58560 ⎘
Duplicating or marking methods; Sheet materials for use therein using pressure to make a masked colour visible, e.g. to make a coloured support visible, to create an opaque or transparent pattern, or to form colour by uniting colour-forming components; Chemical colour-forming components; Additives or binders therefor; Organic colour formers, e.g. leuco dyes characterised solely by tri (aryl or hetaryl)methane derivatives