Transmissive or reflective liquid crystal display and novel process for its manufacture

• US 6,795,138 B2
• Filed: 01/11/2001
• Issued: 09/21/2004
• Est. Priority Date: 01/11/2001
• Status: Expired due to Fees

• Current Assignee: E Ink California, LLC (E Ink Corporation)
• Original Assignee: SiPix Imaging, Inc. (E Ink Holdings Incorporated)
• Inventors: Tseng, Scott C-J, Li, Ying-Syi, Li, Weijin, Phan, Xuan, Liang, Rong-Chang
• Primary Examiner(s): Parker, Kenneth
• Application Number:
  US09/759,212
• Publication Number:
  US 20020126249A1
• Time in Patent Office: 1,349 Days
• Field of Search: 349/156, 349/189, 349/86, 349/92
• US Class Current: 349/92
• CPC Class Codes: C09K 19/544 as dispersing or encapsulating medium around the liquid crystal
• CPC Class Codes: C09K 19/60 Pleochroic dyes
• 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 1/1334 based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals
• CPC Class Codes: G02F 1/13475 in which at least one liquid crystal cell or layer is doped with a pleochroic dye, e.g. GH-LC cell G02F1/13476 takes precedence

Abstract

This invention relates to liquid crystal (LC) displays comprising cells of well-defined shape, size and aspect ratio which cells are filled with a liquid crystal composition preferably containing dichroic dye(s), and novel processes for their manufacture.

Claims

1. A process for the preparation of a liquid crystal display, which process comprises the steps of:

a) providing microcups;

b) filling the microcups with a liquid crystal composition and a dispersion of a thermoset or thermoplastic precursor which has a specific gravity lower than that of the liquid crystal composition; and

c) sealing the filled microcups by hardening the thermoset or thermoplastic precursor dispersion during or after it phase separates and forms a supernatant layer above the liquid crystal composition.

2. The process of claim 1 wherein the liquid crystal composition comprises guest dye(s).

3. The process of claim 1 wherein the thermoset or thermoplastic precursor dispersion comprises a material selected from the group consisting of acrylates or methacrylates, vinyls, polyvalent acrylates or methacrylates, cyanoacrylates, polyvalent vinyls, polyvalent epoxides, polyvalent isocyanates, polyvalent allyls, and oligomers or polymers derived therefrom.

4. The process of claim 3 wherein said polyvalent vinyl is vinyl benzene, vinylsilane, or vinyl ether.

5. The process of claim 3 wherein said oligomers or polymers are derived from those containing crosslinkable functional groups.

25. The process of claim 1 wherein said microcups are washed before being filled.

26. The process of claim 25 wherein said microcups are washed with hexane.

27. The process of claim 25 wherein said microcups are washed with methylethylketone.

6. A process for the preparation of a liquid crystal display, which process comprises the steps of:

a) providing microcups;

b) filling the microcups with a liquid crystal composition;

c) sealing the fill d microcups by overcoating onto said liquid crystal composition a thermoset or thermoplastic precursor composition which is at least partially immiscible with said liquid crystal composition and has a specific gravity lower than that of said liquid crystal composition; and

d) hardening said thermoplastic or thermoset precursor composition.

7. The process of claim 6 wherein the thermoplastic or thermoset precursor composition is diluted with a volatile solvent or solvent mixture which is evaporated after said thermoplastic or thermoset precursor composition is overcoated onto the liquid crystal composition.

8. The process of claim 6 wherein the thermoplastic or thermoset precursor composition is cured by radiation, heat, moisture, or interfacial reactions at the interface between the thermoplastic or thermoset precursor composition and the liquid crystal composition.

9. The process of claim 6 wherein the thermoplastic or thermoset precursor composition comprises a material selected from the group consisting of acrylates or methacrylates, vinyls, polyvalent acrylates or methacrylates, cyanoacrylates, polyvalent vinyls, polyvalent epoxides, polyvalent isocyanates, polyvalent allyls, oligomers or polymers derived therefrom.

10. The process of claim 9 wherein said polyvalent vinyl is vinyl benzene, vinylsilane, or vinyl ether.

11. The process of claim 9 wherein said oligomers or polymers are derived from those containing crosslinkable functional groups.

28. The process of claim 6 wherein said microcups are washed before being filled.

29. The process of claim 28 wherein said microcups are washed with hexane.

30. The process of claim 28 wherein said microcups are washed with methylethylketone.

12. A process for the manufacture of a liquid crystal display, which process comprises the steps of:

a) preparing microcups on a first conductor film;

b) filling the microcups with a liquid crystal composition;

c) sealing the filled microcups; and

d) laminating the sealed microcups with a second conductor film to form a liquid crystal display.

13. The process of claim 12 wherein said second conductor film is pre-coated with an adhesive layer which is hardenable or crosslinkable by heat, moisture or radiation and curable during or after lamination.

15. The process of claim 12 wherein the filling and sealing of the microcups is accomplished by filling the microcups with the liquid crystal composition and a dispersion of a thermoplastic or thermoset precursor composition which has a specific gravity lower than that of the liquid crystal composition, followed by hardening the thermoplastic or thermoset precursor composition during or after it phase separates and forms a supernatant layer above the liquid crystal dispersion.

16. The process of claim 12 wherein the liquid crystal composition comprises guest dye(s).

19. The process of claim 12 wherein the sealing of the filled microcups is accomplished by overcoating onto the liquid crystal composition a thermoplastic or thermoset precursor composition which is at least partially immiscible with said liquid crystal composition and has a specific gravity lower than that of said liquid crystal composition, followed by hardening the thermoplastic or thermoset precursor composition.

31. The process of claim 12 wherein said microcups are prepared embossing the thermoplastic or thermoset precursor layer with a mate mold.

32. The process of claim 12 wherein said microcups are prepared by imagewise exposing a thermoplastic or thermoset precursor layer and removing the unexposed areas.

14. A process for the manufacture of a multi-color liquid crystal display, which process comprises the steps of:

a) preparing microcups on a first conductor film;

b) laminating the microcups with a layer of a positive photoresist;

c) imagewise exposing the positive photoresist to selectively open the microcups in a predetermined area;

d) filling the opened microcups with a liquid crystal composition of a first color;

e) sealing the microcups filled with the liquid crystal composition of the first color;

f) repeating Steps c) to e) in different areas with liquid crystal compositions of different colors to generate groups of microcups filed with the liquid crystal compositions of different colors;

g) removing residual positive photoresist, if any; and

h) laminating the sealed microcups with a second conductor film to form a multi-color liquid crystal display.

17. The process of claim 14 wherein the filling and sealing of the microcups is accomplished by filling the microcups with the liquid crystal composition and a dispersion of a thermoplastic or thermoset precursor composition which has a specific gravity lower than that of the liquid crystal composition, followed by hardening the thermoplastic or thermoset precursor composition during or after it phase separates and forms a supernatant layer above the liquid crystal composition.

18. The process of claim 14 wherein the the liquid crystal composition comprises quest dye(s).

20. The process of claim 14 wherein the sealing of the filled microcups is accomplished by overcoating onto the liquid crystal composition a thermoplastic or thermoset precursor composition which is at least partially immiscible with said liquid crystal composition and has a specific gravity lower than that of said liquid crystal composition, followed by hardening the thermoplastic or thermoset precursor composition.

21. The process of claim 14 wherein an adhesive layer is precoated on the positive photoresist.

22. The process of claim 21 wherein said adhesive is developable by a developer of the positive photoresist.

23. The process of claim 14 wherein color filters are laminated or coated onto the display.

24. The process of claim 23 wherein said color filters are red, green or blue.

33. The process of claim 14 wherein said microcups are prepared by embossing the thermoplastic or thermoset precursor layer with a male mold.

34. The process of claim 14 wherein said microcups are prepared by imagewise exposing a thermoplastic or thermoset precursor layer and removing the unexposed areas.

35. The process of claim 14 wherein said second conductor film is pre-coated with an adhesive layer which is hardenable or cross-linkable by heat, moisture or radiation and curable during or after lamination.