| 摘要 |
PURPOSE:To contrive to stabilize the forming state at orientation and to improve the thickness accuracy of film obtained by a method wherein the maximum orientation stress in the moving direction of film and that in its width direction are specified respectively. CONSTITUTION:The film concerned satisfies the conditions represented by formulae I and II in terms of sigmaMD and sigmaTD, in which sigmaMD is the maximum orientation stress in the moving direction (MD) of film and sigmaTD is that in its width direction (TD). In the formulae I and II, sigmaMD is represented by (FXBMD)/A, in which F is interms of T/r and F is stretching force (kg), BMD is draw ratio in MD, A is the cross-sectional area (cm<2>) of stock film, T is the turning torque (kg.cm) of nip rolls, (r) is the radius (cm) of the nip roll and sigmaTD is repreaented by (DELTAPXR)/t, in which DELTAP is pressure (kg/cm<2>) in a bubble, R is the radius (cm) of the bubble and (t) is the thickness (cm) of the film. Thus, the favorable forming stability is obtained and, at the same time, the thickness accuracy of the film is improved. |
