Curable organopolysiloxane composition and semiconductor device

1. A curable organopolysiloxane composition comprising:

(A) a branched-chain organopolysiloxane that contains in one molecule at least three alkenyl groups and at least 30 mole % of all silicon-bonded organic groups in the form of aryl groups;

(B) a linear-chain organopolysiloxane that contains aryl groups and has both molecular terminals capped with diorganohydrogensiloxy groups, wherein component (B) is used in such an amount that the content of silicon-bonded hydrogen atoms contained in component (B) to one mole of alkenyl groups contained in component (A) is in the range of 0.5 to 2 moles;

(C) a branched-chain organopolysiloxane that contains in one molecule at least three diorganohydrogensiloxy groups and at least 15 mole % of all silicon-bonded organic groups are in the form of aryl groups, wherein the content of the diorganohydrogensiloxy groups contained in this component is in the range of 1 to 20 mole % per total amount of the diorganohydrogensiloxy groups contained in component (B) and in the present component;

(D) a hydrosilylation catalyst in an amount required to accelerate curing of the composition; and

(E) a linear-chain organopolysiloxane that contains in one molecule at least two alkenyl groups and at least 30 mole % of all silicon-bonded organic groups in the form of aryl groups, said component (E) being used in an amount of greater than 0 and equal to or less than 25 parts by mass per 100 parts by mass of component (A).

2. The curable organopolysiloxane composition of claim 1 , wherein component (A) is a branched-chain organopolysiloxane of 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

{wherein R 1 independently designates substituted or unsubstituted monovalent hydrocarbon groups; however, in one molecule at least three groups designated by R 1 are alkenyl groups and at least 30 mole % of all groups designated by R 1 are aryl groups; X designates a hydrogen atom or an alkyl group; and “a” is a positive number, “b” is 0 or a positive number, “c” is 0 or a positive number, “d” is 0 or a positive number, “e” is 0 or a positive number, “b/a” is a number ranging from 0 to 10, “c/a” is a number ranging from 0 to 5, “d/(a+b+c+d)” is a number ranging from 0 to 0.3, and “e/(a+b+c+d)” is a number ranging from 0 to 0.4}.

3. The curable organopolysiloxane composition of claim 1 , wherein component (B) is a linear-chain organopolysiloxane represented by the following general formula:

HR 2 2 SiO(R 2 2 SiO) m SiR 2 2 H

(wherein each R 2 independently designates a substituted or unsubstituted univalent hydrocarbon group, which is free of unsaturated aliphatic bonds; however, in one molecule at least 15 mole % of all groups designated by R 2 are aryl groups; and “m” is an integer ranging from 1 to 1,000).

4. The curable organopolysiloxane composition of claim 1 , wherein component (C) is a branched-chain organopolysiloxane of the following average unit formula:

(HR 2 2 SiO 1/2 ) f (R 2 SiO 3/2 ) g (R 2 2 SiO 2/2 ) h (R 2 3 SiO 1/2 ) i (SiO 4/2 ) j (XO 1/2 ) k

{wherein each R 2 independently designates a univalent hydrocarbon group, which is free of unsaturated aliphatic bonds; however, in one molecule at least 15 mole % of all groups designated by R 2 are aryl groups; X designates a hydrogen atom or an alkyl group; and “f” is a positive number, “g” is a positive number, “h” is 0 or a positive number, “i” is 0 or a positive number, “j” is 0 or a positive number, “k” is 0 or a positive number, “f/g” is a number ranging from 0.1 to 4, “h/g” is a number ranging from 0 to 10, “i/g” is a number ranging from 0 to 5,

“j/(f+g+h+i+j)” is a number ranging from 0 to 0.3, and

“k/(f+g+h+i+j)” is a number ranging from 0 to 0.4}.

5. The curable organopolysiloxane composition of claim 1 , wherein the index of refraction (at 25° C.) in a visible light (589 nm) is equal to or greater than 1.5.

6. The curable organopolysiloxane composition of claim 1 , wherein a cured product obtained by curing the composition has type D durometer hardness equal to or greater than 20.

7. The curable organopolysiloxane composition of claim 1 , wherein a cured product obtained by curing the composition has light transmittance (at 25° C.) that is equal to or greater than 80%.

8. A semiconductor device that contains a semiconductor part comprising a cured product of the curable organopolysiloxane composition according to claim 1 .

9. The semiconductor device of claim 8 , wherein the semiconductor part is a light-emitting element.

10. The curable organopolysiloxane composition of claim 1 , wherein component (A) contains in one molecule at least three vinyl groups and at least 40 mole % of all silicon-bonded organic groups in the form of phenyl groups.

11. The curable organopolysiloxane composition of claim 2 , wherein, in one molecule of component (A);

the alkenyl groups designated by R 1 are vinyl groups, and

the at least 30 mole % of all groups designated by R 1 which are aryl groups comprise at least 40 mole % phenyl groups.

12. The curable organopolysiloxane composition of claim 1 , wherein, in one molecule of component (B), at least 15 mole % of all silicon-bonded organic groups are aryl groups.

13. The curable organopolysiloxane composition of claim 3 , wherein, in one molecule of component (B), at least 30 mole % of all groups designated by R 2 are aryl groups, and “m” is an integer ranging from 1 to 100.

14. The curable organopolysiloxane composition of claim 1 , wherein, in one molecule of component (C), at least 25 mole % of all silicon-bonded organic groups are in the form of phenyl groups.