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L.3 Electrochromic LCD

The dull grey background of the field effect LCDs forced the industry to develop a high contrast display: the electrochromic display. The first electrochromic LCDs applied in watch- displays, were manufactured in 1982 by the Japanese company Sharp for Seiko Japan.

1The only watch with this display ever produced in commercial quantities, was the ECD F623A by Seiko. The function is based on an electro-chemical process of the deposition (oxidation-reduction) of tungstentrioxide on the electrodes when the electrical current is flowing in one direction, and the removing of this material when the current is flowing in the opposite way. This process is comparable to the process of plating / deplating. In contrast with the field effect display, this display has a higher power dissipation and shows greater unreliability in the long term. The advantage is that the digits stay visible, even when no voltage is applied. The production stopped after two years. ETA manufactured a prototype with an electrochromic display in its 'Swissonic 2000' line, which was displayed at the Basle Fair of 1972. The research had been conducted by CEH and Optel and had been based on preceeding American Cyanamid patents.

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Copyright by Pieter Doensen

email: doensen@xs4all.nl

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