Variable data printing (VDP), combined with precision registration of multiple ink layers, empowers a layered deterrent using variable print strategies on each of the multiple layers. This shifts the need for specialized printing techniques to the need to accommodate variable ink approaches. Such layered deterrents can incorporate infrared/ultraviolet fluorescent inks, infrared opaque and transparent black inks, inks containing taggants, magnetic ink, and inks with differential adhesive properties to enable sandwich printing. Overt features printed as part of the same layered deterrent provide excellent payload density in a small printed area. In this paper, the statistical and hardware processes involved in qualifying two layers of such a deterrent for their deployment in product (e.g., document and package) security are presented. The first is a multicolored tiling feature that provides overt security protection. Its color payload is authenticated automatically with a variety of handheld, desktop, and production scanners. The second security feature is covert and involves the underprinting or overprinting of infrared information with the covert tiles. Additional layers using existing security deterrents are also described, affording the user information densities as high as 560 bits/cm2 (70 bytes/cm2).
Steven Simske, Jason Aronoff, "Qualification of a Layered Security Print Deterrent" in Journal of Imaging Science and Technology, 2007, pp 86 - 95, https://doi.org/10.2352/J.ImagingSci.Technol.(2007)51:1(86)