Method of copying

Claim 1

THE METHOD OF PREPARING THE SURFACE OF A HYDROPHILIC PRINTING-PLATE FOR LITHOGRAPHIC PRINTING OF REPRODUCTIONS OF A GRAPHIC ORIGINAL, COMPRISING (1) EXPOSING SAID GRAPHIC ORIGINAL TO BRIEF INTENSE IRRADIATION THROUGH A RADIATION-TRANSMITTING COPY-SHEET HAVING AN ORGANOPHILIC VISIBLY HEAT-SENSITIVE LAYER IN HEAT-CONDUCTIVE CONTACT WITH SAID ORIGINAL FOR PRODUCING IN SAID LAYER A RADIATIONABSORPTIVE AND VISIBLY DISTINCT IMAGE PORTION CORRESPONDING TO THE RADIATION-ABSORPTIVE IMAGE-FORMING AREA OF SAID ORIGINAL, AND (2) EXPOSING THE THUS CONVERTED COPY-SHEET TO FURTHER BRIEF IRRADIATION AT AN INTENSITY AT LEAST EQUAL TO THAT USED IN (1) WHILE HOLDING THE COPY-SHEET WITH ITS ORGANOPHILIC LAYER IN INTIMATE CONTACT WITH SAID PRINTINGPLATE SURFACE, FOR SELECTIVELY TRANSFERRING THE ORGANOPHILIC IMAGE PORTION TO THE HYDROPHILIC PRINTING-PLATE SURFACE; SAID COPY-SHEET BEING FURTHER CHARACTERIZED AS CONSISTING ESSENTIALLY OF A RADIATION-TRANSMISSIVE BASE SHEET AND A VISIBLY HEAT-SENSITIVE ORGANOPHILIC RADIATION-TRANSMISSIVE COATING THEREON, SAID COATING BEING RENDERED VISIBLY DISTINCT AND RADIATION-ABSORPTIVE ON BEING BREFLY HEATED TO CONVERSION TEMPERATURE IN THE THERMOGRAPHIC COPYING PROCESS, THE THUS CONVERTED PORTIONS BEING READILY TRANSFERABLY FROM SAID BASE SHEET ON HEATING TO A TEMPERATURE SUBSTANTIALLY HIGHER THAN SAID CONVERSION TEMPERATURE.