A thermally conductive filler capable of exhibiting high thermal conductive properties with its specific gravity being reduced, a thermally conductive composite material and a wire harness that contains such a thermally conductive filler, and a method for forming a thermally conductive filler that can be used to form such a thermally conductive filler. A thermally conductive filler includes a hollow particle having a polar group on its surface, and a thermally conductive layer containing an inorganic compound that covers the surface of the hollow particle. Also, a thermally conductive composite material contains the thermally conductive filler and a matrix material, the thermally conductive filler being dispersed in the matrix material. Furthermore, a wire harness contains the thermally conductive composite material.

A thermally conductive filler capable of exhibiting high thermal conductive properties with its specific gravity being reduced, a thermally conductive composite material and a wire harness that contains such a thermally conductive filler, and a method for forming a thermally conductive filler that can be used to form such a thermally conductive filler. A thermally conductive filler includes a hollow particle having a polar group on its surface, and a thermally conductive layer containing an inorganic compound that covers the surface of the hollow particle. Also, a thermally conductive composite material contains the thermally conductive filler and a matrix material, the thermally conductive filler being dispersed in the matrix material. Furthermore, a wire harness contains the thermally conductive composite material.

One of the objects of the present invention is to provide a thermally conductive silicone resin composition which has good thermal conductivity, a light weight (namely, a light weight per unit volume), and good reliability in high humidity, and a molded body thereof. The present invention provides a thermally conductive silicone resin composition comprising the following components (A) to (E): (A) an organopolysiloxane having at least two alkenyl groups each bonded to a silicon atom in an amount of 100 parts by mass, (B) an organohydrogen polysiloxane having at least two hydrogen atoms each bonded to a silicon atom in an amount such that a ratio of the number of the hydrogen atom bonded to a silicon atom relative to the number of the alkenyl group in component (A) is 0.1 to 2, (C) a thermally conductive filler in an amount of 2500 to 6000 parts by mass, (D) a catalytic amount of an addition reaction catalyst, and (E) an addition-reaction controlling agent in an amount of 0.01 to 1 part by mass, wherein the thermally conductive filler (C) comprises magnesium oxide having a specific surface area of 0.4 m.sup.2/g or less in an amount of 20 to 50 wt % and aluminum hydroxide in an amount of 10 to 30 wt %, relative to a total weight of component (C).

One of the objects of the present invention is to provide a thermally conductive silicone resin composition which has good thermal conductivity, a light weight (namely, a light weight per unit volume), and good reliability in high humidity, and a molded body thereof. The present invention provides a thermally conductive silicone resin composition comprising the following components (A) to (E): (A) an organopolysiloxane having at least two alkenyl groups each bonded to a silicon atom in an amount of 100 parts by mass, (B) an organohydrogen polysiloxane having at least two hydrogen atoms each bonded to a silicon atom in an amount such that a ratio of the number of the hydrogen atom bonded to a silicon atom relative to the number of the alkenyl group in component (A) is 0.1 to 2, (C) a thermally conductive filler in an amount of 2500 to 6000 parts by mass, (D) a catalytic amount of an addition reaction catalyst, and (E) an addition-reaction controlling agent in an amount of 0.01 to 1 part by mass, wherein the thermally conductive filler (C) comprises magnesium oxide having a specific surface area of 0.4 m.sup.2/g or less in an amount of 20 to 50 wt % and aluminum hydroxide in an amount of 10 to 30 wt %, relative to a total weight of component (C).

A heat dissipation sheet containing a silicone resin and a thermally conductive filler, wherein with respect to the cross-sectional shape of the thermally conductive filler, the average value of an aspect ratio of the 1st to 24th particles from the largest of biaxial average diameters, is in a range of 0.4 or more and 1.4 or less. In addition, an area ratio (Sr) of a total area S of cross-sectional shapes of the particles to a whole area of the cross-sectional view may be in a range of 20% or more and 80% or less, and the particle number ratio may be less than 1. Further, a thermal resistance ratio of a thermal resistance value when a pressure of 0.4 MPa is applied to a thermal resistance value when a pressure of 1.0 MPa is applied may be 1 or more.

A heat dissipation sheet containing a silicone resin and a thermally conductive filler, wherein with respect to the cross-sectional shape of the thermally conductive filler, the average value of an aspect ratio of the 1st to 24th particles from the largest of biaxial average diameters, is in a range of 0.4 or more and 1.4 or less. In addition, an area ratio (Sr) of a total area S of cross-sectional shapes of the particles to a whole area of the cross-sectional view may be in a range of 20% or more and 80% or less, and the particle number ratio may be less than 1. Further, a thermal resistance ratio of a thermal resistance value when a pressure of 0.4 MPa is applied to a thermal resistance value when a pressure of 1.0 MPa is applied may be 1 or more.

Provided is anisotropic graphite for producing an anisotropic graphite composite having excellent thermal conduction property and excellent long-term reliability as a heat dissipating member. Given an X axis, a Y axis orthogonal to the X axis, and a Z axis perpendicular to a plane defined by the X axis and the Y axis, and a crystal orientation plane of the anisotropic graphite is parallel to an X-Z plane, and a specific number of holes each having a specific size are formed in at least one surface out of surfaces of the anisotropic graphite which are parallel to an X-Y plane.

Provided is anisotropic graphite for producing an anisotropic graphite composite having excellent thermal conduction property and excellent long-term reliability as a heat dissipating member. Given an X axis, a Y axis orthogonal to the X axis, and a Z axis perpendicular to a plane defined by the X axis and the Y axis, and a crystal orientation plane of the anisotropic graphite is parallel to an X-Z plane, and a specific number of holes each having a specific size are formed in at least one surface out of surfaces of the anisotropic graphite which are parallel to an X-Y plane.

A hexagonal boron nitride powder having an average longer diameter (L) of primary particles in the hexagonal boron nitride powder of more than 10.0 μm and 30.0 μm or less, an average thickness (D) of the primary particles in the hexagonal boron nitride powder of 1.0 μm or more, a ratio of the average longer diameter (L) to the average thickness (D), [L/D], of 3.0 or more and 5.0 or less, and a content of primary particles having a ratio of a longer diameter (1) to a thickness (d), [l/d], of 3.0 or more and 5.0 or less of 25% or more, a method for producing the hexagonal boron nitride powder, and a resin composition and a resin sheet each containing the hexagonal boron nitride powder.

Provided is: a thermally conductive silicone gel composition which has a high thermal conductivity, and is less likely to flow out and slip off/drop off from a surface on which the gel composition is placed, even when the composition that has not been cured is placed on a sloped surface or in a vertical direction, and has excellent gap-filling ability with respect to a heat dissipation part, etc., and excellent repairability if desired; a thermally conductive member comprising the thermally conductive silicone gel composition; and a heat dissipation structure using the same. The thermally conductive silicone gel composition comprises: (A) an alkenyl group-containing organopolysiloxane; (B) an organohydrogenpolysiloxane; (C) a catalyst for a hydrosilylation reaction; (D) a thermally conductive filler; (E) a silane-coupling agent; and (F) a specific organopolysiloxane having a hydrolyzable silyl group at one end thereof. The gel composition has certain viscosity properties as disclosed herein.