US Patent 7837116 - Credit card with quantum dot IR blocking material

http://www.freepatentsonline.com/7837116.html

This patent from American Express is based on a series of continuations going back to 1999 and includes claims covering a transparent credit card having identification materials including quantum dots to provide proper sensing in an ATM as well as indicia for counting the cards on an assembly line during manufacture. Claim 1 reads:

1. A financial transaction card comprising:

a card body adapted to substantially transmit radiation in a visible light wavelength region;

said card body comprising a machine recognizable compound containing infrared blocking materials associated with said card body, said infrared blocking materials comprising a mixture of an IR-absorbing compound, a phosphor compound, and a quantum dot compound;

said machine recognizable compound blocks transmission of incident infrared radiation.