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Electrochromic Liquid Display

IP.com Disclosure Number: IPCOM000081965D
Original Publication Date: 1974-Sep-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Chang, IF: AUTHOR [+2]

Abstract

Tungstate and molybdate aqueous, clear solutions have been found to exhibit electrochromic effect at very low voltages. The solution is buffered with acid, such as phosphoric acid, acetic acid, etc. Strong acids such as HCl, HNO(3) and H(2)SO(4) may also be used. However, if the concentration of these strong acids is too high, there is a tendency for these solutions to gel.

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Electrochromic Liquid Display

Tungstate and molybdate aqueous, clear solutions have been found to exhibit electrochromic effect at very low voltages. The solution is buffered with acid, such as phosphoric acid, acetic acid, etc. Strong acids such as HCl, HNO(3) and H(2)SO(4) may also be used. However, if the concentration of these strong acids is too high, there is a tendency for these solutions to gel.

A typical tungstate exhibiting a relatively sensitive electrochromic effect is sodium tungstate in a weak acid, such as chlorine-acetic acid. The sodium tungstate solution may be prepared by first dissolving the tungstate in water. Thereafter, acid is added to bring the pH value down. In this regard, the electrochromic effect is more sensitive in the lower pH ranges. Likewise, the electrochromic effect is more sensitive with higher concentrations of tungstate.

The electrochromic effect exhibited by the tungstate and molybdate occurs at a relatively distinct and predictable threshold-voltage level. In this regard, however, it is clear that the threshold voltage depends on the electrode material and shape. Where transparent tin oxide electrodes are employed, for example, a potential greater than one volt applied to the electrodes in contact with the sodium tungstate solution acts to create an intense blue coloration at the negative electrode. A contrast of greater than 20:1 can be obtained with approx.100 mu C/cm/2/ at four volts in one second. Removal of the voltag...