Closed Loop Operation: The Key Tool for UV-curing Processes under Oxygen Reduced Conditions

The core value of UV curing is that it enables users to do things that otherwise would be impossible or not as economical or efficient. Thin coatings, typical printing inks and overprint varnishes, are particularly affected because oxygen replenishment is most effective in the few micrometers below the film surfaces. Well known are the benefits from reducing the oxygen content near to the UV exposed ink or coating surface, but this depends on various factors. Since the curing speed can be described by an equation involving beside other variables the light intensity, oxygen level, photoinitiator concentration, pigment level and film thickness, the improvement in the cure performance can be imagined, if the oxygen content is reduced from 20% (air) to less than 1%. If the oxygen level is decreased the oxygen inhibition process is restricted, the needed photoinitiator concentration is reduced, the curing speed is higher and the production speed can be increased or the light intensity reduced. The BLK-U lamp, designed by 1ST Metz offers improved conditions for UV curing concurrent with reduced oxygen content. The oxygen in the UV-curing unit is replaced by an inert gas (nitrogen) while this concept waives on an additional quartz screen to separate the UV radiation chamber from the substrate. Furthermore the system is equipped with water cooling, requires no air extraction and in addition there is no ozone formation during the operation with reduced oxygen content. Further on BLK-U can also be driven without inert gas.