Thermally conductive composition

1. A thermally conductive composition comprising a thermally conductive filler dispersed in a liquid matrix, wherein

a volume-based median diameter of the thermally conductive filler is 0.5 to 100 μm;

a content of the thermally conductive filler in the thermally conductive composition is 50 to 95 vol %;

the thermally conductive filler comprises a first thermally conductive filler having a Mohs hardness of 3 or more and a second thermally conductive filler having a Mohs hardness of less than 3;

in the first thermally conductive filler in the thermally conductive composition, a content of the first thermally conductive filler that has a Mohs hardness of 4 or more and a particle diameter of 10 μm or more is 1 to 3 vol % based on the whole thermally conductive filler;

in the first thermally conductive filler in the thermally conductive composition, a content of the first thermally conductive filler that has a Mohs hardness of 3 or more and a particle diameter of 30 μm or more is 1 to 3 vol % based on the whole thermally conductive filler;

the viscosity of the thermally conductive composition at 25° C. is in the range of 10 to 600 Pa·s; and

the volume based mixing ratio of the first thermally conductive filler to the second thermally conductive filler (first thermally conductive filler/second thermally conductive filler) is 0.3 to 0.9.

2. The thermally conductive composition according to claim 1 , wherein

a material of the first thermally conductive filler is at least one selected from the group consisting of alumina, aluminum hydroxide, aluminum nitride, silicon carbide, magnesium oxide, zinc oxide and crystalline silica; and

a material of the second thermally conductive filler is at least one selected from the group consisting of aluminum, boron nitride and graphitized carbon.

3. The thermally conductive composition according to claim 1 , wherein the matrix is addition reaction-curable silicone.

4. The thermally conductive composition according to claim 1 , having a density of 2.5 kg/L or less.

5. The thermally conductive composition according to claim 1 , wherein a thermal conductivity of a thermally conductive elastic body obtained by curing the thermally conductive composition is 3 W/m·K or more.

6. The thermally conductive composition according to claim 1 , wherein in an abrasion test for thermally conductive composition using an aluminum jig having a circular sliding contact surface with a diameter of 25 mm, an abrasion loss of the jig is less than 3 mg when the sliding contact surface of the jig is brought into sliding contact with the thermally conductive composition under the conditions of a load of 2 kg, a reciprocating motion frequency of 0.9 Hz, a reciprocating motion stroke length of 25 mm and a number of reciprocating motion times of 1500.

7. The thermally conductive composition according to claim 1 , wherein the viscosity of the thermally conductive composition at 25° C. is in the range of 150 to 600 Pa·s.

8. The thermally conductive composition according to claim 1 , wherein the volume based mixing ratio of the first thermally conductive filler to the second thermally conductive filler (first thermally conductive filler/second thermally conductive filler) is 0.4 to 0.9.