METHOD OF PRODUCTION OF HIGH MOLECULAR WEIGHT ELECTRET ELEMENT

摘要

PURPOSE:After heat treated in a specific temperature range, a polyvinyliden fluoride resin containing beta-type crystals is irradiated with ionizing radiation to from piezo- electric material of organic film with high fabricability and high piezo-electric properties. CONSTITUTION:Films of polyvinylidene fluoride containing beta-type crystals which are prepared through a conventional process for producing oriented high-molecular- weigth films are heat treated in a temperature range from 40 deg.C lower than to 5 deg.C higher than the melting point of the resin, preferably from 20 deg.C lower to 5 deg.C higher for 5 min to 50 hr. Further ionizing radiation is irradiated to the resin in an amount of 0.05-50 Mrad and a direct current electron field is applied with voltage lower than that of dielectric breakdown of polyvinylidene fluoride film, for example, 100-500 KV/cm at room temperature -180 deg.C, preferably 80-160 deg.C for a prescrived period of time.