| 摘要 |
PROBLEM TO BE SOLVED: To enhance heat resistance and vapor deposition processability by specifying the isotacticity and isotactic pentad ratio of a biaxially oriented polypropylene film and also specifying the dielectric breakdown voltage per the sum of the heat shrinkage factors of the film in the machine and width directions thereof and the thickness thereof at specific temp. and the thickness of the film. SOLUTION: The isotacticity of a biaxially oriented polypropylene film is 98.5-99.5%. Herein, the isotacticity is defined by the ratio of the wt. of an insoluble component to the wt. of the film before extraction when the film is extracted with boiling n-heptane. The stereoregularity of the biaxially oriented polypropylene film is evaluated by the pentad ratio due to the absorption peak of a methyl group measured by 13C-NMR and the isotactic pentad ratio of the biaxially oriented polypropylene film exceeds 99%. Further, the sum of the heat shrinkage factors in the machine and width directions of the film at a time of heating at 120 deg.C for 15min is 1.5-3.5% and the DC dielectric breakdown strength of the film at 105 deg.C is 580-(200/d<0.5> ) (V/μm) and the thickness of the film is 2-20μm. |
