Scratch Resistant Coatings Question ?

[Bobb]

Hello:

What can anyone tell me regarding the "scratch resistant" coatings applied to Pastic lenses?

Is this usually a silicon dioxide thin film coating, or a "dip" of some kind?

Do polarized, plastic, sunglass lenses normally (automatically) come with it these days?

Might anyone know if Younger polarized NuPolar plastic lenses come with it from Younger automatically? (hard to reach them)

Thanks,
Bob

[Steve Machol]

Hi Bobb!

I actually saw you post these questions on the sci.med.vision newsgroup.

The hard coating on plastic lenses is definitely not silicon dioxide (quartz). They are liquid polymers applied in both spin and dip coating processes.

As for hard coatings on plastic polarized sunglasses lenses - my guess is that typical drugstore sunglass lenses do not have hard coatings. On the other hand virtually every ophthalmic quality polarized lens does come with a hard coating - at least on the front surface. You'd need to ask your eyecare provider to know for sure what's included.

As for NuPloar - yes to the hard coating on the front surface. Whether a coating is appled to the back surface depends on the laboratory that processes the lenses.

[Duane Metcalfe]

Bobb,
I wish to add a comment to Steve's reply about hard coats. Most coatings applied to lenses are of the IR +/- 1.50, although there are some lens mfg's matching HC IR to lens IR. Factory applied front /back coatings will typically be of a thermally cured nature, 'tho some will be of a UV cured nature. Processing labs will apply a backside coating on surfaced jobs, if requested, and those coatings are typically UV cured for speed in processing and lab efficiency using backside coating machines mfg'd by G-C, Ultra Optics, etc., which are a spin type application followed by the UV cure. There have been recent introductions of thermal coating applicators and their important relevance to AR and mirror coatings. ALL do a good job as intended, your preference should be dictated by additions of add on's.
Hope this is informative for you.

Duane