There are moves to ban the use of mercury in all walks of life, with an initiative started in the UN which has filtered down to the EU. But which is going to leave the printing industry largely unscathed.
Under EU directives, large scale fixed industrial equipment, which includes sheetfed printing machines, will not need to replace mercury vapour lamps – at least not until a viable alternative becomes available, and this is not yet on the horizon.
Some large format inkjet presses will be forced to replace their UV lamps with LED diodes, these being roll fed printers which can be easily moved. But machines like the Inca Onset which are anchored in place, will be able to continue to use mercury vapour lamps.
These are fluorescent tubes, like those used in a wide range of industrial and domestic lighting. For UV curing purposes a small amount of mercury is added during manufacture to ensure that the light generated is dominated by UV energy.
When the UV light hits matched photoinitiators in an ink or varnish, the result is a reaction which creates an instantly hard matrix of colour on a paper, plastic or other impervious substrate. This is the essence of UV printing which has dominated carton printing in the UK in recent decades, has an equally strong hold over label printing and which, through new generation UV technologies, is making inroads into commercial printing.
Sitting in the middle of this swirl of activity is Baldwin, a pressroom peripherals supplier which filled a gap in its drying systems portfolio with the acquisition of Nordson UV. It was timely. The interest in UV is at an all time high, thanks to Komori’s H-UV technology, which was a joint development with Baldwin, and thanks too to press manufacturers who are developing LED UV systems. This includes the likes of Ryobi MHI, Sakurai, KBA and in the background Heidelberg. The German giant currently promotes LE as low energy UV, but is working hard to develop its own LED UV technology.
For Baldwin the centre of expertise for UV is in Slough where is produces the different sizes and styles of lamp, not only for printing but also for water purification systems, a sector where conventional lamps cannot be replaced by light emitting diodes. Some lamp production takes place in the US and some R&D and manufacture for LED is located in Japan, but the bulk of the work takes place along the M4.
Whether doped UV lamps or LED, the appeal is that energy required for drying a sheet is slashed using these technologies and that the sheet in the delivery is perfectly dry for the next process step. Pat Keogh, Baldwin’s vice president UV IR lamps, explains: “On a B1 press a conventional hot air/IR dryer can be running at 80kW/hr to dry a water based coating. With H-UV the energy required is 20kW/hr and there is no need to have a coating. Even with considering the cost of the coating, that’s a 25% saving in drying energy.”
The H-UV project began in 2008 with Baldwin and Komori investigating the application of LEDs, but these were hideously expensive at the time. “The efficiency has been improving all the time. In 2010 about 10% of power input was delivered as UV energy. It’s now about 45%,” he says.
That earlier deficiency led Baldwin and Komori to investigate doping a conventional mercury vapour lamp to tune it to deliver a narrower range of UV power. Komori worked with Toyo Inks on achieving a recipe that would show the sensitivity required to cure a wide range of inks and varnishes.
H-UV is still ahead in this respect, says Keogh. “LED tends to produce UV in the wave lengths that are suited to the process colours, but it’s not so good for silver and there is still the coating problem.” Varnishes that are suited to LED UV have a tendency to yellow when cured, which may or may not be noticeable and acceptable.
However, he acknowledges that LED is on the rise. “If you are buying a four-colour press, LED must be considered because there are suitable inks now for paper, for plastics and foils and there are presses in use in Japan and elsewhere which work well. But for multi-colour work with spot colours, there are still drawbacks. Nobody has put LED only on a six- or eight-colour press because it doesn’t really work, even with the most powerful LEDs available.”
The work with Komori was initially about energy saving, a requirement which gained momentum when the Great East Japan Earthquake was followed by government restrictions on energy consumption. Simply put, all industries had to cut energy consumption. Printers that invest are prohibited from buying machines that increase energy consumption.
This is becoming a wider issue as governments seek to tackle climate change issues. Even in China there is pressure to cut energy consumption and in some countries grants are available to help investment that cuts energy. Larger customers are also starting to show interest in the energy footprint of their suppliers.
If energy saving was the prime driver, it quickly became clear that new generation UV had other benefits. With traditional UV, there has always been greater dot gain than on conventional litho presses. But with H-UV and now LED UV, the dot was actually sharper than conventional printing.
Then there is the ability to print and dry instantly on uncoated papers, using less ink because the colour is held on the surface and is not allowed to soak into the fibres. There is no dry back to lose the intensity of the colours as sheets dry, nor any need to add an aqueous coating which can take away the tactile impact of using an uncoated paper.
Instant drying gives greater lift as well. Almost at once, same day delivery of printing on uncoated papers is achievable. For some of the keenest supporters, this represents a new dawn for offset printing.
The other advantages include no set off powder with the cleaning issues that this creates and a cleaner working environment in the press room.
Baldwin is working with the LED suppliers in Japan and provides the technology to Sakurai. It also works with inkjet press manufacturers where LED UV is more accepted. This is because the demands on the diodes are not so great; the LED is much closer to the substrate for one thing and most applications are for four-colour printing. The arrays are also much smaller than across the width of a press so that the initial cost is much lower.
As the cost of each diode is still around $3 before any integration work and a sheetfed press array can number 300 or so, this is an important consideration. “The economies of scale are making LED viable now for B2 sheetfed,” says Keogh.
It is also making a retro fit system highly appealing. In the US AMS has made a virtue of adding its LED systems to existing presses and Baldwin can do the same. Because the size of the unit is so compact, an LED system will fit on most presses. The Baldwin design positions the LEDs so that energy is concentrated and compensates for gripper bars that might otherwise cast shadows and limit the effectiveness of the system.
“We have designed the optics to focus at the sheet 125mm from the diodes and can achieve the intensity of power at the wavelengths needed,” says Keogh. “And we do not need to run at full power, so have built in redundancy so that if one diode should fail the three closest to it can increase power and compensate.”
This feature has introduced Baldwin to the flatbed inkjet sector where technology is under development. It has also led to acceptance in screen printing because the LEDs it uses can penetrate into the thicker layer of ink that is typical in industrial screen printing. “We aim to show something at Fespa,” he adds.
The technology has gained acceptance at this format and is starting to move into larger formats. Most B1 printers using new generation UV have taken to H-UV because of the current limitations around LED. In the UK B1 H-UV customers include Clays and Image Data Group while Berforts has an SRA1 Komori.
H-UV will also migrate into packaging where the economics of moving from three and more lamp systems to a single lamp represents an attractive potential energy saving. “There are also developments underway with low migration inks for H-UV, but less so for LED,” says Keogh.
Nevertheless LED is growing. It has the support of KBA as well as the Japanese suppliers and Heidelberg is understood to be working on LED technology, preparing for a launch at Drupa. Inks and varnish manufacturers are working to overcome the acknowledged limitations while diode developers are coming up with more powerful LEDs.
It underlines that new generation UV is breathing new life into sheetfed litho and making the process viable in an age where digital printing threatens to become the de facto printing process.
“There are also developments underway with low migration inks for H-UV, but not for LED,” says Baldwin's Pat Keogh.
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Komori H-UV in action at Hertford Offset. Baldwin worked with Komori to perfect this system.
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