Polymeric film and film capacitor

The present invention relates to polymeric films used as electrical insulators or dielectrics. More particularly, it relates to polymeric films small in dielectric loss tangent, excellent in heat resistance and low in friction coefficient between the films, and to film capacitors comprising the polymeric films. By using a polymeric film having a dielectric loss tangent of 0.002 or less measured at a frequency in the range of 1 kHz to 1 GHz at a temperature of 25 ° C., heat generation of dielectric loss of capacitors can be reduced and rising of temperature can be inhibited, and, can highly stand the rise of temperature, whereby further miniaturization and increase in capacity of capacitors become possible. Furthermore, the problems in handling that the films are apt to cut or become entangled at the rewinding step can be greatly improved by using polymeric films which are 1 or less in friction coefficient between the films of the same material. Accordingly, the polymeric films are excellent in performance of insulator film, namely, small in dielectric loss tangent, and, moreover, are free from the problems in handling that the films are apt to cut or become entangled at the rewinding step. Furthermore, the polymeric films are suitable for film capacitors.