| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for evaluating performance of a plastic film whereby a thermal shrinkage percentage of the plastic film can be evaluated in a considerably short time. SOLUTION: Ultrasonic waves are propagated in a plastic film, and a propagation speed of the waves is measured. The measured value is set as an index of a thermal shrinkage percentage of a film face of the plastic film. Alternatively, a polarization transmission intensity of microwaves is measured, and the measured value is used as the index of the thermal shrinkage percentage of the film face of the plastic film. |
