| abstract |
The present invention relates to specific photochromic phenanthropyrans as well as to their use in synthetic resin materials of all types, especially for ophthalmic purposes. In particular, the present invention relates to photochromic compounds derived from 2H-phenanthro[2,1-b]pyrans and 3H-phenanthro[3,4-b]pyrans, which in the open form have especially long wavelength absorption maxima, but in the unexcited state are still colorless. |