Colour Laser Marking Methods of Security Document Precursors

Abstract

A method of colour laser marking a security document precursor including at least: a transparent biaxially stretched polyethylene terephthalate foil; at least one colourless colour forming layer for generating a colour different from black containing at least an infrared absorber a colour forming compound and a polymeric binder; and a laser markable polymeric support or a laser markable layer for generating a black colour; comprising the steps of: laser marking the colourless colour forming layer through the transparent polymeric foil with a infrared laser used in continuous wave mode to generate a colour different from black; and laser marking the laser markable polymeric support or the laser markable layer through the transparent polymeric foil with the same infrared laser but used in a pulsed mode to generate a black colour.

Dependencies are inferred from the claim text.