Element having reversible and fixed light-extinction effects which are variable with temperature

Read the whole patent

Listed from its EPO record in Patent Yard's archive of European patents past their term. Its claims, description and drawings are in the EPO PDF and on Google Patents, and the Claude kit works from them.

Why it's free to use

• Filed January 10, 1980 and granted June 20, 1984. A European patent lasts at most 20 years from filing, so its term ended January 10, 2000.
• A supplementary protection certificate, which can extend a medicine or crop-protection patent, adds at most five and a half years, so even that would have ended by July 10, 2005.
• We check European rights only. A US or other national patent in its family could still be in force: check its family on Espacenet or Google Patents.