Reflective cholesteric displays employing linear polarizer

• US 20050117095A1
• Filed: 12/02/2003
• Published: 06/02/2005
• Est. Priority Date: 12/02/2003
• Status: Abandoned Application

• Current Assignee: Yao-Dong Ma
• Original Assignee: Yao-Dong Ma
• Inventors: Ma, Yao-Dong
• Application Number:
  US10/727,296
• Publication Number:
  US 20050117095A1
• Time in Patent Office: Days
• US Class Current: 349/113
• CPC Class Codes: G02F 1/133514 Colour filters
• CPC Class Codes: G02F 1/133536 Reflective polarizers G02F1/13362 takes precedence
• CPC Class Codes: G02F 1/133553 Reflecting elements associated to illuminating devices G02F1/133605
• CPC Class Codes: G02F 1/133638 Waveplates, i.e. plates with a retardation value of lambda/n
• CPC Class Codes: G02F 1/13718 based on a change of the texture state of a cholesteric liquid crystal

Abstract

The present invention relates to cholesteric displays, and more specifically, to reflective cholesteric displays employing linear polarizer(s). Two display modes have been accomplished and both of them take on black-and-white appearances. The addition of the weak linear polarizer has greatly increased the brightness of the white color while maintaining the black darkness.

Claims

1. A reflective display comprising:

a. a linear polarizer,

b. a reflective half-wave plate,

c. a plurality of transparent conductive patterned substrates juxtaposed to form a cell structure,

d. a cholesteric material with a predetermined reflective wavelength and a predetermined thick-to-pitch ratio and with at least one controllable optical ON texture and at least one controllable optical OFF texture respectively,

wherein the cell structure enclosing the cholesteric material, attaching the linear polarizer on the front outside surface and the reflective half-wave plate on the back outside surface,

whereby a paper white state will be displayed in the controllable optical ON texture area; and

a black state will be displayed in the controllable optical OFF texture area.

2. The reflective display as in claim 1 wherein the paper white ON state is the controllable focal conic state.

3. The reflective display as in claim 1 wherein the black optical OFF state is the controllable planar state.

4. The reflective display as in claim 1 wherein the black optical OFF state is the controllable field-induced nematic state.

5. The reflective display as in claim 1 wherein the reflective half-wave plate is a specula 180°

phase shifter.

6. The reflective display as in claim 1 wherein the predetermined reflective wavelength is in near infrared wave band.

7. The reflective display as in claim 1 wherein the predetermined thick-to-pitch ratio is 5˜

10.

8. The reflective display as in claim 1 wherein the linear polarizer is a weak linear polarizer with single transmittance at least 60% and polarization efficiency at least 30%.

9. The reflective display as in claim 1 further including a color filter layer positioned inside of the cell substrate to achieve a reflective full color display.

10. A reflective display comprising:

a. an absorptive linear polarizer

b. a reflective linear polarizer with crossed polarity to the absorptive linear polarizer,

c. a plurality of transparent conductive patterned substrates juxtaposed to form a cell structure,

d. a cholesteric material with a predetermined reflective wavelength and a predetermined thick-to-pitch ratio and with at least one controllable optical ON texture and at least one controllable optical OFF texture respectively,

wherein the cell structure enclosing the cholesteric material, attaching the absorptive polarizer on the front outside surface and the reflective linear polarizer on the back outside surface,

whereby a paper white state will be displayed in the controllable optical ON texture area; and

a black state will be displayed in the controllable optical OFF texture area.

11. The reflective display as in claim 10 wherein the transmissive optical ON state is the controllable focal conic state.

12. The reflective display as in claim 10 wherein the optical OFF state is the controllable planar state.

13. The reflective display as in claim 10 wherein the optical OFF state is the controllable field-induced nematic state.

14. The reflective display as in claim 10 wherein the reflective linear polarizer is a composite structure of a non-absorptive linear polarizer and an absorptive layer.

15. The reflective display as in claim 10 wherein the reflective linear polarizer is a composite structure of an absorptive linear polarizer and a metal reflector.

16. A reflective display comprising:

a. an absorptive linear polarizer

b. a reflective linear polarizer with in-parallel polarity to the absorptive linear polarizer,

c. a plurality of transparent conductive patterned substrates juxtaposed to form a cell structure,

d. a cholesteric material with a predetermined reflective wavelength and a predetermined thick to pitch ratio and with at least one controllable optical ON texture and at least one controllable OFF texture respectively,

wherein the cell structure enclosing the cholesteric material, attaching the absorptive polarizer on the front outside surface and the reflective linear polarizer on the back outside surface,

whereby a paper white state will be displayed in the controllable optical ON texture area due to the guiding effect of the linear polarizers; and

a black state will be displayed in the controllable optical OFF texture area due to the multi-pass absorption effect of the linear polarizers.

17. The reflective display as in claim 16 wherein the optical ON state is the controllable planar state.

18. The reflective display as in claim 16 wherein the optical ON state is the controllable field-induced nematic state.

19. The reflective display as in claim 16 wherein the optical OFF state is the controllable focal conic state.

20. The reflective display as in claim 16 wherein the reflective linear polarizer is a composite structure of a non-absorptive linear polarizer and an absorptive layer.