This technology is available from Temarex Corporation.
COLOR CHANGING POLYMERS
Title: METHOD OF USING MULTICHROMIC POLYMERS IN PACKAGING
Disclosure 187 U.S. Patent 5,501,945
A method of using packaging material (i.e. bags, wraps, films, pads, trays, paper, molded containers or spacers) to indicate exposure of an article packaged therein to irradiation.
By affixing to or incorporating into the packaging material one or more photochromic dyes, and the exposing the package to one or more radiation frequencies such that the dye absorbs said one or more radiation frequencies, indicating exposure or lack of exposure of said article to irradiation.
The exposure or lack of exposure to irradiation is evident by visually perceptible color change.The subtle or dramatic color change can be in either a temporary or permanent state depending upon application.
The photochromic dye is one or more of fulgides, triaryl methane leuco-cyanides, triaryl methane leuco-hydroxides or triaryl methane leucobisulfites.
This technology is ideally suitable for food preservation, medical device and equipment sterilization, radiation biology and the like wherein a visible indicator is desirable.