Heat resistant security document having an insulating material to prevent premature colour development when passing through heated printing devices.

摘要

A security document (10), which is resistant to premature colour development by heated printing devices, comprising a substrate (12) coated with a composition (14) of an initially colourless colour former, a colour developer and an insulating material (15). This is then further coated with a toner adhesion enhancing coating (16), which also preferably includes the insulating material (15). The security document (10) thus provides an authentication feature and/or an indication of attempted alterations from the use of solvent, heat or abrasives.