Multi-layer light modulator

• US 7,492,497 B2
• Filed: 08/01/2007
• Issued: 02/17/2009
• Est. Priority Date: 08/02/2006
• Status: Active Grant

• Current Assignee: E Ink Corporation (E Ink Holdings Incorporated)
• Original Assignee: E Ink Corporation (E Ink Holdings Incorporated)
• Inventors: Patry, Shamus Ford, Paolini, Richard J. Jr.
• Primary Examiner(s): Mack; Ricky L
• Assistant Examiner(s): PINKNEY, DAWAYNE
• Application Number:
  US11/832,284
• Publication Number:
  US 20080030832A1
• Time in Patent Office: 566 Days
• Field of Search: 359/259, 359/296, 345 84- 85, 345/107, 430 31- 38, 347111-112, 399/131, 204/600
• US Class Current: 359/259
• CPC Class Codes: G02F 1/167 by electrophoresis
• CPC Class Codes: G02F 1/1675 Constructional details

Abstract

A light modulator comprises a plurality of discrete variable transmission electro-optic layers arranged so that light will pass successively through the plurality of layers; the light modulator has a higher transmission range than any of the individual electro-optic layers separately.

Claims

1. A light modulator comprising a plurality of discrete variable transmission electro-optic layers arranged so that light will pass successively through the plurality of layers, wherein the individual electro-optic layers satisfy the relationship:

O≧

0.5R+0.5

where O is the open state transmission of a single electro-optic layer and R is the transmission range of the layer, the light modulator having a higher transmission range than any of the individual electro-optic layers separately.

2. A light modulator according to claim 1 wherein the individual electro-optic layers have an open state transmission of at least about 75 per cent.

3. A light modulator according to claim 1 further comprising two substantially transparent sheets of material disposed on opposed sides of the plurality of discrete variable transmission electro-optic layers, each of the substantially transparent sheets of material having a thickness of at least about 1 mm.

4. A light modulator comprising a plurality of discrete variable transmission electro-optic layers arranged so that light will pass successively through the plurality of layers, two electrodes disposed on opposed sides of the plurality of variable transmission electro-optic layers and arranged to apply an electric field to the electro-optic layers, and voltage supply means for controlling the voltage of the electrodes, the voltage supply means being arranged to apply a first waveform to the electrodes to drive the electro-optic layers to a first optical state in which the layers are substantially non-light-transmissive and to apply a second waveform to the electrodes to drive the electro-optic layers to a second optical state in which the layers are substantially more light-transmissive than in the first optical state, wherein the first waveform comprises a DC voltage and the second waveform comprises an alternating voltage, wherein the individual electro-optic layer satisfy the relationship:

O>

=0.5R+0.5 where O is the transmission of the second optical state of a single electro-optic layer and R is the transmission of the layer.

5. A light modulator according to claim 4 wherein each of the electro-optic layers comprises an electrophoretic medium comprising a plurality of electrically charged particles disposed in a fluid and capable of moving through the fluid on application of an electric field to the medium.

6. A light modulator according to claim 5 wherein the electrophoretic medium comprises a plurality of dark colored charged particles in a liquid.

7. A light modulator according to claim 6 wherein the dark colored particles comprise carbon black or copper chromite.

8. A light modulator according to claim 5 wherein the charged particles and the fluid are confined within a plurality of cavities in a solid medium, the cavities having sidewalls extending substantially perpendicular to the thickness of the electro-optic layer.

9. A light modulator according to claim 4 having only the two electrodes disposed on opposed sides of the plurality of discrete variable transmission electro-optic layers, and not having an electrode between any of the adjacent pairs of electro-optic layers.

10. A light modulator according to claim 4 further comprising at least one electrode between each adjacent pair of electro-optic layers.

11. A light modulator according to claim 4 having at least one layer of optically clear adhesive between an adjacent pair of electro-optic layers.

12. A light modulator according to claim 4 wherein the individual electro-optic layers have a transmission in their second optical state of at least about 75 per cent.

13. A light modulator according to claim 4 having at least three electro-optic layers.

14. A light modulator according to claim 13 comprising not more than six electro-optic layers.

15. A light modulator according to claim 4 further comprising two substantially transparent sheets of material disposed on opposed sides of the plurality of discrete variable transmission electro-optic layers, each of the substantially transparent sheets of material having a thickness of at least about 1 mm.

16. A light modulator according to claim 15 wherein the substantially transparent sheets are formed of glass, so that the light modulator forms a variable transmission window.