Sunglass scratches
July 19, 2006 1:19 PM   Subscribe

Why don't they make sunglasses with the coating on the *inside*?

So, my expensive (hip, cool, livin' to the max lifestyle statement) sunglasses got a scratch on the lenses which results in a bright spot that bothers me when I wear them. Which got me thinking; I don't know of any sunglass manufacturer who makes the glasses with the coating on the back of the glass (i.e., nearer your eye) as opposed to the front. BTW these are not a polarized glass.

OK, so its not UV that your eyes need the coating for - then what? Colour? If the coating was on the inside, yeah, you wouldn't get the groovy look, but conversely you would get sunglasses that even if scratched could conceivably polish to eliminate artifacts.

Having said that, is there a way that I can "colour" or polish the scratch out of my old funky specs? Or am I late with an idea that someone else has already had?
posted by fox_terrier_guy to Clothing, Beauty, & Fashion (3 answers total)
I think that the coating does a lot to prevent reflections and glare.

The reflection problem is more severe in camera lenses because you usually have multiple pieces of glass there, where light reflecting back and forth can lead to some nastiness.
posted by rbs at 1:42 PM on July 19, 2006

Why don't they make sunglasses with the coating on the *inside*?

So you'll buy a new pair when they scratch.
posted by Terminal Verbosity at 2:11 PM on July 19, 2006

Almost all plastic lenses used in eyewear such as sunglasses, including high-index, polycarbonate and traditional plastic materials such as CR-39, have built-in scratch-resistant coatings. Unfortunately, this does not apply to mirrored sunglasses. They have a very thin layer of metal vacuum evaporated on the lenses. Sunglass manufacturers have not been able to successfully apply a scratch-resistant layer on top of the reflective coating used on mirrored sunglasses. In consequence, mirrored sunglasses scratch more easily than non-mirrored sunglasses. This, of course, doesn't prevent manufacturers from placing the reflective coating on the backside. However, mirrored sunglasses generally have an anti-reflective coating on the backside. The anti-reflective coating eliminates lens reflections from light that enters from behind you and bounces off the surface into your eyes. Backside anti-reflective coated sunglass lenses are much more comfortable and less distracting than uncoated sunglasses. Unfortunately, this anti-reflective coating, like the scratch resistent coating, can't be placed on top of the reflective coating.

So manufactures could produce mirrored sunglasses with the relective coating on the backside of the lens, but because they would then have to omit the backside anti-reflective coating the customer would have to put up with backside reflection that are both annoying and uncomfortable.
posted by RichardP at 6:35 PM on July 19, 2006 [1 favorite]

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