DE2205875

• Main Authors: MURAYAMA, NAOHIRO, HASHIZUME, HIDEYUKI, IWAKI, FUKUSHIMA, JP
• Format: Patent
• Language: English
• Published: 15.04.1982
• Subjects: BASIC ELECTRIC ELEMENTS; CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES ORLIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE; ELECTRICITY; MEASURING; MEASURING QUANTITY OF HEAT; MEASURING TEMPERATURE; PHYSICS; TESTING; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR

1376372 Electrets KUREHA KAGAKU KOGYO KK 8 Feb 1972 [9 Feb 1971] 5913/72 Headings H1K and H1M A pyroelectric element comprises an electret formed from a film of a homopolymer or copolymer of vinylidene fluoride having sufficient proportion of the #-type crystal structure that the ratio of infra-red absorption D 530 /D 510 is less than 4À0. Stable pyroelectricity is achieved by depolarizing most of the spacecharge polarization of the electret by shortcircuiting opposite surfaces of the film while heating it at a temperature below its melting temperature and above its working temperature as a pyroelectric element. The copolymerizable monomer may be tetrafluoroethylene, trifluoroethylene hexafluoropropylene, trifluorochloroethylene, vinylidene fluorochloride or vinyl fluoride. In an example copper electrodes are vacuum deposited onto mono-axially stretched polyvinylidene fluoride film, a D.C. potential of 400 kv./cm. is applied for 30 minutes at 90‹ C., then the temperature is reduced to room temperature before removing the field. The surfaces of the film are short-circuited while it is heated at 80‹ C. for one hour, or left at room temperature for, e.g. six months. The electrodes providing the field may alternatively be plates spaced from the film surfaces.