The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Oct. 10, 1978
Filed:
Jun. 17, 1977
Daniel B Hayden, Port Huron, MI (US);
George W Smith, Birmingham, MI (US);
Michael Kaplit, Birmingham, MI (US);
General Motors Corporation, Detroit, MI (US);
Abstract
A twisted nematic liquid crystal device contains a liquid crystal material having dielectric anisotropy .DELTA..epsilon. which is positive for certain values of temperature and frequency of an electrical signal applied across the material and negative for other values of these parameters. The device includes a heater and a test area (separate from the display area of the device) at which transmittance of light is monitored by a heater control circuit. A test frequency chosen to give .DELTA..epsilon..apprxeq.0 at the minimum desired operation temperature of the device is applied across the test area and the light transmittance is monitored to assure that the temperature is high enough. When the temperature is too low, the heater element is automatically energized to increase the temperature of the liquid crystal device.