Electrophoretic display and process for its manufacture

• US 7,052,571 B2
• Filed: 05/12/2004
• Issued: 05/30/2006
• Est. Priority Date: 03/03/2000
• Status: Expired due to Term

• Current Assignee: E Ink Corporation (E Ink Holdings Incorporated)
• Original Assignee: SiPix Imaging, Inc. (E Ink Holdings Incorporated)
• Inventors: Liang, Rong-Chang, Wang, Xiaojia, Haubrich, Jeanne
• Primary Examiner(s): MAYES, MELVIN C
• Application Number:
  US10/845,295
• Publication Number:
  US 20050007650A1
• Time in Patent Office: 748 Days
• Field of Search: 156/277
• US Class Current: 156/277
• CPC Class Codes: G02F 1/133305 Flexible substrates, e.g. plastics, organic film
• CPC Class Codes: G02F 1/133377 Cells with plural compartments or having plurality of liquid crystal microcells partitioned by walls, e.g. one microcell per pixel
• CPC Class Codes: G02F 1/1339 Gaskets; Spacers; Sealing of cells
• CPC Class Codes: G02F 1/1341 Filling or closing of cells
• CPC Class Codes: G02F 1/1347 Arrangement of liquid crystal layers or cells in which the final condition of one light beam is achieved by the addition of the effects of two or more layers or cells
• CPC Class Codes: G02F 1/167 by electrophoresis
• CPC Class Codes: G02F 1/1679 Gaskets; Spacers; Sealing of cells; Filling or closing of cells
• CPC Class Codes: G02F 1/1681 having two or more microcells partitioned by walls, e.g. of microcup type

Abstract

This invention relates to an electrophoretic display comprising cells of well-defined shape, size and aspect ratio, which cells are filled with charged pigment particles dispersed in a solvent, and novel processes for its manufacture.

Claims

1. A process for the manufacture of a multi-color electrophoretic display, which process comprises the steps of:

(a) pattern-wise filling microcups with colorant solutions or dispersions, each of said colorant solutions or dispersions comprising a colorant dissolved or dispersed in a first solvent,

(b) removing said first solvent in said colorant solutions or dispersions to form colorant-containing microcups, and

(c) non-pattern-wise filling said colorant-containing microcups with an electrophoretic fluid comprising charged pigment particles dispersed in a dielectric solvent or solvent mixture in which said colorants are soluble or dispersible.

2. The process of claim 1 wherein the pattern-wise filling of the colorant solutions or dispersions is carried out by a printing method.

3. The process of claim 2 wherein said printing method is flexo printing, litho printing, driographic or waterless litho printing, gravure printing, screen printing, thermal printing, laser ablative transfer printing, inkjet printing or strip coating.

4. The process of claim 1 wherein said pattern-wise filling of the colorant solutions or dispersions is carried out by laminating or coating onto said microcups a positively working photoresist, selectively opening said microcups in a predetermined area and filling the opened microcups with a colorant solution or dispersion of a predetermined color.

5. The process of claim 1 wherein said pattern-wise filling of the colorant solutions or dispersions is carried out by filling said microcups with a filler material, selectively opening the filled microcups in a predetermined area, removing the filler material from the opened microcups and filling the opened microcups with a colorant solution or dispersion of a predetermined color.

6. The process of claim 1 wherein said first solvent is a dielectric solvent.

7. The process of claim 1 wherein said first solvent is a common organic solvent.

8. The process of claim 7 wherein said common organic solvent is selected from the group consisting of hydrocarbons, alkyl ketones, alkyl esters, alcohols, ethers, water and mixtures thereof.

9. The process of claim 1 wherein said colorant solutions or dispersions are of different colors.

10. The process of claim 1 wherein said colorant solutions or dispersions are of the same color but having different optical densities or concentrations.

11. The process of claim 1 wherein said charged pigment particles are of the same color dispersed in a clear and colorless dielectric solvent.

12. The process of claim 1 further comprising top sealing of the filled microcups with a sealing composition having a specific gravity no greater than that of the electrophoretic fluid.

13. The process of claim 12 wherein said top sealing is accomplished by filling the sealing composition and the electrophoretic fluid together into the colorant-containing microcups and hardening the sealing composition during or after it floats to the top of the electrophoretic fluid.

14. The process of claim 13 wherein the hardening of the sealing composition is accomplished by radiation or heat.

15. The process of claim 12 wherein said top sealing is accomplished by overcoating the sealing composition onto said electrophoretic fluid and hardening the sealing composition.

16. The process of claim 15 wherein the hardening of the sealing composition is accomplished by radiation or heat.

17. The process of claim 12 further comprising laminating a conductor film over the filled and sealed microcups optionally with an adhesive layer.

18. The process of claim 1 wherein said solvent is dried off in step (b).

19. A process for the manufacture of an electrophoretic display comprising microcups filled with electrophoretic fluids having different electrophoretic characteristics, which process comprises the steps of:

(a) pattern-wise filling microcups with additive solutions or dispersions of different electrophoretic characteristics, each of said additive solutions or dispersions comprising an additive dissolved or dispersed in a first solvent,

(b) removing said first solvent in said additive solutions or dispersions to form additive-containing microcups, and

(c) non-pattern-wise filling said additive-containing microcups with an electrophoretic fluid comprising charged pigment particles dispersed in a dielectric solvent or solvent mixture in which said additives are soluble or dispersible.

20. The process of claim 19 wherein the pattern-wise filling of the additive solutions or dispersions is carried out by a printing method.

21. The process of claim 20 wherein said printing method is flexo printing, litho printing, driographic or waterless litho printing, gravure printing, screen printing, thermal printing, laser ablative transfer printing, inkjet printing or strip coating.

22. The process of claim 19 wherein said pattern-wise filling of the additive solutions or dispersions is carried out by laminating or coating onto said microcups a positively working photoresist, selectively opening said microcups in a predetermined area and filling the opened microcups with an additive solution or dispersion of a predetermined electrophoretic characteristic.

23. The process of claim 19 wherein said pattern-wise filling of the additive solutions or dispersions is carried out by filling said microcups with a filler material, selectively opening the filled microcups in a predetermined area, removing the filler material from the opened microcups and filling the opened microcups with an additive solution or dispersion of a predetermined electrophoretic characteristic.

24. The process of claim 19 wherein said additive is a surfactant, protective colloid, polymer, viscosity modifier, charge controlling agent, stabilizer, antioxidant, fluorescent material, filler or filler particles.

25. The process of claim 19 wherein said first solvent is a dielectric solvent.

26. The process of claim 19 wherein said first solvent is a common organic solvent.

27. The process of claim 26 wherein said common organic solvent is selected from the group consisting of hydrocarbons, alkyl ketones, alkyl esters, alcohols, ethers, water and mixtures thereof.

28. The process of claim 19 wherein said charged pigment particles are dispersed in a colored dielectric solvent.

29. The process of claim 19 further comprising top sealing of the filled microcups with a sealing composition having a specific gravity no greater than that of the electrophoretic fluid.

30. The process of claim 29 wherein said top sealing is accomplished by filling the sealing composition and the electrophoretic fluid together into the additives-containing microcups and hardening the sealing composition during or after it floats to the top of the electrophoretic fluid.

31. The process of claim 30 wherein the hardening of the sealing composition is accomplished by radiation or heat.

32. The process of claim 29 wherein said top sealing is accomplished by overcoating the sealing composition onto said electrophoretic fluid and hardening the sealing composition.

33. The process of claim 32 wherein the hardening of the sealing composition is accomplished by radiation or heat.

34. The process of claim 29 further comprising laminating a conductor film over the filled and sealed microcups optionally with an adhesive layer.

35. The process of claim 19 wherein said solvent is dried off in step (b).