Abstract: A high dielectric-constant film is disclosed. The film may be comprised of one or more layers. At least one layer is comprised of a thermoplastic polymer having dispersed therein a ferroelectric substance having a dielectric-constant of at least 10. The ferroelectric substance is present in an amount of 5% to 80% by weight based on the weight of the entire film. The film provides a high dielectric-constant and can be produced easily and economically.

Abstract: A biaxially drawn thermoplastic polyester film is prepared by concurrent-biaxially drawing a thermoplastic polyester film by a tenter method at a drawing temperature higher than the glass transition temperature of the thermoplastic polyester while maintaining the preheating temperature of the film just prior to drawing at a level greater than the drawing temperature and maintaining the subsequent heat-treating temperature immediately after drawing lower than the preheating temperature and carrying out a reheat-treating process in a plurality of steps while elevating the temperature in each step over a substantially equal temperature range.