Curable organopolysiloxane resin composition and optical part molded therefrom

1. A curable organopolysiloxane resin composition having a viscosity at 25° C. in the range of 0.001 to 5,000 Pa·s, a total acid number as specified by JIS K 2501 (1992) in the range of 0.0001 to 0.2 mg/g, light transmittance in a cured state equal to or greater than 80% measured at 555 nanometers through a 1 mm thick sample of said cured organopolysiloxane resin composition and light transmittance in the cured state of at least 40% measured at 400 nanometers through a 1 mm thick sample of said cured organopolysiloxane resin composition after said cured organopolysiloxane resin composition is aged at 200° C. for 14 days.

2. The curable organopolysiloxane resin composition of claim 1 , comprising:

(A) 100 parts by weight of an organopolysiloxane resin that contains at least an alkenyl group and a phenyl group and is represented by the following average structural formula:

R 1 a R 2 b SiO (4-a-b)/2   (1)

(where R 1 is an alkenyl group having 2 to 10 carbon atoms, R 2 is an optionally substituted univalent hydrocarbon group (except for an alkenyl group) having 1 to 10 carbon atoms, at least 20 mole % of R 2 comprising phenyl groups; subscript “a” is a number in the range of 0.05 to 0.5, and subscript “b” is a number in the range of 0.80 to 1.80);

(B) 10 to 100 parts by weight of an organohydrogenpolysiloxane having in one molecule at least two silicon-bonded hydrogen atoms and represented by the following average structural formula:

H c R 3 d SiO (4-c-d)/2   (2)

(where R 3 is an optionally substituted univalent hydrocarbon group (except for an alkenyl group) having 1 to 10 carbon atoms; subscript “c” is a number in the range of 0.35 to 1.0, and subscript “d” is a number in the range of 0.90 to 2.0); and

(C) a catalytic quantity of a hydrosilylation-reaction catalyst.

3. The curable organopolysiloxane resin composition according to claim 2 , wherein component (B) comprises (B1) an organohydrogenpolysiloxane having in one molecule at least two silicon-bonded hydrogen atoms or a mixture of constituent (B1) with (B2) an organohydrogenpolysiloxane having in one molecule three or more silicon-bonded hydrogen atoms.

4. The curable organopolysiloxane resin composition according to claim 2 , further comprising (D) 2 to 50 parts by weight of an organooligosiloxane having at least an alkenyl group and a phenyl group and represented by the following average structural formula:

R 6 e R 7 f SiO (4-e-f)/2   (3)

(where R 6 is an alkenyl group having 2 to 10 carbon atoms, R 7 is an optionally substituted univalent hydrocarbon having 1 to 10 carbon atoms (except for an alkenyl group); at least 10 mole % of R 7 being phenyl groups; subscript “e” is a number in the range of 0.40 to 0.80; and subscript “f” is a number in the range of 1.50 to 2.10).

5. The curable organopolysiloxane resin composition according to claim 2 , further comprising (E) 0.01 to 20 parts by weight of an epoxy-containing organic silicon compound.

6. The curable organopolysiloxane resin composition according to claim 5 , wherein epoxy-containing organic silicon compound (E) is a compound represented by the following average structural formula:

R 8 h R 9 i SiO (4-h-i)/2   (4)

(where R 8 is an epoxy-containing organic group, R 9 is an optionally substituted univalent hydrocarbon group that may not have an epoxy group and that contains 1 to 10 carbon atoms; 1 mole % or more of all substituents of component E comprising alkenyl groups; subscript “h” is a number in the range of 0.05 to 1.8; and subscript “i” is a number in the range of 0.10 to 1.80).

7. The curable organopolysiloxane resin composition according to claim 6 , wherein the average structural formula (4) subscript “h” is a number in the range of 0.10 to 1.80 and (h+i)≧2; 3 mole % or more of the total number of substituents of component E being alkenyl groups, and 3 mole % or more of the total number of substituents of component E being phenyl groups.

8. An optical part made from a cured body of a curable organopolysiloxane resin composition according to claim 1 .

9. An optical part made from a cured body of a curable organopolysiloxane resin composition according to claim 1 comprising an optical semiconductor device as an optical semiconductor element coated by a cured body of the curable organopolysiloxane resin composition according to claim 1 .

10. The curable organopolysiloxane resin composition according to claim 3 , further comprising (D) 2 to 50 parts by weight of an organooligosiloxane having at least an alkenyl group and a phenyl group and represented by the following average structural formula:

R 6 e R 7 f SiO (4-e-f)/2   (3)

(where R 6 is an alkenyl group having 2 to 10 carbon atoms, R 7 is an optionally substituted univalent hydrocarbon having 1 to 10 carbon atoms (except for an alkenyl group); at least 10 mole % of R 7 being phenyl groups; subscript “e” is a number in the range of 0.40 to 0.80; and subscript “f” is a number in the range of 1.50 to 2.10).

11. The curable organopolysiloxane resin composition according to claim 3 , further comprising (E) 0.01 to 20 parts by weight of an epoxy-containing organic silicon compound.

12. The curable organopolysiloxane resin composition according to claim 11 , wherein epoxy-containing organic silicon compound (E) is a compound represented by the following average structural formula:

R 8 h R 9 i SiO (4-h-i)/2   (4)

(where R 8 is an epoxy-containing organic group, R 9 is an optionally substituted univalent hydrocarbon group that may not have an epoxy group and that contains 1 to 10 carbon atoms; 1 mole % or more of all substituents of component E comprising alkenyl groups; subscript “h” is a number in the range of 0.05 to 1.8; and subscript “i” is a number in the range of 0.10 to 1.80).

13. The curable organopolysiloxane resin composition according to claim 12 , wherein the average structural formula (4) subscript “h” is a number in the range of 0.10 to 1.80 and (h+i)≧2; 3 mole % or more of the total number of substituents of component E being alkenyl groups, and 3 mole % or more of the total number of substituents of component E being phenyl groups.

14. The curable organopolysiloxane resin composition according to claim 4 , further comprising (E) 0.01 to 20 parts by weight of an epoxy-containing organic silicon compound.

15. The curable organopolysiloxane resin composition according to claim 14 , wherein epoxy-containing organic silicon compound (E) is a compound represented by the following average structural formula:

R 8 h R 9 i SiO (4-h-i)/2   (4)

(where R 8 is an epoxy-containing organic group, R 9 is an optionally substituted univalent hydrocarbon group that may not have an epoxy group and that contains 1 to 10 carbon atoms; 1 mole % or more of all substituents of component E comprising alkenyl groups; subscript “h” is a number in the range of 0.05 to 1.8; and subscript “i” is a number in the range of 0.10 to 1.80).

16. The curable organopolysiloxane resin composition according to claim 15 , wherein the average structural formula (4) subscript “h” is a number in the range of 0.10 to 1.80 and (h+i)≧2; 3 mole % or more of the total number of substituents of component E being alkenyl groups, and 3 mole % or more of the total number of substituents of component E being phenyl groups.