Abstract: A thermal printing medium comprisinga substrate having an upper and lower surface;a heat sensitive layer formed over at least one surface of said substrate and including at least one of a colorless and a lightly colored leuco dye, and a color developing agent which imparts color to said leuco dye; anda protective layer comprised of aqueous resin and filler agent as main components thereof;characterized in that said heat sensitive layer is comprising at least one compound indicated by formula (1) ##STR1## (wherein R indicates an alkyl group having 1 to 10 carbon atoms or a benzyl group which may have a substitutional group) as a color developing agent, and aluminum hydroxide.

Abstract: A thermal printing medium having high mechanical strength, and a label and tag incorporating such a thermal printing medium is disclosed. In additional to high mechanical strength, the thermal printing medium of the present invention provides for excellent printing density and reslution, for which reason the medium is very applicable to bar codes and the like. The thermal printing medium which includes a multilayer structure consisting of a support substrate comprised of polyolefin type cross-laminate film; a thermal developing layer over the above mentioned under layer, comprised chiefly of colorless or lightly colored leuco-type dye and color developer agent; and a protective layer over the above mentioned thermal developing layer.