Metallized polypropylene film

A metallized polypropylene film comprising

• a biaxially stretched polypropylene film and
• a first metal film formed on at least one surface of the biaxially stretched polypropylene film,
• the metallized polypropylene film having a thickness of 0.5 to 4.0 μm, and
• the number of insulation breakdown points multiplied by thickness is 1.90 (points/cm2)·μm or less, as determined under the following conditions for measuring the number of insulation breakdown points:
• a conductive substrate comprising a brass plate, a conductive rubber, and an aluminum foil stacked in this order is prepared, and a 22 μm-thick polypropylene insulating film having a 10 mm×100 mm aperture is placed on the aluminum foil-side surface of the conductive substrate;
• the metallized polypropylene film is placed on the top surface of the insulating film so that the first metal film is exposed to the surface side to thereby bring the metallized polypropylene film into contact with the insulating film and also bring the metallized polypropylene film into contact with the aluminum foil through the aperture;
• an electrode is then placed on the surface of the first metal film;
• a stepwise-increased voltage is applied between the first metal film and the conductive substrate at 391 V/μm, 435 V/μm, 478 V/μm, 521 V/μm, 565 V/μm, and 609 V/μm in this order, 6 times in total, each for 1 minute;
• the cumulative number of insulation breakdown points up to the third voltage application is counted;
• the counted number is divided by the area of the aperture of the insulating film (1000 mm2) to take the resulting value as the number of insulation breakdown points;
• and
• the number of insulation breakdown points is multiplied by the thickness of the metallized polypropylene film to take the resulting value as the number of insulation breakdown points multiplied by thickness ((points/cm2)·μm).