| 摘要 |
PURPOSE:To obtain a polyester film low in dielectric loss at high temperatures and suitable for capacitors, etc., having a second-order transition temperature, a melt specific resistivity, a crystallinity, etc., each in a specified range and prepared by biaxially stretching a polymer based on PET. CONSTITUTION:About 75-95wt.% polyethylene terephthalate is mixed with about 25-5wt.% other polymer (e.g., polyarylate or polycarbonate). The mixture is melt-extruded into an unstretched film and this film is biaxially stretched to obtain an oriented film, which is then heat-treated to obtain the purpose polyester film. This polyester film has a second-order transition temperature as measured with a scanning differential calorimeter >=80 deg.C, and a difference between the second-order transition temperature and the m.p. of 100-170 deg.C, a melt specific resistivity >=1X10<8>.cm and a crystallinity of 8-25% as measured by X-ray diffractometry. |
