Water-based combifuge ink with unique tamper-evident features for anti-counterfeiting applications

Abstract

Unique characteristics of pigments in printing inks are essential in achieving multi-level security features in genuine articles to combat counterfeiting. This study reports the synthesis and characterisation of 6-bromo-5-hydroxy-2-(2-hydroxyethyl)-1H-benzo[de]isoquinoline-1,3(2H)-dione (BHENA) as a biocompatible and thermally stable pigment with attractive features for anti-counterfeiting application. A water-based stable ink was formulated using BHENA pigment and printed on security paper using flexography technique. The homogeneous pale-yellow print dried fast, and displayed good rub-resistance as well as light-fastness. The print proofs demonstrated captivating fluorescence responses upon exposure to different solvents and sodium hydroxide, when viewed under 365 nm ultraviolet (UV) light source, which could provide clear evidence for document tampering. Moreover, a remarkable penetrating fluorescence that show through the rear side of the print can be a novel add-on security feature. The combifuge eco-friendly luminescent ink can thus impart robust tamper-evident security features, especially penetrating UV fluorescence even with minimal pigment concentration, in cheques, legal or confidential documents, certificates, merchandise and electronic barcodes to avoid duplication or sale of fake products. Further, the electrical features and surface morphology analysis of the prints advocate the suitability of formulated water-based ink to achieve low-voltage-driven organic thin-film transistors on security documents and banknotes for anti-forgery applications. Furthermore, an ultra-high frequency organic- Radio frequency identification antenna resonating at 1.03 GHz has been designed and simulated as yet another anti-counterfeiting solution. The antenna has the advantage of compact size, better impedance matching and suitable radiation characteristics, thereby making it as a very competitive candidate for appropriate applications.