coating, die coating, blade coating, dispenser coating, and inkjet coating can be used alone or in combination. By curing the composition layer (coated layer) thus formed, a cured layer with a low coefficient of thermal expansion and a low modulus of elasticity can be formed.

[0113] The curable composition of the present invention can be cured by light or heat. When cured by light, for example, 300 mJ / cm 2 can be used with a mercury lamp, UV-LED, or the like. 2 The above light irradiation can be carried out. When curing by heat, the composition can be cured by heating at a temperature of, for example, 60 to 150°C. [Example]

[0114] The present invention will be described in more detail below based on examples, but the present invention is not limited to the following examples. Note that "parts" and "%" in the following descriptions mean "parts by mass" and "% by mass", respectively.

[0115] raw material [Component (A): Epoxy compound having two or more alicyclic epoxy groups] Celloxide 2021P: 3',4'-epoxycyclohexylmethyl ester manufactured by Daicel Corporation 3,4-Epoxycyclohexanecarboxylate (compound (I-1)), molecular weight: 252, number of alicyclic epoxy groups per molecule: 2, viscosity: 250 mPa·s, epoxy equivalent: 130 g / eq Celloxide 8000: (3,4,3',4'-diepoxy)bicyclohexyl (compound (I-3)) manufactured by Daicel Corporation, molecular weight: 194, number of alicyclic epoxy groups per molecule: 2, viscosity: 60 mPa·s, epoxy equivalent: 100 g / eq

[0116] [Component (B): Inorganic filler] 40SE-C3: Silica manufactured by Admatechs, particle size (median diameter): 3.0 μm, specific surface area: 3.3 m 2 / g SS-1000: Cordierite manufactured by Marusu Yuyaku Co., Ltd., particle size (median diameter): 1.7 μm

[0117] [Component (C): Hollow organic polymer particles] XX-6214Z: Hollow styrene particles manufactured by Sekisui Plastics Co., Ltd., organic polymer: styrene-based polymer, number of pores per particle: 1, porosity: 50%, particle diameter (median diameter): 0.42 μm XX-6368Z: Hollow acrylic particles manufactured by Sekisui Plastics Co., Ltd., number of holes per particle: 1, porosity: 60%, particle diameter (median diameter): 4 μm NC-751C: Sansui hollow thermosetting resin particles, number of holes per particle: 1, porosity: 69%, particle diameter (median diameter): 4.4 μm MFL-80GCA: Hollow acrylonitrile particles manufactured by Matsumoto Fine Chemical Co., Ltd., organic polymer: acrylonitrile polymer, number of holes per particle: 1, porosity: 80%, particle diameter (median diameter): 20 μm

[0118] [Component (D): Cationic polymerization initiator] <Photoacid generator> Irgacure 290: BASF CPI-210S: San-Apro <Thermal acid generator> CXC-1821: King Industries

[0119] [Other ingredients] OXT-221: 3-ethyl-3{[(3-ethyloxetan-3-yl)methoxy]methyl}oxetane (compound IV-1) manufactured by Toagosei Co., Ltd., molecular weight: 214, number of oxetanyl groups per molecule: 2 OXT-121: Oxetane compound (Compound V-1) manufactured by Toagosei Co., Ltd., m2 in formula (V-1) = 1 to 3, weight average molecular weight: 334, number of oxetanyl groups per molecule: 2 OD-X-3100: Polyester polyol manufactured by DIC Corporation, number average molecular weight: 3,000, hydroxyl value: 27.5 to 32.5 mg KOH / g UVS-1331: Photosensitizer manufactured by Air Water Performance Chemicals

[0120] [Epoxy compounds other than component (A)] ZX-1059: A mixture of difunctional bisphenol A epoxy resin and difunctional bisphenol F epoxy resin manufactured by Nippon Steel Chemical & Material Co., Ltd., epoxy equivalent: 165g / eq

[0121] [Organic polymer particles without hollow structure] ARX-805: Acrylic particles manufactured by Sekisui Plastics Co., Ltd., organic polymer: (meth)acrylate polymer, particle size (median diameter): 8 μm

[0122] Example 1 50 parts of an alicyclic epoxy compound (Daicel Corporation, "Celloxide 2021P"), 50 parts of an oxetane compound (Toagosei Co., Ltd., "OXT-221"), and 20 parts of a polyester polyol (DIC Corporation, "OD-X-3100") were mixed uniformly in a high-speed mixer to obtain a mixture. 100 parts of silica (Admatechs Co., Ltd., "40SE-C3") and 40 parts of hollow styrene particles (Sekisui Plastics Co., Ltd., "XX-6214Z") were then blended into the resulting mixture, and the resulting mixture was uniformly dispersed in a high-speed mixer. 2 parts of a photoacid generator (San-Apro Co., Ltd., "CPI-210S") and 1 part of a photosensitizer (Air Water Performance Chemicals, Inc., "UVS-1331") were then mixed uniformly in a high-speed mixer to obtain a curable composition. The obtained curable composition was uniformly applied with a glass rod onto the release-treated surface of a polyethylene terephthalate (PET) film ("NS-80A" manufactured by Toray Industries, Inc., PET film thickness: 38 μm) that had been treated with an alkyd-based release agent, and the film was irradiated with 365 nm ultraviolet light at 30 mW for 100 seconds to obtain a cured product with a thickness of 100 μm.

[0123] <Example 2> A curable composition and a cured product were produced in the same manner as in Example 1, except that 40 parts of hollow acrylic particles ("XX-6368Z" manufactured by Sekisui Plastics Co., Ltd.) were used instead of 40 parts of hollow styrene particles ("XX-6214Z" manufactured by Sekisui Plastics Co., Ltd.).

[0124] Example 3 A curable composition and a cured product were produced in the same manner as in Example 1, except that 90 parts of hollow thermosetting resin particles ("NC-751C" manufactured by Sansui Chemical Co., Ltd.) were used instead of 40 parts of hollow styrene particles ("XX-6214Z" manufactured by Sekisui Chemical Co., Ltd.).

[0125] Example 4 A curable composition and a cured product were produced in the same manner as in Example 1, except that 50 parts of hollow acrylonitrile particles ("MFL-80GCA" manufactured by Matsumoto Fine Chemical Co., Ltd.) were used instead of 40 parts of hollow styrene particles ("XX-6214Z" manufactured by Sekisui Plastics Co., Ltd.).

[0126] <Example 5> A curable composition and a cured product were produced in the same manner as in Example 4, except that 5 parts of hollow styrene particles ("XX-6214Z" manufactured by Sekisui Plastics Co., Ltd.) were added and the amount of silica ("40SE-C3" manufactured by Admatechs Co., Ltd.) used was changed from 100 parts to 200 parts.

[0127] Example 6 A curable composition and a cured product were produced in the same manner as in Example 4, except that the amount of the alicyclic epoxy compound ("Celloxide 2021P" manufactured by Daicel Corporation) used was changed from 50 parts to 60 parts, the amount of the oxetane compound ("OXT-221" manufactured by Toagosei Co., Ltd.) used was changed from 50 parts to 60 parts, and polyester polyol ("OD-X-3100" manufactured by DIC Corporation) was not used.

[0128] Example 7 A curable composition and a cured product were produced in the same manner as in Example 4, except that 5 parts of a photoacid generator (BASF "Irgacure 290") were used instead of 2 parts of a photoacid generator (San-Apro Co., Ltd. "CPI-210S") and 1 part of a photosensitizer (Air Water Performance Chemicals Inc. "UVS-1331").

[0129] Example 8 A curable composition and a cured product were produced in the same manner as in Example 4, except that 100 parts of cordierite ("SS-1000" manufactured by Marusu Yuyaku Co., Ltd.) were used instead of 100 parts of silica ("40SE-C3" manufactured by Admatechs Co., Ltd.).

[0130] Example 9 A curable composition and a cured product were produced in the same manner as in Example 4, except that the amount of the alicyclic epoxy compound (Celloxide 2021P manufactured by Daicel Corporation) used was changed from 50 parts to 100 parts, and the oxetane compound (OXT-221 manufactured by Toagosei Co., Ltd.) was not used.

[0131] Example 10 A curable composition and a cured product were produced in the same manner as in Example 4, except that 50 parts of an alicyclic epoxy compound (manufactured by Daicel Corporation, "Celloxide 2021P") was replaced with 50 parts of an alicyclic epoxy compound (manufactured by Daicel Corporation, "Celloxide 8000").

[0132] Example 11 A curable composition and a cured product were produced in the same manner as in Example 4, except that 50 parts of an oxetane compound ("OXT-121" manufactured by Toagosei Co., Ltd.) was used instead of 50 parts of the oxetane compound ("OXT-221" manufactured by Toagosei Co., Ltd.).

[0133] Example 12 A curable composition and a cured product were produced in the same manner as in Example 11, except that 1 part of a thermal acid generator (King Industries "CXC-1821") was used instead of 2 parts of a photoacid generator (San-Apro Co., Ltd. "CPI-210S") and 1 part of a photosensitizer (Air Water Performance Chemicals Inc. "UVS-1331"), and 50 parts of hollow acrylic particles (Sekisui Plastics Co., Ltd. "XX-6368Z") were used instead of 50 parts of hollow acrylonitrile particles (Matsumoto Fine Chemical Co., Ltd. "MFL-80GCA"). Furthermore, a cured product having a thickness of 100 μm was obtained in the same manner as in Example 11, except that heat curing was carried out by heating in an oven at 120° C. for 30 minutes instead of photocuring by ultraviolet irradiation.

[0134] <Comparative Example 1> A curable composition and a cured product were produced in the same manner as in Example 1, except that hollow styrene particles (manufactured by Sekisui Plastics Co., Ltd., "XX-6214Z") were not used.

[0135] <Comparative Example 2> A curable composition and a cured product were produced in the same manner as in Example 1, except that hollow styrene particles (manufactured by Sekisui Plastics Co., Ltd., "XX-6214Z") were not used and the amount of silica (manufactured by Admatechs Co., Ltd., "40SE-C3") used was changed from 100 parts to 400 parts.

[0136] <Comparative Example 3> A curable composition and a cured product were produced in the same manner as in Example 1, except that 50 parts of acrylic particles ("ARX-805" manufactured by Sekisui Plastics Co., Ltd.) were used instead of 40 parts of hollow styrene particles ("XX-6214Z" manufactured by Sekisui Plastics Co., Ltd.).

[0137] <Comparative Example 4> An attempt was made to produce a curable composition in the same manner as in Example 4, except that silica ("40SE-C3" manufactured by Admatechs Co., Ltd.) was not used. However, the hollow styrene particles could not be sufficiently dispersed, and a uniform composition was not obtained.

[0138] <Comparative Example 5> A curable composition was produced in the same manner as in Example 4, except that 50 parts of a mixture of a difunctional bisphenol A type epoxy resin and a difunctional bisphenol F type epoxy resin ("ZX-1059" manufactured by Nippon Steel Chemical & Material Co., Ltd.) was used instead of 50 parts of the alicyclic epoxy compound ("Celloxide 2021P" manufactured by Daicel Corporation). The obtained curable composition had poor curability and could not form a cured product.

[0139] <Comparative Example 6> A curable composition and a cured product were produced in the same manner as in Example 12, except that 50 parts of an oxetane compound ("OXT-221" manufactured by Toagosei Co., Ltd.) was used instead of 50 parts of the oxetane compound ("OXT-121" manufactured by Toagosei Co., Ltd.) and that hollow acrylic particles ("XX-6368Z" manufactured by Sekisui Plastics Co., Ltd.) were not used. The obtained cured product exhibited significant warping.

[0140] Evaluation Test [Storage modulus measurement] The PET film was peeled off from the cured products obtained in the examples and comparative examples to obtain sheet-like cured products. The cured products were cut into test pieces approximately 7 mm wide and 40 mm long, and dynamic mechanical analysis was performed in tension mode using a dynamic mechanical analyzer DMS-6100 (manufactured by Seiko Instruments Inc.). After loading the test pieces into the analyzer, measurements were performed under the following conditions: a frequency of 1 Hz, and a heating rate of 5°C / min. The storage modulus (GPa) at 25°C was read from the measurement. (Evaluation criteria) ○: Storage modulus (25℃)≦4GPa ×: Storage modulus (25℃) > 4GPa

[0141] [Measurement of average thermal expansion coefficient] The PET film was peeled off from the cured products obtained in the examples and comparative examples to obtain sheet-like cured products. The cured products were cut into test pieces approximately 4 mm wide and 15 mm long, and thermomechanical analysis was performed using a thermomechanical analyzer TMA-SS6100 (Seiko Instruments Inc.) by the tensile load method. After mounting the test pieces in the analyzer, measurements were performed twice consecutively under the measurement conditions of a load of 1 g and a heating rate of 5°C / min. The average thermal expansion coefficient (ppm / °C) from 30°C to 80°C in the second measurement was calculated. (Evaluation criteria) 〇: Average thermal expansion coefficient (30℃~80℃)≦100ppm / ℃ ×: Average thermal expansion coefficient (30℃~80℃) > 100 ppm / ℃

[0142] The types and amounts of components used in the examples and comparative examples, as well as the results of evaluation tests, are shown in Tables 1 to 3. Tables 1 and 2 also show the contents of components (A) to (D) per total component (=solid content) of the curable composition. Note that evaluation tests for storage modulus and average coefficient of thermal expansion could not be performed for Comparative Examples 4 to 6.

[0143] [Table 1]

[0144] [Table 2]

[0145] [Table 3] [Industrial Applicability]

[0146] The curable composition of the present invention can form a cured product that has both a low coefficient of thermal expansion and a low modulus of elasticity, making the curable composition of the present invention extremely useful for bonding optical devices.

[0147] This application is based on patent application No. 2022-048354 filed in Japan on March 24, 2022, the contents of which are incorporated in full herein.

Claims

1. The following components (A) to (D): (A) an epoxy compound having two or more alicyclic epoxy groups; (B) inorganic filler, (C) hollow organic polymer particles, and (D) Cationic polymerization initiator A curable adhesive composition for optical devices, comprising: further comprising an oxetane compound having two or more oxetanyl groups; A curable adhesive composition for optical devices, wherein a cured product having a thickness of 100 μm produced from the curable composition has a storage modulus of 4 GPa or less at 25°C when measured at a frequency of 1 Hz and a heating rate of 5°C / min.

2. The curable composition according to claim 1, wherein the content of component (B) is 5 to 80 mass% based on the solid content of the curable composition.

3. 3. The curable composition according to claim 1, wherein the content of component (C) is 3 to 70 mass% based on the solid content of the curable composition.

4. 3. The curable composition according to claim 1, wherein the mass ratio of component (B):component (C) is 1:10 to 20:

1.

5. The curable composition according to claim 1 or 2, wherein the porosity of component (C) is 20% by volume or more.

6. The curable composition according to claim 1 or 2, wherein the porosity of component (C) is 40 to 85% by volume.

7. 3. The curable composition of claim 1, wherein component (B) is selected from silica and cordierite.

8. The curable composition according to claim 1 or 2, wherein the particle size of component (B) is 0.01 μm or more and 20 μm or less.

9. The specific surface area of ​​component (B) is 0.1 m ２ / g or more 100m ２ The curable composition according to claim 1 or 2, wherein the viscosity is 1 / g or less.

10. 3. The curable composition according to claim 1 or 2, wherein the organic polymer contained in component (C) is an organic polymer constituted of monomers containing one or more monomers selected from aromatic olefin compounds, an organic polymer constituted of monomers containing one or more monomers selected from ethylenically unsaturated carboxylic acid ester compounds, or an organic polymer constituted of monomers containing one or more monomers selected from ethylenically unsaturated nitrile compounds.

11. The curable composition according to claim 1 or 2, wherein the organic polymer contained in component (C) is a thermosetting polymer.

12. The curable composition according to claim 1 or 2, wherein the particle size of component (C) is 0.05 μm or more and 100 μm or less.

13. The curable composition of claim 1 or 2, wherein component (D) is selected from photoacid generators and thermal acid generators.

14. The curable composition of claim 1 or 2, further comprising a polyester polyol.

15. 3. The curable composition according to claim 1, wherein a cured product having a thickness of 100 μm produced from the curable composition has an average thermal expansion coefficient of 100 ppm / °C or less from 30°C to 80°C when measured under a load of 1 g at a heating rate of 5°C / min.

16. An optical device having a cured layer formed from the curable composition according to claim 1 or 2.

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