Eyeglass Lenses

Plastic CR-39 Lens

CR-39 is a plastic polymer commonly used in eyeglass lenses.  It was developed by Columbia Resins in 1940.  The Armorlite Lens Company started manufacturing eyeglass lenses with CR-39 in 1947.  Today CR-39 is made by PPG industries.

CR-39 has an index of refraction of 1.498 and an Abbe number of 58.  Today there are many materials that are thinner, lighter and more impact resistant that CR-39.  One advantage of CR-39 is that the surface is very tough.  It is resistant to scratches, most solvents, and material fatigue.

For safety glasses, CR-39 is rated only for low-impact applications and must be ground to a 3 mm center thickness.  Lenses for nearsightedness are thicker on the edges, so using CR-39 produces a lens with a thick edge.

eyeglass lens