| 摘要 |
PURPOSE:To contrive to enhance strength, heat resistance and dimensional stability while eliminating the precipitation of a low MW substance, by orienting and thermally fixing an unoriented film or sheet comprising a specific heat resistant high-molecular substance under a specific condition to specify tensile modulus in an orienting direction and a heat shrinking ratio at 180 deg.C. CONSTITUTION:A substantially unoriented film, which comprises a heat resistant high-molecular substance of which the secondary transition point is 120 deg.C or more, the m.p. is 280 deg.C or more and the inherent viscosity is 0.4dl/g or more and has crystallinity, is used. This film is oriented at least three times only to a longitudinal uniaxial direction at a temp. from the secondary transition point to 210 deg.C or less and thermally fixed at a temp. of 210 deg.C- below the m.p. In this case, tensile modulus in a longitudinal direction is set to 600kg/mm.<2> or more and heat shrinking ratios at 180 deg.C in longitudinal and lateral directions are set to 4% or less. |
