Thermally conductive polyorganosiloxane composition

A thermally conductive polysiloxane composition comprising:

• (A) a thermally conductive filler;
• (B) a siloxane compound having an alkoxysilyl group and a linear siloxane structure;
• (C) a polyorganosiloxane having at least two alkenyl groups bonded to silicon atoms per molecule;
• (D1) a linear polyorganohydrogensiloxane represented by the following general formula (4):
• wherein:
• R7 is a hydrogen atom,
• R8 is each independently a monovalent hydrocarbon group having no aliphatic unsaturated bond and having 1 to 12 carbon atoms, and
• f is 1 to 200;
• (D2) a polyorganohydrogensiloxane having per molecule at least three units represented by the following general formula (5):
• R9gR10hSiO({4−(g+h)}/2) (5)
• wherein:
• R9 is each independently a monovalent hydrocarbon group having no aliphatic unsaturated bond and having 1 to 12 carbon atoms,
• R10 is a hydrogen atom,
• g is an integer of 0 to 2,
• h is an integer of 1 or 2, and
• g+h is an integer of 1 to 3, with the proviso that a case in which g is 1 and h is 1 is excluded;
• and
• (E) a platinum catalyst,
• wherein (D2) is a polyorganohydrogensiloxane comprising a R112HSiO1/2 unit, wherein R11 is synonymous with R9, and a SiO4/2 unit, and having at least three hydrogen atoms bonded to silicon atoms per molecule,
• wherein a ratio ((HD1+HD2)/ViC) of a sum (HD1+HD2) of a number HD1 of hydrogen atoms bonded to silicon atoms of (D1) and a number HD2 of hydrogen atoms bonded to silicon atoms of (D2) to a number ViC of the alkenyl groups of (C) is 0.85 or less, and
• wherein a ratio of HD1:HD2 is in a range of from 9:1 to 8:2.