Security Ink Technology: A New Invention from Indian Physicists

Technology has made remarkable progress with the time and touched new horizons in this 21st century. This technology proved to be a boon world widely for society. Despite of being achieving so many milestones with latest scientific inventions it have also affected adversely up to a certain extent. One among these adverse affects is ‘counterfeiting or forgery’ i.e. the biggest crime of this century. The crucial solution of this crux is ‘Security Printing’ as every problem has a solution. Security printing facilitates protection against counterfeiting and tempering overtly as well as covertly by combining numerous printing methodologies.

Source: http://www.rotatek.com

Security inks are a special segment and another foundation of security printing. Its importance cannot be underestimated It is the security ink that fosters the credibility of security printing. Various types of security inks are enlisted as below

1. Thermochromic Ink: Thermochromic inks are sensitive to temperature. These inks are reversible or irreversible color changing inks.
2. Invisible Ink: These inks are invisible under normal lighting conditions. In order to detect these inks UV light source is required.
3. Solvent Sensitive Ink: When someone attempts to alter any credentials then it shows a visible indicator and ink will run resulting smudged area. Such inks are sensitive to solvents. 
4. Magnetic Ink: Magnetic inks usually consist of small magnetic particles which are machine readable. Such types of inks are usually used for serial numbering purposes. 
5. Anti-absorption Ink: These inks are used for printing of security documents. Printed areas are visible under Infra-Red light spectrum. These inks are available for letterpress, gravure, offset, screen and intaglio printing. 
6. UV Fluorescent Inks: UV fluorescent ink appears to glow when exposed to ultraviolet light but under normal lighting conditions these inks are invisible
7. Biometric Ink: Biometric inks contain DNA taggants which are machine readable.

Basically, UV Fluorescent Inks have been used to find fake currency notes. As per security purpose, the finding of duplication of the currency notes is challenging task. According to the Reserve Bank of India’s (RBI) report, the new Rs 500 and Rs 2,000 notes introduced after demonetisation are at the risk of duplication. According to the report, the duplication of a new design of Rs 500 notes is accounted to be 121 per cent and of Rs 2,000 notes to be 21.9 per cent in the last year. So, in a latest research, scientists from CSIR-National Physical Laboratory (NPL) in New Delhi have come up with a security ink — which can prevent duplication of printable documents and counterfeiting of currency notes. This research was worked under the combination of fluorescence and phosphorescence phenomenon.

Source: Wikipedia

Counterfeiting is defined as the reproduction of an intellectual property right without receiving permission from the proprietor. It has grown to be a serious global threat nowadays and this includes the duplication of currencies, merchandise, electronic products, official documents, passports, pharmaceuticals, and so forth which causes enormous loss to the economy of any country, as well as a constant risk to the health and safety of consumers worldwide.

The main task of the team was to select compounds, which do not obstruct the formation of the colours on the excitation of the wavelength. For the production of luminescent pigment, two chemical compounds — sodium yttrium fluorite, europium-doped and strontium aluminate with europium-dysprosium — were synthesised to emit red and green colours, respectively. The fluorescence property is through sodium yttrium fluorite, while the phosphorescence is by compound strontium aluminate.

For the feasibility test of the ink, an image was printed on a non-fluorescent white bond paper using a standard screen printing technique. The results showcased the emission of red and green colours under the 254 nm UV excitation when the source was turned on and off. The experimental test was conducted for optical photographs of Tajmahal.

Source: Amit Kumar Gangwar et al, Journal of Materials Chemistry C, 2019

The emissive luminescent security ink and the ink after six months of storage exhibit almost the same viscosity, which confirms that it can be stored for long durations without undergoing any significant changes in its properties. The technique which was a new scalable and inexpensive opportunity to generate unbreakable security features, which are essential for protection against counterfeiting. This can be used in legal confidential certificates, merchandise and electronic barcodes also to avoid duplication or sale of fake products.

References:

Amit Kumar Gangwar et al., Single excitable dual emissive novel luminescent pigment to generate advanced security features for anti-counterfeiting applications, Journal of Materials Chemistry C, 2019.
Vikas Jangra Security Printing: Innovative Technologies with Comprehensive Approach as an Anti-Counterfeiting Tool, International Journal for Scientific Research & Development, 2016

Written By: Ashith VK