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Improved Electrochromic Display Electrolytes

IP.com Disclosure Number: IPCOM000039705D
Original Publication Date: 1987-Jul-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Barclay, DJ: AUTHOR [+2]

Abstract

This article describes an electrochromic display device of the kind in which a visually observable persistent deposit of bipyridinium cations, present in solution, is formed on a display electrode upon passage of electric current through the solution between a counter electrode and the display electrode, the solution comprising the following species: bipyridinium cations, supporting electrolyte, catalytic metal ions, and sulphate ions. The catalytic metal ions are metal ions which undergo electrolytic reduction at a display electrode having a potential more negative than the reduction potential of the bipyridinium cations; suitable metal ions include Tl (I) and Cd (II).

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Improved Electrochromic Display Electrolytes

This article describes an electrochromic display device of the kind in which a visually observable persistent deposit of bipyridinium cations, present in solution, is formed on a display electrode upon passage of electric current through the solution between a counter electrode and the display electrode, the solution comprising the following species: bipyridinium cations, supporting electrolyte,

catalytic metal ions, and

sulphate ions. The catalytic metal ions are metal ions which undergo electrolytic reduction at a display electrode having a potential more negative than the reduction potential of the bipyridinium cations; suitable metal ions include Tl (I) and Cd (II).

The added sulphate ions serve to improve the erase characteristics of the device, significantly increasing display lifetime. If has also been discovered that the addition of sulphate ions greatly broadens the operating temperature over which faster erase occurs, thus permitting room temperature operation. An example of a satisfactory electrolyte for use in a display device, such as that described in U.S. Patent 4,488,782 and European Patent Publication EP-A-0083668 is as follows: phosphate anion 1.5M;

hypophosphite anion 0.6M;

sulphate anion 0.3M;

thallium (I) cation 0.3M;

bipyridinium cation 20mM;

containing sodium or potassium ions

as supporting cation and buffered

to pH 5.0 The aqueous electrolyte may, in addition, contain up to 15% ethanol. The pref...