Patent ID: 8444949

Claim:
A graphite film obtained by subjecting a source material film consisting of a polymer film and/or a carbonized polymer film to a heat treatment at a temperature of 2,000° C. or higher, wherein said graphite film has the area of a white region accounting for not less than 1.0% and not greater than 8.5%, the area of the white region being determined by (a) obtaining an SEM image of said graphite film surface captured at 640×480 pixels, a magnification of 400×, and an accelerating voltage of 5 kV such that a wrinkle of the graphite film surface is observed, (b) carrying out a density measurement of the SEM image to obtain an SEM image having 256 gradations of from a minimum value 0 to maximum value 255 in order to determine an amount of the boundary lines on the surface of the graphite film, (c) binarizing the SEM image in step (b) to black and white with a black/white threshold defined by the following formula: Threshold=(maximum value−minimum value)×0.62, wherein a region brighter than the threshold is white and a region darker than the threshold is black, (d) thinning of the white region of the binarized SEM image into a line width of 1, and (e) measuring the area of a white region of the binarized SEM image.