Digital inkjet printing has become quite popular among label converters in recent years. The technology has seen numerous advancements, allowing printers to deliver high quality in faster response times than ever before. Inkjet has seen its speed and quality boom, which has led to increased adoption. The inks, of course, are vital for the success of many of these capital expenditures.

An ink needs to perform well in a wide variety of areas such as jet-ability, color gamut, adhesion, run speed, open head time, and more. It’s also very important for an ink to perform consistently from batch to batch over a period of years.

“The latest UV curable inkjet inks tend to be safer, run faster, and meet a wider variety of printing applications versus legacy inkjet inks,” explains Tom Shea, regional manager, Digital Inkjet Ink BU, Siegwerk USA. “With that said, our OEM partners generally promote ‘digital press innovations’ wholistically, without focusing specifically on ink performance. It is a given that if a new press runs faster, more reliably, with better image quality, and meets a wider variety of application requirements, much of that innovation comes from ink development.”

In many ways, inkjet inks have been required to keep up with equipment enhancements. As printheads and presses have operated faster and faster, the inks have been tasked with matching the equipment.

“Many of the changes in the inks have been to address the requirements of the printing systems,” states Paul Edwards, vice president, Digital Division, INX International Ink Co. “As time and technology progressed, faster printers with improved quality and driven by higher resolutions (dpi) were featured more as part of the hardware product offerings. Therefore, inks had to be designed to be used in printheads where the viscosities were often lower than they were previously, and the print frequencies were much higher, which is always a challenge for digital UV printing. The inks were required to print at a higher printing speed, and many printers moved to UV LED curing from the early Hg lamp UV systems, which required formulation changes to adapt to this different cure wavelength.”

It’s also important to differentiate inkjet inks into water-based and UV. UV inkjet is now a well-established and proven technology. More recent innovations include UV LED inks to complement traditional UV technologies.

“These new UV inks enable compliance with evolving regulations, deliver higher quality through improved printheads, and support higher productivity, now exceeding 100 m/m. Meanwhile, water-based ink technology is still in the early stages of adoption for these applications,” explains Dan Carpenter, manager, marketing communications, Fujifilm. “Its progress has been driven by advances in high-performance raw materials such as dispersions and polymer binders, as well as improvements in drying hardware. For example, Fujifilm has pigment dispersion technologies that are designed to meet the requirements of advanced inkjet formulations. Their exceptional stability enables ink formulators to work freely with a broad range of ink formulants to create the required performance.” 

There are several challenges that ink formulators are having to overcome in water-based applications. “It is challenging to formulate water-based inks for filmic substrates because of the hydrophobic nature of plastics,” adds Carpenter. “Achieving adhesion involves creating a good chemical interaction with primers, or directly with the substrate. In addition, as print speeds are being driven higher, inks need to dry faster, so the formulator’s challenge is to create an ink that dries rapidly on the substrate without drying in the printhead, which would compromise performance and could even cause printhead failure.”

Sun Chemical’s inks have also been designed to meet evolving regulatory requirements for product labeling while also being low-migration compatible, fully LED-curable at high speeds and producing consistent, reliable brand colors at high throughput. “Sun Chemical develops solutions that improve the entire printing process by ensuring its latest inks exhibit improved receptivity to post-print processes like lamination and foiling, as well as upgraded compatibility with thermal ribbons,” notes Simon Daplyn, product and marketing manager, Sun Chemical. “These upgrades include overprint varnishes and other coatings to ensure converters can provide the most flexible solutions to their clients.”

As the technology has improved, reliability has become a hallmark of the newest inks. For example, maintenance is not nearly the challenge that it once was. “One ink improvement in the press system is reliability, with inkjet nozzle blockage being an issue customers dealt with early on,” states Mike Pruitt, product manager, SurePress, Epson America. “Manufacturers had to previously lower the viscosity of the inks to ensure printheads would not become blocked, which worked to some extent but reduced the ability to achieve higher gamuts and maintain even viscosity across the web. Using improved pigments has allowed higher viscosities to be run, resulting in better prints at faster print speeds.”

The evolution of inkjet inks includes new technologies for a wider selection of printheads, enabling reliable printing with smaller drop sizes and higher resolution at significantly increased speeds. “Advances in pigment dispersions and improved formulation expertise have led to more stable inkjet inks with purer colors and increased reliability, improving system up-time, reducing waste, and lowering energy consumption with LED cure options,” says Daplyn.
The newest inks must adhere to a wide range of evolving regulations. Ensuring that manufacturers’ customers remain in compliance in numerous applications, from food packaging to pharmaceuticals, is critical.

“Siegwerk’s Product Safety Team does an excellent job staying ahead of regulatory changes that affect the market,” says Shea. “Sometimes these changes require Siegwerk to make formulation changes to remain in compliance with the guidelines our customers must abide by. As an example, our Sicura Jet G series, which has been our most popular ink, is just now being released in its third iteration as G3. Of course, with each reformulation, Siegwerk strives to achieve new performance enhancements, so the ink meets the widest set of customer application requirements. In the end, the goal is to provide customers with a headache-free ink that produces great image quality while not causing problems on-press.”

Newer inkjet inks provide more coverage, as well. “The quality of inkjet inks and their compatibility with leading printheads, such as those made by Epson, has resulted in wider color gamuts,” remarks Pruitt. “As measured by Pantone, some inks exceed 85% with only a 4-color CMYK ink set with tolerances as low as 1.5 delta E 2000. Smoother gradients and grey balance are improved too, so that wider gamuts and ICC profiles like GRACol2013 are achievable. The  newer inks are also formulated for lower energy curing, making ‘no chiller systems’ possible, ultimately lowering overall energy consumption for the press system.”

Finding the correct ink is no small task, either. Developing partnerships with suppliers is key in finding the appropriate product for a converter’s range of applications. For example, Sun Chemical works closely with OEMs and integrators to ensure any converter can access the necessary solutions to meet the requirements of the output they want to provide for their brand partners.

“Inks form an integral part of finished labels, making it critical to achieve impactful prints through color, abrasion resistance, brand identity, and compliance,” says Daplyn. “All these things can be accomplished by partnering with Sun Chemical across their full range of labelstock, including SunJet UV, LED and aqueous inkjet inks, SunEvo digital primers, coatings and adhesives, and SunDigiProof digital services for color-accurate inkjet swatches.”

Flexo vs. digital (and inkjet)

Ink manufacturers have perfected their latest products to meet a host of requirements. Specifically, they have engineered inks to perform optimally with a converter’s chosen print method, be it flexographic, toner-based digital, or UV or water-based inkjet.

“Each technology is capable of producing high-quality images at high productivity. Inkjet ink is a very versatile technology, and it can be applied across a broad range of materials, including paper and plastics,” states Carpenter. “Electrophotography (toners) is primarily used on paper-based substrates. Flexo inks, which form a thin, flexible film, are ideal for a very wide range of packaging substrates. Inkjet inks are typically press-ready, applied as process CMYK colors with additional colors to extend the gamut, along with whites. Flexo inks, on the other hand, are often available in a vast array of process and spot colors, including special effects and finishes.”


The printhead should not be overlooked, as inkjet printheads are non-contact in their delivery. “UV inkjet inks begin as a very low viscosity liquid and are polymerized on the substrate via a UV curing process,” says INX’s Edwards. “Flexographic ink technology is a direct printing process where the ink is applied to the substrate using a rotating drum. The flexo inks are much higher in viscosity due to the requirements of this process and are applied at a much lower thickness, although the UV curing chemistry is essentially the same.”

“Due to the digital printing process, inkjet inks are required to have tighter control of materials selection than other applications in terms of purity, particle size, and stability in lower viscosity media,” adds Sun Chemical’s Daplyn. “Because inkjet printheads can be sensitive, it is critical to maintain printhead compatibility alongside high-speed and consistent printing. As a non-contact process, the drop formation and substrate wetting of digital inks must also be carefully managed, especially in contrast with contact print processes where less variables can impact the final print.”

When comparing inkjet to toner, toner-based systems are quite different – but they are a direct printing process. “There are two forms of toner: solid and liquid,” explains Edwards. “They are similar in that the toners essentially consist of pigment and polymers (dispersed in the liquid form), and heat is applied to achieve the adhesion as the polymers of thermoplastic.”

For Siegwerk, it designs both flexo and inkjet inks, with several key distinctions. “To perform properly in a digital print environment, UV inks need to be manufactured to a very tight tolerance that matches the requirements of a specific inkjet printhead and UV curing range,” says Siegwerk’s Shea. “In addition to having a great formulation, there needs to be a high level of quality control implemented during production. This is one of the drivers that keeps the cost of UV curable inkjet ink more expensive than flexo ink. In the inkjet segment, OEMs quickly learn to stay away from relying on cheap, poor-quality inks, because the cost of failed printheads and required service calls becomes very costly.”       

Unlike Siegwerk’s flexo ink business, which is conducted directly with print providers, its inkjet business is managed solely through a channel of printer manufacturers and printhead integrators. These OEM partners distribute Siegwerk ink to their install base of customers. “Since most of these sales are made under the OEM’s private label branding, the Siegwerk name is not well known at the end-user level,” adds Shea. “At the OEM level, Siegwerk promotes a variety of inks that are each tuned to specific printhead technology, and/or printing application. While UV inkjet inks can be used for a wide variety of industrial applications, in keeping with Siegwerk’s core focus, our inks are designed specifically for the labeling and packaging segments – including direct to container or cap and closure printing.”

According to Epson’s Pruitt, the packaging of inkjet inks typically makes them easier to manage as there is no measuring, mixing or draw-downs needed. The inks can be produced and packaged to minimize virus and bacterial contamination, which is desirable in GMP food and pharmaceutical environments.

Ink options

Ink manufacturers offer a multitude of products to meet demand, especially as more converters add inkjet to their print shops. For example, Epson has both AQ-resin (water-based) and UV inkjet presses for the narrow web market. Epson products use Epson inks and printheads to maximize performance.

Fujifilm supplies a variety of solutions, ranging from full production inkjet and toner printing systems to the development and manufacture of OEM inks, and pigment dispersions for ink manufacturers. The recently introduced J Press FP790 flexible packaging inkjet system features water-based inks. Its wide color gamut allows converters to achieve special brand and spot color matching with no need for additional special color inks. It can achieve more than 90% of Pantone colors while also using two white ink channels for high white opacity, all achieved with excellent color stability.    

“In addition to the FP790, we also produce the J Press 750HS that conforms to packaging regulatory requirements for primary and secondary food packaging,” says Carpenter.

INX has been involved in the inkjet printing of labels for many years, both in the development of inks and printing systems. “Our printing technology is used to power the most recent label presses from SEI Laser, where the unique characteristic is that the printer offers laser diecutting,” says INX’s Edwards.

Edwards also notes that understanding inks and printheads is key when making a product selection. Inks need to be adapted for the printing systems and applications required. “It is a common mistake to believe that because a printer uses a specific printhead type, any ink formulated for the head can be chosen for use in that printer,” remarks Edwards. “Converters should know it is important that the ink is designed for the specific print system in question and for the specific application. If this is not the case, then the result is often substandard performance. INX has extensive knowledge of printing systems, ink chemistry, and the application requirements. Many customers understand we are a partner who can be trusted to provide a great solution.”

Meanwhile, Siegwerk offers water-based and UV LED curable inks and functional coatings, both analog and digital. The company boasts SICURA DGT (digital) coatings, primers, and adhesives for digital printing technologies.
Sun Chemical’s newest inkjet inks have been designed with sustainability in mind. Sun Chemical offers a full suite of digital inks for all printhead options and system configurations, as well as the ability to tune solutions for system- or process-specific requirements.

“Sun Chemical’s Streamline GreenGuard Gold-certified eco-solvent and aqueous inks provide improved low-indoor emissions and advanced technology for wide and super wide format printing,” states Daplyn. “Sun Chemical can also support analog post-finishes such as coatings, overprint varnishes, primers, and adhesives.”