Back to results
US 5,254,390 AGranted
Plano-convex base sheet for retroreflective articles and method for making same
AssigneeMinnesota Mining and Manufacturing Company
InventorShih-Lai Lu
Life of this patent
Estimating the term…
Loading patent…
Loading patent…
AssigneeMinnesota Mining and Manufacturing Company
InventorShih-Lai Lu
Estimating the term…
An article comprising a transparent plano-convex base sheet having first and second broad faces, the second face being substantially planar and the first face having an array of substantially hemi-spheroidal 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, and protective overlay. Special images can be formed within the article to enhance the security provided thereby. Also, a method for forming such articles.
A transparent base sheet having first and second broad faces, said second face being substantially planar and said first face having an array of substantially hemi-spheroidal microlenses thereon, said microlenses being wider and shorter than portions of true spheres, the shape of said microlenses and thickness of said base sheet being such that collimated light substantially orthogonally incident to said array is focused approximately at said second face.
A document comprising:
Dependencies are inferred from the claim text.