JP7569794B2 - CURABLE COMPOSITION, CURED PRODUCT, AND METHOD OF USE OF CURABLE COMPOSITION - Google Patents

Description

The present invention relates to a curable composition having a high refractive index and suitable for use in the optical field, a cured product obtained by curing the curable composition, and a method of using the curable composition as an adhesive for fixing optical elements or a sealing material for fixing optical elements.

2. Description of the Related Art Curable compositions have been improved in various ways depending on the intended use, and have come to be widely used in industry as raw materials for optical parts and molded articles, adhesives, coating agents, and the like.
The curable composition has also attracted attention as a composition for fixing optical elements, such as an adhesive for fixing optical elements or a sealing material for fixing optical elements.

Optical elements include various lasers such as semiconductor lasers (LDs), light-emitting elements such as light-emitting diodes (LEDs), light-receiving elements, composite optical elements, optical integrated circuits, and the like.
In recent years, optical elements that emit blue or white light with shorter peak wavelengths have been developed and are widely used. The luminance of such light-emitting elements with shorter peak wavelengths has increased dramatically, and the amount of heat generated by the optical elements has also increased.

However, as optical elements have become brighter in recent years, the cured composition for fixing optical elements is exposed for long periods of time to higher energy light or higher temperatures generated by the optical elements, resulting in a problem of a decrease in adhesive strength.

To solve this problem, Patent Documents 1 to 3 propose compositions for fixing optical elements that contain a polysilsesquioxane compound as the main component.

When an optical element or the like is fixed using a curable composition, a curable composition having an appropriate refractive index may be selected in accordance with the refractive index of the surrounding members in order to increase the light extraction efficiency.
For example, in order to suppress reflection at the interface between the sealant and the fixing material and to increase the light extraction efficiency, it is preferable that the difference between the refractive index of the sealant and the refractive index of the fixing material is small.
Therefore, when a sealant having a relatively high refractive index is used, it is necessary to form the fixing material using a curable composition having a similarly high refractive index.

JP 2004-359933 A JP 2005-263869 A JP 2006-328231 A

The present invention has been made in consideration of the current state of the prior art described above, and aims to provide a curable composition having a high refractive index and suitable for use in the optical field, a cured product obtained by curing the curable composition, and a method of using the curable composition as an adhesive for fixing optical elements or a sealing material for fixing optical elements.

Means for Solving the Problems The present inventors have conducted extensive research into a curable composition containing a polysilsesquioxane compound in order to solve the above problems.
the result,
(i) By using a polysilsesquioxane compound containing a large number of aryl groups as the polysilsesquioxane compound, a curable composition having a high refractive index can be obtained;
(ii) There is a risk of cracks occurring in a cured product of a curable composition containing a polysilsesquioxane compound containing a large number of aryl groups;
(iii) A cured product of a curable composition containing a polysilsesquioxane compound containing a large number of aryl groups tends to have poor adhesion;
(iv) The above problems (ii) and (iii) can be solved by adjusting the amount of aryl groups in the polysilsesquioxane compound, by introducing a specific molecular structure into the polysilsesquioxane compound, and by adding a silane coupling agent to the curable composition.
Thus, the present invention has been completed.

Thus, according to the present invention, there are provided the following curable compositions [1] to [7], cured products [8] and [9], and methods of using the curable compositions [10] and [11].

[1] A curable composition comprising the following component (A) and component (C):
Component (A): Formula (a-1) below

[R ¹ represents an unsubstituted aryl group having 6 to 12 carbon atoms or a substituted aryl group having 6 to 12 carbon atoms.]
A repeating unit represented by the following formula (a-2):

[ ^R2 represents an unsubstituted alkyl group having 1 to 10 carbon atoms or a substituted alkyl group having 1 to 10 carbon atoms.]
The polysilsesquioxane compound has a repeating unit represented by the formula (2) and satisfies the following requirements 1 and 2:
The amount of the repeating unit (1) is 40 mol % or more and less than 80 mol % based on the total amount of the repeating unit (1) and the repeating unit (2).
[Requirement 2]
The amount of the T2 sites is 20 to 70 mol % relative to the total amount of the T sites (T1 sites) represented by the following formula (a-3), the T sites (T2 sites) represented by the following formula (a-4), and the T sites (T3 sites) represented by the following formula (a-5):

(G represents a group represented by ^R1 or ^R2 . ^R3 represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. * represents a silicon atom bonded thereto.)
Component (C): Silane coupling agent [2] The curable composition according to [1], wherein the mass average molecular weight (Mw) of the component (A) is 500 to 25,000.
[3] The curable composition according to [1] or [2], wherein the combined amount of the repeating unit (1) and the repeating unit (2) in the component (A) is 90 to 100 mol % of all repeating units of the component (A).
[4] The curable composition according to any one of [1] to [3], wherein the content of the component (C) is 0.1 to 70 parts by mass per 100 parts by mass of the component (A).
[5] The curable composition according to any one of [1] to [4], wherein the total amount of the component (A) and the component (C) is 50 to 100 mass% of the solid content of the curable composition.
[6] The curable composition according to any one of [1] to [5], further comprising a diluent and having a solid content concentration of 60 mass % or more and less than 100 mass %.
[7] The curable composition according to any one of [1] to [6], having a refractive index (nD) at 25° C. of 1.46 to 1.56.
[8] A cured product obtained by curing the curable composition according to any one of [1] to [7] above.
[9] The cured product according to [8], which is an optical element fixing material.
[10] A method of using the curable composition according to any one of [1] to [7] above as an adhesive for an optical element fixing material.
[11] A method of using the curable composition according to any one of [1] to [7] above as a sealing material for fixing optical elements.

The present invention provides a curable composition having a high refractive index and suitable for use in the optical field, a cured product obtained by curing the curable composition, and a method of using the curable composition as an adhesive for fixing optical elements or a sealing material for fixing optical elements.

The present invention will be described in detail below, dividing it into the following sections: 1) the curable composition, 2) the cured product, and 3) a method for using the curable composition.

1) Curable Composition The curable composition of the present invention contains the following component (A) and component (C).
Component (A): A polysilsesquioxane compound having a repeating unit represented by the above formula (a-1) and a repeating unit represented by the above formula (a-2), which satisfies the above requirements 1 and 2 (hereinafter, may be referred to as "polysilsesquioxane compound (A)").
Component (C): Silane coupling agent

[Component (A)]
The polysilsesquioxane compound (A) constituting the curable composition of the present invention has a repeating unit represented by the following formula (a-1) [repeating unit (1)].

[R ¹ represents an unsubstituted aryl group having 6 to 12 carbon atoms or a substituted aryl group having 6 to 12 carbon atoms.]

Since the repeating unit (1) has R ¹ , the polysilsesquioxane compound having the repeating unit (1) has a high refractive index, and therefore the curable composition of the present invention has a high refractive index.

Examples of the "unsubstituted aryl group having 6 to 12 carbon atoms" for R ¹ include a phenyl group, a 1-naphthyl group, and a 2-naphthyl group.
The "unsubstituted aryl group having 6 to 12 carbon atoms" for R ¹ preferably has 6 carbon atoms.

The number of carbon atoms in the "substituted aryl group having 6 to 12 carbon atoms" of ^R1 is preferably 6. Note that this number of carbon atoms refers to the number of carbon atoms in the portion excluding the substituent (the aryl group portion). Therefore, when ^R1 is a "substituted aryl group having 6 to 12 carbon atoms", the number of carbon atoms in ^R1 may exceed 12.
Examples of the aryl group in the "substituted aryl group having 6 to 12 carbon atoms" of ^R1 include the same as those exemplified as the "unsubstituted aryl group having 6 to 12 carbon atoms".

The number of atoms of the substituent in the "substituted aryl group having 6 to 12 carbon atoms" for R ¹ (excluding the number of hydrogen atoms) is usually 1 to 30, and preferably 1 to 20.
Examples of the substituent in the "substituted aryl group having 6 to 12 carbon atoms" for ^R1 include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, s-butyl, isobutyl, t-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, and isooctyl; halogen atoms such as chlorine and bromine; and alkoxy groups such as methoxy and ethoxy.

Among these, R ¹ is preferably an unsubstituted aryl group having 6 to 12 carbon atoms, and more preferably a phenyl group, because a curable composition having a high refractive index can be efficiently prepared.

The polysilsesquioxane compound (A) may have one type of R ¹ , or may have two or more types of R ¹ .

The polysilsesquioxane compound (A) further has a repeating unit [repeating unit (2)] represented by the following formula (a-2):

[ ^R2 represents an unsubstituted alkyl group having 1 to 10 carbon atoms or a substituted alkyl group having 1 to 10 carbon atoms.]

The polysilsesquioxane compound (A) has a repeating unit (2), which increases the molecular weight and improves the flexibility of the molecular chain. As a result, cracks are less likely to occur in the cured product of the curable composition of the present invention, and the curable composition of the present invention has excellent adhesion.

The "unsubstituted alkyl group having 1 to 10 carbon atoms" of ^R2 preferably has 1 to 6 carbon atoms, and more preferably has 1 to 3 carbon atoms.
Examples of the "unsubstituted alkyl group having 1 to 10 carbon atoms" for ^R2 include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, a t-butyl group, an n-pentyl group, an n-hexyl group, an n-octyl group, an n-nonyl group, and an n-decyl group.

The number of carbon atoms in the "substituted alkyl group having 1 to 10 carbon atoms" of ^R2 is preferably 1 to 6, and more preferably 1 to 3. Note that this number of carbon atoms refers to the number of carbon atoms in the portion excluding the substituent (the alkyl group portion). Therefore, when ^R2 is a "substituted alkyl group having 1 to 10 carbon atoms", the number of carbon atoms in ^R2 may exceed 10.
Examples of the alkyl group in the "substituted alkyl group having 1 to 10 carbon atoms" of ^R2 include the same as those given as the "unsubstituted alkyl group having 1 to 10 carbon atoms".

The number of atoms of the substituent in the "substituted alkyl group having 1 to 10 carbon atoms" (excluding the number of hydrogen atoms) is usually 1 to 30, and preferably 1 to 20.
Examples of the substituent in the "substituted alkyl group having 1 to 10 carbon atoms" include a halogen atom such as a chlorine atom or a bromine atom; a cyano group; and the like.

Among these, ^R2 is preferably an unsubstituted alkyl group having 1 to 10 carbon atoms, more preferably an unsubstituted alkyl group having 1 to 6 carbon atoms, and even more preferably an unsubstituted alkyl group having 1 to 3 carbon atoms.
By using the polysilsesquioxane compound (A) in which R ² is an unsubstituted alkyl group having 1 to 10 carbon atoms, the molecular weight of the polysilsesquioxane compound (A) can be efficiently controlled.

The polysilsesquioxane compound (A) may have one type of R ² or two or more types of R ² .

The polysilsesquioxane compound (A) may be any of a random copolymer, a block copolymer, a graft copolymer, an alternating copolymer, and the like. From the viewpoint of ease of production, etc., a random copolymer is preferred.
The structure of the polysilsesquioxane compound (A) may be any of a ladder structure, a double-decker structure, a cage structure, a partially cleaved cage structure, a cyclic structure, and a random structure.

Repeating unit (1) and repeating unit (2) are represented by the following formula (a-6).

(G represents a group represented by ^R1 or ^R2 . ^R1 and ^R2 have the same meanings as above. _O1/2 represents that an oxygen atom is shared with the adjacent repeating unit.)

As shown in formula (a-6), the polysilsesquioxane compound (A) has a partial structure, generally referred to as a T site, in which three oxygen atoms are bonded to a silicon atom and another group (a group represented by G) is bonded to the silicon atom.
Examples of the T site contained in the polysilsesquioxane compound (A) include a T site (T1 site) represented by the following formula (a-3), a T site (T2 site) represented by the following formula (a-4), and a T site (T3 site) represented by the following formula (a-5).

In formulae (a-3), (a-4) and (a-5), G has the same meaning as above. R ³ represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. Examples of the "alkyl group having 1 to 10 carbon atoms" of R ³ include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an s-butyl group, an isobutyl group and a t-butyl group. A plurality of R ³ may be the same or different from each other. In addition, in the above formulae (a-3) to (a-5), a silicon atom is bonded to *.

When synthesizing the polysilsesquioxane compound (A), the product contains many T1 sites and T2 sites immediately after the start of the reaction, but as the reaction proceeds, the amounts of these sites decrease and the amount of T3 sites gradually increases.
Therefore, polysilsesquioxane compounds having a high content of T1 sites or T2 sites are relatively low molecular weight compounds, whereas polysilsesquioxane compounds having a high content of T3 sites are relatively high molecular weight compounds, and the movement of the molecular chains is restricted.
Furthermore, as shown by the number of remaining reactive groups (—OR ³ ), polysilsesquioxane compounds having a high content of T1 sites and T2 sites have sufficient reactivity, whereas polysilsesquioxane compounds having a high content of T3 sites tend to have poor reactivity.

The polysilsesquioxane compound (A) satisfies the above requirement 1.
That is, in the polysilsesquioxane compound (A), the amount of the repeating unit (1) is 40 mol % or more and less than 80 mol % based on the total amount of the repeating unit (1) and the repeating unit (2).
The curable composition of the present invention has a high refractive index because it contains a polysilsesquioxane compound that satisfies requirement 1. Furthermore, when the curable composition satisfies requirement 1, the cured product is less susceptible to cracking and has improved adhesion.
In order to obtain these effects in a well-balanced manner, the amount of the repeating unit (1) is preferably from 45 to 77 mol %, more preferably from 50 to 74 mol %, and even more preferably from 55 to 71 mol %, based on the total amount of the repeating unit (1) and the repeating unit (2).

The proportions of the repeating units (1) and (2) in the polysilsesquioxane compound (A) can be determined, for example, by measuring ^{the 29} Si-NMR of the polysilsesquioxane compound (A).
The polysilsesquioxane compound (A) is soluble in various organic solvents, such as ketone solvents such as acetone, aromatic hydrocarbon solvents such as benzene, sulfur-containing solvents such as dimethyl sulfoxide, ether solvents such as tetrahydrofuran, ester solvents such as ethyl acetate, halogen-containing solvents such as chloroform, and mixed solvents consisting of two or more of these. Therefore, ^29Si -NMR of the polysilsesquioxane compound (A) in a solution state can be measured using these solvents.

The polysilsesquioxane compound (A) satisfies the above requirement 2.
That is, the polysilsesquioxane compound (A) contains a relatively large amount of T2 sites, with the amount of T2 sites being 20 to 70 mol % relative to the total amount of T1 sites, T2 sites, and T3 sites.
The curable composition of the present invention satisfies the above requirement 2 in addition to requirement 1, and therefore the cured product of the curable composition of the present invention is even less susceptible to cracking and has even improved adhesion.

That is, when a curable composition containing a polysilsesquioxane compound containing a large number of T1 sites is cured, hydrolysis reactions and condensation reactions occur excessively, and cracks are likely to occur in the cured product due to cure shrinkage.
Furthermore, since polysilsesquioxane compounds containing a large number of T3 sites are relatively high molecular weight compounds and have poor mobility, the cured product of a curable composition containing such a polysilsesquioxane compound is prone to residual stress and to cracking.

On the other hand, a curable composition containing a polysilsesquioxane compound containing a large number of T2 sites can be cured without causing excessive hydrolysis reactions or condensation reactions, and therefore cracks are less likely to occur in the cured product.
Furthermore, since a polysilsesquioxane compound containing many T2 sites does not have a particularly high molecular weight and has appropriate mobility, a cured product of a curable composition containing a polysilsesquioxane compound containing many T2 sites is less likely to develop residual stress and is less likely to develop cracks.

Since the above-mentioned effects are easily obtained, the amount of T2 sites relative to the total amount of T1 sites, T2 sites, and T3 sites is 20 to 70 mol%, preferably 22 to 60 mol%, more preferably 24 to 55 mol%, and even more preferably 26 to 50 mol%.

Furthermore, the amount of T1 sites relative to the total amount of T1 sites, T2 sites, and T3 sites is preferably 0 to 40 mol%, more preferably 0 to 30 mol%, even more preferably 0 to 20 mol%, and still more preferably 0 to 10 mol%.
When the polysilsesquioxane compound (A) contains an appropriate amount of T1 sites, a curable composition having superior curability can be obtained.
The amount of T3 sites relative to the total amount of T1 sites, T2 sites, and T3 sites is preferably 10 to 80 mol %, more preferably 20 to 70 mol %, and even more preferably 30 to 50 mol %.
When the polysilsesquioxane compound (A) contains an appropriate amount of T3 sites, the generation of by-products caused by a condensation reaction during curing can be suppressed.

The contents of the T1 site, the T2 site, and the T3 site can be determined by measuring ^{the 29} Si-NMR of the polysilsesquioxane compound (A) in a solution state.
For example, when acetone is used as the measurement solvent and TMS (tetramethylsilane) is used as the internal standard, in formulas (a-3) to (a-6), signals derived from silicon atoms in T sites where G is a phenyl group are observed at −65 to −58 ppm at the T1 site, −74 to −65 ppm at the T2 site, and −82 to −75 ppm at the T3 site, while signals derived from silicon atoms in T sites where G is a methyl group in formulas (a-3) to (a-6) are observed at −50 to −46 ppm at the T1 site, −61 to −52 ppm at the T2 site, and −70 to −61 ppm at the T3 site.

The mass average molecular weight (Mw) of the polysilsesquioxane compound (A) is preferably 500 to 25,000, more preferably 700 to 20,000, even more preferably 1,000 to 15,000, and even more preferably 2,000 to 10,000. By using a polysilsesquioxane compound (A) having a mass average molecular weight (Mw) within the above range, it becomes easier to obtain a curable composition that is less likely to crack after curing.

The molecular weight distribution (Mw/Mn) of the polysilsesquioxane compound (A) is not particularly limited, but is usually 1.0 to 10.0, preferably 1.1 to 6.0, and more preferably 1.1 to 4.0. By using the polysilsesquioxane compound (A) having a molecular weight distribution (Mw/Mn) within the above range, it becomes easier to obtain a curable composition that gives a cured product having excellent heat resistance and adhesiveness.
The weight average molecular weight (Mw) and number average molecular weight (Mn) can be determined, for example, as a polystyrene-equivalent value by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent.

The total amount of repeating units (1) and repeating units (2) in the polysilsesquioxane compound (A) is preferably 90 to 100 mol %, more preferably 95 to 100 mol %, and even more preferably 98 to 100 mol %, of all repeating units in the polysilsesquioxane compound (A).

The refractive index (nD) of the polysilsesquioxane compound (A) at 25° C. is preferably 1.46 to 1.56, more preferably 1.48 to 1.55, and even more preferably 1.50 to 1.55.
When the refractive index (nD) of the polysilsesquioxane compound (A) at 25° C. is within the range of 1.46 to 1.56, a curable composition or cured product having a high refractive index can be easily obtained.
The refractive index (nD) of the polysilsesquioxane compound (A) can be measured using an Abbe refractometer.

In the present invention, the polysilsesquioxane compound (A) may be used alone or in combination of two or more types.

The method for synthesizing the polysilsesquioxane compound (A) is not particularly limited. For example, the polysilsesquioxane compound (A) can be synthesized by polycondensing at least one type of silane compound (1) represented by the following formula (a-7) with at least one type of silane compound (2) represented by the following formula (a-8).

(In the formula, R ¹ has the same meaning as above. R ⁴ represents an alkyl group having 1 to 10 carbon atoms, X ¹ represents a halogen atom, and p represents an integer of 0 to 3. A plurality of R ^4s and a plurality of X ^1s may be the same or different from each other.)

(In the formula, R ² has the same meaning as above. R ⁵ represents an alkyl group having 1 to 10 carbon atoms, X ² represents a halogen atom, and q represents an integer of 0 to 3. A plurality of R ^5s and a plurality of X ^2s may be the same or different from each other.)

Examples of the "alkyl group having 1 to 10 carbon atoms" of R ⁴ and R ⁵ include the same as those given as the "alkyl group having 1 to 10 carbon atoms" of R ³ .
Examples of the halogen atom for X ¹ and X ² include a chlorine atom and a bromine atom.

Specific examples of the silane compound (1) include:
unsubstituted aryltrialkoxysilane compounds, such as phenyltrimethoxysilane and phenyltriethoxysilane;
unsubstituted arylhalogenoalkoxysilane compounds, such as phenylchlorodimethoxysilane, phenylchlorodiethoxysilane, phenyldichloromethoxysilane, and phenyldichloroethoxysilane;
unsubstituted aryltrihalogenosilane compounds such as phenyltrichlorosilane;
Aryltrialkoxysilane compounds having a substituent, such as 4-methylphenyltrimethoxysilane, 4-methoxyphenyltrimethoxysilane, 4-chlorophenyltrimethoxysilane, 4-methylphenyltriethoxysilane, 4-methoxyphenyltriethoxysilane, and 4-chlorophenyltriethoxysilane;
Aryl halogenoalkoxysilane compounds having a substituent, such as 4-methylphenyl chlorodimethoxysilane, 4-methoxyphenyl chlorodimethoxysilane, 4-chlorophenyl chlorodimethoxysilane, 4-methylphenyl dichloromethoxysilane, 4-methoxyphenyl dichloromethoxysilane, and 4-chlorophenyl dichloromethoxysilane;
Aryltrihalogenosilane compounds having a substituent such as 4-methylphenyltrichlorosilane, 4-methoxyphenyltrichlorosilane, and 4-chlorophenyltrichlorosilane; and the like.
These silane compounds (1) can be used either individually or in combination of two or more.

Specific examples of the silane compound (2) include:
unsubstituted alkyltrialkoxysilane compounds, such as methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, and ethyltripoxysilane;
unsubstituted alkylhalogenoalkoxysilane compounds, such as methylchlorodimethoxysilane, methylchlorodiethoxysilane, methyldichloromethoxysilane, methylbromodimethoxysilane, ethylchlorodimethoxysilane, ethylchlorodiethoxysilane, ethyldichloromethoxysilane, and ethylbromodimethoxysilane;
unsubstituted alkyltrihalogenosilane compounds, such as methyltrichlorosilane, methyltribromosilane, ethyltrichlorosilane, and ethyltribromosilane;
Alkyltrialkoxysilane compounds having a substituent, such as 2-cyanoethyltrimethoxysilane, 3-chloropropyltrimethoxysilane, 2-cyanoethyltriethoxysilane, and 3-chloropropyltriethoxysilane;
Alkylhalogenoalkoxysilane compounds having a substituent, such as 2-cyanoethyl chlorodimethoxysilane, 3-chloropropyl chlorodimethoxysilane, 2-cyanoethyl chlorodiethoxysilane, 3-chloropropyl chlorodiethoxysilane, 2-cyanoethyl dichloromethoxysilane, 3-chloropropyl dichloromethoxysilane, 2-cyanoethyl dichloroethoxysilane, and 3-chloropropyl dichloroethoxysilane;
Alkyltrihalogenosilane compounds having a substituent such as 2-cyanoethyltrichlorosilane and 3-chloropropyltrichlorosilane; and the like.
These silane compounds (2) can be used alone or in combination of two or more.

The method of polycondensing the silane compound is not particularly limited. For example, a method of adding a predetermined amount of polycondensation catalyst to a silane compound in a solvent or without a solvent, and stirring at a predetermined temperature can be mentioned. More specifically, a method of adding a predetermined amount of acid catalyst to a silane compound and stirring at a predetermined temperature can be mentioned, (a) a method of adding a predetermined amount of base catalyst to a silane compound and stirring at a predetermined temperature, (b) a method of adding a predetermined amount of acid catalyst to a silane compound and stirring at a predetermined temperature, (c) a method of adding a predetermined amount of acid catalyst to a silane compound and stirring at a predetermined temperature, and then adding an excess amount of base catalyst to make the reaction system basic, and stirring at a predetermined temperature can be mentioned.
Among these, method (a) is preferred because it allows the target polysilsesquioxane compound (A) to be obtained efficiently.

The polycondensation catalyst used may be either an acid catalyst or a base catalyst. Two or more polycondensation catalysts may be used in combination, but it is preferable to use at least an acid catalyst.
Examples of the acid catalyst include inorganic acids such as phosphoric acid, hydrochloric acid, boric acid, sulfuric acid, and nitric acid, and organic acids such as citric acid, acetic acid, methanesulfonic acid, trifluoromethanesulfonic acid, benzenesulfonic acid, and p-toluenesulfonic acid. Among these, at least one selected from phosphoric acid, hydrochloric acid, boric acid, sulfuric acid, citric acid, acetic acid, and methanesulfonic acid is preferable.

Examples of base catalysts include ammonia water; organic bases such as trimethylamine, triethylamine, lithium diisopropylamide, lithium bis(trimethylsilyl)amide, pyridine, 1,8-diazabicyclo[5.4.0]-7-undecene, aniline, picoline, 1,4-diazabicyclo[2.2.2]octane, and imidazole; organic hydroxides such as tetramethylammonium hydroxide and tetraethylammonium hydroxide; metal alkoxides such as sodium methoxide, sodium ethoxide, sodium t-butoxide, and potassium t-butoxide; metal hydrides such as sodium hydride and calcium hydride; metal hydroxides such as sodium hydroxide, potassium hydroxide, and calcium hydroxide; metal carbonates such as sodium carbonate, potassium carbonate, and magnesium carbonate; metal bicarbonates such as sodium bicarbonate and potassium bicarbonate; and the like.

The amount of polycondensation catalyst used is usually in the range of 0.05 to 10 mol%, preferably 0.1 to 5 mol%, based on the total molar amount of the silane compound.

When a solvent is used during polycondensation, the solvent used can be appropriately selected depending on the type of silane compound, etc. Examples include water; aromatic hydrocarbons such as benzene, toluene, and xylene; esters such as methyl acetate, ethyl acetate, propyl acetate, butyl acetate, and methyl propionate; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, s-butyl alcohol, and t-butyl alcohol; and the like. These solvents can be used alone or in combination of two or more.

The amount of solvent used is from 0.1 liters to 10 liters, preferably from 0.1 liters to 2 liters, per mole of the total molar amount of the silane compounds.

The temperature at which the silane compound is polycondensed is usually in the range of 0°C to the boiling point of the solvent used, preferably in the range of 20°C to 100°C. If the reaction temperature is too low, the polycondensation reaction may not proceed sufficiently. On the other hand, if the reaction temperature is too high, it becomes difficult to suppress gelation. The reaction is usually completed within 30 minutes to 30 hours.

When the polysilsesquioxane compound (A) is synthesized by the above method, the portions of ^OR4 or ^X1 of the silane compound (1) and OR5 or ^X2 of the silane compound (2 ⁾ that have not undergone dealcoholization or the like remain in the polysilsesquioxane compound (A). For this reason, the polysilsesquioxane compound (A) may contain repeating units represented by the formulas (a-3) and (a-4) in addition to the repeating units represented by the formula (a-5).

[Component (C)]
The component (C) constituting the curable composition of the present invention is a silane coupling agent.
Since the curable composition of the present invention contains the component (C), the cured product of the curable composition of the present invention has even better adhesiveness at room temperature and at high temperatures.

The silane coupling agent refers to a silane compound having a silicon atom, a functional group, and a hydrolyzable group bonded to the silicon atom.
The functional group refers to a group having reactivity with other compounds (mainly organic substances), and examples thereof include groups having a nitrogen atom, such as an amino group, a substituted amino group, an isocyanate group, a ureido group, and a group having an isocyanurate skeleton; an acid anhydride group (a group having an acid anhydride structure); a vinyl group; an allyl group; an epoxy group; a (meth)acrylic group; and a mercapto group.
In the present invention, the silane coupling agent may be used alone or in combination of two or more kinds.

The content of the silane coupling agent is preferably 0.1 to 70 parts by mass, more preferably 1 to 60 parts by mass, even more preferably 5 to 55 parts by mass, still more preferably 10 to 50 parts by mass, and particularly preferably 15 to 45 parts by mass, relative to 100 parts by mass of the polysilsesquioxane compound (A).
By using a curable composition having a silane coupling agent content within the above range, a cured product having excellent adhesion at room temperature and at high temperatures can be formed.

As the silane coupling agent, a silane coupling agent having a nitrogen atom in the molecule or a silane coupling agent having an acid anhydride structure in the molecule is preferred, and a silane coupling agent having an isocyanurate structure in the molecule or a silane coupling agent having a succinic anhydride structure in the molecule is even more preferred.

Examples of silane coupling agents having a nitrogen atom in the molecule include trialkoxysilane compounds represented by the following formula (c-1), dialkoxyalkylsilane compounds or dialkoxyarylsilane compounds represented by the following formula (c-2), etc.

In the above formula, R ^a represents an alkoxy group having 1 to 6 carbon atoms, such as a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, a t-butoxy group, etc. A plurality of R ^a's may be the same or different.
R ^b represents an alkyl group having 1 to 6 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, or a t-butyl group; or an aryl group having or having no substituent, such as a phenyl group, a 4-chlorophenyl group, a 4-methylphenyl group, or a 1-naphthyl group.

^Rc represents an organic group having a nitrogen atom and having 1 to 10 carbon atoms. ^Rc may further be bonded to another group containing a silicon atom.
Specific examples of the organic group having 1 to 10 carbon atoms for R ^c include an N-2-(aminoethyl)-3-aminopropyl group, a 3-aminopropyl group, an N-(1,3-dimethyl-butylidene)aminopropyl group, a 3-ureidopropyl group, and an N-phenyl-aminopropyl group.

Among the compounds represented by the above formula (c-1) or (c-2), compounds in which R ^c is an organic group bonded to a group containing another silicon atom include those which are bonded to another silicon atom via an isocyanurate skeleton to form an isocyanurate-based silane coupling agent, and those which are bonded to another silicon atom via a urea skeleton to form a urea-based silane coupling agent.

Among these, as silane coupling agents having a nitrogen atom in the molecule, isocyanurate-based silane coupling agents and urea-based silane coupling agents are preferred because they tend to give cured products with superior adhesion, and furthermore, those having four or more alkoxy groups bonded to silicon atoms in the molecule are preferred.
"Having four or more alkoxy groups bonded to a silicon atom" means that the total number of alkoxy groups bonded to the same silicon atom and alkoxy groups bonded to different silicon atoms is four or more.

An example of an isocyanurate-based silane coupling agent having four or more alkoxy groups bonded to a silicon atom is a compound represented by the following formula (c-3). An example of an urea-based silane coupling agent having four or more alkoxy groups bonded to a silicon atom is a compound represented by the following formula (c-4).

In the formula, R ^a has the same meaning as above, and t1 to t5 each independently represent an integer of 1 to 10, preferably an integer of 1 to 6, and particularly preferably 3.

Among these, as silane coupling agents having a nitrogen atom in the molecule, it is preferable to use 1,3,5-N-tris(3-trimethoxysilylpropyl)isocyanurate, 1,3,5-N-tris(3-triethoxysilylpropyl)isocyanurate (hereinafter referred to as "isocyanurate compound"), N,N'-bis(3-trimethoxysilylpropyl)urea, N,N'-bis(3-triethoxysilylpropyl)urea (hereinafter referred to as "urea compound"), and combinations of the above-mentioned isocyanurate compounds and urea compounds.

When the curable composition of the present invention contains a silane coupling agent having a nitrogen atom in the molecule, its content is not particularly limited, but the mass ratio of the above-mentioned (A) component to the silane coupling agent having a nitrogen atom in the molecule [(A) component: silane coupling agent having a nitrogen atom in the molecule] is preferably 100:0.1 to 100:65, more preferably 100:0.3 to 100:60, more preferably 100:1 to 100:50, even more preferably 100:3 to 100:40, and particularly preferably 100:5 to 100:35.
The curable composition containing the component (A) and the silane coupling agent having a nitrogen atom in the molecule in such a ratio will have a cured product with excellent heat resistance and adhesiveness.

A silane coupling agent having an acid anhydride structure in the molecule is an organosilicon compound that has both a group having an acid anhydride structure and a hydrolyzable group in one molecule. Specific examples include compounds represented by the following formula (c-5).

In the formula, Q represents a group having an acid anhydride structure, ^Rd represents an alkyl group having 1 to 6 carbon atoms or a phenyl group having or not having a substituent, ^Re represents an alkoxy group having 1 to 6 carbon atoms or a halogen atom, i and k represent integers of 1 to 3, j represents an integer of 0 to 2, and i+j+k=4. When j is 2, ^Rd may be the same or different from each other. When k is 2 or 3, multiple ^Re may be the same or different from each other. When i is 2 or 3, multiple Q may be the same or different from each other.
Q is represented by the following formula:

(In the formula, h represents an integer from 0 to 10.) Groups represented by (Q1) are particularly preferred.

Examples of silane coupling agents having an acid anhydride structure in the molecule include tri(C1-6)alkoxysilyl(C2-8)alkyl succinic anhydrides such as 2-(trimethoxysilyl)ethyl succinic anhydride, 2-(triethoxysilyl)ethyl succinic anhydride, 3-(trimethoxysilyl)propyl succinic anhydride, and 3-(triethoxysilyl)propyl succinic anhydride;
Di(C1-6)alkoxymethylsilyl(C2-8)alkyl succinic anhydrides, such as 2-(dimethoxymethylsilyl)ethyl succinic anhydride;
(C1-6)alkoxydimethylsilyl(C2-8)alkyl succinic anhydrides such as 2-(methoxydimethylsilyl)ethyl succinic anhydride;

Trihalogenosilyl (C2 to C8) alkyl succinic anhydrides, such as 2-(trichlorosilyl)ethyl succinic anhydride and 2-(tribromosilyl)ethyl succinic anhydride;
Dihalogenomethylsilyl (C2-C8) alkyl succinic anhydrides, such as 2-(dichloromethylsilyl)ethyl succinic anhydride;
halogenodimethylsilyl (C2-8) alkyl succinic anhydrides such as 2-(chlorodimethylsilyl)ethyl succinic anhydride; and the like.

Among these, tri(C1-6)alkoxysilyl(C2-8)alkyl succinic anhydride is preferred as a silane coupling agent having an acid anhydride structure in the molecule, with 3-(trimethoxysilyl)propyl succinic anhydride or 3-(triethoxysilyl)propyl succinic anhydride being particularly preferred.

When the curable composition of the present invention contains a silane coupling agent having an acid anhydride structure in its molecule, its content is not particularly limited, but the mass ratio of the above component (A) to the silane coupling agent having an acid anhydride structure in its molecule [component (A) : silane coupling agent having an acid anhydride structure in its molecule] is preferably 100:0.1 to 100:30, more preferably 100:0.3 to 100:20, more preferably 100:0.5 to 100:15, and even more preferably 100:1 to 100:10.
The curable composition containing the component (A) and a silane coupling agent having an acid anhydride structure in the molecule in such a ratio will have a cured product with superior adhesion.

[Curable Composition]
In the curable composition of the present invention, the total amount of the component (A) and the component (C) is preferably 50 to 100 mass %, and more preferably 70 to 100 mass %, of the solid content of the curable composition.
In the present invention, the term "solid content" refers to components other than the solvent in the curable composition.

The curable composition of the present invention may contain, as the component (B), fine particles having an average primary particle diameter of 5 nm or more and 40 nm or less (hereinafter, sometimes referred to as "fine particles (B)").
The curable composition containing the fine particles (B) has excellent workability in the coating step.
Since this effect is more easily obtained, the average primary particle size of the fine particles (B) is preferably 5 to 30 nm, and more preferably 5 to 20 nm.

The average primary particle diameter of the microparticles (B) is determined by observing the shape of the microparticles using a transmission electron microscope.

Examples of the material of the fine particles (B) include metals; metal oxides; minerals; metal carbonates such as calcium carbonate and magnesium carbonate; metal sulfates such as calcium sulfate and barium sulfate; metal hydroxides such as aluminum hydroxide; metal silicates such as aluminum silicate, calcium silicate and magnesium silicate; inorganic components such as silica; silicone; and organic components such as acrylic polymers.
The fine particles (B) used may be surface-modified.

The fine particles (B) may be used alone or in combination of two or more kinds.
When the curable composition of the present invention contains fine particles (B) [component (B)], the content of component (B) is not particularly limited, but the amount is such that the mass ratio of component (A) to component (B) [component (A) : component (B)] is preferably 100:0.1 to 100:90, more preferably 100:0.2 to 100:60, more preferably 100:0.3 to 100:50, more preferably 100:0.5 to 100:40, and more preferably 100:0.8 to 100:30. By using component (B) within the above range, the effect of adding component (B) can be more effectively exhibited.

The curable composition of the present invention may contain other components as long as the object of the present invention is not impaired.
Examples of other components include antioxidants, ultraviolet absorbers, and light stabilizers.

Antioxidants are added to prevent oxidative deterioration during heating. Examples of antioxidants include phosphorus-based antioxidants, phenol-based antioxidants, and sulfur-based antioxidants.

Phosphorus-based antioxidants include phosphites, oxaphosphaphenanthrene oxides, etc. Phenol-based antioxidants include monophenols, bisphenols, polymeric phenols, etc. Sulfur-based antioxidants include dilauryl-3,3'-thiodipropionate, dimyristyl-3,3'-thiodipropionate, distearyl-3,3'-thiodipropionate, etc.

These antioxidants may be used alone or in combination of two or more. The content of the antioxidant is not particularly limited, but is usually 10% by mass or less based on component (A).

The ultraviolet absorber is added for the purpose of improving the light resistance of the resulting cured product.
Examples of the ultraviolet absorbent include salicylic acids, benzophenones, benzotriazoles, and hindered amines.
The ultraviolet absorbing agent may be used alone or in combination of two or more. The content of the ultraviolet absorbing agent is not particularly limited, but is usually 10 mass % or less based on the component (A).

The light stabilizer is added for the purpose of improving the light resistance of the resulting cured product.
Examples of the light stabilizer include hindered amines such as poly[{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl}{(2,2,6,6-tetramethyl-4-piperidine)imino}hexamethylene{(2,2,6,6-tetramethyl-4-piperidine)imino}].
These light stabilizers may be used alone or in combination of two or more. The content of the light stabilizer is usually 20 mass % or less based on the component (A).

The curable composition of the present invention may contain a diluent. The diluent is not particularly limited as long as it can dissolve or disperse the components of the curable composition of the present invention. One type of diluent may be used, or two or more types may be used in combination.

When the curable composition of the present invention contains a diluent, the content thereof is an amount such that the solids concentration is preferably 60% by mass or more and less than 100% by mass, more preferably 65 to 98% by mass, and even more preferably 70 to 95% by mass.
The polysilsesquioxane compound (A) used in the present invention often has a relatively small molecular weight. A curable composition containing such a polysilsesquioxane compound (A) has good coatability even if it does not contain a large amount of a diluent (i.e., even if the solid content concentration is high).
When a curable composition having a high solid content is used, the cured product contains almost no solvent, and a cured product having consistent properties can be stably formed without strict control of the drying conditions and curing conditions of the coating film.

The curable composition of the present invention has a high refractive index because it contains the polysilsesquioxane compound (A).
The refractive index (nD) of the curable composition of the present invention at 25° C. is usually 1.46 or more, preferably 1.46 to 1.56, more preferably 1.46 to 1.54, and even more preferably 1.47 to 1.53.
The refractive index (nD) of the curable composition can be measured using the method described in the Examples.

The curable composition of the present invention can be prepared, for example, by mixing the above-mentioned components (A) and (C) and, if desired, other components in a predetermined ratio, followed by degassing.
The mixing method and the degassing method are not particularly limited, and known methods can be used.

2) Cured Product The cured product of the present invention is obtained by curing the curable composition of the present invention.
The method for curing the curable composition of the present invention includes heat curing. The heating temperature during curing is usually 100 to 200° C., and the heating time is usually 10 minutes to 20 hours, preferably 30 minutes to 10 hours.

The cured product of the present invention has excellent heat resistance and adhesiveness.
The fact that the cured product of the present invention has these properties can be confirmed, for example, as follows. That is, a predetermined amount of the curable composition of the present invention is applied to the mirror surface of a silicon chip, the applied surface is placed on an adherend, pressed, and cured by heat treatment. This is left for 30 seconds on the measurement stage of a bond tester that has been heated to a predetermined temperature (e.g., 23°C, 100°C), and a stress is applied to the adhesive surface in the horizontal direction (shear direction) from a position 50 μm above the adherend, and the adhesive force between the test piece and the adherend is measured.

The adhesive strength of the cured product of the present invention at 23° C. is preferably 100 N/4 mm ² or more, and more preferably 120 N/4 mm ² or more.
The adhesive strength of the cured product of the present invention at 100°C is preferably 40 N/4 ^mm2 or more, and more preferably 45 N/4 ^mm2 or more.
In this specification, "4 mm ² " means "2 mm square," that is, 2 mm×2 mm (a square with each side being 2 mm).

The cured product of the present invention has a high refractive index and excellent adhesiveness, and is therefore preferably used as an adhesive layer having a high refractive index.
The refractive index (nD) of the cured product of the present invention at 25° C. is usually 1.46 or more, preferably 1.46 to 1.56, more preferably 1.46 to 1.54, and even more preferably 1.47 to 1.53.
The refractive index (nD) of the cured product can be measured using an Abbe refractometer.

Because of the above-mentioned properties, the cured product of the present invention is preferably used as a material for fixing optical elements.

3) Method for Using the Curable Composition The method of the present invention is a method for using the curable composition of the present invention as an adhesive for an optical element fixing material or a sealing material for an optical element fixing material.
Examples of optical elements include light emitting elements such as LEDs and LDs, light receiving elements, composite optical elements, and optical integrated circuits.

<Adhesive for fixing optical elements>
The curable composition of the present invention can be suitably used as an adhesive for fixing optical elements.
The method of using the curable composition of the present invention as an adhesive for an optical element fixing material includes applying the composition to one or both of the adhesive surfaces of the materials to be bonded (such as an optical element and its substrate), pressing the composition, and then heating and curing the composition to firmly bond the materials to be bonded together. The amount of the curable composition to be applied is not particularly limited, and may be any amount that can firmly bond the materials to be bonded together by curing the composition. Usually, the amount is such that the thickness of the coating film of the curable composition becomes 0.5 to 5 μm, preferably 1 to 3 μm.

Substrate materials for bonding optical elements include glasses such as soda lime glass and heat-resistant hard glass; ceramics; sapphire; metals such as iron, copper, aluminum, gold, silver, platinum, chromium, titanium and alloys of these metals, and stainless steel (SUS302, SUS304, SUS304L, SUS309, etc.); and synthetic resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, ethylene-vinyl acetate copolymer, polystyrene, polycarbonate, polymethylpentene, polysulfone, polyether ether ketone, polyether sulfone, polyphenylene sulfide, polyetherimide, polyimide, polyamide, acrylic resin, norbornene resin, cycloolefin resin, glass epoxy resin, etc.

The heating temperature for heat curing varies depending on the curable composition used, but is usually 100 to 200°C. The heating time is usually 10 minutes to 20 hours, preferably 30 minutes to 10 hours.

<Sealing material for fixing optical elements>
The curable composition of the present invention can be suitably used as a sealing material for fixing optical elements.
Examples of the method for using the curable composition of the present invention as a sealing material for fixing optical elements include a method in which the composition is molded into a desired shape to obtain a molded body containing an optical element, and then the molded body is heated and cured to produce a sealed optical element.
The method for molding the curable composition of the present invention into a desired shape is not particularly limited, and any known molding method such as a typical transfer molding method or a casting method can be used.

The heating temperature for heat curing varies depending on the curable composition used, but is usually 100 to 200°C. The heating time is usually 10 minutes to 20 hours, preferably 30 minutes to 10 hours.

The resulting sealed optical element has excellent heat resistance and adhesion because it uses the curable composition of the present invention.

The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples.

(Average Molecular Weight Measurement)
The mass average molecular weight (Mw) and number average molecular weight (Mn) of the polysilsesquioxane compound were measured using the following apparatus and conditions in terms of standard polystyrene.
Apparatus name: HLC-8220GPC, manufactured by Tosoh Corporation Column: TSKgel GMHXL, TSKgel GMHXL, and TSKgel 2000HXL connected in sequence Solvent: Tetrahydrofuran Injection volume: 20 μl
Measurement temperature: 40°C
Flow rate: 0.6 ml/min Detector: differential refractometer

( ^29Si -NMR measurement)
In order to examine the repeating units and their amounts in the polysilsesquioxane compound, ²⁹ Si-NMR measurement was carried out under the following conditions.
Apparatus: Bruker Biospin AV-500
²⁹ Si-NMR resonance frequency: 99.352MHz
Probe: 5 mmφ solution probe Measurement temperature: room temperature (25° C.)
Sample rotation speed: 20 kHz
Measurement method: Inverse gate decoupling method
²⁹ Si Flip angle: 90°
^29Si 90° Pulse width: 8.0 μs
Repeat time: 5s
Number of measurements: 9200 Observation width: 30 kHz

( ^29Si -NMR sample preparation method)
In order to shorten the relaxation time, Fe(acac) ₃ was added as a relaxation reagent and the measurement was performed.
Polysilsesquioxane compound concentration: 15% by mass
Fe(acac) ₃ concentration: 0.6% by mass
Measurement solvent: acetone Internal standard: TMS

(Waveform processing analysis)
For each peak in the spectrum after Fourier transformation, the chemical shift was determined from the position of the peak top, and each peak was integrated in the following range: Based on the obtained values, the proportions of T1 site, T2 site, and T3 site were calculated.
T site having a phenyl group (T1: -65 to -58 ppm, T2: -74 to -65 ppm, T3: -82 to -75 ppm)
T site having a methyl group (T1: -50 to -46 ppm, T2: -61 to -52 ppm, T3: -70 to -61 ppm)

(Refractive Index)
The refractive index (nD) of the polysilsesquioxane compound was measured at 25° C. using a multi-wavelength Abbe refractometer (DR-M2, manufactured by Atago Co., Ltd.).

(Production Example 1)
A 300 ml eggplant-shaped flask was charged with 9.34 g (47.1 mmol) of phenyltrimethoxysilane and 8.40 g (47.1 mmol) of methyltriethoxysilane, and then an aqueous solution of 0.025 g of 35 mass % hydrochloric acid (0.25 mol % of HCl relative to the total amount of silane compounds) dissolved in 5.09 g of distilled water was added with stirring, and the entire volume was stirred at 30° C. for 2 hours, then heated to 80° C. and stirred for 20 hours.
After the reaction solution was cooled to room temperature, 50 g of propyl acetate and 100 g of water were added thereto and subjected to a liquid separation treatment to obtain an organic layer containing a reaction product. Magnesium sulfate was added to this organic layer and subjected to a drying treatment. After removing magnesium sulfate by filtration, the organic layer was concentrated with an evaporator, and the obtained concentrate was then vacuum dried to obtain a polysilsesquioxane compound (A1).

(Production Example 2)
A 300 ml eggplant-shaped flask was charged with 12.55 g (63.3 mmol) of phenyltrimethoxysilane and 4.83 g (27.1 mmol) of methyltriethoxysilane, and then an aqueous solution of 0.024 g of 35 mass % hydrochloric acid (0.25 mol % of HCl relative to the total amount of the silane compound) dissolved in 4.88 g of distilled water was added with stirring, and the entire volume was stirred at 30° C. for 2 hours, then heated to 80° C. and stirred for 20 hours.
While continuing to stir the contents, 17 g of propyl acetate and 0.149 g of 28% by mass ammonia water (2.5 mol % relative to phenyltriethoxysilane) were added thereto, and the temperature was raised to 80° C. and stirring was continued for 20 hours.
The reaction liquid was allowed to cool to room temperature, and then separation, drying, and the like were carried out in the same manner as in Production Example 1 to obtain a polysilsesquioxane compound (A2).

(Production Example 3)
A 300 ml eggplant-shaped flask was charged with 9.34 g (47.1 mmol) of phenyltrimethoxysilane and 8.40 g (47.1 mmol) of methyltriethoxysilane, and then an aqueous solution of 0.294 g of 35 mass % hydrochloric acid (HCl was 3.00 mol % relative to the total amount of silane compounds) dissolved in 5.09 g of distilled water was added with stirring, and the entire volume was stirred at 30° C. for 2 hours, then heated to 80° C. and stirred for 20 hours.
After the reaction solution was cooled to room temperature, 50 g of propyl acetate and 100 g of water were added thereto and subjected to a liquid separation treatment to obtain an organic layer containing a reaction product. Magnesium sulfate was added to this organic layer and subjected to a drying treatment. After removing magnesium sulfate by filtration, the organic layer was concentrated with an evaporator, and the obtained concentrate was then vacuum dried to obtain a polysilsesquioxane compound (A3).

(Comparative Production Example 1)
A 300 ml eggplant-shaped flask was charged with 14.455 g (72.9 mmol) of phenyltrimethoxysilane, and then an aqueous solution of 0.0188 g of 35 mass % hydrochloric acid (0.25 mol % of HCl relative to phenyltrimethoxysilane) dissolved in 3.937 g of distilled water was added with stirring, and the entire volume was stirred at 30° C. for 2 hours, then heated to 70° C. and stirred for 22 hours.
While continuing to stir the contents, 15 g of propyl acetate and 0.0109 g of 28% by mass ammonia water (0.25 mol % relative to phenyltriethoxysilane) were added thereto, and the temperature was raised to 80° C. and stirring was continued for 20 hours.
The reaction liquid was allowed to cool to room temperature, and then separation, drying, and the like were carried out in the same manner as in Production Example 1 to obtain a polysilsesquioxane compound (A4).

(Comparative Production Example 2)
A 300 ml eggplant-shaped flask was charged with 28.77 g (145.1 mmol) of phenyltrimethoxysilane and 0.2675 g (1.5 mmol) of methyltriethoxysilane, and then an aqueous solution of 0.477 g of 35 mass % hydrochloric acid (HCl was 3 mol % relative to the total amount of the silane compound) dissolved in 8.24 g of distilled water was added with stirring, and the entire volume was stirred at 30° C. for 2 hours, then heated to 80° C. and stirred for 20 hours.
The reaction liquid was allowed to cool to room temperature, and then separation, drying and other treatments were carried out in the same manner as in Production Example 1 to obtain a polysilsesquioxane compound (A5).

Details of the obtained polysilsesquioxane compound (PSQ) are shown in Table 1.

The compounds used in the examples, comparative examples, and reference examples are shown below.

(Silane coupling agent)
Silane coupling agent (C1): 1,3,5-N-tris[3-(trimethoxysilyl)propyl]isocyanurate Silane coupling agent (C2): 3-(trimethoxysilyl)propylsuccinic anhydride

(Filler)
Silica fine particles: (manufactured by Nippon Aerosil Co., Ltd., product name "AEROSIL RX300", average primary particle size: 7 nm, specific surface area: 210 m ² /g)

Example 1
5 parts by mass of silica fine particles were added to 100 parts by mass of polysilsesquioxane compound (A1), and further a mixed solvent of diethylene glycol monobutyl ether acetate: tripropylene glycol-n-butyl ether = 40:60 (mass ratio) was added, and the whole was stirred. After dispersion treatment with a three-roll mill, 30 parts by mass of silane coupling agent (C1) and 3 parts by mass of silane coupling agent (C2) were added, and the whole was thoroughly mixed and degassed to obtain a curable composition with a solid content concentration of 80% by mass.

Example 2
A curable composition having a solid content concentration of 80 mass% was obtained in the same manner as in Example 1, except that the polysilsesquioxane compound (A2) was used instead of the polysilsesquioxane compound (A1) in Example 1, the content of the silica fine particles was changed to 20 parts by mass, and the amount of the mixed solvent was further changed.

Example 3
A curable composition having a solid content concentration of 80 mass % was obtained in the same manner as in Example 1, except that the polysilsesquioxane compound (A3) was used instead of the polysilsesquioxane compound (A1) in Example 1.

(Comparative Example 1)
A curable composition having a solid content concentration of 80 mass% was obtained in the same manner as in Example 1, except that the polysilsesquioxane compound (A4) was used instead of the polysilsesquioxane compound (A1), the content of the silica fine particles was changed to 20 parts by mass, and the amount of the mixed solvent was further changed.

(Comparative Example 2)
A curable composition having a solid content concentration of 78 mass% was obtained in the same manner as in Example 1, except that in Example 1, the polysilsesquioxane compound (A5) was used instead of the polysilsesquioxane compound (A1), the silane coupling agent (C1) and the silane coupling agent (C2) were not used, and the amount of the mixed solvent was changed.

(Comparative Example 3)
A curable composition having a solid content concentration of 75 mass% was obtained in the same manner as in Example 1, except that the silane coupling agent (C1) and the silane coupling agent (C2) were not used and the amount of the mixed solvent was changed.

The curable compositions obtained in the Examples, Comparative Examples, and Reference Examples were subjected to the following measurements and tests.
[Refractive index measurement]
The refractive index (nD) of the curable composition was measured at 25° C. using a multi-wavelength Abbe refractometer (DR-M2, manufactured by Atago Co., Ltd.).

[Crack resistance evaluation]
The curable compositions obtained in the examples and comparative examples were applied to the mirror surface of a square glass chip with a side length of 0.5 mm to a thickness of about 2 μm, and the applied surface was placed on an adherend (silver-plated copper plate) and pressed. Thereafter, the composition was heat-treated at 170° C. for 2 hours to harden the composition, and an adherend with a test piece was obtained. For each type of curable composition, 20 adherends with a test piece were prepared. The resin part (fillet part) protruding from the glass chip was observed using a scanning electron microscope (Keyence Corporation, VE-9800S), and the number of samples with cracks was counted. The crack occurrence rate was evaluated as "A" for 0% or more and less than 25%, "B" for 25% or more and less than 50%, and "C" for 50% or more and 100%.

[Adhesive strength evaluation]
The curable compositions obtained in the examples and comparative examples were applied to the mirror surface of a square silicon chip with a side length of 2 mm (area of 4 mm ² ) to a thickness of about 2 μm, and the applied surface was placed on an adherend (silver-plated copper plate) and pressed. Then, the composition was heat-treated at 170° C. for 2 hours to cure the composition, and an adherend with a test piece was obtained. The adherend with the test piece was left for 30 seconds on the measurement stage of a bond tester (manufactured by Daige, series 4000) that had been heated to a predetermined temperature (23° C., 100° C.), and a stress was applied to the adhesive surface in the horizontal direction (shear direction) at a speed of 200 μm/s from a position 50 μm above the adherend, and the adhesive strength (N/4 mm ² ) between the test piece and the adherend at 23° C. and 100° C. was measured.

The measurement and evaluation results are shown in Table 2.

The above examples, comparative examples and reference examples reveal the following.
The curable compositions of Examples 1 to 3 contain polysilsesquioxane compounds (PSQ(A1), PSQ(A2), and PSQ(A3)) having the repeating unit (1), and therefore have an appropriately high refractive index.
The curable compositions of Examples 1 to 3 contain a silane coupling agent. Furthermore, PSQ(A1), PSQ(A2), and PSQ(A3) all have the repeating unit (2) and contain a suitable amount of T2 sites. Therefore, the cured products of Examples 1 to 3 are excellent in crack resistance and adhesion.
On the other hand, the curable composition of Comparative Example 1 also has a high refractive index because it contains a polysilsesquioxane compound (PSQ(A4)) having a high content of the repeating unit (1).
However, since PSQ (A4) does not have the repeating unit (2) and furthermore does not have a high proportion of T2 sites, the cured product of the curable composition of Comparative Example 1 is poor in crack resistance.
On the other hand, the curable compositions obtained in Comparative Examples 2 and 3 did not contain a silane coupling agent, and therefore the cured products thereof did not have sufficient adhesive strength.

Claims (10)

A curable composition comprising the following components (A) and (C):
Component (A): Formula (a-1) below

[R ¹ represents an unsubstituted aryl group having 6 to 12 carbon atoms or a substituted aryl group having 6 to 12 carbon atoms.]
A repeating unit represented by the following formula (a-2):

[ ^R2 represents an unsubstituted alkyl group having 1 to 10 carbon atoms or a substituted alkyl group having 1 to 10 carbon atoms.]
The polysilsesquioxane compound has a repeating unit represented by the formula: [repeating unit (2)], and the total amount of repeating units (1) and (2) in component (A) is 90 to 100 mol % of all repeating units in component (A) , and satisfies the following requirements 1 and 2 [requirement 1].
The amount of the repeating unit (1) is 40 mol % or more and less than 80 mol % based on the total amount of the repeating unit (1) and the repeating unit (2).
[Requirement 2]
The amount of the T2 sites is 20 to 70 mol % relative to the total amount of the T sites (T1 sites) represented by the following formula (a-3), the T sites (T2 sites) represented by the following formula (a-4), and the T sites (T3 sites) represented by the following formula (a-5):

(G represents a group represented by ^R1 or ^R2 . ^R3 represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. * represents a silicon atom bonded thereto.)
Component (C): Silane coupling agent The curable composition according to claim 1, wherein the mass average molecular weight (Mw) of component (A) is 500 to 25,000. 3. The curable composition according to claim 1, wherein the content of the component (C) is 0.1 to 70 parts by mass per 100 parts by mass of the component (A). The curable composition according to any one of claims 1 to 3 , wherein the total amount of the component (A) and the component (C) is 50 to 100 mass % of the solid content of the curable composition. The curable composition according to any one of claims 1 to 4, further comprising a diluent and having a solid content concentration of 60% by mass or more and less than 100% by mass. The curable composition according to any one of claims 1 to 5 , having a refractive index (nD) at 25°C of 1.46 to 1.56. A cured product obtained by curing the curable composition according to any one of claims 1 to 6 . The cured product according to claim 7, which is a material for fixing optical elements. A method for using the curable composition according to any one of claims 1 to 6 as an adhesive for fixing optical elements. A method for using the curable composition according to any one of claims 1 to 6 as a sealing material for fixing optical elements.