Security Inks Raise Our Level of Protection

Published: October 31, 2003, By Dr. Richard M. Podhajny, Ph.D. Contributing Editor

Dramatic advances in digital photographic and reprographic technology were made during the 1990s.

These advances have had an undesirable side effect in that such technology provides counterfeiters greater capability to create counterfeits. Counterfeiting, estimated to account for some 5% of world trade with record losses increasing each year, affects every part of our lives from currency to clothing to medicine.

Countermeasures are being taken to offset these trends. Perhaps the best example is our US currency, where recent changes include anti-counterfeiting features such as watermarks, color-shifting inks, fine line printing patterns, magnetic information, etc. Credit cards have used holography to make such cards nearly impossible to copy, but counterfeiters simply move to less demanding targets.

Security inks come in various forms and are based on a variety of different technologies. Some of these can be as simple as printing a “clear ink” onto paper, which then creates a “water-marked image,” or as sophisticated as an ink that can be authenticated by its special DNA pattern.

The most obvious security inks are those you can view and discern immediately if they are counterfeit. Common examples are inks that change color as you change the angle of view or become visible under a different light source. These include photochromic and liquid crystal-based inks. Fluorescent and phosphorescent inks requiring UV light have been used in many applications. The new US $20 bill has a photochromic thread that glows green under UV light and essentially is invisible to a photocopier.

Thermochromic inks can be printed on a small area of a substrate and authenticated with a touch of a hand.

Inks can be formulated with magnetic pigments that can be read with magnetic scanner or pigments that will change color when exposed to an IR heater. Some pigments specifically are responsive to IR, and both opaque and “invisible” forms are used.

Other types of security inks depend on chemical reaction. These can be inks that change color when in contact with other chemical ingredients. An example is an ink that can react and change color when exposed to solvent or a special solution. The disadvantage of these inks is that once activated, the reactions typically are not reversible.

Our current concerns with terrorism have put a growing focus on security in printing and packaging applications. Besides the more conventional approaches to security that involve some physical or chemical change, biological tracers offer another approach. Rapid and sophisticated analytical techniques have been developed that can read the DNA of a bio-organism. Such Bio Tags can be incorporated into inks and coatings and can be authenticated rapidly via DNA analysis.

Another security approach depends on conductivity circuits. Conductive inks have found an interesting application in which they act essentially as radio frequency receptors for identification. Conductive inks used in printed circuits provide a printed antenna for radio frequency ID tags and circuits on a variety of packaging substrates. Silicon chips combined with these conductive circuits allow radio frequency transmission that can be picked up by a computer. Such products can monitor storage conditions and transmit them to a computer as well as authenticate the product.

Security concerns have been heightened since 9/11, and all aspects of our daily living have been affected. Packaging for food and medical supplies is a lifeline we need to protect us, not only from counterfeiters but terrorists as well. We expect our currency and mail to be protected, but do we have adequate protection for our food and medical packaging products? It's hard to say what is adequate, but certainly there are many technologies available today to extend that level of protection.