Controlled passivation of vacuum deposited aluminum.
SigmAlOx™ fortified aluminum layers show excellent stability against corrosion. Table shows electrical resistance of 1.4 optical density aluminum after full immersion in 92˚c water for 90 seconds. Note little increase in resistance with the SigmAlOx™ treated sample.
The SigmAlOx™ process is a dry, inline, process for building a pure aluminum oxide barrier layer onto thin film aluminum to create a more resilient, stable, and higher performing "fortified," aluminum layer for applications that include barrier films for flexible packaging, window films and metallized capacitor films. In addition to improved barrier and corrosion resistance, the SigmAlOx™ process completely eliminates blocking, or metal "pick-off," which is common in metallized aluminum films.
How it works.
SigmAlOx™ layers are created using a pure oxygen plasma immediately after metal deposition - before the fresh, highly reactive aluminum, layer is able to react with anything else (moisture, contaminated process rollers, the backside of the substrate, etc.). The result is a thin, highly uniform and pure, aluminum oxide barrier layer.
Why it works.
Aluminum is extremely reactive. Because deposition happens in a vacuum it has little to react with until it is exposed to ambient conditions, at which point the aluminum is "passivated." Unfortunately, if passivation occurs in a moisture-containing environment (and it always does) aluminum hydroxides form, which can be porous compared to a pure aluminum oxide formed in the absence of moisture. SigmAlOx™ aluminum oxide layers are less porous, more dense, and offer greater protection compared to passivating layers that form in natural ambient conditions.