Novel optically variable color devices

The recently introduced ROLICURE TM PEARL is a novel optically variable device (OVD) ideally suited for security applications. It may hold high resolution images, (micro-) text or graphical designs. Upon tilt or rotation high contrast positive/negative flips are observed. The optical effect of these devices is based on a proprietary technology of Rolic and includes light scattering at patterned anisotropic microstructures. Since these microstructures are non-periodic no rainbow colors are generated, making these devices easy to authenticate and clearly distinguishable from standard holograms. In this paper, we describe how to modify the optical appearance of our - a priori - colorless ROLICURE TM PEARL feature by addition of distinct color-shift thus further increasing its level of protection and meeting design requirements. This is accomplished by optical interference at additional dielectric and metallic layers in combination with the ROLICURE TM PEARL scattering microstructure. Various configurations are conceivable and have been realised in our labs. Depending on the nature of its dielectric layers red, green and blue colors are obtained and respective photospectra will be presented. While the optical appearance remains attractively bright, excellent color saturation is achievable. Independently from the color-shift which originates from changes of the optical path length under various viewing angles, the contrast inversion of the image is still present and is visualized when the device is tilted or rotated. In general, images of these security devices are easily recognizable within wide viewing angles without need of a point light source.