Biaxially orientated film containing cyclic olefin polymers and alpha-olefin polymers, method for its production, as well as its use in a capacitor

Biaxially orientated film containing

• a) at least 2 cyclic olefin polymers
• and
• b) at least one semi-crystalline alpha-olefin polymer
• wherein the sum of the percentages of all the cyclic olefin polymers in the film is in the range of 1 to 25 percent by weight and all the cyclic olefin polymers contained in the film have a glass transition temperature in the range of 120 to 180° C. and the film contains at least a first cyclic olefin polymer and a second cyclic olefin polymer, wherein the second cyclic olefin polymer has a higher glass transition temperature than the first cyclic olefin polymer and
• wherein the sum of the percentages of all the semi-crystalline alpha-olefin polymers in the film is in the range of 75 to 99 percent by weight and all the semi-crystalline alpha-olefin polymers contained in the film have a crystallite melting temperature in the range of 150 to 170° C. and
• wherein the weighted arithmetic mean of the glass transition temperatures of all the cyclic olefin polymers contained in the film is smaller than or equal to the weighted arithmetic mean of the crystallite melting temperatures of all the semi-crystalline alpha-olefin polymers contained in the film and
• wherein all quantities are based on the overall mass of the film.