| 摘要 |
A magnetic recording flexible disc composed of a polyester film substrate having formed thereon a magnetic layer, the improvement wherein said polyester film is a biaxially oriented film consisting of poly-1,4-cyclohexylene dimethylene terephthalate wherein at least 90 mole % of a glycol component is 1,4-cyclohexanedimethanol and at least 80 mole % of an acid component is terephthalic acid, a maximum value of a temperature dependent expansion in the surface direction of the film is 9x10-6 to 35x10-6/ DEG C., a maximum value of a humidity dependent expansion in the surface direction of the film is 0 to 8.0x10-6/% RH, the difference between the maximum and minimum values of the temperature dependent expansion in the surface direction of the film is 0 to 8.0x10-6/ DEG C., and the difference between the maximum and minimum values of the humidity dependent expansion in the surface direction of the film is 0 to 3.0x10-6/% RH.
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