STRUCTURED SURFACES THAT EXHIBIT COLOR BY ROTATION

摘要

An optically variable device is disclosed having a substrate with an array of pyramidal structures formed upon it or within it. The structures are preferably formed by printing pyramids with an optically variable color-shifting ink using an Intaglio-like printing process. Alternatively the structure can be formed by embossing a layer of ink with positive pyramids so as to yield an array of positive embossed pyramids. Each of the structures form a pyramidal-like having at least three slanted faces and wherein one or more than one color is seen when viewing the pyramids vary as substrate is rotated at least 30 degrees about an axis orthogonal to the substrate. In order to see a color shift the device is rotated around the surface normal of the substrate, while keeping the angle of incidence to the light source the same, and keeping the viewing angle the same. Various forms of pyramids may be used, however pyramids with planar faces are most suitable.