| 摘要 |
PURPOSE:The titled film having a low coefficient of moisture expansion and a small in-plane anisotropy of a coefficient of thermal or moisture expansion and being useful as a base for a flexible magnetic disc, comprising a specified glycol component and a terephthalic acid component. CONSTITUTION:A poly-1,4-cyclohexylenedimethylene terephthalate film comprising a glycol component at least 90mol% of which is 1,4-cyclohexanedimethanol and an acid component at least 80mol% of which is terephthalic acid and orientated so that the refractive index in a plane including longitudinal and lateral directions is 1.585-1.650, the density is 1.220-1.250, the coefficient of thermal expansion is 20-40(X10<-6>/ deg.C), the coefficient of moisture expansion is 3-8 (X10<-6>/% RH), the in-plane anisotropy of a coefficient of thermal expansion is within 6X10<-6>/ deg.C, and the in-plane anisotropy of coefficient of moisture expansion is within 4X10<-6>/% RH. This biaxially orientated film has a low coefficient of moisture expansion, so that when it is used as a base film for a flexible magnetic disc, the off-truck between a head and a magnetic truck is small and a high recording density can be obtained. |
