| abstract |
A biaxially stretched polyester film, being a biaxially stretched film including a modified polybutylene terephthalate (modified PBT) and polyethylene terephthalate (PET), wherein a mass ratio (modified PBT/PET) between the modified PBT and PET is 20/80 to 5/95, the modified PBT is a PBT containing 5 to 20% by mass of a polytetramethylene glycol unit having a molecular weight of 600 to 4,000, the amount of tetrahydrofuran (THF) generated by heat treating the biaxially stretched film in a helium gas atmosphere at 180° C. for 30 minutes is 50 μg/g or less, and the biaxially stretched film has tear linearity in a lengthwise direction thereof. |