A paradigm shift in bank note security; security features in polymer bank notes

 

 

By Ronald G. Gration, Technical Manager, Securency

Introduction

 

Counterfeiting is a serious problem worldwide, and besides banknotes, extends to a variety of products such as designer clothes, watches, compact discs and computer products. Almost anything that can be copied will be, so long as someone sees a commercial advantage in it for themself. There has always been counterfeiting and, in all likelihood, always will be.

 

The counterfeiting of banknotes is more serious because it is a national product and affects each one of us in some way. The threat of counterfeiting is increasing, mainly because of the advancements in reprographic technologies that are currently available, or are in the development stage. Casual crooks are passing poor quality fake notes produced by inkjet printers. The professionals can draw on sophisticated technologies such as colour photocopying and graphic scanning that makes it simpler to produce plausible notes. This type of counterfeiting, though small, is growing fast and certainly questions the value of print as a security feature on banknotes.

 

A paradigm shift is needed to stay ahead of the counterfeiter. The apparent decreasing value of print as a security feature will increase the importance of substrate and add-on features such as optically variable devices. Polymer substrate offers considerable advantages in these areas. A new technology that is just starting its revolutionary life has the potential to present a formidable array of challenges to the counterfeiter.

 

Security features in banknotes

 

Security is a prime requirement of all banknotes. As an anonymous medium of exchange of a valuable negotiable document, it must inherently display exceptional security to gain the confidence and trust of the general public. A wide range of security features available for banknotes are classified into the two main categories: Overt and Covert security features.

 

Most importantly, banknotes must possess easily recognisable overt security features for the person in the street. These features must be difficult to counterfeit or simulate, and should be easily recognisable as genuine in the short time available during a normal transaction, ideally without the need for an additional device. Covert security features, generally protected by secrecy and only detectable with the aid of special devices, are often made use of by automatic cash handling machines and high volume cash handling personnel. Modern banknotes contain a range of these features, with an even higher-level security feature reserved exclusively for the issuing authority.

 

Accurate authentication requires several effective levels of protection against any potential counterfeiter. These barriers may be visual, capable of mechanical verification or sight approval. The range of protection required for the security of banknotes is so large, and the threats so varied, that a range of security devices are needed to counter these pressures. Threats of counterfeiting take two forms. The first, and more important, is that of imitation where direct or indirect copies are made to deceive as to the genuineness of the product. The other is where alteration is made to increase the value of the product.

 

Each country has its own perception of the value of each of the security features available. This could depend on the culture of the country, cash handling habits of the people or counterfeiting techniques usually resorted to in that particular country.

 

Security features & their use in guardian substrate

 

Security features are incorporated in five distinct areas of a banknote:

 

Substrate. Design. Printing. Applied optically variable devices. Machine-readable features.

 

The effectiveness of the security features in each of these areas is enhanced by the use of Guardian polymer substrate. Guardian substrate is produced from a unique clear polymer film that is opacified on both sides by specially developed coatings. The distinctive feature of Guardian substrate is the presence of at least one clear window, a feature that is created during the production of the substrate.

 

Security in substrate

 

Traditional security features in the substrate, such as the watermark and security thread take a different form with Guardian substrate. A 'shadow image' incorporated in the substrate depicts a familiar design when viewed in transmission. A multi-tonal portrait would be more effective because, with Guardian substrate, sharper definitions are possible and can be located in the clear window or on another part of the substrate. The advantage is that the full tonal range from clear to opaque can be used to achieve the different effects. The use of multi-tonal portraits is especially important for banknote designs where the multi-tonal portrait is similar to the intaglio-printed portrait. An added benefit is that the shadow image does not deteriorate as a result of soiling, crumpling or high humidity.

 

Security threads can be incorporated in Guardian substrate, and can be of the conventional type, such as magnetic, fluorescent, phosphorescent, microprinted, clear text, as well as windowed. These security threads can also be made machine-readable. An added benefit with polymer substrate is that the various security threads, besides being straight along the machine direction, can be in a wavy pattern and in any direction. With Guardian substrate, the security thread does not add any significant dimension that could affect the good profile of the substrate.

 

Another feature of Guardian substrate is that it can be made to any colour, and furthermore, the substrate can be a different colour on each side. This is a benefit to the designer who could use the colour of the substrate on each side to complement the design and general colour of the note. A unique feature of Guardian substrate is the transparent or clear window. This feature is readily identifiable and enables the public to quickly ascertain the authenticity of the banknote. It can be of any shape and size, further enhancing the design and aesthetics of the note; in fact, more than one window can be created. This window offers a "window of opportunity" for including a range of printed and applied security features that will increase the security value of the note. A further benefit is that any features applied in the window are visible from both sides of the note.

 

A major advancement in the development of security features for banknotes has been the concept of a self-authenticating banknote. The potential available with polymer substrate is used to its advantage. The transparent window is the focus of these developments by converting the optical properties of the transparent area to a tool for verification. The innovation here is that the tool for verification is carried within the note. The self-authenticating features currently available are:

  • Metameric printed feature that can be checked by the transparent window, which has been converted to an appropriate filter.

  • The SAM feature that can be authenticated by viewing through the required screen created in the transparent window of the banknote.

  • The formation of an identifiable moire pattern that can be created by the use of two windows, each printed with a specific screen pattern.

  • Other similarly exciting self- authentication features are at various stages of development, and will soon be available on Guardian substrate.

Security in design & printing

 

Traditionally, banknotes are designed with the aim of creating a document that is secure, and around this is built the aesthetics. The offset of background print has features such as rainbow printing, see-through registration, screen traps and multi-coloured intricate patterns which are designed to make it difficult to counterfeit, especially by colour photocopy reproduction.

 

Intaglio printing has for decades been the recognised printing method and a 'proud' feature of banknotes. A portrait depicting a three dimensional image is an excellent security feature, as well as being an attractive element of the banknote. Besides this, multi-colour intaglio printing, microprinting, latent images and embossing are common features used as counterfeit deterrents.

 

With Guardian substrate, these conventional security printing and design features are taken to a higher level. Because of the non-fibrous nature of the substrate and evenness of the surface, offset and intaglio prints have excellent resolution of line and sharpness of print. Thus, fine linework in screen traps and microprinting have excellent clarity making reproductions more difficult.

 

The ability of Guardian substrate to accept a relatively permanent emboss is an effective feature that utilises a further element of the intaglio process to enhance banknote security. Unlike conventional rag-based banknotes it is unaffected by humidity. This is achieved by engraved areas of the intaglio printing plate can being left uninked to create an embossed design such as a portrait or a Transitory Image during the intaglio printing process. This is most effective when the uninked design is embossed into the transparent window area, generating an image that is visible in both transmission and reflection.

 

Security in Printing Inks

 

Printing inks also contribute to the security of banknotes. Special security inks such as fluorescent inks, phosphorescent inks, infra-red absorbing and reflecting inks, metameric pairs of inks and optical variable inks are all available to the security printer. Used in appropriate designs these inks can be very effective as banknote security features.

 

All of these special security inks which are normally used on paper substrate can be used on Guardian polymer substrate. Further, because of the flat and even surface of the polymer substrate, the effect of Optical Variable Inks (OVI) is enhanced with Guardian substrate. Another benefit is that the fluorescence resulting from a special type of fluorescent ink can penetrate into the base polymer, thereby creating an indelible specific marking, that can be used for authentication, even if the printing on the banknote is destroyed or deliberately removed.

 

Security in applied features

 

Applied security features, such as optically variable devices, have gained momentum mainly as a deterrent to the escalating use of colour photocopying and computer scanning for counterfeiting banknotes.

 

Guardian polymer substrate enhances the effect, and thereby the security value, of these applied features. The non-fibrous nature of the substrate and the evenness of the surface make it an excellent carrier for these devices. Moreover, an optically variable device applied to the transparent window area can be seen from both sides of a note, with the surrounding transparent area an important security feature in its own right.

 

Security in machine readable features

 

The rapidly increasing requirement to authenticate banknotes by note processing machines and vending machines make machine-readable features a necessity in banknotes. Machine-readable features can be made available in many areas of the banknote - in the substrate, in the printing or as an applied feature.

 

With Guardian polymer substrate there are no restrictions. Machine-readable features, including High Level Authenticating System (HLAS) features for Central Banks, can be readily incorporated in the substrate and are already in use today. In some instances, the substrate requires only very small quantities of the HLAS additive to be effective. As mentioned previously, any printed machine-readable feature that can be incorporated on paper substrate can be similarly printed on Guardian. Guardian substrate has the potential for the inclusion of other third party special machine-readable features. Developments in this field are already well advanced and will be available in the near future.

 

Banknote functionality

 

The durability of banknotes really depends on the length of time that the banknote is functional as a product that can be satisfactorily exchanged, processed and validated. This implies that most of the features of the banknote, especially the machine-readable feature(s), should be intact and effective during its entire circulation life.

 

Banknotes need to work first time and every time, whether being handled manually or by cash handling machines. A banknote that has to be scrutinised for authenticity or has to be tried several times in a vending machine to be successful does not appeal to the general public (or the retailer). People would tend to lose confidence in banknotes and revert to other means of payment. Banknotes need to be attractive and user-friendly. In this regard, substrate and ink suppliers, printers and issuers need to work together to make banknotes as functional as possible. Failure to achieve this would hasten the move to a cashless society where we would all be losers. As one colleague has been heard to say on a number of occasions 'Cash is King'. Well, let us all work together to ensure that this continues to be the case!

 

The future

 

The strategy for Securency is to continue to supply a substrate that is secure, durable, printable and functional.

 

Through a significant R&D program, the aim is to develop and supply innovative and cost effective security features in Guardian polymer substrate itself, and to create the potential for inclusion of other traditional and modern security features during the printing of banknotes.

 

The focus for Securency in the near future is the paradigm shift of security features in banknotes to a new level. This will be accomplished by the introduction of the concept of self-authenticating overt features and readily accessible covert machine-readable features.

 

Self-authenticating features with Guardian polymer substrate enables the general public to be able to verify the authenticity of banknotes instantly and without the aid of an external device. The verifying device to check security would be contained in the note itself, by using to advantage the transparent area in the substrate. Machine-readable features in banknotes would be readily authenticated and accepted at points of sale and note vending machines making use of existing sensors. This will promote the use of banknotes at businesses where authentication with minimum time and effort is of paramount importance.

 

While proven in active circulation, Guardian polymer substrate is in its infancy and the potential for development is unlimited. The current developments are just the tip of the iceberg. We now realise that many of the technological advances related to security can be adapted for polymer substrate. Banknotes on Guardian substrate are able to keep pace with modern technology, and thus become the most secure banknotes in the world.