Thermal imaging materials

Abstract From the Canadian patent

Thermographic materials are colorless when unexposed, but provide an intense dark image when thermally addressed. The materials comprise white ferric organophosphate, ferric organophosphinate, or ferric organophosphonate in a clear binder with a colorless catechol or polycatechol held in said binder in solid solution. The choice of substituents on the catechol nucleus can give a change in the color of the thermal image together and provide good near infrared absorption. Use of mixed catechols can give achromatic black images. These combinations of materials show high stability at ambient temperatures.