| abstract |
Circuit discontinuities in conductor members embedded in pieces of glass, such as windshields, are detected by placing in operative association with the glass a stratum of cholestericphase liquid-crystal material having appropriate color-change temperature-range characteristics. When current is passed through the conductors, color changes are observed in the vicinities of the operating conductors. By using for the cholesteric-phase liquid-crystal material a mixture of at least first and second ingredients, with the first and second ingredients spanning respectively different portions of the temperature range from about 20* C. to about 32* C., desirable and useful indications are rapidly obtained without the use of particular testingenvironment conditions or particular glass-storage conditions. |