US Patent 8186598 - Credit card with quantum dot indicia

http://www.freepatentsonline.com/8186598.html

There has been an interest in developing transparent credit and bank cards but there is difficulty for these cards to be read by ATM machines. This patent from American Express teaches using quantum dot ink for detection by ATM sensors. Claim 1 reads:

1. A card having a portion comprising:

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

a first infrared blocking compound associated with said layer, wherein said first infrared blocking compound comprises a quantum dot compound.