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Photoinitiators – the cure all for inks?

Some swear LED-UV is a more efficient technology, others still aren’t ready to invest. Here is a closer look at the pros and cons of conventional UV and UV-LED curing technologies.

Since its introduction in the 1960s UV or ultraviolet curing has been widely adopted for curing or drying products which are used in a wide range of industries. It’s easy to see why its use has become widespread as it has many benefits over traditional ‘air’ drying techniques, including increased production speeds, reduced rejection rates, higher print quality and a glossier finish.  It also provides much better adhesion to substrates that are notoriously difficult in this regard, such as plastics and other non-absorbent substrates.

In order to accommodate the power output and bandwidth of current LED technology, inks need to be more reactive than those formulated to cure with standard mercury lamps.

The main difference between UV lamps and UV-LED’s is the way in which the UV light is generated.  UV-LED’s, using a variant of the LED technology currently used in domestic lighting, are specially tuned to emit UV light in a very narrow bandwidth. Conventional medium pressure mercury lamps produce UV light across a much wider wavelength range, based on emissions produced by an energy change in the mercury inside the lamp.

UV-LED’s produce a narrow band of power output, so there are only a limited number of photoinitiators that are currently suitable for use with them.  However this may change, as ongoing development work leads to LED’s emitting a broader range of wavelengths, which will allow the use of a wider range of initiators, providing a better curing profile for inks and varnishes.