Liquid crystal cumulative dosimeter
AssigneeTemple University
InventorMortimer M. Labes
Life of this patent
Estimating the term…
Abstract
Cumulative temperature dosimeter utilizes a temperature dependent reaction in a cholesteric liquid crystal composition to produce a color change indicative of temperature exposure over a period of time. Typically, the composition includes, as a solvent, a cholesteric liquid crystal, such as a mixture of p-methoxy-p'-n-butyl-azoxybenzene, cholesteryl nonanoate, cholestyl chloride, and cholesteryl oleyl carbonate. One or more solutes are included, the solutes being reactive at a rate which is temperature dependent, to cause either generation or consumption of mesogenic compounds. In turn, the pitch of the solvent, observable as a visible color change, is affected in proportion to the cumulative temperature exposure of the composition.
Claims18
A cholesteric liquid crystal composition comprising a cholesteric liquid crystal solvent and reactive solutes adapted to enter into a chemical reaction, said liquid crystal solvent having a wavelength of maximum reflection the temperature dependence of which is negligible at the temperatures involved in the reaction, the rate of said reaction being temperature dependent, the products of said reaction being adapted to cause a characteristic change in the light reflecting properties of said composition, the degree of said change being cumulatively indicative of the exposure of said composition to temperature outside of a preselected limit.
A method of determining the cumulative time of exposure of an indicator element to temperatures above a preselected limit said method comprising (1) providing a cholesteric liquid crystal composition comprising a cholesteric liquid crystal solvent and reactive solutes adapted to enter into a chemical reaction at temperatures above said preselected temperature limit, said liquid crystal solvent having a wavelength of maximum reflection the temperature dependence of which is negligible at the temperatures involved in the reaction, the rate of said reaction being temperature dependent, and (2) after a period of time, observing any change in the optical properties of the cholesteric liquid crystal composition.
Dependencies are inferred from the claim text.