Curable silicone composition, cured product thereof, and optical semiconductor device

1. A curable silicone composition comprising:

(A) 100 parts by mass of an organopolysiloxane represented by the following average unit formula:

(R 1 3 SiO 1/2 ) a (R 1 2 SiO 2/2 ) b (R 1 SiO 3/2 ) c (SiO 4/2 ) d (R 2 O 1/2 ) e

wherein each R 1 is independently a phenyl group, a C 1-6 alkyl group, or a C 2-6 alkenyl group; however, from 30 to 80 mole % of all groups designated by R 1 are phenyl groups and from 5 to 20 mole % of all groups designated by R 1 are alkenyl groups; R 2 is a hydrogen atom or a C 1-6 alkyl group; and “a”, “b”, “c”, “d”, and “e” are numbers that respectively satisfy: 0≦a≦0.3, 0≦b≦0.7, 0.3≦c≦0.9, 0≦d≦0.1, 0≦e≦0.1, and a+b+c+d=1;

(B) 5 to 50 parts by mass of an organopolysiloxane that has not more than 10 silicon atoms wherein from 30 to 60 mole % of all silicon-bonded organic groups are C 2-6 alkenyl groups;

(C) 0 to 40 parts by mass of an organopolysiloxane represented by the following general formula:

R 3 3 SiO(R 3 2 SiO) m SiR 3 3

wherein each R 3 independently represents a phenyl group, a C 1-6 alkyl group, or a C 2-6 alkenyl group; however, from 30 to 70 mole % of all groups designated by R 3 are phenyl groups and at least one of all groups designated by R 3 is an alkenyl group; and “m” is an integer from 10 to 100;

(D) an organopolysiloxane that has at least two silicon-bonded hydrogen atoms in one molecule wherein from 20 to 70 mole % of all silicon-bonded organic groups are phenyl groups, in an amount that provides from 0.5 to 2 moles of silicon-bonded hydrogen atoms in this component per 1 mole of the total amount of the alkenyl groups in components (A), (B), and (C);

(E) a hydrosilylation reaction catalyst in a quantity sufficient to accelerate the hydrosilylation reaction between the alkenyl groups in components (A), (B), and (C) and the silicon-bonded hydrogen atoms in component (D);

(F) a white pigment in an amount of at least 25 parts by mass per 100 parts by mass of the total amount of components (A), (B), (C), (D), and (E);

(G) a nonspherical silica or a glass fiber in an amount of at least 20 parts by mass per 100 parts by mass of the total amount of components (A), (B), (C), (D), and (E); and

(H) a spherical silica in an amount of at least 20 parts by mass per 100 parts by mass of the total amount of components (A), (B), (C), (D), and (E),

wherein the content of the total amount of components (F), (G), and (H) is not more than 300 parts by mass per 100 parts by mass of the total amount of components (A), (B), (C), (D), and (E).

2. The curable silicone composition according to claim 1 , that has a viscosity at 25° C. of from 5 to 200 Pa·s.

3. The curable silicone composition according to claim 1 , that cures to form a cured product that has a durometer D hardness of at least 60 and that has a bending strength of at least 5 MPa.

4. The curable silicone composition according to claim 1 , that cures to form a cured product that has a total luminous reflectance of at least 80%.

5. The curable silicone composition according to claim 1 , that cures to form a cured product that has an average linear thermal expansion coefficient in the range from 25 to 200° C. of not more than 200 ppm/° C.

6. A cured product provided by the cure of the curable silicone composition according to claim 1 .

7. An optical semiconductor device that is provided with a light-reflecting material formed of a cured product from the curable silicone composition according to claim 1 .

8. The curable silicone composition according to claim 1 , wherein from 40 to 70 mole % of all groups designated by R 1 are phenyl groups, and 0≦a≦0.25, 0≦b≦0.6, and 0.35≦c≦0.85.

9. The curable silicone composition according to claim 1 , wherein component (B) is selected from 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane, tetrakis(dimethylvinylsiloxy)silane, methyltris(dimethylvinylsiloxy)silane, and phenyltris(dimethylvinylsiloxy)silane.

10. The curable silicone composition according to claim 1 , wherein component (D) is selected from;

(a) an organotrisiloxane having the following general formula:

(HR 4 2 SiO) 2 SiR 4 2

wherein each R 4 in the formula is independently a phenyl group or a C 1-6 alkyl group, and phenyl group content in all groups designated by R 4 is in the range from 30 to 70 mole %;

(b) a straight-chain organopolysiloxane having the following general formula:

R 5 3 SiO(R 5 2 SiO) n SiR 5 3 ; and

(c) a branched-chain organopolysiloxane having the following average unit formula:

(R 5 SiO 3/2 ) p (R 5 2 SiO 2/2 ) q (R 5 3 SiO 1/2 ) r (SiO 4/2 ) s (XO 1/2 ) t ,

wherein each R 5 in the formulas above is independently a hydrogen atom, a phenyl group, or a C 1-6 alkyl group, and at least two of all groups designated by R 5 in the formulas are hydrogen atoms, and phenyl group content in all groups designated by R 5 , excluding the hydrogen atoms, is in the range from 30 to 70 mole %, and

wherein “n” in the formulas is an integer in the range from 5 to 1,000, “p” in the formula is a positive number; “q” is 0 or a positive number; “r” is 0 or a positive number; “s” is 0 or a positive number; “t” is 0 or a positive number; “q/p” is a number in the range from 0 to 10; “r/p” is a number in the range from 0 to 5; “s/(p+q+r+s)” is a number in the range from 0 to 0.3; and “t/(p+q+r+s)” is a number in the range from 0 to 0.4.

11. The curable silicone composition according to claim 1 , wherein at least 50 mass % of component (D) is an organotrisiloxane having the following general formula:

(HR 4 2 SiO) 2 SiR 4 2

wherein each R 4 in the formula is independently a phenyl group or a C 1-6 alkyl group.

12. The curable silicone composition according to claim 11 , wherein phenyl group content in all groups designated by R 4 is in the range from 30 to 70 mole %.