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Subject: Re: Coatings
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Date: 03/28/03 at 2:46 PM
Posted by: jim
In Reply to: Coatings posted by J Clements on 03/28/03 at 10:17 AM:
Dielectric coatings are applied in vacuum ~10^-4 torr with a partial pressure of Oxygen (most cases). Evaporation is normally used (resistive or electron beam) for coating "different color spectrums" appearance parts. This is due to the distribution pattern of a evapoartion source (~cosine distribution)on a flat surface. The difference in thickness causes a change in optical properties and creates the multi-colored patterns. This is normally considered a "junk coating" -or- decrative coating. Depending upon the application their may be a pre-coating or treatment and also a overcoating or treatment. This really depends upon the type/material of part you are coating(substrate)and the final use of the part. Most dielectric materials are hard and in many cases they are the final coating due to thier hard nature. example; anti-scratch coatings on eyeglasses are normally SiO2 applied by electron beam vacuum coating. Hope this helps.
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