Tamper resisting holographic security seal

US5319475A · kind A · utility

Assignee

• De La Rue Holographics Limited · GB

Inventors

• Ralph Kay · Basingstoke, GB
• Keith A. Jones · Lexington, US
• Adam J. Silk · Ormskirk, GB

Key dates

• Filing date: Oct 22, 1992
• Grant date: Jun 7, 1994
• Expiry date: Oct 22, 2012

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10S428/915
• WIPO field: Handling
• WIPO sector: Mechanical engineering

Abstract

A tamper resistant security seal is a laminated tape having a transparent carrier layer (2); an optical, diffraction pattern defining layer (3,4); and an adhesive layer (6) for adhering the tape to a substrate. The optical pattern, such as a hologram, defined by the optical pattern defining layer is visible from outside the laminate. The optical diffraction pattern defining layer (3) is formed by a polymeric layer permanently bonded to the transparent carrier layer which, when heated, causes the diffraction pattern to undergo an irreversible change. The adhesive is a pressure sensitive adhesive. An additional removable support layer may be provided on the carrier. The laminate is constructed so that a reduction in temperature below 0.degree. C. will cause an irreversible change in the diffraction pattern, or is such that subsequent to such a temperature reduction, attempted removal of the tape from a substrate will cause an irreversible change in the diffraction pattern.