Optically-readable cards
US4505498A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Sep 15, 1982 |
| Grant date | Mar 19, 1985 |
| Priority date | — |
| Expiry date | Sep 15, 2002 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S283/904
- WIPO fieldControl
- WIPO sectorInstruments
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.