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 non- reactive 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.
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