Heat-sensitive copy-sheet

Claim 1

THE METHOD OF MAKING A HEAT-STABLE REPRODUCTION ON A HEAT-SENSITIVE COPY-SHEET OF A HEAT-IMAGE OF A GRAPHIC ORIGINAL, COMPRISING: SUBJECTING SAID COPY-SHEET TO SAID HEAT-IMAGE TO CONVERT IMAGE AREAS OF SAID SHEET TO A PERMANENTLY VISIBLY DISTINCT APPEARANCE; AND SUBJECTING AT LEAST THE BACKGROUND AREAS OF SAID SHEET TO ACTINIC RADIATION TO STABILIZE SAID AREAS AGAINST VISIBLE CHANGE ON SUBSEQUENT APPLICATION OF HEAT; SAID COPY-SHEET COMPRISING A VISIBLY HEAT-SENSITIVE LAYER COMPRISING (A) COMPONENTS INTER-REACTIVE AT ELEVATED TEMPERATURES OF ABOUT 90150*C. TO PRODUCE AN AZO DYE BY OXIDATIVE COUPLING AND INCLUDING A HETEROCYCLIC HYDRAZONE AND A NORMALLY SOLID ORGANIC OXIDIZING AGENT FOR THE HYDROZONE LINKAGE HAVING A POSITIVE HALOGEN ATOM, SELECTED FROM THE CLASS CONSISTING OF CHLORINE AND BROMINE ATOMS, ATTACHED TO A NITROGEN ATOM, AND (B) A PHOTOSENSITIVE N-SUBSTITUTED P-AMINOBENZENE DIAZONIUM SALT IN AMOUNT SUFFICIENT, ON DECOMPOSITION UNDER ACTINIC IRRADIATION, TO REDUCE SAID OXIDIZING AGENT, SAID SALT BEING DECOMPOSABLE ON EXPOSURE TO NEAR-ULTRAVIOLET RADIATION WITH FORMATION OF A REDUCING AGENT FOR SAID OXIDIZING AGENT.