Method for preparing an improved liquid crystal clinical thermometer
AssigneeMedical Indicators, Inc.
InventorsRobert J. Witonsky, John W. Scarantino
Life of this patent
Estimating the term…
Abstract
A method is disclosed for improving the signal retention of a liquid crystal sensing element comprising an embossed cavity containing the liquid crystal and a cover layer sealing the liquid crystal in the cavity by heat treating at about 95° C. to about 120° C. for a time sufficient to cause the embossed cavity to shrink to substantially its original form thereby forcing the liquid crystal to be forced up against the cover layer to form a domed structure. Essential to the success of the process is incorporation in the cavity of about 10 to about 50% by volume of air based on the volume of the cavity.
Claims8
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° to about 120° 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.
Dependencies are inferred from the claim text.