| abstract |
BY USING CERTAIN COMPOSITIONS OF MATTER COMPRISING LIQUID CRYSTAL MATERIAL OF THE CHOLESTERIC PHASE HAVING A VISCOSISTY CONTROLLED IN ACCORDANCE WITH A DESIRED LIMIT TEMPERATURE, ONE CAN OBTAIN AN IRREVERSIBLE COLOR CHANGE THAT SERVES AS AN INDICATION THAT SUCH LIMIT TEMPERATURE HAS BEEN EXCEEDED. POSSIBLE USES INCLUDE PACKAGING OF FROZEN FOODS AND DETERMINATION OF BODY TEMPERATURES. CHOLESTERIC LIQUID-CRYSTAL MATERIAL, MICROENCAPSULATED AND/OR IN THIN-FILM FORM, IS FAST-COOLED FROM AN ABOVELIMIT TEMPERATURE AT WHICH IT EXHIBITS A CHARACTERISTIC COLOR OTHER THAN THAT WHICH IT HAS IN THE VICINITY OF THE LIMIT TEMPERATURE, RETAINING ITS HIGH-TEMPERATURE COLOR UNTIL THE LIMIT TEMPERATURE IS EXCEEDED. PARTICULAR CHOLESTERIC-PHASE LIQUID-CRYSTAL MATERIALS AMENABLE TO ACCORDANCE WITH DESIRED LIMIT TEMPERATURES, ARE ALSO TAUGHT. ARTICLES OF MANUFACTURE EMBODYING SUCH COMPOSITIONS ARE DISCLOSED. |