| 摘要 |
PURPOSE: To improve the scuff resistance and to suppress the drop-out when used as a magnetic recording medium by setting the surface roughness parameter relative standard deviation value at least on one surface of a biaxially oriented polyester film to a specific value or less, and hence uniformly forming surface protrusions having high strength. CONSTITUTION: A biaxially oriented polyester film contains polyester as a main ingredient. The relative standard deviation of the surface roughness parameter Ra of four sides of 5μm of at least one surface is set to 0.30 or preferably 0.25 or less. The number of protrusions on at least one surface is 5,000 pieces/mm<2> or more or preferably 10,000 pieces/mm<2> or more. Further, the protrusions of the surface are desired to be protrusions caused mainly by a crystal. The number of the protrusions/number of particles(NR) of the ratio of the number of the protrusions of the surface to the number of the particles contained is desirably 5 or more, or preferably 10 or more. |
