摘要 |
A thin, flexible, portable device (11) may be used as a credit card. The device is encapsulated by front and rear plastics layers. Viewed from the front the device comprises a first electrode of a transparent electrically conductive layer (13); a layer (14) of an electrochromic, metal-sensitive compound which is capable of dissolving metal atoms and which changes color in so doing; a layer of a solid, fast ion conducting electrolyte (15); a second layer of electrochromic material (16), acting as a second electrode; and a layer of electrically conductive material (17). The solid electrolyte layer (15) is substantially non-conductive at room temperature but is highly conductive of metal ions at a raised temperature. To erase information, the entire device is heated to 150 DEG C., and a potential difference is applied between the front electrode (14) and the rear electrode (16), driving all metal atoms out of the front electrochromic material into the rear electrode (16). To write information, a reverse potential is applied and selected localized areas of the device are heated, so that coloration atoms are driven into the electrochromic layer (14) only at selected areas.
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