Photochromic naphthopyran compositions of neutral color
CA 2248117 C · Owner: Ppg Industries, Inc. · Inventors: Kish, Delbert G.; Van Gemert, Barry
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
Described are novel compositions of a carrier and at least two photochromic naphthopyran compounds, selected on the basis of specific criteria that when , exposed to solar ultraviolet radiation exhibit neutral colors of gray or , brown contained within the a* and b* ranges of +10 to -10 in the CIELAB color system. Also described are carriers, i.e. organic solvents and organic polymeric host materials, such as optically clear articles e.g. ophthalmic , lenses or other plastic transparencies that contain or that are coated with the naphthopyran compounds.
Read the whole patent
Listed from its CIPO record in Patent Yard's archive of Canadian patents past their term. Its claims, description and drawings are in the CIPO record and on Google Patents, and the Claude kit works from them.
Why it's free to use
- Filed March 26, 1997 and granted May 20, 2003. A Canadian patent filed from October 1, 1989 lasts 20 years from filing, so its term ended March 26, 2017.
- A certificate of supplementary protection adds at most two years for a drug, so even that would have ended by March 26, 2019.
- We check Canadian rights only. A patent in its family in another country could still be in force: check its family on Google Patents.
Timeline
Timeline From CIPO dates
Sources & verification
Official CIPO records
Everything on this page comes from the CIPO record linked above. Contains information licensed under the Open Government Licence – Canada.