Today, holographic technology remains very much to the fore as part of an array of overt features which make it quick and easy for people to recognise whether or not a banknote is bona fide.
However, new substrate technology – most particularly the introduction of transparent ‘windows’ – is being incorporated on banknotes to provide new levels of anti-counterfeiting complexity.
The commemorative 1,000 Tenge note produced by Papierfabrik Louisenthal for Kazakhstan, and launched earlier this year, takes optical sophistication to a new level. Not only does it feature a hologram showing typical rainbow colours, but also a small microlenticular patch viewed by transmission. The system is called Varifeye, and it combines the best features of paper and polymer.
Previously, a deckle-edge window was created in the paper substrate during the process of cylinder-mould web formation as the stock fibers collect against the deckle, leading to the characteristic feather look.
Change in technological emphasis
Latterly, the window has been cut into the paper after laminating to a polymeric layer. Then a clear stripe of film is laminated over it, and runs from top to bottom of the note. The clear stripe contains the microlenticular image of a camel interchanging with the letter ‘K’ when tilted.
This feature can be viewed by transmission through the window. There’s also a demetallised holographic image of the Astana Baiterek monument above the text ‘Organisation for Security and Co-operation in Europe’, interchanging with the date 2010 which are viewed by reflection where it falls over the paper.
(This technology was first used on the Bulgarian lev banknotes in 2005, which then became the world’s first paper notes with a see-through window).
For polymeric substrates, the Bank of Australia has developed its non-diffractive switching image (NSI). This appears like a dynamic watermark in the clear window of a polymer-based note. Being non-diffractive, the images are seen in varying shades of grey rather than rainbow colours, and switching of the image elements occurs by rotation rather than tilting.
Mexico: embracing the new age
Mexico has also embraced new technology. The country’s 100 peso note has an ingenious feature which outwardly looks holographic, but is in fact transparent optically variable inks (they’re usually opaque) printed on the clear window of a polymer note.
The viewer can look at the feature either by transmission or reflection. The inks change colour in both modes, but the colours seen by transmission are the complementary colours of those seen by reflection.
The latest innovation in holographic technology which makes use of traditional (though modified) embossing technology is the Asterium feature from Toppan printing in Japan.
Viewed in normal direct light this feature appears black, but when inclined at an extreme angle, the rainbow colours of an embossed hologram appear.
The important feature here is the optical black, which gives a new aesthetic to documents and only reveals the colourful security feature as and when required.
Wafer thin security photopolymer
Another innovator, Kurz, has developed a revolutionary wafer thin security photopolymer which can record a volume holographic image for banknotes produced for Banque de Suisse.
Kurz’s success has been to develop the material thin enough for use on a banknote, especially given that the reason this is called a ‘volume’ hologram is that the interference fringes are recorded within the depth of the photo-sensitive material.
Similar developments are taking place in Japan, where Dai Nippon Printing is leading the way.
OVD Kinegram, a division of Leonhard Kurz, continues to push the boundaries with its Kinegram reColor. This has been developed for use as a laminate in conjunction with a window or aperture in the banknote substrate, and provides fundamentally different – not to say unexpected – effects depending on whether the note is viewed from the front or reverse.
On the front the viewer sees a normal metallised reflective, diffractive image, while the reverse view shows a patterned coloured foil also displaying the diffractive features. The trick is performed using different coloured resist lacquers in the demetallisation process.
Transmissive by their very nature
More remarkable still is Kinegram reView, which appears the same, metallic colour on both sides of the image although the images seen on the two faces can be different and unrelated to each other.
One way or another, it seems that the window technology now becoming available to printers of banknotes is here to stay. Formerly, the opaque nature of security printing paper only allowed a watermark to be seen by transmission but most holograms are, by nature, transmissive and rendered reflective by applying a metal coating.
Once the opportunity is presented to allow them to be seen by transmission, as in a window, the opportunities for an optical ‘tour de force’ are increased. This renders the note more visually attractive to inspectors and consumers, and more difficult to simulate by counterfeiters.
However, here’s a cautionary word or two. Any trend towards simplification must be seen as a move in the right direction and run hand in hand with artists and graphic designers’ abilities to make good use of the media or of the public’s ability to appreciate and evaluate the security benefits offered by the latest technology. After all, it’s not as though holograms represent the only security feature on a banknote.
They’re often one of many. For example, the 1000 Tenge note for Kazakhstan has at least 16 features including one to help the blind or partially sighted.
Why was the hologram originally brought into play?
On that basis, it isn’t necessary to fill the hologram with every conceivable feature, but instead better to remember why the hologram was originally introduced: it provided a feature that could not be photocopied.
Photopolymers provide this, so there’s no reason to suppose that holographic technology will not continue to be an integral security feature on future generations of banknotes.
Dr Glenn Wood is with the International Hologram Manufacturers Association (IHMA)
*The IHMA is made up of 90 of the world’s leading hologram companies. IHMA members are the leading producers and converters of holograms for banknote security, anti-counterfeiting, brand protection, packaging, graphics and other commercial applications around the world.
HMA member companies actively co-operate to maintain the highest professional, security and quality standards.
