| 摘要 |
PROBLEM TO BE SOLVED: To provide a biaxially oriented polyethylene-2,6- naphtharenedicarboxylate film useful for producing a magnetic tape capable of recording and reproducing for a long time and very good in running properties and durability. SOLUTION: The biaxially oriented polyester film is characterized in that (1) Young's modulus Y(MD) in the longitudinal direction of the film is 3.9 GPa or above, (2) the ratio TMS(TD)/TMS(MD) of the strength of the transmission microwave in the transverse direction of the film to the same in the machine direction of the film by the molecular orientation meter is 0.5 to 0.9, (3) the ratio (Ra(TD)/Ra(MD)) of the surface roughness Ra(TD) measured in the transverse direction of the film to the same Ra(MD) measured in the machine direction of the film, is 0.3 or above and below 1.0, and also (4) the thickness unevenness of the film is 0.5μm or below.
|
