摘要 |
Photochromic 3H-naphtho[2,1-b]pyran compounds corresponding to formula I in which the groups R<SUB>1 </SUB>to R<SUB>7 </SUB>and B' have defined meanings and the use of such photochromic compounds in synthetic resin articles of all types, particularly for ophthalmic purposes. The photochromic 3H-naphtho[2,1-b]pyran derivatives have particularly long-waved absorption maxima in the open form, and when used in photochromic eyeglass lenses, produce essentially blue color tones which have a high darkening capacity.
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