UV-curable inks : making the difference in wide format printing

The wide-format inkjet production printing arena is witnessing a new revolution. It’s more than just the higher speeds, higher resolutions, streamlined workflow and improved productivity we’ve seen over the past five years. Today, the digital printing market is undergoing an ultraviolet (UV) revolution. Sultan Singh of Apsom Infotex Ltd discusses this trend in detail.

The ultraviolet revolution in  wide format digital printing started a few years ago with the advent of flatbed inkjet printers, designed primarily as complements or digital alternatives to screenprinting. These machines, the majority of which are equipped with UV-curable inks, are becoming increasingly popular in wide-format print production environments of all kinds – not just screenprinting operations – because of the flexibility and productivity they provide. They can equally print on a wide range of substrates – both rigid and flexible media. The use of UV-curable inks also makes flatbed inkjet printers more environmentally friendly – they
do not emit volatile organic compounds (VOCs), thereby reducing the requirement for special ventilation and disposal systems and more easily complying with increasingly onerous environmental regulations in some regions.

The advantages of UV-curable inks have begun to extend beyond the flatbed printing paradigm.

UV-curable inkjet printing is now poised to address roll-fed applications – primarily outdoor advertising, superwide (grand format) printing and high-throughput digital printing. Because of their obvious advantages, it is forecasted that over the next few years, the wide-format printing industry will witness multiple introductions of new roll-to-roll printers equipped with UV-curable inks. In short, roll-fed printers represent the next step in the UV-curable inks printing revolution.

As inkjet printing continues to evolve with increased functionality, higher performance, better cost efficiencies, and continuously improving print quality and colour rendering, the interest in UV-curable inkjet printing technology is set to explode.

A word about wide-format inkjet production printing As wide-format inkjet printing has increased in popularity over the past few years, the breadth of implementations, price points and performance levels has expanded. Today’s range of wide-format inkjet production printers, or grand format printers, as they are sometimes referred to, can open the door to the production of new print applications, new customers,more work from existing customers, higher profit margins – in short, a full suite of profitable new opportunities for your business.

Why UV-curable inks are the next step Ultraviolet (UV) curable inks have been used for many years in the cable and wire industry and in a variety of graphic arts printing technologies including flexography, lithography and screenprinting. UV-curable ink formulations are composed primarily of three components: monomers, oligomers and photo-inhibitors. Monomers are reactive dilutants with a low molecular weight that create a homogeneous solution and impart the surface characteristics of the ink. Oligomers form the chemical backbone of UV-curable inks and determine the final properties of the cured ink layer applied to a substrate including the ink layer’s flexibility, weather resistance and chemical resistance.  Photo-inhibitors control the start and completion of the ink curing process.

The primary factor limiting the use of UV-curable inks in the digital printing market has traditionally been
the ink viscosity restrictions of continuous inkjet (CIJ) printheads. However, new printheads have been developed over the past five years that accommodate dramatically wider range of viscosity.

The ever-increasing need for speedy turnaround in screen and flatbed printing applications has led to the development of inks with faster cure rates and lower UV exposure requirements. The latest UV ink formulations offer higher levels of opacity and the ability to cure with a thinner layer of ink. Additional innovations have led to the development of inks with advanced adhesion, elongation, flexibility, and water resistance properties. All of this has resulted in the development of UV-curable inks that can be successfully used on both rigid and flexible media. And this, in turn, has led to the development of UV-based printing equipment by several manufacturers of wide-format inkjet printers.

Advantages of UV-curable inks UV-curable inks demonstrate a number of advantages over traditional solvent based ink formulations. These include :

Fast curing: UV-curable inks change from liquid to solid immediately when exposed to a UV light source. Printed output, therefore, dries instantly and can be handled and stacked or cut. In contrast, solvent-based inks take a longer time to dry, forcing manufacturers of solvent ink-based roll-fed printing systems to build drying systems into their machines (heated platens, rollers or drying units) to accelerate the process. Because the latent heat required to warm thicker substrates like acrylic panels, rigid PVC sheets and display boards is much greater, the drying techniques used in solvent ink-based systems, do not function effectively for some types of media.

Adhesion: UV-curable inks demonstrate superior adhesion to a very wide range of non- absorbent and unprimed printing substrates and good adhesion to absorbent substrates. Untreated media is less expensive than coated substrates, making printing with UV-curable inks potentially more cost-effective.

Fast and productive: With UV-curable inks since there’s no worry about ink drying times, hence the benefit of fast turnaround times and high levels of productivity.

Long print life: Images printed with UV-curable inks can provide outdoor durability for up to 2 years. In addition, images printed on rigid substrates can be cleaned using strong solvents and cleaners to remove dirt and/or graffiti, giving them a longer useful life. In many cases a lamination requirement can be eliminated, resulting in fewer production steps, increased productivity and lower production costs.

Environment-friendly: UV-curable inks contain virtually no volatile organic compounds and thus have a minimal impact on the environment.

Excellent colour values: The high level of transparency produces a very clean colour gamut making UV-curable inks an exceptionally good choice for four- or 8-color process graphic printing.

Colour consistency: Because UV-curable inks are heated and jetted at a constant temperature and a UV light source fixing or “curing” them on to the media, fluctuations in working environment and temperature get a minimal effect.

Lastly, UV-inks also offer several benefits in inkjet printing systems itself. Since they cure only in response to UV light, stand time for printheads is practically unlimited. Inks do not dry on the printhead, rather with no solvent to evaporate, ink composition remains consistent and the inks retain excellent stability in the printhead, thereby reducing the need for purging and cleaning cycles. Less maintenance means more time for higher productivity.

State of the market and where it’s going

As with many market forecasts and predictions by multiple firms, the numbers don’t always match. But the message is the same. The market for wide-format printers that use UV-curable inks is ready to take off. In short, the newest generation of inkjet production printers that are equipped with UV-curable inks give print service providers the tools to develop innovative new applications with which to go after a plethora of new business opportunities. This alone makes the future for UV-curable inkjet printers extraordinary – a future in which today’s production-oriented wide-format print service providers will surely want to participate.

According to the UK-based firm Web Consulting, the sale of digital printing systems that use UV-curable inks will nearly equal that of solvent ink-based printers in 2006. The firm estimates that more than 4,000 ultraviolet wide-format units will be sold during the next four years.

While the advantages of UV-curable ink technology have found initial widespread acceptance in wide-format flatbed inkjet presses, it is now clear that roll-to-roll printers can benefit equally from this capability. In fact, UV-curable inks are now poised to take roll-fed inkjet printers into a new era of performance and versatility.

(Suntan Singh of Apsom Infotex Ltd can be contacted at: 011-26385096, 26387729, mobile: 09312096406.)