Types of Security Inks
Invisible UV (View Demo)
These are high security inks that are invisible under normal lighting conditions, but under UV light, these glow in a bright colour. The UV LED’s used to read the message written by UV markers emit near-ultraviolet light. When the black light is made to fall upon this UV-visible ink, it makes the ink fluorescent, thereby making the message readable by human eyes. Variable information can be printed on the Hologram using UV inks which are visible only through a UV light source.
This helps in second stage authentication & also in tracking goods throughout the chain of distribution in a covert manner. Invisible UV inks are available in different frequencies and a multitude of colours.
Thermochromic (View Demo)
These are temperature sensitive inks which change colour with a change in temperature (for instance, by rubbing) – The printed text / image appears or disappears when rubbed by a finger or on application of any heat source. Thermochromic inks offer an instant method to authenticate a product for the end user as no device is required. These inks can be reversible or irreversible and are available at different activation temperature ranges. Higher security can be obtained by making the inks dual colour or tri-colour i.e. at different activation temperatures, different colours are visible.
Coin Reactive (View Demo)
These inks react when they come in contact with coins or other metallic objects. When the printed area is rubbed with a coin, it blackens to reveal the hidden text or image. Thus, it acts as an instant authentication tool and is also end user friendly, as no separate device is required for authentication.
Fluorescence (View Demo)
These inks are visible as lighter shades of colour under normal lighting, but when exposed to UV light, these will exhibit different colours of fluorescence depending on the wavelength of the light.
Selectively applied varnish creates controlled repellence if solid areas are overprinted with a liquid gloss varnish. This controlled repellence is characterized by the formation of fine droplets, which add a textured effect to the printed material. The unique texture can be used as a security or aesthetic tool.
Solvent Reactive / Water Reactive (View Demo)
These inks are particularly useful in protecting documents with variably printed information, such as cheques and other financial or legal instruments. When exposed to certain solvents like alcohol, acetone or bleach, these inks will undergo a chemical reaction which will cause them to run, change colour, or leave a stain, hence indicating that the document has been tampered with. Water reactive inks exhibit similar properties when they come in contact with water based fluids.
Optically Variable Ink (OVI)
Optically variable ink is a highly secure anti-counterfeiting ink which finds use in many modern currencies as well as in other critical documentation. The ink displays two distinct colors depending on the angle it is viewed from. It has a very high level of security since it is not widely or easily available, and one has to go through stringent checks and procedures to obtain the same. These inks have color-shifting properties due to which they reflect various color wavelengths in white light differently, depending on the angle of incidence to the surface.