METHOD OF MAKING A PIEZOELECTRIC DEVICE HAVING A PIEZO-ELECTRIC POLYMER FILM SUPPORTED ACROSS A FRAME

1525136 Piezoelectric polymer devices KUREHA KAGAKU KOGYO KK 11 Dec 1975 [13 Dec 1974] 50734/75 Heading H4J A polymer film 1, having electrodes 2, 2' on its two sides has one electrode 2' closely contacted with a base film 3 thicker than the polymer film 1 to form a laminated body. A frame 4 is adhered to the exposed surface of the other electrode 2. The base film 3 is then removed to produce a framed piezoelectric polymer film, free of wrinkles or limp regions, and suitable for use as a diaphragm for headphones, speakers or other electro-acoustic diaphragms. The polymer film 1 is preferably of a polyvinylidene fluoride or polyvinyl fluoride and is polarized under a D.C. field. The base film, of thickness not more than 300 microns is preferably of polyvinylidene fluoride, polyvinyl fluoride, polyvinyl chloride, a polyester or polypropylene. The two films may be closely contacted with each other by moistening one or both contacting surfaces with water or oil or by electrostatical attraction. After closely contacting them any air trapped between them can be removed by pressing with a roller, preferably in a vacuum. Polymer film 1 and base film 3, on separate bobbins (6, 7) Fig. 4 (not shown) may be passed between pressure rollers (8, 9), the resultant laminate (B) being taken up by a bobbin (10). The pressure rollers may be omitted, the two films being pressure contacted by winding the films 1, 3 under tension on the take-up bobbin (10). The laminating process may be performed prior to polarization of the polymer film 1 and also prior to metallization of one side of the polymer film 1. The polymer film 1, metallized on both sides and wound on a bobbin, may be polarized in the wound state using the metallization as electrodes.