Multilayer film for tamper indication by use of optical interference reflection
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United States of America Patent
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Sep 22, 1992
Issued Date -
N/A
app pub date -
Dec 23, 1991
filing date -
Dec 26, 1989
priority date (Note) -
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Abstract
A multilayer film including contiguous layers of two or more diverse thermoplastic materials of differing refractive indices whereby the film retains a permanent color change as evidence of tampering or an attempt at tampering when the yield point of at least one of the diverse materials has been at least equalled by the strain associated with such tampering or with such an attempt at tampering, and where before such yield point is at least equalled the wavelength of an unsuppressed reflectance of normally incident light is not within the visible spectrum while after such yielded point is at least equalled the reflectance is retained in the visible spectrum.
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