In this article, Dr. Mark Deakes, chairman of the International Optical Technologies Association (formerly the International Hologram Manufacturers Association), considers the latest developments in banknote optical security.
Optical technologies are at the forefront of a suite of security features on today’s banknotes, constantly evolving to meet ever-changing threats from counterfeiters and organised crime. Indeed, it’s testimony to their effectiveness that in 2024, less than 0.0019% of banknotes (one in 52,600) were counterfeit in the UK, according to the Bank of England (BOE). Approximately 91,000 counterfeit banknotes with a nominal face value of £1.9 million were taken out of circulation. At any one time, in the UK there is around 4.6 billion genuine banknotes in circulation, with a notional face value of £82 billion. In the US, currency in circulation amounted to US$2.10 trillion as of 2021 (source: Federal Reserve) while the Eurozone has about 30 billion banknotes in circulation, totaling about €1.578 billion, according to the European Central Bank. Banknote numbers are dynamic, with new notes issued to replace worn or damaged ones and to meet changes in demand.
However, while the BOE says counterfeiting has reduced since 2019 as a result of a combination of factors such as the introduction of more robust polymer banknotes, the withdrawal of the older paper designs as well as successful law enforcement strategies, fake banknotes still remain a problem for central banks who must ensure their currencies cannot be duplicated and stay ahead in the war on counterfeiting – and optical security innovation has a key role to play here.
Advanced micro-optics, micro-mirrors, colour shifting, print and diffractive technologies including holographic technologies increasingly feature in central banks’ anti-counterfeit strategies; adapting as the demands placed on security and authentication requirements grow. These technologies create visually dynamic and engaging features that are difficult to replicate, ensuring public trust in banknotes.
The success of technologies such as holography on both polymer and paper banknotes has been down to its role as a level one security feature that’s instantly recognisable. It makes it easy for not only the general public but also cashiers and those operating cash tills in stores, to recognise whether or not a banknote is real or fake. But today holography features within a broader spectrum of optical security devices that meet ever more intricate and nuanced requirements from central government banks and those with responsibility for currency policing.
Global adoption
There’s no doubt the adoption of optically variable security features on banknotes is vital in the global anti-counterfeiting fight. So how are these features driving banknote development? The following examples are all notes that have been issued over the last year.
The Bermuda Monetary Authority’s new 2 and 5 Bermudian dollars (B$), issued in 2024 on SAFEGUARD polymer substrate and designed and printed by the world’s largest commercial currency printer and papermaker De La Rue, incorporate a number of innovative security features including fully and partially transparent half windows, depicting a cloudy sky and an underwater scene viewable from both sides of the notes. Surrounding these windows are additional features integrated into the iridescent ink design of waves, multiple fish, and a sun that come to light when the notes are tilted. In addition, the notes feature a specialised silver ink known for producing highly reflective and visually captivating images in the form of a tuna fish that appears under UV light. The notes also have raised dots that act as an aid to help the visually impaired.
© De La Rue
Bangko Sentral ng Pilipinas (BSP) has now rolled out additional banknotes of the First Philippine Polymer (FPP) banknote series, over two years after the release of the 1,000 piso (PHP) polymer as a trial in April 2022.
Printed by Note Printing Australia, each note includes CCL Secure’s IRISWITCH™ feature, which appears transparent when viewed straight on, but reveals a pearlescent colour when the note is tilted. The ‘switch’ colour has been designed to match the primary colour of a given denomination, which is gold for the PHP 500, lilac for the PHP 100 and red for the PHP 50.
The vertical clear window contains multiple security features, including dynamic metallic wavy lines, the country’s seal, mirrored denomination, BSP logo and (for the PHP 500) a 3D rainbow effect. In common with the PHP 1,000, the PHP 500 also includes a Plasmogram™ Reverso stripe from SURYS, while the two lower denominations feature a shadow thread.
The National Bank of Kazakhstan is in the process of rolling out its new Saka-style series, which draws inspiration from elements of the ancient Saka culture, a key precursor to traditional Kazakh ornamentation.
Advanced features
Advanced security features on the new series include Crane Currency’s RAPID® Vision 5mm wide micro-optics windowed thread, SICPA’s SPARK Flow® Dimension magnetically-orientated colour shifting ink, and either Louisenthal’s Varifeye® ColourChange Patch (on the 1,000 tenge), which shimmers gold in direct light with the mountain top outlining appearing blue in translucent light, or its combinational micro-mirrors and colour shifting feature RollingStar Patch on the other denominations.
Elsewhere, the introduction of the Central Bank of Curacao and Sint Maarten’s new Caribbean guilder is being supported by a public education and awareness programme to promote the currency’s new optical security features and the benefits. Designed and produced by Crane Currency, these notes include a watermark with an electrotype stripe, eye-catching security inks in the shapes of shells which change from blue to green, MOTION SURFACE® micro-optic stripes on the front, and 3 mm-wide micro-optic threads on the reverse.
© Crane Currency
In central America, the 1 Quetzal commemorative note – interestingly, printed on paper rather than its polymer predecessor – issued by the Banco de Guatemala (Banguat) features an octagonal colour change patch, showing the iconic arch of Santa Catalina in Antigua. This is gold in reflected light, with a window on the reverse that appears in transparent blue when the note is held up to the light. When the note is rotated, a change between the years 1924 and 2004 is optically evident.
© Banco de Guatemala
There have been a number of new issues, even series, in Africa over the past year. They include Zambia, which introduced a new series of both banknotes and coins earlier this year. The redesigned banknotes feature enhanced security features to combat counterfeiting, with two higher-value denominations (500 and 200 Kwacha) introduced to promote more efficient transactions. Additionally, the redefined note-coin boundary introduces the new K5 and K2 coins, while the lower-value notes (K10 and K20) are made with durable substrates to ensure longevity in circulation.
The new security features include a RAPID® security thread from Crane Currency on the K10 and K20, RollingStar® (RS) i+ thread from Louisenthal and SICPA’s SPARK® Flow Prime on the K50 and K100, and Louisenthal’s Galaxy® thread and SPARK Flow Prime on the K200 and K500.
The two new coins also have an optically variable feature in the form of a latent image that changes from the letters BOZ to the denomination numeral (2 or 5) when the coin is tilted.
Even more recently, the Bank of Namibia has just launched its new series, under the theme ‘Our Currency, Our Heritage, Our Pride – Meet the Next Generation of the Namibia Dollar’. Designed and printed by De La Rue, the security features of the new Namibian dollars include IGNITE® and PUREIMAGE™ security threads, as well as the Enhanced GEMINI® UV print feature.
This follows the issue, last year, of a new N$60 commemorative polymer banknote, also designed by De La Rue and printed on a polymer substrate, to celebrate the life and legacy of the late President HE Dr. Hage G Geingob. The banknote features two clear windows, with the main window depicting a complex portrait of Dr. Geingob. Security features include ARGENTUM™, a highly reflective mirror-like ink, and ILLUMINATE™, which adds texture and intrigue around the window, along with Enhanced GEMINI™ that is only visible under ultraviolet light for added security.
Despite the use of cash for point-of-sale (POS) payments declining globally for over a decade, cash in the form of banknotes remains an important method for POS transactions in many countries, through preference or by necessity for the estimated 1.7 billion people who do not have access to banking facilities. Banknotes retain an advantage over other forms of payment in that they are convenient, reliable and anonymous, while periods of global uncertainty have invariably seen an increased demand for cash as people look to protect against unforeseen emergencies.
The optical technologies available to printers of banknotes will therefore see the sector continue to forge ahead. Innovation, brand recognition and law enforcement will continue to drive demand, delivering by turns opportunities for ground-breaking applications as the global currency-in-circulation, which currently stands at an estimated $40 trillion, continues to grow year-on-year.
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The International Optical Technologies Association includes the world's leading holography, microlens arrays, micromirrors, plasmonics, nanogratings, colour change, caustics, polarisation, photonic crystals, special print-generated effects. These technologies are used in banknote security, anti-counterfeiting, graphics and other commercial applications. Member companies actively cooperate to maintain the highest professional, security and quality standards.
