Browse Prior Art Database

Materials for Solid State Electrochromic Display

IP.com Disclosure Number: IPCOM000088969D
Original Publication Date: 1977-Aug-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 3 page(s) / 16K

Publishing Venue

IBM

Related People

Scott, BA: AUTHOR [+2]

Abstract

Electrocoloration in WO(3) has been recognized and suggested for display applications as early as 1939. It has been shown to operate in an electrochemical mode, where presumably a H(x)WO(3) bronze is formed by the diffusion of H/+/ into the WO(3) from the acidxelectrolyte. The difficulty with such an operation is that the WO(3) is in contact with rather strong acids, which results in a slow deterioration of the WO(3) surface. At present WO(3) is considered to be the best oxide for this type of operation because of its stability toward acid electrolytes. In other words, WO(3) is used mainly because of its stability rather than other factors such as color, speed, etc.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 47% of the total text.

Page 1 of 3

Materials for Solid State Electrochromic Display

Electrocoloration in WO(3) has been recognized and suggested for display applications as early as 1939. It has been shown to operate in an electrochemical mode, where presumably a H(x)WO(3) bronze is formed by the diffusion of H/+/ into the WO(3) from the acidxelectrolyte. The difficulty with such an operation is that the WO(3) is in contact with rather strong acids, which results in a slow deterioration of the WO(3) surface. At present WO(3) is considered to be the best oxide for this type of operation because of its stability toward acid electrolytes. In other words, WO(3) is used mainly because of its stability rather than other factors such as color, speed, etc.

Other bronze-forming oxides could also be used, but usually they have much lower stability than WO(3) and haven't been generally considered. Recently Green and Richman [*] disclosed a cell using WO(3), but instead of an acid electrolyte such as H(2)SO(4), they used a solid electrolyte, RbAg(4)I(5). In such a configuration the deterioration of the WO(3) would undoubtedly be decreased.

It is here proposed to use other oxides which also form bronzes, but which have been ignored for the acid-electrolyte scheme because of their solubility in acid solution. In addition, a series of nonstoichiometric organic donor salts for such display applications is proposed. By combining these oxides and organic salts with solid electrolytes, the solubility problem can be eliminated without diminishing the electrochromic effect.

A. INORGANIC BRONZES

The following oxides and their bronze-forming ions are proposed:
Oxide Bronze
MoO(3) (Ag, K, Na, La, Cs, Rb)(x)MoO(3) Mo(6)O(17) Na(x)Mo(6)O(17)

V(2)O(5) (Ag, Na, K, Li, Rb, Cs, Cd, Ca, Er, Cu, Ba)(x)V(2)O(5)

TiO(2) (Li, Na, K, Rb, Cs)(x)TiO(2) MnO(2) (Na, K)(x)MnO(2)

WO(3) Sn(x)WO(3)

The solid electrolyte can be of several types that have been studied extensively. If Ag is used as the bronze-forming ion, any of the silver halide superionic conductors, such as AgI or RbAg(4)I(5), can be used. If the alkali metals are used, then Beta alumina as Beta gallia can be the host structure. Copper halides can be used as the source of Cu/+/ ions. In addition, for application with the organic display materials to be listed in section B, halide ion conductors, such as PbCl(2) and PbF(2), can be used.

In addition to the above molybdenum and tungsten oxides, there are a number of others which are not bronzes but show distinct color changes as a function of composition. These are: Oxide Color MoO(2) Wine Red Mo(4)O(11) Deep Purple Mo(8)O(23) Deep Blue Mo(9)O(26) Deep Blue-black

1

Page 2 of 3

MoO(3) Colorless WO(2) Wine Red W(4)O(11) Deep Purple W(18)O(49) -- W(20)O(58) Deep Blue-black WO(3) Colorless

In these materials the color change from colorless (MO(3)) to highly colored (M(x)O(y)) does not depend on the diffusion of another ion into the MO(3) lattice to form a bronze, but rather to the M/+6//M/+4/ ratio in...