Abstract: A novel class of N-substituted triarylmethane sulfonamides is provided which undergo reversible oxidation into colored form and reversible reduction of the oxidized form into colorless form. Preferred embodiments comprise xanthene sulfonamides having N-aryl substituents, e.g., hydroquinone substituents. These compounds possess redox potentials ranging between about +200 to -500 millivolts and thus are useful as dyes for producing photographic, photothermographic, thermal, and pressure-induced images, as well as being useful as redox indicators in a wide variety of biological and chemical reactions.

Abstract: A novel class of bridged indicator dyes is disclosed which possess absorption in the infrared region of the electromagnetic spectrum. These bridged indicator dyes are useful as light-absorbing, pH-sensitive optical filter agents in diffusion transfer photographic processes adapted to be performed in the presence of ambient light and to diffusion transfer products useful in such processes. These indicator dyes will also find utility in titrations and other analytical techniques and products where pH-sensitive indicator dyes are employed and absorption of infrared is useful.

Abstract: Leuco dyes are provided which comprise the coupling product of a N-acyl substituted aromatic amino color developer and a dye-forming coupler moiety substituted at the coupling carbon with a thermally removable leaving group. Thermal imaging systems employing these leuco dyes have the advantage of reduced bubble formation relative to thermal imaging systems employing prior art leuco dyes containing a group which thermally fragments into one or more gases.

Abstract: This invention provides transparent thermographic recording films which exhibit good anti-stick properties, are scratch resistant and substantailly craze-free. The thermographic recording films comprise a transparent support carrying (a) a dye image-forming system comprising a di- or triarylmethane thiolactone dye precursor, an organic silver salt, a heat-fusible organic acidic material, and polyvinylbutyral as the binder; and, (b) a protective topcoat layer positioned above said dye image-forming system and comprising a water-insoluble polymeric binder, a mixture of at least two colloidal silicas having different average particle diameters in the proportion, by weight, of 1 part of silica having an average diameter of 50 nm or smaller and 0.3 to 1 part of silica particles having an average diameter no more than 40% of the larger sized silica particles, the ratio of total silica to binder being at least 3 parts per weight silica to 1 part per weight binder.

Abstract: A thermal imaging method for forming color images is provided which employs as the color image-forming material, a colorless precursor of a preformed image dye possessing at least one thermal protecting group that undergoes fragmentation upon heating and at least one leaving group that undergoes irreversible elimination upon heating, said protecting and leaving groups maintaining the precursor in its colorless form until heat is applied to effect removal of these groups whereby the precursor is converted to an image dye.