Curable composition

Abstract

The present invention addresses the problem of providing a curable composition capable of forming a cured product having both a low thermal expansion coefficient and a low elastic modulus. The present invention pertains to a curable composition containing the following components (A) to (D): (A) an epoxy compound having two or more alicyclic epoxy groups; (B) an inorganic filler; (C) a polyester having a weight-average molecular weight / hydroxyl equivalent of 0.05 or more and less than 2.0; and (D) a cationic polymerization initiator.

Description

Technical Field

[0001] The present invention relates to curable compositions. Background Art

[0002] In the fixation of components in optical devices such as communication base stations, even if the component undergoes a slight positional offset, performance will also be reduced. Therefore, for the curable composition used as an adhesive for fixing components, in order to prevent slight offsets, it is required to be able to form a cured product with a low thermal expansion coefficient. In addition, in the case of using a curable composition as an adhesive in places where vibration is concerned, in order to reduce the impact of vibration, it is required to be able to form a cured product with a low elastic modulus (Patent Document 1).

[0003] Prior art literature Patent Literature Patent Document 1: Japanese Patent Application Laid-Open No. 2012-177013 Summary of the Invention

[0004] Problems to be solved by the invention In order to reach the low thermal expansion coefficient of solidified material, it is considered to coordinate inorganic particles such as silicon dioxide in curable composition, but in this case, the elastic modulus of solidified material can significantly rise.On the other hand, in order to reduce the elastic modulus of solidified material, it is considered to add the method for organic filler, but in this case, the thermal expansion coefficient can rise.Therefore, it is difficult to form a solidified material having both low thermal expansion coefficient and low elastic modulus.

[0005] The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a curable composition capable of forming a cured product having both a low thermal expansion coefficient and a low elastic modulus.

[0006] Means for solving problems The present inventors conducted intensive research to achieve the above-mentioned objectives and, as a result, discovered that a curable composition comprising an epoxy compound having two or more alicyclic epoxy groups, an inorganic filler, a polyester having a weight-average molecular weight / hydroxyl equivalent of 0.05 or more and less than 2.0, and a cationic polymerization initiator can form a cured product having both a low thermal expansion coefficient and a low elastic modulus, thereby completing the present invention. The present invention, based on this finding, is as follows.

[0007] [1] A curable composition comprising the following components (A) to (D): (A) an epoxy compound having two or more alicyclic epoxy groups, (B) Inorganic filling materials, (C) a polyester having a weight average molecular weight / hydroxyl equivalent of 0.05 or more and less than 2.0, and (D) Cationic polymerization initiator. [2] The curable composition according to [1] above, wherein the content of the component (B) is 20 to 90% by mass relative to the solid content of the curable composition. [3] The curable composition according to [1] above, wherein the content of component (B) is 30 to 85% by mass relative to the solid content of the curable composition. [4] The curable composition according to any one of [1] to [3] above, wherein component (B) is selected from silica and cordierite. [5] The curable composition according to any one of [1] to [4] above, wherein component (D) is selected from a photoacid generator and a thermal acid generator. [6] The curable composition according to any one of [1] to [5] above, further comprising an oxetane compound having two or more oxetane groups. [7] The curable composition according to any one of [1] to [6] above, which is used for bonding optical devices. [8] An optical device comprising a cured layer formed from the curable composition according to any one of [1] to [6] above. Effects of the Invention

[0008] According to the curable composition of the present invention, a cured product having both a low thermal expansion coefficient and a low elastic modulus can be formed. DETAILED DESCRIPTION

[0009] Components (A) to (D) and other components (sometimes referred to as "other components" in this specification) in the curable composition of the present invention are described below in order. Unless otherwise specified, each component may be used alone or in combination of two or more.

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

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

[0012] Examples of the alicyclic epoxy compound include compounds represented by any one of formulae (I) to (III):

[0013] [Chemical Formula 1]

[0014] [Where, L 1 represents a single bond, or represents a divalent hydrocarbon group, a carbonyl group, an ether bond, an ester bond, a carbonate bond, an amide bond, or a group formed by connecting multiple thereof, L 2 ~L 7 Each independently represents a divalent hydrocarbon group, a carbonyl group, an ether bond, an ester bond, a carbonate bond, an amide bond, or a group formed by connecting a plurality of them. ] In this specification, the "compound represented by formula (I)" may be abbreviated as "compound (I)", and compounds represented by other formulae may also be abbreviated similarly.

[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 linear or branched. Examples of the alkylene group having 1 to 18 carbon atoms include methylene, methylmethylene, dimethylmethylene, ethylene, trimethylene, and propylene. 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 1,2-cyclopentylene, 1,3-cyclopentylene, 1,2-cyclohexylene, 1,3-cyclohexylene, and 1,4-cyclohexylene. Examples of the cycloalkylidene group having 5 to 7 carbon atoms include cyclopentylidene and cyclohexylidene.

[0016] Preferred examples of compound (I) include compounds represented by any one of formulas (I-1) to (I-8):

[0017] [Chemical Formula 2]

[0018] [Where, 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.] Compound (I-6) and compound (I-8) may 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, and more preferably 1. The alkylene group having 1 to 8 carbon atoms in formula (I-8) may be 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 compound (II) include compounds represented by formula (II-1):

[0021] [Chemical Formula 3]

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

[0024] [Chemical Formula 4]

[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 compound is preferably selected from compounds (I-1) to (I-8), compound (II-1), and compound (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-6).

[0027] Commercially available alicyclic epoxy compounds can be used. Examples of commercially available products include "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 perspective of fluidity of the curable composition at room temperature, the molecular weight of the alicyclic epoxy compound is preferably less than 1000, more preferably 900 or less, further preferably 800 or less, further more preferably 700 or less, and particularly preferably 600 or less. In addition, the lower limit of the molecular weight of the alicyclic epoxy compound is not particularly limited. From the perspective of suppressing the generation of outgas, the molecular weight is preferably 100 or more, more preferably 125 or more, and further preferably 150 or more. It should be noted that when the alicyclic epoxy compound is a compound having repeating units and is a mixture of multiple compounds having different numbers of repeating units, the molecular weight of the alicyclic epoxy compound refers to the weight average molecular weight (sometimes referred to as "Mw" in this specification). This Mw can be calculated, for example, by polystyrene conversion based on gel permeation chromatography (GPC).

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

[0030] The epoxy equivalent of an 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. from the perspective of reactivity. In this specification, the "epoxy equivalent" of an epoxy compound refers to the number of grams of the epoxy compound containing one gram equivalent of epoxy groups. This epoxy equivalent value can be determined according to the method specified in JIS K 7236. The epoxy equivalent can theoretically be calculated by dividing the molecular weight of the epoxy compound by the number of epoxy groups in the compound.

[0031] From the perspective of good curability of the curable composition and a low thermal expansion coefficient of the cured product, the content of component (A) is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and even more preferably 25 parts by mass or more, relative to 100 parts by mass of the total solid content of the components of the curable composition excluding component (B) (i.e., the inorganic filler). Furthermore, since component (D) is added to the curable composition, the content of component (A) is preferably 80 parts by mass or less, more preferably 75 parts by mass or less, and even more preferably 65 parts by mass or less, relative to 100 parts by mass of the total solid content of the components of the curable composition excluding component (B).

[0032] From the perspective of good curability of the curable composition and a low thermal expansion coefficient of the cured product, the content of component (A) is preferably 3% by mass or more, more preferably 5% by mass or more, and even more preferably 7% by mass or more, relative to the solid content of the curable composition. Furthermore, from the perspective of maintaining a balance with the content of component (B) (i.e., the inorganic filler), the content of component (A) is preferably 70% by mass or less, more preferably 60% by mass or less, and even more preferably 50% by mass or less, relative to the solid content of the curable composition.

[0033] In order not to hinder the effect of the present invention, the curable composition of the present invention is preferably free of epoxy compounds other than component (A) (for example, bisphenol A type epoxy resin), or contains epoxy compounds other than component (A) in an amount of 60% by mass or less relative to the total of epoxy compounds other than component (A) and component (A) (that is, the content of epoxy compounds other than component (A) is controlled to be 60% by mass or less relative to the total of epoxy compounds other than component (A) and component (A)). The content of epoxy compounds other than component (A) is more preferably 50% by mass or less, and further preferably 40% by mass or less relative to the total of epoxy compounds other than component (A) and component (A). The curable composition of the present invention is particularly preferably free of epoxy compounds other than component (A). It should be noted that in this specification, "epoxy compound" refers to a compound having an epoxy group.

[0034] <(B) Inorganic Filler> The curable composition of the present invention contains an inorganic filler as component (B). Component (B) contributes to a low thermal expansion coefficient of the cured product. Furthermore, the present invention is speculated to significantly reduce the thermal expansion coefficient of the cured product by utilizing the synergistic effect achieved by the combined use of components (B) and (C). This presumed mechanism is described below, but the present invention is not limited to this presumed mechanism.

[0035] The present invention is characterized in that, in addition to component (B), component (C) (a polyester having a weight-average molecular weight / hydroxyl equivalent of 0.05 or more and less than 2.0) is used. It is speculated that during the curing of the curable composition of the present invention, component (A) (alicyclic epoxy compound) and component (C) undergo phase separation, resulting in a sea-island structure in which component (A) is a sea and component (C) is an island. It is speculated that due to the heat generated during curing, the component (A) portion expands, but when the resulting cured product cools, the component (C) portion contracts more than the component (A) portion. Therefore, it is speculated that during thermal expansion of the cured product, the contraction of the component (C) portion offsets the expansion of the component (A) portion, achieving a low thermal expansion coefficient for the entire cured product.

[0036] As described below, the average thermal expansion coefficients of Examples 1 to 9, which combined components (B) and (C), were significantly lower than those of Comparative Examples 1 or 2, which did not use components (B) or (C). This significant reduction in the average thermal expansion coefficient is presumably due to a synergistic effect resulting from the combined use of components (B) and (C). This synergistic effect is presumably due to the smaller islands of component (C) in the sea-island structure resulting from phase separation between components (A) and (C), resulting in a uniform effect of component (C) throughout the entire cured product.

[0037] Examples of the inorganic filler include silica, alumina, glass, cordierite, 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 zirconate, calcium zirconate, zirconium phosphate, and zirconium tungstate phosphate.

[0038] Component (B) is preferably selected from silica and cordierite, and more preferably silica. Examples of silica include fused silica, fumed silica, crystalline silica, synthetic silica, and hollow silica. From the perspective of preventing silica sedimentation, the silica is preferably a mixture of fused silica and fumed silica. When a mixture of fused silica and fumed silica is used, the mass ratio of fused silica to fumed silica is preferably 10:1 to 200:1, and more preferably 20:1 to 100:1.

[0039] Commercially available inorganic fillers may be used. Examples of commercially available inorganic fillers include "UFP-30" manufactured by Denka Chemical Industry Co., Ltd.; "SP60-05" and "SP507-05" manufactured by Nippon Steel & Sumitomo Metal Materials Co., Ltd.; "40SE-C3," "YC100C," "YA050C," "YA050C-MJE," "YA010C," "SC2500SQ," "SO-C4," "SO-C2," and "SO-C1" manufactured by Yaduma Co., Ltd.; "R-805" manufactured by Evonik Co., Ltd.; "UFP-30," "DAW-03," and "FB-105FD" manufactured by Denka Co., Ltd.; "Silfil NSS-3N," "Silfil NSS-4N," and "Silfil NSS-5N" manufactured by Tokuyama Co., Ltd.; and "SS-1000" manufactured by Marusu Glaze Co., Ltd.

[0040] From the perspective of reducing practical bonding thickness and reducing positional deviation caused by thermal expansion, the particle size of the inorganic filler is preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less. The lower limit of the particle size of the inorganic filler is not particularly limited, but the particle size is preferably 5 nm or more, more preferably 7 nm or more, and even more preferably 10 nm or more.

[0041] In this specification, the " particle size " of inorganic filler refers to the median particle size that can be calculated by the laser diffraction / scattering method based on Mie scattering theory. Specifically, the particle size distribution of inorganic filler can be made on a volume basis by laser diffraction scattering type particle size distribution measuring device, and its median particle size is calculated. More specifically, as a determination sample, 100mg inorganic filler and 10g dispersant can be weighed into a vial and dispersed with ultrasound for 10 minutes. Laser diffraction type particle size distribution measuring device is used, and the wavelength of the light source is set to blue and red. The particle size distribution of the volume basis of the inorganic filler is measured by flow cell mode, and the median particle size is calculated according to the obtained particle size distribution. As a laser diffraction type particle size distribution measuring device, for example, " LA-960 " manufactured by Horiba Manufacturing Co., Ltd. can be cited.

[0042] From the viewpoint of reducing the practical bonding thickness and reducing positional deviation due to thermal expansion, the specific surface area of ​​the inorganic filler is preferably 0.1 m 2 / g or more, more preferably 0.5m 2 / g or more, more preferably 1m 2 The upper limit of the specific surface area of ​​the inorganic filler is not particularly limited, but is preferably 300 m 2 / g or less, more preferably 250m 2 / g or less, more preferably 200m 2The specific surface area of ​​the inorganic filler can be determined by the BET multipoint method using a specific surface area measuring apparatus (Macsorb HM-1210 manufactured by Mountech) by allowing nitrogen to adsorb on the sample surface.

[0043] The inorganic filler material can be surface treated with an appropriate surface treatment agent. By performing the surface treatment, the moisture resistance and dispersibility of the inorganic filler material can be improved. 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; styrene-based silane coupling agents such as p-styryltrimethoxysilane; 3-methacryloxypropylmethyldimethoxysilane; Methacrylic silane coupling agents such as methoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropyltriethoxysilane; acrylic silane coupling agents such as 3-acryloxypropyltrimethoxysilane; N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl Amino-based silane coupling agents such as 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; urea-based silane coupling agents such as 3-ureidopropyltrialkoxysilane; mercapto-based silane coupling agents such as 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane; isocyanates such as 3-isocyanatopropyltriethoxysilane Silane coupling agents; anhydride-based silane coupling agents such as 3-trimethoxysilylpropylsuccinic anhydride; 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 agent may be used alone or in combination.

[0044] Examples of commercially available surface treatment agents include: “KBM-1003” and “KBE-1003” (vinyl silane coupling agents) manufactured by Shin-Etsu Chemical Co., Ltd.; “KBM-303”, “KBM-402”, “KBM-403”, “KBM-4803”, “KBE-402”, and “KBE-403” (epoxy silane coupling agents); “KBM-1403” (styrene silane coupling agent); “KBM-502”, “KBM-503”, “KBE-502”, and “KBE-503” (methacrylic silane coupling agents); “KBM-5103” (acrylic silane coupling agent); “KBM-602”, “KBM-603”, “KBM-903”, “KBE-903”, and “KBE-9103P”, “KBM-573”, and “KBM- "KBM-575" (amino silane coupling agent); "KBM-9659" (isocyanurate silane coupling agent); "KBE-585" (urea silane coupling agent); "KBM-802", "KBM-803" (mercapto silane coupling agent); "KBE-9007N" (isocyanate silane coupling agent); "X-12-967C" (anhydride 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), etc.

[0045] From the viewpoint of improving the dispersibility of the inorganic filler, the degree of surface treatment with a surface treatment agent is preferably limited to a predetermined range. Specifically, the surface treatment is preferably performed with 0.2 to 5 parts by mass of a surface treatment agent relative to 100 parts by mass of the inorganic filler, more preferably with 0.2 to 3 parts by mass of a surface treatment agent, and even more preferably with 0.3 to 2 parts by mass of a surface treatment agent.

[0046] The degree of surface treatment by 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 preferably 0.02 mg / m 2 More preferably, 0.1 mg / m 2 More preferably, 0.2 mg / m 2 On the other hand, from the viewpoint of preventing the viscosity of the curable composition from increasing, the carbon content is preferably 1.0 mg / m2 Less than 0.8 mg / m 2 Below, more preferably 0.5 mg / m 2 the following.

[0047] The amount of carbon per unit surface area of ​​the inorganic filler can be measured after the surface-treated inorganic filler is cleaned with a solvent (e.g., methyl ethyl ketone (MEK)). Specifically, a sufficient amount of MEK can be added as a solvent to the inorganic filler surface-treated with a surface treatment agent, and ultrasonically cleaned at 25°C for 5 minutes. After removing the supernatant and drying the solid component, a carbon analyzer is used to measure the amount of carbon per unit surface area of ​​the inorganic filler. As a carbon analyzer, "EMIA-320V" manufactured by Horiba Manufacturing Co., Ltd. can be used.

[0048] From the perspective of achieving a low thermal expansion coefficient 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 even more preferably 50 parts by mass or more, relative to 100 parts by mass of the total solid content of the components other than component (B) of the curable composition. Furthermore, from the perspective of achieving a low elastic modulus of the cured product, the content of component (B) is preferably 600 parts by mass or less, more preferably 500 parts by mass or less, and even more preferably 400 parts by mass or less, relative to 100 parts by mass of the total solid content of the components other than component (B) of the curable composition.

[0049] From the perspective of achieving a low thermal expansion coefficient of the cured product, the content of component (B) is preferably 20% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more, relative to the solid content of the curable composition. Furthermore, from the perspective of achieving a low elastic modulus of the cured product, the content of component (B) is preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less, relative to the solid content of the curable composition.

[0050] <(C) Polyester having a weight average molecular weight / hydroxyl equivalent of 0.05 or more and less than 2.0> The curable composition of the present invention contains a polyester having a weight average molecular weight (Mw) / hydroxyl equivalent of 0.05 or more and less than 2.0 as component (C). It is presumed that the use of component (C) can achieve a low thermal expansion coefficient of the cured product by the above-mentioned mechanism.

[0051] The Mw of the component (C) can be calculated by polystyrene conversion using gel permeation chromatography (GPC). Specifically, the Mw of the component (C) can be calculated by GPC under the following conditions. Measuring device: Tosoh Corporation "HLC-8420GPC" Column: Tosoh Corporation's guard column "HXL-L" + Tosoh Corporation's "TSK-GEL SuperHZ2000" + Tosoh Corporation's "TSK-GEL SuperHZ2000" + Tosoh Corporation's "TSK-GEL SuperHZ3000" + Tosoh Corporation's "TSK-GELSuperHZ4000" Detector: RI (differential refractometer) Data processing: Tosoh Corporation's "GPC workstation EcoSEC-WorkStation" Column temperature: 40°C Developing solvent: tetrahydrofuran Flow rate: 0.35 ml / min Standard: According to the measurement manual of the above-mentioned "GPC Workstation EcoSEC-WorkStation", the molecular weight is the following monodisperse polystyrene TSKgel F-10, F-4, F-1, A-5000, A-1000, A-500 (manufactured by Tosoh Corporation) Sample: Sample (10 μl) obtained by filtering a 0.2% by mass tetrahydrofuran solution, calculated as the solid content of component (C), through a microfilter.

[0052] In this specification, the "hydroxyl equivalent weight" of a polyester refers to the molecular weight per hydroxyl group of the polyester (i.e., molecular weight of the polyester / number of hydroxyl groups in the polyester). Like molecular weight, this is a dimensionless quantity without units. The hydroxyl equivalent weight of a polyester can be calculated as follows: According to JIS-K0070, the hydroxyl groups in the polyester are acetylated with acetic anhydride-pyridine, followed by hydrolysis, and the residual acetic acid is back-titrated to calculate the hydroxyl value. The following formula is used based on the obtained hydroxyl value. Hydroxyl equivalent weight = 56,100 / hydroxyl number.

[0053] From the viewpoint of low thermal expansion coefficient of the cured product, the Mw / hydroxy equivalent of the component (C) is 0.05 or more and less than 2.0, preferably 0.1 to 1.5, and more preferably 0.15 to 1.0. From the viewpoint of the viscosity of the composition and the toughness of the cured product, the Mw of the component (C) is preferably 300 to 30,000, more preferably 500 to 25,000, and even more preferably 1,000 to 20,000.

[0054] From the perspective of a low thermal expansion coefficient of the cured product, the content of component (C) is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, and even more preferably 20 parts by mass or more, relative to 100 parts by mass of the total solid content of the components of the curable composition other than component (B) (i.e., the inorganic filler). Furthermore, from the perspective of achieving good curability of the curable composition, the content of component (C) is preferably 70 parts by mass or less, particularly preferably 60 parts by mass or less, and even more preferably 50 parts by mass or less, relative to 100 parts by mass of the total solid content of the components of the curable composition other than component (B).

[0055] From the perspective of a low thermal expansion coefficient of the cured product, the content of component (C) is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, relative to the solid content of the curable composition. Furthermore, from the perspective of good curability of the curable composition, the content of component (C) is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less, relative to the solid content of the curable composition.

[0056] Component (C) includes, for example, polyesters obtained by polycondensing dicarboxylic acids with 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; and branched diols such as 1,2-propylene glycol, 1,3-butanediol, 2-methyl-1,3-propanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, and 2-methyl-1,8-octanediol. Each of the dicarboxylic acid and the diol may be used alone or in combination of two or more.

[0057] As component (C), polyesters produced by polycondensation of the above-mentioned dicarboxylic acids and diols can be used, or polyesters available from manufacturers (e.g., DIC Corporation) can be used. The polycondensation of dicarboxylic acids and diols is well known to those skilled in the art and can be appropriately performed by those skilled in the art.

[0058] In order not to impair the effects of the present invention, the curable composition of the present invention preferably does not contain polyesters other than component (C) (i.e., polyesters having a weight-average molecular weight / hydroxyl equivalent of 2.0 or greater), or contains polyesters other than component (C) at a content of 50% by mass or less relative to the total of the polyesters other than component (C) and component (C) (i.e., the content of polyesters other than component (C) is controlled to 50% by mass or less relative to the total of the polyesters other than component (C) and component (C). The content of polyesters other than component (C) relative to the total of the polyesters other than component (C) and component (C) is more preferably 40% by mass or less, and even more preferably 30% by mass or less. The curable composition of the present invention particularly preferably does not contain polyesters other than component (C).

[0059] <(D) Cationic Polymerization Initiator> The present invention contains a cationic polymerization initiator as component (D). In curing by cationic polymerization, the curable composition has a lower cure shrinkage than curing by photoradical polymerization or thermal anionic polymerization, and the resulting cured product has high heat resistance.

[0060] The cationic polymerization initiator of component (D) may be either a photocationic polymerization initiator or a thermal cationic polymerization initiator as long as it can act on the alicyclic epoxy group in the alicyclic epoxy compound of component (A) and the oxetane group in the oxetane compound having two or more oxetane groups described later to initiate a cationic polymerization reaction.

[0061] The photocationic polymerization initiator is preferably a photoacid generator, which is a preparation that generates protons or Lewis acids upon light irradiation. Photoacid generators are well known to those skilled in the art and are not particularly limited in the present invention. Known photoacid generators can be used.

[0062] Representative photoacid generators include, for example, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium hexafluorophosphate, p-(phenylthio)phenyldiphenylsulfonium hexafluoroantimonate, p-(phenylthio)phenyldiphenylsulfonium hexafluorophosphate, 4-chlorophenyldiphenylsulfonium hexafluorophosphate, 4-chlorophenyldiphenylsulfonium hexafluoroantimonate, bis[4-(diphenylsulfonium)phenyl]sulfide bishexafluorophosphate, bis[4-(diphenylsulfonium)phenyl]sulfide bishexafluoroantimonate, (2,4-cyclopentadien-1-yl)[(1-methylethyl)benzene]iron hexafluorophosphate, diallyliodonium hexafluoroantimonate, and the like. Examples of the photoacid generator include those described in WO2018 / 110297 and those described in WO2020 / 171186 (for example, p-(phenylthio)phenyldiphenylsulfonium tris(pentafluoroethyl)trifluorophosphate). Furthermore, examples of the photoacid generator include other known salts containing sulfonium cations and commercially available salts containing sulfonium cations.

[0063] A commercially available photoacid generator can be used. Examples of commercially available products 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," and "CYRACURE UVI-6975" manufactured by Union Carbide Corporation. "UVI-6990", "CYRACUREUVI-950"; "DAICATII" manufactured by Daicel Corporation; "UVAC1591" manufactured by DAICEL-ALLNEX; "CI-2481", "CI-2734", "CI-2823", "CI-2758" manufactured by Nippon Soda Co., Ltd.; "FFC509" manufactured by 3M Company; "BBI-102", "BBI-101", "BBI-103", "MPI-103", "TPS-103", "MDS-103", "DTS-103", "NAT-103", "NDS-103" manufactured by MIDORI Chemical Co., Ltd.

[0064] The thermal cationic polymerization initiator is preferably a thermal acid generator, which is a preparation that generates protons or Lewis acids by heating. Thermal acid generators are well known to those skilled in the art and are not particularly limited in the present invention. Known thermal acid generators can be used.

[0065] Representative thermal acid generators include organic onium salt compounds comprising a pair of cationic components and anionic components as described in WO2019 / 146736. Here, as cationic components, organic sulfonium cations, organic oxonium cations, organic ammonium cations, organic phosphonium cations, organic iodonium cations, etc. are mentioned. In addition, as anionic components, BF4 is mentioned. - 、B(C6F5)4 - 、SbF4 - 、Sb(C6F5)4 - 、AsF6 - PF6 - PF6 - CF3SO3 - 、C4F9SO3 - or (CF3SO2)3C - wait. In addition, as a thermal acid generator, the thermal acid generator described in WO2018 / 110297 can also be mentioned. Furthermore, examples of the thermal acid generator include other known salts containing quaternary ammonium cations and commercially available salts containing quaternary ammonium cations.

[0066] A commercially available thermal acid generator may be used. Examples of the commercially available thermal acid generator include "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"; "TA-60", "TA-60B", "TA-90", "TA-100", "TA-120", "TA-160", "IK-1", "IK-2" manufactured by San-Apro; "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", "SAN-AID SI-150", "SAN-AID SI-150L", "SAN-AID SI-160", "SAN-AID SI-180", "SAN-AID SI-180L", "SAN-AID SI-1 SAN-AID SI-360"; "ADEKA Opton CP-66" and "ADEKA Opton CP-77" manufactured by ADEKA; "FC-520" manufactured by 3M, etc.

[0067] Component (D) is preferably selected from a photoacid generator and a thermal acid generator. Here, either one of the photoacid generator or the thermal acid generator may be used alone, or two or more of the photoacid generator and the thermal acid generator may be used in combination. In addition, both a photoacid generator and a thermal acid generator may be used as component (D). When both a photoacid generator and a thermal acid generator are used, for example, they can be used in the following applications: the curable composition of the present invention is pre-cured by light irradiation and then fully cured by heating.

[0068] From the perspective of good curability of the curable composition, the content of component (D) is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, and even more preferably 0.1 parts by mass or more, relative to 100 parts by mass of the total solid content of the components other than component (B) (i.e., the inorganic filler) of the curable composition. In addition, from the perspective of storage stability of the curable composition, the content of component (D) is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less, relative to 100 parts by mass of the total solid content of the components other than component (B) of the curable composition.

[0069] From the perspective of good curability of the curable composition, the content of component (D) is preferably 0.05% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more, relative to the solid content of the curable composition. Furthermore, from the perspective 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 even more preferably 5% by mass or less, relative to the solid content of the curable composition.

[0070] <Other ingredients> The curable composition of the present invention may further contain other components in addition to components (A) to (D) as needed. Examples of other components include oxetane compounds having two or more oxetane groups and photosensitizers.

[0071] (Oxetane compound having two or more oxetane groups) An oxetane compound having two or more oxetane groups (sometimes referred to simply as an "oxetane compound" in this specification) contributes to low cure shrinkage of the curable composition. The number of oxetane groups in the oxetane compound is preferably 2 to 4, more preferably 2.

[0072] Examples of the oxetane compound include compounds represented by either formula (IV) or formula (V):

[0073] [Chemical Formula 5]

[0074] [Where, R 1 ~R 4 Each independently represents 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 optionally 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, and 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 formed by linking an alkylene group having 1 to 6 carbon atoms and an arylene group having 6 to 10 carbon atoms, or a group represented by any of the following formulas (VI) or (VII):

[0075] [Chemical Formula 6]

[0076] (Where, * indicates the bonding 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.] Compound (V) may be a mixture of compounds having different numbers of repeating units.

[0077] The C1-6 alkyl group in formulas (IV) and (V) may be linear or branched. Examples of the C1-6 alkyl group include methyl, ethyl, propyl, butyl, pentyl, and hexyl.

[0078] Examples of the cycloalkyl group having 5 to 7 carbon atoms in formulae (IV) and (V) include cyclopentyl, cyclohexyl and cycloheptyl.

[0079] 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 in formulae (IV) and (V) include phenyl, naphthyl, tolyl, and xylyl.

[0080] Examples of the aralkyl group having 6 to 16 carbon atoms in formulae (IV) and (V) include benzyl and phenethyl.

[0081] The number of carbon atoms in the alkylene group in the polyoxyalkylene group in formula (V) is preferably 1 to 4. The number of repeating oxyalkylene groups in the polyoxyalkylene group is preferably 2 to 30.

[0082] The alkylene group having 1 to 6 carbon atoms in formulas (VI) and (VII) may be linear or branched. Examples of the alkylene group having 1 to 6 carbon atoms include methylene, ethylene, trimethylene, propylene, tetramethylene, pentamethylene, and hexamethylene.

[0083] Examples of the cycloalkylene group having 5 to 7 carbon atoms in formulae (VI) and (VII) include 1,2-cyclopentylene, 1,3-cyclopentylene, 1,2-cyclohexylene, 1,3-cyclohexylene, 1,4-cyclohexylene, 1,2-cycloheptylene, 1,3-cycloheptylene, and 1,4-cycloheptylene.

[0084] Examples of the arylene group having 6 to 10 carbon atoms in formulae (VI) and (VII) include a phenylenediyl group and a biphenyldiyl group.

[0085] In the divalent group formed by linking an alkylene group having 1 to 6 carbon atoms and an arylene group having 6 to 10 carbon atoms in formulas (VI) and (VII), the number of each of the alkylene group having 1 to 6 carbon atoms and the arylene group having 6 to 10 carbon atoms may be one or more, for example, benzene-4,4-diylbimethylene (-CH2-Ph-CH2-) and biphenyl-4,4'-diylbimethylene (-CH2-Ph-Ph-CH2-).

[0086] The oxetane compound is preferably selected from the compound represented by the following formula (IV-1) and the compound represented by the following formula (V-1), and more preferably the compound represented by the following formula (IV-1). Compound (V-1) may be a mixture of compounds having different numbers of repeating units.

[0087] [Chemical Formula 7]

[0088] [In the above formula (V-1), m2 represents an integer of 1 to 3.]

[0089] Commercially available oxetane compounds may be used, and examples of the commercially available oxetane compounds include "OXT-121" and "OXT-221" manufactured by Toagosei Co., Ltd., and "OXBP" and "OXIPA" manufactured by Ube Industries, Ltd.

[0090] The molecular weight of the oxetane compound is preferably more than 180, more preferably more than 190, further preferably more than 200. The upper limit of the molecular weight of the oxetane compound can be appropriately selected according to the viscosity of the curable composition, but its molecular weight is preferably less than 400. If the molecular weight of the oxetane compound is more than 180, the oxetane compound is difficult to volatilize from the curable composition. It should be noted that the oxetane compound is a compound with 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 weight-average molecular weight (Mw). The Mw can be calculated by, for example, converting the polystyrene based on gel permeation chromatography (GPC).

[0091] From the viewpoint of fluidity of the curable composition at room temperature, the viscosity (25° C.) of the oxetane compound is preferably 1 to 10,000 mPa·s, more preferably 2 to 5,000 mPa·s.

[0092] When an oxetane compound is used, from the viewpoint of low cure shrinkage of the curable composition, its content is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more, relative to a total of 100 parts by mass of the solid content of the components other than component (B) (i.e., inorganic filler) of the curable composition. In addition, when an oxetane compound is used, from the viewpoint of the adhesion of the curable composition, its content is preferably 80 parts by mass or less, more preferably 75 parts by mass or less, and even more preferably 70 parts by mass or less, relative to a total of 100 parts by mass of the solid content of the components other than component (B) of the curable composition.

[0093] When an oxetane compound is used, from the viewpoint of low cure shrinkage of the curable composition, its content is preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more relative to the solid content of the curable composition. Furthermore, when an oxetane compound is used, from the viewpoint of adhesion of the curable composition, its content is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less relative to the solid content of the curable composition.

[0094] (Photosensitizer) When a photocationic polymerization initiator (particularly a photoacid generator) is used as the component (D), it is preferred to use a photosensitizer in order to increase the activity of the photocationic polymerization initiator and improve the curability of the curable composition.

[0095] A photosensitizer is a compound having an absorption band in a longer wavelength region than that of a photocationic polymerization initiator, which, after being excited by light absorption, undergoes electron or energy migration, thereby contributing to the decomposition of the photocationic polymerization initiator and the generation of polymerization-initiating species. The photosensitizer can be appropriately formulated according to the wavelength of the light source used for photocuring. Photosensitizers are well known to those skilled in the art and are not particularly limited in the present invention, and known photosensitizers can be used.

[0096] Specific examples of photosensitizers 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; aromatic diketone compounds such as benzyl and curcumin; and the like.

[0097] In addition, from the viewpoint of maintaining an appropriate level of absorbance in the long-wavelength band, preventing poor dispersion in the curable composition, and improving curability or increasing the curing speed during curing, the photosensitizer is preferably selected from the following compounds: anthracene compounds (e.g., 9,10-dibutoxyanthracene) that have an absorption band in a wavelength region greater than 350 nm and easily generate electron migration with aromatic sulfonium salt-based or aromatic iodonium salt-based photocationic polymerization initiators, or thioxanthracene compounds and quinone compounds.

[0098] Commercially available photosensitizers may be used, for example, "Anthracure UVS-1331," "Anthracure UVS-1101," "Anthracure UVS-581," and "Anthracure UVS-2171" manufactured by Air Water Performance Chemical Co., Ltd.; and 2-isopropylthioxanthone, 2,4-diethylthioxanthone, and 2-ethylanthraquinone manufactured by Tokyo Chemical Industry Co., Ltd.

[0099] When a photosensitizer is used, from the perspective of good curability of the curable composition, its content is preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1 part by mass or more, relative to 100 parts by mass of the total solid content of the components other than component (B) (i.e., inorganic filler) of the curable composition. Furthermore, when a photosensitizer is used, from the perspective of deep curability, its content is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less, relative to 100 parts by mass of the total solid content of the components other than component (B) of the curable composition.

[0100] When a photosensitizer is used, from the perspective of good curability of the curable composition, its content is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.2% by mass or more, relative to the solid content of the curable composition. Furthermore, when a photosensitizer is used, from the perspective of deep curability, its content is preferably 15% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, relative to the solid content of the curable composition.

[0101] <Method for producing curable composition> The curable composition of the present invention can be produced by mixing components (A) to (D) and, if necessary, other components (e.g., an oxetane compound, a photosensitizer, etc.) using a known stirrer or disperser. Examples of the stirrer or disperser 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 AGI homomixer, and a rotation / revolution mixer.

[0102] <Application> The curable composition of the present invention can form a cured product having both a low thermal expansion coefficient and a low elastic modulus. Therefore, the curable composition of the present invention is useful as an adhesive or sealant (particularly an adhesive for fixing precision parts).

[0103] By curable composition of the present invention, a cured layer of an optical device having a low thermal expansion coefficient and a low elastic modulus can be formed. Therefore, curable composition of the present invention can be suitably used for the bonding of optical devices (specifically, the bonding of the components in the optical device). Specifically, curable composition of the present invention can be used as an adhesive for optical fiber arrays, ball lenses, for example.

[0104] The curable composition of the present invention can be cured by light and / or heat. For example, by using a mercury lamp, UV-LED, etc. to cure at 300mJ / cm 2 The above-mentioned light irradiation can cure the curable composition of the present invention containing a photocationic polymerization initiator (particularly a photoacid generator). Alternatively, the curable composition of the present invention containing a thermal cationic polymerization initiator (particularly a thermal acid generator) can be cured by heating at a temperature of 60 to 150°C. Example

[0105] Hereinafter, the present invention will be described in more detail based on Examples, but the present invention is not limited to the following Examples. In addition, "parts" described below refer to "parts by mass."

[0106] 1. Raw materials [Component (A): Epoxy compound having two or more alicyclic epoxy groups] CELLOXIDE 2021P: Compound (I-1) manufactured by Daicel Corporation (molecular weight: 252, number of alicyclic epoxy groups per molecule: 2, viscosity (25°C): 250 mPa·s, epoxy equivalent: 130 g / eq.) CELLOXIDE 2081: Compound (I-6) manufactured by Daicel Corporation (n1 in formula (I-6) = 1, molecular weight: 366, number of alicyclic epoxy groups per molecule: 2, viscosity (25°C): 340 mPa·s, epoxy equivalent: 200 g / eq.)

[0107] [Epoxy compounds other than component (A)] ZX-1059: Bisphenol A epoxy resin manufactured by Nippon Steel Chemicals Co., Ltd. (epoxy equivalent: 165 g / eq.)

[0108] [Component (B): Inorganic filler] 40SE-C3: Fused silica manufactured by Yaduma Co., Ltd. (particle size (median diameter): 3.7 μm) R-805: Aerosil (fumed silica) manufactured by EVONIK (particle size (median diameter): 12 nm) SS-1000: Cordierite manufactured by MARUSU GLAZE Co., Ltd. (Particle size (median diameter): 1.7 μm)

[0109] [Component (C): Polyester having a weight-average molecular weight / hydroxyl equivalent of 0.05 or more and less than 2.0] Polyester A: polyester manufactured by DIC Corporation (weight average molecular weight: 8500, hydroxyl equivalent: 13000, weight average molecular weight / hydroxyl equivalent: 0.65) Polyester B: polyester manufactured by DIC Corporation (weight average molecular weight: 4500, hydroxyl equivalent: 11000, weight average molecular weight / hydroxyl equivalent: 0.41)

[0110] [Polyesters other than component (C)] FPS-120: polyester polyol manufactured by DIC Corporation (weight average molecular weight: 4600, hydroxyl equivalent: 1000, weight average molecular weight / hydroxyl equivalent: 4.6)

[0111] [Component (D): Cationic polymerization initiator] Irgacure 290: Photoacid generator manufactured by BASF CPI-210S: Photoacid generator manufactured by San-Apro CXC-1821: Thermal acid generator manufactured by King Industries

[0112] [Other ingredients] OXT-221: Oxetane compound manufactured by Toagosei Co., Ltd. (Compound (IV-1), molecular weight: 214, number of oxetane groups per molecule: 2, viscosity (25°C): 12.8 mPa·s) UVS-1331: Photosensitizer manufactured by Air Water Performance Chemical Co.

[0113] 2. Preparation of curable composition and cured product <Example 1> Curable compositions having the blending ratios shown in the following table were prepared according to the following procedures, and cured products were prepared using the obtained curable compositions.

[0114] Specifically, 40 parts of "CELLOXIDE 2021P" manufactured by Daicel Corporation were uniformly mixed with 40 parts of "OXT-221" manufactured by Toagosei Co., Ltd. and 40 parts of "Polyester A" manufactured by DIC Corporation using a high-speed rotary mixer to obtain a mixture. 300 parts of "40SE-C3" manufactured by Yaduma Co., Ltd. and 5 parts of "R-805" manufactured by Evonik Co., Ltd. were added to the resulting mixture, and the resulting mixture was uniformly dispersed using a high-speed rotary mixer. 10 parts of "CPI-210S" manufactured by San-Apro Co., Ltd. and 5 parts of "UVS-1331" manufactured by Air Water Performance Chemical Co., Ltd. were uniformly mixed with the resulting mixture using a high-speed rotary mixer to obtain a curable composition. The obtained curable composition was evenly applied using a glass rod onto the release-treated surface of a polyethylene terephthalate (PET) film ("NS-80A" manufactured by Toray Industries, Ltd., PET film thickness: 38 μm) treated with an alkyd release agent, and irradiated with 365 nm ultraviolet rays at 30 mW for 100 seconds to obtain a cured product with a thickness of 100 μm.

[0115] <Example 2> A curable composition and a cured product were produced in the same manner as in Example 1, except that the added amount of "40SE-C3" manufactured by Yaduma Co., Ltd. was changed from 300 parts to 150 parts.

[0116] <Example 3> A curable composition and a cured product were produced in the same manner as in Example 1, except that the added amount of "40SE-C3" manufactured by Yaduma Co., Ltd. was changed from 300 parts to 400 parts.

[0117] <Example 4> A curable composition and a cured product were produced in the same manner as in Example 1, except that 40 parts of "Polyester B" manufactured by DIC Corporation was used instead of 40 parts of "Polyester A" manufactured by DIC Corporation.

[0118] <Example 5> A curable composition and a cured product were produced in the same manner as in Example 1, except that the amount of "CELLOXIDE 2021P" manufactured by Daicel Corporation was changed from 40 parts to 80 parts and "OXT-221" manufactured by Toagosei Co., Ltd. was not used.

[0119] <Example 6> A curable composition and a cured product were produced in the same manner as in Example 1, except that 40 parts of "CELLOXIDE 2081" manufactured by Daicel Corporation was used instead of 40 parts of "CELLOXIDE 2021P" manufactured by Daicel Corporation.

[0120] <Example 7> A curable composition and a cured product were produced in the same manner as in Example 1 except that 10 parts of "Irgacure 290" manufactured by BASF were used instead of 10 parts of "CPI-210S" manufactured by San-Apro and 5 parts of "UVS-1331" manufactured by Air Water Performance Chemical.

[0121] <Example 8> A curable composition and a cured product were produced in the same manner as in Example 1, except that 300 parts of "SS-1000" manufactured by MARUSU GLAZE CO., LTD. was used instead of 300 parts of "40SE-C3" manufactured by YATUMA CO., LTD., and "R-805" manufactured by EVONIK CO., LTD. was not used.

[0122] <Example 9> A curable composition was prepared in the same manner as in Example 1 except that 0.8 parts of "CXC-1821" manufactured by King Industries was used instead of 10 parts of "CPI-210S" manufactured by San-Apro and 5 parts of "UVS-1331" manufactured by Air Water Performance Chemical. Furthermore, a cured product having a thickness of 100 μm was obtained in the same manner as in Example 1 except that thermal curing by heating at 120° C. for 30 minutes in an oven was performed instead of photocuring by ultraviolet irradiation.

[0123] <Comparative Example 1> A curable composition and a cured product were produced in the same manner as in Example 1, except that 40 parts of "FPS-120" manufactured by DIC Corporation was used instead of 40 parts of "Polyester A" manufactured by DIC Corporation.

[0124] <Comparative Example 2> A curable composition and a cured product were produced in the same manner as in Example 1, except that “40SE-C3” manufactured by Yaduma Co., Ltd. and “R-805” manufactured by Evonik Co., Ltd. were not used.

[0125] <Comparative Example 3> A curable composition and a cured product were produced in the same manner as in Example 1 except that 80 parts of "ZX-1059" manufactured by Nippon Steel Chemicals Co., Ltd. was used instead of 40 parts of "CELLOXIDE 2021P" manufactured by Daicel Corporation and 40 parts of "OXT-221" manufactured by Toagosei Co., Ltd.

[0126] 3. Evaluation Test [Determination of storage modulus] By peeling off the PET film from the cured product obtained in the examples and comparative examples, a sheet-like cured product was obtained. The cured product was cut into a test piece of about 7 mm in width and about 40 mm in length, and a dynamic mechanical analysis was performed in the tensile mode using a dynamic mechanical analyzer DMS-7100 (manufactured by Hitachi High-Tech Co., Ltd.). After the test piece was mounted on the above-mentioned device, the measurement was performed under the measurement conditions of a frequency of 1 Hz and a heating rate of 5°C / min. The value of the storage modulus (GPa) at 25°C in the measurement was read and evaluated according to the following criteria. The results are shown in Table 1. (Evaluation Criteria) 0: Storage modulus ≤ 10GPa ×: Storage modulus > 10 GPa

[0127] [Measurement of average thermal expansion coefficient] By peeling off the PET film from the cured product obtained in the examples and comparative examples, a sheet-like cured product was obtained. The cured product was cut into a test piece of about 4 mm in width and about 15 mm in length, and a thermomechanical analysis was performed using a thermomechanical analyzer TMA-7100 (manufactured by Hitachi High-Tech Co., Ltd.) using a tensile load method. After the test piece was mounted on the above-mentioned device, it was continuously measured twice 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 and evaluated according to the following criteria. The results are shown in Table 1. (Evaluation Criteria) 0: Average thermal expansion coefficient ≤40ppm / ℃ ×: Average thermal expansion coefficient > 40ppm / °C

[0128] [Table 1]

[0129] As shown in Table 1 above, in Examples 1 to 9, cured products having a small thermal expansion coefficient and a low storage modulus were obtained.

[0130] In Comparative Example 1, in which a polyester other than component (C) was used, the obtained cured product had a large average thermal expansion coefficient. In Comparative Example 2, in which component (B) was not used, the obtained cured product had a large average thermal expansion coefficient. In Comparative Example 3, in which a bisphenol A-type epoxy resin was used instead of component (A), the curable composition obtained had poor curability, and no evaluable cured product was obtained. Industrial applicability

[0131] The curable composition of the present invention is useful as an adhesive or a sealant (particularly an adhesive for fixing precision parts).

[0132] This application is based on Japanese Patent Application No. 2023-021017 filed in Japan, the entire contents of which are incorporated herein by reference.

Claims

1. A curable composition comprising the following components (A) to (D): (A) an epoxy compound having two or more alicyclic epoxy groups, (B) Inorganic filling materials, (C) a polyester having a weight average molecular weight / hydroxyl equivalent of 0.05 or more and less than 2.0, and (D) Cationic polymerization initiator.

2. The curable composition according to claim 1, wherein The content of the component (B) is 20 to 90% by mass relative to the solid content of the curable composition.

3. The curable composition according to claim 1, wherein The content of the component (B) is 30 to 85% by mass relative to the solid content of the curable composition.

4. The curable composition according to claim 1, wherein Component (B) is selected from silica and cordierite.

5. The curable composition according to claim 1, wherein Ingredient (D) is selected from photoacid generators and thermal acid generators.

6. The curable composition according to claim 1, wherein The present invention further includes an oxetane compound having two or more oxetane groups. 7 . The curable composition according to claim 1 , which is used for bonding optical devices. 8 . An optical device comprising a cured layer formed from the curable composition according to claim 1 .

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