Curable silicone resin composition

1. A curable silicone resin composition comprising:

(A) an organopolysiloxane having at least two alkenyl groups per molecule, each bonded to a silicon atom and showing a viscosity of 10 to 1,000,000 mPa·s at 25° C.,

(B) an organopolysiloxane having a weight average molecular weight of 1,000 to 10,000 and having a resin structure composed of:

10 to 80 mol % of SiO 4/2 unit,

0.1 to 80 mol % of (R 1 ) 2 SiO 2/2 unit, and

1 to 60 mol % of (R 2 ) 3 SiO 1/2 unit,

where:

each R 1 independently represents an alkenyl group having 2 to 8 carbon atoms, or a substituted or unsubstituted, monovalent hydrocarbon group having no aliphatic unsaturated group, and

each R 2 independently represents an alkenyl group having 2 to 8 carbon atoms, or a substituted or unsubstituted, monovalent hydrocarbon group having no aliphatic unsaturated group, provided that at least one among all of R 2 is an alkenyl group;

an amount of a hydroxyl group bonded to a silicon atom in component (B) being 0.01 to 15.0 mass %, relative to a total mass of component (B); and an amount of an alkoxy group bonded to a silicon atom in component (B) being 0.01 to 15.0 mass %, relative to a total mass of component (B),

(C) an organohydrogenpolysiloxane having at least two hydrogen atoms per molecule, each bonded to a silicon atom, and

(D) platinum-group metal catalyst,

wherein

an amount of component (B) is 81 to 100 mass %, relative to a total mass of components (A) and (B); and

the number of the aryl group bonded to a silicon atom is 10 to 90%, relative to a total number of the hydrogen atoms each bonded to a silicon atom and the groups each bonded to a silicon atom, including the aryl group bonded to a silicon atom, in the composition.

2. The curable silicone resin composition according to claim 1 , wherein an amount of component (C) is such that a ratio of the total number of the hydrogen atoms each bonded to a silicon atom in component (C) to the total number of the alkenyl groups each bonded to a silicon atom in components (A) and (B) is 0.1 to 4.0.

3. The curable silicone resin composition according to claim 1 , wherein

a cured product obtained by curing the composition at 150° C. for one hour has a hardness corresponding to at least 70% of a hardness of a cured product obtained by curing the composition at 150° C. for 4 hours, and

the hardness is determined in accordance with JIS K6249:2003.

4. A cured product obtained by curing the curable silicone resin composition according to claim 1 , wherein the cured product has a refractive index of 1.46 to 1.60.

5. The cured product obtained by curing the curable silicone resin composition according to claim 1 , wherein the cured product has a water vapor permeability of 30 g/m 2 day, the cured product having a thickness of 1 mm.

6. The cured product obtained by curing the curable silicone resin composition according to claim 1 , wherein the cured product has a tensile strength of at least 2.0 MPa and an elongation at break of at least 40%, both as determined in accordance with JIS K6249:2003.

7. The curable silicone resin composition according to claim 2 , wherein

a cured product obtained by curing the composition at 150° C. for one hour has a hardness corresponding to at least 70% of a hardness of a cured product obtained by curing the composition at 150° C. for 4 hours, and

the hardness is determined in accordance with JIS K6249:2003.

8. A cured product obtained by curing the curable silicone resin composition according to claim 2 , wherein the cured product has a refractive index of 1.46 to 1.60.

9. A cured product obtained by curing the curable silicone resin composition according to claim 3 , wherein the cured product has a refractive index of 1.46 to 1.60.

10. A cured product obtained by curing the curable silicone resin composition according to claim 7 , wherein the cured product has a refractive index of 1.46 to 1.60.

11. The cured product obtained by curing the curable silicone resin composition according to claim 2 , wherein the cured product has a water vapor permeability of 30 g/m 2 ·day, the cured product having a thickness of 1 mm.

12. The cured product obtained by curing the curable silicone resin composition according to claim 3 , wherein the cured product has a water vapor permeability of 30 g/m 2 ·day, the cured product having a thickness of 1 mm.

13. The cured product obtained by curing the curable silicone resin composition according to claim 7 , wherein the cured product has a water vapor permeability of 30 g/m 2 ·day, the cured product having a thickness of 1 mm.

14. The cured product obtained by curing the curable silicone resin composition according to claim 2 , wherein the cured product has a tensile strength of at least 2.0 MPa and an elongation at break of at least 40%, both as determined in accordance with JIS K6249:2003.

15. The cured product obtained by curing the curable silicone resin composition according to claim 3 , wherein the cured product has a tensile strength of at least 2.0 MPa and an elongation at break of at least 40%, both as determined in accordance with JIS K6249:2003.

16. The cured product obtained by curing the curable silicone resin composition according to claim 7 , wherein the cured product has a tensile strength of at least 2.0 MPa and an elongation at break of at least 40%, both as determined in accordance with JIS K6249:2003.