It is well known that Diffractive Optically Variable Image Devices (DOVIDs) can be copied, duplicated or simulated by the counterfeiters. Some customers consider that such devices are no longer secure and will not use them to protect their product. To avoid counterfeiting, DOVIDs are being made more complicated with the introduction of a large number of simultaneous images, where recognition by customers is strongly compromised. Future trends appear to favor multiple technologies in one device while allowing the consumer to readily identify and remember the device. One approach calls for a combination of the diffractive foil interference found in DOVIDs with thin film interference to create new security devices called SecureShift ChromaGrams. A second approach calls for a combination of diffractive and thin film interference in the form of pigments combined with magnetic fields during the printing process to create another new security device called a "PrintaGramTM".
Each type of enhanced DOVIDs will be discussed in terms of its optical performance, manufacturability, its counterfeit deterrence, and its application.
Iridescent Optically Variable Image Devices (IOVID) for the document security market are currently produced using thin film or diffractive interference phenomena. Special optical effects by diffractive interference depend on the alignment of a series of grooves with differet frequencies and modulations to produce Diffractive Optically Variable Image Devices (DOVIDs). These devices, more commonly know as holograms, have been exclusively restricted to foil applications. In this work, we are taking into consideration basic concepts of thin film and diffractive light interference theory together with some fundamentals of magnetic behavior of materials to create a new family of diffractive pigments. These pigments not only exhibit thin film and diffractive interference but the grooves can also be aligned along predetermined orientations in a magnetic field. This property of groove alignability opens the door to the concept of printable holograms. Different groove alignable diffractive pigments have been produced. The influence of the particle size, loading, and groove frequency has been studied. The microstructure of the groove orientable flakes has been characterized by optical and electron micrscopy, and the optical effects by goniospectrophotometry. Finally, simple DOVIDs have been produced by silkscreen printing to demonstrate the feasibility of the concept.
OVP security pigment, the active ingredient in OVI security ink, is an assembly of high performance microscopic filters. The market acceptance of these filters has led them to become perhaps the most widely distributed interference devices on the planet. Recently, interference devices have been developed that provide the security industry with features beyond proven overt protection. New products are being launched that unite the attributes of optical interference with those of other technologies. One approach integrates thin film interference and diffractive interference to create a host of new security devices. The combined effects are complex and often surprising. The science behind the fusion is explored and the effects demonstrated. Interference pigment technology has also been combined with the science of magnetics to create a new line of OVP security pigments. To facilitate the practical use of such pigments, novel application technology has been developed which allows for the creation of new overt effects. This paper examines pigment designs and describes the physics behind the advanced application technology.
The science of layering security features has long been demonstrated effective in deterring counterfeiting. Now it is possible to provide multiple layers of security within the same device through the integration of proven technologies.
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