CR-39 Standard Plastic Lenses
Most people refer to this lens type as "Regular" or "Plastic" Lenses. The patent of CR-39 allyl diglycol carbonate monomer in 1945 marked a key milestone in the history of the optical industry. This new optical monomer inspired a great deal of creativity and ingenuity, which led to many of the great plastic lens products available today.
Plastic lenses made from CR-39 allyl diglycol carbonate monomer combine the optics of glass with the excellent mechanical, thermal and chemical resistance properties of a thermoset material. CR-39 monomer is used for casting plastic lenses for prescription eyewear, sunglasses and other plastic products requiring high abrasion resistance and high quality optical properties. Plastic lenses from CR-39 monomer give less chromatic aberration compared to polycarbonate lenses, as measured by the Abbe number.
The lens is light weight compared to glass, and may be made in just about any prescription, though many people with higher prescriptions prefer to use . The higher the index, the thinner the lenses. Plastic lenses are great for prescription sunglasses due to their tintability factor and you can virtually tint a plastic lens to any color under the rainbow.
There is a large selection of lens styles that are available in plastic, which increases it versatility and usage. Although it lacks the built-in UVA/UVB blocking properties of other materials, plastics can be treated with UV protective coatings. Plastic also accepts tints easier than any other material.
Compared with other materials, plastic is the choice for the budget-conscious consumer, or the fashion consumer looking for tinted eyewear. Despite the versatility of plastic lenses, they are NOT suitable for drill rimless styles because the material tends to crack and star which compromises the lens and eyewear. Other materials such as polycarbonate, trivex or high index materials are more suited for this style of eyewear.
1. Good optics, lighter than glass
2. Available in many styles
3. Easy to tint