Graphite sheet having excellent thermal conductivity and method for preparing the same
The present invention provides a method for preparing a high-performance graphite sheet by imidizing a polyamic acid resulting from a reaction of dianhydride monomer(s) and diamine monomer(s) to obtain a polyimide film; and carbonizing and/or graphitizing the polyimide film to obtain a high-performance graphite sheet, where the polyimide film contains 2 or more fillers having different average particle diameters, and the thermal conductivity of the graphite sheet is at least 1,400 W/m·K. Further, the present invention provides a graphite sheet obtained by the above method.
1. A method for preparing a high-performance graphite sheet, comprising:
providing a polyimide film containing a first filler having an average particle diameter of 2.0 μm to 2.5 μm, and a second filler having an average particle diameter of 1.0 μm to 1.6 μm; and
carbonizing and graphitizing the polyimide film to obtain the graphite sheet,
wherein the thermal conductivity of the graphite sheet is at least 1,400 W/m·K.
2. The method for preparing the high-performance graphite sheet according to claim 1 , wherein the fillers are sublimated during carbonizing and/or graphitizing step, forming voids in the graphite sheet.
3. The method for preparing the high-performance graphite sheet according to claim 1 , wherein the graphite sheet has a thickness of 15 μm to 40 μm.
4. The method for preparing the high-performance graphite sheet according to claim 1 , wherein the polyimide film contains more than 0% to not more than 40% of the first filler, and at least 60% to less than 100% of the second filler, based on the total of the fillers.
5. The method for preparing the high-performance graphite sheet according to claim 1 , wherein the polyimide film has an average roughness(Ra) of 8 nm to 30 nm.
6. The method for preparing the high-performance graphite sheet according to claim 1 , wherein the content of the fillers is 2000 ppm to 4000 ppm based on the weight of the polyamic acid.
7. The method for preparing the high-performance graphite sheet according to claim 1 , wherein the fillers are at least one selected from the group consisting of calcium carbonate, calcium phosphate dibasic, and barium sulphate.
8. The method for preparing the high-performance graphite sheet according to claim 7 , wherein the fillers are calcium phosphate dibasic and/or barium sulphate.
9. The method for preparing the high-performance graphite sheet according to claim 1 , wherein the heat treatment temperature of the graphitizing step is at least 2700° C.