| abstract |
(57) [Abstract] [Purpose] Even if the film is thinned for long-term recording and reproduction, the tape does not expand or contract and deform easily, and the electromagnetic conversion characteristics are good, causing wrinkles during tape processing. An extremely stable base film for magnetic recording tape that does not have Young's modulus decrease, does not require skew removal during tape processing, and can prevent skew and track deviation that occur when stored at a temperature near room temperature. To provide. [Structure] Made of polyethylene-2,6-naphthalate, Young's modulus in the longitudinal direction is 850 kg / mm 2 or more, Young's modulus in the transverse direction is 550 kg / mm 2 or more, and 3 at 100 ° C. The heat shrinkage when treated for 0 minutes is 1.0% or less in both the vertical and horizontal directions, and the saturation heat shrinkage at 70 ° C. is 0.1% or less in both the vertical and horizontal directions, and 40 ° C. Shrinkage of 0.01% when held at 65% relative humidity for 1 hour A base film for a magnetic recording tape, characterized in that: |