A method of producing a lottery ticket and lottery tickets produced thereby wherein an overprint region is provided over at least a scratch-off layer, the overprint region comprising an image obtained from a design in which the colors in the design have been separated into half tone images of each...http://www.google.co.uk/patents/US5803504?utm_source=gb-gplus-sharePatent US5803504 - Multicolor overprinting of scratch-off lottery tickets
