| 摘要 |
Piezoelectric and pyroelectric elements made from polarized plastics substances such as polyvinylidene fluoride are of considerable interest in a number of fields. Unfortunately, they also suffer from a number of not insignificant drawbacks. Specifically, the maximum thickness of fully-polarized plastics film obtainable is often not sufficient to give the desired sensitivity. A very satisfactory thick piezoelectric/pyroelectric element can, however, be made from these plastics films if, instead of using a single film which is itself thick, there is used a laminar stack of individually thin polarizable plastics films each such film being essentially in face-to-face contact with its two neighbors, and there being no significant gas space/pockets between any two adjacent films, the element being made by a method in which: the required number of films of the unpolarized but polarizable plastics substance is assembled together in the form of a multilayer sandwich adjacent individual films of which are essentially in face-to-face contact; the assembly is heated to a temperature somewhat below the deflection temperature of the plastics substance; while still hot, a polarizing electric field is applied across the assembly, from end face to end face; and while still applying the polarizing field, the assembly is allowed to cool down.
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