| 摘要 |
PCT No. PCT/GB91/00809 Sec. 371 Date Oct. 22, 1992 Sec. 102(e) Date Oct. 22, 1992 PCT Filed May 22, 1991 PCT Pub. No. WO91/18377 PCT Pub. Date Nov. 28, 1991.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 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.
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