LED makes plates entrance

High performance fluorescent lamps were always used in the print down frame, a staple of any print business until computer to plate took over. 

Plate exposure and UV lamps are not confined to litho printing, however. Flexo printing still uses print down frames, albeit heavily modified and developed, in exposing its plates in digital imaging systems because of the processes involved in plate production. Mercury vapour tubes continue to be used in these applications and like UV curing are likely to get a stay of execution until beyond 2027, if suitable lamps are being manufactured.

However, as with curing, LED is encroaching into platemaking. A new generation of plate imagers is using LED instead. The nature of many in flexible packaging and producing flexo plates means that frequent replacement investment is not generally necessary. Even if perhaps the new technology is shown to be significantly better.

Esko argues this case for its XPS Crystal exposure unit. Its LED array, which needs no warm up, scans over the surface of plate rather than flooding it with high intensity UV light. This ensures consistent exposure over the plate area while the degradation inherent in the fluorescent lamp will mean that exposure can vary, from week to week, if not for one plate after another. Consistency for repeat work is difficult.

Xsys, the former Flint and Xeikon flexo division, makes the same point about its Catena E LED exposure unit, saying that the accuracy of the exposure enables consistent resolution of even dots and the small dots needed for fine screening rulings.

However, such technology is by no means universal and many flexo plate houses will prefer to stay with the UV technology they know.