Optically variable security features having covert forensic features

摘要

The invention relates to security feature for identification documents, and in particular to A security feature, comprising a first covert layer comprising a first covert material that is not visible to a human eye under except under a first condition, the first covert layer further comprising a material constructed and arranged to produce, upon an attempted intrusion into any part of the security feature, a first effect that is visible at least under the first condition; an optically variable layer having first and second sides, the first side being disposed adjacent the first covert layer, the optically varying layer being constructed and arranged to cover at least a portion of the first covert layer; and a second covert layer disposed adjacent to the second side of the optically variable layer, the second covert layer being constructed and arranged to cover at least a portion of the optically variable layer, the second covert layer comprising a second covert material that is visible to the human eye only at a second condition.