Plano-convex base sheet for retroreflective articles and method for making same
CA 2092816 C · Owner: Minnesota Mining And Manufacturing Company · Inventors: Lu, Shih-Lai
Overview
Its claims, description and drawings are in the Canadian Patents Database.
Open the CIPO recordAbstract From the Canadian patent
An article comprising a transparent piano-convex base sheet having first and second broad faces, the second face being substantially planar and the first face having an array of substantially hemispheroidal microlenses thereon, the shape of the microlenses and thickness of the base sheet being such that collimated light substantially orthogonally incident to the array is focused approximately at the second face. The article optionally further comprising a specularly reflective layer on the second face which renders the base sheet retroreflective. An optional layer of adhesive over the reflective layer permits the article to be adhered to a document as a tamper-indicating, authenticating …
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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 October 7, 1991 and granted April 23, 2002. A Canadian patent filed from October 1, 1989 lasts 20 years from filing, so its term ended October 7, 2011.
- A certificate of supplementary protection adds at most two years for a drug, so even that would have ended by October 7, 2013.
- 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.