Heat sensitive tamper indicating markings

摘要

The present invention relates to the field of heat sensitive optically variable inks and tamper indicating markings obtained thereof. The present invention relates to the field of irreversible changes in color and/or changes in structure upon a tampering attempt against articles or items comprising said tamper indicating markings through the use of temperature variation. In particular, the present invention provides optically variable ink compositions comprising a plurality of optically variable pigment particles and a plurality of thermally expandable spheres; tamper indicating marking comprising the optically variable ink compositions described herein; their uses as a proof of an illegal action as well as methods for detecting a tampering activity of a marking including the optically variable ink composition described herein.