Nonemissive displays and piezoelectric power supplies therefor

• US 5,930,026 A
• Filed: 10/25/1996
• Issued: 07/27/1999
• Est. Priority Date: 10/25/1996
• Status: Expired due to Term

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Jacobson, Joseph M., Comiskey, Barrett
• Primary Examiner(s): Epps, Georgia
• Assistant Examiner(s): BURKE, MARGARET A
• Application Number:
  US08/738,260
• Time in Patent Office: 1,005 Days
• Field of Search: 359/296, 349/86
• US Class Current: 359/296
• CPC Class Codes: B41J 3/4076 printing on rewritable, bistable "electronic paper" by a focused electric or magnetic field
• CPC Class Codes: G01C 22/006 Pedometers
• CPC Class Codes: G02F 1/13306 Circuit arrangements or driving methods for the control of single liquid crystal cells G02F1/132, G02F1/133382 take precedence
• CPC Class Codes: G02F 1/167 by electrophoresis
• CPC Class Codes: G02F 1/16757 Microcapsules
• CPC Class Codes: G02F 1/1685 Operation of cells; Circuit arrangements affecting the entire cell
• CPC Class Codes: G08B 5/226 with alphanumeric or graphic display means

Abstract

An electrophoretic display has a substantially two-dimensional arrangement of microcapsules each having therein an electrophoretic composition of a dielectric fluid and a suspension of particles that visually contrast with the dielectric liquid and also exhibit surface charges; a pair of electrodes, at least one of which is visually transparent, disposed on and covering opposite sides of the microcapsule arrangement; and means for creating a potential difference between the two electrodes, the potential difference causing the particles to migrate toward one of the electrodes. The display may be powered by one or more piezoelectric elements, which are also suitable for powering other types of nonemissive displays.

Claims

1. An electrophoretic display comprising:

a. an arrangement of discrete microscopic containers, each container being no longer than 500 μ

m along any dimension thereof;

b. first and second electrodes disposed on and covering opposite sides of the arrangement, at least one of the electrodes being substantially visually transparent;

c. means for creating a potential difference between the two electrodes; and

d. within each container, a dielectric fluid and a suspension therein of particles exhibiting surface charges, the fluid and the particles contrasting visually, the potential difference causing the particles to migrate toward one of the electrodes.

2. The display of claim 1 wherein each container is no longer than 5 μ

m along any dimension thereof.

3. The display of claim 1 wherein each container has an average dimension ranging from 25 to 250 μ

m.

4. The display of claim 1 wherein the particles have average diameters no greater than 100 μ

m.

5. The display of claim 1 wherein the particles have average diameters ranging from 5 to 25 μ

m.

6. The display of claim 1 wherein the fluid has a fluid density and the particles each have a particle density, the fluid and particle densities being substantially equal.

7. The display of claim 1 wherein the particles comprise TiO₂ and the dielectric fluid comprises a darkly colored dye therein.

8. The display of claim 1 wherein the dielectric fluid comprises at least one of (i) isoparaffinic petroleum solvent and (ii) trichlorotrifluoroethane.

9. The display of claim 7 wherein the particles each comprise a core and, bound thereto, a charge-control additive.

10. The display of claim 1 wherein the containers have interior surfaces exhibiting a resistivity, the fluid exhibiting a resistivity substantially equal to the resistivities of the interior surfaces.

11. The display of claim 1 wherein the containers are in contact with one another in an array.

12. The display of claim 1 wherein the containers are dispersed in a solid matrix.

13. The display of claim 1 wherein the containers are cavities in a solid matrix.

14. The display of claim 1 wherein the means for creating a potential difference comprises a piezoelectric element.

15. A nonemissive display system comprising:

a. a pair of oppositely disposed electrodes and, located therebetween, at least one display element, the display element being visually responsive to a potential difference between the electrodes;

b. a display piezoelectric element connected to the electrodes, deformation of the piezoelectric element producing the potential difference;

c. a driver piezoelectric element acoustically coupled to the display piezoelectric element;

d. means for applying an AC voltage to the driver element at a driver frequency so as to cause the display piezoelectric element to produce an AC voltage; and

e. means for rectifying the AC voltage from the display piezoelectric element, the rectified voltage providing the potential difference.

16. A nonemissive display system comprising:

a. a pair of oppositely disposed electrodes and, located therebetween, at least one display element, the display element being visually responsive to a potential difference between the electrodes;

b. a display piezoelectric element connected to the electrodes, deformation of the piezoelectric element producing the potential difference;

c. a driver piezoelectric element acoustically coupled to the display piezoelectric element;

d. means for applying an AC voltage to the driver element at a driver frequency so as to cause the display piezoelectric element to produce an AC voltage, the AC voltage providing the potential difference;

e. at least one filter intervening between the display piezoelectric element and the electrodes, the at least one filter configured to (i) pass AC within a predetermined frequency band so that the display is unaffected by driver frequencies outside the predetermined band, or (ii) drop AC within a predetermined frequency band so that the display is affected only by driver frequencies outside the predetermined band; and

f. means, connected to the display piezoelectric element, for rectifying the AC voltage from the filter and thereby providing the potential difference.

17. The display system of claim 16 wherein the at least one filter is a bandpass filter or a notch filter.

18. The display system of claim 16 comprising first and second filters arranged in parallel and oppositely connected to the display element, the first filter passing or dropping AC within a first frequency band and the second filter passing or dropping AC within a second frequency band, selective application to the display piezoelectric element of AC within the first and second frequencies producing opposite visual responses from the display.

19. The display system of claim 18 wherein the first and second filters are bandpass or notch filters.

20. The display system of claim 16 further comprising:

a. a watch case for containing the driver piezoelectric element; and

b. a watch band, attached to the watch case, for bearing the display piezoelectric element.

21. A nonemissive display system comprising:

a. a pair of oppositely disposed electrodes and, located therebetween, at least one display element, the display element being visually responsive to a potential difference between the electrodes; and

b. a display piezoelectric element connected to the electrodes, deformation of the piezoelectric element producing the potential difference;

wherein the display element comprises;

c. a substantially two-dimensional arrangement of discrete microscopic containers, each container being no longer than 500 μ

m along any dimension thereof; and

d. within each container, a dielectric fluid and a suspension therein of particles exhibiting surface charges, the fluid and the particles contrasting visually, the potential difference causing the particles to migrate toward one of the electrodes.