New developments in printing technologies have made it possible to create intaglio structures of enormous richness in fine spatial details. Nowadays relief height of printed intaglio structures can reach up to 50–100 microns thereby creating not only visual, but also strong and significant tactile and haptic sensations (Fig. 1).
Measures to prevent counterfeiting: safety features
Since the introduction of banknotes centuries ago, banknotes were counterfeited. Particularly currencies with wide cross-country distributions are a target. According to “The United States Treasury Bureau of Engraving and Printing” (2005) counterfeited notes worth millions of US Dollars are detected year by year with a trend to increase in countries outside the US (Fig. 2).
Using current high-technology features, numerous security-features are integrated in the banknote design to prevent or to impede counterfeiting. Most widely used features are watermarks, security threads, ultraviolet fibres and ink, special foil elements, hologram patches or stripes, glossy stripes and iridescent stripe/shifting colours.
Measures to prevent counterfeiting: tactility
Up to now, design options for banknotes were largely governed by aesthetical and graphical criterions. Owing to new printing technologies described above, tactile features based on intaglio structures are increasingly employed as a means to recognise authentic banknotes. Reasons for an increasing use of tactility is that safety features are often unknown to the user, and that in many cases technical devices are required to decode them such as ultraviolet ink. The use of haptic features becomes immediately apparent in the following scenario: Imagine a person is receiving a banknote which is visually perfectly counterfeited as in case of high-quality colour prints. However, what is missing is tactility and haptic features. Once a person feels such a note with his fingers, the person will be immediately alarmed. The reason is that tactile/haptic information can override visual information (see Box 1).