Heat developable paper

Claim 1

A HEAT SENSITIVE SHEET ADAPTED FOR DRY HEAT MARKING PROCESSES, STABLE AND LIGHTLY COLORED UNDER NORMAL CONDITIONS AND RESPONSIVE TO HEATING TO AN ACTIVATION TEMPERATURE IN THE RANGE OF 50*C.-150*C. BY CHANGING VISIBLY AND IRREVERSIBLY TO A CONTRASTING COLOR THROUGH THE FORMATION OF A COLORED COMPOUND, SAID SHEET INCLUDING A SOLID STABLE IONIZABLE POLYVALENT METAL SALT AND A SOLID STABLE ORGANIC REAGENT REACTIVE WITH THE METAL IONS OF SAID SALT IN THE PRESENCE OF A LIQUID AMMONIA DEREVATIVE TO FORM A COLORED METALO-ORGANIC COMPOUND BY COVALENT COORDINATE BONDING BETWEEN SAID METAL IONS AND SAID REAGENT, SAID SALT AND REAGENT BEING PRECURSORS OF SAID COLORED COMPOUND PRESENT IN SAID SHEET IN PHYSICALLY DISTINCT POTENITALLY REACTIVE ASSOCIATION, AND A SOLID, STABLE CRYSTALLINE COCRYSTAL ADDUCT OF A LIQUID ORGANIC AMMONIA DERIVATIVE AND A HYDROXYPHENOL CARRIER COMPOUND SELECTED FROM THE CLASS CONSISTING OF BISPHENOLS AND HYDROXYPHENYL SUBSTITUTED CHROMANS, SAID ADDUCT HAVING A DISSOCIATION TEMPERATURE OF BETWEEN 50*C. AND 150*C. AT WHICH TEMPERATURE SAID LIQUID AMMONIA DERIVATIVE IS RELEASED BY SAID CARRIER COMPOUND, CAUSING SAID SALT AND REAGENT TO REACT.