Whilst at the 2016 AIMCAL Web Coating & Handling Conference Europe a couple of weeks ago, it was good to listen to an excellent presentation from Dr. Joseph Brindley of Gencoa on the use of plasma emission in the plasma treater as a method of controlling the process. In the same way that magnetron sputter coating processes can be controlled by the use of plasma emission by keeping constant the ratio between two active emission lines, so too can the plasma treater be kept constant. This technique does open up the possibility of doing more with the plasma emission monitor system, such as looking for the amount of organic material being removed or the by-products of any decomposition or recombination of organics into volatile species. This might then enable the plasma emission also to be a method of determining how contaminated the surface is with organic material, and then allow the power to the plasma treater to be tuned accordingly.
The system developed is more useful than standard plasma emission monitors (PEMs) in that it can be used for more general diagnostics than PEMs. The Optix system has its own plasma generator and so does not require the source of the information to be a plasma but can sample any gas from any part of the system and by passing through the plasma generator it ionises the gas and enables spectroscopic analysis to be carried out. The system does not require additional pumping and it can operate at high pressure making more versatile than residual gas analyzers and lower cost as there is no pumping system required.
I know that the incoming film is often a mystery in terms of surface quality and moisture content and these can be difficult and slow to measure. This is why it is rarely done. Using the PEM it is possible to get some measure of moisture content as the web starts to unwind and compare this to previous rolls as well as ratio it to other gases present. If the PEM is sited in the plasma treater then it can also be programmed to look for hydrocarbons or fractions to see it the surface contamination is high or low. As there will be a gas feed to the plasma treatment zone this too can monitor the water content relative to one of the incoming gases to see how this is varying from roll to roll.
I think this has the potential to be a method of being able to monitor the incoming film variability and so be better able to tune the plasma treatment and optimize it for every roll.
I look forward to the reports at future conferences on the progress of this step forward in being able to customize the plasma treatment of incoming film of variable quality.