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Increasing Speed of Electrochromic Displays

IP.com Disclosure Number: IPCOM000085339D
Original Publication Date: 1976-Mar-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Barclay, D: AUTHOR [+2]

Abstract

Electrochromic displays, wherein display is effected by the selective deposition of colored species on a display electrode, have been suggested. One form of such a display has the display electrodes arranged in rows and columns, but has the disadvantage that the speed at which the display is addressed is limited by the rate at which charge is injected into the electrode.

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Increasing Speed of Electrochromic Displays

Electrochromic displays, wherein display is effected by the selective deposition of colored species on a display electrode, have been suggested. One form of such a display has the display electrodes arranged in rows and columns, but has the disadvantage that the speed at which the display is addressed is limited by the rate at which charge is injected into the electrode.

For a given contrast ratio, this rate is determined essentially by the molar absorptivity of the colored species, the diffusion coefficient and the concentration of the electrochromic material. For organic molecules the concentration is often low.

The rate of charge injection can be increased by providing a very soluble species in the electrolyte, which undergoes electron transfer at a potential more negative (for a reduction display reaction) than the display reaction. The product of the electrochemical reaction then reacts chemically with the display precursor to provide the display color.

For solutions of heptyl viologen dibromide the maximum concentration is about 0.23M. However, zinc (II) solutions can be prepared with concentrations in excess of 2M. Thus one example is an aqueous solution 0.1M in heptyl viologen and 1.0M in a zinc (II) salt.

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