Patent ID: 8129017

Claim:
A carbon fiber strand comprising a bundle of 20,000 to 30,000 carbon fibers, each of which has in the surface thereof, a plurality of creases parallel to the fiber-axis direction of the carbon fiber and in which as measured by scanning probe microscopy, an inter-crease distance in the surface of said carbon fiber is 120 to 160 nm, a crease depth in the surface is 12 to less than 23 nm, an average fiber diameter is 4.5 to 6.5 μm, a specific surface area is 0.9 to 2.3 m 2 /g and a density is 1.76 g/cm 3 or more, wherein said carbon strand has a strand tensile strength of 5,900 MPa or more and a strand tensile modulus of 300 GPa or more; a strand wound on a bobbin with a tension of 9.8 N has a strand width of 5.5 mm or more; and no strand splittings are observed in a strand splitting evaluation method where a running carbon fiber strand with a tension of 9.8 N passes through three stainless-steel rods.