Electrochromic tin oxide

• US 5,876,634 A
• Filed: 12/23/1996
• Issued: 03/02/1999
• Est. Priority Date: 12/26/1995
• Status: Expired due to Fees

• Current Assignee: Monsanto Company (Bayer AG)
• Original Assignee: Monsanto Company (Bayer AG)
• Inventors: Coleman, James P.
• Primary Examiner(s): KOPEC, MARK T
• Application Number:
  US08/773,210
• Time in Patent Office: 799 Days
• Field of Search: 252/518.1, 252/520.1, 428/402, 75/255, 420/557, 420/562
• US Class Current: 252/520.1
• CPC Class Codes: C09K 9/00 Tenebrescent materials, i.e. materials for which the range of wavelengths for energy absorption is changed as a result of excitation by some form of energy
• CPC Class Codes: C09K 9/02 Organic tenebrescent materials
• CPC Class Codes: G02F 1/1523 comprising inorganic material
• CPC Class Codes: H01B 1/08 oxides
• CPC Class Codes: Y10T 428/2982 Particulate matter [e.g., sphere, flake, etc.]

Abstract

Tin oxide doped with an electrochromically effective amount of a metal, e.g. antimony or niobium, which provides a color change when the doped tin oxide is exposed to an electrochemical potential in the presence of mobile ions. Particles of electrochromic doped tin oxide, e.g. coated on a white or pastel pigment substrate, have a contrast ratio greater than 1.2, where contrast ratio is a measure of electrochromic functionality of a material and is the ratio of reflectance of the material in an oxidized state to the color of the material in a reduced state and where color is a photodiode measurement of the value of light reflected off the oxidized or reduced material from a constant source of light shining on the material. Such doped tin oxide-containing particles are useful as electrochromic material in display devices.

Claims

1. A particle comprising electrochromically activated doped tin oxide, said doped tin oxide being electrically conductive in an electrochromically unactivated state, and said activated, doped tin oxide electrochromically exhibiting a contrast ratio greater than 1.2 in comparison to the doped tin oxide in the electrochromically unactivated state.

2. A particle according to claim 1 comprising a doped tin oxide coated on a white or pastel pigment substrate.

3. A particle according to claim 1 comprising an electrochromically effective amount of a metal dopant which provides a color change when said doped tin oxide is exposed to ion transfer in the presence of an electrochemical potential sufficient to cause a redox change in said particle.

4. A particle according to claim 3 wherein said tin oxide is doped with antimony or niobium.

5. A particle according to claim 4 wherein said contrast ratio is at least 2.

6. A particle according to claim 5 doped with antimony.

7. A particle according to claim 2 wherein said pigment substrate is titanium dioxide, silica, alumina, mica, barium sulfate, aluminum borate or a mixture thereof.

8. A particle according to claim 7 wherein said particle has a nominal size in the range of 0.05 to 20 micrometers.

9. A particle according to claim 7 wherein said particle has a nominal size in the range of 0.2 to 10 microns.

10. A particle according to claim 7 wherein said particle has a nominal size in the range of 1 to 5 microns.

11. A particle according to claim 1 in admixture with a white or pastel pigment, wherein the contrast ratio of the mixture is greater than 1.2.

12. A particle according to claim 1 comprising niobium-doped tin oxide over a barium sulfate substrate.

13. A particle according to claim 12 having a contrast ratio greater than 1.5.

14. A particle according to claim 12 prepared by:

(a) adding a tin solution to a dispersion of an insoluble substrate particle in a basic solution,

(b) stirring and adding an acidic niobium solution to the resulting mixture to produce an acidic niobium/tin-containing slurry, and

(c) filtering and drying the particles in the slurry.