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Self-Powered Displays

IP.com Disclosure Number: IPCOM000019260D
Publication Date: 2003-Sep-08
Document File: 2 page(s) / 31K

Publishing Venue

The IP.com Prior Art Database

Related People

John Bryan Vincent: AUTHOR [+4]

Abstract

A self-powered electrochromic display can be made using the materials taught in WO 02/075441. These materials use an oxidation/reduction (redox) material to generate proton or hydroxide ions, thus creating a pH gradient in the cell, and an indicator dye or complex to cause a color change. A display cell consists of the oxidation/reduction material placed between two electrodes of different composition - the preferred embodiment consists of a transparent metal oxide electrode and a metal electrode. This display cell can be used as a galvanic cell (i.e. battery) to power the display (creating a color change due to pH change in the redox material next to the electrode) without external power supply.

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TITLE

Self-Powered Displays

 

AUTHORS

John Bryan Vincent, Derrick, W. Flick, and Mitchell G. Dibbs

The Dow Chemical Company

ABSTRACT

A self-powered electrochromic display can be made using the materials taught in WO 02/075441. These materials use an oxidation/reduction (redox) material to generate proton or hydroxide ions, thus creating a pH gradient in the cell, and an indicator dye or complex to cause a color change. A display cell consists of the oxidation/reduction material placed between two electrodes of different composition - the preferred embodiment consists of a transparent metal oxide electrode and a metal electrode. This display cell can be used as a galvanic cell (i.e. battery) to power the display (creating a color change due to pH change in the redox material next to the electrode) without external power supply.

BACKGROUND

Traditional electrochromic displays require an external power source (battery, etc.) to drive the redox chemistry that effects the color change of the material in the cell. The system used here relies on the oxidation and reduction of a molecule such as hydroquinone to reversibly generate protons or a molecule such as potassium iodate to reversibly generate hydroxide ions near the surface of the electrode. Once a gradient is established in a localized region near the electrode, a pH sensitive dye (i.e. pH indicator dye such as bromocresol purple) incorporated in the material can impart a color change near the electrode. The diffusion resistance of the electrochromic material enables the display cell to develop a voltage difference across the display, which is essentially acting as a galvanic cell (battery) and results in a higher relative pH at the ITO surface in the display. This development of a pH gradient results in a color change of the pH sensitive indicator dye. The main advantage of the system described below is the ability of the electrochromic display to operate without the use of an external power supply (battery, etc.).

EXPERIMENTAL

The following experiments examined the use of redox material with different indicator dyes and different types of metal electrodes. Two illustrative examples are detailed below.

Electronic Display Material

The following reagents were mixed in a small mortar and pestle:

1.0 g hydroquinone, 1.0g titanium dioxide, 0.5g bromocresol purple, 0.5g 600,000 MW polyethylene oxide, 0.5g 8,000MW polyethylene glycol. These materials were ground well. Next, 2.0g of propylene carbonate and 2.0g of 0.17M aqueous solution of sodium chloride were added. Finally, 2 drops of 10% hydrochloric acid were added to the mixture. The material was mixed and then allowed to sit covered overnight before use. The material was bright yellow in color.

EXAMPLE 1:

The electrochromic display material was placed on a piece of 100W ITO PET plastic (purchased from Delta Technologies, Stillwater, MN) which served as the transparent metal oxide electrode. Next, a piece of aluminum foil was placed on the display...