POLYESTER FILM ROLL, MAGNETIC RECORDING MEDIUM, AND ITS MANUFACTURING METHOD

摘要

PROBLEM TO BE SOLVED: To provide a polyester film roll for a magnetic recording medium which does not produce local electrostatic charged marks when smoothing the surface of a roll longer than 10,000 m and can improve the productivity of the magnetic recording medium, and also provide a magnetic recording medium using it. SOLUTION: A film roll for a magnetic recording medium is obtained by winding a base film consisting of a 3-9μm thick polyester film of 10,000-50,000 m on a cylindrical core. The surface roughness WRa of the base film is 0.5-4 nm on surface A and 4 nm or larger on the other side surface B which is rougher than surface A, and the sum of the both WRa is 12 nm at most. Surface A has 5-50 nm high projections at a rate of 1-50/μm2and the surface hardness of this film roll is 800-950. Further, this film has local electrostatic charged marks at a rate of 5/m2or smaller. COPYRIGHT: (C)2007,JPO&INPIT