Inks and Taggants
Printing of invisible messages requires use of special invisible inks. The word “invisible” in this context implies invisibility of a printed insignia to an unaided human eye. The value of invisible printing is in that the insignia becomes “visible” to a specially designed apparatus like a viewer or barcode reader.
Various photonic properties of materials have been exploited to make invisible inks. Human eye has ability to see in the limited range of electromagnetic spectrum of wavelengths stretching from about 400 nm to about 650 nm. V.L. Engineering, Inc., uses inks and powders to print invisible images of barcodes, human readable characters, icons, portraits, signatures and simple marks. These inks and powders reveal themselves through selective absorbance, fluorescence or other effects they do on the impinging light. Typically, invisible inks operate in UV and IR. Fluorescing materials proved to be very effective even in weak concentrations due to the spectral separation between the absorption and emission energies. The invisible inks can be grouped into a number of categories. There are organic dye based inks and inorganic powders. There are down-converters (fluorophores, making Stock shift) and up-converters (fluorophores making non-Stock shift). There are liquid inks suitable for ink-jet printing and there are paste-like inks for flexography printing. We have also developed a thermal transfer ribbon with an invisible pigment for printing by the thermal transfer printers.
Inorganic materials possess certain beneficial properties important in identification and authentication applications as taggants. The main advantages of these materials are:
- chemical stability
- excellent light fastness
- explicit uniqueness of the photochemical signature
V.L. Engineering, Inc., has developed exceptional materials for use as invisible inks and taggants.
There is only one best suitable ink or media for any given application. Many considerations shall be taken into account during the process of ink selection. Printing method, printing speed, substrate material, usage environment, cost, physical dimensions, uniqueness, light fastness, chemical stability, projected life time, availability of compatible detectors, viewers or barcode readers … these are just a few items to think of.
Here is a list of main categories of the inks and taggants that we deal with:
- Ω-taggant (IR to IR proprietary inorganic compound)
- UV to UV inorganic taggant
- Up-converter taggants (IR to VIS) Green, Red, Blue, Yellow, Aquamarine versions available with various time constants and shades of hue
- Inkjettable inks operating in IR
- Inkjettable inks operating in UV
You are welcome to contact us for assistance.