| abstract |
PROBLEM TO BE SOLVED: To provide a stretched film for a capacitor having high withstand voltage characteristics and having a very thin film thickness and excellent workability such as element winding, and a cast raw sheet for obtaining the same. SOLUTION: The weight average molecular weight measured by gel permeation chromatography is 100,000 or more and 500,000 or less, the molecular weight distribution Mw / Mn is 4 or more and 6 or less, and the extraction residue measured by the sequential extraction method. This is a sheet produced by heating and melting a polypropylene resin having a stereoregular component (isotactic component) contained in the resin of 93% to 96% by weight and extruding it from a T-die. Thus, a cast raw sheet having a β crystal fraction measured by the X-ray method of 5% or more and less than 25% is produced. |