Polycarbonate is one of the most commonly used materials for production of safety goggle lenses. This material is soft enough and has a porous surface structure. As a result any smallest particle hitting or scraping a lens leaves a visible mark.
Eventually, the glasses not protected with special coating get covered with a net of micro-scratches, which greatly reduces the lens transparency. To protect the lenses against scratches, they are covered with coating making it extremely flat and smooth — flying particles cannot «catch on» the emerging micro-elements of the surface and cause destruction.
Scratchproof coatings significantly improve safety glasses durability.