Silicone resin composition

1. A silicone resin composition comprising:

a) an alkenyl group-containing polysiloxane represented by a following average composition formula “A”:

R n SiO (4-n)/2 (SiO 2 )  A

wherein R consists of an alkenyl group of 0.1 to 95 mole % and an alkyl group having 1 to 4 carbon atoms; and n is an integer of 1 to 3, and wherein at least one of the hydrogen atoms in the R is substituted by a heteroatom selected from the group consisting of a halogen atom, Si atom, O atom, N atom, and S atom,

the alkenyl group-containing polysiloxane having a weight average molecular weight of 400 to 30000 and including 20 to 80 mole % of a Q unit represented by a following formula:

b) a hydro group-containing polysiloxane represented by a following average composition formula “B”:

R′ m SiO (4-m)/2 (SiO 2 )  B

wherein R′ consists of a hydro group of 0.1 to 95 mole % and an alkyl group having 1 to 4 carbon atoms; and m is an integer of 1 to 3,

the hydro group-containing polysiloxane having a weight average molecular weight of 100 to 10000 and including 10 to 50 mole % of the Q unit represented by the aforementioned formula: and

c) a pair of polysiloxane each having opposite ends sealed with a vinyl group, differing in a range of “k” and represented by a following average composition formula “C”:

wherein R 1 s may be same or different and are individually selected from an alkyl group having 1 to 4 carbon atoms; and k is 20 to 300 or 700 to 1200; and

d) a hydrosilylating catalyst.

2. The composition according to claim 1 , wherein the alkenyl group to be introduced into the R in the average composition formula “A” is selected from those having 2 to 8 carbon atoms.

3. The composition according to claim 2 , wherein the alkenyl group is selected from a group consisting of a vinyl group, allyl group, butenyl group and pentenyl group.

4. The composition according to claim 3 , wherein the alkenyl group is a vinyl group.

5. The composition according to claim 4 , wherein the alkyl group to be introduced into the R in the average composition formula “A” is a methyl group.

6. The composition according to claim 1 , wherein the alkenyl group-containing polysiloxane has a weight average molecular weight ranging from 1,000 to 10,000.

7. The composition according to claim 1 , wherein the R′ in the average composition formula “B” is a methyl group.

8. The composition according to claim 1 , wherein the hydro group-containing polysiloxane has a weight average molecular weight ranging from 200 to 5,000.

9. The composition according to claim 1 , wherein the hydro group-containing polysiloxane is incorporated at a ratio that a number of silicon atoms to which hydrogen atom is bonded falls within a range of 0.5-2 per alkenyl group of an alkenyl group-containing polysiloxane.

10. The composition according to claim 1 , wherein the R 1 to be introduced into the formula “C” is selected from a methyl group and an ethyl group.

11. The composition according to claim 1 , wherein the hydrosilylating catalyst is selected from a group consisting of platinic chloride, a platinum-olefin complex and a platinum-vinyl siloxane complex.

12. The composition according to claim 1 , wherein the hydrosilylating catalyst is incorporated at a ratio ranging from 0.1 to 500 ppm based on a total weight of the composition.

13. The composition according to claim 1 , further comprising at least one selected from a group consisting of chain silicone resin, cyclic silicone resin and cage silicone resin.

14. The composition according to claim 13 , wherein the silicone resin is selected from a group consisting of polyorganoalkenyl siloxane and polyorganohydrogen siloxane.

15. The composition according to claim 1 , further comprising at least one selected from a group consisting of antifoaming agents, fumed silica, silica aerosol, precipitated silica, crushed silica, diatomaceous earth, iron oxide, zinc oxide, titanium oxide, calcium oxide, magnesium carbonate, zinc carbonate, carbon black, pigment, dyestuff, an adhesion assistant, a mildewproofing agent, a heat resistance improver, a flame retardant and an antioxidant.

16. A resin-encapsulated semiconductor device comprising:

a light-emitting element; and

a resin layer encapsulating the light-emitting element, the resin layer being formed of a cured material to be obtained through curing of the silicone resin composition of claim 1 .