Expanded-graphite sheet

Abstract

This invention provides an expanded-graphite sheet whose thermal conductivity in their surfacewise directions is relatively uniform and higher than its thermal conductivity in perpendicular direction and which can be produced efficiently at relatively low cost. Because the expanded-graphite sheet is made of expanded graphite alone and has the thermal conductivities in parallel direction of 350 W/(m·K) or more, its thermal conductivities in parallel direction is much higher than its thermal conductivity in perpendicular direction; therefore, it is suitable for the conduction and diffusion of heat. Besides, the expanded-graphite sheet can be produced easily, in a short time, efficiently, at relatively low cost.

1 . An expanded-graphite sheet with a thermal conductivity of 350 W/(m·K) or more in a direction parallel to the surface.  
   
   
       2 . The expanded-graphite sheet of  claim 1  with an arithmetic mean surface roughness of less than 5 μm.  
   
   
       3 . The expanded-graphite sheet of  claim 1  wherein the difference between the highest and lowest values of local thermal conductivities at various spots on the expanded-graphite sheet is 10% or less of the overall mean thermal conductivity thereof.  
   
   
       4 . The expanded-graphite sheet of  claim 2  wherein the difference between the highest and lowest values of local thermal conductivities at various spots on the expanded-graphite sheet is 10% or less of the overall mean thermal conductivity thereof.  
   
   
       5 . The expanded-graphite sheet of  claim 1  having an electromagnetic-wave-shielding effect of 60 dBμV/m or more in the frequency range of 100-800 MHz.  
   
   
       6 . The expanded-graphite sheet of  claim 2  having an electromagnetic-wave-shielding effect of 60 dBμV/m or more in the frequency range of 100-800 MHz.  
   
   
       7 . The expanded-graphite sheet of  claim 3  having an electromagnetic-wave-shielding effect of 60 dBμV/m or more in the frequency range of 100-800 MHz.  
   
   
       8 . The expanded-graphite sheet of  claim 4  having an electromagnetic-wave-shielding effect of 60 dBμV/m or more in the frequency range of 100-800 MHz.  
   
   
       9 . The expanded-graphite sheet of  claim 1  with a total impurity content of 10 ppm or less.  
   
   
       10 . The expanded-graphite sheet of  claim 2  with a total impurity content of 10 ppm or less.  
   
   
       11 . The expanded-graphite sheet of  claim 3  with a total impurity content of 10 ppm or less.  
   
   
       12 . The expanded-graphite sheet of  claim 4  with a total impurity content of 10 ppm or less.  
   
   
       13 . The expanded-graphite sheet of  claim 1  with a bulk density of 1.6 Mg/m 3  or more.  
   
   
       14 . The expanded-graphite sheet of  claim 2  with a bulk density of 1.6 Mg/m 3  or more.  
   
   
       15 . The expanded-graphite sheet of  claim 3  with a bulk density of 1.6 Mg/m 3  or more.  
   
   
       16 . The expanded-graphite sheet of  claim 4  with a bulk density of 1.6 Mg/m 3  or more.