Metallized polypropylene film
Provided is a metallized polypropylene film having excellent insulation breakdown resistance properties. The metallized polypropylene film of the present invention has a thickness of 0.5 to 4.0 μm and has a feature such that the number of insulation breakdown points multiplied by thickness, as determined under predetermined measurement conditions for measuring the number of insulation breakdown points, is 1.90 (points/cm 2 )·μm or less.
1 . A metallized polypropylene film comprising a polypropylene film and a metal layer stacked on one or both surfaces of the polypropylene film, the metallized polypropylene film having a cumulative insulation breakdown point density of 1000 points/m 2 or less after a cumulative DC voltage application test is performed by applying a stepwise-increased voltage in the range of 350 to 425 V/μm at 20° C., wherein the polypropylene film is treated at a voltage speed ratio per unit width of a cooling roll of 0.20 V min/m 2 or more and 0.45 V min/m 2 or less and at an electrical discharge amount of 1.5 W min/m 2 or more and 3.7 W min/m 2 or less.
2 . The metallized polypropylene film according to claim 1 , wherein the polypropylene film has a thickness of 1.0 to 3.0 μm.
3 . The metallized polypropylene film according to claim 1 , wherein when treated at 120° C. for 15 minutes, the polypropylene film has a thermal shrinkage of 0 to 8% in a first direction and a thermal shrinkage of −2 to 2% in a second direction that is orthogonal to the first direction.
4 . The metallized polypropylene film according to claim 1 , wherein when treated at 140° C. for 15 minutes, the polypropylene film has a thermal shrinkage of 0 to 10% in a first direction and has a thermal shrinkage of −1 to 5% in a second direction that is orthogonal to the first direction.
5 . The metallized polypropylene film according to claim 1 , wherein the polypropylene film has a tensile modulus of elasticity of 1.5 GPa or more in a first direction and a tensile modulus of elasticity of 3 GPa or more in a second direction that is orthogonal to the first direction.
6 . The metallized polypropylene film according to claim 1 , wherein the polypropylene film is a biaxially stretched film.
7 . The metallized polypropylene film according to claim 1 , wherein the polypropylene film is a single-layer film.