Spirofluorenopyrans
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United States of America Patent
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Nov 13, 2001
Grant Date -
N/A
app pub date -
Mar 2, 2001
filing date -
Jul 2, 1999
priority date (Note) -
Expired
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Abstract
The present invention relates to specific photochromic 3H-naphtho[2,1-b]pyran derivatives and to their use in plastics of all types, especially for ophthalmic purposes. In particular, the present invention relates to spiro compounds derived from naphthopyrans and having a fluorene structure, referred to as spirofluorenopyrans, in which an annelated ring system is joined by a spiro bond to the central carbon atom of the fluorene structure.
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