Optically-readable cards

Details Optically-readable cards Optically-readable cards

1982-09-15

1985-03-19

Bell, Paul A.

Printed matter

Having revealable concealed information, fraud preventer or...

Utilizing electromagnetic radiation

235488, 283904, B42D 1500

Patent

active

045054983

ABSTRACT:
An optically-readable value card for use in a vending system for vending goods or services includes a plurality of heat-sensitive optically-readable value elements each of which, upon heating to a first temperature above ambient, changes its color in a reversible manner, but upon heating to a second temperature above ambient and higher than the first temperature, changes to a second color in an irreversible manner. Each of the value elements is in the form of a light window having a layer of a thermochromic material which changes its color in a reversible manner when heated to the first temperature, and a layer of a thermographic material which changes its color in an irreversible manner when heated to the second temperature.

REFERENCES:
patent: 3873813 (1975-03-01), Lahr et al.
patent: 4103150 (1978-07-01), Von Ballmoos
patent: 4143810 (1979-03-01), Greenaway

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