American Hoechst Corporation

Optical Devices, LLC

Lawrence Bolt

Ali Tavasolian

Michael Smith

Michael R Martin

Michael J Hopper

Philip W Morlan, Jr

Daniel T Reiner

There is disclosed a tamper-free identification system, such as an ID card, comprising an information-bearing substrate made of a flexible but substantially rigid material, a partial light reflector superposed over said substrate which produces a substantially nondepolarizing light reflection, and a substantially transparent 90.degree. retarder superposed over said reflector. Said identification card can be manufactured at low cost using techniques known in the art, and with the aid of a simple and inexpensive analyzer such as a linear light polarizer, fraudulent alternations of the identification card can readily be detected.

Identification system comprising a partially reflective retardation

The invention relates to a highly hydrolytically stable polarizer element having a moisture barrier flurocarbon film as its supporting substrate.

High stability polarizer

A polarizer having increased hydrolytic stability is produced by impregnating a polyvinyl alcohol film with an iodine containing composition and then subjecting the substrate to both concentrated infrared and ultraviolet radiation treatments.

Hydrolytically stabilized polarizer

A polarizer having increased hydrolytic stability is produced by impregnating a polyvinyl alcohol substrate with an iodine containing composition and then subjecting the substrate to both concentrated infrared and ultraviolet radiation treatments sufficient to substantially increase the hydrolytic stability of the thusly formed polarizer. The polyvinyl alcohol film had been laminated to a polyester support with a dispersed, aqueous composition of polyvinyl alcohol or polyurethane on its surface.

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Van Nuys, CA, United States of America

Lawrence Bolt