Thermographic copying method and apparatus having means for uniformly pre-heating the copy sheet

Claim 1

A PROCESS OF THERMOGRAPHIC REPRODUCTION WHICH COMPRISES THE STEPS OF: (1) EXPOSING WITH INFRARED RADIATION AN ORIGINAL ADAPTED TO REFLECT SAID RADIATION IN AN IMAGEWISE MANNER; (2) INTERCEPTING AT LEAST ABOUT 20% BUT NOT MORE THAN ABOUT 80% OF SAID RADIATION BY MEANS OF AN INFRARED ABSORBING LAYER ARRANGED BETWEEN THE RADIATION SOURCE AND SAID ORIGINAL, SUBSTANTIALLY THE REMAINDER OF SAID RADIATION BEING TRANSMITTED BY SAID LAYER TO SAID ORIGINAL AND SUBSTANTIALLY REFLECTED FROM THE REFLECTIVE AREAS THEREOF; AND (3) ARRANGING IN HEAT-CONDUCTIVE RELATIONSHIP WITH SAID ABSORBING LAYER A HEAT-SENSITIVE LAYER ADAPTED TO UNDERGO A CHANGE UPON EXPOSURE TO HEAT, WHEREBY SAID ABSORBING LAYER IS HEATED UNIFORMLY BY THE RADIATION DIRECTLY ABSORBED THEREBY AND DIFFERENTIALLY BY THE RADIATION REFLECTED IMAGEWISE FROM SAID ORIGINAL, SAID HEAT-SENSITIVE LAYER BEING CORRESPONDINGLY HEATED THROUGH CONDUCTION FROM SAID ABSORBING LAYER AND ACQUIRING A CORRESPONDINGLY DIFFERENTIATED IMAGE THEREIN.