Sughrue, Rothwell Mion Zinn & Macpeak
Process for producing polymeric piezoelectric elements and the article formed thereby
 A highly piezoelectric polyvinylidene fluoride element is prepared by treating a polyvinylidene fluoride film having an infrared absorbance ratio D.sub.530 /D.sub.510 of not more than 1.2, namely having a major proportion of .beta.-type crystal structure, at a temperature of at least 40.degree.C but below the melting point of the film while applying to the film a direct current voltage of 200 KV/cm to 1,500 KV/cm. The polyvinylidene fluoride film having a major proportion of .beta.-type crystal structure may be obtained by stretching a fabricated article of polyvinylidene fluoride having a major proportion of .alpha.-type crystal structure under specific conditions. 
Kureha Kagaku Kogyo Kabushiki Kaisha
H Y C H B C Y
H01L Y10T C08J H01G B29C C08J Y10T
inventional additional additional inventional inventional inventional additional
Takao Naohiro
Oikawa Murayama