Electrophoretic medium provided with spacers

• US 6,392,786 B1
• Filed: 06/29/2000
• Issued: 05/21/2002
• Est. Priority Date: 07/01/1999
• Status: Expired due to Term

• Current Assignee: E Ink Corporation (E Ink Holdings Incorporated)
• Original Assignee: E Ink Corporation (E Ink Holdings Incorporated)
• Inventors: Albert, Jonathan D.
• Primary Examiner(s): MAI, HUY KIM
• Application Number:
  US09/606,070
• Time in Patent Office: 691 Days
• Field of Search: 359/296, 359/237, 359/250, 359/253, 359/265-273, 359/315, 349/86-90, 349/155, 349/156, 349/158, 204/450, 204/606, 345/84, 345/85, 345/107
• US Class Current: 359/296
• CPC Class Codes: G02F 1/1339 Gaskets; Spacers; Sealing of cells
• CPC Class Codes: G02F 1/167 by electrophoresis
• CPC Class Codes: G02F 1/16757 Microcapsules
• CPC Class Codes: G02F 1/1679 Gaskets; Spacers; Sealing of cells; Filling or closing of cells

Abstract

An encapsulated electrophoretic medium comprises a layer of capsules, each of these capsules comprising a liquid and at least one particle disposed within the liquid and capable of movement upon application of an electric field to the medium. A plurality of spacers are dispersed among the capsules. The medium can be formed by coating a mixture of capsules and spacers on a substrate, or by first coating the capsules and thereafter incorporating the spacers into the layer of capsules.

Claims

1. An encapsulated electrophoretic medium comprising a layer of capsules, each of said capsules comprising a liquid and at least one particle disposed within the liquid and capable of moving therethrough on application of an electric field to the medium, the layer of capsules having the form of a lamina having a thickness substantially less than its other two dimensions, the medium further comprising a plurality of spacers dispersed among the capsules, the dimension of the spacers parallel to the thickness of the lamina being from 0.9 to 1.0 times this thickness.

2. A medium according to claim 1 wherein at least one of the spacers has substantially the form of a sphere.

3. A medium according to claim 1 wherein at least one of the spacers has substantially the form of a rod.

4. A medium according to claim 1 wherein the spacers are formed from glass and/or a polymeric material.

5. A medium according to claim 1 wherein the spacers are formed from a substantially transparent material.

6. A medium according to claim 1 wherein the ratio of spacers to capsules is in the range of from about 1:

100 to about 1;

1,000,000.

7. A medium according to claim 6 wherein the ratio of spacers to capsules is in the range of from about 1:

1,000 to about 1;

100,000.

8. A medium according to claim 1 wherein the liquid has a optical property differing from that of the at least one particle.

9. A medium according to claim 1 wherein the liquid has disposed therein at least one first particle having a first optical property and a first electrophoretic mobility and at least one second particle having a second optical property different from the first optical property and a second electrophoretic mobility different from the first electrophoretic mobility.

10. A medium according to claim 9 wherein the first and second particles bear charges of opposite polarity.

11. A medium according to claim 1 further comprising a binder disposed between the capsules.

12. An electrophoretic display comprising an encapsulated electrophoretic medium according to claim 1 in combination with first and second electrodes disposed on opposed sides of the electrophoretic medium, at least one of the first and second electrodes being light transmissive.

13. An electrophoretic display according to claim 12 further comprising first and second substrates disposed on opposed sides of the electrophoretic medium, the first and second substrates being secured to the first and second electrodes respectively.

14. An electrophoretic display according to claim 13 wherein the first and second electrodes and the first and second substrates are all flexible.

15. An electrophoretic display according to claim 12 further comprising touch sensing means disposed on the opposed side of one of the first and second electrodes from the electrophoretic medium.

16. An electrophoretic display according to claim 12 wherein at least one of the spacers is secured to, or integral with, one of the first and second electrodes.

17. An electrophoretic display according to claim 13 wherein at least one of the spacers is secured to, or integral with, one of the first and second substrates.

18. A method of forming an electrophoretic display, which method comprises:

(a) providing a substrate; and

(b) providing, adjacent the substrate, an encapsulated electrophoretic medium comprising a layer of capsules, each of said capsules comprising a liquid and at least one particle disposed within the liquid and capable of moving therethrough on application of an electric field to the medium, the layer of capsules having the form of a lamina having a thickness substantially less than its other two dimensions, the medium further comprising a plurality of spacers dispersed among the capsules, the dimension of the spacers parallel to the thickness of die lamina being from 0.9 to 1.0 times this thickness.

19. A method according to claim 18 wherein step (b) is effected by providing a mixture of the capsules and the spacers in a binder, and coating the surface of the substrate with said mixture.

20. A method according to claim 18 wherein step (b) is effected by providing a mixture of the capsules with a binder, coating the surface of the substrate with said mixture, and dispersing the spacers among the capsules.

21. A method according to claim 18 further comprising laminating a second substrate to the layer of capsules so that the two substrates lie on opposed sides of said layer.

22. A method according to claim 18 wherein the substrate bears a conductive coating.

23. A method according to claim 18 wherein at least one of the spacers has substantially the form of a sphere.

24. A method according to claim 18 wherein at least one of the spacers has substantially the form of a rod.

25. A method according to claim 18 wherein the spacers are formed from glass and/or a polymeric material.

26. A method according to claim 18 wherein the spacers are formed from a substantially transparent material.

27. A method according to claim 18 wherein the ratio of spacers to capsules is in the range of from about 1:

100 to about 1;

1,000,000.

28. A method according to claim 18 wherein the ratio of spacers to