TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The film comprises white pigments, preferably titanium dioxide, barium sulfate, zinc oxide, calcium carbonate and/or incompatible polymers, where the amount of the white pigment in the film is 1-30 wt.% (based on the total weight of the film) and its particle size (d50) is 0.05-5 mu m. The white pigment is titanium dioxide, which is preferably coated inorganically and optionally additionally coated organically, where the preferred inorganic coating is silicon dioxide and/or aluminum oxide. The film thickness is 12-600 mu m. The biaxially oriented white polyester film has: a degree of whiteness according to Berger of greater than or equal to 40; a transparency of less than 50%; a transparency in the UV-A region at 370 nm of less than 10%; an elastic modulus in each film direction of greater than 1500 N/mm2, and in no film direction of greater than 5000 N/mm2; a F5 value (force at 5% elongation) in each film direction of greater than 40 N/mm2, and in no film direction of greater than 140 N/mm2; a tensile strength in each film direction of greater than 65 N/mm2, and in no film direction of greater than 290 N/mm2; a shrinkage at 150 degrees C (15 minutes) in both film directions of less than 3%, and in no film direction of less than -1% (equivalent to 1% strain); a dielectric strength of at least 40 V/ mu m and a partial discharge resistance with an equation ( PDV(V)=x(V/ mu m)x film thickness( mu m)+y(V), where the x-value is greater than 0.75 (V/ mu m) and the y-value is greater than 100 (V); and a standard viscosity (SV)-value degradation rate of greater than -3 SV-E/hour (SV-E is SV-unit).    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The dicarboxylic acid component is made of at least one benzene dicarboxylic acid. The naphthalene dicarboxylic acid is 2,6-naphthalenedicarboxylic acid and the benzene dicarboxylic acid is terephthalic acid. The main dicarboxylic acid component is terephthalic acid. The secondary-dicarboxylic acid: is 2,6-naphthalene dicarboxylic acid, when the main dicarboxylic acid component is terephthalic acid; and is terephthalic acid, when the main dicarboxylic acid component is 2,6-naphthalene dicarboxylic acid. The secondary-dicarboxylic acid is isophthalic acid. The amount of the secondary dicarboxylic acid component is at least 20 mole-%, preferably 25 mole-%. EXAMPLE - Durastar DS2000 (RTM: Polycyclohexanedimethanol-terephthalate-isophthalate) (75 wt.%), Ti-Pure R-105 (RTM: Polycyclohexanedimethanol terephthalate isophthalate with titanium dioxide (20 wt.%)) (25 wt.%) were mixed and extruded in a twin-screw extruder with degassing. The temperature was maintained at 275 degrees C and the flow rate was 2000 kg per hour. The melt was passed through a slot die onto a cooling roller and then stretched at 105 degrees C by a factor of 3.2 in the longitudinal direction and then at 110 degrees C by a factor of 3.2 in the transverse direction to obtain a film.