THE RISE OF WATER-BASED INKS FOR DIGITAL PRINTING OF DISPLAY GRAPHICS

Water-based inks have gained popularity across the digital-printing landscape due to their low odour and low hazard solutions. Recent years have seen this trend adopted more broadly in wider format and industrial printers for graphics display markets. Items include posters and corrugated point of sale (POP) displays. A particular shift has come since the turn of the decade. 

In these markets, newer technology has caused some companies to move away from high-volume, solvent printers. In their place, printers are using water-based technology for more agile production. However, their use in these markets presents several challenges that need to be addressed. Ideal results can be aided with ink and process optimisations. Sun Chemical will launch its new solution – Streamline Toccata – at FESPA (6–9 May 2025, Berlin, Germany) to enable printers to navigate the complexities of these applications.

One of the main challenges of using water-based inks is the drying process. The ink needs to be dried fast on the substrate, without drying in the printheads. Drying in the printheads can cause nozzle blockages. In addition, with both roll-fed and sheet-fed processes, there is a risk of ink offset onto the back of the roll or onto the reverse of the stacked prints.

Unlike solvent-based inks – which typically evaporate quickly – water-based solutions may require more time to dry. They may also need different processes to accelerate water evaporation. This can impact the efficiency of the printing process, especially in high-speed, digital-printing environments. The drying time is influenced by several factors, including the type of substrate, ambient conditions and drying technology used.

To mitigate this issue, the process can be adapted with efficient drying systems, such as infrared dryers, hot-air dryers or convection ovens. 

Substrate and application requirements, in the use of water-based inks, can be wide ranging and present challenges. While an ink may perform well on a standard blue-back paper, it may struggle to achieve the right image quality and sharpness on a clay-coated corrugated. 

Print quality relies on colour management and drop control onto the surface of the substrate. It prevents colour bleed or feathering, resulting in vibrant and detailed prints. These prints are ideal for indoor posters and POP displays. They can handle high detail, small text and reverse-out print for close-up views. They are also suitable for billboards viewed from a distance.

Substrate differences can be successfully managed by using coatings or primers before printing. These coatings help the ink to adhere better to the surface. However, they add an extra step to the printing process and can increase production costs.

Achieving vibrant and consistent colours with water-based inks can be challenging. Water-based inks often have lower pigment concentrations compared to solvent-based inks. As a result, it can be challenging to match the colour output between the technologies. Additionally, the interaction between the ink and the substrate can affect colour consistency, leading to variations in the final print. 

To overcome this, printers may need to use higher-quality substrates and optimise their printer settings. This can involve manufacturers adjusting the ink formulation, printhead settings and drying parameters. Ink adjustments can be made using higher levels of pigment within water-based inks to enable less ink lay down. In this way, the same colour strength can be achieved, saving ink and limiting the fluid applied to absorbent materials. For example, which is prone to cockling when too much water is applied.

The throw distance with both poster and corrugated display printing is typically higher due to the risk of paper cockling or creasing. In addition, corrugated substrates may not present perfectly flat below the printheads. The further the distance the ink has to fly, the higher the risk of ink misting, which can lead to sticky residues within the print carriage.

Furthermore, pigmented inks have a solid content that can risk drying or sedimentation in the nozzles. Regular maintenance cycles are required to ensure inks are primed for printing at all times. This can be particularly impactful after overnight shutdown or with any stopping of the printer to change substrate, design or process for example.

To minimise these issues, ink formulations can be adapted with higher boiling point co-solvents to slow drying in the nozzles, although, this can lead to onward challenges in drying the ink on the substrate. Some printers are equipped with automated cleaning systems that help reduce downtime and maintain print quality. However, well formulated inks can also minimise the need for such interventions.

“Toccata inks have been designed to maximise pigment loading”

The performance of water-based inks needs to match with other technologies for it to be a viable choice for print-service providers (PSPs). The inks contain resins to ensure the pigment adheres to the substrate to provide the required abrasion and scratch resistance. They also offer protection from weathering effects, such as light fastness and water resistance. It is critical that the performance of the ink is not impacted in any post processes such as glueing, folding, cutting and brushing (when applied to billboards). 

When printing onto matt or gloss display materials, it is important that the ink does not change the overall appearance and take on the nature of the base substrate. To manage these required attributes and maintain consistency, primers and coatings – such as overprint varnishes – can be used to augment the ink’s performance.

While water-based inks may seem more natural and environmentally friendly, there are processing trade-offs. Drying water-based inks requires more energy resulting in higher process costs than their solvent-based counterparts. Advancements in ink formulas are enabling faster drying inks with lower temperature requirements. These factors benefit both the process cost and environmental impact. Reliable inks can also contribute to a reduction in waste, by reducing ink lost to maintenance or reprints.

Regulatory compliance is another important consideration when using any ink. While water-based inks are generally considered safer and more environmentally friendly, they must still meet specific regulatory standards for use in each application. This can include compliance with regulations related to volatile organic compounds (VOCs), heavy metals and other hazardous substances, as well as country-specific, chemical inventory requirements.

Printers need to ensure that the water-based inks used meet all relevant regulatory requirements and that printing processes are compliant with industry standards. This can involve additional testing and certification, such as Greenguard for indoor display posters.

Despite the challenges, Sun Chemical has spent recent years refining the chemistry and process of water-based inks for display and POP graphics. This work has led to significant technological advancements in the development of these inks. Such innovations in ink formulation – alongside printhead technology advancements – have helped address some of the challenges associated with water-based inks.

Sun Chemical’s Streamline Toccata inks, launching at FESPA, are designed for mid-viscosity printheads – such as Kyocera. These inks have marked a step change for the use of water-based inks in these challenging applications. Based on proprietary, Sun Chemical dispersions and optimised resin packages, Toccata inks have been designed to maximise pigment loading. As a result, best colour vibrancy with minimised ink consumption is now possible. 

The unique formula is able to achieve colour balance and image sharpness across a full range of paper and corrugated board. These include blue-back poster, clay-coated corrugate and supplier-specific substrates. PSPs are thus advantaged by flexibility in their choice of materials, without compromising print and application performance. 

To widen the application window of use, the inks can also be used in conjunction with Sun Chemical’s portfolio of primers and coatings for digital-print applications. This opens up the possibility to print both coated and uncoated papers for a wide range of graphics applications. Amongst these are billboards and indoor posters, as well as corrugated display and packaging.

Additionally, Sun Chemical has worked to ensure a fast-drying ink, enabling low temperature and, in some cases ambient temperature drying. These developments significantly reduce the overall energy consumption of the process. At the same time, a high system uptime with minimised maintenance in challenging environments on both scanning and single-pass printer configurations can be achieved.

The market for digital print in display graphics and POP corrugated is in a strong period. This is, in part, driven by a market resurgence of applications, such as poster and billboard printing, with printed media growing in volume as a result of high-level campaigns from companies such as JC Decaux. There has also been a decline in LED displays due to perceived visual and light-pollution effects. There is an additional growth in digital print in such applications due to a need for more agile short-run production to react to consumer trends. 

The demand for water-based inks is expected to grow in the coming years. This pressure is driven by a decline in super wide-format, solvent printers as well as a reduction in print job run lengths requiring flexible, on-demand production. Another contributing factor is the increase in the quality and performance of water-based ink solutions. 

As the industry continues to evolve, it is likely that more innovations will emerge to further address some of the challenges of using water-based inks. This could include the development of new ink formulations, improved printhead technologies and more efficient drying systems.

Water-based inks offer several benefits for PSPs, making them an attractive option for digital poster printing. However, their use presents several challenges, including drying time, substrate compatibility, colour vibrancy, printhead maintenance, environmental conditions, cost considerations, regulatory compliance and technological advancements. By understanding and addressing these challenges, Sun Chemical’s Streamline Toccata inks are designed to provide users with a reliable solution to deliver all the key application requirements. At the same time, Streamline Toccata water-based inks maintain the required colour strength, image quality and drying needs, whilst reducing overall energy consumption.