| 摘要 |
PURPOSE:To obtain the titled film that is free from aniostropy and has excellent mechanical property and dimension stability, by making a film have an F-5 value, a Young's modulus, a double refraction index, a coefficient of thermal expansion, a coefficient of expansion due to humidity, and a coefficient of non- crysstalline orientation in the respective specified ranges. CONSTITUTION:The present film is a biaxially orientated film of a polyethylene naphthalate that has, in every direction in the plane of the film, an F-5 value of 22-35kg/mm.<2>, a Young's modulus of 650-1,100kg/mm.<2>, and a coefficient of thermal expansion of 25-35%. The in-plane deviation of each of these physical values, and the values of the coefficient of thermal expansion and the efficient of expansion due to humidity of the film is 20% or below, and the film should have a birefringent index of 0.02 or below and a non-crystalline orientation of -0.2-0.2. The film is less anisotropic and has excellent mechanical properties and good dimension stability, and is useful as a base film for forming a magnetic recording mediun in particular a ferromagnetic metal thin film. |
