Broadband reflective display, and methods of forming the same

• US 5,875,012 A
• Filed: 01/31/1997
• Issued: 02/23/1999
• Est. Priority Date: 01/31/1997
• Status: Expired due to Term

• Current Assignee: Thomson Licensing (Vantiva SA)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Silverstein, Louis D., Crawford, Greg P., Fiske, Thomas G.
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): Dudek, James A.
• Application Number:
  US08/792,269
• Time in Patent Office: 753 Days
• Field of Search: 349/74, 349/78, 349/86, 349/88, 349/92
• US Class Current: 349/74
• CPC Class Codes: G02F 1/1334 based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals
• CPC Class Codes: G02F 1/13473 for wavelength filtering or for colour display without the use of colour mosaic filters

Abstract

A broadband reflective display has improved reflectivity as well as a lack of haze or opaqueness when viewed from various viewing angles, a reduced drive voltage compared to conventional devices and an improved peak photopic reflectance. The broadband reflective display includes a plurality of pairs of substrates, a plurality of groups of alternating liquid crystal and polymer layers formed between each of the pairs of substrates, each of the groups of liquid crystal and polymer layers being reflective of different wavelengths of light.

Claims

1. A broadband reflective display, comprising:

a plurality of pairs of substrates; and

a plurality of groups of alternating liquid crystal and polymer layers formed between each of the pairs of substrates, each of the groups of liquid crystal and polymer layers being reflective of different wavelengths of light.

2. The broadband reflective display of claim 1, wherein the liquid crystal is a nematic liquid crystal material.

3. The broadband reflective display of claim 1, wherein the liquid crystal and polymer molecules forming the polymer layers are index matched so as to reduce haze in the display when viewed from various viewing angles.

4. The broadband reflective display of claim 1, wherein the plurality of pairs of substrates comprises first, second and third pairs of substrates.

5. The broadband reflective display of claim 1, wherein the different wavelengths of light are selectively tunable.

6. The broadband reflective display of claim 4, wherein the plurality of alternating groups of liquid crystal and polymer layers comprises first, second and third groups of liquid crystal and polymer layers formed between each of the first, second and third pairs of substrates.

7. The broadband reflective display of claim 6, wherein the first, second and third groups of liquid crystal and polymer layers between the first pair of substrates are reflective of light having wavelengths of approximately 610 nm, 630 nm and 650 nm, respectively, the first, second and third groups of liquid crystal and polymer layers between the second pair of substrates are reflective of light having wavelengths of approximately 520 nm, 540 nm and 560 nm, and the first, second and third groups of liquid crystal and polymer layers between the third pair of substrates are reflective of light having wavelengths of approximately 440 nm, 460 nm and 480 nm, respectively.

8. The broadband reflective display of claim 1, wherein the display operates in a reverse mode in which when no electric field is applied, the broadband reflective display is transparent, and when an electric field is applied, the broadband reflective display is reflective of the different wavelengths of light.

9. The broadband reflective display of claim 1, further comprising a rubbed polymer layer formed between the substrates and the liquid crystal so as to cause homogeneous surface boundary conditions between polymer molecules within the polymer sheets and liquid crystal molecules within the liquid crystal.

10. The broadband reflective display of claim 1, further comprising a material inducing homeotropic surfacing anchoring formed between the substrates and the liquid crystal so as to cause homeotropic surface boundary conditions between polymer molecules within the polymer sheets and liquid crystal molecules within the liquid crystal.

11. The broadband reflective display of claim 1, wherein the liquid crystal is a chiral liquid crystal material.

12. The broadband reflective display of claim 1, wherein the liquid crystal is a ferroelectric liquid crystal material.

13. A method of forming a broadband reflective display, comprising:

forming a plurality of pairs of substrates;

forming a plurality of groups of alternating liquid crystal and polymer layers between each of the pairs of substrates, each of the groups of liquid crystal and polymer layers being reflective of different wavelengths of light.

14. The method of forming a broadband reflective display of claim 13, wherein the liquid crystal is an anisotropic liquid crystal material.

15. The method of forming a broadband reflective display of claim 13, further comprising index matching the liquid crystal and the polymer sheets so as to reduce haze in the display when viewed from various viewing angles.

16. The method of forming a broadband reflective display of claim 13, wherein forming a plurality of pairs of substrates comprises forming first, second and third pairs of substrates.

17. The method of forming a broadband reflective display of claim 13, further comprising selectively tuning the different wavelengths of light.

18. The method of forming a broadband reflective display of claim 13, wherein forming the groups of alternating liquid crystal and polymer layers comprises forming first, second and third groups of liquid crystal and polymer layers between each of the first, second and third pairs of substrates.

19. The method of forming a broadband reflective display of claim 18, further comprising forming the first, second and third groups of liquid crystal and polymer layers between the first pair of substrates to be reflective of light having wavelengths of approximately 610 nm, 630 nm and 650 nm, respectively, forming the first, second and third groups of liquid crystal and polymer layers between the second pair of substrates to be reflective of light having wavelengths of approximately 520 nm, 540 nm and 560 nm, and forming the first, second and third groups of liquid crystal and polymer layers between the third pair of substrates to be reflective of light having wavelengths of approximately 440 nm, 460 nm and 480 nm, respectively.

20. The method of forming a broadband reflective display of claim 13, further comprising phase separating the plurality of anisotropic polymer sheets from the liquid crystal material by application of a laser.

21. The method of forming a broadband reflective display of claim 13, further comprising forming a rubbed polymer layer between the substrates and the liquid crystal so as to cause homogeneous surface boundary conditions between polymer molecules within the polymer sheets and liquid crystal molecules within the liquid crystal.

22. The method of forming a broadband reflective display of claim 13, further comprising forming a material inducing homeotropic surface anchoring between the substrates and the liquid crystal so as to cause homeotropic surface boundary conditions between polymer molecules within the polymer sheets and liquid crystal molecules within the liquid crystal.