Photochromic naphthopyrans
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United States of America Patent
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Dec 2, 2008
Grant Date -
May 2, 2002
app pub date -
Dec 13, 2001
filing date -
Jun 19, 1998
priority date (Note) -
Expired
status (Latency Note)
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Abstract
The present invention relates to photochromic 2H-naphtho[1,2-b]pyrans as well as their use in synthetic resins of all types, especially for ophthalmic purposes. In particular, the present invention relates to photochromic naphthopyran compounds, for which a further ring system is bonded to the f side of the naphthopyran. The inventive photochromic dyes generally have the general formula (I) ##STR00001## wherein n, R.sub.1, R.sub.2, R.sub.3, X, B and B' are defined as in claim 1. The inventive compounds are distinguished by good darkening and decolorizing properties and a very good service life.
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