With all the buzz around digital printing over the last decade or so, it’s easy to miss the fact that during that same time span, there have been some huge changes for offset printing as well. Approximately 97% of printed pages still come from offset presses, with only 3% printed digitally. So, any changes to offset technology have the potential to make a big impact both for individual printers and for the industry as a whole. Arguably, the most noticeable change in offset printing technology has been the trend toward UV-curable inks. UV technology has been used in the printing industry for over 30 years, particularly with packaging, label, and business forms printers. But it hasn’t had much penetration in other areas until recently. However, in the last few years, UV has taken off among commercial printers, primarily due to new, low-energy UV technologies introduced by the major press manufacturers.
Brief overview of UV printing
UV curable inks were introduced as an alternative to solvent-based products to provide improved print quality and higher speeds to a dry print. Conventional heat and air drying works by solvent evaporation, a process that shrinks the initial wet coating and can also release environmental pollutants when organic solvents (VOC’s) are present. In UV curing, there’s little or no solvent. Instead, the inks comprise liquid reactive components. These reactive components can be hardened rapidly through the application of UV light, which causes chemical cross-linking (or hardening). Because there’s little or no solvent to evaporate, there’s no volume lost from the wet coating, resulting in higher ink densities and higher gloss on the print. In addition, there are no environmental pollutants from any organic solvents. Through the use of photo-initiators, it’s possible to cure the inks using UV lamps. Some major advantages of UV include:
- Fewer emissions of VOC’s
- Inks can dry on plastic and other non-porous substrates
- Inks do not have to absorb into the stock and dry fast
- If you can get it through the press you can print on it
- Ink dots are left sitting on the substrate, reducing contamination and delivering more vibrant color and detail.
- Higher gloss levels as well as superior rub resistance are possible
Also, low-energy UV offers all the above advantages with a smaller, less expensive system using less energy. Conventional UV lamps consume a lot of power, take up a lot of space and generate a lot of heat. These systems also produce ozone, requiring an extraction system that adds cost to the press. Together, these factors limit the application to print shops where the value of the print product would pay for the equipment and cost of running the UV. More recently, with the advent of higher powered and less expensive UV sources, it’s possible to provide the same amount of energy to the wet sheet but with a lot less power, heat and space, –and there’s no need for an ozone extraction system. With these new low-energy UV systems, such as LED-UV, H-UV, HR-UV, and LEC-UV, equipment and running costs are reduced, and old presses can be modified more easily with the smaller equipment. These less expensive, smaller systems are allowing commercial printers to use UV and take advantage of faster turnarounds, less maintenance through use of less anti-setoff powder, a wider range of substrates, and higher print quality. Craig Bretherton, Product and Marketing Manager at KBA (UK) added: “Commercial printers are also being attracted to this technology as it means difficult-to-dry stocks, such as offset, can be quickly turned around without the need for coating. In addition, due to the lack of a requirement for extraction and coating units in many cases, capital costs to add new drying technologies are not prohibitive.”
Printers in Japan have widely adopted low-energy UV presses, with Ryobi MHI (RMGT) being one of the first press manufacturers to the market with their LED-UV technology, and with Komori offering H-UV technology. Estimates are that about 70% of new presses made in Japan are now low-energy UV presses. In Europe, UV presses are also dominating new press sales. Heidelberg estimates that about 15% of its global installations of presses are UV presses.
New technology means more new technology
Switching to a UV system requires a complete review of all current components that go through the press, and some changes will be necessary. Not only will a printer be changing their inks, they must also look at compatibility with press chemicals, blankets, substrates and more. In particular, UV can be challenging for printing plates. To address this issue, Kodak’s plate scientists and engineers, for example, have developed new plate technology specifically for UV print applications, including low-energy UV. New plate technologies are necessary because in a UV system, the blanket washes and plate cleaners that are required to clean the special UV-curable inks also happen to be aggressive against the coating of printing plates. Also, as the press chemistries have become more eco-friendly, they provide less protection for the plates. Historically, Kodak provided plates that could be baked to withstand the aggressive chemicals used with UV, but baking is also not very environmentally friendly, using a lot of energy and producing excess heat.
Kodak’s newest plates, such as its Electra Max Thermal Plates, deliver superior solvent resistance without baking and are therefore ideal for UV applications. Plus, they require less developer in prepress than previous generation plates, further increasing their environmental benefits. Kodak’s Sonora Process Free Plates reduce even more environmental impact by eliminating the energy, water, and chemical waste from plate processing. They’re suitable for short-run UV print applications – up to 10,000 impressions with Sonora XP Plates, and 30,000 impressions with Sonora UV Plates.
So what’s in store for the future? The predominant thinking is that you can expect many more innovations around offset printing – whether they come from the press manufacturers themselves, other industry suppliers, or even commercial printers.