Patent ID: 6284078
Filing Date: 2001-09-04
Classification: C09K,G01K

Abstract:
A method for preparing a temperature sensing element containing a cholesteric liquid crystal composition, said element displaying a signal having a first colored state at ambient temperatures, and a second colored state when placed at a site the temperature of which is to be determined, said signal being reversible to the first colored state upon the application of pressure to the sensing element which comprises:(a) preparing the sensing element utilizing a substrate, embossing a cavity to a configuration of a predetermined volume into the substrate, depositing a cholesteric liquid crystal composition into the cavity, the liquid crystal composition comprising about 50 to about 90% of the cavity volume, bonding a transparent cover layer in sealing engagement with the substrate thereby forming an enclosure containing the liquid crystal composition in the cavity;(b) subjecting the sensing element so formed to elevated temperatures of about 95.degree. to about 120.degree. C. for a time sufficient to cause the substrate to shrink thereby reducing the embossed cavity volume to a volume substantially the same as its original unembossed configuration, such time being of a duration to avoid damage to the liquid crystal composition at the elevated temperature;whereby the sensing element cavity is inverted, causing the cholesteric liquid crystal composition to be forced upwardly against the cover layer, causing the cover layer to be stressed and taking on a convex domed configuration, with the cholesteric liquid crystal composition trapped in a toroidal configuration between the cover layer and the substrate.