Forgery proof printed document such as lottery ticket, comprises security layer containing compound which can change visible properties when exposed to certain chemicals

摘要

Printed document such as a lottery ticket comprises substrate without metallic strip; data printed on at least part of substrate; and at least one security layer applied above and/or below the data containing a composition which, when exposed to undesirable contact with attacking substance which can make data appear, causes a change in the visible properties. Independent claims are also included for composition for detecting exposure to attacking substance; and method for detecting forgeries in said document using a pH change.