Sunglasses were designed to block the sun’s glare and glare. Since people know how harmful the sun can be for our eyes, they are becoming aware of the use of sunglasses with UV protection. We know that each glass has a different protection factor, but have you ever thought about how sunglasses are made?
Sunglasses can be made of different materials, although the most common are plastic or metal, with lenses made of some type of polycarbonate, basically painted plastic. Glass lenses still exist, but it is increasingly rare to find glass models, since polycarbonate is stronger, lighter and more durable.
Polycarbonate is composed of soluble organic dyes, to which metal oxide pigments are added. The function of these materials is to block or reflect certain frequencies of the sun’s rays, especially blue light since it is the lowest frequency. Materials that offer UV protection are sometimes found in these raw materials, but in other materials UV protection must be applied before the lens are manufactured.
The additives added to the lens should not distort the colors too much because we could have problems such as not being able to differentiate the colors of a traffic light. Gray lenses are the least distortionary for most people, but amber and brown lenses also work well as they are best at stopping blue rays, but distort the other colors. There are some chemicals that are added to lenses to make polarized lenses that better reduce reflections and flare.
1. Anti-reflective back: A few layers of coating on the concave surface of the back of the lens protect the eye from glare and light coming from behind. This technology is applied on Ray ban sunglasses.
2. Colored layer: Gray is the best to appreciate the real colors. Yellow enhances contrast and is best suited for low-light outdoor activities. Vermilion (a mix of peach and pink) is best for cloudy days or sports like skiing. Green and brown colors work well in low or high light.
3. Lenses: Generally made of glass, plastic or polycarbonate. Glass offers the least UV protection, but is the most scratch resistant. Plastic is the best UV filter and is the cheapest option, but also the least resistant. Polycarbonate is the lightest and most durable, and it also filters out UV rays almost completely.
4. Polarizing layer: Multiple thin layers block horizontal light rays (rays that are reflected off other surfaces, such as water) to prevent reflections. If the horizontal and vertical rays were blocked, we would not be able to see well.
5. UV Coating: A coating is applied that filters out two types of ultraviolet rays: A and B.
6. Anti-reflective coating: Multiple layers of various metal oxides reduce glare, and in some cases repel water.
7. Anti-scratch coating: Typically made from an ultra-thin polymer called Teflon, a type of tough plastic that reduces scratches on the lens.
Sunglasses, especially the prescription ones, have gone through a series of processes before reaching consumers. Material technology plays an important role in these processes.