Thermorecording

Claim 1

Process for producing an original having visible light absorptive image markings on a light transparent background by exposing to visible light a heat-sensitive recording layer, which method comprises the steps of imagewise exposing said recording layer to light passing through said original while said original is disposed between said recording layer to light passing through said original while said original is disposed between said recording layer and the source of said light in heat-conductive relation to said recording layer, said recording layer consisting essentially of a hydrophilic water-removable binder having homogeneously distributed therethrough finely divided particles of a hydrophobic thermoplastic polymer normally solid at room temperature and finely divided material capable of absorbing visible light and converting such absorbed light into heat, said layer being generally transparent in the absence of said material, said exposure being for a time lasting no longer than 10 - 1 second to visible light of an intensity of at least 0.3 Watt, second per sq. cm. and sufficient to heat the areas of said layer corresponding to the transparent areas of the original to reduce the water removability thereof not sufficient to heat the areas of said layer corresponding to the image areas of said original to reduce the water removability thereof; and washing said exposed layer with an aqueous liquid to remove therefrom the areas corresponding to said image areas said finely divided light absorbing material being selected from the group consisting of carbon black, graphite, a heavy metal, or an oxide or sulfide of such heavy metal.