We believe a layered approach leads to the most robust document security possible. A layered approach should use a variety of features, including overt and covert ones, as best practices.
One feature gaining traction in the document security sphere is infrared (IR) taggants. Whereas advanced UV pigments fluoresce when exposed to specific wavelengths of light, IR taggants appear invisible to the naked eye until they are exposed to the correct wavelength of infrared light.
Angstrom Technologies, Inc. has been producing advanced IR taggants for 20 years. Read our complete guide to learn more about how infrared taggants can improve your document security measures.
Table of Contents
What Are Infrared Taggants?
Infrared (IR) taggants are substances invisible to the naked eye under visible light conditions. The advanced chemistries of IR taggants make them nearly impossible to replicate using ordinary means, making them perfect for document security purposes.
For example, a holographic feature has lettering on it that appears black to the naked eye. However, when exposed to a specific wavelength of infrared light, it will emit a signature optical response, such as a color.
Another example is the paper upon which passports are printed. Some pages may have features invisible to the naked eye, but then intricate Pantone color patterns could appear when exposed to infrared light.
How Do IR Taggants Work?
Advanced infrared taggants can work in a very specific sequence as a forensic security feature on documents, meaning they can only be seen using advanced technology. For example, IR taggants can exist as nanoparticles or microscopic dots printed on paper that only become visible in the presence of a narrow infrared wavelength. IR taggants might also be a secret security feature, indicating only a very few individuals are aware of this type of security feature.
Mechanism of Detection
IR taggants work when exposed to the correct wavelength of infrared radiation.
The mechanism by which IR taggants respond is not the same as when viewing heat sources through a forward-looking infrared (FLIR) camera. That’s because IR taggants are not designed to become visible when put under a heat source, like the afternoon sunlight.
One method of detecting IR taggants can come from anti-Stokes lines or up-converters. These work when a wavelength of IR light, at a lower energy than visible light, interacts with an IR taggant. The taggant then becomes visible because it gives off a higher energy signature due to absorbing the IR radiation. When using up-converters as an IR taggant, they can be viewed with an IR laser or custom detector.
Up-converters take higher wavelength/lower energy excitation and convert it to lower wavelength/higher energy emission. Down-converting materials to the opposite.
Detection devices can vary. The excitation sources within the device are usually specific to the IR taggant and a narrow wavelength. Many detection devices utilize multiple excitation sources and are programmed to look for specific emissions.
The sweet spot for most of these materials is in the “near IR” range, between 700 nm to 1,000 nm. However, excitation and emission ranges can be in the visible range (400 nm to 700 nm) if you need IR taggants to be visible to the naked eye when exposed to the right wavelengths of IR radiation at close range.
Chemical Composition of IR Taggants
The chemical composition of IR taggants varies depending on what effect you want to achieve. Advanced IR taggants can be fine-tuned for specific wavelengths of infrared reflectance or emission based on your requirements.
In general, IR taggants are inorganic materials (similar to ceramics) and, therefore do not degrade over time and will last the life of the product. The taggants are micron-sized particles and, therefore can be added into most manufacturing or printing processes without impacting the properties.
These up-converters can absorb lower-energy photons (infrared light) and emit higher-energy photons.
Chemists can produce advanced IR taggants with extremely good thermal stability that only become visible when exposed to a very narrow range of infrared radiation. Some covert forensic security elements on documents can have multiple rare-earth metals in the same plastic or ink to achieve specific effects.
Types of IR Taggants
There are five main types of IR taggants, with each of them working in different ways:
- Absorbing UV light and/or IR light and emitting IR light
- Absorbing visible light and emitting IR light
- Absorbing IR light and emitting IR light region at a different wavelength
- Absorbing IR light and emitting it in the visible region (anti-Stokes lines or up-converters)
- Absorbing IR light and not emitting any light at all.
Applications of IR Taggants in Document Security
Advanced IR taggants are typically found in the highest levels of document security for currency, passports, and similar applications when robust document security is required.
IR taggants are utilized by integrating these substances into plastics, fabrics, or specialized inks, meaning they can work on cotton-based currency and polymer banknotes. Thermal stability and very good lifespans are also endemic to advanced IR taggants designed to withstand the life of the document to which they are attached.
Some currencies contain features where visible print completely disappears when viewed under certain wavelengths of near IR radiation. Another application is to throw off counterfeiters using some known covert features that contain IR taggants. For example, one covert feature might be a security ribbon that changes when UV light is applied to it. Thinking that the ribbon is only for UV light, a counterfeiter might not realize there is an IR taggant embedded in the cotton cloth next to the security ribbon as another layer of security.
Advantages of Using Advanced IR Taggants
There are several advantages of advanced IR taggants as a forensic security feature on documents:
- Difficult to find and identify on the document unless someone is trained to look for it, making IR taggants very hard to counterfeit.
- Made of inert inorganic materials that do not react to surrounding media.
- Very good thermal stability.
- Very good chemical stability.
- Inorganic metals that comprise IR taggants have much longer durability and lifespans compared to UV taggants, which are typically made of organic chemicals.
- The sophistication of the equipment necessary to accurately identify IR taggants must be so that it is accurately programmed for the right frequency.
- Very hard to replicate using ordinary means due to the high sophistication of the equipment necessary to reverse engineer these inorganic materials.
- Manufacturers, like Angstrom Technologies, Inc., of these materials must control their distribution through the right chain-of-custody procedures in order for advanced IR taggants to be effective.
There is one main limitation to advanced IR taggants, but it’s actually a benefit because of how these substances operate. You need specific detectors to identify IR taggants at precise wavelengths. They also operate at a very close range, within a few inches. So, if you have a detector that operates at 980nm, you might need to have the device within 6 inches of the document to verify an IR security feature.
Integration of Advanced IR Taggants With Layered Security
IR taggants are very customizable when using a layered security approach for documents.
Detector Sophistication
The sophistication of the detector provides a level of customizability through multiple excitation sources and/or programmability. For example, you can program the detector for one wavelength to show a particular facet of the IR taggant and then switch wavelengths to see a different response in the same feature.
Multi-Layering With UV Taggants
Blending IR Taggants with UV Taggants can also yield similar results. You might have a detector that has both UV and IR wavelengths that would switch between wavelengths, illuminating one feature and then the next in succession. The more layers and diversification of advanced security features, the less likelihood of counterfeiting.
Talk to Angstrom Technologies, Inc., About Advanced Layered Document Security
Angstrom Technologies, Inc. has been innovating advanced IR taggants for 20 years. Contact us or call 859-282-0020 to start the conversation about your document security requirements.
