A/R and UV

[April_01]

If someone wants a plastic lens with a/r, can you put a uv protection coat on the lens also?

[Jana Lewis]

From what I understand, A/R denotes the UV.

[For-Life]

From what I understand, A/R denotes the UV.

Yes, I am pretty sure that AR has 100 percent UV protection.

[Jedi]

From what I understand, all lenses offer a certain percentage of UV protection, coated or not coated. Poly is the only lens that filters out UV rays 100%. Glass, CR-39, Trivex, etc. all block UV to a certain extent. (70-90%, I'm trying to find the actually numbers, so please correct me if I am wrong). A UV treatment can protect certain lenses up to 100% of UV at 400nm. I assume that from the marketing materials provided by lens companies that AR coatings do not exhibit any benefit towards UV protection. I believe that the only major company with a UV component incorporated with their AR coating is Sola, UTMC w/UV 380. I also believe that the UV coating comprimises that ability for the AR coating to adhere to the lens and that is the reason we don't see Crizal, or HCC with a UV component.

I hope Chris and Darryl can provide some more technical background to these statements, but in a nutshell, if you want a full UV protected lens with AR go polycarb with your favorite coating.

[coda]

Poly will block the vast majority of UV and should in most (all?) cases meet the US UV380 and EU UV400 requirements. CR and most or possibly all mid and high index plastics filter some UV but require additional treatment to be truely UV blocking. Glass filters out much less UV than CR etc.

It is an industry assumption that UV blocking agents can cause problems with AR adhesion however there are a number of good 'factory' UV blocking hardcoats that act as acceptable substrates for AR. The real issue is the in lab anti-UV 'dip' processes followed by subsequent AR coating, historically this has been a real AR killer.

[Chris Ryser]

Yes, I am pretty sure that AR has 100 percent UV protection.

The best AR coating on the market has a 99.9% transmission. Any absorbtion of any kind wanted, has to be incorporated in the basic lens.

1. Lens with UV absorbtion or

2. UV treatment applied

3. Hard coat for adherance of AR coat

4. AR coating

From what I understand, all lenses offer a certain percentage of UV protection, coated or not coated. Poly is the only lens that filters out UV rays 100%.

That is correct.

In the old days plastic lenses as CR 39 used to yellow terribly . In the late 70's and early 80's lens manufacturers added clear benzophenone to the monomers for protection to prevent yellowing. Lenses now were absorbing UV B. (Skin will burn at 224nm) Most of the lenses I know of will provide this feature.

Therefore when you guy's are doing a UV treatment you want to cover UV A
from 360nm to 400nm.

Caution = All UV treatments that claim to be clear (non yellowish) will only absorb to 382nm and not to 400. Therfore you are giving a patient only half the value and protection of the UV A range by absorbing only up to 382nm and NOT the wanted 400.

If a lens absorbs UV to 400nm it will show a yellowish tinge, because 400nm is where the visible spectrum starts.

[coda]

The best AR coating on the market has a 99.9% transmission.

Well, that's actually rather an exageration. The best ARs will cut reflectance loss to about .5% but ALL lens materials absorb to some degree or another. If a lens transmits 98% (with AR) that's a real winner.

Additionally the numbers quoted for the AR transmission are only for the 'visible' range of the spectrum. The degree of reflection in the UV varies wildly with reflectance of around 30% at a wavelength of 300nm (for an average AR) to zero around 250 nm (and up and down as the wavelength gets lower).