Thermal diazotype method and developer sheet for use therein

Claim 1

THE METHOD OF MAKING A THERMAL DIAZOTYPE PRINT WHICH COMPRISES FIRST PROVIDING A SENSITIZED SHEET HAVING A BACKING SHEET AND A SENSITIZED COATING INCLUDING A DIAZO COMPOUND, A COUPLING COMPOUND, AN ACIDIC STABILIZING AGENT, AND A HYGROSCOPIC AGENT, THEN SUPERIMPOSING A MASTER TO BE REPRODUCED OVER THE SENSITIZED SHEET AND SUBJECTING THE SUPERIMPOSED SHEET TO ACTINIC RADIATION TO CAUSE THE DECOMPOSITION OF THE DIAZO COMPOUND IN THE EXPOSED PORTIONS OF THE SENSITIZED SHEET, THEREAFTER SUPERIMPOSING OVER THE SENSITIZED SHEET A DEVELOPER SHEET HAVING APPLIED THERETO COATING MATERIAL WHICH INCLUDES PIPERAZINE AND A CRYSTALLINE SALT CONTAINING WATER OF CRYSTALLIZATION, SAID WATER OF CRYSTALLIZATION BEING RELEASED WHEN SUBJECTED TO TEMPERATURES IN EXCESS OF 100*C., AND SUBJECTING SAID SUPERIMPOSED EXPOSED SENSITIZED SHEET AND DEVELOPER SHEET TO AN ELEVATED TEMPERATURE BETWEEN 100* C. AND 180*C. TO VOLATILIZE THE PIPERAZINE AND RELEASE THE WATER OF CRYSTALLIZATION TO THEREBY CAUSE THE COUPLING COMPOUND TO COMBINE WITH THE DIAZO COMPOUND TO FORM A DYE IN THE UNEXPOSED PORTIONS OF THE SENSITIZED SHEET.