Method of using multichromic polymers in packaging

Abstract

Several methods of using dyes within polymers and specifically in packaging materials are disclosed. These dyes respond to specific stimuli and indicate exposure to stimuli by a change or shift in the frequencies of light which they adsorb. The stimuli include temperature, radiation, chemicals (e.g. H.sub.2 O, CO.sub.2, NO.sub.2, ethylene, and SO.sub.2), and tensile or compressive stress. Within packaging materials (or affixed thereto as a label, decal or tag) these dyes could indicate spoilage or the possibility of spoilage, that the product has been irradiated, or that the product has been exposed to an undesirably high or low temperature. Many of the shifts in absorption frequencies result in visible color change which a consumer could quickly identify. The tensile or compressive stress sensitive dyes could indicate whether common opposing interlocking polymeric strips used to seal plastic bags have been effectively interlocked to seal the bags.

Dependencies are inferred from the claim text.