Multilayer film for tamper indication by use of optical interference reflection
First Claim
1. A multilayer optical interference film comprised of contiguous layers of two or more diverse thermoplastic materials of differing refractive indices whereby the film retains a permanent visual 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 yield point is at least equalled the reflectance is retained in the visible spectrum to provide a permanent visual color change.
2 Assignments
0 Petitions
Accused Products
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.
128 Citations
17 Claims
- 1. A multilayer optical interference film comprised of contiguous layers of two or more diverse thermoplastic materials of differing refractive indices whereby the film retains a permanent visual 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 yield point is at least equalled the reflectance is retained in the visible spectrum to provide a permanent visual color change.
Specification