The increasing availability and affordability of UV curing in offset presses is seeing many printers adopting these versatile inks for the first time.
Since the introduction of new compact and cool-running curing lamp technologies, UV inks have stopped being regarded as specialist choices for printing on mainly plastics and are becoming almost mainstream choices for short-run work.
The benefits are plain: the ink cures almost instantly on a wide range of substrates and allows same-day finishing and delivery, which is particularly important to web-to-print operations. There’s no need for spray powder or drying additives in the ink. Modern LE and LED lamps also require much less electricity than conventional heat/IR driers.
On the other hand, UV inks and their curing system have also long been noted for potential health risks to operators and handlers during printing. Are the new technologies doing anything to address these concerns?
On the whole the ink is safe after proper curing, although there are plenty of recommendations and restrictions on using them for primary food packaging, garments and children’s toys in particular.
So let’s start with the scary bits. Unprotected skin and mucus membranes coming into contact with monomers and photoinitiators in uncured UV ink can cause problems such as dermatitis and potentially ‘sensitisation’, which can then trigger lifelong allergic reactions to even tiny amounts of uncured ink.
Offset presses in particular are prone to generating ink mist thrown off rapidly rotating cylinders. You really don’t want to breath this, so air extraction and filters are vital. Uncured mist can also coat nearby surfaces with hazardous sticky stuff. Ink can also get onto the protective clothing of press operators; it’s important to wash this separately from personal clothing to prevent contamination.
Originally, high-pressure mercury vapour lamps had another health hazard. At particular wavelengths of UV, normal atmospheric oxygen (O2) combines to form ozone (O3). This is a very aggressive oxidiser that dries out eyes and breathing passages, causing discomfort and risking infection. Again, extractors are needed, venting to the outside air where ozone quickly reverts to harmless O2.
Modern mercury vapour lamps have special filter glass that reduces or eliminates ozone generation. Low-energy UV lamps (which use low-pressure mercury vapour), and UV-LEDs don’t generate ozone at all.
Ultra violet light itself is also potentially hazardous. Depending on the wavelength, it can damage any exposed skin and in particular eyes. Press manufacturers routinely enclose the lamp areas, apply non-reflective paint and fit UV-filtered inspection glass or plastic, to reduce the risk of direct or reflected exposure to UV light.
As you’d expect, UV inks and lamps are subject to regulations and recommendations from the Health & Safety Executive. HSE communications assistant Jack Rimmer reported on the organisation’s current position on developments in UV lamps in particular: “From a regulatory point of view we would expect any users of UV lamps in the workplace to have carried out a risk assessment as a requirement of The Control of Artificial Optical Radiation at Work Regulations, 2010.
“This has a specific need to consider the exposure limit values (ELVs). Commonly used control measures for operators of such systems can include full face shields, safety eyewear, protective gloves and the wearing of long sleeves.”
Also relevant he said, is the non-binding guide to good practice for implementing Directive 2006/25/EC. “This gives a sound overview of how assessments should be approached and explains which ELVs should be applied.
“The increased use of low-energy UV lamps and their associated inks should be viewed as a positive development in helping to comply with COSHH and radiation regulations, as both developments lead to potential reductions in levels of UV and ozone exposure.”
There’s a lot of information on the HSE website, including a set of ‘P series’ print-related sheets and publications (search for ‘UV ink’ at www.hse.gov.uk). “These represent all our guidance on UV-cured inks,” Rimmer says. “As far as we are aware no work is being undertaken to revise these COSHH essentials publications in light of any new technology.”
That said, the most recent HSE data we’ve been able to find online for UV offset presses is dated 2002, which was before LE and UV-LEDs were available. Rimmer says: “Printing is not currently a priority industry for a programmed inspection campaign on health or other risks and therefore no analysis has been carried out of current trends and compliance with the above COSSH Essentials sheets.
“As with any risk, we will continue to monitor and will respond in future if it becomes apparent these are causing different or greater issues.”
Heidelberg, like most major press makers, now offers a choice of several factory-fitted UV types on its offset presses. There are still traditional mercury lamps, but the big push has been in LE and UV-LED, says Matt Rockley, presses product specialist at Heidelberg UK.
“Heidelberg has GS and CE certification on XL presses with UV,” Rockley says. “It is mandatory and you can’t order the machine without them. There is always ink mist extraction on the machines. When we run high speed – most of ours do 18,000sph with UV – a there is a possibility that ink and water reach a critical limit and you get mist. The guards are enclosed and we fit an extraction system that goes from the press and through a filter mat that traps any airborne particles. This reduces the ink mist exiting the actual printing units.”
Heidelberg takes its safety responsibilities and education very seriously, says Rockley. “Pre and post the sales process we go in and explain this to all the operators and to the production guys as well as the bosses, so that everybody understands what it is, how it works and what can be expected from it. We commissioned a white paper and general handling and safety documentation that is shared with UK customers.
“In terms of handling and so on, we go through the process advantages of course, but we make sure the guys know that they have to use the correct gloves, they know that the machines have had the correct equipment fitted to them such as ink mist extractors.
“We go through the consumables and explain what the conformities are, what the storage of these products need to be, how they need to be handled, the plates, the washes that need to be more aggressive to make sure that they make sure they’re wearing the correct gloves, glasses and so on and so forth.”
Ryobi (now called RMGT) was one of the first companies to offer UV-LEDs as factory-build options for its presses. “This means no ozone and no heat, which affect the environment as well as quality,” says Neil Handforth, sales & marketing director of UK distributor Apex Digital. “Compared to other UV systems, it’s safer and a very simple process. There are no filters to maintain and no warm-up or cool-down period for the lamps
“Every UV-LED press we sell has mist filters fitted to each inking unit. So as much as possible is taken out into a set of disposable filters. It’s not an option, we supply the presses with those devices already fitted.”
Stray UV isn’t a problem, he says. “The LED drier is deep in the press and you can’t see it apart from a strip of Perspex built into the delivery guard where you can just see that the lights go off.”
The main part of the advice tends to come from the ink suppliers, he says. “We don’t get involved in that so the inks and the precautions come from the suppliers. Other than that we would just say to people to use all sensible precautions: avoid skin contact, wipe up any spillages, wear gloves if you are involved in mixing and just generally follow the guidelines that are given to you by the ink manufacturers. We give that advice in whatever process they are using whether conventional or UV.”
Peter Minis, marketing manager for Komori International (Europe) says that its European Graphic Centre in Utrecht, Holland, does lot of work with customers on UV implementation. “By testing European products and supplies, and offering extensive training towards our customers, Komori is able to contribute in making employees competent in health and safety,” he says. “This is tailored to the purchased configuration and level of experience.”
Mark Walkling, product manager at ink maker Sun Chemical says: “As with any mixture of chemicals, whether UV, solvent or water based, you need to take protection against contact.
“With UV the protection required is probably less severe than for solvent because of the VOCs. If you look at the purity of materials compared to 20 years ago they are much, much better, but you still need to take precautions.”
The overall message is that refinement of the inks and the new lamp technologies have helped to reduce the risks, so while they still need care, operator handling issues are now much the same level as for conventional inks.