Curable silicone composition, adhesive, and optical semiconductor device

Abstract

This curable silicone composition comprises (A) an alkenyl group-containing organopolysiloxane having at least two alkenyl groups per molecule, (B) an organohydrogenpolysiloxane having at least two silicon atom-bonded hydrogen atoms per molecule, (C) a thermally conductive filler constituting 5 mass% or more of the total mass of the composition, (D) a cerium-containing organopolysiloxane, and (E) a curing catalyst.

Description

Curable silicone composition, adhesive, and optical semiconductor device

[0001] The present invention relates to a curable silicone composition, more specifically, to a curable silicone composition suitable for use as an adhesive for optical semiconductors. The present invention also relates to an optical semiconductor device equipped with an adhesive comprising a cured product of such a curable silicone composition. This application claims priority based on Japanese Patent Application No. 2023-127893, filed in Japan on August 4, 2023, the contents of which are incorporated herein by reference.

[0002] Curable silicone compositions are used in a wide range of industrial fields because they cure to form cured products that have excellent heat resistance, cold resistance, electrical insulation, weather resistance, water resistance, and transparency. In particular, the cured products are less susceptible to discoloration than other organic materials and show little deterioration in physical properties such as durability, so they are widely used as silicone encapsulants for optical materials, particularly in optical semiconductor devices such as light-emitting diodes (LEDs).

[0003] It is well known to add cerium-containing organopolysiloxanes to such curable silicone compositions in order to improve the heat resistance and / or light resistance of the cured product.

[0004] For example, Patent Document 1 discloses a polymerizable composition comprising (A) a linear organopolysiloxane having at least two alkenyl groups in one molecule, (B) a polymerizable composition having the following average unit formula: (R １ SiO ３／２ ) ａ (R １ ２ SiO ２／２ ) ｂ (R １ ３ SiO １／２ ) ｃ (SiO ４／２ ) ｄ (XO １／２ ) ｅ (In the formula, R １ are each independently an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, or a group in which some or all of the hydrogen atoms of these groups have been substituted with halogen atoms, provided that at least two R１ represents the alkenyl group, X represents a hydrogen atom or an alkyl group, a represents a number from 0 to 0.3, b represents 0 or a positive number, c represents a positive number, d represents a positive number, e represents a number from 0 to 0.4, and a+b+c+d=1, c / d represents a number from 0 to 10, and b / d represents a number from 0 to 0.5. (A) an organopolysiloxane represented by the formula (A) {an amount such that the mass ratio of components (A) to (B) is 1 / 99 to 99 / 1}, (C) an organopolysiloxane having at least two silicon-bonded hydrogen atoms per molecule {an amount such that the number of silicon-bonded hydrogen atoms in component (A) is 0.1 to 10 moles per mole of alkenyl groups combined in components (A) and (B)}, (D) a cerium-containing organopolysiloxane {an amount such that the number of cerium atoms in component (D) is 20 to 2,000 ppm by mass, based on the total mass of the composition}, and (E) a catalytic amount of a hydrosilylation catalyst.

[0005] Furthermore, Patent Document 2 describes a curable white silicone composition comprising (A) an organopolysiloxane having at least two alkenyl groups in one molecule, (B) a cerium-containing organopolysiloxane, (C) a white pigment, and (D) a curing catalyst.

[0006] However, conventional curable silicone compositions have the problem that when they contain large amounts of thermally conductive fillers such as aluminum oxide, their thermal stability decreases, resulting in a decrease in strength after aging at high temperatures.

[0007] Japanese Patent Publication No. 2016-513165 Japanese Patent Publication No. 2021-88678

[0008] An object of the present invention is to provide a curable silicone composition that can form a cured product that exhibits excellent thermal stability even when it contains a large amount of thermally conductive filler.

[0009] Another object of the present invention is to provide an encapsulant containing the curable silicone composition of the present invention. Still another object of the present invention is to provide an optical semiconductor device encapsulated with the encapsulant of the present invention.

[0010] In order to solve the above problems, the present inventors conducted extensive research and surprisingly discovered that a curable silicone composition containing a cerium-containing organopolysiloxane can form a cured product that exhibits excellent thermal stability, even when the composition contains a large amount of thermally conductive filler, and thus arrived at the present invention.

[0011] Accordingly, the present invention relates to a curable silicone composition comprising: (A) an alkenyl-containing organopolysiloxane having at least two alkenyl groups per molecule; (B) an organohydrogenpolysiloxane having at least two silicon-bonded hydrogen atoms per molecule; (C) a thermally conductive filler in an amount of 5% by weight or more, based on the total weight of the composition; (D) a cerium-containing organopolysiloxane; and (E) a curing catalyst.

[0012] The alkenyl group-containing organopolysiloxane (A) preferably contains an MQ resin.

[0013] The thermally conductive filler (C) is preferably a metal oxide.

[0014] The thermally conductive filler (C) preferably contains two types of thermally conductive fillers having different average particle sizes.

[0015] The cerium atoms in the (D) cerium-containing organopolysiloxane are preferably present in an amount of 1 to 100 ppm relative to the total mass of all organopolysiloxane components in the composition.

[0016] The present invention also relates to an adhesive comprising the curable silicone composition of the present invention.

[0017] The present invention also relates to an optical semiconductor device comprising the adhesive according to the present invention.

[0018] The curable silicone composition of the present invention can form a cured product that exhibits excellent thermal stability, even when it contains a certain amount of thermally conductive filler.

[0019] [Curable Silicone Composition] The curable silicone composition according to the present invention contains at least: (A) an alkenyl-containing organopolysiloxane having at least two alkenyl groups per molecule; (B) an organohydrogenpolysiloxane having at least two silicon-bonded hydrogen atoms per molecule; (C) a thermally conductive filler in an amount of 5 mass% or more, based on the total mass of the composition; (D) a cerium-containing organopolysiloxane; and (E) a curing catalyst.

[0020] Each component of the curable silicone composition of the present invention will now be described in detail.

[0021] (A) Alkenyl Group-Containing Organopolysiloxane Having at Least Two Alkenyl Groups Per Molecule Component (A) is a curable organopolysiloxane having at least two alkenyl groups per molecule. The curable silicone composition according to the present invention may contain one type of (A) alkenyl group-containing organopolysiloxane, or may contain two or more types of (A) alkenyl group-containing organopolysiloxanes.

[0022] Examples of the molecular structure of component (A) include linear, partially branched linear, branched, resinous, cyclic, and three-dimensional network structures. Component (A) may be one organopolysiloxane having any of these molecular structures, or a mixture of two or more organopolysiloxanes having any of these molecular structures. In this specification, resinous means that the molecular structure has a branched or three-dimensional network structure.

[0023] The curable silicone composition of the present invention preferably contains, as component (A), a resinous alkenyl group-containing organopolysiloxane. The curable silicone composition of the present invention preferably contains, as component (A), a linear alkenyl group-containing organopolysiloxane. The curable silicone composition of the present invention preferably contains, as component (A), both a resinous alkenyl group-containing organopolysiloxane and a linear alkenyl group-containing organopolysiloxane.

[0024] Examples of alkenyl groups contained in component (A) include alkenyl groups having 2 to 12 carbon atoms, such as vinyl, allyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, and dodecenyl groups, with vinyl groups being preferred.

[0025] Examples of groups bonded to silicon atoms other than alkenyl groups contained in component (A) include halogen-substituted or unsubstituted monovalent hydrocarbon groups other than alkenyl groups, such as alkyl groups having 1 to 12 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, heptyl, octyl, nonyl, decyl, undecyl, and dodecyl; aryl groups having 6 to 20 carbon atoms, such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups having 7 to 20 carbon atoms, such as benzyl, phenethyl, and phenylpropyl; and groups in which some or all of the hydrogen atoms of these groups have been substituted with halogen atoms, such as fluorine, chlorine, or bromine. The silicon atoms in component (A) may contain small amounts of hydroxyl groups or alkoxy groups, such as methoxy and ethoxy, as long as the object of the present invention is not impaired. The groups bonded to silicon atoms in component (A) other than alkenyl groups are preferably selected from alkyl groups having 1 to 6 carbon atoms, particularly methyl groups.

[0026] In one embodiment of the present invention, component (A) may include, as component (A-1), a resin-like alkenyl group-containing organopolysiloxane. (A-1) The resin-like alkenyl group-containing organopolysiloxane is preferably represented by the average unit formula (I-a): (R １ ３ SiO １／２ ) ａ (R １ ２ SiO ２／２ ) ｂ (R １ SiO ３／２ ) ｃ (SiO ４／２ ) ｄ (XO １／２ ) ｅ (In formula (I-a), R１ are the same or different halogen-substituted or unsubstituted monovalent hydrocarbon groups, provided that at least two R １ is an alkenyl group, 0≦a<1, 0≦b<1, 0≦c<0.9, 0≦d<0.5, and 0≦e<0.4, a+b+c+d=1.0, and c+d>0. e can be expressed as the number of (XO) groups when the total number of silicon atoms is 1 (representing the ratio of the number of (XO) groups to the total number of silicon atoms).

[0027] R in the above formula (I-a) １ Examples of halogen-substituted or unsubstituted monovalent hydrocarbon groups include alkyl groups having 1 to 12 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, heptyl, octyl, nonyl, decyl, undecyl, and dodecyl; aryl groups having 6 to 20 carbon atoms, such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups having 7 to 20 carbon atoms, such as benzyl, phenethyl, and phenylpropyl; alkenyl groups having 2 to 12 carbon atoms, such as vinyl, allyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, and dodecenyl; and groups in which some or all of the hydrogen atoms of these groups have been substituted with halogen atoms, such as fluorine, chlorine, or bromine. R １ R may contain a small amount of hydroxyl groups or alkoxy groups such as methoxy groups and ethoxy groups, as long as the object of the present invention is not impaired. １ is preferably selected from alkyl groups having 1 to 6 carbon atoms, in particular methyl groups, and alkenyl groups having 2 to 6 carbon atoms, in particular vinyl groups.

[0028] In the above formula (I-a), X is a hydrogen atom or an alkyl group. The alkyl group for X is preferably an alkyl group having 1 to 3 carbon atoms, and specific examples thereof include a methyl group, an ethyl group, and a propyl group. X is preferably a hydrogen atom.

[0029] In the above formula (I-a), a is preferably in the range of 0.1≦a≦0.8, more preferably in the range of 0.2≦a≦0.7, and even more preferably in the range of 0.3≦a≦0.6. In the above formula (I-a), b is preferably in the range of 0≦b≦0.5, more preferably in the range of 0≦b≦0.3, and particularly in the range of 0≦b≦0.1. In the above formula (I-a), c is preferably in the range of 0≦c<0.5, more preferably in the range of 0≦c≦0.3, and particularly in the range of 0≦c≦0.1. In the above formula (I-a), d is preferably in the range of 0.1≦d≦0.8, more preferably in the range of 0.2≦d≦0.7, and even more preferably in the range of 0.3≦d≦0.6. In the above formula (I-a), e is preferably in the range of 0≦e≦0.15, more preferably in the range of 0≦e≦0.1, and particularly in the range of 0≦e≦0.05.

[0030] In a preferred embodiment of the present invention, the resinous alkenyl group-containing organopolysiloxane of component (A-1) contains SiO ４／２ The resinous alkenyl group-containing organopolysiloxane of component (A-1) contains siloxane units (Q units) represented by the following formula: ２／２ The resin-like alkenyl group-containing organopolysiloxane of component (A-1) may or may not contain siloxane units (D units) represented by the following formula: ３／２ The siloxane unit (T unit) represented by the following formula (1) may or may not be contained, but preferably is not contained.

[0031] In a preferred embodiment of the present invention, the resin-like alkenyl group-containing organopolysiloxane of component (A-1) contains alkenyl groups at the molecular terminals. The resin-like organopolysiloxane of component (A-1) preferably contains SiO １／２ The siloxane unit (M unit) has an alkenyl group on the molecular chain side chain (i.e., SiO ２／２ Siloxane units (D units) represented by the formula: and SiO ３／２ The siloxane unit (T unit) represented by the formula (I) may or may not contain an alkenyl group, but preferably does not contain an alkenyl group.

[0032] In a preferred embodiment of the present invention, the resinous alkenyl group-containing organopolysiloxane of component (A-1) contains an MQ resin or consists solely of an MQ resin. １／２ Siloxane units (M units) represented by the formula: and SiO ４／２ The MQ resin of component (A-1) is preferably represented by the following average unit formula (I-b): Average unit formula (I-b): (R １ ３ SiO １／２ ) ｓ (SiO ４／２ ) ｔ (XO １／２ ) ｕ In the formula, R １ are the same or different halogen-substituted or unsubstituted monovalent hydrocarbon groups, provided that at least two R １ represents an alkenyl group, 0<s<1, 0<t<1, 0≦u<0.4, and s+t=1.0, and u represents the number of (XO) groups when the total number of silicon atoms is 1 (the ratio of the number of (XO) groups to the total number of silicon atoms).

[0033] R in formula (II-b) １ is as explained in formula (II-a).

[0034] In formula (II-b), s is preferably in the range of 0.2≦s≦0.8, more preferably in the range of 0.3≦s≦0.7, and even more preferably in the range of 0.4≦s≦0.6. In formula (II-b), t is preferably in the range of 0.2≦t≦0.8, more preferably in the range of 0.3≦t≦0.7, and particularly in the range of 0.3≦t≦0.7. In formula (II-b), u is preferably in the range of 0≦u≦0.3, more preferably in the range of 0≦u≦0.2, and particularly in the range of 0≦u≦0.1.

[0035] The alkenyl group content of all silicon-bonded organic groups in the resinous alkenyl-group-containing organopolysiloxane of component (A-1) is not particularly limited, but may be, for example, 3 mol % or more, preferably 5 mol % or more, and more preferably 10 mol % or more of the total silicon-bonded organic groups, and 40 mol % or less, preferably 30 mol %, and more preferably 20 mol % or less of the total silicon-bonded organic groups. The alkenyl group content can be determined, for example, by analytical methods such as Fourier transform infrared spectroscopy (FT-IR) or nuclear magnetic resonance (NMR), or by the titration method described below.

[0036] A method for quantifying the amount of alkenyl groups in each component by titration will now be described. The alkenyl group content in organopolysiloxane components can be accurately quantified by a titration method commonly known as the Wyss method. The principle is as follows: First, alkenyl groups in the organopolysiloxane raw material are subjected to an addition reaction with iodine monochloride as shown in formula (1). Next, excess iodine monochloride is reacted with potassium iodide and liberated as iodine by the reaction shown in formula (2). The liberated iodine is then titrated with a sodium thiosulfate solution. Formula (1)CH ２ =CH- + 2ICl → CH ２ I-CHCl- + ICl (excess) Formula (2) ICl+KI → I ２ The amount of alkenyl groups in the component can be quantified from the difference between the amount of sodium thiosulfate required for the +KCl titration and the titer of a separately prepared blank solution.

[0037] The MQ resin of component (A-1) may be solid at room temperature (25°C).

[0038] When component (A) contains one or more types of resinous organopolysiloxane (A-1), there are no particular limitations on the amount thereof, but it is preferably 1 mass % or more, more preferably 3 mass % or more, and even more preferably 5 mass % or more, based on the total mass of the curable silicone composition of the present invention. Furthermore, the amount of component (A-1) is preferably 70 mass % or less, more preferably 60 mass % or less, and even more preferably 50 mass % or less, based on the total mass of the curable silicone composition. In this specification, the upper and lower limits of the numerical ranges can be arbitrarily combined to set the numerical range.

[0039] Component (A) may contain a linear alkenyl group-containing organopolysiloxane as component (A-2). The linear alkenyl group-containing organopolysiloxane of component (A-2) preferably has an average structural formula (I-c): R １ ３ SiO(R １ ２ SiO ２／２ ) ｍ SiR ２ ３ (In formula (I-c), R １ are the same or different halogen-substituted or unsubstituted monovalent hydrocarbon groups, provided that at least two R １ is an alkenyl group, and m is 1 to 500.

[0040] In the above formula (I-c), R １ The halogen-substituted or unsubstituted monovalent hydrocarbon group may be the same as that in formula (I-a) above. In formula (I-c) above, m is preferably 2 to 300, more preferably 5 to 200, even more preferably 10 to 100, and particularly preferably 15 to 50.

[0041] Examples of such component (A-2) include dimethylpolysiloxanes terminally blocked with dimethylvinylsiloxy groups, dimethylpolysiloxanes terminally blocked with diphenylvinylsiloxy groups, dimethylsiloxane-methylphenylsiloxane copolymers terminally blocked with dimethylvinylsiloxy groups, dimethylsiloxane-diphenylsiloxane copolymers terminally blocked with dimethylvinylsiloxy groups, dimethylsiloxane-methylphenylsiloxane copolymers terminally blocked with diphenylvinylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymers terminally blocked with dimethylvinylsiloxy groups, and dimethylsiloxane-methylvinylsiloxane copolymers terminally blocked with dimethylvinylsiloxy groups. Examples include a dimethylsiloxane-methylphenylsiloxane-methylvinylsiloxane copolymer capped with dimethylvinylsiloxy groups, a dimethylsiloxane-diphenylsiloxane-methylvinylsiloxane copolymer capped at both molecular chain terminals with dimethylvinylsiloxy groups, a methylvinylpolysiloxane capped at both molecular chain terminals with trimethylsiloxy groups, a methylvinylsiloxane-methylphenylsiloxane copolymer capped at both molecular chain terminals with trimethylsiloxy groups, a methylvinylsiloxane-diphenylsiloxane copolymer capped at both molecular chain terminals with trimethylsiloxy groups, and a dimethylsiloxane-methylvinylsiloxane copolymer capped at both molecular chain terminals with trimethylsiloxy groups.

[0042] In a preferred embodiment of the present invention, the linear alkenyl-containing organopolysiloxane of component (A-2) may be a linear organopolysiloxane capped with alkenyl groups at both molecular chain terminals, i.e., containing alkenyl groups at both molecular chain terminals. The linear organopolysiloxane of component (A-2) may or may not contain alkenyl groups in molecular chain side chains (i.e., D units), but preferably does not.

[0043] The alkenyl group content (mol % of alkenyl groups relative to all silicon-bonded organic groups in the linear organopolysiloxane) of component (A-2) can be designed as desired, but is typically 1 mol % or more, preferably 2 mol % or more, and more preferably 3 mol % or more, and can be 20 mol % or less, preferably 15 mol % or less, and more preferably 10 mol % or less. The alkenyl group content can be determined, for example, by analysis using a Fourier transform infrared spectrophotometer (FT-IR), nuclear magnetic resonance (NMR), or the titration method described above.

[0044] When component (A) contains linear organopolysiloxane (A-2), its content is not particularly limited, but is preferably 1 mass % or more, more preferably 2 mass % or more, and even more preferably 3 mass % or more, based on the total mass of the curable silicone composition of the present invention. Furthermore, the content of component (A-2) is preferably 50 mass % or less, more preferably 40 mass % or less, and even more preferably 30 mass % or less, based on the total mass of the curable silicone composition of the present invention.

[0045] In one embodiment, component (A) contains a small amount of aryl groups in the silicon-bonded organic groups, or no aryl groups at all. Specifically, the amount of aryl groups relative to the total silicon-bonded organic groups may be 10 mol % or less, 5 mol % or less, 3 mol % or less, or 1 mol % or less.

[0046] The viscosity of the alkenyl group-containing organopolysiloxane (A) is not particularly limited, but may be, for example, 5 mPa s to 5,000 mPa s, and preferably 10 mPa s to 500 mPa s, at 25° C. In this specification, the viscosity of the organopolysiloxane component can be measured using a rotational viscometer in accordance with JIS K7117-1.

[0047] The weight average molecular weight (Mw) of the alkenyl group-containing organopolysiloxane (A) is not particularly limited, but is, for example, in the range of 1,000 to 100,000, and preferably in the range of 1,500 to 15,000. In this specification, the weight average molecular weight can be measured by GPC.

[0048] The total amount of component (A) is not particularly limited, but is preferably 3% by mass or more, preferably 5% by mass or more, and more preferably 10% by mass or more, based on the total mass of the curable silicone composition. Also, component (A) is preferably 90% by mass or less, preferably 80% by mass or less, and more preferably 70% by mass or less, based on the total mass of the curable silicone composition.

[0049] (B) Organohydrogenpolysiloxane having at least two silicon-bonded hydrogen atoms per molecule Component (B) is an organohydrogenpolysiloxane having at least two silicon-bonded hydrogen atoms per molecule, and acts as a crosslinker for the curable silicone composition via a hydrosilylation curing reaction. The curable silicone composition according to the present invention may contain one type of organohydrogenpolysiloxane (B), or may contain two or more types of organohydrogenpolysiloxane (B).

[0050] Examples of the molecular structure of component (B) include linear, partially branched linear, branched, resinous, cyclic, and three-dimensional network structures. Component (B) may be one organohydrogenpolysiloxane having any of these molecular structures, or a mixture of two or more organohydrogenpolysiloxanes having any of these molecular structures. Preferably, the curable silicone composition of the present invention contains a linear organohydrogenpolysiloxane as component (B).

[0051] Examples of groups bonded to silicon atoms other than silicon-bonded hydrogen atoms contained in component (B) include halogen-substituted or unsubstituted monovalent hydrocarbon groups other than alkenyl groups, such as alkyl groups having 1 to 12 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, heptyl, octyl, nonyl, decyl, undecyl, and dodecyl; aryl groups having 6 to 20 carbon atoms, such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups having 7 to 20 carbon atoms, such as benzyl, phenethyl, and phenylpropyl; and groups in which some or all of the hydrogen atoms of these groups have been substituted with halogen atoms, such as fluorine, chlorine, or bromine. The silicon atoms in component (B) may contain small amounts of hydroxyl groups or alkoxy groups, such as methoxy and ethoxy, as long as the object of the present invention is not impaired. The silicon-bonded groups other than silicon-bonded hydrogen atoms in component (B) are preferably selected from alkyl groups having 1 to 6 carbon atoms, particularly methyl groups.

[0052] In one embodiment of the present invention, the component (B) may include a linear organohydrogenpolysiloxane as the component (B-1). The linear organohydrogenpolysiloxane of the component (B-1) is preferably represented by the average structural formula (II): R ２ ３ SiO(R ２ ２ SiO ２／２ ) ｎ SiR ２ ３ (In formula (II), R ２ are hydrogen atoms or the same or different halogen-substituted or unsubstituted monovalent hydrocarbon groups other than alkenyl groups, provided that at least two R ２ is a hydrogen atom, and n is 1 to 200).

[0053] In the above formula (II), R ２Examples of halogen-substituted or unsubstituted monovalent hydrocarbon groups other than alkenyl groups in R include alkyl groups having 1 to 12 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, heptyl, octyl, nonyl, decyl, undecyl, and dodecyl groups; aryl groups having 6 to 20 carbon atoms, such as phenyl, tolyl, xylyl, and naphthyl groups; aralkyl groups having 7 to 20 carbon atoms, such as benzyl, phenethyl, and phenylpropyl groups; and groups in which some or all of the hydrogen atoms of these groups have been substituted with halogen atoms, such as fluorine, chlorine, or bromine atoms. ２ R may contain a small amount of hydroxyl groups or alkoxy groups such as methoxy groups and ethoxy groups, as long as the object of the present invention is not impaired. ２ is preferably selected from a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, in particular a methyl group.

[0054] In the above formula (II), n is preferably 2 to 150, and more preferably 5 to 100.

[0055] In a preferred embodiment of the present invention, the linear organohydrogenpolysiloxane of component (B-1) contains silicon-bonded hydrogen atoms at both molecular chain terminals. The linear organohydrogenpolysiloxane of component (B-1) has silicon-bonded hydrogen atoms in the M units, and the D units may or may not contain silicon-bonded hydrogen atoms, but preferably do not.

[0056] In one embodiment, component (B) contains a small amount of aryl groups in the silicon-bonded organic groups, or no aryl groups at all. Specifically, the amount of aryl groups relative to the total silicon-bonded organic groups may be 10 mol % or less, 5 mol % or less, 3 mol % or less, or 1 mol % or less.

[0057] The content of component (B) is not particularly limited, but is preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more, based on the total mass of the curable silicone composition. In a preferred embodiment, component (B) is contained in an amount of 30% by mass or less, preferably 20% by mass or less, and more preferably 15% by mass or less, based on the total mass of the curable silicone composition.

[0058] Furthermore, in one embodiment of the present invention, component (B) is contained in an amount such that the ratio of silicon-bonded alkenyl groups to silicon-bonded hydrogen atoms (H / Ar) contained in the organopolysiloxane component is 0.5 moles or more, preferably 0.7 moles or more, more preferably 1 mole or more, and especially 1.2 moles or more of silicon-bonded hydrogen atoms per mole of silicon-bonded alkenyl groups in the curable silicone composition; and the curable silicone composition can contain, for example, an amount such that the number of silicon-bonded hydrogen atoms per mole of silicon-bonded alkenyl groups is 5 moles or less, preferably 3 moles or less, more preferably 2.5 moles or less, and even more preferably 2 moles or less.

[0059] (C) Thermally Conductive Filler The thermally conductive filler of component (C) is a component that imparts the desired thermal conductivity to the curable silicone composition of the present invention. The curable silicone composition of the present invention may contain one type of thermally conductive filler (C), or may contain two or more types of thermally conductive fillers (C).

[0060] Examples of component (C) can be selected from the group consisting of pure metals, alloys, metal oxides, metal hydroxides, metal nitrides, metal carbides, metal silicides, carbon, soft magnetic alloys, and ferrites. Component (C) is preferably at least one powder and / or fiber, and is preferably a metal powder, a metal oxide powder, a metal nitride powder, or a carbon powder.

[0061] Examples of pure metals include bismuth, lead, tin, antimony, indium, cadmium, zinc, silver, copper, nickel, aluminum, iron, and metallic silicon. Examples of alloys include alloys of two or more metals selected from the group consisting of bismuth, lead, tin, antimony, indium, cadmium, zinc, silver, aluminum, iron, and metallic silicon. Examples of metal oxides include aluminum oxide (alumina), zinc oxide, silica, magnesium oxide, beryllium oxide, chromium oxide, and titanium oxide. Examples of metal hydroxides include magnesium hydroxide, aluminum hydroxide, barium hydroxide, and calcium hydroxide. Examples of metal nitrides include boron nitride, aluminum nitride, and silicon nitride. Examples of metal carbides include silicon carbide, boron carbide, and titanium carbide. Examples of metal silicides include magnesium silicide, titanium silicide, zirconium silicide, tantalum silicide, niobium silicide, chromium silicide, tungsten silicide, and molybdenum silicide. Examples of carbon include diamond, graphite, fullerene, carbon nanotube, graphene, activated carbon, and amorphous carbon black. Examples of soft magnetic alloys include Fe—Si alloys, Fe—Al alloys, Fe—Si—Al alloys, Fe—Si—Cr alloys, Fe—Ni alloys, Fe—Ni—Co alloys, Fe—Ni—Mo alloys, Fe—Co alloys, Fe—Si—Al—Cr alloys, Fe—Si—B alloys, and Fe—Si—Co—B alloys. Examples of ferrites include Mn-Zn ferrite, Mn-Mg-Zn ferrite, Mg-Cu-Zn ferrite, Ni-Zn ferrite, Ni-Cu-Zn ferrite, and Cu-Zn ferrite.

[0062] Component (C) is preferably selected from metal oxides, and may be particularly selected from aluminum oxide (alumina), zinc oxide, silica, magnesium oxide, beryllium oxide, chromium oxide, and titanium oxide.

[0063] The shape of component (C) is not particularly limited and may be, for example, spherical, needle-like, disk-like, rod-like, or irregular, with spherical being preferred.

[0064] The average particle size of the primary particles of component (C) is not particularly limited, but is preferably in the range of 0.01 to 50 μm, more preferably 0.01 to 20 μm, and even more preferably 0.1 to 5 μm. In this specification, the average particle size refers to the particle size at 50% of the integrated value (D50) in the particle size distribution determined by laser diffraction / scattering method.

[0065] In a preferred embodiment of the present invention, component (C) contains two types of thermally conductive fillers with different average particle sizes. In this embodiment, component (C) preferably contains a combination of component (C-1) having an average particle size of 2 μm or less and component (C-2) having an average particle size of more than 2 μm. The average particle size of component (C-1) having the smaller average particle size is preferably in the range of 0.01 to 1.5 μm, more preferably 0.1 to 1 μm. Furthermore, the average particle size of component (C-2) having the larger average particle size is preferably in the range of 2.5 to 20 μm, more preferably 3 to 5 μm.

[0066] The thermally conductive filler (C) is contained in an amount of 5% by mass or more, based on the total mass of the curable silicone composition. The thermally conductive filler (C) is preferably contained in an amount of 7% by mass or more, and more preferably 10% by mass or more, based on the total mass of the curable silicone composition. In a preferred embodiment, the thermally conductive filler (C) is contained in an amount of 90% by mass or less, and preferably 80% by mass or less, based on the total mass of the curable silicone composition.

[0067] In another embodiment, the content of the thermally conductive filler of component (C) may be 20% by mass or more, 30% by mass or more to 40% by mass or more, 50% by mass or more, 60% by mass or more, or 70% by mass or more, based on the total mass of the curable silicone composition. Component (C) may be contained in an amount of 90% by mass or less, and preferably 80% by mass or less, based on the total mass of the curable silicone composition.

[0068] Furthermore, when component (C) contains components (C-1) and (C-2) having different particle sizes, the content ratio of these components is not particularly limited, but typically the mass ratio of component (C-2) to component (C-1) is within the range of 1:10 to 10:1, preferably within the range of 1:5 to 5:1, and more preferably within the range of 1:3 to 3:1. Furthermore, in a preferred embodiment, component (C-2) is contained in an amount greater than component (C-1); for example, the mass ratio of component (C-2) to component (C-1) is within the range of 1 to 10:1, preferably within the range of 1.25 to 5:1, and more preferably within the range of 1.5 to 3:1.

[0069] (D) Cerium-Containing Organopolysiloxane The curable silicone composition according to the present invention contains a cerium-containing organopolysiloxane as component (D). The cerium-containing organopolysiloxane (D) can be prepared, for example, by reacting cerium chloride or a cerium salt of a carboxylic acid with an alkali metal salt of a silanol group-containing organopolysiloxane. Therefore, in this specification, the term "cerium-containing organopolysiloxane" can refer to a compound obtained by reacting a silanol group-containing organopolysiloxane with a cerium salt, in which the silanol groups of the organopolysiloxane are chemically bonded to cerium atoms.

[0070] Examples of the cerium salts of the above carboxylic acids include cerium 2-ethylhexanoate, cerium naphthenate, cerium oleate, cerium laurate, and cerium stearate. Examples of the cerium chloride include cerium trichloride.

[0071] Examples of the alkali metal salt of the silanol-containing organopolysiloxane include potassium salts of diorganopolysiloxanes having both molecular chain terminals blocked with silanol groups, sodium salts of diorganopolysiloxanes having both molecular chain terminals blocked with silanol groups, potassium salts of diorganopolysiloxanes having one molecular chain terminal blocked with a silanol group and the other molecular chain terminal blocked with a triorganosiloxy group, and sodium salts of diorganopolysiloxanes having one molecular chain terminal blocked with a silanol group and the other molecular chain terminal blocked with a triorganosiloxy group. Examples of groups bonded to silicon atoms in this organopolysiloxane include alkyl groups having 1 to 12 carbon atoms, such as methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, neopentyl, hexyl, cyclohexyl, heptyl, octyl, nonyl, decyl, undecyl, and dodecyl; aryl groups having 6 to 20 carbon atoms, such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups having 7 to 20 carbon atoms, such as benzyl, phenethyl, and phenylpropyl; and groups in which some or all of the hydrogen atoms of these groups have been substituted with halogen atoms, such as fluorine, chlorine, or bromine.

[0072] The above reaction is carried out at room temperature or by heating in an organic solvent such as an alcohol such as methanol, ethanol, isopropanol, or butanol; an aromatic hydrocarbon such as toluene or xylene; an aliphatic hydrocarbon such as hexane or heptane; or mineral spirit, ligroin, or petroleum ether. If necessary, the resulting reaction product is preferably subjected to distillation to remove the organic solvent or low-boiling components, or to filtration of any precipitates. To promote the reaction, dialkylformamide, hexaalkylphosphoamide, or the like may be added. The cerium atom content in the cerium-containing organopolysiloxane thus prepared is preferably within the range of 0.1 to 15% by mass.

[0073] The content of component (D) is not particularly limited, but is preferably an amount such that the content of cerium atoms in the cerium-containing organopolysiloxane (D) is in the range of 1 to 100 ppm, and more preferably in the range of 2 to 50 ppm, relative to the total mass of all organopolysiloxane components in the composition.

[0074] (E) Curing Catalyst The curing catalyst of component (E) is a curing catalyst for hydrosilylation reactions, and is a catalyst for accelerating the curing of the curable silicone composition of the present invention. Examples of this component (E) include platinum-based catalysts such as chloroplatinic acid, alcohol solutions of chloroplatinic acid, platinum-olefin complexes, platinum-1,3-divinyl-1,1,3,3-tetramethyldisiloxane complexes, and platinum-supported powders; palladium-based catalysts such as tetrakis(triphenylphosphine)palladium, palladium black, and mixtures with triphenylphosphine; and rhodium-based catalysts, with platinum-based catalysts being particularly preferred.

[0075] The amount of component (E) blended is a catalytic amount. More specifically, when a platinum catalyst is used as component (E), the amount of platinum atoms, relative to the total mass of the curable silicone composition of the present invention, is preferably 0.01 ppm or more, more preferably 0.1 ppm or more, and even more preferably 1 ppm or more. Furthermore, the amount of platinum atoms, relative to the total mass of the curable silicone composition of the present invention, is preferably 20 ppm or less, more preferably 15 ppm or less, even more preferably 10 ppm or less, and particularly preferably 5 ppm or less.

[0076] (Other Organopolysiloxane Components) The curable silicone composition components according to the present invention may contain an epoxy group-containing organopolysiloxane as an organopolysiloxane component other than components (A) and (B). Preferably, the epoxy group-containing organopolysiloxane is an organopolysiloxane containing at least one epoxy group and at least two alkenyl groups per molecule. The epoxy group-containing organopolysiloxane can function as an adhesion promoter.

[0077] The molecular structure of the epoxy group-containing organopolysiloxane can be exemplified by linear, partially branched linear, branched, resinous, cyclic, and three-dimensional network structures, with resinous epoxy group-containing organopolysiloxanes being preferred. The curable silicone composition according to the present invention may contain one type of epoxy group-containing organopolysiloxane, or may contain a combination of two or more types of epoxy group-containing organopolysiloxanes.

[0078] The epoxy group-containing organopolysiloxane preferably contains, as the alkenyl group, an alkenyl group having 2 to 12 carbon atoms, such as a vinyl group, allyl group, butenyl group, pentenyl group, hexenyl group, heptenyl group, octenyl group, nonenyl group, decenyl group, undecenyl group, or dodecenyl group, preferably a vinyl group. Furthermore, examples of the epoxy group-containing organic group include glycidoxyalkyl groups such as a 2-glycidoxyethyl group, a 3-glycidoxypropyl group, and a 4-glycidoxybutyl group; epoxycycloalkylalkyl groups such as a 2-(3,4-epoxycyclohexyl)-ethyl group and a 3-(3,4-epoxycyclohexyl)-propyl group; and epoxyalkyl groups such as a 3,4-epoxybutyl group and a 7,8-epoxyoctyl group, with a glycidoxyalkyl group being preferred, and a 3-glycidoxypropyl group being particularly preferred.

[0079] Examples of groups bonded to silicon atoms other than alkenyl groups and epoxy-containing organic groups in epoxy-containing organopolysiloxanes include halogen-substituted or unsubstituted monovalent hydrocarbon groups other than alkenyl groups and epoxy-containing organic groups. Examples include alkyl groups having 1 to 12 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, heptyl, octyl, nonyl, decyl, undecyl, and dodecyl; aryl groups having 6 to 20 carbon atoms, such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups having 7 to 20 carbon atoms, such as benzyl, phenethyl, and phenylpropyl; and groups in which some or all of the hydrogen atoms of these groups have been substituted with halogen atoms, such as fluorine, chlorine, or bromine atoms. Preferred are alkyl groups having 1 to 12 carbon atoms, and methyl groups are particularly preferred.

[0080] The resinous epoxy group-containing organopolysiloxane preferably has the following average unit formula (III): (R ３ ３ SiO １／２ ) ｆ (R ３ ２ SiO ２／２ ) ｇ (R ３ SiO ３／２ ) ｈ (SiO ４／２ ) ｉ (XO １／２ ) ｊ {In formula (III), R ３ are each independently a halogen-substituted or unsubstituted monovalent hydrocarbon group, provided that at least two R ３ is an alkenyl group, and at least one R ３ is an epoxy group-containing organic group, X is a hydrogen atom or an alkyl group, 0≦f<1, 0<g<1, 0≦h<0.9, 0≦i<0.5, and 0≦j<0.4, and f+g+h+i=1.0 and h+i>0. j represents the number of (XO) groups when the total number of silicon atoms is 1 (the ratio of the number of (XO) groups to the total number of silicon atoms).

[0081] In the above formula (III), R３ Examples of the halogen-substituted or unsubstituted monovalent hydrocarbon group include the above-mentioned alkenyl groups, epoxy group-containing organic groups, and other monovalent hydrocarbon groups. Furthermore, X in formula (III) is a hydrogen atom or an alkyl group. The alkyl group represented by X is preferably an alkyl group having 1 to 3 carbon atoms, and specific examples thereof include a methyl group, an ethyl group, and a propyl group.

[0082] In the above formula (III), f is preferably in the range of 0≦f≦0.5, more preferably in the range of 0≦f≦0.3, and even more preferably in the range of 0≦f≦0.1. In the above formula (III), g is preferably in the range of 0.1≦g≦0.7, more preferably in the range of 0.2≦g≦0.6, and particularly in the range of 0.3≦g≦0.5. In the above formula (III), h is preferably in the range of 0.2≦h≦0.8, more preferably in the range of 0.3≦h≦0.7, and particularly in the range of 0.4≦h≦0.65. In the above formula (III), i is preferably in the range of 0≦i≦0.4, more preferably in the range of 0≦i≦0.25, and particularly in the range of 0≦i≦0.1. In the above formula (III), j is preferably in the range of 0≦j≦0.3, more preferably in the range of 0≦j≦0.2, and particularly in the range of 0≦j≦0.1.

[0083] In a preferred embodiment of the present invention, the resinous epoxy group-containing organopolysiloxane is a resinous epoxy group-containing organopolysiloxane represented by the above formula (III), where h is greater than 0, i.e., SiO ３／２ The epoxy group-containing resinous organopolysiloxane contains siloxane units (T units) represented by the formula: ４／２ The epoxy group-containing resinous organopolysiloxane may or may not contain a siloxane unit (Q unit) represented by the formula: １／２ The siloxane unit (M unit) represented by the following formula (1) may or may not be contained, but preferably is not contained.

[0084] In a preferred embodiment of the present invention, the epoxy group-containing organopolysiloxane has an epoxy group-containing organic group as a pendant group on a molecular side chain. The epoxy group-containing organopolysiloxane is preferably SiO ３／２ The siloxane unit (T unit) represented by the formula (I) has an epoxy group-containing organic group.

[0085] In a preferred embodiment, the amount of alkenyl groups relative to all silicon-bonded organic groups in the epoxy group-containing organopolysiloxane is not particularly limited, but is preferably 1 mol % or more, more preferably 3 mol % or more, and even more preferably 5 mol % or more, and may be, for example, 30 mol % or less, preferably 20 mol % or less, and more preferably 15 mol % or less.

[0086] The amount of epoxy-containing organic groups relative to all silicon-bonded organic groups in the epoxy-containing organopolysiloxane is not particularly limited, but is preferably 5 mol% or more, more preferably 10 mol% or more, and even more preferably 20 mol% or more, and is, for example, 60 mol% or less, preferably 50 mol% or less. The amount of epoxy-containing organic groups can be determined, for example, by analysis using a Fourier transform infrared spectrophotometer (FT-IR) or nuclear magnetic resonance (NMR).

[0087] The weight average molecular weight (Mw) of the epoxy group-containing organopolysiloxane is not particularly limited, but can be in the range of 1,000 to 10,000. In this specification, the weight average molecular weight can be measured by GPC.

[0088] The content of the epoxy group-containing organopolysiloxane is not particularly limited, but is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.5% by mass or more, based on the total mass of the curable silicone composition of the present invention; and may be 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, based on the total mass of the curable silicone composition of the present invention.

[0089] The curable silicone composition may also contain, as another organopolysiloxane component, a silicone reactive diluent, a cyclic organopolysiloxane having at least two alkenyl groups per molecule. Such a cyclic organopolysiloxane preferably has the average structural formula (IV): (R ４ ２ SiO) ｎ (In formula (IV), R ４ are the same or different halogen-substituted or unsubstituted monovalent hydrocarbon groups, provided that at least two R ４ is an alkenyl group, and n is 4 to 15, preferably 4 to 10, and more preferably 4 to 8.

[0090] In the above formula (IV), R ４ The halogen-substituted or unsubstituted monovalent hydrocarbon group in R is preferably selected from alkyl groups having 1 to 12 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, heptyl, octyl, nonyl, decyl, undecyl, and dodecyl groups; aryl groups having 6 to 20 carbon atoms, such as phenyl, tolyl, xylyl, and naphthyl groups; alkenyl groups having 2 to 12 carbon atoms, such as vinyl, allyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, and dodecenyl groups; and groups in which some or all of the hydrogen atoms of these groups have been substituted with halogen atoms, such as fluorine, chlorine, and bromine atoms. ４ is preferably selected from alkyl groups having 1 to 6 carbon atoms, in particular methyl groups, and alkenyl groups having 2 to 6 carbon atoms, in particular vinyl groups.

[0091] The amount of cyclic organopolysiloxane contained is not particularly limited, but is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.5% by mass or more, based on the total mass of the curable silicone composition of the present invention; and is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, based on the total mass of the curable silicone composition of the present invention.

[0092] (Other Components) The curable silicone composition of the present invention can contain optional components as long as they do not impair the object of the present invention. Examples of these optional components include acetylene compounds, organic phosphorus compounds, vinyl group-containing siloxane compounds, inorganic fillers other than component (C), such as inorganic fillers such as crushed quartz, silica, magnesium carbonate, and diatomaceous earth, inorganic fillers obtained by hydrophobizing the surface of such inorganic fillers with organic silicon compounds, surface treatment agents, hydrosilylation reaction inhibitors, tackifiers, heat resistance agents, cold resistance agents, flame retardants, thixotropy agents, phosphors, solvents, and the like. The amount of these optional components added is typically 0.001 to 20% by mass of the total composition.

[0093] Among the inorganic fillers, examples of silica include fumed silica, dry silica, wet silica, crystalline silica, precipitated silica, etc. The silica may be surface-hydrophobized with an organosilicon compound such as an organoalkoxysilane compound, an organochlorosilane compound, an organosilazane compound, or a low-molecular-weight siloxane compound, or a silane coupling agent, a titanate-based coupling agent, or the like.

[0094] The hydrosilylation reaction inhibitor is a component that inhibits the hydrosilylation reaction of the curable silicone composition. Examples of such curing reaction inhibitors include alkyne alcohols such as 2-methyl-3-butyn-2-ol, 3,5-dimethyl-1-hexyn-3-ol, 2-phenyl-3-butyn-2-ol, 1-ethynyl-1-cyclohexanol, and 1-ethynyl-2-cyclohexanol; enyne compounds such as 3-methyl-3-penten-1-yne and 3,5-dimethyl-3-hexen-1-yne; alkenyl group-containing low-molecular-weight siloxanes such as tetramethyltetravinylcyclotetrasiloxane and tetramethyltetrahexenylcyclotetrasiloxane; and alkynyloxysilanes such as methyl-tris(1,1-dimethylpropynyloxy)silane, vinyl-tris(1,1-dimethylpropynyloxy)silane, and methyl-tris(3-methyl-1-butyn-3-oxy)silane. Preferably, the hydrosilylation reaction inhibitor is selected from the group consisting of alkyne alcohols, and particularly preferably 1-ethynyl-1-cyclohexanol. The amount of reaction inhibitor added is usually 0.001 to 5% by mass of the total composition.

[0095] In one embodiment of the present invention, the curable silicone composition comprises two or more different cure inhibitors. In a preferred embodiment, the curable silicone composition comprises a combination of at least one alkyne alcohol and at least one alkynyloxysilane as cure inhibitors.

[0096] The surface treatment agent is a surface treatment agent for fillers, particularly the thermally conductive filler of component (C), and the type thereof is not particularly limited, but examples thereof include organosilazanes, organocyclosiloxanes, organochlorosilanes, organoalkoxysilanes, alkoxysilylalkyl group-containing organopolysiloxanes, low-molecular-weight linear siloxanes, and organic compounds. Examples of the organic compounds include polyhydric alcohols, alkanolamines or derivatives thereof, organosilicon compounds such as organosiloxanes, higher fatty acids or metal salts thereof, organometallic compounds, organometallic complexes, fluorine-based organic compounds, anionic surfactants, cationic surfactants, and nonionic surfactants.

[0097] The alkoxysilylalkyl group-containing organopolysiloxane used as the surface treatment agent is, for example, an organopolysiloxane having the following formula: (R ａ O) ３ Si-(CH ２ ) ｐ - (R ｂ ２ SiO) ｑ -R ｃ (In the formula, R ａ and R ｂ are each independently C １～４ is an alkyl group, particularly a methyl group, ｃ is C １～１０ Alkyl group, preferably C ２～６ alkyl group, p is 3 to 12, preferably 4 to 10, and q is 50 to 150, preferably 75 to 95.

[0098] The content of the surface treatment agent is not particularly limited, but is typically 0.01% by mass or more, and more preferably 0.05% by mass or more, based on the total mass of the curable silicone composition of the present invention, and may be 10% by mass or less, and more preferably 5% by mass or less, based on the total mass of the curable silicone composition of the present invention.

[0099] In a preferred embodiment of the present invention, the curable silicone composition can be cured to form a cured product with excellent thermal conductivity. For example, in a preferred embodiment, the thermal conductivity of the cured product of the curable silicone composition is 0.5 (W / (m·K)) or more, and more preferably 1.0 (W / (m·K)) or more. There is no particular upper limit for the thermal conductivity, but it is usually less than 3.0 (W / (m·K)). Thermal conductivity can be measured, for example, using a hot disk.

[0100] The curable silicone composition of the present invention can be prepared by mixing the various components. The method for mixing the various components can be any conventionally known method, and is not particularly limited. For example, the composition can be prepared by mixing using a mixing device. There are no particular limitations on such mixing devices, and examples include single- or double-screw continuous mixers, twin-roll mixers, Ross mixers, Hobart mixers, dental mixers, planetary mixers, kneader mixers, and Henschel mixers.

[0101] [Adhesive] The present invention also relates to an adhesive comprising the curable silicone composition of the present invention. Preferably, the adhesive of the present invention can be used as a thermally conductive adhesive. Preferably, the adhesive of the present invention can be used as a die bonding adhesive for optical semiconductor elements and the like. The shape of the adhesive of the present invention is not particularly limited, but is preferably in sheet form. There are no particular limitations on the semiconductors that can be bonded with the adhesive of the present invention, and examples thereof include semiconductors such as SiC and GaN, particularly optical semiconductors such as power semiconductors or light-emitting diodes.

[0102] [Optical Semiconductor Device] The present invention also relates to an optical semiconductor device comprising the adhesive of the present invention. Examples of optical semiconductor elements included in the optical semiconductor device include light emitting diodes (LEDs), semiconductor lasers, photodiodes, phototransistors, solid-state imaging devices, and light emitters and photodetectors for photocouplers, with light emitting diodes (LEDs) being particularly preferred.

[0103] Since light-emitting diodes (LEDs) emit light from the top, bottom, left, and right of the optical semiconductor element, it is preferable that the components constituting the light-emitting diode (LED) are not light-absorbing, and that materials with high light transmittance or high reflectance are preferred. Therefore, it is preferable that the substrate on which the optical semiconductor element is mounted is also made of a material with high light transmittance or high reflectance. Examples of substrates on which such optical semiconductor elements are mounted include conductive metals such as silver, gold, and copper; non-conductive metals such as aluminum and nickel; thermoplastic resins mixed with white pigments such as PPA and LCP; thermosetting resins containing white pigments such as epoxy resins, BT resins, polyimide resins, and silicone resins; and ceramics such as alumina and alumina nitride.

[0104] Specific embodiments of the present invention are described below. Aspect 1: A curable silicone composition comprising: (A) an alkenyl-containing organopolysiloxane having at least two alkenyl groups per molecule; (B) an organohydrogenpolysiloxane having at least two silicon-bonded hydrogen atoms per molecule; (C) a thermally conductive filler in an amount of 5 mass% or more, based on the total mass of the composition; (D) a cerium-containing organopolysiloxane; and (E) a curing catalyst. Aspect 2: The curable silicone composition according to Aspect 1, wherein the alkenyl-containing organopolysiloxane (A) comprises an MQ resin. Aspect 3: The curable silicone composition according to Aspect 1 or 2, wherein the thermally conductive filler (C) is a metal oxide. Aspect 4: The curable silicone composition according to any one of claims 1 to 3, wherein the thermally conductive filler (C) comprises two types of thermally conductive fillers having different average particle sizes. Aspect 5: The curable silicone composition according to any one of aspects 1 to 4, wherein the cerium atoms in the (D) cerium-containing organopolysiloxane are present in an amount of 1 to 100 ppm, relative to the total mass of all organopolysiloxane components in the composition. Aspect 6: An adhesive comprising the curable silicone composition according to any one of aspects 1 to 5. Aspect 7: An optical semiconductor device comprising the adhesive according to aspect 6.

[0105] The curable silicone composition of the present invention will be described in more detail below with reference to the following examples and comparative examples.

[0106] Curable silicone compositions were prepared by mixing the components in the amounts (parts by mass) shown in the tables. Note that Me represents a methyl group, Vi represents a vinyl group, and Ep represents a 3-glycidoxypropyl group. The tables also show simplified structures of the organopolysiloxane components, with the organic groups other than Me in the M, D, or T units shown in parentheses. H / Vi represents the molar ratio of silicon-bonded hydrogen atoms (H) to vinyl groups (Vi) in the organopolysiloxane component. In this specification, (SiO ｘ／２) (where x is an integer of 1 to 4) are shown as "unit formulas," and "structural formulas" are shown as chemical formulas that do not contain such siloxane units. Furthermore, the content of component d in the table indicates the content (ppm) of cerium atoms in component d relative to the total organopolysiloxane components.

[0107] Component a-1: Average unit formula (Me ３ SiO １ / ２ ) ４０．９ (ViMe ２ SiO １ / ２ ) ７．１ (SiO ４ / ２ ) ５２ (OH) ４．９ Resinous alkenyl group-containing organopolysiloxane (solid at 25°C, mass average molecular weight (Mw): 5,100) represented by the following formula: Component a-2: Average structural formula: ViMe ２ SiO(M ２ SiO) ４６ SiMe ２ Component b: a linear alkenyl group-containing organopolysiloxane represented by the average structural formula Me ３ SiO (MeHSiO) ５０ SiMe ３ Component c-1: Aluminum oxide (average particle size: 3.4 μm) Component c-2: Aluminum oxide (average particle size: 0.5 μm) Component d: Cerium-containing dimethylpolysiloxane having a cerium content of 1.4 mass% Component e: A platinum and divinyltetramethyldisiloxane complex having a platinum concentration of 3.0 mass% Component f-1: 1-ethynyl-2-cyclohexanol Component f-2: Methyl-tris-(3-methyl-1-butyn-3-oxy)silane Component g: Average structural formula (ViMeSiO) ４ Component h: a condensation reaction product of a methylvinylsiloxane oligomer capped at both ends with silanol groups and 3-glycidoxypropyltrimethoxysilane (mass average molecular weight (Mw): 1280, viscosity at 25°C: 22.5 mm ２ / s) Component i: fumed silica (surface treated with hexamethyldisilazane and trimethylsilane) Component j: surface treatment agent which is an alkoxysilylalkyl group-containing organopolysiloxane

[0108] [Die Shear Strength] A 25 mm x 75 mm alumina plate was used as the substrate, and five 5 mm x 5 mm x 1 mm alumina chips were used as bonding chips. 0.0080 g ± 0.0005 g of curable silicone composition was applied to each chip, and the chip was placed on the composition. The composition was then cured at 150°C for 2 hours to bond each chip to the substrate. The die shear strength was measured using a bond tester (model number: SS-30WD, test mode: PH50 push, speed: 0.120 mm / sec). The test sample was also aged at 200°C for 1000 hours, and the die shear strength was similarly measured. The results of the die shear strength before and after aging are shown below.

[0109]

[0110] [Thermal Conductivity] The curable silicone composition was cured at 150°C under a pressure of 20 MPa for 15 minutes and then at atmospheric pressure for 105 minutes, yielding a cylindrical cured sample measuring 1 cm in height and 2.1 cm in diameter. The thermal conductivity (W / (m·K)) of this sample was measured using a hot disc (Kyoto Electronics Co., Ltd., model number: TPS 500s). The results are shown in the table below.

[0111]

[0112] [Weight Loss] The curable silicone composition was cured by holding it at a temperature of 150°C under a pressure of 20 MPa for 15 minutes and at atmospheric pressure for 105 minutes, yielding a plate-shaped cured product sample measuring 1 cm x 5 cm x 2 mm. This sample was aged at 200°C, and the weight was measured after 500 hours and 1000 hours, and the weight loss (%) was calculated using the following formula: (initial weight - weight after aging) / initial weight x 100

[0113]

[0114] As can be seen from the results in Table 1, the curable silicone composition of the present invention containing the thermally conductive filler was able to maintain excellent strength and exhibit excellent thermal stability even after aging at high temperatures. Furthermore, as can be seen from the results in Table 2, the curable silicone composition of the present invention containing a high content of thermally conductive filler was able to exhibit high thermal conductivity. Furthermore, as can be seen from the results in Table 3, the curable silicone composition of the present invention showed only a small weight loss of about 1% even after aging at high temperatures for 1000 hours, demonstrating that it was able to maintain its chemical structure even after aging.

[0115] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments. Addition, omission, substitution, and other modifications of the configuration are possible within the scope of the spirit of the present invention. The present invention is not limited by the above description, but is limited only by the scope of the appended claims.

Claims

1. A curable silicone composition comprising: (A) an alkenyl-containing organopolysiloxane having at least two alkenyl groups per molecule; (B) an organohydrogenpolysiloxane having at least two silicon-bonded hydrogen atoms per molecule; (C) at least 5 mass% of a thermally conductive filler based on the total mass of the composition; (D) a cerium-containing organopolysiloxane; and (E) a curing catalyst.

2. The curable silicone composition according to claim 1, wherein (A) the alkenyl-containing organopolysiloxane comprises an MQ resin.

3. The curable silicone composition according to claim 1 or 2, wherein the thermally conductive filler (C) is a metal oxide.

4. The curable silicone composition according to claim 1, wherein the thermally conductive filler (C) comprises two types of thermally conductive filler having different average particle sizes.

5. The curable silicone composition according to claim 1, wherein the cerium atom content of the cerium-containing organopolysiloxane (D) is 1 to 100 ppm, based on the total mass of all organopolysiloxane components in the composition.

6. An adhesive comprising the curable silicone composition according to any one of claims 1 to 5.

7. An optical semiconductor device comprising the adhesive according to claim 6.

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