Heat sensitive system and use thereof

摘要

A heat sensitive system comprises a document having a localized, non-pressure sensitive, coating of chromogenic composition activated at moderate temperatures. Quickly striking the chromogenic composition with a fingernail or blunt object produces a colored image by frictional heat. The chromogenic composition contains a chromogenic compound and a color developer which are non-pressure sensitive and nonreactive at room temperature. The chromogenic composition can be an intimate mixture of the chromogenic compound and the developer or alternatively separate layers of each of the components.