| 摘要 |
PURPOSE:To improve the lateral stretchability of a film by suppressing its longitudinal heat shrinkage by a structure wherein an unoriented film having excellent lateral stretchability is laminated to a longitudinally unidirectionally oriented film within the range, which gives no bad effects to the former film. CONSTITUTION:Firstly, an unoriented film made of resin mainly composed of poly(4- methylpentene-1) (PMP) is uniaxially oriented longitudinally at the draw ratio of 300% of more at a temperature of 80-180 deg.C. Secondly, resin mainly consisting of PMP is laminated to one or both sides of said uniaxially oriented film by melt extrusion by the thickness, the ratio of which to the thickness of the uniaxially oriented film is 1:20 or more. Thirdly, the resultant resin-laminated film is laterally oriented at the draw ratio of 300% or more within the range from 150 deg.C or more to under the melting point of PMP. Said resin may well contain petroleum resin. The content of 5-30% by weight of the petroleum resin is preferable, because the resultant stretchability is better. Further, the content or 70% by weight or more of PMP component in the resin is preferable. If the resin contains less than 70% by weight of PMP component, the crystallizability of the film is lowered and the heat resistance, solvent resistance, electrical characteristics and the like, all of which are the feature of PMP, tend to lower. The film obtained in such a manner as described above contains no un-uniform orientation and has mechanical characteristic excellent as biaxially oriented film. |
