US Patent 8066190 - Transparent credit card with nanostructured ink marking

http://www.freepatentsonline.com/8066190.html

Transparency is a desirable feature of credit and debit cards but can make the inclusion of encoding indicia difficult. This patent from American Express teaches using quantum dots and indium tin oxide nanoparticles in an ink for creating transparent security indicia on these cards readable by UV light. Claim 1 reads:

1. A transaction card having a portion comprising:

a layer that is at least one of translucent and transparent;

a first infrared blocking compound associated with said layer;

a second infrared blocking compound associated with said layer,

wherein said first infrared blocking compound further comprises nanocrystalline indium tin oxide particles,

wherein said second infrared blocking compound comprises a quantum dot compound.