Methods for fabrication of polymer-based optically variable devices

摘要

Polymer-based optically-variable devices (OVDs) for security applications and methods for producing the same. The uniformity of thickness of the structure of such devices is optimized by controlling previously neglected process parameters such as the temperature distribution of the deposition nozzle, the substrate and the deposition drum, their emissivities, the micro-roughness of the substrate, and the rate of monomer re-evaporation. Re-evaporation is minimized by initiating radiation-curing within two seconds of monomer deposition. A method includes equipment reducing all sources of emissivity non-homogeneities, such as surface blemishes in the surface areas exposed to the substrate to preferentially fabricate substrates with haziness less than 5% and gloss greater than 90%. Controlling, a maximum variation of thickness of the transmissive layer of an OVD ensures that no appreciable color-shift variation is visible to the naked eye.

主权项

1. A method for producing an optically variable device (OVD), the method comprising:
adhering an optically-transmissive polymeric layer with a first layer of partially reflective, partially absorptive, and partially transmissive material; and adhering a second layer of partially reflective, partially absorptive, and partially transmissive material to said optically-transmissive polymeric layer to form a multi-layer etalon structure in which, across an entire area of the OVD, said optically-transmissive polymeric layer is an etalon spacer layer between said first and second layers, wherein said optically-transmissive polymeric layer is formed in vacuum by depositing a monomeric layer and radiation curing said monomeric layer within 2 seconds after its deposition and under conditions that result in (i) a maximum variation in thickness thereof not exceeding 5 percent across the entire surface area of the OVD and (ii) minimization of differential re-evaporation of said monomeric layer.