| abstract |
An optical element comprising a substrate which is provided with a transparent coating (9) containing a photochromic material, the transmission of said optical element varying in the visible region in response to a variation in light. The optical element is characterized in that the coating (9) comprises an inorganic network of a silicon oxide and an organic polymer which is chemically bonded to the inorganic network via Si-C bonds. Preferably, also macroscopic particles of a metal oxide are incorporated in the network, the metal preferably being selected from the group formed by Al, Si, Ti, Zr, In and Sn. Preferably, metal-oxide particles are used whose size is above 5 nm. Such photochromic coatings (9) are scratch-resistant and demonstrate a good switching behavior. The coatings are used, for example, on display windows (3) of display devices (1) and on sunglasses. Methods of manufacturing said layers are described. |