The counterfeiting of banknotes and other financial transaction documents as well as visas, passports, ID cards, other official Government security papers and the counterfeiting of software, pharmaceuticals and brand name products is now becoming one of the world's fastest growing areas of criminal activity. With the advent of colour photocopiers and digital scanning devices the traditional security printer's skill and craftsmanship is no longer sufficient to protect the integrity of high value documents (Fagan 1990). According to the International Chamber of Commerce Counterfeiting Intelligence Bureau over 5% of world trade consists of counterfeit product. The cost of this illegal activity amounts to over US$350 billion annually and is growing. To counteract this rapidly evolving threat security printers and central bank issuing authorities have turned to new technology in the form of the diffractive Optically Variable Device (OVD) (Renesse 1994). Mass produced by embossing into hot stamping foil, these diffractive surface relief microstructures have proven to be a highly effective solution to the counterfeiting problem. The key security feature underpinning all optically variable devices is, as the name implies, the variability of the image with changing angle of view or changing angle of illumination by a light source. This image variability can even take the form of a switch between one artwork pattern to a totally different piece of artwork; from the image of a face to the number 50, for example. Because of this image change effect these devices cannot be copied by the usual photographic, computer scanning or printing techniques, and therein lies their attractiveness to security printers who have seen their traditional anti-counterfeiting technologies of intaglio print and watermarking undermined by the counterfeiters using the new computer scanning and copying technologies developed since the 1980's. In developing this discussion the intention is to first describe the origins of OVD technology as applied to financial transaction documents and then explore the history and influence of two particular high security developments in the fabrication of optically variable device (OVD) anti-counterfeiting technology for high security document applications. The focus will be on those features of two technologically competitive technologies, which are perceived by the security printing industry to be significant in reducing the counterfeiting threat to official documents. By comparing the security attributes of these competitive OVD technologies and their influence on different sections of the security printing industry from the early 1970's to the late 1990's, we will be able to draw some general conclusions about the suitability and uniqueness of particular OVD features and their suitability for future extension and development. The security value of the different OVD effects will be classified here according to the degree of difficulty in originating the device, the recognisability and uniqueness of their corresponding optical effects and finally by the degree of availability of these effects from alternative and less secure origination sources. In subsequent sections we will consider in more detail particular applications of the electron beam lithography origination process; the origination process regarded by the security printing industry as providing the most secure and controlled set of optical effects. By control here we mean the ability of the industry and its component suppliers to restrict the availability of these high security effects to high security printing industry applications only and in so doing prevent unscrupulous operators from gaining access to the technology. Finally we will consider the limitations of this current high-end origination process and its corresponding foil based replication process and consider a new paradigm for addressing these limitations in a way that provides a future path for extended developments of the underlying core technology.
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