Method for the production of thermographic copies from an electrostatic powder image

Claim 1

IN A METHOD FOR THE PRODUCTION OF COPIES OF AN ORIGINAL COMPRISING THE STEPS: (1) PRODUCING A LATENT ELECTROSTATIC IMAGE IN AN INSULATING PHOTOCONDUCTIVE LAYER BY THE STEPS COMPRISING UNIFORMLY APPLYING ELECTROSTATIC CHARGES TO SAID PHOTOCONDUCTIVE LAYER AND EXPOSING SAID PHOTOCONDUCTIVE LAYER TO A LIGHT IMAGE OF SAID ORIGINAL TO PRODUCE AN IMAGEWISE PATTERN OF ELECTROSTATIC CHARGES ON SAID PHOTOCONDUCTIVE LAYER; (2) DEVELOPING SAID LATENT ELECTROSTATIC IMAGE ON SAID PHOTOCONDUCTIVE LAYER WITH FREE-FLOWING INFRA-RED ABSORBING POWDER PARTICLES THAT REMAIN IN POWDER FORM UPON EXPOSURE TO HEAT; (3) CONTACTING SAID PHOTOCONDUCTIVE LAYER CARRYING SAID POWDER IMAGE WITH A THERMOGRAPHIC COPY SHEET HAVING A THERMO-SENSITIVE LAYER OF SUBSTANTIALLY LESS INFRA-RED ABSORPTIVITY THAN SAID POWDER PARTICLES, SAID THERMO-SENSITIVE LAYER BEING ADAPTED TO UNDERGO AN IRREVERSIBLE CHANGE IN APPEARANCE UPON EXPOSURE TO HEAT; (4) EXPOSING SAID PHOTOCONDUCTIVE LAYER AND COPY SHEET TO INFRA-RED RADIATION TO PRODUCE SAID IRREVERSIBLE CHANGE IN SAID THERMOSENSITIVE LAYER IN CORRESPONDENCE WITH A HEAT PATTERN PRODUCED BY INFRARED RADIATION ABSORPTION BY SAID POWDER IMAGE, WHILE SAID THERMO-SENSITIVE LAYER IS IN CONTACT WITH SAID POWDER IMAGE; (5) SEPARATING SAID PHOTOCONDUCTIVE LAYER AND SAID COPY SHEET; AND (6) REMOVING THE POWDER PARTICLES FROM SAID LAYERS.