Ink and Ink Dispensers
Ink Selection: Aqueous vs UV inks
By Natasha Jeremic, Digital Printing Ink Development Manager at Domino Printing Sciences
accurate control of the printed drop size and shape, an important contributor to optimum print quality. UV inks are also suitable for applications in which labels require resistance against weathering, chemical exposure, and mechanical damage.
W
ith pressure growing to improve sustainability in the packaging and printing industry, many label converters
are weighing up the advantages and disadvantages of using aqueous versus UV inks for their digital printing processes. There has been a lot of media attention about the lack of recyclability of UV inks, calling for UV ink to be avoided because it contaminates recycling streams. However, a closer look at the subject shows that the presence of any ink reduces the grade of the recyclate and that an optimum approach to recycling printed labels includes a deinking process. With the help of suitable de-inkable primers, this can be successfully applied to both UV and aqueous inks.
Aqueous inks are renowned for their eco- friendliness and versatility. Though thought to be composed predominantly of water, water-based inks can contain equal or greater proportions of other organic solvents. The ratio varies from product to product and can significantly increase the emission of VOCs (volatile organic compounds) into the environment. Despite the lack of hazard labels on aqueous inks, it is true that both aqueous and UV inks can contain components that have an impact on the environment. UV ink technology has gained prominence for its exceptional durability and versatility. Unlike aqueous ink, UV inks do not rely on the physical process of evaporation. Instead, when the printed inks are exposed to ultraviolet light, they instantly undergo the chemical reaction of polymerisation, creating a strong bond with the substrate that ensures durability and longevity even in harsh environments, as well as a resilient finish resistant to fading. This attribute makes UV inks perfect for printing on a wide variety of semi-porous and non-porous materials, with
34 May 2024
To achieve similar durability for aqueous inks, pre- and post-treatment is required; primer to achieve printability on non-porous substrates and varnish or lamination to increase the durability of the ink in demanding applications. Once pre- and post- treatment are applied, water-based inks’ much-lauded alignment with sustainability goals may be drastically reduced, and de-inking processes, similar to the UV process, will be required to achieve full recyclability.
UV inks are renowned for providing high- speed printing for increased productivity in commercial settings. This is enabled by reactive chemistry and the use of UV lamps that provide instant curing, ensuring a smudge- free print. To achieve similar, fast results, aqueous fluids require treatment by very powerful IR (infrared) driers or ovens, which can make their application energy-intensive and, depending on the technology, increase floor space requirements in the factory. To achieve a comparable laydown, surface coverage, and speed for aqueous ink, energy usage could be up to three times greater compared to UV curing, especially when less efficient mercury lamps are used in place of low-energy LEDs.
Considering all this, which option is more environmentally friendly?
The answer depends on the application and energy source available. If printing onto fibre-based, semi-porous media, especially where low-cost energy from renewable sources such as wind or solar is available and less stringent durability needs means that post-treatment can be avoided; aqueous inks are the most environmentally friendly option. If flexible plastic is the substrate of choice, and end-user requirements are demanding, a more sustainable process and lower cost of ownership could be more easily achieved using UV inks.
The evolution of aqueous and UV ink technologies has transformed the printing landscape, offering enhanced performance and sustainability. As advancements continue, these positions are bound to evolve further, but for the time being, both play a vital role in meeting the diverse needs of modern printing applications.
Many environmentally conscious converters are wondering how to weigh up which technology is best for them. This often comes down to the requirements of their brand customers and end-user applications, as their demands will not only affect sustainability goals, but will also impact the overall cost of ownership when considering substrates, printing speed, laydown of the ink, and durability of the print.
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