What chemical substance is there in photochromatic lens?

Asked by  | 20th Mar, 2008, 10:59: PM

Expert Answer:

consists of introducing a photochromic film to a polycarbonate lens during the molding process. As a result the photochromic layer is 0.4 mm below, rather than on, the front surface . This ensures that the photochromic dye is protected behind a strong layer of polycarbonate.hotochromic dyes work by changing their chemical structure when exposed to UV light. When these special molecules are exposed to UV rays, they undergo a chemical process that causes them to change shape. The new molecular structure absorbs portions of the visible light, causing the lenses to darken. The number of molecules that change shape varies with the intensity of the UV rays. In the absence of UV light, the molecules change back to their original form. Photochromic dyes will change back to their original form faster at higher temperatures.

A photochromic complex is a kind of chemical compound that has photoresponsive parts on its ligand. These complexes have a specific structure: photoswitchable organic compounds are attached to metal complexes. For the photocontrollable parts, thermally and photochemically stable chromophores (azobenzene, diarylethene, spiropyran, etc.) are usually used. And for the metal complexes, a wide variety of compounds that have various functions (redox response, luminescence, magnetism, etc.) are applied.

Answered by  | 29th May, 2008, 09:42: AM

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