Grease

Abstract

The present invention provides a grease showing low thermal resistance, which is not significantly deteriorated by a heat cycle, particularly, a grease suitable as a thermally conductive material for heat-generating electronic components. A grease containing one type or at least two types of thermally conductive material powder selected from the group consisting of a thermally conductive material (A), a thermally conductive material (B) and a thermally conductive material (C), wherein the particle size distribution of the thermally conductive material powder measured by a laser diffraction type particle size distribution method, has population peaks in the ranges of from 2.0 to 10 μm, from 1.0 to 1.9 μm and from 0.1 to 0.9 μm, respectively, and the grease contains a base oil having a surface tension of from 25 to 40 dyn/cm at 25° C.

1 . A grease comprising at least one thermally conductive material powder selected from the group consisting of a thermally conductive material (A), a thermally conductive material (B) and a thermally conductive material (C), and a base oil having a surface tension of from 25 to 40 dyn/cm at 25° C., wherein the particle size distribution of the thermally conductive material powder measured by a laser diffraction type particle size distribution method, has population peaks in the ranges of from 2.0 to 10 μm, from 1.0 to 1.9 μm and from 0.1 to 0.9 μm, respectively. 
     
     
         2 . A grease comprising a thermally conductive material (A) having an average particle size of from 2.0 to 10 μm, a thermally conductive material (B) having an average particle size of from 1.0 to 1.9 μm, a thermally conductive material (C) having an average particle size of from 0.1 to 0.9 μm, and a base oil having a surface tension of from 25 to 40 dyn/cm at 25° C. 
     
     
         3 . The grease according to  claim 1 , wherein each of the thermally conductive material (A), (B) and (C) is at least one member selected from the group consisting of metal aluminum, aluminum nitride and zinc oxide. 
     
     
         4 . The grease according to  claim 1 , wherein the thermally conductive material (A) is metal aluminum, the thermally conductive material (B) is aluminum nitride, and the thermally conductive material (C) is zinc oxide. 
     
     
         5 . The grease according to  claim 1 , wherein the viscosity of the base oil is from 300 to 1,000 mPa·s. 
     
     
         6 . The grease according to  claim 1 , wherein the base oil is a silicone oil having an alkyl group. 
     
     
         7 . The grease according to  claim 1 , wherein the content of the thermally conducive materials (A), (B) and (C) is from 60 to 80 vol %. 
     
     
         8 . The grease according to  claim 1 , wherein based on the total thermally conductive material, the thermally conductive material (A) is from 50 to 70 vol %, the thermally conductive material (B) is from 30 to 20 vol % and the thermally conductive material (C) is from 20 to 10 vol %. 
     
     
         9 . The grease according to  claim 1 , which further comprises a silane coupling agent. 
     
     
         10 . The grease according to  claim 1 , which has a thermal resistance of at most 0.2° C./W. 
     
     
         11 . The grease according to  claim 2 , wherein the thermally conductive material (A), (B) or (C) is at least one member selected from the group consisting of metal aluminum, aluminum nitride and zinc oxide. 
     
     
         12 . The grease according to  claim 2 , wherein the thermally conductive material (A) is metal aluminum, the thermally conductive material (B) is aluminum nitride, and the thermally conductive material (C) is zinc oxide. 
     
     
         13 . The grease according to  claim 2 , wherein the viscosity of the base oil is from 300 to 1,000 mPa·s. 
     
     
         14 . The grease according to  claim 3 , wherein the viscosity of the base oil is from 300 to 1,000 mPa·s. 
     
     
         15 . The grease according to  claim 11 , wherein the viscosity of the base oil is from 300 to 1,000 mPa·s. 
     
     
         16 . The grease according to  claim 4 , wherein the viscosity of the base oil is from 300 to 1,000 mPa·s. 
     
     
         17 . The grease according to  claim 12 , wherein the viscosity of the base oil is from 300 to 1,000 mPa·s. 
     
     
         18 . The grease according to  claim 2 , wherein the base oil is a silicone oil having an alkyl group. 
     
     
         19 . The grease according to  claim 2 , wherein the content of the thermally conducive materials (A), (B) and (C) is from 60 to 80 vol %. 
     
     
         20 . The grease according to  claim 2 , wherein based on the total thermally conductive material, the thermally conductive material (A) is from 50 to 70 vol %, the thermally conductive material (B) is from 30 to 20 vol % and the thermally conductive material (C) is from 20 to 10 vol %. 
     
     
         21 . The grease according to  claim 2 , which further comprises a silane coupling agent. 
     
     
         22 . The grease according to  claim 2 , which has a thermal resistance of at most 0.2° C./W.