For the last few decades, the security printing industry has undergone significant changes involving technological complexity. As a result, security inks have developed in aspects which are different from those of conventional printing inks.
FUNCTIONS OF INK-BASED SECURITY FEATURES
Security inks are formulated in relation to their specific security functions aiming at different categories of target users and varied authentication means:
- Public features for all users – authentication by eyesight and touch;
- Embedded features for shopkeepers and cash handling professionals – detection by aided devices;
- Machine-readable features – detection by sensors, machines and automated systems.
Security inks, especially inks for banknote printing, need to be highly resistant for the very reason that the security documents/banknotes are exposed to frequent handling. Like all products destined for public use, banknote inks are subject to Health, Safety and Environmental legislations to ensure the handling of the inks as well as the prints are safe and without negative impact on the environment.
PRINCIPAL APPLICATIONS OF SECURITY INKS
Security inks are dedicated exclusively to security applications such as banknotes, official identity documents (passports, identity cards, birth certificates, etc.), postage stamps, tax banderoles, security labels and product markings.
INKS AND PRINTING PROCESSES
The ideal ink is one which can transfer, print and dry efficiently in different working environments, but in reality, the composition of each security ink can greatly vary depending on a number of printing factors. The pigment size, rheology, viscosity and drying chemistry are formulated to meet the industrial printing performance of different printing processes, machine types, and a combination of substrate variations.
The printing processes involved in the production of banknotes and security documents are: intaglio, silkscreen, offset, flexography, gravure, letterpress (numbering) and inkjet printing.
Intaglio is among the most sophisticated printing processes, and is reserved for security printing. The fine lines and relief of the resulting thick ink layers give banknotes and security documents the visual strength and unmistakeable tactility that allow for intuitive recognition within a fraction of a second.