Optical security in ink: an industry standard that continues to evolve

摘要

The level of security against counterfeiting and forgery that is provided by optically variable ink has led to this technology becoming the industry reference for the protection of high security documents. For this ink to be secure, it must obviously differentiate itself from inks used for purely decorative purposes. Hence, the inks used for protecting high security documents have intense, saturated colors that lie within a specified and restricted color range, a very wide color travel and can be identified with the naked eye or specific optical filters. These characteristics are achieved with sophisticated technologies that result in pronounced optical interference effects. For instance, vacuum deposition techniques are used to produce interference pigment flakes that create the distinctive colors and wide color travel. Another technology, based on liquid crystal pigments, displays rare and specific characteristics under a polarizing filter. Because the inks are ultimately applied to a substrate by a security printer, their chemistry and formulation provide the foundation for the security feature. Building on the proven basis of intense, saturated colors and wide color travel, optically variable inks offer the flexibility to combine the creativity of graphic artists with the know-how of security printers and breakthroughs in printing technology to create ever more secure features that can easily and readily be authenticated by the public.