Polycarbonate lenses were introduced
sometime in the 1980s
by the Gentex Corporation. This new eyeglass lens material had a high index of refraction, making it to be the lightest and thinnest lens material available then.
When did polycarbonate lenses start?
Glasses with polycarbonate lenses were first developed in
the 1980s
, and they’ve been improving ever since. All standard coatings, such as anti-reflective coating, scratch-resistant coating, and tints can be applied to these lenses.
How can I tell if I have polycarbonate lenses?
Try to edge it by hand, if it has strips adhered to edge, it’s poly. Hit it with a hammer, if it doesn’t break and bounces, it’s probably poly. If the optics aren’t as clear as glass or plastic, it’s poly. If
it’s minus check the center thickness
.
When was cr39 invented?
The abbreviation stands for “Columbia Resin #39”, which was the 39th formula of a thermosetting plastic developed by the Columbia Resins project in
1940
.
Which is better CR 39 or polycarbonate?
In comparison to
polycarbonate
, CR-39 provides vastly superior optics, rating just one rung below the material with the highest ABBE value: crown glass. … If you choose CR-39 lenses you commonly find that UV-protection comes at an added cost because, unlike polycarbonate, they aren’t inherently UV-protected.
What are the disadvantages of polycarbonate lenses?
The disadvantages of polycarbonate lenses include the fact that
their abrasion resistance is poor
, but when an anti scratch coating is added to this the impact resistance is reduced slightly. These types of lenses cannot be tinted easily.
Is PVC stronger than polycarbonate?
Though not quite as effective as polycarbonate roofing sheets in resisting impact, the majority of PVC roofing sheets will remain intact in most cases of collision. Unlike polycarbonate sheets, however, PVC roofing sheets
are usually scratch resistant
.
At what prescription should you get high index lenses?
A high-index lens may be recommended if your optical prescription is
above 2.00 diopters
. High-index lenses have a refractive index above 1.50— ranging from 1.53 to 1.74.
How can you tell the difference between polycarbonate and plastic lenses?
Polycarbonate lenses are made of a type of plastic that is more impact-resistant than standard plastic lenses. Polycarbonate lenses are also
much thinner and lighter in weight
. They are considered a high index plastic. Polycarbonate lenses also have built-in ultraviolet protection.
Why are high index lenses so expensive?
Why does all of this matter? Ultimately, high index lenses are
more expensive than other types of lenses due to their inherent material
. The material that is used to produce high index lenses is from a chemical synthetic blend, and the cost to simply produce sheets of the material is high.
What does CR-39 stand for?
An alternative material to polycarbonate is CR39 (
Columbia Resin 39
), a plastic polymer commonly used in the manufacture of eyeglass lenses. Unlike polycarbonate, CR39 requires a UV coating to be added to protect eyes from the sun’s harmful rays.
Who invented CR-39?
CR-39 plastic is actually ADC (Allyl Diglycol Carbonate), invented by an Ohio based company named
Columbia Southern Chemical Company (CSCC) a subsidiary of Pittsburg Plate Glass Company (PPGC)
. CSCC initiated a project named Columbia Resins and achieved its goal on the 39th attempt, hence leading to CR-39.
Does CR-39 block UV?
Results: All the tested lenses absorbed all of the UV-B and
at least 99% of UV-A
. … Conclusions: These data suggest that UV tinted CR-39 lenses provide protection against UV radiation that meets the ANSI Z80. 3-1996 Standard for non-prescription sunglasses and fashion eyewear.
Do I really need polycarbonate lenses?
Greater Protection
: Polycarbonate lenses do not break or shatter easily into harmful pieces on impact. … These eyeglass lenses are also thinner making it less heavy than standard plastic or glass lenses. Inherent Ultraviolet (UV) protection: Polycarbonate lens surfaces offer inbuilt ultraviolet protection.
Is polycarbonate better than CR39?
Polycarbonate lenses have a higher index of refraction (1.586) than CR-39 plastic
(1.498) and are therefore thinner in an equal lens prescription. With a higher index (of refraction), light is bent more efficiently, therefore it requires less material to achieve the eyeglass prescription making the lenses much lighter.
Can polycarbonate lenses crack?
Material Matters
Certain lens materials are more prone to stress fracturing than others. For example, standard plastic is most prone to cracking, polycarbonate is one of the biggest culprits when it comes to stress fracturing but
the crack spreads slowly
.
