Few will have failed to see that UV LED (UltraViolet Light Emitting Diode) curing is being heralded as an alternative to Mercury curing. We wanted to see how the hype matched up to the reality.

But first let’s looks at the UV LED process. It occurs in the same way as a standard mercury lamp. The ink, coating or adhesive when exposed to the UV lamp undergoes a polymerization reaction.

The main difference between the two is the wave lengths emitted from the lamps which are available for curing to take place. A standard lamp has a broad spectrum of wavelengths which spread from UV-C through UV-B and UV-A and visible infrared. As a result, an ink or coating formulation can have a mixture of photoinitiators that cure over this range of wave lengths.

Commercial LED lamps today for narrow web have a narrow wavelength range, with a peak around 385 to 395nm. So, the ink and coating technologies have been reformulated to ensure the reactivity and cure results meet printer’s requirements at this LED output. 

That's the technical differences, but more excitingly for printers is the performance, productivity and environmental advantages.

Firstly, the UV LED with its high peak irradiance, and UV-A and visible light emission, provides a deeper penetrating light source for a better cure of thicker films and darker more opaque colours. For combination printing this means faster speeds and assuredness of cure and adhesion. Secondly, there is improved uptime as UV LED lamps do not need any warm up time, there is no performance degradation so curing is consistent and the lamps last ten times longer than mercury lamps. UV LED also require 50% to 80% less energy than conventional mercury lamps.

Thirdly UV LED removes the need for mercury in the process and there is no requirement to deal with hazardous waste disposal. There are also no o-zone emissions, lamps are not as hot so safer for printer operators and while looking at the blue UV LED light is not recommended the process does not emit UV-C light which is dangerous for eyes. 

After a review of the technology it is clear there are some compelling reasons why UV LED should be carefully considered. Collectively they create a more efficient and sustainable operation that delivers a return on investment in under 12 months.

As for the question over whether there will be any regulatory moves to impact mercury curing, the jury is still out. The official line is that they will be allowed until there is a viable option available. However, considering what I have just covered, I don’t think it will be long before a more definitive position will be taken.

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