JP7535403B2 - Thermosetting composition and cured product - Google Patents

Description

This disclosure relates to a thermosetting composition and a cured product of the thermosetting composition.

In recent years, optical semiconductor devices have become smaller, and the resin (sealant) that covers the optical semiconductor element in such optical semiconductor devices is required to have high heat resistance and transparency. Conventionally, as a sealant for forming a sealant with high heat resistance, for example, an epoxy resin composition containing an epoxy resin having an isocyanuric ring and a polycarboxylic acid resin is known (Patent Document 1).

As a sealant with low viscosity after mixing, for example, a thermosetting composition containing an acid anhydride and an epoxy resin is known (Patent Document 2). The viscosity of this thermosetting composition after mixing is reduced by adjusting the content of cyclohexane-1,2,4-tricarboxylic acid-1,2-anhydride in the acid anhydride and the content of alicyclic epoxy resin in the epoxy resin.

JP 2016-37507 A JP 2008-81596 A

In Patent Document 1, the viscosity of the epoxy resin composition is high. Therefore, there is a problem that it is difficult to pour it into a narrow gap as a sealant for an optical semiconductor. In Patent Document 2, the viscosity at 30°C immediately after the thermosetting composition is prepared is 5 Pa·s or less, but the thermosetting composition is prepared so that the viscosity increase ratio after the thermosetting composition is prepared and left for 7 hours is 5 times or less than that after preparation. That is, the thermosetting composition in Patent Document 2 may include a composition whose viscosity is close to 25 Pa·s after the thermosetting composition is prepared and left for 7 hours. A thermosetting composition whose viscosity is close to 25 Pa·s has a high viscosity and does not have a sufficiently low viscosity. Therefore, when the thermosetting composition is poured into a narrow gap as a sealant for an optical semiconductor, the workability may be reduced. In addition, if the viscosity of the thermosetting composition is high, voids may be generated when sealing the optical semiconductor using a dispenser or the like, and the transparency or reliability may be reduced.

Therefore, the object of the present disclosure is to provide a thermosetting composition that can form a cured product having high heat resistance and transparency, has low viscosity, and exhibits little change in viscosity, and to provide a cured product of the thermosetting composition.

As a result of intensive research to achieve the above object, the inventors of the present disclosure have found that a thermosetting composition containing an epoxy mixture containing triglycidyl isocyanate with a flexible chain introduced therein and an acid anhydride curing agent containing a specific acid anhydride forms a cured product having high heat resistance and transparency, has low viscosity, and can maintain small changes in viscosity. The present disclosure has been completed based on these findings.

［式中、Ｒ¹は、炭素数１～１８のアルキレン基を示し、各Ｒ¹は同一又は異なっていてもよい。］

［式中、Ｒ²は、式（２）で表される酸無水物におけるシクロヘキサン環のいずれの炭素原子上を示す。Ｒ²は、カルボキシル基を含む基を示し、Ｒ²は、一つ又は複数である。］ That is, the present disclosure provides a thermosetting composition comprising an epoxy mixture (A) containing an epoxy compound represented by the following formula (1) and other epoxy compounds, an acid anhydride curing agent (B) containing an acid anhydride represented by the following formula (2), and a curing accelerator (C), and having a viscosity of 1 Pa s or less at 25° C.:

[In the formula, R ¹ represents an alkylene group having 1 to 18 carbon atoms, and each R ¹ may be the same or different.]

[In the formula, ^R2 represents any carbon atom on the cyclohexane ring in the acid anhydride represented by formula (2). ^R2 represents a group containing a carboxyl group, and ^R2 is one or more.]

The curing accelerator (C) may contain one or more curing accelerators selected from compounds consisting of phosphorus-based oxidation accelerators and organic acid metal salts.

The other epoxy compounds may include alicyclic epoxy compounds.

The alicyclic epoxy compound may include a compound having an epoxy group composed of two adjacent carbon atoms and an oxygen atom that constitute an alicyclic ring.

［式中、Ｒ³は単結合又は連結基を示す。上記連結基は、二価の炭化水素基、炭素－炭素二重結合の一部若しくは全部がエポキシ化されたアルケニレン基、カルボニル基、エーテル結合、エステル結合、カーボネート基、アミド基、又はこれらが複数個連結した基である。］ The compound having an epoxy group composed of two adjacent carbon atoms and an oxygen atom constituting the alicyclic ring may at least include a siloxane derivative having two or more epoxy groups in the molecule, or an alicyclic epoxy compound represented by the following formula (1-1):

[In the formula, ^R3 represents a single bond or a linking group. The linking group is a divalent hydrocarbon group, an alkenylene group in which some or all of the carbon-carbon double bonds have been epoxidized, a carbonyl group, an ether bond, an ester bond, a carbonate group, an amide group, or a group in which a plurality of these groups are linked together.]

The acid anhydride curing agent (B) may contain an acid anhydride other than the acid anhydride represented by formula (2).

The thermosetting composition may further contain an antioxidant (D).

The content of the acid anhydride curing agent (B) may be 0.4 to 0.8 equivalents per equivalent of the epoxy mixture (A).

The thermosetting composition may be used for sealing optical semiconductors.

The present disclosure provides a cured product of the above-mentioned thermosetting composition.

The thermosetting composition of the present disclosure has the above-mentioned configuration, and by curing the thermosetting composition, a cured product having high heat resistance and transparency can be formed. In addition, the thermosetting composition of the present disclosure has the above-mentioned configuration, and therefore has low viscosity and can maintain small viscosity changes. This suppresses the occurrence of voids and improves workability when sealing optical semiconductors. In addition, the thermosetting composition of the present disclosure can be suitably used as a composition for sealing optical semiconductors.

The following describes the embodiments for implementing the present disclosure. Each configuration and combination of configurations in each embodiment is merely an example, and additions, omissions, substitutions, and other modifications of configurations are possible as appropriate without departing from the spirit of the present disclosure. The present disclosure is not limited to the embodiments, but is limited only by the claims.

<Thermosetting Composition>
The thermosetting composition of the present disclosure includes an epoxy mixture (A), an acid anhydride curing agent (B), and a curing accelerator (C). The viscosity of the thermosetting composition, the epoxy mixture (A), the acid anhydride curing agent (B), the curing accelerator (C), and other components (additives) that may be included in the thermosetting composition will be described in detail below.

The viscosity of the thermosetting composition of the present disclosure at 25°C (viscosity immediately after mixing all components in the thermosetting composition) is 1 Pa·s or less, preferably 60 to 800 mPa·s, more preferably 100 to 650 mPa·s, and even more preferably 150 to 500 mPa·s. By making the viscosity at 25°C 60 mPa·s or more, the workability during casting tends to improve and the heat resistance of the cured product tends to be further improved. On the other hand, by making the viscosity at 25°C 1 Pa·s or less, the workability during casting tends to improve and the cured product tends to be less prone to defects due to poor casting. The viscosity of the thermosetting composition of the present disclosure at 25°C is measured using an E-type viscometer (trade name "TV-25 type H", manufactured by Toki Sangyo Co., Ltd.) under the following conditions: rotor: standard 1°34' x R24, temperature: 25°C, and rotation speed: 0.5 to 10 rpm.

In addition, the viscosity of the thermosetting composition of the present disclosure at 25° C. changes little. For example, the viscosity immediately after the preparation of the thermosetting composition of the present disclosure (the viscosity immediately after mixing all the components in the thermosetting composition) is defined as the initial viscosity. The viscosity at 25° C. after storing the thermosetting composition at 25° C. for 8 hours after preparation is defined as the viscosity after 8 hours of storage. The viscosity change is calculated by the following formula:
Viscosity change = (viscosity after 8 hours of storage) / (initial viscosity)
The viscosity change of the thermosetting composition of the present disclosure is preferably 2 times or less. When the viscosity change of the thermosetting composition of the present disclosure is 2 times or less, the thermosetting composition of the present disclosure is highly stable and can maintain a low viscosity for a long time. Therefore, the thermosetting composition of the present disclosure can be poured into a narrow gap, etc., and can be used as a resin (sealant) for covering a particularly fine optical semiconductor device, as described later.

[Epoxy mixture (A)]
(Isocyanuric Acid Derivative (A1))
The epoxy mixture (A) of the present disclosure is a mixture of epoxy compounds containing an epoxy compound represented by the following formula (1) (hereinafter, may be simply referred to as an “isocyanuric acid derivative (A1)”) and other epoxy compounds.

In the above formula (1), R ¹ represents a linking group (a divalent group having one or more atoms). Each R ¹ may be the same or different. Examples of R ¹ include a linking group having a divalent hydrocarbon group, a carbonyl group, an ether bond, an ester bond, a carbonate group, an amide group, or a group in which a plurality of these groups are linked together.

The divalent hydrocarbon group may be linear or branched, and may have an alicyclic structure. The divalent hydrocarbon group is preferably linear so that it functions effectively as a flexible chain.

The divalent hydrocarbon group may be a saturated or unsaturated hydrocarbon group. The divalent hydrocarbon group is preferably a saturated hydrocarbon group so that it functions effectively as a flexible chain.

The divalent saturated hydrocarbon group is preferably an alkylene group having 1 to 18 carbon atoms, more preferably an alkylene group having 2 to 10 carbon atoms, and even more preferably an alkylene group having 2 to 7 carbon atoms.

Examples of alkylene groups having 2 to 18 carbon atoms include linear or branched divalent saturated hydrocarbon groups such as methylmethylene, dimethylmethylene, ethylene, propylene, butylene, pentylene, hexylene, heptylene, and octylene, and divalent saturated hydrocarbon groups having an alicyclic structure such as 1,2-cyclopentylene, 1,3-cyclopentylene, 1,2-cyclohexylene, 1,3-cyclohexylene, and 1,4-cyclohexylene.

The isocyanuric acid derivative (A1) is a derivative of isocyanuric acid and is a compound having three oxirane rings in the molecule. The isocyanuric acid derivative (A1) has R ¹ as a flexible chain. Therefore, the viscosity of the thermosetting composition can be kept low. In addition, by including the isocyanuric acid derivative (A1) in the thermosetting composition of the present disclosure, the toughness and thermal shock resistance of the obtained cured product can be improved.

As a representative example of the isocyanuric acid derivative (A1) of the compound represented by the above formula (1), from the viewpoints of availability and viscosity reduction, the compounds represented by the following formulas (1-2) or (1-3) are more preferable.

The compound represented by the above formula (1-2) is 1,3,5-tris(4,5-epoxypentyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione. The compound represented by the above formula (1-3) is 1,3,5-tris(6-oxiranylhexyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione.

In the thermosetting composition of the present disclosure, the isocyanuric acid derivative (A1) may be used alone or in combination of two or more. In addition, as the isocyanuric acid derivative (A1), for example, commercially available products such as "TEPIC-VL" and "TEPIC-FL" (both manufactured by Nissan Chemical Industries, Ltd.) may be used.

The content (mixture amount) of the isocyanuric acid derivative (A1) in the thermosetting composition of the present disclosure is not particularly limited, but is preferably 1 to 50 mass% relative to the total amount (100 mass%) of the epoxy mixture (A), more preferably 3 to 30 mass%, and even more preferably 5 to 20 mass%. By making the content of the isocyanuric acid derivative (A1) 1 mass% or more, the viscosity of the thermosetting composition can be further reduced. On the other hand, if the content of the isocyanuric acid derivative (A1) is 50 mass% or less, the solubility in the thermosetting composition is improved, and a cured product with uniform properties can be obtained.

The content (mixture amount) of the isocyanuric acid derivative (A1) in the thermosetting composition of the present disclosure is not particularly limited, but is preferably 0.5 to 40 mass% relative to the total amount (100 mass%) of the thermosetting composition, more preferably 2 to 25 mass%, and even more preferably 5 to 13 mass%. By making the content of the isocyanuric acid derivative (A1) 0.5 mass% or more, the viscosity of the thermosetting composition can be further reduced. On the other hand, if the content of the isocyanuric acid derivative (A1) is 40 mass% or less, the solubility in the thermosetting composition is improved, and a cured product with uniform properties can be obtained.

Hereinafter, the other epoxy compounds other than the isocyanuric acid derivative (A1) contained in the epoxy mixture (A) will be described. Examples of the other epoxy compounds include alicyclic epoxy compounds. Although an alicyclic epoxy compound is exemplified as the other epoxy compound, the other epoxy compound is not limited thereto, and the mixture may contain two or more types of epoxy compounds.

(Alicyclic epoxy compound (A2))
The epoxy mixture (A) may contain an alicyclic epoxy compound other than the isocyanuric acid derivative (A1). The alicyclic epoxy compound other than the isocyanuric acid derivative (A1) (hereinafter, sometimes referred to as an alicyclic epoxy compound (A2)) is a compound having at least an alicyclic (aliphatic ring) structure and an epoxy group (oxiranyl group) in the molecule (in one molecule). It is preferable that the number of epoxy groups in the molecule (in one molecule) is two or more.

The alicyclic epoxy compound (A2) has excellent stability and transparency. Therefore, the thermosetting composition of the present disclosure is a combination of the isocyanuric acid derivative (A1) and the alicyclic epoxy compound (A2), and thus the composition has excellent stability and transparency while suppressing an increase in viscosity. In addition, the thermosetting composition of the present disclosure is a combination of the isocyanuric acid derivative (A1) and the alicyclic epoxy compound (A2), and thus it is presumed that the solubility in the thermosetting composition is improved and phase separation during curing is suppressed. Therefore, a uniformly dissolved thermosetting composition can be used to obtain a cured product with uniform properties, and therefore it is presumed that the occurrence of cracks in the cured product is suppressed.

Specific examples of the alicyclic epoxy compound (A2) include (i) a compound having an epoxy group composed of two adjacent carbon atoms and an oxygen atom that constitute an alicyclic ring (alicyclic epoxy group), (ii) a compound having an epoxy group directly bonded to an alicyclic ring by a single bond, and (iii) a compound having an alicyclic ring and a glycidyl ether group in the molecule (glycidyl ether type epoxy compound).

<Alicyclic epoxy compound (A21)>
The above-mentioned (i) compound having an epoxy group composed of two adjacent carbon atoms and an oxygen atom constituting an alicyclic ring (alicyclic epoxy group) can be arbitrarily selected from known or commonly used compounds. Among them, from the viewpoint of the transparency and heat resistance of the cured product, the above-mentioned (i) compound having an epoxy group composed of two adjacent carbon atoms and an oxygen atom constituting an alicyclic ring is preferably a compound having a cyclohexene oxide group, and in particular, a compound represented by the following formula (1-1) (hereinafter, sometimes simply referred to as "alicyclic epoxy compound (A21)") is preferable.

In the above formula (1-1), R ³ represents a single bond or a linking group (a divalent group having one or more atoms). Examples of the linking group include a divalent hydrocarbon group, an alkenylene group in which some or all of the carbon-carbon double bonds have been epoxidized, a carbonyl group, an ether bond, an ester bond, a carbonate group, an amide group, and groups in which a plurality of these are linked together. An example of a compound in which R ³ in the above formula (1-1) is a single bond is (3,4,3',4'-diepoxy)bicyclohexyl. The alicyclic epoxy compound (A21) may be a compound having a substituent on the cyclohexane ring.

The divalent hydrocarbon group may be a linear or branched alkylene group having 1 to 18 carbon atoms, or a divalent alicyclic hydrocarbon group. Examples of the linear or branched alkylene group having 1 to 18 carbon atoms include a methylene group, a methylmethylene group, a dimethylmethylene group, an ethylene group, a propylene group, and a trimethylene group. Examples of the divalent alicyclic hydrocarbon group may be a divalent cycloalkylene group (including a cycloalkylidene group) such as a 1,2-cyclopentylene group, a 1,3-cyclopentylene group, a cyclopentylidene group, a 1,2-cyclohexylene group, a 1,3-cyclohexylene group, a 1,4-cyclohexylene group, or a cyclohexylidene group.

Examples of the alkenylene group in the alkenylene group in which some or all of the carbon-carbon double bonds have been epoxidized (sometimes referred to as "epoxidized alkenylene group") include linear or branched alkenylene groups having 2 to 8 carbon atoms, such as vinylene, propenylene, 1-butenylene, 2-butenylene, butadienylene, pentenylene, hexenylene, heptenylene, and octenylene. In particular, the epoxidized alkenylene group is preferably an alkenylene group in which all of the carbon-carbon double bonds have been epoxidized, and more preferably an alkenylene group having 2 to 4 carbon atoms in which all of the carbon-carbon double bonds have been epoxidized.

As the linking group ^R3 , in particular, a linking group containing an oxygen atom is preferred, and specific examples thereof include -CO-, -O-CO-O-, -COO-, -O-, -CONH-, an epoxidized alkenylene group, a group in which a plurality of these groups are linked together, and a group in which one or more of these groups are linked to one or more divalent hydrocarbon groups, etc. Examples of the divalent hydrocarbon group include those exemplified above.

Representative examples of the alicyclic epoxy compound (A21) include an alicyclic epoxy compound having two or more epoxy groups in the molecule, which is represented by the following formula (1-4) (3,4-epoxycyclohexylmethyl(3,4-epoxy)cyclohexanecarboxylate). As the compound represented by the following formula (1-4), for example, a commercially available product such as the product name "CELLOXIDE2021P" (manufactured by Daicel Corporation) can also be used.

When the thermosetting composition of the present disclosure contains an alicyclic epoxy compound (A21), the content of the alicyclic epoxy compound (A21) is not particularly limited, but the ratio of the alicyclic epoxy compound (A21) to the total amount (100 mass%) of the epoxy mixture (A) is preferably 1 to 40 mass%, more preferably 3 to 30 mass%, and even more preferably 4 to 15 mass%. By making the ratio of the alicyclic epoxy compound (A21) 1 mass% or more, the stability and transparency of the thermosetting composition tend to be further improved. On the other hand, for example, by making the ratio of the alicyclic epoxy compound (A21) 40 mass% or less, the thermal shock resistance and moisture resistance of the cured product tend to be further improved.

When the thermosetting composition of the present disclosure contains an alicyclic epoxy compound (A21), the content of the alicyclic epoxy compound (A21) is not particularly limited, but the ratio of the alicyclic epoxy compound (A21) to the total amount (100 mass%) of the thermosetting composition is preferably 0.5 to 30 mass%, more preferably 2 to 20 mass%, and even more preferably 3 to 10 mass%. By making the ratio of the alicyclic epoxy compound (A21) 0.5 mass% or more, the stability and transparency of the thermosetting composition tend to be further improved. On the other hand, for example, by making the ratio of the alicyclic epoxy compound (A21) 30 mass% or less, the thermal shock resistance and moisture resistance of the cured product tend to be further improved.

When the alicyclic epoxy compound (A2) contains the alicyclic epoxy compound (A21), the content of the alicyclic epoxy compound (A21) is not particularly limited, but the ratio of the alicyclic epoxy compound (A21) to the total amount (100 mass%) of the alicyclic epoxy compound (A2) is preferably 1 to 30 mass%, more preferably 2 to 20 mass%, and even more preferably 4 to 15 mass%. By making the ratio of the alicyclic epoxy compound (A21) 1 mass% or more, the stability and transparency of the thermosetting composition tend to be further improved. On the other hand, for example, by making the ratio of the alicyclic epoxy compound (A21) 30 mass% or less, the thermal shock resistance and moisture resistance of the cured product tend to be further improved.

<Siloxane derivative (A22)>
In addition, (i) the compound having an epoxy group composed of two adjacent carbon atoms and an oxygen atom constituting an alicyclic ring may contain, in addition to the above-mentioned alicyclic epoxy compound (A21), a siloxane derivative having two or more epoxy groups in the molecule (per molecule) (hereinafter, sometimes simply referred to as "siloxane derivative (A22)". By containing the siloxane derivative (A22), the thermosetting composition can improve the heat resistance and light resistance of the cured product to a higher level.

The siloxane skeleton (Si-O-Si skeleton) in the siloxane derivative (A22) is not particularly limited, but examples thereof include a cyclic siloxane skeleton; a linear silicone, and a polysiloxane skeleton such as a cage-type or ladder-type polysilsesquioxane. Among them, the siloxane skeleton is preferably a cyclic siloxane skeleton or a linear silicone skeleton from the viewpoint of improving the heat resistance and light resistance of the cured product and suppressing a decrease in luminous intensity. That is, the siloxane derivative (A22) is preferably a cyclic siloxane having two or more epoxy groups in the molecule, or a linear silicone having two or more epoxy groups in the molecule. The siloxane derivative (A22) can be used alone or in combination of two or more.

When the siloxane derivative (A22) is a cyclic siloxane having two or more epoxy groups, the number of Si-O units forming the siloxane ring (equal to the number of silicon atoms forming the siloxane ring) is not particularly limited, but from the viewpoint of improving the heat resistance and light resistance of the cured product, it is preferably 2 to 12, and more preferably 4 to 8.

The mass average molecular weight of the siloxane derivative (A22) is not particularly limited, but from the viewpoint of improving the heat resistance and light resistance of the cured product, it is preferably 100 to 3,000, and more preferably 180 to 2,000.

The number of epoxy groups in one molecule of the siloxane derivative (A22) is not particularly limited as long as it is 2 or more, but from the viewpoint of improving the heat resistance and light resistance of the cured product, 2 to 4 is preferable.

The epoxy equivalent weight (based on JIS K7236) of the siloxane derivative (A22) is not particularly limited, but from the viewpoint of improving the heat resistance and light resistance of the cured product, it is preferably 180 to 400, more preferably 240 to 400, and even more preferably 240 to 350.

The epoxy group in the siloxane derivative (A22) is not particularly limited, but from the viewpoint of improving the heat resistance and light resistance of the cured product, it is particularly preferable that the epoxy group is an epoxy group composed of two adjacent carbon atoms and an oxygen atom that form an aliphatic ring, and among these, a cyclohexene oxide group is particularly preferable.

Specific examples of the siloxane derivative (A22) include 2,4-di[2-(3-{oxabicyclo[4.1.0]heptyl})ethyl]-2,4,6,6,8,8-hexamethyl-cyclotetrasiloxane, 4,8-di[2-(3-{oxabicyclo[4.1.0]heptyl})ethyl]-2,2,4,6,6,8-hexamethyl-cyclotetrasiloxane, 2,4-di[2-(3-{oxabicyclo[4.1.0]heptyl})ethyl]-6,8-dipropyl-2,4,6,8-tetramethyl-cyclotetrasiloxane, 4,8-di[2-(3-{oxabicyclo[4.1.0]heptyl})ethyl]-2,6- Examples of the silsesquioxane include dipropyl-2,4,6,8-tetramethyl-cyclotetrasiloxane, 2,4,8-tri[2-(3-{oxabicyclo[4.1.0]heptyl})ethyl]-2,4,6,6,8-pentamethyl-cyclotetrasiloxane, 2,4,8-tri[2-(3-{oxabicyclo[4.1.0]heptyl})ethyl]-6-propyl-2,4,6,8-tetramethyl-cyclotetrasiloxane, 2,4,6,8-tetra[2-(3-{oxabicyclo[4.1.0]heptyl})ethyl]-2,4,6,8-tetramethyl-cyclotetrasiloxane, and silsesquioxane having two or more epoxy groups in the molecule. More specifically, examples of the silsesquioxane include cyclic siloxanes having two or more epoxy groups in the molecule represented by the following formula.

As the siloxane derivative (A22), for example, an alicyclic epoxy group-containing silicone resin described in JP-A-2008-248169 or an organopolysilsesquioxane resin having at least two epoxy functional groups in one molecule described in JP-A-2008-19422 can be used.

As the siloxane derivative (A22), for example, commercially available products such as "X-40-2678" (manufactured by Shin-Etsu Chemical Co., Ltd.), "X-40-2670" (manufactured by Shin-Etsu Chemical Co., Ltd.), and "X-40-2720" (manufactured by Shin-Etsu Chemical Co., Ltd.), which are cyclic siloxanes having two or more epoxy groups in the molecule, can be used.

When the thermosetting composition of the present disclosure contains a siloxane derivative (A22), the content (mixture amount) of the siloxane derivative (A22) is not particularly limited, but is preferably 40 to 95 mass%, more preferably 50 to 90 mass%, and even more preferably 60 to 85 mass% relative to the total amount (100 mass%) of the epoxy mixture (A). When the content of the siloxane derivative (A22) is 40 mass% or more, a cured product having excellent heat resistance and light resistance can be obtained, and the viscosity of the thermosetting composition can be adjusted to a low level. On the other hand, when the content of the siloxane derivative (A22) is 95 mass% or less, the transparency of the cured product tends to be further improved.

When the thermosetting composition of the present disclosure contains a siloxane derivative (A22), the content (mixture amount) of the siloxane derivative (A22) is not particularly limited, but is preferably 20 to 85 mass%, more preferably 30 to 80 mass%, and even more preferably 40 to 70 mass%, relative to the total amount (100 mass%) of the thermosetting composition. When the content of the siloxane derivative (A22) is 20 mass% or more, a cured product having excellent heat resistance and light resistance can be obtained, and the viscosity of the thermosetting composition can be adjusted to a low level. On the other hand, when the content of the siloxane derivative (A22) is 85 mass% or less, the transparency of the cured product tends to be further improved.

When the thermosetting composition of the present disclosure contains a siloxane derivative (A22), the content (mixture amount) of the alicyclic epoxy compound (A22) is not particularly limited, but the ratio of the alicyclic epoxy compound (A22) to the total amount (100 mass%) of the alicyclic epoxy compound (A22) is preferably 70 to 99 mass%, more preferably 80 to 98 mass%, and even more preferably 85 to 96 mass%. When the ratio of the alicyclic epoxy compound (A22) is 70 mass% or more, a cured product having excellent heat resistance and light resistance can be obtained, and the viscosity of the thermosetting composition can be adjusted to a low level. On the other hand, when the content of the siloxane derivative (A22) is 99 mass% or less, the transparency of the cured product tends to be further improved.

When the alicyclic epoxy compound (A2) contains a siloxane derivative (A22), the content (mixture amount) of the alicyclic epoxy compound (A2) is not particularly limited, but the ratio of the alicyclic epoxy compound (A2) to the total amount (100 mass%) of the epoxy mixture (A) is preferably 1 to 98 mass%, more preferably 3 to 95 mass%, and even more preferably 4 to 92 mass%. By making the ratio of the alicyclic epoxy compound (A2) 1 mass% or more, the stability and transparency of the thermosetting composition are further improved, and the viscosity of the thermosetting composition can be adjusted to a low level. On the other hand, for example, by making the ratio of the alicyclic epoxy compound (A2) 98 mass% or less, the thermal shock resistance of the cured product tends to be further improved.

When the alicyclic epoxy compound (A2) contains a siloxane derivative (A22), the content (mixture amount) of the alicyclic epoxy compound (A2) is not particularly limited, but is preferably 0.5 to 90 mass%, more preferably 2 to 80 mass%, and even more preferably 3 to 70 mass% relative to the total amount (100 mass%) of the thermosetting composition. By making the proportion of the alicyclic epoxy compound (A2) 0.5 mass% or more, the stability and transparency of the thermosetting composition tend to be further improved. On the other hand, for example, by making the proportion of the alicyclic epoxy compound (A2) 90 mass% or less, the thermal shock resistance of the cured product tends to be further improved.

Examples of the compound (ii) having an epoxy group directly bonded to an alicyclic ring via a single bond include compounds represented by the following formula (1-5):

In formula (1-5), R ⁴ is a group (p-valent organic group) obtained by removing p hydroxyl groups (-OH) from a p-valent alcohol in the structural formula, and p and n each represent a natural number. Examples of p-valent alcohols [R ⁴ (OH)p] include polyhydric alcohols (alcohols having 1 to 15 carbon atoms, etc.) such as 2,2-bis(hydroxymethyl)-1-butanol. p is preferably 1 to 6, and n is preferably 1 to 30. When p is 2 or more, n in each group in ( ) (in the outer parentheses) may be the same or different. Specific examples of compounds represented by formula (1-5) include 1,2-epoxy-4-(2-oxiranyl)cyclohexane adducts of 2,2-bis(hydroxymethyl)-1-butanol [for example, product name "EHPE3150" manufactured by Daicel Corporation], etc.

Examples of the above (iii) compounds having an alicyclic ring and a glycidyl ether group in the molecule include glycidyl ethers of alicyclic alcohols (particularly alicyclic polyhydric alcohols). More specifically, for example, compounds obtained by hydrogenating bisphenol A type epoxy compounds such as 2,2-bis[4-(2,3-epoxypropoxy)cyclohexyl]propane and 2,2-bis[3,5-dimethyl-4-(2,3-epoxypropoxy)cyclohexyl]propane (hydrogenated bisphenol A type epoxy compounds); bis[o,o-(2,3-epoxypropoxy)cyclohexyl]methane, bis[o,p-(2,3-epoxypropoxy)cyclohexyl]methane, bis[p,p-(2,3-epoxypropoxy)cyclohexyl]methane, bis[3,5-dimethyl -4-(2,3-epoxypropoxy)cyclohexyl]methane and other hydrogenated bisphenol F type epoxy compounds (hydrogenated bisphenol F type epoxy compounds); hydrogenated biphenol type epoxy compounds; hydrogenated phenol novolac type epoxy compounds; hydrogenated cresol novolac type epoxy compounds; hydrogenated cresol novolac type epoxy compounds of bisphenol A; hydrogenated naphthalene type epoxy compounds; hydrogenated epoxy compounds of epoxy compounds obtained from trisphenolmethane; hydrogenated epoxy compounds of the aromatic epoxy compounds listed below, etc.

Examples of the aromatic epoxy compounds include epi-bis-type glycidyl ether type epoxy resins obtained by a condensation reaction between bisphenols [e.g., bisphenol A, bisphenol F, bisphenol S, fluorene bisphenol, etc.] and epihalohydrin; high molecular weight epi-bis-type glycidyl ether type epoxy resins obtained by further addition reaction of these epi-bis-type glycidyl ether type epoxy resins with the above bisphenols; phenols [e.g., phenol, cresol, xylenol, resorcin, catechol, bisphenol A, bisphenol Examples of such epoxy resins include novolak alkyl type glycidyl ether epoxy resins obtained by condensing polyhydric alcohols obtained by condensing polyhydric alcohols [e.g., formaldehyde, acetaldehyde, benzaldehyde, hydroxybenzaldehyde, salicylaldehyde, etc.] with epihalohydrin; and epoxy compounds in which two phenol skeletons are bonded to the 9-position of the fluorene ring, and glycidyl groups are bonded to the oxygen atoms obtained by removing the hydrogen atoms from the hydroxyl groups of these phenol skeletons, either directly or via alkyleneoxy groups.

In the thermosetting composition of the present disclosure, the alicyclic epoxy compound (A2) may be used alone or in combination of two or more.

The ratio of the content of the alicyclic epoxy compound (A2) to the content of the isocyanuric acid derivative (A1) is not particularly limited, but is preferably 10 to 150 parts by mass, more preferably 20 to 120 parts by mass, and even more preferably 30 to 100 parts by mass, relative to the total amount (100 parts by mass) of the isocyanuric acid derivative (A1). By controlling the ratio of the content of the alicyclic epoxy compound (A2) to the content of the isocyanuric acid derivative (A1) within the above range, a thermosetting composition excellent in stability and transparency can be obtained while suppressing an increase in viscosity.

The content (mixture amount) of the epoxy mixture (A) in the thermosetting composition of the present disclosure is not particularly limited, but is preferably 50 to 95 mass % relative to the total amount (100 mass %) of the thermosetting composition, more preferably 60 to 90 mass %, and even more preferably 70 to 85 mass %.

[Acid anhydride curing agent (B)]
The acid anhydride curing agent (B) in the thermosetting composition of the present disclosure has a function of curing the thermosetting composition by reacting with a compound having an epoxy group such as the above-mentioned isocyanuric acid derivative (A1) or alicyclic epoxy compound (A2). By using the acid anhydride curing agent (B), a cured product having excellent heat resistance and transparency can be obtained.

The acid anhydride curing agent (B) of the present disclosure contains an acid anhydride represented by the following formula (2).

In the formula, the position of R ² indicates any carbon atom of the cyclohexane ring in the acid anhydride represented by formula (2). R ² represents a group containing a carboxyl group, and is preferably a carboxyl group. R ² may be one or more, and may be multiple, but is preferably one. When R ² is a group containing a carboxyl group, the heat resistance and transparency of the thermosetting composition of the present disclosure can be improved. Examples of the acid anhydride contained in the acid anhydride curing agent (B) include trimellitic anhydride and the like.

The acid anhydride represented by formula (2) may further have a substituent on any carbon atom of the cyclohexane ring. Examples of the substituent include an alkyl group having 1 to 4 carbon atoms, such as a methyl group. The number of the substituents may be one or more.

In the thermosetting composition of the present disclosure, the acid anhydride curing agent (B) may be used alone or in combination of two or more. For example, multiple acid anhydrides represented by the above formula (2) may be used. In addition, as the acid anhydride contained in the acid anhydride curing agent (B), an acid anhydride other than the above may be used within a range that does not impair the effects of the present disclosure.

As other acid anhydrides, known or conventional acid anhydride curing agents can be used, and are not particularly limited. Examples of such acid anhydrides include hexahydrophthalic anhydride, 4-methylhexahydrophthalic anhydride, methyltetrahydrophthalic anhydride (4-methyltetrahydrophthalic anhydride, 3-methyltetrahydrophthalic anhydride, etc.), dodecenyl succinic anhydride, methyl end methylene tetrahydrophthalic anhydride, phthalic anhydride, maleic anhydride, tetrahydrophthalic anhydride, methylcyclohexene dicarboxylic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic anhydride, nadic anhydride, methyl nadic anhydride, hydrogenated methyl nadic anhydride, 4-(4-methyl-3-pentenyl)tetrahydrophthalic anhydride, succinic anhydride, adipic anhydride, sebacic anhydride, dodecanedioic anhydride, methylcyclohexene tetracarboxylic anhydride, vinyl ether-maleic anhydride copolymer, alkylstyrene-maleic anhydride copolymer, etc. Among these, from the viewpoint of handling, an acid anhydride that is liquid at 25°C (e.g., methyltetrahydrophthalic anhydride, dodecenyl succinic anhydride, methylendmethylenetetrahydrophthalic anhydride, etc.) is preferred. On the other hand, for an acid anhydride that is solid at 25°C, for example, by dissolving it in an acid anhydride that is liquid at 25°C to form a liquid mixture, the handling of the acid anhydride curing agent (B) in the thermosetting composition of the present disclosure tends to be improved. As the acid anhydride curing agent (B), from the viewpoint of the heat resistance and transparency of the cured product, anhydrides of saturated monocyclic hydrocarbon dicarboxylic acids (including those having substituents such as alkyl groups bonded to the ring) are preferred, and more preferably compounds having a hexahydrophthalic anhydride skeleton.

In addition, commercially available products can also be used as the acid anhydride curing agent (B). For example, commercially available acid anhydride products include those sold under the trade names "RIKACID MH-700" and "RIKACID MH-700F" (both manufactured by New Japan Chemical Co., Ltd.); "HN-5500" (manufactured by Hitachi Chemical Co., Ltd.); and cyclohexane-1,2,4-tricarboxylic acid-1,2-anhydride sold under the trade name "H-TMAn" (manufactured by Mitsubishi Gas Chemical Co., Ltd.).

The content (mixture amount) of the acid anhydride curing agent (B) in the thermosetting composition of the present disclosure is not particularly limited, but is preferably 5 to 60 parts by mass, more preferably 10 to 45 parts by mass, and even more preferably 15 to 40 parts by mass, relative to 100 parts by mass of the total amount of the epoxy mixture (A) (for example, the isocyanuric acid derivative (A1) and the alicyclic epoxy compound (A2)). By making the content of the acid anhydride curing agent (B) 5 parts by mass or more, the curing can be sufficiently advanced, and the toughness of the cured product tends to be further improved. On the other hand, by making the content of the acid anhydride curing agent (B) 60 parts by mass or less, a thermosetting composition with low viscosity and little change in viscosity can be obtained. In addition, when the content of the acid anhydride curing agent (B) is 60 parts by mass or less, coloring is further suppressed, and a cured product with excellent hue tends to be obtained.

The content (mixture amount) of the acid anhydride curing agent (B) in the thermosetting composition of the present disclosure is not particularly limited, but is preferably 3 to 40 mass% relative to the total amount (100 mass%) of the thermosetting composition, more preferably 10 to 37 mass%, and even more preferably 20 to 35 mass%. By making the content of the acid anhydride curing agent (B) 3 mass% or more, curing can be sufficiently advanced, and the toughness of the cured product tends to be further improved. On the other hand, by making the content of the acid anhydride curing agent (B) 40 mass% or less, a thermosetting composition with low viscosity and little viscosity change can be obtained. In addition, when the content of the acid anhydride curing agent (B) is 40 mass% or less, coloring is further suppressed, and a cured product with excellent hue tends to be obtained.

The acid anhydride curing agent (B) in the thermosetting composition of the present disclosure is preferably 0.4 to 0.8 equivalents relative to 1 equivalent of the epoxy mixture (A), more preferably 0.5 to 0.7 equivalents, and even more preferably 0.5 to 0.6 equivalents. 1 equivalent of the epoxy mixture (A) refers to 1 equivalent of the epoxy group in all compounds having an epoxy group contained in the thermosetting composition of the present disclosure. 1 equivalent of the acid anhydride curing agent (B) refers to 1 equivalent of the acid anhydride and carboxyl group contained in the acid anhydride curing agent (B). By making the content of the acid anhydride curing agent (B) 0.4 equivalents or more relative to 1 equivalent of the epoxy mixture (A), the curing can be sufficiently advanced, and the toughness of the cured product tends to be further improved. On the other hand, by making the content of the acid anhydride curing agent (B) 0.8 equivalents or less relative to 1 equivalent of the epoxy mixture (A), a thermosetting composition with low viscosity and little viscosity change can be obtained. In addition, unreacted acid anhydride is likely to color the thermosetting composition of the present disclosure. For this reason, it is preferable that the amount of epoxy groups in the epoxy mixture (A) is in excess of the acid anhydride and carboxyl groups in the acid anhydride curing agent (B). For example, if the number of acid anhydrides and carboxyl groups contained in the acid anhydride curing agent (B) is small relative to the number of epoxy groups contained in the epoxy mixture (A), the amount of unreacted acid anhydrides remaining is suppressed. This tends to suppress coloration of the thermosetting composition of the present disclosure and produce a cured product with excellent hue.

The curing agent in the thermosetting composition of the present disclosure may contain other known or conventional curing agents as long as the effects of the present disclosure are not impaired. For example, the curing agent may be an acid anhydride (acid anhydride curing agent), an amine (amine curing agent), a polyamide resin, an imidazole (imidazole curing agent), a polymercaptan (polymercaptan curing agent), a phenol (phenol curing agent), a polycarboxylic acid, a dicyandiamide, an organic acid hydrazide, etc.

The content (mixture amount) of the acid anhydride curing agent (B) in the curing agent is not particularly limited, but is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more, based on the total amount of the curing agent (100% by mass).

[Curing Accelerator (C)]
The curing accelerator (C) in the thermosetting composition of the present disclosure is a compound that has the function of accelerating the reaction rate when a compound having an epoxy group reacts with the acid anhydride curing agent (B) that is a curing agent. As the curing accelerator (C), a known or conventional curing accelerator can be used, and is not particularly limited. Examples of the curing accelerator include 1,8-diazabicyclo[5.4.0]undecene-7 (DBU) or a salt thereof (e.g., phenol salt, octylate salt, p-toluenesulfonate, formate salt, tetraphenylborate salt, etc.); 1,5-diazabicyclo[4.3.0]nonene-5 (DBN) or a salt thereof (e.g., phenol salt, octylate salt, p-toluenesulfonate, formate salt, tetraphenylborate salt, etc.); benzyldimethylamine, 2,4,6-tris(dimethylamine), imidazoles such as 2-ethyl-4-methylimidazole and 1-cyanoethyl-2-ethyl-4-methylimidazole; phosphate esters; phosphines such as triphenylphosphine and tris(dimethoxy)phosphine; phosphonium compounds such as tetraphenylphosphonium tetra(p-tolyl)borate; organic metal salts such as zinc octoate, tin octoate, and zinc stearate; and metal chelates such as aluminum acetylacetone complex.

The curing accelerator (C) preferably contains one or more curing accelerators selected from compounds consisting of phosphorus-based oxidation accelerators and organic acid metal salts. When the curing accelerator (C) contains a phosphorus-based oxidation accelerator or an organic acid metal salt, it can more easily accelerate the curing of the thermosetting composition of the present disclosure compared to a curing accelerator that is highly basic.

In the thermosetting composition of the present disclosure, the curing accelerator (C) may be used alone or in combination of two or more. As the curing accelerator (C), commercially available products such as those under the trade names "U-CAT SA 506", "U-CAT SA 102", "U-CAT 5003", "U-CAT 18X", and "U-CAT 12XD" (developed products) (all manufactured by San-Apro Co., Ltd.); those under the trade names "TPP-K" and "TPP-MK" (all manufactured by Hokko Chemical Industry Co., Ltd.); and those under the trade names "PX-4ET" and "PX-4MP" (manufactured by Nippon Chemical Industry Co., Ltd.) may also be used.

The content (mixture amount) of the curing accelerator (C) in the thermosetting composition of the present disclosure is not particularly limited, but is preferably 0.01 to 5 parts by mass, more preferably 0.03 to 4 parts by mass, and even more preferably 0.03 to 3 parts by mass, relative to 100 parts by mass of the total amount of the epoxy mixture (A) contained in the thermosetting composition. By making the content of the curing accelerator (C) 0.01 parts by mass or more, a more efficient curing acceleration effect tends to be obtained. On the other hand, by making the content of the curing accelerator (C) 5 parts by mass or less, coloring is further suppressed, and a cured product with excellent hue tends to be obtained.

[Antioxidant (D)]
The thermosetting composition of the present disclosure may contain an antioxidant (D). By containing the antioxidant (D), it is possible to produce a cured product with even better heat resistance (particularly, yellowing resistance). As the antioxidant (D), a known or commonly used antioxidant can be used, and is not particularly limited, but examples thereof include phenol-based antioxidants (phenol-based compounds), hindered amine-based antioxidants (hindered amine-based compounds), phosphorus-based antioxidants (phosphorus-based compounds), and sulfur-based antioxidants (sulfur-based compounds).

Examples of phenolic antioxidants include monophenols such as 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-p-ethylphenol, and stearyl-β-(3,5-di-t-butyl-4-hydroxyphenyl)propionate; 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-butylphenol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol), and 3,9-bis[1,1-dimethyl-2-{β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy}ethyl]2,4,8,1 Bisphenols such as 0-tetraoxaspiro[5.5]undecane; polymeric phenols such as 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, bis[3,3'-bis-(4'-hydroxy-3'-t-butylphenyl)butyric acid]glycol ester, 1,3,5-tris(3',5'-di-t-butyl-4'-hydroxybenzyl)-s-triazine-2,4,6-(1H,3H,5H)trione, and tocopherol.

Examples of hindered amine antioxidants include bis(1,2,2,6,6-pentamethyl-4-piperidyl)[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butylmalonate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, methyl-1,2,2,6,6-pentamethyl-4-piperidylsebacate, and 4-benzoyloxy-2,2,6,6-tetramethylpiperidine.

Examples of phosphorus-based antioxidants include triphenyl phosphite, diphenyl isodecyl phosphite, phenyl diisodecyl phosphite, tris(nonylphenyl) phosphite, diisodecyl pentaerythritol phosphite, tris(2,4-di-t-butylphenyl) phosphite, cyclic neopentane tetrayl bis(octadecyl) phosphite, cyclic neopentane tetrayl bis(2,4-di-t-butylphenyl) phosphite, cyclic neopentane tetrayl bis(2,4 -di-t-butyl-4-methylphenyl)phosphite, bis[2-t-butyl-6-methyl-4-{2-(octadecyloxycarbonyl)ethyl}phenyl]hydrogenphosphite, and other phosphites; 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10-(3,5-di-t-butyl-4-hydroxybenzyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and other oxaphosphaphenanthrene oxides.

Examples of sulfur-based antioxidants include dodecanethiol, dilauryl-3,3'-thiodipropionate, dimyristyl-3,3'-thiodipropionate, and distearyl-3,3'-thiodipropionate.

In the thermosetting composition of the present disclosure, the antioxidant (D) may be used alone or in combination of two or more kinds. The antioxidant (D) may be produced by a known or conventional method, and may be, for example, a commercially available product such as "Irganox 1010" (manufactured by BASF, phenol-based antioxidant), "AO-60" or "AO-80" (manufactured by ADEKA Corporation, phenol-based antioxidant), "Irgafos 168" (manufactured by BASF, phosphorus-based antioxidant), "Adeka STAB HP-10" or "Adeka STAB PEP-36" (manufactured by ADEKA Corporation, phosphorus-based antioxidant), or "HCA" (manufactured by SANKO CO., LTD., phosphorus-based antioxidant).

When the thermosetting composition of the present disclosure contains an antioxidant (D), the content (mixture amount) of the antioxidant (D) is not particularly limited, but is preferably 0.1 to 5 parts by mass, and more preferably 0.3 to 3 parts by mass, relative to the total amount (100 parts by mass) of the epoxy mixture (A) contained in the thermosetting composition. By making the content of the antioxidant (D) 0.1 parts by mass or more, oxidation of the cured product is efficiently prevented, and the heat resistance and yellowing resistance tend to be further improved. On the other hand, by making the content of the antioxidant (D) 5 parts by mass or less, coloring is suppressed, and a cured product with a better hue tends to be obtained.

[Additives]
In addition to the above, the thermosetting composition of the present disclosure may contain various additives within a range that does not impair the effects of the present disclosure. When a compound having a hydroxyl group such as ethylene glycol, diethylene glycol, propylene glycol, or glycerin is contained as the additive, the reaction can proceed slowly. In addition, conventional additives such as silicone-based or fluorine-based defoamers, leveling agents, surfactants, flame retardants, colorants, antioxidants, ultraviolet absorbers, ion adsorbents, pigments, phosphors (e.g., YAG-based phosphor fine particles, inorganic phosphor fine particles such as silicate-based phosphor fine particles, etc.), and release agents can be used within a range that does not impair viscosity or transparency. For example, the thermosetting composition of the present disclosure contains an antioxidant to prevent oxidation of the epoxy group contained in the thermosetting composition, thereby suppressing the deterioration of the thermosetting composition and improving stability.

(Preparation of Thermosetting Composition)
The thermosetting composition of the present disclosure is not particularly limited, but can be prepared by stirring and mixing the above-mentioned components in a heated state as necessary. The thermosetting composition of the present disclosure can be used as a one-liquid composition in which the components are mixed in advance and used as is, or can be used as a multi-liquid (e.g., two-liquid) composition in which two or more components stored separately are mixed in a predetermined ratio before use. The method of stirring and mixing is not particularly limited, and known or conventional stirring and mixing means such as various mixers such as dissolvers and homogenizers, kneaders, rolls, bead mills, and self-revolving stirring devices can be used. After stirring and mixing, the mixture may be degassed under vacuum.

<Optical semiconductor encapsulation composition>
The thermosetting composition of the present disclosure can be preferably used as a composition for sealing an optical semiconductor element in an optical semiconductor device, that is, as an optical semiconductor sealing composition (sealant for an optical semiconductor element in an optical semiconductor device). By using the thermosetting composition of the present disclosure as an optical semiconductor sealing composition, an optical semiconductor device in which an optical semiconductor element is sealed with a cured product having high heat resistance and excellent transparency can be obtained. In addition, the thermosetting composition of the present disclosure can be maintained at a low viscosity, so that it is easy to pour into fine gaps. Therefore, the thermosetting composition of the present disclosure can be used as an encapsulant for an optical semiconductor device having a particularly fine structure.

The thermosetting composition of the present disclosure is not limited to the above-mentioned sealing applications for optical semiconductor elements, but can also be used for various applications such as adhesives, electrical insulating materials, laminates, coatings, inks, paints, sealants, resists, composite materials, transparent substrates, transparent sheets, transparent films, optical elements, optical lenses, optical components, photolithography, electronic paper, touch panels, solar cell substrates, optical waveguides, light guide plates, holographic memories, and optical pickup sensors.

<Cured Product>
By curing the thermosetting composition of the present disclosure, it is possible to obtain a cured product that has high heat resistance and transparency and can be used as an encapsulant for optical semiconductor devices having a particularly fine structure.

As a means for curing the thermosetting composition of the present disclosure, known or conventional means such as heating treatment and light irradiation treatment can be used. The temperature (curing temperature) when curing by heating is not particularly limited, but is preferably 45 to 200°C, more preferably 50 to 190°C, and even more preferably 55 to 180°C. The time for heating when curing (curing time) is not particularly limited, but is preferably 30 to 600 minutes, more preferably 45 to 540 minutes, and even more preferably 60 to 480 minutes. If the curing temperature and curing time are lower than the lower limit of the above range, curing will be insufficient, and conversely, if they are higher than the upper limit of the above range, decomposition of the resin component may occur, so neither is preferable. The curing conditions depend on various conditions, but can be appropriately adjusted, for example, by shortening the curing time when the curing temperature is high, and lengthening the curing time when the curing temperature is low. Curing can be performed in one stage or in multiple stages of two or more stages.

When curing is performed by light irradiation, the antireflective material of the present disclosure can be obtained by irradiating light (radiation) including, for example, i-rays (365 nm), h-rays (405 nm), g-rays (436 nm), etc., at an illuminance of 10 to 1200 mW/cm ² and an exposure dose of 20 to 2500 mJ/cm ^2. From the viewpoint of suppressing deterioration of the cured product due to radiation and from the viewpoint of productivity, the exposure dose of radiation is preferably 20 to 600 mJ/cm ² , more preferably 20 to 300 mJ/cm ^2. For irradiation, a high-pressure mercury lamp, a xenon lamp, a carbon arc lamp, a metal halide lamp, a laser beam, etc. can be used as an irradiation source.

Furthermore, the light transmittance (thickness direction) of the cured product of the present disclosure changes little with aging. For example, the light transmittance (thickness direction) of the cured product of the present disclosure is measured (measurement wavelength: 450 nm) using a spectrophotometer (manufactured by Shimadzu Corporation, product name "UV-2400"). The cured product after the light transmittance measurement is aged in an oven at 120°C for 500 hours. The light transmittance (thickness direction) of the cured product after aging is measured again (measurement wavelength: 450 nm). The change in light transmittance (maintenance rate of light transmittance) is calculated by the following formula:
Transmittance maintenance rate (%)=(light transmittance after aging for 500 hours)/(initial light transmittance)×100
The transmittance retention rate (%) of the cured product of the present disclosure is preferably 95% or more. When the transmittance retention rate (%) of the cured product of the present disclosure is 95% or more, the cured product of the present disclosure has high stability against heat. Therefore, the cured product of the present disclosure can be used as a resin (sealant) for covering an optical semiconductor device exposed to high heat, as described below.

The present disclosure will be explained in more detail below with reference to examples, but the present disclosure is not limited to these examples, and any modifications or improvements that achieve the object of the present disclosure are included in the present disclosure. Note that "-" in Table 1 means that the component was not blended or was not measured. The amounts (proportions) of the components shown in Table 1 are in parts by mass.

<Examples 1 to 4, Comparative Examples 1 to 8>
As epoxy compounds, the trade name "TEPIC-VL" (viscosity 7500 mPa·s: manufactured by Nissan Chemical Co., Ltd.), the trade name "TEPIC-FL" (viscosity 800 mPa·s: manufactured by Nissan Chemical Co., Ltd.), the trade name "CELLOXIDE2021P" (viscosity 240 mPa·s: manufactured by Daicel Corporation), and the trade name "X-40-2678" (viscosity 120 mPa·s: manufactured by Shin-Etsu Chemical Co., Ltd.) were prepared. As acid anhydrides, the trade name "H-TMAn" (manufactured by Mitsubishi Gas Chemical Co., Ltd.) and the trade name "Rikacid MH-700" (manufactured by New Japan Chemical Co., Ltd.) were prepared. As curing accelerators, the trade name "PX-4MP" (manufactured by Nippon Chemical Industry Co., Ltd.) and the trade name "Nikka Octix Zinc (15%)" (manufactured by Nippon Chemical Industry Co., Ltd.) of zinc octylate were prepared. As an antioxidant, a product name "ADEKA STAB PEP-36", 3,9-bis (manufactured by ADEKA Corporation) was prepared. In addition, as an epoxy compound of Comparative Example 5, a product name "YX8000" (viscosity 120 mPa·s: manufactured by Mitsubishi Chemical Corporation) was prepared.

According to the recipe (unit: parts by mass) in Table 1, each epoxy compound and antioxidant were mixed and stirred at 80°C for 1 hour to obtain an epoxy mixture. Next, the epoxy mixture, each acid anhydride, and curing accelerator were charged into a planetary stirring device (product name "Awatori Rentaro AR-250", manufactured by Thinky Corporation) in the mixing ratio shown in Table 1, stirred to mix uniformly, and then degassed to obtain a thermosetting composition.

The resulting thermosetting composition was filled into a mold and heated in a 120°C oven (resin curing oven) for 5 hours. The thickness of the resulting cured product was 3 mm.

[evaluation]
<Viscosity measurement>
The viscosity of the thermosetting composition immediately after preparation was measured using an E-type viscometer (product name "TV-25 type H", manufactured by Toki Sangyo Co., Ltd.). The measurement conditions were rotor: standard 1°34' x R24, temperature: 25°C, and rotation speed: 0.5 to 10 rpm. The thermosetting composition was then stored at 25°C for 8 hours, and the viscosity was measured again, and the change in viscosity was calculated as follows:
Viscosity change = (viscosity after 8 hours of storage) / (initial viscosity)
The evaluation criteria for the viscosity change are as follows:
○: Viscosity change is less than 2 times
×: Viscosity change is more than twice as large or separation occurs

<Appearance of the cured product>
The obtained cured product was visually inspected and the evaluation criteria for the appearance of the cured product were as follows:
○: No cracks and the surface is smooth. ×: Cracks have occurred in the cured product.

<Transmittance measurement>
The light transmittance (thickness direction) of the obtained cured product was measured (measurement wavelength: 450 nm) using a spectrophotometer (manufactured by Shimadzu Corporation, product name "UV-2400"). After the light transmittance measurement, the cured product was aged in an oven at 120°C for 500 hours. The light transmittance (thickness direction) of the cured product after aging was measured again (measurement wavelength: 450 nm). The light transmittance retention rate was calculated as follows.
Transmittance maintenance rate (%)=(light transmittance after aging for 500 hours)/(initial light transmittance)×100

The above results are summarized in Table 1 below.

Each aspect disclosed herein may be combined with any other feature disclosed herein.

The thermosetting composition of the present disclosure provides a cured product with high heat resistance and excellent transparency. In addition, the thermosetting composition of the present disclosure has a low viscosity and can maintain a low viscosity over time. Therefore, the thermosetting composition of the present disclosure can be easily poured into fine gaps and can be used as an encapsulant for optical semiconductor devices with a fine structure. Furthermore, it is not limited to encapsulation applications for optical semiconductor devices and optical semiconductor elements, and can be used for various applications such as adhesives, electrical insulating materials, laminates, coatings, inks, paints, sealants, resists, composite materials, transparent substrates, transparent sheets, transparent films, optical elements, optical lenses, optical components, photomolding, electronic paper, touch panels, solar cell substrates, optical waveguides, light guide plates, holographic memories, and optical pickup sensors.

Claims (8)

An epoxy mixture (A) containing an epoxy compound represented by the following formula (1) and two or more other epoxy compounds;
an acid anhydride curing agent (B) containing an acid anhydride represented by the following formula (2);
A thermosetting composition comprising:
The other epoxy compounds include alicyclic epoxy compounds,
The acid anhydride curing agent (B) contains an acid anhydride other than the acid anhydride represented by the formula (2),
The content of the epoxy mixture (A) is 50 to 95 mass% based on the total amount (100 mass%) of the thermosetting composition,
The content of the epoxy compound represented by the formula (1) is 1 to 50 mass% based on the total amount (100 mass%) of the epoxy mixture (A),
The content of the alicyclic epoxy compound is 10 to 150 parts by mass based on the total amount (100 parts by mass) of the epoxy compound represented by formula (1),
The content of the acid anhydride curing agent (B) is 3 to 37% by mass based on the total amount (100% by mass) of the thermosetting composition,
The content of the curing accelerator (C) is 0.01 to 5 parts by mass based on 100 parts by mass of the total amount of the epoxy mixture (A),
A thermosetting composition having a viscosity of 1 Pa·s or less at 25°C.

[In the formula, R ¹ represents an alkylene group having 2 to 7 carbon atoms, and each R ¹ may be the same or different.]

[In the formula, ^R2 represents any carbon atom on the cyclohexane ring in the acid anhydride represented by formula (2). ^R2 represents a group containing a carboxyl group, and ^R2 is one or more.] The thermosetting composition according to claim 1, wherein the curing accelerator (C) includes one or more curing accelerators selected from the group consisting of phosphorus-based oxidation accelerators and compounds consisting of organic acid metal salts. The thermosetting composition according to claim 1 or 2 , wherein the alicyclic epoxy compound includes a compound having an epoxy group composed of two adjacent carbon atoms and an oxygen atom that constitute an alicyclic ring. The thermosetting composition according to claim 3, wherein the compound having an epoxy group composed of two adjacent carbon atoms and an oxygen atom constituting the alicyclic ring includes at least a siloxane derivative having two or more epoxy groups in the molecule, or an alicyclic epoxy compound represented by the following formula (1-1):

[In the formula, ^R3 represents a single bond or a linking group. The linking group is a divalent hydrocarbon group, an alkenylene group in which some or all of the carbon-carbon double bonds have been epoxidized, a carbonyl group, an ether bond, an ester bond, a carbonate group, an amide group, or a group in which a plurality of these groups are linked together.] The thermosetting composition according to any one of claims 1 to 4 , further comprising an antioxidant (D). The thermosetting composition according to any one of claims 1 to 5 , wherein the content of the acid anhydride curing agent (B) is 0.4 to 0.8 equivalents per equivalent of the epoxy mixture (A). The thermosetting composition according to any one of claims 1 to 6 , which is used for sealing an optical semiconductor. A cured product of the thermosetting composition according to any one of claims 1 to 7 .