BIAXIALLY STRETCHED POLYPROPYLENE FILM FOR CAPACITOR, DEPOSITION-COATED FILM OBTAINED FROM THE SAME, AND CAPACITOR EMPLOYING THE SAME

摘要

A biaxially stretched polypropylene film for capacitors which is a film having a thickness of 1.0-8.0μm obtained by biaxially stretching a cast raw sheet of a crystalline isotactic polypropylene resin. It is characterized by having a weight-average molecular weight (Mw), as determined by gel permeation chromatography, of 250,000-450,000 and a molecular-weight distribution (Mw/Mn) of 4-7 and giving a molecular-weight distribution curve in which the value obtained by subtracting the differential distribution value corresponding to a logarithmic molecular weight of 6 from the differential distribution value corresponding to a logarithmic molecular weight of 4.5 is from 2% to 15%. The film is further characterized by having a mesopentad content, as determined by high-temperature nuclear magnetic resonance spectroscopy, of from 94% to 98%, excluding 98%.