| 摘要 |
A tamper resistant security seal comprises a laminate 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 (3, 4) 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 (2) 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 DEG 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. |
