Polysiloxane composition and cured product thereof

1. A polysiloxane composition comprising:

(A) at least one type of organopolysiloxane that contains at least two unsaturated aliphatic hydrocarbon groups in the molecule,

(B) at least one type of organohydrogenpolysiloxane that contains at least two silicon-bonded hydrogen atoms in the molecule,

(C) a hydrosilylation reaction catalyst, and

(D) inorganic particles in an amount of from 75 to 95 wt. % based on the total weight of the composition, said inorganic particles comprising 90% by weight or greater of silica and having a major axis to minor axis ratio of 1 to 1.2 and in which the proportion of particles having a diameter of 50 μm or greater is 5 wt. % or less of the total quantity of particles,

wherein

a weight fraction of the unsaturated aliphatic hydrocarbon groups in the organopolysiloxane (A) is from 1 to 7 wt. %,

a compounding ratio of the inorganic particles (D) in the polysiloxane composition is from 70 to 85 vol. %,

a value of [the weight fraction of the unsaturated aliphatic hydrocarbon groups in the organopolysiloxane (A)]×[the weight fraction of the silicon-bonded hydrogen atoms in the organohydrogenpolysiloxane (B)] is from 0.04 to 8,

a viscosity of the polysiloxane composition at 25° C. is 500 Pa·s or less, and

the polysiloxane composition provides a cured product having a coefficient of linear expansion at 30 to 300° C. of 80×10 −6 /K or less.

2. The polysiloxane composition according to claim 1 , wherein the viscosity of the organopolysiloxane (A) at 25° C. is from 0.05 to 20 Pa·s.

3. The polysiloxane composition according to claim 1 , wherein the weight fraction of the silicon-bonded hydrogen atoms in the organohydrogenpolysiloxane (B) is 0.1 wt. % or greater.

4. The polysiloxane composition according to claim 1 , wherein the viscosity of the organohydrogenpolysiloxane (B) at 25° C. is 0.1 Pa·s or less.

5. The polysiloxane composition according to claim 1 , wherein the value of [the weight fraction of the unsaturated aliphatic hydrocarbon groups in the organopolysiloxane (A)]×[the weight fraction of the silicon-bonded hydrogen atoms in the organohydrogenpolysiloxane (B)] is from 0.1 to 7.

6. The polysiloxane composition according to claim 1 , wherein the value of [the weight fraction of the unsaturated aliphatic hydrocarbon groups in the organopolysiloxane (A)]×[the weight fraction of the silicon-bonded hydrogen atoms in the organohydrogenpolysiloxane (B)] is from 0.5 to 4.5.

7. The polysiloxane composition according to claim 1 , wherein a value of [the number of moles of the silicon-bonded hydrogen atoms in the organohydrogenpolysiloxane (B)]/[the number of moles of the unsaturated aliphatic hydrocarbon groups in the organopolysiloxane (A)] is from 0.5 to 1.5.

8. The polysiloxane composition according to claim 1 , wherein the hydrosilylation reaction catalyst (C) is a platinum metal-type catalyst.

9. The polysiloxane composition according to claim 1 , comprising at least one type of adhesion-imparting agent (E).

10. The polysiloxane composition according to claim 1 , which does not contain a solvent.

11. The polysiloxane composition according to claim 1 , which provides a cured product having a coefficient of linear expansion at 30 to 300° C. of 50×10 −6 /K or less.

12. A cured product obtained by curing the polysiloxane composition described in claim 1 .

13. The polysiloxane composition according to claim 2 , wherein the weight fraction of the silicon-bonded hydrogen atoms in the organohydrogenpolysiloxane (B) is 0.1 wt. % or greater.

14. A cured product as set forth in claim 12 having a coefficient of linear expansion at 30 to 300° C. of 30×10 −6 /K or less.