US Patent 7638110 Carbon fiber

According to the present invention, there is disclosed a carbon fiber having a strand tensile strength of 6,100 MPa or more, a strand tensile modulus of 340 GPa or more and a density of 1.76 g/cm3 or more and possessing, on the surface, striations oriented in a direction parallel to the fiber axis, wherein the distance between striations in a 2×2 μm area of the carbon fiber surface when observed by a scanning probe microscope is 0.1 to 0.3 μm, the root mean square surface roughness Rms (5 μm) in a 5×5 μm area of the carbon fiber surface when observed by a scanning probe microscope is 20 to 40 nm, and the root mean square surface roughness Rms (0.5 μm) when measured in a 0.5×0.5 μm area is 2 to 12 nm.