7 April 2000 Quarter-wave polymeric interference mirror films
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Abstract
Quarter-wave interference films have seen numerous uses in the field of optical security, due to the strength of reflection, ability to select numerous colors, and especially for their conspicuous color shift. Decorative nanolayer quarter-wave polymeric material of greater than 100 layers have been known for twenty years, but did not have utility in the security market, because of their weak iridescent appearance. Through the use of polymers of higher refractive index difference, 3M has achieved strong reflectors with better band edge control. Extremely efficient broadband mirrors have been made for commercial use. By choosing the reflection to be in the near IR, a unique security laminate film is achieved. It is very transparent at normal incidence, and changes to a brilliant cyan at shallow viewing angles. This material is easily noticed by the typical observer, and is also machine- readable. The polymeric quarter wave mirror films may be fine-line embossed, permanently thinning the layers in that area, and further enhancing their appearance.
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James M. Jonza, James M. Jonza, } "Quarter-wave polymeric interference mirror films", Proc. SPIE 3973, Optical Security and Counterfeit Deterrence Techniques III, (7 April 2000); doi: 10.1117/12.382195; https://doi.org/10.1117/12.382195
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