Solid state device for monitoring integral values of time and temperature of storage of perishables

Abstract

An indicator composition and process capable of changing color in relationship to its exposure to a temperature above and below a base line temperature and to the time of said exposure, for monitoring the time-temperature history of a substrate, depositable as a layer on said substrate, comprising a dispersion of either a binder comprising a reaction inert, neutral finely divided absorbent, in the presence of a reactant comprising a salt of an acid or an organic compound substituted by at least one moiety which, in ionic form, is an anion or a binder/reactant, comprising at least one solid organic polymer whose constituent units contain, as a covalent substituent, at least one moiety which, in ionic form, is an anion; as indicator, at least one acid sensitive pH dye and as activator, at least one base. This composition and process may be utilized to form a solid state device for monitoring integral values of time and temperature during storage of perishables. The device is a single solid indicating layer deposited upon a substrate. The time required for the color change and the activation energy of the device can be varied by varying the concentration and nature of reactants, catalysts, additives and polymeric binder/reactant matrix. The color change can be gradual or abrupt and exhibited as a continuous strip, as alphanumeric symbol(s) or as a line array which can be read by a bar code reader.

Dependencies are inferred from the claim text.