CR-39 sun lenses need a UV coating for full 400nm protection. So do the stock glass lenses of most Ray-Ban sunglasses. Does anyone know how long this coating lasts?
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CR-39 sun lenses need a UV coating for full 400nm protection. So do the stock glass lenses of most Ray-Ban sunglasses. Does anyone know how long this coating lasts?
It depends: some cr39 have full uv400 protection inside monomer cast, so you do not need coatings.Quote:
Originally Posted by Airegin
some are standard cr39 put in a bath of uv chemical (search for chris rysler topic on the board) and if it is done properly it works virtually forever.
UV coating inside hard coat or Ar can works, I do not know the Life time, I think it depends how care you put in lens over years.
Usually Uv-Ar coat are great to block the inside reflex of UV.
I hope this can help a little bit.
Very helpful, thank you. Do you put happen to know how Hoya and Polyvore apply UV400 in their CR-39 sun lenses? And Ray-Ban in their crown glass sun lenses?
Rayban standard crown glass have filter inside the mass of the glass material and on the polar-film- filter also for the polarized version (the polarized film is inside the lens) so they last forever.
Polycore and Hoya I don't know but I think is it is the same... they have to add some chemical on the cr39 mass for the sun production.
If you can have an uncoated sun lens with the uv400 logo they add the protection on the material itself and last forever.
For ex. Zeiss produce uvprotect a 100% clear! standard cr39 lens with uv400 protection.
As long as the molecule that is responsible for the UV excluding properties has a sufficiently long half-life relative to environmental factors (all chemicals eventually degrade, even if it requires cosmic radiation to shatter a molecule, leave it outside long enough [even if it is on the order of centuries or longer], it will happen), and the other constituents of the lens it needs to interact with, there is no reason to think it will necessarily degrade to the point of it being problematic on a human time-scale.
Essentially, you'd have to know the molecule being used that provides this property in order to make a reasonably accurate assessment as to its long term stability relative to external factors.
Who makes the best molecules? :rolleyes:Quote:
Originally Posted by Lelarep
Yes but I don't worry about this. This is an industrial standard from decades for all the manufactorQuote:
Originally Posted by Lelarep
Glass lenses are stable over years, plastic over years yellowing and this is helpfull for cut uv too.
the only concern is when you do the uv treatment on cr39 in-house, If someone do not follow all step and the right time, we can you have problems