Aqueous coating composition for thermal imaging film

A multilayer thermal imaging material which comprises:

• (a) a flexible support;
• (b) a heat-sensitive chemically-reactive layer overlying said support comprising
• a color-forming amount of finely divided, solid colorless noble metal salt of an organic acid,
• a color-developing amount of an alkyl ester of gallic acid, which at thermal copy and printing temperatures is capable of a color-forming reaction with said noble metal salt,
• an image toning amount of phthalazone, and
• a carrier composition in which said noble metal salt and alkyl ester of gallic acid are distributed comprising one or more substantially water-soluble partially-hydrolyzed polyvinyl alcohols and a solubility-enhancing amount of an ammonium salt of styrene/acrylic acid copolymer.

An aqueous heat-sensitive chemically-reactive composition comprising the components:

• a color-forming amount of finely divided, solid colorless noble metal salt of an organic acid,
• a color-developing amount of an alkyl ester of gallic acid, which at thermal copy and printing temperatures is capable of a color-forming reaction with said noble metal salt;
• an image-toning amount of a suitable toning agent;
• and
• an aqueous carrier composition in which said noble metal salt and alkyl ester of gallic acid are distributed comprising the components polyvinyl alcohol and a solubility-enhancing amount of an ammonium salt of a styrene/acrylic acid copolymer, said components being present in the following amounts:
• ______________________________________ Weight % Solids ______________________________________ Noble Metal Salt 10-60 Toning [Image Toner] Agent 2-25 Alkyl Ester of Gallic Acid [Reducing 5-25 Agent] Ammonium Salt of Styrene/Acrylic 3-25 Acid Copolymer [Dispersing Agent] Polyvinyl alcohol [Polymeric Carrier 10-60 Material] ______________________________________

An aqueous heat-sensitive chemically-reactive composition comprising the components:

• a color-forming amount of finely divided silver behenate;
• a color-developing amount of an alkyl ester of gallic acid, which at thermal copy and printing temperatures is capable of a color-forming reaction with said silver behenate;
• an image-toning amount of phthalazone;
• and
• an aqueous carrier composition in which said silver behenate and alkyl ester of gallic acid are distributed, comprising the components one or more substantially water-soluble partially-hydrolyzed polyvinyl alcohols and a solubility-enhancing amount of an ammonium salt of styrene/acrylic acid copolymer dispersing agent, said components being present in the following amounts:
• ______________________________________ Weight % Solids ______________________________________ Silver Behenate 25-40 Phthalazone 3-15 Alkyl Ester of Gallic Acid [Reducing 3-10 Agent] Ammonium Salt of Styrene/Acrylic 5-10 Acid Copolymer Polyvinyl Alcohol 25-50 ______________________________________

A method for forming an aqueous heat-sensitive composition suitable for coating to a support which comprises:

• (a) forming a color-forming dispersion having the following composition by grinding in a concentration of 10%-40% in water to a particle size of about 0.5 to 10 microns:
• ______________________________________ Weight % in Solids ______________________________________ Silver Behenate 10-60 Phthalazone 2-25 Polyvinyl Alcohol 10-60 ______________________________________
• (b) forming a clear, stable color-developing solution having the following composition:
• ______________________________________ Weight % in Solids ______________________________________ Propyl Gallate 5-25 Polyvinyl Alcohol 10-60 [Lupasol FF 3249] Ammonium 3-25 salt of styrene/acrylic acid copolymer Water 10-30 ______________________________________
• the relative amounts of polyvinyl alcohol and said copolymer salt varying from about 50 to 90% polyvinyl alcohol and 10 to 50% copolymer salt,
• (c) mixing the dispersion of (a) and solution of (b) together to form an aqueous heat-sensitive coating composition suitable for use in forming a thermal imaging coating.